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Sample records for sub-fossil chironomid assemblages

  1. The response of chironomid assemblages to mineral richness gradient in the Western Carpathian helocrenes

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    Vít Syrovátka

    2012-10-01

    Full Text Available Chironomid assemblages of helocrene springs were investigated in the Western Carpathians in order to identify potential effect of water mineral richness on the taxonomic structure of the assemblages. A complex gradient considering water chemistry and substratum was used as a measure of basicity (mineral richness. Taxonomic structure, total abundance and abundance of most frequent taxa were related to this gradient with regards to two contrasting habitats: trickle (A and water-loged soil with standing water (B. The variance in chironomid assemblage attributable to basicity was estimated and tested via PERMANOVA as well as the possible effect of the other environmental variables. The response of individual taxa was examined using GAM. The results indicate a strong relationship between basicity and substratum characteristics, with coarser mineral substrata at basic and high amount of organic matter at acidic conditions. Although water chemistry was correlated with and inseparable from these substratum properties, it could not be substituted with them, as they discriminated well only between acidic and basic springs, but did not follow the basicity gradient in either acidic or basic group of springs. Chironomid assemblage showed a strong and systematic response to the complex gradient of mineral richness, which explained the largest portion of variance in both the habitat A and B faunal data and was projected on the first axes of both NMDS ordinations. The assemblage response could be documented by the preference of several taxa for particular mineral richness conditions, while the number of taxa seemed to be highest in the middle of the basicity gradient. As only 17 samples were analysed so far, the results are considered preliminary and, hopefully, more confident results will be available in near future.doi: 10.5324/fn.v31i0.1403.Published online: 17 October 2012.

  2. Assessing the effects of climate and volcanism on diatom and chironomid assemblages in an Andean lake near Quito, Ecuador

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    Neal Michelutti

    2015-12-01

    Full Text Available The tropical Andes are undergoing climate changes that rival those occurring anywhere else on the planet, and are likely to have profound consequences for ecosystems. Paleolimnological investigations of remote mountain lakes can provide details of past environmental change, especially where monitoring data are absent. Here, we reconstruct fossil diatom and chironomid communities spanning the last several hundred years from an Andean lake located in an ecological reserve near Quito, Ecuador. Both diatoms and chironomids recorded assemblage shifts reflective of changing climate conditions. The diatoms are likely responding primarily to temperature-related limnological changes, recording an increase in the number of planktonic taxa in the most recent sediments. This change is consistent with warmer conditions that result in enhanced periods of thermal stratification, allowing planktonic species to proliferate. The chironomids appear to respond mainly to a change in precipitation regime, recording a greater number of terrestrial and semi-terrestrial taxa that have been transported to the lake. A thick tephra deposit at the base of the sediment core affected both diatom and chironomid assemblages. The diatoms registered a change in species composition highlighting the ability of certain taxa to rapidly colonize new environments. In contrast, the chironomids showed a marked drop in abundance immediately following the tephra, but no change in species composition. In both cases the ecological response was short-lived, illustrating the resiliency of the lake to return to baseline conditions following volcanic inputs.

  3. Sub-fossil beetle assemblages associated with the "mammoth fauna" in the Late Pleistocene localities of the Ural Mountains and West Siberia.

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    Zinovyev, Evgeniy

    2011-01-01

    The distribution of beetles at the end of the Middle Pleninglacial (=terminal Quaternary) was examined based on sub-fossil material from the Ural Mountains and Western Siberia, Russia. All relevant localities of fossil insects have similar radiocarbon dates, ranging between 33,000 and 22,000 C14 years ago. Being situated across the vast territory from the southern Ural Mountains in the South to the middle Yamal Peninsula in the North, they allow latitudinal changes in beetle assemblages of that time to be traced. These beetles lived simultaneously with mammals of the so-called "mammoth fauna" with mammoth, bison, and wooly rhinoceros, the often co-occurring mega-mammalian bones at some of the sites being evidence of this. The beetle assemblages found between 59° and 57°N appear to be the most interesting. Their bulk is referred to as a "mixed" type, one which includes a characteristic combination of arcto-boreal, boreal, steppe and polyzonal species showing no analogues among recent insect complexes. These peculiar faunas seem to have represented a particular zonal type, which disappeared since the end of the Last Glaciation to arrive here with the extinction of the mammoth biota. In contrast, on the sites lying north of 60°N, the beetle communities were similar to modern sub-arctic and arctic faunas, yet with the participation of some sub-boreal steppe components, such as Poecilus ravus Lutshnik and Carabus sibiricus Fischer-Waldheim. This information, when compared with our knowledge of synchronous insect faunas from other regions of northern Eurasia, suggests that the former distribution of beetles in this region could be accounted for both by palaeo-environmental conditions and the impact of grazing by large ruminant mammals across the so-called "mammoth savannas".

  4. Sub-fossil beetle assemblages associated with the “mammoth fauna” in the Late Pleistocene localities of the Ural Mountains and West Siberia

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    Zinovyev, Evgeniy

    2011-01-01

    Abstract The distribution of beetles at the end of the Middle Pleninglacial (=terminal Quaternary) was examined based on sub-fossil material from the Ural Mountains and Western Siberia, Russia. All relevant localities of fossil insects have similar radiocarbon dates, ranging between 33,000 and 22,000 C14 years ago. Being situated across the vast territory from the southern Ural Mountains in the South to the middle Yamal Peninsula in the North, they allow latitudinal changes in beetle assemblages of that time to be traced. These beetles lived simultaneously with mammals of the so-called “mammoth fauna” with mammoth, bison, and wooly rhinoceros, the often co-occurring mega-mammalian bones at some of the sites being evidence of this. The beetle assemblages found between 59° and 57°N appear to be the most interesting. Their bulk is referred to as a “mixed” type, one which includes a characteristic combination of arcto-boreal, boreal, steppe and polyzonal species showing no analogues among recent insect complexes. These peculiar faunas seem to have represented a particular zonal type, which disappeared since the end of the Last Glaciation to arrive here with the extinction of the mammoth biota. In contrast, on the sites lying north of 60°N, the beetle communities were similar to modern sub-arctic and arctic faunas, yet with the participation of some sub-boreal steppe components, such as Poecilus ravus Lutshnik and Carabus sibiricus Fischer-Waldheim. This information, when compared with our knowledge of synchronous insect faunas from other regions of northern Eurasia, suggests that the former distribution of beetles in this region could be accounted for both by palaeo-environmental conditions and the impact of grazing by large ruminant mammals across the so-called “mammoth savannas”. PMID:21738409

  5. Sub-fossil beetle assemblages associated with the “mammoth fauna” in the Late Pleistocene localities of the Ural Mountains and West Siberia

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    Evgeniy Zinovyev

    2011-05-01

    Full Text Available The distribution of beetles at the end of the Middle Pleninglacial (=terminal Quaternary was examined based on sub-fossil material from the Ural Mountains and Western Siberia, Russia. All relevant localities of fossil insects have similar radiocarbon dates, ranging between 33,000 and 22,000 C14 years ago. Being situated across the vast territory from the southern Ural Mountains in the South to the middle Yamal Peninsula in the North, they allow latitudinal changes in beetle assemblages of that time to be traced. These beetles lived simultaneously with mammals of the so-called “mammoth fauna” with mammoth, bison, and wooly rhinoceros, the often co-occurring mega-mammalian bones at some of the sites being evidence of this. The beetle assemblages found between 59° and 57°N appear to be the most interesting. Their bulk is referred to as a “mixed” type, one which includes a characteristic combination of arcto-boreal, boreal, steppe and polyzonal species showing no analogues among recent insect complexes. These peculiar faunas seem to have represented a particular zonal type, which disappeared since the end of the Last Glaciation to arrive here with the extinction of the mammoth biota. In contrast, on the sites lying north of 60°N, the beetle communities were similar to modern sub-arctic and arctic faunas, yet with the participation of some sub-boreal steppe components, such as Poecilus ravus Lutshnik and Carabus sibiricus Fischer-Waldheim. This information, when compared with our knowledge of synchronous insect faunas from other regions of northern Eurasia, suggests that the former distribution of beetles in this region could be accounted for both by palaeo-environmental conditions and the impact of grazing by large ruminant mammals across the so-called “mammoth savannas”.

  6. Does Type of Substratum Affects Chironomid Larvae Assemblage Composition? A Study in a River Catchment in Northern Patagonia, Argentina.

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    Mauad, M; Siri, A; Donato, M

    2017-02-01

    Chironomid larvae assemblages were investigated at seven sampling stations in relation to stream habitat type in the Challhuaco-Ñireco river system located in the Nahuel Huapi National Park, in the North-Western part of Rio Negro Province, Argentina. A total of 2229 individuals were sampled and 43 Chironomidae taxa were recorded with Orthocladiinae (29) being the best represented subfamily, followed by Diamesinae (5), Tanypodinae (3), Podonominae (3) and Chironominae (3). Stictocladius spF, Cricotopus (Paratrichocladius) sp6, Cricotopus sp2, Cricotopus sp3 and Parapsectrocladius sp2 were the most abundant taxa. Sites near the source of the river system were dominated by Podonomus sp., Limnophyes sp., Parapsectrocladius sp. and Stictocladius spF, whereas sites close to the river mouth were dominated by Diamesinae sp5 and Cricotopus sp. Rank/abundance plots show that all the analysed sites displayed dominance of some species. Stictocladius spF, Cricotopus sp2, Cricotopus sp3, Cricotopus (Paratrichocladius) sp6, Parapsectrocladius sp. and Limnophyes sp. resulted as dominant species, or being part of a group of dominant species, at least in one sample. Eleven taxa were associated with habitats related with riffle areas and stable substrates with filamentous algae. Species-environment relationships were examined using ordination analysis. Elevation was the most significant environmental variable that explained 22% of the total variability of the chironomid assemblages, showing stronger relationships among sites within an altitudinal gradient than among habitat type. Abundance of chironomids increased from headwaters to the outflow in Nahuel Huapi Lake responding to an altitude gradient as well as some environmental factors such as coarse matter and nutrient concentrations.

  7. Modern diatom, cladocera, chironomid, and chrysophyte cyst assemblages as quantitative indicators for the reconstruction of past environmental conditions in the Alps. II. Nutrients

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    Lotter, A.F.; Birks, H.J.B.; Hofmann, W.; Marchetto, A.

    1998-01-01

    Surface sediments from 68 small lakes in the Alps and 9 welldated sediment core samples that cover a gradient of total phosphorus (TP) concentrations of 6 to 520 ug TP l-1 were studied for diatom, chrysophyte cyst, cladocera, and chironomid assemblages. Inferencemodels for mean circulation log10

  8. Modern diatom, cladocera, chironomid, and chrysophyte cyst assemblages as quantitative indicators for the reconstruction of past environmental conditions in the Alps. I. Climate

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    Lotter, A.F.; Birks, H.J.B.; Hofmann, W.; Marchetto, A.

    1997-01-01

    Diatom, chrysophyte cyst, benthic cladocera, planktonic cladocera, and chironomid assemblages were studied in the surface sediments of 68 small lakes along an altitudinal gradient from 300 to 2350 m in Switzerland. In addition, 43 environmental variables relating to the physical limnology,

  9. Long-term patterns of chironomid assemblages in a high elevation stream/lake network (Switzerland – Implications to global change

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    Brigitte Lods-Crozet

    2012-10-01

    Full Text Available A long-term monitoring program was initiated in 2002 on running and standing waters in a high elevation cirque landscape (Macun in the Swiss National Park. The region comprises contrasting basins with different water sources, a glacier-fed basin and two precipitation-fed basins. Sampling of 26 permanent and temporary ponds (or small lakes and of interconnecting streams (10 sites was conducted from 2002 to 2010. Pond macroinvertebrate assemblages were dominated by chironomids with 42 taxa. The Orthocladiinae were the dominant subfamily in richness and abundance with 22 taxa. The greatest diversity was found in ponds located in the south and outlet basins. The inter-year variability for the same pond is high, but no clear temporal trend was noticed in ponds frequently monitored ponds. The Orthocladiinae subfamily was also the richest in the stream sites where 33 taxa were collected. The north and south basins were separated on the basis of chironomid assemblages. The chironomid assemblages in the stream network shows a temporal trend from 2002 but it cannot be linked to any clear change at the community structure level. The higher richness and abundance in stream sites and ponds of the south basin could be related to a greater heterogeneity in water physico-chemistry and substrata, and by the presence of Bryophyta. The understanding of the environmental factors that influence faunal assemblages is crucial for the protection of this sensitive alpine pond network where a relatively high overall regional diversity (49 taxa is detected. From the literature, temperature is recognized as the driving force on changes in chironomid assemblages in alpine systems. Our results support the use of chironomids as flagship indicators in the assessment of climatic change in alpine landscapes.doi: 10.5324/fn.v31i0.1361.Published online: 17 October 2012.

  10. Relation of chironomids with Aeromonas species

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    Sivan eLaviad

    2016-05-01

    Full Text Available Chironomids (Diptera: Chironomidae, also known as non-biting midges, are one of the most abundant groups of insects in aquatic habitats. They undergo a complete metamorphosis of four life stages of which three are aquatic (egg, larva, pupa, and the adult emerges into the air. Chironomids serve as a natural reservoir of Aeromonas and Vibrio cholerae species. Here we review existing knowledge about the mutual relations between Aeromonas species and chironomids. Using 454-pyrosequencing of the 16S rRNA gene, we found that the prevalence of Aeromonas species in the insects’ egg masses and larvae was 1.6% and 3.3% of the insects’ endogenous microbiota, respectively. Aeromonas abundance per egg mass remained stable during a six-month period of bacterial monitoring. Different Aeromonas species were isolated and some demonstrated the ability to degrade the insect’s egg masses and to prevent eggs hatching. Chitinase was identified as the enzyme responsible for the egg mass degradation. Different Aeromonas species isolated from chironomids demonstrated the potential to protect their host from toxic metals. Aeromonas is a causative agent of fish infections. Fish are frequently recorded as feeding on chironomids. Thus, fish might be infected with Aeromonas species via chironomid consumption. Aeromonas strains are also responsible for causing gastroenteritis and wound infections in humans. Different virulence genes were identified in Aeromonas species isolated from chironomids. Chironomids may infest drinking water reservoirs, hence be the source of pathogenic Aeromonas strains in drinking water. Chironomids and Aeromonas species have a complicated mutual relationship.

  11. New radiocarbon dates for Milu (Elaphurus davidianus) sub-fossils from southeast China

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    Ding, X.F. [State Key Laboratory of Nuclear Physics and Technology and Institute of Heavy Ion Physics, School of Physics, Peking University, Beijing 100871 (China); Shen, C.D., E-mail: cdshen@gig.ac.cn [State Key Laboratory of Isotope Geochemistry, Guangzhou Institute of Geochemistry, Chinese Academy of Sciences, 510640 Guangzhou (China); Ding, P.; Yi, W.X. [State Key Laboratory of Isotope Geochemistry, Guangzhou Institute of Geochemistry, Chinese Academy of Sciences, 510640 Guangzhou (China); Fu, D.P.; Liu, K.X. [State Key Laboratory of Nuclear Physics and Technology and Institute of Heavy Ion Physics, School of Physics, Peking University, Beijing 100871 (China)

    2013-01-15

    Milu (Elaphurus davidianus, Pere David's deer) is one of the few species of large mammals that became extinct in the wild, but survived domestically. A good understanding of expansion and habitat is required if the reintroduction of Milu into the wild is to be implemented. Among the widely reported findings of Milu sub-fossils, only a small fraction have been dated. Here we report new AMS radiocarbon dates on Milu sub-fossil samples unearthed from two sites at Qingdun, Jiangsu and Fujiashan, Zhejiang in southeast China. These AMS {sup 14}C ages of Milu sub-fossils provide new evidence for the presence of Milu expansion in the lower reaches of the Yangtze River during the Holocene Optimum interval from 5000 yr BC to 3000 yr BC. These new ages also have important implications for the reconstruction of the paleoclimate and paleogeography during the Neolithic Period in southeast China.

  12. Desiccation resistance of Chironomid larvae

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    Jan Frouz

    2015-07-01

    Full Text Available Resistance to desiccation in larvae of eight species of aquatic, semiaquatic and terrestrial chironomids (Pseudodiamesa branickii, Macropelopia sp., Prodiamesa olivacea, Micropsectra sp., Chironomus riparius, Chironomus dorsalis, Metriocnemus martini and Camptocladius stercorarius was studied. The larvae were desiccated in exicator at constant conditions (15 °C, 80% RH and changes in moisture and body water content was recorded. The LD-50 for loss of body water was calculated. The lowest resistance to loss of body water was found in larvae from subfamilies Tanypodinae and Diamesinae Macropelopia sp. and P. branickii. They survived loss of 49.7 and 56.6% of original water content (presented values are LD-50. On the other hand the highest resistance to water loss was found in C. dorsalis. M. martini and C. stercorarius. The larvae of these species may survive loss of 67.4, 76.6 and 84.2% of original water content. Nevertheless the survival time under experimental conditions depends more closely on larval size than on lethal level of water loss. The smaller larvae desiccated faster and perished sooner than large ones despite they tolerate higher loss of body water.

  13. The influence of environmental factors and dredging on chironomid larval diversity in urban drainage systems in polders strongly influenced by seepage from large rivers

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    Vermonden, K.; Brodersen, Klaus Peter; Jacobsen, Dean

    2011-01-01

    , in urban waters strongly influenced by seepage of large rivers. Chironomid assemblages were studied in urban surface-water systems (man-made drainage ditches) in polder areas along lowland reaches of the rivers Rhine-Meuse in The Netherlands. Multivariate analysis was used to identify the key environmental...... factors. Taxon richness, Shannon index (H'), rareness of species, and life-history strategies at urban locations were compared with available data from similar man-made water bodies in rural areas, and the effectiveness of dredging for restoring chironomid diversity in urban waters was tested. Three......, chironomid taxon richness was negatively related to sludge layer and %% cover of lemnids. Dredging changed chironomid species composition, and increased taxon richness and life-history strategies indicative of good O2 conditions. Therefore, dredging can be regarded as an effective measure to restore...

  14. A sub-fossil kauri (Agathis australis) tree-ring chronology

    International Nuclear Information System (INIS)

    Bridge, M.C.; Ogden, J.

    1986-01-01

    A 491-year floating tree-ring chronology was constructed using sub-fossil bog kauris, Agathis australis, from a site near Huntly, North Island, New Zealand. The chronology has been approximately dated to within the period 3,500 B.P. to 3,000 B.P. by radiocarbon dating. This is the first sub-fossil New Zealand chronology, and shows the potential for the formation of a long chronology from the present back over several millenia. The applications of this chronology and its possible extensions include radiocarbon calibration for the Southern Hemisphere, and climatic reconstructions based on ring-widths. It will also assist interpretation of the history of the Waikato Valley over the last few millenia

  15. Seasonal variation in Chironomid emergence from coastal pools

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    Alexander T. Egan

    2015-07-01

    Full Text Available Understanding the phenology of emergences can be useful in determining seasonal chironomid life cycle patterns, which are often influenced by ice cover and temperature in cold climates. Lake Superior is the largest lake in North America and with a mean surface temperature of 3.9 °C influences regional climate. Coastal pools at Isle Royale, a wilderness archipelago in the northern part of the lake, occur in dense patches on low-gradient volcanic bedrock between the lakeshore and forest, creating variable microhabitats for Chironomidae. Four sites were sampled monthly from April to October, 2010. Surface-floating pupal exuviae were collected from a series of pools in two zones: a lower zone near the lake influenced by wave splash, and an upper zone near the forest and influenced by upland runoff. We used Jaccard’s and Whittaker’s diversity indexes to test community similarity across months. Temperature loggers in pools collected hourly readings for most of the study. Assemblage emergences were stable in upper pools, with significant similarity across late spring and summer months. Assemblages were seasonally variable in lower pools, with significant dissimilarity across spring, summer, and fall months. Few species in either zone were unique to spring or fall months. However, many summer species in the splash zone had a narrow emergence period occurring during calm weather following distinct increases in mean water temperature. Regardless of input of cold lake water to the lower zone, pools from both zones generally had corresponding temperature trends.

  16. Stable isotopic analysis of fossil chironomids as an approach to environmental reconstruction: state of development and future challenges

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    Oliver Heiri

    2012-10-01

    Full Text Available Remains of chironomid larvae, especially their strongly sclerotized head capsules, can be found abundantly and well preserved in most lake sediment records. These remains mainly consist of chitin and proteins and, since their chemical composition does not seem to be strongly affected by decompositional processes, they can be used to develop palaeoenvironmental reconstructions based on their stable isotopic composition. Here we review available stable isotope studies based on fossil chironomids and indicate future research necessary to further develop this still relatively new research approach. Efforts to produce stable isotope records based on fossil chironomids have mainly examined the elements H, N, C, and O. They have focussed on (1 developing the methodology for preparing samples for isotopic analysis, (2 laboratory studies cultivating chironomid larvae under controlled conditions to determine the factors affecting their stable isotopic composition, (3 ecosystem-scale studies relating stable isotopic measurements of fossil chironomid assemblages to environmental conditions, and (4 developing first down-core records describing past changes in the stable isotopic composition of chironomid assemblages. These studies have shown that chemical sample pretreatment may affect the isotopic composition for some elements. Laboratory runs suggest that the diet of the larvae influences their stable isotopic composition for H, N, C and O, whereas stable isotopes in the ambient water also strongly influence their oxygen and to a lesser extent hydrogen isotopic composition. These experiments also indicate only minor offsets between the nitrogen and carbon isotopic composition of chironomid soft tissue and the fossilizing head capsules, whereas for hydrogen and oxygen this offset remains to be explored. Though few datasets have been published, the available ecosystem studies and developed down-core sediment records indicate that stable isotopes in

  17. Can a calibration in time be used to infer climate for the last 1000 years climate using chironomids (non-biting midges) preserved in lake sediments?

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    Larocque-Tobler, Isabelle; Grosjean, Martin; Kamenik, Christian

    2010-05-01

    Calibrations in space (i.e chironomid samples in many lakes calibrated with meteorological data) are generally used to quantitatively reconstruct air/water temperature. However, developing such transfer functions is time- and money- consuming, thus many chironomid-inferred temperature records are based on transfer functions from other regions. Here, another way of obtaining quantitative climate reconstructions from chironomid assemblages is assessed. A calibration in time (i.e. chironomid assemblage time series calibrated with meteorological data (AD 1864-1950)) was developed using a weighted-average-partial-least-square (WAPLS) model and compared with a calibration in space model for the last 1000 years. The calibration in time had a weaker correlation coefficient (r2=0.71) than the calibration in space (r2=0.86), but the error of prediction (RMSEP=0.58°C) and the maximum bias (Max Bias=0.73°C) outperformed the statistics of the calibration in space (RMSEP=1.5°C; Max Bias=1.72), probably due to the smaller temperature gradient of the calibration and the lower number of chironomid taxa. However, both models provided 70% of inferences with differences with instrumental data <1°C at near-annual resolution and 80% of inferences with differences with instrumental data <1°C when 2-year means were used for comparison. On millenial scale, the calibration in space provided a temperature reconstruction similar to those obtained with other archives/proxies. This better performance might be due to the better represenation of fossil taxa in the calibration in time

  18. Recent warming in a high mountain lake (Laguna Cimera, Central Spain inferred by means of fossil chironomids

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    Manuel TORO

    2000-09-01

    Full Text Available Lake Cimera (Lat. 40°15'50'' N; Long. 05°18'15" W, Zmax = 9.4m, A = 4.5 ha, 2140 m a.s.l, is one of the most remote and unpolluted high mountain lakes on the Sierra de Gredos (Central Spain. Intrannual and interannual variability in maximum water temperature and winter oxygen depletion can be related to climate variability (mainly air temperature, through controlling ice cover length. The extent of the oxygen depletion during ice cover period, which is related to this ice cover length, is a key factor controlling the relative abundance of chironomid (Diptera: Insecta taxa, especially the low oxygen content adapted Chironomus sp. In this way, we have found a high negative correlation between the relative abundance of Chironomus head capsules in the sediment and the reconstructed air temperature in the last 200 years (n = 20, r = -0.75, p <0.001. The interpretation of such relationship throughout the fossil chironomid assemblage points to a recent warming (since ca mid 1980s in Lake Cimera. The ecological interpretation of other taxa also supports this view. When applying to fossil chironomids of Lake Cimera the transfer functions developed to reconstruct summer past temperatures in the Alps, it is also well correlated with reconstructed air temperatures (n = 20, r = 0.45, p <0.01, especially when only the most accurate dating levels (top of the core, ca 75 years are taken into account (n = 13, r = 0.75, p <0.01. However, 1 the linear regressions of both models show significantly different slopes, and 2 chironomid reconstruction underestimates in ca. 3 ºC air reconstruction. The later is probably because the fossil chironomid model has been developed for a different geographical region. Nevertheless, both models provide an independent line of evidence of a recent warming (since ca mid 1980s in Lake Cimera. Our data also supports the use of chironomids head capsules as an effective tool to infer past temperatures.

  19. Carbonate organo-mineral micro- and ultrastructures in sub-fossil stromatolites: Marion lake, South Australia.

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    Perri, E; Tucker, M E; Spadafora, A

    2012-03-01

    Sub-fossil stromatolites (5000-3000 years old) occur on the marginal flat surrounding Marion Lake (South Australia). A micrite/microsparite crystal fabric characterises these fine-grained, well-laminated stromatolites, which lack trapped grains. The internal lamination is characterised by a sub-millimetric alternation of porous and dense laminae. The microfabric of the laminae is ubiquitously composed of a fine (10-20 μm) peloidal texture, with many thinner aphanitic layers. Aggregates of very fine, low-Mg calcite and aragonite constitute both peloidal and aphanitic micrite, which is coated, respectively, by spherulitic and fringing acicular microspar. Micrite, with a high organic matter content, is formed of coalescing nanospheres grading into small polyhedrons, probably composed mainly of aragonite, with less calcite enriched in Mg, Sr, Na and S. Bacteria-like microfossils and relics of extracellular polymeric substance (EPS) occur abundantly within this micritic framework. The former consist of empty moulds and mineralised bodies of coccoid forms, whereas EPS relics consist of sheet-like or filamentous structures that appear both mineralised and more often still preserved as a C-enriched dehydrated substance that represents the main organic matter component of the deposit. Acicular crystals, which show a prismatic elongate shape, are composed of Mg-depleted aragonite that lacks fossils or organic relicts. Degrading EPS and micro-organisms appear gradually to be replaced and entombed by the nanospherical precipitates, implying the existence of processes of organo-mineralisation within an original syn-sedimentary microbial community. Succeeding micron-scale crystals merge to form isolated or connected micritic aggregates (the peloids), followed by the gradual formation of the acicular crystals as purely inorganic precipitates. © 2011 Blackwell Publishing Ltd.

  20. Inferring past environmental changes in three Turkish lakes from sub-fossil Cladocera

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    Çakıroğlu, Ayşe İdil; Levi, Eti E.; Tavşanoğlu, Nihan

    2016-01-01

    Cladocerans are increasingly used in palaeolimnological studies as their community composition is sensitive to both anthropogenic and natural forces in lakes. We present the results of a palaeolimnological investigation of three Turkish shallow lakes located in cold dry steppe and semi-dry Medite......Cladocerans are increasingly used in palaeolimnological studies as their community composition is sensitive to both anthropogenic and natural forces in lakes. We present the results of a palaeolimnological investigation of three Turkish shallow lakes located in cold dry steppe and semi...... correlated with variation in the cladoceran assemblage. Redundancy analysis showed that salinity, macrophyte abundance, fish density, depth and total phosphorus were the most correlated with change in cladoceran assemblage composition with eigenvalues for the first and the second axes being λ1 = 0.312 and λ2...

  1. Influence of selected biotopes on chironomid-based bioassessment ...

    African Journals Online (AJOL)

    ... characterisation of a macroinvertebrate-based pollution effect is usually based on samples collected from three distinct biotopes, i.e., stones, vegetation and sediments. In this study, the influence of reducing the numbers of biotopes on chironomid-based bioassessment of pollution in the Swartkops River was investigated.

  2. Habitat selection by chironomid larvae: fast growth requires fast food

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    Haas, de E.M.; Wagner, C.; Koelmans, A.A.; Kraak, M.H.S.; Admiraal, W.

    2006-01-01

    1. Sediments have been considered as a habitat, a cover from predators and a source of food, but also as a source of potential toxic compounds. Therefore, the choice of a suitable substrate is essential for the development of chironomids. 2. For the midge Chironomus riparius (Meigen 1804) the growth

  3. Habitat selection by chironomid larvae: fast growth requires fast food.

    NARCIS (Netherlands)

    de Haas, E.M.; Wagner, C.; Koelmans, A.A.; Kraak, M.H.S.; Admiraal, W.

    2006-01-01

    1. Sediments have been considered as a habitat, a cover from predators and a source of food, but also as a source of potential toxic compounds. Therefore, the choice of a suitable substrate is essential for the development of chironomids. 2. For the midge Chironomus riparius (Meigen 1804) the growth

  4. Chironomid distribution along a pollution gradient in Ethiopian rivers ...

    African Journals Online (AJOL)

    Water pollution resulting from the rapidly intensifying use of freshwater resources in Ethiopia is increasing the need for continuous follow-up and monitoring of the country's aquatic ecosystems, in order to maintain their biological diversity and water quality. Chironomids (non-biting dipteran midges) are often used for ...

  5. Changes in carbon and nitrogen stable isotopes of chironomid larvae during growth, starvation and metamorphosis.

    Science.gov (United States)

    Doi, Hideyuki; Kikuchi, Eisuke; Takagi, Shigeto; Shikano, Shuichi

    2007-01-01

    We conducted experiments to determine isotope changes in the deposit-feeding chironomid larvae Chironomus acerbiphilus during feeding, starvation and metamorphosis. Isotope changes in chironomid larvae occurred mainly during growth and rarely afterward. This finding indicates that chironomid isotope turnover mainly occurs in conjunction with growth and suggests that chironomid larvae only break down newly assimilated food for energy during periods of no growth. Chironomid delta(13)C values significantly increased throughout the starvation experiment, indicating that chironomids preferentially break down components with lower delta(13)C content during starvation. We found significant changes in chironomid isotope ratios ((15)N enrichment) during pupation. This evidence suggests that the physiological condition of animals (such as during an active growth phase or pre- or post-molting) is important to their stable isotope ratios.

  6. A Late-glacial chironomid record from Hawes Water, northwest England

    Science.gov (United States)

    Bedford, Alan; Jones, Richard. T.; Lang, Barbara; Brooks, Stephen; Marshall, Jim D.

    2004-03-01

    This paper presents the results of a high-resolution Late-glacial chironomid stratigraphy from Hawes Water, a small carbonate lake in northern Lancashire. The samples were from a core taken from the terrestrialised margin of the present lake, which represents an intermediate depth between the true littoral and the profundal. The chironomid assemblage showed a high degree of sensitivity to both broad-scale and short-term temperature changes. Comparison with an existing proxy temperature record (18O) for the site confirmed the presence of four temperature inversions within the Late-glacial Interstadial. A mean July air temperature inference model, derived from acid, soft-water lakes in Norway and Svalbard, was applied to the data. Despite the absence of carbonate lakes within the Norwegian training set, there was a close similarity between trends in estimated July air temperature and the 18O trace, with a particularly strong correspondence in the periods of clay deposition. This suggests that this model is highly robust. The inferred maximum Interstadial temperature was 13.4°C, dropping initially to 7.5°C in the Loch Lomond Stadial. Temperatures reach a maximum of nearly 10°C in this period, cool for a short period before rising rapidly to 13.2°C at the start of the Holocene. These temperatures are similar to but slightly higher than those estimated for Whitrig Bog, southeast Scotland, and lower than those inferred from coleopteran-based models for sites in South Wales. Copyright

  7. A chironomid-based record of temperature variability during the past 4000 years in northern China and its possible societal implications

    Science.gov (United States)

    Wang, Haipeng; Chen, Jianhui; Zhang, Shengda; Zhang, David D.; Wang, Zongli; Xu, Qinghai; Chen, Shengqian; Wang, Shijin; Kang, Shichang; Chen, Fahu

    2018-03-01

    Long-term, high-resolution temperature records which combine an unambiguous proxy and precise dating are rare in China. In addition, the societal implications of past temperature change on a regional scale have not been sufficiently assessed. Here, based on the modern relationship between chironomids and temperature, we use fossil chironomid assemblages in a precisely dated sediment core from Gonghai Lake to explore temperature variability during the past 4000 years in northern China. Subsequently, we address the possible regional societal implications of temperature change through a statistical analysis of the occurrence of wars. Our results show the following. (1) The mean annual temperature (TANN) was relatively high during 4000-2700 cal yr BP, decreased gradually during 2700-1270 cal yr BP and then fluctuated during the last 1270 years. (2) A cold event in the Period of Disunity, the Sui-Tang Warm Period (STWP), the Medieval Warm Period (MWP) and the Little Ice Age (LIA) can all be recognized in the paleotemperature record, as well as in many other temperature reconstructions in China. This suggests that our chironomid-inferred temperature record for the Gonghai Lake region is representative. (3) Local wars in Shanxi Province, documented in the historical literature during the past 2700 years, are statistically significantly correlated with changes in temperature, and the relationship is a good example of the potential societal implications of temperature change on a regional scale.

  8. Persistence of chironomids in metal polluted Andean high altitude streams: does melanin play a role?

    NARCIS (Netherlands)

    Loayza Muro, R.A.; Marticorena-Ruíz, J.K.; Palomino, E.J.; Merritt, C.; de Baat, M.L.; van Gemert, M.; Verweij, R.A.; Kraak, M.H.S.; Admiraal, W.

    2013-01-01

    In high altitude Andean streams an intense solar radiation and coinciding metal pollution allow the persistence of only a few specialized taxa, including chironomids. The aim of the present study was therefore to determine the mechanisms underlying the persistence of chironomids under these multiple

  9. Oxygen Isotopes Archived in Subfossil Chironomids: Advancing a Promising Proxy for Lake Water Isotopes

    Science.gov (United States)

    Lasher, G. E.; Axford, Y.; Blair, N. E.

    2017-12-01

    Oxygen isotopes measured in subfossil chironomid head capsules (aquatic insect remains) in lake sediments are beginning to offer paleoclimate insights from previously under-studied areas of the world. Since the first published pilot study demonstrated the potential of chironomid δ18O to record lake water δ18O (Wooller et al., 2004), subsequent work has refined our understanding of this proxy: confirming via lab cultures that growth water controls head capsule δ18O (Wang et al., 2009), refining laboratory pretreatment protocols, and further validating the method by demonstrating strong agreement between carbonate and chironomid-derived paleo-isotope records (Verbruggen et al., 2009, 2010, 2011). However, outstanding questions remain, including the seasonality of chironomid growth, possible species-dependent vital effects, and diagenetic effects on the protein-chitin complex that comprise chironomid cuticles. To address some of these questions, we summarize available data from paired modern chironomid-lake water δ18O values from around the world and discuss climatic and environmental factors affecting chironomid isotopic signatures. We also present new data on the resistance of these subfossils to diagenesis and degradation throughout the late Quaternary using Fourier Transform Infrared Spectroscopy (FT-IR) and Pyrolysis Gas Chromatography Mass Spectrometry (Py-GC/MS) of chironomid remains up to >100,000 years old. As chironomids are nearly ubiquitous in lakes globally and, we argue, molecularly stable through glacial and interglacial cycles, this proxy has the potential to greatly expand the spatial and temporal resolution of Quaternary paleo-isotopes and thus climate records. In addition to reviewing and presenting new methodological advances, we also present applications of chironomid δ18O from millennial- to centennial-scale Holocene Greenland lake records.

  10. Metal Concentrations and Responses of Chironomid Larvae Exposed to Thailand Pulp and Paper Mill Effluent.

    Science.gov (United States)

    Tokhun, Natsima; Iwai, Chuleemas Boonthai; Noller, Barry N

    2017-11-01

    Pulp and paper mills (PPM) may discharge insufficiently treated waste into rivers and give rise to serious effects with aquatic life. This study investigated the biological response of the chironomid (Chironomus javanus, Kieffer) when exposed to PPM effluent. Effluent concentrations of BOD, COD, TKN, TS, Cr, Cu, Pb and Zn were high. Cd and Cr concentrations in chironomid were the most accumulated. Whole effluent toxicity on the chironomid test organism was significant as expressed by the percent survival and decreased with increasing concentration. Highest dry weight, head capsule and length of the chironomid test organism corresponded to 100% effluent at a specific time. Effect of dilution was assessed by using glutathione S-transferase activity on chironomid and corresponded to 6.25% effluent during 48-96 h which was significantly increased in the chironomid. The results showed that the chironomid was sensitive to PPM effluent and toxicity tests can be used for assessing the effect of effluent on aquatic species.

  11. [Septicaemia of chironomid larvae (Diptera: Chironomidae) promoted by Bacillus cereus and B. thuringiensis].

    Science.gov (United States)

    Khodyrev, V P

    2012-01-01

    Natural factors regulating the population of chironomids were studied. The bacteria Bacillus cereus were isolated from chironomids sampled from Kuyalnitskii Firth after epizooty of Chironomus sp., and bacteria Bacillus thuringiensis spp. israelensis (Bti) were isolated from dead larva of Chironomus plumosus sampled in the Sea of Azov (3-m depth). Bti were characterized by high insecticide activity on midges Anopheles messeae Fall., Aedes cireneus Mg., and Culex pipiens pipiens f. pipiens L.

  12. Fish assemblages

    Science.gov (United States)

    McGarvey, Daniel J.; Falke, Jeffrey A.; Li, Hiram W.; Li, Judith; Hauer, F. Richard; Lamberti, G.A.

    2017-01-01

    Methods to sample fishes in stream ecosystems and to analyze the raw data, focusing primarily on assemblage-level (all fish species combined) analyses, are presented in this chapter. We begin with guidance on sample site selection, permitting for fish collection, and information-gathering steps to be completed prior to conducting fieldwork. Basic sampling methods (visual surveying, electrofishing, and seining) are presented with specific instructions for estimating population sizes via visual, capture-recapture, and depletion surveys, in addition to new guidance on environmental DNA (eDNA) methods. Steps to process fish specimens in the field including the use of anesthesia and preservation of whole specimens or tissue samples (for genetic or stable isotope analysis) are also presented. Data analysis methods include characterization of size-structure within populations, estimation of species richness and diversity, and application of fish functional traits. We conclude with three advanced topics in assemblage-level analysis: multidimensional scaling (MDS), ecological networks, and loop analysis.

  13. Strange Assemblage

    Directory of Open Access Journals (Sweden)

    David Robert Cole

    2014-08-01

    Full Text Available This paper contends that the power of Deleuze & Guattari’s (1988 notion of assemblage as theorised in 1000 Plateaus can be normalised and reductive with reference to its application to any social-cultural context where an open system of dynamic and fluid elements are located. Rather than determining the assemblage in this way, this paper argues for an alternative conception of ‘strange assemblage’ that must be deliberately and consciously created through rigorous and focused intellectual, creative and philosophical work around what makes assemblages singular. The paper will proceed with examples of ‘strange assemblage’ taken from a film by Peter Greenaway (A Zed and 2 Noughts; the film ‘Performance’; educational research with Sudanese families in Australia; the book, Bomb Culture by Jeff Nuttall (1970; and the band Hawkwind. Fittingly, these elements are themselves chosen to demonstrate the concept of ‘strange assemblage’, and how it can be presented. How exactly the elements of a ‘strange assemblage’ come together and work in the world is unknown until they are specifically elaborated and created ‘in the moment’. Such spontaneous methodology reminds us of the 1960s ‘Happenings’, the Situationist International and Dada/Surrealism. The difference that will be opened up by this paper is that all elements of this ‘strange assemblage’ cohere in terms of a rendering of ‘the unacceptable.'

  14. Late Glacial climate and palaeoenvironment in the Southern Carpathian Mountains inferred by chironomid and pollen analyses

    Science.gov (United States)

    Tóth, M.; Heiri, O.; Magyari, E.; Braun, M.; Buczkó, K.; Bálint, M.; Jakab, G.

    2009-04-01

    The Southern Carpathian Mountains have several glacial lakes with their sediments extending back to the Late Glacial period (ca. 11,500-14,700 calibrated radiocarbon years BP). This area has so far missed quantitative palaeoclimate records that are however much needed in order to obtain a continental-scale picture of ecosystem reorganization in response to rapid climatic changes during the Late Glacial. High-resolution chironomid and pollen analyses can both provide such records. In this study these two methods are applied to the sediment sequence of a small sub-alpine lake, Taul dintre Brazi (Retezat Mts, 1740 m a.s.l., 0.5 ha). The lake is situated on base-poor, granite bedrock, within the Picea abies forest belt. Our aim was (1) to study changes in the chironomid fauna, (2) to obtain summer temperature estimates using a chironomid-mean July air temperature inference model, and finally (3) to compare the chironomid-inferred climate record with a pollen-based quantitative climate record (plant functional type method). Here we provide first results from this multi-proxy study. The Late Glacial and Early Holocene part of this core was analysed at 100-200 yr resolution. During the Oldest Dryas the chironomid fauna was dominated by Pseudodiamesa and Tanytarsini species; the start of the Lateglacial interstadial was marked by the diversification of Tanytarsini (Tanytarsus lugens-type, Tanytarsus pallidicornis-type, Paratanytarsus sp, Micropsectra insignilobus-type) and the disappearance of Pseudodiamesa suggesting a distinct increase in summer temperature. At the same time afforestation by Larix, Pinus cembra, Pinus mugo and Picea abies was signaled by the pollen, stomatal and plant macrofossil records. During the Younger Dryas reversal the chironomid fauna showed increasing abundance of Micropsectra insignilobus-type, a chironomid typical for cool, nutrient poor lakes whereas the pollen, plant macrofossil and stomatal records pointed to a decrease of Picea abies

  15. Sieve efficiency in benthic sampling as related to chironomid head capsule width

    Science.gov (United States)

    Hudson, Patrick L.; Adams, Jean V.

    1998-01-01

    The width of the head capsule in chironomid larvae is the most important morphometric character controlling retention of specimens in sieving devices. Knowledge of the range in size of these widths within any chironomid community is fundamental to sampling and interpreting the resulting data. We present the head capsule widths of 30 species of chironomids and relate their size distribution to loss or retention in several experiments using graded sieve sizes. Based on our measurements and those found in the literature we found the head capsule width of fourth instars in half the chironomids species to be less than 350 I?m. Many species may never be collected with the commonly used U.S. Standard No. 30 sieve (589 I?m), and the No. 60 (246 I?m) screen appears to retain most species only qualitatively. We found 70 to 90% of the chironomid larvae and 19 to 34% of their biomass can pass through a No. 80 sieve (177 I?m). The implications of sieve loss and other factors affecting sieving efficiency are discussed.

  16. Diversity and distribution of chironomids (Diptera, Chironomidae in pristine Alpine and pre-Alpine springs (Northern Italy

    Directory of Open Access Journals (Sweden)

    Bruno ROSSARO

    2011-09-01

    Full Text Available The diversity and distribution of chironomids (Diptera, Chironomidae were studied in relation to environmental factors in 81 springs under pristine conditions in the Italian Prealps and Alps (Trentino and Veneto, NE-Italy, 46°N, 10-11°E. Each spring was surveyed once, between May and November, in 2005 or in 2007-2008, within 50 m of the spring's source (eucrenal. A total of 173 macroinvertebrate samples were collected, in which 26,871 chironomids (including larvae, pupae, pupal exuviae and adults were counted. Five subfamilies (Tanypodinae, Diamesinae, Prodiamesinae, Orthocladiinae and Chironominae, 54 genera and 104 species/groups of species were identified. As expected, Orthocladiinae accounted for a large part of specimens (82%, followed by Diamesinae (10%, Chironominae Tanytarsini (6% and Tanypodinae (2%. Together the Chironominae Chironomini and Prodiamesinae contributed less than 0.05% of the fauna. Larvae represented 97.5% of specimens, mostly juveniles (62.6%. Maximum richness and diversity occurred at intermediate altitudes (ca 900-2100 m a.s.l.. Most taxa were found in a small proportion of sites, and frequencies declined gradually for more widely distributed species. A high number (67% of rare (= present in less than 10% of sites taxa were found. Three to 27 taxa were identified per spring. The rheocrene/rheo-helocrene springs were richest in taxa (generally >15 taxa, the mineral spring was poorest, with only three taxa. Most taxa were crenophilous, including lentic, rheobiontic and bryophilous taxa. A Principal Component Analysis (PCA was performed including 98 taxa. Axes were interpreted calculating the correlation coefficients between site scores and 24 environmental factors. The species with the highest scores were Pseudokiefferiella parva, Corynoneura sp. A, Metriocnemus eurynotus gr., Paratrichocladius skirwithensis and Tvetenia calvescens. Five clusters of sites were identified with K-means analysis on the basis of the first

  17. Inter-Colony Fidelity of Sr/Ca Variability in the Massive Caribbean Coral Siderastrea siderea: a Sub-Fossil Example

    Science.gov (United States)

    Maupin, C. R.; Quinn, T. M.; Poore, R. Z.; Lin, K.; Shen, C.

    2008-12-01

    Coral-based reconstructions of climate variability in the Atlantic Warm Pool (AWP) in the pre-instrumental period are sparse. Multi-century Sr/Ca records generated from the skeleton of the widely distributed, massive, slow growing (~0.5 cm yr-1) coral Siderastrea siderea have the potential to address this data gap by providing robust proxies of interannual- to centennial-scale sea surface temperature (SST) variability in the AWP. However, before modern and fossil geochemical time series from S. siderea can be interpreted in terms of climate variability, reproducibility tests must be performed on individual coral colonies from the same location. Here we provide one such assessment of inter-colony reproducibility in the geochemistry of S. siderea using cores from the Dry Tortugas National Park (~24°33'N, 82°53'W). Time series of Sr/Ca from a large colony cored live in the summer of 1993 and a second, sub-fossil colony core, with a high-precision mass spectrometric U/Th date of 110 ± 1.7 (2σ) yrs, are compared. The 25-year overlap exhibits excellent reproducibility in both monthly and monthly anomaly space, and the average absolute difference between monthly data from the two time series is within instrumental precision. The results of this work suggest that individual monthly Sr/Ca records from S. siderea can be deemed representative of local SST variability, and that continuous local Sr/Ca records can be successfully spliced together from living and sub-fossil corals using high precision U/Th dating.

  18. Assessing lake eutrophication using chironomids: understanding the nature of community response in different lake types

    DEFF Research Database (Denmark)

    Langdon, P. G.; Ruiz, Z.; Brodersen, K. P.

    2006-01-01

    in the original calibration or extended datasets. However, since the transfer functions are based on weighted averages of the trophic optima for the taxa present and not on community similarities, reasonable downcore inferences were produced. Ordination analyses also showed that the lakes retain their 'identity......1. Total phosphorus (TP) and chlorophyll a (Chl a) chironomid inference models ( Brodersen & Lindegaard, 1999 ; Brooks, Bennion & Birks, 2001 ) were used in an attempt to reconstruct changes in nutrients from three very different lake types. Both training sets were expanded, particularly at the low....... A response to nutrients (TP or total nitrogen (TN) ) at this site is also indirect, and the TP reconstruction therefore cannot be reliably interpreted. The third lake, March Ghyll Reservoir has little change in historic chironomid communities, suggesting that this well mixed, relatively unproductive lake has...

  19. Environmental factors affecting the distribution of Chironomid larvae of the Seybouse wadi, North-Eastern Algeria

    Directory of Open Access Journals (Sweden)

    Nadjla Chaib

    2013-03-01

    Full Text Available A survey of the Seybouse wadi (North-Eastern Algeria between 2008 and 2011 was conducted in 26 sampling sites located on the main river and its tributaries using chironomids. From 3264 collected larvae, forty-five chironomid species were identified, and were correlated to 13 environmental variables to predict determinant factors affecting their distribution. Indicator value (IndVal analysis was first performed to determine indicator chironomid species according to several factors (sites, seasons, source distance, granulometry, conductivity, water temperature, dissolved oxygen, water velocity, pollution and the abundance of filamentous algae. Co-inertia analysis (CoIA supported the IndVal results, emphasising an upstream/downstream gradient in the first axis, while a granulometry gradient was emphasised by the second axis. A pollution gradient was also highlighted in the plane of the first two axes, separating tolerant Chironomus sp. 1, Cricotopus bicinctus and Cricotopus (Isocladius sylvestris from intolerant species as Phaenopsectra flavipes, Rheotanytarsus sp.1 and Cladotanytarsus sp. 1.

  20. Paleoecología: el uso de los quironómidos fósiles (Diptera: Chironomidae en reconstrucciones paleoambientales durante el Cuaternario en la Patagonia Paleoecology: the use of fossil chironomids (Diptera: Chironomidae for paleoenvironmental reconstructions in Patagonia

    Directory of Open Access Journals (Sweden)

    Julieta Massaferro

    2009-06-01

    the biological indicators from lake sediments more useful in environmental reconstructions. Chironomids have recently acquired great importance due to the promising results obtained regarding climatic reconstructions mainly in Europe and North America. In South America, the use of fossil chironomids in Quaternary studies is still limited and the reason for that is the little regional taxonomic knowledge. Most of these studies were developed in glacial lakes in Patagonia both in Argentina and Chile. The larvae of chironomids are an invaluable paleolimnological tool due to the sensitiveness of these insects to natural and non-natural environmental changes. In addition to that, this group of insects is widely distributed with a high abundance and diversity. Their head capsules can preserve in sediments holding characters which allow their generic and sometimes specific identification. The study of chironomid assemblages can be used with different goals, for instance, to study eutrofication due to their quick response to changes in organic matter, nutrients and heavy metals. However, one of the most significant potentials of this group is its sensitivity to temperature variations, which is why the most important implementation of their study in sediments is centered in climatic reconstructions. This article is a review of the studies developed in Argentinean and Chilean Patagonia, using fossil chironomids for paleoenvironmental reconstructions.

  1. Application of stable isotopes from Australian Chironomid (non-biting midge) head capsules as proxies for past climate change

    International Nuclear Information System (INIS)

    Chang, Jie; Shulmeister, James; Theiling, Bethany

    2013-01-01

    Development of proxies that have the potential to provide long-term and reliable palaeoclimate records is a key to better reconstructing and understanding the past climate system. Ideally these proxies should be widely distributed and common in the environment. Chironomids (non-biting midges) occur in virtually all permanent and semi-permanent terrestrial water bodies. Growth of chironomids is strongly controlled by water temperature. Chironomids have a chitinous head capsule and studies (Wooller et al., 2004; Verbruggen et al., 2011) have shown that the fossilised chitinous heads of non-biting midge larvae act as a ‘time capsule’ that preserves the δ 18 O of the lake water in which they live. Wooller et al (2004) demonstrate a positive correlation between the mean annual air temperature above a lake and δ 18 O of the chironomids in the lake (Figure 1). Therefore, chironomids may be used as a proxy for modern and paleo-water temperature. Fractionation due to temperature is one of the most important controls on lake water δ 18 O in southern Australia. Therefore, δ 18 O from fossilised chironomid heads will be used as a relatively new method for reconstructing past changes in temperature in Australia. The modern range of chironomid δ 18 O values will be developed based on 32 lake surface sediment sampled from South-eastern Australia (10 lakes from News South Wales, 15 from Victoria and 7 from Tasmania during the summers of 2012 and 2013). For these lakes, head capsules of single taxa will be picked to avoid complications from 'vital effects'. These data will serve to establish the relationship of δ 18 O to modern lake temperatures. To cross-check the validity of the δ 18 O relationship we are also developing a transfer function for the chironomids from these lakes. Transfer functions are standard techniques in paleolimnology and several exist for chironomids in the Australasian region (Woodward and Shulmeister, 2006; Rees et al., 2008). They are

  2. IgE antibodies reactive with silverfish, cockroach and chironomid are frequently found in mite-positive allergic patients

    NARCIS (Netherlands)

    Witteman, A. M.; van den Oudenrijn, S.; van Leeuwen, J.; Akkerdaas, J.; van der Zee, J. S.; Aalberse, R. C.

    1995-01-01

    Approximately 30% of the house dust mite allergic patients in The Netherlands have IgE antibodies reactive with silverfish, cockroach and/or chironomid. In allergic patients without IgE antibodies against Dermatophagoides pteronyssinus less than 5% have IgE antibodies reactive with these insects. By

  3. Does nature and persistence of substrate at a mesohabitat scale matter for Chironomidae assemblages? A study of two perennial mountain streams in Patagonia, Argentina.

    Science.gov (United States)

    Epele, Luis Beltrán; Miserendino, María Laura; Brand, Cecilia

    2012-01-01

    Chironomid substrate-specific associations regarding the nature (organic-inorganic) and stability (stable-unstable) of different habitats were investigated at two low order Patagonian streams, during high and low water periods. Nant y Fall and Glyn rivers were visited twice (October 2007 and March 2008) and seven different habitat types were identified. A total of 60 samples were collected using a Surber sampler (0.09 m(-2) and 250 µm) and a set of 23 environmental descriptors including physicochemical parameters and different fractions of particulate organic matter were assessed. 35 Chironomidae taxa were recorded with Orthocladiinae (20), Chironominae (7), and Podonominae (4) being the most well-represented subfamilies. Paratrichocladius sp. 1, Parapsectrocladius sp. 2, Parametriocnemus sp. 1, Pseudochironomus sp., and Rheotanytarsus sp. were the most abundant taxa. According to the relative preference index, at least 14 taxa showed strong affinity for a particular substrate. The structurally complex macrophyte Myriophyllum quitense supported 11 taxa compared with only five taxa found on the less complex Isoetes savatieri. Generally, stable substrates (boulders, cobbles, and rooted plants) supported significantly higher chironomids richness, abundance, and diversity than unstable ones (gravel-sand). Canonical correspondence analysis revealed that detritus (leaves, seeds, and biomass), macrophyte biomass, and secondarily hydraulic variables had high explanatory power on chironomids species composition and structure. This work suggests that more complex substrates showing persistence in the temporal dimension supported a diverse array of chironomids, meaning that the maintenance of natural habitat heterogeneity is essential for the community. Land-use practices having significant effects on ecological stream attributes such as increased turbidity, sediment deposition, and runoff patterns will alter assemblages. Understanding environmental associations of the

  4. Affects and assemblages

    DEFF Research Database (Denmark)

    Samson, Kristine

    Affects and assemblages are Deleuzian Guattarian notions related to aesthetics and spatial territories. In recent urban geography and urban studies these notions are increasingly gaining more impact (Amin & Thrift 2002, Pile 2008, Farías & Bender 2010, Andersen & Harrison 2010, Thrift 2008). What...... happens to aesthetics and how does it change the existing social and geographical understanding of urban space? The paper sets out to reintroduce aesthetical aspects of affects and assemblages in relation to urban space and urban planning. It presupposes urban space as a continuous state of becoming where...... affects and assemblages produce subjective feelings and emotions (Pile 2009) Recently, urban experience designs and events aim at evoking affects through affects and assemblages. A Danish example is the Carlsberg city in Copenhagen another is The High line in Chelsea, New York (Samson 2011). Thus...

  5. Silver bioaccumulation in chironomid larvae as a potential source for upper trophic levels: a study case from northern Patagonia.

    Science.gov (United States)

    Williams, Natalia; Rizzo, Andrea; Arribére, María A; Suárez, Diego Añón; Guevara, Sergio Ribeiro

    2018-01-01

    Silver (Ag) is a pollutant of high concern in aquatic ecosystems, considered among the most toxic metallic ions. In lacustrine environments, contaminated sediments are a source of Ag for the food web. Chironomidae (Insecta: Diptera) are the most abundant, diverse, and representative insect groups in aquatic ecosystems. Chironomid larvae are closely associated to benthic substrates and link primary producers and secondary consumers. Given their trophic position and their life habits, these larvae can be considered the entry point for the transference of Ag, from the benthic deposit to the higher trophic levels of the food web. Previous studies in lakes from Nahuel Huapi National Park (Northern Patagonia) showed Ag enrichment over background levels (0.04-0.1 μg g -1 dry weight) both in biota (bivalves and fish liver) and sediments from sites near human settlements. The aim of this study was to analyze the role of chironomids in the transference of Ag from the benthic reservoir of Lake Moreno Oeste to the food web. The concentration of Ag in chironomid larvae tissue ranged from 0.1 to 1.5 μg g -1 dry weight, reaching a bioaccumulation factor up to 17 over substrates and depending on the associated substrate type, feeding habitats, larval stage, and season. The main Ag transfer to higher trophic levels by chironomids occurs in the littoral zone, mostly from larvae inhabiting submerged vegetation (Myriophyllum quitense) and sediment from vegetated zones. This study presents novel evidence of the doorway role played by chironomid larvae in Ag pathways from the sediments into food webs of freshwater ecosystems.

  6. Anhydrobiosis-associated nuclear DNA damage and repair in the sleeping chironomid: linkage with radioresistance.

    Directory of Open Access Journals (Sweden)

    Oleg Gusev

    Full Text Available Anhydrobiotic chironomid larvae can withstand prolonged complete desiccation as well as other external stresses including ionizing radiation. To understand the cross-tolerance mechanism, we have analyzed the structural changes in the nuclear DNA using transmission electron microscopy and DNA comet assays in relation to anhydrobiosis and radiation. We found that dehydration causes alterations in chromatin structure and a severe fragmentation of nuclear DNA in the cells of the larvae despite successful anhydrobiosis. Furthermore, while the larvae had restored physiological activity within an hour following rehydration, nuclear DNA restoration typically took 72 to 96 h. The DNA fragmentation level and the recovery of DNA integrity in the rehydrated larvae after anhydrobiosis were similar to those of hydrated larvae irradiated with 70 Gy of high-linear energy transfer (LET ions ((4He. In contrast, low-LET radiation (gamma-rays of the same dose caused less initial damage to the larvae, and DNA was completely repaired within within 24 h. The expression of genes encoding the DNA repair enzymes occurred upon entering anhydrobiosis and exposure to high- and low-LET radiations, indicative of DNA damage that includes double-strand breaks and their subsequent repair. The expression of antioxidant enzymes-coding genes was also elevated in the anhydrobiotic and the gamma-ray-irradiated larvae that probably functions to reduce the negative effect of reactive oxygen species upon exposure to these stresses. Indeed the mature antioxidant proteins accumulated in the dry larvae and the total activity of antioxidants increased by a 3-4 fold in association with anhydrobiosis. We conclude that one of the factors explaining the relationship between radioresistance and the ability to undergo anhydrobiosis in the sleeping chironomid could be an adaptation to desiccation-inflicted nuclear DNA damage. There were also similarities in the molecular response of the larvae to

  7. The distribution and abundance of chironomids in high-latitude Eurasian lakes with respect to temperature and continentality: development and application of new chironomid-based climate-inference models in northern Russia

    OpenAIRE

    Nazarova, Larisa; Self, A.; Brooks, S.; Birks, H. J. B.; Porinchu, D.; Odland, A.; Yang, H.; Jones, V. J.

    2011-01-01

    The large landmass of northern Russia has the potential to influence global climate through amplification of climate change. Reconstructing the climate in this region over millennial timescales is crucial for understanding the processes that affect the climate system. Chironomids, preserved in lake sediments, have the potential to produce high resolution, low error, quantitative summer air temperature reconstructions. Canonical correspondence analysis (CCA) of modern surface sediments from 10...

  8. Matching 30 years of ecosystem monitoring with a high resolution microfossil record of chironomid eggs and Cladocera from Lake Mývatn, Iceland

    DEFF Research Database (Denmark)

    Hauptfleisch, Ulf; Einarsson, Arni; Andersen, Thorbjørn Joest

    2011-01-01

    1. Monitoring of the ecosystem of Lake My´vatn, Iceland, since 1975 has revealed extreme fluctuations in important food web components, such as chironomids and cladocerans, with amplitudes of several orders of magnitude and a period of 5–8 years. This study uses sediment cores from the lake to ex...... forcing. The results also indicate the usefulness of chironomid egg capsules in palaeolimnological studies....

  9. Monopelopia caraguata (Chironomidae: Tanypodinae: Pentaneurini) and Phytotelmatocladius delarosai (Chironomidae: Orthocladiinae): Two Phytotelmatous Chironomids Distributed from Florida to Argentina

    OpenAIRE

    Siri, Augusto; Donato, Mariano Humberto

    2017-01-01

    The geographic distribution of the 2 phytotelmatous chironomids Monopelopia caraguata and Phytotelmatocladius delarosai is expanded, and the occurrence of parthenogenesis in the last species is corroborated under laboratory conditions. Se extiende la distribución geográfica de las especies fitotelmáticas Monopelopia caraguata y Phytotelmatocladius delarosai hacia el sur en Argentina, y se corrobora bajo condiciones de laboratorio la ocurrencia de partenogénesis en esta última especie. F...

  10. Translanguaging and Semiotic Assemblages

    Science.gov (United States)

    Pennycook, Alastair

    2017-01-01

    This paper asks what translanguaging could start to look like if it incorporated an expanded version of language and questioned not only to the borders between languages but also the borders between semiotic modes. Developing the idea of spatial repertoires and assemblages, and looking at data from a Bangladeshi-owned corner shop, this paper…

  11. Assemblages of Patient Safety

    DEFF Research Database (Denmark)

    Balatsas Lekkas, Angelos

    2016-01-01

    This thesis identifies how design processes emerge during the use of devices in healthcare, by attending to assemblages where contingencies of risk and harm co-exist with the contribution of healthcare professionals to the safe care of patients. With support from the field of Science and Technology...

  12. Response of chironomid species (Diptera, Chironomidae to water temperature: effects on species distribution in specific habitats

    Directory of Open Access Journals (Sweden)

    L. Marziali

    2013-09-01

    Full Text Available The response of 443 chironomid species to water temperature was analyzed, with the aim of defining their thermal optimum, tolerance limits and thermal habitat. The database included 4442 samples mainly from Italian river catchments collected from the 1950s up to date. Thermal preferences were calculated separately for larval and pupal specimens and for different habitats: high altitude and lowland lakes in the Alpine ecoregion; lowland lakes in the Mediterranean ecoregion; heavily modified water bodies; kryal, krenal, rhithral and potamal in running waters. Optimum response was calculated as mean water temperature, weighted by species abundances; tolerance as weighted standard deviation; skewness and kurtosis as 3rd and 4th moment statistics. The responses were fitted to normal uni- or plurimodal Gaussian models. Cold stenothermal species showed: i unimodal response, ii tolerance for a narrow temperature range, iii optima closed to their minimum temperature values, iv leptokurtic response. Thermophilous species showed: i optima at different temperature values, ii wider tolerance, iii optima near their maximum temperature values, iv platikurtic response, often fitting a plurimodal model. As expected, lower optima values and narrower tolerance were obtained for kryal and krenal, than for rhithral, potamal and lakes. Thermal response curves were produced for each species and were discussed according to species distribution (i.e. altitudinal range in running water and water depth in lakes, voltinism and phylogeny. Thermal optimum and tolerance limits and the definition of the thermal habitat of species can help predicting the impact of global warming on freshwater ecosystems.

  13. The Colonization of Newly Built Fishponds by the Macroinvertebrate Assemblages

    Directory of Open Access Journals (Sweden)

    Pavla Řezníčková

    2016-01-01

    Full Text Available The succession of standing waters by aquatic macroinvertebrates is a present and insufficiently surveyed topic. This study is addressed to the issue of colonisation of newly created small standing waters. Two fishponds situated in the north of Moravia (Czech Republic were studied. The aim of this study was to determine the character and colonisation rate of these ponds by macroinvertebrates, to evaluate the abundance, taxonomic composition and changes in composition of freshwater assemblages as a result of the fish stock influence. Basic abiotic parameters were also measured within the sampling occasions (e.g. water temperature, dissolved oxygen, conductivity, pH, total nitrogen and phosphorus concentrations. Samples of aquatic macroinvertebrates were taken monthly during the years 2012 and 2013, by kick sampling method using the hand net. The character of sampled fishponds was very similar, environmental parameters (e.g. area, substrate, depth etc. were comparable. The colonisation of both fishponds was very fast. The pioneer colonists were mainly insect larvae (e.g. chironomids. Very low numbers of macroinvertebrates as a result of fish stock influence were recorded on both sites during the observation with the highest abundances in summer season.

  14. Fashion, Mediations & Method Assemblages

    DEFF Research Database (Denmark)

    Sommerlund, Julie; Jespersen, Astrid Pernille

    , respectively. The paper thus takes on aesthetics and the social in a manner closely related to a core argument of STS - namely that the scientific fact, and the social processes of constructing, distributing, and using that fact, are co-constructed (Callon, 1986; Latour, 1993). The paper thus contributes......, it is an important ambition of this paper to go into a methodological discussion of how "that which effectively happens" can be approached. To this end, the paper will combine Hennion's term of the "mediator" with John Laws methodological term of "method assemblages". Method assemblages is a suggested as a way...... of handling multiple, fluid realities with multiple, fluid methods. Empirically, the paper works with mediation in fashion - that is efforts the active shaping of relations between producer and consumer through communication, marketing and PR. Fashion mediation is by no means simple, but organise complex...

  15. Distribution, Abundance and Assemblages

    African Journals Online (AJOL)

    E-mail: luis.silva@cd.ieo.es. Cephalopod Species in Mozambican Waters Caught in the. “Mozambique 0307” Survey: Distribution, Abundance and. Assemblages. Luis Silva1, Eduardo Balguerías2, Paula Santana Afonso3, Ignacio Sobrino1, Juan Gil1 and. Candelaria Burgos1. 1Instituto Español de Oceanografía Unidad de ...

  16. The response of chironomid fauna to environmental changes at a freshwater lake in arid Northwestern China over the past 100 years

    Science.gov (United States)

    Zhang, E.

    2016-12-01

    Chironomid fauna is proven to be a useful lacustrine proxy for tracing past climate and environmental changes. However, limited data have been reported from the arid northwestern China, a place hosting abundant chironomid species and quite sensitive to past environmental changes. In this study, we study the chironomid stratigraphy and sediment properties from two short cores collected at the freshwater Bosten Lake in Xinjiang Province in arid northwestern China, in order to reconstruct environmental variations during the past century. We find a sharp decrease of the concentration of midge head capsules and an overwhelmed chrionomid community around 1950s, which probably relate with the rapid sediment accumulations and sudden fine-grain inputs caused by enhanced human activities such as population increase, reclamation of alkaline land, and agriculture activities. After 1950s, Chironomus plumosus-type and Microchironomus dominated but Procladius almost disappeared, indicating a further modification of the lake catchment basin by human activites. We also find that chironomid fauna in the profundal zone was changed much earlier than that in the river month zone, indicating a stronger environmental stress within the lake basin rather than the inflowing river. This study provide a case about the ecological effects of human-induced environmental changes on the chironomid fauna in the arid lacustrine system. The result will help to detect the natural conditions of lake systems and provide the baseline information or "target" for managing and restoring disturbed lake systems in arid northwestern China.

  17. A microcosm test of adaptation and species specific responses to polluted sediments applicable to indigenous chironomids (Diptera)

    Energy Technology Data Exchange (ETDEWEB)

    Bahrndorff, Simon [Centre for Environmental Stress and Adaptation Research, La Trobe University, Bundoora, Victoria 3086 (Australia) and Department of Ecology and Genetics, University of Aarhus, Ny Munkegade, Building 540, DK-8000, Aarhus C (Denmark)]. E-mail: simon.bahrndorff@biology.au.dk; Ward, Jacqueline [Centre for Environmental Stress and Adaptation Research, La Trobe University, Bundoora, Victoria 3086 (Australia); Pettigrove, Vincent [Research and Technology, Melbourne Water Corporation, PO Box 4342, Melbourne, Victoria 3001 (Australia)]. E-mail: vincent.pettigrove@melbournewater.com.au; Hoffmann, Ary A. [Centre for Environmental Stress and Adaptation Research, La Trobe University, Bundoora, Victoria 3086 (Australia) and Centre for Environmental Stress and Adaptation Research, Department of Zoology, University of Melbourne, Bundoora, Victoria 3010 (Australia)]. E-mail: ary@unimelb.edu.au

    2006-02-15

    Chironomids may adapt to pollution stress but data are confined to species that can be reared in the laboratory. A microcosm approach was used to test for adaptation and species differences in heavy metal tolerance. In one experiment, microcosms containing different levels of contaminants were placed in polluted and reference locations. The response of Chironomus februarius to metal contaminants suggested local adaptation: relatively more flies emerged from clean sediment at the reference site and the reverse pattern occurred at the polluted site. However, maternal effects were not specifically ruled out. In another species, Kiefferulus intertinctus, there was no evidence for adaptation. In a second experiment, microcosms with different contaminant levels were placed at two polluted and two unpolluted sites. Species responded differently to contaminants, but there was no evidence for adaptation in the species where this could be tested. Adaptation to heavy metals may be uncommon and species specific, but more sensitive species need to be tested across a range of pollution levels. Factors influencing the likelihood of adaptation are briefly discussed. - A field test for adaptation applicable to indigenous chironomids suggests adaptation to metal contaminants in one species but not in other species.

  18. The effect of 210Pb and stable lead on the induction of mouthpart deformities in chironomid larvae

    International Nuclear Information System (INIS)

    Bird, G.A.; Schwartz, W.J.; Hoffman, D.

    1995-07-01

    To determine whether mouthpart deformities in chironomid larvae from Port Hope Harbour, Ontario, are the result of exposure to ionizing radiation or heavy metals in the sediment, Chironomus tentans larvae were exposed in the laboratory to concentrations of 210 Pb and stable lead representative of contaminant levels in the harbour. Exposure to 100, 1000, and 2000 Bq 210 Pb·g -1 dry sediment had no effect on the survival, growth of the larvae or frequency of deformities. Likewise, exposure to 0.5 and 5.0 mg lead·g -1 dry sediment had no effect on the larvae, but exposure to 35.0 mg lead·g -1 dry sediment resulted in 100% mortality of the larvae. These results indicate that the observed mouthpart deformities in chironomid larvae in Port Hope Harbour are not the result of radiation exposure. They also indicate that heavy metals (lead) may be having an impact on the population. (author). 28 refs., 9 tabs., 4 figs

  19. Field assessment of reproduction-related traits of chironomids using a newly developed emergence platform (E-Board).

    Science.gov (United States)

    Ferrari, Benoît J D; Faburé, Juliette

    2017-03-01

    Further progress in the development of reliable biomonitoring strategies requires to better link effects in aquatic ecological systems to ambient concentrations of chemical contaminants. Among existing tools, in situ bioassays using caging method represent an interesting way to achieve this challenge. However, elaboration of adapted exposure chambers and suitable operating procedures is still required, particularly to assess ecological relevant traits such as those related to the reproduction. In such context, we developed a new device (Emergence board - E-Board) which allows assessing in rivers the development of the Chironomus riparius species from the early fourth instar larvae to the adult stage. The system acts as a suspended matter trap floating in the subsurface of the water equipped of an emergence trap for catching adults. The system was tested in actual field conditions. Its easy handling allowed obtaining data which demonstrated its applicability for assessing the development of the chironomids. Moreover, by adapting energy-based models (DEB) specifically developed in the laboratory for the species C. riparius, we were able to predict the growth pattern and the emergence of chironomids in real environmental conditions. The E-Board represents thus a promising new in situ tool in perspective of evaluation of the quality of the ecosystems. Copyright © 2016. Published by Elsevier Inc.

  20. The impact of sediment removal on the aquatic macroinvertebrate assemblage in a fishpond littoral zone

    Directory of Open Access Journals (Sweden)

    Zdeněk ADÁMEK

    2011-02-01

    Full Text Available Bottom sediment removal, a widely used technique in restoration management of standing water bodies, has a strong influence on communities of aquatic organisms. As most information on the impact of sediment removal on the aquatic environment comes from studies on lakes, the aim of this study was to describe macroinvertebrate assemblage succession in a fishpond (Štěpánek fishpond, Bohemian-Moravian highlands, Czech Republic littoral zone following restoration by sediment removal during the winter of 2003/2004. Semi-quantitative hand net sampling was undertaken one year before (2003 and in each of the following five years (2004–2008 after sediment removal. A significant decrease in both abundance (approx. 90% of individuals and diversity (approx. 30% of taxa of macroinvertebrates was detected immediately after pond restoration. The values gradually increased over subsequent years, reaching comparable abundance and diversity three years after sediment removal. A significant shift was recorded in the taxonomic and functional composition of the macroinvertebrate assemblage after sediment removal. Mayfly larvae were the dominant invertebrates before restoration, while chironomid larvae and oligochaetes dominated after sediment removal. Phytophilous taxa, grazers and scrapers, and swimming or diving invertebrates were common in 2003, whilst open-water taxa preferring mud and other mostly inorganic microhabitats, gatherers/collectors, and burrowing/boring invertebrates were relatively common after sediment removal. In 2008, the assemblage reverted towards the situation before sediment removal, probably connected with a lower water level and accelerated macrophyte bed succession. Principal Component Analysis on the species data confirmed the differences in invertebrate taxonomic structure among sampling years. Succession of the fishpond invertebrate assemblage in the years following sediment removal was mainly influenced by fish farming practice and

  1. A first chironomid-based summer temperature reconstruction (13-5 ka BP) around 49°N in inland Europe compared with local lake development

    Czech Academy of Sciences Publication Activity Database

    Hájková, Petra; Pařil, P.; Petr, L.; Chattová, B.; Matys Grygar, Tomáš; Heiri, O.

    2016-01-01

    Roč. 141, JUN 01 (2016), s. 94-111 ISSN 0277-3791 Institutional support: RVO:67985939 ; RVO:61388980 Keywords : chironomids * diatoms * climate Subject RIV: EH - Ecology, Behaviour; CA - Inorganic Chemistry (UACH-T) Impact factor: 4.797, year: 2016

  2. Fish stomach contents in benthic macroinvertebrate assemblage assessments

    Directory of Open Access Journals (Sweden)

    TH. Tupinambás

    Full Text Available The choice of sampling gears to assess benthic macroinvertebrate communities depends on environmental characteristics, study objectives, and cost effectiveness. Because of the high foraging capacity and diverse habitats and behaviors of benthophagous fishes, their stomach contents may offer a useful sampling tool in studies of benthic macroinvertebrates, especially in large, deep, fast rivers that are difficult to sample with traditional sediment sampling gear. Our objective was to compare the benthic macroinvertebrate communities sampled from sediments with those sampled from fish stomachs. We collected benthic macroinvertebrates and fish from three different habitat types (backwater, beach, riffle in the wet season, drying season, and dry season along a single reach of the Grande River (Paraná River Basin, southeast Brazil. We sampled sediments through use of a Petersen dredge (total of 216 grabs and used gill nets to sample fish (total of 36 samples. We analyzed the stomach contents of three commonly occurring benthophagous fish species (Eigenmannia virescens, Iheringichthys labrosus, Leporinus amblyrhynchus. Chironomids dominated in both sampling methods. Macroinvertebrate taxonomic composition and abundances from fish stomachs differed from those from sediment samples, but less so from riffles than from backwater and beach habitats. Macroinvertebrate taxa from E. virescens stomachs were more strongly correlated with sediment samples from all three habitats than were those from the other two species. The species accumulation curves and higher mean dispersion values, compared with with sediment samples suggest that E. virescens is more efficient than sediment samples and the other fish studied at collecting benthic taxa. We conclude that by analyzing the stomach contents of benthophagous fishes it is possible to assess important characteristics of benthic communities (dispersion, taxonomic composition and diversity. This is especially true

  3. Toxicity of CeO2 nanoparticles at different trophic levels--effects on diatoms, chironomids and amphibians.

    Science.gov (United States)

    Bour, Agathe; Mouchet, Florence; Verneuil, Laurent; Evariste, Lauris; Silvestre, Jérôme; Pinelli, Eric; Gauthier, Laury

    2015-02-01

    The aim of the present work is to provide wider information on the toxicity of cerium dioxide nanoparticles (CeO2 NPs) in aquatic environments, by studying the toxicity of two types of CeO2 NPs for four species (diatoms Nitzschia palea, the sediment-dwelling invertebrate Chironomus riparius, and the amphibian larvae Xenopus laevis and Pleurodeles waltl.). The two types of CeO2 NPs have different intrinsic properties: some of them are small citrate-coated spheres (2-5 nm), and the others are larger uncoated plates (20-60 nm). Acute toxicity (mortality at 48 or 96 h, depending on the test-organism) was assessed for the four species, from 0.1 to 100 mg L(-1) of NPs. Sub-lethal effects were assessed on chironomids exposed between 0.01 and 1 mg L(-1) of NPs. Mortality, growth inhibition and genotoxic effects were evaluated on amphibian larvae from 0.1 to 10 mg L(-1). Results reveal that no acute toxicity occurs on any species after short exposures, even at the highest concentrations. Mortality (35%) is observed on Xenopus larvae after 12d of exposure at the highest concentration of one type of NPs. No significant effects were observed on chironomids during chronic exposure. Xenopus larvae growth was inhibited from 1 mg L(-1) of both NPs while growth inhibition is observed on Pleurodeles only at the highest concentration of one type of NPs. No genotoxicity was observed on Xenopus but Pleurodeles exhibited dose-dependent genotoxic effects when exposed to one type of NPs. Observed differences in toxicity are discussed focusing on the studied compartment, routes of exposure, species and NPs. Copyright © 2014 Elsevier Ltd. All rights reserved.

  4. Holocene temperature variations at a high-altitude site in the Eastern Alps: a chironomid record from Schwarzsee ob Sölden, Austria

    Science.gov (United States)

    Ilyashuk, Elena A.; Koinig, Karin A.; Heiri, Oliver; Ilyashuk, Boris P.; Psenner, Roland

    2011-01-01

    Few well-dated, quantitative Holocene temperature reconstructions exist from high-altitude sites in the Central Eastern Alps. Here, we present a chironomid-based quantitative reconstruction of mean July air temperatures (TJuly) throughout the Holocene for a remote high-mountain lake, Schwarzsee ob Sölden, situated above the treeline at 2796 m a.s.l. in the Austrian Alps. Applying a chironomid-temperature inference model developed from lakes of the Alpine region to a high-resolution chironomid record from the lake provides evidence for early Holocene (ca 10000–8600 cal yr BP) TJuly of up to 8.5 °C, i.e. >4 °C above the modern (1977–2006) mean July temperature. The reconstruction reveals the so-called ‘8.2-ka cold event’ centered at ca 8250–8000 cal yr BP with temperatures ca 3 °C below the early-Holocene thermal maximum. Rather warm (ca 6 °C) and productive conditions prevailed during ca 7900–4500 cal yr BP. The chironomid record suggests a climate transition between ca 5200 and 4500 cal yr BP to cooler TJuly. A distinct cooling trend is evident from ca 4500 until ca 2500 cal yr BP. Thereafter, the study site experienced its coldest conditions (around 4 °C or less) throughout the rest of the Holocene, with the exception of the warming trend during the late 20th century. Beside other factors, the Northern Hemisphere summer insolation seems to be the major driving force for the long-term trends in TJuly at high altitudes in the Eastern Alps. Due to the extreme location of the lake and the limited temperature range represented by the applied calibration data set, the chironomid-based temperature reconstruction fails to track phases of the late-Holocene climatic history with TJuly cooler than 4 °C. Further chironomid-based palaeoclimate model and down-core studies are required to address this problem, provide more realistic TJuly estimates from undisturbed high-altitude lakes in the Alps, and extract a reliable regional

  5. The Parthenogenetic Cosmopolitan Chironomid, Paratanytarsus grimmii, as a New Standard Test Species for Ecotoxicology: Culturing Methodology and Sensitivity to Aqueous Pollutants.

    Science.gov (United States)

    Gagliardi, Bryant S; Long, Sara M; Pettigrove, Vincent J; Hoffmann, Ary A

    2015-09-01

    Chironomids from the genus Chironomus are widely used in laboratory ecotoxicology, but are prone to inbreeding depression, which can compromise test results. The standard Chironomus test species (C. riparius, C. dilutus and C. yoshimatsui) are also not cosmopolitan, making it difficult to compare results between geographic regions. In contrast, the chironomid Paratanytarsus grimmii is cosmopolitan, and not susceptible to inbreeding depression because it reproduces asexually by apomictic parthenogenesis. However, there is no standardised culturing methodology for P. grimmii, and a lack of acute toxicity data for common pollutants (metals and pesticides). In this study, we developed a reliable culturing methodology for P. grimmii. We also determined 24-h first instar LC50s for the metals Cu, Pb, Zn, Cd and the insecticide imidacloprid. By developing this culturing methodology and generating the first acute metal and imidacloprid LC50s for P. grimmii, we provide a basis for using P. grimmii in routine ecotoxicological testing.

  6. Bacterial fauna associating with chironomid larvae from lakes of Bengaluru city, India - A 16s rRNA gene based identification

    Directory of Open Access Journals (Sweden)

    Ramprasad Kuncham

    2017-06-01

    Full Text Available Chironomid larvae that inhabit in aquatic sediments play an important role as vector for bacterial pathogens. Its life cycle consists of four stages i.e. eggs, larvae, pupae and adult. In the present study we identified bacterial species associated with whole larvae of chironomids from 11 lake sediments of Bangalore region using 16s rRNA gene Sanger sequencing. We found that larvae from all lake sediments associated with bacterial species which include key pathogens. Totally we identified 65 bacterial isolates and obtained GenBank accession numbers (KX980423 - KX980487. Phylogenetic tree constructed using MEGA 7 software and tree analysis highlight the predominant bacterial community associated with larvae which include Enterobacteriaceae (43.08%; 28 isolates and Aeromonas (24.62%; 16 isolates, Shewanella, Delftia, Bacillus (6.15%; 4 isolates each, Pseudomonas (4.62%; 3 isolates and Exiguobacterium (3.08%; 2 isolates. Current findings state that among bacterial population Aeromonas, Enterobacter and Escherichia with serotypes are commonly associated with larvae in maximum lake points. In other hand Vibrio, Pseudomonas, Klebsiella, Shigella, Bacillus, and other bacterial species were identified moderately in all lakes. Interestingly, we identified first time Shigella Gram negative, rod shaped pathogenic organism of Enterobacteriaceae and Rheinheimera Gram negative, rod shaped organism associating chironomid larvae.

  7. Bacterial fauna associating with chironomid larvae from lakes of Bengaluru city, India - A 16s rRNA gene based identification.

    Science.gov (United States)

    Kuncham, Ramprasad; Sivaprakasam, Thiyagarajan; Puneeth Kumar, R; Sreenath, P; Nayak, Ravi; Thayumanavan, Tha; Subba Reddy, Gopireddy V

    2017-06-01

    Chironomid larvae that inhabit in aquatic sediments play an important role as vector for bacterial pathogens. Its life cycle consists of four stages i.e. eggs, larvae, pupae and adult. In the present study we identified bacterial species associated with whole larvae of chironomids from 11 lake sediments of Bangalore region using 16s rRNA gene Sanger sequencing. We found that larvae from all lake sediments associated with bacterial species which include key pathogens. Totally we identified 65 bacterial isolates and obtained GenBank accession numbers (KX980423 - KX980487). Phylogenetic tree constructed using MEGA 7 software and tree analysis highlight the predominant bacterial community associated with larvae which include Enterobacteriaceae (43.08%; 28 isolates) and Aeromonas (24.62%; 16 isolates), Shewanella , Delftia , Bacillus (6.15%; 4 isolates each), Pseudomonas (4.62%; 3 isolates) and Exiguobacterium (3.08%; 2 isolates). Current findings state that among bacterial population Aeromonas , Enterobacter and Escherichia with serotypes are commonly associated with larvae in maximum lake points. In other hand Vibrio , Pseudomonas , Klebsiella , Shigella , Bacillus , and other bacterial species were identified moderately in all lakes. Interestingly, we identified first time Shigella Gram negative, rod shaped pathogenic organism of Enterobacteriaceae and Rheinheimera Gram negative, rod shaped organism associating chironomid larvae.

  8. paleoenvironmental settings and assemblage changes

    African Journals Online (AJOL)

    Kasanzu

    formed during the breakup of Gondwana and after the drifting of ..... high peak from NAM 05. On the overall, the identified foraminifera types .... Vol. 43(1), 2017. 75. Plate 1(continuing):. Examples of observed palynomorphs at different sample intervals across the TDP 11 borehole. DISCUSSIONS. Foraminifera assemblages.

  9. Reconstructing grazer assemblages for protected area restoration.

    Directory of Open Access Journals (Sweden)

    Jan A Venter

    Full Text Available Protected area management agencies often struggle to reliably reconstruct grazer assemblages due to a lack of historical distribution data for their regions. Wrong predictions of grazing assemblages could potentially affect biodiversity negatively. The objective of the study was to determine how well grazing herbivores have become established since introduction to the Mkambati Nature Reserve, South Africa, how this was influenced by facilitation and competition, and how indigenous grazer assemblages can best be predicted for effective ecological restoration. Population trends of several grazing species were investigated in in order to determine how well they have become established since introduction. Five different conceivable grazing assemblages reflecting a range of approaches that are commonly encountered during conservation planning and management decision making were assessed. Species packing was used to predict whether facilitation, competition or co-existence were more likely to occur, and the species packing of the different assemblages were assessed using ANCOVA. Reconstructing a species assemblage using biogeographic and biological information provides the opportunity for a grazer assemblage that allows for facilitatory effects, which in turn leads to an ecosystem that is able to maintain its grazer assemblage structure. The strength of this approach lies in the ability to overcome the problem of depauperate grazer assemblages, resulting from a lack of historical data, by using biogeographical and biological processes, to assist in more effectively reconstructing grazer assemblages. Adaptive management of grazer assemblage restoration through reintroduction, using this approach would further mitigate management risks.

  10. Public Sphere as Digital Assemblage

    DEFF Research Database (Denmark)

    Salovaara-Moring, Inka

    the 1990s onwards digitalization brought concepts of network and complexity into the theoretical discourse. This relational turn changed the social ontology of the public sphere into a dynamic and complex system, erasing the division between the fields of reality (the world), representation (discourse...... theories. Drawing from Deleuze & Guattari (1987), Bennett (2010), and Latour (2004) in order to imagine post-human assemblages of public sphere, this paper argues for a relational ontology that emphasizes the complex interactions of political assemblages. Empirically, it draws from the author’s studies......Normative theories of public sphere have struggled with the topic of materiality. The historical narrative of the ‘public sphere’ situated the phenomenon in specific spaces, where practices (public deliberation) and language (discourse) constructed political agencies, and further publics. From...

  11. Macroinvetebrate Assemblages as Indicators of Water Quality of the West Seti River, Bajhang, Nepal

    Directory of Open Access Journals (Sweden)

    Mohana Matangulu

    2017-08-01

    Full Text Available Water quality of the West Seti River, a tributary of the Karnali in West Nepal was assessed using macroinvertebrates as bioindicators. The main objective of the study was to assess the ecological water quality of the West Seti River and to generate a baseline data on macroinvertebrate assemblages. The sampling was conducted during December 2015 and a total of 11 sampling sites were selected from the West Seti River and its tributaries. Qualitative samples of macroinvertebrates were collected from different habitats. Selected physico-chemical parameters such as pH and temperature were estimated on-site. Dissolved oxygen (DO was estimated by Winkler’s method. The macroinvertebrate samples were enumerated and identified up to Family level following standard literature. Chi-square test was performed to see whether macroinvertebrate taxa varied significantly along the altitudinal gradient and between the West Seti River and its tributaries. An ecological assessment tool Nepalese Biotic Score/ Average Score Per Taxon (NEPBIOS/ASPT was applied to assess the water quality of the sampling sites. The pH value ranged from 7.9 to 8.7 indicating the alkaline nature of the river. A total of 1666 individuals belonging to 34 Families and 7 Orders of macro-invertebrates were observed. The highest diversity of the macroinvertebrate taxa was observed at site T5 with nineteen Families whereas the lowest taxa diversity was observed at R3 with only five Families. The variation in macroinvertebrate assemblages between the sub-tropical and temperate zones; and the West Seti River and its tributaries were not significant. NEPBIOS/ASPT revealed a score of Water Quality Class of III-IV at Site R3 indicating that the site was polluted. This site was characterized by the abundance of red Chironomids which are considered as the indicators of organic pollution.International Journal of EnvironmentVolume-6, Issue-3, Jun-Aug 2017, page: 25-45

  12. Trace DNA from insect skins: a comparison of five extraction protocols and direct PCR on chironomid pupal exuviae.

    Science.gov (United States)

    Kranzfelder, Petra; Ekrem, Torbjørn; Stur, Elisabeth

    2016-01-01

    Insect skins (exuviae) are of extracellular origin and shed during moulting. The skins do not contain cells or DNA themselves, but epithelial cells and other cell-based structures might accidentally attach as they are shed. This source of trace DNA can be sufficient for PCR amplification and sequencing of target genes and aid in species identification through DNA barcoding or association of unknown life stages. Species identification is essential for biomonitoring programs, as species vary in sensitivities to environmental factors. However, it requires a DNA isolation protocol that optimizes the output of target DNA. Here, we compare the relative effectiveness of five different DNA extraction protocols and direct PCR in isolation of DNA from chironomid pupal exuviae. Chironomidae (Diptera) is a species-rich group of aquatic macroinvertebrates widely distributed in freshwater environments and considered a valuable bioindicator of water quality. Genomic DNA was extracted from 61.2% of 570 sampled pupal exuviae. There were significant differences in the methods with regard to cost, handling time, DNA quantity, PCR success, sequence success and the ability to sequence target taxa. The NucleoSpin(®) Tissue XS Kit, DNeasy(®) Blood and Tissue kit, and QuickExtract(™) DNA Extraction Solution provided the best results in isolating DNA from single pupal exuviae. Direct PCR and DTAB/CTAB methods gave poor results. While the observed differences in DNA isolation methods on trace DNA will be relevant to research that focuses on aquatic macroinvertebrate ecology, taxonomy and systematics, they should also be of interest for studies using environmental barcoding and metabarcoding of aquatic environments. © 2015 John Wiley & Sons Ltd.

  13. Density and temperature dependent feeding rates in an established and an alien freshwater gammarid fed on chironomid larvae

    Directory of Open Access Journals (Sweden)

    Dieter WALOSZEK

    2011-02-01

    Full Text Available We compared feeding rates of the well-established, non-invasive amphipod Gammarus roeselii with those of the invasive Dikerogammarus villosus at different prey densities and different temperatures in laboratory experiments using chironomid larvae as prey. Feeding rates were very variable in both species but higher in the invader species than in the well-established non-invasive species. These results were age independent. At high temperature (18-20 °C and high prey density (≥1000 prey m-2 one large adult D. villosus consumed 6-9 prey day-1 on average while one G. roeselii consumed 4-7 prey d-1 and one smaller D. villosus of a length of 8-10 mm consumed 2-5 prey d-1 while one G. roeselii of the same length consumed 3 prey d-1. Predation rate decreased considerably from high (18-20 °C to low temperature (3±2 °C, from 9 to 4 prey predator-1 d-1 in D. villosus and from 7.5 to 2.5 prey predator-1 d-1 in G. roeselii. We conclude that both gammarids consumed a biomass in the range of 1/2 to 1/3 to their own biomass and that low predation/feeding rate at low temperature could be a reason why, in some places, indigenous gammarids can re-colonize their former habitats for a short period of time in cold winter and early spring in spite of the presence of the invasive. We further conclude that differences in weight between the species in particular in the experiments with adults can have influenced feeding rates; possibly differences in weight- specific feeding rates are small.

  14. Urban amphibian assemblages as metacommunities.

    Science.gov (United States)

    Parris, Kirsten M

    2006-05-01

    1. Urban ecosystems are expanding throughout the world, and urban ecology is attracting increasing research interest. Some authors have questioned the value of existing ecological theories for understanding the processes and consequences of urbanization. 2. In order to assess the applicability of metacommunity theory to urban systems, I evaluated three assumptions that underlie the theory - the effect of patch area, the effect of patch isolation, and species-environment relations - using data on assemblages of pond-breeding amphibians in the Greater Melbourne area of Australia. I also assessed the relative impact of habitat fragmentation, habitat isolation, and changes to habitat quality on these assemblages. 3. Poisson regression modelling provided support for an important increase in species richness with patch area (pond size) and a decrease in species richness with increasing patch isolation, as measured by surrounding road cover. Holding all other variables constant, species richness was predicted to be 2.8-5.5 times higher at the largest pond than at the smallest, while the most isolated pond was predicted to have 12-19% of the species richness of the least isolated pond. Thus, the data were consistent with the first two assumptions of metacommunity theory evaluated. 4. The quality of habitat at a pond was also important, with a predicted 44-56% decrease in the number of species detected at ponds with a surrounding vertical wall compared with those with a gently sloping bank. This demonstrates that environmental differences between habitat patches were also influencing amphibian assemblages, providing support for the species-sorting and/or mass-effect perspectives of metacommunity theory. 5. Without management intervention, urbanization may lead to a reduction in the number of amphibian species persisting in urban ponds, particularly where increasing isolation of ponds by roads and associated infrastructure reduces the probability of re-colonization following

  15. Phytoplankton assemblage and environmental variables in Ogun ...

    African Journals Online (AJOL)

    Phytoplankton assemblage and environmental variables in Ogun State Coastal Estuary, Nigeria. ... The present study was on the relationship between phytoplankton assemblage and environmental variables. It was carried out ... Keywords: Micro-algae, physico-chemical parameters, brackish environment, Ogun State ...

  16. Recent saltmarsh foraminiferal assemblages from Iceland

    Science.gov (United States)

    Lübbers, Julia; Schönfeld, Joachim

    2018-01-01

    This study reports for the first time boreal to subarctic intertidal foraminiferal assemblages from saltmarshes at Borgarnes and Faskrudsfjördur on Iceland. The composition of living and dead foraminiferal assemblages was investigated along transects from the tidal flat to the highest reach of halophytic plants. The foraminiferal assemblages from Borgarnes showed 18 species in the total foraminiferal assemblage of which only 7 species were recorded in the living fauna. The assemblages were dominated by agglutinated taxa, whereas 3 calcareous species were recorded, of which only Haynesina orbicularis was found in the living fauna. The distribution limit of calcifying species corresponds to the lower boundary of the lower saltmarsh vegetation zone. Furthermore, calcareous tests showed many features of dissolution, which is an indication of a carbonate corrosive environment. The species forming the dead assemblages were mainly derived from the ambient intertidal areas and were displaced by tidal currents into the saltmarsh. The foraminiferal assemblages from Faskrudsfjördur showed two species, of which only one species was recorded in the living fauna. The assemblage was dominated by the agglutinated foraminifer Trochaminita irregularis. The foraminiferal species recorded on Iceland were the same as commonly found elsewhere in Europa. Since no species was found which is endemic to North America, Iceland is considered part of the European bio province. The foraminiferal could have been immigrated to Iceland from Europe through warm water currents, migratory birds or marine traffic since the last Ice Age.

  17. Spatial variability in macroinvertebrate assemblages: comparing ...

    African Journals Online (AJOL)

    Multivariate analysis of macroinvertebrate assemblages showed that assemblages varied regionally with differences most apparent in upland areas, i.e. mountain streams and foothill-cobble beds, with lowland areas less regionally distinct. Within regions, longitudinal zonation into upland and lowland areas was important, ...

  18. Eemian and Holocene interglacial climate in northwest Greenland inferred from insect assemblages, lipid δ2H, and chitin δ18O preserved in lake sediments

    Science.gov (United States)

    McFarlin, J. M.; Axford, Y.; Osburn, M. R.; Lasher, G. E.; Kelly, M. A.; Osterberg, E. C.; Francis, D. R.; Farnsworth, L. B.

    2016-12-01

    We present a millennial-scale reconstruction of Holocene and Last Interglacial (Eemian) climate in northwest Greenland, inferred from insect assemblages (chironomid-inferred temperatures, CITs) and compound-specific organic isotopes (sedimentary lipid δ2H and chitin δ18O). Sediment cores collected from `Wax Lips Lake' (informal name), a non-glacial lake situated chitin δ18O) and the presence of the warm-dwelling insect Chaoboridae. Our record agrees with estimates of the peak LIG temperature anomaly (relative to the last millennium) from ice cores at NEEM (+8±4°C; Dahl-Jensen et al. 2013), also in northern Greenland. Peak LIG temperatures at both sites exceeded those of the Holocene. We pair an independent temperature proxy with proxies recording the stable isotopic composition of precipitation and lake water at this high-latitude site to provide insight on how hydroclimate changed over Arctic Greenland during two different warm periods - the Holocene Thermal Maximum and the LIG. We find general agreement amongst recorders of lake water isotopic composition, including δ18O of chitin from chironomid head capsules and δ2H of aquatic lipids. We infer the isotopic composition of precipitation from δ2H of long-chain n-alkanes from terrestrial plants. The δ2H of long-chain n-alkanes are internally consistent and deviate from lake water during prolonged periods of warmth, indicating changes in precipitation source, effective moisture, and/or seasonality associated with warming. We also briefly discuss our ongoing work to further characterize the source, distribution and isotopic composition of modern plant lipids in Greenlandic lakes, and thus clarify potential controls on past shifts recorded in sedimentary records.

  19. Sediment features, macrozoobenthic assemblages and trophic relationships (δ13C and δ15N analysis) following a dystrophic event with anoxia and sulphide development in the Santa Giusta lagoon (western Sardinia, Italy)

    International Nuclear Information System (INIS)

    Magni, P.; Rajagopal, S.; Velde, G. van der; Fenzi, G.; Kassenberg, J.; Vizzini, S.; Mazzola, A.; Giordani, G.

    2008-01-01

    Macrozoobenthic assemblages and stable carbon (δ 13 C) and nitrogen (δ 15 N) isotope values of various primary producers (macroalgae and angiosperms) and consumers (macroinvertebrate filter/suspension feeders, deposit feeders, detritivores/omnivores and carnivores and fishes) were studied in the Santa Giusta lagoon (Sardinia, Italy) before (spring) and after (autumn) a dystrophic event which occurred in the summer of 2004. A few days after the dystrophy, the physico-chemical characteristics of sediments and macrozoobenthic assemblages were also investigated. In the latter occasion, high total organic carbon (3.9%) and organic matter (15.9%) contents of surface sediments went together with peaks in acid-volatile sulphide concentrations. Certain immediate effects were quite extreme, such as the drastic reduction in macrozoobenthos and the massive fish kill in August 2004. Among the macrozoobenthos, there were few individuals of chironomid larvae and Capitella cf. capitata left. However, by October, chironomid larvae were numerous, indicating a lack of predators (e.g. fish) and competitors. In addition, some bivalve species and polychaetes which were absent, or present in small numbers before the event, became relatively numerous. The results are discussed based on a knowledge of the sulphide tolerance of these species. Stable isotope analysis clearly showed that the basal level of the food web for most consumers consisted mainly of macroalgae and sedimentary organic matter, and that the values before and after the dystrophic event were not significantly different from one another. This indicates that the relations among different trophic levels were quickly restored following the dystrophic event

  20. Giardia duodenalis genetic assemblages and hosts

    Directory of Open Access Journals (Sweden)

    Heyworth Martin F.

    2016-01-01

    Full Text Available Techniques for sub-classifying morphologically identical Giardia duodenalis trophozoites have included comparisons of the electrophoretic mobility of enzymes and of chromosomes, and sequencing of genes encoding β-giardin, triose phosphate isomerase, the small subunit of ribosomal RNA and glutamate dehydrogenase. To date, G. duodenalis organisms have been sub-classified into eight genetic assemblages (designated A–H. Genotyping of G. duodenalis organisms isolated from various hosts has shown that assemblages A and B infect the largest range of host species, and appear to be the main (or possibly only G. duodenalis assemblages that undeniably infect human subjects. In at least some cases of assemblage A or B infection in wild mammals, there is suggestive evidence that the infection had resulted from environmental contamination by G. duodenalis cysts of human origin.

  1. Fish assemblages in southern California kelp forests.

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — This is a point file of fish assemblages calculated from diver surveys in kelp forests in Southern California. Visual census data was combined for two separate...

  2. Phytoplankton assemblage characteristics in recurrently fluctuating environments.

    Directory of Open Access Journals (Sweden)

    Daniel L Roelke

    Full Text Available Annual variations in biogeochemical and physical processes can lead to nutrient variability and seasonal patterns in phytoplankton productivity and assemblage structure. In many coastal systems river inflow and water exchange with the ocean varies seasonally, and alternating periods can arise where the nutrient most limiting to phytoplankton growth switches. Transitions between these alternating periods can be sudden or gradual and this depends on human activities, such as reservoir construction and interbasin water transfers. How such activities might influence phytoplankton assemblages is largely unknown. Here, we employed a multispecies, multi-nutrient model to explore how nutrient loading switching mode might affect characteristics of phytoplankton assemblages. The model is based on the Monod-relationship, predicting an instantaneous growth rate from ambient inorganic nutrient concentrations whereas the limiting nutrient at any given time was determined by Liebig's Law of the Minimum. Our simulated phytoplankton assemblages self-organized from species rich pools over a 15-year period, and only the surviving species were considered as assemblage members. Using the model, we explored the interactive effects of complementarity level in trait trade-offs within phytoplankton assemblages and the amount of noise in the resource supply concentrations. We found that the effect of shift from a sudden resource supply transition to a gradual one, as observed in systems impacted by watershed development, was dependent on the level of complementarity. In the extremes, phytoplankton species richness and relative overyielding increased when complementarity was lowest, and phytoplankton biomass increased greatly when complementarity was highest. For low-complementarity simulations, the persistence of poorer-performing phytoplankton species of intermediate R*s led to higher richness and relative overyielding. For high-complementarity simulations, the

  3. Assessing water source and channel type as factors affecting benthic macroinvertebrate and periphyton assemblages in the highly urbanized Santa Ana River Basin, California

    Science.gov (United States)

    Burton, C.A.; Brown, L.R.; Belitz, K.

    2005-01-01

    The Santa Ana River basin is the largest stream system in Southern California and includes a densely populated coastal area. Extensive urbanization has altered the geomorphology and hydrology of the streams, adversely affecting aquatic communities. We studied macroinvertebrate and periphyton assemblages in relation to two categorical features of the highly engineered hydrologic system-water source and channel type. Four water sources were identified-natural, urban-impacted groundwater, urban runoff, and treated wastewater. Three channel types were identified-natural, channelized with natural bottom, and concrete-lined. Nineteen sites, covering the range of these two categorical features, were sampled in summer 2000. To minimize the effects of different substrate types among sites, artificial substrates were used for assessing macroinvertebrate and periphyton assemblages. Physical and chemical variables and metrics calculated from macroinvertebrate and periphyton assemblage data were compared among water sources and channel types using analysis of variance and multiple comparison tests. Macroinvertebrate metrics exhibiting significant (P water sources included taxa and Ephemeroptera-Plecoptera-Trichoptera richness, relative richness and abundance of nonchironomid dipterans, orthoclads, oligochaetes, and some functional-feeding groups such as parasites and shredders. Periphyton metrics showing significant differences between water sources included blue-green algae biovolume and relative abundance of nitrogen heterotrophic, eutrophic, motile, and pollution-sensitive diatoms. The relative abundance of trichopterans, tanytarsini chironomids, noninsects, and filter feeders, as well as the relative richness and abundance of diatoms, were significantly different between channel types. Most physical variables were related to channel type, whereas chemical variables and some physical variables (e.g., discharge, velocity, and channel width) were related to water source. These

  4. Fish Assemblage Responses to Forest Cover

    Science.gov (United States)

    Burcher, Chris L.; McTammany, Matthew E.; Benfield, E. Fred; Helfman, Gene S.

    2008-03-01

    We investigated whether fish assemblage structure in southern Appalachian streams differed with historical and contemporary forest cover. We compared fish assemblages in 2nd-4th order streams draining watersheds that had increased forest cover between 1950 and 1993 (i.e ., reforesting watersheds). We sampled fish in 50 m reaches during August 2001 and calculated catch-per-unit-effort (CPUE) by taxonomic, distributional, trophic, reproductive, and thermal metrics. We assigned streams to reforestation categories based on cluster analysis of years 1950 and 1993 near-stream forest cover. The relationship between forest cover and assemblage structure was assessed using analysis of variance to identify differences in fish CPUE in five forest cover categories. Streams contained 23 fish species representing six families, and taxa richness ranged from 1 to 13 at 30 stream sites. Streams with relatively low near-stream forest cover were different from streams having moderate to high near-stream forest cover in 1950 and 1993. Fish assemblages in streams having the lowest amount of forest cover (53-75%) were characterized by higher cosmopolitan, brood hider, detritivore/herbivore, intermediate habitat breadths, run-pool dweller, and warm water tolerant fish CPUE compared to streams with higher riparian forest cover. Our results suggest that fish assemblage’s structural and functional diversity and/or richness may be lower in streams having lower recent or past riparian forest cover compared to assemblages in streams having a high degree of near-stream forest cover.

  5. Quantitative summer temperature reconstruction derived from a combined biogenic Si and chironomid record from varved sediments of Lake Silvaplana (south-eastern Swiss Alps) back to AD 1177

    Science.gov (United States)

    Trachsel, M.; Grosjean, M.; Larocque-Tobler, I.; Schwikowski, M.; Blass, A.; Sturm, M.

    2010-09-01

    High-resolution quantitative temperature records are needed for placing the recent warming into the context of long-term natural climate variability. In this study we present a quantitative high-resolution (9-year) summer (June-August) temperature reconstruction back to AD 1177 for the south-eastern Swiss Alps. This region is a good predictor for summer temperatures in large parts of western and central Europe. Our reconstruction is based on a combination of the high-frequency component of annually resolved biogenic silica (bSi flux) data and the low-frequency component of decadal chironomid-inferred temperatures from annually laminated well dated sediments (varves) from proglacial Lake Silvaplana, eastern Swiss Alps. For the calibration (period AD 1760-1949) we assess systematically the effects of six different regression methods (Type I regressions: Inverse Regression IR, Inverse Prediction IP, Generalised Least Squares GLS; Type II regressions: Major Axis MA, Ranged Major Axis RMA and Standard Major Axis SMA) with regard to the predicted amplitude and the calibration statistics such as root-mean-square error of prediction (RMSEP), reduction of error (RE) and coefficient of efficiency (CE). We found a trade-off in the regression model choice between a good representation of the amplitude and good calibration statistics. The band-pass filtered bSi flux record is in close agreement both in the structure and the amplitude with two fully independent reconstructions spanning back to AD 1500 and AD 1177, respectively. All known pulses of negative volcanic forcing are represented as cold anomalies in the bSi flux record. Volcanic pulses combined with low solar activity (Spörer and Maunder Minimum) are seen as particularly cold episodes around AD 1460 and AD 1690. The combined chironomid and bSi flux temperature record (RMSEP = 0.57 °C) is in good agreement with the glacier history of the Alps. The warmest (AD 1190) and coldest decades (17th century; 1680-1700) of our

  6. Machinic Assemblages: Women, Art Education and Space

    Science.gov (United States)

    Tamboukou, Maria

    2008-01-01

    In this paper I explore connections between women, art education and spatial relations drawing on the Deleuzo-Guattarian concept of "machinic assemblage" as a useful analytical tool for making sense of the heterogeneity and meshwork of life narratives and their social milieus. In focusing on Mary Bradish Titcomb, a fin-de-siecle Bostonian woman…

  7. Seasonal variability of macroinvertebrate assemblages in two ...

    African Journals Online (AJOL)

    Whereas more taxa were recorded in autumn than in spring, a higher proportion of sensitive and high-scoring taxa were recorded in spring. In Mpumalanga macroinvertebrate assemblages did not group by season, and differences in SASS scores were not significant, although more taxa were recorded in winter than in ...

  8. Benthic macroinvertebrate assemblages in mangroves and open ...

    African Journals Online (AJOL)

    Benthic macroinvertebrate assemblages in mangroves and open intertidal areas on the Dar es Salaam coast, Tanzania. ... it is recommended that conservation efforts along the Tanzanian coast should focus here. Keywords: benthic macrofauna, community structure, littoral zone, Tanganyika, Western Indian Ocean ...

  9. Macroinvertebrate assemblages as biological indicators of water ...

    African Journals Online (AJOL)

    Benthic macroinvertebrate assemblages at eight stations in the Moiben River, corresponding to different catchment land uses, were assessed in 2006 as indicators of water quality. The relative abundance per taxon, diversity index, richness index, evenness, dominance, percentage of five dominant taxa and percentage ...

  10. Evaluation of benthic macroinvertebrate assemblage for disturbance ...

    Indian Academy of Sciences (India)

    Home; Journals; Journal of Earth System Science; Volume 122; Issue 4. Evaluation of benthic macroinvertebrate assemblage for disturbance zonation in urban rivers using multivariate analysis: Implications for river management. Ram Devi Tachamo Shah Deep Narayan Shah. Volume 122 Issue 4 August 2013 pp 1125- ...

  11. Benthic assemblages of mega epifauna on the Oregon continental margin

    Science.gov (United States)

    Hemery, Lenaïg G.; Henkel, Sarah K.; Cochrane, Guy R.

    2018-01-01

    Environmental assessment studies are usually required by a country's administration before issuing permits for any industrial activities. One of the goals of such environmental assessment studies is to highlight species assemblages and habitat composition that could make the targeted area unique. A section of the Oregon continental slope that had not been previously explored was targeted for the deployment of floating wind turbines. We carried out an underwater video survey, using a towed camera sled, to describe its benthic assemblages. Organisms were identified to the lowest taxonomic level possible and assemblages described related to the nature of the seafloor and the depth. We highlighted six invertebrate assemblages and three fish assemblages. For the invertebrates within flat soft sediments areas we defined three different assemblages based on primarily depth: a broad mid-depth (98–315 m) assemblage dominated by red octopus, sea pens and pink shrimps; a narrower mid-depth (250–270 m) assemblage dominated by box crabs and various other invertebrates; and a deeper (310–600 m) assemblage dominated by sea urchins, sea anemones, various snails and zoroasterid sea stars. The invertebrates on mixed sediments also were divided into three different assemblages: a shallow (~100 m deep) assemblage dominated by plumose sea anemones, broad mid-depth (170–370 m) assemblage dominated by sea cucumbers and various other invertebrates; and, again, a narrower mid-depth (230–270 m) assemblage, dominated by crinoids and encrusting invertebrates. For the fish, we identified a rockfish assemblage on coarse mixed sediments at 170–370 m and another fish assemblage on smaller mixed sediments within that depth range (250–370 m) dominated by thornyheads, poachers and flatfishes; and we identified a wide depth-range (98–600 m) fish assemblage on flat soft sediments dominated by flatfishes, eelpouts and thornyheads. Three of these assemblages (the two

  12. Benthic assemblages of mega epifauna on the Oregon continental margin

    Science.gov (United States)

    Hemery, Lenaïg G.; Henkel, Sarah K.; Cochrane, Guy R.

    2018-05-01

    Environmental assessment studies are usually required by a country's administration before issuing permits for any industrial activities. One of the goals of such environmental assessment studies is to highlight species assemblages and habitat composition that could make the targeted area unique. A section of the Oregon continental slope that had not been previously explored was targeted for the deployment of floating wind turbines. We carried out an underwater video survey, using a towed camera sled, to describe its benthic assemblages. Organisms were identified to the lowest taxonomic level possible and assemblages described related to the nature of the seafloor and the depth. We highlighted six invertebrate assemblages and three fish assemblages. For the invertebrates within flat soft sediments areas we defined three different assemblages based on primarily depth: a broad mid-depth (98-315 m) assemblage dominated by red octopus, sea pens and pink shrimps; a narrower mid-depth (250-270 m) assemblage dominated by box crabs and various other invertebrates; and a deeper (310-600 m) assemblage dominated by sea urchins, sea anemones, various snails and zoroasterid sea stars. The invertebrates on mixed sediments also were divided into three different assemblages: a shallow ( 100 m deep) assemblage dominated by plumose sea anemones, broad mid-depth (170-370 m) assemblage dominated by sea cucumbers and various other invertebrates; and, again, a narrower mid-depth (230-270 m) assemblage, dominated by crinoids and encrusting invertebrates. For the fish, we identified a rockfish assemblage on coarse mixed sediments at 170-370 m and another fish assemblage on smaller mixed sediments within that depth range (250-370 m) dominated by thornyheads, poachers and flatfishes; and we identified a wide depth-range (98-600 m) fish assemblage on flat soft sediments dominated by flatfishes, eelpouts and thornyheads. Three of these assemblages (the two broad fish assemblages and the deep

  13. Evaluation of a commercial Bacillus thuringiensis var. israelensis formulation for the control of chironomid midge larvae (Diptera: Chironomidae) in establishing rice crops in south-eastern Australia.

    Science.gov (United States)

    Stevens, Mark M; Hughes, Peter A; Mo, Jianhua

    2013-01-01

    A commercial formulation of Bacillus thuringiensis var. israelensis (B.t.i.) was evaluated for its potential to control chironomid midge larvae in newly sown rice crops in south-eastern Australia. Two replicated small-plot field trials were conducted using product application rates of 0.5-6 kg/ha. In trial 1 application rates between 2 and 6 kg product/ha all significantly (Plarvae to species level from selected samples indicated that populations of Chironomus tepperi, the principal pest species that attacks the roots of rice seedlings, were reduced at all application rates; elimination of C. tepperi was achieved in trial 1 at an application rate of 2 kg/ha. Consistent with other studies, non-target Tanypodinae were not adversely affected by B.t.i., and in some treatments populations of Tanypodinae exceeded control levels by up to 73%. In the first trial, which was conducted under relatively high pest pressure, plant establishment was significantly (Plarvae in establishing rice crops where members of the Chironominae, the group most susceptible to B.t.i., are the principal species of concern. The high specificity of B.t.i. for nematoceran Diptera should lead to reduced impacts on non-target organisms. Copyright © 2012 Elsevier Inc. All rights reserved.

  14. Fish assemblages in relation to environmental gradients along a ...

    African Journals Online (AJOL)

    Downstream assemblages were distinguished by the presence of marine and brackish water fish species and a relatively low abundance of cichlid fishes. Assemblages from Lake Faé were characterised by a predominance of cichlids. Keywords: fish assemblages; environmental gradients; San Pedro River; Ivory Coast

  15. Influence of Seasonality and Bathymetry on Assemblage Structure of ...

    African Journals Online (AJOL)

    Influence of Seasonality and Bathymetry on Assemblage Structure of Decapod Crustaceans in the Malindi-Ungwana Bay, Kenya. ... Simple Correspondence Analyses segregated the population into SEM assemblages dominated by the Penaeidae and a mixed group NEM assemblage. Canonical Correspondence Analysis ...

  16. Excess density compensation of island herpetofaunal assemblages

    Science.gov (United States)

    Rodda, G.H.; Dean-Bradley, K.

    2002-01-01

    Aim Some species reach extraordinary densities on islands. Island assemblages have fewer species, however, and it is possible that island species differ from their mainland counterparts in average mass. Island assemblages could be partitioned differently (fewer species or smaller individuals) from mainland sites without differing in aggregate biomass (density compensation). Our objective was to determine the generality of excess density compensation in island herpetofaunal assemblages.Location Our bounded removal plot data were obtained from Pacific Island sites (Guam, Saipan and Rota), the West Indies (British Virgin Islands), and the Indian Ocean (Ile aux Aigrettes off Mauritius). The literature values were taken from several locales. Other island locations included Barro Colorado Island, Bonaire, Borneo, Philippine Islands, Seychelle Islands, Barrow Island (Australia), North Brother Island (New Zealand), Dominica and Puerto Rico. Mainland sites included Costa Rica, Ivory Coast, Cameroon, Australia, Thailand, Peru, Brazil, Panama and the USA.Method We added our thirty-nine bounded total removal plots from sixteen island habitats to fifteen literature records to obtain seventy-five venues with estimable density and biomass of arboreal or terrestrial herpetofaunal assemblages. These biomass estimates were evaluated geographically and in relation to sampling method, insularity, latitude, disturbance regime, seasonality, community richness, vegetative structure and climate. Direct data on trophic interactions (food availability, parasitism and predation pressure) were generally unavailable. Sampling problems were frequent for arboreal, cryptic and evasive species.Results and main conclusions We found strong evidence that herpetofaunal assemblages on small islands (mostly lizards) exhibit a much greater aggregate density of biomass (kg ha−1) than those of larger islands or mainland assemblages (small islands show excess density compensation). High aggregate biomass

  17. The endemic Patagonian vespertilionid assemblage is a depauperate ecomorphological vicariant of species-rich neotropical assemblages

    Science.gov (United States)

    Giannini, Norberto P.

    2017-01-01

    Abstract Vespertilionidae is the most diverse chiropteran family, and its diversity is concentrated in warm regions of the World; however, due to physiological and behavioral adaptations, these bats also dominate bat faunas in temperate regions. Here we performed a comparative study of vespertilionid assemblages from two broad regions of the New World, the cold and harsh Patagonia, versus the remaining temperate-to-subtropical, extra-Patagonian eco-regions of the South American Southern Cone. We took an ecomorphological approach and analyzed the craniodental morphological structure of these assemblages within a phylogenetic framework. We measured 17 craniodental linear variables from 447 specimens of 22 currently recognized vespertilionid species of the study regions. We performed a multivariate analysis to define the morphofunctional space, and calculated the pattern and degree of species packing for each assemblage. We assessed the importance of phylogeny and biogeography, and their impact on depauperate (Patagonian) versus rich (extra-Patagonian) vespertilionid assemblages as determinants of morphospace structuring. We implemented a sensitivity analysis associated to small samples of rare species. The morphological patterns were determined chiefly by the evolutionary history of the family. The Patagonian assemblage can be described as a structurally similar but comparatively depauperate ecomorphological version of those assemblages from neighboring extra-Patagonian eco-regions. The Patagonian assemblage seems to have formed by successively adding populations from Northern regions that eventually speciated in the region, leaving corresponding sisters (vicariants) in extra-Patagonian eco-regions that continued to be characteristically richer. Despite being structurally akin, degree of species packing in Patagonia was comparatively very low, which may reflect the effect of limited dispersal success into a harsh region for bat survival. PMID:29492009

  18. Influence of algal farming on fish assemblages

    Energy Technology Data Exchange (ETDEWEB)

    Bergman, Kajsa C.; Svensson, Sara; Oehman, Marcus C. [Stockholm Univ., Dept. of Zoology, Stockholm (Sweden)

    2001-07-01

    We examined the influence of algal farming on fish assemblages in two shallow coastal lagoons in Zanzibar, Tanzania. Fish assemblages were visually investigated using a belt transect method and the line-intercept technique was used to examine the substrate composition. 101 species of fish belonging to 31 families were recorded. Algal farming affected the associated fish fauna in terms of abundance, species richness, trophic identity and fish community composition. However, the impact differed between the lagoons. Algal farms in one lagoon hosted a more abundant and diversified fish fauna than controls, whereas farms in the other lagoon exhibited lower fish densities and similar species diversity compared to controls. The discrepancies between lagoons may be an effect of differences in farming intensity and character of the substratum. (Author)

  19. Consumer–brand assemblages in advertising

    DEFF Research Database (Denmark)

    Bjerrisgaard, Sofie Møller; Kjeldgaard, Dannie; Bengtson, Anders

    2013-01-01

    This paper discusses how the use of tattoos in advertising renders diverse brand–consumer assemblages visible. In considering advertising practitioners as professionals of entanglement, the paper emphasizes the embeddedness of practitioners’ use of tattoo symbolism in institutionalized marketing...... systems and in the cultural history of tattooing. In accordance with recent emphasis on the importance of material devices for understanding contemporary sociality, this paper presents a semiotic analysis of a convenience sample of advertisements depicting tattoos. Tattoos are productive for the study...... of brand–consumer assemblages because they are situated on the human skin, which is a mediator between the individual and the socio-material world. Furthermore, tattoos reproduce discourses of both mainstream fashion and deviant subcultural identification, which imbue tattoo symbolism with communicative...

  20. Intraguild predation in raptor assemblages: A review

    OpenAIRE

    Sergio, Fabrizio; Hiraldo, F.

    2008-01-01

    Intraguild predation, the killing of species that use similar resources, has been largely overlooked in raptor investigations. To help fill this gap in knowledge, we conducted a literature review, focusing on studies that tested the behavioural and demographic impact of intraguild predation on individuals, populations, and assemblages of diurnal and nocturnal raptorial species. Overall, data were available for 39 empirical and experimental studies on 63 populations belonging to 11 killer spec...

  1. Assemblaged by desire: Potterheads’ productive consumption

    Directory of Open Access Journals (Sweden)

    André Luiz Maranhão de Souza Leão

    2018-02-01

    Full Text Available The Harry Potter saga became one of the cultural products with a major impact on the twenty-first century. Its fans, called potterheads, relate in a social space known as fandom. Their practices are based on the appropriation of the cultural text in a productive consumption process within a context of participatory culture. Assuming desire from the perspective of Deleuzian assemblage theory, which presents this concept as a flow of productive energy that is articulated through a collective force, this study aimed to understand how potterheads’ productive consumption is assemblaged by desire. We therefore explored multifocal data concerning practices of potterheads available on digital platforms using Foucauldian Discourse Analysis. Our results revealed that potterheads’ desire assemblage maintains their bond with the canonical universe of the saga, as a way of maintaining identity and security in the transition to adult life, through relationships in the fandom and in pursuit of broader social legitimacy. The study contributes theoretically by adopting the Deleuzian notion of desire as a lens to understand the collective action of consumers in cultural contexts of practice.

  2. Fish assemblages of Mediterranean marine caves.

    Science.gov (United States)

    Bussotti, Simona; Di Franco, Antonio; Francour, Patrice; Guidetti, Paolo

    2015-01-01

    Fish assemblages associated with 14 marine caves and adjacent external rocky reefs were investigated at four Marine Protected Areas (MPAs) along the coasts of Italy. Within the caves sampling was carried out in different sub-habitats: walls, ceilings, bottoms and ends of caves. On the whole, 38 species were recorded inside the 14 caves investigated. Eighteen species were exclusively found inside the caves: they were mainly represented by speleophilic (i.e. species preferentially or exclusively inhabiting caves) gobids (e.g. Didogobius splechtnai) and nocturnal species (e.g. Conger conger). Forty-one species were censused outside, 20 of which were shared with cave habitats. Apogon imberbis was the most common fish found in all 14 caves investigated, followed by Thorogobius ephippiatus (recorded in 13 caves), and Diplodus vulgaris and Scorpaena notata (both censused in 12 caves). Distinct fish assemblages were found between external rocky reefs and the different cave sub-habitats. New data on the distribution of some speleophilic gobids were collected, showing the existence of a pool of species shared by marine caves on a large scale (i.e. hundreds of km). Considering the uniqueness of cave fishes (18 exclusive species and different assemblage structures), the inclusion of marine caves among the habitats routinely investigated for fish biodiversity monitoring could facilitate the achievement of more comprehensive inventories. Due to their contribution to local species diversity and the shelter they provide to species valuable for conservation, marine caves should be prioritized for their inclusion not only within future MPAs through the Mediterranean Sea, but also into larger management spatial planning.

  3. Do landscape factors affect brownfield carabid assemblages?

    International Nuclear Information System (INIS)

    Small, Emma; Sadler, Jon P.; Telfer, Mark

    2006-01-01

    The carabid fauna of 28 derelict sites in the West Midlands (England) were sampled over the course of one growing season (April-October, 1999). The study aimed to investigate the relationship between carabid assemblages and five measures of landscape structure pertinent to derelict habitat. At each site measurements of landscape features pertinent to derelict habitat were made: (i) the proximity of habitat corridors; (ii) the density of surrounding derelict land; (iii) the distance between the site and the rural fringe; and (iv) the size of the site. Concurrent surveys of the soil characteristics, vegetation type, and land use history were conducted. The data were analysed using a combination of ordination (DCA, RDA), variance partitioning (using pRDA) and binary linear regression. The results suggest that:1.There is very little evidence that the carabid assemblages of derelict sites were affected by landscape structure, with assemblages instead being principally related to within-site habitat variables, such as site age (since last disturbance), substrate type and vegetation community. 2.No evidence was found to support the hypothesis that sites away from railway corridors are more impoverished in their carabid fauna than sites on corridors. 3.There are some suggestions from this study that rarer and non-flying specialist species may be affected by isolation, taking longer to reach sites. We infer from this that older sites with retarded succession, and sites in higher densities of surrounding derelict land may eventually become more species rich and that these sites may be important for maintaining populations of rarer and flightless species. 4.Conservation efforts to maintain populations of these species should focus principally on habitat quality issues, such as maintaining early successional habitats that have a diversity of seed producing annuals and perennial plants and enhancing substrate variability rather than landscape issues

  4. Sothi-Siswal Ceramic Assemblage: A Reappraisal

    Directory of Open Access Journals (Sweden)

    Tejas Garge

    2010-12-01

    Full Text Available Harappan evidences in Chautan valley has a unique ceramic tradition. In the light of recent plethora of knowledge as well as against the background of the studies conducted by A. Ghosh, J.S. Nigam, Katy Frenchman, Suraj Bhan & Madhu Bala, we will have to not only reclassify the Sothi-Siswal ceramic assemblage but also alter basic nomenclatures and concepts involve in it. It will give us deep insight in to the process of evolution of Early Harappan cultures vis-à-vis the dynamic of regional cultural complexes.

  5. Moral assemblages of volunteer tourism development in Cusco, Peru

    OpenAIRE

    Burrai, E; Mostafanezhad, M; Hannam, K

    2016-01-01

    In this paper, we develop a conceptual approach from which to examine the moral landscape of volunteer tourism development in Cusco, Peru. Drawing from recent work on assemblage theory in geography and tourism studies, we explore how assemblage thinking can facilitate new understandings of volunteer tourism development. Using assemblage as an analytical framework allows us to understand volunteer tourism as a series of relational, processual, unequal and mobile practices. These practices, we ...

  6. Holocene molluscan assemblages in the Magellan region

    Directory of Open Access Journals (Sweden)

    Sandra Gordillo

    1999-12-01

    Full Text Available In the Magellan region, much of the shoreline of the Beagle Channel coast (54°53´S; 67° - 68°W is bordered by Holocene raised beaches, which contain a large number of molluscs and other shelled taxa. The purpose of this work is to document the presence of various molluscan assemblages deposited with little or no postmortem transportation. An epifaunal Chlamys patagonica palaeocommunity (ca. 8,000 - 7,000 BP and three infaunal (Tawera gayi, Ameghinomya antiqua - Hiatella solida and Ameghinomya antiqua - Ensis macha palaeocommunities (ca. 4,400 - 4,000 BP were recognized. All the assemblages studied represent shallow, subtidal, cold-temperate environments. Based on comparisons with modern benthic communities in this region, these associations show that no remarkable ecologic and climatic changes occurred during the period ca. 8,000 - 4,000 BP. Thus, an apparent stability of modern marine communities over a period of several thousand years is suggested.

  7. Leaf litter as a possible food source for chironomids (Diptera in Brazilian and Portuguese headwater streams Detritos foliares como possível fonte de alimento para Chironomidae (Diptera em riachos de cabeceira brasileiros e portugueses

    Directory of Open Access Journals (Sweden)

    Marcos Callisto

    2007-06-01

    Full Text Available Our objective was to evaluate the potential use of leaf detritus by chironomid larvae. Field and laboratory experiments were performed using leaves and chironomid species collected in Portugal and Brazil. Laboratory experiments under controlled conditions were done using microbial conditioned senescent leaves of Alnus glutinosa (L. Gaertn, Neriumoleander L., Protium heptaphilum (Aubl. March, Protium brasiliense (Spreng Engl., Myrcia guyanensis(Aubl. DC and Miconia chartacea Triana. Laboratory experiments were performed using specimens collected from leaf litter in local streams. Whenever possible, after the experiments, chironomids were allowed to emerge as adults and identified. In Portugal the following taxa were identified: Micropsectra apposita (Walker, 1856, Polypedilum albicorne (Meigen, 1838,Eukiefferiella claripennis Lundbeck (1898, Rheocricotopus (Psilocricotopus atripes Rempel (1937 and Ablabesmyia Johannsen (1905 (Diptera, Chironomidae. Consumption rates ranged from 0.15 ± 0.10 mg (AFDM of leaf animal-1 day-1 (Micropsectra apposita feeding on Alnus glutinosa up to 0.85 ± 0.33 mg (AFDM of leaf animal-1 day-1 (Polypedilum albicorne feeding on Miconia chartacea. In Brazil, the following taxa were identified from leaves: Phaenopsectra sp., Chironomus spp. and Polypedilum sp. and maximum consumption rates reached 0.47 ± 0.28 (AFDM of leaf mg.animal-1.day-1 (Chironomus Meigen (1803 feeding on Protium heptaphilum. Feeding experiments with laboratory cultured specimens, revealed that some chironomids were unable to feed on decomposing leaves (e.g., C. xanthus Rempel (1939 on P.brasiliensis and M.guyanensis. Our results suggest that some stream chironomids (not typical shredders can use leaf litter of riparian vegetation as a complementary food source.O objetivo foi avaliar o potencial uso de detritos foliares por larvas de Chironomidae. Foram realizados experimentos em campo e em laboratório utilizando folhas e larvas de Chironomidae

  8. Here Comes the Sun ... and I Say, "It' an Assemblage"

    Science.gov (United States)

    Skophammer, Karen

    2011-01-01

    In this article, the author discusses how she combines science lesson with a hands-on art project. She used the wonderfully creative suns shown on the Sunday edition of "The CBS Morning Show" to give the students fodder for thought. She describes how to create an assemblage. An assemblage is like a collage, but it moves past the two-dimensional…

  9. Phylogenetic and functional diversity in large carnivore assemblages.

    Science.gov (United States)

    Dalerum, F

    2013-06-07

    Large terrestrial carnivores are important ecological components and prominent flagship species, but are often extinction prone owing to a combination of biological traits and high levels of human persecution. This study combines phylogenetic and functional diversity evaluations of global and continental large carnivore assemblages to provide a framework for conservation prioritization both between and within assemblages. Species-rich assemblages of large carnivores simultaneously had high phylogenetic and functional diversity, but species contributions to phylogenetic and functional diversity components were not positively correlated. The results further provide ecological justification for the largest carnivore species as a focus for conservation action, and suggests that range contraction is a likely cause of diminishing carnivore ecosystem function. This study highlights that preserving species-rich carnivore assemblages will capture both high phylogenetic and functional diversity, but that prioritizing species within assemblages will involve trade-offs between optimizing contemporary ecosystem function versus the evolutionary potential for future ecosystem performance.

  10. No correlation between the diversity and productivity of assemblages: evidence from the phytophage and predator assemblages in various cotton agroecosystems.

    Science.gov (United States)

    Gao, Feng; Men, XingYuan; Ge, Feng

    2014-09-01

    Biodiversity research has shown that primary productivity increases with plant species number, especially in many experimental grassland systems. Here, we assessed the correlation between productivity and diversity of phytophages and natural enemy assemblages associated with planting date and intercropping in four cotton agroecosystems. Twenty-one pairs of data were used to determine Pearson correlations between species richness, total number of individuals, diversity indices and productivity for each assemblage every five days from 5 June to 15 September 2012. At the same trophic level, the productivity exhibited a significant positive correlation with species richness of the phytophage or predator assemblage. A significant correlation was found between productivity and total number of individuals in most cotton fields. However, no significant correlations were observed between productivity and diversity indices (including indices of energy flow diversity and numerical diversity) in most cotton fields for either the phytophage or the predator assemblages. Species richness of phytophage assemblage and total individual numbers were significantly correlated with primary productivity. Also, species richness of natural enemy assemblage and total number of individuals correlated with phytophage assemblage productivity. A negative but not significant correlation occurred between the indices of numerical diversity and energy flow diversity and lower trophic-level productivity in the cotton-phytophage and phytophage-predator assemblages for most intercropped cotton agroecosystems. Our results clearly showed that there were no correlations between diversity indices and productivity within the same or lower trophic levels within the phytophage and predator assemblages in cotton agroecosystems, and inter-cropped cotton fields had a stronger ability to support the natural enemy assemblage and potentially to reduce phytophages.

  11. Partitioning taxonomic diversity of aquatic insect assemblages ...

    Science.gov (United States)

    Biological diversity can be divided into: alpha (α, local), beta (β, difference in assemblage composition among locals), and gamma (γ, total diversity). We assessed the partitioning of taxonomic diversity of Ephemeroptera, Plecoptera and Trichoptera (EPT) and of functional feeding groups (FFG) in Neotropical Savanna (southeastern Brazilian Cerrado) streams. To do so, we considered three diversity components: stream site (α), among stream sites (β1), and among hydrologic units (β2). We also evaluated the association of EPT genera composition with heterogeneity in land use, instream physical habitat structure, and instream water quality variables. The percent of EPT taxonomic α diversity (20.7%) was lower than the β1 and β2 diversities (53.1% and 26.2%, respectively). The EPT FFG α diversity (26.5%) was lower than the β1 diversity (55.8%) and higher than the β2 (17.7%) diversity. The collector-gatherer FFG was predominant and had the greatest β diversity among stream sites (β1, 55.8%). Our findings support the need for implementing regional scale conservation strategies in the Cerrado biome, which has been degraded by anthropogenic activities. Using adaptations of the US EPA’s National Aquatic Resource Survey (NARS) designs and methods, Ferreira and colleagues examined the distribution of taxonomic and functional diversity of aquatic insects among basins, stream sites within basins, and within stream sample reaches. They sampled 160 low-order stre

  12. Climate mediates the effects of disturbance on ant assemblage structure

    Czech Academy of Sciences Publication Activity Database

    Gibb, H.; Sanders, N. J.; Dunn, R. R.; Watson, S.; Photakis, M.; Abril, S.; Andersen, A. N.; Angulo, E.; Armbrecht, I.; Arnan, X.; Baccaro, F. B.; Bishop, T. R.; Boulay, R.; Castracani, C.; Del Toro, I.; Delsinne, T.; Diaz, M.; Donoso, D. A.; Enríquez, M. L.; Fayle, Tom Maurice; Feener Jr., D. H.; Fitzpatrik, M. C.; Gómez, C.; Grasso, D. A.; Groc, S.; Heterick, B.; Hoffmann, B. D.; Lach, L.; Lattke, J.; Leponce, M.; Lessard, J.-P.; Longino, J.; Lucky, A.; Majer, J.; Menke, S. B.; Mezger, D.; Mori, A.; Munyai, T. C.; Paknia, O.; Pearce-Duvet, J.; Pfeiffer, M.; Philpott, S. M.; de Souza, J. L. P.; Tista, M.; Vasconcelos, H. L.; Vonshak, M.; Parr, C. L.

    2015-01-01

    Roč. 282, č. 1808 (2015), article number 20150418 ISSN 0962-8452 Institutional support: RVO:60077344 Keywords : assemblage structure * dominance * global warming Subject RIV: EH - Ecology, Behaviour Impact factor: 4.823, year: 2015

  13. Global assemblages and structural models of International Relations

    DEFF Research Database (Denmark)

    Corry, Olaf

    2014-01-01

    Rather than consigning assemblages to the micro-politics of international relations, the chapter argues that assemblages can also be seen to play a role in the ‘grand’ structures of international relations. Structural IR theory normally only considers how subjects are ordered – hierarchically......, anarchically, in core-periphery relations or in terms of networks. However, not only subjects but also assemblages – the bringing together of previously unconnected elements into novel constellations – play a critical role in structuring international relations. More specifically, one sub......-category of assemblages – those constructed as malleable and governable which I call ‘governance-objects’ – is central to structure in international relations. The chapter begins with standard definitions of what structures are – patterns of interaction between elements – and briefly covers the range of models currently...

  14. Habitat characteristics affecting fish assemblages on a Hawaiian coral reef

    Science.gov (United States)

    Friedlander, A.M.; Parrish, J.D.

    1998-01-01

    Habitat characteristics of a reef were examined as potential influences on fish assemblage structure, using underwater visual census to estimate numbers and biomass of all fishes visible on 42 benthic transects and making quantitative measurements of 13 variables of the corresponding physical habitat and sessile biota. Fish assemblages in the diverse set of benthic habitats were grouped by detrended correspondence analysis, and associated with six major habitat types. Statistical differences were shown between a number of these habitat types for various ensemble variables of the fish assemblages. Overall, both for complete assemblages and for component major trophic and mobility guilds, these variables tended to have higher values where reef substratum was more structurally or topographically complex, and closer to reef edges. When study sites were separately divided into five depth strata, the deeper strata tended to have statistically higher values of ensemble variables for the fish assemblages. Patterns with depth varied among the various trophic and mobility guilds. Multiple linear regression models indicated that for the complete assemblages and for most trophic and mobility guilds, a large part of the variability for most ensemble variables was explained by measures of holes in the substratum, with important contributions from measured substratum rugosity and depth. A strong linear relationship found by regression of mean fish length on mean volume of holes in the reef surface emphasized the importance of shelter for fish assemblages. Results of this study may have practical applications in designing reserve areas as well as theoretical value in helping to explain the organization of reef fish assemblages.

  15. Habitat influence in the morphological diversity of coastal fish assemblages

    Science.gov (United States)

    Farré, Marc; Lombarte, Antoni; Recasens, Laura; Maynou, Francesc; Tuset, Victor M.

    2015-05-01

    Ecological diversity based on quantitative data is widely used to characterize biological communities, but recently morphological and functional traits have also been used to analyse the structure of fish assemblages. This diversity and structure is usually linked to variables such as habitat complexity and composition, depth, and spatial and temporal variations. In this study, several fish assemblages off the Catalan coast (NW Mediterranean) were ecologically and morphologically analysed and compared. The morphological analysis was performed from body shape of fish species using geometric morphology. Moreover, a canonical correspondence analysis (CCA) was used to analyse the effect of local environmental variables such as habitat, locality and depth on the composition and abundance of assemblages. The results revealed greater differences among assemblages in the clustering performed from morphological data, which is linked to habitat complexity, than those shown by the ecological analysis. Moreover, the CCA analysis indicated that type of substratum and the location significantly influenced the composition and structure of the fish assemblages. These results evidenced that morphology provides different and complementary information than ecological analysis because it allows to predict the ecological and functional habits of species within the community, helping to improve the understanding of the fish assemblages structure.

  16. Shelf gradients of echinoid assemblages from the Miocene of Sardinia

    Science.gov (United States)

    Nebelsick, James; Andrea, Mancosu

    2017-04-01

    Well exposed Miocene echinoid assemblages from Sardinia representing various environmental settings including both siliciclastics and carbonates have been studied with respect to reconstructing palaeoenvironmental conditions along a shelf gradient. The basis of this study includes 1) detailed logging of sedimentary facies in the field, 2) interpreting their behavior and life habits of the preserved echinoids by applying functional morphological reconstructions of the echinoid skeletons and comparing them to related Recent echinoid taxa, 3) quantifying taphonomic features of test preservation including predation, abrasion, fragmentation, encrustation and bioerosion, and finally 4) analyzing accompanying fauna and flora as well as trace fossils. The assemblages included clypeasteroid dominated assemblages in shallow water settings where often mass accumulations of sand dollars are present. Spatangoid dominated assemblages are found in more offshore settings where diversity is determined by varying burrowing depths, feeding strategies and resource partitioning accompanied by varying rates of bioturbation and episodes of sediment deposition by storms. Mixed assemblages also occur ranging from shallow to deeper water with varying substrates including sea grass, as well as coarser and finer sediments. Finally, deeper water monotypic assemblages are present in storm-dominated siliciclastic shelf environments including both regular and irregular echinoids. In general, echinoid presence is determined by the ecological preferences of the taxa involved, their propensities for gregarious behavior, the differential preservation potentials of the varied skeletal architectures present as well as sedimentary environment in which they occur.

  17. Factors influencing riverine fish assemblages in Massachusetts

    Science.gov (United States)

    Armstrong, David S.; Richards, Todd A.; Levin, Sara B.

    2011-01-01

    The U.S. Geological Survey, in cooperation with the Massachusetts Department of Conservation and Recreation, Massachusetts Department of Environmental Protection, and the Massachusetts Department of Fish and Game, conducted an investigation of fish assemblages in small- to medium-sized Massachusetts streams. The objective of this study was to determine relations between fish-assemblage characteristics and anthropogenic factors, including impervious cover and estimated flow alteration, relative to the effects of environmental factors, including physical-basin characteristics and land use. The results of this investigation supersede those of a preliminary analysis published in 2010. Fish data were obtained for 669 fish-sampling sites from the Massachusetts Division of Fisheries and Wildlife fish-community database. A review of the literature was used to select fish metrics - species richness, abundance of individual species, and abundances of species grouped on life history traits - responsive to flow alteration. The contributing areas to the fish-sampling sites were delineated and used with a geographic information system to determine a set of environmental and anthropogenic factors that were tested for use as explanatory variables in regression models. Reported and estimated withdrawals and return flows were used together with simulated unaltered streamflows to estimate altered streamflows and indicators of flow alteration for each fish-sampling site. Altered streamflows and indicators of flow alteration were calculated on the basis of methods developed in a previous U.S. Geological Survey study in which unaltered daily streamflows were simulated for a 44-year period (water years 1961-2004), and streamflow alterations were estimated by use of water-withdrawal and wastewater-return data previously reported to the State for the 2000-04 period and estimated domestic-well withdrawals and septic-system discharges. A variable selection process, conducted using principal

  18. The Miocene carnivore assemblage of Greece

    Directory of Open Access Journals (Sweden)

    Koufos, G. D.

    2011-12-01

    Full Text Available The Miocene carnivore assemblage of Greece includes a great number of taxa, described in numerous articles since the first decades of the 19th Century. The present article is a revision of all these taxa, providing information about their history, localities, age, as well as their stratigraphic distribution and palaeoenvironment. The Early/Middle Miocene carnivore record of Greece is poor as the available fossiliferous sites and material are rare. However, the Late Miocene one is quite rich, including numerous taxa. The Miocene localities with carnivores and their age are given in a stratigraphic table covering the European Mammal zones from MN 4 to MN 13. The type locality, holotype, and some historical and morphological remarks are given for each taxon. Several carnivore taxa were erected from Greek material and new photos of their holotypes are given. The stratigraphic distribution of the Greek carnivore taxa indicates that they are covering the time span from ~19.0-5.3Ma. The majority of the Miocene taxa (Adcrocuta, Hyaenictitherium, Plioviverrops, Protictitherium, Ictitherium, Indarctos, Dinocrocuta, Promephitis disappeared at the end of Miocene. The composition of the Early/Middle Miocene carnivore assemblage of Greece includes mainly viverrids (Lophocyon, Euboictis, while the hyaenids, percrocutids, felids and mustelids are very few. On the contrary the Late Miocene assemblage is richer, including more subfamilies and species; the hyaenids and mustelids dominate, while the viverrids are absent. The Late Miocene carnivore guild structure is similar to that of the modern Serengeti, indicating a relatively open, savannah-like environment.

    La asociación de carnívoros miocenos de Grecia incluye un gran número de taxones, descritos en numerosos artículos desde las primeras décadas del siglo XIX. El presente artículo supone un esfuerzo de síntesis de todos estos taxones, suministrando información sobre su

  19. Native bare zone assemblage nucleates myosin filament assembly.

    Science.gov (United States)

    Niederman, R; Peters, L K

    1982-11-15

    Native myosin filaments from rabbit psoas muscle are always 1.5 micrometer long. The regulated assembly of these filaments is generally considered to occur by an initial antiparallel and subsequent parallel aggregation of identical myosin subunits. In this schema myosin filament length is controlled by either a self-assembly or a Vernier process. We present evidence which refines these ideas. Namely, that the intact myosin bare zone assemblage nucleates myosin filament assembly. This suggestion is based on the following experimental evidence. (1) A native bare zone assemblage about 0.3 micrometer long can be formed by dialysis of native myosin filaments to either a pH 8 or a 0.2 M-KCl solution. (2) Upon dialysis back to 0.1 M-KCl, bare zone assemblages and distal myosin molecules recombine to form 1.5 micrometer long bipolar filaments. (3) The bare zone assemblage can be separated from the distal myosin molecules by column chromatography in 0.2 M-KCl. Upon dialysis of the fractionated subsets back to 0.1 M-KCl, the bare zone assemblage retains its length of about 0.3 micrometer. However, the distal molecules reassemble to form filaments about 5 micrometers long. (4) Filaments are formed from mixes of the isolated subsets. The lengths of these filaments vary with the amount of distal myosin present. (5) When native filaments, isolated bare zone assemblages or distal myosin molecules are moved sequentially to 0.6 M-KCl and then to 0.1 M-KCl, the final filament lengths are all about 5 micrometers. The capacity of the bare zone assemblage to nucleate filament assembly may be due to the bare zone myosin molecules, the associated M band components or both.

  20. Public sphere as assemblage: the cultural politics of roadside memorialization.

    Science.gov (United States)

    Campbell, Elaine

    2013-09-01

    This paper investigates contemporary academic accounts of the public sphere. In particular, it takes stock of post-Habermasian public sphere scholarship, and acknowledges a lively and variegated debate concerning the multiple ways in which individuals engage in contemporary political affairs. A critical eye is cast over a range of key insights which have come to establish the parameters of what 'counts' as a/the public sphere, who can be involved, and where and how communicative networks are established. This opens up the conceptual space for re-imagining a/the public sphere as an assemblage. Making use of recent developments in Deleuzian-inspired assemblage theory - most especially drawn from DeLanda's (2006) 'new philosophy of society' - the paper sets out an alternative perspective on the notion of the public sphere, and regards it as a space of connectivity brought into being through a contingent and heterogeneous assemblage of discursive, visual and performative practices. This is mapped out with reference to the cultural politics of roadside memorialization. However, a/the public sphere as an assemblage is not simply a 'social construction' brought into being through a logic of connectivity, but is an emergent and ephemeral space which reflexively nurtures and assembles the cultural politics (and political cultures) of which it is an integral part. The discussion concludes, then, with a consideration of the contribution of assemblage theory to public sphere studies. (Also see Campbell 2009a). © London School of Economics and Political Science 2013.

  1. Riparian influences on stream fish assemblage structure in urbanizing streams

    Science.gov (United States)

    Roy, A.H.; Freeman, B.J.; Freeman, Mary C.

    2007-01-01

    We assessed the influence of land cover at multiple spatial extents on fish assemblage integrity, and the degree to which riparian forests can mitigate the negative effects of catchment urbanization on stream fish assemblages. Riparian cover (urban, forest, and agriculture) was determined within 30 m buffers at longitudinal distances of 200 m, 1 km, and the entire network upstream of 59 non-nested fish sampling locations. Catchment and riparian land cover within the upstream network were highly correlated, so we were unable to distinguish between those variables. Most fish assemblage variables were related to % forest and % urban land cover, with the strongest relations at the largest spatial extent of land cover (catchment), followed by riparian land cover in the 1-km and 200-m reach, respectively. For fish variables related to urban land cover in the catchment, we asked whether the influence of riparian land cover on fish assemblages was dependent on the amount of urban development in the catchment. Several fish assemblage metrics (endemic richness, endemic:cosmopolitan abundance, insectivorous cyprinid richness and abundance, and fluvial specialist richness) were all best predicted by single variable models with % urban land cover. However, endemic:cosmopolitan richness, cosmopolitan abundance, and lentic tolerant abundance were related to % forest cover in the 1-km stream reach, but only in streams that had <15% catchment urban land cover. In these cases, catchment urbanization overwhelmed the potential mitigating effects of riparian forests on stream fishes. Together, these results suggest that catchment land cover is an important driver of fish assemblages in urbanizing catchments, and riparian forests are important but not sufficient for protecting stream ecosystems from the impacts of high levels of urbanization.

  2. Mass coral bleaching causes biotic homogenization of reef fish assemblages.

    Science.gov (United States)

    Richardson, Laura E; Graham, Nicholas A J; Pratchett, Morgan S; Eurich, Jacob G; Hoey, Andrew S

    2018-04-06

    Global climate change is altering community composition across many ecosystems due to nonrandom species turnover, typically characterized by the loss of specialist species and increasing similarity of biological communities across spatial scales. As anthropogenic disturbances continue to alter species composition globally, there is a growing need to identify how species responses influence the establishment of distinct assemblages, such that management actions may be appropriately assigned. Here, we use trait-based analyses to compare temporal changes in five complementary indices of reef fish assemblage structure among six taxonomically distinct coral reef habitats exposed to a system-wide thermal stress event. Our results revealed increased taxonomic and functional similarity of previously distinct reef fish assemblages following mass coral bleaching, with changes characterized by subtle, but significant, shifts toward predominance of small-bodied, algal-farming habitat generalists. Furthermore, while the taxonomic or functional richness of fish assemblages did not change across all habitats, an increase in functional originality indicated an overall loss of functional redundancy. We also found that prebleaching coral composition better predicted changes in fish assemblage structure than the magnitude of coral loss. These results emphasize how measures of alpha diversity can mask important changes in the structure and functioning of ecosystems as assemblages reorganize. Our findings also highlight the role of coral species composition in structuring communities and influencing the diversity of responses of reef fishes to disturbance. As new coral species configurations emerge, their desirability will hinge upon the composition of associated species and their capacity to maintain key ecological processes in spite of ongoing disturbances. © 2018 John Wiley & Sons Ltd.

  3. Environmental characteristics drive variation in Amazonian understorey bird assemblages.

    Directory of Open Access Journals (Sweden)

    Juliana Menger

    Full Text Available Tropical bird assemblages display patterns of high alpha and beta diversity and, as tropical birds exhibit strong habitat specificity, their spatial distributions are generally assumed to be driven primarily by environmental heterogeneity and interspecific interactions. However, spatial distributions of some Amazonian forest birds are also often restricted by large rivers and other large-scale topographic features, suggesting that dispersal limitation may also play a role in driving species' turnover. In this study, we evaluated the effects of environmental characteristics, topographic and spatial variables on variation in local assemblage structure and diversity of birds in an old-growth forest in central Amazonia. Birds were mist-netted in 72 plots distributed systematically across a 10,000 ha reserve in each of three years. Alpha diversity remained stable through time, but species composition changed. Spatial variation in bird-assemblage structure was significantly related to environmental and topographic variables but not strongly related to spatial variables. At a broad scale, we found bird assemblages to be significantly distinct between two watersheds that are divided by a central ridgeline. We did not detect an effect of the ridgeline per se in driving these patterns, indicating that most birds are able to fly across it, and that differences in assemblage structure between watersheds may be due to unmeasured environmental variables or unique combinations of measured variables. Our study indicates that complex geography and landscape features can act together with environmental variables to drive changes in the diversity and composition of tropical bird assemblages at local scales, but highlights that we still know very little about what makes different parts of tropical forest suitable for different species.

  4. Habitat specialization in tropical continental shelf demersal fish assemblages.

    Directory of Open Access Journals (Sweden)

    Ben M Fitzpatrick

    Full Text Available The implications of shallow water impacts such as fishing and climate change on fish assemblages are generally considered in isolation from the distribution and abundance of these fish assemblages in adjacent deeper waters. We investigate the abundance and length of demersal fish assemblages across a section of tropical continental shelf at Ningaloo Reef, Western Australia, to identify fish and fish habitat relationships across steep gradients in depth and in different benthic habitat types. The assemblage composition of demersal fish were assessed from baited remote underwater stereo-video samples (n = 304 collected from 16 depth and habitat combinations. Samples were collected across a depth range poorly represented in the literature from the fringing reef lagoon (1-10 m depth, down the fore reef slope to the reef base (10-30 m depth then across the adjacent continental shelf (30-110 m depth. Multivariate analyses showed that there were distinctive fish assemblages and different sized fish were associated with each habitat/depth category. Species richness, MaxN and diversity declined with depth, while average length and trophic level increased. The assemblage structure, diversity, size and trophic structure of demersal fishes changes from shallow inshore habitats to deeper water habitats. More habitat specialists (unique species per habitat/depth category were associated with the reef slope and reef base than other habitats, but offshore sponge-dominated habitats and inshore coral-dominated reef also supported unique species. This suggests that marine protected areas in shallow coral-dominated reef habitats may not adequately protect those species whose depth distribution extends beyond shallow habitats, or other significant elements of demersal fish biodiversity. The ontogenetic habitat partitioning which is characteristic of many species, suggests that to maintain entire species life histories it is necessary to protect corridors of

  5. Phytoplankton Assemblage Patterns in the Southern Mid-Atlantic Bight

    Science.gov (United States)

    Makinen, Carla; Moisan, Tiffany A. (Editor)

    2012-01-01

    As part of the Wallops Coastal Oceans Observing Laboratory (Wa-COOL) Project, we sampled a time-series transect in the southern Mid-Atlantic Bight (MAB) biweekly. Our 2-year time-series data included physical parameters, nutrient concentrations, and chlorophyll a concentrations. A detailed phytoplankton assemblage structure was examined in the second year. During the 2-year study, chlorophyll a concentration (and ocean color satellite imagery) indicated that phytoplankton blooms occurred in January/February during mixing conditions and in early autumn under stratified conditions. The chlorophyll a concentrations ranged from 0.25 microgram 1(exp -1) to 15.49 microgram 1(exp -1) during the 2-year period. We were able to discriminate approximately 116 different species under phase contrast microscopy. Dominant phytoplankton included Skeletonema costatum, Rhizosolenia spp., and Pseudo-nitzschia pungens. In an attempt to determine phytoplankton species competition/succession within the assemblage, we calculated a Shannon Weaver diversity index for our diatom microscopy data. Diatom diversity was greatest during the winter and minimal during the spring. Diatom diversity was also greater at nearshore stations than at offshore stations. Individual genera appeared patchy, with surface and subsurface patches appearing abruptly and persisting for only 1-2 months at a time. The distribution of individual species differed significantly from bulk variables of the assemblage (chlorophyll a ) and total phytoplankton assemblage (cells), which indicates that phytoplankton species may be limited in growth in ways that differ from those of the total assemblage. Our study demonstrated a highly diverse phytoplankton assemblage throughout the year, with opportunistic species dominating during spring and fall in response to seasonal changes in temperature and nutrients in the southern MAB.

  6. Patterns in reef fish assemblages: Insights from the Chagos Archipelago.

    Science.gov (United States)

    Samoilys, Melita; Roche, Ronan; Koldewey, Heather; Turner, John

    2018-01-01

    Understanding the drivers of variability in the composition of fish assemblages across the Indo-Pacific region is crucial to support coral reef ecosystem resilience. Whilst numerous relationships and feedback mechanisms between the functional roles of coral reef fishes and reef benthic composition have been investigated, certain key groups, such as the herbivores, are widely suggested to maintain reefs in a coral-dominated state. Examining links between fishes and reef benthos is complicated by the interactions between natural processes, disturbance events and anthropogenic impacts, particularly fishing pressure. This study examined fish assemblages and associated benthic variables across five atolls within the Chagos Archipelago, where fishing pressure is largely absent, to better understand these relationships. We found high variability in fish assemblages among atolls and sites across the archipelago, especially for key groups such as a suite of grazer-detritivore surgeonfish, and the parrotfishes which varied in density over 40-fold between sites. Differences in fish assemblages were significantly associated with variable levels of both live and recently dead coral cover and rugosity. We suggest these results reflect differing coral recovery trajectories following coral bleaching events and a strong influence of 'bottom-up' control mechanisms on fish assemblages. Species level analyses revealed that Scarus niger, Acanthurus nigrofuscus and Chlorurus strongylocephalos were key species driving differences in fish assemblage structure. Clarifying the trophic roles of herbivorous and detritivorous reef fishes will require species-level studies, which also examine feeding behaviour, to fully understand their contribution in maintaining reef resilience to climate change and fishing impacts.

  7. A classic Late Frasnian chondrichthyan assemblage from southern Belgium

    Science.gov (United States)

    Ginter, Michał; Gouwy, Sofie; Goolaerts, Stijn

    2017-09-01

    Samples from the Upper Frasnian (Devonian) of Lompret Quarry and Nismes railway section in Dinant Synclinorium, southern Belgium, yielded several chondrichthyan teeth and scales. The teeth belong to three genera: Phoebodus, Cladodoides and Protacrodus. The comparison with selected Late Frasnian chondrichthyan assemblages from the seas between Laurussia and Gondwana revealed substantial local differences of taxonomic composition due to palaeoenvironmental conditions, such as depth, distance to submarine platforms, oxygenation of water, and possibly also temperature. The assemblage from Belgium, with its high frequency of phoebodonts, is the most similar to that from the Ryauzyak section, South Urals, Russia, and the Horse Spring section, Canning Basin, Australia.

  8. Modelling of acid-base titration curves of mineral assemblages

    Directory of Open Access Journals (Sweden)

    Stamberg Karel

    2016-01-01

    Full Text Available The modelling of acid-base titration curves of mineral assemblages was studied with respect to basic parameters of their surface sites to be obtained. The known modelling approaches, component additivity (CA and generalized composite (GC, and three types of different assemblages (fucoidic sandstones, sedimentary rock-clay and bentonite-magnetite samples were used. In contrary to GC-approach, application of which was without difficulties, the problem of CA-one consisted in the credibility and accessibility of the parameters characterizing the individual mineralogical components.

  9. Demersal Assemblages on the Soft Bottoms off the Catalan-Levante Coast of the Spanish Mediterranean

    Directory of Open Access Journals (Sweden)

    Mariano García-Rodríguez

    2011-01-01

    Full Text Available The analysis of 255 bottom trawl samples obtained in annual experimental surveys (2007–2010 along the western Mediterranean shows the existence of five well-defined demersal assemblages that follow a depth distribution: (a upper shelf assemblages, including two assemblages differentiated by the type of substrate (sand-muddy and terrigenous muddy bottoms; (b a middle shelf assemblage; (c an upper slope assemblage; (d a middle slope assemblage. Faunally, they are dominated by fish (37% of 452 total species, followed by crustaceans (22%, molluscs (17%, echinoderms (9%, and other invertebrates (15%. The assemblages identified showed major alterations on the shelf and shelf edge and less pronounced ones on the upper and middle slope. The average diversity values were more or less high, evidencing the high species richness in the western Mediterranean. The identified assemblages may facilitate future multispecies fisheries management based on an ecosystem approach.

  10. The role of depth in regulating water quality and fish assemblages in oxbow lakes

    Science.gov (United States)

    Goetz, Daniel B.; Miranda, Leandro E.; Kroger, Robert; Andrews, Caroline S.

    2015-01-01

    We evaluated water quality and fish assemblages in deep (> 3.0 m; N = 7) and shallow (facilitate development of effective management plans for improving conditions necessary to sustain diverse fish assemblages in agriculturally dominated basins.

  11. Assessing the Mess: Challenges to Assemblage Theory and Teacher Education

    Science.gov (United States)

    Beighton, Chris

    2013-01-01

    This article examines the Deleuzian concept of "assemblage" in educational research in the context of Teacher Education (TE) for the "continuing education" or "Lifelong Learning" sector. Drawing on Deleuze's creative approach to analysis, it draws a portrait of practice which identifies problems and successes in…

  12. Paleoenvironmental significance of clay mineral assemblages in the ...

    Indian Academy of Sciences (India)

    A gravity core SK-221 recovered from the southeastern Arabian Sea near Laccadive–Chagos Ridge was examined to identify the sources of detrital clay minerals and to decipher paleoenvironmental changes for the last 30 kyr. The clay mineral assemblages predominantly consist of illite, kaolinite and chlorite with small ...

  13. Relationships between structural complexity, coral traits, and reef fish assemblages

    Science.gov (United States)

    Darling, Emily S.; Graham, Nicholas A. J.; Januchowski-Hartley, Fraser A.; Nash, Kirsty L.; Pratchett, Morgan S.; Wilson, Shaun K.

    2017-06-01

    With the ongoing loss of coral cover and the associated flattening of reef architecture, understanding the links between coral habitat and reef fishes is of critical importance. Here, we investigate whether considering coral traits and functional diversity provides new insights into the relationship between structural complexity and reef fish communities, and whether coral traits and community composition can predict structural complexity. Across 157 sites in Seychelles, Maldives, the Chagos Archipelago, and Australia's Great Barrier Reef, we find that structural complexity and reef zone are the strongest and most consistent predictors of reef fish abundance, biomass, species richness, and trophic structure. However, coral traits, diversity, and life histories provided additional predictive power for models of reef fish assemblages, and were key drivers of structural complexity. Our findings highlight that reef complexity relies on living corals—with different traits and life histories—continuing to build carbonate skeletons, and that these nuanced relationships between coral assemblages and habitat complexity can affect the structure of reef fish assemblages. Seascape-level estimates of structural complexity are rapid and cost effective with important implications for the structure and function of fish assemblages, and should be incorporated into monitoring programs.

  14. Reef fish and coral assemblages at Maptaput, Rayong Province

    Directory of Open Access Journals (Sweden)

    Voravit Cheevaporn

    2007-06-01

    Full Text Available This study describes the structure of coral and fish assemblages of a group of small islands and pinnacles in the vicinity of Maptaput deep sea port, Rayong Province, Thailand during 2002. The coral and fish assemblages at Saket Island and nearby pinnacle, Hin-Yai, which are located less than 1 km from the deep sea port, had changed. Living coral cover in 2002 was 8% at Hin-Yai and 4% at Saket Island which decreased from 33% and 64%, respectively in the previous report in 1992. Numbers of coral species at Saket Island decreased from 41 species to 13 species. Acropora spp. that previously dominated the area had nearly disappeared. For fishes, a total of 40 species were found in 2002 the numbers decreased to only 6 species at Saket Island and 36 species at Hin-Yai. Fishes that dominated the area are small pomacentrids. After 1997, the conditions of coral and fish assemblages at Saket Island and Hin-Yai had markedly changed, whereas, the conditions found in the nearby area are much better. Sediment load from port construction was the primary cause of the degradation. This should indicate the adverse effect of sedimentation on coral and reef fish assemblages at Maptaput. Coral communities developed on rock pinnacles west of Maptaput deep-sea port are reported and described herein for the first time.

  15. Comparison of Avifaunal Assemblage and their Association with ...

    African Journals Online (AJOL)

    Comparison of Avifaunal Assemblage and their Association with Plant Cover in Protected and Unprotected Montane Grassland Ecosystems in Bale Mountains ... This, in turn, might be due to differences in the level of human-induced factors in the sites, which is higher in unprotected area and of habitat structural diversity ...

  16. Learning in the "Platform Society": Disassembling an Educational Data Assemblage

    Science.gov (United States)

    Williamson, Ben

    2017-01-01

    Schools are increasingly involved in diverse forms of student data collection. This article provides a sociotechnical survey of a data assemblage used in education. ClassDojo is a commercial platform for tracking students' behaviour data in classrooms and a social media network for connecting teachers, students, and parents. The hybridization of…

  17. Microfloral assemblage, age and paleoenvironment of the Upper ...

    African Journals Online (AJOL)

    Microfloral assemblage, age and paleoenvironment of the Upper Cretaceous Patti Formation, southeastern Bida Basin, Nigeria. OJ Ojo, SO Akande. Abstract. No Abstract. Journal of Mining and Geology Vol. 44 (1) 2008: pp. 71-82. Full Text: EMAIL FULL TEXT EMAIL FULL TEXT · DOWNLOAD FULL TEXT DOWNLOAD ...

  18. Seasonality in fish assemblage structure in an East African ...

    African Journals Online (AJOL)

    Correspondence analysis indicated that seasonal fish assemblages were only distinct at the mouth of the creek with less clear seasonal structure in the upper region of the creek. Keywords: conservation, habitat functions, seasons, species abundance. African Journal of Marine Science 2013, 35(2): 163–173 ...

  19. Elk herbivory alters small mammal assemblages in high elevation drainages

    Science.gov (United States)

    Parsons, Elliott W.R.; Maron, John L.; Martin, Thomas E.

    2012-01-01

    Heavy herbivory by ungulates can substantially alter habitat, but the indirect consequences of habitat modification for animal assemblages that rely on that habitat are not well studied. This is a particularly important topic given that climate change can alter plant–herbivore interactions.

  20. Sewage pollution impact on Mediterranean rocky-reef fish assemblages.

    Science.gov (United States)

    Azzurro, Ernesto; Matiddi, Marco; Fanelli, Emanuela; Guidetti, Paolo; La Mesa, Gabriele; Scarpato, Alfonso; Axiak, Victor

    2010-06-01

    The effects of sewage outfalls on subtidal fish assemblages were studied along the NW coasts of Malta (Sicily channel, Mediterranean Sea) by means of underwater visual census. The presence of two spatially distinct outfalls discharging untreated wastewaters allowed to use a balanced symmetrical after control/impact (ACI) design that consisted of two putatively impacted locations and two controls, with four sites nested in each location. Surveys were performed in 2006 at two random dates. The study highlighted significant changes at both assemblage and individual species levels. Fish assemblages structures were different between controls and sewages, where total abundance of fish were higher. The responses of individual species to sewage pollution were mostly related to an anomalous increase of two small opportunistic species i.e. Gobius bucchichii and Parablennius rouxi and to a decrease of species of the genus Symphodus, particularly S. roissali and S. ocellatus. Moreover in correspondence of the outfalls, significant changes of the fish size distribution were detected for several species. These results support the use of fish assemblages as biological indicators for marine coastal waters and demonstrated the possibility to obtain sharp signals of environmental impact from some individual fish species.

  1. Climate mediates the effects of disturbance on ant assemblage structure

    Science.gov (United States)

    Gibb, Heloise; Sanders, Nathan J.; Dunn, Robert R.; Watson, Simon; Photakis, Manoli; Abril, Silvia; Andersen, Alan N.; Angulo, Elena; Armbrecht, Inge; Arnan, Xavier; Baccaro, Fabricio B.; Bishop, Tom R.; Boulay, Raphael; Castracani, Cristina; Del Toro, Israel; Delsinne, Thibaut; Diaz, Mireia; Donoso, David A.; Enríquez, Martha L.; Fayle, Tom M.; Feener, Donald H.; Fitzpatrick, Matthew C.; Gómez, Crisanto; Grasso, Donato A.; Groc, Sarah; Heterick, Brian; Hoffmann, Benjamin D.; Lach, Lori; Lattke, John; Leponce, Maurice; Lessard, Jean-Philippe; Longino, John; Lucky, Andrea; Majer, Jonathan; Menke, Sean B.; Mezger, Dirk; Mori, Alessandra; Munyai, Thinandavha C.; Paknia, Omid; Pearce-Duvet, Jessica; Pfeiffer, Martin; Philpott, Stacy M.; de Souza, Jorge L. P.; Tista, Melanie; Vasconcelos, Heraldo L.; Vonshak, Merav; Parr, Catherine L.

    2015-01-01

    Many studies have focused on the impacts of climate change on biological assemblages, yet little is known about how climate interacts with other major anthropogenic influences on biodiversity, such as habitat disturbance. Using a unique global database of 1128 local ant assemblages, we examined whether climate mediates the effects of habitat disturbance on assemblage structure at a global scale. Species richness and evenness were associated positively with temperature, and negatively with disturbance. However, the interaction among temperature, precipitation and disturbance shaped species richness and evenness. The effect was manifested through a failure of species richness to increase substantially with temperature in transformed habitats at low precipitation. At low precipitation levels, evenness increased with temperature in undisturbed sites, peaked at medium temperatures in disturbed sites and remained low in transformed sites. In warmer climates with lower rainfall, the effects of increasing disturbance on species richness and evenness were akin to decreases in temperature of up to 9°C. Anthropogenic disturbance and ongoing climate change may interact in complicated ways to shape the structure of assemblages, with hot, arid environments likely to be at greatest risk. PMID:25994675

  2. Assemblage of strike-slip faults and tectonic extension and ...

    Indian Academy of Sciences (India)

    12

    Assemblage of strike-slip faults and tectonic. 1 extension and compression analysis: A case. 2 study of a Lower Permian commercial coal. 3 reservoir in China. 4. 5. Shuai Yina,*, Dawei Lvb, Zhonghu Wu c .... high-quality reservoirs, and tectonic action is a leading factor for oil and gas. 70 enrichment. Therefore, it is of great ...

  3. The ichthyoplankton assemblage of the Algoa Bay nearshore region ...

    African Journals Online (AJOL)

    The ichthyoplankton assemblage of the Algoa Bay nearshore region in relation to coastal zone utilization by juvenile fish. ... The various taxa occurring in the ichthyoplankton are discussed in terms of distribution of adults and juveniles, breeding biology and available information on early life history. The paucity of larvae of ...

  4. Changes in faunal assemblages over time represented in rock art ...

    Indian Academy of Sciences (India)

    Changes in faunal assemblages over time represented in rock art, can be distinguished by relative dating techniques. For example in Sahara Tassili region earliest paintings portray wild animals not found in the region today. Later art features domestic cattle reflecting the arrival of pastoralists in the area around 6000 B.P. ...

  5. Cinema Experiences at School: Assemblages as Encounters with Subjectivities

    Science.gov (United States)

    Infante, Marta

    2018-01-01

    The aim of this article is to analyse how 15 students at a public elementary school detach from immobile representations of identity through aesthetic self-expressive work with cinema. Drawing on Deleuze and Guattari's concept of assemblage, I interrogate students' experiences of discrimination and challenge their processes of developing a short…

  6. Changes in density and composition of algal assemblages in certain ...

    African Journals Online (AJOL)

    The water purification plants at Virginia and Bothaville, South Africa, experience problems with cyanobacteria and other algae. Their algal assemblages were studied during 2010 and 2011 to determine the dominant species that may pose problems in purification. Cyanobacteria, diatoms and green algae were the dominant ...

  7. The health of benthic diatom assemblages in lower stretch

    Indian Academy of Sciences (India)

    This study examines the ecological state of epilithic diatom assemblages along the lower stretch of Mandakini, a glacier-fed Himalayan river. The diatoms were sampled at four stations during winter and summer, only once in each season. Valve counts were obtained from Naphrax mounts prepared from each sample.

  8. Temporal variability in epifaunal assemblages associated with temperate gorgonian gardens

    KAUST Repository

    Dias, I.M.

    2015-10-19

    The present study is one of the few that investigate the temporal variability of epifaunal assemblages associated with coral species, particularly the octocorals Eunicella gazella and Leptogorgia lusitanica in south Portugal. The results suggest time rather than colony size as a primary driver of the ecological patterns of these assemblages, which were dominated by amphipods, molluscs and polychaetes. Temporal variability was linked to changes in environmental parameters, namely temperature, chlorophyll a and particulate organic carbon. Hence, temporal variability must be taken into account for the design of future biodiversity assessment studies, as different patterns may be observed depending on the sampling time. Associated epifaunal assemblages were consistently dominated by resident species (i.e. species present in all sampling periods) and a peak of rare species was observed in the transition from spring to summer following the increase of seawater temperature. Turnover was particularly high in the transition between the spring and summer periods. In both hosts, turnover was higher in the small sized colonies, which generally harboured less diverse and less abundant assemblages which also differed from those inhabiting larger size colonies. The high levels of diversity associated with gorgonian colonies highlights the need for the conservation of this priority habitat.

  9. Response of phytoplankton assemblages isolated for short periods ...

    African Journals Online (AJOL)

    The response of phytoplankton assemblages isolated in enclosures for short periods of time was examined in hyper-eutrophic Lake Chivero (Harare, Zimbabwe), to determine the factors that influenced the structure of the phytoplankton community, after noticing a marked decline in the dominance of Microcystis aeruginosa ...

  10. Shikarpur lithic assemblage: New questions regarding Rohri chert blade production

    Directory of Open Access Journals (Sweden)

    Charusmita Gadekar

    2014-03-01

    Full Text Available Recent excavations at Shikarpur, a fortified Harappan site situated near the Gulf of Kuchchh in Gujarat, Western India, brought to light a large collection of Rohri chert blades.  Chert found in the Rohri hill near Sukkur in Sindh, central Pakistan is distinctive and easily identifiable. The wide distribution of standardized Rohri chert blades is often regarded as a testimony to the Harappan efficiency in long distance trade and craft production.  The possibility of localized production of Rohri chert blades in Gujarat is often negated due to the constraints of raw-material availability.  The absence of Rohri chert working debitage from most of the sites in Gujarat, has lent support to this position. The Shikarpur Rohri blade assemblage however incorporates more than 650 blades, a large fluted blade-core and a few Rohri chert debitage.  These have led the excavators to suggest that some of the blades found at Shikarpur were locally produced from raw materials brought to the site from the Rohri hills.  Typo-technological features of the Rohri chert assemblage from Shikarpur have been analysed in this background. These along with metrical features of the assemblage are compared with Rohri chert assemblages from other major Harappan sites in the region to check the validity of the proposed ‘limited local production’.

  11. Improving the energy efficiency of mine fan assemblages

    International Nuclear Information System (INIS)

    De Souza, Euler

    2015-01-01

    Energy associated with ventilating an underground operation comprises a significant portion of a mine operation's base energy demand and is consequently responsible for a large percentage of the total operating costs. Ventilation systems may account from 25 to 40% of the total energy costs and 40–50% of the energy consumption of a mine operation. Fans are the most important mechanical devices used to ventilate underground mines and the total fan power installed in a single mine operation can easily exceed 10,000 kW. Investigations of a number of mine main fan installations have determined their assemblage to be, in general, very energy inefficient. The author has found that 40–80% of the energy consumed by a main fan is used to overcome the resistance of fan assemblage components. This paper presents how engineering design principles can be applied to improve the performance and efficiency of fan installations, resulting in substantial reductions in power consumption, operating cost and greenhouse gas emissions. A detailed case study is presented to demonstrate that, by designing fan assemblages using proper engineering concepts of fluid physics and industrial ventilation design, main fan systems will operate at efficiencies well above 80–90% (compared to common operating efficiencies of between 20 and 65%), resulting in a drastic reduction in a mine's overall costs and base electrical and energy loads. - Highlights: • Increases in fan assemblage efficiencies with minimum capital investment. • Improved designs for substantial fan power and operating cost savings. • General solutions and tactics for improving existing main fan installations. • Case study presented to demonstrate proper design of fan assemblages.

  12. Nematode assemblages in the rhizosphere of spring barley (Hordeum vulgare L.) depended on fertilisation and plant growth phase

    DEFF Research Database (Denmark)

    Madsen, Mette Vestergård

    2004-01-01

    rhizosphere; nitrogen and phosphorus fertilisation; nematode assemblages; plant parasites; barley......rhizosphere; nitrogen and phosphorus fertilisation; nematode assemblages; plant parasites; barley...

  13. Faunistic assemblages of a sublittoral coarse sand habitat of the northwestern Mediterranean

    Directory of Open Access Journals (Sweden)

    Eva Pubill

    2011-02-01

    Full Text Available The sublittoral megabenthic assemblages of a northwestern Mediterranean coarse sandy beach exploited for the bivalve Callista chione were studied. The spatial and bathymetric variability of its distinctive faunal assemblages was characterised by quantitative sampling performed with a clam dredge. The taxa studied were Mollusca Bivalvia and Gastropoda, Crustacea Decapoda, Echinodermata and Pisces, which accounted for over 99% of the total biomass. Three well-differentiated species assemblages were identified: (1 assemblage MSS (Medium Sand Shallow in medium sand (D50=0.37 mm and shallow waters (mean depth =6.5 m, (2 assemblage CSS (Coarse Sand Shallow in coarse sand (D50=0.62 mm in shallow waters (mean depth =6.7 m, and (3 assemblage CSD (Coarse Sand Deep in coarse sand (D50=0.64 mm in deeper waters (mean depth =16.2 m. Assemblage MSS was characterised by the codominance of the bivalves Mactra stultorum and Acanthocardia tuberculata. C. chione was dominant in both density and biomass in assemblages CSS and CSD. The occurrence of the crab Thia scutellata also characterised assemblage CSS, whereas the occurrence of the sea urchin Echinocardium mediterraneum characterised assemblage CSD. A depth breaking point of around 10 m determined the discontinuity between assemblages CSS and CSD, which was related to the closure depth of the beaches in the study area. Species richness was highest in the coarse sand communities; however, Shannon-Wiener diversity and Pielou equitability indexes were higher in the shallow fine sand community.

  14. Conceptualizing Autoethnography as Assemblage: Accounts of Occupational Therapy Practice

    Directory of Open Access Journals (Sweden)

    Sally Denshire PhD

    2013-02-01

    Full Text Available Drawing on theoretical work within ethnography and poststructuralism, this article discusses a conceptualization of autoethnography as assemblage. The concept of assemblage includes but goes beyond the literal bringing together of a range of heterogeneous elements in different modalities to offer different perspectives on a phenomenon. It challenges and displaces boundaries between the individual and the social through a focus on practice, which offers a new ontology of the social. These ideas are illustrated through excerpts from an autoethnographic study of an occupational therapist working with young people in a Sydney children's hospital in the mid-1980s. The article makes visible a material, relational, and affective landscape of remembered practice. Through successive displacements of the self as the primary site of experience and meaning, we seek to contribute new understandings about the potential for autoethnography to engage with professional practice as a space of multiplicity.

  15. Assemblage time series reveal biodiversity change but not systematic loss.

    Science.gov (United States)

    Dornelas, Maria; Gotelli, Nicholas J; McGill, Brian; Shimadzu, Hideyasu; Moyes, Faye; Sievers, Caya; Magurran, Anne E

    2014-04-18

    The extent to which biodiversity change in local assemblages contributes to global biodiversity loss is poorly understood. We analyzed 100 time series from biomes across Earth to ask how diversity within assemblages is changing through time. We quantified patterns of temporal α diversity, measured as change in local diversity, and temporal β diversity, measured as change in community composition. Contrary to our expectations, we did not detect systematic loss of α diversity. However, community composition changed systematically through time, in excess of predictions from null models. Heterogeneous rates of environmental change, species range shifts associated with climate change, and biotic homogenization may explain the different patterns of temporal α and β diversity. Monitoring and understanding change in species composition should be a conservation priority.

  16. A new Lower Triassic ichthyopterygian assemblage from Fossil Hill, Nevada

    Directory of Open Access Journals (Sweden)

    Neil P. Kelley

    2016-01-01

    Full Text Available We report a new ichthyopterygian assemblage from Lower Triassic horizons of the Prida Formation at Fossil Hill in central Nevada. Although fragmentary, the specimens collected so far document a diverse fauna. One partial jaw exhibits isodont dentition with blunt tipped, mesiodistally compressed crowns and striated enamel. These features are shared with the Early Triassic genus Utatsusaurus known from coeval deposits in Japan and British Columbia. An additional specimen exhibits a different dentition characterized by relatively small, rounded posterior teeth resembling other Early Triassic ichthyopterygians, particularly Grippia. This Nevada assemblage marks a southward latitudinal extension for Early Triassic ichthyopterygians along the eastern margin of Panthalassa and indicates repeated trans-hemispheric dispersal events in Early Triassic ichthyopterygians.

  17. Movers and stayers: Novel assemblages in changing environments

    Science.gov (United States)

    Hobbs, Richard L.; Valentine, Leonie E.; Standish, Rachel J.; Jackson, Stephen T.

    2018-01-01

    How species will respond to ongoing climate and other change is of increasing concern.Most attention is given to how species move or are moved, but many species stay.Understanding the dynamics of new species combinations is essential for successful conservation in a changing climate.Increased attention to species movement in response to environmental change highlights the need to consider changes in species distributions and altered biological assemblages. Such changes are well known from paleoecological studies, but have accelerated with ongoing pervasive human influence. In addition to species that move, some species will stay put, leading to an array of novel interactions. Species show a variety of responses that can allow movement or persistence. Conservation and restoration actions have traditionally focused on maintaining or returning species in particular places, but increasingly also include interventions that facilitate movement. Approaches are required that incorporate the fluidity of biotic assemblages into the goals set and interventions deployed.

  18. Characterizing lentic freshwater fish assemblages using multiple sampling methods

    Science.gov (United States)

    Fischer, Jesse R.; Quist, Michael C.

    2014-01-01

    Characterizing fish assemblages in lentic ecosystems is difficult, and multiple sampling methods are almost always necessary to gain reliable estimates of indices such as species richness. However, most research focused on lentic fish sampling methodology has targeted recreationally important species, and little to no information is available regarding the influence of multiple methods and timing (i.e., temporal variation) on characterizing entire fish assemblages. Therefore, six lakes and impoundments (48–1,557 ha surface area) were sampled seasonally with seven gear types to evaluate the combined influence of sampling methods and timing on the number of species and individuals sampled. Probabilities of detection for species indicated strong selectivities and seasonal trends that provide guidance on optimal seasons to use gears when targeting multiple species. The evaluation of species richness and number of individuals sampled using multiple gear combinations demonstrated that appreciable benefits over relatively few gears (e.g., to four) used in optimal seasons were not present. Specifically, over 90 % of the species encountered with all gear types and season combinations (N = 19) from six lakes and reservoirs were sampled with nighttime boat electrofishing in the fall and benthic trawling, modified-fyke, and mini-fyke netting during the summer. Our results indicated that the characterization of lentic fish assemblages was highly influenced by the selection of sampling gears and seasons, but did not appear to be influenced by waterbody type (i.e., natural lake, impoundment). The standardization of data collected with multiple methods and seasons to account for bias is imperative to monitoring of lentic ecosystems and will provide researchers with increased reliability in their interpretations and decisions made using information on lentic fish assemblages.

  19. Seasonal dynamics of fish assemblage in a pond canal

    Czech Academy of Sciences Publication Activity Database

    Musil, J.; Adámek, Zdeněk; Baranyi, Ch.

    2007-01-01

    Roč. 15, č. 3-4 (2007), s. 217-226 ISSN 0967-6120. [New Challenges in Pond Aquaculture . České Budějovice, 26.04.2005-28.04.2005] Institutional research plan: CEZ:AV0Z60930519 Keywords : fish assemblage * pond canal * species richness * seasonal dynamics * alien species Subject RIV: GL - Fishing Impact factor: 0.828, year: 2007

  20. Temporal variation in fish assemblage composition on a tidal flat

    Directory of Open Access Journals (Sweden)

    Henry L. Spach

    2004-03-01

    Full Text Available Annual variation in the fish assemblage characteristics on a tidal flat was studied in coastal Paraná, in southern Brazil. Fish were collected between August 1998 and July 1999, during the diurnal high tide and diurnal and nocturnal low tide of the syzygial (full moon and quadrature (waning moon tides, to characterize temporal change in assemblage composition. A total of 64,265 fish in 133 species were collected. The average number of species and individuals, biomass, species richness, diversity (mass and equitability varied significantly over time . The dissimilarity of the assemblage was greatest in August, September and October in contrast with the period from November to January, with the lowest dissimilarity. The combined action of water temperature, salinity and wind intensity had a great influence over the structure of the fish assemblage.Os peixes de uma planície de maré da praia Balneário de Pontal do Sul, Paraná, foram coletados, na preamar diurna e na baixa-mar diurna e noturna das marés de sizígia e de quadratura, visando caracterizar as mudanças temporais entre agosto de 1998 e julho de 1999. As coletas totalizaram 64.265 peixes de 133 espécies. Foram observadas diferenças significativas na captura média em número de espécies e de peixes, peso total e nos índices de riqueza, diversidade (H' peso e eqüitatividade entre os meses de coleta. A dissimilaridade da ictiofauna foi maior entre os meses de agosto, setembro e outubro em comparação com o período de novembro a janeiro. A ação combinada da temperatura da água, salinidade e intensidade do vento, influenciaram mais sobre a estrutura da assembléia de peixes.

  1. Responses of Salt Marsh Plant Rhizosphere Diazotroph Assemblages to Drought

    Directory of Open Access Journals (Sweden)

    Debra A. Davis

    2018-03-01

    Full Text Available Drought has many consequences in the tidally dominated Spartina sp. salt marshes of the southeastern US; including major dieback events, changes in sediment chemistry and obvious changes in the landscape. These coastal systems tend to be highly productive, yet many salt marshes are also nitrogen limited and depend on plant associated diazotrophs as their source of ‘new’ nitrogen. A 4-year study was conducted to investigate the structure and composition of the rhizosphere diazotroph assemblages associated with 5 distinct plant zones in one such salt marsh. A period of greatly restricted tidal inundation and precipitation, as well as two periods of drought (June–July 2004, and May 2007 occurred during the study. DGGE of nifH PCR amplicons from rhizosphere samples, Principal Components Analysis of the resulting banding patterns, and unconstrained ordination analysis of taxonomic data and environmental parameters were conducted. Diazotroph assemblages were organized into 5 distinct groups (R2 = 0.41, p value < 0.001 whose presence varied with the environmental conditions of the marsh. Diazotroph assemblage group detection differed during and after the drought event, indicating that persistent diazotrophs maintained populations that provided reduced supplies of new nitrogen for vegetation during the periods of drought.

  2. Phytoplankton Assemblages in Selected Freshwaters of New Jersey

    Science.gov (United States)

    Caraballo, Y. A.; Wu, M. S.

    2017-12-01

    Characterizing phytoplankton assemblages in freshwaters is crucial for future management and monitoring of drinking and recreational freshwaters of New Jersey. New Jersey freshwater phytoplankton assemblages are poorly known and there is no list of freshwater phytoplankton taxa in New Jersey. This study seeks to describe phytoplankton assemblages of freshwaters in New Jersey. Results will help address public health, economic and environmental threats related to harmful algal blooms in New Jersey. A total of 49 freshwater sites, including ponds, rivers and reservoirs, were used for this study. Overall results showed 66 taxa of freshwater phytoplankton in 6 major groups and 29 different orders. Green algae had the highest number of taxa, followed by diatoms and blue-greens (cyanobacteria). The most common freshwater taxa in NJ are Synedra spp., Fragilaria spp., Selenastrum capricornutum, Scenedesmus spp., and Anabaena spp. Cyanobacteria species are present in more than half of the sites examined in this study. All ten cyanobacteria taxa present in New Jersey freshwaters are capable of producing the endotoxin lipopolysaccharides (LPS), eight can produce the hepatotoxins and six can produce neutoroxins. In addition, some taxa such as Anabaena spp. are capable of simultaneously producing endotoxins, hepatotoxins, neurotoxins and taste and odor compounds. The presence of taxa capable of producing multiple toxins infers the difficulty of management and treatment as well as increased public health effects.

  3. Seagrass Parameter Affect the Fish Assemblages in Karimunjawa Archipelago

    Science.gov (United States)

    Sri Susilo, Endang; Nugroho Sugianto, Denny; Munasik; Nirwani; Adhi Suryono, Chrisna

    2018-02-01

    Seagrass beds promote high species diversity, abundance and biomass, and become important habitats for some economically important fishes. Plants of seagrasses result in structurally highly complex habitats and offering feeding grounds, shelter from predation as well as nursery areas for diverse fish assemblages. However, research on fish communities in Southeast Asian seagrass bed is rarely conducted. In the present study fish assemblages in seagrass beds with different parameters (cover, diversity and similarity indices, domination) was investigated in the Karimunjawa Islands, Indonesia. The purpose of this study were to assess whether fish assemblages differ concerning on the abundance and the species number. This study was conducted on the seagrass bed on Karimunjawa Islands in Java Sea, particularly in the water of Menjangan Besar and Menjangan Kecil Island. Line-quadrant transect was used to assess seagrass data, while the occurrence and individual number of fish harboured in the selected seagrass bed was counted by using underwater visual census in the stationary point count transects. Seagrass cover in Menjangan Kecil Island (41%) with various canopy included both upper and lower canopy was considerable higher than those in Menjangan Besar Island (5%). Fish diversity, species composition and abundance are considerably different between the two study sites. This study revealed that seagrass density or cover and canopy structure affected the fish abundance and species number harboured.

  4. Giardia Assemblages A and B in Diarrheic Patients: A Comparative Study in Egyptian Children and Adults.

    Science.gov (United States)

    El Basha, Noussa R; Zaki, Mayssa M; Hassanin, Omayma M; Rehan, Mohamed K; Omran, Dalia

    2016-02-01

    Giardia duodenalis is considered the most common intestinal parasite in humans worldwide. Children are especially affected, with more severe consequences than adults. The present study was designed to determine the distribution of assemblages A and B Giardia infection in children and adults, with the use of light microscopy and polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) as diagnostic procedures, and to investigate its associations with clinical and epidemiological data collected from children and adult groups. This cross-sectional study was conducted from October 2012 to October 2013 by collecting fecal samples from 200 children and 200 adults complaining of diarrhea. Samples were subjected to parasitological examination by direct wet smear and formol-ether methods. Genotyping of G. doudenalis samples was conducted by PCR-RFLP analysis. Giardia duodenalis infection caused by assemblages A and B was identified in 60 samples, 34 from children and 26 from adults. Assemblage B was detected in 38 patients (63.34%), and assemblage A was detected in 22 patients (36.66%). Assemblage A was significantly more frequent in children with age range 2-8 yr, and assemblage B was higher in children with age range 6-16 yr old. Diarrhea frequency/day and recurrences per month affected patients infected with assemblage A (P value Giardia assemblages A and B were identified in children and adults, assemblage A infected younger children more frequently and was more closely related to severe clinical manifestations than assemblage B.

  5. Isotopic characteristics of canopies in simulated leaf assemblages

    Science.gov (United States)

    Graham, Heather V.; Patzkowsky, Mark E.; Wing, Scott L.; Parker, Geoffrey G.; Fogel, Marilyn L.; Freeman, Katherine H.

    2014-11-01

    The geologic history of closed-canopy forests is of great interest to paleoecologists and paleoclimatologists alike. Closed canopies have pronounced effects on local, continental and global rainfall and temperature patterns. Although evidence for canopy closure is difficult to reconstruct from the fossil record, the characteristic isotope gradients of the ;canopy effect; could be preserved in leaves and proxy biomarkers. To assess this, we employed new carbon isotopic data for leaves collected in diverse light environments within a deciduous, temperate forest (Maryland, USA) and for leaves from a perennially closed canopy, moist tropical forest (Bosque Protector San Lorenzo, Panamá). In the tropical forest, leaf carbon isotope values range 10‰, with higher δ13Cleaf values occurring both in upper reaches of the canopy, and with higher light exposure and lower humidity. Leaf fractionation (Δleaf) varied negatively with height and light and positively with humidity. Vertical 13C enrichment in leaves largely reflects changes in Δleaf, and does not trend with δ13C of CO2 within the canopy. At the site in Maryland, leaves express a more modest δ13C range (∼6‰), with a clear trend that follows both light and leaf height. Using a model we simulate leaf assemblage isotope patterns from canopy data binned by elevation. The re-sampling (bootstrap) model determined both the mean and range of carbon isotope values for simulated leaf assemblages ranging in size from 10 to over 1000 leaves. For the tropical forest data, the canopy's isotope range is captured with 50 or more randomly sampled leaves. Thus, with a sufficient number of fossil leaves it is possible to distinguish isotopic gradients in an ancient closed canopy forest from those in an open forest. For very large leaf assemblages, mean isotopic values approximate the δ13C of carbon contributed by leaves to soil and are similar to observed δ13Clitter values at forested sites within Panamá, including the

  6. Mnemiopsis leidyi Gut Harbors Seasonally Variant and Commensal Microbial Assemblages

    Science.gov (United States)

    Mariita, R. M.; Hossain, M. J.; Liles, M. R.; Moss, A.

    2016-02-01

    Studies have shown that with widespread use of antibiotics in human and domestic animal populations, antibiotic resistance becomes increasingly common in the environment. Estuaries provide ideal conditions for acquisition and dissemination of drug resistance genes because they serve as sinks for pollution. This study aimed to identify M. leidyi microbial diversity and richness and their potential to act as vectors for antibiotic resistance determinants (ARDs). M. leidyi, although native to study area are highly invasive. Metagenomic analyses indicate that there are temporal variations of bacterioplankton assemblages in M. leidyi gut. Overall, Proteobacteria and Actinobacteria are the most abundant phyla. Despite the temporal dynamics in the microbial assemblages in M. leidyi gut, they seem to retain Propionibacterium acnes (gut microbiota in some insects) and select proteobacteria across all seasons. The results contradict previous studies that suggest that M. leidyi does not have constant a microbiota, but only seasonally variant microbial assemblages. Here we reveal the presence of M. leidyi gut ARDs in winter and summer, probably because of the ctenophores' positive geotaxis during rough surface conditions. Genes responsible for resistance to fluoroquinolones, multidrug resistance efflux pumps, mercuric reductase, copper homeostasis and blaR1 genes were observed. This is the first study to demonstrate that M. leidyi harbors constant microbiota and provides a baseline for understanding M. leidyi gut microbial and ARDs ecology. It also suggests that M. leidyi bacterial taxonomic and functional dynamics is influenced by season. Funding: Alabama EPSCoR GRSP fellowship, AU-CMB fellowship, NSF EPS-1158862, USDA-Hatch 370225-310100 (AGM, ML).

  7. Taming Distraction: The Second Screen Assemblage, Television and the Classroom

    Directory of Open Access Journals (Sweden)

    Markus Stauff

    2016-07-01

    Full Text Available This article argues that television’s resilience in the current media landscape can best be understood by analyzing its role in a broader quest to organize attention across different media. For quite a while, the mobile phone was considered to be a disturbance both for watching television and for classroom teaching. In recent years, however, strategies have been developed to turn the second screen’s distractive potential into a source for intensified, personalized and social attention. This has consequences for television’s position in a multimedia assemblage: television’s alleged specificities (e.g. liveness become mouldable features, which are selectively applied to guide the attention of users across different devices and platforms. Television does not end, but some of its traditional features do only persist because of its strategic complementarity with other media; others are re-adapted by new technologies thereby spreading televisual modes of attention across multiple screens. The article delineates the historical development of simultaneous media use as a ‘problematization’—from alternating (and competitive media use to multitasking and finally complementary use of different media. Additionally, it shows how similar strategies of managing attention are applied in the ‘digital classroom’. While deliberately avoiding to pin down, what television is, the analysis of the problem of attention allows for tracing how old and new media features are constantly reshuffled. This article combines three arguments: (1 the second screen is conceived of as both a danger to attention and a tool to manage attention. (2 To organize attention, the second screen assemblage modulates the specific qualities of television and all the other devices involved. (3 While being a fragile and often inconsistent assemblage, the second screen spreads its dynamics—and especially the problem of attention—far beyond television, e.g. into the realm of

  8. Revisiting Qumran Cave 1Q and its archaeological assemblage

    OpenAIRE

    Taylor, Joan E.; Mizzi, Dennis; Fidanzio, Marcello

    2017-01-01

    Qumran Cave 1Q was the first site of Dead Sea scroll discoveries. Found and partly emptied by local Bedouin, the cave was excavated officially in 1949 and published in the series Discoveries in the Judaean Desert (Volume 1) in 1955. Contents of the cave are found in collections worldwide, and in different institutions in Jerusalem and Amman. While the scrolls are the most highly prized artefacts from this cave, in archaeological terms they are part of an assemblage that needs to be understood...

  9. Elevated land runoff after European settlement perturbs persistent foraminiferal assemblages on the Great Barrier Reef.

    Science.gov (United States)

    Uthicke, S; Patel, F; Ditchburn, R

    2012-01-01

    Coral reefs are under pressure from a variety of human-induced disturbances, but demonstration of ecosystem changes and identification of stressors are often difficult. We tested whether global change or increased agricultural runoff after European settlement of Northeast Australia (ca. 1860) has affected inshore reefs of the Great Barrier Reef. Eleven sediment cores were retrieved from inner reefs, intermediate reefs, and outer-island reefs, and benthic foraminiferal assemblages were analyzed in dated (14C, 210Pb, 137Cs) core sections (N = 82 samples). Data were grouped into six age bands ( 1500 yr). Principal component analysis and two-factor (Zone and Age) permutational analysis of variance (PERMANOVA) suggested that assemblages from the three zones were significantly different from each other over several millennia, with symbiont-bearing (mixotrophic) species dominating the outer reefs. A significant interaction term indicated that within-zone patterns varied. Assemblages in outer reefs unaffected from increased land runoff were persistent until present times. In both other zones, assemblages were also persistent until 150 yr ago, suggesting that benthic foraminiferal assemblages are naturally highly persistent over long (> 2000 yr) timescales. Assemblages in core sections old from inner reefs were significantly (post hoc t test) different from those older than 150 yr. Similarly, assemblages old from intermediate reefs were significantly different compared to older assemblages. A multivariate regression tree (environmental variables: Zone and Age) explained 56.8% of the variance in foraminiferal assemblages and confirmed patterns identified by PERMANOVA. With some exceptions, changes on the inner and intermediate reefs were consistent with a model predicting that increased nutrients and higher turbidity enhance relative abundance of heterotrophic species. Given that assemblages did not change in outer-island reefs (not impacted by runoff) we argue that changes

  10. Temporal changes in taxonomic and functional diversity of fish assemblages downstream from mountaintop mining

    Science.gov (United States)

    Hitt, Nathaniel P.; Chambers, Douglas B.

    2014-01-01

    Mountaintop mining (MTM) affects chemical, physical, and hydrological properties of receiving streams, but the long-term consequences for fish-assemblage structure and function are poorly understood. We sampled stream fish assemblages using electrofishing techniques in MTM exposure sites and reference sites within the Guyandotte River basin, USA, during 2010–2011. We calculated indices of taxonomic diversity (species richness, abundance, Shannon diversity) and functional diversity (functional richness, functional evenness, functional divergence) to compare exposure and reference assemblages between seasons (spring and autumn) and across years (1999–2011). We based temporal comparisons on 2 sites that were sampled during 1999–2001 by Stauffer and Ferreri (2002). Exposure assemblages had lower taxonomic and functional diversity than reference assemblages or simulated assemblages that accounted for random variation. Differences in taxonomic composition between reference and exposure assemblages were associated with conductivity and aqueous Se concentrations. Exposure assemblages had fewer species, lower abundances, and less biomass than reference assemblages across years and seasons. Green Sunfish (Lepomis cyanellus) and Creek Chub (Semotilus atromaculatus) became numerically dominant in exposure assemblages over time because of their persistence and losses of other taxa. In contrast, species richness increased over time in reference assemblages, a result that may indicate recovery from drought. Mean individual biomass increased as fish density decreased and most obligate invertivores were apparently extirpated at MTM exposure sites. Effects of MTM were not related to physical-habitat conditions but were associated with water-quality variables, which may limit quality and availability of benthic macroinvertebrate prey. Simulations revealed effects of MTM that could not be attributed to random variation in fish assemblage structure.

  11. Effects of hydrologic connectivity on aquatic macroinvertebrate assemblages in different marsh types

    Science.gov (United States)

    Kang, Sung-Ryong; King, Sammy L.

    2013-01-01

    Hydrologic connectivity can be an important driver of aquatic macroinvertebrate assemblages. Its effects on aquatic macroinvertebrate assemblages in coastal marshes, however, are relatively poorly studied. We evaluated the effects of lateral hydrologic connectivity (permanently connected ponds: PCPs; temporary connected ponds: TCPs), and other environmental variables on aquatic macroinvertebrate assemblages and functional feeding groups (FFGs) in freshwater, brackish, and saline marshes in Louisiana, USA. We hypothesized that (1) aquatic macroinvertebrate assemblages in PCPs would have higher assemblage metric values (density, biomass, Shannon-Wiener diversity) than TCPs and (2) the density and proportional abundance of certain FFGs (i.e. scrapers, shredders, and collectors) would be greater in freshwater marsh than brackish and saline marshes. The data in our study only partially supported our first hypothesis: while freshwater marsh PCPs had higher density and biomass than TCPs, assemblage metric values in saline TCPs were greater than saline PCPs. In freshwater TCPs, long duration of isolation limited access of macroinvertebrates from adjacent water bodies, which may have reduced assemblage metric values. However, the relatively short duration of isolation in saline TCPs provided more stable or similar habitat conditions, facilitating higher assemblage metric values. As predicted by our second hypothesis, freshwater PCPs and TCPs supported a greater density of scrapers, shredders, and collectors than brackish and saline ponds. Aquatic macroinvertebrate assemblages seem to be structured by individual taxa responses to salinity as well as pond habitat attributes.

  12. Mollusc life and death assemblages on a tropical rocky shore as proxies for the taphonomic loss in a fossil counterpart

    DEFF Research Database (Denmark)

    Sørensen, Anne Mehlin; Surlyk, Finn

    2013-01-01

    a lower taxonomic agreement to the death assemblage than found in previous published studies. Rocky shore life and death assemblages thus appear to show lower taxonomic agreement compared to muddy or sandy shelf assemblages due to the mix after death with the sandy beach assemblage. A hypothetical fossil......Comparison of a modern rocky shore mollusc life assemblage from Thailand with the associated death assemblage, and interpretation of the fossilization potential of the latter, are used to investigate the fidelity in reconstruction of ancient analogues. The fauna from the death assemblage represents...... species from the rocky shore and the associated sandy pocket beaches, and only a few exotic species from other, completely different habitats are present. The environmental fidelity between the life and death assemblage is thus high, with the majority of species from the death assemblage representing...

  13. How could discharge management affect Florida spring fish assemblage structure?

    Science.gov (United States)

    Work, Kirsten; Codner, Keneil; Gibbs, Melissa

    2017-08-01

    Freshwater bodies are increasingly affected by reductions in water quantity and quality and by invasions of exotic species. To protect water quantity and maintain the ecological integrity of many water bodies in central Florida, a program of adopting Minimum Flows and Levels (MFLs) has begun for both lentic and lotic waters. The purpose of this study was to determine whether there were relationships between discharge and stage, water quality, and biological parameters for Volusia Blue Spring, a first magnitude spring (discharge > 380,000 m 3 day -1 or 100 mgd) for which an MFL program was adopted in 2006. Over the course of fourteen years, we assessed fish density and diversity weekly, monthly, or seasonally with seine and snorkel counts. We evaluated annual changes in the assemblages for relationships with water quantity and quality. Low discharge and dissolved oxygen combined with high stage and conductivity produced a fish population with a lower density and diversity in 2014 than in previous years. Densities of fish taxonomic/functional groups also were low in 2014 and measures of water quantity were significant predictors of fish assemblage structure. As a result of the strong relationships between variation in discharge and an array of chemical and biological characteristics of the spring, we conclude that maintaining the historical discharge rate is important for preserving the ecological integrity of Volusia Blue Spring. Copyright © 2017 Elsevier Ltd. All rights reserved.

  14. Phytoplankton assemblage of a small, shallow, tropical African reservoir.

    Science.gov (United States)

    Mustapha, Moshood K

    2009-12-01

    I measured physico-chemical properties and phytoplankton in the small, shallow tropical reservoir of Oyun (Offa, Nigeria) between January 2002 and December 2003. I identified 25 phytoplankton genera in three sampling stations. Bacillariophyceae dominated (75.3%), followed by Chlorophyceae (12.2%), Cyanobacteria (11.1%) and Desmidiaceae (0.73%). The high amount of nutrients (e.g. nitrate, phosphate, sulphate and silica) explain phytoplankton heterogeneity (p<0.05). Phytoplankton was abundant during the rainy season, but the transition period had the richest assemblage and abundance. Fluctuations in phytoplankton density were a result of seasonal changes in concentration of nutrients, grazing pressure and reservoir hydrology. The reservoir is eutrophic with excellent water quality and a diverse phytoplankton assemblage: fish production would be high. These conditions resulted from strategies such as watershed best management practices (BMPs) to control eutrophication and sedimentation, and priorities for water usage established through legislation. Additional measures are recommended to prevent oligotrophy, hypereutrophy, excessive phytoplankton bloom, toxic cyanobacteria, and run-off of organic waste and salts.

  15. Marine assemblages respond rapidly to winter climate variability.

    Science.gov (United States)

    Morley, James W; Batt, Ryan D; Pinsky, Malin L

    2017-07-01

    Even species within the same assemblage have varied responses to climate change, and there is a poor understanding for why some taxa are more sensitive to climate than others. In addition, multiple mechanisms can drive species' responses, and responses may be specific to certain life stages or times of year. To test how marine species respond to climate variability, we analyzed 73 diverse taxa off the southeast US coast in 26 years of scientific trawl survey data and determined how changes in distribution and biomass relate to temperature. We found that winter temperatures were particularly useful for explaining interannual variation in species' distribution and biomass, although the direction and magnitude of the response varied among species from strongly negative, to little response, to strongly positive. Across species, the response to winter temperature varied greatly, with much of this variation being explained by thermal preference. A separate analysis of annual commercial fishery landings revealed that winter temperatures may also impact several important fisheries in the southeast United States. Based on the life stages of the species surveyed, winter temperature appears to act through overwinter mortality of juveniles or as a cue for migration timing. We predict that this assemblage will be responsive to projected increases in temperature and that winter temperature may be broadly important for species relationships with climate on a global scale. © The Authors Global Change Biology Published by John Wiley & Sons Ltd.

  16. Avian assemblages in the lower Missouri river floodplain

    Science.gov (United States)

    Thogmartin, W.E.; Gallagher, M.; Young, N.; Rohweder, J.J.; Durbian, F.; Knutson, M.G.

    2009-01-01

    Floodplain habitat provides important migration and breeding habitat for birds in the midwestern United States. However, few studies have examined how the avian assemblage changes with different stages of floodplain forest succession in the midwestern United States. In spring and summer from 2002 to 2004, we conducted 839 point counts in wet prairie/forbs fields, 547 point counts in early successional forests, and 434 point counts in mature forests to describe the migrating and breeding bird assemblage in the lower Missouri River floodplain. We recorded 131, 121, and 141 species in the three respective habitats, a number higher than most locations in the midwestern United States and comprising > 15% of all avian species in North America. Avian species diversity generally increased from west to east along the river, differed among land cover classes, but overlapped between seasons (migration and breeding) and years. Wet prairies were particularly important for conservation as there were 20 species of high conservation concern observed, including Dickcissels (Spiza americana). Important species for monitoring biotic integrity included the Northern Harrier (Circus cyaneus) and Bobolink (Dolichonyx oryzivorus) in wet prairie, Bell's Vireo (Vireo bellii) in early successional forest, and Northern Parula (Parula americana) and Prothonotary Warbler (Protonotaria citrea) in mature forest. ?? 2009, The Society of Wetland Scientists.

  17. "Controlling ourselves, by ourselves": risk assemblages on Malaysia's assembly lines.

    Science.gov (United States)

    Root, Robin

    2008-01-01

    Since the early 1990s, the Malaysian government has identified factories as high risk for HIV and AIDS. Signaling epidemiological concerns over the rising rates of HIV among factory workers, a significant proportion of whom are women, the label also appeared to reconstitute stereotypes of factory women as dangerously sexual and of factories as immoral spaces. Drawing on ethnographic research in the export processing zones of Penang, Malaysia in the mid-1990s, I examine the meanings and experiences of HIV risk among factory women themselves. Data were analyzed using discourse and grounded theory methods, the former to identify women's multiple modes of rationalizing HIV risks, and the latter to theorize the sources and significance of women's HIV risk assemblages. The heuristic of assemblages as localized knowledge spaces helped to show that biomedical and socioreligious risk lexica operated not as fixed epistemological categories but as situational resources in women's risk scripts. Overall, women desired multiple risk knowledges to help them "control themselves by themselves," a project of reflexive self-shaping mediated by the diverse and discordant discourses of gender, ethnicity, and modernity in Malaysia that shaped how HIV risks were engendered and experienced.

  18. Spatial scaling of functional structure in bird and mammal assemblages.

    Science.gov (United States)

    Belmaker, Jonathan; Jetz, Walter

    2013-04-01

    Differences in trait composition, or functional structure, of assemblages across spatial scales may stem from the ability to tolerate local conditions (environmental filters) and from assembly rules (biological filters). However, disentangling their respective roles has proven difficult, and limited generalities have emerged from research on the spatial scaling of functional structure. Here we quantify differences in trait composition among 679 spatially nested (i.e., paired regional pool and local community) bird and mammal assemblages worldwide. Among the regional pool, we identify species with trait combinations within the range observed locally as the ecological species pool. The ecological species pool has a trait structure that is generally different from that of the regional pool, consistent with the operation of environmental filters. In contrast, local species trait structure generally shows little difference from that of the ecological pool. We find notable deviations from expectations based on equiprobable draws from the ecological pool. However, these deviations vary little across scales and broad environmental gradients. For mammals, but not birds, this is consistent with assembly rules. Thus, by conceptualizing ecological pools, we demonstrate that functional structure is jointly determined by processes causing both low and high functional differences between scales and are able to quantify their relative importance.

  19. The 'Goldilocks' effect: preservation bias in vertebrate track assemblages.

    Science.gov (United States)

    Falkingham, P L; Bates, K T; Margetts, L; Manning, P L

    2011-08-07

    Finite-element analysis was used to investigate the extent of bias in the ichnological fossil record attributable to body mass. Virtual tracks were simulated for four dinosaur taxa of different sizes (Struthiomimus, Tyrannosaurus, Brachiosaurus and Edmontosaurus), in a range of substrate conditions. Outlines of autopodia were generated based upon osteology and published soft-tissue reconstructions. Loads were applied vertically to the feet equivalent to the weight of the animal, and distributed accordingly to fore- and hindlimbs where relevant. Ideal, semi-infinite elastic-plastic substrates displayed a 'Goldilocks' quality where only a narrow range of loads could produce tracks, given that small animals failed to indent the substrate, and larger animals would be unable to traverse the area without becoming mired. If a firm subsurface layer is assumed, a more complete assemblage is possible, though there is a strong bias towards larger, heavier animals. The depths of fossil tracks within an assemblage may indicate thicknesses of mechanically distinct substrate layers at the time of track formation, even when the lithified strata appear compositionally homogeneous. This work increases the effectiveness of using vertebrate tracks as palaeoenvironmental indicators in terms of inferring substrate conditions at the time of track formation. Additionally, simulated undertracks are examined, and it is shown that complex deformation beneath the foot may not be indicative of limb kinematics as has been previously interpreted, but instead ridges and undulations at the base of a track may be a function of sediment displacement vectors and pedal morphology.

  20. Life history theory predicts fish assemblage response to hydrologic regimes.

    Science.gov (United States)

    Mims, Meryl C; Olden, Julian D

    2012-01-01

    The hydrologic regime is regarded as the primary driver of freshwater ecosystems, structuring the physical habitat template, providing connectivity, framing biotic interactions, and ultimately selecting for specific life histories of aquatic organisms. In the present study, we tested ecological theory predicting directional relationships between major dimensions of the flow regime and life history composition of fish assemblages in perennial free-flowing rivers throughout the continental United States. Using long-term discharge records and fish trait and survey data for 109 stream locations, we found that 11 out of 18 relationships (61%) tested between the three life history strategies (opportunistic, periodic, and equilibrium) and six hydrologic metrics (two each describing flow variability, predictability, and seasonality) were statistically significant (P history strategies, with 82% of all significant relationships observed supporting predictions from life history theory. Specifically, we found that (1) opportunistic strategists were positively related to measures of flow variability and negatively related to predictability and seasonality, (2) periodic strategists were positively related to high flow seasonality and negatively related to variability, and (3) the equilibrium strategists were negatively related to flow variability and positively related to predictability. Our study provides important empirical evidence illustrating the value of using life history theory to understand both the patterns and processes by which fish assemblage structure is shaped by adaptation to natural regimes of variability, predictability, and seasonality of critical flow events over broad biogeographic scales.

  1. Pollen assemblages as paleoenvironmental proxies in the Florida Everglades

    Science.gov (United States)

    Willard, D.A.; Weimer, L.M.; Riegel, W.L.

    2001-01-01

    Analysis of 170 pollen assemblages from surface samples in eight vegetation types in the Florida Everglades indicates that these wetland sub-environments are distinguishable from the pollen record and that they are useful proxies for hydrologic and edaphic parameters. Vegetation types sampled include sawgrass marshes, cattail marshes, sloughs with floating aquatics, wet prairies, brackish marshes, tree islands, cypress swamps, and mangrove forests. The distribution of these vegetation types is controlled by specific environmental parameters, such as hydrologic regime, nutrient availability, disturbance level, substrate type, and salinity; ecotones between vegetation types may be sharp. Using R-mode cluster analysis of pollen data, we identified diagnostic species groupings; Q-mode cluster analysis was used to differentiate pollen signatures of each vegetation type. Cluster analysis and the modern analog technique were applied to interpret vegetational and environmental trends over the last two millennia at a site in Water Conservation Area 3A. The results show that close modern analogs exist for assemblages in the core and indicate past hydrologic changes at the site, correlated with both climatic and land-use changes. The ability to differentiate marshes with different hydrologic and edaphic requirements using the pollen record facilitates assessment of relative impacts of climatic and anthropogenic changes on this wetland ecosystem on smaller spatial and temporal scales than previously were possible. ?? 2001 Elsevier Science B.V.

  2. Pollen assemblages as paleoenvironmental proxies in the Florida Everglades.

    Science.gov (United States)

    Willard, D A.; Weimer, L M.; Riegel, W L.

    2001-04-01

    Analysis of 170 pollen assemblages from surface samples in eight vegetation types in the Florida Everglades indicates that these wetland sub-environments are distinguishable from the pollen record and that they are useful proxies for hydrologic and edaphic parameters. Vegetation types sampled include sawgrass marshes, cattail marshes, sloughs with floating aquatics, wet prairies, brackish marshes, tree islands, cypress swamps, and mangrove forests. The distribution of these vegetation types is controlled by specific environmental parameters, such as hydrologic regime, nutrient availability, disturbance level, substrate type, and salinity; ecotones between vegetation types may be sharp. Using R-mode cluster analysis of pollen data, we identified diagnostic species groupings; Q-mode cluster analysis was used to differentiate pollen signatures of each vegetation type. Cluster analysis and the modern analog technique were applied to interpret vegetational and environmental trends over the last two millennia at a site in Water Conservation Area 3A. The results show that close modern analogs exist for assemblages in the core and indicate past hydrologic changes at the site, correlated with both climatic and land-use changes. The ability to differentiate marshes with different hydrologic and edaphic requirements using the pollen record facilitates assessment of relative impacts of climatic and anthropogenic changes on this wetland ecosystem on smaller spatial and temporal scales than previously were possible.

  3. Rock encrusting assemblages: Structure and distribution along the Baltic Sea

    Science.gov (United States)

    Grabowska, Monika; Grzelak, Katarzyna; Kukliński, Piotr

    2015-09-01

    Aquatic community structure and dynamics are generally controlled by a variety of biological and physical factors. Among these factors in marine ecosystems, salinity is known to have a significant effect on species occurrence and composition. In this study, we investigated the large-scale distribution and abundance of encrusting fauna along a salinity gradient on the shallow Baltic Sea rocky coast. Rock samples collected from 14 locations distributed between the Gulf of Bothnia (salinity 0.6) and Skagerrak (salinity 28) supported a total number of 24 encrusting species. The faunas were composed mostly of marine species with opportunistic life histories; however, some brackish water specialists were also present. The number of species and abundance counts is strongly positively correlated with increases in salinity. No encrusting faunas were recorded below salinity level 4. Multivariate analysis (nMDS) revealed three major groups based on species composition that differed in terms of abundance and number of species. Each group was associated with specific salinity conditions. The first assemblage type occurred within salinity 4-7, the second within salinity between 22 and 27, and the third type was a mixture between the two observed at a salinity of approximately 17. This study indicates that to determine the assemblage structure of the Baltic Sea encrusting fauna, analyses at the family level were found to be a reliable surrogate for species composition.

  4. Multilocus genotyping of human Giardia isolates suggests limited zoonotic transmission and association between assemblage B and flatulence in children.

    Directory of Open Access Journals (Sweden)

    Marianne Lebbad

    2011-08-01

    Full Text Available BACKGROUND: Giardia intestinalis is one of the most common diarrhea-related parasites in humans, where infection ranges from asymptomatic to acute or chronic disease. G. intestinalis consists of eight genetically distinct genotypes or assemblages, designated A-H, and assemblages A and B can infect humans. Giardiasis has been classified as a possible zoonotic disease but the role of animals in human disease transmission still needs to be proven. We tried to link different assemblages and sub-assemblages of G. intestinalis isolates from Swedish human patients to clinical symptoms and zoonotic transmission. METHODOLOGY/PRINCIPAL FINDINGS: Multilocus sequence-based genotyping of 207 human Giardia isolates using three gene loci: ß-giardin, glutamate dehydrogenase (gdh, and triose phosphate isomerase (tpi was combined with assemblage-specific tpi PCRs. This analysis identified 73 patients infected with assemblage A, 128 with assemblage B, and six with mixed assemblages A+B. Multilocus genotypes (MLGs were easily determined for the assemblage A isolates, and most patients with this genotype had apparently been infected through anthroponotic transmission. However, we also found evidence of limited zoonotic transmission of Giardia in Sweden, since a few domestic human infections involved the same assemblage A MLGs previously reported in Swedish cats and ruminants. Assemblage B was detected more frequently than assemblage A and it was also more common in patients with suspected treatment failure. However, a large genetic variability made determination of assemblage B MLGs problematic. Correlation between symptoms and assemblages was found only for flatulence, which was significantly more common in children less than six years of age infected with assemblage B. CONCLUSIONS/SIGNIFICANCE: This study shows that certain assemblage A subtypes are potentially zoonotic and that flatulence is connected to assemblage B infections in young children. Determination

  5. Studies of Cystoseira assemblages in Northern Atlantic Iberia

    Directory of Open Access Journals (Sweden)

    García-Fernández, Alicia

    2016-06-01

    Full Text Available The Iberian Peninsula contains 24 specific and infraespecific taxa of the genus Cystoseira, but only 6 inhabit in Northern Iberia: C. baccata, C. foeniculacea, C. humilis var. myriophylloides, C. nodicaulis, C. tamariscifolia, and C. usneoides. The Cystoseira assemblages exhibit a complex structure and stratification that allows the presence of a large associate biota and a rich epiphytic flora. Although in the Mediterranean Sea several species have been analyzed in depth, the Atlantic ones are less studied. A revision of the literature (1931-2014 and grey information was made to know the diversity of the North Atlantic Iberian Cystoseira assemblages. The community of C. baccata harbors the biggest number of species (215, followed by C. tamariscifolia (162 and C. usneoides (126, whereas the community with fewest species was the C. foeniculacea one (34. More than 70 species were present in the majority of the Cystoseira assemblages. In this article, are revised also environmental issues in the Cystoseira assemblages, as pollution and anthropogenic pressures or disturbances that cause regression in their communities, and effects of biological invasions by non-native species. As a conclusion, it will necessary to study the Cystoseira assemblage in depth, starting by research of C. baccata along Northern Iberia, as it is an exclusive and widely distributed Atlantic species with very scarce information concerning its role in structuring the communities.La Península Ibérica contiene 24 táxones del género Cystoseira, pero sólo 6 habitan en las costas del norte: C. baccata, C. foeniculacea, C. humilis var. myriophylloides, C. nodicaulis, C. tamariscifolia y C. usneoides. Las comunidades de Cystoseira muestran una estructura compleja debido a su estratificación, lo que permite el desarrollo de una amplia biota asociada y una gran riqueza de flora epífita. Aunque diversas especies mediterráneas han sido analizadas en profundidad, las atl

  6. Recovery of macrobenthic assemblages following experimental sand burial

    Directory of Open Access Journals (Sweden)

    José J. Barrón

    2008-09-01

    Full Text Available This research was supported by a fund provided by the Instituto de Ciencias del Mar y Limnología (UNAM and a fund provided to Celia Olabarria in 2004 and 2005 by the University of Vigo for overseas short stays.AbstractPeriodic inundation by sand is a very common feature of rocky coasts throughout the world. Even so, there have been few direct observations or experiments to investigate the role of sediments on intertidal rocky shores. We designed a field experiment in Mazatlán Bay, Mexico, to test the initial impact and subsequent recovery of intertidal macrobenthic assemblages exposed to sand burial at two sites of varying wave exposure. Both sites supported different natural assemblages. Treatment plots for the addition of sediment and control plots (50 × 50 cm, separated by at least 1.5 m, were randomly placed across the mid-water tidal level. The initial response of the resident macrobenthos and the subsequent recolonization was monitored over a period of 95 days. The main effect of sediment deposition at both sites was mortality and removal of biota due to smothering. The recovery process was rapid and may in part have been the result of the mechanism by which the small, disturbed patches were recolonized. Most of the invertebrates colonized the patches as adults; several seaweeds exhibited vegetative growth as the major mechanism of colonization (e.g., Ulva lactuca Linnaeus, 1753, Amphiroa valonioides Yendo, 1902 and Chaetomorpha antennina (Borgensen Kutzing, 1849. The rate of recovery varied between the sites, however. Recovery of species numbers proceeded quickly at the sheltered site (day 7, but took 95 days at the exposed site. In contrast, biomass reached control levels by day 45 at the sheltered site, but already by day 15 at the exposed site. By day 95, the assemblages recovered to 83.5% and 81% similarity with the controls at the sheltered and exposed sites respectively. Although differences in wave exposure could be very

  7. Testing for functional convergence of temperate rainforest tree assemblages in Chile and New Zealand

    NARCIS (Netherlands)

    Lusk, C.H.; Jimenez-Castillo, M.; Aragón, R.; Easdale, T.A.; Poorter, L.; Hinojosa, L.F.; Mason, N.W.H.W.H.

    2016-01-01

    An important tenet of biogeography and comparative ecology is that disjunct assemblages in similar physical environments are functionally more similar to each other than to assemblages from other environments. Temperate rainforests in South America, New Zealand and Australia share certain

  8. Assessing tree species assemblages in highly disturbed Puerto Rican karst landscapes using forest inventory data.

    Science.gov (United States)

    Thomas James Brandeis

    2006-01-01

    Tree species assemblages described by landscape-scale forest inventory data both agreed and differed from those described by intensive, site specific studies in Puerto Rico’s highly disturbed northern karst belt. Species assemblages found on hill tops (typified by Tabebuia heterophylla or Bursera simaruba with Coccoloba diversifolia, Licaria parvifolia, and Drypetes...

  9. Citizenship agendas, urban governance and social housing in the Netherlands: An assemblage approach

    NARCIS (Netherlands)

    Koster, M.

    2015-01-01

    This article combines recent conceptualizations of citizenship beyond the nation state with new perspectives on governance assemblages comprising both state and non-state actors. Focusing on Dutch social housing, this study explores how such governance assemblages produce agendas that attempt to

  10. Lions as Bone Accumulators? Paleontological and Ecological Implications of a Modern Bone Assemblage from Olduvai Gorge.

    Science.gov (United States)

    Arriaza, Mari Carmen; Domínguez-Rodrigo, Manuel; Yravedra, José; Baquedano, Enrique

    2016-01-01

    Analytic models have been developed to reconstruct early hominin behaviour, especially their subsistence patterns, revealed mainly through taphonomic analyses of archaeofaunal assemblages. Taphonomic research is used to discern which agents (carnivores, humans or both) generate the bone assemblages recovered at archaeological sites. Taphonomic frameworks developed during the last decades show that the only large-sized carnivores in African biomes able to create bone assemblages are leopards and hyenas. A carnivore-made bone assemblage located in the short-grassland ecological unit of the Serengeti (within Olduvai Gorge) was studied. Taphonomic analyses of this assemblage including skeletal part representation, bone density, breakage patterns and anatomical distribution of tooth marks, along with an ecological approach to the prey selection made by large carnivores of the Serengeti, were carried out. The results show that this bone assemblage may be the first lion-accumulated assemblage documented, although other carnivores (namely spotted hyenas) may have also intervened through postdepositional ravaging. This first faunal assemblage potentially created by lions constitutes a new framework for neotaphonomic studies. Since lions may accumulate carcasses under exceptional circumstances, such as those documented at the site reported here, this finding may have important consequences for interpretations of early archaeological and paleontological sites, which provide key information about human evolution.

  11. Fish assemblage patterns as a tool to aid conservation in the ...

    African Journals Online (AJOL)

    Patterns in fish assemblage data across 88 sites were analysed and related to landscape environmental variables using statistical techniques of multivariate ordination, cluster analysis, and regression tree analysis. We identified 6 distinct fish assemblage types, which were separated by altitude and human influence, ...

  12. Inventory and Spatial Assemblage Study of Reef Fish in the Area of ...

    African Journals Online (AJOL)

    This study represents the first qualitative census of the reef fish assemblage of coral reefs in the vicinity of Andavadoaka, south-west Madagascar. Observational data of fish species sightings were collected over the course of a year, while visual census data, with low observer bias, detailing fish assemblage from the four ...

  13. Microplastic-associated Bacterial Assemblages in the Intertidal Zone

    Science.gov (United States)

    Jiang, P.; Zhao, S.; Zhu, L.; Li, D.

    2017-12-01

    Plastic debris is posing a planetary-scale threat. As a zone where terrestrial and marine ecosystems interactions occur, the accumulation of plastic marine debris (PMD) in intertidal environments has been well documented. But the information of plastic-associated microbial community (the "Plastisphere") in the intertidal zone is scanty. Utilizing the high-throughput sequencing, we profiled the bacterial communities attached to microplastic samples from the intertidal locations around Yangtze estuary. The structure and composition of Plastisphere communities in current study varied significantly with geographical stations. The taxonomic composition on microplastic samples implied their sedimental and aquatic origins. Some members of hydrocarbon degrading microorganisms and potential pathogens were detected on microplastic. Overall, our findings fuel the evidence for the occurrence of diverse microbial assemblages on PMD and improving our understanding of Plastisphere ecology, which could support the management action and policy change related to PMD.

  14. Molluscicidal metabolites from an assemblage of Palmyra Atoll cyanobacteria.

    Science.gov (United States)

    Pereira, Alban R; Etzbach, Lena; Engene, Niclas; Müller, Rolf; Gerwick, William H

    2011-05-27

    Molluscicides can play an important role in the control of schistosomiasis because snails of the genus Biomphalaria act as intermediate hosts for the parasite. Schistosomiasis is one of 13 neglected tropical diseases with high morbidity and mortality that collectively affect one billion of the world's poorest population, mainly in developing countries. Thiopalmyrone (1) and palmyrrolinone (2), metabolites isolated from extracts of a Palmyra Atoll environmental assemblage of two cyanobacteria, cf. Oscillatoria and Hormoscilla spp., represent new and potent molluscicidal chemotypes against Biomphalaria glabrata (LC50=8.3 and 6.0 μM, respectively). A slight enhancement in molluscicidal effect (LC50=5.0 μM) was observed when these two natural products were utilized as an equimolar binary mixture.

  15. The (Big Data-security assemblage: Knowledge and critique

    Directory of Open Access Journals (Sweden)

    Claudia Aradau

    2015-10-01

    Full Text Available The Snowden revelations and the emergence of ‘Big Data’ have rekindled questions about how security practices are deployed in a digital age and with what political effects. While critical scholars have drawn attention to the social, political and legal challenges to these practices, the debates in computer and information science have received less analytical attention. This paper proposes to take seriously the critical knowledge developed in information and computer science and reinterpret their debates to develop a critical intervention into the public controversies concerning data-driven security and digital surveillance. The paper offers a two-pronged contribution: on the one hand, we challenge the credibility of security professionals’ discourses in light of the knowledge that they supposedly mobilize; on the other, we argue for a series of conceptual moves around data, human–computer relations, and algorithms to address some of the limitations of existing engagements with the Big Data-security assemblage.

  16. Description of viral assemblages associated with the Gorgonia ventalina holobiont

    Science.gov (United States)

    Hewson, I.; Brown, J. M.; Burge, C. A.; Couch, C. S.; LaBarre, B. A.; Mouchka, M. E.; Naito, M.; Harvell, C. D.

    2012-06-01

    The diversity and function of viruses in coral holobionts has only recently received attention. The non-reef building gorgonian octocoral, Gorgonia ventalina, is a major constituent of Caribbean reefs. We investigated viral communities associated with G. ventalina tissues to understand their role in gorgonian ecology. Pyrosequencing was used to prepare a total of 514,632 sequence reads of DNA- and RNA-based mixed-community viral genomes (metaviromes). RNA viral assemblages were comprised of primarily unidentifiable reads, with most matching host transcripts and other RNA metaviromes. DNA metaviromes were similar between healthy and diseased tissues and comprised of contiguous sequences (contigs) that matched primarily metazoan and bacterial proteins. Only ~5% of contigs matched viral proteins that were primarily cyanophage and viruses of Chlorella and Ostreococcus. Our results confirm that DNA and RNA viruses comprise a component of the gorgonian holobiont, suggesting that they may play a role in the ecology of G. ventalina.

  17. Queer Gamer Assemblages and the Affective Elements of Digital Games

    Directory of Open Access Journals (Sweden)

    Spencer Taylor Berdiago Ruelos

    2018-01-01

    Full Text Available Centering a discussion of gaming as an embodied experience, this essay explores the affective and embodied relationship between LGBT/queer gamers and video games. Drawing on qualitative interviews with seven queer gamers, I argue in that we should understand gamers as socio-technological assemblages, in order to illustrate how gamer identity, subjectivity, and sociality are enacted through the relationship between the body of a gamer and the game technologies. I further expand upon this by tending to how queer gamers talk about their embodied experiences and affective connections to various games through worlding and storytelling elements. These stories illustrate how games create affective possibilities for connection and belonging for queer gamers. I conclude by arguing that an attention to gaming as an embodied experience expands our conceptualizations of play and helps us understand the worldmaking practices that queer gamers often employ.

  18. Contrasting species and functional beta diversity in montane ant assemblages.

    Science.gov (United States)

    Bishop, Tom R; Robertson, Mark P; van Rensburg, Berndt J; Parr, Catherine L

    2015-09-01

    Beta diversity describes the variation in species composition between sites and can be used to infer why different species occupy different parts of the globe. It can be viewed in a number of ways. First, it can be partitioned into two distinct patterns: turnover and nestedness. Second, it can be investigated from either a species identity or a functional-trait point of view. We aim to document for the first time how these two aspects of beta diversity vary in response to a large environmental gradient. Maloti-Drakensberg Mountains, southern Africa. We sampled ant assemblages along an extensive elevational gradient (900-3000 m a.s.l.) twice yearly for 7 years, and collected functional-trait information related to the species' dietary and habitat-structure preferences. We used recently developed methods to partition species and functional beta diversity into their turnover and nestedness components. A series of null models were used to test whether the observed beta diversity patterns differed from random expectations. Species beta diversity was driven by turnover, but functional beta diversity was composed of both turnover and nestedness patterns at different parts of the gradient. Null models revealed that deterministic processes were likely to be responsible for the species patterns but that the functional changes were indistinguishable from stochasticity. Different ant species are found with increasing elevation, but they tend to represent an increasingly nested subset of the available functional strategies. This finding is unique and narrows down the list of possible factors that control ant existence across elevation. We conclude that diet and habitat preferences have little role in structuring ant assemblages in montane environments and that some other factor must be driving the non-random patterns of species turnover. This finding also highlights the importance of distinguishing between different kinds of beta diversity.

  19. Spatial segregation in eastern North Pacific skate assemblages.

    Directory of Open Access Journals (Sweden)

    Joseph J Bizzarro

    Full Text Available Skates (Rajiformes: Rajoidei are common mesopredators in marine benthic communities. The spatial associations of individual species and the structure of assemblages are of considerable importance for effective monitoring and management of exploited skate populations. This study investigated the spatial associations of eastern North Pacific (ENP skates in continental shelf and upper continental slope waters of two regions: central California and the western Gulf of Alaska. Long-term survey data were analyzed using GIS/spatial analysis techniques and regression models to determine distribution (by depth, temperature, and latitude/longitude and relative abundance of the dominant species in each region. Submersible video data were incorporated for California to facilitate habitat association analysis. We addressed three main questions: 1 Are there regions of differential importance to skates?, 2 Are ENP skate assemblages spatially segregated?, and 3 When skates co-occur, do they differ in size? Skate populations were highly clustered in both regions, on scales of 10s of kilometers; however, high-density regions (i.e., hot spots were segregated among species. Skate densities and frequencies of occurrence were substantially lower in Alaska as compared to California. Although skates are generally found on soft sediment habitats, Raja rhina exhibited the strongest association with mixed substrates, and R. stellulata catches were greatest on rocky reefs. Size segregation was evident in regions where species overlapped substantially in geographic and depth distribution (e.g., R. rhina and Bathyraja kincaidii off California; B. aleutica and B. interrupta in the Gulf of Alaska. Spatial niche differentiation in skates appears to be more pronounced than previously reported.

  20. Spatial segregation in eastern North Pacific skate assemblages.

    Science.gov (United States)

    Bizzarro, Joseph J; Broms, Kristin M; Logsdon, Miles G; Ebert, David A; Yoklavich, Mary M; Kuhnz, Linda A; Summers, Adam P

    2014-01-01

    Skates (Rajiformes: Rajoidei) are common mesopredators in marine benthic communities. The spatial associations of individual species and the structure of assemblages are of considerable importance for effective monitoring and management of exploited skate populations. This study investigated the spatial associations of eastern North Pacific (ENP) skates in continental shelf and upper continental slope waters of two regions: central California and the western Gulf of Alaska. Long-term survey data were analyzed using GIS/spatial analysis techniques and regression models to determine distribution (by depth, temperature, and latitude/longitude) and relative abundance of the dominant species in each region. Submersible video data were incorporated for California to facilitate habitat association analysis. We addressed three main questions: 1) Are there regions of differential importance to skates?, 2) Are ENP skate assemblages spatially segregated?, and 3) When skates co-occur, do they differ in size? Skate populations were highly clustered in both regions, on scales of 10s of kilometers; however, high-density regions (i.e., hot spots) were segregated among species. Skate densities and frequencies of occurrence were substantially lower in Alaska as compared to California. Although skates are generally found on soft sediment habitats, Raja rhina exhibited the strongest association with mixed substrates, and R. stellulata catches were greatest on rocky reefs. Size segregation was evident in regions where species overlapped substantially in geographic and depth distribution (e.g., R. rhina and Bathyraja kincaidii off California; B. aleutica and B. interrupta in the Gulf of Alaska). Spatial niche differentiation in skates appears to be more pronounced than previously reported.

  1. Benthic macroinvertebrate assemblages in the US nearshore zone of Lake Erie, 2009: Status and linkages to landscape-derived stressors

    Science.gov (United States)

    Benthic macroinvertebrate assemblages have been used as indicators of ecological condition because their responses integrate localized environmental conditions of the sediments and overlying water. Assemblages of benthic invertebrates in the near coastal region are of particular...

  2. An empirical, hierarchical typology of tree species assemblages for assessing forest dynamics under global change scenarios.

    Directory of Open Access Journals (Sweden)

    Jennifer K Costanza

    Full Text Available The composition of tree species occurring in a forest is important and can be affected by global change drivers such as climate change. To inform assessment and projection of global change impacts at broad extents, we used hierarchical cluster analysis and over 120,000 recent forest inventory plots to empirically define forest tree assemblages across the U.S., and identified the indicator and dominant species associated with each. Cluster typologies in two levels of a hierarchy of forest assemblages, with 29 and 147 groups respectively, were supported by diagnostic criteria. Groups in these two levels of the hierarchy were labeled based on the top indicator species in each, and ranged widely in size. For example, in the 29-cluster typology, the sugar maple-red maple assemblage contained the largest number of plots (30,068, while the butternut-sweet birch and sourwood-scarlet oak assemblages were both smallest (6 plots each. We provide a case-study demonstration of the utility of the typology for informing forest climate change impact assessment. For five assemblages in the 29-cluster typology, we used existing projections of changes in importance value (IV for the dominant species under one low and one high climate change scenario to assess impacts to the assemblages. Results ranged widely for each scenario by the end of the century, with each showing an average decrease in IV for dominant species in some assemblages, including the balsam fir-quaking aspen assemblage, and an average increase for others, like the green ash-American elm assemblage. Future work should assess adaptive capacity of these forest assemblages and investigate local population- and community-level dynamics in places where dominant species may be impacted. This typology will be ideal for monitoring, assessing, and projecting changes to forest communities within the emerging framework of macrosystems ecology, which emphasizes hierarchies and broad extents.

  3. Environmental variables measured at multiple spatial scales exert uneven influence on fish assemblages of floodplain lakes

    Science.gov (United States)

    Dembkowski, Daniel J.; Miranda, Leandro E.

    2014-01-01

    We examined the interaction between environmental variables measured at three different scales (i.e., landscape, lake, and in-lake) and fish assemblage descriptors across a range of over 50 floodplain lakes in the Mississippi Alluvial Valley of Mississippi and Arkansas. Our goal was to identify important local- and landscape-level determinants of fish assemblage structure. Relationships between fish assemblage structure and variables measured at broader scales (i.e., landscape-level and lake-level) were hypothesized to be stronger than relationships with variables measured at finer scales (i.e., in-lake variables). Results suggest that fish assemblage structure in floodplain lakes was influenced by variables operating on three different scales. However, and contrary to expectations, canonical correlations between in-lake environmental characteristics and fish assemblage structure were generally stronger than correlations between landscape-level and lake-level variables and fish assemblage structure, suggesting a hierarchy of influence. From a resource management perspective, our study suggests that landscape-level and lake-level variables may be manipulated for conservation or restoration purposes, and in-lake variables and fish assemblage structure may be used to monitor the success of such efforts.

  4. C9.A/14 steelwork joints de poutres par plaque frontale : assemblages par gousset

    CERN Document Server

    2015-01-01

    Les Tables de résistances ultimes des assemblages boulonnés par plaque frontale et par gousset, complétées par une description des modèles de calcul et des exemples d’application, ont pour but de faciliter la tâche de l'ingénieur et du constructeur. Cette première partie C9.A/14 contient les chapitres suivants: - Joints de poutres par plaque frontale en acier S235 et S355 - Assemblages par gousset en acier S235 et S355 Les Tables contiennent des données relatives à la géométrie ainsi que les valeurs de calcul correspondantes des résistances ultimes des assemblages ; elles remplacent le chapitre « Assemblages par plaques frontales et boulons HR » des anciennes Tables C9.1 de 1983 / 2002. Le calcul de ces assemblages par plaque frontale est basé sur les hypothèses du modèle de la méthode des composants décrite dans la norme SN EN 1993-1-8. Les vérifications sont effectuées selon la norme SIA 263:2013. Les assemblages par gousset remplacent les assemblages par double cornière, (telle...

  5. Differences in stability of seed-associated microbial assemblages in response to invasion by phytopathogenic microorganisms

    Directory of Open Access Journals (Sweden)

    Samir Rezki

    2016-04-01

    Full Text Available Seeds are involved in the vertical transmission of microorganisms from one plant generation to another and consequently act as reservoirs for the plant microbiota. However, little is known about the structure of seed-associated microbial assemblages and the regulators of assemblage structure. In this work, we have assessed the response of seed-associated microbial assemblages of Raphanus sativus to invading phytopathogenic agents, the bacterial strain Xanthomonas campestris pv. campestris (Xcc 8004 and the fungal strain Alternaria brassicicola Abra43. According to the indicators of bacterial (16S rRNA gene and gyrB sequences and fungal (ITS1 diversity employed in this study, seed transmission of the bacterial strain Xcc 8004 did not change the overall composition of resident microbial assemblages. In contrast seed transmission of Abra43 strongly modified the richness and structure of fungal assemblages without affecting bacterial assemblages. The sensitivity of seed-associated fungal assemblage to Abra43 is mostly related to changes in relative abundance of closely related fungal species that belong to the Alternaria genus. Variation in stability of the seed microbiota in response to Xcc and Abra43 invasions could be explained by differences in seed transmission pathways employed by these micro-organisms, which ultimately results in divergence in spatio-temporal colonization of the seed habitat.

  6. Viral assemblage composition in Yellowstone acidic hot springs assessed by network analysis.

    Science.gov (United States)

    Bolduc, Benjamin; Wirth, Jennifer F; Mazurie, Aurélien; Young, Mark J

    2015-10-01

    Understanding of viral assemblage structure in natural environments remains a daunting task. Total viral assemblage sequencing (for example, viral metagenomics) provides a tractable approach. However, even with the availability of next-generation sequencing technology it is usually only possible to obtain a fragmented view of viral assemblages in natural ecosystems. In this study, we applied a network-based approach in combination with viral metagenomics to investigate viral assemblage structure in the high temperature, acidic hot springs of Yellowstone National Park, USA. Our results show that this approach can identify distinct viral groups and provide insights into the viral assemblage structure. We identified 110 viral groups in the hot springs environment, with each viral group likely representing a viral family at the sub-family taxonomic level. Most of these viral groups are previously unknown DNA viruses likely infecting archaeal hosts. Overall, this study demonstrates the utility of combining viral assemblage sequencing approaches with network analysis to gain insights into viral assemblage structure in natural ecosystems.

  7. Influence of a large dam on the longitudinal patterns of fish assemblages in Qingyi Stream.

    Science.gov (United States)

    Sui, Xiao-Yun; Lu, Zhi; Yan, Yun-Zhi; Chen, Yi-Feng; Jia, Yin-Tao

    2014-09-01

    Using seasonally collected data (2009-2010) from 15 sampling sites that represent first- to fifth-order streams within the Qingyi watershed, we examined the spatio-temporal patterns of fish assemblages along two longitudinal gradients to explore the effects of a large dam on fish assemblages at the watershed scale. No significant variation was observed in either species richness or assemblage structure across seasons. Species richness significantly varied according to stream order and gradient. Dam construction appeared to decrease species richness upstream substantially, while a significant decrease between gradients only occurred within fourth-order streams. Along the gradient without the large dam, fish assemblage structures presented distinct separation between two neighboring stream orders, with the exception of fourth-order versus fifth-order streams. However, the gradient disrupted by a large dam displayed the opposite pattern in the spatial variation of fish assemblages related with stream orders. Significant between-gradient differences in fish assemblage structures were only observed within fourth-order streams. Species distributions were determined by local habitat environmental factors, including elevation, substrate, water depth, current discharge, wetted width, and conductivity. Our results suggested that dam construction might alter the longitudinal pattern in fish species richness and assemblage structure in Qingyi Stream, despite the localized nature of the ecological effect of dams.

  8. Are soil mite assemblages structured by the identity of native and invasive alien grasses?

    Science.gov (United States)

    St John, Mark G; Wall, Diana H; Hunt, H William

    2006-05-01

    Associations between plants and animals in aboveground communities are often predictable and specific. This has been exploited for the purposes of estimating the diversity of animal species based on the diversity of plant species. The introduction of invasive alien plants into an ecosystem can result in dramatic changes in both the native plant and animal assemblages. Few data exist at the species level to determine whether belowground animal assemblages share the same degree of association to plants. The hypotheses that soil mites (Acari) form assemblages specifically associated with different native grass species in an unmanipulated natural ecosystem and that invasive alien grasses will impact soil mite assemblage composition in this setting were tested. Soil mites sampled beneath five native and two invasive alien species of grasses at the Konza Prairie Biological Station, Kansas, USA, were similarly abundant, species rich, diverse, and taxonomically distinct. No mite species had affinities for a specific grass species. There was no evidence from analysis of similarity, canonical correspondence analysis, or a nonparametric assemblage analysis that the assemblage composition of soil mites was specific to grass species. Results suggest that soil mite assemblages were more related to characteristics of the plant assemblage as a whole or prevailing soil conditions. The most recent invasive alien grass did not support a successionally younger mite fauna, based on the ratio of mesostigmatid to oribatid mites, and neither of the two invasive grasses influenced mite assemblage structure, possibly because they had not yet substantially altered the soil environment. Our results suggest that extrapolations of soil mite diversity based on assumptions of plant specificity would be invalid.

  9. Aquatic insect assemblages associated with subalpine stream segment types in relict glaciated headwaters

    Science.gov (United States)

    Kubo, Joshua S.; Torgersen, Christian E.; Bolton, Susan M.; Weekes, Anne A.; Gara, Robert I.

    2013-01-01

    1. Aquatic habitats and biotic assemblages in subalpine headwaters are sensitive to climate and human impacts. Understanding biotic responses to such perturbations and the contribution of high-elevation headwaters to riverine biodiversity requires the assessment of assemblage composition among habitat types. We compared aquatic insect assemblages among headwater stream segment types in relict glaciated subalpine basins in Mt. Rainier National Park, Washington, USA. 2. Aquatic insects were collected during summer and autumn in three headwater basins. In each basin, three different stream segment types were sampled: colluvial groundwater sources, alluvial lake inlets, and cascade-bedrock lake outlets. Ward's hierarchical cluster analysis revealed high β diversity in aquatic insect assemblages, and non-metric multidimensional scaling indicated that spatial and temporal patterns in assemblage composition differed among headwater stream segment types. Aquatic insect assemblages showed more fidelity to stream segment types than to individual basins, and the principal environmental variables associated with assemblage structure were temperature and substrate. 3. Indicator species analyses identified specific aquatic insects associated with each stream segment type. Several rare and potentially endemic aquatic insect taxa were present, including the recently described species, Lednia borealis (Baumann and Kondratieff). 4. Our results indicate that aquatic insect assemblages in relict glaciated subalpine headwaters were strongly differentiated among stream segment types. These results illustrate the contribution of headwaters to riverine biodiversity and emphasise the importance of these habitats for monitoring biotic responses to climate change. Monitoring biotic assemblages in high-elevation headwaters is needed to prevent the potential loss of unique and sensitive biota.

  10. Consistency of temporal and habitat-related differences among assemblages of fish in coastal lagoons

    Science.gov (United States)

    Gray, Charles A.; Rotherham, Douglas; Johnson, Daniel D.

    2011-12-01

    The consistency of habitat-related differences in coastal lagoon fish assemblages was assessed across different spatial and temporal scales. Multimesh gillnets were used to sample assemblages of fish on a monthly basis for 1-year in three habitats (shallow seagrass, shallow bare and deep substrata) at two locations (>1 km apart), in each of two coastal lagoons (approximately 500 km apart), in southeastern Australia. A total of 48 species was sampled with 34 species occurring in both lagoons and in all three habitats; species caught in only one lagoon or habitat occurred in low numbers. Ten species dominated assemblages and accounted for more than 83% of all individuals sampled. In both lagoons, assemblages in the deep habitat consistently differed to those in the shallow strata (regardless of habitat). Several species were caught more frequently or in larger numbers in the deep habitat. Assemblages in the two shallow habitats did not differ consistently and were dominated by the same species and sizes of fish, possibly due to habitat heterogeneity and the scale and method of sampling. Within each lagoon, very few between location differences in assemblages within each habitat were observed. Consistent differences in assemblages were detected between lagoons for the shallow bare and deep habitats, indicating there were some intrinsic differences in ichthyofauna between lagoons. Assemblages in spring differed to those in summer, which differed to those in winter for the shallow bare habitat in both lagoons, and the deep habitat in only one lagoon. Fish-habitat relationships are complex and differences in the fish fauna between habitats were often temporally inconsistent. This study highlights the need for greater testing of habitat relationships in space and time to assess the generality of observations and to identify the processes responsible for structuring assemblages.

  11. Pampean lizard assemblage from subtropical Brazil: a temporal analysis

    Directory of Open Access Journals (Sweden)

    Gisele R. Winck

    2011-12-01

    Full Text Available The increasing human occupation of natural environments is one of the greatest threats to biodiversity. To mitigate the negative anthropogenic effects, it is necessary to understand the characteristics of natural populations and the natural history of species. A study was conducted with an assemblage of lizards from a disturbed area of the Pampa biome, from February 2001 to January 2004. The assemblage showed a unimodal seasonal pattern, with the recruitment period occurring during the warmer months. The captures were seasonal for two of the three monitored years, and concentrated within warmer months. The minimum temperature explained the number of catches for the assemblage as a whole. However, when the species were analyzed individually, the temperature only explained the seasonal occurrence of Teius oculatus. The abundance of species was significantly different in the third year of study for Cercosaura schreibersii and Ophiodes striatus. This latter species was no longer registered in the study area from May 2003 until the end of the study. Therefore, O. striatus may be more sensitive to environmental changes, considering the events of change in vegetation during the study. With frequent and increasing environmental disturbances, it is necessary to take conservation measures and encourage the increase of knowledge on Pampean lizards.O crescimento da ocupação humana sobre ambientes naturais é uma das maiores ameaças à biodiversidade. Para amenizar os efeitos negativos antropogênicos, é necessário entender as características das populações naturais, e a história natural das espécies. Um estudo foi conduzido com uma assembeia de lagartos de uma área perturbada do Pampa, de fevereiro de 2002 a janeiro de 2004. A assembleia apresentou padrão sazonal unimodal, com recrutamento ocorrendo durante os meses mais quentes. As capturas foram sazonais durante dois dos três anos monitorados, e concentradas nos meses mais quentes. A

  12. Identification of a novel assemblage G subgenotype and a zoonotic assemblage B in rodent isolates of Giardia duodenalis in the Canary Islands, Spain.

    Science.gov (United States)

    Fernández-Álvarez, Ángela; Martín-Alonso, Aarón; Abreu-Acosta, Néstor; Feliu, Carlos; Hugot, Jean-Pierre; Valladares, Basilio; Foronda, Pilar

    2014-02-01

    The flagellated parasite Giardia duodenalis is known as one of the most common causes of protozoal diarrhoea in both humans and animals worldwide. The aim of the present work was to perform the first study of G. duodenalis in rodents in the Canary Islands (Spain) and analyse the level of genetic variation and the potential zoonotic role of the isolates. Stool samples were collected from 284 wild rodents and Giardia cysts were detected by light microscopy. The overall prevalence of giardiasis was 25 · 4% and ranged from 19 · 4% in El Hierro to 34% in Gran Canaria. Positive samples were further characterized by PCR and nucleotide sequencing of the triose phosphate isomerase (TPI), β-giardin (BG) and glutamate dehydrogenase (GDH) genes. Our study revealed assemblage G as the most frequent genotype and identified two rodent-infecting G. duodenalis haplotypes of this assemblage, HI and HII. Phylogenetic analysis supported the monophyly of haplotype HI, which we suggest to be considered as a novel G. duodenalis sub-assemblage GII, due to the high genetic distances among this sub-genotype and assemblage G. Furthermore, G. duodenalis assemblage B was detected in an inhabited area in La Palma, a fact that may pose a potential risk of G. duodenalis transmission from rodents to humans.

  13. Decomposition rates and termite assemblage composition in semiarid Africa

    Science.gov (United States)

    Schuurman, G.

    2005-01-01

    Outside of the humid tropics, abiotic factors are generally considered the dominant regulators of decomposition, and biotic influences are frequently not considered in predicting decomposition rates. In this study, I examined the effect of termite assemblage composition and abundance on decomposition of wood litter of an indigenous species (Croton megalobotrys) in five terrestrial habitats of the highly seasonal semiarid Okavango Delta region of northern Botswana, to determine whether natural variation in decomposer community composition and abundance influences decomposition rates. 1 conducted the study in two areas, Xudum and Santawani, with the Xudum study preceding the Santawani study. I assessed termite assemblage composition and abundance using a grid of survey baits (rolls of toilet paper) placed on the soil surface and checked 2-4 times/month. I placed a billet (a section of wood litter) next to each survey bait and measured decomposition in a plot by averaging the mass loss of its billets. Decomposition rates varied up to sixfold among plots within the same habitat and locality, despite the fact that these plots experienced the same climate. In addition, billets decomposed significantly faster during the cooler and drier Santawani study, contradicting climate-based predictions. Because termite incidence was generally higher in Santawani plots, termite abundance initially seemed a likely determinant of decomposition in this system. However, no significant effect of termite incidence on billet mass loss rates was observed among the Xudum plots, where decomposition rates remained low even though termite incidence varied considerably. Considering the incidences of fungus-growing termites and non-fungus-growing termites separately resolves this apparent contradiction: in both Santawani and Xudum, only fungus-growing termites play a significant role in decomposition. This result is mirrored in an analysis of the full data set of combined Xudum and Santawani data

  14. Diatom assemblage in a tropical lake of northeastern Brazil

    Directory of Open Access Journals (Sweden)

    Lilian Rodrigues do Nascimento

    2010-02-01

    Full Text Available The composition and spatial variation of diatom assemblage in surface sediments of Caçó Lake (shallow, mesotrophic and weakly acid lake - Maranhão State, Brazil were analyzed in order to know the distribution pattern of the species along the lake during rainy season (April 1999. Four zones were established in the lake based on 21 diatoms species and habitat affinities. The first three zones (prime three meters deep to six meters deep were marked by the occurrence of Pinnularia gigas, Frustulia rhomboides, Encyonopsis krasskei, Eunotia camelus, E. femoriformis and E. monodon. Zone IV (seven to nine meters deep was inhabited mainly by Surirella biseriata and Fragilariforma floridana. During the beginning of the rainy season, the diatom assemblage in Caçó Lake was composed mainly by benthic and epiphytic forms that reflected the low lake levels and the abundance of littoral vegetation present in this lake.Com o objetivo de se conhecer a dinâmica espacial e a distribuição das diatomáceas contidas no sedimento superficial do lago Caçó, durante o período de chuvas (abril de 1999 foram realizadas coletas em um "transect" horizontal. A partir da observação destas coletas efetuadas a cada 1 metro pode-se observar que a distribuição das diatomáceas esteve fortemente ligada a ocorrência do banco de macrófitas da sua margem, com a ocorrência maciça das espécies epifíticas e bentônicas. A análise de agrupamento de dados permitiu uma melhor visualização, da sua distribuição a cada profundidade e também das associações específicas em cada zona. Os resultados deste estudo permitiram concluir que a ocorrência e distribuição das diatomáceas do Lago Caçó está fortemente ligada ao banco de macrófitas localizado em suas margens, definindo assim zonas características dentro do lago.

  15. Vertical stratification of the termite assemblage in a neotropical rainforest.

    Science.gov (United States)

    Roisin, Yves; Dejean, Alain; Corbara, Bruno; Orivel, Jerôme; Samaniego, Mirna; Leponce, Maurice

    2006-08-01

    The importance of termites as decomposers in tropical forests has long been recognized. Studies on the richness and diversity of termite species and their ecological function have flourished in more recent times, but these have been mostly conducted in a thin stratum within a standing man's reach. Our aims were to evaluate the specific richness and composition of the termite assemblage in the canopy of a tropical rainforest and to determine its originality with respect to the sympatric ground-level fauna. We conducted systematic searches for canopy termites, together with conventional sampling of the sympatric ground-level fauna, in the San Lorenzo forest, Panama. We hypothesized that (1) the canopy accommodates two categories of wood-feeding termites (long-distance foragers and small-colony "one-piece" species) and possibly soil-feeders in suspended soil-like habitats; (2) due to the abundance of soil-feeders, the overall diversity of the ground fauna is higher than that of the canopy; (3) differences in microclimate and resource accessibility favour vertical stratification among wood-feeders. Sixty-three canopy samples yielded ten species of termites, all wood-feeders. Five of these were not found at ground level, although a total of 243 ground samples were collected, representing 29 species. In addition to long-distance foragers (Microcerotermes and Nasutitermes spp.) and small-colony termites (mostly Kalotermitidae), the canopy fauna included Termes hispaniolae, a wood-feeding Termitidae from an allegedly soil-feeding genus, living in large dead branches. Soil-feeders were absent from the canopy, probably because large epiphytes were scarce. As predicted, the ground fauna was much richer than that of the canopy, but the species richness of both habitats was similar when only wood-feeders were considered. Vertical stratification was strongly marked among wood-feeders, as all common species, apart from the arboreal-nesting Microcerotermes arboreus, could

  16. Multi-regional synthesis of temporal trends in biotic assemblages in streams and rivers of the continental United States

    Science.gov (United States)

    Miller, Matthew P.; Brasher, Anne M.D.; Keenen, Jonathan G.

    2013-01-01

    Biotic assemblages in aquatic ecosystems are excellent integrators and indicators of changing environmental conditions within a watershed. Therefore, temporal changes in abiotic environmental variables often can be inferred from temporal changes in biotic assemblages. Algae, macroinvertebrate, and fish assemblage data were collected from 91 sampling sites in 4 geographic regions (northeastern/north-central, southeastern, south-central, and western), collectively encompassing the continental United States, from 1993 to 2009 as part of the U.S. Geological Survey National Water-Quality Assessment Program. This report uses a multivariate approach to synthesize temporal trends in biotic assemblages and correlations with relevant abiotic parameters as a function of biotic assemblage, geographic region, and land use. Of the three groups of biota, algal assemblages had temporal trends at the greatest percentage of sites. Of the regions, a greater percentage of sites in the northeastern/north-central and western regions had temporal trends in biotic assemblages. In terms of land use, a greater percentage of watersheds draining agricultural, urban, and undeveloped areas had significant temporal changes in biota, as compared to watersheds with mixed use. Correlations between biotic assemblages and abiotic variables indicate that, in general, macroinvertebrate assemblages correlated with water quality and fish assemblages correlated with physical habitat. Taken together, results indicate that there are regional differences in how individual biotic assemblages (algae, macroinvertebrates, and fish) respond to different abiotic drivers of change.

  17. Flow of Fluid and Particle Assemblages in Rotating Systems

    Science.gov (United States)

    Kizito, John; Hiltner, David; Niederhaus, Charles; Kleis, Stanley; Hudson, Ed; Gonda, Steve

    2004-01-01

    NASA-designed bioreactors have been highly successful in growing three-dimensional tissue structures in a low shear environment both on earth and in space. The goal of the present study is to characterize the fluid flow environment within the HFB-S bioreactor and determine the spatial distribution of particles that mimic cellular tissue structures. The results will be used to obtain optimal operating conditions of rotation rates and media perfusehnfuse rates which are required for cell culture growth protocols. Two types of experiments have been performed so far. First, we have performed laser florescent dye visualization of the perfusion loop to determine the mixing times within the chamber. The second type of experiments involved particles which represent cellular tissue to determine the spatial distribution with the chamber. From these experiments we established that mixing times were largely dependant on the speed ratio and sign of the difference between the spinner and the dome. The shortest mixing times occurred when the spinner rotates faster than the dome and longest mixing times occurs with no relative motion between the dome and spinner. Also, we have determined the spatial and temporal distribution of particle assemblages within the chamber.

  18. Continental drift and climate change drive instability in insect assemblages.

    Science.gov (United States)

    Li, Fengqing; Tierno de Figueroa, José Manuel; Lek, Sovan; Park, Young-Seuk

    2015-06-17

    Global change has already had observable effects on ecosystems worldwide, and the accelerated rate of global change is predicted in the future. However, the impacts of global change on the stability of biodiversity have not been systematically studied in terms of both large spatial (continental drift) and temporal (from the last inter-glacial period to the next century) scales. Therefore, we analyzed the current geographical distribution pattern of Plecoptera, a thermally sensitive insect group, and evaluated its stability when coping with global change across both space and time throughout the Mediterranean region--one of the first 25 global biodiversity hotspots. Regional biodiversity of Plecoptera reflected the geography in both the historical movements of continents and the current environmental conditions in the western Mediterranean region. The similarity of Plecoptera assemblages between areas in this region indicated that the uplift of new land and continental drift were the primary determinants of the stability of regional biodiversity. Our results revealed that climate change caused the biodiversity of Plecoptera to slowly diminish in the past and will cause remarkably accelerated biodiversity loss in the future. These findings support the theory that climate change has had its greatest impact on biodiversity over a long temporal scale.

  19. Simplification of arboreal marsupial assemblages in response to increasing urbanization.

    Directory of Open Access Journals (Sweden)

    Bronwyn Isaac

    Full Text Available Arboreal marsupials play an essential role in ecosystem function including regulating insect and plant populations, facilitating pollen and seed dispersal and acting as a prey source for higher-order carnivores in Australian environments. Primarily, research has focused on their biology, ecology and response to disturbance in forested and urban environments. We used presence-only species distribution modelling to understand the relationship between occurrences of arboreal marsupials and eco-geographical variables, and to infer habitat suitability across an urban gradient. We used post-proportional analysis to determine whether increasing urbanization affected potential habitat for arboreal marsupials. The key eco-geographical variables that influenced disturbance intolerant species and those with moderate tolerance to disturbance were natural features such as tree cover and proximity to rivers and to riparian vegetation, whereas variables for disturbance tolerant species were anthropogenic-based (e.g., road density but also included some natural characteristics such as proximity to riparian vegetation, elevation and tree cover. Arboreal marsupial diversity was subject to substantial change along the gradient, with potential habitat for disturbance-tolerant marsupials distributed across the complete gradient and potential habitat for less tolerant species being restricted to the natural portion of the gradient. This resulted in highly-urbanized environments being inhabited by a few generalist arboreal marsupial species. Increasing urbanization therefore leads to functional simplification of arboreal marsupial assemblages, thus impacting on the ecosystem services they provide.

  20. Hospitality within hospital meals—Socio-material assemblages

    DEFF Research Database (Denmark)

    Justesen, Lise; Gyimóthy, Szilvia; Mikkelsen, Bent E.

    2016-01-01

    Hospital meals and their role in nutritional care have been studied primarily from a life and natural science perspective. This article takes a different approach and explores the idea of hospitality inspired by Jacques Derrida’s work on the ontology of hospitality. By drawing on ethnographic fie...... and management involved in hospital food service and in nutritional care to work more systematically with the environment for improved hospital meal experiences in the future......Hospital meals and their role in nutritional care have been studied primarily from a life and natural science perspective. This article takes a different approach and explores the idea of hospitality inspired by Jacques Derrida’s work on the ontology of hospitality. By drawing on ethnographic...... fieldwork in a Danish hospital, hospitality practices were studied using a socio-material assemblage approach. The study showed that rethinking the meal event could change the wards into temporary “pop-up-restaurants,” transcending the hospital context and providing a scene for shifting host...

  1. Simplification of Arboreal Marsupial Assemblages in Response to Increasing Urbanization

    Science.gov (United States)

    Isaac, Bronwyn; White, John; Ierodiaconou, Daniel; Cooke, Raylene

    2014-01-01

    Arboreal marsupials play an essential role in ecosystem function including regulating insect and plant populations, facilitating pollen and seed dispersal and acting as a prey source for higher-order carnivores in Australian environments. Primarily, research has focused on their biology, ecology and response to disturbance in forested and urban environments. We used presence-only species distribution modelling to understand the relationship between occurrences of arboreal marsupials and eco-geographical variables, and to infer habitat suitability across an urban gradient. We used post-proportional analysis to determine whether increasing urbanization affected potential habitat for arboreal marsupials. The key eco-geographical variables that influenced disturbance intolerant species and those with moderate tolerance to disturbance were natural features such as tree cover and proximity to rivers and to riparian vegetation, whereas variables for disturbance tolerant species were anthropogenic-based (e.g., road density) but also included some natural characteristics such as proximity to riparian vegetation, elevation and tree cover. Arboreal marsupial diversity was subject to substantial change along the gradient, with potential habitat for disturbance-tolerant marsupials distributed across the complete gradient and potential habitat for less tolerant species being restricted to the natural portion of the gradient. This resulted in highly-urbanized environments being inhabited by a few generalist arboreal marsupial species. Increasing urbanization therefore leads to functional simplification of arboreal marsupial assemblages, thus impacting on the ecosystem services they provide. PMID:24608165

  2. Re-Equilibration Processes in Fluid Inclusion Assemblages

    Directory of Open Access Journals (Sweden)

    Ronald J. Bakker

    2017-07-01

    Full Text Available Post-entrapment modifications reduce the reliability of fluid inclusions to determine trapping conditions in rock. Processes that may modify fluid inclusion properties are experimentally identified in this study using synthetic fluid inclusions in quartz with a well-defined composition and density. Modifications are characterized with microthermometry (homogenization and dissolution temperatures and Raman-spectroscopy in binary fluid systems H2O-D2O and H2O-NaCl. Three distinct processes were identified in this study: (1 diffusion of H2O and D2O; (2 crystal-recovery, expulsion of H2O and accumulation of quartz in inclusions (preferential H2O loss; (3 irreversible total volume increase at the α-β quartz transition. Diffusion is caused by H2O fugacity gradients and can be modelled according to classical diffusion models. The variability of re-equilibrated properties in fluid inclusion assemblages depends on time, temperature, diffusion distance and the size of fluid inclusions. Negative pressure gradients (internal under-pressure induce the crystal-recovery process, in which H2O is preferentially extracted from inclusions that simultaneously shrink by the inward growth of quartz. This process reduces the H2O concentration and increases the fluid density by total volume loss. Temperature and time are also controlling factors of this process, which is able to transport H2O against fugacity gradients.

  3. A postglacial coleopterous assemblage from Lockport Gulf, New York

    Science.gov (United States)

    Miller, Randy F.; Morgan, Alan V.

    1982-03-01

    The Lockport Gulf site near Lockport, New York, is a 1.9-m sequence of organic-rich marls having a basal date of approximately 10,920 yr B.P. Six bulk samples with a combined weight of 48 kg produced over 780 individual fossil insects representing five orders, as well as molluscs and abundant plant macrofossils. Coleoptera were represented by 24 families. Several major beetle groups (Carabidae, ground beetles; Hydrophilidae, water scavenger beetles; Elmidae, riffle beetles; Staphylinidae, rove beetles; and Scolytidae, bark beetles) indicate a riffle-and-pool stream, surrounded by marsh, with open riparian habitats and nearby trees. Two zones were recognized based on the Coleoptera assemblages. The Zone 1 fauna (ca. 10,920-9800 yr B.P.) was dominated by boreal forest taxa with abundant bark beetles indicating the presence of spruce trees. In Zone 2 (ca. 9700-9100 yr B.P.) the combination of species with a restricted modern distribution in the Great Lakes-St. Lawrence Forest region and pine and deciduous tree inhabitants suggests a change in vegetation by 9700 yr B.P. Thermal estimates from a faunal analysis indicate that the climatic conditions were stable across the spruce-pine transition, with the mean July temperature in the range of 16° to 18°C.

  4. Response of neotropical bat assemblages to human land use.

    Science.gov (United States)

    García-Morales, Rodrigo; Badano, Ernesto I; Moreno, Claudia E

    2013-10-01

    Neotropical bats are sensitive to human-induced habitat changes, and some authors believe bats can be used as bioindicators. In the literature, however, the results are disparate. Some results show bat diversity deceases as disturbance increases, whereas others indicate no effect. Determining the general response patterns of bats when they encounter different degrees of human-induced disturbance across the Neotropics would help to determine their usefulness as bioindicators. In a series of meta-analyses, we compared the occurrence frequency of bat species between well-preserved forests and human-use areas. We obtained data through an extensive review of published peer-reviewed articles, theses, and reports. The overall effect size indicated that human-use areas harbored more bat species than well-preserved forests. Different response patterns emerged when meta-analyses were conducted separately by family, feeding habit, vegetation stratum, and conservation status. Our results suggest that bat assemblages display strong responses to forest loss and land-use change and that the direction and magnitude of these responses depends on the bat group under study and the type of disturbance. Our results are consistent with the idea that bats are useful for assessing the effects of habitat changes in the Neotropics. However, with our meta-analyses we could not detect fine differences in bat feeding habits, especially within Phyllostomidae, or elucidate the effect of landscape configuration. © 2013 Society for Conservation Biology.

  5. Coexistence in a multispecies assemblage of eagles in central Asia

    Science.gov (United States)

    Katzner, T.E.; Bragin, E.A.; Knick, S.T.; Smith, A.T.

    2003-01-01

    We evaluated factors that permit species coexistence in an exceptional assemblage of similar raptor species at the Naurzum Zapovednik (a national nature reserve) in north-central Kazakhstan. White-tailed Sea-Eagle (Haliaeetus albicilla), Imperial Eagle (Aquila heliaca), Golden Eagle (A. chrysaetos), and Steppe Eagle (A. nipalensis) all breed at the Zapovednik. Steppe Eagle use of nesting resources was distinct from that of tree-nesting species. We evaluated differences in nest tree and nest habitat characteristics, nest dimensions and positions, and nest spacing among the three forest-dwelling eagle species to distinguish between the effects of inter- and intraspecific resource limitations on species coexistence. Although the different species bred in similar habitat and sometimes reused other species' nests, the dimensions, positions and locations of their nests often differed. These differences did not appear to result from interspecific competition. Nest spacing trends were also species specific; Imperial Eagles generally nested farther from other eagle nests than did Golden Eagles and White-tailed Sea-Eagles. Intraspecific variation in habitat, physical characteristics, and spacing patterns of Imperial Eagle nests was extensive throughout the nature reserve. Although interspecific partitioning of nesting habitat may allow coexistence of ground-nesting Steppe Eagles, interspecific competition did not appear to be a primary determinant of the use of nest habitat, space, or nests by tree-nesting species. Rather, interspecific effects appeared secondary to intraspecific effects in determining coexistence of tree-nesting eagles at this site.

  6. Asian longhorned beetle complicates the relationship between taxonomic diversity and pest vulnerability in street tree assemblages

    Data.gov (United States)

    U.S. Environmental Protection Agency — Urban foresters routinely emphasise the importance of taxonomic diversity to reduce the vulnerability of tree assemblages to invasive pests, but it is unclear to...

  7. Tidal Channel Diatom Assemblages Reflect within Wetland Environmental Conditions and Land Use at Multiple Scales

    Science.gov (United States)

    We characterized regional patterns of the tidal channel benthic diatom community and examined the relative importance of local wetland and surrounding landscape level factors measured at multiple scales in structuring this assemblage. Surrounding land cover was characterized at ...

  8. Coral reef fish assemblages along a disturbance gradient in the northern Persian Gulf: A seasonal perspective.

    Science.gov (United States)

    Ghazilou, Amir; Shokri, Mohammad Reza; Gladstone, William

    2016-04-30

    Seasonal dynamics of coral reef fish assemblages were assessed along a gradient of potential anthropogenic disturbance in the Northern Persian Gulf. Overall, the attributes of coral reef fish assemblages showed seasonality at two different levels: seasonal changes irrespective of the magnitude of disturbance level (e.g. species richness), and seasonal changes in response to disturbance level (e.g. total abundance and assemblage composition). The examined parameters mostly belonged to the second group, but the interpretation of the relationship between patterns of seasonal changes and the disturbance level was not straightforward. The abundance of carnivorous fishes did not vary among seasons. SIMPER identified the family Nemipteridae as the major contributor to the observed spatiotemporal variations in the composition of coral reef fish assemblages in the study area. Copyright © 2015 Elsevier Ltd. All rights reserved.

  9. Effects of immune supplementation and immune challenge on bacterial assemblages in the avian cloaca

    NARCIS (Netherlands)

    Matson, Kevin D.; Versteegh, Maaike A.; van der Velde, Marco; Tieleman, B. Irene

    Relationships between avian physiology and bacterial assemblages in the cloaca are poorly understood. We used molecular techniques to analyze cloacal swabs from pigeons that were subjected to two immunological manipulations: lysozyme supplementation and endotoxin challenge. From the swabs, we

  10. Landform-Sediment Assemblages Units of the Upper Mississippi River Valley

    Data.gov (United States)

    Iowa State University GIS Support and Research Facility — Wisconsinan and Holocene Landform-Sediment Assemblages of the Upper Mississippi River Valley. Knowledge of the spatial distribution of natural and cultural resources...

  11. Partitioning taxonomic diversity of aquatic insect assemblages and functional feeding groups in Neotropical Savanna headwater streams

    Science.gov (United States)

    Biological diversity can be divided into: alpha (α, local), beta (β, difference in assemblage composition among locals), and gamma (γ, total diversity). We assessed the partitioning of taxonomic diversity of Ephemeroptera, Plecoptera and Trichoptera (EPT) and of functional feedin...

  12. Environmental indicators of macroinvertebrate and fish assemblage integrity in urbanizing watersheds

    Science.gov (United States)

    Urbanization compromises the biotic integrity and health of streams, and indicators of integrity loss are needed to improve assessment programs and identify mechanisms of urban effects. We investigated linkages between landscapes and assemblages in 31 wadeable Piedmont streams i...

  13. Partitioning taxonomic diversity of aquatic insect assemblages and functional feeding groups in Neotropical Savanna headwater streams

    Science.gov (United States)

    Biological diversity can be divided into: alpha (α, local), beta (β, difference in assemblage composition among locals), and gamma (γ, total diversity). We assessed the partitioning of taxonomic diversity of Ephemeroptera, Plecoptera and Trichoptera (EPT) and of ...

  14. Surface water connectivity drives richness and composition of Arctic lake fish assemblages

    Science.gov (United States)

    Laske, Sarah M.; Haynes, Trevor B.; Rosenberger, Amanda E.; Koch, Joshua C.; Wipfli, Mark S.; Whitman, Matthew; Zimmerman, Christian E.

    2016-01-01

    Surface water connectivity can influence the richness and composition of fish assemblages, particularly in harsh environments where colonisation factors and access to seasonal refugia are required for species persistence.

  15. Functional diversity of macrobenthic assemblages decreases in response to sewage discharges

    NARCIS (Netherlands)

    Gusmao, Joao B.; Brauko, Kalina M.; Eriksson, Britas K.; Lana, Paulo C.

    We analyzed the effects of sewage discharge on a subtropical estuary by comparing the functional diversity of intertidal macroinvertebrate assemblages in contaminated with non-contaminated reference areas. Functional structure was assessed using biological traits analysis (BTA) and four multivariate

  16. Macrobenthic assemblage in the soft sediment of Marmugao Harbour, Goa (central west coast of India)

    Digital Repository Service at National Institute of Oceanography (India)

    Ansari, Z.A.; Sreepada, R.A.; Kanti, A.; Gracias, E.S.

    Survey of the macroinvertebrate fauna in soft sediment of 18 stations in the Marmugao Harbour revealed spatial heterogeneity based on environmental parameters and benthic assemblage. Based on the presence/absence of the families five associations...

  17. ANALISIS PERMUKIMAN PEMULUNG SEBAGAI SEBUAH ASSEMBLAGE STUDI KASUS: PERMUKIMAN PEMULUNG DI WILAYAH JURANGMANGU, TANGERANG SELATAN

    Directory of Open Access Journals (Sweden)

    Eka Permanasari

    2017-01-01

    There are some research on social and economical condition of informal waste-picker settlements. However, the research on the urban assemblage of informal waste-picker settlements are not very common. Therefore, this research focus on how the social and economical condition shape the informal waste-picker settlements in terms of urban assemblage.   This research investigates the development and transformation of the informal waste-picker settlements in two prime locations in Jurangmangu, South Tangerang. The methods are through observation and interview to key persons (leaders on each settlement. The urban assemblage on these waste-picker settlements is heavily influenced by social and economical condition and activity of their users.   Key words: waste picker settlements, urban assemblage, informality

  18. Leaf and root-associated fungal assemblages do not follow similar elevational diversity patterns.

    Directory of Open Access Journals (Sweden)

    Aurore Coince

    Full Text Available The diversity of fungi along environmental gradients has been little explored in contrast to plants and animals. Consequently, environmental factors influencing the composition of fungal assemblages are poorly understood. The aim of this study was to determine whether the diversity and composition of leaf and root-associated fungal assemblages vary with elevation and to investigate potential explanatory variables. High-throughput sequencing of the Internal Transcribed Spacer 1 region was used to explore fungal assemblages along three elevation gradients, located in French mountainous regions. Beech forest was selected as a study system to minimise the host effect. The variation in species richness and specific composition was investigated for ascomycetes and basidiomycetes assemblages with a particular focus on root-associated ectomycorrhizal fungi. The richness of fungal communities associated with leaves or roots did not significantly relate to any of the tested environmental drivers, i.e. elevation, mean temperature, precipitation or edaphic variables such as soil pH or the ratio carbon∶nitrogen. Nevertheless, the ascomycete species richness peaked at mid-temperature, illustrating a mid-domain effect model. We found that leaf and root-associated fungal assemblages did not follow similar patterns of composition with elevation. While the composition of the leaf-associated fungal assemblage correlated primarily with the mean annual temperature, the composition of root-associated fungal assemblage was explained equally by soil pH and by temperature. The ectomycorrhizal composition was also related to these variables. Our results therefore suggest that above and below-ground fungal assemblages are not controlled by the same main environmental variables. This may be due to the larger amplitude of climatic variables in the tree foliage compared to the soil environment.

  19. The relative importance of regional, local, and evolutionary factors structuring cryptobenthic coral-reef assemblages

    Science.gov (United States)

    Ahmadia, Gabby N.; Tornabene, Luke; Smith, David J.; Pezold, Frank L.

    2018-03-01

    Factors shaping coral-reef fish species assemblages can operate over a wide range of spatial scales (local versus regional) and across both proximate and evolutionary time. Niche theory and neutral theory provide frameworks for testing assumptions and generating insights about the importance of local versus regional processes. Niche theory postulates that species assemblages are an outcome of evolutionary processes at regional scales followed by local-scale interactions, whereas neutral theory presumes that species assemblages are formed by largely random processes drawing from regional species pools. Indo-Pacific cryptobenthic coral-reef fishes are highly evolved, ecologically diverse, temporally responsive, and situated on a natural longitudinal diversity gradient, making them an ideal group for testing predictions from niche and neutral theories and effects of regional and local processes on species assemblages. Using a combination of ecological metrics (fish density, diversity, assemblage composition) and evolutionary analyses (testing for phylogenetic niche conservatism), we demonstrate that the structure of cryptobenthic fish assemblages can be explained by a mixture of regional factors, such as the size of regional species pools and broad-scale barriers to gene flow/drivers of speciation, coupled with local-scale factors, such as the relative abundance of specific microhabitat types. Furthermore, species of cryptobenthic fishes have distinct microhabitat associations that drive significant differences in assemblage community structure between microhabitat types, and these distinct microhabitat associations are phylogenetically conserved over evolutionary timescales. The implied differential fitness of cryptobenthic fishes across varied microhabitats and the conserved nature of their ecology are consistent with predictions from niche theory. Neutral theory predictions may still hold true for early life-history stages, where stochastic factors may be more

  20. Molluscan assemblages on coral reefs and associated hard substrata in the northern Red Sea

    Science.gov (United States)

    Zuschin, M.; Hohenegger, J.; Steininger, F.

    2001-09-01

    Information on spatial variability and distribution patterns of organisms in coral reef environments is necessary to evaluate the increasing anthropogenic disturbance of marine environments (Richmond 1993; Wilkinson 1993; Dayton 1994). Therefore different types of subtidal, reef-associated hard substrata (reef flats, reef slopes, coral carpets, coral patches, rock grounds), each with different coral associations, were investigated to determine the distribution pattern of molluscs and their life habits (feeding strategies and substrate relations). The molluscs were strongly dominated by taxa with distinct relations to corals, and five assemblages were differentiated. The Dendropoma maxima assemblage on reef flats is a discrete entity, strongly dominated by this encrusting and suspension-feeding gastropod. All other assemblages are arranged along a substrate gradient of changing coral associations and potential molluscan habitats. The Coralliophila neritoidea- Barbatia foliata assemblage depends on the presence of Porites and shows a dominance of gastropods feeding on corals and of bivalves associated with living corals. The Chamoidea- Cerithium spp. assemblage on rock grounds is strongly dominated by encrusting bivalves. The Drupella cornus-Pteriidae assemblage occurs on Millepora- Acropora reef slopes and is strongly dominated by bivalves associated with living corals. The Barbatia setigera- Ctenoides annulata assemblage includes a broad variety of taxa, molluscan life habits and bottom types, but occurs mainly on faviid carpets and is transitional among the other three assemblages. A predicted degradation of coral coverage to rock bottoms due to increasing eutrophication and physical damage in the study area (Riegl and Piller 2000) will result in a loss of coral-associated molluscs in favor of bivalve crevice dwellers in dead coral heads and of encrusters on dead hard substrata.

  1. Do arthropod assemblages fit the grassland and savanna biomes of South Africa?

    OpenAIRE

    Monique Botha; Stefan J. Siebert; Johnnie van den Berg

    2016-01-01

    The long-standing tradition of classifying South Africa's biogeographical area into biomes is commonly linked to vegetation structure and climate. Because arthropod communities are often governed by both these factors, it can be expected that arthropod communities would fit the biomes. To test this hypothesis, we considered how well arthropod species assemblages fit South Africa's grassy biomes. Arthropod assemblages were sampled from six localities across the grassland and savanna biomes by ...

  2. Spatial and temporal variation of fish assemblages in a subtropical small stream of the Huangshan Mountain

    Directory of Open Access Journals (Sweden)

    Yunzhi YAN,Shan HE, Ling CHU, Xiuying XIANG, Yanju JIA, Juan TAO, Yifeng CHEN

    2010-12-01

    Full Text Available Spatial and temporal variation of fish assemblages were investigated seasonally from May 2007 to February 2008 across 11 study sites in a subtropical small stream, the Puxi Stream, of the Huangshan Mountain. Along the longitudinal gradient from headwater to downstream, fish species richness and abundance increased gradually, but then decreased significantly at the lower reaches. The highest species richness and abundance were observed in August and the lowest in February. Based on analysis of similarities (ANOSIM, fish assemblages were significantly different in spatial variation but not in temporal variation. Although differences were observed both among sites and among stream orders, the lower R value in order-variation suggested stream order was not the optimal factor explaining the spatial variation of fish assemblages. In addition, dam construction did not significantly alter fish assemblages in the sites adjacent to and immediately downstream to dams. Using cluster analysis and non-metric Multi Dimensional Scaling analysis (NMS, assemblages were separated into three groups at a Bray-Curtis similarity value of 42%: the upper, middle and lower groups. Following analysis of similarity percentages of species contributions (SIMPER, shifts in occurrence or abundance of S. curriculus, Z. platypus, R. bitterling and A. fasciatus contributed most to the differences amongst the three groups. Standard Deviation Redundancy Analysis (RDA suggested that habitat structure (such as elevation, substrate, and flow velocity contributed to the spatial and temporal pattern of fish assemblages in the Puxi Stream. In conclusion, the fish assemblages in Puxi Stream presented significant spatial but not temporal variation. Human disturbance has perhaps induced the decrease in species diversity in the lower reaches. However, no significant change was observed for fish assemblages in sites far from and immediately downstream from low-head dams [Current Zoology 56 (6

  3. Snake assemblages of Marajó Island, Pará state, Brazil

    Directory of Open Access Journals (Sweden)

    Gerson Moreira Rodrigues

    2016-01-01

    Full Text Available ABSTRACT We describe the diversity, natural history and structure of snake assemblages from Marajó Island, state of Pará, Brazil, after analyzing 439 specimens deposited in herpetological collections. We tested the hypothesis that snake assemblages from forest and open areas of Marajó Island are distinct with regard to their structure, composition and functional groups. To compare the snake composition of the forest and open areas of Marajó with other comparable assemblages in Brazil, Principal Coordinate Analysis and Clustering tests were performed. A total of 61 species of snakes was recorded for Marajó, with ten species cited for the first time for the study area (Atractus natans Hoogmoed & Prudente, 2003, A. schach (Boie, 1827, Dendrophidion dendrophis (Schlegel, 1837, Helicops hagmanni Roux, 1910, Hydrops martii (Wagler in Spix, 1824, Lygophis meridionalis (Schenkel, 1901, Erythrolamprus typhlus (Linnaeus, 1758, Philodryas argentea (Daudin, 1803, Siphlophis cervinus (Laurenti, 1768, and Thamnodynastes sp.. The composition and structure of snake assemblages between forested and open were different, with five functional groups of snakes in forest areas, and three groups in open areas, based on habit and habitat. In all, 19 species were exclusive to forest areas, 10 were exclusive to open areas and 26 species were recorded in both areas. Our results revealed greater richness for forested areas, probably due to greater habitat heterogeneity. The species composition for forested area in Marajó was similar to that found in other Amazonian assemblages, while that for open areas was more similar to the Pantanal region than other open area assemblages. The general structure of the snake assemblage of Marajó was dominated by anurophagous, terrestrial and diurnal species. Terrestrial, arboreal and semi-arboreal snakes showed a seasonal offspring production pattern, while the pattern for aquatic and semi-aquatic species was aseasonal. The

  4. Survival of ship biofouling assemblages during and after voyages to the Canadian Arctic.

    Science.gov (United States)

    Chan, Farrah T; MacIsaac, Hugh J; Bailey, Sarah A

    2016-01-01

    Human-mediated vectors often inadvertently translocate species assemblages to new environments. Examining the dynamics of entrained species assemblages during transport can provide insights into the introduction risk associated with these vectors. Ship biofouling is a major transport vector of nonindigenous species in coastal ecosystems globally, yet its magnitude in the Arctic is poorly understood. To determine whether biofouling organisms on ships can survive passages in Arctic waters, we examined how biofouling assemblage structure changed before, during, and after eight round-trip military voyages from temperate to Arctic ports in Canada. Species richness first decreased (~70% loss) and then recovered (~27% loss compared to the original assemblages), as ships travelled to and from the Arctic, respectively, whereas total abundance typically declined over time (~55% total loss). Biofouling community structure differed significantly before and during Arctic transits as well as between those sampled during and after voyages. Assemblage structure varied across different parts of the hull; however, temporal changes were independent of hull location, suggesting that niche areas did not provide protection for biofouling organisms against adverse conditions in the Arctic. Biofouling algae appear to be more tolerant of transport conditions during Arctic voyages than are mobile, sessile, and sedentary invertebrates. Our results suggest that biofouling assemblages on ships generally have poor survivorship during Arctic voyages. Nonetheless, some potential for transporting nonindigenous species to the Arctic via ship biofouling remains, as at least six taxa new to the Canadian Arctic, including a nonindigenous cirripede, appeared to have survived transits from temperate to Arctic ports.

  5. Spatial and seasonal patterns in fish assemblage in Corrego Rico, upper Parana River basin

    Directory of Open Access Journals (Sweden)

    Erico L. H Takahashi

    Full Text Available The upper Paraná River basin drains areas of intensive industry and agriculture, suffering negative impacts. The Córrego Rico flows through sugar cane fields and receives urban wastewater. The aim of this work is to describe and to compare the fish assemblage structure in Córrego Rico. Six standardized bimonthly samples were collected between August 2008 and June 2009 in seven different stretches of Córrego Rico. Fishes were collected with an experimental seine and sieves, euthanized, fixed in formalin and preserved in ethanol for counting and identification. Data were recorded for water parameters, instream habitat and riparian features within each stretch. Non-metric multidimensional scaling, species richness and diversity analysis were performed to examine spatial and seasonal variation in assemblage structure. Fish assemblage structure was correlated with instream habitat and water parameters. The fish assemblage was divided in three groups: upper, middle and lower reaches. High values of richness and diversity were observed in the upper and lower stretches due to connectivity with a small lake and Mogi Guaçu River, respectively. Middle stretches showed low values of richness and diversity suggesting that a small dam in the middle stretch negatively impacts the fish assemblage. Seasonal differences in fish assemblage structure were observed only in the lower stretches.

  6. Structure of Mesophotic Reef Fish Assemblages in the Northwestern Hawaiian Islands.

    Directory of Open Access Journals (Sweden)

    Atsuko Fukunaga

    Full Text Available Mesophotic coral ecosystems (MCEs support diverse communities of marine organisms with changes in community structure occurring along a depth gradient. In recent years, MCEs have gained attention due to their depths that provide protection from natural and anthropogenic stressors and their relative stability over evolutionary time periods, yet ecological structures of fish assemblages in MCEs remain largely un-documented. Here, we investigated composition and trophic structure of reef fish assemblages in the Northwestern Hawaiian Islands (NWHI along a depth gradient from 1 to 67 m. The structure of reef fish assemblages as a whole showed a clear gradient from shallow to mesophotic depths. Fish assemblages at mesophotic depths had higher total densities than those in shallower waters, and were characterized by relatively high densities of planktivores and invertivores and relatively low densities of herbivores. Fishes that typified assemblages at mesophotic depths included six species that are endemic to the Hawaiian Islands. The present study showed that mesophotic reefs in the NWHI support unique assemblages of fish that are characterized by high endemism and relatively high densities of planktivores. Our findings underscore the ecological importance of these undersurveyed ecosystems and warrant further studies of MCEs.

  7. Patterns of Spatial Variation of Assemblages Associated with Intertidal Rocky Shores: A Global Perspective

    Science.gov (United States)

    Cruz-Motta, Juan José; Miloslavich, Patricia; Palomo, Gabriela; Iken, Katrin; Konar, Brenda; Pohle, Gerhard; Trott, Tom; Benedetti-Cecchi, Lisandro; Herrera, César; Hernández, Alejandra; Sardi, Adriana; Bueno, Andrea; Castillo, Julio; Klein, Eduardo; Guerra-Castro, Edlin; Gobin, Judith; Gómez, Diana Isabel; Riosmena-Rodríguez, Rafael; Mead, Angela; Bigatti, Gregorio; Knowlton, Ann; Shirayama, Yoshihisa

    2010-01-01

    Assemblages associated with intertidal rocky shores were examined for large scale distribution patterns with specific emphasis on identifying latitudinal trends of species richness and taxonomic distinctiveness. Seventy-two sites distributed around the globe were evaluated following the standardized sampling protocol of the Census of Marine Life NaGISA project (www.nagisa.coml.org). There were no clear patterns of standardized estimators of species richness along latitudinal gradients or among Large Marine Ecosystems (LMEs); however, a strong latitudinal gradient in taxonomic composition (i.e., proportion of different taxonomic groups in a given sample) was observed. Environmental variables related to natural influences were strongly related to the distribution patterns of the assemblages on the LME scale, particularly photoperiod, sea surface temperature (SST) and rainfall. In contrast, no environmental variables directly associated with human influences (with the exception of the inorganic pollution index) were related to assemblage patterns among LMEs. Correlations of the natural assemblages with either latitudinal gradients or environmental variables were equally strong suggesting that neither neutral models nor models based solely on environmental variables sufficiently explain spatial variation of these assemblages at a global scale. Despite the data shortcomings in this study (e.g., unbalanced sample distribution), we show the importance of generating biological global databases for the use in large-scale diversity comparisons of rocky intertidal assemblages to stimulate continued sampling and analyses. PMID:21179546

  8. Population-based analyses of Giardia duodenalis is consistent with the clonal assemblage structure

    Directory of Open Access Journals (Sweden)

    Takumi Katsuhisa

    2012-08-01

    Full Text Available Abstract Background Giardia duodenalis is a common protozoan parasite of humans and animals. Genetic characterization of single loci indicates the existence of eight groups called assemblages, which differ in their host distribution. Molecular analyses challenged the idea that G. duodenalis is a strictly clonal diplomonad by providing evidence of recombination within and between assemblages. Particularly, inter-assemblage recombination events would complicate the interpretation of multi-locus genotyping data from field isolates: where is a host infected with multiple Giardia genotypes or with a single, recombined Giardia genotype. Methods Population genetic analyses on the single and multiple-locus level on an extensive dataset of G. duodenalis isolates from humans and animals were performed. Results Our analyses indicate that recombination between isolates from different assemblages are apparently very rare or absent in the natural population of Giardia duodenalis. At the multi-locus level, our statistical analyses are more congruent with clonal reproduction and can equally well be explained with the presence of multiple G. duodenalis genotypes within one field isolate. Conclusions We conclude that recombination between G. duodenalis assemblages is either very rare or absent. Recombination between genotypes from the same assemblage and genetic exchange between the nuclei of a single cyst needs further investigation.

  9. Structure of Mesophotic Reef Fish Assemblages in the Northwestern Hawaiian Islands.

    Science.gov (United States)

    Fukunaga, Atsuko; Kosaki, Randall K; Wagner, Daniel; Kane, Corinne

    2016-01-01

    Mesophotic coral ecosystems (MCEs) support diverse communities of marine organisms with changes in community structure occurring along a depth gradient. In recent years, MCEs have gained attention due to their depths that provide protection from natural and anthropogenic stressors and their relative stability over evolutionary time periods, yet ecological structures of fish assemblages in MCEs remain largely un-documented. Here, we investigated composition and trophic structure of reef fish assemblages in the Northwestern Hawaiian Islands (NWHI) along a depth gradient from 1 to 67 m. The structure of reef fish assemblages as a whole showed a clear gradient from shallow to mesophotic depths. Fish assemblages at mesophotic depths had higher total densities than those in shallower waters, and were characterized by relatively high densities of planktivores and invertivores and relatively low densities of herbivores. Fishes that typified assemblages at mesophotic depths included six species that are endemic to the Hawaiian Islands. The present study showed that mesophotic reefs in the NWHI support unique assemblages of fish that are characterized by high endemism and relatively high densities of planktivores. Our findings underscore the ecological importance of these undersurveyed ecosystems and warrant further studies of MCEs.

  10. Coral reef fish assemblages at Clipperton Atoll (Eastern Tropical Pacific and their relationship with coral cover

    Directory of Open Access Journals (Sweden)

    Aurora M. Ricart

    2016-11-01

    Full Text Available Clipperton Atoll, one of the most isolated coral reefs worldwide, is of great scientific interest due to its geomorphology and high levels of endemism. This study explored the reef fish assemblage structure of Clipperton Atoll and its relationship with live coral cover. Nine stations were sampled at three sites and three depths (6, 12 and 20 m around the reef, measuring fish species richness and biomass and hermatypic coral cover (at genus level. We evaluated variation in species richness, biomass and diversity of fish assemblages among sites and depths, as well as the relationship between the entire fish assemblage composition and live coral cover. The results showed that species richness and biomass were similar among sites, but differed across depths, increasing with depth. In contrast, diversity differed among sites but not among depths. Multivariate analyses indicated that fish assemblage composition differed among sites and depths in relation to changes in cover of coral of the genera Pocillopora, Porites, Pavona and Leptoseris, which dominate at different depths. The results showed that fish species richness and diversity were low at Clipperton Atoll and that, in isolated coral reefs with a low habitat heterogeneity and low human disturbance, live coral cover has a significant influence on the spatial variation of the reef fish assemblages. This study highlights the importance of coral habitat structure in shaping coral reef fish assemblages.

  11. Effects of environmental and water quality parameters on the functioning of copepod assemblages in tropical estuaries

    Science.gov (United States)

    Araujo, Adriana V.; Dias, Cristina O.; Bonecker, Sérgio L. C.

    2017-07-01

    We examined changes in the functioning of copepod assemblages with increasing pollution in estuaries, using sampling standardization of the salinity range to enable comparisons. Copepod assemblages were analyzed in four southeast Brazilian estuaries with different water quality levels and hydrodynamic characteristics over two years. We obtained mesozooplankton samples together with environmental and water quality parameters in the estuaries, every two months under predetermined salinities ranging from 15 to 25. The values of parameters, except species size, associated with the functioning of the copepod assemblages (biomass, productivity, and turnover rate) did not differ among estuaries. However, in the more polluted estuaries, the biomass and productivity of copepod assemblages of mesozooplankton were negatively correlated with concentration of pollution indicator parameters. Conversely, in the less polluted estuaries some degree of enrichment still seems to increase the system biomass and productivity, as these parameters were inversely related to indicators of improved water quality. The pollution level of estuaries distorted the relationship between temperature and the efficiency of converting energy to organic matter. In the less polluted estuaries, the relationship between turnover rate and temperature was over 70%, while in the most polluted estuaries, this relationship was only approximately 50%. Our results demonstrated that the functioning of assemblages in the estuaries was affected differently by increasing pollution depending on the water quality level of the system. Thus, investigating the functioning of assemblages can be a useful tool for the analysis of estuarine conditions.

  12. Patterns of spatial variation of assemblages associated with intertidal rocky shores: a global perspective.

    Directory of Open Access Journals (Sweden)

    Juan José Cruz-Motta

    2010-12-01

    Full Text Available Assemblages associated with intertidal rocky shores were examined for large scale distribution patterns with specific emphasis on identifying latitudinal trends of species richness and taxonomic distinctiveness. Seventy-two sites distributed around the globe were evaluated following the standardized sampling protocol of the Census of Marine Life NaGISA project (www.nagisa.coml.org. There were no clear patterns of standardized estimators of species richness along latitudinal gradients or among Large Marine Ecosystems (LMEs; however, a strong latitudinal gradient in taxonomic composition (i.e., proportion of different taxonomic groups in a given sample was observed. Environmental variables related to natural influences were strongly related to the distribution patterns of the assemblages on the LME scale, particularly photoperiod, sea surface temperature (SST and rainfall. In contrast, no environmental variables directly associated with human influences (with the exception of the inorganic pollution index were related to assemblage patterns among LMEs. Correlations of the natural assemblages with either latitudinal gradients or environmental variables were equally strong suggesting that neither neutral models nor models based solely on environmental variables sufficiently explain spatial variation of these assemblages at a global scale. Despite the data shortcomings in this study (e.g., unbalanced sample distribution, we show the importance of generating biological global databases for the use in large-scale diversity comparisons of rocky intertidal assemblages to stimulate continued sampling and analyses.

  13. Effects of macroalgal identity on epifaunal assemblages: native species versus the invasive species Sargassum muticum

    Science.gov (United States)

    Gestoso, Ignacio; Olabarria, Celia; Troncoso, Jesús S.

    2012-06-01

    Seaweeds are a refuge from stressful conditions associated with life on rocky intertidal shores, and there is evidence that different macrophytes support different assemblages of mobile epifauna. Introduction of non-indigenous macroalgae may have a great impact on associated epifaunal assemblages and ecosystem processes in coastal areas. Previous studies have reported conflicting evidences for the ability of epifauna to colonize non-indigenous species. Here, we analyzed epifaunal assemblages associated with three species of macroalgae that are very abundant on intertidal shores along the Galician coast: the two native species Bifurcaria bifurcata and Saccorhiza polyschides and the invasive species Sargassum muticum. We collected samples of each species from three different sites at three different times to test whether variability of epifaunal assemblages was consistent over space and time. Epifaunal assemblages differed between the three macroalgae. Results suggested that stability and morphology of habitat played an important role in shaping the structure of epifaunal assemblages. This study also showed that the invasive S. muticum offered a suitable habitat for many invertebrates.

  14. Patterns in larval fish assemblages under the influence of the Brazil current

    Science.gov (United States)

    Katsuragawa, M.; Dias, J. F.; Harari, J.; Namiki, C.; Zani-Teixeira, M. L.

    2014-10-01

    The present work investigates the composition of larval fish assemblages in the area under the influence of the Brazil Current (BC) off the Southeastern Brazilian Bight. Ichthyoplankton was sampled during two oceanographic cruises (November-December/1997 - spring; May/2001 - autumn) with bongo nets oblique tows. Seasonal variation and a coastal-ocean pattern in the distribution of larval fish was observed and was influenced by the dynamics of the water masses, Coastal Water (CW), Tropical Water (TW) and South Atlantic Central Water (SACW), the last two of which were transported by the BC. During spring, the shelf assemblage was dominated by larvae of small pelagic fishes, such as Sardinella brasiliensis, Engraulis anchoita and Trachurus lathami, and was associated with the enrichment of shallow water by the SACW upwelling. In autumn, the abundance of coastal species larvae was reduced, and the shelf assemblage was dominated by Bregmaceros cantori. A transitional assemblage occurred during the spring, and comprised mesopelagic and coastal species. In both seasons, the oceanic assemblage was dominated by the mesopelagic families, Myctophidae, Sternopthychidae and Phosichthyidae. The oceanographic conditions also demonstrated clear differences between the northern and southern subareas, particularly in the shelf zone. This was especially the case during autumn when a latitudinal gradient in larval fish assemblages became more pronounced.

  15. Comparative analysis of different survey methods for monitoring fish assemblages in coastal habitats

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    Duncan G.L. Baker

    2016-03-01

    Full Text Available Coastal ecosystems are among the most productive yet increasingly threatened marine ecosystems worldwide. Particularly vegetated habitats, such as eelgrass (Zostera marina beds, play important roles in providing key spawning, nursery and foraging habitats for a wide range of fauna. To properly assess changes in coastal ecosystems and manage these critical habitats, it is essential to develop sound monitoring programs for foundation species and associated assemblages. Several survey methods exist, thus understanding how different methods perform is important for survey selection. We compared two common methods for surveying macrofaunal assemblages: beach seine netting and underwater visual census (UVC. We also tested whether assemblages in shallow nearshore habitats commonly sampled by beach seines are similar to those of nearby eelgrass beds often sampled by UVC. Among five estuaries along the Southern Gulf of St. Lawrence, Canada, our results suggest that the two survey methods yield comparable results for species richness, diversity and evenness, yet beach seines yield significantly higher abundance and different species composition. However, sampling nearshore assemblages does not represent those in eelgrass beds despite considerable overlap and close proximity. These results have important implications for how and where macrofaunal assemblages are monitored in coastal ecosystems. Ideally, multiple survey methods and locations should be combined to complement each other in assessing the entire assemblage and full range of changes in coastal ecosystems, thereby better informing coastal zone management.

  16. Can global weed assemblages be used to predict future weeds?

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    Louise Morin

    Full Text Available Predicting which plant taxa are more likely to become weeds in a region presents significant challenges to both researchers and government agencies. Often it is done in a qualitative or semi-quantitative way. In this study, we explored the potential of using the quantitative self-organising map (SOM approach to analyse global weed assemblages and estimate likelihoods of plant taxa becoming weeds before and after they have been moved to a new region. The SOM approach examines plant taxa associations by analysing where a taxon is recorded as a weed and what other taxa are recorded as weeds in those regions. The dataset analysed was extracted from a pre-existing, extensive worldwide database of plant taxa recorded as weeds or other related status and, following reformatting, included 187 regions and 6690 plant taxa. To assess the value of the SOM approach we selected Australia as a case study. We found that the key and most important limitation in using such analytical approach lies with the dataset used. The classification of a taxon as a weed in the literature is not often based on actual data that document the economic, environmental and/or social impact of the taxon, but mostly based on human perceptions that the taxon is troublesome or simply not wanted in a particular situation. The adoption of consistent and objective criteria that incorporate a standardized approach for impact assessment of plant taxa will be necessary to develop a new global database suitable to make predictions regarding weediness using methods like SOM. It may however, be more realistic to opt for a classification system that focuses on the invasive characteristics of plant taxa without any inference to impacts, which to be defined would require some level of research to avoid bias from human perceptions and value systems.

  17. Epilithic algal assemblages in the Forsmark Biotest basin

    Energy Technology Data Exchange (ETDEWEB)

    Snoeijs, P.

    1987-04-01

    The Forsmark Biotest Basin is an artificial offshore brackish lake, through which the cooling water is led from the Forsmark Nuclear Power Station on the Swedish east coast. The Biotest Basin differs from the Bothnian Sea surrounding it by a temperature elevation of up to 10 degrees C, no ice cover in winter, and an artificial, fast current. At 11 sites in- and outside the basin, benthic algal assemblages on stones in the hydrolittoral belt were sampled every third week during one year. Cover abundances were estimated for all algae occurring on the stones, but for diatoms only when they formed blooms. The results of the vegetation analyses are given. Diversity indices and dominance-diversity curves were computed for each site on the basis of pooled data for the cold season and for the rest of the year. The algae included both unicellular and multicellular forms. In total 88 taxa were distinguished in the species lists: 29 Cyanophyta, 7 Rhodophyta, 1 Chrysophyceae, 9 Fucophyceae, 17 Diatomophyceae and 25 Chlorophyta. In terms of percentage cover-abundance, blue-green and green algae increased with temperature, while red and brown algae and diatoms decreased with temperature in the interval between the minimum (0 degrees C) and the maximum (25.7 degrees C) water temperatures that were measured during the investigation period. Melosira spp. and Nitzschia filiformis proved to be the diatoms most favoured by the cooling water discharge. Lower diversity and greater dominance of one or a few species over the other was caused by thermal discharge at sites with fast-flowing water, but the opposite occurred at sites with quiescent water, mainly due to a greater number and higher abundances of blue-green algal species and thread-like green algae at the latter sites. This report also gives some notes on taxonomy of the encountered species.

  18. Isolating magnetic moments from individual grains within a magnetic assemblage

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    Béguin, A.; Fabian, K.; Jansen, C.; Lascu, I.; Harrison, R.; Barnhoorn, A.; de Groot, L. V.

    2017-12-01

    Methods to derive paleodirections or paleointensities from rocks currently rely on measurements of bulk samples (typically 10 cc). The process of recording and storing magnetizations as function of temperature, however, differs for grains of various sizes and chemical compositions. Most rocks, by their mere nature, consist of assemblages of grains varying in size, shape, and chemistry. Unraveling the behavior of individual grains is a holy grail in fundamental rock magnetism. Recently, we showed that it is possible to obtain plausible magnetic moments for individual grains in a synthetic sample by a micromagnetic tomography (MMT) technique. We use a least-squares inversion to obtain these magnetic moments based on the physical locations and dimensions of the grains obtained from a MicroCT scanner and a magnetic flux density map of the surface of the sample. The sample used for this proof of concept, however, was optimized for success: it had a low dispersion of the grains, and the grains were large enough so they were easily detected by the MicroCT scanner. Natural lavas are much more complex than the synthetic sample analyzed so far: the dispersion of the magnetic markers is one order of magnitude higher, the grains differ more in composition and size, and many small (submicron) magnetic markers may be present that go undetected by the MicroCT scanner. Here we present the first results derived from a natural volcanic sample from the 1907-flow at Hawaii. To analyze the magnetic flux at the surface of the sample at room temperature, we used the Magnetic Tunneling Junction (MTJ) technique. We were able to successfully obtain MicroCT and MTJ scans from the sample and isolate plausible magnetic moments for individual grains in the top 70 µm of the sample. We discuss the potential of the MMT technique applied to natural samples and compare the MTJ and SSM methods in terms of work flow and quality of the results.

  19. Eco-cities as an Assemblage of Worlding Practices

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    Zack Lee

    2015-09-01

    Full Text Available Eco-cities are gaining attention in policy and academic circles over the past few years. Yet they pose difficulties as objects of study since they have been diversely defined and implemented. This paper argues that eco-cities are better understood as an assemblage of worlding practices. Combining these two concepts foregoes the emphasis on the eco-city’s physical structures and focuses more on its policy environment and its relations with other locations. The case study being examined is the Philippine’s Clark Green, the country’s first eco-city project. Its main proponent is an independent government agency, the Bases Conversion and Development Authority (BCDA, tasked with developing former military locations for civilian uses. Their vision is to create a world-class project built by international stakeholders in order to elevate the status of the Philippines and the Filipinos. They have chosen to emulate the Songdo International Business District in South Korea as their benchmark model. Not only are they adopting the ideas of a smart city but also similar strategies to enter the international education and logistics industries. The paper will show how the BCDA uses the eco-city idea as a tool to enter various national and international discourses that extend beyond the project’s geographical boundaries. Yet the strategies and visions of an independent government-owned corporation are tempered by challenges from local stakeholders, conflicting national priorities, and failures from similar policies applied elsewhere. The paper highlights the need for worlding projects to be embedded in their own national context for greater policy coordination.

  20. Particle assemblage characterization in the Rhone River ROFI

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    Many, Gaël; Bourrin, François; Durrieu de Madron, Xavier; Pairaud, Ivane; Gangloff, Aurélien; Doxaran, David; Ody, Anouck; Verney, Romaric; Menniti, Christophe; Le Berre, David; Jacquet, Matthias

    2016-05-01

    An innovative experiment was carried out in the vicinity of the Rhône River mouth in February 2014. An instrumental package, composed of a CTD, a LISST-100 type B (1.25-250 μm), and a LISST-HOLO (20-2000 μm), was used to characterize the hydrological parameters and suspended particles properties (concentration, size, composition, shape, and effective density) in the region of freshwater influence (ROFI) of the Rhône River. Besides, a coastal SLOCUM glider, equipped with a CTD and optical backscattering sensors at several wavelengths, was deployed to detail the spatial description of the hydrological parameters and some particle properties. Large river discharge (annual flood ~ 5000 m3 s- 1) and strong wind conditions favored the dispersal of the river plume on the shelf. Surface suspended particulate matter concentrations decreased rapidly seaward from 20 mg L- 1 next to the river mouth to 1.5 mg L- 1 at the shelf break. A persistent bottom nepheloid layer was observed across the shelf with concentrations decreasing from 8 mg L- 1 at the coast to 1 mg L- 1 at the shelf break. Observations showed that most of suspended particles were mainly flocculated in micro and macro-flocs (30-400 μm) in inner-shelf waters. The particle assemblage in the Rhône River plume and in the bottom nepheloid layer became progressively finer seaward and the associated effective density increased from 370 to 1600 kg m- 3. Outside the plume, planktonic organisms increasingly contributed to the total volume concentration. Finally, we demonstrated the ability of gliders, equipped with optical backscattering sensors at several wavelengths, to describe the fine scale distributions of suspended particles, and provide an index of their size distribution.

  1. Next generation sequencing reveals the hidden diversity of zooplankton assemblages.

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    Penelope K Lindeque

    Full Text Available BACKGROUND: Zooplankton play an important role in our oceans, in biogeochemical cycling and providing a food source for commercially important fish larvae. However, difficulties in correctly identifying zooplankton hinder our understanding of their roles in marine ecosystem functioning, and can prevent detection of long term changes in their community structure. The advent of massively parallel next generation sequencing technology allows DNA sequence data to be recovered directly from whole community samples. Here we assess the ability of such sequencing to quantify richness and diversity of a mixed zooplankton assemblage from a productive time series site in the Western English Channel. METHODOLOGY/PRINCIPLE FINDINGS: Plankton net hauls (200 µm were taken at the Western Channel Observatory station L4 in September 2010 and January 2011. These samples were analysed by microscopy and metagenetic analysis of the 18S nuclear small subunit ribosomal RNA gene using the 454 pyrosequencing platform. Following quality control a total of 419,041 sequences were obtained for all samples. The sequences clustered into 205 operational taxonomic units using a 97% similarity cut-off. Allocation of taxonomy by comparison with the National Centre for Biotechnology Information database identified 135 OTUs to species level, 11 to genus level and 1 to order, <2.5% of sequences were classified as unknowns. By comparison a skilled microscopic analyst was able to routinely enumerate only 58 taxonomic groups. CONCLUSIONS: Metagenetics reveals a previously hidden taxonomic richness, especially for Copepoda and hard-to-identify meroplankton such as Bivalvia, Gastropoda and Polychaeta. It also reveals rare species and parasites. We conclude that Next Generation Sequencing of 18S amplicons is a powerful tool for elucidating the true diversity and species richness of zooplankton communities. While this approach allows for broad diversity assessments of plankton it may

  2. Palynological assemblages of non-marine rocks at the Permian Triassic boundary, western Guizhou and eastern Yunnan, South China

    Science.gov (United States)

    Peng, Yuanqiao; Yu, Jianxin; Gao, Yongqun; Yang, Fengqing

    2006-12-01

    Marine and non-marine facies of the Permian-Triassic boundary stratigraphic set (PTBST) are well developed in South China. Palynological assemblages enable subdivision and correlation of the Permian-Triassic boundary (PTB) rocks. Three palynological assemblages are recognized across the PTBST in two terrestrial PTB sections in western Guizhou and eastern Yunnan, South China. Assemblage 1 (Xuanwei Formation) is a Late Permian palynological assemblage dominated by ferns and pteridosperms, with minor gymnosperms. Most taxa are typical long-ranging Paleozoic forms, but the appearance of Lueckisporites confirms a Late Permian age for this assemblage. Assemblage 2 (PTBST) is marked by an abrupt decrease in palynomorph abundance and diversity, and thriving fungal/algal(?) spores. Assemblage 2 is still dominated by ferns and pteridosperms, with a few gymnosperms, but is characterized by a mixed palynoflora containing both Late Permian and Early Triassic elements. Most taxa are typical Late Permian ones also found in Assemblage 1, however, some taxa of Early Triassic aspect, e.g. Lundbladispora and Taeniaesporites, appeared for the first time. In Assemblage 3 (top Xuanwei Formation and Kayitou Formation), the proportion of gymnosperm pollen increases rapidly, exceeding that of ferns and pteridosperms, but the abundance of palynomorphs is still low. Typical Early Triassic taxa (such as Lundbladispora, Aratrisporites and Taeniaesporites) are present in greater abundance and confirms an Early Triassic age for this assemblage.

  3. Groundwater declines are linked to changes in Great Plains stream fish assemblages.

    Science.gov (United States)

    Perkin, Joshuah S; Gido, Keith B; Falke, Jeffrey A; Fausch, Kurt D; Crockett, Harry; Johnson, Eric R; Sanderson, John

    2017-07-11

    Groundwater pumping for agriculture is a major driver causing declines of global freshwater ecosystems, yet the ecological consequences for stream fish assemblages are rarely quantified. We combined retrospective (1950-2010) and prospective (2011-2060) modeling approaches within a multiscale framework to predict change in Great Plains stream fish assemblages associated with groundwater pumping from the United States High Plains Aquifer. We modeled the relationship between the length of stream receiving water from the High Plains Aquifer and the occurrence of fishes characteristic of small and large streams in the western Great Plains at a regional scale and for six subwatersheds nested within the region. Water development at the regional scale was associated with construction of 154 barriers that fragment stream habitats, increased depth to groundwater and loss of 558 km of stream, and transformation of fish assemblage structure from dominance by large-stream to small-stream fishes. Scaling down to subwatersheds revealed consistent transformations in fish assemblage structure among western subwatersheds with increasing depths to groundwater. Although transformations occurred in the absence of barriers, barriers along mainstem rivers isolate depauperate western fish assemblages from relatively intact eastern fish assemblages. Projections to 2060 indicate loss of an additional 286 km of stream across the region, as well as continued replacement of large-stream fishes by small-stream fishes where groundwater pumping has increased depth to groundwater. Our work illustrates the shrinking of streams and homogenization of Great Plains stream fish assemblages related to groundwater pumping, and we predict similar transformations worldwide where local and regional aquifer depletions occur.

  4. Patterns of benthic assemblages invaded and non-invaded by Grateloupia turuturu across rocky intertidal habitats

    Science.gov (United States)

    Freitas, Cristiano; Araújo, Rita; Bertocci, Iacopo

    2016-09-01

    Intertidal benthic assemblages invaded and non-invaded by the introduced Asian red alga Grateloupia turuturu were compared at a rocky shore along the NW coast of Portugal. The structure of whole assemblages, the total richness of taxa and the abundance of individual taxa were examined as response variables in two different habitats (rock pools and emergent rock), two shore levels (low and mid intertidal) and two dates of sampling (June 2013 and June 2014). Invaded and non-invaded assemblages differed consistently across habitats and shore levels. Such differences were driven by 13 (with the green alga genus Ulva, the red alga Chondrus crispus and the mussel Mytilus galloprovincialis driving the total dissimilarity) out of the total 37 taxa identified. Individual taxa revealed idiosyncratic patterns, in several cases (C. crispus, M. galloprovincialis, articulated coralline algae of the genus Corallina and the crustose sporophyte of the red alga Mastocarpus stellatus) there were differences in the abundance of a taxon between invaded and non-invaded assemblages varying with levels of some other experimental factors. The total number of taxa was higher in invaded compared to non-invaded assemblages for each combination of habitat and shore level. Patterns of invasion by G. turuturu along the Portuguese continental coast were recently described in terms of its temporal and spatial distribution, but never examined in terms of differences between invaded and non-invaded assemblages. Such information is very limited for other geographic areas where this species is recorded out of its native range of distribution. Therefore, the present study provides a new contribution to the understanding of modifications of native assemblages associated with the invasion of G. turuturu, opening avenues of research aimed at specifically examining the factors and processes likely responsible for the invasion dynamics and success of this species.

  5. Sponge assemblages on the deep Mediterranean continental shelf and slope (Menorca Channel, Western Mediterranean Sea)

    Science.gov (United States)

    Santín, Andreu; Grinyó, Jordi; Ambroso, Stefano; Uriz, Maria J.; Gori, Andrea; Dominguez-Carrió, Carlos; Gili, Josep-Maria

    2018-01-01

    Sponge assemblages on continental shelves and slopes around the world have been known about for centuries. However, due to limitations of the traditional sampling systems, data about individual sponge species rather than assemblages have been reported. This study characterizes sponge assemblages over a wide bathymetric range ( 50-350 m depth) and covering the entire continental shelf and the upper slope of the Menorca Channel, an area soon to be declared a Marine Protected Area (MPA) as part of the Natura 2000 Network. Quantitative analysis of 85 video-transects (a total linear distance of 75 km), together with representative collections to confirm species identifications, allowed us to discriminate six major assemblages. Differences in the assemblages mainly corresponded to differences in substrate type and depth. On the inner continental shelf, a semi-sciaphilous Axinellid assemblage dominated the rocky outcrops. Maërl beds on the inner continental shelf were dominated by Haliclona (Reniera) mediterranea, whereas the horny sponge Aplysina cavernicola and several other haliclonids mostly dominated maërl beds and rocky substrates of the outer shelf. Soft sediments on the shelf break hosted a monospecific Thenea muricata assemblage, whereas rocky substrates of the shelf break were characterized by a mixture of encrusting, columnar and fan-shaped sponges. Finally, the upper slope was dominated by Hamacantha (Vomerula) falcula and the hexactinellid Tretodictyum reiswigi. Overall, sponge diversity showed its highest values above the shelf break, plummeting severely on the upper slope. Despite this diversity decrease, we found very high densities (> 70 ind./m2) of sponges over vast areas of both the shelf break and the upper slope.

  6. Effects of management legacies on stream fish and aquatic benthic macroinvertebrate assemblages.

    Science.gov (United States)

    Quist, Michael C; Schultz, Randall D

    2014-09-01

    Fish and benthic macroinvertebrate assemblages often provide insight on ecological conditions for guiding management actions. Unfortunately, land use and management legacies can constrain the structure of biotic communities such that they fail to reflect habitat quality. The purpose of this study was to describe patterns in fish and benthic macroinvertebrate assemblage structure, and evaluate relationships between biota and habitat characteristics in the Chariton River system of south-central Iowa, a system likely influenced by various potential management legacies (e.g., dams, chemical removal of fishes). We sampled fishes, benthic macroinvertebrates, and physical habitat from a total of 38 stream reaches in the Chariton River watershed during 2002-2005. Fish and benthic macroinvertebrate assemblages were dominated by generalist species tolerant of poor habitat quality; assemblages failed to show any apparent patterns with regard to stream size or longitudinal location within the watershed. Metrics used to summarize fish assemblages and populations [e.g., presence-absence, relative abundance, Index of Biotic Integrity for fish (IBIF)] were not related to habitat characteristics, except that catch rates of piscivores were positively related to the depth and the amount of large wood. In contrast, family richness of benthic macroinvertebrates, richness of Ephemeroptera, Trichoptera, and Plecoptera taxa, and IBI values for benthic macroinvertebrates (IBIBM) were positively correlated with the amount of overhanging vegetation and inversely related to the percentage of fine substrate. A long history of habitat alteration by row-crop agriculture and management legacies associated with reservoir construction has likely resulted in a fish assemblage dominated by tolerant species. Intolerant and sensitive fish species have not recolonized streams due to downstream movement barriers (i.e., dams). In contrast, aquatic insect assemblages reflected aquatic habitat, particularly

  7. Changing bee and hoverfly pollinator assemblages along an urban-rural gradient.

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    Adam J Bates

    Full Text Available The potential for reduced pollination ecosystem service due to global declines of bees and other pollinators is cause for considerable concern. Habitat degradation, destruction and fragmentation due to agricultural intensification have historically been the main causes of this pollinator decline. However, despite increasing and accelerating levels of global urbanization, very little research has investigated the effects of urbanization on pollinator assemblages. We assessed changes in the diversity, abundance and species composition of bee and hoverfly pollinator assemblages in urban, suburban, and rural sites across a UK city.Bees and hoverflies were trapped and netted at 24 sites of similar habitat character (churchyards and cemeteries that varied in position along a gradient of urbanization. Local habitat quality (altitude, shelter from wind, diversity and abundance of flowers, and the broader-scale degree of urbanization (e.g. percentage of built landscape and gardens within 100 m, 250 m, 500 m, 1 km, and 2.5 km of the site were assessed for each study site. The diversity and abundance of pollinators were both significantly negatively associated with higher levels of urbanization. Assemblage composition changed along the urbanization gradient with some species positively associated with urban and suburban land-use, but more species negatively so. Pollinator assemblages were positively affected by good site habitat quality, in particular the availability of flowering plants.Our results show that urban areas can support diverse pollinator assemblages, but that this capacity is strongly affected by local habitat quality. Nonetheless, in both urban and suburban areas of the city the assemblages had fewer individuals and lower diversity than similar rural habitats. The unique development histories of different urban areas, and the difficulty of assessing mobile pollinator assemblages in just part of their range, mean that complementary studies in

  8. Juvenile bottlenecks and salinity shape grey mullet assemblages in Mediterranean estuaries

    Science.gov (United States)

    Cardona, Luis; Hereu, Bernat; Torras, Xavier

    2008-05-01

    Previous research has suggested that competitive bottlenecks may exist for the Mediterranean grey mullets (Osteichthyes, Mugilidae) at the fry stage with the exotic Cyprinus carpio (Osteichthyes, Cyprinidae) playing a central role. As a consequence, the structure of grey mullet assemblages at later stages is thought to reflect previous competition as well as differences in osmoregulatory skills. This paper tests that hypothesis by examining four predictions about the relative abundance of five grey mullet species in 42 Western Mediterranean estuary sites from three areas (Aiguamolls de l'Empordà, Ebro Delta and Minorca) differing in the salinity level and occurrence of C. carpio. Field data confirmed the predictions as: (1) Liza aurata and Mugil cephalus were scarce everywhere and never dominated the assemblage; (2) Liza saliens dominated the assemblage where the salinity level was higher than 13; (3) Liza ramado always dominated the assemblage where the salinity level was lower than 13 and C. carpio was present; and (4) Chelon labrosus dominated the assemblage only where the salinity level was lower than 13 and C. carpio was absent. The catch per unit effort of C. labrosus of any size was smaller in the presence of C. carpio than where it had not been introduced, which is in agreement with the juvenile competitive bottleneck hypothesis. Discriminant analysis confirmed that the assemblage structure was linked to the salinity level and the occurrence of C. carpio for both early juveniles and late juveniles as well as adults. The data reported here reveal that the structure of grey mullet assemblages inhabiting Mediterranean estuaries is determined by salinity and competitive interactions at the fry stage.

  9. Shining light on benthic macroalgae: mechanisms of complementarity in layered macroalgal assemblages.

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    Leigh W Tait

    Full Text Available Phototrophs underpin most ecosystem processes, but to do this they need sufficient light. This critical resource, however, is compromised along many marine shores by increased loads of sediments and nutrients from degraded inland habitats. Increased attenuation of total irradiance within coastal water columns due to turbidity is known to reduce species' depth limits and affect the taxonomic structure and architecture of algal-dominated assemblages, but virtually no attention has been paid to the potential for changes in spectral quality of light energy to impact production dynamics. Pioneering studies over 70 years ago showed how different pigmentation of red, green and brown algae affected absorption spectra, action spectra, and photosynthetic efficiency across the PAR (photosynthetically active radiation spectrum. Little of this, however, has found its way into ecological syntheses of the impacts of optically active contaminants on coastal macroalgal communities. Here we test the ability of macroalgal assemblages composed of multiple functional groups (including representatives from the chlorophyta, rhodophyta and phaeophyta to use the total light resource, including different light wavelengths and examine the effects of suspended sediments on the penetration and spectral quality of light in coastal waters. We show that assemblages composed of multiple functional groups are better able to use light throughout the PAR spectrum. Macroalgal assemblages with four sub-canopy species were between 50-75% more productive than assemblages with only one or two sub-canopy species. Furthermore, attenuation of the PAR spectrum showed both a loss of quanta and a shift in spectral distribution with depth across coastal waters of different clarity, with consequences to productivity dynamics of diverse layered assemblages. The processes of light complementarity may help provide a mechanistic understanding of how altered turbidity affects macroalgal assemblages

  10. Environmental constraints on the compositional and phylogenetic beta-diversity of tropical forest snake assemblages.

    Science.gov (United States)

    Moura, Mario R; Costa, Henrique C; Argôlo, Antônio J S; Jetz, Walter

    2017-09-01

    The ongoing biodiversity crisis increases the importance and urgency of studies addressing the role of environmental variation on the composition and evolutionary history of species assemblages, but especially the tropics and ectotherms remain understudied. In regions with rainy summers, coexistence of tropical ectothermic species may be determined by the partitioning of the climatic niche, as ectotherms can rely on water availability and thermoregulatory behaviour to buffer constraints along their climatic niche. Conversely, tropical ectotherms facing dry summers would have fewer opportunities to climatic niche partitioning and other processes rather than environmental filtering would mediate species coexistence. We used 218 snake assemblages to quantify the compositional (CBD) and phylogenetic (PBD) beta-diversity of snakes in the Atlantic Forest (AF) hotspot, South America. We identify two AF regions with distinct climatological regimes: dry summers in the northern-AF and rainy summers in the southern-AF. While accounting for the influence of multiscale spatial processes, we disentangle the relative contribution of thermal, water-related and topographic conditions in structuring the CBD and PBD of snake assemblages, and determine the extent in which snake assemblages under distinct climatological regimes are affected by environmental filtering. Thermal conditions best explain CBD and PBD of snakes for the whole AF, whereas water-related factors best explain the structure of snake assemblages within a same climatological regime. CBD and PBD patterns are similarly explained by spatial factors but snake assemblages facing dry summers are more affected by spatial processes operating at fine to intermediate spatial scale, whereas those assemblages in regions with rainy summers have a stronger signature of coarse-scale processes. As expected, environmental filtering plays a stronger role in southern-AF than northern-AF, and the synergism between thermal and water

  11. Occurrence and diversity of Giardia duodenalis assemblages in livestock in the UK.

    Science.gov (United States)

    Minetti, C; Taweenan, W; Hogg, R; Featherstone, C; Randle, N; Latham, S M; Wastling, J M

    2014-12-01

    Giardia duodenalis is a common intestinal parasite in humans and a wide range of livestock species. It is a genetically heterogeneous parasite that has been characterized in seven distinct genetic assemblages or cryptic species, and molecular markers can be used to differentiate both animal-specific and potentially zoonotic genotypes. Little is known about G. duodenalis and the range of assemblages occurring in domestic livestock species in the UK. Here, we present data on the occurrence and molecular diversity of G. duodenalis detected in the faeces or large intestinal contents of cattle, sheep, pigs, goats and camelids from farms in the north-west of England. Both healthy and clinically diseased animals were included in the survey. The presence of Giardia spp. and assemblages was determined by sequencing of the small-subunit ribosomal RNA gene. The potential association of infection with various clinical and epidemiological parameters was studied in cattle using both univariate and multivariate analyses. Giardia spp. were detected in 127 (34.3%) of the 370 animals tested. G. duodenalis assemblage E was found to be predominant in cattle and sheep, followed by assemblage A. Mixed infections with assemblages A and E were also detected. Interestingly, some cattle, sheep and pigs were found to be infected with more unexpected assemblages (C, D, F). Pre-weaned calves were more likely to test positive than adult animals, but no association between the occurrence of overt intestinal disease and G. duodenalis infection was detected. The common occurrence of assemblage A and the finding of unusual assemblages in atypical hosts suggest that in future, a multilocus analysis should be used to confirm the actual diversity of G. duodenalis in livestock and the presence of potentially zoonotic genotypes. These data also suggest that there is a need to re-evaluate the clinical significance of G. duodenalis infection in livestock. © 2014 The Authors. Transboundary and

  12. Influence of environmental factors on fish assemblages in streams of the Elbe and Oder basins

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    Luboš Kůra

    2015-11-01

    Full Text Available The effects of environmental parameters on changes in the structure of fish assemblages were studied in the Elbe and the Odra basin. Research was done at 819 sites surveyed in the field during the period 1993-2007. The impact of 46 factors derived from the maps through a GIS was tested as well as the impact of 10 factors recognized in the field. To evaluate the influence of these factors the indirect (DCA and direct (CCA multivariate cluster analysis were used. Analyses were performed with data on presence-absence and relative abundance of each species. DCA well reflects changes in assemblages in the longitudinal profile of streams. CCA refers to a significant influence of regional and temporal variability and influence of individual factors. The fish assemblages are best characterized by distance from the source location, stream slope, altitude of locality, representation of arable land in the basin, number of ponds in the sub-basin above the locality, type of waters (salmonid or cyprinid, and water temperature (the only of the parameters of the field. The analyzed factors better reflect the variability in fish assemblages of the Odra than of Elbe river basin. The analysis showed good practical efficiency of processing information from a large sample of data from ichthyological surveys. The tools of GIS and the use of statistical methods make possible to characterize basic ecological requirements of most species and specify conditions determining specific composition of fish assemblages.

  13. Temporal distribution of intertidal macrozoobenthic assemblages in a Nanozostera noltii-dominated area (Lagoon of Venice).

    Science.gov (United States)

    Tagliapietra, D; Pessa, G; Cornello, M; Zitelli, A; Magni, P

    2016-03-01

    We describe the temporal distribution of intertidal macrozoobenthic assemblages in a small marsh pond of the Lagoon of Venice colonized by the seagrass Nanozostera noltii (Hornemman) Tomlinson et Posluzny. Three stations ranging in the degree of N. noltii cover were selected about 100 m apart and sampled 9 times at regular intervals from March 1996 to March 1997. We applied the concepts of resistance and resilience to "natural stress" (e.g. extent of protection from seagrass meadows, exposure of macrozoobenthic assemblages to high temperatures in summer) with the aim to assess the stability of a community along a gradient of seagrass coverage. Results showed that the most structured and taxa-rich macrozoobenthic assemblage occurred at the station covered by a continuous stand of N. noltii, where permanent taxa (i.e. found in 100% of samples) were almost double than those found at the other stations. During the annual cycle, the macrozoobenthic assemblages showed a cyclical pattern, with temporal fluctuations increasing as they moved further away from the seagrass beds. We propose the role of N. noltii offering structural complexity and stability as the more probable explanation to the observed differences between stations in the intertidal assemblages. Copyright © 2015 Elsevier Ltd. All rights reserved.

  14. Avian Assemblages at Bird Baths: A Comparison of Urban and Rural Bird Baths in Australia.

    Science.gov (United States)

    Cleary, Gráinne P; Parsons, Holly; Davis, Adrian; Coleman, Bill R; Jones, Darryl N; Miller, Kelly K; Weston, Michael A

    2016-01-01

    Private gardens provide habitat and resources for many birds living in human-dominated landscapes. While wild bird feeding is recognised as one of the most popular forms of human-wildlife interaction, almost nothing is known about the use of bird baths. This citizen science initiative explores avian assemblages at bird baths in private gardens in south-eastern Australia and how this differs with respect to levels of urbanisation and bioregion. Overall, 992 citizen scientists collected data over two, four-week survey periods during winter 2014 and summer 2015 (43% participated in both years). Avian assemblages at urban and rural bird baths differed between bioregions with aggressive nectar-eating species influenced the avian assemblages visiting urban bird baths in South Eastern Queensland, NSW North Coast and Sydney Basin while introduced birds contributed to differences in South Western Slopes, Southern Volcanic Plains and Victorian Midlands. Small honeyeaters and other small native birds occurred less often at urban bird baths compared to rural bird baths. Our results suggest that differences between urban versus rural areas, as well as bioregion, significantly influence the composition of avian assemblages visiting bird baths in private gardens. We also demonstrate that citizen science monitoring of fixed survey sites such as bird baths is a useful tool in understanding large-scale patterns in avian assemblages which requires a vast amount of data to be collected across broad areas.

  15. Environmental influences on fish assemblage distribution of an estuarine coastal lagoon, Ria de Aveiro (Portugal

    Directory of Open Access Journals (Sweden)

    L. Pombo

    2005-03-01

    Full Text Available Fish assemblage was examined for patterns in spatial and seasonal structure within an estuarine coastal lagoon, Ria de Aveiro. Two years of variation in abiotic conditions were recorded to identify factors responsible for maintaining the structure of fish assemblages. Nine sites were sampled monthly with a traditional “chincha” beach-seine net between November 1998 and October 2000. Fish abundance and biomass changed significantly between sites. Temperature was found to be the most important abiotic factor affecting the abundance (number of fish distribution of fish assemblage, which is more related to seasonal migrations than to spatial migrations. Salinity was the most important abiotic factor affecting the fish biomass, with temperature also having a major influence. The other abiotic parameters analysed also showed some influence on the distribution of fish, although, isolated from the other controlled and/or uncontrolled factors, they could not fully explain all the differences between assemblages. Feeding analysis indicates that fish assemblage is mostly dependent on small benthic and pelagic crustaceans and/or detritus, although they can feed opportunistically on other prey. The low spatial segregation of fish in relation to feeding preference indicates that, in a food-rich lagoon such as Ria de Aveiro, the environmental-biological interactions appear to have a greater effect on fish distribution than do biological interactions.

  16. Spatial and seasonal variations of fish assemblages in mangrove creek systems in Zanzibar (Tanzania)

    Science.gov (United States)

    Mwandya, Augustine W.; Gullström, Martin; Andersson, Mathias H.; Öhman, Marcus C.; Mgaya, Yunus D.; Bryceson, Ian

    2010-11-01

    Spatial and seasonal variations of fish assemblage composition were studied in three non-estuarine mangrove creeks of Zanzibar (Tanzania). Fish were collected monthly for one year at three sites (lower, intermediate and upper reaches) in each creek using a seine net (each haul covering 170 m 2). Density, species number and diversity of fish were all higher at sites with dense cover of macrophytes (seagrass and macroalgae) than over unvegetated sandy sites. In general, fish assemblages mainly comprised juveniles of a few abundant taxa, e.g. Mugil cephalus, Mugilidae spp. and Leiognathus equulus at sites with mud substratum and Gerres oyena, Lethrinus harak and Sillago sihama at sites dominated by macrophytes. Multivariate analyses revealed significant separations in fish assemblage composition within the two creeks where the bottom substratum differed among sites. Overall, season seemed to have little effect on density, species number, diversity index ( H') and assemblage structure of fish. Water condition variables were also relatively stable across the season, although a short-term fluctuation primarily induced by decreased salinity, occurred during the heavy rains in April and May. Fish assemblage structure was not significantly affected by any of the abiotic factors tested. However, significant regressions were found between the other fish variables and environmental variables, but since these associations were mostly species-specific and generally inconsistent, we suggest that the overall distribution patterns of fish were mainly an effect of particular substrate preferences of fish species rather than contemporary water conditions.

  17. Avian Assemblages at Bird Baths: A Comparison of Urban and Rural Bird Baths in Australia

    Science.gov (United States)

    Cleary, Gráinne P.; Parsons, Holly; Davis, Adrian; Coleman, Bill R.; Jones, Darryl N.; Miller, Kelly K.; Weston, Michael A.

    2016-01-01

    Private gardens provide habitat and resources for many birds living in human-dominated landscapes. While wild bird feeding is recognised as one of the most popular forms of human-wildlife interaction, almost nothing is known about the use of bird baths. This citizen science initiative explores avian assemblages at bird baths in private gardens in south-eastern Australia and how this differs with respect to levels of urbanisation and bioregion. Overall, 992 citizen scientists collected data over two, four-week survey periods during winter 2014 and summer 2015 (43% participated in both years). Avian assemblages at urban and rural bird baths differed between bioregions with aggressive nectar-eating species influenced the avian assemblages visiting urban bird baths in South Eastern Queensland, NSW North Coast and Sydney Basin while introduced birds contributed to differences in South Western Slopes, Southern Volcanic Plains and Victorian Midlands. Small honeyeaters and other small native birds occurred less often at urban bird baths compared to rural bird baths. Our results suggest that differences between urban versus rural areas, as well as bioregion, significantly influence the composition of avian assemblages visiting bird baths in private gardens. We also demonstrate that citizen science monitoring of fixed survey sites such as bird baths is a useful tool in understanding large-scale patterns in avian assemblages which requires a vast amount of data to be collected across broad areas. PMID:26962857

  18. Abiotic proxies for predictive mapping of nearshore benthic assemblages: implications for marine spatial planning.

    Science.gov (United States)

    McHenry, Jennifer; Steneck, Robert S; Brady, Damian C

    2017-03-01

    Marine spatial planning (MSP) should assist managers in guiding human activities toward sustainable practices and in minimizing user conflicts in our oceans. A necessary first step is to quantify spatial patterns of marine assemblages in order to understand the ecosystem's structure, function, and services. However, the large spatial scale, high economic value, and density of human activities in nearshore habitats often makes quantifying this component of marine ecosystems especially daunting. To address this challenge, we developed an assessment method that employs abiotic proxies to rapidly characterize marine assemblages in nearshore benthic environments with relatively high resolution. We evaluated this assessment method along 300 km of the State of Maine's coastal shelf (GIS layers for abiotic conditions allowed us to scale up important assemblage attributes to define key foundational ecological principles of MSP and to find priority regions where some bottom-disturbing activities would have minimal impact to benthic assemblages. We conclude that abiotic proxies can be strong forcing functions for the assembly of marine communities and therefore useful tools for spatial extrapolations of marine assemblages in congested (heavily used) nearshore habitats. © 2016 by the Ecological Society of America.

  19. Opposing Patterns of Seasonal Change in Functional and Phylogenetic Diversity of Tadpole Assemblages

    Science.gov (United States)

    Strauß, Axel; Guilhaumon, François; Randrianiaina, Roger Daniel; Wollenberg Valero, Katharina C.; Vences, Miguel; Glos, Julian

    2016-01-01

    Assemblages that are exposed to recurring temporal environmental changes can show changes in their ecological properties. These can be expressed by differences in diversity and assembly rules. Both can be identified using two measures of diversity: functional (FD) and phylogenetic diversity (PD). Frog communities are understudied in this regard, especially during the tadpole life stage. We utilised tadpole assemblages from Madagascan rainforest streams to test predictions of seasonal changes on diversity and assemblage composition and on diversity measures. From the warm-wet to the cool-dry season, species richness (SR) of tadpole assemblages decreased. Also FD and PD decreased, but FD less and PD more than expected by chance. During the dry season, tadpole assemblages were characterised by functional redundancy (among assemblages—with increasing SR), high FD (compared to a null model), and low PD (phylogenetic clustering; compared to a null model). Although mutually contradictory at first glance, these results indicate competition as tadpole community assembly driving force. This is true during the limiting cool-dry season but not during the more suitable warm-wet season. We thereby show that assembly rules can strongly depend on season, that comparing FD and PD can reveal such forces, that FD and PD are not interchangeable, and that conclusions on assembly rules based on FD alone are critical. PMID:27014867

  20. Seasonal changes in fish assemblage structure at a shallow seamount in the Gulf of California.

    Science.gov (United States)

    Jorgensen, Salvador J; Klimley, A Peter; Muhlia-Melo, Arturo; Morgan, Steven G

    2016-01-01

    Seamounts have generally been identified as locations that can promote elevated productivity, biomass and predator biodiversity. These properties attract seamount-associated fisheries where elevated harvests can be obtained relative to surrounding areas. There exists large variation in the geological and oceanographic environment among the thousands of locations that fall within the broad definition of seamount. Global seamount surveys have revealed that not all seamounts are hotspots of biodiversity, and there remains a strong need to understand the mechanisms that underlie variation in species richness observed. We examined the process of fish species assembly at El Bajo Espiritu Santo (EBES) seamount in the Gulf of California over a five-year study period. To effectively quantify the relative abundance of fast-moving and schooling fishes in a 'blue water' habitat, we developed a simplified underwater visual census (UVC) methodology and analysis framework suitable for this setting and applicable to future studies in similar environments. We found correlations between seasonally changing community structure and variability in oceanographic conditions. Individual species responses to thermal habitat at EBES revealed three distinct assemblages, a 'fall assemblage' tracking warmer overall temperature, a 'spring assemblage' correlated with cooler temperature, and a 'year-round assemblage' with no significant response to temperature. Species richness was greatest in spring, when cool and warm water masses stratified the water column and a greater number of species from all three assemblages co-occurred. We discuss our findings in the context of potential mechanisms that could account for predator biodiversity at shallow seamounts.

  1. Megafloral assemblage similar to Karharbari biozone from Talchir Coalfield of Mahanadi Basin, Orissa

    Energy Technology Data Exchange (ETDEWEB)

    Singh, K.J.; Goswami, S.; Chandra, S. [Birbal Sahni Institute of Paleobotany, Lucknow (India)

    2006-08-15

    A rich collection of plant megafossils have been studied from the rocks of Karharbari Formation (Early Permian=Lower Artinskian) at South Balanda Colliery (Latitude 20 degrees 56' Longitude 85 degrees 14'), Talchir Coalfield, Angul district, Orissa. The lower Gondwana rocks in this coalfield have been represented by Talchir, Karharbari, Barakar, Barren Measures and the Kamthi Formations (in ascending order) representing earliest Permian to Late Permian. Palaeobotanical studies have been extensively carried out in the past by a number of workers in almost all the Lower Gondwana formations except the Karharbari Formation. Megafloral assemblage has been recovered for the first time from Karharbari sediments of the Lower Gondwana deposits in this coalfield. The specimens are preserved as impressions and compressions on blackish grey fine-grained shales of the South Balanda Colliery exposed just above the carbonaceous shales. The lowermost coal seam i.e. seam no. 1/Karharbari seam of this coalfield exists below the above-mentioned two shale bands. The megafloral assemblage consists of Phyllotheca westensis, Noeggerathiopsis hislopii, Euryphyllum whittianum, E. maithyi, Macrotaeniopteris feddeni, Buriadia heterophylla, Glossopteris browniana, G. communis, Gangamopteris cyclopleroides and Surangephyllum elongatum. The genus Buriadia dominates the total assemblage (about 80%). The assemblage has been compared thoroughly with the known megafloral assemblages of Karharbari Formation.

  2. Fish assemblage relationships with physical characteristics and presence of dams in three eastern Iowa rivers

    Science.gov (United States)

    Pierce, Clay; Nicholas L. Ahrens,; Anna K. Loan-Wilsey,; Gregory A. Simmons,; Gregory T. Gelwicks,

    2013-01-01

    Fish assemblages in rivers of the Midwestern United States are an important component of the region's natural resources and biodiversity. We characterized the physical environment and presence of dams in a series of reaches in three eastern Iowa rivers tributary to the Mississippi River and related these characteristics to the fish assemblages present. Some physical characteristics were similar among the 12 study reaches, whereas others differed substantially. We found a total of 68 species across the 12 study reaches; 56 in the Turkey River, 51 in the Maquoketa River and 50 in the Wapsipinicon River. Seventeen species could be described as ‘downstream-distributed’; 15 being found only in the lowest reach of one or more rivers and the other two being found only in the lowest reaches or two or more contiguous reaches including the lowest reach. Two species could be described as ‘upstream-distributed’, being found only in an uppermost reach. Non-metric multidimensional scaling ordination illustrated similarities among reaches, and five physical variables were significantly correlated with assemblage similarities. Catchment area and number of dams between reaches and the Mississippi River were strongly correlated with assemblage similarities, but the directions of their effects were opposite. Catchment area and number of dams were confounded. The collective evidence to date suggests that the pervasiveness of dams on rivers significantly alters fish assemblages, making underlying patterns of species change and relationships with naturally varying and human-influenced physical characteristics along a river's course difficult to discern.

  3. Similarity between the dead and living foraminiferal assemblages of the NE sector of Guanabara Bay (Brazil

    Directory of Open Access Journals (Sweden)

    Maria Virgínia Alves Martins

    2016-12-01

    Full Text Available Guanabara Bay (GB, located at the coast of Rio de Janeiro State (Brazil, is an ecosystem rich in biodiversity both in terms of mega, macro and microfauna. However, the factors that control their distribution are still poorly understood. This work intends to identify the possible factors affecting the distribution of benthic foraminifera in the bay by comparing living and dead assemblages in selected sediment fractions. Substantial differences in terms of density, diversity and equitability of the species in the living and dead assemblages and in different sediment fractions (63-150 μm, 150-250 μm, 250-500 μm are identified. Lower similarity (<70% between the living and dead assemblages are associated with areas impacted by organic matter and may be mainly ascribed to either loss of tests due to dissolution, currents remobilization and abrasion, or inclusion of allochthonous species transported by currents. This work suggests that the use of the living plus dead assemblages or dead assemblages can reduce the accuracy of the results if the work intends to evaluate the environmental conditions.

  4. Morphological diversity at different spatial scales in a Neotropical bat assemblage.

    Science.gov (United States)

    Villalobos, Fabricio; Arita, Héctor T

    2014-10-01

    The morphology of species can be used to represent their ecological position and infer potential processes determining the structure of species assemblages. This ecomorphological approach has been widely applied to the study of bat assemblages which mainly focuses on a single spatial scale and particular guilds. We extended such an ecomorphological approach to a multi-scale analysis of a Neotropical bat assemblage and its constituent guilds (aerial and gleaning insectivores, frugivores, and nectarivores) to describe their structure at different spatial scales and determine the relative importance of inter-specific competition, habitat filtering, or stochastic processes shaping such structures. We measured the occupied morphological space (size) defined by wing and skull morphology independently and the nearest-neighbour distance (structure) among species within these spaces at each spatial scale. Observed patterns were compared with random expectations derived from null models for statistical inference. When controlling for species richness and regional sampling effects in the null models, we did not find a significant effect of spatial scale in the morphological structure of the studied bat assemblage and guilds. Morphological structure followed the same patterns across scales as those expected from random drawings of sample size alone. Similar results were obtained regardless of morphological complex (wing and skull) and guilds. At both the assemblage and guild levels, bat morphological structure seems to be determined by regional, abiotic processes (e.g. habitat filtering) shaping the composition and organization of the species pool.

  5. Stable isotope analyses of web-spinning spider assemblages along a headwater stream in Puerto Rico

    Directory of Open Access Journals (Sweden)

    Sean P. Kelly

    2015-10-01

    Full Text Available Web-spinning spiders that inhabit stream channels are considered specialists of aquatic ecosystems and are major consumers of emerging aquatic insects, while other spider taxa are more commonly found in riparian forests and as a result may consume more terrestrial insects. To determine if there was a difference in spider taxa abundance between riverine web-spinning spider assemblages within the stream channel and the assemblages 10 m into the riparian forest, we compared abundances for all web-spinning spiders along a headwater stream in El Yunque National Forest in northeast Puerto Rico. By using a nonmetric dimensional scaling (NMDS abundance analysis we were able to see a clear separation of the two spider assemblages. The second objective of the study was to determine if aquatic insects contributed more to the diet of the spider assemblages closest to the stream channel and therefore stable isotope analyses of δ15N and δ13C for web-spinning spiders along with their possible prey were utilized. The results of the Bayesian mixing model (SIAR however showed little difference in the diets of riverine (0 m, riparian (10 m and upland (25 m spiders. We found that aquatic insects made up ∼50% of the diet for web-spinning spiders collected at 0 m, 10 m, and 25 m from the stream. This study highlights the importance of aquatic insects as a food source for web-spinning spiders despite the taxonomic differences in assemblages at different distances from the stream.

  6. Seafloor massive sulfide deposits support unique megafaunal assemblages: Implications for seabed mining and conservation.

    Science.gov (United States)

    Boschen, Rachel E; Rowden, Ashley A; Clark, Malcolm R; Pallentin, Arne; Gardner, Jonathan P A

    2016-04-01

    Mining of seafloor massive sulfides (SMS) is imminent, but the ecology of assemblages at SMS deposits is poorly known. Proposed conservation strategies include protected areas to preserve biodiversity at risk from mining impacts. Determining site suitability requires biological characterisation of the mine site and protected area(s). Video survey of a proposed mine site and protected area off New Zealand revealed unique megafaunal assemblages at the mine site. Significant relationships were identified between assemblage structure and environmental conditions, including hydrothermal features. Unique assemblages occurred at both active and inactive chimneys and are particularly at risk from mining-related impacts. The occurrence of unique assemblages at the mine site suggests that the proposed protected area is insufficient alone and should instead form part of a network. These results provide support for including hydrothermally active and inactive features within networks of protected areas and emphasise the need for quantitative survey data of proposed sites. Copyright © 2016 The Authors. Published by Elsevier Ltd.. All rights reserved.

  7. Floral neighborhood influences pollinator assemblages and effective pollination in a native plant.

    Science.gov (United States)

    Bruckman, Daniela; Campbell, Diane R

    2014-10-01

    Pollinators represent an important intermediary by which different plant species can influence each other's reproductive fitness. Floral neighbors can modify the quantity of pollinator visits to a focal species but may also influence the composition of visitor assemblages that plants receive leading to potential changes in the average effectiveness of floral visits. We explored how the heterospecific floral neighborhood (abundance of native and non-native heterospecific plants within 2 m × 2 m) affects pollinator visitation and composition of pollinator assemblages for a native plant, Phacelia parryi. The relative effectiveness of different insect visitors was also assessed to interpret the potential effects on plant fitness of shifts in pollinator assemblage composition. Although the common non-native Brassica nigra did not have a significant effect on overall pollinator visitation rate to P. parryi, the proportion of flower visits that were made by native pollinators increased with increasing abundance of heterospecific plant species in the floral neighborhood other than B. nigra. Furthermore, native pollinators deposited twice as many P. parryi pollen grains per visit as did the nonnative Apis mellifera, and visits by native bees also resulted in more seeds than visits by A. mellifera. These results indicate that the floral neighborhood can influence the composition of pollinator assemblages that visit a native plant and that changes in local flower communities have the potential to affect plant reproductive success through shifts in these assemblages towards less effective pollinators.

  8. Effect of copper on multiple successional stages of a marine fouling assemblage.

    Science.gov (United States)

    McElroy, David J; Hochuli, Dieter F; Doblin, Martina A; Murphy, Richard J; Blackburn, Robert J; Coleman, Ross A

    2017-11-01

    Copper based paints are used to prevent fouling on the hulls of ships. The widely documented effect of copper on hull assemblages may be primarily due to direct effects on the invertebrates themselves or indirect effects from copper absorbed into the microbial biofilm before settlement has commenced. Artificial units of habitat were exposed to varied regimes of copper to examine (1) the photosynthetic efficiency and pigments of early-colonising biofilms, and (2) subsequent macroinvertebrate assemblage change in response to the different regimes of copper. Macroinvertebrate assemblages were found to be less sensitive to the direct effects of copper than indirect effects as delivered through biofilms that have been historically exposed to copper, with some species more tolerant than others. This raises further concern for the efficacy of copper as a universal antifoulant on the hulls of ships, which may continue to assist the invasion of copper-tolerant invertebrate species.

  9. Soil metal concentrations and vegetative assemblage structure in an urban brownfield

    International Nuclear Information System (INIS)

    Gallagher, Frank J.; Pechmann, Ildiko; Bogden, John D.; Grabosky, Jason; Weis, Peddrick

    2008-01-01

    Anthropogenic sources of toxic elements have had serious ecological and human health impacts. Analysis of the soil samples from a brownfield within Liberty State Park, Jersey City, NJ, USA, showed that arsenic, chromium, lead, zinc and vanadium exist at concentrations above those considered ambient for the area. Accumulation and translocation features were characterized for the dominant plant species of four vegetative assemblages. The trees Betula populifolia and Populus deltoides were found to be accumulating Zn in leaf tissue at extremely high levels. B. populifolia, P. deltoides and Rhus copallinum accumulated Cr primarily in the root tissue. A comparison of soil metal maps and vegetative assemblage maps indicates that areas of increasing total soil metal load were dominated by successional northern hardwoods while semi-emergent marshes consisting mostly of endemic species were restricted primarily to areas of low soil metal load. - The study yields insight into the impact of metal contaminates soils on vegetative assemblage structure and development

  10. Changes in mesophotic reef fish assemblages along depth and geographical gradients in the Northwestern Hawaiian Islands

    Science.gov (United States)

    Fukunaga, Atsuko; Kosaki, Randall K.; Wagner, Daniel

    2017-09-01

    Mesophotic coral ecosystems (MCEs) extend from 30 to 150 m in depth and support diverse communities of marine organisms. We investigated changes in the structure of mesophotic reef fish assemblages (27-100 m) in the Northwestern Hawaiian Islands (NWHI) along depth and geographical gradients using open- and closed-circuit trimix diving. There were clear changes in the assemblage structure from the southeastern to the northwestern end of the NWHI and from shallow to deep waters. Interactive effects of depth and location were also detected. MCEs in the NWHI can be treated as three regions: southeastern and mid regions primarily separated by the presence and absence, respectively, of the introduced species Lutjanus kasmira, and a northwestern region where fish assemblages are largely composed of endemic species. These spatial patterns may be explained, at least in part, by differences in temperature among the regions.

  11. Effects of Climate Change and Various Grassland Management Practices on Grasshopper (Orthoptera Assemblages

    Directory of Open Access Journals (Sweden)

    Zoltán Kenyeres

    2014-01-01

    Full Text Available Influence of different grassland management practices on Orthoptera assemblages inhabiting humid grassland areas was studied since 2003 to 2011. The examined sites were within the protected area of Balaton Uplands National Park. The physiognomy and climatic conditions of the studied habitats were similar but their land use types were significantly different. After the preliminary analyses of Nonmetric multidimensional scaling, neighbour joining clustering, and Spearman rank correlation, we examined the possible effects of such independent variables as land use (nonmanagement, mowing, grazing, microclimate (humidity and temperature, regional macroclimate (annual and monthly mean temperatures and rainfall, using General Linear Mixed Models, and canonical correlation analysis. Our results showed that the effect of grassland management practices on the organization of Orthoptera assemblages was at least as important as that of macro- and microclimate. Furthermore, grassland management could intensify the influence of several local and regional parameters. These results can help finding the most suitable type of grassland management to conserve the grasshopper assemblages.

  12. Mean latitudinal range sizes of bird assemblages in six Neotropical forest chronosequences

    DEFF Research Database (Denmark)

    Dunn, Robert R.; Romdal, Tom Skovlund

    2005-01-01

    understood. We examined how the mean latitudinal range sizes of species in Neotropical bird species assemblages shift during forest clearance and subsequent regeneration. We tested the hypothesis that bird species assemblages in early successional habitats tend to have larger latitudinal ranges than those...... in more mature forests. Location We considered breeding bird chronosequence data from six Neotropical forests. Results Breeding bird assemblages were found to have the species with the largest average latitudinal range sizes in cleared areas, intermediate in young secondary forests and smallest in old...... secondary and mature forests. Similar differences were also found when we compared congeners differing in their successional preferences. Sizes of regional ranges (within the Neotropics) did not, however, differ consistently among successional stages. The larger latitudinal (but not regional) ranges...

  13. First deep screening of bacterial assemblages associated with corals of the Tropical Eastern Pacific.

    Science.gov (United States)

    Hernández-Zulueta, Joicye; Araya, Rubén; Vargas-Ponce, Ofelia; Díaz-Pérez, Leopoldo; Rodríguez-Troncoso, Alma P; Ceh, Janja; Ríos-Jara, Eduardo; Rodríguez-Zaragoza, Fabián A

    2016-12-01

    Bacterial assemblages associated with the hermatypic corals Pocillopora damicornis and P. verrucosa, the surrounding seawater and the sediment at six coral reef sites in the north section of the Tropical Eastern Pacific were assessed using MiSeq Illumina sequencing of the V4 region of the 16S rDNA. The bacterial microbiota in both coral species, seawater and sediment were stable to seasonal variations. Bacterial assemblages between the same substrates were not significantly different from each other in the six sites sampled. Interestingly, the bacterial composition between substrates within the same site was significantly different, or not, depending on the conservation status of the site. Moreover, we found species-specific bacterial OTUs in both coral species. Analyzing the relationship between bacterial composition and environmental variables revealed a positive correlation between bacterial assemblages and dissolved oxygen, ammonium and silicate. © FEMS 2016. All rights reserved. For permissions, please e-mail: journals.permissions@oup.com.

  14. Spatial variability in macroinvertebrate assemblages along and among neighbouring equatorial glacier-fed streams

    DEFF Research Database (Denmark)

    Kuhn, J.; Andino, P.; Calvez, R.

    2011-01-01

    , following a supposed decrease in environmental harshness along the streams. Relationships between faunal metrics and the four environmental variables mean temperature, the stability index, chlorophyll a and coarse particulate organic matter also varied among the three streams. Generalised linear model...... and temperature and stability as main driving factors were met by our three replicate equatorial glacial streams. Qualitative departures from the model were mainly because of zoogeographical differences. We demonstrated that variability in assemblages between comparable sites in closely situated streams...... Andes of Ecuador. Our main goals were (i) to determine overall longitudinal patterns in density, taxon richness and the composition of macroinvertebrate assemblages and driving factors in equatorial glacial streams and (ii) to examine variability among replicate streams in faunal metrics and assemblages...

  15. How does the Taquari River influence in the cladoceran assemblages in three oxbow lakes?

    Directory of Open Access Journals (Sweden)

    EA. Panarelli

    Full Text Available This study examined the cladoceran assemblages in three oxbow lakes of the Taquari River floodplain, near the transition between the plateau and the plain. We sought to answer the following questions: does the Taquari River function as a geographical barrier or dispersal corridor for Cladocera? Can different degrees of connection induce different structures in the assemblages in each lake? Cladocerans and limnological variables were sampled every other month for one year. Forty-one species were recorded, four of which were common to all the lakes. Our results indicated that the different degrees of connection between the river and the oxbow lakes favoured environmental heterogeneity and diversification in the cladoceran assemblages. The greatest dissimilarity between the two lakes connected with the river indicates that in this case the river functions better as a barrier than a dispersal corridor.

  16. Environmental influence on coprophagous Scarabaeidae (Insecta, Coleoptera) assemblages in the Pantanal of Mato Grosso.

    Science.gov (United States)

    Tissiani, A S O; Sousa, W O; Santos, G B; Ide, S; Battirola, L; Marques, M I

    2015-11-01

    Here we examine assemblage structure of coprophagous Scarabaeidae (dung beetles) in the Pantanal of the state of Mato Grosso with respect to flooding regimes, soil texture, leaf litter volume and tree dominance in native and exotic pastures. Samples were collected along 30 transects of 250 m in length in a 5×5 km grid (25 km2). Five pitfalls baited with human feces were placed in each transect. A total of 1692 individuals in 19 species were captured, the majority in the subfamily Scarabaeinae and Aphodiinae. Assemblages were influenced by the duration of flooding and leaf litter volume. None of the other habitat variables was correlated with species richness. Cultivated pastures with exotic grasses were unimportant for composition of the assemblages of beetles. These results indicate that duration of flooding is the most important regulating force in this community.

  17. Bone assemblages track animal community structure over 40 years in an African savanna ecosystem.

    Science.gov (United States)

    Western, David; Behrensmeyer, Anna K

    2009-05-22

    Reconstructing ancient communities depends on how accurately fossil assemblages retain information about living populations. We report a high level of fidelity between modern bone assemblages and living populations based on a 40-year study of the Amboseli ecosystem in southern Kenya. Relative abundance of 15 herbivorous species recorded in the bone assemblage accurately tracks the living populations through major changes in community composition and habitat over intervals as short as 5 years. The aggregated bone sample provides an accurate record of community structure time-averaged over four decades. These results lay the groundwork for integrating paleobiological and contemporary ecological studies across evolutionary and ecological time scales. Bone surveys also provide a useful method of assessing population changes and community structure for modern vertebrates.

  18. Functional redundancy patterns reveal non-random assembly rules in a species-rich marine assemblage.

    Directory of Open Access Journals (Sweden)

    Nicolas Guillemot

    Full Text Available The relationship between species and the functional diversity of assemblages is fundamental in ecology because it contains key information on functional redundancy, and functionally redundant ecosystems are thought to be more resilient, resistant and stable. However, this relationship is poorly understood and undocumented for species-rich coastal marine ecosystems. Here, we used underwater visual censuses to examine the patterns of functional redundancy for one of the most diverse vertebrate assemblages, the coral reef fishes of New Caledonia, South Pacific. First, we found that the relationship between functional and species diversity displayed a non-asymptotic power-shaped curve, implying that rare functions and species mainly occur in highly diverse assemblages. Second, we showed that the distribution of species amongst possible functions was significantly different from a random distribution up to a threshold of ∼90 species/transect. Redundancy patterns for each function further revealed that some functions displayed fast rates of increase in redundancy at low species diversity, whereas others were only becoming redundant past a certain threshold. This suggested non-random assembly rules and the existence of some primordial functions that would need to be fulfilled in priority so that coral reef fish assemblages can gain a basic ecological structure. Last, we found little effect of habitat on the shape of the functional-species diversity relationship and on the redundancy of functions, although habitat is known to largely determine assemblage characteristics such as species composition, biomass, and abundance. Our study shows that low functional redundancy is characteristic of this highly diverse fish assemblage, and, therefore, that even species-rich ecosystems such as coral reefs may be vulnerable to the removal of a few keystone species.

  19. Origin of an Assemblage Massively Dominated by Carnivorans from the Miocene of Spain

    Science.gov (United States)

    Domingo, M. Soledad; Alberdi, M. Teresa; Azanza, Beatriz; Silva, Pablo G.; Morales, Jorge

    2013-01-01

    Carnivoran-dominated fossil sites provide precious insights into the diversity and ecology of species rarely recovered in the fossil record. The lower level assemblage of Batallones-1 fossil site (Late Miocene; Madrid Basin, Spain) has yielded one of the most abundant and diversified carnivoran assemblage ever known from the Cenozoic record of mammals. A comprehensive taphonomic study is carried out here in order to constrain the concentration mode of this remarkable assemblage. Another distinctive feature of Batallones-1 is that the accumulation of carnivoran remains took place in the context of a geomorphological landform (cavity formation through a piping process) practically unknown in the generation of fossil sites. Two characteristics of the assemblage highly restrict the probable causes for the accumulation of the remains: (1) the overwhelming number of carnivorans individuals; and (2) the mortality profiles estimated for the four most abundant taxa do not correspond to the classic mortality types but rather were the consequence of the behavior of the taxa. This evidence together with other taphonomic data supports the hypothesis that carnivoran individuals actively entered the cavity searching for resources (food or water) and were unable to exit. The scarcity of herbivores implies that the shaft was well visible and avoided by these taxa. Fossil bones exhibit a very good preservation state as a consequence of their deposition in the restricted and protective environment of the chamber. Batallones-1 had another assemblage (upper level assemblage) that was dominated by herbivore remains and that potentially corresponded to the final stages of the cavity filling. PMID:23650542

  20. Larval assemblages of large and medium-sized pelagic species in the Straits of Florida

    Science.gov (United States)

    Richardson, David E.; Llopiz, Joel K.; Guigand, Cedric M.; Cowen, Robert K.

    2010-07-01

    Critical gaps in our understanding of the distributions, interactions, life histories and preferred habitats of large and medium-size pelagic fishes severely constrain the implementation of ecosystem-based, spatially structured fisheries management approaches. In particular, spawning distributions and the environmental characteristics associated with the early life stages are poorly documented. In this study, we consider the diversity, assemblages, and associated habitat of the larvae of large and medium-sized pelagic species collected during 2 years of monthly surveys across the Straits of Florida. In total, 36 taxa and 14,295 individuals were collected, with the highest diversity occurring during the summer and in the western, frontal region of the Florida Current. Only a few species (e.g. Thunnus obesus, T. alalunga, Tetrapturus pfluegeri) considered for this study were absent. Small scombrids (e.g. T. atlanticus, Katsuwonus pelamis, Auxis spp.) and gempylids dominated the catch and were orders of magnitude more abundant than many of the rare species (e.g. Thunnus thynnus,Kajikia albida). Both constrained (CCA) and unconstrained (NMDS) multivariate analyses revealed a number of species groupings including: (1) a summer Florida edge assemblage (e.g. Auxis spp., Euthynnus alleterattus, Istiophorus platypterus); (2) a summer offshore assemblage (e.g. Makaira nigricans, T. atlanticus, Ruvettus pretiosus, Lampris guttatus); (3) an ubiquitous assemblage (e.g. K. pelamis, Coryphaena hippurus, Xiphias gladius); and (4) a spring/winter assemblage that was widely dispersed in space (e.g. trachipterids). The primary environmental factors associated with these assemblages were sea-surface temperature (highest in summer-early fall), day length (highest in early summer), thermocline depth (shallowest on the Florida side) and fluorescence (highest on the Florida side). Overall, the results of this study provide insights into how a remarkable diversity of pelagic species

  1. Structure of mangrove meiofaunal assemblages associated with local sediment conditions in subtropical eastern australia

    Science.gov (United States)

    Abdullah, Maizah M.; Lee, S. Y.

    2017-11-01

    Meiofauna are ubiquitous but poorly-studied components of soft-bottom marine habitats around the world, including mangroves. The dynamic environmental conditions and heterogeneous sediments of mangroves present challenges to understanding the structure of mangrove meiofaunal assemblages at various spatial and temporal scales. In this study, we investigated the meiofaunal assemblage structure of sediments colonised by three mangrove species, namely, Avicennia marina, Rhizophora stylosa and Aegiceras corniculatum, at three locations in subtropical eastern Australia. Spatial and temporal variations were tested by sampling at the three mangrove locations (i.e. Tallebudgera, Currumbin and Terranora) in autumn, with samplings repeated at Tallebudgera at two other times broadly representing during dry/cool winter and wet/hot summer seasons. We examined the variability of the sediment environments within each of the different mangrove species, and investigated how meiofaunal assemblages would respond to the particular changes in their habitats to result in differences in assemblage structure between and within sites. Total meiofaunal density was highest in Tallebudgera and Currumbin and lowest in Terranora (mean density of 424, 393 and 239 ind.10 cm-2, respectively). In Tallebudgera, the density was higher in winter and summer (mean density of 546 and 530 ind.10 cm-2, respectively). The meiofaunal assemblage in this study shows a trend and association with the environmental variables. High availability of food proxies such phaeopigments, Chl a or TOC, with moderate tannin content and appropriate habitat structure (sediment particle size, belowground root biomass and/or moisture content provide the best condition for the meiofauna to achieve the highest density. However, given the complex dynamic habitats and the spatial heterogeneity of the mangrove environments across different locations and seasons, no clear generalization could be made regarding the key environmental

  2. Dissecting the multi-scale spatial relationship of earthworm assemblages with soil environmental variability.

    Science.gov (United States)

    Jiménez, Juan J; Decaëns, Thibaud; Lavelle, Patrick; Rossi, Jean-Pierre

    2014-12-05

    Studying the drivers and determinants of species, population and community spatial patterns is central to ecology. The observed structure of community assemblages is the result of deterministic abiotic (environmental constraints) and biotic factors (positive and negative species interactions), as well as stochastic colonization events (historical contingency). We analyzed the role of multi-scale spatial component of soil environmental variability in structuring earthworm assemblages in a gallery forest from the Colombian "Llanos". We aimed to disentangle the spatial scales at which species assemblages are structured and determine whether these scales matched those expressed by soil environmental variables. We also tested the hypothesis of the "single tree effect" by exploring the spatial relationships between root-related variables and soil nutrient and physical variables in structuring earthworm assemblages. Multivariate ordination techniques and spatially explicit tools were used, namely cross-correlograms, Principal Coordinates of Neighbor Matrices (PCNM) and variation partitioning analyses. The relationship between the spatial organization of earthworm assemblages and soil environmental parameters revealed explicitly multi-scale responses. The soil environmental variables that explained nested population structures across the multi-spatial scale gradient differed for earthworms and assemblages at the very-fine- (30 m), fine (10-20 m) and very fine scales (<10 m). Variation partitioning analysis revealed that the soil environmental variability explained from less than 1% to as much as 48% of the observed earthworm spatial variation. A large proportion of the spatial variation did not depend on the soil environmental variability for certain species. This finding could indicate the influence of contagious biotic interactions, stochastic factors, or unmeasured relevant soil environmental variables.

  3. Associations of benthic macroinvertebrate assemblages with environmental variables in the upper Clear Creek watershed, California

    Science.gov (United States)

    Brown, Larry R.; May, Jason T.; Wulff, Marissa

    2012-01-01

    Benthic macroinvertebrates are integral components of stream ecosystems and are often used to assess the ecological integrity of streams. We sampled streams in the upper Clear Creek drainage in the Klamath—Siskiyou Ecoregion of northwestern California in fall 2004 (17 sites) and 2005 (original 17 plus 4 new sites) with the objectives of documenting the benthic macroinvertebrate assemblages supported by the streams in the area, determining how those assemblages respond to environmental variables, assessing the biological condition of the streams using a benthic index of biotic integrity (IBI), and understanding the assemblages in the context of biodiversity of the ecoregion. We collected both reach-wide (RW) and targeted-riffle (TR) macroinvertebrate samples at each site. The macroinvertebrate assemblages were diverse, with over 150 genera collected for each sampling protocol. The macroinvertebrate assemblages appeared to be most responsive to a general habitat gradient based on stream size, gradient, flow, and dominance of riffles. A second important habitat gradient was based on elevation and dominance of riffles. A gradient in water quality based on concentrations of dissolved ions and metals was also important. Models based on these 3 gradients had Spearman's rank correlations with macroinvertebrate taxonomic composition of 0.60 and 0.50 for the TR and RW samples, respectively. The majority (>50%) of the sites were in good or very good biological condition based on IBI scores. The diversity of macroinvertebrate assemblages is associated with the diversity of habitats available in the Klamath—Siskiyou Ecoregion. Maintaining the aquatic habitats in good condition is important in itself but is also vital to maintaining biodiversity in this diverse and unique ecoregion.

  4. Flood disturbance effects on benthic diatom assemblage structure in a semiarid river network.

    Science.gov (United States)

    Tornés, Elisabet; Acuña, Vicenç; Dahm, Clifford N; Sabater, Sergi

    2015-02-01

    Disturbances such as floods and droughts play a central role in determining the structure of riverine benthic biological assemblages. Extreme disturbances from flash floods are often restricted to part of the river network and the magnitude of the flood disturbance may lessen as floods propagate downstream. The present study aimed to characterize the impact of summer monsoonal floods on the resistance and resilience of the benthic diatom assemblage structure in nine river reaches of increasing drainage size within the Gila River in the southwestern United States. Monsoonal floods had a profound effect on the diatom assemblage in the Gila River, but the effects were not related to drainage size except for the response of algal biomass. During monsoons, algal biomass was effectively reduced in smaller and larger systems, but minor changes were observed in medium systems. Resistance and resilience of the diatom assemblage to floods were related to specific species traits, mainly to growth forms. Tightly adhered, adnate and prostrate species (Achnanthidium spp., Cocconeis spp.) exhibited high resistance to repeated scour disturbance. Loosely attached diatoms, such as Nitzschia spp. and Navicula spp., were most susceptible to drift and scour. However, recovery of the diatom assemblage was very quick indicating a high resilience, especially in terms of biomass and diversity. Regional hydroclimatic models predict greater precipitation variability, which will select for diatoms resilient to bed-mobilizing disturbances. The results of this study may help anticipate future benthic diatom assemblage patterns in the southwestern United States resulting from a more variable climate. © 2014 Phycological Society of America.

  5. Molecular Characterization of Giardia lamblia: First Report of Assemblage B in Human Isolates from Rio de Janeiro (Brazil).

    Science.gov (United States)

    Faria, Clarissa Perez; Zanini, Graziela Maria; Dias, Gisele Silva; da Silva, Sidnei; Sousa, Maria do Céu

    2016-01-01

    Despite the high prevalence of giardiasis, the genetic characterization of Giardia lamblia has been poorly documented in Brazil and molecular epidemiology research has only been conducted in the last few years. The aim of this study was to determine the prevalence of different G. lamblia assemblages and detect mixed infections among patients with giardiasis. The cross-section survey was conducted among patients attending the FIOCRUZ in Rio de Janeiro. In order to discriminate the genetic assemblages/sub-assemblages, G. lamblia isolates were characterized by PCR-RFLP and qPCR using four loci genes (bg, gdh, tpi and orfC4). Of the 65 positive samples, 41 (63.1%) were successfully amplified by nested-PCR of bg and gdh genes. Among them, 16 were typed as sub-assemblage AII, 7 as BIII, 4 as BIV and 8 as a mixture of BIII and BIV. After the analysis by qPCR assay, a total of 55 (84.6%) samples were amplified using at least one locus: bg gene was amplified in 38 (58.5%) samples, gdh in 41 (63.1%), tpi in 39 (60%), and orfC4 in 39 (60%). Multilocus genotyping results showed that 29 (52.7%) samples belonged to Assemblage A and 26 (47.3%) samples belonged to Assemblage B. In 2011 and 2012, 20 (74.1%) samples belonged to Assemblage A and 7 (25.9%) belonged to Assemblage B. In subsequent years (2013-2015) there was a predominance of Assemblage B, 19 (67.9%) versus 9 (32.1%) Assemblage A. This is the first time that Assemblage B of G. lamblia was reported in human clinical samples from Rio de Janeiro (Brazil) and is the first report about genetic characterization using four genes. The qPCR assemblage-specific showed no mixed infections by Assemblages A and B. A switch in genetic profile over the years was observed, firstly predominance of Assemblage A and lastly of Assemblage B.

  6. Sediment and carbon deposition vary among vegetation assemblages in a coastal salt marsh

    Science.gov (United States)

    Kelleway, Jeffrey J.; Saintilan, Neil; Macreadie, Peter I.; Baldock, Jeffrey A.; Ralph, Peter J.

    2017-08-01

    Coastal salt marshes are dynamic, intertidal ecosystems that are increasingly being recognised for their contributions to ecosystem services, including carbon (C) accumulation and storage. The survival of salt marshes and their capacity to store C under rising sea levels, however, is partially reliant upon sedimentation rates and influenced by a combination of physical and biological factors. In this study, we use several complementary methods to assess short-term (days) deposition and medium-term (months) accretion dynamics within a single marsh that contains three salt marsh vegetation types common throughout southeastern (SE) Australia.We found that surface accretion varies among vegetation assemblages, with medium-term (19 months) bulk accretion rates in the upper marsh rush (Juncus) assemblage (1.74 ± 0.13 mm yr-1) consistently in excess of estimated local sea-level rise (1.15 mm yr-1). Accretion rates were lower and less consistent in both the succulent (Sarcocornia, 0.78 ± 0.18 mm yr-1) and grass (Sporobolus, 0.88 ± 0.22 mm yr-1) assemblages located lower in the tidal frame. Short-term (6 days) experiments showed deposition within Juncus plots to be dominated by autochthonous organic inputs with C deposition rates ranging from 1.14 ± 0.41 mg C cm-2 d-1 (neap tidal period) to 2.37 ± 0.44 mg C cm-2 d-1 (spring tidal period), while minerogenic inputs and lower C deposition dominated Sarcocornia (0.10 ± 0.02 to 0.62 ± 0.08 mg C cm-2 d-1) and Sporobolus (0.17 ± 0.04 to 0.40 ± 0.07 mg C cm-2 d-1) assemblages.Elemental (C : N), isotopic (δ13C), mid-infrared (MIR) and 13C nuclear magnetic resonance (NMR) analyses revealed little difference in either the source or character of materials being deposited among neap versus spring tidal periods. Instead, these analyses point to substantial redistribution of materials within the Sarcocornia and Sporobolus assemblages, compared to high retention and preservation of organic inputs in the Juncus assemblage. By

  7. Taxonomic resolution and functional traits in the analysis of tropical oribatid mite assemblages.

    Science.gov (United States)

    Minor, Maria A; Ermilov, Sergey G; Tiunov, Alexei V

    2017-12-01

    We analysed species-level datasets representing Oribatida assemblages along a gradient of old-growth primary tropical forests, secondary forests, and plantation forests in Dong Nai Biosphere Reserve, Vietnam. We identified patterns in abundance, species richness and species assemblages of Oribatida, then applied taxonomic sufficiency approach to the datasets. Using three levels of higher-taxon aggregation, we evaluated whether aggregated datasets are useful in identifying ecological patterns, in comparison to species-level data. Species-level data on Oribatida assemblages clearly separated plantation forests from other forest environments; there was no significant separation between primary and secondary forests. Geographical structuring of species-level assemblages was significant, separating sites from two regions of the reserve. There was a significant concordance between multivariate ordination plots produced for species-level and aggregated (families, suborders/superfamilies) datasets, with Oribatida assemblages of plantation forests consistently separated from two other forest types. Mycobatidae (at family level) and Ceratozetoidea (at suborder/superfamily level) were indicators of plantation forests. The coarsest taxonomic resolution dataset with only four aggregated groups produced no separation of Oribatida assemblages by forest type or region. Moderate level of taxonomic aggregation applied to Oribatida community data did not cause great differences in patterns revealed by multivariate analysis, and therefore could be a valid approach to analysing the structure of tropical Oribatida assemblages. The taxonomic level of suborders and Brachypylina superfamilies appears to be the best compromise for ecological information and ease of identification. Two traits-body size and reproductive mode-were recorded for collected Oribatida species. Community-weighted mean trait value, modified Mason's index of functional divergence, and Rao's index of functional

  8. Intra-Diegetic Cameras as Cinematic Actor Assemblages in Found Footage Horror Cinema

    DEFF Research Database (Denmark)

    Rødje, Kjetil

    2017-01-01

    performance, cameras here take on roles as active agents with the potential to affect other elements within the images as well as the films’ audiences. In found footage horror the assemblage mode of operation creates suspense, since the vulnerability of the camera threatens the viewer's access to the depicted...... events. While human characters and individual entities making up the camera assemblage are disposable, the recording is not. Found footage horror crucially hinges upon the survival of the footage. I will further suggest that these films allow filmmakers to experiment with the acting capabilities of intra...

  9. Bacterial assemblages of the eastern Atlantic Ocean reveal both vertical and latitudinal biogeographic signatures

    Directory of Open Access Journals (Sweden)

    C. J. Friedline

    2012-06-01

    Full Text Available Microbial communities are recognized as major drivers of the biogeochemical processes in the oceans. However, the genetic diversity and composition of those communities is poorly understood. The aim of this study is to investigate the composition of bacterial assemblages in three different water layer habitats: surface (2–20 m, deep chlorophyll maximum (DCM; 28–90 m, and deep (100–4600 m at nine stations along the eastern Atlantic Ocean from 42.8° N to 23.7° S. The sampling of three discrete, predefined habitat types from different depths, Longhurstian provinces, and geographical locations allowed us to investigate whether marine bacterial assemblages show spatial variation and to determine if the observed spatial variation is influenced by current environmental conditions, historical/geographical contingencies, or both. The PCR amplicons of the V6 region of the 16S rRNA from 16 microbial assemblages were pyrosequenced, generating a total of 352 029 sequences; after quality filtering and processing, 257 260 sequences were clustered into 2871 normalized operational taxonomic units (OTU using a definition of 97% sequence identity. Community ecology statistical analyses demonstrate that the eastern Atlantic Ocean bacterial assemblages are vertically stratified and associated with water layers characterized by unique environmental signals (e.g., temperature, salinity, and nutrients. Genetic compositions of bacterial assemblages from the same water layer are more similar to each other than to assemblages from different water layers. The observed clustering of samples by water layer allows us to conclude that contemporary environments are influencing the observed biogeographic patterns. Moreover, the implementation of a novel Bayesian inference approach that allows a more efficient and explicit use of all the OTU abundance data shows a distance effect suggesting the influence of historical contingencies on the composition of bacterial

  10. Identification and mapping of bottom fish assemblages in Davis Strait and southern Baffin Bay

    DEFF Research Database (Denmark)

    Jørgensen, Ole A; Hvingel, Carsten; Møller, P. R.

    2005-01-01

    The bathymetry of Baffin Bay, with shallow sills both to the north and south, creates a relatively isolated body of deep polar water, unique among the Arctic Seas. During 263 trawl hauls completed during October 1999 and September to November 2001, 116 fish species were collected in Davis Strait...... and the southern Baffin Bay (61 degrees 44.1' N-73 degrees 52.8' N, depths of 145-1484 m). The abundance data for the 80 benthic species were used for analyses of the fish fauna diversity and fish assemblages. As a first step, seven assemblages were found by a standard type of cluster analysis. A Bayesian...

  11. Sensitivity of metrics of phylogenetic structure to scale, source of data and species pool of hummingbird assemblages along elevational gradients.

    Science.gov (United States)

    González-Caro, Sebastián; Parra, Juan L; Graham, Catherine H; McGuire, Jimmy A; Cadena, Carlos Daniel

    2012-01-01

    Patterns of phylogenetic structure of assemblages are increasingly used to gain insight into the ecological and evolutionary processes involved in the assembly of co-occurring species. Metrics of phylogenetic structure can be sensitive to scaling issues and data availability. Here we empirically assess the sensitivity of four metrics of phylogenetic structure of assemblages to changes in (i) the source of data, (ii) the spatial grain at which assemblages are defined, and (iii) the definition of species pools using hummingbird (Trochilidae) assemblages along an elevational gradient in Colombia. We also discuss some of the implications in terms of the potential mechanisms driving these patterns. To explore how source of data influence phylogenetic structure we defined assemblages using three sources of data: field inventories, museum specimens, and range maps. Assemblages were defined at two spatial grains: coarse-grained (elevational bands of 800-m width) and fine-grained (1-km(2) plots). We used three different species pools: all species contained in assemblages, all species within half-degree quadrats, and all species either above or below 2000 m elevation. Metrics considering phylogenetic relationships among all species within assemblages showed phylogenetic clustering at high elevations and phylogenetic evenness in the lowlands, whereas those metrics considering only the closest co-occurring relatives showed the opposite trend. This result suggests that using multiple metrics of phylogenetic structure should provide greater insight into the mechanisms shaping assemblage structure. The source and spatial grain of data had important influences on estimates of both richness and phylogenetic structure. Metrics considering the co-occurrence of close relatives were particularly sensitive to changes in the spatial grain. Assemblages based on range maps included more species and showed less phylogenetic structure than assemblages based on museum or field inventories

  12. Sensitivity of metrics of phylogenetic structure to scale, source of data and species pool of hummingbird assemblages along elevational gradients.

    Directory of Open Access Journals (Sweden)

    Sebastián González-Caro

    Full Text Available Patterns of phylogenetic structure of assemblages are increasingly used to gain insight into the ecological and evolutionary processes involved in the assembly of co-occurring species. Metrics of phylogenetic structure can be sensitive to scaling issues and data availability. Here we empirically assess the sensitivity of four metrics of phylogenetic structure of assemblages to changes in (i the source of data, (ii the spatial grain at which assemblages are defined, and (iii the definition of species pools using hummingbird (Trochilidae assemblages along an elevational gradient in Colombia. We also discuss some of the implications in terms of the potential mechanisms driving these patterns. To explore how source of data influence phylogenetic structure we defined assemblages using three sources of data: field inventories, museum specimens, and range maps. Assemblages were defined at two spatial grains: coarse-grained (elevational bands of 800-m width and fine-grained (1-km(2 plots. We used three different species pools: all species contained in assemblages, all species within half-degree quadrats, and all species either above or below 2000 m elevation. Metrics considering phylogenetic relationships among all species within assemblages showed phylogenetic clustering at high elevations and phylogenetic evenness in the lowlands, whereas those metrics considering only the closest co-occurring relatives showed the opposite trend. This result suggests that using multiple metrics of phylogenetic structure should provide greater insight into the mechanisms shaping assemblage structure. The source and spatial grain of data had important influences on estimates of both richness and phylogenetic structure. Metrics considering the co-occurrence of close relatives were particularly sensitive to changes in the spatial grain. Assemblages based on range maps included more species and showed less phylogenetic structure than assemblages based on museum or field

  13. Sensitivity of Metrics of Phylogenetic Structure to Scale, Source of Data and Species Pool of Hummingbird Assemblages along Elevational Gradients

    Science.gov (United States)

    González-Caro, Sebastián; Parra, Juan L.; Graham, Catherine H.; McGuire, Jimmy A.; Cadena, Carlos Daniel

    2012-01-01

    Patterns of phylogenetic structure of assemblages are increasingly used to gain insight into the ecological and evolutionary processes involved in the assembly of co-occurring species. Metrics of phylogenetic structure can be sensitive to scaling issues and data availability. Here we empirically assess the sensitivity of four metrics of phylogenetic structure of assemblages to changes in (i) the source of data, (ii) the spatial grain at which assemblages are defined, and (iii) the definition of species pools using hummingbird (Trochilidae) assemblages along an elevational gradient in Colombia. We also discuss some of the implications in terms of the potential mechanisms driving these patterns. To explore how source of data influence phylogenetic structure we defined assemblages using three sources of data: field inventories, museum specimens, and range maps. Assemblages were defined at two spatial grains: coarse-grained (elevational bands of 800-m width) and fine-grained (1-km2 plots). We used three different species pools: all species contained in assemblages, all species within half-degree quadrats, and all species either above or below 2000 m elevation. Metrics considering phylogenetic relationships among all species within assemblages showed phylogenetic clustering at high elevations and phylogenetic evenness in the lowlands, whereas those metrics considering only the closest co-occurring relatives showed the opposite trend. This result suggests that using multiple metrics of phylogenetic structure should provide greater insight into the mechanisms shaping assemblage structure. The source and spatial grain of data had important influences on estimates of both richness and phylogenetic structure. Metrics considering the co-occurrence of close relatives were particularly sensitive to changes in the spatial grain. Assemblages based on range maps included more species and showed less phylogenetic structure than assemblages based on museum or field inventories

  14. SESAM – a new framework integrating macroecological and species distribution models for predicting spatio-temporal patterns of species assemblages

    DEFF Research Database (Denmark)

    Guisan, Antoine; Rahbek, Carsten

    2011-01-01

    , and ecological assembly rules to constrain predictions of the richness and composition of species assemblages obtained by stacking predictions of individual species distributions. We believe that such a framework could prove useful in many theoretical and applied disciplines of ecology and evolution, both......Two different approaches currently prevail for predicting spatial patterns of species assemblages. The first approach (macroecological modelling, MEM) focuses directly on realized properties of species assemblages, whereas the second approach (stacked species distribution modelling, S-SDM) starts...... with constituent species to approximate the properties of assemblages. Here, we propose to unify the two approaches in a single ‘spatially explicit species assemblage modelling’ (SESAM) framework. This framework uses relevant designations of initial species source pools for modelling, macroecological variables...

  15. Singapore's "Global Assemblage": Digging into the Culture of Education Policy Making

    Science.gov (United States)

    Koh, Aaron

    2011-01-01

    As a meta-concept, "globalization" has the tendency to create master categories such as an emergent global/izing education policy. This paper critiques the thinking and assumptions that underpin a global education policy. The paper proposes that "global assemblage" is a more helpful conceptual thinking about the way education…

  16. Brown rot in inner heartwood: why large logs support characteristics saproxylic beetle assemblages of conservation concern

    Science.gov (United States)

    Marie Yee; Simon J. Grove; Alastair M.M. Richardson; Caroline L. Mohammed

    2006-01-01

    It is not clear why large diameter logs generally host saproxylic beetle assemblages that are different from those of small diameter logs. In a study in Tasmanian wet eucalypt forest, two size-classes of Eucalyptus obliqua logs (>100cm and 30-60cm diameter) were destructively sampled to assess their beetle fauna and the associations of this fauna...

  17. Spatial and temporal dynamics of drosophilid larval assemblages associated to fruits

    Directory of Open Access Journals (Sweden)

    Renata Alves da Mata

    2015-03-01

    Full Text Available The study of organisms and their resources is critical to further understanding population dynamics in space and time. Although drosophilids have been widely used as biological models, their relationship with breeding and feeding sites has received little attention. Here, we investigate drosophilids breeding in fruits in the Brazilian Savanna, in two contrasting vegetation types, throughout 16 months. Specifically, larval assemblages were compared between savannas and forests, as well as between rainy and dry seasons. The relationships between resource availability and drosophilid abundance and richness were also tested. The community (4,022 drosophilids of 23 species and 2,496 fruits of 57 plant taxa varied widely in space and time. Drosophilid assemblages experienced a strong bottleneck during the dry season, decreasing to only 0.5% of the abundance of the rainy season. Additionally, savannas displayed lower richness and higher abundance than the forests, and were dominated by exotic species. Both differences in larval assemblages throughout the year and between savannas and gallery forests are consistent with those previously seen in adults. Although the causes of this dynamic are clearly multifactorial, resource availability (richness and abundance of rotten fruits was a good predictor of the fly assemblage structure.

  18. Seasonal dynamics of ectomycorrhizal fungus assemblages on oak seedlings in the southeastern Appalachian Mountains

    Science.gov (United States)

    John F. Walker; Orson K. Jr. Miller; Jonathan L. Horton

    2008-01-01

    The potential for seasonal dynamics in ectomycorrhizal (EM) fungal assemblages has important implications for the ecology of both the host trees and the fungal associates. We compared EM fungus distributions on root systems of out-planted oak seedlings at two sites in mixed southeastern Appalachian Mountain forests at the Coweeta Hydrologic Laboratory in North Carolina...

  19. Environmental Variability and Macrophyte Assemblages in Coastal Lagoon Types of Western Greece (Mediterranean Sea

    Directory of Open Access Journals (Sweden)

    Chrysoula Christia

    2018-02-01

    Full Text Available Coastal lagoon types of Western Greece were allocated to a spectrum of meso to polyhaline chocked lagoons; poly to euhaline restricted lagoons; and euhaline restricted lagoons along the Ionian Sea coast. This diversity comprises wide ranges of physical, chemical and environmental parameters in a seasonal and annual scale, which explains the variability in the distribution of benthic macrophytes. Four different macrophyte assemblages were distinguished, characterized by annual or perennial species. Extensive statistical analysis showed that salinity and nitrate concentrations had a great impact on the composition and distribution of macrophyte assemblages into lagoon types that also changed their abundance on a seasonal and annual scale. During the monitoring period, an important salinity shift in a chocked lagoon might cause the gradual loss of Zostera noltii and its replacement by Ruppia cirrhosa. Restricted lagoons were characterized by higher species diversity, while the other three identified macrophyte assemblages were dominated by the angiosperms Ruppia cirrhosa and Cymodocea nodosa. This integrated study of coastal lagoons is likely to be broadly applicable, since it was based on important parameters affecting such ecosystems, and the provided links between macrophyte assemblages and abiotic factors are of critical importance to improve management and environmental policies.

  20. The spatial distribution of coastal fish assemblage in Côte d'Ivoire's ...

    African Journals Online (AJOL)

    The spatial distribution of coastal fish assemblage in Côte d'Ivoire's Exclusive Economic Zone (EEZ), West Africa. Soumaïla Sylla, Kouadio Fréderic Kouakou, Christian Bernard Tia, Stanislas Silvain Yao, Boua Célestin Atse ...

  1. Soil, but not cultivar, shapes the structure of arbuscular mycorrhizal fungal assemblages associated with strawberry.

    Science.gov (United States)

    Santos-González, Juan C; Nallanchakravarthula, Srivathsa; Alström, Sadhna; Finlay, Roger D

    2011-07-01

    Arbuscular mycorrhizal fungi are widespread plant symbionts occurring in most agricultural crops, where they can play key roles in the growth and health of their plant hosts. Plant benefits can depend on the identity of the associated arbuscular mycorrhizal fungi (AMF), but little is known about the identity of the fungal partners in most agricultural systems. In this study, we describe the AMF assemblages associated with four cultivars of strawberry in an outdoor experiment using two field soils with different origin and management history. Assemblages were characterised by clone library sequencing of 18S rRNA gene fragments. Soil dramatically influenced the degree of mycorrhizal colonisation and AMF assemblage structure in the roots. No differences were observed between cultivars. Fungi belonging to the genus Acaulospora dominated the AMF assemblages in one soil, but they were not detected in the other. These results suggest that physicochemical soil characteristics and management can play a role in determining the identity and structure of microbial communities associated with particular hosts in agricultural systems.

  2. Effect of oil palm on the Plecoptera and Trichoptera (Insecta) assemblages in streams of eastern Amazon.

    Science.gov (United States)

    de Paiva, Carina Kaory Sasahara; de Faria, Ana Paula Justino; Calvão, Lenize Batista; Juen, Leandro

    2017-08-01

    The production of oil palm is expected to increase in the Amazon region. However, expansion of oil palm plantation leads to significant changes in the physical structure of aquatic ecosystems, mainly through the reduction of riparian vegetation that is essential for aquatic biodiversity. Here, we evaluated the effects of oil palm on the physical habitat structure of Amazonian stream environments and assemblages of Plecoptera and Trichoptera (PT), ​both found in these streams. We compared streams sampled in oil palm plantations (n = 13) with natural forest areas ("reference" streams, n = 8), located in the eastern Amazon, Brazil. Our results showed that oil palm streams were more likely to be in close proximity to roads, had higher pH values, and higher amounts of fine substrate deposited in the channel than reference streams. Further, these environmental changes had important effects on the aquatic invertebrate assemblages, reducing the abundance and richness of PT. Nevertheless, the genera composition of the assemblages did not differ between reference and oil palm (PERMANOVA, pseudo-F (1,19)  = 1.891; p = 0.111). We conclude that oil palm production has clear negative impacts on aquatic environments and PT assemblages in Amazonian streams. We recommend that oil palm producers invest more in planning of road networks to avoid the construction of roads near to the riparian vegetation. This planning can minimize impacts of oil palm production on aquatic systems in the Amazon.

  3. Detecting carbon uptake by individual algae in multi-species assemblages

    Science.gov (United States)

    Knowing how different algal species utilize carbon (C) can help predict how assemblage changes will alter energy input and flow in ecosystems, and can help refine algal species selection for bioengineering applications. Fourier-transform infrared (FTIR) microspectroscopy was used to measure inorgani...

  4. Microhabitat influence on larval fish assemblages within vegetated beds: Implications for restoration

    Science.gov (United States)

    We examined larval and juvenile fish assemblage structure in relation to microhabitat variables within the St. Louis River estuary, a drowned river mouth of Lake Superior. Fish were sampled in vegetated beds throughout the estuary, across a gradient of vegetation types and densit...

  5. Microhabitat Influence on Larval Fish Assemblages Within Vegetated Beds: Implications for Tubenose Goby Detection and Invasion

    Science.gov (United States)

    We examined larval and juvenile fish assemblage structure in relation to microhabitat variables within the St. Louis River estuary, a drowned river mouth of Lake Superior. Fish were sampled in vegetated beds throughout the estuary, across a gradient of vegetation types and densit...

  6. Lower Miocene plant assemblage with coastal-marsh herbaceous monocots from the Vienna Basin (Slovakia

    Directory of Open Access Journals (Sweden)

    Kvaček Zlatko

    2014-06-01

    Full Text Available A new plant assemblage of Cerová-Lieskové from Lower Miocene (Karpatian deposits in the Vienna Basin (western Slovakia is preserved in a relatively deep, upper-slope marine environment. Depositional conditions with high sedimentation rates allowed exceptional preservation of plant remains. The plant assemblage consists of (1 conifers represented by foliage of Pinus hepios and Tetraclinis salicornioides, a seed cone of Pinus cf. ornata, and by pollen of the Cupressaceae, Pinaceae, Pinus sp. and Cathaya sp., and (2 angiosperms represented by Cinnamomum polymorphum, Platanus neptuni, Potamogeton sp. and lauroid foliage, by pollen of Liquidambar sp., Engelhardia sp. and Craigia sp., and in particular by infructescences (so far interpreted as belonging to cereal ears. We validate genus and species assignments of the infructescences: they belong to Palaeotriticum Sitár, including P. mockii Sitár and P. carpaticum Sitár, and probably represent herbaceous monocots that inhabited coastal marshes, similar to the living grass Spartina. Similar infructescences occur in the Lower and Middle Miocene deposits of the Carpathian Foredeep (Slup in Moravia, Tunjice Hills (Žale in Slovenia, and probably also in the Swiss Molasse (Lausanne. This plant assemblage demonstrates that the paleovegetation was represented by evergreen woodland with pines and grasses in undergrowth, similar to vegetation inhabiting coastal brackish marshes today. It also indicates subtropical climatic conditions in the Vienna Basin (central Paratethys, similar to those implied by other coeval plant assemblages from Central Europe

  7. Different surrounding landscapes may result in different fish assemblages in East African seagrass beds

    NARCIS (Netherlands)

    Dorenbosch, M.; Grol, M.G.G.; Nagelkerken, I.; Velde, G. van der

    2006-01-01

    Few studies have considered how seagrass fish assemblages are influenced by surrounding habitats. This information is needed for a better understanding of the connectivity between tropical coastal ecosystems. To study the effects of surrounding habitats on the composition, diversity and densities of

  8. Asian longhorned beetle complicates the relationship between taxonomic diversity and pest vulnerability in street tree assemblages

    Science.gov (United States)

    Urban foresters routinely emphasise the importance of taxonomic diversity to reduce the vulnerability of tree assemblages to invasive pests, but it is unclear to what extent diversity reduces vulnerability to polyphagous (i.e. generalist) pests. Drawing on field data from seven c...

  9. Comparison of termite assemblages along a landuse gradient on peat areas in Sarawak, Malaysia.

    NARCIS (Netherlands)

    Vaessen, T.; Verwer, C.; Demies, M.; Kaliang, H.; Meer, van der P.J.

    2011-01-01

    VAESSEN T, VERWER C, DEMIES M, KALIANG H & VAN DER MEER PJ. 2011. Comparison of termite assemblages along a landuse gradient on peat areas in Sarawak, Malaysia. In this study we assessed the species density and relative abundance of termites in peat land in Sarawak, Malaysia. Termites were

  10. Structure and composition of the liana assemblage of a mixed rainforest in the Congo Basin

    NARCIS (Netherlands)

    Ewango, C.E.N.; Bongers, F.; Makana, J.R.; Poorter, L.; Sosef, M.S.M.

    2015-01-01

    Background and aims – The Congo Basin lowland forest represents one of the largest tropical forest blocks in the world, but its liana assemblage has never been characterized. We evaluate liana floristics, diversity, and structure in the Ituri Forest, and determine the effects of forest structure and

  11. Influence of matrix type on tree community assemblages along tropical dry forest edges.

    Science.gov (United States)

    Benítez-Malvido, Julieta; Gallardo-Vásquez, Julio César; Alvarez-Añorve, Mariana Y; Avila-Cabadilla, Luis Daniel

    2014-05-01

    • Anthropogenic habitat edges have strong negative consequences for the functioning of tropical ecosystems. However, edge effects on tropical dry forest tree communities have been barely documented.• In Chamela, Mexico, we investigated the phylogenetic composition and structure of tree assemblages (≥5 cm dbh) along edges abutting different matrices: (1) disturbed vegetation with cattle, (2) pastures with cattle and, (3) pastures without cattle. Additionally, we sampled preserved forest interiors.• All edge types exhibited similar tree density, basal area and diversity to interior forests, but differed in species composition. A nonmetric multidimensional scaling ordination showed that the presence of cattle influenced species composition more strongly than the vegetation structure of the matrix; tree assemblages abutting matrices with cattle had lower scores in the ordination. The phylogenetic composition of tree assemblages followed the same pattern. The principal plant families and genera were associated according to disturbance regimes as follows: pastures and disturbed vegetation (1) with cattle and (2) without cattle, and (3) pastures without cattle and interior forests. All habitats showed random phylogenetic structures, suggesting that tree communities are assembled mainly by stochastic processes. Long-lived species persisting after edge creation could have important implications in the phylogenetic structure of tree assemblages.• Edge creation exerts a stronger influence on TDF vegetation pathways than previously documented, leading to new ecological communities. Phylogenetic analysis may, however, be needed to detect such changes. © 2014 Botanical Society of America, Inc.

  12. Airborne bacterial assemblage in a zero carbon building: A case study.

    Science.gov (United States)

    Leung, M H Y; Tong, X; Tong, J C K; Lee, P K H

    2018-01-01

    Currently, there is little information pertaining to the airborne bacterial communities of green buildings. In this case study, the air bacterial community of a zero carbon building (ZCB) in Hong Kong was characterized by targeting the bacterial 16S rRNA gene. Bacteria associated with the outdoor environment dominated the indoor airborne bacterial assemblage, with a modest contribution from bacteria associated with human skin. Differences in overall community diversity, membership, and composition associated with short (day-to-day) and long-term temporal properties were detected, which may have been driven by specific environmental genera and taxa. Furthermore, time-decay relationships in community membership (based on unweighted UniFrac distances) and composition (based on weighted UniFrac distances) differed depending on the season and sampling location. A Bayesian source-tracking approach further supported the importance of adjacent outdoor air bacterial assemblage in sourcing the ZCB indoor bioaerosol. Despite the unique building attributes, the ZCB microbial assemblage detected and its temporal characteristics were not dissimilar to that of conventional built environments investigated previously. Future controlled experiments and microbial assemblage investigations of other ZCBs will undoubtedly uncover additional knowledge related to how airborne bacteria in green buildings may be influenced by their distinctive architectural attributes. © 2017 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd.

  13. Microbial assemblages in soil microbial succession after glacial retreat in Svalbard (High Arctic)

    Czech Academy of Sciences Publication Activity Database

    Kaštovská, Klára; Elster, Josef; Stibal, Marek; Šantrůčková, H.

    2005-01-01

    Roč. 50, č. 3 (2005), s. 396-407 ISSN 0095-3628 Institutional research plan: CEZ:AV0Z6005908 Keywords : microbial assemblages * deglaciated soil * Svalbard Subject RIV: EF - Botanics Impact factor: 2.674, year: 2005

  14. The Roman-Irish Bath: Medical/health history as therapeutic assemblage.

    Science.gov (United States)

    Foley, Ronan

    2014-04-01

    The invention of a new form of hot-air bath in Blarney, Ireland in 1856, variously known in its lifetime as the Roman-Irish or Turkish Bath, acted as the starting point for a the production of a globalised therapeutic landscape. Tracking the diffusion of the Roman-Irish bath template from its local invention in Ireland to a global reach across the Victorian world and recognizing its place within a wider hydrotherapeutic history, this paper frames that diffusion as a valuable empirical addition to assemblage theory. The specific empirical history of the spread of the Roman-Irish/Turkish bath idea is drawn from primary archival and secondary historical sources. It is then discussed and, drawing from work on assemblage theory, analyzed against three broad themes: mobile networks, socio-material practices and contested emergence. The emergent relational geographies of the Roman-Irish Bath identify important roles for the diffusion and transformation of specific medical settings, identities and functions. These were linked in turn to competing social-healing pathways wherein bodies were technologically and morally managed, to produce a more inhabited form of therapeutic assemblage. In all cases the differential diffusion of the bath idea, it's shifting and fractured material forms and multiple inhabitations and discourses were contested and mobile and spoke to an assemblage approach which has ripe potential for exploration across a range of medical/health geography settings. Copyright © 2014 Elsevier Ltd. All rights reserved.

  15. A multi-scaled approach to evaluating the fish assemblage structure within southern Appalachian streams USA.

    Science.gov (United States)

    Kirsch, Joseph; Peterson, James T.

    2014-01-01

    There is considerable uncertainty about the relative roles of stream habitat and landscape characteristics in structuring stream-fish assemblages. We evaluated the relative importance of environmental characteristics on fish occupancy at the local and landscape scales within the upper Little Tennessee River basin of Georgia and North Carolina. Fishes were sampled using a quadrat sample design at 525 channel units within 48 study reaches during two consecutive years. We evaluated species–habitat relationships (local and landscape factors) by developing hierarchical, multispecies occupancy models. Modeling results suggested that fish occupancy within the Little Tennessee River basin was primarily influenced by stream topology and topography, urban land coverage, and channel unit types. Landscape scale factors (e.g., urban land coverage and elevation) largely controlled the fish assemblage structure at a stream-reach level, and local-scale factors (i.e., channel unit types) influenced fish distribution within stream reaches. Our study demonstrates the utility of a multi-scaled approach and the need to account for hierarchy and the interscale interactions of factors influencing assemblage structure prior to monitoring fish assemblages, developing biological management plans, or allocating management resources throughout a stream system.

  16. Agency and Assemblage in Pattern Generalisation: A Materialist Approach to Learning

    Science.gov (United States)

    Ferrara, Francesca; Ferrari, Giulia

    2017-01-01

    In this paper, we draw on the contemporary perspective of inclusive materialism offered by de Freitas and Sinclair to contribute to current discussions on the role of the body in the learning of mathematics. Using the notions of "distributed agency" and "assemblage," we illustrate the way in which three students engage with a…

  17. Impacts of exotic mangroves and mangrove control on tide pool fish assemblages

    Science.gov (United States)

    Richard A. MacKenzie; Cailtin L. Kryss

    2013-01-01

    Fish were sampled from tide pools in Hawaii to determine how exotic mangroves Rhizophora mangle and the use of herbicides to chemically eradicate them are impacting tide pool fish assemblages. Ecological parameters were compared among mangrove-invaded, native vegetated, and non-vegetated tide pools before and after mangroves had been chemically...

  18. Spatial changes in sublittoral soft-bottom polychaete assemblages due to river inputs and sewage discharges

    Science.gov (United States)

    Cardell, María José; Sardà, Rafael; Romero, Javier

    1999-07-01

    Spatial changes in species composition and structure of sublittoral soft-bottom polychaete assemblages along a transect parallel to the shoreline off the Barcelonès and Maresme regions on the Spanish Catalan coast (NW Mediterranean sea) are described. The transect (20 m mean depth) covers 30 km through an area affected by both water sewage discharges and river outflow. These effluents generate a spatial gradient of both silt and organic enrichment, according to the prevailing southerly currents in the zone. South of the effluents, eutrophized sediments supported a macrofaunal assemblage which was typical of polluted bottoms, characterized by the massive presence of Capitella capitata and Malacoceros fuliginosus, high abundance and biomass, low values of species richness, and a simplified trophic structure dominated by surface and subsurface-deposit feeders. North of the effluents, both the mud and organic matter content in sediment decreased drastically and the polychaete assemblages described were progressively less affected with distance. Thus, a clear change in species composition, as well as low values of abundance and biomass, increases in species richness, and a more complex trophic structure on the polychaete assemblages was observed north rather than south of the effluents.

  19. Distribution patterns of fish assemblages in an Eastern Mediterranean intermittent river

    Directory of Open Access Journals (Sweden)

    Vardakas L.

    2015-01-01

    Full Text Available The distribution patterns of fish assemblages within streams can provide insights for river type classifications and may warrant specific conservation actions. However, there is limited knowledge of how fish assemblages assort along a longitudinal axis in Mediterranean intermittent streams. Patterns in spatial and temporal distribution of fish communities were analysed in a Mediterranean intermittent river (Evrotas River located in Southern Greece, hosting three endemic range restricted species of high conservation concern, during the period 2007−2009, with 80% of the river’s total length desiccating in the 2007 and 2008 droughts. The general trend was an increase in fish density and species richness along an upstream-downstream gradient. Fish assemblages from upstream to downstream were characterized by a decrease of the most rheophilic species (Squalius keadicus and an increase of the most stagnophilic species (Tropidophoxinellus spartiaticus. Three river segments, characterized by a high degree of homogeneity were delineated. Habitat and environmental preferences for the studied fish species were identified, with elevation and low flowing habitats being the most important environmental factors affecting fish distribution patterns. The current study provides evidence that even in an intermittent river an assemblage pattern following a longitudinal gradient can be identified, mainly due to the lack of instream barriers that allows recolonization after flow resumption.

  20. Instability of copronecrophagous beetle assemblages (Coleoptera: Scarabaeinae) in a mountainous tropical landscape of Mexico.

    Science.gov (United States)

    Halffter, Gonzalo; Pineda, Eduardo; Arellano, Lucrecia; Escobar, Federico

    2007-12-01

    We analyzed changes over time in species composition and functional guild structure (temporal beta diversity) for natural assemblages and those modified by humans in a fragmented, tropical mountain landscape. The assemblages belong to cloud forests (the original vegetation type), secondary forests, traditional shaded coffee plantations, commercial shaded coffee plantations, and a cattle pasture. Copronecrophagous beetles, subfamily Scarabaeinae (Insecta: Coleoptera: Scarabaeidae), were used as the indicator group. This group has been used in previous studies and other tropical forests and has been found to be a good indicator of the effects of anthropogenic change. For each assemblage, we compared samples that were collected several years apart. Changes were found in species composition, order of abundance, and in the proportion that a given species is present in the different functional groups. The changes that occurred between samplings affected the less abundant species in the cloud forest and in the pasture. In the other vegetation types, both abundant and less abundant species were affected. Their order of abundance and proportion in the different guilds also changed. This study shows that, although landscape richness remains relatively constant, richness at the local level (alpha diversity) changes notably even over short lapses of time. This could be a characteristic of landscapes with intermediate degrees of disturbance (such as those that have been partially modified for human use), where assemblage composition is very fluid.

  1. Impacts of discarded plastic bags on marine assemblages and ecosystem functioning.

    Science.gov (United States)

    Green, Dannielle Senga; Boots, Bas; Blockley, David James; Rocha, Carlos; Thompson, Richard

    2015-05-05

    The accumulation of plastic debris is a global environmental problem due to its durability, persistence, and abundance. Although effects of plastic debris on individual marine organisms, particularly mammals and birds, have been extensively documented (e.g., entanglement and choking), very little is known about effects on assemblages and consequences for ecosystem functioning. In Europe, around 40% of the plastic items produced are utilized as single-use packaging, which rapidly accumulate in waste management facilities and as litter in the environment. A range of biodegradable plastics have been developed with the aspiration of reducing the persistence of litter; however, their impacts on marine assemblages or ecosystem functioning have never been evaluated. A field experiment was conducted to assess the impact of conventional and biodegradable plastic carrier bags as litter on benthic macro- and meio-faunal assemblages and biogeochemical processes (primary productivity, redox condition, organic matter content, and pore-water nutrients) on an intertidal shore near Dublin, Ireland. After 9 weeks, the presence of either type of bag created anoxic conditions within the sediment along with reduced primary productivity and organic matter and significantly lower abundances of infaunal invertebrates. This indicates that both conventional and biodegradable bags can rapidly alter marine assemblages and the ecosystem services they provide.

  2. Experimental effects of grazers on autotrophic species assemblages across a nitrate gradient in Florida springs

    Science.gov (United States)

    Springs face accelerated degradation of ecosystem structure, namely in the form of autotrophic species assemblage shifts from submerged vascular macrophytes to benthic filamentous algae. Increasing nitrate concentrations have been cited as a primary driver of this shift and numeric nutrient criteria...

  3. Abundance, size composition and benthic assemblages of two Mediterranean echinoids off the

    Directory of Open Access Journals (Sweden)

    Elzahrae Elmasry

    2015-12-01

    Full Text Available This study is concerned with the variability in abundance, size composition and benthic assemblages of two echinoid species, the common sea urchin Paracentrotus lividus (Lamarck, 1816 and black urchin Arbacia lixula (Linnaeus, 1758 in the Southeastern Mediterranean (SEM along the coast of Alexandria, Egypt. Four seasonal trips were made during the years 2014–2015 covering 55 km of the shore with depths ranging between 3 and 9 m. The sea urchin species composition, density and size structure and distribution were compared. The associated macrobenthic invertebrates with prominent presence and biomass were observed as well as other benthic fauna and flora associations. The present results showed that P. lividus was the dominant echinoid spatially and temporally. A. lixula showed frequent occurrence in Sidi Bishr and Sidi Gaber stations in the spring season. The most dominant size class was the medium to large-sized classes for P. lividus and large-sized classes for A. lixula. The commercial size for the edible P. lividus represented 33% of the sampled population. Furthermore, the most dominant macrobenthic assemblages beside the echinoid population were primarily oysters, sea cucumbers, and mussels. Beside these, assemblage of seaweeds (red, green, brown and crustose algae, Porifera, Cnidaria, Crustacea, other Echinodermata, Bivalvia, Gastropoda, Tunicata, Bryozoa and Annelida were found. The present study shows that the investigated area represents stable habitats for the echinoid population with rich and diversified algal assemblages as well as other potential food resources.

  4. Iterative evolution of sympatric seacow (Dugongidae, Sirenia assemblages during the past ~26 million years.

    Directory of Open Access Journals (Sweden)

    Jorge Velez-Juarbe

    Full Text Available Extant sirenians show allopatric distributions throughout most of their range. However, their fossil record shows evidence of multispecies communities throughout most of the past ∼26 million years, in different oceanic basins. Morphological differences among co-occurring sirenian taxa suggest that resource partitioning played a role in structuring these communities. We examined body size and ecomorphological differences (e.g., rostral deflection and tusk morphology among sirenian assemblages from the late Oligocene of Florida, early Miocene of India and early Pliocene of Mexico; each with three species of the family Dugongidae. Although overlapping in several ecomorphological traits, each assemblage showed at least one dominant trait in which coexisting species differed. Fossil sirenian occurrences occasionally are monotypic, but the assemblages analyzed herein show iterative evolution of multispecies communities, a phenomenon unparalleled in extant sirenian ecology. As primary consumers of seagrasses, these communities likely had a strong impact on past seagrass ecology and diversity, although the sparse fossil record of seagrasses limits direct comparisons. Nonetheless, our results provide robust support for previous suggestions that some sirenians in these extinct assemblages served as keystone species, controlling the dominance of climax seagrass species, permitting more taxonomically diverse seagrass beds (and sirenian communities than many of those observed today.

  5. Using benthic diatom assemblages to assess human impacts on streams across a rural to urban gradient.

    Science.gov (United States)

    Yang, Ying; Cao, Jin-Xiang; Pei, Guo-Feng; Liu, Guo-Xing

    2015-11-01

    Benthic diatom assemblages on the natural substrata were investigated at 21 sites of the Ganhe River watershed (China) once per season and in addition, early spring in 2013. A total of 487 diatom taxa from 36 genera were identified during five investigations. The assemblages were dominated by Achnanthidium minutissimum (Kützing) Czarnecki and Cocconeis placentula in the rural reach, whereas Navicula, Nitzschia, and Gomphonema species were characteristic of urbanized sites. Our results suggest that biodiversity was positively related to high nutrient levels and strongly negatively related to diatom-based indices. The periphyton biomass (expressed as chlorophyll a and ash-free dry mass) was not related to water quality. Canonical correspondence analysis (CCA) showed that the nutrient concentration gradient was the most important factor that affected the diatom assemblage composition and species distribution. The diatom-based indices (specific pollution sensitivity index (IPS), biological diatom index (IBD), and trophic diatom index (TDI)) were significantly positively correlated with water quality and are adequate for use in China. Slight changes in the biodiversity and diatom-based indices followed a temporal pattern. The species composition was less related to the season or hydrological characteristics of the river but more strongly related to differences in the trophic status. In this region, urbanization masked the impact of rural land use on benthic diatoms. The research will expand the understanding of using benthic diatom assemblages for water quality monitoring in urban streams and improve watershed-scale management and conservation efforts in the Ganhe River, China.

  6. Grass assemblages and diversity of conservation areas on the coastal plain south of Maputo Bay, Mozambique

    Directory of Open Access Journals (Sweden)

    S. J. Siebert

    2004-09-01

    Full Text Available A floristic analysis of the grass species assemblages of the Licuati Forest and Maputo Elephant Reserves south of Maputo Bay, Mozambique, is presented. Sampling of grass data was undertaken in six previously described, major vegetation types. TWINSPAN divisions distinguished grass assemblages that are characteristic for these major vegetation types of the study area. The results were supported by an Indirect Gradient Analysis. Further TWINSPAN divisions of a larger Maputaland data set indicated a floristic relationship between grass assemblages of similar major vegetation types in the study area and South Africa. This relationship was supported by high similarity values (> 65%, obtained with Sorenson's Coefficient. The coefficient also indicated varying degrees of similarity between grass assemblages of different major vegetation types within the study area. A rich diversity of 115 grass species and infraspecific taxa was recorded for the study area. The Chloridoideae and Panicoideae dominate the grass diversity and the genera with the most species include Eragrostis, Panicum and Digitaria. Most grass species in the study area are perennials and have a tufted growth form, but this varies considerably between vegetation types.

  7. Assemblage characteristics and diet of fish in the shallow coastal waters of James Ross Island, Antarctica

    Czech Academy of Sciences Publication Activity Database

    Jurajda, Pavel; Roche, Kevin Francis; Sedláček, I.; Všetičková, Lucie

    2016-01-01

    Roč. 39, č. 12 (2016), s. 2299-2309 ISSN 0722-4060 R&D Projects: GA ČR GBP505/12/G112 Institutional support: RVO:68081766 Keywords : Antarctic Peninsula * Fish assemblage structure * Notothenioidei * Shallow coastal waters * Ice pack * Czech Antarctic Station Subject RIV: EH - Ecology, Behaviour Impact factor: 1.949, year: 2016

  8. Attributing functions to ectomycorrhizal fungal identities in assemblages for nitrogen acquisition under stress.

    Science.gov (United States)

    Pena, Rodica; Polle, Andrea

    2014-02-01

    Mycorrhizal fungi have a key role in nitrogen (N) cycling, particularly in boreal and temperate ecosystems. However, the significance of ectomycorrhizal fungal (EMF) diversity for this important ecosystem function is unknown. Here, EMF taxon-specific N uptake was analyzed via (15)N isotope enrichment in complex root-associated assemblages and non-mycorrhizal root tips in controlled experiments. Specific (15)N enrichment in ectomycorrhizas, which represents the N influx and export, as well as the exchange of (15)N with the N pool of the root tip, was dependent on the fungal identity. Light or water deprivation revealed interspecific response diversity for N uptake. Partial taxon-specific N fluxes for ectomycorrhizas were assessed, and the benefits of EMF assemblages for plant N nutrition were estimated. We demonstrated that ectomycorrhizal assemblages provide advantages for inorganic N uptake compared with non-mycorrhizal roots under environmental constraints but not for unstressed plants. These benefits were realized via stress activation of distinct EMF taxa, which suggests significant functional diversity within EMF assemblages. We developed and validated a model that predicts net N flux into the plant based on taxon-specific (15)N enrichment in ectomycorrhizal root tips. These results open a new avenue to characterize the functional traits of EMF taxa in complex communities.

  9. The health of benthic diatom assemblages in lower stretch of a ...

    Indian Academy of Sciences (India)

    This study examines the ecological state of epilithic diatom assemblages along the lower stretch of Mandakini, a glacier-fed Himalayan river. The diatoms were sampled at four stations during winter and summer, only once in each season. Valve counts were obtained from Naphrax mounts prepared from each sample.

  10. Trait estimation in herbaceous plant assemblages from in situ canopy spectra

    NARCIS (Netherlands)

    Roelofsen, H.D.; Bodegom, van P.M.; Kooistra, L.; Witte, J.M.

    2013-01-01

    Estimating plant traits in herbaceous plant assemblages from spectral reflectance data requires aggregation of small scale trait variations to a canopy mean value that is ecologically meaningful and corresponds to the trait content that affects the canopy spectral signal. We investigated estimation

  11. Large-scale patterns in morphological diversity and species assemblages in Neotropical Triatominae (Heteroptera: Reduviidae).

    Science.gov (United States)

    Fergnani, Paula Nilda; Ruggiero, Adriana; Ceccarelli, Soledad; Menu, Frédéric; Rabinovich, Jorge

    2013-12-01

    We analysed the spatial variation in morphological diversity (MDiv) and species richness (SR) for 91 species of Neotropical Triatominae to determine the ecological relationships between SR and MDiv and to explore the roles that climate, productivity, environmental heterogeneity and the presence of biomes and rivers may play in the structuring of species assemblages. For each 110 km x 110 km-cell on a grid map of America, we determined the number of species (SR) and estimated the mean Gower index (MDiv) based on 12 morphological attributes. We performed bootstrapping analyses of species assemblages to identify whether those assemblages were more similar or dissimilar in their morphology than expected by chance. We applied a multi-model selection procedure and spatial explicit analyses to account for the association of diversity-environment relationships. MDiv and SR both showed a latitudinal gradient, although each peaked at different locations and were thus not strictly spatially congruent. SR decreased with temperature variability and MDiv increased with mean temperature, suggesting a predominant role for ambient energy in determining Triatominae diversity. Species that were more similar than expected by chance co-occurred near the limits of the Triatominae distribution in association with changes in environmental variables. Environmental filtering may underlie the structuring of species assemblages near their distributional limits.

  12. Differential response of fish assemblages to coral reef-based seaweed farming.

    Directory of Open Access Journals (Sweden)

    E James Hehre

    Full Text Available As the global demand for seaweed-derived products drives the expansion of seaweed farming onto shallow coral ecosystems, the effects of farms on fish assemblages remain largely unexplored. Shallow coral reefs provide food and shelter for highly diverse fish assemblages but are increasingly modified by anthropogenic activities. We hypothesized that the introduction of seaweed farms into degraded shallow coral reefs had potential to generate ecological benefits for fish by adding structural complexity and a possible food source. We conducted 210 transects at 14 locations, with sampling stratified across seaweed farms and sites adjacent to and distant from farms. At a seascape scale, locations were classified by their level of exposure to human disturbance. We compared sites where (1 marine protected areas (MPAs were established, (2 neither MPAs nor blast fishing was present (hence "unprotected", and (3 blast fishing occurred. We observed 80,186 fish representing 148 species from 38 families. The negative effects of seaweed farms on fish assemblages appeared stronger in the absence of blast fishing and were strongest when MPAs were present, likely reflecting the positive influence of the MPAs on fish within them. Species differentiating fish assemblages with respect to seaweed farming and disturbance were typically small but also included two key target species. The propensity for seaweed farms to increase fish diversity, abundance, and biomass is limited and may reduce MPA benefits. We suggest that careful consideration be given to the placement of seaweed farms relative to MPAs.

  13. Comparing demersal fish assemblage between periods of contrasting climate and fishing pressure

    NARCIS (Netherlands)

    Hofstede, ter R.; Rijnsdorp, A.D.

    2011-01-01

    Fish communities are dynamic and their structure is known to change over time. Traditionally, these changes were considered to be fisheries-induced, but recent analyses also suggest that global warming could affect the distribution, abundance, and assemblage composition of marine fish. However,

  14. Diagramming Assemblages of Sex/Gender and Sexuality as Environmental Education

    Science.gov (United States)

    Bazzul, Jesse; Santavicca, Nicholas

    2017-01-01

    This article explores ethico/political/ontological orientations made possible by an exploration of sex/gender and sexuality. Drawing from materialist theorists such as Karen Barad, Gilles Deleuze, and Felix Guattari, we employ the concept of assemblages to tease out the reality that our shared world is always already in a state of queer becoming.…

  15. Community Composition and Diversity of Coastal Bacterioplankton Assemblages in Lakes Michigan, Erie, and Huron.

    Science.gov (United States)

    Olapade, Ola A

    2018-04-01

    The Laurentian Great Lakes, including Lakes Superior, Michigan, Huron, Erie, and Ontario, located in the eastern part of North America are considered the largest of freshwater lakes in the world; however, very little is known about the diversity and distribution of indigenous microbial assemblages within these vast bodies of freshwater systems. Therefore, to delineate the microbial structure and community composition in these aquatic environments, combinations of high-throughput sequencing and fluorescent in situ hybridization (FISH) approaches were utilized to quantitatively characterize the occurrence, diversity, and distribution of bacterioplankton assemblages in six different sites located along the coastal regions of Lakes Michigan, Huron, and Erie. Phylogenetic examination showed a diverse bacterial community belonging to 11 different taxonomic groups. Pyrosequencing results revealed that the majority of the sequences were clustered into four main groups, i.e., Proteobacteria, Bacteriodetes, Actinobacteria, and Cyanobacteria, while fluorescent in situ hybridization also showed the numerical dominance of members of the Gammaproteobacteria and the Cytophaga-Flavobacterium in the six lake sites examined. Overall, the assemblages were shown to be quite diverse in distribution among the lake sites examined, comprising mostly of various heterotrophic populations, with the exception of the Lake Erie-Sandusky Bay site with more than 50% domination by autotrophic Cyanobacteria. This indicates that combinations of factors including water chemistry and various anthropogenic disturbances as well as the lake morphometric characteristics are probably influencing the community structure and diversity of the bacterial assemblages within the systems.

  16. An empirical, hierarchical typology of tree species assemblages for assessing forest dynamics under global change scenarios

    Science.gov (United States)

    Jennifer K. Costanza; John W. Coulston; David N. Wear

    2017-01-01

    The composition of tree species occurring in a forest is important and can be affected by global change drivers such as climate change. To inform assessment and projection of global change impacts at broad extents, we used hierarchical cluster analysis and over 120,000 recent forest inventory plots to empirically define forest tree assemblages across the U.S., and...

  17. Tropical rain-forest matrix quality affects bat assemblage structure in secondary forest patches

    NARCIS (Netherlands)

    Vleut, I.; Levy-Tacher, I.; Galindo-Gonzalez, J.; Boer, de W.F.; Ramirez-Marcial, N.

    2012-01-01

    We studied Phyllostomidae bat assemblage structure in patches of secondary forest dominated by the pioneer tree Ochroma pyramidale, largely (.85%) or partially (,35%) surrounded by a matrix of tropical rain forest, to test 3 hypotheses: the highest bat diversity and richness is observed in the

  18. Relative roles of grey squirrels, supplementary feeding, and habitat in shaping urban bird assemblages.

    Directory of Open Access Journals (Sweden)

    Colin Bonnington

    Full Text Available Non-native species are frequently considered to influence urban assemblages. The grey squirrel Sciurus carolinensis is one such species that is widespread in the UK and is starting to spread across Europe; it predates birds' nests and can compete with birds for supplementary food. Using distance sampling across the urbanisation intensity gradient in Sheffield (UK we test whether urban grey squirrels influence avian species richness and density through nest predation and competition for supplementary food sources. We also assess how urban bird assemblages respond to supplementary feeding. We find that grey squirrels slightly reduced the abundance of breeding bird species most sensitive to squirrel nest predation by reducing the beneficial impact of woodland cover. There was no evidence that grey squirrel presence altered relationships between supplementary feeding and avian assemblage structure. This may be because, somewhat surprisingly, supplementary feeding was not associated with the richness or density of wintering bird assemblages. These associations were positive during the summer, supporting advocacy to feed birds during the breeding season and not just winter, but explanatory capacity was limited. The amount of green space and its quality, assessed as canopy cover, had a stronger influence on avian species richness and population size than the presence of grey squirrels and supplementary feeding stations. Urban bird populations are thus more likely to benefit from investment in improving the availability of high quality habitats than controlling squirrel populations or increased investment in supplementary feeding.

  19. "Peeling an onion": Layering as a methodology to understand learning as an embodied assemblage of practice

    DEFF Research Database (Denmark)

    Kristensen, Liv Kondrup

    2017-01-01

    of learning that are grounded in the body. These assemblages can be found by e.g. considering how laboratory science equipment physically configure lessons and in doing so, become part of epistemic configurations, or how bodies and movement not only pertain to different modes of communication, but also...

  20. Uniform functional structure across spatial scales in an intertidal benthic assemblage.

    Science.gov (United States)

    Barnes, R S K; Hamylton, Sarah

    2015-05-01

    To investigate the causes of the remarkable similarity of emergent assemblage properties that has been demonstrated across disparate intertidal seagrass sites and assemblages, this study examined whether their emergent functional-group metrics are scale related by testing the null hypothesis that functional diversity and the suite of dominant functional groups in seagrass-associated macrofauna are robust structural features of such assemblages and do not vary spatially across nested scales within a 0.4 ha area. This was carried out via a lattice of 64 spatially referenced stations. Although densities of individual components were patchily dispersed across the locality, rank orders of importance of the 14 functional groups present, their overall functional diversity and evenness, and the proportions of the total individuals contained within each showed, in contrast, statistically significant spatial uniformity, even at areal scales across all spatial scales. Although assemblage species composition is known to be homogeneous in some soft-sediment marine systems over equivalent scales, this combination of patchy individual components yet basically constant functional-group structure seems as yet unreported. Copyright © 2015 Elsevier Ltd. All rights reserved.

  1. Epifaunal colonization of the Loch Linnhe artificial reef: influence of substratum on epifaunal assemblage structure.

    Science.gov (United States)

    Brown, Craig J

    2005-01-01

    A one-year study was carried out off the west coast of Scotland to compare the epifaunal colonization of concrete material used in the construction of the Loch Linnhe artificial reef with that on four other types of artificial substrata (preservative treated wood, rubber, steel and PVC). Settlement panels made from each of the materials were submerged in a vertical orientation during four seasonal exposure periods. There were clear seasonal trends across the four exposure periods with higher epifaunal biodiversity on all types of panel in the spring and summer exposure periods. Epifaunal assemblage structure was significantly different between the five types of material after each three-month exposure period. Concrete, preservative treated wood and PVC tended to have the highest species diversities. A successional study was also carried out. Over a 12-month exposure period epifaunal biodiversity increased on all five materials. After 12 months of exposure, the epifaunal assemblage structure was still significantly different between materials but had become more similar indicating a successional change towards a stable assemblage on all panels. The results indicate that material type and season have a significant effect on epifaunal assemblage structure after short (three-month) periods of submersion but that these effects are reduced with increasing length of exposure. The study concludes that the choice of construction material for an artificial reef will have little effect on the long-term epifaunal community structure, as long as the material is physically stable, non-toxic and offers a high degree of habitat complexity.

  2. Castaways can't be choosers - Homogenization of rafting assemblages on floating seaweeds

    Science.gov (United States)

    Gutow, Lars; Beermann, Jan; Buschbaum, Christian; Rivadeneira, Marcelo M.; Thiel, Martin

    2015-01-01

    After detachment from benthic habitats, the epibiont assemblages on floating seaweeds undergo substantial changes, but little is known regarding whether succession varies among different seaweed species. Given that floating algae may represent a limiting habitat in many regions, rafting organisms may be unselective and colonize any available seaweed patch at the sea surface. This process may homogenize rafting assemblages on different seaweed species, which our study examined by comparing the assemblages on benthic and floating individuals of the fucoid seaweeds Fucus vesiculosus and Sargassum muticum in the northern Wadden Sea (North Sea). Species richness was about twice as high on S. muticum as on F. vesiculosus, both on benthic and floating individuals. In both seaweed species benthic samples were more diverse than floating samples. However, the species composition differed significantly only between benthic thalli, but not between floating thalli of the two seaweed species. Separate analyses of sessile and mobile epibionts showed that the homogenization of rafting assemblages was mainly caused by mobile species. Among these, grazing isopods from the genus Idotea reached extraordinarily high densities on the floating samples from the northern Wadden Sea, suggesting that the availability of seaweed rafts was indeed limiting. Enhanced break-up of algal rafts associated with intense feeding by abundant herbivores might force rafters to recolonize benthic habitats. These colonization processes may enhance successful dispersal of rafting organisms and thereby contribute to population connectivity between sink populations in the Wadden Sea and source populations from up-current regions.

  3. The effect of silver nanoparticles on seasonal change in arctic tundra bacterial and fungal assemblages.

    Science.gov (United States)

    Kumar, Niraj; Palmer, Gerald R; Shah, Vishal; Walker, Virginia K

    2014-01-01

    The impact of silver nanoparticles (NPs) and microparticles (MPs) on bacterial and fungal assemblages was studied in soils collected from a low arctic site. Two different concentrations (0.066% and 6.6%) of Ag NPs and Ag MPs were tested in microcosms that were exposed to temperatures mimicking a winter to summer transition. Toxicity was monitored by differential respiration, phospholipid fatty acid analysis, polymerase chain reaction-denaturing gradient gel electrophoresis and DNA sequencing. Notwithstanding the effect of Ag MPs, nanosilver had an obvious, additional impact on the microbial community, underscoring the importance of particle size in toxicity. This impact was evidenced by levels of differential respiration in 0.066% Ag NP-treated soil that were only half that of control soils, a decrease in signature bacterial fatty acids, and changes in both richness and evenness in bacterial and fungal DNA sequence assemblages. Prominent after Ag NP-treatment were Hypocreales fungi, which increased to 70%, from only 1% of fungal sequences under control conditions. Genera within this Order known for their antioxidant properties (Cordyceps/Isaria) dominated the fungal assemblage after NP addition. In contrast, sequences attributed to the nitrogen-fixing Rhizobiales bacteria appeared vulnerable to Ag NP-mediated toxicity. This combination of physiological, biochemical and molecular studies clearly demonstrate that Ag NPs can severely disrupt the natural seasonal progression of tundra assemblages.

  4. Diversity and spatial distribution patterns of polychaete assemblages in the Paso Ancho, Straits of Magellan Chile

    Science.gov (United States)

    Montiel, Américo; Quiroga, Eduardo; Gerdes, Dieter

    2011-03-01

    The polychaete fauna of the Paso Ancho Basin in the Straits of Magellan was studied by means of three different sampling gears: a multibox corer, an Agassiz trawl, and a Rauschert dredge. A total of 1743 polychaete specimens belonging to 166 species from 36 families were collected at 10 stations. Significant differences were found between the catches of the three gears in terms of species numbers. The multibox corer brought up 63% of all species caught, especially macroinfauna polychaetes, the Rauschert dredge caught 16%, mostly small-bodied macroepifauna species and the Agassiz Trawl brought up 6% of the total species, largely mega-epifauna polychaetes. Only 15% of the total species occurred in more than one of the gears and only one species was found parallel in all three gears thus indicating that the combination of these gears allowed a better description of the polychaete communities than possible by just one of the gears. Using the Abundance-based Coverage Estimator and combining all species from the three different gears led to an asymptotic value of the species accumulation curve of 223 species for the Paso Ancho. Non-metric multidimensional scaling based on presence/absence data distinguished between shallow (120 m) polychaete assemblages. The shallow assemblage showed higher species richness values than the deep assemblage, and the taxonomical composition, too, differed considerably between both assemblages.

  5. Seasonal changes in caddis larvae assemblages in river-floodplain habitats along a hydrological connectivity gradient

    NARCIS (Netherlands)

    Van den Brink, F.W.B.; Van der Velde, G.; Wijnhoven, S.

    2013-01-01

    In order to assess the impact of seasonality versus connectivity on the ecological quality of the Lower Rhine river-floodplain habitats, we studied the seasonal variation in diversity and species assemblages of caddis larvae by monthly sampling of the littoral zone of four water bodies over a

  6. Linking shrimp assemblages with rates of detrital processing along an elevational gradient in a tropical stream

    Science.gov (United States)

    James G. March; Jonathan P. Benstead; Catherine M. Pringle; Mark W. Ruebel

    2001-01-01

    We experimentally excluded freshwater shrimp assemblages (Atyidae, Xiphocarididae, and Palaemonidae) to examine their effects on detrital processing and benthic insect biomass at three sites along an elevational gradient in a tropical stream in Puerto Rico. We also determined which shrimp taxon was responsible for leaf decay in a subsequent laboratory experiment. At...

  7. Flow seasonality and fish assemblage in a tropical river, French Guiana, South America

    Directory of Open Access Journals (Sweden)

    Francisco Leonardo Tejerina-Garro

    Full Text Available The objective of this study is to verify the existence of a seasonal pattern of variation in the fish assemblages of a tropical river using taxonomic and functional descriptors. Fish were sampled using gillnets at two sites on the Comté River, a large-sized river 254.8 km long, flowing entirely through rainforest areas of French Guiana. Samplings were conducted every other month from August 1998 to July 2000. Four types of fish assemblage descriptors were used: the species descriptor (number of individual fish of each species in the sample; the family descriptor (number of individual fish of each family in the sample; the trophic descriptor (distribution of the fish biomass in each feeding guild and the specific maximum observed size - MOS (number of individual fish in each of four classes of MOS: 300 mm. Results point out that changes in the fish assemblage are related to water level oscillations. The role of migration seems to be weak and is limited to trophic displacements characteristic of few species. In the low-water season, characterized by weak water level oscillation, fish species and families belonging to piscivorous or aquatic invertivorous guilds were predominant, whereas in the high-water season the environment is submitted to strong variations caused by fast and large water level oscillations, and the fish assemblage was characterized by species or families with an opportunistic omnivorous diet.

  8. Lower Miocene plant assemblage with coastal-marsh herbaceous monocots from the Vienna Basin (Slovakia)

    Science.gov (United States)

    Kvaček, Zlatko; Teodoridis, Vasilis; Kováčová, Marianna; Schlögl, Ján; Sitár, Viliam

    2014-06-01

    A new plant assemblage of Cerová-Lieskové from Lower Miocene (Karpatian) deposits in the Vienna Basin (western Slovakia) is preserved in a relatively deep, upper-slope marine environment. Depositional conditions with high sedimentation rates allowed exceptional preservation of plant remains. The plant assemblage consists of (1) conifers represented by foliage of Pinus hepios and Tetraclinis salicornioides, a seed cone of Pinus cf. ornata, and by pollen of the Cupressaceae, Pinaceae, Pinus sp. and Cathaya sp., and (2) angiosperms represented by Cinnamomum polymorphum, Platanus neptuni, Potamogeton sp. and lauroid foliage, by pollen of Liquidambar sp., Engelhardia sp. and Craigia sp., and in particular by infructescences (so far interpreted as belonging to cereal ears). We validate genus and species assignments of the infructescences: they belong to Palaeotriticum Sitár, including P. mockii Sitár and P. carpaticum Sitár, and probably represent herbaceous monocots that inhabited coastal marshes, similar to the living grass Spartina. Similar infructescences occur in the Lower and Middle Miocene deposits of the Carpathian Foredeep (Slup in Moravia), Tunjice Hills (Žale in Slovenia), and probably also in the Swiss Molasse (Lausanne). This plant assemblage demonstrates that the paleovegetation was represented by evergreen woodland with pines and grasses in undergrowth, similar to vegetation inhabiting coastal brackish marshes today. It also indicates subtropical climatic conditions in the Vienna Basin (central Paratethys), similar to those implied by other coeval plant assemblages from Central Europe

  9. The scales of variability of stream fish assemblage at tributary confluences

    Directory of Open Access Journals (Sweden)

    István Czeglédi

    2015-12-01

    Full Text Available Tributary confluences play an important role in the dispersal of organisms, and consequently, in shaping regional scale diversity in stream networks. Despite their importance in dispersal processes, little is known about how ecological assemblages are organized in these habitats. We studied the scales of variability of stream fish assemblages over three seasons using a hierarchical sampling design, which incorporated three tributaries, three sites at the mouth of each tributary and using four sampling units at each site. We found strong scale dependent variability in species richness, composition and relative abundance. Most of the variation was accounted for by the interactive effect of season, between stream and between site effects, while habitat structure of the sampling units had a relatively minor role. Species richness showed a continuous decrease from the mainstem river in most cases, while species composition and relative abundance changed less consistently along the longitudinal profile. Consequently, we found that not only the junctions presented a strong filter on the species pool, but some species were filtered out if they passed this critical habitat bottleneck. Spatial position of the tributaries along the river also contributed to assemblage variability in the confluences. Overall, our results suggest high variability in fish assemblages across multiple scales at tributary confluences. Environmental management should take a more critical care on the filtering role of tributary confluences in species dispersal, for better understanding patterns and processes in the branches of dendritic stream networks.

  10. Toward a Social Ontology for Science Education: Introducing Deleuze and Guattari's Assemblages

    Science.gov (United States)

    Bazzul, Jesse; Kayumova, Shakhnoza

    2016-01-01

    This essay's main objective is to develop a theoretical, ontological basis for critical, social justice-oriented science education. Using Deleuze and Guattari's notion of assemblages, rhizomes, and arborescent structures, this article challenges authoritarian institutional practices, as well as the subject of these practices, and offers a way for…

  11. Deep-reef fish assemblages of the Great Barrier Reef shelf-break (Australia).

    Science.gov (United States)

    Sih, Tiffany L; Cappo, Mike; Kingsford, Michael

    2017-09-07

    Tropical mesophotic and sub-mesophotic fish ecology is poorly understood despite increasing vulnerability of deeper fish assemblages. Worldwide there is greater fishing pressure on continental shelf-breaks and the effects of disturbances on deeper fish species have not yet been assessed. Difficult to access, deeper reefs host undocumented fish diversity and abundance. Baited Remote Underwater Video Stations (BRUVS) with lights were used to sample deeper habitats (54-260 m), in the Great Barrier Reef (GBR), Australia. Here we describe fish biodiversity, relative abundance and richness, assessing the prediction that depth would drive assemblage structure in the GBR. Distinct groups of fishes were found with depth whilst overall richness and abundance decreased steeply between 100 and 260 m. Commercially-valuable Lutjanidae species from Pristipomoides and Etelis genera, were absent from shallower depths. Few fish species overlapped between adjacent depth strata, indicating unique assemblages with depth. We also detected new location records and potential new species records. The high biodiversity of fish found in shelf-break environments is poorly appreciated and depth is a strong predictor of assemblage composition. This may pose a challenge for managers of commercial fisheries as distinct depth ranges of taxa may translate to more readily targeted habitats, and therefore, an inherent vulnerability to exploitation.

  12. Spatial and temporal variability in the larval fish assemblage of a ...

    African Journals Online (AJOL)

    Spatial and temporal variability in the larval fish assemblage of a warm temperate South African estuary, with notes on the effects of artificial channelling. ... Larval fishes were sampled within the estuary and marina for a period of two years. Samples were collected seasonally at 14 different sampling stations along the main ...

  13. Differential response of fish assemblages to coral reef-based seaweed farming.

    Science.gov (United States)

    Hehre, E James; Meeuwig, J J

    2015-01-01

    As the global demand for seaweed-derived products drives the expansion of seaweed farming onto shallow coral ecosystems, the effects of farms on fish assemblages remain largely unexplored. Shallow coral reefs provide food and shelter for highly diverse fish assemblages but are increasingly modified by anthropogenic activities. We hypothesized that the introduction of seaweed farms into degraded shallow coral reefs had potential to generate ecological benefits for fish by adding structural complexity and a possible food source. We conducted 210 transects at 14 locations, with sampling stratified across seaweed farms and sites adjacent to and distant from farms. At a seascape scale, locations were classified by their level of exposure to human disturbance. We compared sites where (1) marine protected areas (MPAs) were established, (2) neither MPAs nor blast fishing was present (hence "unprotected"), and (3) blast fishing occurred. We observed 80,186 fish representing 148 species from 38 families. The negative effects of seaweed farms on fish assemblages appeared stronger in the absence of blast fishing and were strongest when MPAs were present, likely reflecting the positive influence of the MPAs on fish within them. Species differentiating fish assemblages with respect to seaweed farming and disturbance were typically small but also included two key target species. The propensity for seaweed farms to increase fish diversity, abundance, and biomass is limited and may reduce MPA benefits. We suggest that careful consideration be given to the placement of seaweed farms relative to MPAs.

  14. Stable isotope and calcareous nannofossil assemblage record of the late Paleocene and early Eocene (Cicogna section)

    Science.gov (United States)

    Agnini, Claudia; Spofforth, David J. A.; Dickens, Gerald R.; Rio, Domenico; Pälike, Heiko; Backman, Jan; Muttoni, Giovanni; Dallanave, Edoardo

    2016-04-01

    We present records of stable carbon and oxygen isotopes, CaCO3 content, and changes in calcareous nannofossil assemblages across an 81 m thick section of upper Paleocene-lower Eocene marine sedimentary rocks now exposed along the Cicogna Stream in northeast Italy. The studied stratigraphic section represents sediment accumulation in a bathyal hemipelagic setting from approximately 57.5 to 52.2 Ma, a multi-million-year time interval characterized by perturbations in the global carbon cycle and changes in calcareous nannofossil assemblages. The bulk carbonate δ13C profile for the Cicogna section, once placed on a common timescale, resembles that at several other locations across the world, and includes both a long-term drop in δ13C and multiple short-term carbon isotope excursions (CIEs). This precise correlation of widely separated δ13C records in marine sequences results from temporal changes in the carbon composition of the exogenic carbon cycle. However, diagenesis has likely modified the δ13C record at Cicogna, an interpretation supported by variations in bulk carbonate δ18O, which do not conform to expectations for a primary signal. The record of CaCO3 content reflects a combination of carbonate dilution and dissolution, as also inferred at other sites. Our detailed documentation and statistical analysis of calcareous nannofossil assemblages show major differences before, during and after the Paleocene-Eocene Thermal Maximum. Other CIEs in our lower Paleogene section do not exhibit such a distinctive change; instead, these events are sometimes characterized by variations restricted to a limited number of taxa and transient shifts in the relative abundance of primary assemblage components. Both long-lasting and short-lived modifications to calcareous nannofossil assemblages preferentially affected nannoliths or holococcoliths such as Discoaster, Fasciculithus, Rhomboaster/Tribrachiatus, Sphenolithus and Zygrhablithus, which underwent distinct variations in

  15. Giardia in a selected population of dogs and cats in Germany - diagnostics, coinfections and assemblages.

    Science.gov (United States)

    Sommer, M F; Rupp, P; Pietsch, M; Kaspar, A; Beelitz, P

    2018-01-15

    Infections with the zoonotic endoparasite Giardia duodenalis are widely spread among dogs and cats worldwide. Since the question whether the infection might be transmitted from domestic animals to their owners is still an important topic, a reliable detection of patent Giardia infections and the determination of the associated Giardia assemblages is of major concern. The objectives of the present study were to determine the prevalence of Giardia infections in dogs and cats living in Germany using different diagnostic tests and to identify the Giardia assemblages of infected animals. Furthermore, a possible correlation of coinfections with other endoparasites was analysed. All samples were investigated by enzyme-linked immunosorbent assay (ELISA), merthiolate-iodine-formalin concentration technique (MIFC) and zinc chloride flotation. ELISA-positive samples were additionally screened with a direct immunofluorescence assay (IFA). Faecal DNA was extracted from all Giardia cyst-positive samples and used for multilocus sequence typing with nested PCRs targeting the following gene loci: SSU rRNA (SSU), glutamate dehydrogenase (gdh) and triosephosphate isomerase (tpi). Samples from dogs and cats tested positive for Giardia coproantigen (ELISA) in 30.6% and 17.9%, respectively. The MIFC technique revealed Giardia cysts in 33.9% of canine and in 34.6% of feline ELISA-positive samples, while using IFA, cysts were present in 90.4% of canine and in 76.9% of feline ELISA-positive samples. Coinfections with other endoparasites besides Giardia were found in both dogs and cats, yet a statistically significant correlation could solely be drawn for the canine samples. The success rate of the different PCR protocols varied between 23.1% (tpi) and 91.3% (SSU) for dogs and between 25.0% (gdh) and 90.0% (SSU) for cats. Dog-specific Giardia assemblages C and D were detected in 42 and 55 canine isolates, respectively. The cat-specific Giardia assemblage F was detected in 14 feline isolates

  16. Phylogenetic structure of bacterial assemblages co-occurring with Ostreopsis cf. ovata bloom.

    Science.gov (United States)

    Vanucci, Silvana; Guidi, Flavio; Pistocchi, Rossella; Long, Richard A

    2016-05-01

    Extensive blooms of the toxic epiphytic/benthic dinoflagellate Ostreopsis cf. ovata are being reported with increasing frequency and spatial distribution in temperate coastal regions including the Mediterranean. These blooms are of human and environmental health concern due to the production of isobaric palytoxin and a wide range of ovatoxins by Ostreopsis cf. ovata. Bacterial-microalgal interactions are important regulators in algal bloom dynamics and potentially toxin dynamics. This study investigated the bacterial assemblages co-occurring with O. cf. ovata (OA) and from ambient seawaters (SW) during the early and peak phases of bloom development in NW Adriatic Sea. Fractions of the bacterial assemblages co-occurring with O. cf. ovata (OA) and more closely associated to the mucilage layer (LA) embedding O. cf. ovata cells were also reported. In total, 14 bacterial phyla were detected by targeted 454 pyrosequencing of the 16S rRNA gene. The dominant bacterial phyla in the OA assemblages were Proteobacteria and Bacteroidetes; while at the class level, Alphaproteobacteria were the most abundant (83 and 66%, relative abundance, early and peak bloom phases), followed by Flavobacteria (7 and 19%, early and peak phases). Actinobacteria and Cyanobacteria were of minor importance (<5% of the relative bacterial abundance each). Gammaproteobacteria showed a notably presence in OA assemblage only at the early phase of the bloom (genus Haliea, 13%). The Alphaproteobacteria were predominately composed by the genera Ruegeria, Jannaschia and Erythrobacter which represented about half of the total phylotypes' contribution of OA at both early and peak phases of the O. cf. ovata bloom, suggesting interactions between this consortium and the microalga. Moreover, the highest contribution of Ruegeria (30% of the total phylotypes) was observed at the early phase of the bloom in LA assemblage. Microbial assemblages associated with the ambient seawaters while being also dominated by

  17. Effect of riparian vegetation on diatom assemblages in headwater streams under different land uses.

    Science.gov (United States)

    Hlúbiková, Daša; Novais, Maria Helena; Dohet, Alain; Hoffmann, Lucien; Ector, Luc

    2014-03-15

    Differences in the structure of diatom assemblages in headwaters with contrasting shading conditions and different land use in the buffer zone and upper catchment were studied in order to evaluate the influence of the lack of riparian vegetation on the biofilm. The objective was to ascertain whether a riparian buffer can mitigate the negative influence of human induced disturbance and pollution on diatom assemblages in headwaters. Four streams were selected in order to maximize the differences in the land cover and minimize other environmental gradients. Multivariate statistics, different comparative and permutation tests and correlations were applied to compare the diatom assemblages, the Specific Polluosensitivity Index (IPS) and the diatom ecological guilds (low profile, high profile and motile) among the sites studied and to evaluate their responses to disturbances. The analysis showed that low profile diatoms typically dominated in forested headwaters with limited resources, whilst assemblages at impacted sites showed a wider range of growth forms. In unimpacted streams, the diatom assemblages were influenced by temperature, pH, conductivity and calcium, as usually reported for oligotrophic streams with high natural disturbance due to fast current and shading. In both shaded and unshaded impacted streams, the importance of nutrients and land use disturbance, especially urbanization, prevailed. This trend was also reflected by the IPS index that showed consistently lower values at impacted sites, correlating most significantly with nutrients. The diatom species composition as well as diatom guilds at impacted sites were similar, regardless of the presence or absence of riparian vegetation, and were significantly influenced by seasonal changes. Our results indicate that diatoms react sensitively to alterations of the water environment in headwaters, induced by anthropogenic activities, and these impacts are not buffered by an intact riparian zone. Diatoms

  18. Sequence analysis of mtDNA COI barcode region revealed three haplotypes within Culex pipiens assemblage.

    Science.gov (United States)

    Koosha, Mona; Oshaghi, Mohammad Ali; Sedaghat, Mohammad Mehdi; Vatandoost, Hassan; Azari-Hamidian, Shahyad; Abai, Mohammad Reza; Hanafi-Bojd, Ahmad Ali; Mohtarami, Fatemeh

    2017-10-01

    Members of the Culex (Culex) pipiens assemblage are known vectors of deadly encephalitides, periodic filariasis, and West Nile virus throughout the world. However, members of this assemblage are morphologically indistinguishable or hard to distinguish and play distinct roles in transmission of the diseases. The current study aimed to provide further evidence on utility of the two most popular nuclear (ITS2-rDNA) and mitochondrial (COI barcode region) genetic markers to identify members of the assemblage. Culex pipiens assemblage specimens from different climate zones of Iran were collected and identified to species level based on morphological characteristics. Nucleotide sequences of the loci for the specimens plus available data in the GenBank were analyzed to find species specific genetic structures useful for diagnosis purposes. ITS2 region was highly divergent within species or populations suggesting lack of consistency as a reliable molecular marker. In contrast, sequence analysis of 710 bp of COI gene revealed three fixed haplotypes named here "C, T, H" within the assemblage which can be distinguished by HaeIII and AluI enzymes. There were a correlation between the haplotypes and the world climate regions, where the haplotypes H/T and C are present mainly in temperate and tropical regions of the world, respectively. In the New world, Australia, and Japan only haplotype H is found. In conjunction between tropical and temperate regions such Iran, China, and Turkey, a mix of C/H or C/H/T are present. Although, the haplotypes are not strictly species-specific, however, Cx. quinquefasciatus was mainly of haplotype C. Due to the lack of mating barrier and questionable taxonomic situation of the complex members, the mentioned haplotypes in combination with other morphological and molecular characters might be used to address the genetic structure of the studied populations. Copyright © 2017 Elsevier Inc. All rights reserved.

  19. Orthoptera assemblages associated with macrophytes of floodplain lakes of the Paraná River

    Directory of Open Access Journals (Sweden)

    Soledad Capello

    2013-03-01

    Full Text Available Orthoptera assemblages associated with macrophytes of floodplain lakes of the Paraná River. The Orthoptera assemblage composition varies considerably, depending on habitat type. This study examines the spatiotemporal relationship between plant diversity, hydrometric level, environmental variables and the Orthoptera richness and abundance in floodplain lakes connected permanently or temporarily with the main channel of the Paraná River. The grasshoppers were collected fortnightly (April 2006May 2007. A total of 17 species were recorded and classified according to their frequency of occurrence in constant (7, accessory (4, or accidental (6 species. In the two lakes, the greater species richness and abundance was recorded in summer, thereby coinciding with the highest water level of the Paraná River. The most significant correlation between the orthopteran richness and abundance was with the water level. The aquatic plant richness was significantly different between the lakes, but the vegetation was dominated by Eichhornia crassipes (Mart. Solms. (Liliales, Pontederiaceae. The lake, which was connected permanently, presented the highest values of diversity and abundance, proving to be a more diverse assemblage. The beta diversity was higher in the temporary connected lake than in the permanently connected one. The orthopterans assemblages were different between the lakes, Cornops aquaticum and Tucayaca gracilis were the species that contributed more to the level of dissimilarity. C. aquaticum was more representative in the lake temporarily connected, while T. gracilis in the permanent connected one. The water level of the Paraná River and the connectivity of the floodplain lakes play an important role to explain the abundance and richness of their orthopteran assemblages.

  20. Environmental Factors Support the Formation of Specific Bacterial Assemblages on Microplastics

    Science.gov (United States)

    Oberbeckmann, Sonja; Kreikemeyer, Bernd; Labrenz, Matthias

    2018-01-01

    While the global distribution of microplastics (MP) in the marine environment is currently being critically evaluated, the potential role of MP as a vector for distinct microbial assemblages or even pathogenic bacteria is hardly understood. To gain a deeper understanding, we investigated how different in situ conditions contribute to the composition and specificity of MP-associated bacterial communities in relation to communities on natural particles. Polystyrene (PS), polyethylene (PE), and wooden pellets were incubated for 2 weeks along an environmental gradient, ranging from marine (coastal Baltic Sea) to freshwater (waste water treatment plant, WWTP) conditions. The associated assemblages as well as the water communities were investigated applying high-throughput 16S rRNA gene sequencing. Our setup allowed for the first time to determine MP-dependent and -independent assemblage factors as subject to different environmental conditions in one system. Most importantly, plastic-specific assemblages were found to develop solely under certain conditions, such as lower nutrient concentration and higher salinity, while the bacterial genus Erythrobacter, known for the ability to utilize polycyclic aromatic hydrocarbons (PAH), was found specifically on MP across a broader section of the gradient. We discovered no enrichment of potential pathogens on PE or PS; however, the abundant colonization of MP in a WWTP by certain bacteria commonly associated with antibiotic resistance suggests MP as a possible hotspot for horizontal gene transfer. Taken together, our study clarifies that the surrounding environment prevailingly shapes the biofilm communities, but that MP-specific assemblage factors exist. These findings point to the ecological significance of specific MP-promoted bacterial populations in aquatic environments and particularly in plastic accumulation zones. PMID:29403454

  1. Temporal variation in plankton assemblages and physicochemistry of Devils Lake, North Dakota

    Science.gov (United States)

    Leland, H.V.; Berkas, W.R.

    1998-01-01

    Seasonal and annual variation in biomass and structure of algal assemblages of hyposaline Devils Lake were examined in relation to turbidity, ambient concentrations of major ions, trace elements and nutrients, and the standing crop of herbivores. Lake level declined during the early years of study, but rose markedly in subsequent years as historically large volumes of water flowed into this hydrologically-closed basin. Winter algal assemblages were dominated (in biomass) most years by small, non-motile chlorophytes ( Choricystis minor, Kirchneriella lunaris or Dunaliella sp.), or Euglena sp. in the most saline sub-basin. Spring assemblages were dominated by diatoms (Stephanodiscus cf. minutulus, Surirella peisonis, Cyclotella meneghiniana and Entomoneis paludosa were especially prominent) or chlorophytes ( C. minor) until the lake level rose. C. minor abundances then declined in spring assemblages and diatoms ( Stephanodiscus cf. agassizensis and S. niagarae; E. paludosa in the more saline sub-basins) dominated. The potential for nitrogen-deficient conditions for phytoplankton growth was evidenced most summers and early autumns by consistently high concentrations of reactive-P relative to inorganic-N and blooms of the N-fixing cyanophyte Aphanizomenon flos-aquae; Microcystis aeruginosa typically was a co-dominant (>30% of biomass) in these assemblages. Pulses of diatoms ( S. cf. agassizensis and C. meneghiniana) occurred in summers following unusually prolonged periods of calm weather or large water inflows. Physical (irradiance, turbulence) and chemical (major nutrients) variables were the primary factors associated with phytoplankton growth. Transparency and major nutrient concentrations accounted for more of the annual variation in phytoplankton structure than did salinity. Seasonal abundance patterns of the dominant zooplankton (the copepod Diaptomus sicilis; the cladocerans Ceriodaphnia quadrangula, Chydorus sphaericus, Daphnia pulex and Diaphanosoma birgei

  2. Spatial and temporal structure of fish assemblages in an ''inverse estuary'', the Sine Saloum system (Senegal)

    Science.gov (United States)

    Simier, M.; Blanc, L.; Aliaume, C.; Diouf, P. S.; Albaret, J. J.

    2004-01-01

    As a consequence of the Sahelian drought, the Sine Saloum, a large estuarine system located in Senegal (West Africa), has become an "inverse estuary" since the late sixties, i.e. salinity increases upstream and reaches 100 in some places. To study the fish assemblages of such a modified system, a survey was conducted in 1992, collecting fish every two months with a purse seine at eight sites spread over the three main branches of the estuary. A total of 73 species belonging to 35 families were identified. Eight species comprised 97% of the total numbers of fish. The predominant species was a small clupeid, Sardinella maderensis, representing more than half of the total biomass and nearly 70% of the total number of fish. The spatio-temporal structure of the fish assemblages was studied using the STATIS-CoA method, which combines the multitable approach with the correspondence analysis method. Whatever the season, a strong spatial organization of fish assemblages was observed, mainly related to depth and salinity. Three types of assemblages were identified. In shallow water areas, fish assemblages were dominated by Mugilidae, Gerreidae and Cichlidae and were stable with time. In open water areas, large fluctuations in the species composition were observed, due to the occasional presence of large schools of pelagic species: in the southern area, where salinity and water transparency were the lowest, the main species were Ilisha africana, Brachydeuterus auritus and Chloroscombrus chrysurus, associated with a few Sciaenidae and Tetraodontidae, while the poorest areas were characterized by only two dominant species, S. maderensis and Scomberomorus tritor.

  3. Diversity and abundance of invertebrate epifaunal assemblages associated with gorgonians are driven by colony attributes

    KAUST Repository

    Curdia, Joao

    2015-03-20

    The present study aimed to explicitly quantify the link between the attributes of shallow-water gorgonian colonies (Octocorallia: Alcyonacea) and the ecological patterns of associated non-colonial epifaunal invertebrates. Based on multiple regression analysis, we tested the contribution of several attributes (colony height, width, and area, fractal dimension as a measure of colony complexity, lacunarity as a measure of the heterogeneity, and “colonial” epibiont cover) to abundance and taxonomic richness of associated assemblages. The results highlight the variation in the response of epifaunal assemblages to the gorgonian colony characteristics. The nature and intensity of the relationships were gorgonian species-dependent and varied from one taxonomic group to another. For both gorgonian species analyzed, the strongest predictor of species richness and abundance of the epifaunal assemblages was “colonial” epibiont cover, possibly due to a trophic effect (direct or indirect enhancement of food availability) combined with the surface available for colonization (species–area effect). Although structural complexity is usually indicated as the main driver for rich and abundant coral-associated assemblages, no significant relationship was observed between fractal dimension and the community descriptors; lacunarity, which reflects the sizes of the inter-branch spaces, was only linked to taxonomic richness in the assemblages associated with Leptogorgia lusitanica. The validity of the paradigm that structural complexity enhances biodiversity may be scale-dependent. In the case of gorgonians, the effect of complexity at the “garden” level may be more relevant than at the individual colony level. This reinforces the need for the conservation of gorgonian aggregation areas as a whole in order to preserve host diversity and size structure. © 2015 Springer-Verlag Berlin Heidelberg

  4. A comparison of the influences of urbanization in contrasting environmental settings on stream benthic algal assemblages

    Science.gov (United States)

    Potapova, M.; Coles, J.F.; Giddings, E.M.P.; Zappia, H.

    2005-01-01

    Patterns of stream benthic algal assemblages along urbanization gradients were investigated in three metropolitan areas-Boston (BOS), Massachusetts; Birmingham (BIR), Alabama; and Salt Lake City (SLC), Utah. An index of urban intensity derived from socioeconomic, infrastructure, and land-use characteristics was used as a measure of urbanization. Of the various attributes of the algal assemblages, species composition changed along gradients of urban intensity in a more consistent manner than biomass or diversity. In urban streams, the relative abundance of pollution-tolerant species was often higher than in less affected streams. Shifts in assemblage composition were associated primarily with increased levels of conductivity, nutrients, and alterations in physical habitat. Water mineralization and nutrients were the most important determinants of assemblage composition in the BOS and SLC study areas; flow regime and grazers were key factors in the BIR study area. Species composition of algal assemblages differed significantly among geographic regions, and no particular algal taxa were found to be universal indicators of urbanization. Patterns in algal biomass and diversity along urban gradients varied among study areas, depending on local environmental conditions and habitat alteration. Biomass and diversity increased with urbanization in the BOS area, apparently because of increased nutrients, light, and flow stability in urban streams, which often are regulated by dams. Biomass and diversity decreased with urbanization in the BIR study area because of intensive fish grazing and less stable flow regime. In the SLC study area, correlations between algal biomass, diversity, and urban intensity were positive but weak. Thus, algal responses to urbanization differed considerably among the three study areas. We concluded that the wide range of responses of benthic algae to urbanization implied that tools for stream bioassessment must be region specific. ?? 2005 by the

  5. Environmental Factors Support the Formation of Specific Bacterial Assemblages on Microplastics

    Directory of Open Access Journals (Sweden)

    Sonja Oberbeckmann

    2018-01-01

    Full Text Available While the global distribution of microplastics (MP in the marine environment is currently being critically evaluated, the potential role of MP as a vector for distinct microbial assemblages or even pathogenic bacteria is hardly understood. To gain a deeper understanding, we investigated how different in situ conditions contribute to the composition and specificity of MP-associated bacterial communities in relation to communities on natural particles. Polystyrene (PS, polyethylene (PE, and wooden pellets were incubated for 2 weeks along an environmental gradient, ranging from marine (coastal Baltic Sea to freshwater (waste water treatment plant, WWTP conditions. The associated assemblages as well as the water communities were investigated applying high-throughput 16S rRNA gene sequencing. Our setup allowed for the first time to determine MP-dependent and -independent assemblage factors as subject to different environmental conditions in one system. Most importantly, plastic-specific assemblages were found to develop solely under certain conditions, such as lower nutrient concentration and higher salinity, while the bacterial genus Erythrobacter, known for the ability to utilize polycyclic aromatic hydrocarbons (PAH, was found specifically on MP across a broader section of the gradient. We discovered no enrichment of potential pathogens on PE or PS; however, the abundant colonization of MP in a WWTP by certain bacteria commonly associated with antibiotic resistance suggests MP as a possible hotspot for horizontal gene transfer. Taken together, our study clarifies that the surrounding environment prevailingly shapes the biofilm communities, but that MP-specific assemblage factors exist. These findings point to the ecological significance of specific MP-promoted bacterial populations in aquatic environments and particularly in plastic accumulation zones.

  6. Large-scale spatial distribution patterns of gastropod assemblages in rocky shores.

    Directory of Open Access Journals (Sweden)

    Patricia Miloslavich

    Full Text Available Gastropod assemblages from nearshore rocky habitats were studied over large spatial scales to (1 describe broad-scale patterns in assemblage composition, including patterns by feeding modes, (2 identify latitudinal pattern of biodiversity, i.e., richness and abundance of gastropods and/or regional hotspots, and (3 identify potential environmental and anthropogenic drivers of these assemblages. Gastropods were sampled from 45 sites distributed within 12 Large Marine Ecosystem regions (LME following the NaGISA (Natural Geography in Shore Areas standard protocol (www.nagisa.coml.org. A total of 393 gastropod taxa from 87 families were collected. Eight of these families (9.2% appeared in four or more different LMEs. Among these, the Littorinidae was the most widely distributed (8 LMEs followed by the Trochidae and the Columbellidae (6 LMEs. In all regions, assemblages were dominated by few species, the most diverse and abundant of which were herbivores. No latitudinal gradients were evident in relation to species richness or densities among sampling sites. Highest diversity was found in the Mediterranean and in the Gulf of Alaska, while highest densities were found at different latitudes and represented by few species within one genus (e.g. Afrolittorina in the Agulhas Current, Littorina in the Scotian Shelf, and Lacuna in the Gulf of Alaska. No significant correlation was found between species composition and environmental variables (r≤0.355, p>0.05. Contributing variables to this low correlation included invasive species, inorganic pollution, SST anomalies, and chlorophyll-a anomalies. Despite data limitations in this study which restrict conclusions in a global context, this work represents the first effort to sample gastropod biodiversity on rocky shores using a standardized protocol across a wide scale. Our results will generate more work to build global databases allowing for large-scale diversity comparisons of rocky intertidal assemblages.

  7. Riverine Landscape Patch Heterogeneity Drives Riparian Ant Assemblages in the Scioto River Basin, USA.

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    Paradzayi Tagwireyi

    Full Text Available Although the principles of landscape ecology are increasingly extended to include riverine landscapes, explicit applications are few. We investigated associations between patch heterogeneity and riparian ant assemblages at 12 riverine landscapes of the Scioto River, Ohio, USA, that represent urban/developed, agricultural, and mixed (primarily forested, but also wetland, grassland/fallow, and exurban land-use settings. Using remotely-sensed and ground-collected data, we delineated riverine landscape patch types (crop, grass/herbaceous, gravel, lawn, mudflat, open water, shrub, swamp, and woody vegetation, computed patch metrics (area, density, edge, richness, and shape, and conducted coordinated sampling of surface-active Formicidae assemblages. Ant density and species richness was lower in agricultural riverine landscapes than at mixed or developed reaches (measured using S [total number of species], but not using Menhinick's Index [DM], whereas ant diversity (using the Berger-Park Index [DBP] was highest in agricultural reaches. We found no differences in ant density, richness, or diversity among internal riverine landscape patches. However, certain characteristics of patches influenced ant communities. Patch shape and density were significant predictors of richness (S: R2 = 0.72; DM: R2=0.57. Patch area, edge, and shape emerged as important predictors of DBP (R2 = 0.62 whereas patch area, edge, and density were strongly related to ant density (R2 = 0.65. Non-metric multidimensional scaling and analysis of similarities distinguished ant assemblage composition in grass and swamp patches from crop, gravel, lawn, and shrub as well as ant assemblages in woody vegetation patches from crop, lawn, and gravel (stress = 0.18, R2 = 0.64. These findings lend insight into the utility of landscape ecology to river science by providing evidence that spatial habitat patterns within riverine landscapes can influence assemblage characteristics of riparian

  8. Herbivores, tidal elevation, and species richness simultaneously mediate nitrate uptake by seaweed assemblages.

    Science.gov (United States)

    Bracken, Matthew E S; Jones, Emily; Williams, Susan L

    2011-05-01

    In order for research into the consequences of biodiversity changes to be more applicable to real-world ecosystems, experiments must be conducted in the field, where a variety of factors other than diversity can affect the rates of key biogeochemical and physiological processes. Here, we experimentally evaluate the effects of two factors known to affect the diversity and composition of intertidal seaweed assemblages--tidal elevation and herbivory--on nitrate uptake by those assemblages. Based on surveys of community composition at the end of a 1.5-year press experiment, we found that both tide height and herbivores affected seaweed community structure. Not surprisingly, seaweed species richness was greater at lower tidal elevations. Herbivores did not affect richness, but they altered the types of species that were present; seaweed species characterized by higher rates of nitrate uptake were more abundant in herbivore-removal plots. Both tide height and herbivores affected nitrate uptake by seaweed assemblages. Individual seaweed species, as well as entire seaweed assemblages, living higher on the shore had greater rates of biomass-specific nitrate uptake, particularly at high ambient nitrate concentrations. Grazed seaweed assemblages exhibited reduced nitrate uptake, but only at low nitrate concentrations. We evaluated the effect of seaweed richness on nitrate uptake, both alone and after accounting for effects of tidal elevation and herbivores. When only richness was considered, we found no effect on uptake. However, when simultaneous effects of richness, tide height, and herbivores on uptake were evaluated, we found that all three had relatively large and comparable effects on nitrate uptake coefficients and that there was a negative relationship between seaweed richness and nitrate uptake. Particularly because effects of richness on uptake were not apparent unless the effects of tide height and herbivory were also considered, these results highlight the

  9. Dynamics of avian haemosporidian assemblages through millennial time scales inferred from insular biotas of the West Indies.

    Science.gov (United States)

    Soares, Leticia; Latta, Steven C; Ricklefs, Robert E

    2017-06-20

    Although introduced hemosporidian (malaria) parasites (Apicomplexa: Haemosporida) have hastened the extinction of endemic bird species in the Hawaiian Islands and perhaps elsewhere, little is known about the temporal dynamics of endemic malaria parasite populations. Haemosporidian parasites do not leave informative fossils, and records of population change are lacking beyond a few decades. Here, we take advantage of the isolation of West Indian land-bridge islands by rising postglacial sea levels to estimate rates of change in hemosporidian parasite assemblages over a millennial time frame. Several pairs of West Indian islands have been connected and separated by falling and rising sea levels associated with the advance and retreat of Pleistocene continental glaciers. We use island isolation following postglacial sea-level rise, ca. 2.5 ka, to characterize long-term change in insular assemblages of hemosporidian parasites. We find that assemblages on formerly connected islands are as differentiated as assemblages on islands that have never been connected, and both are more differentiated than local assemblages sampled up to two decades apart. Differentiation of parasite assemblages between formerly connected islands reflects variation in the prevalence of shared hemosporidian lineages, whereas differentiation between islands isolated by millions of years reflects replacement of hemosporidian lineages infecting similar assemblages of avian host species.

  10. Megabenthic assemblages in the continental shelf edge and upper slope of the Menorca Channel, Western Mediterranean Sea

    Science.gov (United States)

    Grinyó, Jordi; Gori, Andrea; Greenacre, Michael; Requena, Susana; Canepa, Antonio; Lo Iacono, Claudio; Ambroso, Stefano; Purroy, Ariadna; Gili, Josep-Maria

    2018-03-01

    Highly diverse megabenthic assemblages dominated by passive and active suspension feeders have been recently reported in shelf edge environments of the Mediterranean Sea. Due to their frequent association with species of commercial interest, these assemblages have been heavily impacted by fishing. The vulnerability and low resilience of these assemblages, composed mainly by long-living and slow-growing species, have motivated the implementation of management measures such as the restriction of bottom trawling, and the establishment of large protected areas embracing these environments. The Menorca Channel is one of such areas recently included in the European Union Natura 2000 network. Quantitative analysis of video transects recorded at 95-360 m depth by manned submersible and remotely operated vehicles were used to characterize megabenthic assemblages and to assess their geographical and bathymetric distribution. Six different assemblages were identified, mainly segregated by substrate type and depth. Hard substrates hosted coral gardens and sponge grounds, whereas soft sediments were mainly characterized by large extensions of the crinoid Leptometra phalangium and the brachiopod Gryphus vitreus. The good preservation of most of the observed assemblages is probably related to a low bottom trawling pressure, which mainly concentrates deeper on the adjacent continental slope. Because of their biological and ecological value, management and conservation measures need to be established to preserve these benthic assemblages.

  11. Assemblage organization in stream fishes: effects of environmental variation and interspecific interactions

    Science.gov (United States)

    Grossman, G.D.; Ratajczak, R.E.; Crawford, M. M.; Freeman, Mary C.

    1998-01-01

    We assessed the relative importance of environmental variation, interspecific competition for space, and predator abundance on assemblage structure and microhabitat use in a stream fish assemblage inhabiting Coweeta Creek, North Carolina, USA. Our study encompassed a ten year time span (1983-1992) and included some of the highest and lowest flows in the last 58 years. We collected 16 seasonal samples which included data on: 1) habitat availability (total and microhabitat) and microhabitat diversity, 2) assemblage structure (i.e., the number and abundances of species comprising a subset of the community), and 3) microhabitat use and overlap. We classified habitat availability data on the basis of year, season, and hydrologic period. Hydrologic period (i.e., pre-drought [PR], drought [D], and post-drought [PO]) represented the temporal location of a sample with respect to a four-year drought that occurred during the study. Hydrologic period explained a greater amount of variance in habitat availability data than either season or year. Total habitat availability was significantly greater during PO than in PR or D, although microhabitat diversity did not differ among either seasons or hydrologic periods. There were significantly fewer high-flow events (i.e., > 2.1 m3/s) during D than in either PR or PO periods. We observed a total of 16 species during our investigation, and the total number of species was significantly higher in D than in PR samples. Correlation analyses between the number of species present (total and abundant species) and environmental data yielded limited results, although the total number of species was inversely correlated with total habitat availability. A cluster analysis grouped assemblage structure samples by hydrologic period rather than season or year, supporting the contention that variation in annual flow had a strong impact on this assemblage. The drought had little effect on the numerical abundance of benthic species in this assemblage

  12. Associations among fish assemblage structure and environmental variables in Willamette Basin streams, Oregon

    Science.gov (United States)

    Waite, I.R.; Carpenter, K.D.

    2000-01-01

    As part of the U.S. Geological Survey's National Water-Quality Assessment Program, fish were collected from 24 selected stream sites in the Willamette Basin during 1993-1995 to determine the composition of the fish assemblages and their relation to the chemical and physical environment. Variance in fish relative abundance was greater among all sites than among spatially distinct reaches within a site (spatial variation) or among multiple sampled years at a site (temporal variation). Therefore, data from a single reach in an individual year was considered to be a reliable estimator of the fish assemblage structure at a site when the data were normalized by percent relative abundance. Multivariate classification and ordination were used to examine patterns in environmental variables and fish relative abundance over differing spatial scales (among versus within ecoregions). Across all ecoregions (all sites), fish assemblages were primarily structured along environmental gradients of water temperature and stream gradient (coldwater, high-gradient forested sites versus warmwater, low-gradient Willamette Valley sites); this pattern superseded patterns that were ecoregion specific. Water temperature, dissolved oxygen, and physical habitat (e.g., riparian canopy and percent riffles) were associated with patterns of fish assemblages across all ecoregions; however, pesticide and total phosphorus concentrations were more important than physical habitat within the Willamette Valley ecoregion. Consideration of stream site stratification (e.g., stream size, ecoregion, and stream gradient), identification of fish to species level (particularly the sculpin family), and detailed measurement of habitat, diurnal dissolved oxygen, and water temperature were critical in evaluating the composition of fish assemblages in relation to land use. In general, these low-gradient valley streams typical of other agricultural regions had poor riparian systems and showed increases in water

  13. Lake Bacterial Assemblage Composition Is Sensitive to Biological Disturbance Caused by an Invasive Filter Feeder.

    Science.gov (United States)

    Denef, Vincent J; Carrick, Hunter J; Cavaletto, Joann; Chiang, Edna; Johengen, Thomas H; Vanderploeg, Henry A

    2017-01-01

    One approach to improve forecasts of how global change will affect ecosystem processes is to better understand how anthropogenic disturbances alter bacterial assemblages that drive biogeochemical cycles. Species invasions are important contributors to global change, but their impacts on bacterial community ecology are rarely investigated. Here, we studied direct impacts of invasive dreissenid mussels (IDMs), one of many invasive filter feeders, on freshwater lake bacterioplankton. We demonstrated that direct effects of IDMs reduced bacterial abundance and altered assemblage composition by preferentially removing larger and particle-associated bacteria. While this increased the relative abundances of many free-living bacterial taxa, some were susceptible to filter feeding, in line with efficient removal of phytoplankton cells of <2 μm. This selective removal of particle-associated and larger bacteria by IDMs altered inferred bacterial functional group representation, defined by carbon and energy source utilization. Specifically, we inferred an increased relative abundance of chemoorganoheterotrophs predicted to be capable of rhodopsin-dependent energy generation. In contrast to the few previous studies that have focused on the longer-term combined direct and indirect effects of IDMs on bacterioplankton, our study showed that IDMs act directly as a biological disturbance to which freshwater bacterial assemblages are sensitive. The negative impacts on particle-associated bacteria, which have been shown to be more active than free-living bacteria, and the inferred shifts in functional group representation raise the possibility that IDMs may directly alter bacterially mediated ecosystem functions. IMPORTANCE Freshwater bacteria play fundamental roles in global elemental cycling and are an intrinsic part of local food webs. Human activities are altering freshwater environments, and much has been learned regarding the sensitivity of bacterial assemblages to a variety of

  14. Effects of floods on fish assemblages in an intermittent prairie stream

    Science.gov (United States)

    Franssen, N.R.; Gido, K.B.; Guy, C.S.; Tripe, J.A.; Shrank, S.J.; Strakosh, T.R.; Bertrand, K.N.; Franssen, C.M.; Pitts, K.L.; Paukert, C.P.

    2006-01-01

    1. Floods are major disturbances to stream ecosystems that can kill or displace organisms and modify habitats. Many studies have reported changes in fish assemblages after a single flood, but few studies have evaluated the importance of timing and intensity of floods on long-term fish assemblage dynamics. 2. We used a 10-year dataset to evaluate the effects of floods on fishes in Kings Creek, an intermittent prairie stream in north-eastern, Kansas, U.S.A. Samples were collected seasonally at two perennial headwater sites (1995-2005) and one perennial downstream flowing site (1997-2005) allowing us to evaluate the effects of floods at different locations within a watershed. In addition, four surveys during 2003 and 2004 sampled 3-5 km of stream between the long-term study sites to evaluate the use of intermittent reaches of this stream. 3. Because of higher discharge and bed scouring at the downstream site, we predicted that the fish assemblage would have lowered species richness and abundance following floods. In contrast, we expected increased species richness and abundance at headwater sites because floods increase stream connectivity and create the potential for colonisation from downstream reaches. 4. Akaike Information Criteria (AIC) was used to select among candidate regression models that predicted species richness and abundance based on Julian date, time since floods, season and physical habitat at each site. At the downstream site, AIC weightings suggested Julian date was the best predictor of fish assemblage structure, but no model explained >16% of the variation in species richness or community structure. Variation explained by Julian date was primarily attributed to a long-term pattern of declining abundance of common species. At the headwater sites, there was not a single candidate model selected to predict total species abundance and assemblage structure. AIC weightings suggested variation in assemblage structure was associated with either Julian date

  15. Megabenthic assemblages at the Hudson Canyon head (NW Atlantic margin): Habitat-faunal relationships

    Science.gov (United States)

    Pierdomenico, Martina; Gori, Andrea; Guida, Vincent G.; Gili, Josep-Maria

    2017-09-01

    The distribution of megabenthic communities at the head of Hudson Canyon and adjacent continental shelf was studied by means of underwater video transects and still photo imagery collected using a towed camera system. The goal was to explore the relationships between faunal distribution and physical seafloor conditions and to test the hypothesis that increased seafloor heterogeneity in the Hudson Canyon supports a larger diversity of benthic communities, compared with the adjacent continental shelf. Hierarchical cluster analysis was performed to identify benthic assemblages as defined in imagery. The BIO-ENV procedure and the Canonical Correspondence Analysis were carried out to elucidate species groupings in relation to terrain variables extracted from bathymetric data. Species accumulation curves were generated to evaluate species turn over in and out of Hudson Canyon. The results indicate that seafloor morphology is the main physical factor related to benthic community composition and distribution. Assemblages dominated by sponges, zoanthids and cup corals colonized the canyon margins and flanks, and were associated with coarse-grained sediments, while sea pen assemblages were observed along muddy seafloor within the thalweg. An assemblage dominated by sea stars occurred on the shelf, associated with a sandy seafloor. Some assemblages were exclusively observed in the canyon area, suggesting that the increased variability of seafloor composition, together with the oceanographic processes specific to the canyon area, enhance beta diversity. The colonization by benthic suspension feeders within the canyon, in contrast to shelf assemblages, mainly composed of carnivores and detritus feeders could be favored the intense hydrodynamics at the canyon head that increase the availability of suspended organic matter. From the perspective of management and conservation of marine resources, the results obtained support the relevance of Hudson Canyon as a biodiversity hotspot

  16. The Effects of Sub-Regional Climate Velocity on the Distribution and Spatial Extent of Marine Species Assemblages.

    Science.gov (United States)

    Kleisner, Kristin M; Fogarty, Michael J; McGee, Sally; Barnett, Analie; Fratantoni, Paula; Greene, Jennifer; Hare, Jonathan A; Lucey, Sean M; McGuire, Christopher; Odell, Jay; Saba, Vincent S; Smith, Laurel; Weaver, Katherine J; Pinsky, Malin L

    2016-01-01

    Many studies illustrate variable patterns in individual species distribution shifts in response to changing temperature. However, an assemblage, a group of species that shares a common environmental niche, will likely exhibit similar responses to climate changes, and these community-level responses may have significant implications for ecosystem function. Therefore, we examine the relationship between observed shifts of species in assemblages and regional climate velocity (i.e., the rate and direction of change of temperature isotherms). The assemblages are defined in two sub-regions of the U.S. Northeast Shelf that have heterogeneous oceanography and bathymetry using four decades of bottom trawl survey data and we explore temporal changes in distribution, spatial range extent, thermal habitat area, and biomass, within assemblages. These sub-regional analyses allow the dissection of the relative roles of regional climate velocity and local physiography in shaping observed distribution shifts. We find that assemblages of species associated with shallower, warmer waters tend to shift west-southwest and to shallower waters over time, possibly towards cooler temperatures in the semi-enclosed Gulf of Maine, while species assemblages associated with relatively cooler and deeper waters shift deeper, but with little latitudinal change. Conversely, species assemblages associated with warmer and shallower water on the broad, shallow continental shelf from the Mid-Atlantic Bight to Georges Bank shift strongly northeast along latitudinal gradients with little change in depth. Shifts in depth among the southern species associated with deeper and cooler waters are more variable, although predominantly shifts are toward deeper waters. In addition, spatial expansion and contraction of species assemblages in each region corresponds to the area of suitable thermal habitat, but is inversely related to assemblage biomass. This suggests that assemblage distribution shifts in

  17. The Effects of Sub-Regional Climate Velocity on the Distribution and Spatial Extent of Marine Species Assemblages.

    Directory of Open Access Journals (Sweden)

    Kristin M Kleisner

    Full Text Available Many studies illustrate variable patterns in individual species distribution shifts in response to changing temperature. However, an assemblage, a group of species that shares a common environmental niche, will likely exhibit similar responses to climate changes, and these community-level responses may have significant implications for ecosystem function. Therefore, we examine the relationship between observed shifts of species in assemblages and regional climate velocity (i.e., the rate and direction of change of temperature isotherms. The assemblages are defined in two sub-regions of the U.S. Northeast Shelf that have heterogeneous oceanography and bathymetry using four decades of bottom trawl survey data and we explore temporal changes in distribution, spatial range extent, thermal habitat area, and biomass, within assemblages. These sub-regional analyses allow the dissection of the relative roles of regional climate velocity and local physiography in shaping observed distribution shifts. We find that assemblages of species associated with shallower, warmer waters tend to shift west-southwest and to shallower waters over time, possibly towards cooler temperatures in the semi-enclosed Gulf of Maine, while species assemblages associated with relatively cooler and deeper waters shift deeper, but with little latitudinal change. Conversely, species assemblages associated with warmer and shallower water on the broad, shallow continental shelf from the Mid-Atlantic Bight to Georges Bank shift strongly northeast along latitudinal gradients with little change in depth. Shifts in depth among the southern species associated with deeper and cooler waters are more variable, although predominantly shifts are toward deeper waters. In addition, spatial expansion and contraction of species assemblages in each region corresponds to the area of suitable thermal habitat, but is inversely related to assemblage biomass. This suggests that assemblage distribution

  18. Coral assemblages are structured along a turbidity gradient on the Southwestern Gulf of Mexico, Veracruz

    Science.gov (United States)

    Jordán-Garza, A. G.; González-Gándara, C.; Salas-Pérez, J. J.; Morales-Barragan, A. M.

    2017-04-01

    Corals on the reef corridor of the southwestern Gulf of Mexico have evolved on a terrigenous shallow continental shelf under the influence of several natural river systems. As a result, water turbidity on these reefs can be high, with visibility as low as Mexico. Completeness of the data set was assessed using species accumulation curves and non-parametric estimators of species richness. Differences in coral assemblages' composition between the reef systems were investigated using univariate (ANOVA) and multivariate (nMDS, ANOSIM, SIMPER) analyses and the relationship between the assemblages and environmental data was assessed using a forward selection process in canonical correspondence analysis (CCA) to eliminate non-significant environmental variables. The northern and central Veracruz reef systems share a similar number of coral species (p=0.78 mult. comp.) and both showed higher species richness than the southern system (pMexico.

  19. Current status and multidecadal biogeographical changes in rocky intertidal algal assemblages: The northern Spanish coast

    Science.gov (United States)

    Fernández, C.

    2016-03-01

    The biogeographic border between the Eastern and the Atlantic subregions of the Lusitanian Province situated on the west coast of Asturias (N. of Spain) has moved westwards in recent years. A comparative study, consisting in a resurvey of 20 shores sampled in 1977, covering 200 km showed a large-scale change affecting the mid and low eulittoral. Cold-temperate canopy species such as kelps (Laminaria hyperborea, Laminaria. ochroleuca and Saccorhiza polyschides), fucoids (Fucus serratus, Fucus vesiculosus and Himanthalia elongata) and Chondrus crispus have almost disappeared and replaced by warm-temperate species such as Cystoseira baccata, Cystoseira tamariscifolia, Bifurcaria bifurcata and coralline algae (Ellisolandia elongata, Lithophyllum incrustans and Mesophyllum lichenoides). The loss of canopy-species can have consequences for the assemblage, especially in the case of fucoid-dominated assemblages.

  20. Effects of drought on the composition and structure of benthic macroinvertebrate assemblages – a case study

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    Pavla Řezníčková

    2013-01-01

    Full Text Available Natural drying up of streams is not common in Central Europe. Nevertheless, the recurrent drying up of small streams in last decades has shown an urgent need to pay attention to the impact of global climate change. This strong disturbance influences conditions in streams markedly and causes changes in the taxonomical and functional structure of biota. The aim of the study was to compare aquatic macroinvertebrate assemblages of one intermittent and one permanent brook in South Moravia. The study was carried out in two stretches with otherwise comparable environmental parameters. Lower densities of macroinvertebrates were found at the intermittent site the difference was statistically significant. The number of taxa and diversity were significantly higher at the permanent site. Functional structure of the assemblages also varied. The shares of rheobionts, grazers and predators differed.

  1. Shifts in coral-assemblage composition do not ensure persistence of reef functionality

    Science.gov (United States)

    Alvarez-Filip, Lorenzo; Carricart-Ganivet, Juan P.; Horta-Puga, Guillermo; Iglesias-Prieto, Roberto

    2013-12-01

    Coral communities are changing rapidly worldwide through loss of coral cover and shifts in species composition. Although many reef-building corals are likely to decline, some weedy opportunistic species might increase in abundance. Here we explore whether the reshuffling of species can maintain ecosystem integrity and functioning. Using four common Caribbean reef-building coral genera we modeled rates of reef construction and complexity. We show that shifting coral assemblages result in rapid losses in coral-community calcification and reef rugosity that are independent of changes in the total abundance of reef corals. These losses are considerably higher than those recently attributed to climate change. Dominance patterns of coral assemblages seem to be the most important driver of the functioning of coral reefs and thus, the future of these ecosystems might depend not only on reductions of local and global stressors, but also on the maintenance of keystone coral species.

  2. Upper Arenigian to lower Llanvirnian acritarch assemblages from South China: a preliminary evaluation.

    Science.gov (United States)

    Brocke, R; Li, J; Wang, Y

    2000-12-01

    Acritarchs from the interval corresponding to the late Arenigian and early Llanvirnian in British stratigraphy have rarely been described from China, and they are documented herein for the first time. A biostratigraphic correlation of certain acritarch taxa with the Undulograptus austrodentatus graptolite Biozone, which constitutes the base of the Darriwilian Stage, is still premature for China and elsewhere. According to recent studies on different sections from South China, it appears that at least four distinctive species (Ampullula suetica, Dicrodiacrodium ancoriforme, Hoegklintia rayii nov. comb., Liliosphaeridium intermedium) may characterize an interval that corresponds to levels just below or within the Darriwilian Stage. In this context, the acritarch assemblages of the lower to upper Arenigian and of the lower Llanvirnian sequences from different localities of the Yangtze Platform are described. Four acritarch assemblages are distinguished for this time interval and their possible correlations with other areas are discussed.

  3. Initial stresses in two-layer metal domes due to imperfections of their production and assemblage

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    Lebed Evgeniy Vasil’evich

    2015-04-01

    Full Text Available The process of construction of two-layer metal domes is analyzed to illustrate the causes of initial stresses in the bars of their frames. It has been noticed that it is impossible to build such structures with ideal geometric parameters because of imperfections caused by objective reasons. These imperfections cause difficulties in the process of connection of the elements in the joints. The paper demonstrates the necessity of fitting operations during assemblage that involve force fitting and yield initial stresses due to imperfections. The authors propose a special method of computer modeling of enforced elimination of possible imperfections caused by assemblage process and further confirm the method by an analysis of a concrete metal dome.

  4. Temporal variation in the organization of a Neotropical assemblage of leaf-nosed bats (Chiroptera: Phyllostomidae)

    Science.gov (United States)

    Ribeiro Mello, Marco Aurelio

    2009-03-01

    In the present study, I described the organization of a Neotropical bat assemblage, and tested whether this organization was variable in time. In an Atlantic Forest reserve in southeastern Brazil bats were captured monthly with mist nets over 4 years, and individuals were classified into guilds. I analyzed only leaf-nosed bats, and observed that guilds of fruit-eating bats dominated the assemblage. This pattern was repeated across months and years. However, among frugivores, canopy and understory guilds peaked during different months, but in both cases during the rainy season, while variation among habitat-opportunistic species was not explained by rainfall. The most reliable ecological service delivered by phyllostomid bats in the area is seed dispersal, although other services may be also important in particular seasons. My results suggest that the observed patterns of temporal species turnover are related to the abundance of preferred food items.

  5. Ground beetle (Coleoptera: Carabidae) assemblages in narrow hedgerows in a Danish agricultural landscape

    DEFF Research Database (Denmark)

    Lövei, G. L.; Magura, T.

    2015-01-01

    The role of hedgerows in supporting ground beetles (Coleoptera: Carabidae) in a Danish agricultural landscape was examined. Nine old, well established single-row hedges were selected for the study, three each of a native species (hawthorn, Crataegus monogyna), a non-native deciduous one (rowan...... Sorbus intermedia), and the non-native spruce (Picea spp.). We hypothesised that hedgerows with deciduous trees harbour more diverse ground beetle assemblages than hedges composed of non-native conifer trees. We also investigated which vegetation structure characteristics might influence the ground...... beetle assemblages. The number of ground beetle individuals and species were significantly the highest in the hawthorn hedges and significantly decreased from the hedges with rowan toward the spruce hedges. The elevated number of ground beetle individuals and species in the hawthorn hedges were due...

  6. Burrow casts from the Lystrosaurus-Procolophon Assemblage-zone, Karoo Sequence, South Africa

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    G.H. Groenewald

    1991-09-01

    Full Text Available Five types of burrow casts from the Lystrosaurus- Procolophon Assemblage-zone (Palingkloof Member and Katberg Formation, Triassic, Karoo sequence. South Africa are associated with casts of desiccation cracks and red mudstone. Vertebrate remains of Lystrosaurus sp. and Procolophon sp. indicate that these animals probably made the burrows during the Triassic. It is possible that burrowing was an adaptive advantage during periods of severe and unfavourable climatic conditions. Similar burrow casts were found in the Dicynodon-Theriognathus Assemblage-zone, suggesting a burrowing habit for fauna represented in this zone. In structure, the burrow casts resemble those of Scoyenia, Thalassinoides, Histioderma, Gyrolithes and Planolites reported from Germany, France, Asia, Ireland, Spain and the United States of America.

  7. Shifts in coral-assemblage composition do not ensure persistence of reef functionality.

    Science.gov (United States)

    Alvarez-Filip, Lorenzo; Carricart-Ganivet, Juan P; Horta-Puga, Guillermo; Iglesias-Prieto, Roberto

    2013-12-12

    Coral communities are changing rapidly worldwide through loss of coral cover and shifts in species composition. Although many reef-building corals are likely to decline, some weedy opportunistic species might increase in abundance. Here we explore whether the reshuffling of species can maintain ecosystem integrity and functioning. Using four common Caribbean reef-building coral genera we modeled rates of reef construction and complexity. We show that shifting coral assemblages result in rapid losses in coral-community calcification and reef rugosity that are independent of changes in the total abundance of reef corals. These losses are considerably higher than those recently attributed to climate change. Dominance patterns of coral assemblages seem to be the most important driver of the functioning of coral reefs and thus, the future of these ecosystems might depend not only on reductions of local and global stressors, but also on the maintenance of keystone coral species.

  8. Sediment and carbon deposition vary among vegetation assemblages in a coastal salt marsh

    Directory of Open Access Journals (Sweden)

    J. J. Kelleway

    2017-08-01

    Full Text Available Coastal salt marshes are dynamic, intertidal ecosystems that are increasingly being recognised for their contributions to ecosystem services, including carbon (C accumulation and storage. The survival of salt marshes and their capacity to store C under rising sea levels, however, is partially reliant upon sedimentation rates and influenced by a combination of physical and biological factors. In this study, we use several complementary methods to assess short-term (days deposition and medium-term (months accretion dynamics within a single marsh that contains three salt marsh vegetation types common throughout southeastern (SE Australia.We found that surface accretion varies among vegetation assemblages, with medium-term (19 months bulk accretion rates in the upper marsh rush (Juncus assemblage (1.74 ± 0.13 mm yr−1 consistently in excess of estimated local sea-level rise (1.15 mm yr−1. Accretion rates were lower and less consistent in both the succulent (Sarcocornia, 0.78 ± 0.18 mm yr−1 and grass (Sporobolus, 0.88 ± 0.22 mm yr−1 assemblages located lower in the tidal frame. Short-term (6 days experiments showed deposition within Juncus plots to be dominated by autochthonous organic inputs with C deposition rates ranging from 1.14 ± 0.41 mg C cm−2 d−1 (neap tidal period to 2.37 ± 0.44 mg C cm−2 d−1 (spring tidal period, while minerogenic inputs and lower C deposition dominated Sarcocornia (0.10 ± 0.02 to 0.62 ± 0.08 mg C cm−2 d−1 and Sporobolus (0.17 ± 0.04 to 0.40 ± 0.07 mg C cm−2 d−1 assemblages.Elemental (C : N, isotopic (δ13C, mid-infrared (MIR and 13C nuclear magnetic resonance (NMR analyses revealed little difference in either the source or character of materials being deposited among neap versus spring tidal periods. Instead, these analyses point to substantial redistribution of materials within the Sarcocornia and

  9. The effects of sewage discharge on shallow hard substrate sessile assemblages.

    Science.gov (United States)

    Terlizzi, A; Fraschetti, S; Guidetti, P; Boero, F

    2002-06-01

    On rocky shores, sewage discharges can modify natural distribution patterns of sessile organisms. The impact of sewage on shallow hard substrate assemblages has been assessed along SW Apulian coast (Ionian Sea, Italy), providing a framework to evaluate the benefits of future sewage displacement to deeper waters. Four locations (three controls and one putatively impacted) were selected and three sites were chosen at each location. Each site was sampled by 10 replicate photographic records. Univariate analyses revealed that the outfall did not affect the spatial distribution of number of taxa, total cover and abundance of some dominant taxa (mostly algae, sponges and bryozoans). The outfall negatively influenced the natural distribution pattern of filamentous green algae, whilst some algae (i.e. Gelidiales and Colpomenia sinuosa) were exclusively present at the impacted location. Multivariate analyses revealed that the outfall heavily modified the natural pattern of variability in the structure of the assemblage.

  10. Characterisation of the woody assemblages of Zululand coastal thornveld along the Nseleni river

    Directory of Open Access Journals (Sweden)

    Jannie P. van der Linden

    2008-12-01

    Full Text Available A classification of the woody component of the riparian vegetation of Zululand coastal thornveld is analysed using the height classes of different woody species as an indication of age. A total of 43 randomly stratified plots was selected using aerial photographs to include all the different plant communities in this rare and endemic vegetation type. A floristic survey of the woody component was conducted within each sample plot. Species data recorded included tree cover and tree richness. Environmental data recorded included altitude, soil type, soil chemistry, aspect and slope. The data set was analysed with TWINSPAN and four woody-plant assemblages were identified. An ordination using CANOCO was applied to examine the relationships between species distribution and associated environmental gradients. Changes in the species composition of woody assemblages occurred along an environmental gradient determined by soil properties and past land use.

  11. Human impacts on functional and taxonomic homogenization of plateau fish assemblages in Yunnan, China

    Directory of Open Access Journals (Sweden)

    Guohuan Su

    2015-07-01

    Full Text Available Human activities and the consequent extinctions of native species and invasions of non-native species have been changing the composition of species assemblages worldwide. These anthropogenic impacts alter not only the richness of assemblages but also the biological dissimilarity among them. However, much of the research effort to date has focused on changes in taxonomic dissimilarity (i.e. accounting for species composition whether assessments of functional dissimilarity (i.e. accounting for the diversity of biological traits are much more scarce, despite revealing important complimentary information by accounting for changes in the diversity of biological traits. Here, we assess the temporal (1950s against 2000s changes in both taxonomic and functional dissimilarities of freshwater fish assemblages across lakes from the Yunnan Plateau in China. The Jaccard index to quantify the changes in both taxonomic and functional dissimilarity. We then partitioned dissimilarity to extract its turnover component and measured the changes in the contribution of turnover to dissimilarity. We found that functional and taxonomic homogenization occurred simultaneously. However, patterns between these two processes differed for some lakes. Taxonomic and functional homogenizations were stronger when the historical level of taxonomic dissimilarity among assemblages was high. The impact of extinctions of native species and invasions of non-native species on homogenization was otherwise complex to disentangle with no significant effect of any of the studied environmental factors. In agreement with other studies, our study proved that change in taxonomic dissimilarity cannot be used to predict changes in functional dissimilarity and, as an indicator of ecosystem functioning, functional dissimilarity should be used together with taxonomic dissimilarity to attain a more holistic understanding of human impacts on natural ecosystems.

  12. Ecological shifts in Mediterranean coralligenous assemblages related to gorgonian forest loss.

    Science.gov (United States)

    Ponti, Massimo; Perlini, Rossella Angela; Ventra, Vincenzo; Grech, Daniele; Abbiati, Marco; Cerrano, Carlo

    2014-01-01

    Mediterranean gorgonian forests are threatened by several human activities and are affected by climatic anomalies that have led to mass mortality events in recent decades. The ecological role of these habitats and the possible consequence of their loss are poorly understood. Effects of gorgonians on the recruitment of epibenthic organisms were investigated by manipulating presence of gorgonians on experimental panels at 24 m depth, for Eunicella cavolinii, and at 40 m depth, for Paramuricea clavata, at two sites: Tavolara Island (Tyrrhenian Sea) and Portofino Promontory (Ligurian Sea). After 4 months, the most abundant taxa on the panels were encrusting green algae, erect red algae and crustose coralline algae at 24 m depth and encrusting brown algae and erect red algae at 40 m depth. Assemblages on the panels were significantly affected by the presence of the gorgonians, although effects varied across sites and between gorgonian species. Species diversity and evenness were lower on panels with gorgonian branches. Growth of erect algae and recruitment of serpulid polychaetes were also affected by the presence of the gorgonians, primarily at Tavolara. Crustose coralline algae and erect sponges were more abundant on E. cavolinii panels at 24 m depth, while encrusting bryozoans were more abundant on P. clavata panels at 40 m depth. Effects of gorgonians on recruited assemblages could be due to microscale modification of hydrodynamics and sediment deposition rate, or by a shading effect reducing light intensity. Gorgonians may also intercept settling propagules, compete for food with the filter-feeders and/or for space by producing allelochemicals. Presence of gorgonians mainly limits the growth of erect algae and enhances the abundance of encrusting algae and sessile invertebrates. Therefore, the gorgonian disappearances may cause a shift from assemblages characterised by crustose coralline algae to filamentous algae assemblages, decreasing complexity and resilience

  13. Markedly Divergent Tree Assemblage Responses to Tropical Forest Loss and Fragmentation across a Strong Seasonality Gradient.

    Science.gov (United States)

    Orihuela, Rodrigo L L; Peres, Carlos A; Mendes, Gabriel; Jarenkow, João A; Tabarelli, Marcelo

    2015-01-01

    We examine the effects of forest fragmentation on the structure and composition of tree assemblages within three seasonal and aseasonal forest types of southern Brazil, including evergreen, Araucaria, and deciduous forests. We sampled three southernmost Atlantic Forest landscapes, including the largest continuous forest protected areas within each forest type. Tree assemblages in each forest type were sampled within 10 plots of 0.1 ha in both continuous forests and 10 adjacent forest fragments. All trees within each plot were assigned to trait categories describing their regeneration strategy, vertical stratification, seed-dispersal mode, seed size, and wood density. We detected differences among both forest types and landscape contexts in terms of overall tree species richness, and the density and species richness of different functional groups in terms of regeneration strategy, seed dispersal mode and woody density. Overall, evergreen forest fragments exhibited the largest deviations from continuous forest plots in assemblage structure. Evergreen, Araucaria and deciduous forests diverge in the functional composition of tree floras, particularly in relation to regeneration strategy and stress tolerance. By supporting a more diversified light-demanding and stress-tolerant flora with reduced richness and abundance of shade-tolerant, old-growth species, both deciduous and Araucaria forest tree assemblages are more intrinsically resilient to contemporary human-disturbances, including fragmentation-induced edge effects, in terms of species erosion and functional shifts. We suggest that these intrinsic differences in the direction and magnitude of responses to changes in landscape structure between forest types should guide a wide range of conservation strategies in restoring fragmented tropical forest landscapes worldwide.

  14. Large-Scale Assessment of Mediterranean Marine Protected Areas Effects on Fish Assemblages

    Science.gov (United States)

    Guidetti, Paolo; Baiata, Pasquale; Ballesteros, Enric; Di Franco, Antonio; Hereu, Bernat; Macpherson, Enrique; Micheli, Fiorenza; Pais, Antonio; Panzalis, Pieraugusto; Rosenberg, Andrew A.; Zabala, Mikel; Sala, Enric

    2014-01-01

    Marine protected areas (MPAs) were acknowledged globally as effective tools to mitigate the threats to oceans caused by fishing. Several studies assessed the effectiveness of individual MPAs in protecting fish assemblages, but regional assessments of multiple MPAs are scarce. Moreover, empirical evidence on the role of MPAs in contrasting the propagation of non-indigenous-species (NIS) and thermophilic species (ThS) is missing. We simultaneously investigated here the role of MPAs in reversing the effects of overfishing and in limiting the spread of NIS and ThS. The Mediterranean Sea was selected as study area as it is a region where 1) MPAs are numerous, 2) fishing has affected species and ecosystems, and 3) the arrival of NIS and the northward expansion of ThS took place. Fish surveys were done in well-enforced no-take MPAs (HP), partially-protected MPAs (IP) and fished areas (F) at 30 locations across the Mediterranean. Significantly higher fish biomass was found in HP compared to IP MPAs and F. Along a recovery trajectory from F to HP MPAs, IP were similar to F, showing that just well enforced MPAs triggers an effective recovery. Within HP MPAs, trophic structure of fish assemblages resembled a top-heavy biomass pyramid. Although the functional structure of fish assemblages was consistent among HP MPAs, species driving the recovery in HP MPAs differed among locations: this suggests that the recovery trajectories in HP MPAs are likely to be functionally similar (i.e., represented by predictable changes in trophic groups, especially fish predators), but the specific composition of the resulting assemblages may depend on local conditions. Our study did not show any effect of MPAs on NIS and ThS. These results may help provide more robust expectations, at proper regional scale, about the effects of new MPAs that may be established in the Mediterranean Sea and other ecoregions worldwide. PMID:24740479

  15. Spatial arrangement overrules environmental factors to structure native and non-native assemblages of synanthropic harvestmen.

    Directory of Open Access Journals (Sweden)

    Christoph Muster

    Full Text Available Understanding how space affects the occurrence of native and non-native species is essential for inferring processes that shape communities. However, studies considering spatial and environmental variables for the entire community - as well as for the native and non-native assemblages in a single study - are scarce for animals. Harvestmen communities in central Europe have undergone drastic turnovers during the past decades, with several newly immigrated species, and thus provide a unique system to study such questions. We studied the wall-dwelling harvestmen communities from 52 human settlements in Luxembourg and found the assemblages to be largely dominated by non-native species (64% of specimens. Community structure was analysed using Moran's eigenvector maps as spatial variables, and landcover variables at different radii (500 m, 1000 m, 2000 m in combination with climatic parameters as environmental variables. A surprisingly high portion of pure spatial variation (15.7% of total variance exceeded the environmental (10.6% and shared (4% components of variation, but we found only minor differences between native and non-native assemblages. This could result from the ecological flexibility of both, native and non-native harvestmen that are not restricted to urban habitats but also inhabit surrounding semi-natural landscapes. Nevertheless, urban landcover variables explained more variation in the non-native community, whereas coverage of semi-natural habitats (forests, rivers at broader radii better explained the native assemblage. This indicates that some urban characteristics apparently facilitate the establishment of non-native species. We found no evidence for competitive replacement of native by invasive species, but a community with novel combination of native and non-native species.

  16. Loss of functional diversity of ant assemblages in secondary tropical forests.

    Science.gov (United States)

    Bihn, Jochen H; Gebauer, Gerhard; Brandl, Roland

    2010-03-01

    Secondary forests and plantations increasingly dominate the tropical wooded landscape in place of primary forests. The expected reduction of biodiversity and its impact on ecological functions provided by these secondary forests are of major concern to society and ecologists. The potential effect of biodiversity loss on ecosystem functioning depends largely on the associated loss in the functional diversity of animal and plant assemblages, i.e., the degree of functional redundancy among species. However, the relationship between species and functional diversity is still poorly documented for most ecosystems. Here, we analyze how changes in the species diversity of ground-foraging ant assemblages translate into changes of functional diversity along a successional gradient of secondary forests in the Atlantic Forest of Brazil. Our analysis uses continuous measures of functional diversity and is based on four functional traits related to resource use of ants: body size, relative eye size, relative leg length, and trophic position. We find a strong relationship between species and functional diversity, independent of the functional traits used, with no evidence for saturation in this relationship. Recovery of species richness and diversity of ant assemblages in tropical secondary forests was accompanied by a proportional increase of functional richness and diversity of assemblages. Moreover, our results indicate that the increase in functional diversity along the successional gradient of secondary forests is primarily driven by rare species, which are functionally unique. The observed loss of both species and functional diversity in secondary forests offers no reason to believe that the ecological functions provided by secondary forests are buffered against species loss through functional redundancy.

  17. Exotic birds increase generalization and compensate for native bird decline in plant-frugivore assemblages.

    Science.gov (United States)

    García, Daniel; Martínez, Daniel; Stouffer, Daniel B; Tylianakis, Jason M

    2014-11-01

    Exotic species are thought to alter the structure of natural communities and disrupt ecosystem functioning through invasion. Nevertheless, exotic species may also provide ecological insurance when they contribute to maintain ecosystem functions after the decline of native species following anthropogenic disturbance. Here, this hypothesis is tested with the assemblage of frugivorous birds and fleshy-fruited plants of New Zealand, which has suffered strong historical declines in native birds while simultaneously gaining new frugivores introduced by European settlers. We studied the plant-frugivore assemblage from measures of fruit and bird abundances and fruit consumption in nine forest patches, and tested how this changed across a gradient of relative abundance of exotic birds. We then examined how each bird species' role in the assemblage (the proportion of fruits and the number of plant species consumed) varied with their relative abundance, body size and native/exotic status. The more abundant and, to a lesser extent, larger birds species consumed a higher proportion of fruits from more plant species. Exotic birds consumed fruits less selectively and more proportionate to the local availability than did native species. Interaction networks in which exotic birds had a stronger role as frugivores had higher generalization, higher nestedness and higher redundancy of plants. Exotic birds maintained frugivory when native birds became rarer, and diversified the local spectrum of frugivores for co-occurring native plants. These effects seemed related to the fact that species abundances, rather than trait-matching constraints, ultimately determined the patterns of interactions between birds and plants. By altering the structure of plant-frugivore assemblages, exotic birds likely enhance the stability of the community-wide seed dispersal in the face of continued anthropogenic impact. © 2014 The Authors. Journal of Animal Ecology © 2014 British Ecological Society.

  18. Dynamics Of A Rodent Assemblage In A Cerrado Of Southeast Brazil

    OpenAIRE

    Vieira M.V.

    1997-01-01

    Seasonal variation of densities of cerrado rodents have been studied mostly near the center of cerrado phytogeographic province. Herein, I describe the dynamics of a rodent assemblage at the southern border of the cerrado province, in Itirapina, SP. Density was estimated by mark-recapture from September 1985 through September 1986, on a 1.32ha grid composed mostly of campo cerrado. Four rodents were captured, Clyomys bishopi, Oryzomys subflavus, Oligoryzomys eliurus, and Bolomys lasiurus. The...

  19. Disentangling the effects of a century of eutrophication and climate warming on freshwater lake fish assemblages.

    Directory of Open Access Journals (Sweden)

    Peter C Jacobson

    Full Text Available Eutrophication and climate warming are profoundly affecting fish in many freshwater lakes. Understanding the specific effects of these stressors is critical for development of effective adaptation and remediation strategies for conserving fish populations in a changing environment. Ecological niche models that incorporated the individual effects of nutrient concentration and climate were developed for 25 species of fish sampled in standard gillnet surveys from 1,577 Minnesota lakes. Lake phosphorus concentrations and climates were hindcasted to a pre-disturbance period of 1896-1925 using existing land use models and historical temperature data. Then historical fish assemblages were reconstructed using the ecological niche models. Substantial changes were noted when reconstructed fish assemblages were compared to those from the contemporary period (1981-2010. Disentangling the sometimes opposing, sometimes compounding, effects of eutrophication and climate warming was critical for understanding changes in fish assemblages. Reconstructed abundances of eutrophication-tolerant, warmwater taxa increased in prairie lakes that experienced significant eutrophication and climate warming. Eutrophication-intolerant, warmwater taxa abundance increased in forest lakes where primarily climate warming was the stressor. Coolwater fish declined in abundance in both ecoregions. Large changes in modeled abundance occurred when the effects of both climate and eutrophication operated in the same direction for some species. Conversely, the effects of climate warming and eutrophication operated in opposing directions for other species and dampened net changes in abundance. Quantifying the specific effects of climate and eutrophication will allow water resource managers to better understand how lakes have changed and provide expectations for sustainable fish assemblages in the future.

  20. Giardia assemblage A: human genotype in muskoxen in the Canadian Arctic

    Directory of Open Access Journals (Sweden)

    Nagy John

    2008-09-01

    Full Text Available Abstract As part of an ongoing program assessing the biodiversity and impacts of parasites in Arctic ungulates we examined 72 fecal samples from muskoxen on Banks Island, Northwest Territories, Canada for Giardia and Cryptosporidium. Cryptosporidium spp. were not detected, but 21% of the samples were positive for Giardia. Sequencing of four isolates of Giardia demonstrated G. duodenalis, Assemblage A, a zoonotic genotype.

  1. Disentangling the effects of solar radiation, wrack macroalgae and beach macrofauna on associated bacterial assemblages.

    Science.gov (United States)

    Rodil, Iván F; Fernandes, Joana P; Mucha, Ana P

    2015-12-01

    Wrack detritus plays a significant role in shaping community dynamics and food-webs on sandy beaches. Macroalgae is the most abundant beach wrack, and it is broken down by the combination of environmental processes, macrofauna grazing, and microbial degradation before returning to the sea as nutrients. The role of solar radiation, algal species and beach macrofauna as ecological drivers for bacterial assemblages associated to wrack was investigated by experimental manipulation of Laminaria ochroleuca and Sargassum muticum. We examined the effects of changes in solar radiation on wrack-associated bacterial assemblages by using cut-off filters: PAR + UVA + UVB (280-700 nm; PAB), PAR + UVA (320-700 nm; PA), PAR (400-700 nm; P), and a control with no filter (C). Results showed that moderate changes in UVR are capable to promote substantial differences on bacterial assemblages so that wrack patches exposed to full sunlight treatments (C and PAB) showed more similar assemblages among them than compared to patches exposed to treatments that blocked part of the solar radiation (P and PA). Our findings also suggested that specific algal nutrient quality-related variables (i.e. nitrogen, C:N ratio and phlorotannins) are main determinants of bacterial dynamics on wrack deposits. We showed a positive relationship between beach macrofauna, especially the most abundant and active wrack-users, the amphipod Talitrus saltator and the coleopteran Phaleria cadaverina, and both bacterial abundance and richness. Moderate variations in natural solar radiation and shifts in the algal species entering beach ecosystems can modify the role of wrack in the energy-flow of nearshore environments with unknown ecological implications for coastal ecosystems. Copyright © 2015 Elsevier Ltd. All rights reserved.

  2. Factors affecting assemblage attributes of freshwater Oligochaeta in Neotropical shallow floodplain lakes

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    Vanessa Ernandes de Amo

    2017-12-01

    Full Text Available Abstract Aim: Identify the effects of sediment composition and water conditions on diversity, richness, evenness, density and composition of freshwater Oligochaeta in shallow floodplain lakes. Methods We sampled 13 shallow floodplain lakes quarterly during the year 2010 in the Upper Paraná River floodplain. In each lake, four sediment samples were taken from the shore and central regions, three of them were used for biological analysis, and one for granulometric analysis. Concomitantly, temperature, dissolved oxygen, pH, conductivity, alkalinity, turbidity and chlorophyll-a were also measured. Initially, the biological samples were analyzed by a stereoscopic microscope. Oligochaeta individuals were identified under optical microscope at the lowest possible taxonomic level. For data analysis, we quantified density, richness, evenness and diversity index of freshwater Oligochaeta. In order to show differences between the months and the analyzed lakes, in relation to the percentages of coarse and fine organic material, the nonparametric Kruskal Wallis test was used. We also calculated the sediment granulometric diversity using the Shannon-Wienner index, using a simple regression analysis. We correlated assemblage attributes of Oligochaeta with sediment diversity and the assemblage species with the limnological variables using the Spearman correlation. Results A total of 2,090 individuals were found distributed among 27 species. From the total individuals number, 57% were Pristina americana, followed by Dero (Dero righii with 13%. Assemblage attributes were not significantly correlated with sediment diversity, and 7 of the 27 species recorded showed significant correlations with at least some of the abiotic variables. Conclusions We verified that the abiotic variables of the water present greater influence on the attributes of the assemblage of freshwater Oligochaeta, when compared with sediment influences. Although we found low local diversity of

  3. Species composition, richness and nestedness of lizard assemblages from Restinga habitats along the brazilian coast

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    CFD. Rocha

    Full Text Available Habitat fragmentation is well known to adversely affect species living in the remaining, relatively isolated, habitat patches, especially for those having small range size and low density. This negative effect has been critical in coastal resting habitats. We analysed the lizard composition and richness of restinga habitats in 16 restinga habitats encompassing three Brazilian states (Rio de Janeiro, Espírito Santo and Bahia and more than 1500km of the Brazilian coast in order to evaluate if the loss of lizard species following habitat reduction occur in a nested pattern or at random, using the “Nestedness Temperature Calculator” to analyse the distribution pattern of lizard species among the restingas studied. We also estimated the potential capacity that each restinga has to maintain lizard species. Eleven lizard species were recorded in the restingas, although not all species occurred in all areas. The restinga with the richest lizard fauna was Guriri (eight species whereas the restinga with the lowest richness was Praia do Sul (located at Ilha Grande, a large coastal island. Among the restingas analysed, Jurubatiba, Guriri, Maricá and Praia das Neves, were the most hospitable for lizards. The matrix community temperature of the lizard assemblages was 20.49° (= P <0.00001; 5000 randomisations; randomisation temperature = 51.45° ± 7.18° SD, indicating that lizard assemblages in the coastal restingas exhibited a considerable nested structure. The degree in which an area is hospitable for different assemblages could be used to suggest those with greater value of conservation. We concluded that lizard assemblages in coastal restingas occur at a considerable level of ordination in restinga habitats and that some restinga areas such as Jurubatiba, Guriri, Maricá and Praia das Neves are quite important to preserve lizard diversity of restinga environments.

  4. Large-scale assessment of Mediterranean marine protected areas effects on fish assemblages.

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    Paolo Guidetti

    Full Text Available Marine protected areas (MPAs were acknowledged globally as effective tools to mitigate the threats to oceans caused by fishing. Several studies assessed the effectiveness of individual MPAs in protecting fish assemblages, but regional assessments of multiple MPAs are scarce. Moreover, empirical evidence on the role of MPAs in contrasting the propagation of non-indigenous-species (NIS and thermophilic species (ThS is missing. We simultaneously investigated here the role of MPAs in reversing the effects of overfishing and in limiting the spread of NIS and ThS. The Mediterranean Sea was selected as study area as it is a region where 1 MPAs are numerous, 2 fishing has affected species and ecosystems, and 3 the arrival of NIS and the northward expansion of ThS took place. Fish surveys were done in well-enforced no-take MPAs (HP, partially-protected MPAs (IP and fished areas (F at 30 locations across the Mediterranean. Significantly higher fish biomass was found in HP compared to IP MPAs and F. Along a recovery trajectory from F to HP MPAs, IP were similar to F, showing that just well enforced MPAs triggers an effective recovery. Within HP MPAs, trophic structure of fish assemblages resembled a top-heavy biomass pyramid. Although the functional structure of fish assemblages was consistent among HP MPAs, species driving the recovery in HP MPAs differed among locations: this suggests that the recovery trajectories in HP MPAs are likely to be functionally similar (i.e., represented by predictable changes in trophic groups, especially fish predators, but the specific composition of the resulting assemblages may depend on local conditions. Our study did not show any effect of MPAs on NIS and ThS. These results may help provide more robust expectations, at proper regional scale, about the effects of new MPAs that may be established in the Mediterranean Sea and other ecoregions worldwide.

  5. Using assemblage data in ecological indicators: A comparison and evaluation of commonly available statistical tools

    Science.gov (United States)

    Smith, Joseph M.; Mather, Martha E.

    2012-01-01

    Ecological indicators are science-based tools used to assess how human activities have impacted environmental resources. For monitoring and environmental assessment, existing species assemblage data can be used to make these comparisons through time or across sites. An impediment to using assemblage data, however, is that these data are complex and need to be simplified in an ecologically meaningful way. Because multivariate statistics are mathematical relationships, statistical groupings may not make ecological sense and will not have utility as indicators. Our goal was to define a process to select defensible and ecologically interpretable statistical simplifications of assemblage data in which researchers and managers can have confidence. For this, we chose a suite of statistical methods, compared the groupings that resulted from these analyses, identified convergence among groupings, then we interpreted the groupings using species and ecological guilds. When we tested this approach using a statewide stream fish dataset, not all statistical methods worked equally well. For our dataset, logistic regression (Log), detrended correspondence analysis (DCA), cluster analysis (CL), and non-metric multidimensional scaling (NMDS) provided consistent, simplified output. Specifically, the Log, DCA, CL-1, and NMDS-1 groupings were ≥60% similar to each other, overlapped with the fluvial-specialist ecological guild, and contained a common subset of species. Groupings based on number of species (e.g., Log, DCA, CL and NMDS) outperformed groupings based on abundance [e.g., principal components analysis (PCA) and Poisson regression]. Although the specific methods that worked on our test dataset have generality, here we are advocating a process (e.g., identifying convergent groupings with redundant species composition that are ecologically interpretable) rather than the automatic use of any single statistical tool. We summarize this process in step-by-step guidance for the

  6. Impacts of temperature on primary productivity and respiration in naturally structured macroalgal assemblages.

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    Leigh W Tait

    Full Text Available Rising global temperatures caused by human-mediated change has already triggered significant responses in organismal physiology, distribution and ecosystem functioning. Although the effects of rising temperature on the physiology of individual organisms are well understood, the effect on community-wide processes has remained elusive. The fixation of carbon via primary productivity is an essential ecosystem function and any shifts in the balance of primary productivity and respiration could alter the carbon balance of ecosystems. Here we show through a series of tests that respiration of naturally structured algal assemblages in southern New Zealand greatly increases with rising temperature, with implications for net primary productivity (NPP. The NPP of in situ macroalgal assemblages was minimally affected by natural temperature variation, possibly through photo-acclimation or temperature acclimation responses, but respiration rates and compensating irradiance were negatively affected. However, laboratory experiments testing the impacts of rising temperature on several photosynthetic parameters showed a decline in NPP, increasing respiration rates and increasing compensating irradiance. The respiration Q10 of laboratory assemblages (the difference in metabolic rates over 10°C averaged 2.9 compared to a Q10 of 2 often seen in other autotrophs. However, gross primary productivity (GPP Q10 averaged 2, indicating that respiration was more severely affected by rising temperature. Furthermore, combined high irradiance and high temperature caused photoinhibition in the laboratory, and resulted in 50% lower NPP at high irradiance. Our study shows that communities may be more severely affected by rising global temperatures than would be expected by responses of individual species. In particular, enhanced respiration rates and rising compensation points have the potential to greatly affect the carbon balance of macroalgal assemblages through declines in

  7. Bathymetric and regional changes in benthic macrofaunal assemblages on the deep Eastern Brazilian margin, SW Atlantic

    Science.gov (United States)

    Bernardino, Angelo Fraga; Berenguer, Vanessa; Ribeiro-Ferreira, Venina P.

    2016-05-01

    Deep-sea continental slopes have valuable mineral and biological resources in close proximity to diverse, undersampled and fragile marine benthic ecosystems. The eastern Brazilian Continental Margin (19.01°S to 21.06°S, 37.88°W to 40.22°W) is an important economic region for both fishing and oil industries, but is poorly understood with respect to the structure of the soft-sediment benthic fauna, their regional distribution and their bathymetric patterns. To identify spatial and temporal patterns of benthic macrofaunal assemblages on the slope (400 to 3000 m), the Espirito Santo Basin Assessment Project (AMBES, coordinated by Cenpes-Petrobras) sampled 42 stations across the Brazilian Eastern Slope during both Summer 2012 and Winter 2013. We found a significant decrease in macrofaunal abundance at the 400 m isobath along the slope near the northern region of the Espirito Santo Basin, suggesting benthic responses to upwelling events towards the south in Campos Basin and southern Espirito Santo Basin. The taxonomic diversity and assemblage composition also changed significantly across depth zones with mid-slope peaks of diversity at 1000-1300 m. In general, macrofaunal assemblages were strongly related to slope depth, suggesting a strong influence of productivity gradients and water mass distribution on this oligotrophic margin. Sediment grain size was marginally important to macrofaunal composition on the upper slope. In general, macrofaunal assemblages on the slope of Espirito Santo Basin are similar to other areas of the SE Brazilian margin, but regional changes in response to productivity and depth need to be considered for management strategies in the face of increasing economic activities off-shore.

  8. Lake Bacterial Assemblage Composition Is Sensitive to Biological Disturbance Caused by an Invasive Filter Feeder

    OpenAIRE

    Vincent J. Denef; Hunter J. Carrick; Joann Cavaletto; Edna Chiang; Thomas H. Johengen; Henry A. Vanderploeg; Angela D. Kent

    2017-01-01

    ABSTRACT One approach to improve forecasts of how global change will affect ecosystem processes is to better understand how anthropogenic disturbances alter bacterial assemblages that drive biogeochemical cycles. Species invasions are important contributors to global change, but their impacts on bacterial community ecology are rarely investigated. Here, we studied direct impacts of invasive dreissenid mussels (IDMs), one of many invasive filter feeders, on freshwater lake bacterioplankton. We...

  9. Post-Fossilization Processes and their implications for understanding Ediacaran macrofossil assemblages

    OpenAIRE

    Matthews, JJ; Liu, AG; McIlroy, D

    2017-01-01

    Fossil assemblages from Newfoundland’s Avalon Peninsula preserve diverse examples of the enigmatic Ediacaran macrobiota, offering some of the earliest evidence for large and complex multicellular life. These fossils are exposed on extensive coastal bedding planes in extraordinary abundances, permitting palaeoecological studies based on census data from spatially extensive palaeocommunities. Such studies have been used to constrain the reproductive strategy and phylogenetic placement of Ediaca...

  10. Demersal fish assemblages on seamounts and other rugged features in the northeastern Caribbean

    Science.gov (United States)

    Quattrini, Andrea M.; Demopoulos, Amanda W. J.; Singer, Randal; Roa-Varon, Adela; Chaytor, Jason D.

    2017-05-01

    Recent investigations of demersal fish communities in deepwater (>50 m) habitats have considerably increased our knowledge of the factors that influence the assemblage structure of fishes across mesophotic to deep-sea depths. While different habitat types influence deepwater fish distribution, whether different types of rugged seafloor features provide functionally equivalent habitat for fishes is poorly understood. In the northeastern Caribbean, different types of rugged features (e.g., seamounts, banks, canyons) punctuate insular margins, and thus create a remarkable setting in which to compare demersal fish communities across various features. Concurrently, several water masses are vertically layered in the water column, creating strong stratification layers corresponding to specific abiotic conditions. In this study, we examined differences among fish assemblages across different features (e.g., seamount, canyon, bank/ridge) and water masses at depths ranging from 98 to 4060 m in the northeastern Caribbean. We conducted 26 remotely operated vehicle dives across 18 sites, identifying 156 species of which 42% of had not been previously recorded from particular depths or localities in the region. While rarefaction curves indicated fewer species at seamounts than at other features in the NE Caribbean, assemblage structure was similar among the different types of features. Thus, similar to seamount studies in other regions, seamounts in the Anegada Passage do not harbor distinct communities from other types of rugged features. Species assemblages, however, differed among depths, with zonation generally corresponding to water mass boundaries in the region. High species turnover occurred at depths influencing community structure of benthic fauna, while considerably adding to the knowledge of mesophotic and deep-sea fish biogeography.

  11. Diversity and composition of estuarine and lagoonal fish assemblages of Socotra Island, Yemen.

    Science.gov (United States)

    Lavergne, E; Zajonz, U; Krupp, F; Naseeb, F; Aideed, M S

    2016-05-01

    Estuarine and lagoonal surveys of Socotra Island and selected sites on the Hadhramout coast of Yemen were conducted with the objective of documenting and analysing fish diversity and assemblage structure. A total of 74 species in 35 families were recorded, among which 65 species in 32 families were from Socotra and 20 species in 17 families were from mainland Yemen. Twenty-one species represent new faunal records for Socotra. Including historic records re-examined in this study, the total fish species richness of estuaries and lagoons of Socotra Island reaches 76, which is relatively high compared to species inventories of well-researched coastal estuaries in southern Africa. Five species dominate the occurrence and abundance frequencies: Terapon jarbua, Hyporhamphus sindensis, Aphanius dispar, Ambassis gymnocephala and Chelon macrolepis. Rarefaction and extrapolation analyses suggest that the actual number of fish species inhabiting some of those estuaries might be higher than the one observed. Thus, additional sampling at specific sites should be conducted to record other less conspicuous species. Ordination and multivariate analyses identified four main distinct assemblage clusters. Two groups are geographically well structured and represent northern Socotra and mainland Yemen, respectively. The other two assemblage groups tend to be determined to a greater extent by the synchrony between physical (e.g. estuary opening periods) and biological (e.g. spawning and recruitment periods) variables than by geographical location. Finally, the single intertidal lagoon of Socotra represents by itself a specific fish assemblage. The high proportion of economically important fish species (38) recorded underscores the paramount importance of these coastal water bodies as nursery sites, and for sustaining vital provisioning ecosystem services. © 2016 The Fisheries Society of the British Isles.

  12. Assemblage of drosophilids (Diptera, Drosophilidae inhabiting flooded and nonflooded areas in the extreme South of Brazil

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    L.B. Duarte

    Full Text Available ABSTRACT Several studies on the potential use of drosophilid assemblages as bioindicator systems have been carried out in the last years. Nevertheless, the successful application of these organisms in these systems requires adequate filling of several knowledge gaps. In this sense, little is known about drosophilid assemblages in wetlands and flooded areas. The present study provides the first survey of drosophilid species inhabiting such environments in the extreme South of Brazil and compares general beta-diversity patterns between assemblages of flooded versus nonflooded areas. The specimens were collected with banana-baited traps, and the assemblages recovered in eight wetlands of the southernmost coast of Brazil were compared to those recovered from seven nonflooded areas of the Pampa and Atlantic Forest biomes. A total of 5028 and 2571 individuals encompassing 27 and 37 species were collected in the flooded and nonflooded areas, respectively. The differential species composition patterns presented between these areas was statistically supported, which seems to be related to the lower beta-diversity presented by swamps, especially in regard to dominance patterns. So, the open and climatically harsher environment provided by wetlands possibly constitutes a hostile environment for the entry and, mainly, for the persistence of several native Drosophilidae species, in contrast to some exotic and more plastic species (as Drosophila simulans and Zaprionus indianus. Since the diversity gradient of flooded areas does not seem to be related to the conservation status of the swamp, our results question the use of Drosophilidae species as bioindicators of environmental disturbance and antropic influence in wetlands.

  13. Effects of land use intensification on fish assemblages in Mediterranean climate streams

    OpenAIRE

    Matono, Paula; Sousa, Dárcio; Ilheu, Maria

    2013-01-01

    Southern Portugal is experiencing a rapid change in land use due to the spread of intensive farming systems, namely olive production systems, which can cause strong negative environmental impacts and affect the ecological integrity of aquatic ecosystems. This study aimed to identify the main environmental disturbances related with olive grove intensification on Mediterranean climate streams in southern Portugal, and to evaluate their effects on fish assemblage structure and integrity. Twenty ...

  14. Long-term changes in the fish assemblage of a neotropical hydroelectric reservoir.

    Science.gov (United States)

    Orsi, M L; Britton, J R

    2014-06-01

    The changes in the fish assemblage of the Capivara Reservoir, Brazil, were assessed over a 20 year period. Of 50 native fishes present in the initial samples, 27 were no longer present in the final samples, but there had been an addition of 11 invasive fishes, suggesting the occurrence of substantial shifts in fish diversity and abundance. © 2014 The Fisheries Society of the British Isles.

  15. Bait effects in sampling coral reef fish assemblages with stereo-BRUVs.

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    Stacey R Dorman

    Full Text Available Baited underwater video techniques are increasingly being utilised for assessing and monitoring demersal fishes because they are: 1 non extractive, 2 can be used to sample across multiple habitats and depths, 3 are cost effective, 4 sample a broader range of species than many other techniques, 5 and with greater statistical power. However, an examination of the literature demonstrates that a range of different bait types are being used. The use of different types of bait can create an additional source of variability in sampling programs. Coral reef fish assemblages at the Houtman Abrolhos Islands, Western Australia, were sampled using baited remote underwater stereo-video systems. One-hour stereo-video recordings were collected for four different bait treatments (pilchards, cat food, falafel mix and no bait (control from sites inside and outside a targeted fishery closure (TFC. In total, 5209 individuals from 132 fish species belonging to 41 families were recorded. There were significant differences in the fish assemblage structure and composition between baited and non-baited treatments (P<0.001, while no difference was observed with species richness. Samples baited with cat food and pilchards contained similar ingredients and were found to record similar components of the fish assemblage. There were no significant differences in the fish assemblages in areas open or closed to fishing, regardless of the bait used. Investigation of five targeted species indicated that the response to different types of bait was species-specific. For example, the relative abundance of Pagrus auratus was found to increase in areas protected from fishing, but only in samples baited with pilchards and cat food. The results indicate that the use of bait in conjunction with stereo-BRUVs is advantageous. On balance, the use of pilchards as a standardised bait for stereo-BRUVs deployments is justified for use along the mid-west coast of Western Australia.

  16. Flows, droughts, and aliens: factors affecting the fish assemblage in a Sierra Nevada, California, stream.

    Science.gov (United States)

    Kiernan, Joseph D; Moyle, Peter B

    2012-06-01

    The fishes of Martis Creek, in the Sierra Nevada of California (USA), were sampled at four sites annually over 30 years, 1979-2008. This long-term data set was used to examine (1) the persistence and stability of the Martis Creek fish assemblage in the face of environmental stochasticity; (2) whether native and alien fishes responded differently to a natural hydrologic regime (e.g., timing and magnitude of high and low flows); and (3) the importance of various hydrologic and physical habitat variables in explaining the abundances of native and alien fish species through time. Our results showed that fish assemblages were persistent at all sample sites, but individual species exhibited marked interannual variability in density, biomass, and relative abundance. The density and biomass of native fishes generally declined over the period of study, whereas most alien species showed no significant long-term trends. Only alien rainbow trout increased in both density and biomass at all sites over time. Redundancy analysis identified three hydrologic variables (annual 7-day minimum discharge, maximum winter discharge, and number of distinct winter floods) and two habitat variables (percentage of pool habitat and percentage of gravel substrate) that each explained a significant portion of the annual variation in fish assemblage structure. For alien taxa, their proportional contribution to the total fish assemblage was inversely related to mean annual streamflow, one-day maximum discharge in both winter and spring, and the frequency of springtime floods. Results of this study highlight the need for continuous annual monitoring of streams with highly variable flow regimes to evaluate shifts in fish community structure. Apparent successes or failures in stream management may appear differently depending on the time series of available data.

  17. Recent disturbances augment community shifts in coral assemblages in Moorea, French Polynesia

    KAUST Repository

    Pratchett, Morgan S.

    2010-09-19

    Coral reefs are often subject to disturbances that can cause enduring changes in community structure and abundance of coral reef organisms. In Moorea, French Polynesia, frequent disturbances between 1979 and 2003 caused marked shifts in taxonomic composition of coral assemblages. This study explores recent changes in live cover and taxonomic structure of coral communities on the north coast of Moorea, French Polynesia, to assess whether coral assemblages are recovering (returning to a previous Acropora-dominated state) or continuing to move towards an alternative community structure. Coral cover declined by 29.7% between July 2003 and March 2009, mostly due to loss of Acropora and Montipora spp. Coral mortality varied among habitats, with highest levels of coral loss on the outer reef slope (7-20 m depth). In contrast, there was limited change in coral cover within the lagoon, and coral cover actually increased on the reef crest. Observed changes in coral cover and composition correspond closely with the known feeding preferences and observed spatial patterns of Acanthaster planci L., though observed coral loss also coincided with at least one episode of coral bleaching, as well as persistent populations of the corallivorous starfish Culcita novaeguineae Muller & Troschel. While climate change poses an important and significant threat to the future structure and dynamics coral reef communities, outbreaks of A. planci remain a significant cause of coral loss in Moorea. More importantly, these recent disturbances have followed long-term shifts in the structure of coral assemblages, and the relative abundance of both Pocillopora and Porites continue to increase due to disproportionate losses of Acropora and Montipora. Moreover, Pocillopora and Porites dominate assemblages of juvenile corals, suggesting that there is limited potential for a return to an Acropora-dominated state, last recorded in 1979. © 2010 Springer-Verlag.

  18. Soil nematode assemblages as bioindicators of radiation impact in the Chernobyl Exclusion Zone.

    Science.gov (United States)

    Lecomte-Pradines, C; Bonzom, J-M; Della-Vedova, C; Beaugelin-Seiller, K; Villenave, C; Gaschak, S; Coppin, F; Dubourg, N; Maksimenko, A; Adam-Guillermin, C; Garnier-Laplace, J

    2014-08-15

    In radioecology, the need to understand the long-term ecological effects of radioactive contamination has been emphasised. This requires that the health of field populations is evaluated and linked to an accurate estimate of received radiological dose. The aim of the present study was to assess the effects of current radioactive contamination on nematode assemblages at sites affected by the fallout from the Chernobyl accident. First, we estimated the total dose rates (TDRs) absorbed by nematodes, from measured current soil activity concentrations, Dose Conversion Coefficients (DCCs, calculated using EDEN software) and soil-to-biota concentration ratios (from the ERICA tool database). The impact of current TDRs on nematode assemblages was then evaluated. Nematodes were collected in spring 2011 from 18 forest sites in the Chernobyl Exclusion Zone (CEZ) with external gamma dose rates, measured using radiophotoluminescent dosimeters, varying from 0.2 to 22 μGy h(-1). These values were one order of magnitude below the TDRs. A majority of bacterial-, plant-, and fungal-feeding nematodes and very few of the disturbance sensitive families were identified. No statistically significant association was observed between TDR values and nematode total abundance or the Shannon diversity index (H'). The Nematode Channel Ratio (which defines the relative abundance of bacterial- versus fungal-feeding nematodes) decreased significantly with increasing TDR, suggesting that radioactive contamination may influence nematode assemblages either directly or indirectly by modifying their food resources. A greater Maturity Index (MI), usually characterising better soil quality, was associated with higher pH and TDR values. These results suggest that in the CEZ, nematode assemblages from the forest sites were slightly impacted by chronic exposure at a predicted TDR of 200 μGy h(-1). This may be imputable to a dominant proportion of pollutant resistant nematodes in all sites. This might

  19. Viral infections stimulate the metabolism and shape prokaryotic assemblages in submarine mud volcanoes

    Science.gov (United States)

    Corinaldesi, Cinzia; Dell'Anno, Antonio; Danovaro, Roberto

    2012-01-01

    Mud volcanoes are geological structures in the oceans that have key roles in the functioning of the global ecosystem. Information on the dynamics of benthic viruses and their interactions with prokaryotes in mud volcano ecosystems is still completely lacking. We investigated the impact of viral infection on the mortality and assemblage structure of benthic prokaryotes of five mud volcanoes in the Mediterranean Sea. Mud volcano sediments promote high rates of viral production (1.65–7.89 × 109 viruses g−1 d−1), viral-induced prokaryotic mortality (VIPM) (33% cells killed per day) and heterotrophic prokaryotic production (3.0–8.3 μgC g−1 d−1) when compared with sediments outside the mud volcano area. The viral shunt (that is, the microbial biomass converted into dissolved organic matter as a result of viral infection, and thus diverted away from higher trophic levels) provides 49 mgC m−2 d−1, thus fuelling the metabolism of uninfected prokaryotes and contributing to the total C budget. Bacteria are the dominant components of prokaryotic assemblages in surface sediments of mud volcanoes, whereas archaea dominate the subsurface sediment layers. Multivariate multiple regression analyses show that prokaryotic assemblage composition is not only dependant on the geochemical features and processes of mud volcano ecosystems but also on synergistic interactions between bottom-up (that is, trophic resources) and top-down (that is, VIPM) controlling factors. Overall, these findings highlight the significant role of the viral shunt in sustaining the metabolism of prokaryotes and shaping their assemblage structure in mud volcano sediments, and they provide new clues for our understanding of the functioning of cold-seep ecosystems. PMID:22170423

  20. Disentangling the effects of a century of eutrophication and climate warming on freshwater lake fish assemblages.

    Science.gov (United States)

    Jacobson, Peter C; Hansen, Gretchen J A; Bethke, Bethany J; Cross, Timothy K

    2017-01-01

    Eutrophication and climate warming are profoundly affecting fish in many freshwater lakes. Understanding the specific effects of these stressors is critical for development of effective adaptation and remediation strategies for conserving fish populations in a changing environment. Ecological niche models that incorporated the individual effects of nutrient concentration and climate were developed for 25 species of fish sampled in standard gillnet surveys from 1,577 Minnesota lakes. Lake phosphorus concentrations and climates were hindcasted to a pre-disturbance period of 1896-1925 using existing land use models and historical temperature data. Then historical fish assemblages were reconstructed using the ecological niche models. Substantial changes were noted when reconstructed fish assemblages were compared to those from the contemporary period (1981-2010). Disentangling the sometimes opposing, sometimes compounding, effects of eutrophication and climate warming was critical for understanding changes in fish assemblages. Reconstructed abundances of eutrophication-tolerant, warmwater taxa increased in prairie lakes that experienced significant eutrophication and climate warming. Eutrophication-intolerant, warmwater taxa abundance increased in forest lakes where primarily climate warming was the stressor. Coolwater fish declined in abundance in both ecoregions. Large changes in modeled abundance occurred when the effects of both climate and eutrophication operated in the same direction for some species. Conversely, the effects of climate warming and eutrophication operated in opposing directions for other species and dampened net changes in abundance. Quantifying the specific effects of climate and eutrophication will allow water resource managers to better understand how lakes have changed and provide expectations for sustainable fish assemblages in the future.

  1. Ecological shifts in Mediterranean coralligenous assemblages related to gorgonian forest loss.

    Directory of Open Access Journals (Sweden)

    Massimo Ponti

    Full Text Available Mediterranean gorgonian forests are threatened by several human activities and are affected by climatic anomalies that have led to mass mortality events in recent decades. The ecological role of these habitats and the possible consequence of their loss are poorly understood. Effects of gorgonians on the recruitment of epibenthic organisms were investigated by manipulating presence of gorgonians on experimental panels at 24 m depth, for Eunicella cavolinii, and at 40 m depth, for Paramuricea clavata, at two sites: Tavolara Island (Tyrrhenian Sea and Portofino Promontory (Ligurian Sea. After 4 months, the most abundant taxa on the panels were encrusting green algae, erect red algae and crustose coralline algae at 24 m depth and encrusting brown algae and erect red algae at 40 m depth. Assemblages on the panels were significantly affected by the presence of the gorgonians, although effects varied across sites and between gorgonian species. Species diversity and evenness were lower on panels with gorgonian branches. Growth of erect algae and recruitment of serpulid polychaetes were also affected by the presence of the gorgonians, primarily at Tavolara. Crustose coralline algae and erect sponges were more abundant on E. cavolinii panels at 24 m depth, while encrusting bryozoans were more abundant on P. clavata panels at 40 m depth. Effects of gorgonians on recruited assemblages could be due to microscale modification of hydrodynamics and sediment deposition rate, or by a shading effect reducing light intensity. Gorgonians may also intercept settling propagules, compete for food with the filter-feeders and/or for space by producing allelochemicals. Presence of gorgonians mainly limits the growth of erect algae and enhances the abundance of encrusting algae and sessile invertebrates. Therefore, the gorgonian disappearances may cause a shift from assemblages characterised by crustose coralline algae to filamentous algae assemblages, decreasing

  2. Assessing disruption of longitudinal connectivity on macroinvertebrate assemblages in a semiarid lowland river

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    Marta Leiva

    2017-12-01

    Full Text Available Abstract Aim: Our aim in this study was evaluate the effects of flow regulation for irrigation on the macroinvertebrate assemblages in a semiarid river. Methods We sampled two reaches in Dulce River; one placed upstream a weir that diverts flow into a network of irrigation channels and the other downstream that weir, in the assessment of the fluvial discontinuity. We assess the differences among reaches and sites, environmental variables, invertebrate density, richness and Shannon-Wiener index applying non-parametric analyses of variance Kruskal Wallis. The similarity percentage analysis (SIMPER was used to identify which species contributed to the dissimilarities on macroinvertebrate assemblage structure. Canonical Correspondence Analysis (CCA was performed with the total set of samples to explore macroinvertebrate distribution in reaches and associations of the assemblages with habitat variables. Results The density, richness and Shannon index values did not show differences between the reaches located upstream and downstream. Beta diversity (Whittaker was 0.72 among upstream sites, 0.56 among downstream sites and higher species turnover (0.73 was obtained between both reaches. The Canonical Correspondence Analysis explained 46.71% of the variance differentiating upstream sites explained by higher values of organic matter of bottom sediments and discharge, high density of Nais communis, Bothrioneurum americanum, Pelomus, Stephensoniana trivandrana, Pristina menoni, P. jenkinae, P.longidentata, P. americana, Dero obtusa, Endotribelos, Heleobia and Turbellaria. The downstream sites were associated to coarser substratum and higher density of Lopescladius, Polypedilum, Cricotopus, Thienamaniella, Cryptochironomus, Baetidae, Nematoda and Corbicula fluminea. Conclusions The low-flow disturbance had effects on the composition of the benthic invertebrate assemblages, but attributes (such as density and richness showed a lower variability probably

  3. Studies of Cystoseira assemblages in Northern Atlantic Iberia

    OpenAIRE

    García-Fernández, Alicia; Bárbara, Ignacio

    2016-01-01

    The Iberian Peninsula contains 24 specific and infraespecific taxa of the genus Cystoseira, but only 6 inhabit in Northern Iberia: C. baccata, C. foeniculacea, C. humilis var. myriophylloides, C. nodicaulis, C. tamariscifolia, and C. usneoides. The Cystoseira assemblages exhibit a complex structure and stratification that allows the presence of a large associate biota and a rich epiphytic flora. Although in the Mediterranean Sea several species have been analyzed in depth, the Atlantic ones a...

  4. Short-term responses of reptile assemblages to fire in native and weedy tropical savannah

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    Rickard Abom

    2016-04-01

    Full Text Available Fire is frequently used as a management tool to reduce the cover of weeds, to reduce the amount of fuel available for future fires, and to create succession mosaics that may enhance biodiversity. We determined the influence of fire on wildlife, by quantifying reptile assemblage composition in response to fire in a weedy environment characterised by very short-term fire return intervals (<2 years. We used reptiles because they are often understudied, and are only moderately vagile compared to other vertebrates, and they respond strongly to changes in vegetation structure. We repeatedly sampled 24 replicate sampling sites after they had been unburned for two years, just prior to burning (pre-burnt, just after burning (post-burnt, and up to 15 months after burning (revegetated and monitored vegetation structure and reptile richness, abundance and assemblage composition. Our sites were not spatially auto-correlated, and were covered by native kangaroo grass (Themeda triandra, black spear grass (Heteropogon contortus, or an invasive weed (grader grass, Themeda quadrivalvis. Reptile abundance and richness were highest when sites had been unburned for 2 years, and greatly reduced in all areas post burning. The lowest reptile abundances occurred in sites dominated by the weed. Reptile abundance and richness had recovered in all grass types 15 months after burning, but assemblage composition changed. Some species were present only in before our focus fire in native grass, and their populations did not recover even 15 months post-burning. Even in fire-prone, often-burnt habitats such as our study sites, in which faunal richness and abundance were not strongly influenced by fire, reptile assemblage composition was altered. To maintain faunal biodiversity in fire-prone systems, we suggest reducing the frequency of prescribed fires, and (if possible excluding fire from weedy invasions if it allows native grasses to return.

  5. Spatio-temporal patterns and predictions of phytoplankton assemblages in a subtropical river delta system

    DEFF Research Database (Denmark)

    Wang, Chao; Li, Xinhui; Wang, Xiangxiu

    2016-01-01

    Spatial and seasonal sampling within a subtropical river delta system, the Pearl River Delta (China), provided data to determine seasonal phytoplankton patterns and develop prediction models. The high nutrient levels and frequent water exchanges resulted in a phytoplankton community with greatest...... similarities. These groups were distinct with respect to species richness, biomass and indicators, especially for groups representing spatial dimension. The Linear Discriminant Analysis (LDA) model indicated that the spatial patterns of phytoplankton assemblages were mostly explained by water quality variables...

  6. Vertical distribution, diversity and assemblages of mesopelagic fishes in the western Mediterranean

    Science.gov (United States)

    Olivar, M. P.; Bernal, A.; Molí, B.; Peña, M.; Balbín, R.; Castellón, A.; Miquel, J.; Massutí, E.

    2012-04-01

    The mesopelagic fish community of the western Mediterranean was studied during two cruises carried out in December 2009 and July 2010 in the shelf and slope zones around the Balearic Islands. Much of what was previously known about this deep water group of fishes in the Mediterranean Sea came from studies performed using planktonic and small midwater nets. This study was the first attempt to use large pelagic trawls and small nets combined with information about the main sound scattering layers to analyse mesopelagic fish composition, diversity and species assemblages. This community is characterised by a relatively low diversity compared to other oceanic regions of the world, with Myctophiformes and Stomiiformes being the main contributors. Bathymetry and the level of the water column were the most important factors structuring the investigated fish assemblages, and similar vertical patterns were observed for the different species collected during the two study periods. A shelf assemblage composed of a few species of myctophids, with Notoscopelus elongatus being the main contributor, was distinguished. The slope assemblage included both Myctophiformes and Stomiiformes that showed differences in their day-night main location along the water column. In terms of species behaviour, two important groups were detected. The first was non-migrant or weakly migrant species, with the paradigmatic example being the gonostomatid Cyclothone braueri, which occurred at a depth of 400-600 m; this species is partly responsible for the permanent acoustic (38 kHz) response at this depth. The second group, near-surface migrants at night, was represented by most of the juvenile and adult myctophids, exemplified by Ceratoscopelus maderensis, with the exception of just a few of the largest size classes of some species, such as Lampanyctus crocodilus and N. elongatus that remain near the bottom.

  7. Deep-sea nematode assemblages from a commercially important polymetallic nodule area in the Central Indian Ocean Basin

    Digital Repository Service at National Institute of Oceanography (India)

    Singh, R.; Miljutin, D.M.; Miljutina, M.; Martinez, P.A.; Ingole, B.S.

    The Central Indian Ocean Basin (CIOB) is an important area for prospective mining for polymetallic nodules. However, little is known about the biodiversity or community structure of abyssal benthic assemblages in the area. The aim of this study...

  8. Mesohabitat-specific Macroinvertebrate Assemblage Responses to Water Quality Variation in Mid-continent (North America) Great Rivers

    Science.gov (United States)

    We compared the responsiveness of macroinvertebrate assemblages to water quality stressors (ions, nutrients, dissolved metals and suspended sediment) in two mesohabitats within the main-channel macrohabitat of three mid-continent North American rivers, the Upper Mississippi, Miss...

  9. Foraminiferal assemblages and their use as indicators of sediments movement: a study in the shelf region off Navapur, India

    Digital Repository Service at National Institute of Oceanography (India)

    Nigam, R.

    water runoff and organic matter content in the sediments. A comparison of living and dead tests distribution of important assemblages indicates movement of sediment towards east southeast and thus a current. The study is particularly important...

  10. Spatial Distribution of Benthic Macroinvertebrate Assemblages in Relation to Environmental Variables in Korean Nationwide Streams

    Directory of Open Access Journals (Sweden)

    Yung-Chul Jun

    2016-01-01

    Full Text Available Conserving and enhancing freshwater biodiversity are global issues to ensure ecosystem integrity and sustainability. To meet this, it is critical to understand how the biological assemblages are determined by environmental gradients in different spatial scales. Nevertheless, information on their large-scale environmental relationships remains scarce in Korea. We aimed to understand nationwide spatial distribution patterns of benthic macroinvertebrates and important environmental factors affecting their distribution in 388 streams and rivers across Korea. A total of 340 taxa, belonging to 113 families in 23 orders of five phyla, were identified. Assemblage composition in most Korean streams included a few predominant colonizers and a majority of rare taxa. Cluster analysis based on benthic macroinvertebrates classified a total of 720 sampling sites into five clusters according to the pollution levels from fast-flowing less polluted streams with low electrical conductivity to moderately or severely polluted streams with high electrical conductivity and slow water velocity. Canonical correspondence analysis revealed that altitude, water velocity and streambed composition were the most important determinants, rather than watershed and water chemistry variables, for explaining the variation in macroinvertebrate assemblage patterns. The results provide basic information for establishing the conservation and restoration strategies of macroinvertebrate biodiversity against anthropogenic disturbances and developing more confident bio-assessment tools for diagnosing stream ecosystem integrity.

  11. Occurency of Giardia duodenalis assemblages in river water sources of Black Sea, Turkey.

    Science.gov (United States)

    Koloren, Zeynep; Seferoğlu, Onuralp; Karanis, Panagiotis

    2016-12-01

    A total of 420 environmental water samples and 120 drinking water samples from 45 different sampling sites of the Black Sea in Turkey were collected between 2012 and 2014. Genomic DNA was isolated from all the investigated water samples and comparativelly analyzed by Loop-mediated isothermal amplification (LAMP) of the elongation factor 1 Alfa (EF1α) gene, and by nested Polymerase Chain Reaction (nPCR) of the small subunit (SSU) rRNA and semi-nested PCR (snPCR) of the glutamate dehydrogenase gene (GDH). 141 (58.7%), 125 (52.1%) and 120 (50%) samples respectivelly were positive by each method. Out of 240 environmental samples collected from 25 sites of Samsun Province have been found positive for G. duodenalis by LAMP, nPCR and snPCR, respectively. 55 (30.5%), 50 (27.8%) and 47 (26.1%) of 180 environmental samples collected from 20 other sampling sites of Giresun Province were positive for Giardia by LAMP, nPCR and snPCR, respectively. Five PCR products from different samples of the Giresun Province and 10 other samples from the Samsun Province were found positive for G. duodenalis assemblage B. Five PCR products from Giresun Province and 5 samples from Samsun Province were found positive for G. duodenalis assemblage A. This is the first report about G. duodenalis assemblages A and B from water samples investigations in Black Sea of Turkey. Copyright © 2016 Elsevier B.V. All rights reserved.

  12. Balanced Fertilization Decreases Environmental Filtering on Soil Bacterial Community Assemblage in North China

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    Youzhi Feng

    2017-12-01

    Full Text Available Although increasing evidences have emerged for responses of soil microorganisms to fertilizations, the knowledge regarding community assemblages that cause variations in composition is still lacking, as well as the possible feedback to soil fertility. Phylogenetic conservatism of species indicates their similar environmental preferences and/or function traits and phylogenetic signals further can infer community assemblages and influenced ecological processes. Here, we calculated the mean pairwise phylogenetic distance and nearest relative index, characterizing phylogenetic signal and the undergone ecological process to evaluate the community assembly of soil bacterial phylotypes in 20-year fertilized soils. The bacterial community assembly is structured by environmental filtering, regardless of fertilization regime. Soil phosphorous (P availability imposes selection on community assemblage and influences their community turnover among fertilizations. When P nutrient lacks, the effect of environmental filtering becomes stronger, hence bacterial functional traits become more coherent; this process results into increased intraspecific interactions characterized by co-occurrence network analysis. In contrast, when P nutrient becomes abundant, the environmental selection is mitigated; function traits are evened. This process reduces intraspecific interactions and increases carbon sequestration efficiency, which is finally of great favor to the increases in soil fertility. This study has made the first attempt, at the bacterial level, to understand how fertilization affects agroecosystems. When more phylogenetic information on how nutrient cycling-related microbes respond to fertilization becomes available, the systematic knowledge will eventually provide guidance to optimal fertilization strategies.

  13. Benthic assemblages of rock pools in northern Portugal: seasonal and between-pool variability

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    Iacopo Bertocci

    2012-11-01

    Full Text Available We investigated the seasonal (winter vs summer and within season and spatial (between-pool variability of benthic assemblages of rock pools at mid-intertidal level along the shore of Viana do Castelo (North Portugal. Physical traits of rock pools, including size, depth and position along the shore, were also compared between pools. While pools did not differ for any of the examined physical traits, results indicated a clear seasonal difference in the structure of assemblages, including a total of 49 macroalgal and 13 animal taxa. This finding was driven by six taxa that are more abundant in winter (the reef-forming polychaete Sabellaria alveolata, the articulated coralline algae Corallina spp., the brown alga Bifurcaria bifurcata, the encrusting coralline alga Lithophyllum incrustans, the red alga Chondracanthus acicularis and the grazing snails Gibbula spp. and four algal taxa that are more abundant in summer (the invasive brown Sargassum muticum, the green Ulva spp., the kelp Laminaria ochroleuca and the filamentous red Ceramium spp.. These data provide a new contribution to the knowledge of rock pool systems and have potential implications for monitoring programmes aimed at assessing ecological modifications related to natural and anthropogenic disturbances and for identifying processes responsible for the variability of rock pool assemblages.

  14. Calling phenology of a diverse amphibian assemblage in response to meteorological conditions

    Science.gov (United States)

    Plenderleith, T. Lynette; Stratford, Danial; Lollback, Gregory W.; Chapple, David G.; Reina, Richard D.; Hero, Jean-Marc

    2017-12-01

    The strong association between amphibian activity, breeding and recruitment with local environmental conditions raises concerns regarding how changes in climate may affect the persistence of species populations into the future. Additionally, in a highly diverse assemblage of anurans, competition for breeding sites affects the time and duration of activity, as species compete for limited resources such as water. Meteorological conditions are strong drivers of amphibian activity, so we assessed whether temperature, rainfall, atmospheric pressure and humidity were associated with the calling phenology of an assemblage of anurans in South East Queensland, Australia. We performed calling surveys and collected digital recordings at 45 ponds in an area known for high anuran diversity. We performed detection analyses to investigate the influence of 10 meteorological variables in detection of calling activity in 19 amphibian species. Our results suggest four breeding strategies in the assemblage: explosive summer breeders, prolonged breeders, opportunistic breeders and a winter breeder. Classifying these species into associations provides a framework for understanding how species respond to environmental conditions. Explosive breeders (i.e. species demonstrating short and highly synchronised breeding periods) were particularly responsive to temperature. Our findings help elucidate the breeding phenology of frogs and provide valuable information on their mating systems in native Australian forests. This study highlights the difficulties of surveying even common anurans. We highlight the importance of predictability and stability in climate and the vulnerability of species for which reproduction appears to require highly specific environmental cues.

  15. Cost-benefit of three different methods for studying Mediterranean rocky benthic assemblages

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    Natàlia Sant

    2017-03-01

    Full Text Available Here we compare the applicability, the information provided and the cost-benefit of three sampling methods usually used in the study of rocky benthic assemblages. For comparative purposes, sampling was performed seasonally and along a depth gradient (0-50 m in the Cabrera Archipelago (western Mediterranean. The destructive scraping (collection method was the least cost-effective but provided the best qualitative and quantitative information. The in situ visual method was the most time-effective but provided low levels of taxonomic resolution and its accuracy decreased with depth due to the increasing difficulty of recognizing species in situ due to nitrogen narcosis, reduced light and cold. The photoquadrat method showed intermediate values of cost-effectiveness and information but was not suitable for multilayered assemblages, as it only accounted for the overstory. A canonical correspondence analysis showed that depth was highlighted as the main environmental gradient (16.0% of variance by the three methods. However, differences due to the sampling method (7.9% of variance were greater than differences due to temporal variability (5.8% of variance, suggesting that the three methods are valid but their selection has to be carefully assessed in relation to the targeted assemblages and the specific goals of each study.

  16. Spatial relationships between polychaete assemblages and environmental variables over broad geographical scales.

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    Lisandro Benedetti-Cecchi

    2010-09-01

    Full Text Available This study examined spatial relationships between rocky shore polychaete assemblages and environmental variables over broad geographical scales, using a database compiled within the Census of Marine Life NaGISA (Natural Geography In Shore Areas research program. The database consisted of abundance measures of polychaetes classified at the genus and family levels for 74 and 93 sites, respectively, from nine geographic regions. We tested the general hypothesis that the set of environmental variables emerging as potentially important drivers of variation in polychaete assemblages depend on the spatial scale considered. Through Moran's eigenvector maps we indentified three submodels reflecting spatial relationships among sampling sites at intercontinental (>10,000 km, continental (1000-5000 km and regional (20-500 km scales. Using redundancy analysis we found that most environmental variables contributed to explain a large and significant proportion of variation of the intercontinental submodel both for genera and families (54% and 53%, respectively. A subset of these variables, organic pollution, inorganic pollution, primary productivity and nutrient contamination was also significantly related to spatial variation at the continental scale, explaining 25% and 32% of the variance at the genus and family levels, respectively. These variables should therefore be preferably considered when forecasting large-scale spatial patterns of polychaete assemblages in relation to ongoing or predicted changes in environmental conditions. None of the variables considered in this study were significantly related to the regional submodel.

  17. Multi-scale analysis of hermatypic coral assemblages at Mexican Central Pacific

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    Joicye Hernández-Zulueta

    2017-03-01

    Full Text Available The Mexican Central Pacific is located in a zone of oceanographic transition between two biogeographic provinces with particular conditions that affect the associated fauna. The objective of this study was to evaluate the variation of hermatypic coral assemblages in this region and to determine their relationship with the heterogeneity of the benthonic habitat and spatial variables. A total of 156 transects were carried out at 41 sites in the years 2010 and 2011. The sampling effort returned 96.7% of the coral richness expected for the area, with a total of 15 species recorded. The results showed that richness, diversity and cover of corals varied only at the site and state scales. However, the composition and coverage of all coral species, as well as the benthonic habitat structure, differed significantly across the study scales (i.e. sites, zones and states. Canonical redundancy analysis showed that variation in the richness, diversity and assemblages of corals was explained by the cover of live corals, articulated calcareous algae, sandy substrate, sponges and fleshy macroalgae. This study suggests that local scale (i.e. site variation in the coral assemblages of the Mexican Central Pacific is the result of the heterogeneity of the benthonic habitat, while geomorphological and oceanographic characteristics play a greater role at regional scale.

  18. Effect of phase shift from corals to Zoantharia on reef fish assemblages.

    Science.gov (United States)

    Cruz, Igor C S; Loiola, Miguel; Albuquerque, Tiago; Reis, Rodrigo; Nunes, José de Anchieta C C; Reimer, James D; Mizuyama, Masaru; Kikuchi, Ruy K P; Creed, Joel C

    2015-01-01

    Consequences of reef phase shifts on fish communities remain poorly understood. Studies on the causes, effects and consequences of phase shifts on reef fish communities have only been considered for coral-to-macroalgae shifts. Therefore, there is a large information gap regarding the consequences of novel phase shifts and how these kinds of phase shifts impact on fish assemblages. This study aimed to compare the fish assemblages on reefs under normal conditions (relatively high cover of corals) to those which have shifted to a dominance of the zoantharian Palythoa cf. variabilis on coral reefs in Todos os Santos Bay (TSB), Brazilian eastern coast. We examined eight reefs, where we estimated cover of corals and P. cf. variabilis and coral reef fish richness, abundance and body size. Fish richness differed significantly between normal reefs (48 species) and phase-shift reefs (38 species), a 20% reduction in species. However there was no difference in fish abundance between normal and phase shift reefs. One fish species, Chaetodon striatus, was significantly less abundant on normal reefs. The differences in fish assemblages between different reef phases was due to differences in trophic groups of fish; on normal reefs carnivorous fishes were more abundant, while on phase shift reefs mobile invertivores dominated.

  19. Effect of phase shift from corals to Zoantharia on reef fish assemblages.

    Directory of Open Access Journals (Sweden)

    Igor C S Cruz

    Full Text Available Consequences of reef phase shifts on fish communities remain poorly understood. Studies on the causes, effects and consequences of phase shifts on reef fish communities have only been considered for coral-to-macroalgae shifts. Therefore, there is a large information gap regarding the consequences of novel phase shifts and how these kinds of phase shifts impact on fish assemblages. This study aimed to compare the fish assemblages on reefs under normal conditions (relatively high cover of corals to those which have shifted to a dominance of the zoantharian Palythoa cf. variabilis on coral reefs in Todos os Santos Bay (TSB, Brazilian eastern coast. We examined eight reefs, where we estimated cover of corals and P. cf. variabilis and coral reef fish richness, abundance and body size. Fish richness differed significantly between normal reefs (48 species and phase-shift reefs (38 species, a 20% reduction in species. However there was no difference in fish abundance between normal and phase shift reefs. One fish species, Chaetodon striatus, was significantly less abundant on normal reefs. The differences in fish assemblages between different reef phases was due to differences in trophic groups of fish; on normal reefs carnivorous fishes were more abundant, while on phase shift reefs mobile invertivores dominated.

  20. Scale-dependent diversity patterns affect spider assemblages of two contrasting forest ecosystems

    Science.gov (United States)

    Schuldt, Andreas; Assmann, Thorsten; Schaefer, Matthias

    2013-05-01

    Spiders are important generalist predators in forests. However, differences in assemblage structure and diversity can have consequences for their functional impact. Such differences are particularly evident across latitudes, and their analysis can help to generate a better understanding of region-specific characteristics of predator assemblages. Here, we analyse the relationships between species richness, family richness and functional diversity (FD) as well as α- and β-components of epigeic spider diversity in semi-natural temperate and subtropical forest sites. As expected, within-plot and overall spider species and family richness were higher in the subtropical plots. In contrast, local FD within plots was similar between sites, and differences in FD only became evident at larger spatial scales due to higher species turnover in the subtropical forests. Our study indicates that the functional effects of predator assemblages can change across spatial scales. We discuss how differences in richness and functional diversity between contrasting forest ecosystems can depend on environmental heterogeneity and the effects of species filters acting at local scales. The high turnover observed in the species-rich subtropical forests also requires a more regional perspective for the conservation of the overall diversity and the ecological functions of predators than in less diverse forests, as strategies need to account for the large spatial heterogeneity among plots.

  1. Bacterioplankton assemblages in coastal ponds reflect the influence of hydrology and geomorphological setting.

    Science.gov (United States)

    Huggett, Megan J; Kavazos, Christopher R J; Bernasconi, Rachele; Czarnik, Robert; Horwitz, Pierre

    2017-06-01

    The factors that shape microbial community assembly in aquatic ecosystems have been widely studied; yet it is still unclear how distinct communities within a connected landscape influence one another. Coastal lakes are recipients of, and thus are connected to, both marine and terrestrial environments. Thus, they may host microbial assemblages that reflect the relative degree of influence by, and connectivity to, either system. In order to address this idea, we interrogated microbial community diversity at 49 sites in seven ponds in two seasons in the Lake MacLeod basin, a system fed by seawater flowing inland through underground karst. Environmental and spatial variation within ponds explain <9% of the community structure, while identity of the pond that samples were taken from explains 50% of community variation. That is, ponds each host distinct assemblages despite similarities in size, environment and position in the landscape, indicating a dominant role for local species sorting. The ponds contain a substantial amount of previously unknown microbial taxa, reflecting the unusual nature of this inland system. Rare marine taxa, possibly dispersed from seawater assemblages via the underground karst connection, are abundant within the inland system, suggesting an important role for regional dispersal within the metacommunities. © FEMS 2017. All rights reserved. For permissions, please e-mail: journals.permissions@oup.com.

  2. An early geikiid dicynodont from the Tropidostoma Assemblage Zone (late Permian of South Africa

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    Christian F. Kammerer

    2017-01-01

    Full Text Available Based on specimens previously identified as Tropidostoma, a new taxon of dicynodont (Bulbasaurus phylloxyron gen. et sp. nov. from the Karoo Basin of South Africa is described. Bulbasaurus is a medium-sized dicynodont (maximum dorsal skull length 16.0 cm restricted to the Tropidostoma Assemblage Zone (early Lopingian of the Beaufort Group. Bulbasaurus can be distinguished from Tropidostoma by an array of characters including the presence of a tall, sharp premaxillary ridge, large, rugose, nearly-confluent nasal bosses, a nasofrontal ridge, massive tusks, robust pterygoids, prominently twisted subtemporal bar, and absence of a distinct postfrontal. Inclusion of Bulbasaurus in a phylogenetic analysis of anomodont therapsids recovers it as a member of Geikiidae, a clade of otherwise later Permian dicynodonts such as Aulacephalodon and Pelanomodon. Bulbasaurus exhibits many of the characters typical of adult Aulacephalodon, but at substantially smaller skull size (these characters are absent in comparably-sized Aulacephalodon juveniles, suggesting that the evolution of typical geikiid morphology preceded gigantism in the clade. Bulbasaurus is the earliest known geikiid and the only member of the group known from the Tropidostoma Assemblage Zone; discovery of this taxon shortens a perplexing ghost lineage and indicates that abundant clades from the later Permian of South Africa (e.g., Geikiidae, Dicynodontoidea may have originated as rare components of earlier Karoo assemblage zones.

  3. Foraminiferal assemblages from a transitional tropical upwelling zone in the Golfe d'Arguin, Mauritania

    Science.gov (United States)

    Reymond, Claire E.; Mateu-Vicens, Guillem; Westphal, Hildegard

    2014-07-01

    With the growing pressure of eutrophication in tropical regions, the Mauritian shelf provides a natural situation to understand the variability in mesotrophic assemblages. Site-specific dynamics occur throughout the 1200 m depth gradient. The shallow assemblages divide into three types of warm-water mesotrophic foraminiferal assemblages, which is not only a consequence of high primary productivity restricting light to the benthos but due to low pore water oxygenation, shelf geomorphology, and sediment partitioning. In the intermediate depth (approx. 500 m), the increase in foraminiferal diversity is due to the cold-water coral habitat providing a greater range of micro niches. Planktonic species characterise the lower bathyal zone, which emphasizes the reduced benthic carbonate production at depth. Although, due to the strong hydrodynamics within the Golf, planktonic species occur in notable abundances through out the whole depth gradient. Overall, this study can easily be compared to other tropical marine settings investigating the long-term effects of tropical eutrophication and the biogeographic distribution of carbonate producing organisms.

  4. Characteristics of the mesophotic megabenthic assemblages of the vercelli seamount (north tyrrhenian sea.

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    Marzia Bo

    2011-02-01

    Full Text Available The biodiversity of the megabenthic assemblages of the mesophotic zone of a Tyrrhenian seamount (Vercelli Seamount is described using Remotely Operated Vehicle (ROV video imaging from 100 m depth to the top of the mount around 61 m depth. This pinnacle hosts a rich coralligenous community characterized by three different assemblages: (i the top shows a dense covering of the kelp Laminaria rodriguezii; (ii the southern side biocoenosis is mainly dominated by the octocorals Paramuricea clavata and Eunicella cavolinii; while (iii the northern side of the seamount assemblage is colonized by active filter-feeding organisms such as sponges (sometimes covering 100% of the surface with numerous colonies of the ascidian Diazona violacea, and the polychaete Sabella pavonina. This study highlights, also for a Mediterranean seamount, the potential role of an isolated rocky peak penetrating the euphotic zone, to work as an aggregating structure, hosting abundant benthic communities dominated by suspension feeders, whose distribution may vary in accordance to the geomorphology of the area and the different local hydrodynamic conditions.

  5. Termite assemblages in five semideciduous Atlantic Forest fragments in the northern coastland limit of the biome

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    Heitor Bruno de Araújo Souza

    2012-03-01

    Full Text Available Termites are abundant organisms in tropical ecosystems and strongly influence the litter decomposition and soil formation. Despite their importance, few studies about their assemblage structures have been made in Brazilian Atlantic Forest fragments, especially in the area located north of the São Francisco River. This study aims to analyze the assemblage composition of five Atlantic Forest fragments located in the northern biome limit along the Brazilian coast. A standardized sampling protocol of termites was applied in each fragment. Thirty-three termite species belonging to twenty genera and three families were found in the forest fragments. The wood-feeder group was dominant both concerning to species richness and number of encounters in all areas. In sites northern to 7°S, there is an evident simplification of the termite assemblage composition regarding species richness and number of encounters by feeding group. This fact is apparently due to a higher sandy level in soils and to semideciduous character of the vegetation in the northern fragments. Thus, even on the north of São Francisco River, termite biodiversity is heterogeneously spread with highest density of species in the portion between 07°S and São Francisco River mouth (10°29'S.

  6. Seasonal fluctuations of ichthyoplankton assemblage in the northeastern South China Sea influenced by the Kuroshio intrusion

    Science.gov (United States)

    Huang, Delian; Zhang, Xia; Jiang, Zhijian; Zhang, Jingping; Arbi, Iman; Jiang, Xin; Huang, Xiaoping; Zhang, Wenjing

    2017-09-01

    The distribution and assemblage of ichthyoplankton related to local hydrographic features, especially intrusion of the Kuroshio Current (KC) and Guangdong Coastal Current (GCC) in the northeastern South China Sea (NESCS) were investigated in this study. A total of 193 species of ichthyoplankton belonging to 141 genera and 66 families were recognized in summer 2015 and late-winter 2016. The ichthyoplankton assemblage was identified with distinct seasonal differences, and the differences were responded well with the oceanography conditions. In summer, the assemblages were identified into offshore and inshore groups, as controlled by the South China Sea Warm Current (SCSWC) in off-shelf, upwelling, and the diluted water from the Pearl River in inshore. In winter, three groups were divided, representing the southwestern inshore, intrusion of the KC in the eastern offshore, and the GCC in the northern inshore area, respectively. Furthermore, Sigmops gracilis and Vinciguerria sp.3 were probably brought into the NESCS by intrusion of the KC from the eastern Luzon Strait. In addition, high ichthyoplankton abundance was found in high chlorophyll a located in upwelling areas in the northern coastal area in summer and in the southwestern Taiwan Bank in winter, respectively. The nutrition outcropped by the upwelling together, and those brought from the Pearl River probably supported high food availability of the ichthyoplankton in the northern coast of the NESCS.

  7. Tidal management sffects sub-adult fish assemblages in impounded South Carolina Marshes

    Science.gov (United States)

    Carswell, Ben L.; Peterson, James T.; Jennings, Cecil A.

    2015-01-01

    In coastal South Carolina, most impounded marshes are managed for waterfowl; fewer are managed for fishes. Tidal control is central to each strategy but raises concerns that nursery function could be impaired. This research examined the assemblage composition of fishes during early-life stages. We sampled two impoundments of each management type monthly in 2008 and 2009. We used light traps to collect 61,527 sub-adult fish representing 21 species and 16 families and push nets to collect 12,670 sub-adult fish representing 13 species and 11 families. The effective number of species detected at larval stage in “fish” impoundments (summer mean = 2.52 ± 0.20, winter mean = 2.02 ± 0.66) was greater than in “waterfowl” impoundments (summer mean = 1.27 ± 0.14, winter mean = 1.06 ± 0.09); CI = 90 %. Species richness did not differ between management types, but hierarchical linear models predicted differences in assemblage composition. These findings underscore the importance of frequent water exchange for maintaining diverse assemblages of early-life-stage fishes in marsh impoundments.

  8. Molecular characterisation of Giardia intestinalis assemblages from human isolates at a tertiary care centre of India

    Directory of Open Access Journals (Sweden)

    V Tak

    2014-01-01

    Full Text Available Purpose: The aim of the study was to determine the genetic heterogeneity of Giardia intestinalis isolates detected in stool samples of the study population using polymerase chain reaction assay and restriction fragment length polymorphism. We also tried to correlate the association/differences between the clinical symptomatology and infection by different assemblages (genotypes of G. intestinalis. Materials and Methods: This cross-sectional study was conducted from April 2008 to June 2010. A total of 40 adults (n = 40 and 42 children (n = 42 below the age of 12 years with the clinical suspicion of giardiasis and with the onset of one or more of the following five symptoms, i.e., loose stool, nausea, weight loss, fatigue and foul smelling faeces and confirmed laboratory diagnosis of giardiasis at least once during the current episode of diarrhoea were included in this study. Results: Of the 82 patients (males 66 enrolled in the study, 70 (85% presented with diarrhoea (56 males and 12 (15% without diarrhoea (10 males. Out of 70 diarrheic patients, 61 (87% had chronic diarrhoea, 8 (11.5% had acute diarrhoea and 1 (1.5% had persistent diarrhoea. Of the total patients, 63 (77% were clinically assessed and were apparently immunocompetent, whereas, 19 (23% immunocompromised patients had different underlying conditions besides giardiasis. Genotyping identified all 82 (100% isolates as assemblage B. Conclusion: We found that assemblage B of G. intestinalis presents with all kinds of clinical features ranging from asymptomatic carriage to acute, persistent or chronic diarrhoea.

  9. Relations between altered stramflow variability and fish assemblages in Eastern USA streams

    Science.gov (United States)

    Meador, Michael R.; Carlisle, Daren M.

    2012-01-01

    Although altered streamflow has been implicated as a major factor affecting fish assemblages, understanding the extent of streamflow alteration has required quantifying attributes of the natural flow regime. We used predictive models to quantify deviation from expected natural streamflow variability for streams in the eastern USA. Sites with >25% change in mean daily streamflow variability compared with what would be expected in a minimally disturbed environment were defined as having altered streamflow variability, based on the 10th and 90th percentiles of the distribution of streamflow variability at 1279 hydrological reference sites. We also used predictive models to assess fish assemblage condition and native species loss based on the proportion of expected native fish species that were observed. Of the 97 sites, 49 (50.5%) were classified as altered with reduced streamflow variability, whereas no sites had increased streamflow variability. Reduced streamflow variability was related to a 35% loss in native fish species, on average, and a >50% loss of species with a preference for riffle habitats. Conditional probability analysis indicated that the probability of fish assemblage impairment increased as the severity of altered streamflow variability increased. Reservoir storage capacity and wastewater discharges were important predictors of reduced streamflow variability as revealed by random forest analysis. Management and conservation of streams will require careful consideration of natural streamflow variation and potential factors contributing to altered streamflow within the entire watershed to limit the loss of critical stream habitats and fish species uniquely adapted to live in those habitats.

  10. Assessing fish assemblages similarity above and below a dam in a Neotropical reservoir with partial blockage

    Directory of Open Access Journals (Sweden)

    FG. Araújo

    Full Text Available Damming rivers disrupts the water flow and changes the ichthyofauna organisation. We investigated an impoundment with permanent connection and homogeneous environmental conditions between the zones above and below the dam. Temperature was comparatively higher during wet season irrespective of zone, and both zones had higher dissolved oxygen, conductivity and transparency in the dry season. A total of 1687 individuals comprising 27 species were collected in the downriver zone, while the reservoir had 879 individuals and 23 species. Each zone had different fish assemblage composition and structure, but assemblages were not explained by the examined environmental variables (r2 = 0.08; p = 0.307. Migratory species such as Pimelodus maculatus, Pimelodus fur, Leporinus copelandii and Prochilodus lineatus were the most affected, and probably are prevented to perform upriver migrations. On the other hand, lentic adapted species such as G. brasiliensis, Hoplias malabaricus and Hoplosternum littorale successfully colonised the reservoir. Therefore we conclude that the presence of the lateral hydrological connectivity alone does not guarantee the ecological connectivity since fish assemblage similarity differed between the two zones. Fish passage facilities should be monitored and managed to evaluate and improve their functionality.

  11. How complementary are epibenthic assemblages in artificial and nearby natural rocky reefs?

    KAUST Repository

    Carvalho, Susana

    2013-12-01

    The present study analyses the composition, structure and trophic function of epibenthic assemblages in two artificial reefs (ARs) 16 years after deployment and in nearby natural reefs (NRs), aiming at providing insights on the complementarity between both habitats. Current findings suggest that after 16 years the ARs (concrete blocks), located in southern Portugal, do not act as surrogates for NRs, as epibenthic assemblages differed between reef types in composition, structure and trophic function. NRs showed higher diversity and complementarity (i.e. beta-diversity) than ARs, evidencing higher redundancy. Higher heterogeneity within NRs was also evidenced by the multi-dimensional scaling analysis based on abundance, biomass and trophic composition. NRs presented higher abundance of molluscs and biomass of sponges, resulting in differences in the trophic function: suspension-feeding dominated the NRs, while within ARs there was an ascendency of carnivory. Although not acting as surrogates for NRs and provided that no adverse effects (e.g. establishment of non-native species) were detected, ARs may have a significant contribution for the increase of regional diversity, as evidenced by the highest complementarity levels observed between assemblages in both reefs. © 2013 Elsevier Ltd.

  12. Effects of anthropogenic impacts on benthic macroinvertebrates assemblages in subtropical mountain streams

    Directory of Open Access Journals (Sweden)

    Leticia M. Mesa

    2013-12-01

    Full Text Available The nature of the riparian and surrounding landscape has been modified by anthropogenic activities, which may subsequently alter the composition and functional structure of macroinvertebrate assemblages. The effect of these changes on function of benthic fauna is difficult to assess due to the scarce knowledge on functional structures in tropical streams. In this study we evaluate whether sites impacted and unimpacted by anthropogenic alterations differed in assemblage composition and density, richness and diversity of each functional feeding group. The selection of the sites was related to their distinct riparian characteristics, following the QBRy riparian quality index. Collector-gatherer was the dominant functional feeding group, comprising 91% of total density, whereas the proportion of shredders was very low, representing less of 0.5% of total density. Asemblage composition of macroinvertebrates differed between impacted and unimpacted sites. Predators were dominant in taxa number, representing about 60% of total taxa richness. In addition, the diversity and richness of collector-gatherers differed significantly between degraded and unimpacted sites, reflecting the sensitivity of this group to environmental changes and the utility to be used in the assessment of anthropogenic modifications. The results of this study reinforce the idea that riparian corridor management is critical for the distribution of macroinvertebrate assemblages as well as functional organization of lotic streams.

  13. Variability in the structure of epiphytic assemblages of in relation to human interferences in the Gulf of Gabes, Tunisia

    OpenAIRE

    Ben Brahim, Mounir; Hamza, Asma; Hannachi, Imen; Rebai, Ahmed; Jarboui, Othman; Bouain, Abderrahmen; Aleya, Lotfi

    2010-01-01

    Abstract In this study we evaluate whether the pattern of spatial variability of the macro-epiphytes assemblages of leaves of Posidonia oceanica differed in relation to anthropogenic interference in the Gulf of Gabes (southern coast of Tunisia). A hierarchical sampling design was used to compare epiphytic assemblages at 5m depth in terms of abundance and spatial variability at disturbed and control locations. The results indicate that the biomass and mean percentage cover decreased...

  14. Anomalously diverse Early Triassic ichnofossil assemblages in northwest Pangea: A case for a shallow-marine habitable zone

    Science.gov (United States)

    Beatty, Tyler W.; Zonneveld, J.-P.; Henderson, Charles M.

    2008-10-01

    Early Triassic trace fossil assemblages from the northwest marginof Pangea record a diverse suite of postextinction infauna.These ichnofossil assemblages occurred within well-oxygenated,shallow-marine refuges in a Panthalassa Ocean otherwise characterizedby widespread anoxia. We propose an environmentally controlledmodel for their distribution, in which wave aeration, enhancedby frequent storms, gave rise to an optimal zone for benthiccolonization. Within this habitable zone extinction pressureswere ameliorated and postextinction recovery duration was minimized.

  15. An Early Permian plant assemblage from the Taiyuan Formation of northern China with compression/impression and permineralized preservation.

    Science.gov (United States)

    Hilton, J; Wang, S -J.; Galtier, J; Li, C -S.

    2001-04-01

    A small but diverse fossil flora is described from the Early Permian Taiyuan Formation occurring at the Yangshuling mine in Pingquan district of Hebei Province, northern China. Fossils occur as compression/impressions within mudrocks and fine-grained sandstones and also as carbonate permineralizations within volcaniclastic tuffs. All are fragmentary and contain lycopsids, sphenopsids, ferns and seed plants, and include several new species. In the compression assemblage sphenopsid and pteridosperm foliage accounts for the majority of the fossils recognised with only a few other kinds of plant organs present. In contrast, the permineralized assemblage is dominated by cordaitaleans with a composition similar to that occurring in coal-ball assemblages elsewhere in the Taiyuan Formation. From the taxonomic synthesis presented it is apparent that the Yangshuling permineralized assemblage contains many of the plant taxa diagnostic of the northern realm of the Early Permian Cathaysian flora, and preserves a representative sample of the wetland coal-swamp vegetation of this time. The permineralized assemblage at Yangshuling represents the first example of anatomically preserved plants from volcaniclastic lithologies from the Palaeozoic of China, raising the possibility of similarly preserved plant-fossil assemblages elsewhere in the Cathaysian realm.

  16. Environmental stressors as a driver of the trait composition of benthic macroinvertebrate assemblages in polluted Iberian rivers.

    Science.gov (United States)

    Kuzmanovic, Maja; Dolédec, Sylvain; de Castro-Catala, Nuria; Ginebreda, Antoni; Sabater, Sergi; Muñoz, Isabel; Barceló, Damià

    2017-07-01

    We used the trait composition of macroinvertebrate communities to identify the effects of pesticides and multiple stressors associated with urban land use at different sites of four rivers in Spain. Several physical and chemical stressors (high metal pollution, nutrients, elevated temperature and flow alterations) affected the urban sites. The occurrence of multiple stressors influenced aquatic assemblages at 50% of the sites. We hypothesized that the trait composition of macroinvertebrate assemblages would reflect the strategies that the assemblages used to cope with the respective environmental stressors. We used RLQ and fourth corner analysis to address the relationship between stressors and the trait composition of benthic macroinvertebrates. We found a statistically significant relationship between the trait composition and the exposure of assemblages to environmental stressors. The first RLQ dimension, which explained most of the variability, clearly separated sites according to the stressors. Urban-related stressors selected taxa that were mainly plurivoltine and fed on deposits. In contrast, pesticide impacted sites selected taxa with high levels of egg protection (better egg survival), indicating a potentially higher risk for egg mortality. Moreover, the trait diversity of assemblages at urban sites was low compared to that observed in pesticide impacted sites, suggesting the homogenization of assemblages in urban areas. Copyright © 2017 The Authors. Published by Elsevier Inc. All rights reserved.

  17. Soil nematode assemblages as bioindicators of radiation impact in the Chernobyl Exclusion Zone

    Energy Technology Data Exchange (ETDEWEB)

    Lecomte-Pradines, C., E-mail: catherine.lecomte-pradines@irsn.fr [Institute for Radioprotection and Nuclear Safety, IRSN/PRP-ENV/SERIS, LECO, Building 186, Cadarache 13115 Saint Paul lez Durance cedex (France); Bonzom, J.-M. [Institute for Radioprotection and Nuclear Safety, IRSN/PRP-ENV/SERIS, LECO, Building 186, Cadarache 13115 Saint Paul lez Durance cedex (France); Della-Vedova, C. [Magelis, 6, rue Frederic Mistral, 84160 Cadenet (France); Beaugelin-Seiller, K. [Institute for Radioprotection and Nuclear Safety, IRSN/PRP-ENV/SERIS, LM2E, Building 159, Cadarache 13115 Saint Paul lez Durance cedex (France); Villenave, C. [ELISOL Environment, Building 12, Campus de la Gaillarde, 2 place Viala, 34060 Montpellier cedex 2 (France); Gaschak, S. [Chernobyl Center for Nuclear Safety, Radioactive Waste and Radioecology, International Radioecology Laboratory, 07100 Slavutych (Ukraine); Coppin, F. [Institute for Radioprotection and Nuclear Safety, IRSN/PRP-ENV/SERIS, L2BT, Building 186, Cadarache 13115 Saint Paul lez Durance cedex (France); Dubourg, N. [Institute for Radioprotection and Nuclear Safety, IRSN/PRP-ENV/SERIS, GARM Building 186, Cadarache 13115 Saint Paul lez Durance cedex (France); Maksimenko, A. [Chernobyl Center for Nuclear Safety, Radioactive Waste and Radioecology, International Radioecology Laboratory, 07100 Slavutych (Ukraine); Adam-Guillermin, C. [Institute for Radioprotection and Nuclear Safety, IRSN/PRP-ENV/SERIS, LECO, Building 186, Cadarache 13115 Saint Paul lez Durance cedex (France); Garnier-Laplace, J. [Institute for Radioprotection and Nuclear Safety, IRSN/PRP-ENV/SERIS, Building 159, Cadarache 13115 Saint Paul lez Durance cedex (France)

    2014-08-15

    In radioecology, the need to understand the long-term ecological effects of radioactive contamination has been emphasised. This requires that the health of field populations is evaluated and linked to an accurate estimate of received radiological dose. The aim of the present study was to assess the effects of current radioactive contamination on nematode assemblages at sites affected by the fallout from the Chernobyl accident. First, we estimated the total dose rates (TDRs) absorbed by nematodes, from measured current soil activity concentrations, Dose Conversion Coefficients (DCCs, calculated using EDEN software) and soil-to-biota concentration ratios (from the ERICA tool database). The impact of current TDRs on nematode assemblages was then evaluated. Nematodes were collected in spring 2011 from 18 forest sites in the Chernobyl Exclusion Zone (CEZ) with external gamma dose rates, measured using radiophotoluminescent dosimeters, varying from 0.2 to 22 μGy h{sup −1}. These values were one order of magnitude below the TDRs. A majority of bacterial-, plant-, and fungal-feeding nematodes and very few of the disturbance sensitive families were identified. No statistically significant association was observed between TDR values and nematode total abundance or the Shannon diversity index (H′). The Nematode Channel Ratio (which defines the relative abundance of bacterial- versus fungal-feeding nematodes) decreased significantly with increasing TDR, suggesting that radioactive contamination may influence nematode assemblages either directly or indirectly by modifying their food resources. A greater Maturity Index (MI), usually characterising better soil quality, was associated with higher pH and TDR values. These results suggest that in the CEZ, nematode assemblages from the forest sites were slightly impacted by chronic exposure at a predicted TDR of 200 μGy h{sup −1}. This may be imputable to a dominant proportion of pollutant resistant nematodes in all sites

  18. Ambiguous taxa: Effects on the characterization and interpretation of invertebrate assemblages

    Science.gov (United States)

    Cuffney, T.F.; Bilger, Michael D.; Haigler, A.M.

    2007-01-01

    Damaged and immature specimens often result in macroinvertebrate data that contain ambiguous parent-child pairs (i.e., abundances associated with multiple related levels of the taxonomic hierarchy such as Baetis pluto and the associated ambiguous parent Baetis sp.). The choice of method used to resolve ambiguous parent-child pairs may have a very large effect on the characterization of invertebrate assemblages and the interpretation of responses to environmental change because very large proportions of taxa richness (73-78%) and abundance (79-91%) can be associated with ambiguous parents. To address this issue, we examined 16 variations of 4 basic methods for resolving ambiguous taxa: RPKC (remove parent, keep child), MCWP (merge child with parent), RPMC (remove parent or merge child with parent depending on their abundances), and DPAC (distribute parents among children). The choice of method strongly affected assemblage structure, assemblage characteristics (e.g., metrics), and the ability to detect responses along environmental (urbanization) gradients. All methods except MCWP produced acceptable results when used consistently within a study. However, the assemblage characteristics (e.g., values of assemblage metrics) differed widely depending on the method used, and data should not be combined unless the methods used to resolve ambiguous taxa are well documented and are known to be comparable. The suitability of the methods was evaluated and compared on the basis of 13 criteria that considered conservation of taxa richness and abundance, consistency among samples, methods, and studies, and effects on the interpretation of the data. Methods RPMC and DPAC had the highest suitability scores regardless of whether ambiguous taxa were resolved for each sample separately or for a group of samples. Method MCWP gave consistently poor results. Methods MCWP and DPAC approximate the use of family-level identifications and operational taxonomic units (OTU), respectively. Our

  19. Demersal fish assemblages off the Seine and Sedlo seamounts (northeast Atlantic)

    Science.gov (United States)

    Menezes, Gui M.; Rosa, Alexandra; Melo, Octávio; Pinho, Mário R.

    2009-12-01

    Seamounts are thought to support special biological communities, and often maintain high standing stocks of demersal and benthopelagic fishes. Seamount fish fauna have been described in several studies but few works have included species taken below 600 m. The demersal fish assemblages of the Seine and Sedlo seamounts (northeast Atlantic) from the summits to 2000 m depth were investigated based on longline survey catch data, conducted as part of the OASIS project. A total of 41 fish species from 24 families were caught at Seine near Madeira, and 30 species from 19 families were caught at Sedlo north of the Azores. Both fish faunas have high affinities with the neighbouring areas of the Azores, Madeira and with the eastern North Atlantic and the Mediterranean Sea. Overall abundances and mean body weights were slightly higher at Sedlo seamount, appearing in conformity with the latitudinal effect of increasing species abundance and productivity from south to north. The differential influence of the Mediterranean Water at each seamount may contribute to explain (a) the differences found in vertical distribution of common species, which tend to distribute deeper at Seine, and (b) the observed changes in the species composition and dominance in deeper waters. Multivariate analysis revealed a vertical structure that is approximately coincident with the expected zonation of water masses at each seamount. Physiological tolerance to the prevailing vertical hydrological conditions may explain the species distribution and the large-scale vertical assemblage structure found. However, further ecological factors like productivity patterns affecting the amount and quality of the available food appear to shape the abundance, diversity or dominance patterns of functional groups within those main assemblages. At Seine, the species Trachurus picturatus dominated the catches, mainly at the shallower edge of the plateau, appearing consistent with the sound-scattering layer interception

  20. Stable Isotope Systematics in Grasshopper Assemblages Along an Elevation Gradient, Colorado

    Science.gov (United States)

    Kohn, M. J.; Evans, S.; Dean, J.; Nufio, C.

    2012-12-01

    Insects comprise over three quarters of all animal species, yet studies of body water isotopic composition are limited to only the cockroach, the hoverfly, and chironomid flies. These studies suggest that oxygen and hydrogen isotopic compositions in body water are primarily controlled by dietary water sources, with modification from respiratory and metabolic processes. In particular, outward diffusion of isotopically depleted water vapor through insect spiracles at low humidity enriches residual body water in 18O and 2H (D). Stable isotope compositions (δ18O and δD) also respond to gradients in elevation and humidity, but these influences remain poorly understood. In this study, we measured grasshopper body water and local vegetation isotopic compositions along an elevation gradient in Colorado to evaluate three hypotheses: 1) Insect body water isotopic composition is directly related to food source water composition 2) Water vapor transport alters body water isotopic compositions relative to original diet sources, and 3) Elevation gradients influence isotopic compositions in insect body water. Thirty-five species of grasshopper were collected from 14 locations in Colorado grasslands, ranging in elevation from 450 to 800 meters (n=131). Body water was distilled from previously frozen grasshopper specimens using a vacuum extraction line, furnaces (90 °C), and liquid nitrogen traps. Water samples were then analyzed for δ18O and δD on an LGR Liquid Water Isotope Analyzer, housed in the Department of Geosciences, Boise State University. Grasshopper body water isotopic compositions show wide variation, with values ranging between -76.64‰ to +42.82‰ in δD and -3.06‰ to +26.78‰ in δ18O. Precipitation δ18O values over the entire Earth excluding the poles vary by approximately 30‰, comparable to the total range measured in our single study area. Most grasshopper values deviate from the global meteoric water line relating δ18O and δD in precipitation