WorldWideScience
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Twilight vertical migrations of zooplankton in a Chilean fjord  

Science.gov (United States)

Time series of acoustic backscatter and vertical velocity profiles were obtained at three sites along a Chilean fjord with the purpose of determining dominant structures of vertical migrations of the sound scattering layer. Ancillary data obtained with stratified net samples indicated that the sound scattering layer may have been dominated by euphausiids and decapods. Therefore, distributions of acoustic backscatter anomalies and vertical velocities were attributed to vertical migrations of predominantly these organisms. Migration patterns were dominated by twilight excursions in which organisms swam toward the water surface at sunset, spent 100 m). This migration strategy can also be termed 'semidiel migration' as two double excursions were linked to light levels. The reasons for this twilight migration remain uncertain. But it is possible that the up and down motion around sunset was related to predation avoidance, hunger-satiation state, ontogeny, seaward transport evasion, or reaction to the environmental shock from the pycnocline, or a combination of all or some of them. In contrast, the sunrise double excursion was probably linked to feeding requirements by organisms that need to spend the day at great depth with no food available. This study demonstrated the existence of semidiel patterns throughout the fjord and through prolonged periods. In addition, identification of this pattern by acoustic backscatter was complemented by direct vertical velocity measurements. It is proposed that twilight vertical migration is a common strategy in Chilean fjords.

Valle-Levinson, Arnoldo; Castro, Leonardo; Cáceres, Mario; Pizarro, Oscar

2014-12-01

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Zooplankton diel vertical migration and contribution to deep active carbon flux in the NW Mediterranean  

Science.gov (United States)

The diel vertical migration (DVM) of zooplankton contributes to the biological pump transporting material from surface to deep waters. We examined the DVM of the zooplankton community in different size fractions (53-200 ?m, 200-500 ?m, 500-1000 ?m, 1000-2000 ?m and > 2000 ?m) during three cruises carried out in the open NW Mediterranean Sea. We assessed their metabolic rates from empirical published relationships and estimated the active fluxes of dissolved carbon to the mesopelagic zone driven by migrant zooplankton. Within the predominantly oligotrophic Mediterranean Sea, the NW region is one of the most productive ones, with a seasonal cycle characterized by a prominent spring bloom. The study area was visited at three different phases of the seasonal cycle: during the spring bloom, the post-bloom, and strongly stratified oligotrophic conditions. We found seasonal differences in DVM, less evident during the bloom. Changes in DVM intensity were related to the composition of the zooplanktonic assemblage, which also varied between cruises. Euphausiids appeared as the most active migrants in all seasons, and their life cycle conditioned the observed pattern. Immature stages, which are unable to perform large diel vertical movements, dominated during the bloom, in contrast to the higher relative importance of migrating adults in the other two sampling periods. The amount of dissolved carbon exported was determined by the migrant zooplankton biomass, being highest during the post-bloom (2.2 mmol C respired m- 2 d- 1, and up to 3.1 mmol C exported m- 2 d- 1 when DOC release estimations are added). The active transport by diel migrants represented a substantial contribution to total carbon export to deep waters, especially under stratified oligotrophic conditions, revealing the importance of zooplankton in the biological pump operating in the study area.

Isla, Alejandro; Scharek, Renate; Latasa, Mikel

2015-03-01

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Effects of the proximal factors on the diel vertical migration of zooplankton in a plateau meso-eutrophic lake Erhai, China  

OpenAIRE

To study the proximal factors inducing diel vertical migration (DVM) in large and small zooplankton species in a plateau lake in China, we investigated the DVM of crustacean zooplankton in lake Erhai bimonthly from November 2009 to September 2010. We hypothesized that the factors affecting DVM behaviour in different-sized zooplankton were different. A linear regression was used to assess the relationships between environmental variables and the vertical distribution of zooplankton. All crusta...

Cuilin Hu; Shengrui Wang; Longgen Guo; Ping Xie

2014-01-01

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Temporal variability of vertical migration of zooplankton at deep-sea floor in the Amundsen Sea, Antarctica  

Science.gov (United States)

Vertical migration of zooplankton is ubiquitous behavior in marine plankton community. Observations on diel, seasonal, and interannual variation of zooplankton behavior can support the knowledge for understanding of marine ecosystems. However, daily and seasonal rhythms are little observed in the deep-sea with seasonally ice-covered water. We described the pattern of diel vertical distribution (DVM) above deep-sea floor in a seasonally ice-covered Amundsen Sea. Times series of acoustic backscatter was observed using a bottom-moored, upward-looking Acoustic Doppler current profiler (ADCP) in the depth of 250-550 m. Multi-frequency acoustic backscatter data (38 and 120 kHz, EK60) were collected to identify the composition of DVM between fish and zooplankton using a dB differencing technique. The seasonal vertical distribution of zooplankton was clearly governed by the seasonal phase of surface solar radiation (SSR) and sea ice condition (SIC), while water temperature did not affect on the DVM variation. The main depths of zooplankton were primarily distributed near 250 m with high SSR and low SIC period and found near bottom in the lowermost layers (>400 m) with low SSR and high SIC between mid-April and mid-November. The temporal variation of main depths of zooplankton was significantly correlated with both SSR and SIC (r = 0.87 and -0.70, respectively, pperiod. Mean daily cycles of acoustic backscatter showed distinctive DVM pattern dependence on the SIC. During the low SIC in austral summer, DVM initiate to descent at sunrise, reach a maximum depth at around the highest levels of SSR, and ascend at sunset. However, DVM was not associated with sun's periodicity and remained above the bottom with high acoustic backscatter strength with high SIC in austral winter. It is shown that light is the proximate cue for diel cycle of DVM and both light and sea ice conditions control the seasonal variation of DVM because high SIC can cause to block out the detectable light intensity for DVM. These results might contribute to the knowledge about zooplankton ecology near bottom under ice-covered region at the high-latitude Southern Ocean. We also speculate that DVM of zooplankton can influence the accumulation and resuspension of organic matter near bottom as a contributor of biological pump.

Sul La, Hyoung; Ha, Ho Kyung; Kang, Chan Young; Wåhlin, Anna; Park, Jisoo; Lee, SangHoon; Shin, Hyoung Chul

2014-05-01

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Efecto de la zona de mínimo oxígeno sobre la migración vertical de zooplancton gelatinoso en la bahía de Mejillones / The effect of the oxygen minimum zone on vertical migration of gelatinous zooplankton in Mejillones Bay  

Scientific Electronic Library Online (English)

Full Text Available SciELO Chile | Language: Spanish Abstract in spanish Se analizó la distribución estacional y migración vertical de zooplancton gelatinoso colectado en la bahía de Mejillones. Se identificaron 39 especies distribuidas en 14 de hidromedusas, 20 de sifonóforos y 5 de quetognatos. Las especies dominantes fueron Obelia spp., Liriope tetraphylla, Solmundell [...] a bitentaculata, Rophalonema velatum, Muggiaea atlantica, Sphaeronectes gracilis, Sagitta enfiata y S. bierii, las que presentaron un estrecho rango de distribución vertical y migración nictimeral, debido a la infiuencia de la Zona de Mínimo Oxígeno (ZMO) ( Abstract in english The seasonal distribution and vertical migration of gelatinous zooplankton collected in Mejillones Bay was analyzed. The 39 species identified included 14 hydromedusae, 20 siphonophores, and 5 chaetognates. The dominant species were Obelia spp., Liriope tetraphylla, Solmundella bitentaculata, Rophal [...] onema velatum, Muggiaea atlantica, Sphaeronectes gracilis, Sagitta enfiata, and S. bierii. Their vertical distribution and nictimeral migration ranges were narrow due to the infiuence of the Oxygen Minimum Zone (OMZ) (

Pedro, Apablaza; Sergio, Palma.

2006-11-01

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Efecto de la zona de mínimo oxígeno sobre la migración vertical de zooplancton gelatinoso en la bahía de Mejillones The effect of the oxygen minimum zone on vertical migration of gelatinous zooplankton in Mejillones Bay  

Directory of Open Access Journals (Sweden)

Full Text Available Se analizó la distribución estacional y migración vertical de zooplancton gelatinoso colectado en la bahía de Mejillones. Se identificaron 39 especies distribuidas en 14 de hidromedusas, 20 de sifonóforos y 5 de quetognatos. Las especies dominantes fueron Obelia spp., Liriope tetraphylla, Solmundella bitentaculata, Rophalonema velatum, Muggiaea atlantica, Sphaeronectes gracilis, Sagitta enfiata y S. bierii, las que presentaron un estrecho rango de distribución vertical y migración nictimeral, debido a la infiuencia de la Zona de Mínimo Oxígeno (ZMO (The seasonal distribution and vertical migration of gelatinous zooplankton collected in Mejillones Bay was analyzed. The 39 species identified included 14 hydromedusae, 20 siphonophores, and 5 chaetognates. The dominant species were Obelia spp., Liriope tetraphylla, Solmundella bitentaculata, Rophalonema velatum, Muggiaea atlantica, Sphaeronectes gracilis, Sagitta enfiata, and S. bierii. Their vertical distribution and nictimeral migration ranges were narrow due to the infiuence of the Oxygen Minimum Zone (OMZ (< 1 mL·L-1, whose upper limit was quite shallow (25-50 m. In spring, the majority of the dominant species presented nictimeral movements due to the greater oxygenation of the water column. On the other hand, in summer, when the thermocline was more intense, and in winter, when the OMZ neared the surface, the majority of the dominant species showed no changes in their vertical distribution throughout the daily cycle. Obelia spp. had a shallow distribution, related principally to the presence of the thermocline. R. velatum, however, was well adapted to the scant dissolved oxygen in the OMZ

Pedro Apablaza

2006-11-01

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Diel vertical migration patterns of three zooplankton populations in a Chilean lake Patrones de migración vertical de tres poblaciones de zooplancton en un lago chileno  

OpenAIRE

In this work we analyzed the depth-distribution, at noon and midnight, of three zooplankton populations which are common inhabitants of lakes from central Chile and coexist in lake El Plateado. The species were Tumeodiaptomus diabolicus, Diaphanosoma chilense and Bosmina longirostris. Also, we analyzed the association between the depth-specific abundances of the groups and the depth-specific temperature and oxygen values during the sampling period. Our results show that: (1) the three populat...

RODRIGO RAMOS-JILIBERTO; Carvajal, Jose? L.; MAURICIO CARTER; Zu?n?iga, Luis R.

2004-01-01

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Trophic ecology and vertical patterns of carbon and nitrogen stable isotopes in zooplankton from oxygen minimum zone regions  

Science.gov (United States)

The unique physical and biogeochemical characteristics of oxygen minimum zones (OMZs) influence plankton ecology, including zooplankton trophic webs. Using carbon and nitrogen stable isotopes, this study examined zooplankton trophic webs in the Eastern Tropical North Pacific (ETNP) OMZ. ?13C values were used to indicate zooplankton food sources, and ?15N values were used to indicate zooplankton trophic position and nitrogen cycle pathways. Vertically stratified MOCNESS net tows collected zooplankton from 0 to 1000 m at two stations along a north-south transect in the ETNP during 2007 and 2008, the Tehuantepec Bowl and the Costa Rica Dome. Zooplankton samples were separated into four size fractions for stable isotope analyses. Particulate organic matter (POM), assumed to represent a primary food source for zooplankton, was collected with McLane large volume in situ pumps. The isotopic composition and trophic ecology of the ETNP zooplankton community had distinct spatial and vertical patterns influenced by OMZ structure. The most pronounced vertical isotope gradients occurred near the upper and lower OMZ oxyclines. Material with lower ?13C values was apparently produced in the upper oxycline, possibly by chemoautotrophic microbes, and was subsequently consumed by zooplankton. Between-station differences in ?15N values suggested that different nitrogen cycle processes were dominant at the two locations, which influenced the isotopic characteristics of the zooplankton community. A strong depth gradient in zooplankton ?15N values in the lower oxycline suggested an increase in trophic cycling just below the core of the OMZ. Shallow POM (0-110 m) was likely the most important food source for mixed layer, upper oxycline, and OMZ core zooplankton, while deep POM was an important food source for most lower oxycline zooplankton (except for samples dominated by the seasonally migrating copepod Eucalanus inermis). There was no consistent isotopic progression among the four zooplankton size classes for these bulk mixed assemblage samples, implying overlapping trophic webs within the total size range considered.

Williams, Rebecca L.; Wakeham, Stuart; McKinney, Rick; Wishner, Karen F.

2014-08-01

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Plankton vertical migrations - Implications for the pelagic ecosystem  

OpenAIRE

Habitat selection is an important behavior of many organisms. The direction and strength of this behavior is often characterized as a result of a trade off between predator avoidance and obtaining resources. A characteristic example of this trade off may be seen in organisms in the pelagic ecosystem in the form of vertical migrations. Diel vertical migration (DVM) is a predator avoidance behavior of many zooplankton species, which is marked by a significant shift in the vertical distribution ...

Haupt, Florian

2011-01-01

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Importance of Arctic zooplankton seasonal migrations for ?-hexachlorocyclohexane bioaccumulation dynamics.  

Science.gov (United States)

Like most zooplankton, Calanus hyperboreus undergoes seasonal migration spending late spring and summer grazing at the surface and the rest of the year in diapause at depth. As a result, in the Arctic Ocean this copepod resides for part of the year in the hexachlorocyclohexane (HCH) enriched surface water and for part of the year at depth where HCH undergoes significant microbial degradation resulting in far lower concentrations (~3 times for ?-HCH). We collected C. hyperboreus from summer and winter from the Amundsen Gulf and measured their ?-HCH concentrations, enantiomeric compositions, and bioaccumulation factors (BAFs) to investigate how this copepod responds to the change in exposure to ?-HCH. C. hyperboreus collected in winter were also cultured for 5 weeks under surface water conditions without feeding to investigate bioconcentration dynamics following spring ascent. Concentration of ?-HCH was 2-3 times higher in individuals from the summer than those from the winter. Log BAF from the summer (feeding period) does not exceed log BCF (bioconcentration factor) from the culturing experiment (no feeding) suggesting that ?-HCH concentration in C. hyperboreus is maintained through equilibration rather than feeding. After the spring ascent from deep waters, C. hyperboreus approach equilibrium partitioning with the higher surface water concentrations of ?-HCH within 3-4 weeks with about 60% of bioconcentration taking place in the first week. The C. hyperboreus ?-HCH chiral signature also reflects ambient seawater and can therefore be used as a determinant of residence depth. Even though a single cycle of seasonal migration does not result in a significant redistribution of ?-HCH in the water column, this process could have a significant cumulative effect over longer time scales with particular local importance where the zooplankton biomass is high and the ocean depth is great enough to provide substantial vertical concentration gradients. PMID:23570325

Pu?ko, Monika; Walkusz, W; Macdonald, R W; Barber, D G; Fuchs, C; Stern, G A

2013-05-01

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Vertical distribution of zooplankton: density dependence and evidence for an ideal free distribution with costs  

Directory of Open Access Journals (Sweden)

Full Text Available Abstract Background In lakes with a deep-water algal maximum, herbivorous zooplankton are faced with a trade-off between high temperature but low food availability in the surface layers and low temperature but sufficient food in deep layers. It has been suggested that zooplankton (Daphnia faced with this trade-off distribute vertically according to an "Ideal Free Distribution (IFD with Costs". An experiment has been designed to test the density (competition dependence of the vertical distribution as this is a basic assumption of IFD theory. Results Experiments were performed in large, indoor mesocosms (Plankton Towers with a temperature gradient of 10°C and a deep-water algal maximum established below the thermocline. As expected, Daphnia aggregated at the interface between the two different habitats when their density was low. The distribution spread asymmetrically towards the algal maximum when the density increased until 80 % of the population dwelled in the cool, food-rich layers at high densities. Small individuals stayed higher in the water column than large ones, which conformed with the model for unequal competitors. Conclusion The Daphnia distribution mimics the predictions of an IFD with costs model. This concept is useful for the analysis of zooplankton distributions under a large suite of environmental conditions shaping habitat suitability. Fish predation causing diel vertical migrations can be incorporated as additional costs. This is important as the vertical location of grazing zooplankton in a lake affects phytoplankton production and species composition, i.e. ecosystem function.

Lampert Winfried

2005-04-01

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Initial size structure of natural phytoplankton communities determines the response to Daphnia diel vertical migration  

OpenAIRE

Diel vertical migration (DVM) is a common behavior of many pelagic herbivorous zooplankton species in response to predation pressure. It is characterized by a twice daily habitat shift of the zooplankton species: staying in the epilimnion only during night time and migrating down in the crack of dawn in deeper water layers, staying there during the day time. This causes a discontinuous grazing regime and previous studies have shown that the direction and strength of phytoplankton community re...

Maarten Boersma; Florian Haupt; Maria Stockenreiter; Herwig Stibor

2012-01-01

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Importance of light, temperature, zooplankton and fish in predicting the nighttime vertical distribution of Mysis diluviana  

Science.gov (United States)

The opossum shrimp Mysis diluviana (formerly M. relicta) performs large amplitude diel vertical migrations in Lake Ontario and its nighttime distribution is influenced by temperature, light and the distribution of its predators and prey. At one location in southeastern Lake Ontario, we measured the vertical distribution of mysids, mysid predators (i.e. planktivorous fishes) and mysid prey (i.e. zooplankton), in addition to light and temperature, on 8 occasions from May to September, 2004 and 2005. We use these data to test 3 different predictive models of mysid habitat selection, based on: (1) laboratory-derived responses of mysids to different light and temperature gradients in the absence of predator or prey cues; (2) growth rate of mysids, as estimated with a mysid bioenergetics model, given known prey densities and temperatures at different depths in the water column; (3) ratio of growth rates (g) and mortality risk (??) associated with the distribution of predatory fishes. The model based on light and temperature preferences was a better predictor of mysid vertical distribution than the models based on growth rate and g:?? on all 8 occasions. Although mysid temperature and light preferences probably evolved as mechanisms to reduce predation while increasing foraging intake, the response to temperature and light alone predicts mysid vertical distribution across seasons in Lake Ontario. ?? Inter-Research 2009.

Boscarino, B.T.; Rusdtam, L.G.; Eillenberger, J.L.; O'Gorman, R.

2009-01-01

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Interactions of migrating zooplankton with shallow topography: predation by rockfishes and intensification of patchiness  

Science.gov (United States)

Stratified net tows, multiple-frequency sonar and drifter drogues, combined with analysis of rockfish stomachs, were used to investigate the processes taking place when vertically migrating plankton are swept onto a shallow bank in the Southern California Bight. Euphausia pacifica, the dominant migrating plankter near the bank, was also a dominat item in the stomachs of Sebastes spp. when currents in predawn hours advected water from deep water toward the bank. In the morning, schools of 12 kHz scatterers, apparently rockfish, ascended tens of meters above the bottom toward the descending plankton. Net tow estimates of euphausiid biomass and the acoustic backscatterigg at 200 and 520 Hz were much lower above the bank than in a nearby deep-water area, particularly during early evening. At night and during predawn hours, a relatively high abundance of zooplankton, with densities similar to the deep-water area, was usually found near the edge of the bank. Causes of the observed recurrent lack of migrating plankton above a seamount in early evening could be diurnal predation by epibenthic fish or daytime advection of migrators around the seamount, thereby creating a "hole" above it. The formation of such "holes" can intensify the regional patchiness of plankton near shallow seamounts. Historical data of CalCOFI night-time tows show that the biomass of euphausiids, but not that of the weakly migrating chaetognaths, is significantly more variable (patchy) at stations near offshore shallow topography than at nearby deep-water stations. The similarity in the mean biomass of euphausiids at the two station sets suggests that the contribution of predation to the observed intensifications of patchiness may be insignificant.

Genin, Amatzia; Haury, Loren; Greenblatt, Paul

1988-02-01

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Vertical distribution of zooplankton in the water column of Lago Amapá, Rio Branco, Acre, Brazil  

OpenAIRE

The aim of investigation was to study the model of vertical distribution in Lago Amapá, taking into consideration the seasonality of its zooplanktonic composition. Lago Amapá (10º2'36"S and 67º50'24"W) is located in the floodplain of the Rio Acre. Samplings were conducted at three different depths of the water column, to study the vertical distribution of zooplankton populations and determine some physico-chemical and biological parameters of Lago Amapá. Weekly samples were taken with a ...

Erlei Cassiano Keppeler; Elsa Rodrigues Hardy

2004-01-01

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Vertical oceanic transport of alpha-radioactive nuclides by zooplankton fecal pellets  

International Nuclear Information System (INIS)

This paper gives the results of research to explain the role played by marine plankton metabolism in the vertical oceanic transport of the alpha-emitting nuclides. The common Mediterranean euphausiid, Meganyctiphanes norvegica, was selected as the typical zooplanktonic species that is the focus of this work. Measurements of 239240Pu, 238U, 232Th, and 210Po are reported in whole euphausiids and in euphausiid fecal pellets and molts. The resulting data are inserted into a simple model that describes the flux of an element through a zooplanktonic animal. Concentrations of the nuclides concerned are high in fecal pellets, at levels which are typical of geological rather than biological material. It is suggested that zooplanktonic fecal pellets play a significant role in the vertical oceanic transport of plutonium, thorium, and polonium

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Zooplankton data: Vertical distributions of zooplankton in the Norweigian and Greenland Seas during summer, 1989  

Energy Technology Data Exchange (ETDEWEB)

Recent studies of zooplankton populations in the Greenland Sea have focused on processes at the Marginal Ice Zone (MIZ) and the areas immediately adjacent to it under the ice and in open water. These studies have shown a relatively short period of intense secondary productivity which is closely linked temporally and spatially to phytoplankton blooms occurring near the ice edge in spring and early summer. During the summer of 1989 we participated in a project focusing on benthic and water column processes in the basins of the Norwegian and Greenland Seas. This study allowed us to compare biological processes at the MIZ with those occurring in the open waters of the Greenland Sea, and to compare processes at both of these locations with those in the Norwegian Sea. The data presented in this report are the results of zooplankton net tows covering the upper 1000 meters of the water column over the Norwegian Sea basin and the Greenland Sea basin, and the upper 500 meters of open water adjacent to the MIZ in the Greenland Sea. Sampling was conducted between 12 and 29 July 1989.

Lane, P.V.Z.; Smith, S.L.; Schwarting, E.M.

1993-08-01

18

Enhancement of anammox by the excretion of diel vertical migrators.  

Science.gov (United States)

Measurements show that anaerobic ammonium oxidation with nitrite (anammox) is a major pathway of fixed nitrogen removal in the anoxic zones of the open ocean. Anammox requires a source of ammonium, which under anoxic conditions could be supplied by the breakdown of sinking organic matter via heterotrophic denitrification. However, at many locations where anammox is measured, denitrification rates are small or undetectable. Alternative sources of ammonium have been proposed to explain this paradox, for example through dissimilatory reduction of nitrate to ammonium and transport from anoxic sediments. However, the relevance of these sources in open-ocean anoxic zones is debated. Here, we bring to attention an additional source of ammonium, namely, the daytime excretion by zooplankton and micronekton migrating from the surface to anoxic waters. We use a synthesis of acoustic data to show that, where anoxic waters occur within the water column, most migrators spend the daytime within them. Although migrators export only a small fraction of primary production from the surface, they focus excretion within a confined depth range of anoxic water where particle input is small. Using a simple biogeochemical model, we suggest that, at those depths, the source of ammonium from organisms undergoing diel vertical migrations could exceed the release from particle remineralization, enhancing in situ anammox rates. The contribution of this previously overlooked process, and the numerous uncertainties surrounding it, call for further efforts to evaluate the role of animals in oxygen minimum zone biogeochemistry. PMID:25288743

Bianchi, Daniele; Babbin, Andrew R; Galbraith, Eric D

2014-11-01

19

Initial size structure of natural phytoplankton communities determines the response to Daphnia diel vertical migration  

Directory of Open Access Journals (Sweden)

Full Text Available Diel vertical migration (DVM is a common behavior of many pelagic herbivorous zooplankton species in response to predation pressure. It is characterized by a twice daily habitat shift of the zooplankton species: staying in the epilimnion only during night time and migrating down in the crack of dawn in deeper water layers, staying there during the day time. This causes a discontinuous grazing regime and previous studies have shown that the direction and strength of phytoplankton community responses to zooplankton DVM most probably depends on the size of phytoplankton species. To examine the influence of zooplankton DVM on different sized phytoplankton communities, we designed an experiment where we manipulated the size distribution of a natural phytoplankton community a priori in field mesocosms. We investigated the influence of DVM of the cladoceran Daphnia hyalina on two different phytoplankton communities, by the use of deep (10 m field enclosures. Epilimnetic lake water, containing a summer phytoplankton community, was filtered with two different mesh sizes (11 mm and 64 mm. The 11 mm phytoplankton community (“small” contained mainly small algal species, while the 64 mm community (“large” had a wider range of phytoplankton sizes. To simulate zooplankton DVM, D. hyalina were placed in mesh cages that were lowered or raised (“migration” as dictated by the study design; a “no migration” (representing absence of DVM treatment was also tested. Phytoplankton abundance was measured using chlorophyll-a and biovolume; size distribution of the algae and nutrient availability was also determined in each treatment. The results indicated that DVM had contrasting effects on the two evaluated phytoplankton communities. Comparison of “migration” and “no migration” zooplankton treatments showed that nutrient availability and total phytoplankton biovolume was higher in (1 “no migration” treatments with phytoplankton communities comprising mainly small algae and (2 “migration” treatments with phytoplankton communities of a broader size spectrum of algae. Hence our study showed two different mechanisms of how zooplankton DVM may influence the phytoplankton community dynamics. Nutrient cycling was an important factor in phytoplankton communities of mainly small algae, whereas the refuge effect was the main driver of phytoplankton dynamics in phytoplankton communities of a large size spectrum of algae.

Maarten Boersma

2012-01-01

20

Differences in vertical and horizontal distribution of fish larvae and zooplankton, related to hydrography  

DEFF Research Database (Denmark)

Planktonic fish larvae have little influence on their horizontal distribution, while they are able to control their vertical position in the water column. While prey and light are among the factors with an apparent influence on the vertical distribution, the effects of other factors are less clear. Notably, distributional differences between larvae of different fish species are poorly understood. Information on the horizontal distribution of larvae of 27 species and the vertical distribution of seven species of Gadidae, two Pleuronectidae and one Scophthalmidae, was compiled from one survey in the northern North Sea. Horizontally, fish larvae aggregated near frontal structures, correlating with high densities of zooplankton. Increasing length and decreasing numbers indicated an origin in the western North Sea, followed by an eastward drift. Vertically, the different species exhibited similarities but also notable differences in their vertical distribution. Most gadoid species aggregated in the upper (B40 m)or middle water column (40 m) during the day with an increase in abundance at shallower depths during the night, while all flatfish were distributed at greater depths under all light conditions. Hence, larvae differed in their distributional patterns, but the relative depth distributions among the species in the larval community generally remained constant

Höffle, Hannes; Nash, Richard D.M.

2013-01-01

21

Bacteria dispersal by hitchhiking on zooplankton  

DEFF Research Database (Denmark)

Microorganisms and zooplankton are both important components of aquatic food webs. Although both inhabit the same environment, they are often regarded as separate functional units that are indirectly connected through nutrient cycling and trophic cascade. However, research on pathogenic and nonpathogenic bacteria has shown that direct association with zooplankton has significant influences on the bacteria's physiology and ecology. We used stratified migration columns to study vertical dispersal of hitchhiking bacteria through migrating zooplankton across a density gradient that was otherwise impenetrable for bacteria in both upward and downward directions (conveyor-belt hypothesis). The strength of our experiments is to permit quantitative estimation of transport and release of associated bacteria: vertical migration of Daphnia magna yielded an average dispersal rate of 1.3 x 10(5) x cells x Daphnia(-1) x migration cycle(-1) for the lake bacterium Brevundimonas sp. Bidirectional vertical dispersal by migrating D. magna was also shown for two other bacterial species, albeit at lower rates. The prediction that diurnally migrating zooplankton acquire different attached bacterial communities from hypolimnion and epilimnion between day and night was subsequently confirmed in our field study. In mesotrophic Lake Nehmitz, D. hyalina showed pronounced diel vertical migration along with significant diurnal changes in attached bacterial community composition. These results confirm that hitchhiking on migrating animals can be an important mechanism for rapidly relocating microorganisms, including pathogens, allowing them to access otherwise inaccessible resources.

Grossart, Hans-Peter; Dziallas, Claudia

2010-01-01

22

Do Daphnia use metalimnetic organic matter in a north temperate lake? An analysis of vertical migration  

Science.gov (United States)

Diel vertical migration of zooplankton is influenced by a variety of factors including predation, food, and temperature. Research has recently shifted from a focus on factors influencing migration to how migration affects nutrient cycling and habitat coupling. Here we evaluate the potential for Daphnia migrations to incorporate metalimnetic productivity in a well-studied northern Wisconsin lake. We use prior studies conducted between 1985 and 1990 and current diel migration data (2008) to compare day and night Daphnia vertical distributions with the depth of the metalimnion (between the thermocline and 1% light depth). Daphnia migrate from a daytime mean residence depth of between about 1.7 and 2.5 m to a nighttime mean residence depth of between 0 and 2.0 m. These migrations are consistent between the prior period and current measurements. Daytime residence depths of Daphnia are rarely deep enough to reach the metalimnion; hence, metalimnetic primary production is unlikely to be an important resource for Daphnia in this system.

Brosseau, Chase Julian; Cline, Timothy J.; Cole, Jonathan J.; Hodgson, James R.; Pace, Michael L.; Weidel, Brian C.

2012-01-01

23

Zooplankton vertical-distribution in relation to the hydrology in the nw levantine and the se aegean seas (spring 1986)  

OpenAIRE

Zooplankton composition and vertical distribution, and its relation to the hydrological regime are studied in the NW Levantine and SE Aegean Seas. The area is characterized by intense sub-basin and mesoscale variability. Various gyres and eddies as well as currents and jets affect the vertical and horizontal transport of the identified water masses. Furthermore, in late winter LIW is generated exclusively in this region of the Eastern Mediterranean, mainly in the Rhodes cyclonic gyre and to a...

Pancuccipapadopoulou, Ma; Siokoufrangou, I.; Theocharis, A.; Georgopoulos, D.

1992-01-01

24

Vertical and horizontal distribution of zooplankton and polar cod in southern Baffin Bay (66-71°N) in September 2009  

DEFF Research Database (Denmark)

Zooplankton are the link connecting primary producers to higher trophic levels, and knowing their distribution and community is important for predicting the distribution of predator species, like fish, seabirds, and marine mammals. However, data from open Arctic oceans are still scarce. In autumn, tens of millions of the planktivorous little auks (Alle alle) (about 75 % of the world’s population) and millions of thick-billed murres (Uria lomvia) pass through the Baffin Bay. To investigate their potential food sources, we investigated the spatial and vertical distribution of zooplankton and small fishes in the upper 500 m of southern Baffin Bay in September 2009. The zooplankton community was dominated by copepods (55 % of abundance in the upper 500 m), primarily of the genus Calanus. Other important zooplankton taxa included Limacina helicina, Chaetognatha, and Cirripedia nauplii. On the Greenland Shelf, most Calanus were late copepodite stages and most were found at the depths of >200 m, suggesting they werein diapause. On the Canadian Shelf, there were relatively more Calanus in the near-surface layers, which were probably still actively feeding and which were available to visual predators such as seabirds and fish. The acoustic survey showed the highest density of polar cod Boreogadus saida in the upper 50 m on the western part of the Greenland Shelf. A particularly high biomass of both zooplankton and polar cod was found in the central part of the basin in association with a local relatively shallow area

Kjellerup, Sanne; Dünweber, Michael

2015-01-01

25

Centropages behaviour: Swimming and vertical migration  

Science.gov (United States)

The evolutionary success of any species living in a variable environment depends on its capacity to enhance the probability of finding food and mates, and escaping predators. In the case of copepods of the genus Centropages, as in all planktonic copepods, their swimming behaviour is closely tied to these vital aspects, and shows a high degree of plasticity and adaptive capacity. Swimming mechanisms of Centropages change radically during development, mainly in the transition between naupliar stages to the 1st copepodite; nauplii do not produce feeding currents, whereas copepodites do. Adults and late developmental stages of C. typicus, C. hamatus and C. velificatus spend most of the time in slow swimming and resting breaks, with occasional and brief fast swimming (escape reactions) and grooming events. Slow swimming is closely related to the creation of feeding currents, and results from the beating of the cephalic appendages in a “fling and clap” manner. The proportion of time allocated to the different swimming activities depends on sensory cues like type and concentration of food, presence of potential mates, light intensity, hydrodynamic flow, etc. The responses of Centropages to changes in flow velocity fluctuations (small-scale turbulence) are similar to the escape responses (fast swimming) triggered by the presence of potential predators. Centropages generally have standard nocturnal vertical migration patterns involving considerable vertical displacements. This behaviour is closely related to the narrow spectral sensitivity and the low intensity threshold of the genus, and has important consequences for the active vertical transport of matter and energy. The variety of responses of Centropages to environmental changes, and in general all the aspects related to its swimming behaviour seem to be controlled by the trade-off between energetic gains (food intake), losses (swimming energy expenditure), and predation risk. Behavioural plasticity and adaptation appear to be the most relevant characteristics for the success of the genus in a wide range of marine environments.

Alcaraz, Miguel; Saiz, Enric; Calbet, Albert

2007-02-01

26

Diel Vertical Migration Thresholds of Karenia brevis (Dinophyceae).  

Science.gov (United States)

Light and nutrient availability change throughout dinoflagellate diel vertical migration (DVM) and/or with subpopulation location in the water column along the west Florida shelf. Typically, the vertical depth of the shelf is greater than the distance a subpopulation can vertical...

27

Vertical distribution, composition, and abundance of crustacean zooplankton in the offshore waters of Lake Michigan  

International Nuclear Information System (INIS)

During 1975, zooplankton samples were collected on eight cruises (April to November) in the southern basin of Lake Michigan. Four stations in the northern basin were also sampled in January during a cruise aboard the USCGC Westwind. One of the goals of this study was to quantitatively estimate the standing crop of herbivorous crustacean zooplankton in units that would represent their functional roles as consumers of phytoplankton

28

Effects of net cages on the vertical distribution of zooplankton in a semi-arid reservoir, northeastern Brazil / Interferência de tanques-rede na distribuição vertical do zooplâncton num açude do semi-árido, nordeste do Brasil  

Scientific Electronic Library Online (English)

Full Text Available SciELO Brazil | Language: English Abstract in portuguese OBJETIVO: O açude do Carneiro é um ambiente aquático utilizado para atividades de aquicultura em tanques-rede, localizado na região semi-árida do nordeste do Brasil. A distribuição vertical foi avaliada com a finalidade de determinar os efeitos do enriquecimento orgânico induzido pela aquicultura no [...] s movimentos do zooplâncton. MÉTODOS: três réplicas amostrais foram coletadas à meia noite (0:00 horas) e ao meio dia (12:00 horas ) em cada uma de três profundidades da coluna d'água (i.e. superfície: 0 m; meio: 2 m e fundo: 4 m) em duas áreas (próximo e distante dos tanques-rede). As amostras foram coletadas utilizando uma garrafa de Van Dorn com 3 L de capacidade volumétrica. Os indivíduos coletados foram preservados em uma solução de formol a 4% saturada com açúcar e, posteriormente, identificados e quantificados com uma câmara de contagem Sedgwick-Rafter sob microscópio, considerando um mínimo de 100 indivíduos por subamostra. RESULTADOS: a riqueza de espécies e a densidade foram maiores na estação N (próxima aos tanques-rede) quando comparadas com a estação F (distante dos tanques-rede). Com poucas exceções, espécies de Rotifera não exibiram padrões típicos de migração vertical, concentrando-se nas camadas mais profundas durante o dia e nas camadas intermediárias durante a noite. Brachionus dolabratus e Hexarthra mira foram as únicas espécies que mostraram padrões de migração vertical inversos na estação N, em oposição aos padrões do copépodo ciclopóide Termocyclops crassus. Além disso, padrões de migração vertical não foram claros para as espécies de Cladocera e Copepoda próximos aos tanques-rede, mas foram evidentes na estação F. CONCLUSÕES: a presença de tanques-rede para peixes aumentou a riqueza de espécies (a maioria rotíferos) e a densidade de zooplâncton. Movimentos verticais foram mais pronunciados nos locais distantes dos tanques-rede, sugerindo que o aumento da disponibilidade de alimento reduziu a necessidade dos movimentos verticais típicos durante o dia, nos locais próximos aos tanques-rede. Abstract in english AIM: Carneiro reservoir is an aquatic environment used for net cage aquaculture activities, located in the semi-arid region of northeastern Brazil. Vertical distribution was evaluated in order to determine the effects of organic enrichment induced by aquaculture on zooplankton movements. METHODS: th [...] ree replicate samples were collected during midday and midnight at each of three depths along the water column (i.e. surface: 0 m; middle: 2 m and bottom: 4 m) at two sites (near and far from the net cages). Samples were collected using a 3 L volume capacity Van Dorn bottle. The collected individuals were preserved in a 4% formaldehyde solution saturated with sugar and, later, identified and counted on a Sedgwick-Rafter chamber under a microscope, considering a minimum of 100 individuals per subsample. RESULTS: higher species richness and density were observed at the N station (nearby the net cages) compared to the F station (distant from the net cages). With few exceptions, Rotifer species did not exhibit typical vertical migration patterns, concentrating at bottom depths during daytime and at intermediate depths during nighttime. Brachionus dolabratus and Hexarthra mira were the only species to show reverse vertical migration at the N station, in opposition to patterns of the cyclopoid copepod Termocyclops crassus. Furthermore, vertical migration patterns were not clear for Cladocera and Copepoda species nearby the net cages, but were rather clear at the F station. CONCLUSIONS: the presence of fish net cages increased zooplankton species richness (mostly rotifers) and density. Vertical movements were more pronounced at sites distant from net cages, suggesting that the increased food availability reduced the need for the typical vertical movements during daytime at sites nearby the net cages.

Glécia Trinta de Paula, Freitas; Maria Cristina, Crispim; Hênio do Nascimento de, Melo Júnior.

2012-06-01

29

Vertical migration and positioning behavior of copepods in a mangrove estuary: Interactions between tidal, diel light and lunar cycles  

Science.gov (United States)

Two-hourly zooplankton samplings encompassing tidal (semi-diurnal), diel (24 h), and lunar (4 phases) cycles during the dry (July 2003) and wet (November 2003) monsoon periods were conducted in the Matang estuary to investigate the vertical distribution and behavior of five different groups of copepods (estuarine, euryhaline, marine euryhaline, stenohaline and nocturnal pontellids) in response to the tidal and light regime. Diel vertical migration (DVM) was evident for all copepod groups but the observed patterns differed among species and sampling period (wet or dry and neap or spring tide). Tidally-induced vertical migration (TVM), superimposed by DVM, was observed for estuarine, marine euryhaline and stenohaline copepods but not for euryhaline and nocturnal pontellid copepods. Estuarine copepods tended to ascend during night-flood tide and descent to the bottom during day-ebb tide; this suggests a selective mechanism to penetrate upstream and maintain position in the estuary. In contrast, the marine euryhaline and stenohaline copepods remained at the bottom especially during day-flood tide and ascended into the water column during night-ebb tide; this suggests a selective mechanism to avoid upstream transport. Euryhaline copepods did not respond to tidal advection probably due to their wide range of salinity tolerance, while the large nocturnal pontellid copepods have strong swimming ability. Adaptive vertical migration appears to be a major factor structuring the copepod community in tropical estuaries, and its occurrence in most copepods suggests that neritic marine zooplankton tidally-advected into estuaries and nearshore waters can survive better than previously thought.

Chew, Li-Lee; Chong, Ving Ching; Ooi, Ai Lin; Sasekumar, A.

2015-01-01

30

Wave-equation interferometric migration of vertical seismic profile data  

Science.gov (United States)

Interferometric migration is a recently developed method that is proved to be a powerful imaging tool for vertical seismic profile (VSP) data. Synthetic and field data examples demonstrate that, it is robust to velocity estimation errors, and can sometimes produce reflectivity images much more accurate than standard migration methods. In this thesis, a wave-equation interferometric migration (WEIM) method is developed for three-dimensional (3-D) migration of VSP multiples. With WEIM, for each receiver gather of 3-D VSP data, only one 3-D receiver gather of travel times and one 3-D wavefield extrapolation need to be calculated for the migration of free-surface multiples. Compared to the expensive acquisition and processing costs of a 3-D surface seismic survey, the tremendous efficiency in obtaining a 3-D subsurface image volume by migration of 3-D VSP free-surface multiples suggests that a 3-D VSP survey might also serve as a cost effective four-dimensional monitoring tool for some oil fields. WEIM is also applied to image vertical subsurface structures. such as salt flanks which are difficult to image by conventional surface seismic surveys.

He, Ruiqing

31

Optimal foraging and diel vertical migration in a life history model  

DEFF Research Database (Denmark)

Zooplankton such as copepods are known to perform diel vertical migration, avoiding the food rich surface during bright hours to avoid visual predator when they are most dangerous, and returning to the surface to feed at night. The resolution of this foraging behaviour requires fine time scale in the model, unsuited for life history modeling. We propose a method based on optimal foraging theory to take into account the emergent feeding rates as a function of the copepod metabolic cost, latitude, time and predation. We predict that copepods will balance their growth rate and mortality, playing a safe strategy when food is plentiful, but taking greater risks at low food concentrations. We apply these concepts to high latitude ecosystems where there is a strong seasonal variation in both food availability and day length. Specifically, during the summer, the midnight sun will force the animals to take more risk and maintain some feeding at the surface to cover their nutritional needs, compensate for predationmortality and sustain their growth

Sainmont, Julie; Andersen, Ken Haste

32

Diet of Littoraria scabra, while vertically migrating on mangrove trees: Gut content, fatty acid, and stable isotope analyses  

Science.gov (United States)

The snail, Littoraria scabra, is a dominant grazer on tropical mangrove trees, and may play an important role in the food web dynamics of these ecosystems. Its daily vertical migration to avoid tidal submersion results in exposure to varying food types and abundances. A comprehensive diet analysis - gut contents, fatty acid profiles, and stable isotopes ( ?15N and ?13C) - was conducted on snails migrating along mangrove trees and snails maintained in non-tidal mesocosms at Nananu-i-ra, Fiji Islands. In addition, fatty acid profiles and stable isotope signatures were obtained from surface scrapings of mangrove roots, trunks, branches, and leaves. Results from this multi-technique study indicate that L. scabra is mainly a generalist herbivore, which easily shifts diets depending on food availability, and which also has the ability to ingest and assimilate zooplankton. Ingestion of greater quantities of diverse foods (i.e., microalgae, foliose/corticated macrophytes, filamentous algae, mangrove tissues, zooplankton) takes place in the bottom areas of mangrove trees (roots and trunks) during low tides, while top areas (branches and leaves) provide limited food resources for snails feeding during high tides. However, snails preferentially assimilate microalgae and bacteria, regardless of their feeding habitat (different areas within mangrove trees and non-tidal mesocosms). The daily vertical movements of this snail result in variable feeding times, ingestion of different food types and amounts, and different assimilations. These findings also suggest that organic matter derived from mangrove tissues may not be readily transferred to higher trophic levels through this grazing pathway.

Alfaro, Andrea C.

2008-09-01

33

Diel vertical migration arising in a habitat selection game  

DEFF Research Database (Denmark)

Predator and prey react to each other, adjusting their behavior to maximize their fitness and optimizing their food intake while keeping their predation risk as low as possible. In a pelagic environment, prey reduce their predation mortality by adopting a diel vertical migration (DVM) strategy, avoiding their predator during their peak performance by finding refuge in deep layers during daylight hours and feeding at the surface during the night. Due to the duality of the interaction between prey and predator, we used a game theory approach to investigate whether DVM can be a suitable strategy for the predator as well as the prey. We formulated three scenarios in plankton ecology in order to address this question. A novel finding is that mixed strategies emerge as optimal over a range of the parameter space, where part of the predator or prey population adopts a DVM while the rest adopt one or other "sit and wait" strategies

Sainmont, Julie; Thygesen, Uffe HØgsbro

2013-01-01

34

Effects of net cages on the vertical distribution of zooplankton in a semi-arid reservoir, northeastern Brazil Interferência de tanques-rede na distribuição vertical do zooplâncton num açude do semi-árido, nordeste do Brasil  

OpenAIRE

AIM: Carneiro reservoir is an aquatic environment used for net cage aquaculture activities, located in the semi-arid region of northeastern Brazil. Vertical distribution was evaluated in order to determine the effects of organic enrichment induced by aquaculture on zooplankton movements. METHODS: three replicate samples were collected during midday and midnight at each of three depths along the water column (i.e. surface: 0 m; middle: 2 m and bottom: 4 m) at two sites (near and far from the n...

Glécia Trinta de Paula Freitas; Maria Cristina Crispim; Hênio do Nascimento de Melo Júnior

2012-01-01

35

Exact solutions in a model of vertical gas migration  

Energy Technology Data Exchange (ETDEWEB)

This work is motivated by the growing interest in injectingcarbon dioxide into deep geological formations as a means of avoidingatmospheric emissions of carbon dioxide and consequent global warming.One of the key questions regarding the feasibility of this technology isthe potential rate of leakage out of the primary storage formation. Weseek exact solutions in a model of gas flow driven by a combination ofbuoyancy, viscous and capillary forces. Different combinations of theseforces and characteristic length scales of the processes lead todifferent time scaling and different types of solutions. In the case of athin, tight seal, where the impact of gravity is negligible relative tocapillary and viscous forces, a Ryzhik-type solution implies square-rootof time scaling of plume propagation velocity. In the general case, a gasplume has two stable zones, which can be described by travelling-wavesolutions. The theoretical maximum of the velocity of plume migrationprovides a conservative estimate for the time of vertical migration.Although the top of the plume has low gas saturation, it propagates witha velocity close to the theoretical maximum. The bottom of the plumeflows significantly more slowly at a higher gas saturation. Due to localheterogeneities, the plume can break into parts. Individual plumes alsocan coalesce and from larger plumes. The analytical results are appliedto studying carbon dioxide flow caused by leaks from deep geologicalformations used for CO2 storage. The results are also applicable formodeling flow of natural gas leaking from seasonal gas storage, or formodeling of secondary hydrocarbon migration.

Silin, Dmitriy B.; Patzek, Tad W.; Benson, Sally M.

2006-06-27

36

Utilization and documentation of vertical oil migration in deep basins  

Energy Technology Data Exchange (ETDEWEB)

Use of the model of a hot, deep, origin of oil places rigid constraits on the migration and entrapment of crude oil. Specifically, oil originating from depth migrates vertically up faults and is emplaced in traps at shallower depths. Review of petroleum-producing basins worldwide shows oil occurrence in these basins conforms to the restraints of this hypothesis. Most of the world's oil is found in the very deepest sedimentary basins, and production over or adjacent to the deep basin is cut by, or directly updip from, faults dipping into the basin deep. Generally, the greater the fault throw, the great the reserves. Fault-block highs next to deep sedimentary troughs are the best target areas by the present concept. Traps along major basin-forming faults are quite prospective. The structural style of a basin governs the distribution, types, and amounts of hydrocarbons expected, and hence the exploration strategy. Production in delta depocenters (Niger) is in structures cut by or updip from major growth faults, and structures not associated with such faults are barren. Production in block-fault basins is on horsts next to deep seimentary troughs (Sirte, North Sea). In basins whose sediment thickness, structure and geologic history are known to a moderate degree, the main oil occurrences can be specifically predicted by analysis of fault systems and possible hydrocarbon migration routes. Use of the concept permits the identification of significant targets which have either been downgraded or ignored in the past, such as production in or just updip from thrust belts, stratigraphic traps over the deep basin associated with major faulting, production over the basin deep, and regional stratigraphic trapping updip from established production along major fault zones. 18 figures, 6 tables.

Price, L.C.

1980-04-01

37

Importance des phénomènes de migration verticale des hydrocarbures Significance of Vertical Migration Phenomea of Hydrocarbons  

Directory of Open Access Journals (Sweden)

Full Text Available Cette publication a pour but de démonter les mécanismes de migration verticale des hydrocarbures et d'en analyser les conséquences, à partir d'exemples concrets choisis sur les domaines d'activité de la Société Nationale Elf Aquitaine (Production [SNEA (PJ. Les hydrocarbures, huile et gaz, rassemblés en phase individualisée évoluent dans un milieu poreux, fin, généralement mouillé à l'eau. Dans un tel environnement la migration suppose des pressions capillaires élevées. On démontre que cette condition se realise plus particulièrement sur Ies zones hautes fermées où les élements d'hydrocarbures expulses de la roche mère peuvent se rassembler en amas de taille importante, développant une forte poussee d'Archimède. De même le gaz, du fait de sa masse volumique faible par rapport à celle de l'eau, manifestera une grande aptitude à la migration verticale, ce qui conduira souvent à une redistribution verticale des hydrocarbures non conforme au schéma diagénétique classique : présence d'un gisement de gaz en surface et huile en profondeur. Combinés à l'effet Gussow, phénomène de refoulement de l'huile par le gaz hors de la fermeture critique d'une structure, les processus envisagés ici, où tes accidents tectoniques tiennent une place importante, aboutiront généralement à sil: aerer spatialement l'huile et le gaz. Ces transferts semblent s'accompagner fréquemment de modifications dans la composition chimique des huiles : augmentation des teneurs en soufre, en métaux traces, en hydrocarbures aromatiques, et alourdissement des huiles The purpose of this article is ta described the vertical migration mechanisms of hydrocarbons and to analyze their conséquences, on the basis of concrete examples selected in the fields of activities carried on by Société Nationale Elf Aquitaine (SNEA. When hydrocarbons (ai( and gas are gathered in a distinct phase, they evolve in a fine porous medium that is usually water wet. In such on environment, migration requires high capillary pressures. lt is shown that such conditions occur especially in high closed zones where the hydrocarbons driven out of the source rock con gather together in a large-sized mass, thus building up a high degree of buoyancy. In the same way, because gas has a louver specific gravity thon water, it has a great tendency ta migrote vertically, which often brings about a vertical redistribution of hydrocarbons that does not conform ta the conventional diagenetic pattern, i. e. the presence of a gas pool above a deeper ail pool.

Chiarelle A.

2006-11-01

38

Depth-selection patterns and diel vertical migration of Daphnia ambigua (Crustacea: Cladocera) in lake El Plateado / Patrones de selección de profundidad y migración vertical de Daphnia ambigua (Crustacea: Cladocera) en el lago El Plateado  

Scientific Electronic Library Online (English)

Full Text Available SciELO Chile | Language: English Abstract in spanish Los lagos templados y sub-tropicales a menudo presentan una marcada estructura vertical durante la estación cálida que involucra importantes diferencias espaciales de variables físicas, químicas y biológicas. El zooplancton se encuentra por ello expuesto a un ambiente marcadamente heterogéneo en su [...] dimensión vertical. En este trabajo analizamos la distribución vertical del cladócero D. ambigua en el lago eutrófico y monomíctico El Plateado, a mediodía y a medianoche, y su relación con la distribución vertical de la temperatura del agua y concentración de oxígeno disuelto. Intentamos también definir si esta población exhibe o no una conducta de migración vertical. Los resultados muestran cambios significativos en la distribución vertical día/noche de D. ambigua durante su periodo de crecimiento, con excepción de la última fecha. Los datos revelan también que la profundidad promedio seleccionada por D. ambigua disminuye en el tiempo, así como la amplitud de la migración vertical. Dentro del periodo de estratificación del lago, la temperatura aparece positivamente correlacionada y el oxígeno negativamente correlacionado con la frecuencia de D. ambigua. Se sugiere que la concentración de oxígeno juega un papel crucial en la modulación de la conducta de migración vertical de D. ambigua en el lago El Plateado, con importantes consecuencias para el entendimiento del patrón atípico de dinámica poblacional que presenta esta especie Abstract in english Eutrophic temperate and sub-tropical lakes often exhibit a marked vertical structure during the warm season that involves important spatial differences of physical, chemical and biological variables. Therefore, zooplankton is exposed to a highly heterogeneous environment in the vertical dimension. I [...] n this work, We analyze the depth-distribution of the cladoceran Daphnia ambigua in the eutrophic, monomictic lake El Plateado at midday and midnight, along with its relationship with the vertical distribution of water temperature and dissolved oxygen concentration. We also attempt to define whether or not this population exhibits a diel vertical migration. The results show significant changes in the day/night vertical distribution of D. ambigua during its growing season, with the exception of the last date. Also, the data revealed that average depth selected by D. ambigua becomes shallower with time, and the amplitude of the vertical migration decreases throughout the season. During the period of lake stratification, temperature appears positively correlated, and oxygen negatively correlated to the frequency of D. ambigua. It is suggested that oxygen concentration plays a crucial role in modulating the vertical migration behavior of D. ambigua in lake El Plateado, which has important consequences for understanding the atypical pattern of population dynamics exhibited by this species

RODRIGO, RAMOS-JILIBERTO; LUIS R., ZÚÑIGA.

2001-09-01

39

Potential acidification impacts on zooplankton in CCS leakage scenarios  

International Nuclear Information System (INIS)

Highlights: • Effects of CCS techniques and ocean acidification on zooplankton are under-studied. • Vulnerable zooplankton are meso-, bathypelagic and vertically migrating species. • Impacts include impaired calcification, reproduction, development and survival. • Need for modelling studies combining physico-chemical with ecological impacts. -- Abstract: Carbon capture and storage (CCS) technologies involve localized acidification of significant volumes of seawater, inhabited mainly by planktonic species. Knowledge on potential impacts of these techniques on the survival and physiology of zooplankton, and subsequent consequences for ecosystem health in targeted areas, is scarce. The recent literature has a focus on anthropogenic greenhouse gas emissions into the atmosphere, leading to enhanced absorption of CO2 by the oceans and a lowered seawater pH, termed ocean acidification. These studies explore the effects of changes in seawater chemistry, as predicted by climate models for the end of this century, on marine biota. Early studies have used unrealistically severe CO2/pH values in this context, but are relevant for CCS leakage scenarios. Little studied meso- and bathypelagic species of the deep sea may be especially vulnerable, as well as vertically migrating zooplankton, which require significant residence times at great depths as part of their life cycle

40

Horizontal distribution of Fukushima-derived radiocesium in zooplankton in the northwestern Pacific Ocean  

Directory of Open Access Journals (Sweden)

Full Text Available The magnitude of the 9.0 Tohoku earthquake and the ensuing tsunami on 11 March 2011, inflicted heavy damage on the Fukushima Dai-ichi nuclear power plant (FNPP1. Fission products were emitted, falling over a broad range in the northern hemisphere, and water contaminated with radionuclides leaked into the ocean. In this study, we described the horizontal distribution of the Fukushima-derived radiocesium in zooplankton and in seawater in the western North Pacific Ocean (500–2100 km from the FNPP1 10 months after the accident. 134Cs and 137Cs were detected in zooplankton and seawater from all the stations. Because of its short half-lives, 134Cs detected in our samples could only be derived from the FNPP1 accident. The highest 137Cs activity in zooplankton was same order of magnitude as that one month after the accident, and average activity was one or two orders of magnitude higher than 137Cs activities observed before the accident around Japan. Horizontally, the radiocesium activity concentrations in zooplankton were high at around 25° N while those in surface seawater were high at around the transition area between the Kuroshio and the Oyashio Currents (36–40° N. We observed subsurface radiocesium maxima in density range of the North Pacific Subtropical Mode Water and occurrence of many diel vertical migratory zooplanktons. These suggested that the high activity concentrations in the subtropical zooplankton at around 25° N were connected to the subsurface radiocesium and active vertical migration of zooplankton. However, the high activity concentrations of radiocesium in subsurface seawater did not necessarily follow the higher radiocesium activity in zooplankton. Biological characteristics of zooplankton community possibly influenced how large was contamination of radiocesium in the community but it is still unknown what kind of biological factors were important.

M. Kitamura

2013-04-01

41

Reproducing {sup 137}Cs vertical migration in Spanish soils - Reproducing {sup 137}Cs and {sup 90}Sr vertical migration in Spanish mainland  

Energy Technology Data Exchange (ETDEWEB)

As a result of caesium's and strontium's activity migration study developed in Spanish mainland soils, there has been obtained convective - diffusive migration equation that will reproduce adequately the movement that an activity deposit would follow in this land. Taking into account the dependence on rain that apparent convection velocity shows, it has been defined a new migration parameter that depends only on soil's properties. By means of a least square method and fitting the migration equation to experimental activity profiles, the values showed by the migration parameters in the studied soils, characteristics of that area, have been obtained. After that, there have been obtained the mean values of these parameters for each defined group that, depending on soil's texture, have been observed in the study performed about the movement of both radionuclides in soils and to whom these soils belong. Using these mean values and obtained equation, it has been properly reproduce those vertical activity profiles that were experimentally determined. In order to validate these values, a new sampling programme is carrying out in the north of Spain and, with obtained new sampling points' information, is going to verify if, indeed, obtained mean values also reproduce these new sampling points' activity vertical profile. (authors)

Olondo, C.; Legarda, F.; Herranz, M.; Idoeta, R. [The University of the Basque Country - UPV/EHU, Nuclear Engineering and Fluid Mechanics Dept. Faculty of Engineering, Alda. Urquijo 48013, Bilbao (Spain)

2014-07-01

42

Size distribution of particles and zooplankton across the shelf-basin system in southeast Beaufort Sea: combined results from an Underwater Vision Profiler and vertical net tows  

Science.gov (United States)

The size distribution and mean spatial trends of large particles (>100 ?m, in equivalent spherical diameter, ESD) and mesozooplankton were investigated across the Mackenzie Shelf (southeast Beaufort Sea, Arctic Ocean) in July-August 2009. Our main objective was to combine results from an Underwater Vision Profiler 5 (UVP5) and traditional net tows (200 ?m mesh size) to characterize the structural diversity and functioning of the Arctic shelf-basin ecosystem and to assess the large-scale correspondence between the two methodological approaches. The core dataset comprised 154 UVP5 profiles and 29 net tows conducted in the shelf (isobath), slope (100-1000 m) and basin (>1000 m) regions of the study area. The mean abundance of total particles and zooplankton in the upper water column (50 %) when progressing offshore and as the ESD of particles was increasing. Both the UVP5 and net tows determined that copepods dominated the zooplankton community (~78-94 % by numbers) and that appendicularians were generally the second most abundant group (~1-11 %). The vertical distribution patterns of copepods and appendicularians indicated a close association between primary production and the main grazers. Manual taxonomic counts and ZooScan image analyses shed further light on the size-structure and composition of the copepod community - which was dominated at ~95 % by a guild of 10 typical taxa. The size distributions of copepods, as evaluated with the 3 methods (manual counts, ZooScan and UVP5), showed consistent patterns co-varying in the same order of magnitude over the upper size range (>1 mm ESD). Copepods 1 mm ESD. Our results illustrate that the combination of traditional sampling methods and automated imaging techniques is a powerful approach that enabled us to conclude on the prevalence of a relatively high productivity regime and dominant herbivorous food web over the shelf when compared with the low-productive recycling system detected offshore.

Forest, A.; Stemmann, L.; Picheral, M.; Burdorf, L.; Robert, D.; Fortier, L.; Babin, M.

2012-04-01

43

Size distribution of particles and zooplankton across the shelf-basin system in southeast Beaufort Sea: combined results from an Underwater Vision Profiler and vertical net tows  

Directory of Open Access Journals (Sweden)

Full Text Available The size distribution and mean spatial trends of large particles (>100 ?m, in equivalent spherical diameter, ESD and mesozooplankton were investigated across the Mackenzie Shelf (southeast Beaufort Sea, Arctic Ocean in July–August 2009. Our main objective was to combine results from an Underwater Vision Profiler 5 (UVP5 and traditional net tows (200 ?m mesh size to characterize the structural diversity and functioning of the Arctic shelf-basin ecosystem and to assess the large-scale correspondence between the two methodological approaches. The core dataset comprised 154 UVP5 profiles and 29 net tows conducted in the shelf (<100 m isobath, slope (100–1000 m and basin (>1000 m regions of the study area. The mean abundance of total particles and zooplankton in the upper water column (<75 m depth declined exponentially with increasing distance from shore. Vertical and latitudinal patterns in total particle concentration followed those of chlorophyll a (chl a concentration, with maximum values between 30 and 70 m depth. Based on the size-spectra derived from the UVP5 dataset, living organisms (0.1–10 mm ESD accounted for an increasingly large proportion of total particle abundance (from 0.1 % to >50 % when progressing offshore and as the ESD of particles was increasing. Both the UVP5 and net tows determined that copepods dominated the zooplankton community (~78–94 % by numbers and that appendicularians were generally the second most abundant group (~1–11 %. The vertical distribution patterns of copepods and appendicularians indicated a close association between primary production and the main grazers. Manual taxonomic counts and ZooScan image analyses shed further light on the size-structure and composition of the copepod community – which was dominated at ~95 % by a guild of 10 typical taxa. The size distributions of copepods, as evaluated with the 3 methods (manual counts, ZooScan and UVP5, showed consistent patterns co-varying in the same order of magnitude over the upper size range (>1 mm ESD. Copepods <1 mm were not well quantified by the UVP5, which estimated that only ~13–25 % of the assemblage was composed of copepods <1 mm ESD compared with ~77–89 % from the net tow estimates. However, the biovolume of copepods was overwhelmingly dominated (~93–97 % by copepods >1 mm ESD. Our results illustrate that the combination of traditional sampling methods and automated imaging techniques is a powerful approach that enabled us to conclude on the prevalence of a relatively high productivity regime and dominant herbivorous food web over the shelf when compared with the low-productive recycling system detected offshore.

A. Forest

2012-04-01

44

Size distribution of particles and zooplankton across the shelf-basin system in Southeast Beaufort Sea: combined results from an Underwater Vision Profiler and vertical net tows  

Directory of Open Access Journals (Sweden)

Full Text Available The size distribution and mean spatial trends of large particles (>100 ?m, in equivalent spherical diameter, ESD and mesozooplankton were investigated across the Mackenzie Shelf (Southeast Beaufort Sea, Arctic Ocean in July–August 2009. Our main objective was to combine results from an Underwater Vision Profiler 5 (UVP5 and traditional net tows (200 ?m mesh size to characterize the structural diversity and functioning of the Arctic shelf-basin ecosystem and to assess the large-scale correspondence between the two methodological approaches. The core dataset comprised 154 UVP5 profiles and 29 net tows conducted in the shelf (<100 m isobath, slope (100–1000 m and basin (>1000 m regions of the study area. The mean abundance of total particles and zooplankton in the upper water column (<75 m depth declined exponentially with increasing distance from shore. Vertical and latitudinal patterns in total particle concentration followed those of chlorophyll-a (chl-a concentration, with maximum values between 30 and 70 m depth. Based on the size-spectra derived from the UVP5 dataset, living organisms (0.1–10 mm ESD accounted for an increasingly large proportion of total particle abundance (from 0.1% to > 50 % when progressing offshore and as the ESD of particles was increasing. Both the UVP5 and net tows determined that copepods dominated the zooplankton community (~78–94 % by numbers and that appendicularians were generally the second most abundant group (~1–11 %. The vertical distribution patterns of copepods and appendicularians indicated a close association between primary production and the main grazers. Manual taxonomic counts and ZooScan image analyses shed further light on the size-structure and composition of the copepod community – which was dominated at ~95 % by a guild of 10 typical taxa. The size distributions of copepods, as evaluated with the 3 methods (manual counts, ZooScan and UVP5, showed consistent patterns co-varying in the same order of magnitude over the upper size range (>1 mm ESD. Copepods < 1 mm were not well quantified by the UVP5, which estimated that only ~13–25 % of the assemblage was composed of copepods < 1 mm ESD compared with ~77–89 % from the net tow estimates. However, the biovolume of copepods was overwhelmingly dominated (~93–97 % by copepods >1 mm ESD. Our results illustrate that the combination of traditional sampling methods and automated imaging techniques is a powerful approach that enabled us to conclude on the prevalence of a relatively high productivity regime and dominant herbivorous food web over the shelf when compared with the low-productive recycling system detected offshore.

A. Forest

2011-11-01

45

INFLUENCE OF CLASTIC DIKES ON VERTICAL MIGRATION OF CONTAMINANTS IN THE VADOSE ZONE AT HANFORD  

Science.gov (United States)

This research will test the hypothesis that clastic dikes at the Hanford Site provide preferential pathways that enhance the vertical movement of moisture and contaminants through the vadose zone. Studies indicate that contaminants have migrated to greater depths at the Hanford ...

46

Control of turbulent flow in vertical slot fishways for the migration of small fish species  

OpenAIRE

The improvement of devices that allow the upstream migration of fishes through engineering constructions or natural obstructions in rivers is now a real priority to maintain the biodiversity. Vertical slot fishways are commonly used and are very effective in ensuring unhindered passage of the species of large size fishes.

David, Laurent; Wang, Ruey-wen; Chambon, Franc?ois-marie; Texier, Alain; Larinier, Michel; Baran, Philippe

2009-01-01

47

Exploring Physical and Biological Mechanisms for Zooplankton Retention in the Estuarine Transition Zone of a Riverine Estuary  

Science.gov (United States)

In this study, we use a coupled three-dimensional physical-biological model to investigate zooplankton retention in the estuarine transition zone (ETZ) of the St. Lawrence Estuary (SLE). Varying from well-mixed to partially stratified, the hydrodynamic environment of the SLE is defined by a large tidal range, strong salinity gradients, a large freshwater river flow, and complex bathymetry. The physical-biological model used for this study consisted of two parts: a circulation model and a zooplankton transport model. The circulation model is a three-dimensional Eulerian hydrodynamic model (TRIM3D) driven by the wind, tides, and freshwater outflow. The zooplankton transport model is a three-dimensional Lagrangian particle tracking model which simulates zooplankton movement using velocity fields derived from the three-dimensional circulation model. The circulation model is calibrated using field data such as salinity, pressure, and current time series from different locations in the ETZ. The transport and distribution of three zooplankton taxa, non-native zebra mussel veligers, resident mysids, and larval smelt, were simulated for this study. By simulating these three taxa, we were able to investigate the effect of a range of swimming speeds on zooplankton retention in the ETZ. We present the results of simulations exploring the efficiency of tidal vertical migration, a commonly described biological retention mechanism that is characterized by zooplankton migration up to the surface on flood and down to the bottom on ebb. Tidal vertical migration, also known as selective tidal stream transport, was investigated for several swimming speeds and endogenous rhythms.

Simons, R. D.; Monismith, S. G.

2002-12-01

48

Computer Simulation of Larval Transport Through Tidal Channels: Role of Vertical Migration  

Science.gov (United States)

A two-dimensional computer model is used to investigate the long-term net advective transport of larvae in tidal channels. Simulations are made over l-year time periods for Adderley Channel in the Exuma Cays of the Bahama Islands, and Aransas Pass on the Texas Gulf coast. Tidal conditions at these two locations are dominated by semi-diurnal and diurnal constituents, respectively. Larval transport is simulated by the product of the predicted tidal current and the larval concentration in each of five layers. The vertical distribution of larvae is a function of vertical migration, which acts to concentrate larvae in top and bottom layers, and turbulent diffusion, which tends to produce vertically uniform concentrations. The effect of turbulent mixing is inversely related to the vertical swimming ability of the larvae and reduces substantially the net transport of slower swimmers. Both light and tidal phase cued migrations are considered. Diel migration results in a distinct annual cycle in the transport of larvae, as diurnal tidal constituents cycle in and out of phase with light and dark conditions. However, little long-term net transport is indicated. Migration according to tidal phase produces a negligible annual cycle, but a substantial quasi-steady net transport of larvae is indicated for both study sites. In other simulations, non-tidal currents are introduced to represent freshwater outflow and low-frequency estuarine-shelf exchanges, and unspecified retention mechanisms are incorporated into the model. For these study sites, both non-tidal transport and larval retention dominate the effect of vertical migration.

Smith, Ned P.; Stoner, Allan W.

1993-07-01

49

Zooplankton in the eastern tropical north Pacific: Boundary effects of oxygen minimum zone expansion  

Science.gov (United States)

Oxygen minimum zones (OMZs) may be expanding in their worldwide spatial and vertical extent as a result of global climate change. Here, we highlight structural and functional features of pelagic OMZ zooplankton communities, especially the little known mesopelagic lower oxycline zooplankton assemblage in the eastern tropical north Pacific (ETNP). Day and night vertically-stratified zooplankton samples were collected with a MOCNESS plankton net system to depths of 1000 m during two cruises in 2007 and 2008 as part of the Eastern Tropical Pacific Project. Size-fractionated biomass and selected species distributions were analyzed. A spatial comparison between two stations, Tehuantepec Bowl (TB) and Costa Rica Dome (CRD), with different OMZ thicknesses especially in 2008, was used as a proxy for future potential climate change to show how variability in oxycline depth at the upper and lower OMZ boundaries may have broad consequences for biological distributions and ecosystem function. The same zooplankton biomass features were present at both locations but responded differently to changes in OMZ thickness and boundary depths. The impact of habitat compression was quantified by the change in proportion of zooplankton biomass in the upper water column. The thermocline was the location of peak zooplankton biomass regardless of OMZ extent. At the lower oxycline, a unique zooplankton assemblage and secondary biomass peak (sharp order of magnitude jump from OMZ core biomass levels) occurred that was strongly associated with a specific oxygen concentration of 2 ?M. In 2008, the lower oxycline biomass peak deepened by over 200 m at TB with its expanded OMZ compared to CRD, despite a temperature difference of ?2 °C, while remaining at the same oxygen level. In contrast, another secondary biomass peak corresponding to the daytime depth of diel vertical migration, and occurring within the upper oxycline or OMZ core, was present at the same depth and temperature at both locations, despite different oxygen concentrations. A dense monospecific layer of the copepod Eucalanus inermis was sometimes present just above the distinctive more persistent lower oxycline assemblage. While the general ontogenetic migration of this species was previously known, its precise positioning relative to oxygen concentration and the lower oxycline community is a new finding. The vertical re-positioning of biomass layers at the thermocline and lower OMZ boundaries, and the increased depth range of low oxygen water that diel vertical migrators and sinking particles must transit in an expanded OMZ, could have widespread effects on species distributions, the biological pump, and benthic-pelagic coupling.

Wishner, Karen F.; Outram, Dawn M.; Seibel, Brad A.; Daly, Kendra L.; Williams, Rebecca L.

2013-09-01

50

Vertical migration during tidal transport of megalopae of Necora puber in coastal shallow waters during daytime  

Science.gov (United States)

For meroplanktonic larvae that must settle in coastal areas, their successful return to the shore is determined largely by physical transport processes; however, many organisms perform vertical movements to aid successful recruitment. In this study, daytime tidal vertical migration of megalopae of the velvet swimming crab Necora puber was investigated across two different exposures in the shallow waters of Plymouth Sound. Crabs were collected using a plankton net at the surface and near the bottom during flood and ebb tides. Distribution of the pelagic postlarvae was patchy and the abundance varied spatially in tens and thousands of metres. In temporal scales, the annual pattern was dominated by low occurrence of megalopae, punctuated by episodic peaks of high abundance. Most megalopae were collected at the surface irrespective of the tidal phase. The effect of wave exposure on the vertical migration of megalopae was not clear, although there was a general higher abundance of megalopae on exposed shores. Daytime abundance in the water column appears to be regulated by the tidal cycle, as megalopae were more abundant during flood than ebb tides. Although the megalopae do not appear to make large vertical migrations, this behaviour should produce a net shoreward transport.

Lee, James T.; Coleman, Ross A.; Jones, Malcolm B.

2005-11-01

51

Dynamic patterns of zooplankton transport and migration in Catuama Inlet (Pernambuco, Brazil), with emphasis on the decapod crustacean larvae / Patrones dinámicos de transporte y migración de zooplancton en el estuario Catuama (Pernambuco, Brasil), con énfasis en las larvas de crustáceos decápodos  

Scientific Electronic Library Online (English)

Full Text Available SciELO Chile | Language: English Abstract in spanish Esta investigación tiene como objetivo cuantificar y modelar el transporte de zooplancton, con énfasis en las larvas de Crustacea Decapoda. El muestreo se realizó a tres profundidades con una bomba de plancton acoplada a una red con malla de 300 /¿m. Se obtuvieron los datos de corrientes con un ADCP [...] . Los datos mostraron la existencia de campos de corrientes y de transporte vertical y horizontal heterogéneos. Se identificaron 27 grupos de Decapoda (larvas de Sergestidae, Porcellanidae, Upogebiidae, Caridea, Brachyura). La mayoría de las especies y fases larvales mostraron patrones de migración vertical característicos, en fase con los ciclos de la marea diurnos, favoreciendo la retención o exportación del estuario. Abstract in english The objective of this study was to quantify and to model zooplankton transport with emphasis on decapod crustacean larvae. Sampling was carried out at three depths with a plankton pump coupled to a 300-/¿m mesh. Current data were obtained with an ADCP. Our data showed the existence of vertically and [...] horizontally heterogeneous current and transport fields. We identified 27 groups of Decapoda (larvae of Sergestidae, Porcellanidae, Upogebiidae, Cari dea, Brachyura). Most of the species and larval phases showed characteristic vertical migration patterns, in phase with the diurnal tidal cycles, thus enhancing retention or export from the estuary.

Ralf, Schwamborn; Mauro de Meló, Júnior; Sigrid Neumann, Leitão; Werner, Ekau; Maryse Nogueira, Paranaguá.

52

Dynamic patterns of zooplankton transport and migration in Catuama Inlet (Pernambuco, Brazil, with emphasis on the decapod crustacean larvae Patrones dinámicos de transporte y migración de zooplancton en el estuario Catuama (Pernambuco, Brasil, con énfasis en las larvas de crustáceos decápodos  

Directory of Open Access Journals (Sweden)

Full Text Available The objective of this study was to quantify and to model zooplankton transport with emphasis on decapod crustacean larvae. Sampling was carried out at three depths with a plankton pump coupled to a 300-/¿m mesh. Current data were obtained with an ADCP. Our data showed the existence of vertically and horizontally heterogeneous current and transport fields. We identified 27 groups of Decapoda (larvae of Sergestidae, Porcellanidae, Upogebiidae, Cari dea, Brachyura. Most of the species and larval phases showed characteristic vertical migration patterns, in phase with the diurnal tidal cycles, thus enhancing retention or export from the estuary.Esta investigación tiene como objetivo cuantificar y modelar el transporte de zooplancton, con énfasis en las larvas de Crustacea Decapoda. El muestreo se realizó a tres profundidades con una bomba de plancton acoplada a una red con malla de 300 /¿m. Se obtuvieron los datos de corrientes con un ADCP. Los datos mostraron la existencia de campos de corrientes y de transporte vertical y horizontal heterogéneos. Se identificaron 27 grupos de Decapoda (larvas de Sergestidae, Porcellanidae, Upogebiidae, Caridea, Brachyura. La mayoría de las especies y fases larvales mostraron patrones de migración vertical característicos, en fase con los ciclos de la marea diurnos, favoreciendo la retención o exportación del estuario.

Ralf Schwamborn

2008-01-01

53

Diel vertical migrations of age 0+ percids in a shallow, well-mixed reservoir  

OpenAIRE

The distribution of age 0+ percids (perch, Perca fluviatilis and pikeperch, Sander lucioperca) was investigated in a shallow, wellmixed reservoir during a 24-h period in late May, using acoustic and netting methods. Diel vertical migrations (DVMs) were acoustically recorded between the layers close to the bottom and the whole water column. The netting data showed a high abundance of larvae and juveniles at night (nearly 1 ind m-3, or 6 ind m-2), whereas negligible numbers of age 0+ percids we...

Sed?a, Jaromi?r; Macha?c?ek, Jir?i?; Peterka, Jir?i?; Mate?na, Josef; Hejzlar, Josef; Kubec?ka, Jan; Vas?ek, Mojmi?r; Kratochvi?l, Michal; C?ech, Martin

2010-01-01

54

Vertical migration, nitrate uptake and denitrification: survival mechanisms of foraminifers (Globobulimina turgida) in low oxygen conditions  

OpenAIRE

15NO3? isotope labelling experiments were performed to investigate foraminiferal nitrate uptake strategies and the role of pseudopodial networks in nitrate uptake. Globobulimina turgida were placed below the nitrate penetration depth in homogenized sediment cores incubated in artificial seawater containing 15NO3?. A nylon net prevented the vertical migration of foraminifera to strata containing nitrate and oxygen, but allowed potential access to such strata by extension of pseudopods. No ...

Koho, K. A.; Pin?a-ochoa, E.; Geslin, E.; Risgaard-petersen, N.

2011-01-01

55

Vertical Distribution of Daily Migrating Mesopelagic Fish in Respect to Nocturnal Lights  

KAUST Repository

The nighttime distribution of vertically migrating mesopelagic fish in relation to nocturnal light was studied during a circumglobal survey, in the Red Sea, and in a fjord at high latitude. The study was based on data derived from ship borne echo sounders (circumglobal and the Red Sea) as well as using upward looking echo sounders mounted on the bottom (Masfjorden, Norway). We also applied a numerical model for analyzing diel vertical migration patterns. The effect of the lunar cycle was the focus in studies at low latitudes, while seasonal changes in nocturnal light climate was in focus at high latitude. Lunar phase significantly affected the distribution of mesopelagic fish at the global scale and in the Red Sea. During nights near full moon, scattering layers of mesopelagic fish distributed deeper than during darker phases of the moon. At high latitude, mesopelagic fish switched its behavior along with seasonal changes in nocturnal lights. In autumn, the population of the studied fish (Maurolicus mueleri) formed separated layers. Juveniles performed normal diel vertical migration followed by midnight sinking, with midnight sinking mainly related to temperature minima and also for avoiding predators. Meanwhile the adults did not migrate vertically, reducing foraging but increasing the adult survival. From late winter to mid-Spring, interrupted ascents behavior was noted in the afternoon. Predator avoidance, satiation, and finding temperature optimum might be the reason behind interrupted ascents. At lighter nights in mid-summer, M. muelleri took on schooling behavior, likely as an anti-predator behavior permitting access to the upper waters in the absence of darkness.

Prihartato, Perdana

2014-12-01

56

Migration of 85Sr and 137Cs in vertical soil profiles  

International Nuclear Information System (INIS)

Vertical distribution of Sr-85 and Cs-137 in undisturbed single-contaminated agricultural soils was studied in laboratory conditions during their irrigation with wet atmospheric precipitation in dependence on time for about one year. The soil samples were collected from several sites in the surroundings of the Dukovany and Jaslovske Bohunice nuclear power plants using a special auger. The samples were placed into polyethylene columns. The activity of radionuclides in the soil profiles after their separation into single layers was determined with a Ge(Li) semiconductor gamma spectrometer. Based on the exponential depth distribution of radionuclides, the values of their migration parameters as such the relaxation depth, migration rate and retardation factor were calculated. The effect of the permanent grass cover and of zeolite on the migration parameters of the two radionuclides was also investigated

57

Numerical simulations of tidally cued vertical migrations of flatfish larvae in the North Sea  

Science.gov (United States)

A coupled Eulerian-Lagrangian Hybrid Ecological Model was applied to model the transport of flatfish larvae at different scenarios of tidally cued activity. Hydrodynamic data were supplied by a two-dimensional hydrodynamic model of the southern North Sea and were used as input in a Lagrangian particle model in which the flatfish larvae were represented by particles, which responded differently to tidal cues—in this case, hydrostatic pressure. It was used to investigate the interference of vertical migration, in phase with the tidal rhythm, with the specific circulation pattern of the North Sea, by comparison with passive particle advection and diffusion. Instead of what was anticipated after tests in a simple one-dimensional tidal flow, the horizontal advection was not increased, which would allow a greater distance between spawning ground and nursery area. Rather, tidally cued vertical migration turns the direction of transport towards the nearest coast in the North Sea. This is caused by the phase difference between the onshore component of the water velocity and the along-shore component in this area. Tidally cued vertical migration would also be a very efficient mechanism to enter the Wadden Sea through a tidal inlet. The application of the present model looks promising but needs fine-tuning and calibration with real larval distributions and behaviour during the transport phase.

de Graaf, M.; Jager, Z.; Vreugdenhil, C. B.; Elorche, M.

2004-02-01

58

Vertical distribution, migration rates, and model comparison of actinium in a semi-arid environment.  

Science.gov (United States)

Vertical soil characterization and migration of radionuclides were investigated at four radioactively contaminated sites on Kirtland Air Force Base (KAFB), New Mexico to determine the vertical downward migration of radionuclides in a semi-arid environment. The surface soils (0-15 cm) were intentionally contaminated with Brazilian sludge (containing (232)Thorium and other radionuclides) approximately 40 years ago, in order to simulate the conditions resulting from a nuclear weapons accident. Site grading consisted of manually raking or machine disking the sludge. The majority of the radioactivity was found in the top 15 cm of soil, with retention ranging from 69 to 88%. Two models, a compartment diffusion model and leach rate model, were evaluated to determine their capabilities and limitations in predicting radionuclide behavior. The migration rates of actinium were calculated with the diffusion compartment and the leach rate models for all sites, and ranged from 0.009 to 0.1 cm/yr increasing with depth. The migration rates calculated with the leach rate models were similar to those using the diffusion compartment model and did not increase with depth (0.045-0.076, 0.0 cm/yr). The research found that the physical and chemical properties governing transport processes of water and solutes in soil provide a valid radionuclide transport model. The evaluation also showed that the physical model has fewer limitations and may be more applicable to this environment. PMID:16243414

McClellan, Y; August, R A; Gosz, J R; Gann, S; Parmenter, R R; Windsor, M

2006-01-01

59

Vertical distribution, migration rates, and model comparison of actinium in a semi-arid environment  

Energy Technology Data Exchange (ETDEWEB)

Vertical soil characterization and migration of radionuclides were investigated at four radioactively contaminated sites on Kirtland Air Force Base (KAFB), New Mexico to determine the vertical downward migration of radionuclides in a semi-arid environment. The surface soils (0-15 cm) were intentionally contaminated with Brazilian sludge (containing {sup 232}Thorium and other radionuclides) approximately 40 years ago, in order to simulate the conditions resulting from a nuclear weapons accident. Site grading consisted of manually raking or machine disking the sludge. The majority of the radioactivity was found in the top 15 cm of soil, with retention ranging from 69 to 88%. Two models, a compartment diffusion model and leach rate model, were evaluated to determine their capabilities and limitations in predicting radionuclide behavior. The migration rates of actinium were calculated with the diffusion compartment and the leach rate models for all sites, and ranged from 0.009 to 0.1 cm/yr increasing with depth. The migration rates calculated with the leach rate models were similar to those using the diffusion compartment model and did not increase with depth (0.045-0.076, 0.0 cm/yr). The research found that the physical and chemical properties governing transport processes of water and solutes in soil provide a valid radionuclide transport model. The evaluation also showed that the physical model has fewer limitations and may be more applicable to this environment.

McClellan, Y. [Sandia National Laboratories, Mail Stop 0748, Albuquerque, NM 87185 (United States)]. E-mail: ymcclel@sandia.gov; August, R.A. [Naval Research Laboratory (NRL), Washington, DC 20375 (United States); Gosz, J.R. [University of New Mexico, Department of Biology, Albuquerque, NM 87131 (United States); Gann, S. [NRL S and T Reserve Unit, Chattanooga, TN 37406 (United States); Parmenter, R.R. [University of New Mexico, Department of Biology, Albuquerque, NM 87131 (United States); Windsor, M. [NRL S and T Reserve Unit, Chattanooga, TN 37406 (United States)

2006-07-01

60

Vertical distribution, migration rates, and model comparison of actinium in a semi-arid environment  

International Nuclear Information System (INIS)

Vertical soil characterization and migration of radionuclides were investigated at four radioactively contaminated sites on Kirtland Air Force Base (KAFB), New Mexico to determine the vertical downward migration of radionuclides in a semi-arid environment. The surface soils (0-15 cm) were intentionally contaminated with Brazilian sludge (containing 232Thorium and other radionuclides) approximately 40 years ago, in order to simulate the conditions resulting from a nuclear weapons accident. Site grading consisted of manually raking or machine disking the sludge. The majority of the radioactivity was found in the top 15 cm of soil, with retention ranging from 69 to 88%. Two models, a compartment diffusion model and leach rate model, were evaluated to determine their capabilities and limitations in predicting radionuclide behavior. The migration rates of actinium were calculated with the diffusion compartment and the leach rate models for all sites, and ranged from 0.009 to 0.1 cm/yr increasing with depth. The migration rates calculated with the leach rate models were similar to those using the diffusion compartment model and did not increase with depth (0.045-0.076, 0.0 cm/yr). The research found that the physical and chemical properties governing transport processes of water and solutes in soil provide a valid radionuclide transport model. The evaluation also showed that the physical model has fewer limitations and may be more applicable to this environmenty be more applicable to this environment

61

UV B-induced vertical migrations of cyanobacteria in a microbial mat  

International Nuclear Information System (INIS)

Exposure to moderate doses of UV B (0.35 to 0.79 W m-2 s-1 or 0.98 to 2.2 ?mol of photons m-2 s-1 at 310 nm) caused the surface layers of microbial mats from Solar Lake, Sinai, Egypt, to become visibly lighter green. Concurrent with the color change were rapid and dramatic reductions in gross photosynthesis and in the resultant high porewater oxygen concentrations in the surface layers of the mats. The depths at which both maximum gross photosynthesis and maximum oxygen concentrations occurred were displaced downward. In contrast, gross photosynthesis in the deeper layers of the mats increased in response to UV B incident upon the surface. The cessation of exposure to UV B partially reversed all of these changes. Taken together, these responses suggest that photoautotrophic members of the mat community, most likely the dominant cyanobacterium Microcoleus chthonoplastes, were migrating in response to the added UV B. The migration phenomenon was also observed in response to increases in visible radiation and UV A, but UV B was ca. 100-fold more effective than visible radiation and ca. 20-fold more effective than UV A in provoking the response. Migrating microorganisms within this mat are apparently able to sense UV B directly and respond behaviorally to limit their exposure to UV. Because of strong vertical gradients of light and dissolved substances in microbial mats, the migration and the resultant vertical redistribution od the resultant vertical redistribution of photosynthetic activity have important consequences for both the photobiology of the cyanobacteria and the net primary productivity of the mat ecosystem

62

Vertical distribution and diel vertical migration of krill beneath snow-covered ice and in ice-free waters.  

Science.gov (United States)

A bottom mounted upward looking Simrad EK60 120-kHz echo sounder was used to study scattering layers (SLs) and individuals of the krill Meganyctiphanes norvegica. The mooring was situated at 150-m depth in the Oslofjord, connected with an onshore cable for power and transmission of digitized data. Records spanned 5 months from late autumn to spring. A current meter and CTD was associated with the acoustic mooring and a shore-based webcam monitored ice conditions in the fjord. The continuous measurements were supplemented with intermittent krill sampling campaigns and their physical and biological environment. The krill carried out diel vertical migration (DVM) throughout the winter, regardless of the distribution of potential prey. The fjord froze over in mid-winter and the daytime distribution of a mid-water SL of krill immediately became shallower associated with snow fall after freezing, likely related to reduction of light intensities. Still, a fraction of the population always descended all the way to the bottom, so that the krill population by day seemed to inhabit waters with light levels spanning up to six orders of magnitude. Deep-living krill ascended in synchrony with the rest of the population in the afternoon, but individuals consistently reappeared in near-bottom waters already <1 h after the ascent. Thereafter, the krill appeared to undertake asynchronous migrations, with some krill always being present in near-bottom waters even though the entire population appeared to undertake DVM. PMID:24616550

Vestheim, Hege; Røstad, Anders; Klevjer, Thor A; Solberg, Ingrid; Kaartvedt, Stein

2014-03-01

63

Proximate control of diel vertical migration in Phyllosoma larvae of the Caribbean spiny lobster Panulirus argus.  

Science.gov (United States)

Phyllosoma larvae of the spiny lobster Panulirus argus undergo diel vertical migration (DVM), in which they are at depth during the day and nearer the surface at night. This study determined the visual spectral sensitivity of Stage I larvae and investigated whether light plays a proximate role in DVM as an exogenous cue and as an entrainment cue for an endogenous rhythm in vertical migration. Under constant conditions, larvae have a circadian rhythm (24.5-h period) in vertical swimming that resulted in a twilight DVM pattern. The behavioral response spectrum and electroretinogram recording indicated two photoreceptor spectral classes with maxima at 360 and 486 nm. When stimulated in an apparatus that simulated the underwater angular light distribution, dark-adapted larvae showed only positive phototaxis, with a threshold intensity of 1.8 × 10(13) photons m(-2) s(-1) (3.0 × 10(-5) ?moles photons m(-2) s(-1)). They have an avoidance response to predator shadows in which they descend upon sudden decreases in light intensity of more than 69%. When stimulated with relative rates of decrease in light intensity as occur at sunset they ascended, whereas they descended upon relative rates of light intensity increase as occur at sunrise. Thus, the DVM pattern is controlled by both an endogenous circadian rhythm in swimming and behavioral responses to light at sunrise and sunset. PMID:21183442

Ziegler, Tracy A; Cohen, Jonathan H; Forward, Richard B

2010-12-01

64

On the lateral migration of a slightly deformed bubble rising near a vertical plane wall  

CERN Document Server

Deformation-induced lateral migration of a bubble slowly rising near a vertical plane wall in a stagnant liquid is numerically and theoretically investigated. In particular, our focus is set on a situation with a short clearance $c$ between the bubble interface and the wall. Motivated by the fact that numerically and experimentally measured migration velocities are considerably higher than the velocity estimated by the available analytical solution using the Fax\\'{e}n mirror image technique for $a/(a+c)\\ll 1$ (here $a$ is the bubble radius), when the clearance parameter $\\varepsilon(= c/a)$ is comparable to or smaller than unity, the numerical analysis based on the boundary-fitted finite-difference approach solving the Stokes equation is performed to complement the experiment. The migration velocity is found to be more affected by the high-order deformation modes with decreasing $\\varepsilon$. The numerical simulations are compared with a theoretical migration velocity obtained from a lubrication study of a n...

Sugiyama, Kazuyasu

2010-01-01

65

Bio-physical coupling in the formation of zooplankton and fish aggregations over abrupt topographies  

Science.gov (United States)

Aggregations of zooplankton, micronekton and fish are frequently observed above seamounts, canyons and shelf breaks. The aggregations are produced by five different mechanisms, all driven by ocean currents. Upwelling is frequently generated when ambient currents impinge on abrupt topographies. Nevertheless, upwelling enhances local production of zooplankton and fish only over large topographies such as shelf breaks, where the residence time of the upwelled water is sufficiently long to allow enrichment in primary production to propagate up the food web and augment the growth of resident animals. Daily accumulations occur over topographies at shallow and intermediate depths when the topography blocks the morning descent of migrating zooplankton. This mechanism is common over seamounts. Two other mechanisms are driven by behavioral response to vertical currents when zooplankton swims vertically in order to maintain depth: accumulations by depth retention against upwelling are common at depths to which migrating zooplankton descend during the day, while depth retention against downwelling seems to operate only in the upper water column (e.g., along topographically generated fronts). The fifth mechanism is driven by the amplification of currents over abrupt topographies. Strong currents enhance population growth of resident animals by augmenting fluxes of suspended food. A feed-rest hypothesis is proposed to explain how site-attached planktivorous fish can benefit from strong currents at sites with ample quiescence shelters in which the fish rest during non-feeding intervals. Four of the above mechanisms generate "trophic focusing", a process by which prey from immense volumes of flowing water is accumulated (or trapped) in a relatively small confined area. The ensuing subsidy of prey propagates up the food web, supporting aggregations of higher predators, such as fish, marine mammals and fishermen. Abrupt topographies can have an important role in determining trophic interactions in the marine realm.

Genin, Amatzia

2004-09-01

66

Generalization of some results of a vertical radionuclide migration study in soils of 30-km zone  

International Nuclear Information System (INIS)

Results of radionuclide distribution study in a vertical profile of soils are presented under different landscape geochemical conditions in 1989-1991. It is ascertained that radionuclide migration process in geochemical profile of soils of 30-km zone is in early stage of development. More than 90% of radioactivity concentrates in the upper 5-10 cm layer whereas measurable radioactivity fixes at a depth up to 1 m. The process of deepening of radioactivity reserve center takes place in the surface soil layer. Now it equals 1,5-3 cm. Peculiarities of the vertical radionuclide distribution haven't brightly pronounced character depending on soil types and are at the formation stage. 12 figs.; 2 tabs

67

Vertical distribution and diel vertical migration of krill beneath snow-covered ice and in ice-free waters  

KAUST Repository

A bottom mounted upward looking Simrad EK60 120-kHz echo sounder was used to study scattering layers (SLs) and individuals of the krill Meganyctiphanes norvegica. The mooring was situated at 150-m depth in the Oslofjord, connected with an onshore cable for power and transmission of digitized data. Records spanned 5 months from late autumn to spring. A current meter and CTD was associated with the acoustic mooring and a shore-based webcam monitored ice conditions in the fjord. The continuous measurements were supplemented with intermittent krill sampling campaigns and their physical and biological environment.The krill carried out diel vertical migration (DVM) throughout the winter, regardless of the distribution of potential prey. The fjord froze over in mid-winter and the daytime distribution of a mid-water SL of krill immediately became shallower associated with snow fall after freezing, likely related to reduction of light intensities. Still, a fraction of the population always descended all the way to the bottom, so that the krill population by day seemed to inhabit waters with light levels spanning up to six orders of magnitude. Deep-living krill ascended in synchrony with the rest of the population in the afternoon, but individuals consistently reappeared in near-bottom waters already? 1 h after the ascent. Thereafter, the krill appeared to undertake asynchronous migrations, with some krill always being present in near-bottom waters even though the entire population appeared to undertake DVM. The Author 2013. Published by Oxford University Press. All rights reserved.

Vestheim, Hege

2013-11-11

68

Zooplankton fecal pellets, marine snow, phytodetritus and the ocean's biological pump  

Science.gov (United States)

The 'biological pump' is the process by which photosynthetically-produced organic matter in the ocean descends from the surface layer to depth by a combination of sinking particles, advection or vertical mixing of dissolved organic matter, and transport by animals. Particulate organic matter that is exported downward from the euphotic zone is composed of combinations of fecal pellets from zooplankton and fish, organic aggregates known as 'marine snow' and phytodetritus from sinking phytoplankton. Previous reviews by Turner and Ferrante (1979) and Turner (2002) focused on publications that appeared through late 2001. Since that time, studies of the biological pump have continued, and there have been >300 papers on vertical export flux using sediment traps, large-volume filtration systems and other techniques from throughout the global ocean. This review will focus primarily on recent studies that have appeared since 2001. Major topics covered in this review are (1) an overview of the biological pump, and its efficiency and variability, and the role of dissolved organic carbon in the biological pump; (2) zooplankton fecal pellets, including the contribution of zooplankton fecal pellets to export flux, epipelagic retention of zooplankton fecal pellets due to zooplankton activities, zooplankton vertical migration and fecal pellet repackaging, microbial ecology of fecal pellets, sinking velocities of fecal pellets and aggregates, ballasting of sinking particles by mineral contents, phytoplankton cysts, intact cells and harmful algae toxins in fecal pellets, importance of fecal pellets from various types of zooplankton, and the role of zooplankton fecal pellets in picoplankton export; (3) marine snow, including the origins, abundance, and distributions of marine snow, particles and organisms associated with marine snow, consumption and fragmentation of marine snow by animals, pathogens associated with marine snow; (4) phytodetritus, including pulsed export of phytodetritus, phytodetritus from Phaeocystis spp., picoplankton in phytodetritus, the summer export pulse (SEP) of phytodetritus in the subtropical North Pacific, benthic community responses to phytodetritus; (5) other components of the biological pump, including fish fecal pellets and fish-mediated export, sinking carcasses of animals and macrophytes, feces from marine mammals, transparent exopolymer particles (TEP); (6) the biological pump and climate, including origins of the biological pump, the biological pump and glacial/interglacial cycles, the biological pump and contemporary climate variations, and the biological pump and anthropogenic climate change. The review concludes with potential future modifications in the biological pump due to climate change.

Turner, Jefferson T.

2015-01-01

69

Type I Planet Migration in a Magnetized Disk. II. Effect of Vertical Angular Momentum Transport  

CERN Document Server

We study the effects of a large-scale, ordered magnetic field in protoplanetary disks on Type I planet migration using a linear perturbation analysis in the ideal-MHD limit. We focus on wind-driving disks, in which a magnetic torque $\\propto B_{0z} \\partial B_{0\\varphi}/\\partial z$ (where $B_{0z}$ and $B_{0\\varphi}$ are the equilibrium vertical and azimuthal field components) induces vertical angular momentum transport. We derive the governing differential equation for the disk response and identify its resonances and turning points. For a disk containing a slightly subthermal, pure-$B_{0z}$ field, the total 3D torque is close to its value in the 2D limit but remains lower than the hydrodynamic torque. In contrast with the 2D pure-$B_{0\\varphi}$ field model considered by Terquem (2003), inward migration is not reduced in this case when the field amplitude decreases with radius. The presence of a subdominant $B_{0\\varphi}$ component whose amplitude increases from zero at $z=0$ has little effect on the torque w...

Bans, Alissa; Uribe, Ana

2015-01-01

70

Providing food for zooplankton in the aboratory  

International Nuclear Information System (INIS)

We are currently working in the laboratory with a species of zooplankton named Euphausiacea, but more commonly known as krill. This form of animal life is found abundantly in sea-water all over the world and serves as ideal food for numerous species of fish and cetaceans. Krill live in aggregates, often consisting of several thousand individuals, and migrate vertically each day; during the migration they feed, inter alia, on smaller crustaceans such as Copepoda. It is therefore highly instructive to study the part played by this form of animal life in the concentration and transport of radioactive substances in the sea. To make this possible, we have had to acclimatize the krill to laboratory conditions. In doing so many problems have been encountered, since it is a delicate creature and often difficult to keep alive. More specifically, one of our main worries has been to find food approximating as closely as possible the natural sustenance of Euphausiacea, food that is readily assimilable and relatively simple to procure. Artemia salina appeared to meet our requirements and we have begun rearing it on a mass scale

71

Zooplankton abundance, species composition and ecology of tropical high-mountain crater lake Wonchi, Ethiopia  

Directory of Open Access Journals (Sweden)

Full Text Available The highlands of Ethiopia represent some of the remnants of undisturbed aquatic ecosystems; they are however highly threatened by significant socio–economic developments and associated anthropogenic impacts. Lake Wonchi is one of the few remaining fairly pristine high–mountain crater lakes in the central highlands and has never been investigated in detail. We present a first study on zooplankton taxa composition, abundance and biomass conducted over more than one year including the underlying environmental drivers. The lake is basic (pH 7.9-8.9, dilute (specific conductivity 185-245 µS cm-1 and oligotrophic with mean trophic status index of 36. The zooplankton community composition showed low species richness comprising a total of fourteen taxa with six cladocerans, one copepod and seven rotifers. Simpson´s index of diversity with values between 0.6 and 0.8 pointed towards a homogenous taxa occurrence within the single sample units. The overall mean (±SD standing biomass of zooplankton was 62.02±25.76 mg dry mass m-3,which is low compared to other highland and rift valley lakes in Ethiopia. Cyclopoid copepods, in particular Thermocyclops ethiopiensis were the most abundant group and contributed 50% to the total zooplankton abundance followed by cladocerans (38% and rotifers (12%. Non-metric multi-dimensional scaling resulted in a 3-dimensional model, which revealed similar community composition on successive sampling dates except in December/January and May. Temperature, alkalinity, conductivity and nitrate-N had significant influence on this seasonal pattern. A weak, but significant positive correlation (r=0.482, N=20, P=0.037 between Chlorophyll a and zooplankton biomass mirrors a bottom-up effect of phytoplankton biomass on zooplankton dynamics. The zooplankton of Lake Wonchi displayed some degree of segregation along the epi– and metalimnion during this study, but diel vertical migration was not observed. The results show that fish predation is not the key factor in structuring the vertical distribution of zooplankton in Lake Wonchi.

Fasil Degefu

2014-02-01

72

Vertical Migration as a Driving Mechanism for Mud Diapirism in the Hordaland Group  

Energy Technology Data Exchange (ETDEWEB)

During the Late Palaeocene to Early Eocene opening of the North Atlantic, vast amounts of volcanic ashes were sent into the atmosphere. The tuffs of the Balder Formation were deposited throughout the North Atlantic. Onshore ash deposits were later eroded and transported into the marine North Sea basin and contributed significantly to the Eocene and Oligocene deposits. The large amounts of smectite in the clays of the Hordaland Group are believed to have provenance in the volcanic related rocks. The Hordaland Group has been mobilised syn and post deposition. The mobilised sediments, which show up as a highly chaotic reflection pattern on seismic sections, cover large areas in the northern North Sea. This work suggests that vertical migrating gas, which intruded the Hordaland Group, is an important mechanism for the formation of the large mud diapirs above the Viking Graben.

Loeseth, H.; Wensaas, L.; Gading, M.; Vik, E.

1999-07-01

73

Use of X-ray fluorescence analysis in studying vertical element migration in weathering zone  

International Nuclear Information System (INIS)

The vertical migration of elements was studied in a model area of the Zelivka river basin. The VRS 2 Zeiss GDR analyzer, connected to automatic processor KSR 4 100, were used for the study of concentration variations. Soil samples were taken from bore holes drilled to a depth of the solid bedrock (0 to 6 m). The contents of SiO2, Al2O3, Fe2O3, K2O, CaO, TiO2, P2O5 and MnO were determined in concentration ranges from 10-2 to 101%. The method was tested in comparative measurements against conventional methods of chemical analysis. (author)

74

Inventory and vertical migration of 137Cs in Spanish mainland soils  

International Nuclear Information System (INIS)

In this study the total activity of 137Cs deposited per unit area over the Spanish peninsular territory was analysed using a 150 x 150 km2 mesh grid, with samples taken from 29 points. The deposited activities ranged between 251 and 6074 Bq/m2. A linear relationship was obtained between these values and the mean annual rainfall at each sampling point which allowed a map to be drawn, using GIS software, which shows the distribution of total deposited 137Cs activity across the Spanish mainland. At twelve of these sampling points the vertical migration profile of 137Cs was obtained. These profiles are separated into two groups with different behaviour, one of which includes clay and loam soils and the other containing sandy soils. For both groups of profiles the parameters of the convective-diffusive model, which describes the vertical migration of 137Cs in the soil, v (apparent convection velocity) and D (apparent diffusion coefficient) were calculated. - Highlights: ? Measured the 137Cs activity in Spanish mainland, being within a range of [251, 6074] Bq/m2, with a mean value of 1726 Bq/m2. ? Establishment of the 137Cs background by means of a 137Cs inventory map showing its distribution in the Spanish mainland. ? 137Cs shows two different behaviour tendencies in soil depending on it. ? The parameters which govern the applied modelers which govern the applied model have been obtained for the analysed profiles. ? Analysed those parameters, the two tendencies have been reflected in the obtained values.

75

Inventory and vertical migration of {sup 137}Cs in Spanish mainland soils  

Energy Technology Data Exchange (ETDEWEB)

In this study the total activity of {sup 137}Cs deposited per unit area over the Spanish peninsular territory was analysed using a 150 x 150 km{sup 2} mesh grid, with samples taken from 29 points. The deposited activities ranged between 251 and 6074 Bq/m{sup 2}. A linear relationship was obtained between these values and the mean annual rainfall at each sampling point which allowed a map to be drawn, using GIS software, which shows the distribution of total deposited {sup 137}Cs activity across the Spanish mainland. At twelve of these sampling points the vertical migration profile of {sup 137}Cs was obtained. These profiles are separated into two groups with different behaviour, one of which includes clay and loam soils and the other containing sandy soils. For both groups of profiles the parameters of the convective-diffusive model, which describes the vertical migration of {sup 137}Cs in the soil, v (apparent convection velocity) and D (apparent diffusion coefficient) were calculated. - Highlights: > Measured the {sup 137}Cs activity in Spanish mainland, being within a range of [251, 6074] Bq/m{sup 2}, with a mean value of 1726 Bq/m{sup 2}. > Establishment of the {sup 137}Cs background by means of a {sup 137}Cs inventory map showing its distribution in the Spanish mainland. > {sup 137}Cs shows two different behaviour tendencies in soil depending on it. > The parameters which govern the applied model have been obtained for the analysed profiles. > Analysed those parameters, the two tendencies have been reflected in the obtained values.

Legarda, F. [Dept. Nuclear Engineering and Fluid Mechanics, University of the Basque Country, Alda Urquijo, s/n, E-48013 Bilbao (Spain); Romero, L.M. [CIEMAT, Centro de Investigaciones Energeticas, Medioambientales y Tecnologicas, Av. Complutense 22, 28040 Madrid (Spain); Herranz, M. [Dept. Nuclear Engineering and Fluid Mechanics, University of the Basque Country, Alda Urquijo, s/n, E-48013 Bilbao (Spain); Barrera, M. [CIEMAT, Centro de Investigaciones Energeticas, Medioambientales y Tecnologicas, Av. Complutense 22, 28040 Madrid (Spain); Idoeta, R. [Dept. Nuclear Engineering and Fluid Mechanics, University of the Basque Country, Alda Urquijo, s/n, E-48013 Bilbao (Spain); Valino, F. [CIEMAT, Centro de Investigaciones Energeticas, Medioambientales y Tecnologicas, Av. Complutense 22, 28040 Madrid (Spain); Olondo, C., E-mail: kontxi.olondo@ehu.es [Dept. Nuclear Engineering and Fluid Mechanics, University of the Basque Country, Alda Urquijo, s/n, E-48013 Bilbao (Spain); Caro, A. [CIEMAT, Centro de Investigaciones Energeticas, Medioambientales y Tecnologicas, Av. Complutense 22, 28040 Madrid (Spain)

2011-06-15

76

Vertical migration of cryptosporidium parvum in unsaturated sand columns under transient flow conditions  

Energy Technology Data Exchange (ETDEWEB)

The objective of this study was to identify the effect of lag time and residual water saturation on the vertical migration of Cryptosporidium parvum oocysts under transient flow conditions experienced across vegetated filter strips (VFS) receiving runoff from livestock areas. The vertical migration of C. parvum oocysts through unsaturated soils was studied in laboratory sand columns. Approximately 1x10{sup 5} C. parvum oocysts and 1x10{sup 5} carboxylated latex microspheres (4.5 {mu}m diameter, Polysciences, Inc.) were applied to the top of sand columns at the beginning of each run. Transient water applications to the top of the sand columns (73 cm per hour) simulated an unusually high rate of pond overflow to the inlet area of a VFS after a large storm event, followed by a lag period of either 4 or 48 hours and a repeated water application. Residual water saturation conditions, during the lag period, were controlled to either 2.9 or 12.6 percent by applying a mild vacuum to the bottom of the sand column. The oocysts and microspheres were enumerated along the sand column profile using epifluorescence microscopy. The median travel distance for oocysts was 8.7 {+-} 1.1 cm at 12.6 percent residual saturation versus 6.7 {+-} 0.8 cm for 2.9 percent residual saturation. Lag time did not have a statistically significant effect on median travel distance. The study indicates that surface applied C. parvum oocysts have limited mobility through a uniform unsaturated sand medium experiencing high rates of transient water infiltration. (author)

Ebihara, T.; Mackert, S.D.; Graham, D.W. [Univ. of Kansas, Dept. of Civil, Environmental and Architectural Engineering, Lawrence, Kansas (United States)

2002-06-15

77

Spatial and temporal habitat partitioning by zooplankton in the Bornholm Basin (central Baltic Sea)  

Science.gov (United States)

The deep basins in the Baltic Sea such as the Bornholm Basin (BB) are subject to seasonal changes in the strength of physico-chemical stratification. These depth-related changes in key abiotic factors are strong drivers of habitat partitioning by the autochthonous zooplankton community. Species-specific ecophysiological preferences often result in both seasonal and inter-annual changes in vertical abundance that, when combined with depth-specific water currents, also lead to horizontal differences in spatial distribution. The present study documented the seasonal and depth-specific changes in the abundance and species composition of zooplankton in the BB based upon broad-scale survey data: 832 vertically-resolved (10 m) multinet samples collected at nine stations between March 2002 and May 2003. Changes in the zooplankton community were significantly correlated with changes in ambient hydrography. Each of five taxa (Bosmina coregoni maritima, Acartia spp., Pseudocalanus spp., Temora longicornis, Synchaeta spp.) contributed >10% to the zooplankton community composition. The appearance of cladocerans was mainly correlated with the phenology of thermocline development in the spring. The cladoceran B. coregoni maritima was a dominant member of this community during the warmest periods, preferring the surface waters above the thermocline. Copepods exhibited distinct, ontogenetic and seasonal changes in their distribution. The rotifers (Synchaeta sp.) were the most abundant zooplankton in May. Based on a multivariate approach and the evaluation of vertical distribution patterns, five major habitat utilisation modes were identified that were based, to a large extent, on the dynamics of thermal and haline stratification of the Baltic Sea. Our statistical analysis of one of the most thorough datasets collected on Baltic zooplankton in recent decades reveals some of the factors that make this stratified system highly dynamic with respect to the spatial overlap between predators and prey. As fish and gelatinous plankton often feed in distinct layers and/or exhibit feeding migrations, the inhomogeneous distribution of potential prey can result in a spatial mismatch. Based on the five modes identified at the community level for zooplankton, we discuss how climate-driven hydrographic variability may influence the strength of trophic coupling within the Bornholm Basin.

Schulz, Jan; Peck, Myron A.; Barz, Kristina; Schmidt, Jörn Oliver; Hansen, Frank C.; Peters, Janna; Renz, Jasmin; Dickmann, Miriam; Mohrholz, Volker; Dutz, Jörg; Hirche, Hans-Jürgen

2012-12-01

78

Spatial and temporal habitat partitioning by zooplankton in the Bornholm Basin (central Baltic Sea)  

DEFF Research Database (Denmark)

The deep basins in the Baltic Sea such as the Bornholm Basin (BB) are subject to seasonal changes in the strength of physico-chemical stratification. These depth-related changes in key abiotic factors are strong drivers of habitat partitioning by the autochthonous zooplankton community. Species-specific ecophysiological preferences often result in both seasonal and inter-annual changes in vertical abundance that, when combined with depth-specific water currents, also lead to horizontal differences in spatial distribution. The present study documented the seasonal and depth-specific changes in the abundance and species composition of zooplankton in the BB based upon broad-scale survey data: 832 vertically-resolved (10 m) multinet samples collected at nine stations between March 2002 and May 2003. Changes in the zooplankton community were significantly correlated with changes in ambient hydrography. Each of five taxa (Bosmina coregoni maritima, Acartia spp., Pseudocalanus spp., Temora longicornis, Synchaeta spp.) contributed >10% to the zooplankton community composition. The appearance of cladocerans was mainly correlated with the phenology of thermocline development in the spring. The cladoceran B. coregoni maritima was a dominant member of this community during the warmest periods, preferring the surface waters above the thermocline. Copepods exhibited distinct, ontogenetic and seasonal changes in their distribution. The rotifers (Synchaeta sp.) were the most abundant zooplankton in May. Based on a multivariate approach and the evaluation of vertical distribution patterns, five major habitat utilisation modes were identified that were based, to a large extent, on the dynamics of thermal and haline stratification of the Baltic Sea. Our statistical analysis of one of the most thorough datasets collected on Baltic zooplankton in recent decades reveals some of the factors that make this stratified system highly dynamic with respect to the spatial overlap between predators and prey. As fish and gelatinous plankton often feed in distinct layers and/or exhibit feeding migrations, the inhomogeneous distribution of potential prey can result in a spatial mismatch. Based on the five modes identified at the community level for zooplankton, we discuss how climate-driven hydrographic variability may influence the strength of trophic coupling within the Bornholm Basin

Schultz, J.; Peck, M.A.

2012-01-01

79

Vertical distribution and population structure of copepods along the northern Mid-Atlantic Ridge  

OpenAIRE

The Mid-Atlantic Ridge (MAR) between 40°N (Azores) and 63°N (Iceland) is the largest topographic feature in the North Atlantic Ocean. Despite generally limited surface production, there is evidence that the mid-ocean ridges are ecologically important for higher trophic levels relative to the surrounding open ocean. Vertical migrations of zooplankton are one of the primary mechanisms for the vertical transfer of carbon from surface waters to the deeper waters and sediments. The complicated t...

Falkenhaug, Tone; Gislason, A?stthor; Gaard, Eilif

2007-01-01

80

A functional and morphological approach to evaluate the vertical migration of estuarine intertidal nematodes during a tidal cycle  

Science.gov (United States)

We tested herein the hypothesis that exposure time significantly contributes to the vertical distribution profile of nematodes during a tidal cycle as a function of distinct feeding and locomotion behaviors, conditioned by body morphology. We showed that the vertical distribution profile of the slender with filiform tail, numerically dominant Terschellingia longicaudata is in fact significantly correlated with sediment changes induced by tidal variation. Conversely, none of the other nematode species showed unequivocal evidence of vertical migration. Horizontal spatial heterogeneity also influenced the vertical distribution of nematode associations, probably as a response to varying temperature and desiccation levels at the sediment surface. The resulting vertical profiles for individual or species groups are a trade-off among locomotory and feeding strategies and concordant morphological adaptations.

Brustolin, M. C.; Thomas, M. C.; Lana, P. C.

2013-03-01

81

Spatial/temporal variations in zooplankton biomass and ecological characteristics of major species in the southern part of the Japan Sea: a review  

Science.gov (United States)

During the 1990s many studies on zooplankton in the Japan Sea have been carried out. In this review, I have synthesized the study of horizontal distribution, seasonal and annual variations of zooplankton biomass, and ecological characteristics of major component species in the southern Japan Sea, which area is influenced by the warm Tsushima Current. The zooplankton biomass (annual mean) in the southern Japan Sea was lower than in the subarctic Pacific, including the northern Japan Sea, and similar to biomass levels in Kuroshio waters. Temporal variations in zooplankton biomass showed both seasonal and year-to-year components. Seasonal biomass increases to a maximum in spring with a weak secondary peak in autumn. As for long-term changes, 3-6 year cycles were identified, with the dynamics of the surface warm Tsushima Current and the subsurface cold water playing important roles in determining the yearly zooplankton community structure and biomass. Cold water species in the southern Japan Sea had extensive diel vertical migrations whose range is restricted in summer by the development of a thermocline. Among these species, the herbivores Euphausia pacifica and Metridia pacifica encounter a lower food supply, resulting in lower growth rates. The vertical dispersal of epipelagic carnivorous zooplankton such as Sagitta elegans and Themisto japonica to the deep-sea is probably facilitated by reduced interspecific competition. Their interaction with Japan Sea Proper Water, characterized by near-zero temperatures in the meso- and bathypelagic zones suppresses growth rates of the mesopelagic zooplankton. The lack of micronektonic predators in the mesopelagic zone may allow the persistence of slow growing populations.

Iguchi, Naoki

2004-05-01

82

Seasonal and annual variability of vertically migrating scattering layers in the northern Arabian Sea  

Science.gov (United States)

A 30-month time series of mean volume backscattering strength (MVBS) data obtained from moored acoustic Doppler current profilers (ADCPs) is used to analyze the evolution of vertically migrating scattering layers and their seasonal and annual variability in the Arabian and Oman Seas. Substantial diel vertical migration (DVM) is observed almost every day at all three mooring sites. Two daytime layers (Layers D1 and D2) and one nighttime layer (Layer E1) are typically present. The greatest biomass is observed near the surface during the night in Layer E1 and at depth between 250 and 450 m during the daytime in Layer D2. All layers are deepest during the spring inter-monsoon and shallowest during the summer/fall southwest monsoon (SWM). Seasonal modulation of the D2 biomass change is evident in our high-resolution data. The lowest biomass in D2 is measured in the early summer (May or June) followed by a rapid biomass increase during the SWM (June-November) until the biomass reaches a maximum at the end of the SWM season. Short-period oscillations in D2 biomass are often seen with periods ranging from days to one month. Occasionally, a lower nighttime layer E2 is formed between 180 and 270 m, mostly near the time of full moons. The upper daytime layer D1 is centered at 200 m and densely concentrated. It is only formed during the winter northeast monsoon (NEM) and the spring inter-monsoon. The influence of physical processes on layer distribution is also investigated. Interestingly, the two daytime layers are found to be formed at the two boundaries of the Persian Gulf outflow water (PGW) and follow the seasonal depth change of the PGW. The timing of the DVM and the formation, persistence, decay and reformation of the deep scattering layers seem to be governed by light, both solar and lunar. The scattering strength, the layer depth and the layer thickness are likewise closely related to the Moon phase at night. Cloud coverage, the isotherm and the isohaline also appear to affect the distribution and depth of the scattering layers. The continuous multiple-year acoustic data from ADCPs allow us, for the first time, to study the seasonal and annual variations of scattering layers in this region.

Wang, Zhankun; DiMarco, Steven F.; Ingle, Stephanie; Belabbassi, Leila; Al-Kharusi, Lubna H.

2014-08-01

83

More active vertical migration of 137 Cs towards the groundwater level within areas of intensive agricultural activities  

International Nuclear Information System (INIS)

Effect of agricultural pollutants upon the rate of 137 Cs migration in soil profiles has been studied. To estimate changes in the radiocaesium migration capacity with the presence of high amounts of potassic fertilizers were applied within experimental plots with podzolic and peat-boggy soils. The results of layer-by layer soil and ground testing within experimental and untreated (without KCL) plots were used to estimate an increase of the diffusion coefficient and 137 Cs migration rate in these soils in the period from June to September. Experimental results obtained suggest that the soil section enrichment with potassium provides a several times increase of radiocaesium vertical migration along soil profiles towards the groundwater level

84

Risks of increased UV-B radiation for zooplankton  

International Nuclear Information System (INIS)

Zooplankters are for several reasons bound to luminous water layers and are consequently prone to the danger of UV-B radiation. Despite their various protective mechanisms (e.g. pigmentation, circardian vertical migration) and strong UV-B absorption in natural waters, this danger cannot be eliminated altogether. In eutrophic lakes during summer a few hours of exposure to sunlight can already be lethal for some species. Other species which are able to populate even shallow pools in mountainous regions may survive in similar conditions. Escape from death through UV-B radiation of course does not exclude sublethal impairment of these organisms' fitness. Such inconspicuous tendencies are nevertheless capable of altering the species make-up of pelagic biocoenoses. As the current conditions have been shown to lead to both lethal and sublethal impairment, it must be assumed that the risks for zooplankton will continue to grow with increasing UV-B radiation, especially in oligatrophic lakes. (orig.)

85

Diet of larvae and juvenile perch, Perca fluviatilis performing diel vertical migrations in a deep reservoir.  

Czech Academy of Sciences Publication Activity Database

Ro?. 57, ?. 3 (2008), s. 313-323. ISSN 0139-7893 R&D Projects: GA AV ?R(CZ) IAA600170502; GA AV ?R(CZ) 1QS600170504; GA ?R(CZ) GA206/06/1371 Institutional research plan: CEZ:AV0Z60170517 Keywords : 0+fish * Slapy Reservoir * digestive tracts fullness * zooplankton Subject RIV: EG - Zoology Impact factor: 0.522, year: 2008

Kratochvíl, Michal; Peterka, Ji?í; Kube?ka, Jan; Mat?na, Josef; Vašek, Mojmír; Vaní?ková, I.; ?ech, Martin; Se?a, Jaromír

2008-01-01

86

Diel vertical migrations of age 0+ percids in a shallow, well-mixed reservoir  

Directory of Open Access Journals (Sweden)

Full Text Available The distribution of age 0+ percids (perch, Perca fluviatilis and pikeperch, Sander lucioperca was investigated in a shallow, wellmixed reservoir during a 24-h period in late May, using acoustic and netting methods. Diel vertical migrations (DVMs were acoustically recorded between the layers close to the bottom and the whole water column. The netting data showed a high abundance of larvae and juveniles at night (nearly 1 ind m-3, or 6 ind m-2, whereas negligible numbers of age 0+ percids were present in the water column during the day (3% of night abundance. Age 0+ percids remained during the day in the layer very close to bottom. Smaller pikeperch larvae dominated the pelagic age 0+ fish assemblage during daylight, while larger perch prevailed at night. A strong difference between day and night abundances along with a clear pattern discerned by acoustic methods revealed the DVM of age 0+ percids. Analyses of the fish digestive tract contents indicate that DVM was not governed by feeding behaviour, but rather a defensive strategy against predation. This is in agreement with the size distribution of age 0+ percids, since they were smaller in water column during the day as opposed to the night.

Jaromír SE?A

2010-08-01

87

Aurelia labiata medusae (Scyphozoa) in Roscoe Bay avoid tidal dispersion by vertical migration  

Science.gov (United States)

Aurelia labiata reside year around in Roscoe Bay on the west coast of Canada in spite of tides that exchange as much as 10% to 30% of the bay's water twice daily. Large numbers of medusae drift eastward over a gravel bar and out of the bay on ebb tides, only to return on flood tides. Drogues released into the tidal stream at the middle of an ebb tide drifted about 700 m out of the bay and into an adjacent large body of water. With the aid of a viewing box and lift net it was observed that after drifting out of the bay on an ebb tide, medusae remained within 300 m of the bay because they swam into still or counter current water below the turbulent ebb stream. When the tide turned to flood, medusae rose into the still water, became embedded in the nonturbulent flood stream, and drifted back into the bay. Vertical migration appears to enable the dense population of medusae to stay in a single location. This enhances reproductive success by keeping males and females in close proximity and increases survival by keeping the population in a favourable location.

Albert, David J.

2007-05-01

88

Global fallout 137Cs accumulation and vertical migration in selected soils from South Patagonia  

International Nuclear Information System (INIS)

The spatial distribution and vertical migration of global fallout 137Cs were studied in soils from South Patagonia at the austral region of South America in semi-natural and natural environments located between 50-54 deg. S and 68-74 deg. W. The 137Cs areal activity density varied from 222 to 858 Bq m-2, and was found to be significantly positively correlated (ps of 137Cs in the soil in such polar isotundra climate has been determined to be 0.056 cm y-1. This value is higher than vs determined under polar climate (-0.012 cm y-1) and is near to the upper limit of vs-values determined in temperate environments from Chile (0.019 cm y-1). The median value of the diffusion coefficient Ds (0.048 cm2 y-1) is similar to Ds observed in an Antarctic region (0.043 cm2 y-1) and lower than Ds in temperate regions of Chile (1.24 cm2 y-1). About 35 years after the highest depositions, 137Cs had penetrated ositions, 137Cs had penetrated to a depth of 6-14 cm in the Patagonian soils and can be expected to remain in the rooting zone of grass for many decades. Nevertheless, because of its low transfer to steppe grass observed at this region, the radioecological sensitivity of this ecosystem with respect to fallout radiocesium seems to be lower than in other polar regions

89

Inter- and intra-specific diurnal habitat selection of zooplankton during the spring bloom observed by Video Plankton Recorder  

DEFF Research Database (Denmark)

Diel vertical migration (DVM) is a common behavior adopted by zooplankton species. DVM is a prominent adaptation for avoiding visual predation during daylight hours and still being able to feed on surface phytoplankton blooms during night. Here, we report on a DVM study using a Video Plankton Recorder (VPR), a tool that allows mapping of vertical zooplankton distributions with a far greater spatial resolution than conventional zooplankton nets. The study took place over a full day–night cycle in Disko Bay, Greenland, during the peak of the phytoplankton spring bloom. The sampling revealed a large abundance of copepods performing DVM (up during night and down during day). Migration behavior was expressed differently among the abundant groups with either a strong DVM (euphausiids), an absence of DVM (i.e., permanently deep; ostracods) or a marked DVM, driven by strong surface avoidance during the day and more variable depth preferences at night (Calanus spp.). The precise individual depth position provided by the VPR allowed us to conclude that the escape from surface waters during daytime reduces feeding opportunities but also lowers the risk of predation (by reducing the light exposure) and thereby is likely to influence both state (hunger, weight and stage) and survival. The results suggest that the copepods select day and night time habitats with similar light levels (~10?9 ?mol photon s?1 m?2). Furthermore, Calanus spp. displayed state-dependent behavior, with DVM most apparent for smaller individuals, and a deeper residence depth for the larger individuals.

Sainmont, Julie; Gislason, Astthor

2014-01-01

90

Distribution of zooplankton populations within and adjacent to a thermal plume  

International Nuclear Information System (INIS)

Zooplankton distributions in the 1-m stratum differed between ambient waters and the thermal plume of the Donald C. Cook Nuclear Power Plant. Zooplankton were most abundant in the warmest waters of the plume with the region of high densities extending over an approximate area of 0.2 to 0.3 km2. Water temperature was not a reliable indicator of alterations in zooplankton populations. Alterations were primarily due to upward vertical displacment of deep-living zooplankton. Large horizontal variability in zooplankton densities and use of conventional sampling procedures (vertically hauled nets, widely spaced stations) prevent traditionally designed monitoring programs from detecting such alterations. Zooplankton may experience indirect mortality losses in the plume if transfer of deep-living zooplankton to the surface layers makes them more visible to visual-feeding fish predators, and turbulences in the plume reduce zooplankters' ability to detect and avoid such predators. (auth)

91

Cross-shelf transport of pink shrimp larvae: Interactions of tidal currents, larval vertical migrations and internal tides  

Science.gov (United States)

Transport and behavior of pink shrimp Farfantepenaeus duorarum larvae were investigated on the southwestern Florida (SWF) shelf of the Gulf of Mexico between the Dry Tortugas spawning grounds and Florida Bay nursery grounds. Stratified plankton samples and hydrographic data were collected at 2 h intervals at 3 stations located on a cross-shelf transect. At the Marquesas station, midway between Dry Tortugas and Florida Bay, internal tides were recognized by anomalously cool water, a shallow thermocline with strong density gradients, strong current shear, and a high concentration of pink shrimp larvae at the shallow thermocline. Low Richardson numbers occurred at the pycnocline depth, indicating vertical shear instability and possible turbulent transport from the lower to the upper layer where myses and postlarvae were concentrated. Analysis of vertically stratified plankton suggested that larvae perform vertical migrations and the specific behavior changes ontogenetically; protozoeae were found deeper than myses, and myses deeper than postlarvae. Relative concentrations of protozoea in the upper, middle and bottom layers were consistent with a diel vertical migration, whereas that of postlarvae and myses were consistent with the semidiurnal tides in phase with the flood tide. Postlarvae, the shallowest dwellers that migrate with a semidiurnal periodicity, experienced the largest net onshore flux and larval concentrations were highly correlated with the cross-shelf current. These results provide the first evidence of an onshore tidal transport (a type of selective tidal stream transport, STST), in decapod larvae migrating in continental shelf waters offshore, ca. 100 km from the coast and at a depth of 20 m, while approaching the coastal nursery grounds. Longer time series would be necessary to establish whether internal tides play any role in the larval onshore transport of this species and determine if the STST is the dominant onshore transport mechanism. ?? Inter-Research 2007 .

Criales, M.M.; Browder, J.A.; Mooers, C.N.K.; Robblee, M.B.; Cardenas, H.; Jackson, T.L.

2007-01-01

92

137Cs content and vertical migration in the soil of Kozhanovskoe and Svyatoe on the based lake-sides based  

International Nuclear Information System (INIS)

Paper deals with the dynamics and the situation of 137Cs soil contamination of the sides of the Kozhanovskoe and the Svyatoe lakes on the Beseda river. The parameters of the contamination vertical migration in the soil were evaluated on the basis of the comparison of the experimental and the simulated deep soil distribution of 137Cs: the rate of the directed transfer with soil moisture, the diffusion factor and the average rate of the vertical migration. It is shown that at present the top 5 cm depth soil layer depending on its type and the landscape may contain from 20 up to 90% of 137Cs. The values of the diffusion factor, the rate of the directed transfer and the vertical migration considered to be the average ones for the 12 year, the 13 year and the 20 year period following the Chernobyl NPP accident constitute respectively 0.1-2.8 cm2/year, 0.1-0.3 cm/year and 0.1-0.8 cm/year

93

Vertical migration of the toxic dinoflagellate Karenia brevis and the impact on ocean optical properties  

Science.gov (United States)

Vertical migration behavior is found in many harmful algal blooms; however, the corresponding impact on ocean optical properties has not been quantified. A near-monospecific population of the dinoflagellate Karenia brevis was encountered off the west coast of Florida. The community was tracked for 24 hours by following a Lagrangian drifter deployed at the beginning of the experiment. A suite of inherent optical and cellular measurements was made. Over the 24 hour period, the K. brevis population increased during the day with concentrations peaking in the late afternoon (1600 local daylight time) in the upper 2 m of the water column. The increase in K. brevis in surface waters resulted in enhanced reflectance at the sea surface with distinct spectral changes. There was a 22% decrease in the relative amount of the green reflectance due to increased pigment absorption. There was enhanced red (35%) and infrared (75%) light reflectance due to the increased particle backscatter and chlorophyll a fluorescence; however, the relative impact of the fluorescence was relatively small despite high cell numbers due to the significant fluorescence quenching present in K. brevis. The relative change in the blue light reflectance was not as large as the change in green light reflectance, which is surprising given the pigment absorption in the blue wavelengths of light. The increased blue light pigment absorption was offset by a significant decrease in nonalgal particle absorption. The inverse relationship between K. brevis and nonalgal particles was robust. This relationship may reflect low grazing on K. brevis populations due to the neurotoxins associated with this dinoflagellate. The low-grazing pressure may provide the mechanism by which this slow-growing dinoflagellate can achieve high cell numbers in the ocean.

Schofield, Oscar; Kerfoot, John; Mahoney, Kevin; Moline, Mark; Oliver, Matthew; Lohrenz, Steven; Kirkpatrick, Gary

2006-06-01

94

Comparing the diel vertical migration of Karlodinium veneficum (dinophyceae) and Chattonella subsalsa (Raphidophyceae): PSII photochemistry, circadian control, and carbon assimilation.  

Science.gov (United States)

Diel vertical migration (DVM) is thought to provide an adaptive advantage to some phytoplankton, and may help determine the ecological niche of certain harmful algae. Here we separately compared DVM patterns between two species of harmful algae isolated from the Delaware Inland Bays, Karlodinium veneficum and Chattonella subsalsa, in laboratory columns. We interpreted the DVM patterns of each species with Photosystem II (PSII) photochemistry, rates of carbon assimilation, and specific growth rates. Each species migrated differently, wherein K. veneficum migrated closer to the surface each day with high population synchrony, while C. subsalsa migrated near to the surface from the first day of measurements with low population synchrony. Both species appeared to downregulate PSII in high light at the surface, but by different mechanisms. C. subsalsa grew slower than K. veneficum in low light intensities (?bottom of columns), and exhibited maximal rates of C-assimilation (Pmax) at surface light intensities, suggesting this species may prefer high light, potentially explaining this species' rapid surface migration. Contrastingly, K. veneficum showed declines in carbon assimilation at surface light intensities, and exhibited a smaller reduction in growth at low (bottom) light intensities (compared to C. subsalsa), suggesting that this species' step-wise migration was photoacclimative and determined daily migration depth. DVM was found to be under circadian control in C. subsalsa, but not in K. veneficum. However, there was little evidence for circadian regulation of PSII photochemistry in either species. Migration conformed to each species' physiology, and the results contribute to our understanding each alga's realized environmental niche. PMID:25618815

Tilney, Charles L; Hoadley, Kenneth D; Warner, Mark E

2015-02-01

95

Zooplankton from Lake Magelungen, Central Sweden 1960-1963  

International Nuclear Information System (INIS)

The investigation of the zooplankton of Lake Magelungen, Central Sweden, was carried out over a period of three years. The aim of the investigation was to illustrate the qualitative and quantitative composition of the zooplankton before the release of waste water from the Aagesta Heat and Power Station began. Vertical sampling series were collected once a month at three different stations in the lake. The highest volumes of zooplankton were obtained in the summer. The ciliates predominated when the conditions were unfavourable for other zooplankton, as in winter just below the ice. The rotifers dominated during and immediately after the spring circulation. With one exception the crustaceans reached their peak volume values in August or September. The composition of the zooplankton indicates that Lake Magelungen is highly eutrophic

96

Trophic transfer of microcystins through the lake pelagic food web: evidence for the role of zooplankton as a vector in fish contamination.  

Science.gov (United States)

An in situ study was performed to investigate the role of zooplankton as a vector of microcystins (MCs) from Planktothrix rubescens filaments to fish during a metalimnic bloom of P. rubescens in Lake Hallwil (Switzerland). The concentrations of MCs in P. rubescens and various zooplanktonic taxa (filter-feeders and predators) were assessed in different water strata (epi-, meta- and hypolimnion) using replicated sampling over a 24-hour survey. The presence of P. rubescens in the gut content of various zooplanktonic taxa (Daphnia, Bosmina and Chaoborus) was verified by targeting the cyanobacterial nucleic acids (DNA). These results highlighted that cyanobacterial cells constitute a part of food resource for herbivorous zooplanktonic taxa during metalimnic bloom periods. Furthermore, presence of MCs in Chaoborus larvae highlighted the trophic transfer of MCs between herbivorous zooplankton and their invertebrate predators. Our results suggest that zooplanktonic herbivores by diel vertical migration (DVM) act as vectors of MCs by encapsulating grazed cyanobacteria. As a consequence, they largely contribute to the contamination of zooplanktonic predators, and in fine of zooplanktivorous whitefish. Indeed, we estimated the relative contribution of three preys of the whitefish (i.e. Daphnia, Bosmina and Chaoborus) to diet contamination. We showed that Chaoborus and Daphnia were the highest contributor as MC vectors in the whitefish diet (74.6 and 20.5% of MC-LR equivalent concentrations, respectively). The transfer of MCs across the different trophic compartments follows complex trophic pathways involving various trophic levels whose relative importance in fish contamination might vary at daily and seasonal scale. PMID:23906853

Sotton, Benoît; Guillard, Jean; Anneville, Orlane; Maréchal, Marjorie; Savichtcheva, Olga; Domaizon, Isabelle

2014-01-01

97

Attenuation of particulate organic carbon flux in the Scotia Sea, Southern Ocean, is controlled by zooplankton fecal pellets  

Science.gov (United States)

The Southern Ocean (SO) is an important CO2 reservoir, some of which enters via the production, sinking, and remineralization of organic matter. Recent work suggests that the fraction of production that sinks is inversely related to production in the SO, a suggestion that we confirm from 20 stations in the Scotia Sea. The efficiency with which exported material is transferred to depth (transfer efficiency) is believed to be low in high-latitude systems. However, our estimates of transfer efficiency are bimodal, with stations in the seasonal ice zone showing intense losses and others displaying increases in flux with depth. Zooplankton fecal pellets dominated the organic carbon flux and at stations with transfer efficiency >100% fecal pellets were brown, indicative of fresh phytodetritus. We suggest that active flux mediated by zooplankton vertical migration and the presence of sea ice regulates the transfer of organic carbon into the oceans interior in the Southern Ocean.

Cavan, E. L.; Le Moigne, F. A. C.; Poulton, A. J.; Tarling, G. A.; Ward, P.; Daniels, C. J.; Fragoso, G. M.; Sanders, R. J.

2015-02-01

98

Diel vertical migration of copepods in a Brazilian lake: a mechanism for decreasing risk of Chaoborus predation? A migração vertical de copépodos em um lago brasileiro: um mecanismo para diminuir o risco de predação por Chaoborus?  

OpenAIRE

A comparison between two studies on diel vertical migration of two cyclopoid copepod species, in Lake Monte Alegre, undertaken in 1985/86 and 1999, revealed a change in their migratory behavior. In summer, during a period of marked stratification with low dissolved oxygen near the bottom, the organisms avoided the deepest layers, and migration was nocturnal or undetectable, in both periods. On other occasions, with partial or total circulation in the lake, a weak twilight migration of copepod...

Perticarrari A.; Arcifa, M. S.; Rodrigues, R. A.

2004-01-01

99

137Cs vertical migration in a deciduous forest soil following the Fukushima Dai-ichi Nuclear Power Plant accident  

International Nuclear Information System (INIS)

The large amount of 137Cs deposited on the forest floor because of the Fukushima Dai-ichi Nuclear Power Plant accident represents a major potential long-term source for mobile 137Cs. To investigate 137Cs mobility in forest soils, we investigated the vertical migration of 137Cs through seepage water, using a lysimetric method. The study was conducted in a deciduous forest soil over a period spanning 2 month to 2 y after the Fukushima nuclear accident. Our observations demonstrated that the major part of 137Cs in the litter layer moved into the mineral soil within one year after the accident. On the other hand, the topsoil prevented migration of 137Cs, and only 2% of 137Cs in the leachate from litter and humus layer penetrated below a 10 cm depth. The annual migration below a 10 cm depth accounted for 0.1% of the total 137Cs inventory. Therefore, the migration of 137Cs by seepage water comprised only a very small part of the total 137Cs inventory in the mineral soil, which was undetectable from the vertical distribution of 137Cs in the soil profile. In the present and immediate future, most of the 137Cs deposited on the forest floor will probably remain in the topsoil successively, although a small but certain amount of bioavailable 137Cs exists in forest surface soil. -- Highlights: • Lysimeter captured 137Cs mobility in a forest soil after the Fukushima accident. • Major part of 137Cs in the litter layer moved into the mineral soil within a year. • Litter-leachate 137Cs was predominantly adsorbed within the topsoil. • The annual migration below a 10 cm depth was 0.1% of the total 137Cs inventory

100

Vertical migration and dispersion of sprat ( Sprattus sprattus ) and herring ( Clupea harengus ) schools at dusk in the Baltic Sea  

DEFF Research Database (Denmark)

In populations of herring (Clupea harengus) or sprat (Sprattus sprattus), one typically observes a pattern of schools forming at dawn and dispersing at dusk, usually combined with vertical migration. This behaviour influences interactions with other species; hence a better understanding of the processes could contribute to deeper insight into ecosystem dynamics. This paper reports field measurements of the dispersal at dusk and examines two hypotheses through statistical modelling: that the vertical migration and the dissolution of schools is determined by decrease in light intensity, and that the dissolution of schools can be modelled by diffusion, i.e. active repulsion is not required. The field measurements were obtained during 3 days in March at one location in the Baltic Sea and included continuous hydroacoustical monitoring, trawl samples, and hydrographical CTD data. Echogram patterns were analysed using the school detection module in Echoview® and local light intensities were calculated using a model for surface illuminance. The data and the analysis support that schools migrate upwards during dusk, possibly trying to remain aggregated by keeping the local light intensities above a critical threshold, that schools initiate their dissolution when ambient light intensity drops below this critical threshold, and that fish subsequently swim in an uncorrelated random walk pattern.

Nilsson, Lars Anders Fredrik; Thygesen, Uffe HØgsbro

2003-01-01

101

Microplastic ingestion by zooplankton.  

Science.gov (United States)

Small plastic detritus, termed "microplastics", are a widespread and ubiquitous contaminant of marine ecosystems across the globe. Ingestion of microplastics by marine biota, including mussels, worms, fish, and seabirds, has been widely reported, but despite their vital ecological role in marine food-webs, the impact of microplastics on zooplankton remains under-researched. Here, we show that microplastics are ingested by, and may impact upon, zooplankton. We used bioimaging techniques to document ingestion, egestion, and adherence of microplastics in a range of zooplankton common to the northeast Atlantic, and employed feeding rate studies to determine the impact of plastic detritus on algal ingestion rates in copepods. Using fluorescence and coherent anti-Stokes Raman scattering (CARS) microscopy we identified that thirteen zooplankton taxa had the capacity to ingest 1.7-30.6 ?m polystyrene beads, with uptake varying by taxa, life-stage and bead-size. Post-ingestion, copepods egested faecal pellets laden with microplastics. We further observed microplastics adhered to the external carapace and appendages of exposed zooplankton. Exposure of the copepod Centropages typicus to natural assemblages of algae with and without microplastics showed that 7.3 ?m microplastics (>4000 mL(-1)) significantly decreased algal feeding. Our findings imply that marine microplastic debris can negatively impact upon zooplankton function and health. PMID:23692270

Cole, Matthew; Lindeque, Pennie; Fileman, Elaine; Halsband, Claudia; Goodhead, Rhys; Moger, Julian; Galloway, Tamara S

2013-06-18

102

Foraging, bioenergetic and predation constraints on diel vertical migration: field observations and modelling of reverse migration by young-of-the-year herring Clupea harengus.  

Science.gov (United States)

Diel vertical migration (DVM) of young-of-the-year (YOY) herring Clupea harengus and one of their major predators, pikeperch Sander lucioperca, was examined using bottom-mounted hydroacoustics in Himmerfjärden, a brackish bay of the Baltic Sea, in summer. In contrast to previous studies on DVM of C. harengus aggregated across size and age classes, YOY C. harengus showed a reverse DVM trajectory, deeper at night and, on average, shallower during the day. This pattern was observed consistently on five acoustic sampling occasions in 3 years and was corroborated by two out of three trawl surveys. Large acoustic targets (target strength >-33 dB, probably piscivorous S. lucioperca >45 cm) showed a classic DVM trajectory, shallow at night and deeper during the day. Variability in YOY C. harengus vertical distribution peaked at dawn and dusk, and their vertical distribution at midday was distinctly bimodal. This reverse DVM pattern was consistent with bioenergetic model predictions for YOY C. harengus which have rapid gut evacuation rates and do not feed at night. Reverse DVM also resulted in low spatial overlap with predators. PMID:21284628

Jensen, O P; Hansson, S; Didrikas, T; Stockwell, J D; Hrabik, T R; Axenrot, T; Kitchell, J F

2011-02-01

103

Marine zooplankton studies in Brazil: a brief evaluation and perspectives  

Directory of Open Access Journals (Sweden)

Full Text Available Marine zooplankton research in Brazil has been primarily descriptive, with most studies focusing on community structure analysis and related issues. The composition and spatial distribution of several taxonomic groups are currently well known, although less-abundant and small-sized taxa as well as initial stages of almost all species have received little attention. Some numerically important taxa such as heterotrophic protists, ctenophores, acoel turbellarians and ostracods remain virtually unstudied. Large sectors of the continental shelf have not been sampled in detail, particularly those areas influenced by the North Brazil Current (5ºN-15ºS. Zooplankton abundance and biomass in offshore waters have seldom been quantified, and information on the distribution and vertical migration of meso- and bathypelagic species are lacking. Additional faunistic assessments must target those less-studied taxa and geographical locations. However, priority in ecological studies should be given to process-oriented investigations aimed at understanding the mechanisms controlling zooplankton distribution, trophic interactions within pelagic food webs and production cycles in relation to the physical environment. An effort should be made to incorporate state-of-the-art sampling technology and analytical methods into future research projects.As pesquisas sobre o zooplâncton marinho no Brasil têm sido primariamente descritivas, com a maioria dos estudos enfocando a análise da estrutura da comunidade e assuntos relacionados. A composição e a distribuição espacial de muitos grupos taxonômicos encontram-se bem estudadas, embora os táxons menos abundantes e de menores dimensões, assimcomo os estágios iniciais do ciclo de vida da maioria das espécies, tenham recebido pouca atenção. Alguns táxons numericamenteimportantes encontram-se pouco estudados, como no caso dos protistas heterotróficos, ctenóforos, turbelários acelos e ostrácodes. Amplos setores da plataforma continental não têm sido suficientemente amostrados, em particular nas áreas influenciadas pela Corrente Norte do Brasil (5ºN-15ºS. As áreas oceânicas têm sido também pouco estudadas e praticamente inexistem dados sobre a distribuição espacial e vertical das espécies meso- e batipelágicas. Levantamentos faunísticos adicionais devem focalizar os táxons e locais menos conhecidos. No entanto, sob o ponto de vista ecológico é necessário darprioridade a estudos de processos voltados ao entendimentodos mecanismos que governam a distribuição, as interações tróficas nas teias alimentares pelágicas e os ciclos de produção do zooplâncton em relação ao ambiente físico. Deve ser feito um esforço para incorporar novas tecnologias de amostragem e métodos analíticos em futuros projetos de pesquisa.

Rubens M. Lopes

2007-09-01

104

Inventory and vertical migration of 90Sr fallout and 137Cs/90Sr ratio in Spanish mainland soils  

International Nuclear Information System (INIS)

In this paper the inventory of 90Sr in 34 points distributed along the Spanish peninsular territory is presented. Obtained values range between 173 Bq/m2 and 2047 Bq/m2. From these data set and those 137Cs data obtained in a previous work the 137Cs/90Sr activity ratio has been established, laying this value between 0.9 and 3.6. Also the migration depth of both radionuclides has been analysed obtaining for 137Cs an average value 57% lower than that obtained for 90Sr. Additionally, this paper presents the results obtained in 11 sampling points in which the activity vertical profile has been measured. These profiles have been analysed to state the behaviour of strontium in soils and after, by using a convective-diffusive model, the parameters of the model which governs the vertical migration of 90Sr in the soil, v (apparent convection velocity) and D (apparent diffusion coefficient) have been evaluated. Mean values obtained are 0.20 cm/year and 3.67 cm2/year, respectively. - Highlights: ? Measured 90Sr activity in Spanish mainland, being within a range of [173, 2047] Bq/m2, with a mean value of 793 Bq/m2. ? Compared the migration capacity of 137Cs and 90Sr in the same soils. ? 90Sr shows a unique behaviour tendency in soil. ? The parameters which govern the applied model have been obtained applied model have been obtained for the analysed profiles. ? Analysed those parameters' values also reflects this unique tendency.

105

Age-specific light preferences and vertical migration patterns of a Great Lakes invasive invertebrate, Hemimysis anomala  

Science.gov (United States)

We use a combination of spectral sensitivity analyses, laboratory behavioral observations and field distributions of a vertically migrating invertebrate, Hemimysis anomala (a recent invasive species to the Laurentian Great Lakes of North America), to determine if light preference and timing of emergence has an ontogenetic component. Juvenile Hemimysis (?3.4 and 10?2.4 mylux— a Hemimysis-specific unit of brightness derived from visual pigment analyses (wavelength of maximum absorbance = 500 nm; 1 mylux ~ 159 lx). These preferred light levels are equivalent to those present during nautical twilight on the Earth's surface and were several orders of magnitude brighter than those most preferred by adults (> 4.5 mm) in the laboratory (10?6.4 to 10?7.4 mylux). Both size classes completely avoided light levels of 10?0.4 mylux and greater, which are representative of daytime light levels at the Earth's surface. Net hauls taken at ~ 20-min intervals from sunset to the end of nautical twilight on two sampling occasions on Seneca Lake, New York (sampling depth = 2 m) revealed that juveniles emerged into the water column during civil twilight. Adult Hemimysis emerged later during nautical twilight when juveniles had already reached their maximum abundance in the water column. Laboratory-derived light preferences successfully predicted the timing of emergence and time of maximal abundance of both size classes on both sampling occasions. This study is one of the first to demonstrate that Hemimysis diel vertical migration has an ontogenetic component and to report the specific light levels likely to initiate and limit vertical movements.

Boscarino, Brent T.; Halpin, Kathleen E.; Rudstam, Lars G.; Walsh, Maureen G.; Lantry, Brian F.

2012-01-01

106

Zooplankton community structure in a cyclonic and mode-water eddy in the Sargasso Sea  

Science.gov (United States)

Mesoscale eddies are important suppliers of nutrients to the surface waters of oligotrophic gyres, but little is known about the biological response, particularly that of higher trophic levels, to these physical perturbations. During the summers of 2004 and 2005, we followed the development of a cyclonic eddy and an anti-cyclonic mode-water eddy in the Sargasso Sea. Zooplankton (>150 ?m) were collected across both eddies in 9 discrete depth intervals between 0 and 700 m. Comparison of the abundance of major taxa of mesozooplankton in the upper 150 m at eddy center and outside the eddies (day and night) indicated that the cyclone and mode-water eddy supported similar mesozooplankton communities, with several taxa significantly higher in abundance inside than outside the eddies, when compared with the Bermuda Atlantic Time-series Study site as representative of mean conditions. In both eddies copepod peak abundance occurred in the 50-100 m depth interval, coincident with the chlorophyll a maximum, suggesting elevated food concentration in the eddies may have influenced zooplankton vertical distribution. The two eddies differed in the strength of diel vertical migration of zooplankton, as indicated by the ratio of night:day abundance in the epipelagic zone, which was higher at the center of the mode-water eddy for most taxa. Over the sampling interval of 1-2 months, abundance of the three most common taxa (copepods, chaetognaths, and ostracods) decreased in the cyclone and increased in the mode-water eddy. This further supports previous findings that over the sampling period the cyclone was in a decay phase, while the mode-water eddy was sustaining nutrient fluxes and high phytoplankton concentrations. A more detailed analysis of community structure in the mode-water eddy indicated the 0-700 m integrated abundance of doliolids was significantly higher inside the mode-water eddy than outside. The presence of a mesopelagic (200-700 m) layer of lepadid barnacle cyprids in this eddy highlights the potential of eddies to transport and disperse biota. We conclude that when compared with average ambient conditions (as measured at BATS), mesoscale eddies can influence zooplankton behavior and alter zooplankton community structure which can affect food-web interactions and biogeochemical cycling in the open ocean.

Eden, Bethany R.; Steinberg, Deborah K.; Goldthwait, Sarah A.; McGillicuddy, Dennis J., Jr.

2009-10-01

107

Long-Term Dynamics Of Radionuclide Vertical Migration In Soils Of The Chernobyl Nuclear Power Plant Exclusion Zone  

International Nuclear Information System (INIS)

The radioactive fallout from the Chernobyl Nuclear Power Plant (ChNPP) accident consisted of fuel and condensation components. An important radioecological task associated with the late phase of the accident is to evaluate the dynamics of radionuclide mobility in soils. Identification of the variability (or invariability) in the radionuclide transfer parameters makes it possible to (1) accurately predict migration patterns and biological availability of radionuclides and (2) evaluate long-term exposure trends for the population who may reoccupy the remediated abandoned areas. In 1986-1987, a number of experimental plots were established within various tracts of the fallout plume to assist with the determination of the long-term dynamics of radionuclide vertical migration in the soils. The transfer parameters for 137Cs, 90Sr, and 239,240Pu in the soil profile, as well as their ecological half-time of the radionuclide residence (T1/2ecol) values in the upper 5-cm thick soil layers of different grasslands were estimated at various times since the accident. Migration characteristics in the grassland soils tend to decrease as follows: 90Sr > 137Cs (ge) 239,240Pu. It was found that the 137Cs absolute T1/2ecol values are 3-7 times higher than its radioactive decay half-life value. Therefore, changes in the exposure dose resulting from the soil deposited 137Cs now depend only on its radioactive decay. The 90Sr T1/2ecol values for the 21st year after the fallout tend to decrease, indicating an intensification of its migration capabilities. This trend appears consistent with a pool of mobile 90Sr forms that grows over time due to destruction of the fuel particles.

108

Flight periodicity and the vertical distribution of high-altitude moth migration over southern Britain  

OpenAIRE

The continuous operation of insect-monitoring radars in the UK has permitted, for the first time, the characterization of various phenomena associated with high-altitude migration of large insects over this part of northern Europe. Previous studies have taken a case-study approach, concentrating on a small number of nights of particular interest. Here, combining data from two radars, and from an extensive suction- and light-trapping network, we have undertaken a more systematic, longer-term s...

Wood, Curtis Ron; Reynolds, D. R.; Wells, P. M.; Barlow, Janet Fraser; Woiwod, I. P.; Chapman, J. W.

2009-01-01

109

Vertical migration of fallout 137Cs in agricultural soils from Southern Chile  

International Nuclear Information System (INIS)

Total inventories and depth distributions of atomic weapons testing fallout 137Cs were determined at four sites in Chile. Cesium inventories are always higher than previously estimated for the Southern Hemisphere and depend on annual rainfall. From the measured depth distributions cesium migration rates of 137Cs transport by the convection-dispersion equation yielded a better accordance with the measured depth distributions than the application of a compartmental model

110

Vertical migration, nitrate uptake and denitrification: survival mechanisms of foraminifers (Globobulimina turgida) under low oxygen conditions  

Science.gov (United States)

15NO3- isotope labelling experiments were carried out to study foraminiferal nitrate uptake strategies and the role of pseudopodial networks in nitrate uptake. Globobulimina turgida were placed below the nitrate penetration depth in homogenised sediment cores, which were subsequently incubated in artificial seawater containing the label. The physical migration of foraminifera to strata containing nitrate and oxygen was prevented by a nylon net, however, potential access to such strata by extension of pseudopods was still possible. As no 15NO3- was found in G. turgida in the experimental cores, we concluded that foraminifera cannot extend their pseudopods for nitrate uptake through several millimetres of sediment. In stead they must physically migrate upwards closer to nitrate-containing strata. The foraminiferal migration patterns in the control cores (with no nylon net) were observed to be erratic, suggesting that individuals move in random orientations until they find favourable conditions (i.e. free nitrate or oxygen). A second experiment showed that foraminifera actively collect nitrate in both the presence and absence of oxygen, although uptake was initiated faster if oxygen was absent from the environment. However, no systematic influence of the size of the intracellular nitrate pool on nitrate uptake was observed, as specimens containing a large range of intracellular nitrate (636-19992 pmol/cell) were measured to take up 15NO3- at comparable rates.

Koho, K. A.; Pina-Ochoa, E.; Geslin, E.; Risgaard-Petersen, N.

2012-04-01

111

Effects of nanoparticle migration on hydromagnetic mixed convection of alumina/water nanofluid in vertical channels with asymmetric heating  

Science.gov (United States)

The effects of nanoparticle migration on mixed convection of alumina/water nanofluid inside a vertical channel in the presence of a uniform magnetic field have been investigated theoretically. Walls are subjected to different heat fluxes; q lw ' ' for the left wall and q rw ' ' for the right wall, and nanoparticles are assumed to have a slip velocity relative to the base fluid induced by the Brownian motion and thermophoresis. Considering hydrodynamically and thermally fully developed flow, the governing equations including continuity, momentum, and energy equations have been reduced to two-point ordinary boundary value differential equations and they have been solved numerically. It is shown that nanoparticles eject themselves from the heated walls, construct a depleted region, and accumulate in the core region, but they are more likely to accumulate toward the wall with the lower heat flux. In addition, inclusion of nanoparticles in the presence of a magnetic field has a negative effect on the performance.

Malvandi, A.; Ganji, D. D.

2015-02-01

112

Type I Planet Migration in a Magnetized Disk. I. Effect of Large-Scale Vertical and Azimuthal Field Components  

CERN Document Server

We study the effects of a large-scale, ordered magnetic field in protoplanetary disks on Type I planet migration using a combination of numerical simulations in 2D and 3D and a linear perturbation analysis. Steady-state models of such disks require the inclusion of magnetic diffusivity. To make progress using ideal MHD, we focus on simplified field configurations, involving purely vertical ($B_z$) and azimuthal ($B_\\varphi$) field components and a combination of the two. For each of the models we calculate the locations of the relevant resonances and of the turning points, which delineate the propagation regions of the MHD waves that transport angular momentum from the planet to the disk. We use both numerical and semianalytic methods to evaluate the cumulative back torque acting on the planet, and explore the effect of spatial gradients in the disk's physical variables on the results. We conclude that, under realistic (3D) circumstances, a large-scale magnetic field can slow down the inward migration that ch...

Uribe, Ana; Königl, Arieh

2015-01-01

113

Soft-lubrication effect on the lateral migration of a slightly deformed bubble rising near a vertical plane wall  

CERN Document Server

Deformation-induced lateral migration of a bubble slowly rising near a vertical plane wall in a stagnant liquid is numerically and theoretically investigated. In particular, our focus is set on a situation with a small clearance $c$ between the bubble interface and the wall. Motivated by the fact that experimentally measured migration velocity (Takemura et al. (2002, J. Fluid Mech. {\\bf 461}, 277)) is higher than the velocity estimated by the available analytical solution (Magnaudet et al. (2003, J. Fluid Mech. {\\bf 476}, 115)) using the Fax\\'{e}n mirror image technique for $\\kappa(=a/(a+c))\\ll 1$ (here $a$ is the bubble radius), when the clearance parameter $\\varepsilon(=c/a)$ is comparable to or smaller than unit, the numerical analysis based on the boundary-fitted finite-difference approach by solving the Stokes equation is performed to complement the experiment. To improve the understandings of a role of the squeezing flow within the bubble-wall gap, the theoretical analysis based on a soft-lubrication ap...

Sugiyama, Kazuyasu

2008-01-01

114

Type I Planet Migration in a Magnetized Disk. I. Effect of Large-scale Vertical and Azimuthal Field Components  

Science.gov (United States)

We study the effects of a large-scale, ordered magnetic field in protoplanetary disks on Type I planet migration using a combination of numerical simulations in 2D and 3D and a linear perturbation analysis. Steady-state models of such disks require the inclusion of magnetic diffusivity. To make progress using ideal MHD, we focus on simplified field configurations, involving purely vertical (Bz) and azimuthal ({{B}\\varphi }) field components and a combination of the two. For each of the models we calculate the locations of the relevant resonances and of the turning points, which delineate the propagation regions of the MHD waves that transport angular momentum from the planet to the disk. We use both numerical and semianalytic methods to evaluate the cumulative back torque acting on the planet, and explore the effect of spatial gradients in the disk’s physical variables on the results. We conclude that, under realistic (3D) circumstances, a large-scale magnetic field can slow down the inward migration that characterizes the underlying unmagnetized disk—by up to a factor of ?2 when the magnetic pressure approaches the thermal pressure—but it cannot reverse it. A previous inference that a pure-B? field whose amplitude decreases fast enough with radius leads to outward migration applies only in 2D. In fact, we find that, in 3D, a pure-B? disk undergoes a rapid transition to turbulence on account of a magnetorotational instability that is triggered by the planet-induced appearance of a weak Bz component.

Uribe, Ana; Bans, Alissa; Königl, Arieh

2015-03-01

115

Vertical Migration in the Sediment-Dwelling Sulfur Bacteria Thioploca spp. in Overcoming Diffusion Limitations.  

Science.gov (United States)

In order to investigate the environmental requirements of the filamentous sulfur bacteria Thioploca spp., we tested the chemotactic responses of these sedimentary microorganisms to changes in oxygen, nitrate, and sulfide concentrations. A sediment core with a Thioploca mat, retrieved from the oxygen-minimum zone on the Chilean shelf, was incubated in a recirculating flume. The addition of 25 (mu)mol of nitrate per liter to the seawater flow induced the ascent of the Thioploca trichomes (length, up to 70 mm) in their mostly vertically oriented gelatinous sheaths. The upper ends of the filaments penetrated the sediment surface and protruded 1 to 3 mm into the flowing water before they bent downstream. By penetrating the diffusive boundary layer, Thioploca spp. facilitate efficient nitrate uptake in exposed trichome sections that are up to 30 mm long. The cumulative length of exposed filaments per square centimeter of sediment surface was up to 92 cm, with a total exposed trichome surface area of 1 cm(sup2). The positive reaction to nitrate overruled a negative response to oxygen, indicating that nitrate is the principal electron acceptor used by Thioploca spp. in the anoxic environment; 10-fold increases in nitrate fluxes after massive emergence of filaments strengthened this hypothesis. A positive chemotactic response to sulfide concentrations of less than 100 (mu)mol liter(sup-1) counteracted the attraction to nitrate and, along with phobic reactions to oxygen and higher sulfide concentrations, controlled the vertical movement of the trichomes. We suggest that the success of Thioploca spp. on the Chilean shelf is based on the ability of these organisms to shuttle between the nitrate-rich boundary layer and the sulfidic sediment strata. PMID:16535328

Huettel, M; Forster, S; Kloser, S; Fossing, H

1996-06-01

116

137Cs concentration in zooplankton and its relation to taxonomic composition in the western North Pacific Ocean  

International Nuclear Information System (INIS)

To study the role of zooplankton in the transport of 137Cs in the ocean, zooplankton samples were collected in October 2005 and June 2006 in the western North Pacific Ocean. The peak zooplankton biomass was observed in the surface layer, and gelatinous plankton was more abundant in October 2005 than in June 2006 reflecting exchange of water masses. The concentrations of 137Cs in zooplankton varied from 11 to 24 mBq kg wet-1 and were higher in October 2005 than in June 2006. The elevated abundance of gelatinous zooplankton probably led to higher concentration of 137Cs in zooplankton in October 2005. Annual export fluxes of 137Cs by ontogenetic vertical migrant copepods were estimated to be 0.8 and 0.6 mBq m-2 year-1 at 200 and 1000 m depths, respectively; this suggested that transport of 137Cs by zooplankton may be no trivial pathway

117

Zooplankton of West Madagascar  

Science.gov (United States)

During six week survey (August - October 2009) in Western and Northern coast of Madagascar, the R/V 'Dr. Fridtjof Nansen' has carried out a study of the pelagic ecosystem. In collaboration with Agulhas & Somali Current Large Marine Ecosystems project (ASCLME) and South West Indian Ocean Fisheries Project (SWIOFP), the aim of the survey was to establish the physical, chemical and biological characteristics of the Western Madagascar shelf region as a whole. Zooplankton samples were collected with Hydrobios Multinet at all environmental stations ranging from 200 m depth to the surface. The Multinet was equipped with 5 nets for depth-stratified sampling. The nets were fitted with 180 µm mesh size and the water flow through the nets was measured. The Multinet was deployed and retrieved at a rate of ~ 1.5 m per second and was obliquely hauled. The five nets were triggered at the pre-selected depth intervals 0-25m, 25-50m, 50-80m, 80-120m and 120-200m. All samples were stored in marked bottles and preserved with buffered formaldehyde of 4% for further analysis. As results,the zooplankton abundance was influenced by physico-chemical factors. During the study period 34 Family of zooplankton were identified which are dominated by Copepoda (58,69%) followed by Radiolaria (12,06%), Appendicularia (6,47%), Sagitta (5,11%), Larvae (4,57%), Ostracoda (3,13%), pelagic Foraminifera (2,15%). Family of zooplankton with abundance Copepods distribution depends on site and depth. During this study, the number of identified species is always superior to 50 for all sampling sites. The findings of the present study will help to improve the scientific knowledge of the marine ecosystem of the west coast of Madagascar.

Bemiasa, John; Remanevy, Sitraka

2014-05-01

118

Influence of dinoflagellate diurnal vertical migrations on dimethylsulfoniopropionate and dimethylsulfide distribution and dynamics (St. Lawrence Estuary, Canada)  

Energy Technology Data Exchange (ETDEWEB)

Many biological processes control the production of climatically active dimethyl sulfide (DMS) in the ocean. Peaks in DMS often coincide with the collapse of algal blooms and the release of dimethylsulfoniopropionate (DMSP), the algal precursor of DMS. Large fluctuations in DMSP and DMS concentrations have been recently reported. While the cause for this is not well understood, it may be due to the vertical migration of dinoflagellates, physiological response to the light regime, and the impact of light on bacterial utilization of DMSP and DMS. This study, conducted in July 2000 in the lower St. Lawrence Estuary, gathered information on the influence of the diurnal migration of DMSP-rich dinoflagellates on the distribution and cycling of DMSP and DMS. A water mass with high concentration of Alexandrium tamarense and Scrippsiella trochoidea was localized through a series of short rosette casts. The water mass was marked and followed for 34 hours during calm conditions. Diel patterns were noted in particulate DMSP, dissolved DMSP and DMS with minimum concentrations during the night and maximum concentrations around noon. Similar diel variations were noted in DMSP-normalized to chlorophyll 'a', suggesting a light-induced de novo DMSP synthesis during the day. Accumulation of DMS around noon may be due to the physiological response of the algae and bacteria to light. Biological gross DMS production and bacterial DMS consumption were decoupled, resulting in prompt fluctuations in DMS. The study showed that DMS concentrations in DMSP-rich dinoflagellate systems containing DMSP lyases can vary by as much as a factor of 10 over a 24 hour period. 36 refs., 2 tabs., 7 figs.

Merzouk, A.; Levasseur, M. [Laval Univ., Sainte-Foy, PQ (Canada). Dept. of Biology; Scarratt, M.; Michaud, S. [Fisheries and Oceans Canada, Maurice Lamontagne Inst., Mont Joli, PQ (Canada); Gosselin, M. [Quebec Univ., Rimouski, PQ (Canada). Institut des Sciences de la Mer de Rimouski

2004-05-01

119

Do littoral macrophytes influence crustacean zooplankton  

OpenAIRE

In a meso-eutrophic reservoir, cladoceran and copepod assemblages were characterised in two sampling sites: One located in the pelagic zone (site 1) and the other in the shallow littoral zone (site 2), the latter colonised by emergent macrophytes. Samples were collected biweekly from June to July 2001 and from May to July 2002 at the two sites. At site 1, crustacean zooplankton samples were obtained by vertical hauls using a Wisconsin type net of 64 mm mesh size. At site 2 several ra...

Geraldes, Ana Maria; Boavida, Maria Jose?

2004-01-01

120

Diel vertical migration patterns in two populations of Chaoborus flavicans larvae (Diptera: Chaoboridae in response to fish kairomones  

Directory of Open Access Journals (Sweden)

Full Text Available Diel vertical migration (DVM of larvae of the phantom midge Chaoborus flavicans (Diptera: Chaoboridae inhabiting a fishless pond and a fish-abundant lake (Lake Nakanuma was studied in the field and in the laboratory. In the fishless pond, dissolved oxygen concentration and water temperature were homogeneously distributed in the vertical profiles and Chaoborus larvae did not show DVM. In contrast, there was thermal stratification and an anoxic layer in Lake Nakanuma, and 2nd, 3rd and 4th instar Chaoborus larvae exhibited DVM. Fourth instar Chaoborus larvae collected from the two populations were introduced into thermally stratified acrylic tubes containing 'fish water' (water conditioned by fish and containing only the fish 'smell' or control water free of fish smell after a two-day acclimatization, and the larval positions in the tubes were analysed during the day and at night. The two populations of Chaoborus larvae showed different DVM patterns in the control water: the larvae from Lake Nakanuma exhibited DVM, whereas those from the fishless pond did not. Chaoborus larvae from Lake Nakanuma responded to the fish kairomones, exhibiting marked DVM in the fish water, whereas little response to the fish smell was recognized in the larvae from the fishless pond. The presence of a difference in response between the two populations implies that they had genetically different patterns of expression of DVM and thus different behavioural responses to the fish smell. The fish smell tended to cause the Chaoborus larvae in the tubes to increase their depth, during both the day and night. The effects of the fish smell became ambiguous with time, suggesting microbial degradation of the fish kairomones.

Takayuki HANAZATO

2008-08-01

121

The contribution of zooplankton faecal pellets to deep carbon transport in the Scotia Sea (Southern Ocean)  

Science.gov (United States)

The northern Scotia Sea contains the largest seasonal uptake of atmospheric carbon dioxide yet measured in the Southern Ocean. This study examines one of the main routes by which this carbon fluxes to the deep ocean, through the production of faecal pellets (FPs) by the zooplankton community. Deep sediment traps were deployed in two sites with contrasting ocean productivity regimes (P3, naturally iron-fertilized and P2, iron-limited), within the same water mass. The magnitude and seasonal pattern of particulate organic carbon (POC) and FPs in the traps was markedly different between the two sites. Maximum fluxes at P3 (22.91 mg C m-2 d-1; 2534 × 10 FP m-2 d-1) were an order of magnitude higher than at P2 (4.01 mg C m-2 d-1; 915 × 10 FP m-2 d-1), with flux at P3 exhibiting a double seasonal peak, compared to a single flatter peak at P2. The maximum contribution of FP carbon to the total amount of POC was twice as high at P3 (91%) compared to P2 (40%). The dominant FP category at P3 varied between round, ovoidal, cylindrical and tabular over the course of the year while, at P2, ovoidal FPs were consistently dominant, always making up more than 60% of the FP assemblage. There was also a difference in the FP state between the two sites, with FPs being relatively intact at P3, while FPs were often fragmented with broken peritrophic membranes at P2. The exception was ovoidal FPs, which were relatively intact at both sites. Our observations suggest that there was community shift from an herbivorous to an omnivorous diet from spring through to autumn at P3 while detritivores had a higher relative importance over the year at P2. Furthermore, the flux was mainly a product of the vertically migrating zooplankton community at P3 while the FP flux was more likely to be generated by deeper-dwelling zooplankton feeding on recycled material at P2. The results demonstrate that the feeding behavior and vertical distribution of the zooplankton community plays a critical role in controlling the magnitude of carbon export to the deep ocean in this region.

Manno, C.; Stowasser, G.; Enderlein, P.; Fielding, S.; Tarling, G. A.

2014-11-01

122

Assessment of vertical scar migration after classical abdominoplasty followed by lower abdominal flap fixation / Avaliação da migração vertical da cicatriz pós-abdominoplastia clássica com fixação do retalho abdominal inferior  

Scientific Electronic Library Online (English)

Full Text Available SciELO Brazil | Language: English Abstract in portuguese INTRODUÇÃO: Na cirurgia plástica, uma constante preocupação é a cicatriz pós-operatória. É muito importante para o cirurgião conhecer a evolução natural da cicatriz. A cicatriz de abdominoplastia tem a tendência natural de subir com o passar do tempo. Neste estudo, calculou-se a migração vertical na [...] tural da cicatriz pós-abdominoplastia, avaliando o efeito da fixação do retalho abdominal inferior na prevenção dessa ascensão. MÉTODO: Estudo prospectivo e randomizado, realizado na 38ª Enfermaria da Santa Casa de Misericórdia do Rio de Janeiro durante o ano de 2010, incluindo 20 pacientes do sexo feminino com indicação de abdominoplastia, divididas em dois grupos, A e B, aleatoriamente. Nas pacientes do grupo A, foi realizada abdominoplastia clássica, segundo técnica preconizada pelo Prof. Ivo Pitanguy, e no grupo B foi incluída a fixação do retalho abdominal inferior por meio de sutura interessando a fáscia de Scarpa e a aponeurose do músculo reto abdominal. Duas semanas e seis meses após a cirurgia, foi medida a distância vertical em 16 pacientes, após aplicação dos critérios de exclusão, calculando-se a média de migração vertical e a diferença média entre os dois grupos. RESULTADOS: A diferença média de migração vertical ao longo de toda a cicatriz foi de 0,4 cm, sendo a média geral de migração nos grupo A (controle) e B (casos com fixação) de 1,06 cm e 0,68 cm, respectivamente. CONCLUSÕES: A cicatriz pós-abdominoplastia sofre migração vertical ao longo do tempo, sendo menor quando o retalho inferior é fixado. O cirurgião deve estar ciente da migração sofrida pela cicatriz para melhor planejamento da posição de sua incisão Abstract in english BACKGROUND: In plastic surgery, the postoperative scar is a frequent concern. It is very important for the surgeon to understand the natural evolution of the scar. The abdominoplasty scar has a natural tendency to move upwards over time. In this study, the extent of natural vertical scar migration a [...] fter abdominoplasty was calculated and the effect of fixing the lower abdominal flap to prevent this rise was assessed. METHODS: This prospective and randomized study was conducted at the 38th Nursing service of Santa Casa de Misericórdia do Rio de Janeiro, during 2010, and included 20 female patients with an indication for abdominoplasty. The patients were randomly divided into two groups, A and B. Classical abdominoplasty was performed in group A patients, according to the technique recommended by Prof. Ivo Pitanguy. Patients in group B also underwent lower abdominal flap fixation by suturing of Scarpa's fascia and the rectus abdominis muscle aponeurosis. At both two weeks and six months after surgery, the distance of vertical scar movement was measured in 16 patients after application of exclusion criteria. The average vertical migration and the mean difference between the groups were calculated. RESULTS: The average difference between the groups in vertical migration throughout the scar was 0.4 cm, with a mean overall migration of 1.06 cm and 0.68 cm in groups A (control group) and B (cases with fixation), respectively. CONCLUSIONS: The scar formed after abdominoplasty undergoes vertical migration over time; this migration is decreased when the lower abdominal flap is fixed. The surgeon should be aware of scar migration for better planning of the incision location

123

Migraciones verticales de Alexandrium excavatum (Braarud Balech et Tangen en columnas experimentales Vertical migration of Alexandrium excavatum (Braaruud Balech et Tangen In experimental columns  

Directory of Open Access Journals (Sweden)

Full Text Available As migrações verticais nicterais do dinoflagelado Alexandrium excavatum, foram observadas em uma coluna de vidro (50 cm de altura e 8 cm de diâmetro, durante um ciclo de 14 horas de luz/10 horas de escuro. As amostras foram tomadas a cada 2 ou 3 horas em superfície, meio e fundo. Verificou-se que os organismos de A. excavatum se agregam em superfície durante o dia e descem à noite. Os efeitos da estratificação da temperatura e exaustão dos nutrientes sobre o padrão da migração vertical foram examinados. A presença da termoclina de 6ºC retardou o movimento de migração. A deficiência do nitrogênio na camada superior da cultura antecipou a migração dos organismos em direção ao fundo, durante o dia; a adição de nitrato à camada de fundo antecipou a migração em direção à superfície, durante a noite. A velocidade de absorção do nitrato, no escuro, por células deficientes em nitrogênio, foi determinada a partir da diminuição da concentração desse nutriente na cultura. A taxa de absorção de nitrato foi elevada durante a primeira hora, decresceu nas três horas seguintes e foi nula a seguir. Sugere-se que a habilidade de A excavatum para absorver nitrato no período de escuro, juntamente com a migração vertical, possam ser mecanismos que regulem o seu florescimento.Diel vertical migrations of the marine dinoflagellate A excavatum were followed in a laboratory water column, and the effects of temperature stratification and nitrogen depletion on patterns of migration were examined. It was found that A. excavatum is a vertical migrator aggregating at surface during daylight, and descending at night. A six-degree thermocline did not restrict its migration but delayed the vertical movements. Nitrogen depletion in the culture was correlated with earlier downward migration in the day, and nitrate assimilation in the dark was confirmed. In another essay, with a nitrogen deficient culture, nocturnal nitrate uptake per cell was measured. It is suggested that the ability of A. excavatum to take up nitrate in the dark working together with diurnal vertical migration could be important mechanisms regulating bloom developments.

Betina Andrea Santos

1992-01-01

124

Migraciones verticales de Alexandrium excavatum (Braarud) Balech et Tangen en columnas experimentales / Vertical migration of Alexandrium excavatum (Braaruud) Balech et Tangen in experimental columns  

Scientific Electronic Library Online (English)

Full Text Available SciELO Brazil | Language: Spanish Abstract in portuguese As migrações verticais nicterais do dinoflagelado Alexandrium excavatum, foram observadas em uma coluna de vidro (50 cm de altura e 8 cm de diâmetro), durante um ciclo de 14 horas de luz/10 horas de escuro. As amostras foram tomadas a cada 2 ou 3 horas em superfície, meio e fundo. Verificou-se que o [...] s organismos de A. excavatum se agregam em superfície durante o dia e descem à noite. Os efeitos da estratificação da temperatura e exaustão dos nutrientes sobre o padrão da migração vertical foram examinados. A presença da termoclina de 6ºC retardou o movimento de migração. A deficiência do nitrogênio na camada superior da cultura antecipou a migração dos organismos em direção ao fundo, durante o dia; a adição de nitrato à camada de fundo antecipou a migração em direção à superfície, durante a noite. A velocidade de absorção do nitrato, no escuro, por células deficientes em nitrogênio, foi determinada a partir da diminuição da concentração desse nutriente na cultura. A taxa de absorção de nitrato foi elevada durante a primeira hora, decresceu nas três horas seguintes e foi nula a seguir. Sugere-se que a habilidade de A excavatum para absorver nitrato no período de escuro, juntamente com a migração vertical, possam ser mecanismos que regulem o seu florescimento. Abstract in spanish [...] Abstract in english Diel vertical migrations of the marine dinoflagellate A excavatum were followed in a laboratory water column, and the effects of temperature stratification and nitrogen depletion on patterns of migration were examined. It was found that A. excavatum is a vertical migrator aggregating at surface duri [...] ng daylight, and descending at night. A six-degree thermocline did not restrict its migration but delayed the vertical movements. Nitrogen depletion in the culture was correlated with earlier downward migration in the day, and nitrate assimilation in the dark was confirmed. In another essay, with a nitrogen deficient culture, nocturnal nitrate uptake per cell was measured. It is suggested that the ability of A. excavatum to take up nitrate in the dark working together with diurnal vertical migration could be important mechanisms regulating bloom developments.

Betina Andrea, Santos; Jose Ignacio, Carreto.

125

Length Related Diurnal Vertical Migration of Cod (Gadus morhua L.), Haddock (Melanogrammus aeglefinus L.) and Redfish (Sebastes spp.) in the Barents Sea  

OpenAIRE

Vertical fish migrations can increase variability in bottom survey data, especially if unknown diurnal length-frequency distribution is different between layers. Surveys, using echo sounder technique to estimate demersal fish found pelagic, can be seriously biased when using nearby bottom station to estimate the length distribution of pelagic fish. Knowledge about different length-frequency distribution between layers is very important for accurate stock assessments calculations. Three fish s...

Einarsson, Haraldur Arnar

2001-01-01

126

Determination of effective vertical migration velocity and residence times of 137Cs in sediments of Mumbai Harbor Bay using compartment models  

International Nuclear Information System (INIS)

The vertical concentration profile of 137Cs in core sediment of Mumbai Harbour Bay has been studied by the compartment models. Based on the measured concentrations of 137Cs in the sediment layers, the transport parameters as residence half life and effective migration velocity were determined. The residence half lives were observed to be 5 years and 13.6 years in cores L-3 and L-5 respectively. The corresponding effective migration velocity was obtained to be 7.2 cm/y and 3.23 cm/y over the core length of 36 cm and 44 cm respectively. The migration velocities obtained were well within reported values in literatures. (author)

127

A video-plankton and microstructure profiler for the exploration of in situ connections between zooplankton and turbulence  

Science.gov (United States)

Turbulence and mixing are ubiquitous in the environment of planktonic organisms and critical in large-scale physical and chemical oceanographic budgets. Recent studies have shown conflicting results on the contribution of zooplankton to ocean mixing as well as the impact of turbulence on zooplankton feeding and swimming behavior. Some of the confusion arises from the lack of properly resolved, simultaneous and co-located observations of zooplankton and turbulence. This paper introduces and discusses results from preliminary deployments of a Video Plankton Recorde-Vertical Microstructure Profiler (VP-VMP), which is shown to provide good quality, high-resolution, simultaneous observations of zooplankton and turbulence. Non-turbulent shear spectra associated with a zooplankton layer are discussed in terms of automating the rejection of unreliable dissipation estimates, the shear created by individual organisms and profiler avoidance. Comparing these fine-scale observations of zooplankton and turbulence with bulk measures and possible future improvements are also discussed.

Ross, Tetjana

2014-07-01

128

Effects of physical processes on structure and transport of thin zooplankton layers in the coastal ocean  

Science.gov (United States)

Thin layers of plankton are recurrent features in a variety of coastal systems. These layers range in thickness from a few centimeters to a few meters. They can extend horizontally for kilometers and have been observed to persist for days. Densities of organisms found within thin layers are far greater than those above or below the layer, and as a result, thin layers may play an important role in the marine ecosystem. The paramount objective of this study was to understand the physical processes that govern the dynamics of thin layers of zooplankton in the coastal ocean. We deployed instruments to measure physical processes and zooplankton distribution in northern Monterey Bay; during an 11 d period of persistent upwelling-favorable winds, 7 thin zooplankton layers were observed. These zooplankton layers persisted throughout daylight hours, but were observed to dissipate during evening hours. These layers had an average vertical thickness of 1.01 m. No layers were found in regions where the Richardson number was layers. Thin zooplankton layers were also located in regions of reduced flow. In addition, our observations show that the vertical depth distribution of thin zooplankton layers is modulated by high-frequency internal waves, with periods of 18 to 20 min. Results from this study clearly show an association between physical structure, physical processes and the presence of thin zooplankton layers in Monterey Bay. With this new understanding we may identify other coastal regions that have a high probability of supporting thin layers. ?? Inter-Research 2005.

McManus, M.A.; Cheriton, O.M.; Drake, P.J.; Holliday, D.V.; Storlazzi, C.D.; Donaghay, P.L.; Greenlaw, C.F.

2005-01-01

129

Diel vertical migration of copepods in a Brazilian lake: a mechanism for decreasing risk of Chaoborus predation? A migração vertical de copépodos em um lago brasileiro: um mecanismo para diminuir o risco de predação por Chaoborus?  

Directory of Open Access Journals (Sweden)

Full Text Available A comparison between two studies on diel vertical migration of two cyclopoid copepod species, in Lake Monte Alegre, undertaken in 1985/86 and 1999, revealed a change in their migratory behavior. In summer, during a period of marked stratification with low dissolved oxygen near the bottom, the organisms avoided the deepest layers, and migration was nocturnal or undetectable, in both periods. On other occasions, with partial or total circulation in the lake, a weak twilight migration of copepodites and adults in 1985 was replaced by the reverse in 1999. Differences were found among stages, with the weakest or undetectable migration being observed for nauplii. The migratory pattern change for copepodites and adults might be related with a recent predation pressure increase by Chaoborus larvae on copepods, after the virtual disappearance of their main cladoceran prey.A comparação entre dois estudos sobre migração vertical diária de duas espécies de copépodos ciclopóides no Lago Monte Alegre, realizados entre 1985/86 e 1999, revelou mudança em seu comportamento migratório. No verão, durante período de marcada estratificação, com pouco oxigênio dissolvido próximo ao fundo, as camadas mais profundas foram evitadas pelos organismos e a migração foi noturna ou não ocorreu. Em outras ocasiões, com circulação parcial ou total do lago, uma fraca migração crepuscular de copepoditos e adultos, em 1985, foi substituída por reversa em 1999. Foram encontradas diferenças entre os estágios, sendo que os náuplios não migraram ou migraram fracamente. A mudança do padrão migratório de copepoditos e adultos poderia estar relacionada a recente aumento da predação de copépodos por larvas de Chaoborus, depois do desaparecimento virtual do cladócero, sua presa principal.

Perticarrari A.

2004-05-01

130

Diel vertical migration of copepods in a Brazilian lake: a mechanism for decreasing risk of Chaoborus predation? / A migração vertical de copépodos em um lago brasileiro: um mecanismo para diminuir o risco de predação por Chaoborus?  

Scientific Electronic Library Online (English)

Full Text Available SciELO Brazil | Language: English Abstract in portuguese A comparação entre dois estudos sobre migração vertical diária de duas espécies de copépodos ciclopóides no Lago Monte Alegre, realizados entre 1985/86 e 1999, revelou mudança em seu comportamento migratório. No verão, durante período de marcada estratificação, com pouco oxigênio dissolvido próximo [...] ao fundo, as camadas mais profundas foram evitadas pelos organismos e a migração foi noturna ou não ocorreu. Em outras ocasiões, com circulação parcial ou total do lago, uma fraca migração crepuscular de copepoditos e adultos, em 1985, foi substituída por reversa em 1999. Foram encontradas diferenças entre os estágios, sendo que os náuplios não migraram ou migraram fracamente. A mudança do padrão migratório de copepoditos e adultos poderia estar relacionada a recente aumento da predação de copépodos por larvas de Chaoborus, depois do desaparecimento virtual do cladócero, sua presa principal. Abstract in english A comparison between two studies on diel vertical migration of two cyclopoid copepod species, in Lake Monte Alegre, undertaken in 1985/86 and 1999, revealed a change in their migratory behavior. In summer, during a period of marked stratification with low dissolved oxygen near the bottom, the organi [...] sms avoided the deepest layers, and migration was nocturnal or undetectable, in both periods. On other occasions, with partial or total circulation in the lake, a weak twilight migration of copepodites and adults in 1985 was replaced by the reverse in 1999. Differences were found among stages, with the weakest or undetectable migration being observed for nauplii. The migratory pattern change for copepodites and adults might be related with a recent predation pressure increase by Chaoborus larvae on copepods, after the virtual disappearance of their main cladoceran prey.

Perticarrari, A.; M. S., Arcifa; R. A., Rodrigues.

2004-05-01

131

Distribution and abundance of zooplankton populations in Crater Lake, Oregon  

Science.gov (United States)

The zooplankton assemblages in Crater Lake exhibited consistency in species richness and general taxonomic composition, but varied in density and biomass during the period between 1988 and 2000. Collectively, the assemblages included 2 cladoceran taxa and 10 rotifer taxa (excluding rare taxa). Vertical habitat partitioning of the water column to a depth of 200 m was observed for most species with similar food habits and/or feeding mechanisms. No congeneric replacement was observed. The dominant species in the assemblages were variable, switching primarily between periods of dominance of Polyarthra-Keratella cochlearis and Daphnia. The unexpected occurrence and dominance of Asplanchna in 1991 and 1992 resulted in a major change in this typical temporal shift between Polyarthra-K. cochlearis and Daphnia. Following a collapse of the zooplankton biomass in 1993 that was probably caused by predation from Asplanchna, Kellicottia dominated the zooplankton assemblage biomass between 1994 and 1997. The decline in biomass of Kellicottia by 1998 coincided with a dramatic increase in Daphnia biomass. When Daphnia biomass declined by 2000, Keratella biomass increased again. Thus, by 1998 the assemblage returned to the typical shift between Keratella-Polyarthra and Daphnia. Although these observations provided considerable insight about the interannual variability of the zooplankton assemblages in Crater Lake, little was discovered about mechanisms behind the variability. When abundant, kokanee salmon may have played an important role in the disappearance of Daphnia in 1990 and 2000 either through predation, inducing diapause, or both. ?? 2007 Springer Science+Business Media B.V.

Larson, G.L.; McIntire, C.D.; Buktenica, M.W.; Girdner, S.F.; Truitt, R.E.

2007-01-01

132

Multidimensional zooplankton observations on the northern West Spitsbergen Shelf  

Science.gov (United States)

Climate change in the Arctic influences the ocean circulation and the hydrographic regime which leads to substantial reconstruction of the zooplankton community, notably a northward shift of dominant boreal species. These unstable Arctic environmental conditions are expected to affect the pelagic food web, which is highly dependent on the consumption of Calanus copepods. The present study is based on multidisciplinary zooplankton observations carried out with net sampling, a Laser Optical Plankton Counter and high frequency echosounding during two summer seasons on the West Spitsbergen Shelf. The extent of northward advection of surface Atlantic origin waters was greater in 2009 than in 2010. Our study determined the position of the surface frontal system and confirmed hydrographical separation of distinctive waters together with their associated fauna. Very abundant assemblages of C. finmarchicus dominated Atlantic origin waters in both years while a higher share of C. glacialis was observed in Arctic origin waters during colder 2010. The observed zooplankton assemblages ranged in size up to a few kilometres horizontally and > 40 m vertically. Combined implementation of conventional sampling, acoustic and optical methods provided a full spatial zooplankton distribution picture in an area of great importance as a potential feeding ground for planktivores.

Trudnowska, E.; Szczucka, J.; Hoppe, L.; Boehnke, R.; Hop, H.; Blachowiak-Samolyk, K.

2012-09-01

133

Seasonal variation of zooplankton abundance, composition and biomass in the Chabahar Bay, Oman Sea  

Directory of Open Access Journals (Sweden)

Full Text Available Temporal and spatial variation of zooplankton abundance, composition and biomass were examined on the Chabahar Bay, Oman Sea. The Chabahar Bay, a subtropical and semi-enclosed bay, provides an ideal breeding ground for many fish and shellfish. Five stations were investigated along the Bay. This area is under the influence of the Indian Ocean seasonal monsoons. Zooplankton was collected with vertical plankton tows using 100 µm mesh nets. Copepods dominated the zooplankton community followed by larvacea, cladocera and chaetognatha. Fifteen taxa of zooplankton were identified. Oithona nana and Euterpina acutifrons were dominated in the whole year and Larvacea showed a bloom in Northeast Monsoon. A Two-way ANOVA indicated that there were differences in abundance and biomass between sampling periods and between stations were significant. The peak zooplankton abundance in NE Monsoon could be due to winter cooling, with entrainment of nutrients into the upper layer producing phytoplankton blooms. The decline of zooplankton abundance and biomass in South West Monsoon and post-monsoon could be explained by decrease in chlorophyll a concentrations. The present result showed the composition and distribution of zooplankton differed between the monsoon seasons, resulted from changes in hydrographic conditions.

Neda Fazeli

2013-12-01

134

Light-Sensitive Vertical Migration of the Japanese Eel Anguilla japonica Revealed by Real-Time Tracking and Its Utilization for Geolocation  

Science.gov (United States)

Short-time tracking (one to eight days) of the Japanese eel (Anguilla japonica) using ultrasonic transmitter was performed in the tropical-subtropical area adjacent to the spawning area and temperate area off the Japanese Archipelago. Of 16 eels (11 wild and five farmed) used, 10 wild eels displayed clear diel vertical migration (DVM) from the beginning, while the other five farmed eels tracked for 19 to 66 hours did not. During daytime, a significantly positive correlation between migration depth and light intensity recorded on the vessel was observed in the 10 wild eels, indicating that the eels were sensitive to sunlight even at the middle to lower mesopelagic zone (500 to 800 m). During nighttime, the eel migration depth was observed to be associated with the phase, rising and setting of the moon, indicating that the eels were sensitive to moonlight at the upper mesopelagic zone (<300 m). Two of 10 wild eels were in the yellow stage but shared similar DVM with the silver stage eels. Swimbladders of three silver stage eels were punctured before releasing, but very little effect on DVM was observed. The eels very punctually initiated descent upon nautical dawn and ascent upon sunset, enabling us to determine local times for sunrise and sunset, and hence this behavior may be used for geolocating eels. In fact, estimated positions of eels based on the depth trajectory data were comparable or even better than those obtained by light-based archival tag in other fish species. PMID:25875179

Chow, Seinen; Okazaki, Makoto; Watanabe, Tomowo; Segawa, Kyohei; Yamamoto, Toshihiro; Kurogi, Hiroaki; Tanaka, Hideki; Ai, Ken-ichiro; Kawai, Miho; Yamamoto, Shin-ichi; Mochioka, Noritaka; Manabe, Ryotaro; Miyake, Yoichi

2015-01-01

135

Zooplankton distributions and transport across the northeastern tidal front of Georges Bank  

Science.gov (United States)

Tidal fronts are important sites of contact and mixing between zooplankton populations on and off Georges Bank in the northwest Atlantic. This study, a component of the US GLOBEC program, examined crossfrontal distributions of zooplankton, especially the copepod Calanus finmarchicus, across the northeastern tidal front of Georges Bank relative to the tidal cycle, frontal structure, flow field, and day/night cycle. A unique feature was a precisely executed sampling strategy designed to isolate spatial, tidal, and day/night effects. Vertically stratified zooplankton sampling was done along tidally coordinated crossfrontal transects and during time series studies at specific locations. Zooplankton taxa differed in their spatial and vertical distributions relative to the front and the hydrographic structure of the water column. There were significant associations between zooplankton assemblages and spatial location, depth, and water mass. Zooplankton distributions generally tracked water masses but usually showed crossbank abundance gradients. Consistent differences between day and night distributions were not apparent for most taxa. Meroplankton (larvae of benthic animals) were derived primarily from onbank populations. The zooplankton community was advected with the tidal flow. Crossfrontal distributions characteristic of onbank and offbank flow regimes clearly differentiated tidal phases and interacted with the flow field and topography. Salinity (a proxy for water mass) and depth interacted in controlling vertical distributions. As tidal forcing sloshed water masses up and down the bank slope, some taxa followed isohalines through depth changes while other taxa maintained themselves within a relatively limited depth or salinity regime. Surface convergence and downwelling, tidal upwelling of bottom water, and mid-depth tidal pumping influenced crossfrontal exchange.

Wishner, Karen F.; Outram, Dawn M.; Ullman, David S.

2006-11-01

136

Melatonin signaling controls circadian swimming behavior in marine zooplankton.  

Science.gov (United States)

Melatonin, the "hormone of darkness," is a key regulator of vertebrate circadian physiology and behavior. Despite its ubiquitous presence in Metazoa, the function of melatonin signaling outside vertebrates is poorly understood. Here, we investigate the effect of melatonin signaling on circadian swimming behavior in a zooplankton model, the marine annelid Platynereis dumerilii. We find that melatonin is produced in brain photoreceptors with a vertebrate-type opsin-based phototransduction cascade and a light-entrained clock. Melatonin released at night induces rhythmic burst firing of cholinergic neurons that innervate locomotor-ciliated cells. This establishes a nocturnal behavioral state by modulating the length and the frequency of ciliary arrests. Based on our findings, we propose that melatonin signaling plays a role in the circadian control of ciliary swimming to adjust the vertical position of zooplankton in response to ambient light. PMID:25259919

Tosches, Maria Antonietta; Bucher, Daniel; Vopalensky, Pavel; Arendt, Detlev

2014-09-25

137

ANNUAL REPORT. INFLUENCE OF CLASTIC DIKES ON VERTICAL MIGRATION OF CONTAMINANTS IN THE VADOSE ZONE AT HANFORD  

Science.gov (United States)

This research is testing the hypothesis that clastic dikes at the Hanford Site provide preferential pathways that enhance the vertical movement of moisture and contaminants through the vadose zone. Current flow and transport models of the vadose zone at the 200 Areas are based on...

138

Model Simulation of Diurnal Vertical Migration Patterns of Different-Sized Colonies of Microcystis Employing a Particle Trajectory Approach  

OpenAIRE

Microcystis, a genus of potentially harmful cyanobacteria, is known to proliferate in stratified freshwaters due to its capability to change cell density and regulate buoyancy. In this study, a trajectory model was developed to simulate the cell density change and spatial distribution of Microcystis cells with nonuniform colony sizes. Simulations showed that larger colonies migrate to the near-surface water layer during the night to effectively capture irradiation and become heavy enough to s...

Chien, Yu Ching; Wu, Shian Chee; Chen, Wan Ching; Chou, Chih Chung

2013-01-01

139

Zooplankton in the Arctic outflow  

Science.gov (United States)

Climate changes in the Arctic cause the changes in the current system that may have cascading effect on the structure of plankton community and consequently on the interlinked and delicately balanced food web. Zooplankton species are by definition incapable to perform horizontal moving. Their transport is connected with flowing water. There are zooplankton species specific for the definite water masses and they can be used as markers for the different currents. That allows us to consider zooplankton community composition as a result of water mixing in the studied area. Little is known however about the mechanisms by which spatial and temporal variability in advection affect dynamics of local populations. Ice conditions are also very important in the function of pelagic communities. Melting time is the trigger to all "plankton blooming" processes, and the duration of ice-free conditions determines the food web development in the future. Fram Strait is one of the key regions for the Arctic: the cold water outflow comes through it with the East Greenland Current and meets warm Atlantic water, the West Spitsbergen Current, producing complicated hydrological situation. During 2007 and 2008 we investigated the structure functional characteristics of zooplankton community in the Fram Strait region onboard KV "Svalbard" (April 2007, April and May 2008) and RV "Jan Mayen" (May 2007, August 2008). This study was conducted in frame of iAOOS Norway project "Closing the loop", which, in turn, was a part of IPY. During this cruises multidisciplinary investigations were performed, including sea-ice observations, CTD and ADCP profiling, carbon flux, nutrients and primary production measurements, phytoplankton sampling. Zooplankton was collected with the Hydro-Bios WP2 net and MultiNet Zooplankton Sampler, (mouth area 0.25 m2, mesh size 180 um).Samples were taken from the depth strata of 2000-1500, 1500-1000, 1000-500,500-200, 200-100, 100-60, 60-30, 30-0 m. Gut fluorescence content were measured in dominant species to investigate effect of Chl a concentration and phytoplankton composition on ingestion rate. Egg production experiments were carried out under different food conditions. Rare deep water zooplankton species were also investigated to increase our knowledge in the Arctic biodiversity. Copepods Calanus finmarchicus is known as a marker of the Atlantic water mass, Calanus glacialis and Calanus hyperboreus, vice versa, are the coldwater Arctic species. In our study we investigated three Calanus species distribution and analyzed their ecological status. Changes in zooplankton composition results in the alteration of energy transfer within the pelagic food web ("cold" and "warm" scenarios) with potential consequences for growth and survival of seabirds Little Auk (Alle alle) and Black-legged kittiwake (Rissa tridactyla). We discuss the advection effect on the zooplankton community, compare the population development phases with phytoplankton bloom phases (match-mismatch), estimate grazing impact on phytoplankton community and consider different life strategies for the three different Calanus species.

Soloviev, K. A.; Dritz, A. V.; Nikishina, A. B.

2009-04-01

140

Zooplankton interactions with the oxygen minimum zone in the eastern south pacific / Interacciones del zooplancton con la zona de mínimo oxigeno en el Pacífico sur oriental  

Scientific Electronic Library Online (English)

Full Text Available SciELO Chile | Language: English Abstract in spanish El zooplancton de la zona de surgencia costera en el Pacífico Sur Oriental se encuentra afecto a una zona de mínimo de oxígeno muy somera (ZMO). En el presente trabajo, se resume la información disponible de las especies del zooplancton que interactuan con la ZMO en la región de surgencia del norte [...] de Chile. Los datos provienen desde los cruceros MinOx y ZOMEI realizados en marzo del 2000 y octubre del 2005, respectivamente a bordo del R/V Vidal Gormáz de la Armada de Chile. Cerca de 19 especies de copépodos y 10 de eufáusidos se analizaron en su distribución vertical y conducta migratoria. Varias especies abundantes se encuentran restringidas por la ZMO a la capa superior de 50 m. Sin embargo, otras especies abundantes habitan temporal o permanentemente la ZOM, contribuyendo sustancialmente al flujo vertical de C producido en la zona fótica a través de la migración vertical activa. La dinámica poblacional y las estrategias de los ciclos de vida, así como las adaptaciones metabólicas de las distintas especies, pueden no solo modular la contribución de ellas a los flujos verticales de C, sino que además a la mantención y persistencia de la masa de agua deficiente en oxígeno. Abstract in english Zooplankton in the coastal upwelling zone off the eastern South Pacific must cope with a shallow oxygen minimum zone. In this work, I summarize available information on the zooplankton species that interact with the OMZ in the upwelling region off northern Chile. Data are available from the MinOx cr [...] uise carried out in March 2000 and the ZOMEI cruise perfomed in October 2005, both onboard the R/V Vidal Gormaz of the Chilean navy. Nineteen species of copepods and 10 of euphausiids were analyzed in their vertical distribution and migrating behavior. Several abundante species appeared constrained by the OMZ and restricted to the upper 50m layer. However, other abundant species inhabit temporarily or permanently the OMZ contributing substantially to the vertical flux of C produced in the photic zone through active vertical migration. Population dynamics and life cycle strategies, as well as metabolic adaptations of the species, may not only modulate their contributions to vertical fluxes of C, but also to the maintenance and persistence of the oxygen-depleted water mass.

Rubén, Escribano.

2006-10-01

141

Zooplankton interactions with the oxygen minimum zone in the eastern south pacific Interacciones del zooplancton con la zona de mínimo oxigeno en el Pacífico sur oriental  

Directory of Open Access Journals (Sweden)

Full Text Available Zooplankton in the coastal upwelling zone off the eastern South Pacific must cope with a shallow oxygen minimum zone. In this work, I summarize available information on the zooplankton species that interact with the OMZ in the upwelling region off northern Chile. Data are available from the MinOx cruise carried out in March 2000 and the ZOMEI cruise perfomed in October 2005, both onboard the R/V Vidal Gormaz of the Chilean navy. Nineteen species of copepods and 10 of euphausiids were analyzed in their vertical distribution and migrating behavior. Several abundante species appeared constrained by the OMZ and restricted to the upper 50m layer. However, other abundant species inhabit temporarily or permanently the OMZ contributing substantially to the vertical flux of C produced in the photic zone through active vertical migration. Population dynamics and life cycle strategies, as well as metabolic adaptations of the species, may not only modulate their contributions to vertical fluxes of C, but also to the maintenance and persistence of the oxygen-depleted water mass.El zooplancton de la zona de surgencia costera en el Pacífico Sur Oriental se encuentra afecto a una zona de mínimo de oxígeno muy somera (ZMO. En el presente trabajo, se resume la información disponible de las especies del zooplancton que interactuan con la ZMO en la región de surgencia del norte de Chile. Los datos provienen desde los cruceros MinOx y ZOMEI realizados en marzo del 2000 y octubre del 2005, respectivamente a bordo del R/V Vidal Gormáz de la Armada de Chile. Cerca de 19 especies de copépodos y 10 de eufáusidos se analizaron en su distribución vertical y conducta migratoria. Varias especies abundantes se encuentran restringidas por la ZMO a la capa superior de 50 m. Sin embargo, otras especies abundantes habitan temporal o permanentemente la ZOM, contribuyendo sustancialmente al flujo vertical de C producido en la zona fótica a través de la migración vertical activa. La dinámica poblacional y las estrategias de los ciclos de vida, así como las adaptaciones metabólicas de las distintas especies, pueden no solo modular la contribución de ellas a los flujos verticales de C, sino que además a la mantención y persistencia de la masa de agua deficiente en oxígeno.

Rubén Escribano

2006-10-01

142

Levels of 137Cs in muddy sediments on the seabed in the Bay of Cadiz (Spain). Part II. Model of vertical migration of 137Cs  

International Nuclear Information System (INIS)

This second part of the study reports the development of a model to describe the vertical migration of the artificial radioisotope 137Cs in the sediment column on the seabed of the Bay of Cadiz. The application of the model provides an overall picture of the process of sedimentation in the Inner Bay of Cadiz. The spatial distribution of the rate of sedimentation enables us to study the sources of sediments and the means by which the sediments have been transported. A method has been derived from the rate of sedimentation to perform the dating of the layers of sediment. The model describes the behaviour of 137Cs in the area under study, taking into account the time of residence in the zones that are the source of accumulation, the origin of the sedimentary material, together with the diffusion of the radionuclide in the sediment of the seabed

143

Comparative vertical migration of twenty on isolates of the insect parasitic nematode Heterorhabditis spp. in sand at 20°C  

OpenAIRE

Vingt et un isolats d'Hétérorhabditides, appartenant principalement à six groupes taxonomiques et provenant de dix pays différents, ont été testés pour leur migration vers le bas, à 20°C, dans des colonnes remplies de sable et pourvues ou non d'une larve de #Galleria mellonella$ déposée au fond. Les nématodes présents dans la couche supérieure (1,5 cm), la partie médiane (6 cm) et la partie inférieure (1,5 cm) des colonnes sont dénombrés à des intervalles de 8h et, occasion...

Westermann, P. R.

1995-01-01

144

Influence of Irrigation Rate and Soil Type on the Vertical Migration of Iron and Manganese in the Soils of South-East Spain  

International Nuclear Information System (INIS)

The citrus plantations in south-east Spain, situated largely on calcareous soils which are submitted to intensive cultivation, are investigating nutritional changes caused mainly by deficiencies of trace elements, especially iron and manganese, which result in a lower yield and premature exhaustion of the trees. The paper deals with a radioactive tracer study of the behaviour of these ions in soils and with the factors influencing their migration to the root zone; the object of the work is to develop a rational and economic fertilization policy. The work has been based on two types of soil, representing extreme situations encountered in practice; one soil is calcareous and the other non-calcareous. A set of columnsiwas assembled, each column having a length of 1 m and a cross-section of 32 cm2 ; solutions of 59Fe and 54Mn were added to these columns both in sulphate and chelate form. A definite amount of water, proportional to the requirements .of citrus plantations, was intermittently passed through these columns. Soil samples were taken periodically and the total activity and the activity of the assimilable and non-assimilable fractions of the elements being studied were measured. At the same time an apparatus involving a collimated scintillation detector was developed to follow the vertical migration of these ions in soils; the water drained from the columns after each irrigation was analysed radiochemically for the same purpose. (ad radiochemically for the same purpose. (author)

145

Survival probability of larval sprat in response to decadal changes in diel vertical migration behavior and prey abundance in the Baltic Sea  

DEFF Research Database (Denmark)

We employed a coupled three-dimensional biophysical model to explore long-term inter- and intra-annual variability in the survival of sprat larvae in the Bornholm Basin, a major sprat spawning area in the Baltic Sea. Model scenarios incorporated observed decadal changes in larval diel vertical distribution and climate-driven abiotic and biotic environmental factors including variability in the abundance of different, key prey species (calanoid copepods) as well as seasonal changes, long-term trends, and spatial differences in water temperature. Climate forcing affected Baltic sprat larval survival both directly (via changes in temperature) and indirectly (via changes in prey populations). By incorporating observed changes in larval diel vertical migration, decadal changes in modeled and observed survival of Baltic sprat agreed well. Higher larval survival (spawning stock biomass) was predicted in the 1990s compared to the 1980s. After changing their foraging strategy by shifting from mid-depth, low prey environment to near-surface waters, first-feeding larvae encountered much higher rates of prey encounter and almost optimal feeding conditions and had a much higher growth potential. Consequently, larvae were predicted to experience optimal conditions to ensure higher survival throughout the later larval and early juvenile stages. However, this behavioral shift also increased the susceptibility of larvae to unfavorable winddriven surface currents, contributing to the marked increase in interannual variability in recruitment observed during the past decade.

Hinrichsen, Hans-Harald; Peck, Myron A.

2010-01-01

146

Vertical nutrient and trace element migration in cambisoils after application of residues from anaerobic digestion of pig manure  

Science.gov (United States)

Cambisols sampled in alpine pastures were packed into soil columns in order to monitor downward migration of nutrient and trace elements, applied within the residue from anaerobic digestion of a pig manure. 2 rain events per week were simulated. The manure added substantial amounts of K, ammonium, Na, Ca, P, S, Cl, B, Zn and Cu to the soil, whereas Mg, Mn, Ni, Cr, Pb, Cd and V were at the same level. In the eluates, total elemental composition as well as nitrate and ammonium were monitored. Addition of soluble Fe (at 1000 mg/l as FeCl3) decreased the release of soluble sulphate, but had no significant effect on the release of Fe and P. During subsequent rain events, exchangeable K remained enriched in the topsoil, wheras total sulfur moved to deeper layers. After 8 weeks, the columns were dismantled and analyzed for quasi-total and mobile fractions. Both in topsoils and subsoils, manure addition finally increased soil pH in case of low P soils, but decreased soil pH in case of high pH soils. Effects of manure applications on groundwater formation processes will be discussed.

Sager, Manfred; Unterfrauner, Hans

2013-04-01

147

Model Simulation of Diurnal Vertical Migration Patterns of Different-Sized Colonies of Microcystis Employing a Particle Trajectory Approach.  

Science.gov (United States)

Microcystis, a genus of potentially harmful cyanobacteria, is known to proliferate in stratified freshwaters due to its capability to change cell density and regulate buoyancy. In this study, a trajectory model was developed to simulate the cell density change and spatial distribution of Microcystis cells with nonuniform colony sizes. Simulations showed that larger colonies migrate to the near-surface water layer during the night to effectively capture irradiation and become heavy enough to sink during daytime. Smaller-sized colonies instead took a longer time to get to the surface. Simulation of the diurnally varying Microcystis population profile matched the observed pattern in the field when the radii of the multisized colonies were in a beta distribution. This modeling approach is able to take into account the history of cells by keeping track of their positions and properties, such as cell density and the sizes of colonies. It also serves as the basis for further developmental modeling of phytoplanktons that are forming colonies and changing buoyancy. PMID:23633893

Chien, Yu Ching; Wu, Shian Chee; Chen, Wan Ching; Chou, Chih Chung

2013-04-01

148

{sup 137}Cs concentration in zooplankton and its relation to taxonomic composition in the western North Pacific Ocean  

Energy Technology Data Exchange (ETDEWEB)

To study the role of zooplankton in the transport of {sup 137}Cs in the ocean, zooplankton samples were collected in October 2005 and June 2006 in the western North Pacific Ocean. The peak zooplankton biomass was observed in the surface layer, and gelatinous plankton was more abundant in October 2005 than in June 2006 reflecting exchange of water masses. The concentrations of {sup 137}Cs in zooplankton varied from 11 to 24 mBq kg wet{sup -1} and were higher in October 2005 than in June 2006. The elevated abundance of gelatinous zooplankton probably led to higher concentration of {sup 137}Cs in zooplankton in October 2005. Annual export fluxes of {sup 137}Cs by ontogenetic vertical migrant copepods were estimated to be 0.8 and 0.6 mBq m{sup -2} year{sup -1} at 200 and 1000 m depths, respectively; this suggested that transport of {sup 137}Cs by zooplankton may be no trivial pathway.

Kaeriyama, Hideki [Nakaminato Laboratory for Marine Radioecology, National Institute of Radiological Sciences, Isozaki 3609, Hitachinaka, Ibaraki 311-1202 (Japan)], E-mail: hideki_k@nirs.go.jp; Watabe, Teruhisa [Nakaminato Laboratory for Marine Radioecology, National Institute of Radiological Sciences, Isozaki 3609, Hitachinaka, Ibaraki 311-1202 (Japan); Kusakabe, Masashi [Nakaminato Laboratory for Marine Radioecology, National Institute of Radiological Sciences, Isozaki 3609, Hitachinaka, Ibaraki 311-1202 (Japan); Fundamental Technology Center, National Institute of Radiological Sciences, 4-9-1 Anagawa, Inage-ku, Chiba 263-8555 (Japan)

2008-12-15

149

Calvert Cliffs zooplankton entrainment study. Final report  

International Nuclear Information System (INIS)

Entrainment studies to evaluate plant effects on zooplankton were conducted at the Calvert Cliffs Nuclear Plant. Specific effects tested were (a) the spatial and temporal variation of zooplankton density; (b) pump sampling efficiency; (c) delayed mortality; (d) vital staining as an indicator of mortality

150

Zooplankton data report: Winter MIZEX, 1987  

Energy Technology Data Exchange (ETDEWEB)

The Marginal Ice Zone Experiment (MIZEX) was an interdisciplinary, international Arctic research program designed to study the atmospheric, oceanic, and ice interactions in the Fram Strait region of the Greenland Sea. This report focuses on zooplankton data collected during the winter MIZEX program of 1987. The primary objectives of our group during MIZEX 87 were to study the distribution of zooplankton species in relation to the ice-edge, the Polar Front, and the mesoscale eddy field, and to study zooplanktonic physiology just prior to the spring phytoplankton bloom. The data in this report are quantitative analyses of zooplankton samples collected while aboard the research vessel HAKON MOSBY during MIZEX 87. This is the third in a series of data reports on zooplankton collected in the Fram Strait region during the MIZEX project. A complete catalog of the reports generated from the MIZEX program is archived at the National Snow and Ice Data Center in Boulder, Colorado, USA. 1 ref., 3 tabs.

Smith, S.L.; Lane, P.V.Z.; Schwartling, E.M.; Beck, B.

1988-12-01

151

Abundance, composition, and distribution of crustacean zooplankton in relation to hypolimnetic oxygen depletion in west-central Lake Erie  

Science.gov (United States)

Samples of crustacean zooplankton were collected monthly in west-central Lake Erie in April and June to October 1968, and in July and August 1970, before and during periods of hypolimnetic dissolved oxygen (DO) depletion. The water column at offshore stations was thermally stratified from June through September 1968, and the hypolimnion contained no DO in mid-August of 1968 or 1970. Composition, abundance, and vertical distribution of crustacean zooplankton changed coincidentally with oxygen depletion. From July to early August, zooplankton abundance dropped 79% in 1968 and 50% in 1970. The declines were attributed largely to a sharp decrease in abundance of planktonic Cyclops bicuspidatus thomasi. Zooplankton composition shifted from mainly cyclopoid copepods in July to mainly cladocerans and copepod nauplii in middle to late August. We believe that mortality of adults and dormancy of copepodites in response to anoxia was the probable reason for the late summer decline in planktonic C. b. thomasi.

Heberger, Roy F.; Reynolds, James B.

1977-01-01

152

Mechanisms controlling lateral and vertical porewater migration of depleted uranium (DU) at two UK weapons testing sites  

Energy Technology Data Exchange (ETDEWEB)

Uranium associations with colloidal and truly dissolved soil porewater components from two Ministry of Defence Firing Ranges in the UK were investigated. Porewater samples from 2-cm depth intervals for three soil cores from each of the Dundrennan and Eskmeals ranges were fractionated using centrifugal ultrafiltration (UF) and gel electrophoresis (GE). Soil porewaters from a transect running downslope from the Dundrennan firing area towards a stream (Dunrod Burn) were examined similarly. Uranium concentrations and isotopic composition were determined using Inductively Coupled Plasma-Mass Spectrometry (ICP-MS) and Multi-Collector-Inductively Coupled Plasma-Mass Spectrometry (MC-ICP-MS), respectively. The soils at Dundrennan were Fe- and Al-rich clay-loam soils whilst at Eskmeals, they were Fe- and Al-poor sandy soils; both, however, had similar organic matter contents due to the presence of a near-surface peaty layer at Eskmeals. These compositional features influenced the porewater composition and indeed the associations of U (and DU). In general, at Dundrennan, U was split between large (100 kDa-0.2 {mu}m) and small (3-30 kDa) organic colloids whilst at Eskmeals, U was mainly in the small colloidal and truly dissolved fractions. Especially below 10 cm depth, association with large Fe/Al/organic colloids was considered to be a precursor to the removal of U from the Dundrennan porewaters to the solid phase. In contrast, the association of U with small organic colloids was largely responsible for inhibiting attenuation in the Eskmeals soils. Lateral migration of U (and DU) through near-surface Dundrennan soils will involve both large and small colloids but, at depth, transport of the smaller amounts of U remaining in the porewaters may involve large colloids only. For one of the Dundrennan cores the importance of redox-related processes for the re-mobilisation of DU was also indicated as Mn{sup IV} reduction resulted in the release of both Mn{sup II} and U{sup VI} into the truly dissolved phase. - Research Highlights: {yields} U associations in soil porewaters at DU munitions sites were investigated. {yields} U distribution among colloidal/dissolved fractions varied with soil type and depth. {yields} U association with large Fe-Al-organic colloids led to removal from soil porewaters. {yields} Small organic colloidal association inhibited U removal from sandy soil porewaters. {yields} Reductive dissolution of Mn can release 'truly dissolved' U into soil porewaters.

Graham, Margaret C., E-mail: Margaret.Graham@ed.ac.uk [School of GeoSciences, Crew Building, University of Edinburgh, The King' s Buildings, West Mains Road, Edinburgh, EH9 3JN (United Kingdom); Oliver, Ian W.; MacKenzie, Angus B.; Ellam, Robert M. [Scottish Universities Environmental Research Centre (SUERC), Rankine Avenue, Scottish Enterprise Technology Park, East Kilbride, G75 0QF (United Kingdom); Farmer, John G. [School of GeoSciences, Crew Building, University of Edinburgh, The King' s Buildings, West Mains Road, Edinburgh, EH9 3JN (United Kingdom)

2011-04-15

153

Vertical segregation of Calanus finmarchicus copepodites during the spring bloom  

Science.gov (United States)

Factors influencing the vertical distribution of the most abundant grazer in the Norwegian Sea were studied in the open ocean. During May 5-14 2003 the upper 60 m of an oceanic area (10,000 km 2) in the northern Norwegian Sea were covered with a towed instrument platform collecting simultaneously in situ data on hydrography, chlorophyll a concentration and zooplankton abundance with high resolution in space and time. A consistent vertical distribution pattern of Calanus finmarchicus differing markedly from previously reported data was observed: CII-CIII copepodites were located below moderate to high chlorophyll a concentration, at depths below 30 m. CIV copepodites were located slightly higher in the water column and CV copepodites and adults were consistently found in the upper chlorophyll-rich layer. Partial constrained correspondence analysis revealed that the effect of physical factors and diel vertical migration was clearly secondary to chlorophyll a concentration in explaining the observed vertical segregation. The effects of toxic algae and predation are discussed in evolutionary context. These findings underline the importance of understanding stage-specific behaviour to build realistic models.

Basedow, Sünnje L.; Edvardsen, Are; Tande, Kurt S.

154

Trait-based approaches to zooplankton communities  

DEFF Research Database (Denmark)

Zooplankton are major primary consumers and predators in most aquatic ecosystems. They exhibit tremendous diversity of traits, ecological strategies and, consequently, impacts on other trophic levels and the cycling of materials and energy. An adequate representation of this diversity in community and ecosystem models is necessary to generate realistic predictions on the functioning of aquatic ecosystems but remains extremely challenging. We propose that the use of trait-based approaches is a promising way to reduce complexity while retaining realism in developing novel descriptions of zooplankton in ecosystem models. Characterizing zooplankton traits and trade-offs will also be helpful in understanding the selection pressures and diversity patterns that emerge in different ecosystems along major environmental gradients. Zooplankton traits can be characterized according to their function and type. Some traits, such as body size and motility, transcend several functions and are major determinants of zooplankton ecological strategies. Future developments of trait-based approaches to zooplankton should assemble a comprehensive matrix of key traits for diverse groups and explore it for general patterns; develop novel predictive models that explicitly incorporate traits and associated trade-offs; and utilize these traits to explain and predict zooplankton community structure and dynamics under different environmental conditions, including global change scenarios

Lichtman, E.; Ohman, M.D.

2013-01-01

155

Fish-mediated trait compensation in zooplankton  

DEFF Research Database (Denmark)

1. Environmental factors fluctuate spatially and temporally, and organisms that can alter phenotype in response to these changes may increase their fitness. Zooplankton are known to be able to induce body pigmentation in response to ultraviolet radiation (UVR) and to reduce the pigmentation when exposed to fish predators. Hence, reduced pigmentation because of the presence of fish could potentially lead to UVR damage, which calls for alternative protective echanisms. 2. We exposed zooplankton to fish cues and UVR stress to assess whether body pigmentation and cellular antioxidants are flexible predation and UVR defences. 3. Zooplankton exposed to fish predator cues (no direct predation) reduced their pigmentation by c. 30% in 20 days. However, they were able to rapidly counteract negative UVR effects by increasing the activity of antioxidant defences such as glutathione S-transferase (GST). When exposed to UVR, the GST activity increased by c. 100% in zooplankton that had previously reduced their pigmentation because of fish cues. Transparency in the zooplankton did not lead to considerably higher UVR damage, here measured as inhibition of olinesterase (ChE). 4. We conclude that zooplankton pigmentation and antioxidant enzymes are flexible UVR defence systems, which can be induced when needed. Zooplankton may employ antioxidant defences when pigmentation is reduced to counteract predation risk and thereby rapidly respond to detrimental effects of UVR exposure, that is, they can compensate one trait with another

Hylander, Samuel; Souza, M.S.

2012-01-01

156

Estructura comunitaria del zooplancton asociada con el fitoplancton y las masas de agua del Estrecho de Bransfield y la Isla Elefante durante el verano austral del 2006 / Zooplankton community structure and its association with the phytoplankton and water masses from the Bransfield strait and elephant island during 2006 austral summer  

Scientific Electronic Library Online (English)

Full Text Available SciELO Peru | Language: Spanish Abstract in spanish Durante el verano austral del año 2006, la abundancia y distribución espacial del zooplancton y su asociación con algunas variables físicas (masas de agua) y biológicas (fitoplancton) fueron investigadas en el Estrecho de Bransfield y al sureste de la Isla Elefante. La comunidad estuvo compuesta pri [...] ncipalmente por copépodos, siendo las especies más abundantes Metridia gerlachei y Ctenocalanus sp. Mediante el análisis cluster se diferenciaron 3 grupos de estaciones asociados con las masas de agua. Un grupo se halló al sureste de la Isla Elefante y del Estrecho de Bransfield, donde predominó la masa de agua del mar de Weddell. Allí el fitoplancton fue escaso, mientras que el zooplancton fue abundante. Esto puede ser un ejemplo de un control top-down debido al pastoreo. Otro grupo se distribuyó al noroeste del Estrecho, donde predominaron las aguas del mar de Bellingshausen, en esta zona el zooplancton tuvo abundancias bajas, mientras que el fitoplancton fue encontrado en altas concentraciones. El último grupo fue encontrado en el centro del estrecho, en donde se encuentra el Frente de Bransfield. A pesar de las altas abundancias de fitoplancton, la mayoría de especies zooplanctónicas presentaron bajas abundancias, pudiendo ser por las fuertes turbulencias que se forman en el Frente. Sin embargo, Metridia gerlachei fue la más abundante en esta zona probablemente por su extensa migración vertical. Abstract in english During the austral summer of 2006 the spatial distribution of zooplankton and its association with some abiotic (water masses) and biotic variables (phytoplankton) were investigated in the Bransfield Strait and to the southeast of Elephant Island, Southern Ocean. The zooplankton community was mainly [...] composed of copepods; the main species present were Metridia gerlachei and Ctenocalanus sp. Nearest neighbor cluster analysis of zooplankton indicated the presence of three major station groupings which were influenced by water masses. One group was found in the southeast of the Bransfield Strait and Elephant Island, where the Weddell water masses predominated. This showed low phytoplankton abundance, whilst zooplankton abundance was high. This may be an example of top down grazing control. A second group was found in the northwest of the Strait, where the Bellingshausen water masses predominated. Here the zooplankton abundance was low, whilst the phytoplankton was found in high concentrations. A third group was found in the Bransfield front. Despite the high abundances of phytoplankton located here, zooplankton abundance was low. This could be due to the strong turbulence at the front. However, Metridia gerlachei was found in much higher concentrations here than other copepods. This species may be able to cope with such conditions due to its extensive diurnal vertical migrations.

Jessica, Bonicelli P.; Diana, López P.; Noemí, Ochoa L.; Rachael S., Shreeve.

2008-12-01

157

Ground-water hydrology and the effects of vertical leakage and leachate migration on ground-water quality near the Shelby County landfill, Memphis, Tennessee  

Science.gov (United States)

An investigation of potential leakage of leachate from the Shelby County landfill near Memphis, West Tennessee, was conducted during 1986-87. The migration of leachate from the landfill to the shallow alluvial aquifer system and the potential leakage to the deeper confined Memphis aquifer of Tertiary age were investigated. A network of observation wells was drilled to determine water levels and aquifer properties in the shallow and deep aquifers as well as in the confining layer. Water samples were collected to define potential leachate occurrence. A depression in the water table within the shallow alluvial aquifer was defined from the water-level data. Drawdowns within the cone of depression are as much as 14 feet lower than the adjoining Wolf River. Recharge from the river and leachate from the landfill moves toward the depression. The presence of leachate within the shallow aquifer was confirmed from determinations of dissolved solids and dissolved chloride concentrations and comparisons with areas away from the aflected zone. Leakage from the water-table aquifer to the Memphis aquifer was confirmed from chemical analyses and hydraulic-head data. Dissolved-solids concentrations in water samples from the upper Memphis aquifer near the landfill are higher than in samples from the Memphis aquifer in unaffected areas. Tritium activities in water samples from the upper Memphis aquifer were as high as 34 pico-Curies per liter indicating recent recharge to the Memphis aquifer. The presence of synthetic organic compounds and elevated concentrations of dissolved solids, chloride, and trace metals indicate the leachate has aflected water quality in the alluvial aquifer. Vertical migration of ground water could transmit leachate down to the Memphis aquifer. Although water-quality data indicate that water is leaking from the alluvial aquifer to the Memphis aquifer, most of the data do not indicate the occurrence of leachate in the Memphis aquifer. Chemical data from one well in the Memphis aquifer near the landfill indicates a slightly elevated dissolved-chloride concentration, but the data are limited.

Bradley, M.W.

1991-01-01

158

FUNCTIONAL BIOASSAYS UTILIZING ZOOPLANKTON: A COMPARISON  

Science.gov (United States)

Functional zooplankton bioassays based on ingestion, reproduction and respiration are described, with methods for a new ingestion bioassay included. ll bioassays are compared using three indices, including the variability of controls, the range of experimental responses, and a li...

159

Future marine zooplankton research - a perspective  

DEFF Research Database (Denmark)

During the Second Marine Zooplankton Colloquium (MZC2) 3 issues were added to those developed 11 yr ago during the First Marine Zooplankton Colloquium (MZC1). First, we focused on hot spots, i.e., locations where zooplankton occur in higher than regular abundance and/or operate at higher rates, We should be able to determine the processes leading to such aggregations and rates, and quantify their persistence. Second, information on the level of individual species, even of highly abundant ones, is limited, Concerted efforts should be undertaken with highly abundant to dominant species or genera (e.g., Oithona spp,, Calanus spp., Oikopleura spp., Euphausia superba) to determine what governs their abundance and its variability. Third, zooplankton clearly influence biogeochemical cycling in the ocean, but our knowledge of the underlying processes remains fragmentary. Therefore a thorough assessment of variables that still need to be quantified is required to obtain an understanding of zooplankton contributions tobiogeochemical cycling. Combining studies on the 7 issues from MZC1 with the 3 from MZC2 should eventually lead to a comprehensive understanding of (1) the mechanisms governing the abundance and existence of dominant zooplankton taxa, and (2) the control of biodiversity and biocomplexity, for example, in the tropical ocean where diversity is high. These recommendations come from an assemblage of chemical, physical and biological oceanographers with experience in major interdisciplinary studies, including modeling. These recommendations are intended to stimulate efforts within the oceanographic community to facilitate the development of predictive capabilities for major biological processes in the ocean.

Bathmann, U.; Bundy, M.H.

2001-01-01

160

Neustonic microplastic and zooplankton in the North Western Mediterranean Sea.  

Science.gov (United States)

Neustonic microplastic and zooplankton abundance was determined in the North Western Mediterranean Sea during a summer cruise between July 9th and August 6th 2010, with a break between July 22 th and 25th due to a strong wind event. Ninety percent of the 40 stations contained microplastic particles (size 0.3-5mm) of various compositions: e.g., filaments, polystyrene, thin plastic films. An average concentration of 0.116 particles/m(2) was observed. The highest abundances (>0.36 particles/m(2)) were observed in shelf stations. The neustonic plastic particles concentrations were 5 times higher before than after the strong wind event which increased the mixing and the vertical repartition of plastic particles in the upper layers of the water column. The values rise in the same order of magnitude than in the North Pacific Gyre. The average ratio between microplastics and mesozooplankton weights was 0.5 for the whole survey and might induce a potential confusion for zooplankton feeders. PMID:22325448

Collignon, Amandine; Hecq, Jean-Henri; Glagani, François; Voisin, Pierre; Collard, France; Goffart, Anne

2012-04-01

161

Distribución espacial de larvas de crustáceos decápodos planctónicos en canales orientales de la isla Chiloé, Chile / Vertical distribution of planktonic decapods crustacean larvae in oriental channels of the Chiloé Island, Chile  

Scientific Electronic Library Online (English)

Full Text Available Se analiza la distribución vertical y abundancia de larvas de crustáceos decápodos planctónicos en canales orientales de la isla Chiloé. Se relaciona la distribución de larvas con la hora de captura y marea, que interferirían con las migraciones verticales u ontogénicas descritas para el meroplancto [...] n. De las especies identificadas, las larvas de Neotrypaea uncinata fueron las más abundantes. Su distribución vertical, fue inversa a la descrita para la migración circadiaria de zooplancton, sin que se encontraran diferencias significativas en la abundancia en los dos estratos de profundidad. Las abundancias de larvas de Cancridae y Pinnotheridae, fueron las únicas que tuvieron diferencias significativas en ambos estratos, aunque inversas al patrón de distribución vertical circadiaria. La amplitud de marea y dinámica oceanográfica descrita para los canales del área de estudio, serían determinantes en la distribución de las larvas en el sector, sobreponiéndose el transporte de ellas al comportamiento migratorio descrito para el zooplancton en general. Abstract in english The vertical distribution and abundance of planktonic decapods larvae in channels from the inside part of Chiloé Island is analyzed. The larvae distribution is related with the capture daytime and the tide conditions and which could interfere with the vertical or ontogenic migrations described for t [...] he meroplankton. From the identified species, the Neotrypaea uncinata larvae were the most abundant. Their vertical distribution was inverse to the one described by the circadian migration of the zooplankton, without detecting significant differences among the abundances in both sampled strata. The abundance of Cancridae and Pinnotheridae larvae were the only ones that had significant differences in the two strata, although they were inverse to the pattern of circadian vertical distribution. The tide height and the oceanographic dynamic described for the channels of the area under study would be decisive in the distribution of larvae in the sector, overcoming their transport to the migratory behavior described for the zooplankton in general.

Armando, Mujica; María L, Nava.

162

Ecological zonation of zooplankton in the COAST study region off central Oregon in June and August 2001 with consideration of retention mechanisms  

Science.gov (United States)

To determine the mechanisms that might explain retention and/or loss of plankton during the coastal upwelling season, one needs an understanding of the vertical migration behavior and ontogenetic changes in vertical distribution and data on direction and magnitude of currents at depths where the animals reside. In this paper we compare and contrast the cross-shelf distributions of four copepod species, Calanus marshallae, Pseudocalanus mimus, Acartia longiremis, and Centropages abdomalis, and the euphausiid Euphausia pacifica, from sampling during the Coastal Ocean Advances in Shelf Transport (COAST) program. The COAST study region was off central Oregon (44°-45°N), ranged from the nearshore zone out to ˜1000 m isobath, and was a trapezoid 120 km in length and 40 km wide in the north by 100 km wide in the south. Plankton were sampled along three transects, in the north, middle, and southern portions of the study region. For the two most abundant copepods, C. marshallae and P. mimus, sampling with a Multiple Opening/Closing Net and Environmental Sampling System showed that naupliar and early copepodite stages were found within the warm phytoplankton-rich upper 20 m of the water column but that copepodite stages C3 through adult were found at progressively deeper strata in the water column. Similarly, euphausiid larvae were most abundant within the upper 20 m, whereas juveniles and adults lived deeper in the water column. Diel vertical migration was observed only in the older developmental stages. Because older stages occupy different strata than younger stages, there is cross-shelf displacement of zooplankton.

Lamb, Jesse; Peterson, William

2005-10-01

163

Elemental concentration of zooplankton and their particulate products  

International Nuclear Information System (INIS)

Since zooplankton fecal pellets and molts are major vectors in the vertical transport of zinc in the sea, analyses have been made also for other trace metals in these particulate products. Euphausiids and pelagic shrimp were collected live off the Monaco coast by taking several short oblique tows with an Issacs-Kidd midwater trawl. Animals were placed in clean sea water, sorted according to species and immediately transported to the laboratory in plastic containers filled with filtered sea water taken at the collection site. Samples of microplankton, which serve as food for the macroplankton were also taken. Elemental concentrations in whole euphausiids and shrimp were measured. It was observed that molt analyses strongly support the contention that crustacean molts play an important role in the transport of metals and radionuclides in marine ecosystems. Molts can release metals to the water column or sediments upon decomposition or serve as a rich source of metals for organisms of other trophic levels which ingest them

164

A Review: Potentiality of Zooplankton as Bioindicator  

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Full Text Available Problem statement: This review tended to summarize some recent research on zooplankton as bioindicator in India and some other countries of the world. Approach: These researches were mainly on fresh water bodies. Results: Qualitative as well as quantitative analysis were done by Shannon diversity index (H', Evenness index (J, Species Richness index (S and Saprobic index. In most of the cases zooplankton population size was correlated with biotic and abiotic parameters (pH, alkalinity, temperature, dissolve oxygen, transparency, phosphate, chlorine. Species of Rotifers, Cladocerans, Copepods and Ostracods were found in all cases. Species variation of these order deceased in polluted water. Some species were not found in some highly polluted area though these species have high tolerance level. Conclusion/Recommendations: All the results of the studies indicated that potentiality of zooplankton as bioindicator is very high. Other countries can develop these concepts to monitor water quality.

Zannatul Ferdous

2009-01-01

165

Modeling the interactions between the seasonal and diel migration behaviors of Calanus finmarchicus and the circulation in the Gulf of St. Lawrence (Canada)  

Science.gov (United States)

The Gulf of St.-Lawrence (GSL) is a dynamic region supporting a productive pelagic ecosystem. This environment presents unique opportunities to study the interactions between the population dynamics of planktonic species and the variability of physical processes. The copepod Calanus finmarchicus is a dominant component of zooplankton biomass and abundance in the GSL. We developed a 3-D coupled physical-biological numerical model in order to study the population dynamics of C. finmarchicus in the GSL for the year 1999. We coupled a life cycle model of C. finmarchicus representing the average properties of the population in terms of egg production, development, migration behavior and mortality to a regional circulation model driven by realistic atmospheric, hydrological and oceanic forcing. The distribution and abundance patterns of C. finmarchicus were sensitive to the migration behavior owing to the strong vertical and horizontal shears in the circulation. Both the timing of seasonal ontogenetic vertical migrations and the diel vertical migrations appeared to be essential to produce simulation results similar to the observations and to ensure the perennial presence of a local population in the GSL.

Maps, Frédéric; Zakardjian, Bruno A.; Plourde, Stéphane; Saucier, François J.

2011-11-01

166

Densities and Diel Vertical Migration of Mysis relicta in Lake Superior: A Comparison of Optical Plankton Encounter and Net-based Approaches  

Science.gov (United States)

In this study, we used data from an OPC, and LOPC, and vertical net tows to estimate densities and describe the day/night vertical distribution of Mysis at a series of stations distributed throughout Lake Superior, and to evaluate the efficacy of using (L)OPC for examining DVM of...

167

ZOOPLANKTON OCCURANCE DURING MONSOON SEASON FROM EKRUK TANK, SOLAPUR  

Directory of Open Access Journals (Sweden)

Full Text Available In the present study zooplankton occurrence and abundance were investigated from Ekruk tank, Solapur. Samples were collected bimonthly for a duration of four months in monsoon season (July to October 2012. The results showed that the occurrence of zooplanktons such as Rotifers, Copepods and Cladocerans during the investigation. Physico- chemical parameters of given water plays an important role in occurrence and abundance of zooplankton species. These environmental factors mainly affect the distribution of zooplankton species from Ekruk tank, Solapur. Our results are discussed in the light of the seasonal effect on the occurrence of zooplankton community.

M. R. Gurav , K. R. Rao

2014-06-01

168

Effect of Water Hyacinth (Eichornia crassippes Infestation on Zooplankton Populations in Awba Reservoir, Ibadan South-West Nigeria  

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Full Text Available The effects of water hyacinth infestation on the distribution, abundance and species composition of zooplankton in Awba reservoir were investigated. Samples were collected in each of the sampling areas (water hyacinth infested and open water by vertical zooplankton hauls using 64 um bolting silk net. The samples were immediately fixed in 4% formalin for preservation. The species composition of the zooplankton from the sampled areas consisted of 3 taxa, comprising of 6 species of Cladocera (Moina sp., Ceriodaphnia sp., Pleuroxus sp., Diaphanosoma sp., Chydorus sp. and Leydigia sp. 6 species of Rotifers (Asplanchna sp., Trichocerca, Filinia sp., Polyarthra sp., Brachionus sp. and Lecane sp. and 3 species of Copepoda (Cycloid copepods, Copepodite nauphii and Calanoid copepods. However, the study showed that the Rotifers had higher numerical abundance in the study areas. Water hyacinth infested area had a total density of 95 individuals/L while open water had 215 individuals/L. The study showed that the density of zooplanktons were significantly lower (p< 0.05 in the infested area. Biotic indices such as Margalef`s and Simpson`s indices were lower in the infested area while Shannon-wiener diversity index was significantly lower (p< 0.05 in the water hyacinth infested area. The result suggests that water hyacinth dense mats affected the numerical abundance of the zooplanktons.

K.S. Chukwuka

2007-01-01

169

Rapid removal of plutonium from the oceanic surface layer by zooplankton faecal pellets  

International Nuclear Information System (INIS)

In view of the possibility that increasing quantities of Pu may in due course be introduced into the marine environment, it is important to have a detailed knowledge of its oceanic behaviour. It has been suggested that algae and perhaps the phytoplanktonic mass may have an important role in determining the chemical and physical forms of Pu predominant in the ocean. The role of the zooplanktonic mass has not been investigated in detail, but it is known that for several elements zooplankton metabolism may be an important biological factor in the removal of elements from the surface layers of the ocean. The particular importance of zooplankton faecal pellets in this process has been stressed, and it has been found that M. norvegica is rich in the naturally-occurring ?-emitter 210Po when compared with whole organism levels. A study is here described for Pu, and it is reported that M. norvegica faecal pellets are relatively rich in Pu. It is suggested that zooplankton faecal pellet deposition might be an important vector in the vertical oceanic transport of this element. Experimental details are given and results are shown in tabular form. The implications of the high concentrations of Pu in faecal pellets are described, and rough estimates are made for the removal time of Pu from the upper mixed ocean layers by zooplankton pellets alone; the result is 3.6 years. It is suggested that faecal pellets may have a significant role in the removal of Pu from the surfa role in the removal of Pu from the surface layers of the sea. (U.K.)

170

Zooplankton may serve as transmission vectors for viruses infecting algal blooms in the ocean.  

Science.gov (United States)

Marine viruses are recognized as a major driving force regulating phytoplankton community composition and nutrient cycling in the oceans. Yet, little is known about mechanisms that influence viral dispersal in aquatic systems, other than physical processes, and that lead to the rapid demise of large-scale algal blooms in the oceans. Here, we show that copepods, abundant migrating crustaceans that graze on phytoplankton, as well as other zooplankton can accumulate and mediate the transmission of viruses infecting Emiliania huxleyi, a bloom-forming coccolithophore that plays an important role in the carbon cycle. We detected by PCR that >80% of copepods collected during a North Atlantic E. huxleyi bloom carried E. huxleyi virus (EhV) DNA. We demonstrated by isolating a new infectious EhV strain from a copepod microbiome that these viruses are infectious. We further showed that EhVs can accumulate in high titers within zooplankton guts during feeding or can be adsorbed to their surface. Subsequently, EhV can be dispersed by detachment or via viral-dense fecal pellets over a period of 1 day postfeeding on EhV-infected algal cells, readily infecting new host populations. Intriguingly, the passage through zooplankton guts prolonged EhV's half-life of infectivity by 35%, relative to free virions in seawater, potentially enhancing viral transmission. We propose that zooplankton, swimming through topographically adjacent phytoplankton micropatches and migrating daily over large areas across physically separated water masses, can serve as viral vectors, boosting host-virus contact rates and potentially accelerating the demise of large-scale phytoplankton blooms. PMID:25438947

Frada, Miguel José; Schatz, Daniella; Farstey, Viviana; Ossolinski, Justin E; Sabanay, Helena; Ben-Dor, Shifra; Koren, Ilan; Vardi, Assaf

2014-11-01

171

Zooplankton succession in fingerling production ponds  

Science.gov (United States)

Many pond cultured species require a range of zooplankton species for consumption before they can be weaned onto manufactured feed. The widest variety of plankton species develops when empty ponds are filled and fertilized. Use of organic and inorganic fertilizers facilitates the development of ba...

172

ZOOPLANKTON NUTRITIONAL VALUE: NURSERY POND FERTILIZATION EFFECTS  

Science.gov (United States)

Little information is available on the utilization of natural productivity (i.e. zooplankton) by catfish fry. Although fry and fingerlings survive on prepared diets, many nutrients acquired by fry in ponds are most likely derived from natural food consumption. Experiments were conducted to answer ...

173

Zooplankton assemblage of Oyun Reservoir, Offa, Nigeria  

Directory of Open Access Journals (Sweden)

Full Text Available The influence of physico-chemical properties of Oyun Reservoir, Offa, Nigeria (a shallow tropical African reservoir on its zooplankton composition and abundance were investigated at three stations for two years between January 2002 and December 2003. Diversity is not high: only three groups of zooplankton were found: Rotifera with eight genera; and Cladocera and Copepoda with three genera each. Rotifera dominated numerically (71.02%, followed by Cladocera (16.45% and Copepoda (12.53%. The zooplankton was more prevalent during the rainy season, and there were variations in the composition and abundance along the reservoir continuum. Factors such as temperature, nutrients, food availability, shape and hydrodynamics of the reservoir, as well as reproductive strategies of the organisms, strongly influence the generic composition and population density of zooplankton. Prevention of ecological deterioration of the water body would greatly should result in a more productive water body, rich in zooplankton and with better fisheries. Rev. Biol. Trop. 57 (4: 1027-1047. Epub 2009 December 01.La influencia de las propiedades fisicoquímicas del Reservorio Oyun, Offa, Nigeria (un embalse tropical somero sobre la composición y abundancia del zooplancton fue investigada en tres estaciones entre enero de 2002 y diciembre de 2003. La diversidad no resultó muy alta con tres grupos de zooplancton: Rotifera con ocho géneros, y Cladocera y Copepoda con tres géneros cada uno. Rotifera dominó (71.02%, seguido de Cladocera (16.45% y Copepoda (12.53%. El zooplancton fue más común durante la temporada de lluvias, y hubo variaciones en su composición y abundancia a lo largo del embalse. Factores tales como la temperatura, los nutrientes, la disponibilidad de alimentos, la forma y la hidrodinámica del embalse, así como las estrategias reproductivas de los organismos, influyen fuertemente en la composición genérica y la densidad poblacional del zooplancton. La prevención del deterioro ecológico de esta masa de agua, resultaría en un cuerpo de agua más productivo, rico en zooplancton y con mejor pesca.

Moshood K Mustapha

2009-12-01

174

Influence of spatial heterogeneity on the type of zooplankton functional response: A study based on field observations  

Science.gov (United States)

Mathematical models of plankton dynamics are sensitive to the choice of type of zooplankton functional response, i.e., to how the rate of intake of food varies with the food density. Conventionally, the conclusion on the actual type of functional response for a given zooplankton species is made based upon laboratory analysis on experimental feeding. In this paper, we show that such an approach can be too simplistic and misleading. Based on real ocean data obtained from three expeditions of R/V Jan Mayen in the Barents Sea in 2003-2005, we demonstrate that vertical heterogeneity in algal distribution as well as active vertical movement of herbivorous zooplankton can modify the type of trophic response completely. In particular, we found that the rate of average intake of algae by Calanus glacialis exhibits a Holling type III response, instead of Holling type I or II found previously in laboratory experiments. We argue that this conceptual discrepancy is due to the ability of the zooplankton to feed in layers with high algal density and to avoid depths with lower algal density. Since theoretical studies would predict enhancing in system stability in the case of Holling type III, our results may be of importance for understanding the main factors controlling plankton dynamics.

Morozov, Andrew; Arashkevich, Elena; Reigstad, Marit; Falk-Petersen, Stig

2008-10-01

175

Power-plant-related estuarine zooplankton studies  

International Nuclear Information System (INIS)

In-plant studies examining the effects of entrainment on zooplankton and field studies examining zooplankton abundance, composition, and distribution in the Chesapeake Bay in the vicinity of Calvert Cliffs Nuclear Power Plant have been conducted from 1974 to the present. The evolution of these studies, with particular emphasis on design and statistical treatment, is discussed. Entrainment study designs evolved from discrete sampling episodes at 4-h intervals over 24 h to a time-series sampling design in which sampling took place every 30 min over 24 and 48-h periods. The near-field study design and samping methods have included replicated net tows, using 0.5-m nets, and replicated and nonreplicated pumped sampling, using a high-speed centrifugal pump. 16 refs

176

Distribution and diversity of Zooplanktons in Madhya Pradesh, India  

Directory of Open Access Journals (Sweden)

Full Text Available The distribution and diversity of zooplankton in aquatic ecosystems terms depends mainly on the physico-chemical proportion of water. Pollution of water bodies by different sources will result in drastic changes in zooplankton potential of the ecosystem. The Narmada river is gifted with varied diversity of zooplanktons. The present study was carried out for the period of two years from October 2009 to September 2011. The study was carried out at selected sampling station Omkareshwar. During the present investigation, 39 species of zooplankton were identified. As far the qualitative (species wise abundance is concerned, eight species belonging of Phyla protozoa, fifteen species of Rotifera, nine species of Cladocera and seven species belonging to Copepoda were recorded. Zooplankton diversity was maximum during months from January to April. The study aims to overcome the pollution caused in Narmada river due to various anthropogenic activities and domestic wastes. The study aims to conserve the zooplanktons which are declining day by day.

Shailendra Sharma, C. M Solanki, Dhanvi Sharma, Zahoor Pir

2013-03-01

177

ZOOPLANKTON OCCURANCE DURING MONSOON SEASON FROM EKRUK TANK, SOLAPUR  

OpenAIRE

In the present study zooplankton occurrence and abundance were investigated from Ekruk tank, Solapur. Samples were collected bimonthly for a duration of four months in monsoon season (July to October 2012). The results showed that the occurrence of zooplanktons such as Rotifers, Copepods and Cladocerans during the investigation. Physico- chemical parameters of given water plays an important role in occurrence and abundance of zooplankton species. These environmental factors ma...

M R Gurav, K. R. Rao; Kshirsagar, Sunetra S.

2014-01-01

178

Changing zooplankton seasonality in a changing ocean: Comparing time series of zooplankton phenology  

Science.gov (United States)

Marine zooplankton must deal with seasonal variations of the upper-ocean environment that are both intense and prolonged compared to their life spans. This leads to large seasonal fluctuations of population size, and strong evolutionary tuning of demographic processes (e.g. reproduction, somatic and population growth, and dormancy) for optimal match with the average annual alternation between good and poor growing conditions. However, neither environmental nor zooplankton seasonal cycles are exactly repetitive year-to-year. Recent analyses of several long zooplankton time series have found large (1-3 months) interannual variability of seasonal timing. In this paper, we compare and synthesize results from these studies. Variability in zooplankton phenology is often correlated with anomalies of one or more environmental variables. The most common phenology correlate is water temperature during and before the growing season, and the most common phenologic response to temperature is “earlier when and where warmer”. But several species with seasonal maxima in late summer or autumn have a clear “later when warmer” response. Covariance of seasonal timing with temperature must therefore involve more than thermal acceleration of physiological rates. We suggest that water temperature (relatively slowly and smoothly varying in aquatic environments) is also used by zooplankton as a timing cue, much as terrestrial biota uses day-length. During recent warming trends, temperature-linked changes in seasonal timing may have moved some species outside their locally-optimal seasonal windows (e.g. Calanus finmarchicus in the North Sea, and Pseudocalanus elongatus in the Adriatic), and have been a major contributor to changes in community composition. Between-location similarities of zooplankton phenology and temperature anomaly time series decay with increasing site-to-site spatial separation. The decorrelation scale is several thousand kilometers in the subarctic Pacific, but a thousand kilometers or less in marginal seas of the NE Atlantic.

Mackas, D. L.; Greve, W.; Edwards, M.; Chiba, S.; Tadokoro, K.; Eloire, D.; Mazzocchi, M. G.; Batten, S.; Richardson, A. J.; Johnson, C.; Head, E.; Conversi, A.; Peluso, T.

2012-05-01

179

The northwestern Indian Ocean during the monsoons of 1979: distribution, abundance, and feeding of zooplankton  

Energy Technology Data Exchange (ETDEWEB)

Upwelling induced by the separation of the Somali Current from the coast of east Africa is associated with low surface temperatures, high concentrations of nitrate, and blooms of phytoplankton. Coefficients of concordance, based upon 17 taxa of zooplankton collected at 33 stations in the southwest monsoon and 15 stations in the northeast monsoon, were consistently larger for the southwest monsoon and indicative of a general response of the zooplankton in the northwestern Indian Ocean. The largest coefficients of concordance in the southwest monsoon were among adult females of Paracalanus denudatus, Paracalanus parvus, and Paracalanus aculeatus and of Calanoides carinatus and Eucalanus spp. Coefficients of concordance among copepodids of six taxa had a trend similar to adult females in the southwest monsoon. During the southwest monsoon, total biomass of zooplankton was significantly greater within areas of upwelling than outside; adult females and copepodids of C. carinatus and Eucalanus spp. were significantly more abundant within the upwelling regions, along with adult females of Clausocalanus furcatus and Clausocalanus minor. The upwelling regions, which are associated with a reproductively active population of the large-bodied C. carinatus, are the primary features affecting distributions of zooplankton during the southwest monsoon and the main difference between monsoons. The ontogenetic migration of C. carinatus is essentially an annual life-history strategy and therefore on the same temporal scale as the reversals in the monsoonal winds and associated upwelling. The ability of C. carinatus to ingest readily the diatoms that dominate the upwelling regions and to store lipid is crucial to its dominance of the areas of upwelling both in numbers and biomass.

Smith, S.L.

1982-01-01

180

Intercomparison of zooplankton (net) sampling systems: Results from the ICES/GLOBEC sea-going workshop  

Science.gov (United States)

An inter-comparison and evaluation of methods for sampling and determination of zooplankton distribution and biomass was conducted in a fjord environment (Storfjorden at Møre, Norway) from 2 to 13 June 1993. The inter-comparison was carried out with the German R/V “A. v. Humboldt” and the Norwegian R/V “Johan Hjort” and involved a total number of 38 scientific personnel from 8 countries. The inter-comparisons included the MOCNESS, BIONESS, MultiNet, LHPR, OPC, CPR, Gulf-V, CalCOFI 1-m Ring Net, and WP-2 net. In addition, acoustics data were collected with a Simrad EK500 echosounder operating on 4 frequencies (18, 38, 120, 200 kHz) and hydrographic, nutrient, phytoplankton, and meteorological data were collected to characterize the environment in which the comparisons were made; environmental changes were minor during the study. The results of this study corroborate the results of earlier studies. Mesh size of the net had a major influence on the biomass and species composition of the zooplankton community. There is a consistent relationship between retention (or escapement through the mesh) and the width of the organisms; about 50% of the organisms escape through the mesh at a width equal to the mesh size. The effect of towing speed on the extrusion of smaller organisms through the net can be substantial and adds to the loss due to escapement. Active avoidance of the sampler is only important for the larger macrozooplankton and not a significant problem for the mesozooplankton. Different vertical, oblique, and multiple opening/closing net systems produced similar estimates of zooplankton when operated with comparable mesh-sized nets and a sufficiently high mesh open area to mouth opening ratio. The choice of mesh size is important and 150 ?m mesh is possibly an optimal mesh size for use in coastal waters with neritic zooplankton communities. Replicate tow variability was also consistent with earlier studies and reflects the need to understand the interplay between the underlying patchiness of the zooplankton distributions and the method of sampling. No single net is suitable to sample across the wide size range of zooplankton from small mesozooplankton to macrozooplankton. Recent large interdisciplinary programs to assess marine ecosystem structure and dynamics have recognized this through the use of nets designed to sample particular size fractions in combination with video and acoustic remote sensing techniques.

Skjoldal, Hein Rune; Wiebe, Peter H.; Postel, Lutz; Knutsen, Tor; Kaartvedt, Stein; Sameoto, Douglas D.

2013-01-01

181

Experiments on the influence of Chaoborus brasiliensis Theobald, 1901 (Diptera: Chaoboridae) on the diel vertical migration of microcrustaceans from Lake Monte Alegre, Brazil / Experimentos sobre a influência de Chaoborus brasiliensis (Diptera: Chaoboridae) sobre a migração vertical de microcrustáceos do Lago Monte Alegre, Brasil  

Scientific Electronic Library Online (English)

Full Text Available SciELO Brazil | Language: English Abstract in portuguese O objetivo deste trabalho foi avaliar se a migração vertical dos microcrustáceos do Lago Monte Alegre é relacionada aos predadores invertebrados, nomeadamente larvas de Chaoborus brasiliensis. A hipótese testada no experimento foi a de que o comportamento migratório da presa seria dependente do cont [...] ato físico com as larvas de Chaoborus ou dos "kairomones" liberados por elas. Dois experimentos foram realizados no laboratório, com dois tratamentos e três réplicas cada. Os experimentos foram feitos dentro de cilindros de acrílico de 1,5 m de altura e 0,20 m de diâmetro. Os tratamentos do Experimento I foram: A) predador e "kairomones" presentes e B) predador e "kairomones" presentes, mas o predador isolado em tubos de rede dentro do cilindro, não tendo contato físico com a presa. Os tratamentos do Experimento II foram: A) predador e "kairomones" ausentes e B) igual ao Experimento I. Fatores físicos e químicos (temperatura, oxigênio dissolvido, pH, condutividade elétrica) e alimento (algas) não influenciaram a distribuição vertical das presas, pois eles estavam quase homogeneamente distribuídos na coluna d'água em ambos os experimentos; as concentrações de alimento não foram limitantes. Copépodos adultos (Tropocyclops prasinus meridionalis e Thermocyclops decipiens) realizaram migração reversa no tratamento B dos dois experimentos; o cladócero Daphnia gessneri migrou de modo noturno no tratamento A do Experimento I; migração vertical não foi detectada para copepoditos, bem como para larvas de Chaoborus. Os experimentos indicaram que Daphnia respondeu ao contato físico com as larvas de Chaoborus e não aos "kairomones". Copépodos adultos foram aparentemente mais sensíveis aos "kairomones". Abstract in english The aim of this work was to evaluate whether diel vertical migration of microcrustaceans from Lake Monte Alegre is related to invertebrate predators, namely larvae of Chaoborus brasiliensis. The hypothesis tested in the experiments was that the migratory behaviour of prey would depend on physical co [...] ntact with Chaoborus brasiliensis larvae or with kairomones released by them. Two experiments were undertaken in the laboratory, with two treatments and three replicates each. Experiments were carried out in acrylic cylinders 1.5 m high and 0.20 m in diameter. Treatments in Experiment I were: A) predator and kairomones present and B) predator and kairomones present, but predator isolated in net tube inside the cylinder, having no physical contact with prey. Treatments in Experiment II were: A) predator and kairomones absent and B) the same as in experiment I. Physical and chemical factors (temperature, dissolved oxygen, pH, electrical conductivity) and food (algae) did not influence vertical distribution of prey, as they were almost homogeneously distributed in the water column in both experiments; food concentrations were not limiting. Adult copepods (Tropocyclops prasinus meridionalis and Thermocyclops decipiens) showed reverse migration in the treatment B of both experiments; the cladoceran Daphnia gessneri migrated nocturnally in the treatment A of the Experiment I; vertical migration was undetectable for copepodites, as well as for Chaoborus larvae. The experiments indicated that Daphnia responded to physical contact with Chaoborus larvae but not to kairomones alone. Adult copepods seemed to be more sensitive to kairomones.

WJ., Minto; MS., Arcifa; A., Perticarrari.

2010-02-01

182

Seasonal and interannual changes in zooplankton community in the coastal zone of the North-Eastern Black Sea.  

Science.gov (United States)

The phenological response of zooplankton community is a result of simultaneous effect of several factors: feeding conditions, predation abundance, periods of reproduction of common species and hydrodynamic regime. The Black sea ecosystem is one of the best studied in the world, otherwise there is still some illegibility about ecosystem functioning and especially about environmental factors influence on zooplankton dynamics. For the last twenty years pelagic system of the Black Sea has changed dramatically. The invasion of ctenophore Mnemiopsis leidyi in the middle of eighties caused significant decrease in zooplankton biomass. It also altered plankton structure and shifted periods of mass reproduction of the abundant species and biomass maximums. For instance, before the invasion of Mnemiopsis the maximum of zooplankton biomass was observed in autumn (data by A. Pasternak, 1983), and after that the maximum moved to the spring (data by V.S. Khoroshilov, 1999). The incursion of ctenophore Beroe ovata feeding on Mnemiopsis in the nineties has led to the enhancement of zooplankton community. Although the detailed analysis of seasonal zooplankton dynamics wasn't performed in the recent years. The object of our research was to study seasonal and interannual changes in zooplankton community in the coastal area of the North-Eastern Black Sea. Analysis of interannual, seasonal and spatial changes in zooplankton distribution, abundance and species composition along with age structure of dominant populations were performed based on investigations during 2005-2008 years in the North-Eastern Black Sea. Plankton samples were obtained monthly since June 2005 till December 2008. Plankton was collected at three stations at depths 25m, 50m and 500-1000m along the transect from the Blue Bay to the open sea. Sampling of gelatinous animals was conducted in parallel to the zooplankton sampling. Simultaneously with plankton sampling CTD data were obtained. The feeding conditions were obtained using SSC satellite data. For studying vertical distribution of zooplankton depth stratified samples were collected in different seasons. To evaluate seasonal variations in reproduction and offspring development of dominant mesozooplankton populations, we analyzed age structure of five species: four herbivorous copepods - Acartia clausi, Pseudocalanus elongatus, Paracalanus parvus and Calanus euxinus, and carnivorous chaethognaths Parasagitta setosa. Periods of mass reproduction varied in different years. The possible reason for this variation is the effect of climate change and top-predators on seasonal shift in zooplankton dynamics. Whereas timing of reproduction is related to life strategy of species, an intensity of reproduction and success of new generations depend on food supply. The impact of food conditions on abundance and age structure of herbivores was studied in the different seasons. Vertical distribution of different species also altered from year to year. Thus, in "warm" July 2007 (sea surface temperature 27°C) most of the Calanus euxinus population concentrated in the deeper layers than in "cold" July 2005 (sea surface temperature 22°C).

Nikishina, A. B.; Arashkevich, E. G.; Louppova, N. E.; Soloviev, K. A.

2009-04-01

183

Trophic structure of zooplankton in the Fram Strait in spring and autumn 2003  

Science.gov (United States)

The trophic structure of zooplankton was investigated in Fram Strait (north western Svalbard) in spring and autumn of 2003. Depth-stratified zooplankton samples were collected at 12 stations on the shelf (˜200 m), across the shelf-slope (˜500 m) and over deep water (>750 m), using a Multiple Plankton Sampler equipped with 0.180-mm mesh size nets. Higher zooplankton abundance and estimated biomass were found in the shelf area. Abundance and biomass were two times higher in August, when sea-surface temperature was higher than in May. Herbivores dominated numerically in May, and omnivores in August, suggesting a seasonal sequence of domination by different trophic groups. Cirripedia nauplii and Fritillaria borealis prevailed in spring, whereas copepod nauplii and Calanus finmarchicus were numerically the most important herbivores in autumn. Small copepods, Oithona similis and Triconia borealis, were the most numerous omnivorous species in both seasons, but their abundances increased in autumn. Chaetognatha (mainly Eukrohnia hamata) accounted for the highest abundance and biomass among predatory taxa at all deep-water stations and during both seasons. Regarding vertical distribution, herbivores dominated numerically in the surface layer (0-20 m), and omnivores were concentrated somewhat deeper (20-50 m) during both seasons. Maximum abundance of predators was found in the surface layer (0-20 m) in spring, and generally in the 20-50 m layer in autumn. This paper presents the first comprehensive summary of the zooplankton trophic structure in the Fram Strait area. Our goals are to improve understanding of energy transfer through this ecosystem, and of potential climate-induced changes in Arctic marine food webs.

Blachowiak-Samolyk, Katarzyna; Kwasniewski, Slawek; Dmoch, Katarzyna; Hop, Haakon; Falk-Petersen, Stig

2007-11-01

184

Harvesting and Processing Zooplankton for Use as Supplemental Fry Feed  

Science.gov (United States)

We present the methods that we used to capture and dry large zooplankton from ponds to feed to channel catfish Ictalurus punctatus fry. Using a submersible pump and canister filter, we were able to capture about 1.0 kg (wet weight; 200 g in terms of dry weight) of zooplankton from well-fertilized po...

185

COMPARISONS OF ZOOPLANKTON COMMUNITY SIZE STRUCTURE IN THE GREAT LAKES  

Science.gov (United States)

Zooplankton mean-size and size-spectra distribution potentially reflect the condition of trophic interactions and ecosystem health because they are affected by both resource availability and planktivore pressure. We assessed zooplankton mean-size and size-spectra using an optical...

186

Selective uptake of 55Fe from seawater by zooplankton  

International Nuclear Information System (INIS)

Iron-55 was measured in water and mixed zooplankton collected in the South Pacific Ocean. The ratios of the specific activity of 55Fe (pCi/g Fe) between plankton and water from the same locations appear to be about 100, which suggests that zooplankton took up 55Fe in preference to stable iron in the South Pacific Ocean

187

Evaluation of Zooplankton in Hatchery Diets for Channel Catfish Fry  

Science.gov (United States)

The efficacy of zooplankton as a supplemental hatchery diet for fry of channel catfish Ictalurus punctatus was evaluated. When a commercial diet is used as a reference, fry fed exclusively on zooplankton–either live or dried–performed poorly in their growth rate. However, when live or dried zooplan...

188

Upslope transport of near-bed zooplankton  

Science.gov (United States)

Zooplankton residing just above the deep-sea floor is an important component of the benthic/benthopelagic food chain. Consuming planktonic particulates and organisms, holoplankton and meroplankton are prey for fish and large invertebrates. Mechanisms controlling their abundances have been explored over relatively long time scales (months to years). Here, zooplankton were sampled every 2 h for 2.2 d using a moored, automated, serial zooplankton pump. The physical regime (currents and temperature) 1-100 m above bottom was measured during an inclusive 24-d period. The study site was located on the upper continental slope (750 m) of the Mid-Atlantic Bight, between the productive shelf and more impoverished rise and abyss. The coupled biological and physical records indicated tidally driven, net upslope transport of the holoplankton. The copepod (74.5% of collections) time series showed marked periodicity with a peak frequency of ˜13 h, approximately the diurnal tide (Fourier analysis). Local maxima corresponded with minimal water temperatures. Moreover, tidal cross-slope flow was highly coherent and 90° out of phase with temperature. Thus, maximal copepod concentrations, originating in colder deeper water, would be transported up the slope by the tide. Estimated net displacement of ˜1 km/d would deliver the animals to continental-shelf depths within a couple weeks. Time series of the much less abundant larvaceans (urochordates) (15.3%) and polychaete larvae (8.9%) showed periodicities with peak frequencies of 8-9 h. Statistical significance of the periodic signals could not be determined due to low numbers. Revealing holoplankton dynamics on scales of hours, this study may contribute to understanding of, for example, copepod feeding and aggregation near the deep-sea floor.

Zimmer, Cheryl Ann

2009-09-01

189

Zooplankton assemblage of Oyun Reservoir, Offa, Nigeria  

Scientific Electronic Library Online (English)

Full Text Available SciELO Costa Rica | Language: English Abstract in spanish La influencia de las propiedades fisicoquímicas del Reservorio Oyun, Offa, Nigeria (un embalse tropical somero) sobre la composición y abundancia del zooplancton fue investigada en tres estaciones entre enero de 2002 y diciembre de 2003. La diversidad no resultó muy alta con tres grupos de zooplanct [...] on: Rotifera con ocho géneros, y Cladocera y Copepoda con tres géneros cada uno. Rotifera dominó (71.02%), seguido de Cladocera (16.45%) y Copepoda (12.53%). El zooplancton fue más común durante la temporada de lluvias, y hubo variaciones en su composición y abundancia a lo largo del embalse. Factores tales como la temperatura, los nutrientes, la disponibilidad de alimentos, la forma y la hidrodinámica del embalse, así como las estrategias reproductivas de los organismos, influyen fuertemente en la composición genérica y la densidad poblacional del zooplancton. La prevención del deterioro ecológico de esta masa de agua, resultaría en un cuerpo de agua más productivo, rico en zooplancton y con mejor pesca. Abstract in english The influence of physico-chemical properties of Oyun Reservoir, Offa, Nigeria (a shallow tropical African reservoir) on its zooplankton composition and abundance were investigated at three stations for two years between January 2002 and December 2003. Diversity is not high: only three groups of zoop [...] lankton were found: Rotifera with eight genera; and Cladocera and Copepoda with three genera each. Rotifera dominated numerically (71.02%), followed by Cladocera (16.45%) and Copepoda (12.53%). The zooplankton was more prevalent during the rainy season, and there were variations in the composition and abundance along the reservoir continuum. Factors such as temperature, nutrients, food availability, shape and hydrodynamics of the reservoir, as well as reproductive strategies of the organisms, strongly influence the generic composition and population density of zooplankton. Prevention of ecological deterioration of the water body would greatly should result in a more productive water body, rich in zooplankton and with better fisheries. Rev. Biol. Trop. 57 (4): 1027-1047. Epub 2009 December 01.

Moshood K, Mustapha.

1027-10-01

190

Short term changes in zooplankton community during the summer-autumn transition in the open NW Mediterranean Sea: species composition, abundance and diversity  

Directory of Open Access Journals (Sweden)

Full Text Available Short term changes in zooplankton community were investigated at a fixed station in offshore waters of the Ligurian Sea (Dynaproc 2 cruise, September–October 2004. Mesozooplankton was sampled with vertical WP2 hauls (200 µm mesh-size and large mesozooplankton, macrozooplankton and micronekton with a BIONESS multinet sampler (500 µm mesh-size. Temporal variations of total biomass, species composition and abundance of major taxa were studied. Intrusions of low salinity water masses were observed two times during the cruise. The first one, which was the most important, was associated with changes in zooplankton community composition. Among copepods, the abundance of Calocalanus, Euchaeta, Heterorhabdus, Mesocalanus, Nannocalanus, Neocalanus, Pleuromamma and also calanoid copepodites increased markedly. Among non-copepod taxa, only small ostracods abundance increased. After this low salinity event, abundance of all taxa nearly returned to their initial values. The influence of salinity on each zooplankton taxon was confirmed by a statistical analysis (Perry's method. Shannon diversity index, Pielou evenness and species richness were used to describe temporal variations of large copepod (>500 µm diversity. Shannon index and Pielou evenness decreased at the beginning of the low salinity water intrusions, but not species richness. We suggest that low salinity water masses contained its own zooplankton community and passed through the sampling area, thus causing the replacement of zooplankton population.

V. Raybaud

2008-05-01

191

Extended Stolt F-K migration  

Energy Technology Data Exchange (ETDEWEB)

Despite their understanding that depth migration is a more powerful imaging tool than time migration, time migration still constitutes the majority of migration done today. In selecting a time-migration algorithm, three primary criteria are of concern: accuracy in imaging steep dips, accuracy in the presence of vertical velocity variation, and computational effort. The ideal algorithm would be efficient and unlimited in its ability to image steep dips in arbitrary vertical velocity structures. It would also accommodate gentle lateral velocity variations deemed acceptable for time-migration methods. A particularly attractive algorithm to consider is Stolt's f-k method: it is computationally efficient and has unlimited dip accuracy for constant-velocity media. Although Stolt's method can handle moderate vertical variations, errors become unacceptable for steep dips in the presence of large vertical velocity variation. An extension to Stolt migration removes its restrictions on vertical velocity variation, yielding accuracy comparable to phase-shift migration at only a fraction of the computational time. This extended Stolt method is based on partitioning the velocity field in a manner analogous to that in cascaded finite-difference migration and performing a number of stages of Stolt migrations. In each stage, the migration velocity field is closer to a constant - the ideal situation for Stolt migration - than when the migration is done conventionally (i.e., in just one stage). Empirical results and error analyses show that four stages of extended Stolt migration are sufficient to migrate steeply dipping events accurately in nearly any vertically varying velocity field. In fact, for a wide range of velocity fields and dips, as few as two stages will produce phase-shift quality images. The method can be used for two-dimensional, two-pass three-dimensional, and single-pass three-dimensional migrations.

Beasley, C.; Lynn, W.; Larner, K.; Nguyen, H.V.

1988-03-01

192

Observational approaches to community structure, from microbes to zooplankton : Report of breakout group microbes and zooplankton  

OpenAIRE

Knowledge about the structure (Table 1) and dynamics of plankton communities in the ocean is essential to understanding and predicting the effects of climate change on marine ecosystems, e.g. regional variations in the draw down of CO2 from the atmosphere, effects of ocean acidification and warming on marine biota. Phytoplankton constitutes the base of most of the marine food web and provides about 50% of the global primary production. Zooplankton forms a critical link to higher trophic level...

Karlson, Bengt; Lopes, Rubens M.; Berdalet, Elisa; Piera, Jaume

2009-01-01

193

Vertical distribution and in situ feeding of marine particle-grazers in relation to their food, the microplankton  

International Nuclear Information System (INIS)

A cruise was completed to measure the vertical distributions of plant biomass, growth, size and species composition, nutritional content and the zooplankton biomass and species composition. There were no consistent differences in the size spectra of particles between the regions of highest plant biomass and highest growth rates. Species known to be noxious or distasteful to the zooplankton were not members of either assemblage. The nutritional content of the particulate matter was greatest at the plant biomass maximum. Thus there was no evidence that the region of higher plant growth rates was a better place for zooplankton to feed. The diurnal distribution of zooplankton biomass was not consistently related to the vertical distributions of plant biomass, primary productivity, or productivity/chlorophyll. At night, the vertical distribution of zooplankton biomass was consistently related to the vertical distribution of plant biomass. There were species whose vertical distributions were consistently related to either the vertical distribution of plant biomass or productivity/chlorophyll a but not primary productivity, contrary to the observations of others. The total grazing pressure, measured in situ with a new design of grazing chamber and an isotopic carrier which labels the particulate matter day and night, indicated that the daily production of plant carbon was much greater than its rate of removal by the grazers. Thus, it is not necessary for the grazer biomass m is not necessary for the grazer biomass maximum to be located above the chlorophyll a maximum in order for that feature to persist

194

Bacterial diversity associated with freshwater zooplankton  

DEFF Research Database (Denmark)

Bacterial community compositions (BCC) associated with the cladoceran Bosmina coregoni and the cyclopoid copepod Thermocyclops oithonoides in oligotrophic Lake Stechlin versus eutrophic Lake Dagow (northeastern Germany) were compared using molecular techniques. We also transplanted the zooplankton from their native lake to the other lake, and studied changes in their associated BCC as a result of the modified ambient environment. Bacterial community composition associated with B. coregoni was quite conservative between the oligotrophic and eutrophic lakes, and most of the bacteria belonged to Alpha- and Betaproteobacteria. In contrast, BCC associated with T. oithonoides was highly variable and dependent on the environment, and Betaproteobacteria and Bacteroidetes were the most represented among the bacteria. Thermocyclops oithonoides from the oligotrophic lake was more able to retain its bacteria after being transplanted to the eutrophic lake than vice versa. This suggests that bacteria in oligotrophic water were more firmly attached to the copepod and better in resisting environmental fluctuations than those in eutrophic water.

Grossart, Hans-Peter; Dziallas, Claudia

2009-01-01

195

GUIDELINES FOR ZOOPLANKTON SAMPLING IN QUANTITATIVE BASELINE AND MONITORING PROGRAMS  

Science.gov (United States)

Methods applicable to zooplankton sampling and analysis in quantitative baseline and monitoring surveys are evaluated and summarized. Specific recommendations by managers must take into account characteristics of the water mass under investigation, the abundance of contained zoop...

196

BENEFICIAL USE IMPAIRMENT #13: DEGRADATION OF PHYTOPLANKTON AND ZOOPLANKTON POPULATIONS  

Science.gov (United States)

Pursuant to the Great Lakes Water Quality Agreement and Annex 2, the Detroit River possesses several impaired beneficial uses. Beneficial Use #13 addresses phyto- and zooplankton populatioins and whether or not they are degraded or impaired....

197

High Mortality of Red Sea Zooplankton under Ambient Solar Radiation  

OpenAIRE

High solar radiation along with extreme transparency leads to high penetration of solar radiation in the Red Sea, potentially harmful to biota inhabiting the upper water column, including zooplankton. Here we show, based on experimental assessments of solar radiation dose-mortality curves on eight common taxa, the mortality of zooplankton in the oligotrophic waters of the Red Sea to increase steeply with ambient levels of solar radiation in the Red Sea. Responses curves linking solar radiatio...

Al-aidaroos, Ali M.; El-sherbiny, Mohsen M. O.; Satheesh, Sathianeson; Mantha, Gopikrishna; Agusti?, Susana; Carreja, Beatriz; Duarte, Carlos M.

2014-01-01

198

Climate Impacts on Zooplankton Population Dynamics in Coastal Marine Ecosystems  

OpenAIRE

The 20-year US GLOBEC (Global Ocean Ecosystem Dynamics) program examined zooplankton populations and their predators in four coastal marine ecosystems. Program scientists learned that environmental controls on zooplankton vital rates, especially the timing and magnitude of reproduction, growth, life-cycle progression, and mortality, determine species population dynamics, seasonal and spatial distributions, and abundances. Improved knowledge of spatial-temporal abundance and distribution of in...

Batchelder, Harold P.; Daly, Kendra L.; Davis, Cabell S.; Rubao Ji; Ohman, Mark D.; Peterson, William T.; Runge, Jeffrey A.

2013-01-01

199

On autumn zooplankton of Semipalatinsk test site water-bodies  

International Nuclear Information System (INIS)

The autumn zooplankton in six water-bodies with mineralization diapason from 0.27 to 343.0 g/l was investigated. The species composition and number of structural characteristics were determined. The state of the zooplankton community by biodiversity and development indices is determined as normal. The observed increase of body dimensions in some species of Rotatoria and Microcrustacea requires the additional research. (author)

200

Procedures involved in radioecological studies with marine zooplankton  

International Nuclear Information System (INIS)

Various procedures in marine radioecological experiments with zooplankton are considered in the light of the possibility of establishing reference methods for marine radiobiological studies. Methods for collection, handling and maintenance prior to and during experiments are suggested for various types of zooplankton. The importance of physiological and physico-chemical parameters are discussed in the context of the experimental design with the aim of achieving comparable results among workers involved in this field of research. (author)

201

Effect of advection on variations in zooplankton at a single location near Cabo Nazca, Peru  

Energy Technology Data Exchange (ETDEWEB)

Temporal variations in the biomass and species composition of zooplankton at a single midshelf station in an upwelling area off Peru can be explained to a large extent by onshore-offshore advection in the upper 20 m of the water column. During periods of strong or sustained near-surface onshore flow, peaks in biomass of zooplankton were observed at midshelf and typically oceanic species of copepod were collected. In periods of offshore flow at the surface, a copepod capable of migrating into oxygen-depleted layers deeper than 30 m was collected. A simple translocation model of advection applied to the cross-shelf distribution of Paracalanus parvus suggests that the fluctuations in P. pavus observed in the midshelf time-series were closely related to onshore-offshore flow in the upper 20 m. Fluctuations in abundance of the numerically dominant copepod, Acartia tonsa, were apparently affected by near surface flow also. The population age-structure suggests that A. tonsa was growing at maximal rates, due in part to its positive feeding response to the dinoflagellate/diatom assemblage of phytoplankton.

Smith, S L; Brink, K H; Santander, H; Cowles, T J; Huyer, A

1980-04-01

202

Planet Migration  

OpenAIRE

Planet migration is the process by which a planet's orbital radius changes in time. The main agent for causing gas giant planet migration is the gravitational interaction of the young planet with the gaseous disk from which it forms. We describe the migration rates resulting from these interactions based on a simple model for disk properties. These migration rates are higher than is reasonable for planet survival. We discuss some proposed models for which the migration rates...

Thommes, Edward W.; Lissauer, Jack J.

2010-01-01

203

Bird Migration  

Science.gov (United States)

The songs of spring are in the air, as northbound birds grace the skies. The following websites cover various aspects of the amazing and ancient phenomenon of bird migration. Hosted by the U.S. Geological Survey Northern Prairie Wildlife Research Center, the (1) first site is an online publication from the U.S. Fish and Wildlife Service on the Migration of Birds. This publication provides an extensive account of migration including sections on Techniques for Studying Migration, Evolution of Migration, Flight Speed and Rate of Migration, and many more. The (2) second site from birdnature.com is a webpage describing the Flyway Systems of North America accompanied by clearly labeled maps. The (3) third site from the University of Lund, Sweden introduces various research studies in the field of Migration Ecology including research information on Orientation and Navigation, Migration patterns, the Lund Wind Tunnel, and more. The (4) fourth site presents the Canadian Migration Monitoring Network, a standardized effort involving multiple stations in southern Canada and the northern United States to gather baseline data on northern breeding birds. Site visitors can link to information about species population trends, latest sightings, and to sites for any of the 22 stations. Journey North hosts the (5) fifth site, which tracks migrating bald eagles through the spring of 2004, providing migration updates, information about tracking bald eagle migration, and related educational lessons and activities. A National Geographic 2004 feature, Crane Cam is the (6) sixth site providing multimedia shows, a photo gallery, map, and viewings from a live remote camera at Audubon's Rowe Sanctuary. The (7) seventh site features an interactive Migration Game created by the Migratory Bird Center at the Smithsonian National Zoological Park. The (8) final site, from the Whyfiles contains brief sections on various aspects of bird migration such as navigation, flight strategies, raptor migration, and declining numbers of migrating songbirds. This site also links to information about monarch migration.

204

Mesoscale physical variability affects zooplankton production in the Labrador Sea  

Science.gov (United States)

Surface distribution (0-100 m) of zooplankton biomass and specific aminoacyl-tRNA synthetases (AARS) activity, as a proxy of structural growth, were assessed during winter 2002 and spring 2004 in the Labrador Sea. Two fronts formed by strong boundary currents, several anticyclonic eddies and a cyclonic eddy were studied. The spatial contrasts observed in seawater temperature, salinity and fluorescence, associated with those mesoscale structures, affected the distributions of both zooplankton biomass and specific AARS activity, particularly those of the smaller individuals. Production rates of large organisms (200-1000 ?m) were significantly related to microzooplankton biomass (63-200 ?m), suggesting a cascade effect from hydrography through microzooplankton to large zooplankton. Water masses defined the biomass distribution of the three dominant species: Calanus glacialis was restricted to cold waters on the shelves while Calanus hyperboreus and Calanus finmarchicus were widespread from Canada to Greenland. Zooplankton production was up to ten-fold higher inside anticyclonic eddies than in the surrounding waters. The recent warming tendency observed in the Labrador Sea will likely generate weaker convection and less energetic mesoscale eddies. This may lead to a decrease in zooplankton growth and production in the Labrador basin.

Yebra, L.; Harris, R. P.; Head, E. J. H.; Yashayaev, I.; Harris, L. R.; Hirst, A. G.

2009-05-01

205

Accumulation of microcystins by a tropical zooplankton community.  

Science.gov (United States)

In the current study, the hepatotoxic peptide microcystins, were measured in the zooplankton community of Jacarepaguá Lagoon during a 6-month period. Concurrent phytoplankton and seston samples were obtained. Microcystins were measured in seston and phytoplankton by High Performance Liquid Chromatography (HPLC), and in zooplankton by an Enzyme-Linked Immunosorbant Assay (ELISA). Zooplankton community was comprised mainly by the rotifers Brachionus angularis and B. plicatilis, the cladocerans Moina micrura and Ceriodaphnia cornuta and the copepod Metacyclops mendocinus. Phytoplankton was dominated by Microcystis aeruginosa during all the studied period. Microcystins in zooplankton ranged from 0.3 to 16.4 microg g(-1) DW, while in the sestonic samples they ranged from undetectable values to 5.8 ng g(-1) DW. Microcystins in net phytoplankton ranged from 0.3 to 3.9 mg g(-1) DW. We conclude that zooplankton from Jacarepaguá Lagoon were efficient accumulators of microcystins from seston and that these animals can be potential vectors in the transferring of such toxins to higher trophic levels in the aquatic food chain. PMID:12127737

Ferrão-Filho, Aloysio da S; Kozlowsky-Suzuki, Betina; Azevedo, Sandra M F O

2002-09-24

206

Changes in fatty acid and hydrocarbon composition of zooplankton assemblages related to environmental conditions  

Energy Technology Data Exchange (ETDEWEB)

Changes in zooplankton fatty acid and hydrocarbon patterns are described in relation to changes in environmental conditions and species composition. The regulation of zooplankton abundance by sea nettle-ctenophore interaction was examined in a small Rhode Island coastal pond. Sea nettles were nettles were able to eliminate ctenophores from the pond and subsequently zooplankton abundance increased. During one increase in zooplankton abundance, it was found that polyunsaturated fatty acids decreased while monounsaturated fatty acids increased. It was concluded that this shift in biochemical pattern was due to food limitation. In addition, zooplankton fatty acids were used in multivariate discriminant analysis to classify whether zooplankton were from coastal or estuarine environments. Zooplankton from coastal environments were characterized by higher monounsaturate fatty acids. Zooplankton hydrocarbon composition was affected by species composition and by pollution inputs. The presence of Calanus finmarchicus was detected by increased levels of pristane.

Lambert, R.M.

1989-01-01

207

Marine snow, zooplankton and thin layers: indications of a trophic link from small-scale sampling with the Video Plankton Recorder  

DEFF Research Database (Denmark)

Marine aggregates of biogenic origin, known as marine snow, are considered to play a major role in the ocean’s particle flux and may represent a concentrated food source for zooplankton. However, observing the marine snow?zooplankton interaction in the field is difficult since conventional net sampling does not collect marine snow quantitatively and cannot resolve so-called thin layers in which this interaction occurs. Hence, field evidence for the importance of the marine snow?zooplankton link is scarce. Here we employed a Video Plankton Recorder (VPR) to quantify small-scale (metres) vertical distribution patterns of fragile marine snow aggregates and zooplankton in the Baltic Sea during late spring 2002. By using this non-invasive optical sampling technique we recorded a peak in copepod abundance (ca. 18 ind. l?1) associated with a pronounced thin layer (50 to 55 m) of marine snow (maximum abundance of 28 particles l?1), a feature rarely resolved. We provide indirect evidence of copepods feeding on marine snow by computing a spatial overlap index that indicated a strong positively correlated distribution pattern within the thin layer. Furthermore we recorded images of copepods attached to aggregates and demonstrating feeding behaviour, which also suggests a trophic interaction. Our observations highlight the potential significance of marine snow in marine ecosystems and its potential as a food resource for various trophic levels, from bacteria up to fish

Möller, Klas O.; St. John, Michael

2012-01-01

208

Zooplankton abundance and diversity in Lake Bracciano, Latium, Italy  

Directory of Open Access Journals (Sweden)

Full Text Available The zooplankton community structure in Lake Bracciano (Latium, Central Italy was studied in monthly surveys throughout an annual cycle (November 1998 – October 1999. The seasonal cycles and population dynamics of the dominant species are described and discussed. Copepods numerically dominated the community throughout the study period with calanoid Eudiaptomus padanus etruscosexsetosus making up the largest share of zooplankton density; moreover it accounted for the largest portion of total biovolume. Cladocerans represented a significant component of the zooplankton in the summer and autumn months. No substantial differences in regard to results of previous investigations (1971, 1972, 1984 were observed. The only differences for which there is evidence consist of the appearance of Filinia terminalis, never previously found in the lake, and the replacement of Keratella cochlearis instead of Kellicottia longispina as dominant species. However, the results of the comparison of the different investigations confirm that the trophic state of the pelagial region may be classified as oligo-mesotrophic.

Fiorenza G. MARGARITORA

2002-08-01

209

Zooplankton-mediated nutrient limitation patterns in marine phytoplankton: an experimental approach with natural communities  

OpenAIRE

Zooplankton nutrient recycling has been shown to substantially affect nutrient availability for phytoplankton. However, investigations are required to determine whether zooplankton also influence nutrient limitation in marine phytoplankton communities, and whether grazing by different zooplankton groups results in different patterns of phytoplankton nutrient limitation. We performed laboratory experiments under different nutrient supply conditions on a variety of phytoplankton communities wit...

Trommer, Gabriele; Pondaven, Philippe; Siccha, Michael; Stibor, Herwig

2012-01-01

210

Reaction of fresh water zooplankton community to chronic radiation exposure  

International Nuclear Information System (INIS)

The characteristic features of ecological community as a whole and cenosis of zooplankton organisms as part of it determine the intensity of the processes of self-purification of water and the formation of a particular body of water. Identifying features of the structure and composition of the zooplankton community of aquatic ecosystems exposed to different levels of radiation exposure, it is necessary to identify patterns of changes in zooplankton and hydro-biocenosis as a whole. Industrial reservoirs, the storage of liquid low-level radioactive waste 'Mayak' for decades, have high radiation load. A large range of levels of radioactive contamination (total volume beta-activity in water varies from 2.2x103 to 2.3x107 Bq/l, total volume alpha-activity - from 2.6x10-1 to 3.1x103 Bq/l) provides a unique opportunity to study ecosystems in a number of reservoirs with increasing impact of radiation factor. We studied five reservoirs that were used as the storage of low-and intermediate-level liquid radioactive waste pond and one comparison water body. In parallel with zooplankton sampling water samples were collected for hydro-chemical analysis. 41 indicators were analysed in order to assess the water chemistry. To determine the content of radionuclides in the various components of the ecosystem samples were collected from water, bottom sediments and plankton. Sampling of zooplankton for the quantitative analysis was performed using the method of weighted average auto bathometer. Apshteyn's plankton net of the surface horizon was used for qualitative analysis of the species composition of zooplankton. Software package ERICA Assessment Tool 2012 was used for the calculation of the absorbed dose rate. Species diversity and biomass of zooplankton, the share of rotifers in the number of species, abundance and biomass decrease with the increase of the absorbed dose rate and salinity. The number of species in a sample decreases with the increase of the absorbed dose according to the S-shaped function. 5 % reduction in species diversity corresponds to 1.1x102 mcGy/hr, 50 % reduction - 1.1x103 mcGy/hr. Margalef's index and Shannon's index were 5% lower at 9.1x102 mcGy/hr and 50% lower at 1.7x103 mcGy/hr, that points to simplified communication in the plankton community. Quantitative indicators of zooplankton are less sensitive to changes in the aquatic environment under study than indicators of species richness and the complexity of relationships in the community. Document available in abstract form only. (authors)

211

International Migration  

Science.gov (United States)

This Website, Push and Pull Factors of International Migration, features background and preliminary research data from a joint project of Eurostat and The Netherlands Interdisciplinary Demographic Institute the goal of which is to "improve understanding of the direct and indirect causes and mechanisms of international migration to the European Union from an internationally comparative perspective. The project is an effort to respond to the fact that "international migration flows have increased in magnitude and complexity over the past decades." Separate sections of the site provide information on the aim, objectives, and approach of the project; the research design; as well as a summary of first results on recent migration, migration motives, migration networks, and migration intentions; and further bibliographic and Web-based resources. The project is under the auspices of the Commission of the European Communities.

212

The Effect of Radial Migration on Galactic Disks  

Science.gov (United States)

We study the radial migration of stars driven by recurring multi-arm spiral features in an exponential disk embedded in a dark matter halo. The spiral perturbations redistribute angular momentum within the disk and lead to substantial radial displacements of individual stars, in a manner that largely preserves the circularity of their orbits and that results, after 5 Gyr (~40 full rotations at the disk scale length), in little radial heating and no appreciable changes to the vertical or radial structure of the disk. Our results clarify a number of issues related to the spatial distribution and kinematics of migrators. In particular, we find that migrators are a heavily biased subset of stars with preferentially low vertical velocity dispersions. This "provenance bias" for migrators is not surprising in hindsight, for stars with small vertical excursions spend more time near the disk plane, and thus respond more readily to non-axisymmetric perturbations. We also find that the vertical velocity dispersion of outward migrators always decreases, whereas the opposite holds for inward migrators. To first order, newly arrived migrators simply replace stars that have migrated off to other radii, thus inheriting the vertical bias of the latter. Extreme migrators might therefore be recognized, if present, by the unexpectedly small amplitude of their vertical excursions. Our results show that migration, understood as changes in angular momentum that preserve circularity, can strongly affect the thin disk, but cast doubts on models that envision the Galactic thick disk as a relic of radial migration.

Vera-Ciro, Carlos; D'Onghia, Elena; Navarro, Julio; Abadi, Mario

2014-10-01

213

Radial migration in barred galaxies  

Science.gov (United States)

In this talk, I will present the result of high resolution numerical simulations of disk galaxies with various bulge/disk ratios evolving isolated, showing that: • Most of migration takes place when the bar strength is high and decreases in the phases of low activity (in agreement with the results by Brunetti et el. 2011, Minchev et al. 2011). • Most of the stars inside the corotation radius (CR) do not migrate in the outer regions, but stay confined in the inner disk, while stars outside CR can migrate either inwards or outwards, diffusing over the whole disk. • Migration is accompanied by significative azimuthal variations in the metallicity distribution, of the order of 0.1 dex for an initial gradient of ~-0.07 dex/kpc. • Boxy bulges are an example of stellar structures whose properties (stellar content, vertical metallicity, [?/Fe] and age gradients, ..) are affected by radial migration (see also Fig. 1).

Di Matteo, P.; Haywood, M.; Combes, F.; Semelin, B.; Babusiaux, C.; Gomez, A.

2015-03-01

214

Structure of zooplankton community in Cernavoda Danube river area  

International Nuclear Information System (INIS)

This study presents the influence of the municipal wastewater and thermal discharge from Cernavoda Nuclear Power Plant over the zooplankton community in some key stations on the Danube River. The analyses are based on samples collected in the spring and summer seasons of the years 1999-2001 and 2007. (author)

215

Zooplankton Diversity Of Dnyanganga Reservoir Near Khamgaon, Maharashtra  

Directory of Open Access Journals (Sweden)

Full Text Available :Study on zooplankton diversity of Dnyanganga Reservoir in Botha forest of Buldana district was carried out during 2008-09. The zooplankton study reveals that the Copepods are major in occurrence, 3079 in number (32.28%; Cladocera are 2323(24.36%; Rotifers in 2976(31.20%; and Ostracods are 1158 in number (12.14%. The lake exhibited high magnitude in winter season and the low during summer. The less number of genera might be attributed to low nutrients in the reservoir which consequently resulted in less productivity or might be due to depletion of important factors such as dissolved oxygen and PH. The reduction in the number of species may also due to predation and variation in the pH of water which is always associated with the species composition of zooplankton inhibiting among them .In winter, it is biotic interaction operating through feeding pressure rather than water quality seems to affect the zooplankton diversity and density particularly the stocked fish species play an important role in harvesting species of copepoda and Cladocera, thereby reducing their predatory pressure on other groups. The Rotifera and particle feeder Cladocera were higher in winter and can be linked to favorable temperature and availability of abundant food in the form of bacteria, nanoplankton and suspended detritus matter .Total 26 types of genera were recorded which indicates variable nature of productivity the Dnyanganga Reservoir .

G. B. Kale

2013-09-01

216

FORAGE FISH AND ZOOPLANKTON COMMUNITY COMPOSITION IN WESTERN LAKE SUPERIOR  

Science.gov (United States)

We assessed the abundance, size, and species composition of the fish and zooplankton communities of western Lake Superior during 1996 and 1997. Data were analyzed for 3 ecoregions (Duluth-Superior (1), Apostle Islands (2), Minnesota coast (3) differing in lake bathymetry, phsiodo...

217

Phytoplankton and zooplankton of the Lednicke rybniky fishponds  

International Nuclear Information System (INIS)

During the years 2001-2002 (April - August) samples of phytoplankton and zooplankton were taken on Lednice ponds (south Moravia, Czech Republic). Physical and chemical parameters were also measured. The monitoring was intended to bring basic information about the situation of ponds ecosystems. Also, the acquired data contributed to optimization of the fish stock of these particular ponds. (authors)

218

Vertical zonation and distributions of calanoid copepods through the lower oxycline of the Arabian Sea oxygen minimum zone  

Science.gov (United States)

This paper provides the first comprehensive analysis of calanoid copepod vertical zonation and community structure at midwater depths (300-1000 m) through the lower oxygen gradient (oxycline) (0.02 to ?0.3 ml/L) of an oxygen minimum zone (OMZ). Feeding ecology was also analyzed. Zooplankton were collected with a double 1 m 2 MOCNESS plankton net in day and night vertically-stratified oblique tows from 1000 m to the surface at six stations during four seasons as part of the 1995 US Joint Global Ocean Flux Study (JGOFS) Arabian Sea project. The geographic comparison between a eutrophic more oxygenated onshore station and an offshore station with a strong OMZ served as a natural experiment to elucidate the influence of depth, oxygen concentration, season, food resources, and predators on the copepod distributions. Copepod species and species assemblages of the Arabian Sea OMZ differed in their spatial and vertical distributions relative to environmental and ecological characteristics of the water column and region. The extent and intensity of the oxycline at the lower boundary of the OMZ, and its spatial and temporal variability over the year of sampling, was an important factor affecting distributional patterns. Calanoid copepod species showed vertical zonation through the lower OMZ oxycline. Clustering analyses defined sample groups with similar copepod assemblages and species groups with similar distributions. No apparent diel vertical migration for either calanoid or non-calanoid copepods at these midwater depths was observed, but some species had age-related differences in vertical distributions. Subzones of the OMZ, termed the OMZ Core, the Lower Oxycline, and the Sub-Oxycline, had different copepod communities and ecological interactions. Major distributional and ecological changes were associated with surprisingly small oxygen gradients at low oxygen concentrations. The calanoid copepod community was most diverse in the most oxygenated environments (oxygen >0.14 ml/L), but the rank order of abundance of species was similar in the Lower Oxycline and Sub-Oxycline. Some species were absent or much scarcer in the OMZ Core. Two copepod species common in the Lower Oxycline were primarily detritivorous but showed dietary differences suggesting feeding specialization. The copepod Spinocalanus antarcticus fed primarily on components of the vertical particulate flux and suspended material, a less versatile diet than the co-occurring copepod Lucicutia grandis. Vertical zonation of copepod species through the lower OMZ oxycline is probably a complex interplay between physiological limitation by low oxygen, potential predator control, and potential food resources. Pelagic OMZ and oxycline communities, and their ecological interactions in the water column and with the benthos, may become even more widespread and significant in the future ocean, if global warming increases the extent and intensity of OMZs as predicted.

Wishner, Karen F.; Gelfman, Celia; Gowing, Marcia M.; Outram, Dawn M.; Rapien, Mary; Williams, Rebecca L.

2008-08-01

219

Environmental migrations of radionuclides and heavy metals  

International Nuclear Information System (INIS)

The environmental local and distant migrations of radium 226, lead 210, uranium, thorium and heavy metals such as cadmium, lead, mercury and vanadium were studied. Their vertical migration in atmosphere as well as cumulation in soil, plants and human tissues are discussed. (A.S.)

220

Biomass of zooplankton in the eastern Arctic Ocean - A base line study  

Science.gov (United States)

Only a few historical assessments of the zooplankton biomass in the Arctic Ocean exist are difficult to compare due to methodological differences including incomplete sampling of the water column. We present assessments of the zooplankton biomass for 66 locations scattered over the Eurasian and Makarov Basins of the Arctic Ocean and analyze regional variability and factors affecting the biomass distribution. The study is based on material from several summer expeditions of RV Polarstern (1993-1998) that was collected and processed using consistent methods, i.e. stratified sampling of the entire water column from the bottom to the surface with very similar gear and standardized calculation of biomass. Total zooplankton biomass varied strongly from 1.9 to 23.9 g DW m -2 dry mass. Regional variability was mainly related to the circulation pattern, but local food availability was also important. A belt of elevated biomass along the Eurasian continental margin was associated with the advection of Atlantic pelagic populations within the Arctic Ocean Boundary Current along the Siberian shelves and returning branches along mid-ocean ridges. Biomass was highest in the core of the Atlantic inflow and remained rather stable along the continental margins, but species composition changed, pointing to different adaptation levels to local conditions by advected species. Biomass gradually decreased towards the shelves and basins and was lowest in the centers of the basins north of 85°N. In the slope region, three Calanus species ( C. hyperboreus, C. glacialis, C. finmarchicus) and Metridia longa contributed most to the biomass, chaetognaths ( Eukrohnia hamata) were also important. In the basins, C. hyperboreus was dominant, copepods made up to 97% of total biomass. Vertical distribution was similar at all stations with biomass maxima in the upper 50 m layer except for stations near Fram Strait and northern Kara Sea, the gateways of Atlantic water to the Arctic Ocean, where maxima where between 25 and 100 m. As there was only very little interannual variability of temperature and current velocity in the regions of the Atlantic inflow we suggest that the majority of our samples, collected in 1993 and 1995, represents the phase of the 1990s warm event in the Nordic Seas.

Kosobokova, Ksenia; Hirche, Hans-Jürgen

2009-09-01

221

The impact of fish predation and cyanobacteria on zooplankton size structure in 96 subtropical lakes.  

Science.gov (United States)

Zooplankton are relatively small in size in the subtropical regions. This characteristic has been attributed to intense predation pressure, high nutrient loading and cyanobacterial biomass. To provide further information on the effect of predation and cyanobacteria on zooplankton size structure, we analyzed data from 96 shallow aquaculture lakes along the Yangtze River. Contrary to former studies, both principal components analysis and multiple regression analysis showed that the mean zooplankton size was positively related to fish yield. The studied lakes were grouped into three types, namely, natural fishing lakes with low nutrient loading (Type1), planktivorous fish-dominated lakes (Type 2), and eutrophic lakes with high cyanobacterial biomass (Type 3). A marked difference in zooplankton size structure was found among these groups. The greatest mean zooplankton size was observed in Type 2 lakes, but zooplankton density was the lowest. Zooplankton abundance was highest in Type 3 lakes and increased with increasing cyanobacterial biomass. Zooplankton mean size was negatively correlated with cyanobacterial biomass. No obvious trends were found in Type 1 lakes. These results were reflected by the normalized biomass size spectrum, which showed a unimodal shape with a peak at medium sizes in Type 2 lakes and a peak at small sizes in Type 3 lakes. These results indicated a relative increase in medium-sized and small-sized species in Types 2 and 3 lakes, respectively. Our results suggested that fish predation might have a negative effect on zooplankton abundance but a positive effect on zooplankton size structure. High cyanobacterial biomass most likely caused a decline in the zooplankton size and encouraged the proliferation of small zooplankton. We suggest that both planktivorous fish and cyanobacteria have substantial effects on the shaping of zooplankton community, particularly in the lakes in the eastern plain along the Yangtze River where aquaculture is widespread and nutrient loading is high. PMID:24124552

Zhang, Jing; Xie, Ping; Tao, Min; Guo, Longgen; Chen, Jun; Li, Li; Xuezhen Zhang; Zhang, Lu

2013-01-01

222

Migration Ecology  

Science.gov (United States)

This site from the University of Lund, Sweden, introduces various research studies in the field of Migration Ecology including research information on "Orientation and navigation," "Flight," "Migration patterns," and "Energetics." The mission of the group is "to forward, by research and teaching, the understanding of adaptive values and evolutionary possibilities and limitations in animal migration, -flight, -orientation and energetics." Many of the group's publications are available for free as PDFs, and the site offers a simple search mechanism to help visitors find the publications they are seeking.

Alerstam, Thomas

223

Estimation of zooplankton mortality caused by an Arctic glacier outflow  

Directory of Open Access Journals (Sweden)

Full Text Available The outflow of freshwater from underwater channels in the Kongsbreen tidal glacier in Kongsfjorden, Svalbard, 79oN, was measured as 138.8 m3 s-1 at the peak of the melting season. Experiments on local marine plankton mortality show that when exposed to salinities below 9 PSU, all copepods die within 15 minutes. We estimate that during 100 days of the melting season, as many as 85 tonnes wet weight (WW of plankton is removed from the water column due to osmotic shock, which makes up 15% of the standing zooplankton biomass of the fjord. The dead zooplankton sinks after exposure to low salinities and is probably an important food source for scavenging benthic fauna in the fjord. This mechanism could be responsible for the high numbers of Onisimus caricus near the glacier front.

Marek J. Zaj±czkowski

2001-09-01

224

Ecological considerations on the lake Bolonha zooplankton, Belém, Pará, Brazil  

Directory of Open Access Journals (Sweden)

Full Text Available Zooplankton population of the lake Bolonha were sampled in three stations in September of 1993. The objective was to determine the basic characteristics of the populations, as the composition and density of species, besides some environmental parameters. Fifty six species were determined, thirty of them were of Rotifera, nineteen Cladocera and seven Copepoda. Among Rotifera, the most frequent organisms were Brachionus zahniseri gessneri, Polyarthra vulgaris and Tricocerca similis, while enter Cladocera, Bosminopsis deitersi and Bosmina hagmanni were the most important in density terms. For Copepoda, the nauplii and copepodits they were the ones that presented the largerst densities, but Oithona amazonica and Notodiaptomus amazonicus deserve to be registered for they have also presented a great density. The lake Bolonha came with a great diversity of zooplanktonic organisms, needing, meantime of more intensive studies, because that number in biodiversity terms should increase considerable.

Nuno Filipe Alves Correia de Melo

2006-04-01

225

210Po and 210Pb in zooplankton fecal pellets  

International Nuclear Information System (INIS)

210Po and 210Pb concentrations in fecal pellets from the zooplanktonic euphausiid Meganyctiphanes norvegica are reported. The 210Po : 210Pb activity ratio is 2.2 +- 0.3, a value in good agreement with that found in suspended particulate matter in surface seawater. Estimates of 210Po and 210Pb removal times from the mixed layer by fecal pellets alone yield values which are of the same order of magnitude as the removal times for these nuclides by all routes. It is suggested that there is a high probability that zooplanktonic fecal pellets play a significant role in the removal of both these nuclides from the surface layers of the ocean. (orig.)

226

Spatial and temporal variation in mercury bioaccumulation by zooplankton in Lake Champlain (North America).  

Science.gov (United States)

Trophic transfer of Hg across lakes within a region has been related to multiple environmental factors, but the nature of these relationships across distinct basins within individual large lakes is unknown. We investigated Hg bioaccumulation in zooplankton in basins of differing trophic status in Lake Champlain (Vermont, USA) to determine the strongest predictors of Hg bioaccumulation. Zooplankton were sampled in Malletts Bay (oligotrophic) and Missisquoi Bay (eutrophic) in 2005-2008. Zooplankton in the eutrophic basin had lower concentrations of total Hg and MeHg than those in the oligotrophic basin in all years but 2007, when no bloom occurred in Missisquoi. In addition, Hg concentrations in seston and small zooplankton, sampled during 2009 at 12 sites spanning the lake, decreased with increasing phytoplankton and zooplankton biomass. Thus, Hg bioaccumulation in zooplankton across basins in Lake Champlain is related to trophic status, as observed previously in multiple lake studies. PMID:21995871

Chen, Celia; Kamman, Neil; Williams, Jason; Bugge, Deenie; Taylor, Vivien; Jackson, Brian; Miller, Eric

2012-02-01

227

Operation Migration  

Science.gov (United States)

Operation Migration, a nonprofit conservation organization dedicated to teaching safe migratory routes to endangered and threatened birds, was co-founded by William Lishman -- the pilot who pioneered the use of ultralight aircraft to lead birds in flight. Operation Migration is part of a consortium created to safeguard the endangered Whooping crane against extinction. Visitors to this Web site can track the progress of seven ultralight-led Whooping cranes now making their way from Wisconsin to Florida for the winter. The Web site provides daily field reports of the migration, a map charting the progress of the flock, loads of photos, crane biographies, video clips, and more. The site also relates the engaging story of how Operation Migration got started, one that should sound familiar to those who've seen the feature film Fly Away Home.

228

Studies on the zooplankton of the deep subalpine Lake Garda.  

OpenAIRE

The specific composition and seasonal dynamics of the zooplankton of Lake Garda have been studied through monthly surveys in two annual cycles (December 1994-November 1995 and January-December 1997). The assemblage is largely dominated by Copipodiaptomus steueri, a typical calanoid presently identified in deep (Garda, Iseo) and shallow lakes of NE Italy and in the hinterland of the central Adriatic region (Dalmatia and Marche Region). Cladocerans and the smaller rotifers represent a significa...

Naselli-flores, Luigi; Salmaso, Nico

1999-01-01

229

Flow disturbances generated by feeding and swimming zooplankton  

DEFF Research Database (Denmark)

Interactions between planktonic organisms, such as detection of prey, predators, and mates, are often mediated by fluid signals. Consequently, many plankton predators perceive their prey from the fluid disturbances that it generates when it feeds and swims. Zooplankton should therefore seek to minimize the fluid disturbance that they produce. By means of particle image velocimetry, we describe the fluid disturbances produced by feeding and swimming in zooplankton with diverse propulsion mechanisms and ranging from 10-µm flagellates to greater than millimeter-sized copepods. We show that zooplankton, in which feeding and swimming are separate processes, produce flow disturbances during swimming with a much faster spatial attenuation (velocity u varies with distance r as u ? r?3 to r?4) than that produced by zooplankton for which feeding and propulsion are the same process (u ? r?1 to r?2). As a result, the spatial extension of the fluid disturbance produced by swimmers is an order of magnitude smaller than that produced by feeders at similar Reynolds numbers. The “quiet” propulsion of swimmers is achieved either through swimming erratically by short-lasting power strokes, generating viscous vortex rings, or by “breast-stroke swimming.” Both produce rapidly attenuating flows. The more “noisy” swimming of those that are constrained by a need to simultaneously feed is due to constantly beating flagella or appendages that are positioned either anteriorly or posteriorly on the (cell) body. These patterns transcend differences in size and taxonomy and have thus evolved multiple times, suggesting a strong selective pressure to minimize predation risk.

KiØrboe, Thomas; Jiang, Haisong

2014-01-01

230

Flow disturbances generated by feeding and swimming zooplankton.  

Science.gov (United States)

Interactions between planktonic organisms, such as detection of prey, predators, and mates, are often mediated by fluid signals. Consequently, many plankton predators perceive their prey from the fluid disturbances that it generates when it feeds and swims. Zooplankton should therefore seek to minimize the fluid disturbance that they produce. By means of particle image velocimetry, we describe the fluid disturbances produced by feeding and swimming in zooplankton with diverse propulsion mechanisms and ranging from 10-µm flagellates to greater than millimeter-sized copepods. We show that zooplankton, in which feeding and swimming are separate processes, produce flow disturbances during swimming with a much faster spatial attenuation (velocity u varies with distance r as u ? r(-3) to r(-4)) than that produced by zooplankton for which feeding and propulsion are the same process (u ? r(-1) to r(-2)). As a result, the spatial extension of the fluid disturbance produced by swimmers is an order of magnitude smaller than that produced by feeders at similar Reynolds numbers. The "quiet" propulsion of swimmers is achieved either through swimming erratically by short-lasting power strokes, generating viscous vortex rings, or by "breast-stroke swimming." Both produce rapidly attenuating flows. The more "noisy" swimming of those that are constrained by a need to simultaneously feed is due to constantly beating flagella or appendages that are positioned either anteriorly or posteriorly on the (cell) body. These patterns transcend differences in size and taxonomy and have thus evolved multiple times, suggesting a strong selective pressure to minimize predation risk. PMID:25071196

Kiørboe, Thomas; Jiang, Houshuo; Gonçalves, Rodrigo Javier; Nielsen, Lasse Tor; Wadhwa, Navish

2014-08-12

231

Zooplankton of Lake Orta after liming: an eleven years study  

OpenAIRE

Lake Orta (N. Italy) was severely polluted from 1927 by an effluent from a rayon factory, which discharged great amounts of ammonium nitrogen and copper into the lake. In the mid nineteen fifties, some plating factories also started dumping chromium and aluminum. As a result of ammonium oxidation, the lake became very acid and the concentration of metals in the waters reached very high values. Phytoplankton, zooplankton and fish disappeared suddenly from the lake which was by 1930 classified ...

Pasteris, Andrea; Bonacina, Carla

2001-01-01

232

A stochastic analysis for a phytoplankton-zooplankton model  

International Nuclear Information System (INIS)

A simple phytoplankton-zooplankton nonlinear dynamical model was proposed to study the coexistence of all the species and a Hopf bifurcation was observed. In order to study the effect of environmental robustness on this system, we have stochastically perturbed the system with respect to white noise around its positive interior equilibrium. We have observed that the system remains stochastically stable around the positive equilibrium for same parametric values in the deterministic situation

233

Acoustic estimation of size distribution and abundance of zooplankton  

OpenAIRE

A series of investigations were undertaken to observe and describe the sound backscattering process from larger zooplankton (euphausiids). The target strength versus frequency, size, and aspect angle of the organism was measured. The target strength is highly dependent on the density and sound speed contrasts between the target and the medium, and both these parameters were measured. From the target strength observations it was concluded that the fluid sphere model was insufficient as a scatt...

Kristensen, A?ge; Dalen, John

1986-01-01

234

Spring Migration  

Science.gov (United States)

The Spring Migration site from eNature.com and the National Wildlife Federation provides an online reference for bird enthusiasts that shows the dates that each species can be expected to return to its summer habitat. Site visitors can choose from a large number of species found in their range. Maps show summer and winter habitat ranges and migration patterns. The site also provides photos, field guide information, and bird call audio for each species.

235

Migration chemistry  

International Nuclear Information System (INIS)

Migration chemistry, the influence of chemical -, biochemical - and physico-chemical reactions on the migration behaviour of pollutants in the environment, is an interplay between the actual natur of the pollutant and the characteristics of the environment, such as pH, redox conditions and organic matter content. The wide selection of possible pollutants in combination with varying geological media, as well as the operation of different chemical -, biochemical - and physico-chemical reactions compleactes the prediction of the influence of these processes on the mobility of pollutants. The report summarizes a wide range of potential pollutants in the terrestrial environment as well as a variety of chemical -, biochemical - and physico-chemical reactions, which can be expected to influence the migration behaviour, comprising diffusion, dispersion, convection, sorption/desorption, precipitation/dissolution, transformations/degradations, biochemical reactions and complex formation. The latter comprises the complexation of metal ions as well as non-polar organics to naturally occurring organic macromolecules. The influence of the single types of processes on the migration process is elucidated based on theoretical studies. The influence of chemical -, biochemical - and physico-chemical reactions on the migration behaviour is unambiguous, as the processes apparently control the transport of pollutants in the terrestrial environment. As the simple, conventional KD concept breaks down, it is suggested that the migration process should be described in terms of the alternative concepts chemical dispersion, average-elution-time and effective retention. (AB) (134 refs.)

236

Specificity of zooplankton distribution in meteorite crater ponds (Morasko, Poland  

Directory of Open Access Journals (Sweden)

Full Text Available This study was conducted in order to define the most important factors responsible for the zooplankton community structure inhabiting four meteorite crater ponds, located near the city of Pozna? (Poland. The functioning of the meteorite craters resembled that of other small water bodies, where seasonality, physical-chemical features (mainly chlorophyll a concentration, pH and conductivity or biological parameters (lack of fish structured zooplankton assemblages. Rotifer species richness and abundance were highest in the autumn (12 species and 5107 ind L-1 on average, while crustaceans prevailed in the summer (12 and 201, respectively. The dominating structure also depended on the season, with pelagic species occurring in the spring and autumn and mainly littoral species in the summer. Moreover, the temporary nature of the craters caused great differentiation in zooplankton among ponds and favoured organisms adapted to living in astatic reservoirs, e.g. bdelloids, Daphnia pulex or Macrocyclops viridis. The co-occurrence of a variable community of small crustaceans with large daphnids indicated the existence of an additional ecological niche – a thick layer of sediments. Despite the occurrence of adverse living conditions (oxygen deficiencies and periodic drying and the eutrophic character of the waters, these ponds were a source of many rare species (e.g. Keratella paludosa, even in the status of dominants. Protective measures (a nature reserve allowed the area of meteorite fall to remain quite natural, despite its location close to an urban area.

Kuczy?ska-Kippen N.

2013-07-01

237

Considerations on the biochemical composition of some freshwater zooplankton species.  

Directory of Open Access Journals (Sweden)

Full Text Available The mean elemental (C, H, N and biochemical composition (lipids, carbohydrates and proteins of some abundant crustacean zooplankton species of Italian insubric lakes has been estimated by the analysis of samples collected at different seasons from various environments (Lake Maggiore, Lake Varese, Lake Comabbio, Lake Monate. From each sample an adequate number of specimens of each abundant species was sorted and analyzed by a CHN elemental analyzer. The percentage of lipids, carbohydrates and proteins and the calorific content were calculated from the elemental composition according to Gnaiger & Bitterlich (1984. Inter- and intraspecific variability of biochemical composition was quite high, while elemental composition and calorific content were less variable. An estimate of the mean elemental and biochemical composition of each species was obtained by pooling the data. These mean values have been used to estimate the pools of elements and compounds in the crustacean zooplankton of Lake Comabbio to provide an example of the importance of a multiple approach in zooplankton studies.

Nicoletta RICCARDI

1999-02-01

238

Studies on the zooplankton of the deep subalpine Lake Garda.  

Directory of Open Access Journals (Sweden)

Full Text Available The specific composition and seasonal dynamics of the zooplankton of Lake Garda have been studied through monthly surveys in two annual cycles (December 1994-November 1995 and January-December 1997. The assemblage is largely dominated by Copipodiaptomus steueri, a typical calanoid presently identified in deep (Garda, Iseo and shallow lakes of NE Italy and in the hinterland of the central Adriatic region (Dalmatia and Marche Region. Cladocerans and the smaller rotifers represent a significant component of the zooplankton from spring to autumn. A re-examination of the results obtained in previous studies does not seem to demonstrate substantial shifts in the composition of the dominant species. The only documentable and consolidated differences are constituted by the disappearance of Sida crystallina since the '50s and the appearance of new rotifers since the '70s and the '80s. It is stressed that, owing to the fragmentation of the available studies and the use of different methodologies, the qualitative and quantitative modifications of the zooplankton should be interpreted with special caution, requiring further in-depth and continuous monitoring for the meaning they could have as possible signs of modifications of the trophic structure of the lake. However, the results of the comparison of the different investigations do not seem to contrast with the substantial stability of the oligo-mesotrophic character of the lake formally documented since the '70s.

Luigi NASELLI-FLORES

1999-02-01

239

Spatial variations in zooplankton diversity in waters contaminated with composite effluents  

OpenAIRE

Zooplankton species are cosmopolitan in their clean freshwater habitat and are also found in industrial and municipal wastewaters. The present study records for the first time the aspects of zooplankton diversity in relation to physico-chemical environment of five selected sites of the East Calcutta wetlands, a Ramsar site of Kolkata city, India, heavily contaminated by industrial and municipal wastewaters. The study revealed the occurrence of 22 species of zooplankton, among these 3 species ...

Chatterjee, Asitava; Chattopadhyay, Buddhadeb; Goswami, Abhishek Roy; Mukhopadhyay, Subhra Kumar

2007-01-01

240

A global analysis of zooplankton in natural and artificial fresh waters  

OpenAIRE

Water-body size and location influence zooplankton diversity in freshwaters, but less is known about systematic variations in zooplankton community composition between natural and artificial waters on different continents. We used meta-analysis to assess how zooplankton in artificial water bodies across different biomes might differ from natural water bodies of similar size. Among 79 lakes, ponds and reservoirs (11 artificial and 68 natural), proximity to other water bodies apparently increas...

Merrix-jones, Faye L.; Ormerod, Stephen J.; Thackeray, Stephen J.

2013-01-01

241

The characteristic of a zooplankton in the contaminated bottom stream of the Pripyat' river and backwaters  

International Nuclear Information System (INIS)

The researches of zooplankton are conducted on two stations on the Pripyat' river, but also on two backwaters which are in the Chernobyl NPP contamination zone. The rotifera is dominant group of zooplankton. Their quantity is more than 10 samples/litter. An absolute and relative fertility of rotifera is determined. It is established an structural and functional reorganization of the rotifera dominant complexes occurs. Any influence of contamination on a zooplankton condition is not found out. 5 refs., 2 tabs., 2 figs

242

Stable carbon isotope signatures of zooplankton in some reservoirs in Korea  

OpenAIRE

Dissolved organic carbon (DOC) concentrations and zooplankton and particulate organic matter (POM) ?13C values weremeasured in five reservoirs in Korea. Zooplankton ?13C and POM ?13C showed large range from -33‰ to -22‰ and a significantdifference among the reservoirs. One eutrophic reservoir, Lake Masan, showed unique characteristics with the highestzooplankton density, the highest ?13C, and the highest DOC. Zooplankton ?13C was similar to POM ?13C, implying thatzooplankton occupie...

Bomchul Kim; Lee Jeayong; Yunkyoung Lee; Changwon Jang; Owen, Jeffrey S.; Jai-Ku Kim; Jaesung Eum; Sungmin Jung

2013-01-01

243

Influence of a tidal front on zooplankton abundance, assemblages and life histories in Península Valdés, Argentina  

Science.gov (United States)

The complex biophysical interactions that occur in Península Valdés tidal front offer an appropriate scenario to study how zooplankton species respond to the environmental setting. In that sense, we studied why some zooplankton assemblages come to dominate in certain areas, focusing on the differential use that each life history stage makes on the hydrodynamic regimes. Environmental data and zooplankton samples were taken across the tidal front, covering well-mixed, frontal and stratified waters. Zooplankton abundance, assemblage structure, specific composition and life histories were analyzed in relation to depth, temperature, stratification level of the water column and chlorophyll a. Zooplankton-specific composition did not vary across the different zones of the front but, due to differences in relative abundance, three assemblages were detected in coincidence with the three zones analyzed. Most zooplankton adult groups and early life stages were related to the stratification level of the water column. This environmental factor best explained the coupling of the three different zooplankton assemblages with the three zones of the frontal system. This distributional pattern was clearly observed in the copepods group. Despite different copepod species prevailing in different parts of the tidal front, the frontal interface appears to be an important breeding area for all copepod species. The stratification level would be the main factor responsible for the zooplankton distributional pattern across the tidal front, although other physical and biological processes, such as transport, retention and life history strategies could be conditioning the establishment of different zooplankton populations in this complex frontal system.

Derisio, Carla; Alemany, Daniela; Acha, Eduardo M.; Mianzan, Hermes

2014-11-01

244

Phytoplanktons and zooplanktons diversity in karachi coastal seawater under high and low tide during winter monsoon  

International Nuclear Information System (INIS)

This paper represents the population density of phytoplanktons and zooplanktons recorded during the marine environmental studies at Karachi coast in the month of February 2011. Samples were collected by towing net, preserved and quantification and identification was carried out under light microscope. Twenty-three phytoplanktons species and nine zooplankton groups were recorded in the seawater from the sampling area of 10 square kilometers. Coscinodiscus and Copepods were dominant in the population of phytoplankton and zooplankton, respectively. Phytoplankton population density increased while zooplankton abundance decreased offshore from the coastline in the open sea. (author)

245

Vertical Farm  

Science.gov (United States)

With the continued growth of the human population of the Earth, there is increasing concern with the planet's ability to provide sustenance for all of its inhabitants. This compelling website by Dickson Despommier and his colleagues at Columbia University provides a worthy alternative to other forms of agriculture: the vertical farm. As Dr. Despommier notes on the site, "..they offer the promise of urban renewal, sustainable production of a safe and varied food supply (year-round crop production), and the eventual repair of ecosystems that have been sacrificed for horizontal farming." The site offers a great deal of information about these vertical farms, a detailed essay on the importance of such farms, a number of potential designs, and a discussion forum. Finally, there are a number of plans that indicate how this type of farm might be effectively created and sustained.

246

Stable carbon isotopes of zooplankton lipid components as a tool to differentiate between pelagic and ice algae as a food source for zooplankton in the Arctic Ocean  

Science.gov (United States)

Every summer in the Arctic, the ice cover melts and releases sea-ice algae into the surrounding waters. How important are these algae, consisting mostly of diatoms, as a major food source for zooplankton and higher trophic levels? The answer to this question is timely, given predictions for the loss of summer sea ice cover this century. We are investigating the use of compound specific carbon isotopes as a tool to differentiate between lipids found in zooplankton which feed on diatoms living in the open ocean and zooplankton which feed on diatoms derived from the ice. To this effect we analyse the carbon isotopic signature of the major fatty acids and alcohols and that of the major sterols collected during the Arctic ICE CHASER expedition aboard the RRV James Clark Ross in 2008. Twenty three zooplankton samples comprised of 11 different species were collected in four different depth intervals at three different sites around Svalbard. The sites had variable ice cover, from open water to solid ice. We analysed the lipid composition of the zooplankton samples with special emphasis on the fatty acids and fatty alcohols bound as esters. Esters are produced by zooplankton to function as an energy reservoir. Initial results such as the occurrence of Brassicasterol, 24 methylencholest 5 en-3?-ol and Desmosterol, high amounts of the C20:5?3 fatty acid and high C16:1?7/C16:0-fatty acid ratios suggest that diatoms are an important part of the zooplankton diet.

Bendle, J. A.; Moossen, H.; Jamieson, R.; Wold, A.; Falk-Peterson, S.

2009-12-01

247

A demonstration of prestack migration error in transversely isotropic media  

Energy Technology Data Exchange (ETDEWEB)

Migration errors arise for steep events from anisotropic media when poststack migration is done with an algorithm that does not take anisotropy into account. Here, the authors demonstrate imaging errors that arise in prestack migration that ignores anisotropy present in the model. They generated data for an inhomogeneous, transversely isotropic medium with a vertical axis of symmetry (VTI), and analyzed the results of common-offset migration that ignores anisotropy.

Jaramillo, H.; Larner, K. [Colorado School of Mines, Golden, CO (United States)

1994-12-31

248

A three-dimensional biophysical model of Karenia brevis dynamics on the west Florida shelf: A look at physical transport and potential zooplankton grazing controls  

Science.gov (United States)

The development of accurate predictive models of toxic dinoflagellate blooms is of great ecological importance, particularly in regions that are most susceptible to their detrimental effects. This is especially true along the west Florida shelf (WFS) and coast, where episodic bloom events of the toxic dinoflagellate Karenia brevis often wreak havoc on the valuable commercial fisheries and tourism industries of west Florida. In an effort to explain the dynamics at work within the maintenance and termination phases of a red tide, a simple three-dimensional coupled biophysical model was used in the analysis of the October 1999 red tide offshore Sarasota, Florida. Results of the numerical experiments indicate that: (1) measured and modeled flowfields were capable of transporting the observed offshore inoculum of K. brevis to within 16 km of the coastal boundary; (2) background concentrations (1000 cells L -1) of K. brevis could grow to a red tide of over 2×10 6 cells L -1 in little more than a month, assuming an estuarine initiation site with negligible offshore advection, no grazing losses, negligible competition from other phytoplankton groups, and no nutrient limitation; (3) maximal grazing pressure could not prevent the initiation of a red tide or cause its termination, assuming no other losses to algal biomass and a zooplankton community ingestion rate similar to that of Acartia tonsa; and (4) the light-cued ascent behavior of K. brevis served as an aggregational mechanism, concentrating K. brevis at the 55 ?E m -2 s -1 isolume when mean concentrations of K. brevis exceeded 100,000 cells L -1. Further improvements in model fidelity will be accomplished by the future inclusion of phytoplankton competitors, disparate nutrient availability and limitation schemes, a more realistic rendering of the spectral light field and the attendant effects of photo-inhibition and compensation, and a mixed community of vertically-migrating proto- and metazoan grazers. These model refinements are currently under development and shall be used to aid progress toward an operational model of red tide forecasting along the WFS.

Milroy, Scott P.; Dieterle, Dwight A.; He, Ruoying; Kirkpatrick, Gary J.; Lester, Kristen M.; Steidinger, Karen A.; Vargo, Gabriel A.; Walsh, John J.; Weisberg, Robert H.

2008-01-01

249

A one-month study of the zooplankton community at a fixed station in the Ligurian Sea: the potential impact of the species composition on the mineralization of organic matter  

Directory of Open Access Journals (Sweden)

Full Text Available The cruise project was designed to study temporal variations of the ecosystem during the summer-autumn transition and focused on the part played by zooplankton as top-down controllers, and the relative importance of top-down versus bottom-up controls. Zooplankton should play a key role both in the vertical transfer of particulate organic matter and in the mineralisation of organic matter. Although the importance of species diversity is well recognized, the impact of diversity on carbon fluxes is rarely considered. Trophic roles of zooplankton range from strict herbivory to strict carnivory, with all possible combinations (i.e. omnivory between these two extremes. Feeding strategies are also very diverse, for example, active predators, passive filter feeders or suspension feeders co-exist (Bamstedt at al., 2000. As the metabolic cost of these different trophic roles and ways of feeding should be different, a physiological diversity must be considered in any assessment of the role of zooplankton in the flux of organic matter (e.g. Longhurts and Harrison, 1989. At a minimum,, species and functional diversities contribute to the diversity of exported organic matter (Steinberg et al., 2000; Madin et al., 2001. Fecal pellets, the organic matter egested by zooplankton, differ in form, size and weight, and hence in their sedimentation and degradation rates (Turner, 2002. The downward flux of organic matter thus depends on not only on physical and chemical processes but also on biological variables.

The area sampled, located in the central part of the Ligurian Sea is next to the DYFAMED site, a time-series station monthly monitored for several years now. The zone is considered to be oligotrophic and protected from strong advective processes (Andersen and Prieur, 2000. The two cruises DYNAmic of the rapid PROCess (DYNAPROC 1 in May 1995 and DYNAPROC 2, the present study were devoted to factors controlling the vertical flux of matter on short time scales. The aim of the work presented here was to estimate, at a fixed station in the Ligurian Sea (NW Mediterranean Sea,the impact of zooplankton on organic matter fluxes. We determined the species composition and then for the dominant species of the community, we estimated rates of, oxygen consumption, carbon dioxide production and ammonium excretion. Our sampling period, the summer-autumn transition featuring strong wind events, offered contrasting situations for primary and export production (Marty et al., 2008. We thus have the opportunity to estimate how the zooplankton, from a species-specific point of view, react to these changes.

L. Mousseau

2009-01-01

250

Use of molecular markers as indicators for winter zooplankton grazing on toxic benthic cyanobacteria colonies in an urban Colorado lake  

OpenAIRE

Laboratory experiments provide no general answer to the question of whether zooplankton affects cyanobacteria or are affected by prokaryotes. A cyanobacterium may be grazed upon as small colonies, and the same species, as larger colonies, may inhibit zooplankton feeding. Within zooplankton, different species or groups may be affected differently. With this background we set out to detect winter zooplankton grazing and toxicity of overwintering populations of Microcystis aeruginosa. A polymera...

Oberholster, Paul Johan; Botha, Anna-maria; Cloete, T. E.

2006-01-01

251

Vertical optimetry  

International Nuclear Information System (INIS)

The invention refers to the technical installation for visualization of electrostatic images, in particular to the metrologic engineering provided for measurement of dynamic deviations of the exterior dimensions of the photo-thermoplastic data/carrying medium when during recording the optical information on a real time basis. The vertical optimeter includes a support, onto which it is installed an optical system, containing a tube with light source, a visualization tube provided with a video camera, a mechanism for rough control of the cell motion for optical recording on the photo-thermoplastic medium. The vertical optimeter additionally contains two more optical systems: one installed coaxial with the first optical system, includes a visualization tube tube provided with a digital video camera, a semitransparent mirror installed onto the support over the axes of the visualization tube. The other optical system, sensitive to the infrared radiation, is installed onto the support and contains the consecutively joined a detector of the infrared radiation, an electric drive, joined with the cell for optical recording drive, joined with the cell for optical recording of the information. The result of the invention consists in excluding the optical errors, due to the fine control of the optical data recording cell motion and due to the recording of dynamic errors, released from both sides

252

Monarch Migration.  

Science.gov (United States)

Describes the Monarch Watch program that tracks the migration of the monarch butterfly. Presents activities that introduce students to research and international collaboration between students and researchers. Familiarizes students with monarchs, stimulates their interest, and helps them generate questions that can lead to good research projects.…

Williamson, Brad; Taylor, Orley

1996-01-01

253

Spatial and temporal variation in mercury bioaccumulation by zooplankton in Lake Champlain (North America)  

International Nuclear Information System (INIS)

Trophic transfer of Hg across lakes within a region has been related to multiple environmental factors, but the nature of these relationships across distinct basins within individual large lakes is unknown. We investigated Hg bioaccumulation in zooplankton in basins of differing trophic status in Lake Champlain (Vermont, USA) to determine the strongest predictors of Hg bioaccumulation. Zooplankton were sampled in Malletts Bay (oligotrophic) and Missisquoi Bay (eutrophic) in 2005–2008. Zooplankton in the eutrophic basin had lower concentrations of total Hg and MeHg than those in the oligotrophic basin in all years but 2007, when no bloom occurred in Missisquoi. In addition, Hg concentrations in seston and small zooplankton, sampled during 2009 at 12 sites spanning the lake, decreased with increasing phytoplankton and zooplankton biomass. Thus, Hg bioaccumulation in zooplankton across basins in Lake Champlain is related to trophic status, as observed previously in multiple lake studies. - Highlights: ? Lake Champlain zooplankton Hg was lower in the eutrophic than the oligotrophic basin. ? Algal blooms in years present biodiluted Hg in plankton. ? Lake-wide spatial patterns of Hg in plankton decreased with increasing biomass. ? Lake-wide Hg bioaccumulation patterns are consistent with multiple lake studies. - Large spatiotemporal variations in MeHg bioaccumulation in zooplankton within a single large lake were linked to spatial variation in trophic status acrosariation in trophic status across basins and to inter-annual variation in algal density.

254

SPATIAL PATTERNS IN ASSEMBLAGE STRUCTURES OF PELAGIC FORAGE FISH AND ZOOPLANKTON IN WESTERN LAKE SUPERIOR  

Science.gov (United States)

This manuscript reports on the spatial distribution of zooplankton and forage fish in western Lake Superior. Fish and zooplankton assemblages are shown to differ substantially in abundance and size structure both between the open lake and nearshore regions and between two differe...

255

PHYTOPLANKTON AND ZOOPLANKTON SEASONAL DYNAMICS IN A SUBTROPICAL ESTUARY: IMPORTANCE OF CYANOBACTERIA  

Science.gov (United States)

Murrell, Michael C. and Emile M. Lores. 2004. Phytoplankton and Zooplankton Seasonal Dynamics in a Subtropical Estuary: Importance of Cyanobacteria. J. Plankton Res. 26(3):371-382. (ERL,GB 1190). A seasonal study of phytoplankton and zooplankton was conducted from 1999-20...

256

Effect of Main-stem Dams on Zooplankton Communities of the Missouri River (USA)  

Science.gov (United States)

We examined the distribution and abundance of zooplankton from 146 sites on the Missouri River and found large shifts in the dominance of major taxa between management zones of this regulated river. Crustacean zooplankton were dominant in the inter-reservoir zone of the river, an...

257

CONSTANT, NOCTURNAL OR NO AERATION: EFFECTS ON WATER QUALITY AND ZOOPLANKTON IN HEAVILY FERTILIZED NURSERY PONDS.  

Science.gov (United States)

Sunshine bass fingerling production depends upon an initial high concentration of rotifers followed by high densities in crustacean zooplankton in culture ponds. Increased fertilization promotes increased amounts of zooplankton but often causes poor water quality which aeration may alleviate. The e...

258

Assessment of Zooplankton Size Fractionation for Monitoring Fry and Fingerling Culture Ponds  

Science.gov (United States)

Methodology was formulated for use in the rapid assessment of zooplankton in channel catfish ponds. Understanding zooplankton prey size is useful for effective pond management. Size fractionation using differential sieve sizes was an effective means of separating size classes in live material, whe...

259

EFFECTS OF TOXIC SUBSTANCES ON ZOOPLANKTON POPULATIONS: A GREAT LAKES PERSPECTIVES  

Science.gov (United States)

In this chapter, we discuss (1) how toxic substances can affect zooplankton, both at the species and community level, (2) modifying factors affecting toxicity, (3) the effects of various environmental pertubations, including toxic substances, on Great Lakes zooplankton, and (4) t...

260

a Three-Dimensional Acoustical Imaging System for Zooplankton Observations  

Science.gov (United States)

This dissertation describes the design, testing, and use of a three-dimensional acoustical imaging system, called Fish TV, or FTV, for tracking zooplankton swimming in situ. There is an increasing recognition that three -dimensional tracks of individual plankters are needed for some studies in behavioral ecology including, for example, the role of individual behavior in patch formation and maintenance. Fish TV was developed in part to provide a means of examining zooplankton swimming behavior in a non-invasive way. The system works by forming a set of 64 acoustic beams in an 8 by 8 pattern, each beam 2 ^circ by 2^circ , for a total coverage of 16^circ by 16^circ. The 8 by 8 beams form two dimensions of the image; range provides the third dimension. The system described in the thesis produces three-dimensional images at the rate of approximately one per second. A set of laboratory and field experiments is described that demonstrates the capabilities of the system. The final field experiment was the in situ observation of zooplankton swimming behavior at a site in the San Diego Trough, 15 nautical miles southwest of San Diego. 314 plankters were tracked for one minute. It was observed that there was no connection between the acoustic size of the animals and their repertoire of swimming behaviors. Other contributions of the dissertation include the development of two novel methods for generating acoustic beams with low side lobes. The first is the method of dense random arrays. The second is the optimum mean square quantized aperture method. Both methods were developed originally as ways to "build a better beam pattern" for Fish TV, but also have general significance with respect to aperture theory.

McGehee, Duncan Ewell

261

210Po uptake by zooplankton during a one year cycle in relation to trophic conditions in Monaco Bay  

International Nuclear Information System (INIS)

Former evidence showed that in oligotrophic waters in French Polynesia there is an inverse correlation between zooplankton biomass and zooplankton 210Po concentration. To study the same phenomenon in a more seasonal environment, monthly samples of zooplankton, water, fecal pellets, and particulate organic matter were obtained in Monaco monthly and analyzed for 210Po content

262

Infestation of zooplankton with Triaenophorus and Proteocephalus procercoids (Cestoda in a deep oligotrophic lake  

Directory of Open Access Journals (Sweden)

Full Text Available In spring 2004, a massive infestation of the whitefish population in the Austrian Lake Achensee with Triaenophorus crassus was observed. Procercoids, the larval stage of parasitic cestodes, infest copepods as their first intermediate host. Therefore, in spring 2011, zooplankton samples were taken weekly at two sampling sites and depth ranges to determine the abundances of crustaceans as well as percentages of infected copepods and temporal occurrence of parasites. In addition, whitefish (Coregonus lavaretus stomach contents were analysed for food spectrum and parasite infestation. From the end of June to mid-August, procercoids of Triaenophorus spp. were detected in Cyclops abyssorum, the only first intermediate host for this parasite in Lake Achensee. Highest percentages of infected copepods were reached in mid-July (prevalence: 0.38%. Furthermore, an infestation of Proteocephalus sp. was observed in this copepod species, which occurred earlier until the end of the sampling period (prevalence: 1.34%. Besides C. abyssorum, also Eudiaptomus gracilis was occasionally infected with Proteocephalus (prevalence: 0.05%. The procercoids were found in both depth ranges, with no clear vertical infestation preference. More female C. abyssorum were Triaenophorus-infected than males, while the opposite was observed for Proteocephalus infection. The whitefish stomachs contained large numbers of Proteocephalus and Triaenophorus procercoids, coinciding with the occurrence of these parasites in the copepods.

Peter Anegg

2014-02-01

263

Neustonic microplastic and zooplankton in the North Western Mediterranean Sea  

OpenAIRE

Neustonic microplastic and zooplankton abundance was determined in the North Western Mediterranean Sea during a summer cruise between July 9th and August 6th 2010, with a break between July 22th and 25th due to a strong wind event. Ninety percent of the 40 stations contained microplastic particles (size 0.3-5 mm) of various compositions: e.g., filaments, polystyrene, thin plastic films. An average concentration of 0.116 particles/m² was observed. The highest abundances (> 0.36 particles/...

Collignon, Amandine; Hecq, Jean-henri; Galgani, Franc?ois; Voisin, Pierre; Collard, France; Goffart, Anne

2012-01-01

264

Zooplankton Variation of Murat River (Elaz??- within the borders Palu district  

Directory of Open Access Journals (Sweden)

Full Text Available Zooplankton of Murat River was examined from monthly taken samples between June 2011 and May 2012. As a result of research were identified total 33 species, 25 of them belong to Rotifera, 6 belong to Cladocera, 2 belong to Copepoda. Zooplanktonik species were comprised as 75.76% Rotifera 18.18% Cladocera and 6.06% Copepoda species. There was marked decrease in at the zooplankton species diversity in winter months. There was sharp increase at the zooplankton species diversity in spring and in summer months. Especially in spring month’s zooplankton were recorded in highest species and numbers individual. The most species were determined in April (nine species. At least species were determined January (four species. pH, dissolved oxygen, water temperature were measured of the study area. The study has got an importance as to be the first research on zooplankton in this area.

Hilal Bulut

2014-01-01

265

Neuronal Migration Disorders  

Science.gov (United States)

NINDS Neuronal Migration Disorders Information Page Table of Contents (click to jump to sections) What is Neuronal Migration Disorders? Is there ... being done? Clinical Trials Organizations What is Neuronal Migration Disorders? Neuronal migration disorders (NMDs) are a group ...

266

Zooplankton community pattern associated with a California Current cold filament  

Science.gov (United States)

In July 1988 we sampled upper layer zooplankton distributions in and around a major cold filament located off Point Arena, California. Average zooplankton biomass levels declined inshore to offshore, but relatively high levels extended seaward along the cool side of the filament jet. A series of transverse station lines shows strong shifts in community composition across the axis of the filament. The cross-filament compositional sequence was recognizably similar along each line, giving an impression (supported by cluster analysis and along-flow versus cross-flow spatial autocorrelation) of banding parallel to the filament axis. The "standard" sequence was characterized by local maxima of Dolioletta gegenbauri in nonfilament waters to the south and east, Euphausia pacifica along the southeast margin of the filament, Eucalanus californicus and euphausiid larvae within the cool core of the filament and extending partway across the strong seaward jet on the north and west margin of the filament, and heteropod larvae, chaetognaths, Dolioletta, and a mixture of small copepods (including several with southern and offshore faunal affinities) along the warm side of the jet and extending into nonfilament waters to the north and west. A "core" group of samples characterized by high abundance of Eucalanus matched the trajectories of drifters released at the upstream end of the filament. Both crossed geopotential anomaly contours (to larger ?) as they moved out the filament, suggesting a cross-jet component of motion.

Mackas, David L.; Washburn, Libe; Smith, Sharon L.

1991-08-01

267

Vertical distribution and trophic interactions of krill, sprat and gadoids in the inner Oslofjord during winter  

OpenAIRE

ABSTRACT Vertical distribution and trophic interactions of zooplankton and fish were studied at a 150 m deep station in Bunnefjorden ? the innermost part of the Oslofjord - during winter 2005/2006. Focus was on the krill Meganyctiphanes norvegica, the small clupeid fish sprat (Sprattus sprattus) and gadoids, mainly whiting (Merlangius merlangus). Bunnefjorden is characterized by hypoxy in the bottom water, and the study was part of more long-lasting investigations addressing how hypoxy may i...

Brun, Helene

2007-01-01

268

EVALUATION OF OPTICALLY ACQUIRED ZOOPLANKTON SIZE-SPECTRUM DATA AS A POTENTIAL TOOL FOR ASSESSMENT OF CONDITION IN THE GREAT LAKES  

Science.gov (United States)

An optical zooplankton counter (OPC) potentially provides as assessment tool for zooplankton condition in ecosystems that is rapid, economical, and spatially extensive. We collected zooplankton data with an optical zooplankton counter in 20 near-shore regions of four of the Laure...

269

Zooplankton community analysis in the Changjiang River estuary by single-gene-targeted metagenomics  

Science.gov (United States)

DNA barcoding provides accurate identification of zooplankton species through all life stages. Single-gene-targeted metagenomic analysis based on DNA barcode databases can facilitate longterm monitoring of zooplankton communities. With the help of the available zooplankton databases, the zooplankton community of the Changjiang (Yangtze) River estuary was studied using a single-gene-targeted metagenomic method to estimate the species richness of this community. A total of 856 mitochondrial cytochrome oxidase subunit 1 (cox1) gene sequences were determined. The environmental barcodes were clustered into 70 molecular operational taxonomic units (MOTUs). Forty-two MOTUs matched barcoded marine organisms with more than 90% similarity and were assigned to either the species (similarity>96%) or genus level (similarity<96%). Sibling species could also be distinguished. Many species that were overlooked by morphological methods were identified by molecular methods, especially gelatinous zooplankton and merozooplankton that were likely sampled at different life history phases. Zooplankton community structures differed significantly among all of the samples. The MOTU spatial distributions were influenced by the ecological habits of the corresponding species. In conclusion, single-gene-targeted metagenomic analysis is a useful tool for zooplankton studies, with which specimens from all life history stages can be identified quickly and effectively with a comprehensive database.

Cheng, Fangping; Wang, Minxiao; Li, Chaolun; Sun, Song

2014-07-01

270

First evidence for zooplankton feeding sustaining key physiological processes in a scleractinian cold-water coral.  

Science.gov (United States)

Scleractinian cold-water corals (CWC) represent key taxa controlling deep-sea reef ecosystem functioning by providing structurally complex habitats to a high associated biodiversity, and by fuelling biogeochemical cycles via the release of organic matter. Nevertheless, our current knowledge on basic CWC properties, such as feeding ecology and key physiological processes (i.e. respiration, calcification and organic matter release), is still very limited. Here, we show evidence for the trophic significance of zooplankton, essentially sustaining levels of the investigated key physiological processes in the cosmopolitan CWC Desmophyllum dianthus (Esper 1794). Our results from laboratory studies reveal that withdrawal (for up to 3 weeks) of zooplankton food (i.e. Artemia salina) caused a significant decline in respiration (51%) and calcification (69%) rates compared with zooplankton-fed specimens. Likewise, organic matter release, in terms of total organic carbon (TOC), decreased significantly and eventually indicated TOC net uptake after prolonged zooplankton exclusion. In fed corals, zooplankton provided 1.6 times the daily metabolic C demand, while TOC release represented 7% of zooplankton-derived organic C. These findings highlight zooplankton as a nutritional source for D. dianthus, importantly sustaining respiratory metabolism, growth and organic matter release, with further implications for the role of CWC as deep-sea reef ecosystem engineers. PMID:21993785

Naumann, Malik S; Orejas, Covadonga; Wild, Christian; Ferrier-Pagès, Christine

2011-11-01

271

Zooplankton-based assessment of the trophic state of a tropical forest river in Nigeria  

Directory of Open Access Journals (Sweden)

Full Text Available In this study, we explore the usefulness of zooplankton as a tool for assessing the trophic status of a Nigerian forest river. The river was sampled monthly and investigated for water physico-chemistry and zooplankton community structure using basic statistical measurement of diversity indices to characterize the zooplankton fauna. The trophic sta­tus of the river evaluated from its physico-chemical parameters indicates that the river is oligotrophic. The zooplankton composition was typical of a tropical freshwater river, with a total of 40 species, made up of 16 rotifers, 12 cladocerans, and 12 copepods and their developing stages in the following order of dominance: Rotifera > Cladocera > Cyclopoida > Calanoida. There were strong correlations between the lake's trophic status and its zooplankton communities. The zoo­plankton community was dominated by numerous species of rotifers and crustaceans, which are typical of oligotrophic to mesotrophic systems, such species including Conochilus dossuarius and Synchaeta longipes. However, the most dominant zooplankton species in West African freshwater ecosystems, viz., Keratella tropica, Keratella quadrata, Brachionus angularis, Trichocerca pusilla, Filinia longiseta, Pompholyx sulcata, and Proales sp., and others that are indicator species of high trophic levels, were not recorded in the river. The river is very clear and can be used for all manner of recreational activities.

Imoobe T.O.T.

2009-01-01

272

Zooplankton responses to sandbar opening in a tropical eutrophic coastal lagoon  

Science.gov (United States)

The effects of a disturbance by sandbar opening on the zooplankton community were evaluated through a long-term study in an eutrophic and oligohaline system, Imboassica Lagoon, Rio de Janeiro, Brazil. Zooplankton samples and limnological data were collected monthly from March 2000 to February 2003. Before the sandbar was opened in February 2001, the lagoon showed eutrophic conditions, with high mean nutrient concentrations and low salinity (total nitrogen - TN = 190.28 ?M, chlorophyll a content - Chl. a = 104.60 ?g/L and salinity = 0.87'). During this period, the zooplankton species present, such as the rotifers Brachionus calyciflorus and Brachionus havanaensis, were typical of freshwater to oligohaline and eutrophic environments. After the sandbar opening, the lagoon changed to a lower trophic status and increased salinity (TN = 55.11 ?M, Chl. a = 27.56 ?g/L and salinity = 19.64'). As a result, the zooplankton community came to consist largely of the rotifer Brachionus plicatilis, marine copepods and meroplanktonic larvae, mainly Gastropoda. Salinity was the main force structuring the zooplankton community after the sandbar opening. Two years after this episode, the prior zooplankton community had not reestablished itself, indicating a low resilience to this disturbance. The conditions developed prior to a sandbar opening can be crucial to the community responses in the face of this disturbance and for the capacity of the original zooplankton community to re-establish itself.

Santangelo, Jayme M.; de M. Rocha, Adriana; Bozelli, Reinaldo L.; Carneiro, Luciana S.; de A. Esteves, Francisco

2007-02-01

273

Reduced growth and survival of larval razorback sucker fed selenium-laden zooplankton.  

Science.gov (United States)

Four groups of larval razorback sucker, an endangered fish, were exposed to selenium-laden zooplankton and survival, growth, and whole-body residues were measured. Studies were conducted with 5, 10, 24, and 28-day-old larvae fed zooplankton collected from six sites adjacent to the Green River, Utah. Water where zooplankton were collected had selenium concentrations ranging from site (Sheppard Bottom pond 1) up to 94 microg/g in fish fed zooplankton from North Roadside Pond. Limited information prior to the studies suggested that the Sheppard pond 1 site was relatively clean and suitable as a reference treatment; however, the nearly complete mortality of larvae and elevated concentrations of selenium in larvae and selenium and other elements in zooplankton indicated that this site was contaminated with selenium and other elements. Selenium concentrations in whole-body larvae and in zooplankton from all sites were close to or greater than toxic thresholds where adverse effects occur in fish. Delayed mortality occurred in larvae fed the two highest selenium concentrations in zooplankton and was thought due to an interaction with other elements. PMID:15883091

Hamilton, Steven J; Buhl, Kevin J; Bullard, Fern A; McDonald, Susan F

2005-06-01

274

Efectos del herbicida Paraquat sobre el zooplancton Effects of Paraquat herbicide on zooplankton  

OpenAIRE

The effects of 0.1; 0.2; 0.4 and 0.8 mlPQ/L were analized on a zooplankton community, to determine the most sensitive species and to analize the occurence of physical abnormalities. A total of 40 taxa were determined. Paraquat affected significantly the zooplankton density but not the species richness. A progressive state of deformation of these organisms was also observed. Paraquat showed to be highly toxic for the zooplankton, so this herbicide should be strictly regulated in aquatic and te...

Ana María Gagneten

2002-01-01

275

Invasive property into water of pulsed intense relativistic electron beam and its irradiation effect to zooplankton  

International Nuclear Information System (INIS)

Zooplankton contained in seawater or 3-wt% salt solution has been successfully inactivated using a pulsed intense relativistic electron beam (PIREB). A treatment chamber is filled with seawater or 3-wt% salt solution containing zooplankton, and is irradiated using the PIREB (2 MeV, 0.4 kA, 140 ns). The PIREB invasive properties indicated that seawater, brackish water and 3-wt% salt solution are similar. We found that up to 40% of zooplanktons are inactivated by one shot of PIREB irradiation. (author)

276

Radiocesium in zooplankton in seawaters off Miyagi, Fukushima, and Ibaraki prefectures  

International Nuclear Information System (INIS)

Zooplankton samples in seawaters were collected off Miyagi, Fukushima, and Ibaraki prefectures from May 2012 to January 2013. Activity concentrations of 134Cs and 137Cs in zooplankton varied from 0.1 to 9.1 Bq/kg-wet weight, and from 0.1 to 12.8 Bq/kg-wet weight, and were higher in May 2012 than in the other sampling months. We also estimated the zooplankton-to-water activity ratio of 137Cs to be 20-754 L/kg. (author)

277

Relation between 234Th scavenging and zooplankton biomass in Mediterranean surface waters  

International Nuclear Information System (INIS)

Dissolved and particulate 234Th activities were determined and phyto-and zooplankton biomass were periodically measured 8 miles off Nice (Mediterranean Sea) during spring 1987. The results show a strong variability of 234Th distribution on short time scales in northwestern Mediterranean surface waters. The good correlation observed the zooplankton biomass and the rate of 234Th export to deep water in particulate form is agreement with the assumption that the residence time of particulate 234Th in oceanic surface waters is controlled by zooplankton grazing. Moreover, our results indicate the importance of salps in particular as efficient removers of small suspended particles in surface waters

278

Miracle of Winged Migration  

Science.gov (United States)

This site, from the Why Files contains brief sections on various aspects of bird migration such as navigation, flight strategies, raptor migration, and declining numbers of migrating songbirds. This site also links to information about monarch migration and the effects of global warming on migration of birds and butterflies alike.

Tenenbaum, David

279

Migration of Birds  

Science.gov (United States)

Hosted by the U.S. Geological Survey Northern Prairie Wildlife Research Center, this site is an online publication from the U.S. Fish and Wildlife Service on the Migration of Birds. This publication provides an extensive account of migration including sections on Techniques for Studying Migration, Evolution of Migration, Flight Speed and Rate of Migration, and many more.

Lincoln, Frederick C.

280

VERTIGO (VERtical Transport In the Global Ocean): A study of particle sources and flux attenuation in the North Pacific  

Energy Technology Data Exchange (ETDEWEB)

The VERtical Transport In the Global Ocean (VERTIGO) study examined particle sources and fluxes through the ocean's 'twilight zone' (defined here as depths below the euphotic zone to 1000 m). Interdisciplinary process studies were conducted at contrasting sites off Hawaii (ALOHA) and in the NW Pacific (K2) during 3 week occupations in 2004 and 2005, respectively. We examine in this overview paper the contrasting physical, chemical and biological settings and how these conditions impact the source characteristics of the sinking material and the transport efficiency through the twilight zone. A major finding in VERTIGO is the considerably lower transfer efficiency (T{sub eff}) of particulate organic carbon (POC), POC flux 500/150 m, at ALOHA (20%) vs. K2 (50%). This efficiency is higher in the diatom-dominated setting at K2 where silica-rich particles dominate the flux at the end of a diatom bloom, and where zooplankton and their pellets are larger. At K2, the drawdown of macronutrients is used to assess export and suggests that shallow remineralization above our 150 m trap is significant, especially for N relative to Si. We explore here also surface export ratios (POC flux/primary production) and possible reasons why this ratio is higher at K2, especially during the first trap deployment. When we compare the 500 m fluxes to deep moored traps, both sites lose about half of the sinking POC by >4000 m, but this comparison is limited in that fluxes at depth may have both a local and distant component. Certainly, the greatest difference in particle flux attenuation is in the mesopelagic, and we highlight other VERTIGO papers that provide a more detailed examination of the particle sources, flux and processes that attenuate the flux of sinking particles. Ultimately, we contend that at least three types of processes need to be considered: heterotrophic degradation of sinking particles, zooplankton migration and surface feeding, and lateral sources of suspended and sinking materials. We have evidence that all of these processes impacted the net attenuation of particle flux vs. depth measured in VERTIGO and would therefore need to be considered and quantified in order to understand the magnitude and efficiency of the ocean's biological pump.

Buesseler, K.O.; Trull, T.W.; Steinberg, D.K.; Silver, M.W.; Siegel, D.A.; Saitoh, S.-I.; Lamborg, C.H.; Lam, P.J.; Karl, D.M.; Jiao, N.Z.; Honda, M.C.; Elskens, M.; Dehairs, F.; Brown, S.L.; Boyd, P.W.; Bishop, J.K.B.; Bidigare, R.R.

2008-06-10

281

VERTIGO (VERtical Transport In the Global Ocean): A study of particle sources and flux attenuation in the North Pacific  

Science.gov (United States)

The VERtical Transport In the Global Ocean (VERTIGO) study examined particle sources and fluxes through the ocean's "twilight zone" (defined here as depths below the euphotic zone to 1000 m). Interdisciplinary process studies were conducted at contrasting sites off Hawaii (ALOHA) and in the NW Pacific (K2) during 3-week occupations in 2004 and 2005, respectively. We examine in this overview paper the contrasting physical, chemical and biological settings and how these conditions impact the source characteristics of the sinking material and the transport efficiency through the twilight zone. A major finding in VERTIGO is the considerably lower transfer efficiency ( Teff) of particulate organic carbon (POC), POC flux 500/150 m, at ALOHA (20%) vs. K2 (50%). This efficiency is higher in the diatom-dominated setting at K2 where silica-rich particles dominate the flux at the end of a diatom bloom, and where zooplankton and their pellets are larger. At K2, the drawdown of macronutrients is used to assess export and suggests that shallow remineralization above our 150-m trap is significant, especially for N relative to Si. We explore here also surface export ratios (POC flux/primary production) and possible reasons why this ratio is higher at K2, especially during the first trap deployment. When we compare the 500-m fluxes to deep moored traps, both sites lose about half of the sinking POC by >4000 m, but this comparison is limited in that fluxes at depth may have both a local and distant component. Certainly, the greatest difference in particle flux attenuation is in the mesopelagic, and we highlight other VERTIGO papers that provide a more detailed examination of the particle sources, flux and processes that attenuate the flux of sinking particles. Ultimately, we contend that at least three types of processes need to be considered: heterotrophic degradation of sinking particles, zooplankton migration and surface feeding, and lateral sources of suspended and sinking materials. We have evidence that all of these processes impacted the net attenuation of particle flux vs. depth measured in VERTIGO and would therefore need to be considered and quantified in order to understand the magnitude and efficiency of the ocean's biological pump.

Buesseler, K. O.; Trull, T. W.; Steinberg, D. K.; Silver, M. W.; Siegel, D. A.; Saitoh, S.-I.; Lamborg, C. H.; Lam, P. J.; Karl, D. M.; Jiao, N. Z.; Honda, M. C.; Elskens, M.; Dehairs, F.; Brown, S. L.; Boyd, P. W.; Bishop, J. K. B.; Bidigare, R. R.

2008-07-01

282

Zooplankton mortality due to entrainment in the cooling water circuit of a power station  

International Nuclear Information System (INIS)

Zooplankton mortality, both the instant (0 h) and delayed (24 h) due to entrainment has been studied at two different locations in the cooling water circuit of Madras Atomic Power Station at Kalpakkam. Among the four dominant groups of zooplankton studied, calanoids the largest organisms (average length 1036±246 ?m) with regards to the size as compared to other groups, registered the highest mortality (70.63%). However, the barnacle larvae with their smallest average size (408±105 ?m), suffered the lowest mortality. Thus, the mortality occurred corresponded to the average size of the zooplankton groups. The mortality showed significant difference among the four different groups of zooplankton (p=6 ml/day (in terms of displacement volume) is equivalent to 116.2 kg C/Day. (author)

283

EFFECTS OF DIFFERENT MIXING SCHEDULES ON PHYTOPLANKTON, ZOOPLANKTON AND NUTRIENTS IN MARINE MICROCOSMS  

Science.gov (United States)

An experiment was carried out with different mixing schedules in marine microcosms. Continuous mixing resulted in higher chlorophyll concentrations, lower nutrient concentrations and lower zooplankton biomass than no mixing. No mixing caused water-column stratifications of chloro...

284

Radiocesiums (134Cs, 137Cs) in zooplankton in the waters of Miyagi, Fukushima and Ibaraki Prefectures  

International Nuclear Information System (INIS)

Concentrations of radiocesium (134Cs and 137Cs) were measured in zooplankton in the waters of Miyagi, Fukushima, and Ibaraki Prefectures from May 2012 to January 2013. They varied from 0.1 to 9.1 Bq/kg-wet, and from 0.1 to 12.8 Bq/kg-wet for 134Cs and 137Cs, respectively. The zooplankton-to-water concentration ratio (CR) of 137Cs was calculated to be 20-1410 L/kg. Export fluxes of 137Cs by zooplankton were estimated to be 13-165 mBq/m2/y. The contribution of zooplankton for the downward transport of 137Cs was at most 18 % of the previously reported export fluxes of 137Cs by sinking particles as obtained from sediment trap observations. (author)

285

Eutrophication and warming effects on long-term variation of zooplankton in Lake Biwa  

OpenAIRE

We compiled and analyzed long-term (1961–2005) zooplankton community data in response to environmental variations in Lake Biwa. Environmental data indicate that Lake Biwa had experienced eutrophication (according to the total phosphorus concentration) in the late 1960s and recovered to a normal trophic status around 1985, and then has exhibited warming since 1990. Total zooplankton abundance showed a significant correlation with total phytoplankton biomass. Following a classic pattern, the ...

Hsieh, C. H.; Sakai, Y.; Ban, S.; Ishikawa, K.; Ishikawa, T.; Ichise, S.; Yamamura, N.; Kumagai, M.

2011-01-01

286

Effects of the Distribution of a Toxic Microcystis Bloom on the Small Scale Patchiness of Zooplankton  

OpenAIRE

Toxic cyanobacterial blooms can strongly affect freshwater food web structures. However, little is known about how the patchy occurrence of blooms within systems affects the spatial distribution of zooplankton communities. We studied this by analysing zooplankton community structures in comparison with the spatially distinct distribution of a toxic Microcystis bloom in a small, shallow, eutrophic lake. While toxic Microcystis was present at all sites, there were large spatial differences in t...

Reichwaldt, Elke S.; Song, Haihong; Ghadouani, Anas

2013-01-01

287

Predicting zooplankton response to environmental changes in a temperate estuarine ecosystem  

OpenAIRE

Abstract A novel strategy that allows to predict the responses of zooplanktonic species to environmental conditions in an estuarine temperate ecosystem (Mondego estuary) is presented. It uses 12 indicator species from the zooplanktonic Mondego database (102 species) that are common members of the different habitats, characterized by their specific hydrological conditions. Indicator-species analysis (ISA) was used to define and describe which species were typical of each of the five sampling ...

Marques, So?nia; Azeiteiro, Ulisses; Leandro, Se?rgio; Queiroga, Henrique; Primo, Ana; Martinho, Filipe; Viegas, Ivan; Pardal, Miguel

2008-01-01

288

Do zooplankton contribute to an ultraviolet clear-water phase in lakes?  

OpenAIRE

Seasonal increases in the ultraviolet (UV) transparency of the surface waters of an oligotrophic lake in Pennsylvania suggest that clear-water phase (CWP) events similar to those previously observed for visible light also exist for the potentially damaging UV wavelengths. Seasonal increases in zooplankton grazers indicate that they play a role in these changes in UV that is similar to the role that zooplankton play in CWP events involving longer-wavelength visible, or photosynthetically activ...

Williamson, C. E.; Lange, H. J.; Leech, D. M.

2007-01-01

289

Scavenging and retention of metals by zooplankton fecal pellets and marine snow  

Science.gov (United States)

The scavenging and retention of nine metals in different batches of zooplankton fecal pellets and marine snow were studied in the laboratory using radiotracer techniques. Dissolved 60Co, 65Zn, 106Ru, 109Cd, 110mAg, 141Ce, 154Eu, 237Pu and 241AM were scavenged from seawater onto euphausiid fecal pellets, marine snow and copepod fecal pellets recovered from sediment traps and onto copepod fecal pellets freshly produced in the laboratory. Kd values for the different radioisotopes ranged from 8.4 × 10 2 to 1.9 × 10 5. The radiolabeled fecal pellets and marine snow, resuspended into unlabelled seawater at 2 and 15°C, displayed metal depurations curves generally conforming to a two-compartment model, with overall retention half-times ( t r 1/2s) varying with each metal and type of debris. 109Cd was retained least effectively and 106Ru was generally retained for the longest periods, with t r 1/2s up to 66 days. The t r 1/2s of 141Ce, 154Eu, 237Pu and 241Am in each type of debris were comparable and were not appreciably affected by temperature. 60Co, 65Zn, 109Cd and 110mAg were released into the dissolved phase more rapidly at 15 than at 2°C. Metal binding on copepod fecal pellets and marine snow was generally greater than on euphausiid fecal pellets. These results provide direct evidence that fecal pellets and marine snow can effectively scavenge metals from seawater; of the metals examined, zinc and cadmium are likely to be remineralized most rapidly in surface waters, while the others are likely to be vertically transported hundreds to thousands of meters.

Fisher, Nicholas S.; Nolan, Canice V.; Fowler, Scott W.

1991-10-01

290

Effect of removal of free-floating macrophytes on zooplankton habitat in shallow wetland  

Directory of Open Access Journals (Sweden)

Full Text Available Submerged macrophytes improve the structural heterogeneity of microhabitats in aquatic ecosystems, often providing an important habitat for zooplankton. However, excessive development of free-floating macrophytes on the water surface can reduce the biomass of submerged macrophytes and result in a relatively simple habitat structure. We hypothesized that controlling the development of free-floating macrophytes would result in a more complex habitat structure by promoting the development of submerged macrophytes. After applying three experimental treatments (NR, no removal; IR, intermediate removal; CR, complete removal of free-floating macrophytes, we found that CR of free-floating macrophytes improved the growth and development of submerged macrophytes and supported a large zooplankton assemblage. However, the largest zooplankton assemblage (in terms of abundance and diversity was recorded after the IR treatment. Although submerged macrophytes were abundant in the CR treatment, the number, abundance, and density of zooplankton species were much lower than those in the IR treatment. Preferential selection of different macrophyte types by zooplankton presumably led to variation in plant utilization of niches, and the simultaneous presence of different macrophyte life forms created a complex microhabitat structure that induced high species diversity and zooplankton density.

Choi Jong-Yun

2014-01-01

291

Incorporation of nitrogen from N2 fixation into amino acids of zooplankton  

DEFF Research Database (Denmark)

Eurytemora affinis (Copepoda) were fed 15N-labeled Rhodomonas salina (Cryptophyta) or 15N-labeled Nodularia spumigena (Cyanobacteria) in excess under controlled laboratory conditions. Zooplankton collected from the Baltic Sea were fed natural phytoplankton amended with 15N-labeled N. spumigena. We quantified the direct incorporation of 15N tracer from N2-fixing N. spumigena (diazotroph nitrogen) and ammonium-utilizing R. salina into the amino acid nitrogen (AA-N) of zooplankton using complementary gas chromatography– combustion–isotope ratio mass spectrometry, gas chromatography–mass spectrometry, and elemental analysis– isotope ratio mass spectrometry approaches. Specific and mass-specific TN and AA-N incorporation rates of the 15N tracers were calculated for zooplankton. Highest incorporation of 15N was found in field zooplankton relying on N. spumigena and in E. affinis relying on R. salina. Lowest incorporation was found in E. affinis relying on N. spumigena. Decreasing specific and mass-specific rates during field experiments possibly were due to food shortage, whereas decreasing rates in E. affinis grazing on R. salina were more likely due to satiation. Specific and mass-specific rates were consistently low in E. affinis when exposed to N. spumigena, suggesting that these animals were reluctant to feed on N. spumigena. Essential isoleucine received most of the diazotroph nitrogen in field zooplankton, while nonessential amino acids received most 15N tracer in E. affinis. N. spumigena was clearly an important amino acid nitrogen source for Baltic Sea zooplankton

Loick-Wilde, Natalie; Dutz, Jörg

2012-01-01

292

Modification of meander migration by bank failures  

Science.gov (United States)

Meander migration and planform evolution depend on the resistance to erosion of the floodplain materials. To date, research to quantify meandering river adjustment has largely focused on resistance to erosion properties that vary horizontally. This paper evaluates the combined effect of horizontal and vertical floodplain material heterogeneity on meander migration by simulating fluvial erosion and cantilever and planar bank mass failure processes responsible for bank retreat. The impact of stream bank failures on meander migration is conceptualized in our RVR Meander model through a bank armoring factor associated with the dynamics of slump blocks produced by cantilever and planar failures. Simulation periods smaller than the time to cutoff are considered, such that all planform complexity is caused by bank erosion processes and floodplain heterogeneity and not by cutoff dynamics. Cantilever failure continuously affects meander migration, because it is primarily controlled by the fluvial erosion at the bank toe. Hence, it impacts migration rates and meander shapes through the horizontal and vertical distribution of erodibility of floodplain materials. Planar failures are more episodic. However, in floodplain areas characterized by less cohesive materials, they can affect meander evolution in a sustained way and produce preferential migration patterns. Model results show that besides the hydrodynamics, bed morphology and horizontal floodplain heterogeneity, floodplain stratigraphy can significantly affect meander evolution, both in terms of migration rates and planform shapes. Specifically, downstream meander migration can either increase or decrease with respect to the case of a homogeneous floodplain; lateral migration generally decreases as result of bank protection due to slump blocks; and the effect on bend skewness depends on the location and volumes of failed bank material caused by cantilever and planar failures along the bends, with possible achievement of downstream bend skewness under certain conditions.

Motta, D.; Langendoen, E. J.; Abad, J. D.; García, M. H.

2014-05-01

293

Comparing seasonal dynamics of the Lake Huron zooplankton community between 1983-1984 and 2007 and revisiting the impact of Bythotrephes planktivory  

Science.gov (United States)

Zooplankton community composition can be influenced by lake productivity as well as planktivory by fish or invertebrates. Previous analyses based on long-term Lake Huron zooplankton data from August reported a shift in community composition between the 1980s and 2000s: proportional biomass of calanoid copepods increased while that of cyclopoid copepods and herbivorous cladocerans decreased. Herein, we used seasonally collected data from Lake Huron in 1983–1984 and 2007 and reported similar shifts in proportional biomass. We also used a series of generalized additive models to explore differences in seasonal abundance by species and found that all three cyclopoid copepod species (Diacyclops thomasi, Mesocylops edax, Tropocyclops prasinus mexicanus) exhibited higher abundance in 1983–1984 than in 2007. Surprisingly, only one (Epischura lacustris) of seven calanoid species exhibited higher abundance in 2007. The results for cladocerans were also mixed with Bosmina spp. exhibiting higher abundance in 1983–1984, while Daphnia galeata mendotae reached a higher level of abundance in 2007. We used a subset of the 2007 data to estimate not only the vertical distribution of Bythotrephes longimanus and their prey, but also the consumption by Bythotrephes in the top 20 m of water. This epilimnetic layer was dominated by copepod copepodites and nauplii, and consumption either exceeded (Hammond Bay site) or equaled 65% (Detour site) of epilimnetic zooplankton production. The lack of spatial overlap between Bythotrephes and herbivorous cladocerans and cyclopoid copepod prey casts doubt on the hypothesis that Bythotrephes planktivory was the primary driver underlying the community composition changes in the 2000s.

Bunnell, David B.; Keeler, Kevin M.; Puchala, Elizabeth A.; Davis, Bruce M.; Pothoven, Steven A.

2012-01-01

294

Model migration schedules incorporating student migration peaks  

OpenAIRE

This paper proposes an extension of the standard parameterised model migration schedule to account for highly age-concentrated student migration. Many age profiles of regional migration are characterised by sudden 'spiked' increases in migration intensities in the late teenage years, which are related to leaving school, and, in particular, to entry into higher education. The standard model schedule does not appear to be effective in describing the pattern at these ages. This paper t...

Tom Wilson

2010-01-01

295

The effects of power plant passage on zooplankton mortalities: Eight years of study at the Donald C. Cook Nuclear Plant  

International Nuclear Information System (INIS)

Zooplankton mortalities resulting from passage through the Donald C. Cook Nuclear Plant (southeastern Lake Michigan) were studied over an 8-year (1975-1982) period. The power plant operated at a low ?T (0C) and discharge water temperatures did not exceed 350C (except September 1978). While zooplankton mortalities were significantly greater in discharge than intake waters, differences were small, averaging <3%. There was no evidence of additional delayed effects on zooplankton mortality following plant passage. There was no relationship between zooplankton mortalities and temperature (?T, discharge water temperature). Mechanical stresses appeared to be the major cause of zooplankton mortality. The authors hypothesize that fish predation, rather than power plant operation, probably was the major source of zooplankton mortality in inshore waters during much of the year. (author)

296

Decadal evolution of the Ligurian Sea zooplankton linked to environmental fluctuations. From imaging systems to size-based models.  

OpenAIRE

Imaging methods have recently emerged as tools to measure the zooplankton dynamics. These methods give both taxonomic and size structure information on the community. The two kinds of information are necessary to understand the zooplankton dynamics and its links to the environment. Yet, the present work will focalize more on the zooplankton size structuration information. The manuscript is organized in three chapters: methodology, ecological analysis and description of an eleven years time se...

Vandromme, Pieter

2010-01-01

297

Recovery of acid damaged zooplankton communities: measurement, extent, and limiting factors  

Energy Technology Data Exchange (ETDEWEB)

Acidification due to anthropogenic sulphur dioxide and nitrogen oxide emissions has affected biota in thousands of lakes in eastern North America and Europe. This paper addressed the current status of zooplankton communities severely affected by acidification. The purpose was to critically review the various methods available for assessing zooplankton community recovery; to summarize the evidence for zooplankton recovery in regions historically affected by acidification; and to review the current understanding of the factors that influence zooplankton community recovery. Most studies assessing zooplankton recovery consider species richness, indicator species, and relative species abundances. Many studies have used species richness as the sole indicator of recovery. However, the authors suggested that additional metrics should be considered in analyses to make conclusions more robust. Studies conducted in eastern North America and Europe have shown that given adequate time, zooplankton communities in all regions appear to be at least partially recovering in chemically recovered lakes with pH values above 6.0. However, the review of zooplankton recovery in acidified regions has shown that water quality has not yet reached this threshold and that recovery of affected communities is still not complete, even for lakes that have chemically recovered. Water quality conducive to the survival and reproduction of colonizing individuals is an important prerequisite for biological recovery. It was concluded that region- and lake-specific management approaches may be needed because factors limiting biological recovery, such as slow chemical recovery, dispersal limitation, and community resistance, vary in importance among and within regions. 140 refs., 3 tabs., 1 fig.

Gray, D.K.; Arnott, S.E. [Queen' s Univ., Kingston, ON (Canada). Dept. of Biology

2009-07-01

298

Zooplankton of an urban coastal lagoon: composition and association with environmental factors and summer fish kill  

Scientific Electronic Library Online (English)

Full Text Available SciELO Brazil | Language: English Abstract in english Zooplankton may be regarded as a sensitive tool for monitoring environmental variations in coastal lagoons due to their ability to immediately react to changes in the water column trophic features and salinity levels. As a coastal lagoon with a broad history of anthropic influence, Rodrigo de Freita [...] s Lagoon (Rio de Janeiro, Brazil) is widely used for water sports and artisanal fishing. The present study aimed to expand the knowledge base about zooplankton in the Rodrigo de Freitas Lagoon by assessing the composition and time-spatial distribution of the major zooplankton groups. Samples were collected fortnightly from at four distinct sampling points August 2001 to July 2002. At each point, salinity, temperature, dissolved oxygen and water transparency were measured. During the study period, the lagoon behaved as an spatially homogeneous environment in what regards the abiotic variables. However, all these variables showed significant differences along the time, mainly related to seasonality (air temperature and rainy and dry periods). The zooplankton community showed low taxonomic richness, with the predominance of species commonly found in coastal lagoons, especially with mesohaline conditions, as well as those found in estuaries. An interesting fact was the rise in zooplankton abundance at all sampling points right after a fish kill event. Such increase was caused mainly by the Brachionus plicatilis O.F. Müller 1786 species. Thus, the zooplankton community was affected by physical and chemical factors, mainly by the dissolved oxygen decline event and variations in the influx of seawater into the lagoon. In addition, phytoplankton availability and fish predation pressure were suggested as important regulating factors of the zooplankton community.

Leonardo C. e, Souza; Christina W. C., Branco; Patrícia, Domingos; Sérgio L. C., Bonecker.

2011-06-01

299

Zooplankton of an urban coastal lagoon: composition and association with environmental factors and summer fish kill  

Directory of Open Access Journals (Sweden)

Full Text Available Zooplankton may be regarded as a sensitive tool for monitoring environmental variations in coastal lagoons due to their ability to immediately react to changes in the water column trophic features and salinity levels. As a coastal lagoon with a broad history of anthropic influence, Rodrigo de Freitas Lagoon (Rio de Janeiro, Brazil is widely used for water sports and artisanal fishing. The present study aimed to expand the knowledge base about zooplankton in the Rodrigo de Freitas Lagoon by assessing the composition and time-spatial distribution of the major zooplankton groups. Samples were collected fortnightly from at four distinct sampling points August 2001 to July 2002. At each point, salinity, temperature, dissolved oxygen and water transparency were measured. During the study period, the lagoon behaved as an spatially homogeneous environment in what regards the abiotic variables. However, all these variables showed significant differences along the time, mainly related to seasonality (air temperature and rainy and dry periods. The zooplankton community showed low taxonomic richness, with the predominance of species commonly found in coastal lagoons, especially with mesohaline conditions, as well as those found in estuaries. An interesting fact was the rise in zooplankton abundance at all sampling points right after a fish kill event. Such increase was caused mainly by the Brachionus plicatilis O.F. Müller 1786 species. Thus, the zooplankton community was affected by physical and chemical factors, mainly by the dissolved oxygen decline event and variations in the influx of seawater into the lagoon. In addition, phytoplankton availability and fish predation pressure were suggested as important regulating factors of the zooplankton community.

Leonardo C. e Souza

2011-06-01

300

Eutrophication and warming effects on long-term variation of zooplankton in Lake Biwa  

Directory of Open Access Journals (Sweden)

Full Text Available We compiled and analyzed long-term (1961–2005 zooplankton community data in response to environmental variations in Lake Biwa. Environmental data indicate that Lake Biwa had experienced eutrophication (according to the total phosphorus concentration in the late 1960s and recovered to a normal trophic status around 1985, and then has exhibited warming since 1990. Total zooplankton abundance showed a significant correlation with total phytoplankton biomass. Following a classic pattern, the cladoceran/calanoid and cyclopoid/calanoid abundance ratio was related positively to eutrophication. The zooplankton community exhibited a significant response to the boom and bust of phytoplankton biomass as a consequence of eutrophication-reoligotriphication and warming. Moreover, our analyses suggest that the Lake Biwa ecosystem exhibited a hierarchical response across trophic levels; that is, higher trophic levels may show a more delayed response or no response to eutrophication than lower ones.

We tested the hypothesis that the phytoplankton community can better explain the variation of the zooplankton community than bulk environmental variables, considering that the phytoplankton community may directly affect the zooplankton succession through predator-prey interactions. Using a variance partition approach, however, we did not find strong evidence to support this hypothesis. We further aggregated zooplankton according to their feeding types (herbivorous, carnivorous, omnivorous, and parasitic and taxonomic groups, and analyzed the aggregated data. While the pattern remains similar, the results are less clear comparing the results based on finely resolved data. Our research suggests that zooplankton can be bio-indicators of environmental changes; however, the efficacy depends on data resolution.

C. H. Hsieh

2011-05-01

301

Zooplankton of Lake Orta after liming: an eleven years study  

Directory of Open Access Journals (Sweden)

Full Text Available Lake Orta (N. Italy was severely polluted from 1927 by an effluent from a rayon factory, which discharged great amounts of ammonium nitrogen and copper into the lake. In the mid nineteen fifties, some plating factories also started dumping chromium and aluminum. As a result of ammonium oxidation, the lake became very acid and the concentration of metals in the waters reached very high values. Phytoplankton, zooplankton and fish disappeared suddenly from the lake which was by 1930 classified as “sterile”. Later on, about the fifties, a small population of Cyclops abyssorum re-colonised the lake together with some rotifers, in particular Hexarthra fennica. In mid eighties following the introduction of anti-pollution legislation, ammonium loads were greatly reduced and Daphnia obtusa was recorded. The lake waters however were still very acid, prompting the proposal of the Istituto Italiano di Idrobiologia to lime the lake with calcium carbonate to neutralise the excess acidity and reconstruct the alkaline reserve. This was done successfully from May 1989 to June 1990. pH values began to rise and in the same time the metal concentrations decreased, so that at present the lake waters are almost “normal”. In the meantime, due to the increased pH values, D. obtusa was replaced by D. longispina and, as toxic metal concentrations became lower, Megacyclops viridis, Bosmina longirostris, Diaphanosoma brachyurum, Keratella quadrata, Asplanchna priodonta. and other Brachionidae species appeared. Diaptomidae are still absent, except for some specimens of Arctodiaptomus wierzejskii.

Andrea PASTERIS

2001-02-01

302

Fatty acid transformation in zooplankton: from seston to benthos  

DEFF Research Database (Denmark)

All organic matter, fatty acids (FA) in particular, is transformed in the pelagic plankton food web before reaching fishes or benthic organisms. Mesozooplankton (0.2 to 2 mm) is the main conduit for FA transfer, and FA profiles in sedimenting matter should therefore be significantly affected by its activity. To test this hypothesis, we sampled seston, zooplankton and sediment trap material for FA analysis during 5 campaigns spanning 4 seasons at a coastal site on the west coast of Sweden. Saturated (SAFAs) and monounsaturated (MUFAs) FAs dominated seston and trap material, while copepods contained 75 to 90% polyunsaturated FAs (PUFAs). Sedimentation of bulk particulate organic carbon did not vary significantly with season (coefficient of variation, CV = 33%), while pigment (CV = 49%) and in particular faecal pellet fluxes (CV = 100%) were highly variable as a result of copepod feeding activity. Copepod feeding, pellet production and egg production were all high after the spring bloom and in summer and autumn.Overall, 5 to 25% of the sedimenting FAs were affected by copepod feeding activities, and the supply of PUFAs to the benthos was significantly enhanced by copepod grazing activity. SAFAs and MUFAs were enriched by 5 to 10% in sediment traps, while the proportion of the most important PUFA, docosahexaenoic acid, was reduced by up to 15% in summer and autumn. In conclusion, the periods of significant input of PUFAs to the sediment coincide with the period of highest transformation by the mesozooplankton, which in the present study was summer and autumn.

Tiselius, Peter; Hansen, Benni Winding

2012-01-01

303

Parasitic Chytrids sustain zooplankton growth during inedible algal bloom  

Directory of Open Access Journals (Sweden)

Full Text Available This study assesses the quantitative impact of parasitic chytrids on the planktonic food web of two contrasting freshwater lakes during different algal bloom situations. Carbon-based food web models were used to investigate the effects of chytrids during the spring diatom bloom of Lake Pavin (oligo-mesotrophic and the autumn cyanobacteria bloom of Lake Aydat (eutrophic. Linear inverse modelling was employed to estimate undetermined flows in both lakes. The Monte Carlo Markov chain linear inverse modelling procedure provided estimates of the ranges of model-derived fluxes. Model results confirm recent theories on the probable impact of parasites on food web function as grazers and recyclers. During blooms of “inedible” algae (unexploited by planktonic herbivores, the epidemic growth of chytrids channelled 19-20% of the primary production in both lakes through the production of grazer-exploitable zoospores. The parasitic throughput represents 50 and 57% of the zooplankton diet respectively in the oligo-mesotrophic and in the eutrophic lakes. Parasites also affected ecological network properties as longer carbon path lengths and loop strength, and contributed to increase the stability of the aquatic food web, notably in the oligo-mesotrophic Lake Pavin.# The first two authors contributed equally to this work

SerenaRasconi

2014-05-01

304

Parasitic chytrids sustain zooplankton growth during inedible algal bloom.  

Science.gov (United States)

This study assesses the quantitative impact of parasitic chytrids on the planktonic food web of two contrasting freshwater lakes during different algal bloom situations. Carbon-based food web models were used to investigate the effects of chytrids during the spring diatom bloom in Lake Pavin (oligo-mesotrophic) and the autumn cyanobacteria bloom in Lake Aydat (eutrophic). Linear inverse modeling was employed to estimate undetermined flows in both lakes. The Monte Carlo Markov chain linear inverse modeling procedure provided estimates of the ranges of model-derived fluxes. Model results confirm recent theories on the impact of parasites on food web function through grazers and recyclers. During blooms of "inedible" algae (unexploited by planktonic herbivores), the epidemic growth of chytrids channeled 19-20% of the primary production in both lakes through the production of grazer exploitable zoospores. The parasitic throughput represented 50% and 57% of the zooplankton diet, respectively, in the oligo-mesotrophic and in the eutrophic lakes. Parasites also affected ecological network properties such as longer carbon path lengths and loop strength, and contributed to increase the stability of the aquatic food web, notably in the oligo-mesotrophic Lake Pavin. PMID:24904543

Rasconi, Serena; Grami, Boutheina; Niquil, Nathalie; Jobard, Marlène; Sime-Ngando, Télesphore

2014-01-01

305

Zooplankton diversity across three Red Sea reefs using pyrosequencing  

KAUST Repository

Coral reefs are considered among the most diverse ecosystems on Earth, yet little is known about the diversity of plankton in the surrounding water column. Moreover, few studies have utilized genomic methods to investigate zooplankton diversity in any habitat. This study investigated the diversity of taxa by sampling 45 stations around three reef systems in the central/southern Red Sea. The diversity of metazoan plankton was investigated by targeting the 18S rRNA gene and clustering OTUs at 97% sequence similarity. A total of 754 and 854 metazoan OTUs were observed in the data set for the 1380F and 1389F primer sets respectively. The phylum Arthropoda dominated both primer sets accounting for ~60% of reads followed by Cnidaria (~20%). Only about 20% of OTUs were shared between all three reef systems and the relation between geographic distance and Jaccard Similarity measures was not significant. Cluster analysis showed that there was no distinct split between reefs and stations from different reefs clustered together both for metazoans as a whole and for the phyla Arthropoda, Cnidaria and Chordata separately. This suggests that distance may not be a determining factor in the taxonomic composition of stations.

El-Sherbiny, Mohsen M.

2014-07-30

306

International Migration and Remittances  

OpenAIRE

Human migration is a physical movement by human beings from one geographical areato another geographical area. Migration is internal as well as external. At theinternational level, no universally accepted definition for “Migrant” exists. The UniteNations defines “migration as an individual who has resided in a foreign country formore than one year irrespective of the causes, voluntary or involuntary, and the means,regular or irregular, used migrate”. Key terms of migrations is documen...

Dattatray Sitaram Bagade

2012-01-01

307

Migration and trade  

OpenAIRE

Theoretical and empirical research in economics suggests that bilateral migration triggers bilateral trade through a number of channels. This paper assesses the functional form of the impact of migration on trade flows in a quasi-experimental setting. We provide evidence that the relationship is not log-linear. In particular, at small levels of migration (stocks) the elasticity of trade to migration is quite high, and it declines to zero at about 4,000 immigrants. If migration stocks exceed s...

Egger, Peter H.; Ehrlich, Maximilian Von; Nelson, Douglas R.

2011-01-01

308

Zooplankton characterisation of Pampean saline shallow lakes, habitat of the Andean flamingoes  

Directory of Open Access Journals (Sweden)

Full Text Available The lowland saline shallow lakes in the Pampa de las Lagunas (Argentina, constitute an important habitat for flamingoes Phoenicopterus chilensis Molina and Phoenicoparrus andinus (Philippii. Little is known about the zooplankton communities of these systems, and their relationships with the temporal and spatial distribution of flamingoes. Ten shallow lakes in the Pampean region were studied in 2009 and 2010 winters, and in 2010 summer in order to assess the abundance, size and biomass of zooplankton and the density of flamingoes populations. Zooplankton was represented by 28 species. Copepods and cladocerans were dominant when salinity was lower (winter and summer of 2010. Seasonal changes were recorded in composition and mean abundance of zooplankton. Significant differences were  observed in mean size of zooplankton showing a negative relationship with the abundance of P. chilensis, which can be interpreted as a consequence of the selective flamingoes zooplanktophagy feeding upon the largest members of this community. Other community parameters, such as abundance, biomass, diversity and composition, did not show an apparent direct relationship with the presence or abundance of flamingoes.

Susana B. José de Paggi

2013-10-01

309

Variability of zooplankton communities at Condor seamount and surrounding areas, Azores (NE Atlantic)  

Science.gov (United States)

Seamounts are common topographic features around the Azores archipelago (NE Atlantic). Recently there has been increasing research effort devoted to the ecology of these ecosystems. In the Azores, the mesozooplankon is poorly studied, particularly in relation to these seafloor elevations. In this study, zooplankton communities in the Condor seamount area (Azores) were investigated during March, July and September 2010. Samples were taken during both day and night with a Bongo net of 200 µm mesh that towed obliquely within the first 100 m of the water column. Total abundance, biomass and chlorophyll a concentrations did not vary with sampling site or within the diel cycle but significant seasonal variation was observed. Moreover, zooplankton community composition showed the same strong seasonal pattern regardless of spatial or daily variability. Despite seasonal differences, the zooplankton community structure remained similar for the duration of this study. Seasonal variability better explained our results than mesoscale spatial variability. Spatial homogeneity is probably related with island proximity and local dynamics over Condor seamount. Zooplankton literature for the region is sparse, therefore a short review of the most important zooplankton studies from the Azores is also presented.

Carmo, Vanda; Santos, Mariana; Menezes, Gui M.; Loureiro, Clara M.; Lambardi, Paolo; Martins, Ana

2013-12-01

310

The effect of zooplankton on the dynamics and molecular composition ofcarbohydrates during an experimental algal bloom  

DEFF Research Database (Denmark)

The accumulation and degradation of carbohydrates (aldoses) were investigated during diatom blooms in two mesocosms. The effects of macrozooplankton were explored by addition of zooplankton to one mesocosm (+Z). Aldoses accumulated at a steady rate of 4.9 µM C d-1 from day 9 in the mesocosm without zooplankton (-Z), while zooplankton induced an increased rate to 10.3 µM C d-1. The surplus of 14 µM dissolved combined carbohydrates (DCCHO) in the +Z mesocosm after 22 days was caused by higher concentrations of arabinose, galactose and rhamnose. The increase was 50, 25 and 25% respectively in the +Z mesocosm, compared with the -Z mesocosm. The introduction of zooplankton had a significant effect on the rate of biodegradation and the fraction of refractory aldoses. The accumulated aldoses became less labile and a larger fraction was refractory with the presence of zooplankton. During degradation the fraction of dissolved organic carbon (DOC) explained by aldoses decreased in the -Z mesocosm while it increased with the presence of grazers. In the +Z mesocosm, two new peaks appeared on the chromatograms and contributed about 4% to the total area of aldoses. It is hypothesised that these two peaks are an indicator of the presence of grazers.

Kragh, J. T.; SØndergaard, M.

2006-01-01

311

Combined effect of predatory zooplankton and allelopathic aquatic macrophytes on algal suppression.  

Science.gov (United States)

The present study evaluated the combined effects of four typical predatory zooplankton and allelopathic aquatic macrophytes on algal control in a microcosm system. It would determine the effects of diverse species and biological restoration on the growth of harmful water-bloom microalgae in great lakes polluted by excess nutrients. It was found that the mixtures of each zooplankton and the floating plant Nymphoides peltatum had stronger inhibitory effects on harmful water-bloom microalgae than the individual species in clean or eutrophic water bodies. In addition, a community of four zooplankton types had a synergistic effect on algal inhibition. Algal suppression by the zooplankton community was enhanced significantly when the macrophyte was co-cultured in the microcosm. Furthermore, Chlorella pyrenoidosa was more susceptible than Microcystis aeruginosa when exposed to grazing by zooplankton and the allelopathic potential of the macrophyte. Algal inhibition was also weaker in eutrophic conditions compared with the control. These findings indicate that diverse species may enhance algal inhibition. Therefore, it is necessary to restore biological diversity and rebuild an ecologically balanced food chain or web to facilitate the control of harmful algal blooms in eutrophic lakes. PMID:25409583

Zuo, Shengpeng; Wan, Kun; Ma, Sumin

2015-01-01

312

Mechanism for enhanced uptake of radionuclides by zooplankton in French Polynesian oligotrophic waters  

International Nuclear Information System (INIS)

Full text: A study of natural radionuclides in zooplankton collected during 1990-92 from the low productivity waters of French Polynesia has demonstrated the presence of enhanced Po-210 concentrations, although paradoxically the region is remote from continental sources of Po-210's progenitor, Rn-222. The study has also demonstrated an inverse and nonlinear relationship between zooplankton biomass and their Po-210 concentration. Po-210 in zooplankton increases exponentially to previously unreported levels up to 3200 Bq/kg dry weight, as their biomasses decline to levels as low as 0.14 mg dry weight/cubic metre. A validated mathematical model, incorporating the established role of zooplankton in the removal of Po-210 from the water column, captures the shape of this empirical relationship and also explains this biomass-related mechanism that increases Po-210 concentrations in zooplankton. Our results, analysis and further studies point to the enhanced vulnerability of such low productivity marine systems to contamination by particle-reactive radionuclides and stable elements like Po-210, relative to more productive systems

313

In different pressure an experimental study on migration of radon  

International Nuclear Information System (INIS)

The migration study of Radon in the air is the foundation theory problems of radon measurement and protection. Basing on experiment, this paper uses the method of active carbon accumulated measuring radon to study the migration regularity of radon gas in different gas pressure. Through series experiments, following conclusions can be obtained: the migration velocity of radon in the air is related with the air pressure, with greater air pressure, the conveyance speed is faster. Especially at low-pressure state the downward migration is more apparent. Through the comparison of measurement results of radon in vertical direction and a horizontal direction, the migration ability of radon in the vertical height is far larger than that in the horizontal direction whatever the pressure is. The average speed of radon in different pressures cases are estimated as follows: the upward migration average speed under atmospheric environment is 1.02 × 10-6 m/s, the downward migration average speed is 2.08 × 10-6 m/s; The upward migration average speed under -0.06 MPa vacuum environment is 0 91 × 10-6 m/s, the downward migration average speed is 2.77 × 10-6 m/s. As is consistent with the practical measurement result. (authors)

314

Global Vertical Reference Frame.  

Czech Academy of Sciences Publication Activity Database

Ro?. 33, - (2004), s. 404-407. ISSN 1436-3445 Institutional research plan: CEZ:AV0Z1003909 Keywords : geopotential WO * vertical systems * global vertical frame Subject RIV: BN - Astronomy, Celestial Mechanics, Astrophysics

Burša, Milan; Kenyon, S.; Kouba, J.; Šíma, Zdislav; Vatrt, V.; Vojtíšková, M.

2004-01-01

315

Capturing quantitative zooplankton information in the sea: Performance test of laser optical plankton counter and video plankton recorder in a Calanus finmarchicus dominated summer situation  

Science.gov (United States)

We compared two optical plankton counters, the Laser Optical Plankton Counter (LOPC) and the Video Plankton Recorder (VPR) for their abundance estimates of Calanus finmarchicus during an early summer situation (June 2008) in two North Norwegian fjords. The LOPC was mounted on the VPR frame in order to sample the same body of water. The combined system of LOPC and VPR was operated by vertical profiling from the surface to 100 m of depth in several locations of the fjords representing different blooming conditions and zooplankton community structures. Data from the two instruments, as well as from CTD-F, were logged concurrently and retrieved on deck after about 15 depth profiles. Primary data were analysed according to standard routines, and choices made during sampling and analyses (sampling volume, selection of size range, transparency of particles, statistics) are discussed. Data were averaged for every 5, 10 and 15 m depth bins. The vertical profiles of C. finmarchicus CIV-CVI abundance that were obtained by LOPC and VPR, respectively, showed a striking similarity. No significant differences between profiles sampled by these two instruments were observed when data were binned into 15 m bins. At low abundances (Calanus sp. L-1) profiles were significantly different when data were binned into 5- or 10-m bins. This is attributed to the small sampling volumes of the LOPC and the VPR, and to very patchy distributions of copepods, resulting in a high standard deviation between consecutive profiles. Based on the results we conclude that the time is mature for a more extensive use of optical instruments to estimate zooplankton abundances and distributions in the sea.

Basedow, Sünnje L.; Tande, Kurt S.; Norrbin, M. Fredrika; Kristiansen, Stian A.

2013-01-01

316

Metal and proton toxicity to lake zooplankton: A chemical speciation based modelling approach  

International Nuclear Information System (INIS)

The WHAM-FTOX model quantifies the combined toxic effects of protons and metal cations towards aquatic organisms through the toxicity function (FTOX), a linear combination of the products of organism-bound cation and a toxic potency coefficient for each cation. We describe the application of the model to predict an observable ecological field variable, species richness of pelagic lake crustacean zooplankton, studied with respect to either acidification or the impacts of metals from smelters. The fitted results give toxic potencies increasing in the order H+ TOX to relate combined toxic effects of protons and metal cations towards lake crustacean zooplankton. • The fitted results give toxic potencies increasing in the order H+ TOX model has been applied to field data for pelagic lake crustacean zooplankton. The fitted results give metal toxic potencies increasing in the order H+ < Al < Cu < Zn < Ni

317

Zooplankton composition in five oxbow lakes from the Upper Juruá River, Acre State, Brazil  

Directory of Open Access Journals (Sweden)

Full Text Available This work was conducted in five oxbow lakes located between Cruzeiro do Sul and Rodrigues Alves counties (Acre State, Brazil, to provide additional information about the composition of zooplankton assemblages in the Upper Juruá River. Samples were collected from May 2009 to May 2010, and fixed with 4% formalina. The numeric density (ind.m -3 was obtained from subsequent sub-samples (1 mL. The study recorded 19 zooplankton families. Rotifers showed higher species richness (81 species, followed by cladocerans (3 species and various forms of copepods and other organisms. Higher zooplankton means of numeric density was found in Novo Lake, with rotifers (1879 ind.m -3, cladocerans (207 ind.m -3, copepods (870 ind.m -3 . Diversity and numeric density were similar to other Neotropical aquatic ecosystems.

Maria José Alencar dos Santos

2013-12-01

318

In situ detrimental impacts of Prorocentrum donghaiense blooms on zooplankton in the East China Sea.  

Science.gov (United States)

Large-scale algal blooms of the dinoflagellate Prorocentrum donghaiense have occurred frequently in the East China Sea (ECS) in recent decades. However, its impacts on the zooplankton in situ are still under not well understood. During a spring P. donghaiense bloom (April-May 2013) along the northern coast of Fujian Province (120°-121°30?E, 26°30?-28°N), we found that the bloom decreased the abundance of copepods and had no significant effect on chaetognaths and small jellyfish. However, the abundance of small jellyfish increased over the course of the study. The zooplankton community changed from being copepod and small jellyfish- to small jellyfish-dominated during the bloom. In the bloom areas, the copepod Calanus sinicus showed higher mortality and lower egg production rates (EPR) than those in the non-bloom areas. The results suggested that P. donghaiense blooms had detrimental effects on the structure of zooplankton community and the recruitments of C. sinicus. PMID:25242234

Lin, Jia-Ning; Yan, Tian; Zhang, Qing-Chun; Wang, Yun-Feng; Liu, Qing; Zhou, Ming-Jiang

2014-11-15

319

Monitoring of genotoxicity in marine zooplankton induced by toxic metals in Ennore estuary, Southeast coast of India.  

Science.gov (United States)

The present study provides preliminary in-situ data on genetic integrity of marine zooplankton. Paracalanus parvus, Oithona rigida and Euterpina acutifrons were collected during four different seasons (summer, pre-monsoon, monsoon and post-monsoon) from 2011 to 2012 in Ennore and Kovalum estuaries. DNA damage levels in different zooplankton were analyzed by comet assay and were correlated with different environmental stressors. Spatial and temporal variations in DNA damage was observed in all the species. Zooplankton from Ennore estuary showed significantly lower genetic integrity. Particulate, sediment, and zooplankton fractions of Pb, Ni, Cu, Cr and Co were associated with high DNA damage during the period of lowest pH, salinity and dissolved oxygen. Zn and Cd showed lower genotoxic impact than the other metals. Feeding modes strongly influenced the genetic integrity in the zooplankton species studied. These results support the use of comet assay as a tool in effectively monitoring genotoxicity in marine plankton communities. PMID:25287225

Goswami, Prasun; Thirunavukkarasu, Subramani; Godhantaraman, Nallamuthu; Munuswamy, Natesan

2014-11-15

320

Zooplankton assemblages and biomass during a 4-period survey in a northern Mediterranean coastal lagoon.  

Science.gov (United States)

The authors proposed to examine zooplankton biomass at three stations inside (T and Z) and outside (M) a coastal lagoon of the north-western Mediterranean Sea. Station T represented the lagoon central area, and station Z was positioned in a shellfish farming sector, while the seaside station (M) served as a reference of marine environment. Analyses were designed to outline the net zooplankton assemblages (taxonomic structures and length distributions) in different environmental conditions, including the farming activity. A discriminant analysis of environmental variables determined that temperature, salinity and phytoplankton implied mainly in spatial pattern of the samples. An ordination of taxa biomasses showed two main factors which might contribute to the organisation of the zooplankton assemblages: the geographical position and the thermal period. The geographical position integrated the lagoon-sea water exchange under forcing parameters (habitat, tides and winds). The thermal period reflected both the populations development cycles and the environmental constraints (temperature, salinity, trophic resources). The resulting effects appeared in structured zooplankton assemblages in space and time. The number of 50 microns interval length classes and of taxa decreased from the seaside and the lagoon central area free of farming activity to the shallower farming zone. But the biomass-length distribution profiles did not closely follow such an expected opposition between opened and confined areas: more extended profiles were observed at station Z. Biomass dominant size classes concerned the range up to 300 microns. This size category appeared to collapse in terms of biomass from the seaside or central area of the lagoon towards the farming area, similarly to zooplankton global biomass fluctuations. Difference between biomass levels and between biomass structures suggested that net zooplankton partly acted as food competitors of macro-filtering organisms, and as preys for farming shellfish and associated epifauna. This impact mainly concerned microzooplankton populations. PMID:11257882

Lam-Hoai, T; Rougier, C

2001-01-01

321

Vertical axis wind turbines  

Science.gov (United States)

A vertical axis wind turbine is described. The wind turbine can include a top ring, a middle ring and a lower ring, wherein a plurality of vertical airfoils are disposed between the rings. For example, three vertical airfoils can be attached between the upper ring and the middle ring. In addition, three more vertical airfoils can be attached between the lower ring and the middle ring. When wind contacts the vertically arranged airfoils the rings begin to spin. By connecting the rings to a center pole which spins an alternator, electricity can be generated from wind.

Krivcov, Vladimir (Miass, RU); Krivospitski, Vladimir (Miass, RU); Maksimov, Vasili (Miass, RU); Halstead, Richard (Rohnert Park, CA); Grahov, Jurij (Miass, RU)

2011-03-08

322

Evaluation of sound extinction and echo interference in densely aggregated zooplankton  

Directory of Open Access Journals (Sweden)

Full Text Available The investigation of sound extinction and echo interference is important as regards the accurate assessment of the abundance of densely aggregated zooplankton. To study these effects,the analytical model describing sound backscattering by an aggregation of isotropic scatterers (Rytov et al. 1978, Sun & Gimenez 1992 has been extended to the case of densely aggregated elongated zooplankton. The evaluation of the effects in the case of a dense krill aggregation demonstrates that they can be significant and should be taken into account.

Natalia Gorska

2000-09-01

323

Current status of zooplankton in reservoir R-3 of the 'Mayak' production association  

International Nuclear Information System (INIS)

One of the commonly used objects for the study of human influence on aquatic ecosystems is zooplankton. Zooplankton community is a sensitive component of biota in reservoir which can change their functional parameters and species composition in response to exposure to different factors. The role of zooplankton in the transformation of energy and in the biotic cycling of the substance is very important. The study of the responses of this element in the water ecosystem with anthropogenic influences, including radioactive contamination, is an important task. The object of the study was the zooplankton in the reservoir R-3, Chelyabinsk region, Russia. R-3 is located in the buffer zone of the 'Mayak' PA and is the storage for low-level radioactive waste. In addition to the high content of radionuclides (the average specific activity of 90Sr in water was 2.8 kBq/l, 137Cs - 0.7 kBq/l), this reservoir is characterized by high values of dichromate oxidizability and phosphate contamination. Previously, the study of the zooplankton of this reservoir was conducted in 1952, regular observations were not organized. Assessment of the current status of the community, more than half a century residing in the conditions of radioactive and chemical contamination, seems highly interesting. Sampling was carried out in 2011-2012 at three stations: in the upper, middle, and near the dam of the reservoir by the method of weighted average of samples with bathometer. Analysis of samples showed that the zooplankton community consists of the following major groups: rotifers and cladocerans and copepods crustaceans. In total in R-3 27 species of zooplankton, including 19 species of rotifers, 3 species of copepod and 3 species of cladocerans, as well as two species of ciliates were discovered. Zooplankton abundance in 2011 was 9±9 million individuals/m3 (given the mean and standard deviation), in 2012 - 26.0±0.9 million individuals/m3. The main contribution was that of rotifers: 88.5 % of the total number of zooplankton organisms in 2011 and 97.5 % - in 2012. In general, the studied community is characterized by a high degree of heterogeneity of the structure without overwhelming dominance of one species. When compared with data obtained in 1952 by team headed by A.N. Marey, it could be said that the crustacean species has almost completely disappeared from zooplankton community along with the increase in the total abundance of planktonic animals which is two or three orders of magnitude higher due to the development of rotifers. These changes are characteristic of eutrophication processes that obviously play an important role in shaping the modern image of the zooplankton community in the reservoir R-3. Further investigation is required to determine the stability of the changes and clarify the role of radiation and chemical factors in these processes. Document available in abstract form only. (authors)

324

Reverse time migration in tilted transversely isotropic media  

Energy Technology Data Exchange (ETDEWEB)

This paper presents a reverse time migration (RTM) method for the migration of shot records in tilted transversely isotropic (TTI) media. It is based on the tilted TI acoustic wave equation that was derived from the dispersion relation. The RTM is a full depth migration allowing for velocity to vary laterally as well as vertically and has no dip limitations. The wave equation is solved by a tenth-order finite difference scheme. Using 2D numerical models, we demonstrate that ignoring the tilt angle will introduce both lateral and vertical shifts in imaging. The shifts can be larger than 0.5 wavelength in the vertical direction and 1.5 wavelength in the lateral direction.

Zhang, Linbing; Rector III, James W.; Hoversten, G. Michael

2004-07-01

325

Migration and Adult Education  

Science.gov (United States)

The objective of this paper is to highlight the role of adult education as a tool in addressing labour migration issues, specifically those concerning the protection of migrant workers' rights and the transformation of the impact of migration into positive holistic developmental gains. The view of labour migration as a means to forge the economic…

Gois, William

2007-01-01

326

On Marriage and Migration  

OpenAIRE

Marriage, migration and related phenomena such as marital stability, fertility and investment in human capital may be better explained by studying marriage and migration jointly. We thus proceed in this paper to explore the role of migration in obtaining joint labour-market and marriage-market equilibrium. This facilitates identification of several novel and testable hypotheses.

Stark, Oded

1988-01-01

327

Signatures of Currency Vertices  

Science.gov (United States)

Many real-world networks have broad degree distributions. For some systems, this means that the functional significance of the vertices is also broadly distributed, in other cases the vertices are equally significant, but in different ways. One example of the latter case is metabolic networks, where the high-degree vertices — the currency metabolites — supply the molecular groups to the low-degree metabolites, and the latter are responsible for the higher-order biological function, of vital importance to the organism. In this paper, we propose a generalization of currency metabolites to currency vertices. We investigate the network structural characteristics of such systems, both in model networks and in some empirical systems. In addition to metabolic networks, we find that a network of music collaborations and a network of e-mail exchange could be described by a division of the vertices into currency vertices and others.

Holme, Petter

2009-03-01

328

Signatures of currency vertices  

CERN Document Server

Many real-world networks have broad degree distributions. For some systems, this means that the functional significance of the vertices is also broadly distributed, in other cases the vertices are equally significant, but in different ways. One example of the latter case is metabolic networks, where the high-degree vertices -- the currency metabolites -- supply the molecular groups to the low-degree metabolites, and the latter are responsible for the higher-order biological function, of vital importance to the organism. In this paper, we propose a generalization of currency metabolites to currency vertices. We investigate the network structural characteristics of such systems, both in model networks and in some empirical systems. In addition to metabolic networks, we find that a network of music collaborations and a network of e-mail exchange could be described by a division of the vertices into currency vertices and others.

Holme, Petter

2008-01-01

329

Zooplankton community structure in relation to environmental factors and ecological assessment of water quality in the Harbin Section of the Songhua River  

Science.gov (United States)

To study the relationship between zooplankton community structure and environmental factors and water quality in the Harbin Section of the Songhua River, investigations were carried out in June, August, and October 2011. Canonical correspondence analysis (CCA) and saprobic indices were used to process and analyze the data. Seasonal variability was identified as a significant source of variation, which explains the fluctuation in zooplankton density. In autumn, the dry season, water residence time increased and zooplankton biomass and abundance accumulated in the slow flowing waters. Zooplankton abundance increased when food conditions improved. Therefore, the total zooplankton abundance in autumn is much higher than that in spring and summer. According to the saprobic indices, all the sample sites had mesosaprobic water and water quality was worse in autumn. CCA revealed that temperature accounted for most of the spatial variation in the zooplankton community. Moreover, pH, dissolved oxygen saturation, and turbidity were important factors affecting zooplankton community distribution.

Li, Xiaoyu; Yu, Hongxian; Ma, Chengxue

2014-11-01

330

Interactions between piscivores, zooplanktivores and zooplankton in submerged macrophytes : Preliminary observations from enclosure and pond experiments  

DEFF Research Database (Denmark)

The effects of piscivores upon zooplanktivore behaviour and distribution and the impact of zooplanktivores on the abundance and distribution of zooplankton are well documented. However, the potential indirect effect of piscivores reducing the predation pressure upon grazing zooplankton through behavioural changes of zooplanktivores has received little attention, even though this may be an important mechanism in enhancing the stability of submerged macrophytes in shallow lakes. Preliminary observations from an unreplicated large-scale field enclosure experiment and a replicated pond experiment suggest that this mechanism is plausible with the set of piscivores (pike Esox lucius and perch Perca fluviatilis) and the zooplanktivores (0+ roach Rutilus rutilus and perch) common in temperate Europe. The presence of piscivores typically changed the habitat use and the activity level of zooplanktivores and the presence of zooplanktivores typically changed the habitat selection of cladoceran zooplankton. In the case ofpiscivore/zooplanktivore interactions, the risk of predation was enough to generate clear responses even where the losses to predation were low. However, only in the enclosure experiment was an indirect impact of the presence of piscivores, enabling Daphnia spp. to utilise open water in the presence of a high density of zooplanktivorous fish observed. Whether the magnitude and direction of the effect of piscivores is sufficient to benefit zooplankton may depend on the functional group (capable of foraging within structured habitats) of the predator (both piscivore and zooplanktivore), absolute and relative densities of predator and prey and predator dietary choice.

Jacobsen, Lene; Perrow, M.R.

1997-01-01

331

Correlations between zooplankton assemblages and environmental factors in the downtown rivers of Shanghai, China  

Science.gov (United States)

Most urban rivers play an important role in urban flood control and drainage in China, but pollution is fast becoming an issue of greater importance in water management. In this study, 63 zooplankton species were recorded in four downtown rivers in Shanghai between November 2007 and October 2008. Of these, 44 species belonged to the Rotifera, 13 to Cladocera, and six to Copepoda. The three most frequently occurring zooplankton ( Brachionus calyciflorus, Microcyclops leuckarti, and Asplanchna priodonta) accounted for 80.00%, 76.84%, and 53.68%, respectively. Rotifera were found to be dominant, comprising 86.26% of total zooplankton, while cladoceran and copepod abundance amounted to 5.08% and 8.67%, respectively. Water temperature, salinity, electrical conductivity, and total nitrogen were of the greatest significance in the occurrence of zooplankton. Two species ( Schmackeria forbesi and Lepadella ovalis) were notably more sensitive to environmental factors such as salinity and electrical conductivity than other species. The population size and community were inversely correlated with the increasing nutrient levels of the four rivers, suggesting that the water quality of the four rivers had been gradually recovering from a severe eutrophic state and that water conditions of the rivers had been gradually improved.

Yu, Na; Li, Erchao; Feng, Dexiang; Xiao, Baicai; Wei, Chaoqun; Zhang, Meiling; Chen, Liqiao

2014-11-01

332

A review of zooplankton investigations of the Black Sea over the last decade  

Science.gov (United States)

Investigations performed in the last decade indicate that there have been important changes in the zooplankton composition and structure in the Black Sea. However, contrasting events taking place in different regions of the Black Sea indicate a non-uniform structure of its ecosystem. Several fodder zooplankton species have either disappeared from or substantially decreased in number at different sampling sites of the Black Sea over the last one or two decades. Some other species adapted to thrive in eutrophic conditions have either appeared or increased in quantity. Meanwhile the biomass of the fodder zooplankton has also fluctuated considerably through the years. However, there seems to be a reverse trend in the long-term variation of fodder zooplankton between the shallow western and deep eastern areas. Over the last few decades the abundance of fish larvae has decreased significantly when compared either to past records or with larval abundances of other seas. This was shown to be due mainly to malnutrition of larvae. One of the most striking changes in the ichthyoplankton has been the shift in the spawning areas of the main fish species, the anchovy Engraulis encrasicolus from the northwestern to the southeastern Black Sea. Even the invading ctenophore Mnemiopsis were found to be starving. The condition of other species ( Calanus euxinus and Pleurobrachia pileus) disclosed the fact that cyclonic regions where chlorophyll and nutrient concentrations are high, provide better nutrition than anticyclonic regions.

Kideys, Ahmet E.; Kovalev, Alexander V.; Shulman, Gregory; Gordina, Anna; Bingel, Ferit

2000-03-01

333

Relative abundance of resident versus oceanic zooplankton over an interisland reef  

International Nuclear Information System (INIS)

Zooplankton were collected from various substrate types. Densities were determined and results indicated that demersal plankton were abundant on the Japtan reef flat. Behavioral mechanisms were exhibited by many organisms including swimming near the substrate or in the lees of coral heads. Demersal plankton may provide an important food source for nocturnally foraging fishes

334

EFFECTS OF ZOOPLANKTON GRAZING ON PHYTOPLANKTON COMMUNITIES IN ESCAMBIA BAY, FL  

Science.gov (United States)

Studies of microheterotroph and meso-zooplankton grazing in nutrient enriched natural waters of Escambia Bay have been conducted for the past two years. These studies include experimental scale (1 l, 8 l, and 80 l) and lab/field comparisons. Sites for these studies include oligoh...

335

Field responses to zooplankton populations to temperature changes caused by reactor operations  

International Nuclear Information System (INIS)

Field determinations of thermal tolerance limits for zooplankton have helped in the definition of experiments needed to evaluate the effects of reactor operations upon these animals. Currently, the rates of births and deaths for populations of Cladocera are being quantified in hyperthermal and nonhyperthermal areas of the reactor cooling reservoir, Par Pond

336

EFFECTS OF COMPLEX EFFLUENTS FROM THE RIVER RAISIN ON ZOOPLANKTON GRAZING IN LAKE ERIE  

Science.gov (United States)

Functional ecosystem tests should reflect the hazards of toxic chemicals, as well as stimulation by nutrients, by measuring a single flux of phytoplankton to the dominant members of the community. he flux of phytoplankton and detritus to zooplankton is reflected by the filtering ...

337

EVALUATION OF ZOOPLANKTON SIZE-SPECTRUM AS AN INDICATOR FOR GREAT LAKES NEARSHORE WATERS  

Science.gov (United States)

Initial evaluation of a biological indicator for zooplankton communities in lakes has been encouraging. Tge method uses an optical counter which makes measurements in situ, towing behind a vessel allows rapid surveys over extensive areas in a relatively short time. Application th...

338

Zooplankton feeding ecology and the experimental acidification of Little Rock Lake  

International Nuclear Information System (INIS)

There is considerable variety in both the selective behavior of suspension feeders and the quality of food available to them. The author reviews this variability and incorporate it in a simple model of particle selection that quantifies the consequences of selective feeding under various feeding conditions. To evaluate the concept that selective feeding enhances fitness, the author tests the hypothesis than an herbivorous zooplankton selects food items that best support its reproduction. Investigations of zooplankton herbivory in experimentally acidified Little Rock Lake indicate that acidification from pH 6.2 to pH 5.2 has not directly impaired feeding rates, while effects on selective feeding behavior are evident. Assessment of the effects of lake acidification on large predatory zooplankton indicate that Chaoborus spp. and water mite populations remain as yet unaffected, while Epischura lacustris and Leptodora kindtii have both declined in the acidified basin. Methodological tests show that preservation of labelled zooplankton by rapid freezing on dry ice minimizes loss of 14C and 32P. 14C retention approximates 100%, while 32P retention is more variable

339

Phosphorus flux through a littoral ecosystem: The importance of cladoceran zooplankton and young fish  

International Nuclear Information System (INIS)

Foodchain relationships in water within a helophytic vegetation stand were experimentally investigated using 33P as tracer. The results proved the importance of cladoceran zooplankton (mainly Bosmina longispina Leydig) in the control of phytoplankton and the importance of young fish in the control of Bosmina abundance in the littoral water. (author)

340

ANALYSIS AND INTERPRETATION OF ZOOPLANKTON SAMPLES COLLECTED DURING PHASE II OF THE EASTERN LAKE SURVEY  

Science.gov (United States)

Samples from 146 lakes in the northeastern United States, collected during Phase II of the Eastern Lake Survey (ELS-II) were analyzed for abundance of each species and each size class of zooplankton. n estimate of sampling and counting error was provided by replication of lake sa...

341

First study on the zooplankton of the Kerid (Kerið Crater Lake, Iceland  

Directory of Open Access Journals (Sweden)

Full Text Available We studied the qualitative composition of zooplankton of the Kerid Crater Lake. We found 10 taxa from which five rotifers and two lower crustaceans. Three of the recorded species are new to the freshwater fauna of Iceland: the rotifer species Keratella cf. americana Carlin, 1943 and Colurella sulcata (Stenroos, 1898, and the crustacean harpacticoid Bryocamptus (Bryocamptus minutus (Claus, 1863.

Vesela Evtimova

2014-04-01

342

Potential drivers of sinking particle's size spectra and vertical flux of particulate organic carbon (POC): Turbulence, phytoplankton, and zooplankton  

Science.gov (United States)

Phytoplankton spring blooms in temperate and high-latitude shelf seas are commonly associated with an enhanced particulate organic carbon (POC) export of aggregates from the euphotic zone. In contrast, a postbloom situation is usually linked to a predominant POC retention, where small cells (upper 100 m. We deployed sediment traps, partly modified with gel jars, at four depths along a stratification and phytoplankton bloom gradient in the Barents Sea, an Arctic shelf sea. The highest POC export (60 m: 923 mg C m-2 d-1) was found in deep-mixed, postbloom Atlantic influenced waters, despite the high grazer abundance (12,000 individuals m-3). Particle size spectra indicated that this flux was dominated by particles of 0.05-1.00 mm equivalent spherical diameter (ESDimage) with a POC:volume ratio matching copepod fecal pellets. Large particles (0.5-2.8 mm ESDimage) dominated the flux at a stratified, late peak bloom station in Arctic Waters and a stratified, late bloom situation at the Polar Front, but with lower POC:volume ratio and POC flux (60 m: <823 mg C m-2 d-1). Accordingly, a high POC flux at the base of the euphotic zone is not necessarily driven by large phytoplankton aggregates, but can also occur during a postbloom situation in form of small fecal pellet fragments with high POC content.

Wiedmann, Ingrid; Reigstad, Marit; Sundfjord, Arild; Basedow, Sünnje

2014-10-01

343

Ecological investigation of zooplankton abundance in the river Haraz, northeast Iran: Impact of environmental variables  

Directory of Open Access Journals (Sweden)

Full Text Available The influence of physicochemical properties of Haraz river on its zooplankton composition and abundance were investigated at three sites for one year between August 2009 and July 2010. The present study records for the first time the aspects of zooplankton diversity and composition in relation to the physicochemical environment of the Haraz river. Only three groups of zooplankton were found: Rotifera with eighteen genera; Cladocera with nine and Copepoda with six genera. Rotifera was the predominant group (64.89%, followed by Cladocera (19.62% and Copepoda (15.32%. Upstream, the abundance was 805 individuals/m3, while it varied from 922 to 1126 ind/m3 downstream. Alkaline pH and nutrients were the main environmental factors which affected zooplankton abundance in the river. Site variation in dominance, diversity, evenness and richness were calculated. The study revealed that the presence of certain species, such as Lepadella sp., Mesocyclops sp., Polyarthra sp. and Brachionus sp. is considered to be a biological indicator for eutrophication. The calculated Jack1 values of sites 1 to 3 were 7.624, 16.426 and 19.221, respectively. The Shannon-Wiever species diversity index (H’ values were also different for all the three sites viz., site 1 (1.992, site 2 (1.21 and site 3 (2.48. Simpson’s dominance index (H value was highest at site 1 (0.692, indicating maximum dominance, whereas at site 3 dominance was the lowest (0.227 and diversity was the highest. Overall, our results showed that changes in the water quality of the river Haraz have considerable effects on the composition of zooplankton assemblages that can potentially affect the functioning of these ecosystems.

Jafari Naser

2011-01-01

344

Spatial and temporal variability of water quality and zooplankton in an artisanal salina  

Science.gov (United States)

Conditions in artisanal salterns, or salinas, vary depending on their physical structure, seasonal effects, and the two periods of the salt production cycle. They therefore constitute unique wetland habitats, with particular communities that are still poorly studied. Water quality and zooplankton of a working artisanal salina were studied to evaluate spatial variability between sections and temporal variability between the salt production and flooded periods and between seasons. Zooplankton communities were related to environmental conditions. Sampling took place every second week, during almost two years, at six sites of the Tanoerias salina in Aveiro, Portugal: at the beginning and centre of the salina inlet channel, in a supply pond, in two evaporator and one crystalliser ponds. Since salt production occurs in the warm season only, seasonal effects concur with those caused by the salt production cycle. Results showed significant differences in temperature, dissolved oxygen (DO) and biochemical oxygen demand (BOD 5) between salt production and flooded periods, i.e. summer and spring/winter seasons. Salinity and alkalinity were linked to salt production with extreme values in the salt-producing crystalliser pond. Zooplankton communities varied between seasons, but also with the salina section and the salt production cycle. Zooplankton densities and diversity tended to be lower during salt production, particularly under the extreme living conditions in the salina crystalliser pond. Variation in zooplankton communities between samples was mainly influenced by temperature, i.e. season, at the salina inlet, by BOD 5 or DO, also related to temperature and season, in the first ponds and by nutrients throughout the system.

Vieira, Natividade; Bio, Ana

2011-02-01

345

Bridging the gap between marine biogeochemical and fisheries sciences; configuring the zooplankton link  

Science.gov (United States)

Exploring climate and anthropogenic impacts on marine ecosystems requires an understanding of how trophic components interact. However, integrative end-to-end ecosystem studies (experimental and/or modelling) are rare. Experimental investigations often concentrate on a particular group or individual species within a trophic level, while tropho-dynamic field studies typically employ either a bottom-up approach concentrating on the phytoplankton community or a top-down approach concentrating on the fish community. Likewise the emphasis within modelling studies is usually placed upon phytoplankton-dominated biogeochemistry or on aspects of fisheries regulation. In consequence the roles of zooplankton communities (protists and metazoans) linking phytoplankton and fish communities are typically under-represented if not (especially in fisheries models) ignored. Where represented in ecosystem models, zooplankton are usually incorporated in an extremely simplistic fashion, using empirical descriptions merging various interacting physiological functions governing zooplankton growth and development, and thence ignoring physiological feedback mechanisms. Here we demonstrate, within a modelled plankton food-web system, how trophic dynamics are sensitive to small changes in parameter values describing zooplankton vital rates and thus the importance of using appropriate zooplankton descriptors. Through a comprehensive review, we reveal the mismatch between empirical understanding and modelling activities identifying important issues that warrant further experimental and modelling investigation. These include: food selectivity, kinetics of prey consumption and interactions with assimilation and growth, form of voided material, mortality rates at different age-stages relative to prior nutrient history. In particular there is a need for dynamic data series in which predator and prey of known nutrient history are studied interacting under varied pH and temperature regimes.

Mitra, Aditee; Castellani, Claudia; Gentleman, Wendy C.; Jónasdóttir, Sigrún H.; Flynn, Kevin J.; Bode, Antonio; Halsband, Claudia; Kuhn, Penelope; Licandro, Priscilla; Agersted, Mette D.; Calbet, Albert; Lindeque, Penelope K.; Koppelmann, Rolf; Møller, Eva F.; Gislason, Astthor; Nielsen, Torkel Gissel; St. John, Michael

2014-12-01

346

The influence of advection on zooplankton community composition in an Arctic fjord (Kongsfjorden, Svalbard)  

Science.gov (United States)

A continuous, high-resolution time series of zooplankton and hydrographic data were collected from Kongsfjorden between April and September 2002 using a sediment trap and instrumentation deployed on a mooring. The time series has, for the first time, demonstrated the close relationship between water mass advection and changes in zooplankton community structure in Kongsfjorden. Zooplankton identified in the trap samples included 31 species/genera and seven higher taxa representing ubiquitous, boreal and Arctic biogeographic origins. Correspondence Analysis (CA) identified three phases of zooplankton community composition in 2002. Phase I, from 18 April to 29 May, consisted primarily of resident Calanus finmarchicus and Calanus glacialis stage CVI females. Phase II, from 30 May to 23 June, was dominated by meroplankton, Oikopleura cf. vanhoeffeni, C. finmarchicus early life stages (CI to CIII), Calanus hyperboreus and Themisto abyssorum. Phase III, from 4 July to 8 September, comprised C. finmarchicus (predominantly CV), C. glacialis CV, C. hyperboreus CIV and a greater diversity of other copepod species, in particular, increasing numbers of Oithona similis. Transition between the zooplankton community phases was abrupt and clearly associated with the advection of water masses into the fjord from the adjacent shelf. Peaks of the Arctic species C. glacialis, C. hyperboreus and T. abyssorum in late May were associated with a change in the dominant fjordic water mass from local Winter Cooled Water (WCW) to an influx of Arctic Water (ArW) from the coastal current. A temperature increase of 2.75 °C in the upper water column signified the transition from Phase II to Phase III with the dominant water mass changing from ArW to Atlantic Water (AW) from the West Spitsbergen Current.

Willis, Kate; Cottier, Finlo; Kwasniewski, Slawek; Wold, Anette; Falk-Petersen, Stig

2006-06-01

347

Spatio-temporal variability of the North Sea cod recruitment in relation to temperature and zooplankton.  

Science.gov (United States)

The North Sea cod (Gadus morhua, L.) stock has continuously declined over the past four decades linked with overfishing and climate change. Changes in stock structure due to overfishing have made the stock largely dependent on its recruitment success, which greatly relies on environmental conditions. Here we focus on the spatio-temporal variability of cod recruitment in an effort to detect changes during the critical early life stages. Using International Bottom Trawl Survey (IBTS) data from 1974 to 2011, a major spatio-temporal change in the distribution of cod recruits was identified in the late 1990s, characterized by a pronounced decrease in the central and southeastern North Sea stock. Other minor spatial changes were also recorded in the mid-1980s and early 1990s. We tested whether the observed changes in recruits distribution could be related with direct (i.e. temperature) and/or indirect (i.e. changes in the quantity and quality of zooplankton prey) effects of climate variability. The analyses were based on spatially-resolved time series, i.e. sea surface temperature (SST) from the Hadley Center and zooplankton records from the Continuous Plankton Recorder Survey. We showed that spring SST increase was the main driver for the most recent decrease in cod recruitment. The late 1990s were also characterized by relatively low total zooplankton biomass, particularly of energy-rich zooplankton such as the copepod Calanus finmarchicus, which have further contributed to the decline of North Sea cod recruitment. Long-term spatially-resolved observations were used to produce regional distribution models that could further be used to predict the abundance of North Sea cod recruits based on temperature and zooplankton food availability. PMID:24551103

Nicolas, Delphine; Rochette, Sébastien; Llope, Marcos; Licandro, Priscilla

2014-01-01

348

Bridging the gap between marine biogeochemical and fisheries sciences; configuring the zooplankton link  

DEFF Research Database (Denmark)

Exploring climate and anthropogenic impacts on marine ecosystems requires an understanding of how trophic components interact. However, integrative end-to-end ecosystem studies (experimental and/or modelling) are rare. Experimental investigations often concentrate on a particular group or individual species within a trophic level, while tropho-dynamic field studies typically employ either a bottom-up approach concentrating on the phytoplankton community or a top-down approach concentrating on the fish community. Likewise the emphasis within modelling studies is usually placed upon phytoplankton- dominated biogeochemistry or on aspects of fisheries regulation. In consequence the roles of zooplankton communities (protists and metazoans) linking phytoplankton and fish communities are typically under-represented if not (especially in fisheries models) ignored. Where represented in ecosystem models, zooplankton are usually incorporated in an extremely simplistic fashion, using empirical descriptions merging various interacting physiological functions governing zooplankton growth and development, and thence ignoring physiological feedback mechanisms. Here we demonstrate, within a modelled plankton food-web system, how trophic dynamics are sensitive to small changes in parameter values describing zooplankton vital rates and thus the importance of using appropriate zooplankton descriptors. Through a comprehensive review, we reveal the mismatch between empirical understanding and modelling activities identifying important issues that warrant further experimental and modelling investigation. These include: food selectivity, kinetics of prey consumption and interactions with assimilation and growth, form of voided material, mortality rates at different age-stages relative to prior nutrient history. In particular there is a need for dynamic data series in which predator and prey of known nutrient history are studied interacting under varied pH and temperature regimes

Mitra, Aditee; Castellani, Claudia

2014-01-01

349

A model to resolve organochlorine pharmacokinetics in migrating humpback whales.  

Science.gov (United States)

Humpback whales are iconic mammals at the top of the Antarctic food chain. Their large reserves of lipid-rich tissues such as blubber predispose them to accumulation of lipophilic contaminants throughout their lifetime. Changes in the volume and distribution of lipids in humpback whales, particularly during migration, could play an important role in the pharmacokinetics of lipophilic contaminants such as the organochlorine pesticide hexachlorobenzene (HCB). Previous models have examined constant feeding and nonmigratory scenarios. In the present study, the authors develop a novel heuristic model to investigate HCB dynamics in a humpback whale and its environment by coupling an ecosystem nutrient-phytoplankton-zooplankton-detritus (NPZD) model, a dynamic energy budget (DEB) model, and a physiologically based pharmacokinetic (PBPK) model. The model takes into account the seasonal feeding pattern of whales, their energy requirements, and fluctuating contaminant burdens in the supporting plankton food chain. It is applied to a male whale from weaning to maturity, spanning 20 migration and feeding cycles. The model is initialized with environmental HCB burdens similar to those measured in the Southern Ocean and predicts blubber HCB concentrations consistent with empirical concentrations observed in a southern hemisphere population of male, migrating humpback whales. Results show for the first time some important details of the relationship between energy budgets and organochlorine pharmacokinetics. PMID:24733631

Cropp, Roger; Nash, Susan Bengtson; Hawker, Darryl

2014-07-01

350

Prestack migration error in transversely isotropic media  

Energy Technology Data Exchange (ETDEWEB)

Previous studies have shown the dependence of migration error on reflector dip when poststack migration is done with an algorithm that ignores the presence of anisotropy. Here we do a numerical study of the offset dependence of migration error that can be expected when common-offset data from factorized transversely isotropic media are imaged by an isotropic prestack migration algorithm. Anisotropic ray tracing, velocity analysis and prestack migration in the common-offset domain are the basic tools for this analysis, which we apply to models with constant vertical gradient in velocity that are characterized by a particular combination of Thomsen`s anisotropy parameters: {eta} {triple_bond} ({epsilon} - {delta})/(1+2{delta}). The results show show that the offset dependence of error in imaged position, and therefore the quality of stacked, imaged data, depends largely, but not completely, on the anisotropy parameter {eta}. Generally, the larger the value of {eta}, the larger the problem of mis-stacking. Over a wide range of reflector dip, time-misalignment of imaged features on common-reflection-point gathers is considerably less than the error in imaged position on the zero-offset data. For all the model parameters studied, we expect stacking quality to be worst for reflector dip around 50 degrees. Reflections from horizontal reflectors and those with dip close to 90 degrees should stack well in all cases, and mis-stacking is not severe for overturned reflectors.

Jaramillo, H.; Larner, K. [Colorado School of Mines, Golden, CO (United States)

1995-12-31

351

Prestack migration error in transversely isotropic media  

Energy Technology Data Exchange (ETDEWEB)

Previous studies have shown the dependence of migration error on reflector dip when poststack migration is done with an algorithm that ignores the presence of anisotropy. Here we do a numerical study of the offset dependence of migration error that can be expected when common-offset data from factorized transversely isotropic media are imaged by an isotropic prestack migration algorithm. Anisotropic ray tracing, velocity analysis and prestack migration on the common-offset domain are the basic tools for this analysis, which we apply to models with constant vertical gradient in velocity that are characterized by a particular combination of Thomsen`s anisotropy parameters: {eta} {identical_to} ({epsilon} - {delta})/(1 + 2{delta}). The results show that the offset dependence of error in imaging position, and therefore the quality of stacked, imaged data, depends largely, but not completely, on the anisotropy parameter {eta}. Generally, the larger the value of {eta}, the larger the problem of mis-stacking. Over a wide range of reflector dip, time-misalignment of of imaged features on common-reflection-point gathers is considerably less than the error in imaged position of the zero-offset data. For all the model parameters studied, we expected stacking quality to be worst for reflector dip around 50 degrees. Reflections from horizontal reflectors and those with dip close to 90 degrees should stack well in all cases, and mis-stacking is not severe for overturned reflectors. (author). 9 refs., 4 figs

Jaramillo, Herman; Larner, Ken [Colorado School of Mines, Golden, CO (United States). Center for Wave Phenomena

1995-12-31

352

[Competition and adaptation in community of migrating fish populations].  

Science.gov (United States)

Within a discrete scheme the process of population migration is set by some non-negative Markov matrix. When studying an appropriate class of competition models, nonlinear methods of the convex analysis (the theory of monotonous operators) proved to be highly effective. For special matrixes (cyclic and perron ones) conditions of steady coexistence and competitor replacement in community have been found. Modeling mechanisms of adaptation of a route of migration for separate population and also for the family of populations from one vertical trophic chain have been provided. The major characteristic of a route of migration turned out to be the relative time of population dwelling in one or another area. Specific (perron) vectors of migration matrixes correspond to these populations. It is revealed that in the course of coadaptation perron vectors of predator and victim migration matrixes practically coincide. PMID:22594295

Il'ichev, V G

2012-01-01

353

Twenty-year follow-up study of radiocesium migration in soil  

International Nuclear Information System (INIS)

The profile of 137Cs present in undisturbed soil due to the Chernobyl accident was measured repeatedly for ?20 y. The vertical migration of 137Cs in soil is a very slow process. The mean vertical migration velocity is estimated at ?0.1-0.2 cm y-1. A method based on in situ gamma spectrometry measurements and Monte Carlo computations, aimed at estimating the profile of 137Cs without performing any soil sampling, is investigated. (authors)

354

Migration Policy Institute  

Science.gov (United States)

Founded in 2001, the Migration Policy Institute (MPI) evolved from a program at the Carnegie Foundation for International Peace. Since its inception, the MPI has been dedicated to examining the trends and processes associated with the movement of various people worldwide. The homepage offers a wide array of resources for the general public, journalists, and academicians. Looking at the â??In Focusâ? area on the homepage, visitors can download new working papers and reports with titles such as â??The New â??Boatâ?? Peopleâ? and â??Immigration Enforcement at the Worksite, Making it Workâ?. From the homepage, users can also make their way to the Migration Information Source website which contains global migration data, country migration profiles, and a glossary of migration terms. Visitors with specific questions can also view a list of experts in a variety of topics related to migration and email them directly.

355

Radial Migration Does Little for Galactic Disc Thickening  

CERN Document Server

Non-axisymmetric components, such as spirals and central bars, play a major role in shaping galactic discs. An important aspect of the disc secular evolution driven by these perturbers is the radial migration of stars. It has been suggested recently that migration can populate a thick-disc component from inner-disc stars with high vertical energies. Since this has never been demonstrated in simulations, we study in detail the effect of radial migration on the disc velocity dispersion and disc thickness, by separating simulated stars into migrators and non-migrators. We apply this method to three isolated barred Tree-SPH N-body galaxies with strong radial migration. Contrary to expectations, we find that as stellar samples migrate, on the average, their velocity dispersion change (by as much as 50%) in such a way as to approximately match the non-migrating population at the radius at which they arrive. We show that, in fact, migrators suppress heating in parts of the disc. To confirm the validity of our findin...

Minchev, I; Quillen, A C; Dehnen, W; Martig, M; Siebert, A

2012-01-01

356

Vertical distributions of autumn spawned larval herring ( Clupea harengus L.) in the North Sea  

Science.gov (United States)

Vertical distributions of autumn spawned herring larvae were sampled at 10 sites in the North Sea between October 1987 and March 1988 during the Autumn Circulation Experiment (ACE). Several different patterns of vertical migrations occurred. Diel variations in the vertical distributions were found in all stages of development, from yolk-sac to pre-metamorphosis (35 mm). During diel migrations larvae were closer to the surface during daylight than at night. The amplitude of diel vertical migrations increased with the length of the larvae. Semi-diel cycles in the vertical distributions were rare, and appeared to be related to the tidal cycle rather than crepuscular periods. Diel cycles in vertical distribution could not be detected at sites in the southeastern North Sea, characterized by water depths less than 45 m, high vertical shear and high light attenuation coefficients. It is suggested that strong turbulence inhibits diel vertical migrations by herring larvae. This feature has important consequences for the advection of larvae in the North Sea.

Heath, M.; Brander, K.; Munk, P.; Rankine, P.

1991-12-01

357

Migration and Environmental Hazards  

OpenAIRE

Losses due to natural hazards (e.g., earthquakes, hurricanes) and technological hazards (e.g., nuclear waste facilities, chemical spills) are both on the rise. One response to hazard-related losses is migration, with this paper offering a review of research examining the association between migration and environmental hazards. Using examples from both developed and developing regional contexts, the overview demonstrates that the association between migration and environmental hazards varies b...

Hunter, Lori M.

2005-01-01

358

Migration in Burkina Faso  

OpenAIRE

Migration plays an important role in development and as a strategy for poverty reduction. A recent World Bank investigation finds a significant positive relationship between international migration and poverty reduction at the country level (Adams and Page 2003). Burkina Faso, whose conditions for agriculture are far from favorable, has a long history of migratory movement, and migration within West Africa has long taken place in response to drought and low agricultural productivity. In recen...

Wouterse, F. S.

2007-01-01

359

Regime shifts in shallow lakes: the importance of seasonal fish migration  

DEFF Research Database (Denmark)

Shallow eutrophic lakes commonly exist in two alternative stable states: a clear-water state and a turbid water state. A number of mechanisms, including both abiotic and biotic processes, buffer the respective states against changes, whereas other mechanisms likely drive transitions between states. Our earlier research shows that a large proportion of zooplanktivorous fish populations in shallow lakes undertake seasonal migrations where they leave the lake during winter and migrate back to the lake in spring. Based on our past research, we propose a number of scenarios of how feedback processes between the individual and ecosystem levels may affect stability of alternative stable states in shallow lakes when mediated by fish migration. Migration effects on shallow lakes result from processes at different scales, from the individual to the ecosystem. Our earlier research has shown that ecosystem properties, including piscivore abundance and zooplankton productivity, affect the individual state of zooplanktivorous fish, such as growth rate or condition. Individual state, in turn, affects the relative proportion and timing of migrating zooplanktivorous fish. This change, in turn, may stabilize states or cause runaway processes that eventually lead to state shifts. Consequently, such knowledge of processes coupled to seasonal migration of planktivorous fish should increase our understanding of shallow lake dynamics.

Brönmark, Christer; Brodersen, Jakob

2010-01-01

360

Subsurface migration of petroleum hydrocarbons: A case study of immiscible migration and chromatographic separation  

International Nuclear Information System (INIS)

The subsurface distribution of a leaked crude oil illustrates the combined influence of both the chemical and physical properties of soil and free product on the migration of petroleum hydrocarbons. Immiscible phase behavior was observed, as well as chromatographic-like separation of the lighter constituents of the crude oil from the heavier constituents. After downward migration through approximately 50 ft of unsaturated, heterogeneous alluvial sediments, the crude oil formed a horizontal plume on top of a perched, saturated zone. Immiscible phase trapping is evident from the occurrence of very high concentration of hydrocarbons in both the vertical and horizontal plumes. Samples taken from the vertical zone of contamination indicate a transition from heavier hydrocarbons near the surface to lighter hydrocarbons at depth. This phenomenon is attributed to chromatographic-like separation of the heavier hydrocarbons by the soil, possibly due to preferential solubility of the lighter hydrocarbons in percolating ran water

361

Seasonal dynamics and Trophic interactions of phytoplankton and zooplankton in the Vistula Lagoon of the Baltic Sea  

Science.gov (United States)

The trophic relationships of the phytoplankton and zooplankton in the Vistula Lagoon in 2008-2010 were investigated. In the current period, the lagoon is an eutrophic water body with summer blooms of blue-green algae. The trophic level of the Vistula Lagoon influences both the composition and quantitative characteristics of the communities of phytoplankton and zooplankton and the trophic relationships between them. In the analyzed period, the consumption of phytoplankton by the zooplankton on the average in the growing season was 28%, which is 1.5 times higher than in the late 1970s. The high grazing pressure of the zooplankton on the phytoplankton reduces its biomass, production, and the intensity of the blooming by the blue-green algae in the Vistula Lagoon.

Dmitrieva, O. A.; Semenova, A. S.

2012-11-01

362

MARYLAND/VIRGINIA CHESAPEAKE BAY AND TRIBUTARIES ZOOPLANKTON COUNT, BIOMASS AND BIOVOLUME FILES (AND RELATED EVENT FILES)  

Science.gov (United States)

As part of the Chesapeke Bay Program zooplankton counts, biomass, and biovolume data have been collected by the Maryland Department of the Environment /Maryland Department of Natural Resources and the Virginia Department of Environmental Quality. Available data sets include: 1)...

363

Small-scale zooplankton community variability in a northern British Columbia fjord system  

Science.gov (United States)

We have used multivariate classification, ordination, and discriminant function analyses to describe the small-scale spatial pattern of zooplankton community composition in a northern British Columbia fjord system. Finely ground tailings from a molybdenum mine were discharged into one branch of the fjord (Alice Arm) during a 17-month span which included our two sampling periods (August 1981 and June 1982). Our study had two major objectives. The first was to learn whether or not the zooplankton community was strongly altered in the vicinity of the tailings discharge, and the second was to characterize the intensity and dominant spatial grain scale of 'normal' community variability in the remainder of the deep inlet system. Zooplankton were collected by water column integrating oblique net hauls. The statistical analyses examined relative and absolute changes in the contribution of individual species to the local zooplankton community. Within each time period, the range of spatial variability was small in comparison both to the between-time period (probably seasonal) differences within the inlet, and to the range of spatial variability observed by identical analysis methods in open continental shelf waters to the south. However, despite this small overall community variance, we found a reasonably consistent regional partitioning of the inlet; the samples most similar in composition tended to be those from the same or adjoining locations. Sites near the turbid heads of the branching inlet (including those near the tailings discharge) had higher concentrations of Euphausia pacifica and other large non-copepod zooplankton, and relatively low concentrations of the copepod Neocalanus plumchrus. The magnitude of the between region-differences was small and did not appear to be increasing with time; we therefore conclude that the impact of tailings discharge on zooplankton community structure was relatively minor. The distance over which neighbouring samples show significant compositional correlation is smaller in the inlet than in open coastal waters previously studied; we interpret this as due largely to the absence of meso-scale horizontal turbulent eddies within the inlet.

Mackas, David L.; Anderson, Edward P.

1986-01-01

364

Zooplankton structure and potential food web interactions in the plankton of a subtropical chain-of-lakes.  

Science.gov (United States)

This study evaluates the taxonomic and size structure of macro-zooplankton and its potential role in controlling phytoplankton in the Kissimmee Chain-of-Lakes, six shallow interconnected lakes in Florida, U.S. Macro-zooplankton species biomass and standard limnological attributes (temperature, pH, total phosphorus [TP], chlorophyll a [Chl a], and Secchi transparency) were quantified on a bimonthly basis from April 1997 to February 1999. Concentrations of TP ranged from below 50 to over 150 microg l(-1). Peak concentrations of particulate P coincided with maximal Chl a, and in one instance a high concentration of soluble reactive P followed. The cladoceran zooplankton was dominated by small species, including Eubosmina tubicen, Ceriodaphnia rigaudi, and Daphnia ambigua. The exotic daphnid, D. lumholtzii, periodically was abundant. The copepods were strongly dominated by Diaptomus dorsalis, a species previously shown to be highly resistant to fish predation. These results, and findings of controlled experiments on a nearby lake with a nearly identical zooplankton species complement, suggest that fish predation may be a major factor structuring the macro-zooplankton assemblage. Zooplankton biomass, on the other hand, may be affected by resource availability. There was a significant positive relationship between average biomass of macro-zooplankton and the average concentration of TP among the six lakes. No such relationship existed between zooplankton biomass and Chl a, suggesting that the predominant food web in these systems may be based on bacteria-plankton, as has been documented in nearby Lake Okeechobee. All of the zooplankton taxa encountered in the Kissimmee Chain-of-Lakes (except Mesocyclops edax) are known bacteria grazers in Florida lakes. Phytoplankton biomass, measured as Chl a, was strongly associated with TP, both within and across lakes. Phytoplankton biomass was not associated with the biomass of zooplankton. These results, when considered in the context of nutrient-addition, zooplankton-exclosure studies on Lake Okeechobee, support the hypothesis that phytoplankton biomass in subtropical lakes is regulated by "bottom-up," rather than "top-down" forces. PMID:12805947

Havens, Karl E

2002-04-01

365

Concerning calculation methods and limitations of proxy-estimates of Proteins, Carbohydrates and Lipids in crustacean zooplankton from CHN analyses  

OpenAIRE

The present comments resulted from a discussion I had with Dr. Riccardi about the validity of proxy estimates of protein, carbohydrate, and lipid in various zooplankton species of Northern Italian lakes (Riccardi & Mangoni 1999). For these estimates the authors used a calculation method proposed by Gnaiger & Bitterlich (1984; below referred to as G&B). The reason why I questioned the application of the unmodified G&B model to zooplankton was that carbohydrate in crustaceans is...

Vollenweider, Richard A.

2000-01-01

366

Plankton studies in San Francisco Bay; VI, Zooplankton species composition and abundance in the North Bay, 1979-1980  

Science.gov (United States)

Data are presented that summarize zooplankton species composition and abundance in North San Francisco Bay during 1979 and 1980. Sampling was conducted once monthly at six stations during 1979 and twice monthly at sixteen stations during 1980. Samples were collected by pump at three depths in the shipping channel and at one depth over the shoals. Subsamples were enumerated while alive. Total zooplankton biomass, as carbon, was calculated from estimated carbon quotas and abundances of each organism enumerated.

Hutchinson, Anne

1982-01-01

367

Role of Zooplankton Diversity in Vibrio cholerae Population Dynamics and in the Incidence of Cholera in the Bangladesh Sundarbans ?  

OpenAIRE

Vibrio cholerae, a bacterium autochthonous to the aquatic environment, is the causative agent of cholera, a severe watery, life-threatening diarrheal disease occurring predominantly in developing countries. V. cholerae, including both serogroups O1 and O139, is found in association with crustacean zooplankton, mainly copepods, and notably in ponds, rivers, and estuarine systems globally. The incidence of cholera and occurrence of pathogenic V. cholerae strains with zooplankton were studied in...

Magny, Guillaume Constantin; Mozumder, Pronob K.; Grim, Christopher J.; Hasan, Nur A.; Naser, M. Niamul; Alam, Munirul; Sack, R. Bradley; Huq, Anwar; Colwell, Rita R.

2011-01-01

368

[Variations of zooplankton's community structure in reclaimed waters of Nanhui east tidal flat of Shanghai, East China].  

Science.gov (United States)

From October 2010 to July 2011, an investigation was conducted on the zooplankton communities in reclaimed and natural waters in Nanhui east tidal flat to study the seasonal variations of the zooplankton's species composition, abundance, biomass, dominant species, and biodiversity, aimed to explore the differences in the zooplankton's community structure within and outside the reclaimed waters and the relationships of the community structure with several indispensable environmental factors such as water salinity, water temperature, and human activities. A total of 30 zooplankton species were identified, among which, 24 species were in reclaimed waters and dominated by rotifers, and 14 species were in natural waters and dominated by copepods. The average abundance of the zooplankton was obviously higher in reclaimed waters than in natural waters, but the average biomass was in adverse. The dominant species in reclaimed waters were freshwater species, such as Brachionus angularis, B. calyciflorus, and Mesocyclops leuckarti, while those in natural waters were brackish species, such as Sinocalanus sinensis, Schmackeria poplesia, and Tortanus vermiculus. Both in reclaimed and in natural waters, the dominant species had seasonal alternation. The Shannon index (H) and Pielou evenness index (J) of the zooplankton communities were higher in natural waters, but the Margalef species richness (d) and simplicity index (C) were higher in reclaimed waters. Cluster analysis and MDS evaluation indicated that there was an obvious difference in the community structure of zooplankton between reclaimed and natural waters. Reclamation could be the primary cause for the variations of the zooplankton's community structure in reclaimed waters, and environmental factors such as water salinity and tidal power also contributed to the variations. PMID:23189711

Li, Qiang; Ma, Chang-An; Lü, Wei-Wei; Tian, Wei; Yu, Ji; Zhao, Yun-Long

2012-08-01

369

Vertical Line Test  

Science.gov (United States)

In this activity, students try to connect given points on a graph in a way that they will pass the vertical line test. If the points can't be made to pass the vertical line test, the student must adjust the points so they will pass the test. This activity allows students to explore the vertical line test for functions. This activity includes supplemental materials, including background information about the topics covered, a description of how to use the application, and exploration questions for use with the java applet.

2011-05-24

370

Effects of acidification and cadmium pollution on the populations and habitats of limnetic zooplankton; Effekter av forsuring og kadmium-forurensning paa populasjoner og samfunn av limnisk zooplankton  

Energy Technology Data Exchange (ETDEWEB)

The conference paper deals with executed field tests on the adding of cadmium alone or combined with acidification of an enclosed space under different nutrient and predatory conditions. The addition of cadmium changed the biomass and the composition of the phytoplankton. In combination with the added nutrient salts, the biomass of special algae increased in the Cd loaded spaces, and the addition of acid changed the effect of Cd concentration by increased production of the same. The effect of a given Cd concentration on the zooplankton varied in a wide range of environmental conditions. 22 refs., 1 tab.

Schartau, A.K.L. [Norsk Inst. for Naturforskning, Trondheim (Norway)

1996-01-01

371

Depth migration of Cs 137 in soils of the Shatsk national natural park  

International Nuclear Information System (INIS)

The results of analysis of radiocaesium contamination density vertical distribution in the soils of Shatsk National Natural Park during 1994-2007 were presented. The technique of calculation of 89 main characteristics of Cs 137 migration in the soils was proposed based on the diffusion-drift model of migration. The obtained results are evidence that the migration of radiocesium in soils is defined by its equilibrium state. (authors)

372

Some regularities in migration of 90Sr and 137Cs on flood plain  

International Nuclear Information System (INIS)

The vertical and the horisontal 90Sr and 137Cs migration in soils of a small river, is considered. It is shown that the intensive radionuclide migration in soils takes place under the effect of flood waters. At this time a great violation of isotopic ratio is observed. Zones of sweeping and radionuclide accumulation in flood plains formed without any visible violation of soil and vegetation cover are found. The coefficient of water 90Sr migration in soils is determined

373

Vertical distribution of natural radionuclides in soils  

Science.gov (United States)

Low-level alpha spectrometry techniques using semiconductor detectors (PIPS) and liquid scintillation counters (LKB Quantulus 1220™) were used in order to determine the activity concentration of 238U, 232Th, 234U, 230Th, 226Ra, and 210Pb in soil samples. The soils were collected from an old disused uranium mine located in southwest Spain. The soils were selected with different levels of influence from the installation, in such a way that they had different levels of radioactive contamination. The vertical profiles in the soils (down to 40 cm depth) were studied in order to evaluate the vertical distribution of the natural radionuclides. The possible contamination of subsurface waters depends strongly on vertical migration, and the transfer to plants (herbs, shrubs, and trees) also will depend on the distribution of the radionuclides in the root zone. The study of the activity ratios between radionuclides belonging to the same series allowed us to assess the differing behaviour of the radionuclides involved. The vertical profiles for these radionuclides were different at each sampling point, showing the local impact of the installation. However, the profiles per point were similar for the long-lived radionuclides of the 238TJ series (238U, 234U, 230Th, and 226Ra). Also, a major disequilibrium was observed between 210Pb and 226Ra in the surface layer, due to 222Rn emanation and subsequent surface deposition of 210Pb.

Blanco Rodríguez, P.; Tomé, F. Vera; Lozano, J. C.

2012-04-01

374

Effects of natural banks of free-floating plants on zooplankton community in a shallow subtropical lake in Southern Brazil  

Scientific Electronic Library Online (English)

Full Text Available The aim of this study was to test the effects of natural free-floating plants on zooplankton distribution in a shallow subtropical lake. First, the hypothesis that free-floating plants have an effect on physico-chemicals, leading to a decrease on nutrient availability and influencing the phytoplankt [...] on biomass and zooplankton community was tested. Second, the hypothesis that free-floating plants act as a refuge for zooplankton was tested. Three microhabitats were selected: free-floating plants, littoral area and open water. Results demonstrated that the effects of different microhabitats on phytoplankton biomass and physico-chemicals were not significant, indicating a weak influence of the plants. Zooplankton densities were higher in free-floating plants and littoral area, although the effect of microhabitats was weak for most of the predominant genera. The absence of free-floating plant effects on phytoplankton and physico-chemicals showed that it was not a factor influencing the microcrustacean distribution in the microhabitats. Low differences in densities of zooplankton among microhabitats and low abundance of large-bodied cladocerans led to reject the hypothesis that free-floating plants act as a refuge for zooplankton.

Vanessa, Gazulha; Mônica, Montú; David da Motta, Marques; Claúdia Costa, Bonecker.

2011-08-01

375

Effects of natural banks of free-floating plants on zooplankton community in a shallow subtropical lake in Southern Brazil  

Directory of Open Access Journals (Sweden)

Full Text Available The aim of this study was to test the effects of natural free-floating plants on zooplankton distribution in a shallow subtropical lake. First, the hypothesis that free-floating plants have an effect on physico-chemicals, leading to a decrease on nutrient availability and influencing the phytoplankton biomass and zooplankton community was tested. Second, the hypothesis that free-floating plants act as a refuge for zooplankton was tested. Three microhabitats were selected: free-floating plants, littoral area and open water. Results demonstrated that the effects of different microhabitats on phytoplankton biomass and physico-chemicals were not significant, indicating a weak influence of the plants. Zooplankton densities were higher in free-floating plants and littoral area, although the effect of microhabitats was weak for most of the predominant genera. The absence of free-floating plant effects on phytoplankton and physico-chemicals showed that it was not a factor influencing the microcrustacean distribution in the microhabitats. Low differences in densities of zooplankton among microhabitats and low abundance of large-bodied cladocerans led to reject the hypothesis that free-floating plants act as a refuge for zooplankton.

Vanessa Gazulha

2011-08-01

376

Zooplankton spatial and diurnal variations in the Changjiang River estuary before operation of the Three Gorges Dam  

Science.gov (United States)

Estuarine plankton communities can serve as indicators of ecosystem modification in response to anthropogenic influences. The main objectives of this study were to describe the spatial distribution and diurnal variability in zooplankton abundance and biomass over almost entire salinity gradient of the Changjiang (Yangtze) River estuary and to provide a background reference for future studies. To accomplish this, data were collected from 29 stations in the estuary from May 19 to 26, 2003, including two anchor stations. The spatial and diurnal variations in zooplankton characteristics, i.e. abundance, biomass, and gross taxonomic composition, were examined. Generally, both the abundance and biomass gradually increased seaward and presented distinct spatial variations. In addition, the spatial data revealed a significant correlation between abundance and biomass; however, there was no significant correlation between abundance and biomass for the diurnal data. Although the zooplankton composition indicated distinct spatial differences in terms of dominant groups, copepods accounted for >50% of the total zooplankton abundance in most regions and times. Three zooplankton assemblages were recognized through hierarchical cluster analysis. These assemblages existed along the salinity gradient from fresh water to seawater, and their positions coincided with those of the three principal water masses in the estuary. The assemblages were classified as: (1) true estuarine, (2) estuarine and marine, and (3) euryhaline marine, which were characterized by the copepods Sinocalanus dorrii, Labidocera euchaeta, and Calanus sinicus, respectively. Both spatial and diurnal data indicated that there was no significant correlation between zooplankton abundance/biomass and depth-integrated phytoplankton abundance.

Gao, Xuelu; Song, Jinming; Li, Xuegang

2011-05-01

377

210Po/210Pb dynamics in relation to zooplankton biomass and trophic conditions during an annual cycle in northwestern Mediterranean coastal waters  

International Nuclear Information System (INIS)

Monthly sampling in northwestern Mediterranean coastal waters was undertaken to better understand the relationship between zooplankton biomass and the cycling of the natural radionuclide 210Po/210Pb pair during a one-year period (October 1995–November 1996). In conjunction with mesozooplankton collections and 210Po/210Pb measurements in seawater, zooplankton and their fecal pellets, the biochemical composition of particulate organic matter (POM) was also examined at three depths (0, 20 and 50 m) as an indicator of trophic conditions. During May 1996, a strong zooplankton “bloom” was observed which was preceded by a prolonged increase in POM (protein + carbohydrates + lipids) starting at the end of March, and further demonstrated by a concomitant increase in the concentration of smaller particles, two features that are typical of mesotrophic waters. Simultaneous measurements of 210Po in sea water and zooplankton showed an inverse trend between these two parameters during the sampling period, with the two lowest 210Po concentrations in the dissolved phase of seawater coincident with the highest radionuclide concentrations in the zooplankton; however, this apparent relationship was not statistically significant over the entire year. Freshly excreted mesozooplankton and salp fecal pellets, which have been strongly implicated in the removal and downward transport of these radionuclides from the upper wthese radionuclides from the upper water column, contained 210Po and 210Pb levels ranging from 175 to 878 and 7.5–486 Bq kg?1 dry weight, respectively. Salp pellets contained 5 and 10 times more 210Po and 210Pb than in fecal pellets produced by mixed zooplankton, a finding most likely related to their different feeding strategies. During the zooplankton biomass peak observed in May, the 210Po concentration in zooplankton was at a minimum; however, in contrast to what has been reported to occur in some open sea oligotrophic waters, over the year no statistically significant inverse relationship was found between zooplankton biomass and 210Po concentration in zooplankton. This observation may have resulted from the general lack of very low biomass concentrations (?3) measured in these coastal waters, biomass levels which commonly occur in open ocean oligotrophic regions. - Highlights: ? This a one year sampling of zooplankton and water at 3 different depths to study 210Po and 210Pb in them. ? A zooplankton bloom was present in May after an extended period of a higher primary productivity proxy. ? An inverse trend was found for 210Po in zooplankton and water or the dissolved phase. ? Maximum zooplankton biomass showed minimum 210Po in zooplankton and a maximum in the dissolved phase. ? A dilution phenomenon is present in zooplankton and water, depending zooplankton or particle concentration.

378

Micromachined electrostatic vertical actuator  

Science.gov (United States)

A micromachined vertical actuator utilizing a levitational force, such as in electrostatic comb drives, provides vertical actuation that is relatively linear in actuation for control, and can be readily combined with parallel plate capacitive position sensing for position control. The micromachined electrostatic vertical actuator provides accurate movement in the sub-micron to micron ranges which is desirable in the phase modulation instrument, such as optical phase shifting. For example, compact, inexpensive, and position controllable micromirrors utilizing an electrostatic vertical actuator can replace the large, expensive, and difficult-to-maintain piezoelectric actuators. A thirty pound piezoelectric actuator with corner cube reflectors, as utilized in a phase shifting diffraction interferometer can be replaced with a micromirror and a lens. For any very precise and small amplitudes of motion` micromachined electrostatic actuation may be used because it is the most compact in size, with low power consumption and has more straightforward sensing and control options.

Lee, Abraham P. (Walnut Creek, CA); Sommargren, Gary E. (Santa Cruz, CA); McConaghy, Charles F. (Livermore, CA); Krulevitch, Peter A. (Pleasanton, CA)

1999-10-19

379

Migration Information Source  

Science.gov (United States)

Recently introduced by the Migration Policy Institute, the Migration Information Source Web site offers visitors a fantastic opportunity to stay on top of trends and changes in global migration. Looking at migration from many levels and on many planes, the site considers migrations on both national and international fronts. With a dropdown menu of the countries for which data is available (currently western European countries, Australia, and the US), the database is fully searchable, with more options on the way. Perhaps most interesting to those directly working in statistical, sociological, or ethnographic analyses of migration, the resource is broadly accessible and offers compelling glimpses of migrant populations, their reasons for moving, and their rates of assimilation into host countries. For those unfamiliar with field-specific terms employed in the site's reports, there is a detailed glossary of common terms and phrases. Closer to home, the Migration Information site presents an elaborate array of reports and studies on US-Mexico relations, with an emphasis on the ever-broadening trend toward northward migration in the Americas.

380

Monarchs and Migration  

Science.gov (United States)

A large resource of information about Monarch butterflies, migration, metamorphosis, and conservation. Many photos from various places highlight the information. This is a teaching focused set of pages. Of major interest are their many links, which deal with migration routes, roosting sites, and various other activities of interest.

0000-00-00

381

Migration of Egyptians.  

Science.gov (United States)

This study is concerned with recent trends in emigration from Egypt, with particular emphasis on the migration of Egyptians to the Arab oil-exporting countries of the Middle East since 1973. The benefits and costs of this migration for Egypt are considered. PMID:12279539

Oweiss, I M

1980-07-01

382

Biological processes in the water column of the South Atlantic Bight: Zooplankton responses. Final report  

Energy Technology Data Exchange (ETDEWEB)

This study sought to determine and understand the major processes governing the abundance, distribution, composition and eventual fate of zooplankton on the southeastern shelf of the US in relation to water circulation. Over much of the shelf circulation is dominated by the Gulf Stream and/or atmospheric forcing. Most of our studies concentrated on processes on the middle and outer shelf. On the latter, pronounced biological production occurs year-round at frequent intervals and is due to Gulf Stream eddies which move by at an average frequency of one every week. These eddies are rich in nutrients which, when upwelled into the euphoric zone, lead to pronounced primary production which then triggers zooplankton production.

Paffenhofer, G.A.

1992-09-25

383

Biological processes in the water column of the South Atlantic Bight: Zooplankton responses  

Energy Technology Data Exchange (ETDEWEB)

This study sought to determine and understand the major processes governing the abundance, distribution, composition and eventual fate of zooplankton on the southeastern shelf of the US in relation to water circulation. Over much of the shelf circulation is dominated by the Gulf Stream and/or atmospheric forcing. Most of our studies concentrated on processes on the middle and outer shelf. On the latter, pronounced biological production occurs year-round at frequent intervals and is due to Gulf Stream eddies which move by at an average frequency of one every week. These eddies are rich in nutrients which, when upwelled into the euphoric zone, lead to pronounced primary production which then triggers zooplankton production.

Paffenhofer, G.A.

1992-09-25

384

Phytoplankton response to winter warming modified by large-bodied zooplankton: an experimental microcosm study  

Directory of Open Access Journals (Sweden)

Full Text Available While several field investigations have demonstrated significant effects of cool season (winter or spring warming on phytoplankton development, the role played by large-bodied zooplankton grazers for the responses of phytoplankton to winter warming is ambiguous. We conducted an outdoor experiment to compare the effect of winter warming (heating by 3°C in combination with presence and absence of Daphnia grazing (D. similis on phytoplankton standing crops and community structure under eutrophic conditions. When Daphnia were absent, warming was associated with significant increases in phytoplankton biomass and cyanobacterial dominance. In contrast, when Daphnia were present, warming effects on phytoplankton dynamics were offset by warming-enhanced grazing, resulting in no significant change in biomass or taxonomic dominance. These results emphasize that large-bodied zooplankton like Daphnia spp. may play an important role in modulating the interactions between climate warming and phytoplankton dynamics in nutrient rich lake ecosystems.

Hu He

2014-02-01

385

Method for the in situ study of pollutant effects on natural zooplankton communities  

International Nuclear Information System (INIS)

A new method was developed and tested for the in situ study of pollutant effects on zooplankton communities in large lakes which does not suffer the limitations of large enclosures. In each of five experiments conducted in northern Green Bay, Lake Michigan, two to four samples of lower epilimnion water for each of four levels of added pollutant (Cd) plus controls were incubated in situ in opaque, polyethylene carboys (2 to 5 gallon size) for 4 to 15 days. In each experiment 2 to 4 additional samples, which were not incubated, were also taken. This new method appears to overcome some of the limitations imposed by the use of large, transparent bags or open-top tubes in large lakes for studies of pollutant effects on zooplankton, at least for short- to intermediate-term effects

386

Changes in zooplankton abundance and diversity after ballast water exchange in regional seas.  

Science.gov (United States)

A study of the efficiency of ballast water exchange (BWE) in regional seas was carried out to assess this management method in reducing the risk of introducing non-native species. Zooplankton samples were taken before and after exchange on ten voyages where BWE took place (North Sea, English Channel, Irish Sea and Bay of Biscay). Zooplankton abundance was always reduced after exchange, but diversity increased on eight occasions. The greatest changes occurred when the source port water was of low salinity and when exchange took place in deeper waters further from land. However, it was clear that BWE did not remove all the source port taxa and this method is unlikely to provide a consistent and effective method of managing ballast water in regional seas. PMID:18348891

McCollin, Tracy; Shanks, Aileen M; Dunn, John

2008-05-01

387

Structure, seasonal dynamics and distribution of zooplankton in lake Drukshiai in 1994  

International Nuclear Information System (INIS)

Investigations on the zooplankton of Lake Drukshiai were carried out in 1994. There were registered 62 taxons of protozoa and 50 taxons of metazoa, and compared with the data of 1979 - 1986 the diversity of species composition decreased 2.1 times. Eurytermic and stenothermic thermophylic species prevailed in the plankton biocenosis. In protozooplankton dominated ciliates of subclasses teolotricha and spirotricha, in metazooplankton -planctonic crustacea (Copopeda and Cladocera). Rotifers (Rotaria) were abundant only in the shallow and heated water outlet area. Seasonal dynamics of protozooplankton indicated one maximum in spring and metazooplankton - in summer. High diferentiation in quantity and biomass of zooplankton in the lake revealed different level of eutrophication of some areas. (author). 7 refs., 5 figs

388

Vertical instabilities in JET  

International Nuclear Information System (INIS)

The vertical position of the JET plasma is actively stabilised by an externally applied radial magnetic field. Without feedback the vertical position is unstable due to the destabilising effect of the iron magnetic circuit and due to the quadrupole magnetic field required to obtain the desired elongation b/a=1.4...1.9 of the plasma cross section. If the stabilisation fails the plasma moves vertically and disrupts causing large vertical and asymmetric radial forces at the vessel which are of concern when operating at high current. A sudden technical failure of the stabilisation system has been regarded as the most serious fault case and must be considered as possible even though faults of this kind did not occur in JET. The expected effects of a complete stabilisation failure have been studied by deliberately disabling the feedback during the pulse. All vertical instabilities observed during normal operation can be ascribed to the existence of a limited stabilisation range and to the effects of large amplitude perturbations leading to saturation and degradation of the stabilisation system. In the following the electromagnetic aspects of vertical instabilities in JET are examined and the implications for the planned operation with a divertor coil inside the vessel are outlined. (author) 5 refs., 3 figs

389

Zooplankton abundance, species composition and ecology of tropical high-mountain crater lake Wonchi, Ethiopia  

OpenAIRE

The highlands of Ethiopia represent some of the remnants of undisturbed aquatic ecosystems; they are however highly threatened by significant socio–economic developments and associated anthropogenic impacts. Lake Wonchi is one of the few remaining fairly pristine high–mountain crater lakes in the central highlands and has never been investigated in detail. We present a first study on zooplankton taxa composition, abundance and biomass conducted over more than one year including the underl...

Fasil Degefu; Michael Schagerl

2014-01-01

390

Carbon partitioning in the food web of a high mountain lake: from bacteria to zooplankton  

OpenAIRE

The organisms of the microbial loop in Lake Paione Superiore (LPS), a high mountain lake in the Italian Alpine region, were studied together with phytoplankton and zooplankton for three successive years. The biomass of bacteria, HNF (heterotrophic nanoflagellates), ciliates and phytoplankton, as mean carbon concentration in the three years, was 30 and 37 ?g C l-1 near the surface (SUR) and the bottom (BOT) respectively. Under the ice-cover the mean biomass carbon decreased especially at the ...

Pugnetti, Alessandra; Manca, Marina; Callieri, Cristiana

1999-01-01

391

Carbon partitioning in the food web of a high mountain lake: from bacteria to zooplankton  

Directory of Open Access Journals (Sweden)

Full Text Available The organisms of the microbial loop in Lake Paione Superiore (LPS, a high mountain lake in the Italian Alpine region, were studied together with phytoplankton and zooplankton for three successive years. The biomass of bacteria, HNF (heterotrophic nanoflagellates, ciliates and phytoplankton, as mean carbon concentration in the three years, was 30 and 37 ?g C l-1 near the surface (SUR and the bottom (BOT respectively. Under the ice-cover the mean biomass carbon decreased especially at the BOT, whereas at SUR the decrease was less evident due to the maintenance of higher phytoplankton biomass (mixotrophic flagellates. In LPS ~50% of the carbon was confined in bacteria, 20% in protozoa and 30% in phytoplankton. The ratio Autotrophs/Heterotrophs was lower than 1 (mean: 0,97 at SUR and 0,58 at BOT thus indicating a system with a predominance of the heterotrophs. This might be the result of light inhibition of algal growth coupled to a production of dissolved carbon, utilized by bacteria. During late summer the peak of Daphnia longispina, the main component of the zooplankton of LPS, increased the carbon content in the lake to a total of 158 and 300 ?g C l-1 in 1997 and 1998 respectively. At the late summer peaks, zooplankton represented from 78 to 89% of the total carbon of the pelagic communities. Furthermore, the presence of Daphnia could be responsible for a decrease in the biomass carbon of a variety of organisms (algae, protozoa and bacteria. It may be possible that this is an instance of zooplankton grazing on algae, protozoa and also bacteria, as Daphnia has very broad niches and may eat pico-, nanoplankton and small ciliates. In the oligotrophic LPS, a diet which also includes protozoa could give Daphnia a further chance of survival, as ciliates are an important source of fatty acids and sterols.

Alessandra PUGNETTI

1999-08-01

392

The Zooplankton Species Composition and Abundance in Sombreiro River, Niger Delta, Nigeria  

Directory of Open Access Journals (Sweden)

Full Text Available The zooplankton species composition and abundance in Sombreiro River, in the Niger Delta of Nigeria was studied for a period of two years (August, 2007-July, 2009, using filtration technique. 25 ?m mesh size plankton net was towed from a dugout boat at about 5-105–1 for about a minute. The net content was washed out into a wide mouth plastic container and preserved in 10% formalin solution after proper labeling. A total of seventeen (17 species belonging to six (6 taxonomic groups were recorded from Sombreiro River. The groups Cladocera and Copepoda were represented by five species each consisting of 29.4% by composition. This was followed by three species of Protozoa (17.6%, two species of Rotifera (11.8%, Decapod crustacean (5.9% and Euphasiacea (5.9%, one specie each. Copepoda was the highest, 46.5%. This was followed by Cladocera (23.3%. The others were Protozoa (11.2%, Euphasiacea (9.6%, Rotifera (7.9% and Decapod Crustacean (1.5%. The low zooplankton diversity observed in this study is common in tropical waters. The dominance of cladocera and copepoda in the study area is common to River Nun, in the Niger Delta and Schelde estuary in Belgium. Sombreiro River zooplankton abundance is higher than that of River Nun but lower than that of Imo River in the Niger Delta. These differences are attributed to duration of sampling and natural conditions of the water bodies. The zooplankton abundance was well distributed in the stations except Mysis sp. (Decapod Crustacean which showed spatial discontinuity in abundance.

E.N. Ezekiel

2011-05-01

393

Effect of demographic noise in a phytoplankton-zooplankton model of bloom dynamics  

OpenAIRE

An extension of the Truscott-Brindley model (Bull. Math. Biol. {\\bf 56}, 981 (1994)) is derived to account for the effect of demographic fluctuations. In the presence of seasonal forcing, and sufficiently shallow water conditions, the fluctuations induced by the discreteness of the zooplankton component appear sufficient to cause switching between the bloom and no-bloom cycle predicted at the mean-field level by the model.The destabilization persists in the thermodynamic lim...

Olla, Piero

2012-01-01