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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 grazing in a eutrophic lake: implications of diel vertical migration  

International Nuclear Information System (INIS)

During summer and fall, depth profiles of zooplankton community grazing were determined in situ during day and night in the Schoehsee, a small eutrophic lake. Labeled algae of two different sizes were mixed with the natural suspension of phytoplankton in a grazing chamber. A small blue-green alga (Synechococcus, 1 ?m) was labeled with 32P; a larger green alga (Scenedesmus, 4-15 ?m) was labeled with 14C. During summer, grazing in the upper 5 m was negligible during day but strong at night. Hence, algae grow relatively unimpeded by grazing during daytime but are harvested at night. Vertical and diel differences in grazing rates disappeared when the vertical migration ceased in fall. Selectivity of grazing was controlled by the zooplankton species composition. Eudiaptomus showed a strong preference for Scenedesmus. Daphnia showed a slight preference for Scenedesmus, but Ceriodaphnia preferred Synechococcus. Cyclopoid copepodites did not ingest the small blue-green. Because Daphnia and Eudiaptomus were dominant, grazing rates on larger cells were usually higher than grazing rates on the small cells. Negative electivity indices for scenedesmus occurred only when the biomass of large crustaceans was extremely low (near the surface, during day). Zooplankton biomass was the main factor controlling both vertical and seasonal variations in grazing. Highest grazing rates (65%/d) were measured during fall when zooplankton abundance was high. Because differnkton abundance was high. Because differential losses can produce substantial errors in the results, it was necessary to process the samples on the boat immediately after collection, without preservation

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Exposure to sublethal chromium and endosulfan alter the diel vertical migration (DVM) in freshwater zooplankton crustaceans.  

Science.gov (United States)

Among zooplankton behaviors, diel migrations constitute one of the most effective predator avoidance strategy and confer metabolic and demographic advantages. We aim to examine whether sublethal concentrations of two widespread pollutants (a pesticide with endosulfan and chromium as potassium dichromate) alter the depth selection, vertical migration and grouping of five freshwater species: Argyrodiaptomus falcifer, Notodiaptomus conifer, Pseudosida variabilis, Ceriodaphnia dubia and Daphnia magna. In a series of experimental assays, performed with 150 cm length transparent tubes, we analyzed the ascents and descents movements through periods of 24 h. Among controls, the copepods showed a tendency to remain closest to the surface, however, N. conifer registered a downward movement of 18.14 cm between 06:00 and 12:00. The cladoceran P. variabilis occupied the deeper position (85 cm), C. dubia showed a tendency to hike to the surface at 06:00 (57.7 cm) descending to lower levels at 18:00. D. magna showed a constant movement of ascent between 00:00 and 18:00, making an average travel of 29.4 cm. When subjected to pollutants, these behaviors were altered. It is hypothesized that a reduction in swimming activity and disorientation would be the main cause of such alterations. The high sensitivity of this endpoint sugests it to be adecuate as a complement in future standard toxicity tests. PMID:21842398

Gutierrez, María Florencia; Gagneten, Ana María; Paggi, Juan Cesar

2012-01-01

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Acoustic backscatter observations with implications for seasonal and vertical migrations of zooplankton and nekton in the Amundsen shelf (Antarctica)  

Science.gov (United States)

High-temporal resolution profiles of acoustic backscatter were collected in the Dotson Trough on the Amundsen shelf in the Antarctica, using a bottom-moored, upward-looking acoustic Doppler current profiler (ADCP). This data set was used to examine the impact of seasonal variations in surface solar radiation (SSR), sea ice concentration (SIC), and Circumpolar Deep Water (CDW) thickness on acoustic backscatter in the lower water column (250-540-m depth). A recorded high acoustic backscatter (-75 to -70 dB) at depth >400 m from April to November compared to the rest of the year (-90 to -80 dB) suggests that zooplankton and nekton migrated towards the bottom during winter. The depth of maximum mean volume backscattering strength showed a significant correlation with SSR, SIC and CDW thickness. A daily cycle of vertical migration was also recorded. This varied with changing surface ice conditions. When sea ice cover was low, the acoustic backscatter descended at sunrise, and ascended at sunset. When sea ice cover was high, the daily migration was not pronounced, and the layer of high acoustic backscatter remained near the bottom. This is the first study of seasonal and vertical migration of zooplankton and nekton that has been conducted on the Amundsen Sea shelf, one of the world's most productive areas. The findings provide implications to understand the behavior of zooplankton and nekton below the euphotic zone in the Southern Ocean.

La, H. S.; Ha, H. K.; Kang, C. Y.; Wåhlin, A. K.; Shin, H. C.

2015-01-01

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Evidence for tidally-induced vertical migration of some gelatinous zooplankton in the Wadden Sea area near Sylt  

Science.gov (United States)

Gelatinous zooplankton is more abundant in the Wadden Sea area of North Sylt than in the adjacent North Sea. The hypothesis is tested that medusae maintain their position in the North Sylt Wadden Sea by ascending to the surface at flood tides and descending to the bottom during ebb tides, thus avoiding the strong ebb currents which could carry them out of this food-rich area. Surface sampling at a main tidal channel revealed great differences between high tide and low tide abundances of five species of medusae in the surface layer. Rathkea octopunctata, Sarsia tubulosa, Eucheilota macultata and Pleurobrachia pileus were all more abundant around high tide than during low tide. Bongo net sampling in different depth layers revealed that Pleurobrachia pileus, Bougainvillia ramosa and Eucheilota maculata showed a preference for the surface layers around high tide, whereas most of the individuals were found in the deepest layer around low tide. The results suggest tidally-induced vertical migration of medusae in tidal channels. This may assist maintenance of the populations in the Wadden Sea area near Sylt.

Kopacz, U.

1994-06-01

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The effects of diel vertical migration of Daphnia on zooplankton-phytoplankton interactions  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Zooplankter, die eine tagesperiodischen Vertikalwanderung (TPV) durchführen halten sich nur nachts in der Oberflächenschicht der Gewässer auf, den Tag dagegen verbringen sie in tieferen Schichten. Die vorliegende Arbeit beschäftigt sich mit den Auswirkungen der TPV von Daphnien auf Phytoplanktondynamiken und Populationsparameter der Daphnien. Dazu führte ich sowohl Freiland- als auch Laborversuche durch, in denen ich jeweils ‘Migrations-’ mit ‘Nicht-Migrations-’ Ansätzen verglic...

Reichwaldt, Elke S.

2004-01-01

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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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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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Vertical distribution of zooplankton in the epipelagic zone off Sharm El-Sheikh, Red Sea, Egypt  

Directory of Open Access Journals (Sweden)

Full Text Available The purpose of the present study was to track the seasonal vertical distribution of zooplankton abundance in the epipelagic zone off Sharm El-Sheikh, Red Sea. Zooplankton samples were collected seasonally within the depth ranges of 0-25, 25-50, 50-75, 75-100 m at a single station off Sharm El-Sheikh City. The present study is a trial to expand knowledge about the structure as well as the vertical distribution of the epipelagic zooplankton community in the Gulf of Aqaba in general and in its southern part in particular. The results indicate the occurrence of 52 copepod species and several species of other planktonic groups in the study area; the zooplankton standing crop fluctuated between 1124 and 4952 organisms m-3. Copepods appeared to be the predominant component, forming an average of 86.5% of the total zooplankton count, and with other groups demonstrated a markedly different seasonal vertical distribution. Twelve bathypelagic copepod species were reported during the present study, and five species were new to the area, having migrated northwards from the main basin of the Red Sea.

Mahnoud Hassan Hanafi

2012-06-01

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

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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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Concentrations of 137Cs and trace elements in zooplankton, and their vertical distributions off Rokkasho, Japan  

International Nuclear Information System (INIS)

Zooplankton samples were collected at about 50 m depth with a large ring net (160-cm mouth diameter, 0.5-mm mesh) in May, June, October 2005 and June 2006 off Rokkasho, Japan where a nuclear fuel reprocessing plant will be in full-scale operation in the near future. Plankters in each sample were separated based on their species. Eight samples were used for the determination of 137Cs concentration and the other 21 samples were used for the determination of its stable isotope, Cs along with some other trace elements. All the samples were characterized by five dominant species, i.e. euphausiids, chaetognaths, copepods; Neocalanus spp., amphipods; Themisto spp. and Cyphocaris sp. Plankton samples were also taken at three to five discrete depths between the surface and ? 1,000 m in depth during daytime and nighttime for analysis of vertical distribution patterns of biomass, and for assessment of daily vertical migration activity. Integrated net zooplankton biomass at nighttime ranged from 0.85 to 8.74 g-DW m-2 in the 0-150 m layer without any appreciable day-night differences in the vertical distribution; below the layer, it decreased significantly. Only in spring, appreciable day-night differences in the vertical distribution were observed at the shallowest station. Concentrations of Cs and Co did not show significant difference among the five species. However, higher concentrations of Sr were observed in two amphipods. It is likely that amphipods had a different biological process in Sr metabolism from others. The concentration of 137Cs in zooplankton was usually very low and sometimes under the detection limit. In the present study, the highest concentration of 137Cs in zooplankton was 24 mBq kg-WW-1, corresponding to the concentration factor (CF) of 14, if the value of 1.7 mBq L-1 was given to the 137Cs concentration in seawater. The water-column inventory of 137Cs in a zooplankton community is calculated to be 0.29 to 1.95 mBq m-2, based on the data on biomass and concentration of 137Cs. The fraction of the water-column inventory of 137Cs in zooplankton to the total 137Cs was 0.5 - 1.3x10-6. (author)

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The zooplankton of Marguerite Bay, western Antarctic Peninsula—Part II: Vertical distributions and habitat partitioning  

Science.gov (United States)

The vertical distribution patterns of the dominant zooplankton in the vicinity of Marguerite Bay on the west side of the Antarctic Peninsula were studied during austral fall of 2001 and 2002, using net and concurrent environmental data. Vertical distributions of zooplankton usually were similar to those reported for other Antarctic regions. Maximum abundances of the copepods Ctenocalanus spp. and Calanus propinquus, the euphausiids Euphausia superba, Euphausia crystallorophias, and Thysanoessa macrura, and appendicularians primarily occurred in shallow Antarctic Surface Water (250 m), in warmer modified Circumpolar Deep Water. Other dominant copepods ( Calanoides acutus, Metridia gerlachei, Oithona spp., Paraeuchaeta spp., and Rhincalanus gigas), pteropods, and chaetognaths had depths of maximum abundance within the pycnocline or in deeper warmer waters. Overlapping depth distributions suggest that E. superba would have the highest prey encounter rates with M. gerlachei, Ctenocalanus spp., C. propinquus, and Oithona spp. during fall, although most of the copepod community was deeper than the euphausiid community. Even though the three euphausiid species occupied similar depth ranges on average, at any given location E. superba, E. crystallorophias, and T. macrura depths of maximum abundance often did not overlap, suggesting vertical habitat partitioning behavior. The vertical patterns of copepods, euphausiids, amphipods, and mysids did not have a consistent association with the distributions of pigments, temperature, salinity, or density. Instead, the observed vertical distributions are mainly attributed to different behaviors, including seasonal vertical migration to deeper water for overwintering (i.e., C. acutus, R. gigas, ostracods, chaetognaths, pteropods) and vertical habitat partitioning to reduce competition (i.e., euphausiids). Migration into deep water and aggregation behavior (i.e., euphausiids) also reduce the risk of predation.

Marrari, Marina; Daly, Kendra L.; Timonin, Alexander; Semenova, Tatjana

2011-07-01

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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  

Digital Repository Infrastructure Vision for European Research (DRIVER)

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 nict...

Pedro Apablaza; Sergio Palma

2006-01-01

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Schooling of the vertically migrating mesopelagic fish Maurolicus muelleri in light summer nights  

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Vertically migrating Maurolicus muelleri arrested their nocturnal ascent below the peak zooplankton concentrations during Light summer nights at 62 degrees N. At 69 degrees N, the behavior was further modified, with M, muelleri forming schools in the upper layer at night. We suggest that M. muelleri used schooling as an antipredator strategy due to the absence of dark periods.

Kaartvedt, Stein; Knutsen, Tor; Holst, Jens Christian

1998-01-01

16

Vertical flux regulation by zooplankton in the northern Barents Sea during Arctic spring  

Science.gov (United States)

The influence of zooplankton on vertical carbon export was investigated during three field investigations conducted on and off the northern Barents Sea shelf during bloom conditions in July 2003, 2004 and May 2005. Short-term patterns in vertical flux of organic matter were measured at high vertical resolution (eight depths) in the upper 200 m at 11 stations. Vertical flux of particulate organic carbon (POC) was highly variable between stations and depths, depending on water mass characteristics such as stratification, phytoplankton bloom development, and zooplankton-related activities. Detailed investigations of the vertical flux composition revealed that faecal pellets (FPs) produced by larger meso- and macrozooplankton comprised on average 20% of the vertical POC flux (average for all depths and stations). The relative importance of FP carbon (FPC) increased with depth, and at depths >60 m FPC comprised ˜30% of the vertical POC flux. The main contributors to the FPC flux varied depending on the prevailing water masses and the phytoplankton bloom stage. FPs produced by older copepodite stages of Calanus spp. dominated at most stations, while FP produced by appendicularians and euphausiids dominated at certain depths and stations. A conservative grazing estimate obtained by calculating the ingestion necessary to support the measured FPC at 50 m depth, suggests that average zooplankton community carbon ingestion equals the vertical POC export. This study clearly shows that zooplankton is important for vertical flux regulation. Zooplankton ingest POC in the range of 22-44% of the daily primary production, but accelerate the vertical flux through production of fast-sinking FP.

Wexels Riser, Christian; Wassmann, Paul; Reigstad, Marit; Seuthe, Lena

2008-10-01

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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

Seasonal variations in vertical migration of glacier lanternfish, Benthosema glaciale  

The seasonal variations in glacier lanternfish (Benthosema glaciale) vertical distribution and diel vertical migration (DVM) were studied by use of a bottom-mounted upward-facing 38 kHz echo sounder deployed at 392 m depth and cabled to shore in Masfjorden (~6052?N, ~524?E), Norway. Acoustic data from July 2007-October 2008 were analyzed, and scattering layers below ~220 m during daytime were attributed to glacier lanternfish based on net sampling in this, and previous studies, as well as from analysis of the acoustic data. At these depths, three different diel behavioral strategies were apparent: normal diel vertical migration (NDVM), inverse DVM (IDVM), and no DVM (NoDVM). NoDVM was present all year, while IDVM was present in autumn and winter, and NDVM was present during spring and summer. The seasonal differences in DVM behavior seem to correlate with previously established seasonal distribution of prey. We hypothesize that in regions with seasonally migrating zooplankton, such as where calanoid copepods overwinter at depth, similar plasticity in DVM behavior might occur in other populations of lanternfishes. 2012 The Author(s).

Dypvik, Eivind

2012-06-05

19

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

20

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 migrationzooplankton 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

 
 
 
 
21

Vertical zooplankton distribution on the northeastern Florida shelf and its relation to temperature and food abundance  

Energy Technology Data Exchange (ETDEWEB)

The vertical distribution of abundant zooplankton on the northeastern (NE) Florida shelf was measured and related to depth, temperature and concentration of particulate matter. High particle concentrations were observed in low-temperature near-bottom intrusions of upwelled Gulf Stream water. Patterns of vertical distribution differed among the abundant zooplankton taxa. Abundances of the calanoids Eucalanus pileatus and Temora turbinata, late copepodids and adults of the cyclopoid Oncaea sp., the cladoceran Penilia avirostris and larvae of the cephalochordate Branchistoma sp. generally increased with increasing depth. E. pileatus, T. turbinata, Oncaea sp. and P. avirostris increased with increasing concentration of particulate matter. Abundances of young specimens of the tunicate Oikopleura, the calanoid Centropages furcatus and during one period, the cyclopoid Oithona sp. were greatest in the upper mixed layer and the thermocline. The abundance of Eucalanus, T. turbinata and the late copepodids/adults of Oncae showed a significantly positive correlation to the abundance of particulate matter. 8 figures, 3 tables.

Paffenhoefer, G.A.

1983-01-01

22

Elastic kirchhoff migration for vertical seismic profiles  

International Nuclear Information System (INIS)

Elastic Kirchhoff migration is implemented for the VSP recording geometry. The resulting migration formula requires measurement of the stress as well as the displacement. Since stress is not measured in a VSP, and in many cases the horizontal component of displacement is not measured, approximate migration formulas are given for these cases. The elastic migration formula for the case where only the vertical components are available, is the same as the acoustic migration formula, where the pressure data are replaced by the magnitudes of the elastic data as reconstructed from the vertical components, and the acoustic Green's functions are replaced with either the P or S wave elastic Green's functions. Two expressions for migration of two component displacement data are presented. In the first, the terms involving traction data are simply ignored. In the second, an improved backpropagation operator for the displacement field is obtained by replacing the traction data in the Kirchhoff integral by displacement data using Hooke's law. The migration expressions for the cases where two component data are available produce images which are less contaminated by artifacts than the migration images of one component data

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Creation of vertical radionuclide migration data base  

International Nuclear Information System (INIS)

Date base 'Landscape-geochemical polygons' for collection, handling and long-term storage of radiation monitoring results was created. This program allows to include into the database soil characteristics such as soil type, texture of soil, description of genetic horizons and so on. It allows to study vertical migration taking into consideration soil and landscape characteristics. (authors)

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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

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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

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

Directory of Open Access Journals (Sweden)

Full Text Available 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 Van Dorn sampler. The species showed greater concentrations at the by means of water column. Thirty-eight zooplankton species were found in the samples represented by Rotifera (30, Cladocera (5 and Cyclopoida (3. The temperature of the water column showed a tendency toward relatively high values (about 30ºC with little variation, consequently resulting in low viscosity. Based of Jaccard's index, it was seen that during the low-water phase, S1 and S3 of the three sampling stations studied, had greater similarity (Cj = 0.7058 in the middle of the water column. Lago Amapá showed characteristics in line with the intermediate disturbance hypothesis model, favoring colonization by opportunistic species such as rotifers.O objetivo desta investigação foi observar a distribuição vertical da comunidade do zooplâncton no Lago Amapá (10º2'36"S e 67º50'24"W, localizado na planície de inundação do Rio Acre. Amostragens foram conduzidas em três diferentes profundidades da coluna da água, considerando aspectos sazonais do zooplâncton, parâmetros físicos, químicos e biológicos. Coletas foram realizadas semanalmente com Garrafa de Van Dorn. As espécies apresentaram maiores concentrações no meio da coluna da água. Foram encontradas 38 espécies, assim distribuídas: Rotifera (30, Cladocera (5 e Cyclopoida (3. A temperatura da coluna da água em geral apresentou-se alta, em torno de 30ºC, com pequena variação, resultando em baixa viscosidade. O índice de Jaccard, comparando-se as três estações de coletas, demonstrou que durante a fase de águas baixas, as estações 1 e 3 foram as mais similares (Cj = 0.7058, especialmente no meio da coluna da água. Lago Amapá apresentou características em conformidade com o Modelo do Distúrbio Intermediário, favorecendo a colonização de grupos oportunistas, tais como rotíferos.

Erlei Cassiano Keppeler

2004-06-01

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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

28

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

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Lake Ontario zooplankton in 2003 and 2008: community changes and vertical redistribution  

Science.gov (United States)

Lake-wide zooplankton surveys are critical for documenting and understanding food web responses to ecosystem change. Surveys in 2003 and 2008 during the binational intensive field year in Lake Ontario found that offshore epilimnetic crustacean zooplankton declined by a factor of 12 (density) and factor of 5 (biomass) in the summer with smaller declines in the fall. These declines coincided with an increase in abundance of Bythotrephes and are likely the result of direct predation by, or behavioral responses to this invasive invertebrate predator. Whole water column zooplankton density also declined from 2003 to 2008 in the summer and fall (factor of 4), but biomass only declined in the fall (factor of 2). The decline in biomass was less than the decline in density because the average size of individual zooplankton increased. This was due to changes in the zooplankton community composition from a cyclopoid/bosminid dominated community in 2003 to a calanoid dominated community in 2008. The increase in calanoid copepods was primarily due to the larger species Limnocalanus macrurus and Leptodiaptomus sicilis. These coldwater species were found in and below the thermocline associated with a deep chlorophyll layer. In 2008, most of the zooplankton biomass resided in or below the thermocline during the day. Increased importance of copepods in deeper, colder water may favor cisco and rainbow smelt over alewife because these species are better adapted to cold temperatures than Alewife.

Rudstam, Lars G.; Holeck, Kristen T.; Bowen, Kelly L.; Watkins, James M.; Weidel, Brian C.; Luckey, Frederick J.

2014-01-01

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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

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Effects of diel vertical migration on ephippia production in Daphnia  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Fish presence in experimentally simulated temperature conditions (limno-towers) led to diel vertical migration and resulted in a decrease of ephippia production in Daphnia pulicaria. Diel fluctuation of food, temperature and day length similar to those experienced by migrating Daphnia were tested in laboratory experiments with flow-through-systems. Daphnids were kept under these conditions for 15 days and the proportions of females producing an ephippium were determined. In addition, maturati...

Alekseev, Victor

2004-01-01

32

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

33

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

International Nuclear Information System (INIS)

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)

34

Pelagic and sympagic contribution of organic matter to zooplankton and vertical export in the Barents Sea marginal ice zone  

Science.gov (United States)

The structure and function of the marine food web strongly regulate the cycling of organic matter derived from primary production by phytoplankton and ice algae in Arctic shelf seas. Improved knowledge of trophic relationships and export of organic matter from the surface layer is needed to better understand how the Arctic marine ecosystem may respond to climate-related changes in distribution of sea ice, water masses, and associated primary production regimes. Pelagic and sympagic inputs of organic matter to dominant meso- and macrozooplankton species and vertical export were investigated in the northern Barents Sea by means of stable carbon and nitrogen isotopes (? 13C and ? 15N). Samples were collected during spring and summer (2003-2005) from a total of 13 stations with different ice conditions, abundances of ice algae, and phytoplankton bloom phases. ? 13C signatures were different in organic matter of phytoplankton (mean -24.3‰) and ice algal origin (mean -20.0‰). Stable carbon isotope compositions showed that most of the energy assimilated by zooplankton originated from pelagic primary production, but at times ice algae also contributed to zooplankton diets. Trophic level (TL) estimates of copepods ( Calanus glacialis and Calanus hyperboreus) and krill ( Thysanoessa inermis and Thysanoessa longicaudata), calculated based on ? 15N values, varied among stations from 1.3 to 2.7 and from 1.5 to 3.1, for respective taxa. TL in C. glacialis was significantly and inversely related to the depth-integrated phytoplankton chlorophyll a concentration. A similar trend, although weaker, also was observed for the other species. This relationship indicates that copepods graze primarily on the abundant autotrophic biomass during the peak bloom phase. At stations with lower chlorophyll a concentration, the TL of Calanus spp. was 1.0 higher, indicating omnivory outside the peak bloom phase in response to changed food availability. The majority of organic matter exported from the euphotic zone was derived from pelagic primary production, but at 3 of 11 stations within the marginal ice zone (MIZ), the ice algal signal dominated the isotope composition of sinking material. The ? 13C of settling organic matter was positively related to the vertical flux of particulate organic carbon, with maximum values around -21‰ during the peak bloom phase. Sedimentation of isotopically light copepod faecal pellets (mean ? 13C -25.4‰) was reflected in a depletion of 13C in the sinking material. The results illustrate tight pelagic-benthic coupling in the Barents Sea MIZ through vertical export of fresh phytodetritus during phytoplankton blooms and episodic export of ice algae.

Tamelander, Tobias; Reigstad, Marit; Hop, Haakon; Carroll, Michael L.; Wassmann, Paul

2008-10-01

35

Vertical Migrations and Feeding Rhythms of Mesozooplanktonic Organisms in the Rhône River Plume Area (North-west Mediterranean Sea)  

Science.gov (United States)

The vertical distribution of mesozooplankton was studied for a 24-h period at a fixed station. The most abundant taxa ( Clausocalanus spp., Paracalanus parvus, Temora stylifera, Centropages typicus, Acartia clausi, Microsetella spp., appendicularians, doliolids and chaetognaths), exhibited nocturnal upward migration into the chlorophyll-rich and low-salinity plume waters (surface to 1 m depth) while the cladocerans Podon polyphemoides and Penilia avirostris exhibited reverse migrations. Feeding activity (gut fluorescence) was investigated for T. stylifera, C. typicus and A. clausi . The chlorophyll gut contents of these copepods were highest at night in the plume waters (0 and 1 m). Nocturnal feeding and migration appeared synchronized for T. stylifera but not for C. typicus, which migrated later (middle of the night) than the other copepods in the upper layer. Respiration rates were measured and compared, on a carbon basis, to algal ingestion rates. The budgets suggested the energetic advantage of the nocturnal migration in the plume for C. typicus and T. stylifera which appeared able to produce significantly more organic matter in the plume waters than in the deeper waters. Acartia clausi could not balance its metabolic budget in both plume and marine waters suggesting a poor adaptation of this species to the algal trophic conditions. Metabolic O:N ratios measured for total zooplankton were lower in marine water (about 10) than in plume water (about 20) suggesting other trophic behaviour than herbivorous feeding (carnivorous, detritivorous …) for animals living under the plume.

Pagano, Marc; Gaudy, Raymond; Thibault, Delphine; Lochet, François

1993-09-01

36

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

37

Inverse vertical migration and feeding in glacier lanternfish (Benthosema glaciale)  

A bottom-mounted upward-facing 38-kHz echo sounder was deployed at ~400 m and cabled to shore in Masfjorden (~60 52?N, ~5 24?E), Norway. The scattering layers seen during autumn (September-October) 2008 were identified by trawling. Glacier lanternfish (Benthosema glaciale) were mainly distributed below ~200 m and displayed three different diel behavioral strategies: normal diel vertical migration (NDVM), inverse DVM (IDVM) and no DVM (NoDVM). The IDVM group was the focus of this study. It consisted of 2-year and older individuals migrating to ~200-270 m during the daytime, while descending back to deeper than ~270 m during the night. Stomach content analysis revealed increased feeding during the daytime on overwintering Calanus sp. We conclude that visually searching glacier lanternfish performing IDVM benefit from the faint daytime light in mid-waters when preying on overwintering Calanus sp. 2011 The Author(s).

Dypvik, Eivind

2011-11-08

38

Effects of diel vertical migration on ephippia production in Daphnia  

Directory of Open Access Journals (Sweden)

Full Text Available Fish presence in experimentally simulated temperature conditions (limno-towers led to diel vertical migration and resulted in a decrease of ephippia production in Daphnia pulicaria. Diel fluctuation of food, temperature and day length similar to those experienced by migrating Daphnia were tested in laboratory experiments with flow-through-systems. Daphnids were kept under these conditions for 15 days and the proportions of females producing an ephippium were determined. In addition, maturation time, survival to maturation, size of the first clutch and female dry weight (without eggs on day 15 were traced. The most important factor affecting ephippia production in migrating Daphnia was photoperiod change, and when mother and embryo are exposed to alternating light conditions, these are thought to have the effect on the mother of acting as a signal to stop ephippia production. Such effects might be explained by the different sensitiveness to light intensity in females carrying an embryo and an embryo itself in broods. Fish presence forced Daphnia to stay in low-light conditions during daytime hours, to avoid attacks by fish. The Daphnia were able to check light intensity constantly by short vertical jumps above a light-threshold that was confirmed experimentally in limno-towers. The dim conditions were possibly light enough for adults to check day length, but were too dark for embryos shaded by the mother's body. Food conditions played a relatively small role in the process, and no effects of temperature on ephippia production were found. As expected, food affected the size of the first clutch, and temperature controlled the time to maturation. Photoperiod had a marginally significant influence on the time to maturation in Daphnia. A hypothesis on the role of photoperiod as the key factor for Daphnia life cyclic recurrence and other seasonal adaptations is proposed.

Victor ALEKSEEV

2004-09-01

39

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

40

Vertical distribution and relative abundance of gelatinous zooplankton, in situ observations near the Mid-Atlantic Ridge  

Science.gov (United States)

Fourteen dives were conducted with the ROVs Aglantha and Bathysaurus to depths of 2335 m along the Mid-Atlantic Ridge (42?52'- 53?17'N). The most frequently observed gelatinous fauna in order of overall abundance included medusae, ctenophores, siphonophores, appendicularians, and tunicates. All of these animals, except the tunicates, occurred throughout the water column. Their relative abundances differed with depth and location. Identification to species was limited to easily recognized fauna because relatively few gelatinous animals were collected. Each group of gelatinous zooplankton tended to be most numerous in a region just south of the Charlie-Gibbs Fracture Zone. Medusae (mainly Aeginura grimaldii) were the most frequently encountered animals (up to 25 individuals per 100m3). On a vertical scale their abundance peaked from 550 to 800 m and these maxima were consistently within the SAIW and NACWe. In the NACW their densities were notably lower (up 2 individuals per 100m3) and the majority of the population was deeper, ranging from 800 to 1050 m. Ctenophores (mainly Bathocyroe fosteri) were most prominent (as many as 27 individuals per 100m3) in a zone from 300 to 600 m in the NACWe. Appendicularians (primarily oikopleurids) had a broader vertical distribution in all water masses, mainly from 450 to 1000 m. Up to 12 houses per 100m3 were noted in the NACWe, and these estimates are considered to be very conservative. Sorties near the sea floor (as deep as 2100 m) indicated these detritivores were a prominent component (up to 5 houses per 100m3) of the epibenthic macrozooplankton. Siphonophores (mostly calycophorans) reached densities of about 14 colonies per 100m3 in the NACWe and occurred mainly from 300 to 600 m, at most locations. Tunicates (salps and doliolids) were patchy in their distribution and infrequently observed. Salps were numerous (up to 3 solitary individuals per 100m3) at only one location (sta. 50) near the surface. Deep-living doliolids (up to 1 individual per 100m3) appeared from 400 to 500 m at this site and occasionally within the same depth range at most of the other stations.

Youngbluth, M.; Sørnes, T.; Hosia, A.; Stemmann, L.

2008-01-01

 
 
 
 
41

Vertical migration of 137Cs in the South Caspian soil  

International Nuclear Information System (INIS)

In order to study the vertical migration of anthropogenic 137Cs, soil inventories of this radionuclide were measured in two regions selected on the basis of a previous comprehensive survey in the northern Iranian province of Guilan located in the South Caspian region. Ten sampling stations were randomly chosen in these regions and split-level sampling was carried out to a depth of 30 cm. Sample analysis was performed using a HPGe detector system. In situ gamma measurements in both regions were also carried out with the aid of a portable germanium spectrometer. The experimental data were then compared with the solution of the convection-dispersion equation (CDE) with the proper initial and boundary conditions to evaluate initial deposition as well as transport parameter values. The solution, including the effects of both considered sources, i.e. global fallout and Chernobyl releases, fits the measured data well. The effective convection velocity and dispersion coefficients of 137Cs lie in the range of 0-0.25 cm.y-1 and 0.32-0.75 cm2.y-1, respectively, indicating a very slow migration rate in the area. Most of the deposited 137Cs still remained in the top 10-cm layer. Moreover, the fitted depth profiles were then employed to correct the surface activities of 137Cs estimated by in situ measurements. (authors)

42

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

43

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

44

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

45

Post-Feeding Thermotaxis and Daily Vertical Migration in a Larval Fish  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Many aquatic animals make daily vertical migrations, typically ascending into warm shallow strata for the night and descending to cooler, deeper layers of lakes or oceans for the day. Although some organisms may migrate to avoid predation(1?3) researchers have also suggested that daily migration is a thermoregulatory strategy allowing ectotherms to lower their metabolic rates in cold, deep waters, thus conserving energy(4,5). Tests of this hypothesis, however, have been equivocal(6?8). He...

Wurtsbaugh, Wayne A.; Neverman, D.

1988-01-01

46

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

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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-life, the 134Cs detected in our samples could only be derived from the FNPP1 accident. The highest 137Cs activity in zooplankton was the same order of magnitude as it was 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 the occurrence of many diel vertical migratory zooplankton. 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 correlate with the higher radiocesium activity in zooplankton. Activity concentrations of radiocesium in zooplankton might be influenced not only by the environmental radiocesium activity concentrations but also by other factors, which are still unknown.

M. Kitamura

2013-08-01

47

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

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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

48

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 (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

49

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

Science.gov (United States)

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 (turbulence, phytoplankton, bloom stage, and zooplankton abundance on the sinking particles' size spectra and POC flux to improve the understanding of the downward flux mechanisms in the 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

50

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  

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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

51

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  

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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

52

Zooplankton Distribution in Four Western Norwegian Fjords  

Science.gov (United States)

A multi-instrumental array constructed in the Laboratoire d'Ecologie du Plancton Marin in Villefranche sur mer, France, named the Underwater Video Profiler (UVP), was used to investigate the vertical distribution of zooplankton in four western Norwegian fjords in the summer 1996. Six distinct zoological groups were monitored. The fauna included: (a) small crustaceans (mainly copepods), (b) ctenophores (mainly lobates), (c) siphonophores (mainly physonects), (d) a scyphomedusa Periphylla periphylla, (e) chaetognaths and (f) appendicularians. The use of the non-disturbing video technique demonstrated that the distribution of large zooplankton is heterogeneous vertically and geographically. Furthermore, the abundance of non-migrating filter feeders in the deep basins of the fjords indicates that there is enough food (living and non-living particulate organic matter) to support their dietary needs. This adaptation may be considered as a strategy for survival in fjords. Specifically, living in dark, deep water reduces visual predation and population loss encountered in the upper layer due to advective processes.

Gorsky, G.; Flood, P. R.; Youngbluth, M.; Picheral, M.; Grisoni, J.-M.

2000-01-01

53

Estimated biomass of vertically migrating mesopelagic fish off New Zealand  

Science.gov (United States)

The regional distribution and abundance of mesopelagic fishes migrating from deeper waters into the epipelagic zone over the Chatham Rise, the Campbell Plateau and Snares Shelf to the east and south of New Zealand is unknown, despite mesopelagic fish being important prey for the hoki ( Macruronus novaezelandiae Hector 1871) that support New Zealand's largest fishery. We calculate the biomass of mesopelagic fish (primarily Maurolicus australis, Lampanyctodes hectoris and Symbolophorus boops) that migrate into the upper 200 m during the "night" using acoustic backscatter and new estimates of target strength. The Chatham Rise supported 665×10 3 t of mesopelagic fish in December 2000-January 2001, compared to 438×10 3 t of mesopelagic fish on the Campbell Plateau/Snares Shelf in November-December 2000 (the regional surveys are separated by ?1 month). There were strong regional differences in biomass. Mesopelagic fish biomass was greater in the Mernoo Bank region of the western Chatham Rise (18.2 t km -2) than on the eastern Chatham Rise (0.4 t km -2) . Highest area backscattering coefficients for the subantarctic region occurred on the Snares Shelf (13.4 t km -2) rather than on the Campbell Plateau (0.3 t km -2) . Mesopelagic fish biomass on the eastern Chatham Rise and Campbell Plateau were comparable to acoustic estimates from the mid-slope south of Tasmania (0.7 t km -2) . The biomass densities of mesopelagic fish on the Snares Shelf off New Zealand were of magnitude similar to the highest acoustic estimates from the Arabian Sea (13.1- 13.8 t km -2). The biomass measured in the Mernoo region off New Zealand ?1.3 times the highest acoustic estimates in the Arabian Sea. The regional distribution of high density patches of mesopelagic fish measured acoustically were spatially coincident with the largest trawl catch rates for hoki on the Chatham Rise. This suggests that hoki abundance is related to the spatial distribution of their food resources.

McClatchie, S.; Dunford, A.

2003-10-01

54

Zooplankton spatial distributions in coastal waters of the northern Arabian Sea, August, 1995  

Science.gov (United States)

The spatial distribution of zooplankton biomass was surveyed in coastal waters of the northern Arabian Sea during the 1995 Southwest Monsoon (August) on cruise MB 95-06 of the NOAA Ship Malcolm Baldrige. Vertical patterns of displacement volumes from a limited set of paired day-night MOCNESS tows suggest there was little diel vertical migration in the coastal waters off the southern Arabian Peninsula. Zooplankton biomass varied from 5.2 to 15.1 g dw m -2 (178-517 mM C m -2) in the upper 200-300 m of Omani coastal waters. Distributions of acoustic backscatter were mapped in eight daytime acoustic Doppler current profiler transects in coastal waters off Oman and Somalia. Several transects contained maxima in acoustic backscatter that coincided with cool, fresh surface features that were several tens of kilometers wide. Although there was considerable scatter in the relationship between acoustically determined biomass (ADB) of zooplankton and surface temperature, there was a trend of increased biomass in the cool surface temperatures of the Omani upwelling zone. Acoustic transects crossed two filaments that extended seaward from upwelling centers off Oman and Somalia. Estimated zooplankton ADB exported from the upwelling zones in the surface features was on the order of 300 kg dw s -1. The physical and biological characteristics of filaments maintain zooplankton associated with upwelling areas, such as Calanoides carinatus, as they are advected offshore from coastal upwelling zones.

Hitchcock, Gary L.; Lane, Peter; Smith, Sharon; Luo, Jiangang; Ortner, Peter B.

55

Will the application of Ammonium-Ferric-Hexacyano-Ferrate enhance the vertical migration of radiocaesium?  

International Nuclear Information System (INIS)

The consideration of a possible enhanced vertical migration of radiocaesium with the application of ammonium-ferric-hexacyano-ferrate (AFCF) as countermeasure, due to the colloidal nature of AFCF, made us set up a series of migration experiments. For the study two soil types were considered, which were either left unplanted or cultivated with ryegrass. Two AFCF concentrations, 1 and 10 g m-2, and an untreated control were applied. A simple diffusion-convection model was fitted to the data.The application of AFCF did not enhance the downward migration of radiocaesium in the profile. Moreover, for an unplanted sandy soil the application of AFCF significantly retarded the migration: 10 g AFCF m-2 decreased the convection term, V, from 0·78 to 0·42 cm a-1 and the diffusion component, D, from 0·21 to 0·09 cm2 a-1. For all other experimental conditions (unplanted loamy soil, ryegrass cultivated sandy and loamy soil), the application of AFCF did not have any effect on radiocaesium migration. Since AFCF does not promote the vertical migration of radiocaesium, enhanced groundwater contamination is improbable. (Copyright (c) 1998 Elsevier Science B.V., Amsterdam. All rights reserved.)

56

Vertical migrations of herring, Clupea harengus, larvae in relation to light and prey distribution  

DEFF Research Database (Denmark)

The influence of light and prey abundance on the vertical distribution of herring larvae was evaluated by three investigations made under calm weather conditions in the North Sea off the Scottish coast. The investigations took place at different time after hatching and the vertical distributions of three size groups of larvae (mean sizes 8,15 and 19 mm) were related to time of day and the vertical distribution of copepods. No migratory behaviour of copepods was observed but their vertical distribution differed between investigations. In the investigation on intermediate sized larvae, copepod density peaked at the pycnocline (40 m). Larvae concentrated at this depth at noon. At dawn and dusk larvae migrated towards the surface and the vertical distributions fluctuated semidielly. In the two other investigations, copepods were homogeneously distributed in the water column and after migration towards the surface at dawn larvae stayed in the upper water column during the day. The observations suggest that the daytime vertical distribution of larvae in calm weather is mainly determined by feeding conditions: the larvae move to depths were light is sufficient for feeding, and refinement within that zone is made according to a compromise between optimal light conditions for feeding and optimal prey densities.

Munk, Peter; KiØrboe, Thomas

1989-01-01

57

Light, temperature and nitrogen as interacting factors affecting diel vertical migrations of dinoflagellates in culture  

Energy Technology Data Exchange (ETDEWEB)

Diel vertial migrations of the marine dinoflagellates Gonyaulax polyedra Stein and Ceratium furca (Ehr.) Clap. et Lachm, were followed in a laboratory tube (2.02 m x 0.25 m) under a 12:12h light:dark cycle. The effects of temperature stratification, two levels of surface irradiance and nitrogen depletion on patterns of vertical migrations were examined. At temperatures between 22 to 26/sup 0/C with small temperature gradients, both species migrated at a rate of 0.7 to 1.0 mh/sup -1/. Steeper thermoclines (ca. 0.8/sup 0/C 0.1 m/sup -1/) with temperatures below ca. 20/sup 0/C caused a marked decrease in swimming speed which resulted in accumulations of cells in these thermocline regions. Under conditions of nutrient sufficiency both algae migrated into the surface layers at irradiance values of over 1000 ..mu..E m/sup -2/s/sup -1/. Increasing nitrogen depletion caused the downward migration of both algae to commence progressively earlier in the day and before the end of the light period. The earlier downward migrations enabled a more complete descent through the thermocline. Nitrogen depleted cells of Gonyaulax continued to undertake vertical migrations but avoided high irradiances thus forming sub-surface maxima at irradiance levels close to 150..mu..E m/sup -2/s/sup -1/. Ceratium cells which exhausted both inorganic nitrogen and phosphorus ceased to migrate accompanied by a large change in cellular fluorescence.

Heaney, S.I.; Eppley, R.W.

1981-01-01

58

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

59

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.

60

Vertical Migrations of a Deep-Sea Fish and Its Prey  

Digital Repository Infrastructure Vision for European Research (DRIVER)

It has been speculated that some deep-sea fishes can display large vertical migrations and likely doing so to explore the full suite of benthopelagic food resources, especially the pelagic organisms of the deep scattering layer (DSL). This would help explain the success of fishes residing at seamounts and the increased biodiversity found in these features of the open ocean. We combined active plus passive acoustic telemetry of blackspot seabream with in situ environmental and biological (back...

Afonso, Pedro; Mcginty, Niall; Grac?a, Gonc?alo; Fontes, Jorge; Ina?cio, Mo?nica; Totland, Atle; Menezes, Gui

2014-01-01

 
 
 
 
61

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

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

62

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

63

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

64

Diel variations of the bathymetric distribution of zooplankton groups and biomass in Cap-Ferret Canyon, France  

Science.gov (United States)

The bathymetric distribution, abundance and diel vertical migrations (DVM) of zooplankton were investigated along the axis of the Cap-Ferret Canyon (Bay of Biscay, French Atlantic coast) by a consecutive series of synchronous net hauls that sampled the whole water column (0-2000 m in depth) during a diel cycle. The distribution of appendicularians (maximum 189 individuals m -3), cladocerans (maximum 287 individuals m -3), copepods (copepods4 mm, maximum 13 individuals m -3), ostracods (maximum 8 individuals m -3), siphonophores (maximum >2 individuals m -3) and peracarids (maximum >600 individuals 1000 m -3) were analysed and represented by isoline diagrams. The biomass of total zooplankton (maximum 18419 ?g C m -3, 3780 ?g N m -3) and large copepods (>4 mm maximum 2256 ?g C m -3, 425 ?g N m -3) also were determined. Vertical migration was absent or affected only the epipelagic zone for appendicularians, cladocerans, small copepods and siphonophores. Average amplitude of vertical migration was about 400-500 m for ostracods, some hyperiids and mysids, and large copepods, which were often present in the epipelagic, mesopelagic, and bathypelagic zones. Large copepods can constitute more than 80% of the biomass corresponding to total zooplankton. They may play an important role in the active vertical transfer of carbon and nitrogen.

Maycas, Encarna Ribera; Bourdillon, André; Macquart-Moulin, Claude; Passelaigue, Françoise; Patriti, Gilbert

1999-10-01

65

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

66

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

67

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

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

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

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

70

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

71

Vertical migrations of a deep-sea fish and its prey.  

Science.gov (United States)

It has been speculated that some deep-sea fishes can display large vertical migrations and likely doing so to explore the full suite of benthopelagic food resources, especially the pelagic organisms of the deep scattering layer (DSL). This would help explain the success of fishes residing at seamounts and the increased biodiversity found in these features of the open ocean. We combined active plus passive acoustic telemetry of blackspot seabream with in situ environmental and biological (backscattering) data collection at a seamount to verify if its behaviour is dominated by vertical movements as a response to temporal changes in environmental conditions and pelagic prey availability. We found that seabream extensively migrate up and down the water column, that these patterns are cyclic both in short-term (tidal, diel) as well as long-term (seasonal) scales, and that they partially match the availability of potential DSL prey components. Furthermore, the emerging pattern points to a more complex spatial behaviour than previously anticipated, suggesting a seasonal switch in the diel behaviour mode (benthic vs. pelagic) of seabream, which may reflect an adaptation to differences in prey availability. This study is the first to document the fine scale three-dimensional behaviour of a deep-sea fish residing at seamounts. PMID:24859231

Afonso, Pedro; McGinty, Niall; Graça, Gonçalo; Fontes, Jorge; Inácio, Mónica; Totland, Atle; Menezes, Gui

2014-01-01

72

Vertical distribution and migration of global fallout Pu in forest soils in southwestern China.  

Science.gov (United States)

Soil samples collected in southwestern China were analyzed for Pu isotopes. The (240)Pu/(239)Pu atom ratios were around 0.18, which indicated the dominant source of global fallout. Consistent sub-surface maximums followed by exponential decline of (239+240)Pu activities in the soil cores were observed. Most of the Pu has still remained in the 0-10 cm layers since its deposition. Convection velocities and dispersion coefficients for Pu migration in the soils were estimated by the convection-dispersion equation (CDE) model. The effective convection velocities and effective dispersion coefficients ranged from 0.05 to 0.11 cm/y and from 0.06 to 0.29 cm(2)/y, respectively. Other factors that control the vertical migration of Pu in soil besides precipitation, soil particle size distribution and organic matter were suggested. Long-term migration behaviors of Pu in the soils were simulated. The results provide the Pu background baseline for further environmental monitoring and source identification of non-global fallout Pu inputs in the future. PMID:24963802

Bu, Wenting; Zheng, Jian; Guo, Qiuju; Uchida, Shigeo

2014-10-01

73

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

74

Acceleration of vertical migration of corneal epithelial cells in albino rats during chronic immobilization stress  

International Nuclear Information System (INIS)

This paper studies the effect of chronic immobilization stress on the kinetics of corneal epithelial cells from the basal layer into higher layers. Experiments were carried out on 49 male rats. The animals were given an intraperitoneal injection of tritium-thymidine and an additional application of 5 microCi of tritium-thymidine was made to its surface because the cornea has no blood supply. The animals were killed and the cornea removed for investigation. Values of the index of labeled nuclei and intensity of thymidine labeling, characterizing DNA synthesis in the corneas of the control and experimental animals showed no significant change compared with their values in a pervious series of experiments. Chronic exposure to stress increased the velocity of vertical migration of the cells from the basal layer toward the outer layers of the cornea

75

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

76

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

77

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

International Nuclear Information System (INIS)

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 1x105 C. parvum oocysts and 1x105 carboxylated latex microspheres (4.5 ?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 med through a uniform unsaturated sand medium experiencing high rates of transient water infiltration. (author)

78

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

79

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

80

VERTICAL MIGRATION OF RADIONUCLIDES IN THE VICINITY OF THE CHERNOBYL CONFINEMENT SHELTER  

Energy Technology Data Exchange (ETDEWEB)

Studies on vertical migration of Chernobyl-origin radionuclides in the 5-km zone of the Chernobyl Nuclear Power Plant (ChNPP) in the area of the Red Forest experimental site were completed. Measurements were made by gamma spectrometric methods using high purity germanium (HPGe) detectors with beryllium windows. Alpha-emitting isotopes of plutonium were determined by the measurement of the x-rays from their uranium progeny. The presence of {sup 60}Co, {sup 134,137}Cs, {sup 154,155}Eu, and {sup 241}Am in all soil layers down to a depth of 30 cm was observed. The presence of {sup 137}Cs and {sup 241}Am were noted in the area containing automorphous soils to a depth of 60 cm. In addition, the upper soil layers at the test site were found to contain {sup 243}Am and {sup 243}Cm. Over the past ten years, the {sup 241}Am/{sup 137}Cs ratio in soil at the experimental site has increased by a factor of 3.4, nearly twice as much as would be predicted based solely on radioactive decay. This may be due to 'fresh' fallout emanating from the ChNPP Confinement Shelter.

Farfan, E.; Jannik, T.; Marra, J.

2011-10-01

 
 
 
 
81

Vertical Migration Of Radionuclides In The Vicinity Of The Chernobyl Confinement Shelter  

International Nuclear Information System (INIS)

Studies on vertical migration of Chernobyl-origin radionuclides in the 5-km zone of the Chernobyl Nuclear Power Plant (ChNPP) in the area of the Red Forest experimental site were completed. Measurements were made by gamma spectrometric methods using high purity germanium (HPGe) detectors with beryllium windows. Alpha-emitting isotopes of plutonium were determined by the measurement of the x-rays from their uranium progeny. The presence of 60Co, 134,137Cs, 154,155Eu, and 241Am in all soil layers down to a depth of 30 cm was observed. The presence of 137Cs and 241Am were noted in the area containing automorphous soils to a depth of 60 cm. In addition, the upper soil layers at the test site were found to contain 243Am and 243Cm. Over the past ten years, the 241Am/137Cs ratio in soil at the experimental site has increased by a factor of 3.4, nearly twice as much as would be predicted based solely on radioactive decay. This may be due to 'fresh' fallout emanating from the ChNPP Confinement Shelter.

82

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

83

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

84

Zooplankton from Lake Magelungen, Central Sweden 1960-1963  

Energy Technology Data Exchange (ETDEWEB)

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

Almquist, Elisabeth

1970-11-15

85

Diel vertical migration of larval and early-juvenile burbot optimises survival and growth in a deep, pre-alpine lake  

Digital Repository Infrastructure Vision for European Research (DRIVER)

1. Burbot larvae (Lota lota) perform a substantial diel vertical migration (DVM) of increasing amplitude in the pelagic zone during a 3-month period before migrating to the littoral zone as early-juveniles. We hypothesised that feeding in the warm surface layers at night and then spending the day in cold water below the thermocline reduces metabolic costs and earns burbot larvae an energetic advantage. 2. To test our hypothesis, we mimicked the temperature conditions experienced by vertically...

Donner, Michael; Eckmann, Reiner

2011-01-01

86

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

87

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

88

Vertical migration of Chernobyl-derived radiocesium in Bavarian grassland soils  

International Nuclear Information System (INIS)

Although the behavior of radiocesium in terrestrial ecosystems has been studied in detail, as recently reviewed by Avery, long-term migration data on Chernobyl-derived radiocesium in grassland soils are scarce, especially in typical soils of Western Europe. The objective of the present investigation was therefore to determine the migration of Chernobyl-derived radiocesium within the root zone (ca. 0-15 cm) of ten undisturbed Bavarian grassland soils. To obtain information on the large-scale spatial variability of the cesium migration the sampling sites were selected randomly within an area of about 100x200 km. The migration of radiocesium was characterized by the corresponding residence half-times in the various soil layers at each site. (orig./AJ)

89

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

90

Evidence of vertical migration in the Ipanema bat Pygoderma bilabiatum (Chiroptera: Phyllostomidae: Stenodermatinae  

Directory of Open Access Journals (Sweden)

Full Text Available Migration is defined as a seasonal and cyclic population movement observed in all animal classes and studied mainly in vertebrates. A considerable part of the knowledge on migration comes from birds, for which migration is an important aspect of their biology. In the case of bats, females usually migrate larger distances than males in some species. The present study analyzes the seasonal occurrence of Pygoderma bilabiatum (Wagner, 1843 at different elevations, in order to test for a pattern that evidences migration, using data from the states of Espírito Santo, Minas Gerais, Rio de Janeiro, São Paulo, Paraná, Santa Catarina, and Rio Grande do Sul, Brazil. A total of 529 specimens of P. bilabiatum were captured. Pygoderma bilabiatum seems to be more frequent at intermediate and high elevations (over 80% of all captures were made above 250 m a.s.l. and at latitudes above 22°S, where rainfall is high (over 1,500 mm and temperatures are mild (16-23°C. Sex ratio varied with elevation; it was skewed towards males at lower elevations (N = 9, r² = 0.60, F = 12.311, p = 0.008, Sex ratio = 0.0004*elevation + 0.976, though females predominated at all altitudinal bands and in all states analyzed.

Carlos E. L. Esbérard

2011-12-01

91

Zooplankton body composition  

DEFF Research Database (Denmark)

I compiled literature on zooplankton body composition, from protozoans to gelatinous plankton, and report allometric relations and average body composition. Zooplankton segregate into gelatinous and non-gelatinous forms, with few intermediate taxa (chaetognaths, polychaetes, and pteropods). In most groups body composition is size independent. Exceptions are protozoans, chaetognaths, and pteropods, where larger individuals become increasingly watery. I speculate about the dichotomy in body composition and argue that differences in feeding mechanisms and predator avoidance strategies favor either a watery or a condensed body form, and that in the intermediate taxa the moderately elevated water content is related to buoyancy control and ambush feeding

KiØrboe, Thomas

2013-01-01

92

Evidence of vertical migration in the Ipanema bat Pygoderma bilabiatum (Chiroptera: Phyllostomidae: Stenodermatinae)  

Scientific Electronic Library Online (English)

Full Text Available SciELO Brazil | Language: English Abstract in english Migration is defined as a seasonal and cyclic population movement observed in all animal classes and studied mainly in vertebrates. A considerable part of the knowledge on migration comes from birds, for which migration is an important aspect of their biology. In the case of bats, females usually mi [...] grate larger distances than males in some species. The present study analyzes the seasonal occurrence of Pygoderma bilabiatum (Wagner, 1843) at different elevations, in order to test for a pattern that evidences migration, using data from the states of Espírito Santo, Minas Gerais, Rio de Janeiro, São Paulo, Paraná, Santa Catarina, and Rio Grande do Sul, Brazil. A total of 529 specimens of P. bilabiatum were captured. Pygoderma bilabiatum seems to be more frequent at intermediate and high elevations (over 80% of all captures were made above 250 m a.s.l.) and at latitudes above 22°S, where rainfall is high (over 1,500 mm) and temperatures are mild (16-23°C). Sex ratio varied with elevation; it was skewed towards males at lower elevations (N = 9, r² = 0.60, F = 12.311, p = 0.008, Sex ratio = 0.0004*elevation + 0.976), though females predominated at all altitudinal bands and in all states analyzed.

Carlos E. L., Esbérard; Isaac P. de, Lima; Pedro H., Nobre; Sérgio L., Althoff; Tássia, Jordão-Nogueira; Daniela, Dias; Fernando, Carvalho; Marta E., Fabián; Margareth L., Sekiama; Artur Stanke, Sobrinho.

2011-12-01

93

Can vertical migrations of dinoflagellates explain observed bioluminescence patterns during an upwelling event in Monterey Bay, California?  

Science.gov (United States)

Extensive AUVs surveys showed that during the development of upwelling, bioluminescent dinoflagellates from the northern part of the Monterey Bay, California (called the upwelling shadow area), were able to avoid advection by southward flowing currents along the entrance to the Bay, while non-bioluminescent phytoplankton were advected by currents. It is known that vertical swimming of dinoflagellates to deeper layers helps them avoid losses due to advection. In the present paper, we investigate if modeling dinoflagellates' vertical swimming can explain the observed dinoflagellates' ability to avoid advection during the upwelling development. The dynamics of a dinoflagellate population is modeled with the tracer model with introduced vertical swimming velocity. Three swimming behaviors are considered: sinking, swimming to the target depth and diel vertical migration. Velocities in all swimming cases are considered in the ranges of documented velocities for the observed dinoflagellates species during the upwelling development in the Monterey Bay. Our modeling confirmed that observed bioluminescent dinoflagellates' avoidance of advection during the upwelling development can be explained by their vertical swimming ability. In the case of swimming with 20 m/day (which is half of observed maximum swimming velocity), around 40% of dinoflagellates population from the northern part of the Bay were advected along the entrance to the Bay in comparison to the case without swimming. This is in agreement with the ratio of around 45% of observed mean bioluminescence intensity at the entrance to the Bay to the observed mean intensity in the northern part of the Bay. This mechanism also helps explain the general persistence of dinoflagellates in this part of the coastline.

Shulman, Igor; Penta, Bradley; Moline, Mark A.; Haddock, Steven H. D.; Anderson, Stephanie; Oliver, Matthew J.; Sakalaukus, Peter

2012-01-01

94

Seasonal migration, vertical activity and winter temperature experience of Greenland halibut Reinhardtius hippoglossoides (Walbaum) in West Greenland waters  

DEFF Research Database (Denmark)

The deep-water flatfish Greenland halibut Reinhardtius hippoglossoides (Walbaum) is common along the West Greenland coast. In the northwestern fjords, Greenland halibut is an important socio-economic resource for the Greenland community, but due to the deep and partly ice-covered environment, very little is known about its behavior and habitat characteristics. We tagged adult Greenland halibut in the waters off Ilulissat with electronic data storage tags that collected information on depth, temperature, and time. Although clear differences between individuals in migration and vertical behavior were present, we discovered a consistent seasonal migration from the relatively shallow-water Disko Bay area into the deep waters of the Ilulissat Icefjord, where the fish resided in the winter months before returning to Disko Bay. Vertical activity was pronounced at both locations, with fish covering vertical distances of up to 100 m within 15 min. During the winter months, the fish experienced temperatures between ca.0 and 4°C, with most experiencing temperatures of 2 to 3°C. Irrespective of year and quarter of the year, the fish experienced warmer water and a broader range of temperatures when resident in Disko Bay (mean range 2.6°C) than when resident in the ice fjord (mean range 1.4°C). Using the tagged halibut as a 'live tool,' we show that parts of the ice fjord are hundreds of meters deeper than previously thought. We also document the first seawater temperature measurements made beneath the Jakobshavn Isbræ outlet glacier, revealing a positive relationship between depth and temperature for the upper 600 m and a between-year variation in temperatures beneath the ice sheet in 2001, 2002, and 2003

Boje, Jesper; Neuenfeldt, Stefan

2014-01-01

95

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.

96

LONG-TERM DYNAMICS OF RADIONUCLIDE VERTICAL MIGRATION IN SOILS OF THE CHERNOBYL NUCLEAR POWER PLANT EXCLUSION ZONE  

Energy Technology Data Exchange (ETDEWEB)

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 {sup 137}Cs, {sup 90}Sr, and {sup 239,240}Pu in the soil profile, as well as their ecological half-time of the radionuclide residence (T{sub 1/2}{sup ecol}) 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: {sup 90}Sr > {sup 137}Cs {ge} {sup 239,240}Pu. It was found that the {sup 137}Cs absolute T{sub 1/2}{sup ecol} values are 3-7 times higher than its radioactive decay half-life value. Therefore, changes in the exposure dose resulting from the soil deposited {sup 137}Cs now depend only on its radioactive decay. The {sup 90}Sr T{sub 1/2}{sup ecol} 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 {sup 90}Sr forms that grows over time due to destruction of the fuel particles.

Farfan, E

2009-11-19

97

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

Digital Repository Infrastructure Vision for European Research (DRIVER)

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

98

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

99

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

100

Abundancia estacional y distribución vertical del zooplancton gelatinoso carnívoro en una área de surgencia en el norte del Sistema de la Corriente de Humboldt Seasonal abundance and vertical distribution of the carnivorous gelatinous zooplankton in an upwelling area of the northern Humboldt Current System  

Directory of Open Access Journals (Sweden)

Full Text Available Se analizó la abundancia estacional y distribución vertical del zooplancton gelatinoso colectado en cuatro cruceros efectuados frente a la bahía de Mejillones. En esta zona se identificaron 44 especies macroplanctónicas distribuidas en 23 de sifonóforos, 17 de hidromedusas, y 4 de ctenóforos, de las cuales 8 especies, Sphaeronectes irregularis, Rhizophysa eysenhardti, Amphogona apicata, Proboscidactyla stellata, Sarsia coccometra, Pleurobrachia bachei, Thalassocalyce inconstans y Velamen parallelum, se registran por primera vez para el Sistema de la Corriente de Humboldt. Se determinó un incremento de abundancia en primavera y verano, con densas agregaciones (> 2.600 ind·100 m-3 en octubre de Aglaura hemistoma, Solmundella bitentaculata, Muggiaea atlantica y Pleurobrachia bachei, y en febrero de Obelia spp. Las mayores densidades se determinaron en la estación más costera y en el frente oceánico, mientras que en la estación oceánica se registró una fuerte disminución de abundancia. La mayoría de las especies dominantes se encontraron en los primeros 100 m de la columna de agua, con una mayor concentración de ejemplares en los primeros 25 o 50 m de profundidad. Esta distribución vertical estaría limitada por la capa de mínimo oxígeno (The seasonal abundance and vertical distribution of gelatinous zooplankton collected during four cruises off Mejillones bay were analyzed. In this area we identified 44 species of macroplankton distributed in 23 siphonophores, 17 hydromedusae, and 4 ctenophores. Eight species, Sphaeronectes irregularis, Rhizophysa eysenhardti, Amphogona apicata, Proboscidactyla stellata, Sarsia coccometra, Pleurobrachia bachei, Thalassocalyce inconstans and Velamen parallelum, are the first records in the Humboldt Current System. The seasonal distribution showed an increase in abundance in spring and summer, with the highest aggregations (> 2600 ind·100 m-3 of Aglaura hemistoma, Solmundella bitentaculata, Muggiaea atlantica and Pleurobrachia bachei in October and Obelia spp. in February. The highest densities were observed in the coastal station and in the oceanic front, while the oceanic station was characterized by a strong decrease in abundance. The vertical distribution showed that the most dominant species were founded in the first 100 m of the water column, with a higher concentration of organisms in the first 25 or 50 m of depth. This vertical distribution could be limited by presence of a minimum dissolved oxygen layer (< 1 ml·L-1 in shallow waters (30-50 m during de upwelling events

Sergio Palma

2004-01-01

 
 
 
 
101

Abundance, biomass, vertical migration and estimated development rate of the copepod Calanus finmarchicus in the southern Gulf of Maine during late spring  

Science.gov (United States)

Abundance, biomass, diel vertical migration and estimated in situ development in the copepod Calanus finmarchicus were investigated during late spring in 1988 and 1989 in the southern Gulf of Maine. This region is an important feeding ground for the planktivorous right whale, Eubalaena glacialis. The 1988 study took place during the declining spring bloom, with phytoplankton biomass variable, but relatively high. The 1989 study occurred after seasonal stratification, and phytoplankton biomass was low. During the 1988 cruise the dominant stage in C. finmarchicus shifted from C1-C2 to C4-C5. Stage durations during 1988 (4.0 days for C3 and 6.6 days for C4), estimated from the temporal change in stage distribution, were similar to maximal values observed in the laboratory. In contrast, during 1989 stages C4 and C5 were dominant throughout the study period and development rate was slow (estimated C4 stage duration about 24 days). Diel vertical migration patterns changed, from an absence of migration at the first two 1988 stations where younger stages predominated (C1-C3), to a very strong diel vertical migration at the later 1988 stations where stages C3-C3 predominated. This was not a simple ontogenetic change in migratory behavior since all copepodite stages at each station showed similar patterns. During 1989 dense aggregations of C. finmarchicus remained in the surface layer both day and night, and no diel vertical migration was observed. A small, nonmigratory population of late-stage C. finmarchicus was found at depth. Individual body size of these copepods was considerably greater than those found at the surface. Differences in development rate between years reflect differences in the food environment, brought about by seasonal hydrographic changes and the development of more intense stratification. Diel vertical migration patterns, however, did not show a simple relation with food availability, and it is suggested that predation may play an important role in regulating the behavior of the copepods.

Durbin, Edward G.; Gilman, Sharon L.; Campbell, Robert G.; Durbin, Ann G.

102

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

103

A new thermo-hydrodynamic method for estimating convective heat flux associated with vertical fluid migration.  

Science.gov (United States)

Ample field observations in areas of known oil and gas deposists reveal an existence of excess temperature anomalies associated with the hydrocarbon-bearing structures. These observations are explained in terms of upward migration of heated fluids. In this case there is a deviation from a linear temperature distribution with depth due to a convective component of the heat flux. We propose a new method based on in situ measurements of the thermal field that allows one to take into account both conductive and convective components of the heat flow. In addition to the usual measurements of temperature, we determine the the curvature of the geothermograms, which characterizes the degree of deviation of the heat transfer from a conductive regime. Correspondingly, in addition to the commonly used geothermal gradient, we introduce new parameters, such as the radius of curvature of the geotherms (R), the coefficient of curvature of the geotherms (K), the Knudsen criterion (Kn), and parameter F. We present analytic expressions for the determination of these parameters, and evaluate these parameters for several natural objects. We demonstrate the usefulness of the proposed method for 1) forecasts of the presence of the deep-seated hydrocarbon deposits; 2) estimates of the abnornally elevated gas content in the deep-seated coal deposits, and determination of zones with high risk of methane bursts; 3) studies of the hydro-geothermal conditions of the geothermal areas; 4) determination and localization of leaks along the buried industrial pipelines. We present examples illustrating the application of our method for the abovementioned tasks.

Fialko, O.; Kovalchuk, L.

2002-12-01

104

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

105

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

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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

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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

Paul, Kaufmann; Luís Gustavo Moraes, Prado; Vinícius Volpe D' Angieri, Basile; Francesco, Mazzarone; Ivo, Pitanguy.

2011-09-01

107

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.

108

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

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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

109

Research into vertical radionuclide migration at the R and D center of radioenvironmental studies on field test sites, National Academy of Sciences of Ukraine  

International Nuclear Information System (INIS)

Detection of Chernobyl radionuclides in groundwater and water bearing rocks at a relatively great depth has spurred the researchers to search for the mechanisms responsible for fast vertical migration of different pollutants from the surface downwards. By using as tracers the radionuclides that entered the environment as a result of Chernobyl accident, the authors have made an attempt to look into the regularities of pollutant migration in some specific landscapes, i.e. in water sink morphosculptures, hypothetical dislocations, and also within the depression cones of major water intakes

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The influence of light on the diel vertical migration of young-of-the-year burbot Lota lota in Lake Constance  

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The diel vertical distribution of young-of-the-year (YOY) burbot Lota lota in the pelagic zone of Lake Constance was compared to light intensity at the surface and to the light intensity at their mean depth. Lota lota larvae inhabited the pelagic zone of Lake Constance from the beginning of May until the end of August. From early June, after the stratification of the water column, fish performed diel vertical migrations (DVM) between the hypolimnion and epilimnion. The amplitude of DVM inc...

Probst, Wolfgang Nikolaus; Eckmann, Reiner

2009-01-01

111

A modeling study to explore on-shelf transport of oceanic zooplankton in the Eastern Bering Sea  

Science.gov (United States)

The Eastern Bering Sea shelf is divided into distinct hydrographic domains by structural fronts. Despite frontal obstructions to cross-shelf transport, each year large oceanic copepods—primarily Neocalanus spp.—are known to dominate the biomass of the outer-shelf zooplankton communities, and in some years are advected into the middle-shelf domain. Using ROMS (the Regional Ocean Modeling System), coupled with a float tracking model designed to represent ontogenetic vertical migration behavior of Neocalanus, we explored the mechanisms, timing, and location of the transport of oceanic zooplankton onto the eastern Bering Sea shelf from overwintering sources along the Gulf of Alaska and Bering Sea shelf breaks, under a variety of environmental conditions. Our float tracking experiments suggest that the timing of on-shelf transport and the distribution of oceanic zooplankton on the shelf can vary substantially between one year and another. The Bering, Pribilof, and Zhemchug Canyons and Cape Navarin were all regions of elevated on-shelf float transport. Wind direction was the primary factor controlling inter-annual variability in the timing, amount, and location of the on-shelf transport of our Neocalanus floats. Float transport across the northern and southern shelves responded in opposite directions to inter-annual differences in wind forcing: southeasterly wind enhanced on-shelf transport of the Neocalanus floats along the southern shelf but suppressed on-shelf transport over the northern shelf. Conversely, northwesterly wind suppressed on-shelf zooplankton transport onto the southern shelf but promoted enhanced transport around Cape Navarin on the northern shelf. Transport of the Neocalanus floats onto the shelf can be very episodic, reflecting the short duration of winds that promote on-shelf transport. Relatively short (days to weeks) periods of southeasterly wind between March and April significantly impacted the number of floats transported onto the shelf. The relative importance of different source areas to supplying oceanic zooplankton to the Bering Sea shelf does not appear to vary much from year to year. Our model results suggest that the Neocalanus found on the southern shelf most likely originate from overwintering sites in the Alaska Stream or the Eastern Bering Sea shelf break south of the Pribilof Islands, while Neocalanus found on the northern shelf most likely originate from sites north of the Pribilof Islands.

Gibson, G. A.; Coyle, K. O.; Hedstrom, K.; Curchitser, E. N.

2013-07-01

112

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?  

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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

113

Start feeding of salmonids with lake zooplankton  

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Fry and small fingerlings of Atlantic salmon (Salmo salar) and rainbow trout (Salmo gairdneri) were fed with lake zooplankton in small fine-meshed cages. The zooplankton were pumped into cages. Growth rates and food selection are discussed.

Holm, Jens Christian; Hansen, Tom; Møller, Dag

1982-01-01

114

Stable isotope and signature fatty acid analyses suggest reef manta rays feed on demersal zooplankton.  

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Assessing the trophic role and interaction of an animal is key to understanding its general ecology and dynamics. Conventional techniques used to elucidate diet, such as stomach content analysis, are not suitable for large threatened marine species. Non-lethal sampling combined with biochemical methods provides a practical alternative for investigating the feeding ecology of these species. Stable isotope and signature fatty acid analyses of muscle tissue were used for the first time to examine assimilated diet of the reef manta ray Manta alfredi, and were compared with different zooplankton functional groups (i.e. near-surface zooplankton collected during manta ray feeding events and non-feeding periods, epipelagic zooplankton, demersal zooplankton and several different zooplankton taxa). Stable isotope ?(15)N values confirmed that the reef manta ray is a secondary consumer. This species had relatively high levels of docosahexaenoic acid (DHA) indicating a flagellate-based food source in the diet, which likely reflects feeding on DHA-rich near-surface and epipelagic zooplankton. However, high levels of ?6 polyunsaturated fatty acids and slightly enriched ?(13)C values in reef manta ray tissue suggest that they do not feed solely on pelagic zooplankton, but rather obtain part of their diet from another origin. The closest match was with demersal zooplankton, suggesting it is an important component of the reef manta ray diet. The ability to feed on demersal zooplankton is likely linked to the horizontal and vertical movement patterns of this giant planktivore. These new insights into the habitat use and feeding ecology of the reef manta ray will assist in the effective evaluation of its conservation needs. PMID:24167562

Couturier, Lydie I E; Rohner, Christoph A; Richardson, Anthony J; Marshall, Andrea D; Jaine, Fabrice R A; Bennett, Michael B; Townsend, Kathy A; Weeks, Scarla J; Nichols, Peter D

2013-01-01

115

Vertical migration of 60Co, 137Cs and 226Ra in agricultural soils as observed in lysimeters under crop rotation.  

Science.gov (United States)

In most studies quantifying the migration parameters - apparent migration velocity and apparent dispersion coefficient - of radionuclides in the soil by model calculations, these parameters are determined for undisturbed soils. For soils disturbed by ploughing, however, no such data are available in the literature. Therefore, in the present study, the migration parameters of (137)Cs, (60)Co and (226)Ra were estimated for ploughed soils by means of a convection-dispersion model. The depth distributions of the radionuclides were determined in four lysimeters (area: 1m(2), depth of soil monolith: 0.75m) filled with artificially contaminated soils of different types in July 1990. The lysimeters were cropped with agricultural plants. The soil in each lysimeter was ploughed manually once a year until 1996 (plough depth 20cm). In July 1999, soil samples were collected from three pits in each lysimeter. The depth distributions of all radionuclides proved to be very similar in each soil pit. The spatial variability of the depth distributions of a given radionuclide within the lysimeters was about the same as their variability between the four lysimeters. Evaluation of the migration parameters revealed that the convective transport of the radionuclides was always rather small or even zero, while the dispersive transport caused a "melting" process of the initially sharp activity edge at the lower border of the Ap horizon. These results are explained by the high evapotranspiration (80-90% of the total precipitation plus irrigation) and the small amounts of seepage water during the observation period of 9 years. PMID:15603900

Shinonaga, T; Schimmack, W; Gerzabek, M H

2005-01-01

116

Vertical migration of 60Co, 137Cs and 226Ra in agricultural soils as observed in lysimeters under crop rotation  

International Nuclear Information System (INIS)

In most studies quantifying the migration parameters - apparent migration velocity and apparent dispersion coefficient - of radionuclides in the soil by model calculations, these parameters are determined for undisturbed soils. For soils disturbed by ploughing, however, no such data are available in the literature. Therefore, in the present study, the migration parameters of 137Cs, 60Co and 226Ra were estimated for ploughed soils by means of a convection-dispersion model. The depth distributions of the radionuclides were determined in four lysimeters (area: 1 m2, depth of soil monolith: 0.75 m) filled with artificially contaminated soils of different types in July 1990. The lysimeters were cropped with agricultural plants. The soil in each lysimeter was ploughed manually once a year until 1996 (plough depth 20 cm). In July 1999, soil samples were collected from three pits in each lysimeter. The depth distributions of all radionuclides proved to be very similar in each soil pit. The spatial variability of the depth distributions of a given radionuclide within the lysimeters was about the same as their variability between the four lysimeters. Evaluation of the migration parameters revealed that the convective transport of the radionuclides was always rather small or even zero, while the dispersive transport caused a 'melting' process of the initially sharp activity edge at the lower border of the Ap horizon. These results are rder of the Ap horizon. These results are explained by the high evapotranspiration (80-90% of the total precipitation plus irrigation) and the small amounts of seepage water during the observation period of 9 years

117

Zooplankton of Munzur River (Tunceli, Turkey  

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Full Text Available The zooplankton fauna of Munzur river was studied between June 2009 to May 2010. A total of 11 taxa were recorded. Out of these 8 species belonging to rotifera 2 to Cladocera 1 to Copepoda were recorded. The most species of zooplankton were found in June and July (11 species while the minimum species were found in January (1 specie. Most of the zooplankton species were belonged to Rotifera. Also, it was found that the most common family in the study area was belonged to Brachionidae (4 species. All zooplankton species identified are considered as new record for Munzur river.

Serap Saler

2011-01-01

118

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)

119

Vertical random variability of the distribution coefficient in the soil and its effect on the migration of fallout radionuclides  

International Nuclear Information System (INIS)

In the field, the distribution coefficient, Kd, for the sorption of a radionuclide by the soil cannot be expected to be constant. Even in a well defined soil horizon, Kd will vary stochastically in horizontal as well as in vertical direction around a mean value. The horizontal random variability of Kd produce a pronounced tailing effect in the concentration depth profile of a fallout radionuclide, much less is known on the corresponding effect of the vertical random variability. To analyze this effect theoretically, the classical convection-dispersion model in combination with the random-walk particle method was applied. The concentration depth profile of a radionuclide was calculated one year after deposition assuming constant values of the pore water velocity, the diffusion/dispersion coefficient, and the distribution coefficient (Kd = 100 cm3 x g-1) and exhibiting a vertical variability for Kd according to a log-normal distribution with a geometric mean of 100 cm3 x g-1 and a coefficient of variation of CV 0.53. The results show that these two concentration depth profiles are only slightly different, the location of the peak is shifted somewhat upwards, and the dispersion of the concentration depth profile is slightly larger. A substantial tailing effect of the concentration depth profile is not perceivable. Especially with respect to the location of the peak, a very spect to the location of the peak, a very good approximation of the concentration depth profile is obtained if the arithmetic mean of the Kd-values (Kd = 113 cm3 x g-1) and a slightly increased dispersion coefficient are used in the analytical solution of the classical convection-dispersion equation with constant Kd. The evaluation of the observed concentration depth profile with the analytical solution of the classical convection-dispersion equation with constant parameters will, within the usual experimental limits, hardly reveal the presence of a log-normal random distribution of Kd in the vertical direction in contrast to the horizontal direction. (author)

120

The influence of light on the diel vertical migration of young-of-the-year burbot Lota lota in Lake Constance.  

Science.gov (United States)

The diel vertical distribution of young-of-the-year (YOY) burbot Lota lota in the pelagic zone of Lake Constance was compared to light intensity at the surface and to the light intensity at their mean depth. Lota lota larvae inhabited the pelagic zone of Lake Constance from the beginning of May until the end of August. From early June, after the stratification of the water column, fish performed diel vertical migrations (DVM) between the hypolimnion and epilimnion. The amplitude of DVM increased constantly during the summer and reached 70 m by the end of August. Lota lota started their ascent to the surface after sunset and descended into the hypolimnion after sunrise. As the YOY fish grew from May to August, they experienced decreasing diel maximum light intensities: in May and early June L. lota spent the day at light intensities >40 W m(-2), but they never experienced light intensities >0.1 W m(-2) after the end of June. From this time, L. lota experienced the brightest light intensities during dusk and dawn, suggesting feeding opportunities at crepuscular hours. The present study implies, that YOY L. lota in the pelagic zone of Lake Constance increased their DVM amplitude during the summer to counteract a perceived predation risk related to body size and pigmentation. PMID:20735530

Probst, W N; Eckmann, R

2009-01-01

 
 
 
 
121

Water pulse migration through semi-infinite vertical unsaturated porous column with special relative-permeability functions: Exact solutions  

Science.gov (United States)

The paper presents certain exact solutions describing the vertical movement of a water pulse through a semi-infinite unsaturated porous column. The saturation-based form of the Richards' equation is used with special power law relative-permeability functions. Both capillary and gravity effects are taken into account. Three exact solutions are derived corresponding to three relative-permeability functions, linear, quadratic and cubic. The Richards' equation is nonlinear for the three cases. The solutions are obtained by applying a general similarity transformation. They are explicit in space and time variables and do not contain any approximation. They describe the evolution of the water saturation in the vertical column and they can be used to predict the post-infiltration movement of a finite quantity of water. Exact expressions of the masses of water leaving a given depth are also derived for the three cases. We analyze the effect of relative-permeability and capillary pressure. The proposed solutions are also useful for checking numerical schemes. One of the exact solutions is used to validate numerical solution obtained from an arbitrary initial condition. Results show that the numerical solution converges to the exact solution for large times.

Hayek, Mohamed

2014-09-01

122

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

123

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

124

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

125

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

International Nuclear Information System (INIS)

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 ?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 wastion 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 MnIV reduction resulted in the release of both MnII and UVI into the truly dissolved phase. - Research Highlights: ? U associations in soil porewaters at DU munitions sites were investigated. ? U distribution among colloidal/dissolved fractions varied with soil type and depth. ? U association with large Fe-Al-organic colloids led to removal from soil porewaters. ? Small organic colloidal association inhibited U removal from sandy soil porewaters. ? Reductive dissolution of Mn can release 'truly dissolved' U into soil porewaters.

126

Near-surface enrichment of zooplankton over a shallow back reef: implications for coral reef food webs  

Science.gov (United States)

Zooplankton were 3-8 times more abundant during the day near the surface than elsewhere in the water column over a 1-2.4 m deep back reef in Moorea, French Polynesia. Zooplankton were also significantly more abundant near the surface at night although gradients were most pronounced under moonlight. Zooplankton in a unidirectional current became concentrated near the surface within 2 m of departing a well-mixed trough immediately behind the reef crest, indicating that upward swimming behavior, rather than near-bottom depletion by reef planktivores, was the proximal cause of these gradients. Zooplankton were highly enriched near the surface before and after a full lunar eclipse but distributed evenly throughout the water column during the eclipse itself supporting light as a proximal cue for the upward swimming behavior of many taxa. This is the first investigation of the vertical distribution of zooplankton over a shallow back reef typical of island barrier reef systems common around the world. Previous studies on deeper fringing reefs found zooplankton depletion near the bottom but no enrichment aloft. In Moorea, where seawater is continuously recirculated out the lagoon and back across the reef crest onto the back reef, selection for upward swimming behavior may be especially strong, because the surface serves both as a refuge from predation and an optimum location for retention within the reef system. Planktivorous fish and corals that can forage or grow even marginally higher in the water column might have a substantial competitive advantage over those nearer the bottom on shallow reefs. Zooplankton abundance varied more over a few tens of centimeters vertical distance than it did between seasons or even between day and night indicating that great care must be taken to accurately assess the availability of zooplankton as food on shallow reefs.

Alldredge, A. L.; King, J. M.

2009-12-01

127

Eclipse effects on field crops and marine zooplankton: the 29 March 2006 total solar eclipse  

Science.gov (United States)

Some effects in the biosphere from the Total Solar Eclipse of 29 March 2006 were investigated in field crops and marine zooplankton. Taking into account the decisive role of light on plant life and productivity, measurements of photosynthesis and stomatal behaviour were conducted on seven important field-grown cereal and leguminous crops. A drop in photosynthetic rates, by more than a factor of 5 in some cases, was observed, and the minimum values of photosynthetic rates ranged between 3.13 and 10.13 ?mol CO2 m-2 s-1. The drop in solar irradiance and the increase in mesophyll CO2-concentration during the eclipse did not induce stomatal closure thus not blocking CO2 uptake by plants. Light effects on the photochemical phase of photosynthesis may be responsible for the observed depression in photosynthetic rates. Field studies addressing the migratory responses of marine zooplankton (micro-zooplankton (ciliates), and meso-zooplankton) due to the rapid changes in underwater light intensity were also performed. The light intensity attenuation was simulated with the use of accurate underwater radiative transfer modeling techniques. Ciliates, responded to the rapid decrease in light intensity during the eclipse adopting night-time behaviour. From the meso-zooplankton assemblage, various vertical migratory behaviours were adopted by different species.

Economou, G.; Christou, E. D.; Giannakourou, A.; Gerasopoulos, E.; Georgopoulos, D.; Kotoulas, V.; Lyra, D.; Tsakalis, N.; Tzortziou, M.; Vahamidis, P.; Papathanassiou, E.; Karamanos, A.

2008-08-01

128

Eclipse effects on field crops and marine zooplankton: the 29 March 2006 Total Solar Eclipse  

Directory of Open Access Journals (Sweden)

Full Text Available The effects in the biosphere from the Total Solar Eclipse of 29 March 2006 were investigated in field crops and marine zooplankton. Taking into account the decisive role of light on the photoenergetic and photoregulatory plant processes, measurements of photosynthesis and stomatal behaviour were conducted on seven important field-grown cereal and leguminous crops. A drop in photosynthetic rates, by more than a factor of 5 in some cases, was observed, and the minimum values of photosynthetic rates ranged between 3.13 and 10.13 ?mol CO2 m?2 s?1. However, since solar irradiance attenuation has not at the same time induced stomatal closure thus not blocking CO2 uptake by plants, it is probably other endogenous factors that has been responsible for the observed fall in photosynthetic rates. Field studies addressing the migratory responses of marine zooplankton (micro-zooplankton (ciliates, and meso-zooplankton due to the rapid changes in underwater light intensity were also performed. The light intensity attenuation was simulated with the use of accurate underwater radiative transfer modeling techniques. Ciliates, responded to the rapid decrease in light intensity during the eclipse adopting night-time behaviour. From the meso-zooplankton assemblage, various vertical migratory behaviours were adopted by different species.

G. Economou

2008-01-01

129

Eclipse effects on field crops and marine zooplankton: the 29 March 2006 total solar eclipse  

Directory of Open Access Journals (Sweden)

Full Text Available Some effects in the biosphere from the Total Solar Eclipse of 29 March 2006 were investigated in field crops and marine zooplankton. Taking into account the decisive role of light on plant life and productivity, measurements of photosynthesis and stomatal behaviour were conducted on seven important field-grown cereal and leguminous crops. A drop in photosynthetic rates, by more than a factor of 5 in some cases, was observed, and the minimum values of photosynthetic rates ranged between 3.13 and 10.13 ?mol CO2 m?2 s?1. The drop in solar irradiance and the increase in mesophyll CO2-concentration during the eclipse did not induce stomatal closure thus not blocking CO2 uptake by plants. Light effects on the photochemical phase of photosynthesis may be responsible for the observed depression in photosynthetic rates. Field studies addressing the migratory responses of marine zooplankton (micro-zooplankton (ciliates, and meso-zooplankton due to the rapid changes in underwater light intensity were also performed. The light intensity attenuation was simulated with the use of accurate underwater radiative transfer modeling techniques. Ciliates, responded to the rapid decrease in light intensity during the eclipse adopting night-time behaviour. From the meso-zooplankton assemblage, various vertical migratory behaviours were adopted by different species.

G. Economou

2008-08-01

130

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

131

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

132

"Trophic overyielding": phytoplankton diversity promotes zooplankton productivity.  

Science.gov (United States)

Diversity-productivity relationships at the primary producer level have been extensively studied, especially for terrestrial systems. Here, we explore whether the diversity of aquatic primary producers (phytoplankton) has effects on higher trophic levels (zooplankton). We investigated the effect of phytoplankton diversity on an artificial zooplankton community in a laboratory experiment where phytoplankton biomass and elemental composition (carbon-to-phosphorus ratio) were kept constant. Phytoplankton diversity increased the means of both zooplankton growth rate and abundance while suppressing their variability, and sustained higher zooplankton diversity. Likely explanations include resource complementarity effects among phytoplankton species as food entities, as well as niche complementarity effects among Daphnia species as competitors. By affecting the productivity as well as the variability of the next trophic level, biodiversity of primary producers may have far-reaching consequences in aquatic food webs. PMID:23431601

Striebel, Maren; Singer, Gabriel; Stibor, Herwig; Andersen, Tom

2012-12-01

133

A Review: Potentiality of Zooplankton as Bioindicator  

Digital Repository Infrastructure Vision for European Research (DRIVER)

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 ...

Zannatul Ferdous; Muktadir, A. K. M.

2009-01-01

134

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

135

Abundancia estacional y distribución vertical del zooplancton gelatinoso carnívoro en una área de surgencia en el norte del Sistema de la Corriente de Humboldt Seasonal abundance and vertical distribution of the carnivorous gelatinous zooplankton in an upwelling area of the northern Humboldt Current System  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Se analizó la abundancia estacional y distribución vertical del zooplancton gelatinoso colectado en cuatro cruceros efectuados frente a la bahía de Mejillones. En esta zona se identificaron 44 especies macroplanctónicas distribuidas en 23 de sifonóforos, 17 de hidromedusas, y 4 de ctenóforos, de las cuales 8 especies, Sphaeronectes irregularis, Rhizophysa eysenhardti, Amphogona apicata, Proboscidactyla stellata, Sarsia coccometra, Pleurobrachia bachei, Thalassocalyce inconstans y Velame...

Sergio Palma; Pedro Apablaza

2004-01-01

136

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

137

Cryptic zooplankton ``swimmers'' in upper ocean sediment traps  

Science.gov (United States)

Sediment traps are the major oceanographic tool for collecting passively sinking particulate material (the "particle flux") in the ocean. Sediment traps in the upper ocean also collect actively sinking zooplankton that are usually manually removed prior to analysis. Microscospic analysis of sediment trap samples collected over a 19-month period in the eastern North Pacific reveals that zooplankton "swimmers" are a larger problem than previously recognized. Zooplankton that are cryptic (i.e. difficult to see or distinguish from the detrital material) and difficult to remove (principally gelatinous zooplankton) may have contributed up to 20 mg C m -2 day -1 to the "particulate flux", with the highest values in the upper 150 m. This swimmer problem is in addition to the previously recognized presence of crustaceans and other large metazoans in traps. Additionally, the detritus-laden, mucous-feeding structures (houses)of larvaceans probably enter the traps with the larvaceans and would be impossible to remove. We estimate that the contribution of the cryptic swimmers and larvacean houses could be as much as 96% of the measured carbon flux. The contribution is greatest in the euphotic zone and drops sharply below 200 m. Subtracting out this potential artifact at the VERTEX station results in vertical profiles of organic carbon flux that differ dramatically from the standard flux profile for carbon in the upper ocean: specifically, the implied "regeneration" rate is greatly reduced. Screened traps (300 ?m screens below the baffles) contained numerous metazoans smaller than the screen mesh size. These traps also contained lower levels of other types of sinking particles, and it is unclear to what extent the screens reduced the relative contribution of swimmers to the trap-collected carbon. Although the expanded swimmer problem presented here is now documented at just the VERTEX site, we expect it exists elsewhere. The extent of this swimmer problem requires resolution before sediment traps, especially those deployed in the upper few 100 m, can be used to measure the "flux of particulate material."

Michaels, Anthony F.; Silver, Mary W.; Gowing, Marcia M.; Knauer, George A.

1990-08-01

138

Zooplankton distribution and feeding in the Arctic Ocean during a Phaeocystis pouchetii bloom  

Digital Repository Infrastructure Vision for European Research (DRIVER)

In early summer 2007 we determined the vertical distribution of mesozooplankton (>200 ?m) and assessed the copepod feeding rates in 19 stations distributed along the East Greenland Current and the Fram Strait. The study coincided with a bloom of the haptophyte Phaeocystis pouchetii in the colonial form. Copepods dominated the zooplankton community numerically, and were mainly distributed within the upper 150 m (except for Metridia longa and Oithona spp., that inhabited deeper waters), withou...

Saiz, Enric; Calbet, Albert; Isari, Stamatina; Anto?, Meritxell; Velasco, Eva M.; Almeda, Rodrigo; Movilla, Juan Ignacio; Alcaraz, Miquel

2013-01-01

139

Size-structured risk assessments govern Daphnia migration  

Digital Repository Infrastructure Vision for European Research (DRIVER)

One of the more fascinating phenomena in nature is animal mass migrations and in oceans and freshwaters, diel variations in depth distribution of zooplankton are a phenomenon that has intrigued scientists for more than a century. In our study, we show that zooplankton are able to assess the threat level of ultraviolet radiation and adjust their depth distribution to this level at a very fine tuned scale. Moreover, predation risk induces a size-structured depth separation, such that small indi...

Hansson, Lars-anders; Hylander, Samuel

2009-01-01

140

LIMNETIC ZOOPLANKTON OF LAKES IN KATMAI NATIONAL MONUMENT, ALASKA  

Science.gov (United States)

The limnetic zooplankton in lakes of the Naknek River system in southwestern Alaska was sampled extensively during 1962-63. The numerically dominant forms of limnetic zooplankton were Diaptomus, Cyclops, Daphnia, Bosmina, coregoni, Kellicotia, and Conochilus. Some littoral and be...

 
 
 
 
141

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  

Digital Repository Infrastructure Vision for European Research (DRIVER)

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 contact 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 carr...

Wj, Minto; Ms, Arcifa; Perticarrari, A.

2010-01-01

142

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 SciELO Chile | Language: Spanish Abstract in spanish 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.

143

Emergent and floating-leaved macrophytes as refuge for zooplankton in a eutrophic temperate lake without submerged vegetation  

DEFF Research Database (Denmark)

Several studies have shown that submerged macrophytes provide a refuge for zooplankton against fish predation, whereas the role of emergent and floating-leaved species, which are often dominant in eutrophic turbid lakes, is far less investigated. Zooplankton density in open water and amongst emergent and floating-leaved vegetation was monitored in a small, eutrophic lake (Frederiksborg Slotssø) in Denmark during July-October 2006. Emergent and floating-leaved macrophytes harboured significantly higher densities of pelagic as well as plant-associated zooplankton species, compared to the open water, even during periods where the predation pressure was presumably high (during the recruitment of 0+ fish fry). Zooplankton abundance in open water and among vegetation exhibited low values in July and peaked in August. Bosmina and Ceriodaphnia dominated the zooplankton community in the littoral vegetated areas (up to 4,400 ind l-1 among Phragmites australis and 11,000 ind l-1 between Polygonum amphibium stands), whereas the dominant species in the pelagic were Daphnia (up to 67 ind l-1) and Cyclops (41 ind l-1). The zooplankton density pattern observed was probably a consequence of concomitant modifications in the predation pressure, refuge availability and concentration of cyanobacteria in the lake. It is suggested that emergent and floating-leaved macrophytes may play an important role in enhancing water clarity due to increased grazing pressure by zooplankton migrating into the plant stands. As a consequence, especially in turbid lakes, the ecological role of these functional types of vegetation, and not merely that of submerged macrophyte species, should be taken into consideration.

Cazzanelli, Matteo; Perlt, Trine Warming

2008-01-01

144

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

145

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

146

Influence of the Columbia River plume on cross-shelf transport of zooplankton  

Science.gov (United States)

A high-resolution sampling strategy along a cross-shelf transect near the mouth of the Columbia River was used to determine the distribution, abundance, and spatial relationship between plankton and a tidally modulated river plume. During a strong ebb tide, zooplankton-sized particles were concentrated on the seaward side of the plume front and transported 15 km across the shelf at a rate of 38 cm s-1, roughly fivefold faster than typical wind-driven transport in the region. Physical processes associated with the developing plume vertically depressed relatively dense layers of phytoplankton and zooplankton an average of 7 m deeper into the water column beneath the plume and up to 10 km beyond the extent of the plume front. The enhanced cross-shelf transport by the Columbia River plume is unique for this region of the Northern California Current. Its impact on the vertical and horizontal distribution of zooplankton shifts prey availability for higher trophic levels, such as larval fish, that primarily feed in the upper water column.

Peterson, Jay O.; Peterson, William T.

2009-02-01

147

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

148

Swimming in turbulence: zooplankton fitness in terms of foraging efficiency and predation risk  

DEFF Research Database (Denmark)

Turbulence impacts zooplankton fitness in opposing manners, by increasing contacts with prey but at the same time increasing contacts with predators. We investigate the fitness of individual zooplankton in terms of a trade-off between energetic gains and costs, and risk of predation. Through idealized descriptions of foraging and predation in a turbulent water column, we determine how fast a zooplankter should swim, if at all, and where should it position itself in the vertical to maximize its fitness given certain environmental conditions. Suspension feeding has an advantage over ambush feeding at high turbulence levels, whereas cruise feeding becomes optimal at low turbulence levels. In general, behaviours that seek out low levels of turbulence increase an individual's fitness, a prediction that runs counter to turbulent encounter rate arguments, and exposes the fallacy of examining only the foraging aspects of the fitness trade-off.

Visser, Andre; Mariani, Patrizio

2009-01-01

149

ZOOPLANKTON OCCURANCE DURING MONSOON SEASON FROM EKRUK TANK, SOLAPUR  

Digital Repository Infrastructure Vision for European Research (DRIVER)

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

150

Influence of various cultivation techniques in combination with fertilization on the vertical radionuclide redistribution in soil and the radionuclide migration into plants  

International Nuclear Information System (INIS)

The plan of experiments has included 3 ranges of cultivation depths, i.e. 8 to 10 cm cultivation; 8 to 10 cm cultivation and 28 to 30 cm cultivation, in combination with using agrochemical ameliorants such as zeolites, Na humate, dung and mineral fertilizers. In 1990 average soil contamination with Cs-137 was 10-12 Ci/sq km. The results have demonstrated that radionuclide migration in cultivated soils differs substantially from that one of virgin lands. As far as soil amelioration methods are concerned, cultivation techniques are considered to be the major factors affecting the variations in radiation level. As the cultivation depth grows, surface gamma-radiation background and specific radionuclide content in soil are reducing. At the same time the thickness of the radiocontaminated layer and intensity of radionuclide migration grow. 1 refs.; 4 tabs

151

Vertical migration of {sup 60}Co, {sup 137}Cs and {sup 226}Ra in agricultural soils as observed in lysimeters under crop rotation  

Energy Technology Data Exchange (ETDEWEB)

In most studies quantifying the migration parameters - apparent migration velocity and apparent dispersion coefficient - of radionuclides in the soil by model calculations, these parameters are determined for undisturbed soils. For soils disturbed by ploughing, however, no such data are available in the literature. Therefore, in the present study, the migration parameters of {sup 137}Cs, {sup 60}Co and {sup 226}Ra were estimated for ploughed soils by means of a convection-dispersion model. The depth distributions of the radionuclides were determined in four lysimeters (area: 1 m{sup 2}, depth of soil monolith: 0.75 m) filled with artificially contaminated soils of different types in July 1990. The lysimeters were cropped with agricultural plants. The soil in each lysimeter was ploughed manually once a year until 1996 (plough depth 20 cm). In July 1999, soil samples were collected from three pits in each lysimeter. The depth distributions of all radionuclides proved to be very similar in each soil pit. The spatial variability of the depth distributions of a given radionuclide within the lysimeters was about the same as their variability between the four lysimeters. Evaluation of the migration parameters revealed that the convective transport of the radionuclides was always rather small or even zero, while the dispersive transport caused a 'melting' process of the initially sharp activity edge at the lower border of the Ap horizon. These results are explained by the high evapotranspiration (80-90% of the total precipitation plus irrigation) and the small amounts of seepage water during the observation period of 9 years.

Shinonaga, T. [Division of Environmental and Life Science, ARC Seibersdorf Research, A-2444 Seibersdorf (Austria)]. E-mail: t.shinonaga@iaea.org; Schimmack, W. [Institute of Radiation Protection, GSF-National Research Center for Environment and Health, D-85764 Neuherberg (Germany); Gerzabek, M.H. [Division of Environmental and Life Science, ARC Seibersdorf Research, A-2444 Seibersdorf (Austria); Department for Forest and Soil Sciences, University of Natural Resources and Applied Life Science, Gregor-Mendel-Strasse 33, A-1180 Vienna (Austria)

2005-07-01

152

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

153

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

Science.gov (United States)

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, Sharon L.

1982-11-01

154

Long-term changes of the zooplankton variability in a turbid environment: The Gironde estuary (France)  

Science.gov (United States)

Zooplanktonic variability at the maximum turbidity zone was investigated for the Gironde estuary for 18 years. This ecosystem is characterized by a high concentration of suspended matter and five dominant zooplankton species: the copepods Eurytemora affinis, Acartia bifilosa, A. tonsa and the mysids Neomysis integer and Mesopodopsis slabberi. Four major sources of variation in density were analyzed: (a) spatial variation (vertical and longitudinal variability) and (b) temporal variation (seasonal and annual variability) in the oligo-mesohaline area of the estuary. Temporal variability was related to environmental parameters: temperature, salinity, suspended matter concentration and active chlorophyll in the water column. Seasonal and annual variability were identified as significant sources of variation which explains the fluctuations of all zooplankton densities. No long-term trend was observed for zooplankton densities except for A. tonsa, a species recently introduced into the oligo-mesohaline area of the estuary. Temperature and salinity were important factors explaining the interannual variability of E. affinis as well as of both mysids. Suspended matter concentration controlled the long-term trends of E. affinis and A. tonsa. Annual variability of A. bifilosa and both mysid species was also explained by the proportion of active chlorophyll. Seasonal variability, calculated as the between-month variation, represented the dominant type of variability for all species. Seasonal variations of copepods were essentially explained by salinity. N. integer was significantly correlated with temperature and copepod densities, whereas M. slabberi was correlated with temperature and salinity. Zooplankton also showed significant spatial variation. Mysids demonstrated significant differences between surface and bottom densities whereas vertical variability of copepod densities did not represent a significant source of variation. In terms of longitudinal variability, density of E. affinis was similar along the salinity gradient, whereas Acartia spp. and mysids occurred at significantly greater densities at the downstream station. The high turbidity, which characterizes the Gironde estuary, seems to be a determining factor that acts directly on copepod temporal variability and indirectly on mysid long-term fluctuations by limiting the nutritional quality of the environment.

David, Valérie; Sautour, Benoît; Chardy, Pierre; Leconte, Michel

2005-08-01

155

Seasonal Variations of the Zooplankton Composition and Abundance in the Istanbul Strait  

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Full Text Available Composition and variation of zooplankton of the Istanbul Strait were studied to obtain information on the distribution, abundance and biomass of dominant zooplankton species in the both layers of Black Sea and Mediterranean Sea of Istanbul Strait and to determine the exchange of these species between those layers. Samples were collected vertically, using WP2 nets. In winter sampling period, the copepod Acartia clausi took part in the first place in abundance and meroplankton of bivalves occupied the second place. In the samples collected during spring period, diversity and abundance of different species were higher than other seasonal periods. Noctiluca scintillans with an abundance value of 2380 ind./m-3 was the dominant species, which was followed by A. clausi with 2156 ind./m-3 in the samples collected from the upper layer, while A. clausi showed the highest abundance with 924 ind./m-3, followed by the meroplankton of bivalves with 840 ind./m-3 in the samples collected from the lower layer. In summer period, A. clausi with 952 ind./m-3 and Penilia avirostris with 840 ind./m3 were collected intensively. In the Black Sea water average zooplankton abundance in winter period were 3485 ind./m-3 and during this time A. clausi was found to be the dominant species (976 ind./m-3. A second increase in the population of zooplankton was observed in the autumn period with a total abundance of 5969 ind./m-3. This study carried out seasonally through the year was important in determining dominant species of Istanbul Strait, towards understanding the ecology of the region.

Ahmet Nuri Tarkan

2005-01-01

156

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  

Directory of Open Access Journals (Sweden)

Full Text Available 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 contact 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.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 contato 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".

WJ. Minto

2010-02-01

157

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

158

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

159

Inter-annual fluctuations of zooplankton communities in the Bay of Villefranche-sur-mer from 1995 to 2005 (Northern Ligurian Sea, France  

Directory of Open Access Journals (Sweden)

Full Text Available An integrated analysis of the pelagic ecosystems of the Ligurian Sea is performed combining time series (1995–2005 of several zooplankton groups (one group for copepods smaller than 0.724 mm3 and nine groups for individuals larger than 0.724 mm3, i.e. large copepods, decapod larvæ, other crustaceans, chaetognaths, appendicularians, pteropods, thaliaceans, gelatinous predators and other zooplankton, chlorophyll-a, nutrients, salinity, temperature, density, and local weather at Point B coastal station (Northern Ligurian Sea. From 1995 to 2000 winters were wet and mild resulting in lower winter sea surface density. These years showed lower than average nutrients and zooplankton concentrations while chlorophyll-a biomass was high. After 2000, winters were colder and dryer resulting in higher sea surface density. Nutrients and zooplankton showed higher concentrations while chlorophyll-a was lower than average. The ca. 2000 change was observed for most zooplankton groups with a one-year delay for some groups. Inter-annual variability within each period was also observed. The observed patterns suggest that the pelagic ecosystem trophic state at the studied point is mostly set by the winter forcing on the vertical mixing that upwells nutrients to the surface sustaining primary production. Surprisingly, low chlorophyll-a biomass in high nitrate and zooplankton conditions during the well mixed years suggest that phytoplankton biomass is controlled by grazers. The proposed mechanisms of stronger winter vertical mixing hold for most of the time series, but specific years with contradicting patterns suggest also the possible influence of the summer climate. A review of recent literature suggests that changes in the pelagic ecosystem are not limited to the studied site but concern also the central Ligurian Sea.

P. Vandromme

2011-11-01

160

Inter-annual fluctuations of zooplankton communities in the Bay of Villefranche-sur-mer from 1995 to 2005 (Northern Ligurian Sea, France)  

Science.gov (United States)

An integrated analysis of the pelagic ecosystems of the Ligurian Sea is performed combining time series (1995-2005) of several zooplankton groups (one group for copepods smaller than 0.724 mm3 and nine groups for individuals larger than 0.724 mm3, i.e. large copepods, decapod larvæ, other crustaceans, chaetognaths, appendicularians, pteropods, thaliaceans, gelatinous predators and other zooplankton), chlorophyll-a, nutrients, salinity, temperature, density, and local weather at Point B coastal station (Northern Ligurian Sea). From 1995 to 2000 winters were wet and mild resulting in lower winter sea surface density. These years showed lower than average nutrients and zooplankton concentrations while chlorophyll-a biomass was high. After 2000, winters were colder and dryer resulting in higher sea surface density. Nutrients and zooplankton showed higher concentrations while chlorophyll-a was lower than average. The ca. 2000 change was observed for most zooplankton groups with a one-year delay for some groups. Inter-annual variability within each period was also observed. The observed patterns suggest that the pelagic ecosystem trophic state at the studied point is mostly set by the winter forcing on the vertical mixing that upwells nutrients to the surface sustaining primary production. Surprisingly, low chlorophyll-a biomass in high nitrate and zooplankton conditions during the well mixed years suggest that phytoplankton biomass is controlled by grazers. The proposed mechanisms of stronger winter vertical mixing hold for most of the time series, but specific years with contradicting patterns suggest also the possible influence of the summer climate. A review of recent literature suggests that changes in the pelagic ecosystem are not limited to the studied site but concern also the central Ligurian Sea.

Vandromme, P.; Stemmann, L.; Berline, L.; Gasparini, S.; Mousseau, L.; Prejger, F.; Passafiume, O.; Guarini, J.-M.; Gorsky, G.

2011-11-01

 
 
 
 
161

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

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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

162

Laws of the transformation of the photon angle and energy spectra at the soil surface during vertical migration 137Cs and 134Cs  

International Nuclear Information System (INIS)

Dose burdens due to external photon bombardment are estimated with the aid of databases characterizing the local conditions, i.e., the time during which inhabitants were in the open, the composition and distribution of nuclides in the soil layer, the gamma screening factor, etc. Since these parameters usually differ substantially, conservative estimates are taken in order to obtain representative values whereby underestimation of the dose is avoided. The behavior of the radionuclides in the environment must be simulated to obtain a more precise prediction of dose burdens. The models used in this case should be somewhat conservative. In this paper, the authors propose the following treatment, simulating photon migration and transport in a soil layer. In the first stage the evolution of the radionuclide distribution function in the soil layer is studied and the distribution of radioactive substances is calculated analytically and numerically calculate as a function of the depth in the soil. In the second stage the ?-ray propagation in the soil and in the atmosphere is estimated from the known distribution of radionuclides at the given chemical composition of the soil and numerical Monte Carlo calculations are carried out to determine the screening factor and the ?-ray spectrum

163

Mesoscale distribution and community composition of zooplankton in the Mozambique Channel  

Science.gov (United States)

Recent studies have shown the Mozambique Channel to exhibit high mesoscale variability, but how mesoscale features influence the zooplankton community in this region is not known. The biovolume, biomass, vertical distribution and community composition of mesozooplankton (>200 µm) associated with mesoscale eddies in the Mozambique Channel was investigated during four cruises in September 2007, December 2008, November 2009 and April/May 2010. Stations were categorized according to their location in cyclonic (cold-core) or anticyclonic (warm-core) eddies, frontal, divergence or shelf regions. Mean mesozooplankton biovolume in the upper 200 m was 0.33 ml m-3, with zooplankton largely concentrated in the upper 100 m during all four cruises (weighted mean depth=66.6 m). Sampling depth was the most important predictor of biovolume, which was greatest for net samples with a mid-depth of 0-40 m, but declined deeper in the water column. Biovolume at the shelf (0.37 ml m-3), divergence and cyclonic eddy stations (0.31 ml m-3) was significantly greater than at frontal and anticyclonic eddy stations (0.20 ml m-3). Mean biovolume was significantly higher during 2008 and 2010 compared to 2007 and 2009, and was also significantly higher for samples collected at night (and twilight) than during the day. The mesozooplankton community in 2007 was strongly dominated by small copepods (~70-80% abundance) followed by appendicularians (10%), ostracods (8%) and chaetognaths (7%). The most abundant copepods were the Paracalanids, Oncaea spp., Oithona spp. and Corycaeus spp. Multivariate analysis showed that the communities in 2007 and 2008 were most strongly structured by depth, but classification (cyclonic/anticyclonic) was also important in 2007 when mesoscale features were more strongly developed. Zooplankton assemblages showed a high degree of homogeneity, with differences between mesoscale features largely due to differing abundances of similar taxa. These observations suggest that mesoscale eddy and shelf interactions play a fundamental role in shaping the Mozambique Channel pelagic ecosystem through the concentration, enhanced growth and redistribution of zooplankton communities. Although frontal areas between eddies were poor in zooplankton biomass, the extensive inter-eddy divergence areas were as rich in biomass as the small cyclonic eddy core regions. These patterns are important for understanding the favorability of observed foraging areas for higher trophic levels.

Huggett, Jenny A.

2014-02-01

164

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

165

Rostock zooplankton studies off West Africa  

Science.gov (United States)

Since the beginning of the seventies, upwelling research has become increasingly popular in the path of the Canary and Benguela Current, because of economic consideration, particularly in the relation to fisheries and marine geology. Many expeditions were carried out between 1970 and 1977, including 8 cruises of the German R. V. “A. v. Humboldt” operating from Rostock. Measurements covered scales ranging in time from minutes to several years and in space from hundreds of metres to several thousands of kilometres. Zooplankton studies focussed on quantitative, metabolic, taxonomic, and parasitological aspects. Plankton was collected with a WP-2-UNESCO standard net to a maximum depth of 200 m. The epipelagic mesozooplankton consists mainly of copepods, especially calanoids with developmental times of about 20 to 23 days. After an upwelling event, zooplankton is able to double its biomass. This typical biomass increase is independent of coastal distance and depth. The upwelling response lasts about 3 weeks in nearsurface waters, and 6 to 8 weeks in depths below 75m. A relationship was observed between the duration of seasonal upwelling (that means the numbers of single upwelling events) and the cumulative increase of biomass. This net growth rate of zooplankton biomass is most pronounced at the shelf break, the area with the highest fish biomass, and in the upper 25 m. Differences between the expected and the real rate values in conjunction with the known amount of nutritive demands of fishes allow the estimation of the fish biomass in a given area. The near coastal Ekman upwelling, which is an event in the time scale of about two weeks, also shows seasonality in some areas. Off Northwest Africa the largest expansion was recorded in the first half of the year, extending from 10° N to 24° N, more than 400 km offshore and at least down to 200 m. It contracts in the second half of the year to an area between 20°N and 22°N, 100 to 200 km off the coast and in an average depth of 25 m. These zooplankton biomass patterns are superimposed by mesoscale phenomena, originated by other than Ekman upwelling events. Those are, for example, long coastal parallel waves, producing cells of intensified upwelling and downwelling, and eddies, caused by instabilities in a frontal zone parallel to the coast. Different water masses can be distinguished by indicator species, species combinations or the significant absence of species. This was demonstrated for chaetognaths. The calanoid Calanus helgolandicus (Claus, 1863), a typical species of the North Atlantic, indicates North Atlantic Central Water, whereas Calanoides carinatus (Krøyer, 1849) is an indicator of South Atlantic Central Water. Finally, comparisons of near coastal current regimes, transport velocities, and developmental rates of calanoids allow one to conclude that a suitable mechanism is present to maintain plankton in the coastal environment.

Postel, L.; Arndt, E. A.; Brenning, U.

1995-03-01

166

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

167

The use of a Cs-137 vertical migration model to study the temporal evolution of heavy metals in coastal sediments of the Bay of Cadiz (Spain)  

International Nuclear Information System (INIS)

The evolution of heavy metals (Zn, Cd, Pb, Hg) in sea bed sediments of the Bay of Cadiz (Spain) has been studied. Four sediment cores were collected from the Inner Bay zone where sediment textural composition is mainly formed by silt and clay with high organic content, showing a very high absorption capacity for the substances solved in the aquatic medium. The dating of the sediments has been performed using the fallout radionuclide 137Cs as a tracer. Due to the high vertical mobility of this radionuclide in the sediment column, as a consequence of its molecular diffusion and the bioturbation existing in the area, the observed profiles are continuous and the 1963 maximum in fallout activity could not be assigned. The one dimensional diffusion-advection equation has been applied, considering the residence time of the radionuclide in the marshes zone, to develop a model that permits to interpret the profiles and to estimate the sedimentation rate, in order to infer the recent chronology of the sediment layers. By using the 210Pb dating method with the CRS model in one station, it can be showed that the sedimentation rate could be assumed to be constant during a longer period of time. In consequence, the sediment dating has been extended up to 100 years backwards, allowing the study of the evolution of heavy metals during the last century. The sediment dating shows that the heavy metal pollution of the Inner Bay has been produced simultaneously in t Bay has been produced simultaneously in the whole zone, during the industrial development of the environment. The increase of heavy metals Zn and Cd started in the second half of the XX century, while the enhancement of Pb and Hg concentration started at the beginning of the XX century. Heavy metal concentrations reached maximum levels during the eighties decade, afterward a remarkable decrease in surface sediments has been observed, which could be attributed to the restrictive environmental measurements undertaken at the zone, in particular the control of industrial effluents and the decreasing use of leaded fuels

168

Hydrostatic Pressure and Temperature Effects on the Membranes of a Seasonally Migrating Marine Copepod  

Science.gov (United States)

Marine planktonic copepods of the order Calanoida are central to the ecology and productivity of high latitude ecosystems, representing the interface between primary producers and fish. These animals typically undertake a seasonal vertical migration into the deep sea, where they remain dormant for periods of between three and nine months. Descending copepods are subject to low temperatures and increased hydrostatic pressures. Nothing is known about how these organisms adapt their membranes to these environmental stressors. We collected copepods (Calanoides acutus) from the Southern Ocean at depth horizons ranging from surface waters down to 1000 m. Temperature and/or pressure both had significant, additive effects on the overall composition of the membrane phospholipid fatty acids (PLFAs) in C. acutus. The most prominent constituent of the PLFAs, the polyunsaturated fatty acid docosahexanoic acid [DHA – 22:6(n-3)], was affected by a significant interaction between temperature and pressure. This moiety increased with pressure, with the rate of increase being greater at colder temperatures. We suggest that DHA is key to the physiological adaptations of vertically migrating zooplankton, most likely because the biophysical properties of this compound are suited to maintaining membrane order in the cold, high pressure conditions that persist in the deep sea. As copepods cannot synthesise DHA and do not feed during dormancy, sufficient DHA must be accumulated through ingestion before migration is initiated. Climate-driven changes in the timing and abundance of the flagellated microplankton that supply DHA to copepods have major implications for the capacity of these animals to undertake their seasonal life cycle successfully. PMID:25338196

Pond, David W.; Tarling, Geraint A.; Mayor, Daniel J.

2014-01-01

169

Zooplankton Feeding on the Nuisance Flagellate Gonyostomum semen  

Digital Repository Infrastructure Vision for European Research (DRIVER)

The large bloom-forming flagellate Gonyostomum semen has been hypothesized to be inedible to naturally occurring zooplankton due to its large cell size and ejection of long slimy threads (trichocysts) induced by physical stimulation. In a grazing experiment using radiolabelled algae and zooplankton collected from lakes with recurring blooms of G. semen and lakes that rarely experience blooms, we found that Eudiaptomus gracilis and Holopedium gibberum fed on G. semen at high rates, whereas Dap...

Johansson, Karin S. L.; Vrede, Tobias; Lebret, Karen; Johnson, Richard K.

2013-01-01

170

Effects of typhoons on gelatinous carnivore zooplankton off Northern Taiwan  

Digital Repository Infrastructure Vision for European Research (DRIVER)

We examine the effect of typhoons, as potential drivers of nutrient pulse events, on gelatinous carnivore zooplankton. The period investigated spanned from 2007 to 2010, where seasonal abundance and taxonomic composition of the gelatinous zooplankton community was recorded off North Taiwan. Typhoon effects were assessed in the abundance, diversity and species richness of the gelatinous carnivore populations. Significant associations between typhoons and gelatinous carnivores were found in tim...

Lopez-lopez, Lucia; Molinero, Juan Carlos; Tseng, Li-chun; Chen, Qing-chao; Houng, Jian-wen; Hwang, Jiang-shiou

2012-01-01

171

The Uday river’s littoral zooplankton in the region of the national nature park «Pyriatynskiy»  

Directory of Open Access Journals (Sweden)

Full Text Available The ecological-faunistic analysis of the littoral zooplankton of the middle part of the Uday River has been performed for the first time. The research was conducted to confirm a reason to create the National Nature Park «Pyriatynskiy» in this region. The species diversity of the littoral zooplankton obtained from six scientific stations on the Uday River was established. The specific features of the zooplankton’s distribution in biotopes in summer days were revealed. The comparative description of biotopical distribution of zooplankton of different stations is presented. The basic ecological indices of zooplankton populations (density and biomass were determined.

V. N. Trokhymets

2012-12-01

172

Migration without migraines  

Energy Technology Data Exchange (ETDEWEB)

Accurate velocity models are a necessity for reliable migration results. Velocity analysis generally involves the use of methods such as normal moveout analysis (NMO), seismic traveltime tomography, or iterative prestack migration. These techniques can be effective, and each has its own advantage or disadvantage. Conventional NMO methods are relatively inexpensive but basically require simplifying assumptions about geology. Tomography is a more general method but requires traveltime interpretation of prestack data. Iterative prestack depth migration is very general but is computationally expensive. In some cases, there is the opportunity to estimate vertical velocities by use of well information. The well information can be used to optimize poststack migrations, thereby eliminating some of the time and expense of iterative prestack migration. The optimized poststack migration procedure defined here computes the velocity model which minimizes the depth differences between seismic images and formation depths at the well by using a least squares inversion method. The optimization methods described in this paper will hopefully produce ``migrations without migraines.``

Lines, L.; Burton, A.; Lu, H.X. [Memorial Univ. of Newfoundland, St. John`s (Canada)

1994-12-31

173

Integrated measurements of acoustical and optical thin layers I: Vertical scales of association  

Science.gov (United States)

This study combined measurements from multiple platforms with acoustic instruments on moorings and on a ship and optics on a profiler and an autonomous underwater vehicle (AUV) to examine the relationships between fluorescent, bioluminescent, and acoustically scattering layers in Monterey Bay during nighttime hours in July and August of 2006 and May of 2008. We identified thin bioluminescent layers that were strongly correlated with acoustic scattering at the same depth but were part of vertically broad acoustic features, suggesting layers of unique composition inside larger biomass features. These compositional thin layers nested inside larger biomass features may be a common ecosystem component and are likely to have significant ecological impacts but are extremely difficult to identify as most approaches capable of the vertical scales of measurement necessary for the identification of sub-meter scale patterns assess bulk properties rather than specific layer composition. Measurements of multiple types of thin layers showed that the depth offset between thin phytoplankton and zooplankton layers was highly variable with some layers found at the same depth but others found up to 16 m apart. The vertical offset between phytoplankton and zooplankton thin layers was strongly predicted by the fraction of the water column fluorescence contained within a thin phytoplankton layer. Thin zooplankton layers were only vertically associated with thin phytoplankton layers when the phytoplankton in a layer accounted for more than about 18-20% of the water column chlorophyll. Trophic interactions were likely occurring between phytoplankton and zooplankton thin layers but phytoplankton thin layers were exploited by zooplankton only when they represented a large fraction of the available phytoplankton, suggesting zooplankton have some knowledge of the available food over the entire water column. The horizontal extent of phytoplankton layers, discussed in the second paper in this series, is likely an important factor contributing to this selective exploitation by zooplankton. The pattern of vertical offset between phytoplankton and zooplankton layers was consistent between studies in different years and using different combinations of platforms, indicating the importance of the relationship between zooplankton layers and the fraction of phytoplankton within a layer at night within Monterey Bay. These results highlight the value of integrating measurements of various types of organisms to understand thin layers processes and the importance of assessing ecological interactions in plankton thin layers within the context of the properties of the entire water column, like the animals themselves do.

Benoit-Bird, Kelly J.; Moline, Mark A.; Waluk, Chad M.; Robbins, Ian C.

2010-01-01

174

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

175

Locomotor adaptations of some gelatinous zooplankton.  

Science.gov (United States)

Swimming behaviour and locomotor adaptations are described in chaetognaths, larvacean tunicates, some cnidaria, and thaliacean tunicates. The first two groups swim by oscillating a flattened tail, the others by jet propulsion. In chaetognaths, the locomotor muscle fibres are extensively coupled and relatively sparsely innervated, they exhibit compound spike-like potentials. The motoneurons controlling the rhythmic activity of the locomotor muscle lie in a ventral ganglion whose organization is briefly described. Rhythmic swimming bursts in larvaceans are similarly driven by a caudal ganglion near the base of the tail, but each caudal muscle cell is separately innervated by two sets of motor nerves, as well as being coupled to its neighbours. The external epithelium is excitable, and linked to the caudal ganglion by the axons of central cells. Mechanical stimulation of the epithelium evokes receptor potentials followed by action potentials and by bursts of rapid swimming. The trachyline medusa Aglantha and the small siphonophore Chelophyes also show rapid escape responses; in Aglantha these are driven by a specialized giant axon system lacking in other hydromedusae, and in Chelophyes. Slow swimming in Aglantha apparently involves a second nerve supply to the same muscle sheets used in rapid swimming, whereas in Chelophyes slow swimming results from the activity of the smaller posterior nectophore. Slow swimming in siphonophores is more economical than the rapid responses. In the hydrozoan medusa Polyorchis (as in Chelophyes) action potentials in the locomotor muscle sheet change in shape during swimming bursts, and their duration is related to the size of the medusa; they are not simply triggers of muscular contraction. The two groups of thaliacean tunicates are specialized differently. Doliolum is adapted for single rapid jet pulses (during which it achieves instantaneous velocities of 50 body lengths s-l), whilst salps are adapted for slow continuous swimming. The cost of locomotion is greater in Doliolum. Few gelatinous zooplankton show special adaptations both for rapid escape movements, and for slow sustained swimming, those that do deserve further study. PMID:2871635

Bone, Q

1985-01-01

176

Body size and food size in freshwater zooplankton.  

Science.gov (United States)

We used double-label liquid scintillation techniques to measure the efficiencies with which eight different-sized zooplankton species ingested four cell types relative to a standard cell type (Chlamydomonas). Efficiency ratios (ERs: clearance rate on cell type X / clearance rate on Chlamydomonas) on the three ultraplankton (Diaptomus copepodites and adults); (iii) species having extremely low ERs on all ultraplankton (mean ER Diaptomus nauplii). These functional groups follow neither taxonomic nor body-length groupings. We conclude that zooplankton body length may influence the maximal particle size a species can ingest but has little influence on the ingestion of smaller particles. Two frequently used models relating zooplankton body size and food size are unrealistic. PMID:16593521

Bogdan, K G; Gilbert, J J

1984-10-01

177

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

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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

178

High mortality of Red Sea zooplankton under ambient solar radiation.  

Science.gov (United States)

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 radiation doses with zooplankton mortality were evaluated by exposing organisms, enclosed in quartz bottles, allowing all the wavelengths of solar radiation to penetrate, to five different levels of ambient solar radiation (100%, 21.6%, 7.2%, 3.2% and 0% of solar radiation). The maximum mortality rates under ambient solar radiation levels averaged (±standard error of the mean, SEM) 18.4±5.8% h(-1), five-fold greater than the average mortality in the dark for the eight taxa tested. The UV-B radiation required for mortality rates to reach ½ of maximum values averaged (±SEM) 12±5.6 h(-1)% of incident UVB radiation, equivalent to the UV-B dose at 19.2±2.7 m depth in open coastal Red Sea waters. These results confirm that Red Sea zooplankton are highly vulnerable to ambient solar radiation, as a consequence of the combination of high incident radiation and high water transparency allowing deep penetration of damaging UV-B radiation. These results provide evidence of the significance of ambient solar radiation levels as a stressor of marine zooplankton communities in tropical, oligotrophic waters. Because the oligotrophic ocean extends across 70% of the ocean surface, solar radiation can be a globally-significant stressor for the ocean ecosystem, by constraining zooplankton use of the upper levels of the water column and, therefore, the efficiency of food transfer up the food web in the oligotrophic ocean. PMID:25309996

Al-Aidaroos, Ali M; El-Sherbiny, Mohsen M O; Satheesh, Sathianeson; Mantha, Gopikrishna; Agust?, Susana; Carreja, Beatriz; Duarte, Carlos M

2014-01-01

179

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)

180

Zooplankton Diversity Of Dnyanganga Reservoir Near Khamgaon, Maharashtra  

Digital Repository Infrastructure Vision for European Research (DRIVER)

: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 r...

Kale, G. B.

2013-01-01

 
 
 
 
181

Material properties of zooplankton and nekton from the California current  

Science.gov (United States)

This study measured the material properties of zooplankton, Pacific hake (Merluccius productus), Humboldt squid (Dosidicus gigas), and two species of myctophids (Symbolophorus californiensis and Diaphus theta) collected from the California Current ecosystem. The density contrast (g) was measured for euphausiids, decapods (Sergestes similis), amphipods (Primno macropa, Phronima sp., and Hyperiid spp.), siphonophore bracts, chaetognaths, larval fish, crab megalopae, larval squid, and medusae. Morphometric data (length, width, and height) were collected for these taxa. Density contrasts varied within and between zooplankton taxa. The mean and standard deviation for euphausiid density contrast were 1.059 +/- 0.009. Relationships between zooplankton density contrast and morphometric measurements, geographic location, and environmental conditions were investigated. Site had a significant effect on euphausiid density contrast. Density contrasts of euphausiids collected in the same geographic area approximately 4-10 days apart were significantly higher (p pen, and beak. The density contrasts varied within and between fish taxa, as well as among squid body parts. Effects of animal length and environmental conditions on nekton density contrast were investigated. The sound speed contrast (h) was measured for Pacific hake flesh, myctophid flesh, Humboldt squid mantle, and Humboldt squid braincase. Sound speed varied within and between nekton taxa. The material properties reported in this study can be used to improve target strength estimates from acoustic scattering models which would increase the accuracy of biomass estimates from acoustic surveys for these zooplankton and nekton.

Becker, Kaylyn

182

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)

183

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...

184

Climate Impacts on Zooplankton Population Dynamics in Coastal Marine Ecosystems  

Directory of Open Access Journals (Sweden)

Full Text Available 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 individual zooplankton taxa coupled with new information linking higher trophic level predators (salmon, cod, haddock, penguins, seals to their prey yielded mechanistic descriptions of how climate variation impacts regionally important marine resources. Coupled ecological models driven by improved regional-scale climate scenario models developed during GLOBEC enable forecasts of plausible future conditions in coastal ecosystems, and will aid and inform decision makers and communities as they assess, respond, and adapt to the effects of environmental change. Multi-region synthesis revealed that conditions in winter, before upwelling, or seasonal stratification, or ice melt (depending on region had significant and important effects that primed the systems for greater zooplankton population abundance and productivity the following spring-summer, with effects that propagated to higher trophic levels.

Harold P. Batchelder

2013-12-01

185

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

186

[Zooplankton in north branch waters of Changiiang Estuary].  

Science.gov (United States)

Based on the investigation data during the high-water (July, 2003) and low-water (January, 2004) periods, a causal analysis was made on the variation of zooplankton distribution in the north branch waters of the Changjiang Estuary. The results showed that in high-water period, the average of zooplankton biomass was 234.38 mg x m(-3), being 141.35 mg x m(-3) in flood tide and 327.40 mg x m(-3) in ebb tide, while in low-water period, it was 188.81 mg x m(-3), being 184.69 mg x m(-3) in flood tide and 192.93 mg x m(-3) in ebb tide. The biomass increased from the east to the west in flood tide, but a contrary trend was observed in ebb tide. The species number did not change obviously both in flood tide and in ebb tide. The value of diversity index (H') was higher in flood tide than in ebb tide. In high-water period, the biomass near the north shore was higher than that near the south shore, but it was contrary in the ebb tide. The difference between the waters of two shores was not obvious in low-water period as in high-water period, though the trend of biomass variation was similar. The variation of zooplankton distribution in the north branch waters of the Changjiang Estuary had a close relation with the seasonal changes of zooplankton biomass outside the Changjiang Estuary and the tide, but not significantly related with the Changjiang runoff water. Coriolis force accounted for the difference of zooplankton biomass in the waters of two shores via tide movement. PMID:16252880

Xu, Zhaoli

2005-07-01

187

Fine-scale vertical distribution of coastal and offshore copepods in the Golfo de Arauco, central Chile, during the upwelling season  

Science.gov (United States)

In order to understand the mechanism by which zooplankters from different origins co-occur during the upwelling season within Golfo de Arauco, one of the most productive areas in central Chile, we assessed short term variations in the vertical distribution of the most abundant copepod species. Fine-scale, day and night vertical zooplankton sampling was done with a pump over 12 days in summer. The water column in the gulf consisted of three layers: Equatorial Subsurface Water of low dissolved oxygen content in the deeper part of the water column, strong temperature and oxygen gradients at mid-depth (15-25 m), and a layer of warmer, more oxygenated, less saline water at the surface. Copepods within the gulf originated from offshore, from the continental shelf, and from the coastal area. Most taxa showed distinctive vertical distributions. Three copepod groups were identified by their mean weighted depths of residence. One group included shallow residents found above the thermocline/oxycline ( Acartia tonsa, Centropages brachiatus, Corycaeus sp., Paracalanus parvus, Oncaea sp.). A second group was comprised by species distributed at or below the thermocline/oxycline ( Oithona sp., Oncaea conifera, Lucicutia sp., Metridia sp., Heterorhabdus papilliger). The third group was composed of vertical migrators that crossed the thermocline/oxycline ( Calanus chilensis, Calanoides patagoniensis, Aetideus armatus, Pleuromamma piseki). In spite of their different vertical distribution ranges, the most abundant and frequent copepod species ( P. parvus, C. chilensis, C. patagoniensis, C. brachiatus) share a common capacity to withstand wide ranges of oxygen concentration and temperature. This characteristic, along with the capacity to vary their life strategies under different environmental conditions, seems to facilitate the maintenance of large numbers of copepods in coastal waters along the Humboldt Current.

Castro, Leonardo R.; Troncoso, Victor A.; Figueroa, Dante R.

2007-11-01

188

Zooplankton response to organic carbon level in lakes of differing trophic states  

Directory of Open Access Journals (Sweden)

Full Text Available Water eutrophication is associated with an increase in the organic carbon content (both particulate and dissolved forms, which may affect the functioning of the zooplankton community. Mesotrophic and eutrophic lakes in the Masurian Lake District (Poland were selected to evaluate the relationship between the organic carbon level and the zooplankton community. The lakes differed significantly in most environmental variables. RDA analysis was performed to evaluate the impact of environmental variables on zooplankton. The variables that significantly explained the variance in the zooplankton community abundance (Monte Carlo permutation test included dissolved and particulate organic carbon, Secchi disc visibility, soluble reactive phosphorus and total nitrogen. The response of zooplankton to an increasing level of organic carbon is functional rather than quantitative. In the mesotrophic system, the results of the redundancy analysis indicated relatively strong positive relationships between dissolved organic carbon and zooplankton biomass, and negative correlations between chlorophyll a and zooplankton biomass. The above suggests that indirect organic carbon utilization by zooplankton could partly compensate for the poor feeding conditions of planktonic animals (decreased phytoplankton availability. In the eutrophic lake, elevated organic carbon levels are partly limited by zooplankton, which is suggested by the positive relationship between particulate organic matter and the total zooplankton biomass (RDA results. The positive relationship between the biomass of copepods and organic carbon in particulate and dissolved forms implies that copepods benefit from the increased heterotrophic carbon flow that is activated in the eutrophic lake.

Bowszys M.

2014-03-01

189

Acute, chronic and sublethal effects of the synthetic pyrethroid, fenvalerate, on zooplankton in the laboratory and the field  

Energy Technology Data Exchange (ETDEWEB)

Toxicity tests were conducted in the laboratory and field with four species of zooplankton to determine acute, chronic and sublethal effects of the synthetic pyrethroid, fenvalerate. Rates of filtration and ingestion of /sup 14/C-labelled algae, Chlamydomonas reinhardii by Daphnia galeata mendotae, Ceriodaphnia lacustris and Diaptomus oregonensis were decreased significantly at both acute and sublethal concentrations of fenvalerate after only 24-h of exposure. Rates of assimilation of algae by D. galeata mendotae, C. lacustris and D. oregonensis were decreased at concentrations of 0.05 ..mu..g fenvalerate/L. Chronic exposure of D. galeata mendotae throughout their life cycle to sublethal levels of fenvalerate resulted in increased longevity but decreased production of young at 0.005 ..mu..g/L. Higher concentrations caused a decrease in survival. Application of fenvalerate to large volume enclosures in Lake St. George at concentrations of 0.1, 0.05 and 0.01 ..mu..g/L resulted in changes in community grazing rates, individual filtration rates, community structure, and diurnal migrations. Fenvalerate was extremely toxic to freshwater zooplankton in both the laboratory and field at levels that could result from drift of the pesticide during the use in agriculture or forestry.

Day, K.E.

1986-01-01

190

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

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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

191

Reaction of fresh water zooplankton community to chronic radiation exposure  

Energy Technology Data Exchange (ETDEWEB)

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 2.2x10{sup 3} to 2.3x10{sup 7} Bq/l, total volume alpha-activity - from 2.6x10{sup -1} to 3.1x10{sup 3} 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 1.1x10{sup 2} mcGy/hr, 50 % reduction - 1.1x10{sup 3} mcGy/hr. Margalef's index and Shannon's index were 5% lower at 9.1x10{sup 2} mcGy/hr and 50% lower at 1.7x10{sup 3} 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)

Osipov, D.; Pryakhin, E. [Urals Research Center for Radiation Medicine - URCRM (Russian Federation); Ivanov, I. [FSUE Mayak PA (Russian Federation)

2014-07-01

192

Estimation of zooplankton mortality caused by an Arctic glacier outflow  

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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

193

Importance of zooplankton in the diets of Tinca tinca (L., from Danube Delta shallow lakes  

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Full Text Available This study was initiated to examine the role of zooplankton in the diet of Tinca tinca (Linnaeus, 1758 fish species and evaluate zooplankton’s spatial and temporal distribution from Danube Delta shallow lakes in June 2007 (e.g., Cuibul cu Lebede, Uzlina, Isac, Furtuna, Nebunu, Merhei, Miazazi, Rosu, Rosulet. Fish predationappears to be the ultimate factor governing the presence or absence of certain crustaceans zooplankton species. The habitat preferred by the tench is characteristically sheltered and shallow with abundant vegetation. It is now widely accepted that predation plays a critical role in determinig zooplankton community structure in shallow lakes. Food quality may be more important than food quantity with respect to both growth and reproduction in animal population. Ecological limitation studies performed on primary consumers, proved the importance zooplankton population [5].

TUDOR Mihaela

2009-09-01

194

Vertical distribution of phytoplankton functional groups in a tropical shallow lake: driving forces on a diel scale / Distribuição vertical de grupos funcionais fitoplanctônicos em um lago tropical raso: forças direcionadoras em escala nictemeral  

Scientific Electronic Library Online (English)

Full Text Available SciELO Brazil | Language: English Abstract in portuguese OBJETIVO: Analisar a distribuição vertical dos grupos funcionais fitoplanctônicos em dois ciclos nictemerais em um lago tropical monomítico raso; MÉTODOS: As amostragens das variáveis abióticas, comunidades fitoplanctônica e zooplanctônica foram realizadas a intervalos de 3 horas ao longo de 24 hora [...] s em perfis verticais, nos períodos de estratificação (fevereiro) e de circulação (julho); RESULTADOS: A elevada estabilidade térmica e a atelomixia parcial favoreceram a coexistência de grupos funcionais sensíveis a desestratificação N A e F, compostos por desmidias e clorofícias cocoides e pelos grupos S2 e Lo, persistentes durante a circulação, e compostos por cianobactérias filamentosas não fixadoras de N2 e dinoflagelados, respectivamente. A descontinuidade na distribuição vertical dos grupos funcionais com dominância de N A e F no epilímnio e de R e Lo no metalímnio e hipolímnio foi característica da estratificação, e diferenças entre períodos diurno e noturno não foram significativas. CONCLUSÕES: A redução em até 80% da biomassa do grupo NA durante a circulação indica a influência da estabilidade térmica e atelomixia parcial como fatores determinantes na compartimentalização dos grupos funcionais, restringindo a migração vertical diurna (MVD) e a perda por sedimentação durante a estratificação. Abstract in english AIM: This study analyzed the vertical distribution of phytoplankton functional groups in two diel cycles in a warm monomictic shallow tropical lake; METHODS: Sampling of the abiotic variables, phytoplankton and zooplankton communities was performed at intervals of 3 hours over 24 hours in vertical p [...] rofiles, in the stratification (February) and circulation (July) periods; RESULTS: The high thermal stability and the partial atelomixis favored the coexistence of functional groups that are sensitive to destratification, N A and F, composed by desmids and Chlorophyceae coccoids, and groups S2 and Lo, which persisted during the circulation, and were composed by filamentous cyanobacteria which do not fix N2 and dinoflagellates, respectively. The discontinuity in the vertical distribution of the functional groups, with dominance of N A and F in the epilimnion and R and Lo in the metalimnion and hypolimnion, was characteristic of the stratification, and differences between the daytime and nighttime periods were not significant. CONCLUSIONS: The reduction of 80% of the biomass of the NA group during the mixing period indicates the influence of thermal stability and partial atelomixis as determinant factors in the compartmentalization of functional groups, restricting daytime vertical migration (DVM) and loss by sedimentation during the stratification period.

Luciana Gomes, Barbosa; Paulina Maria Maia, Barbosa; Francisco Antonio Rodrigues, Barbosa.

2011-03-01

195

Vertical distribution of phytoplankton functional groups in a tropical shallow lake: driving forces on a diel scale Distribuição vertical de grupos funcionais fitoplanctônicos em um lago tropical raso: forças direcionadoras em escala nictemeral  

Directory of Open Access Journals (Sweden)

Full Text Available AIM: This study analyzed the vertical distribution of phytoplankton functional groups in two diel cycles in a warm monomictic shallow tropical lake; METHODS: Sampling of the abiotic variables, phytoplankton and zooplankton communities was performed at intervals of 3 hours over 24 hours in vertical profiles, in the stratification (February and circulation (July periods; RESULTS: The high thermal stability and the partial atelomixis favored the coexistence of functional groups that are sensitive to destratification, N A and F, composed by desmids and Chlorophyceae coccoids, and groups S2 and Lo, which persisted during the circulation, and were composed by filamentous cyanobacteria which do not fix N2 and dinoflagellates, respectively. The discontinuity in the vertical distribution of the functional groups, with dominance of N A and F in the epilimnion and R and Lo in the metalimnion and hypolimnion, was characteristic of the stratification, and differences between the daytime and nighttime periods were not significant. CONCLUSIONS: The reduction of 80% of the biomass of the NA group during the mixing period indicates the influence of thermal stability and partial atelomixis as determinant factors in the compartmentalization of functional groups, restricting daytime vertical migration (DVM and loss by sedimentation during the stratification period.OBJETIVO: Analisar a distribuição vertical dos grupos funcionais fitoplanctônicos em dois ciclos nictemerais em um lago tropical monomítico raso; MÉTODOS: As amostragens das variáveis abióticas, comunidades fitoplanctônica e zooplanctônica foram realizadas a intervalos de 3 horas ao longo de 24 horas em perfis verticais, nos períodos de estratificação (fevereiro e de circulação (julho; RESULTADOS: A elevada estabilidade térmica e a atelomixia parcial favoreceram a coexistência de grupos funcionais sensíveis a desestratificação N A e F, compostos por desmidias e clorofícias cocoides e pelos grupos S2 e Lo, persistentes durante a circulação, e compostos por cianobactérias filamentosas não fixadoras de N2 e dinoflagelados, respectivamente. A descontinuidade na distribuição vertical dos grupos funcionais com dominância de N A e F no epilímnio e de R e Lo no metalímnio e hipolímnio foi característica da estratificação, e diferenças entre períodos diurno e noturno não foram significativas. CONCLUSÕES: A redução em até 80% da biomassa do grupo NA durante a circulação indica a influência da estabilidade térmica e atelomixia parcial como fatores determinantes na compartimentalização dos grupos funcionais, restringindo a migração vertical diurna (MVD e a perda por sedimentação durante a estratificação.

Luciana Gomes Barbosa

2011-03-01

196

Zooplankton fecal pellets link fossil fuel and phosphate deposits  

Science.gov (United States)

Fossil zooplankton fecal pellets found in thinly bedded marine and lacustrine black shales associated with phosphate, oil, and coal deposits, link the deposition of organic matter and biologically associated minerals with planktonic ecosystems. The black shales were probably formed in the anoxic basins of coastal marine waters, inland seas, and rift valley lakes where high productivity was supported by runoff, upwelling, and outwelling. Copyright ?? 1981 AAAS.

Porter, K.G.; Robbins, E.I.

1981-01-01

197

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

198

Zooplankton of Lake Orta after liming: an eleven years study  

Digital Repository Infrastructure Vision for European Research (DRIVER)

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

199

Considerations on the biochemical composition of some freshwater zooplankton species.  

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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

200

Effects of temperature on the metabolic stoichiometry of Arctic zooplankton  

Science.gov (United States)

We assessed the relationship between zooplankton metabolism (respiration and inorganic N and P excretion) and "in situ" temperature through a grid of stations representing a range of natural temperature variation during the ATOS-Arctic cruise (July 2007). The objective was to explore not only the direct effects of temperature on zooplankton carbon respiratory losses (hereafter CR) and NH4-N and PO4-P excretion rates (hereafter NE and PE, respectively), but also to investigate whether these metabolic pathways responded similarly to temperature, and so how temperature could affect the stoichiometry of the metabolic products. Metabolic rates, normalised to per unit of zooplankton carbon biomass, increased with increasing temperature following the Arrhenius equation. However, the activation energy differed for the various metabolic processes considered. Respiration, CR, was the metabolic activity least affected by temperature, followed by NE and PE, and as a consequence the values of the CR : NE, CR : PE and NE : PE atomic quotients were inversely related to temperature. The effects of temperature on the stoichiometry of the excreted N and P products would contribute to modifying the nutrient pool available for phytoplankton and induce qualitative and quantitative shifts in the size, community structure and chemical composition of primary producers that could possibly translate to the whole Arctic marine food web.

Alcaraz, M.; Almeda, R.; Saiz, E.; Calbet, A.; Duarte, C. M.; Agustí, S.; Santiago, R.; Alonso, A.

2013-02-01

 
 
 
 
201

Zooplankton distribution in the superficial layer of the Sheksna Reservoir  

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Full Text Available The results of the studies of zooplankton collected in the superficial layer in different parts of the Sheksna Reservoir at the beginning of the August 2007 are presented. A total of 71 species have been recorded among which crustaceans prevail in the number of species, abundance and biomass. Zooplankton is distributed unevenly in the surface layer; the maximum density and biomass are recorded in the north-eastern part of the Lake Beloye – 164 000 ind/m3 and 1.06 g/m3, in the Sizma extension – 124 000 ind/m3 and 1.60 g/m3 and in the near-dam reach - 185 000 ind/m3 and 1.36 g/m3, respectively. The minimum values are recorded near the mouths of rivers Kovzha Belozerskaya (17 000 ind/m3 and 0.10 g/m3 and Kema (10 000 ind/m3 and 0.06 g/m3. Because of high concentration of fine-dispersed mineral suspended matter the water transparency decreases significantly. The water is polluted with the oil products and the rotifers of the genus Brachionus – indicators of polluted water – are dominated in the plankton. Zooplankton in the surface layer where blue-green algae are in mass differs from deeper horizons in lower abundance and biomass.

V. N. Stolbunova

2012-03-01

202

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

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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

203

Abundance and diversity of zooplankton in semi intensive prawn (Macrobrachium rosenbergii) farm  

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The present study was carried out on the seasonal abundance and diversity of zooplankton in a semi- intensive prawn farm of Bagerhat district from July to December, 2008. Plankton samples were collected by conical shaped monofilament nylon net (Plankton net) and Lugol’s solution was used for preservation. The zooplankton abundance was influenced by physico-chemical factors. During the study period 11 genera of zooplankton under 5 orders were recorded from the study ponds namely Copepoda, Ro...

Shil, Jadobendro; Ghosh, Alokesh Kumar; Rahaman, S. M. Bazlur

2013-01-01

204

Acoustic backscatter from zooplankton and fish explored through an optimized model framework  

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The purpose of this work has been to test complementary methods in order to classify marine organisms, with particularly attention to zooplankton and fish. Algorithms to separate fish and zooplankton have been developed and implemented at IMR and at IRD. A novel optimised model framework based on known scattering models are used to classify zooplankton and to separate these from fish. Acoustic data from up to 6 frequencies were collected to test the scattering model framework, while concurren...

Lebourges-dhaussy, A.; Knutsen, Tor; Korneliussen, Rolf J.

2004-01-01

205

Richness of Phytoplankton and Zooplankton in Water Streams at Jobolarangan Forest  

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Plankton is components of aquatic ecosystem. Phytoplankton play as primary producers, zooplankton play an important role in the higher order in the transfer of energy primary producers, the alga, to the higher order consumers such as aquatic insects, larval fish, and some adult fish. Streams of Jobolarangan forest may show phytoplankton and zooplankton that unique. The objectives of this research were to know diversity of phytoplankton and zooplankton and to determined their density. Plankton...

WIRYANTO; AINUR ROHIMAH; ARI SUSILOWATI

2001-01-01

206

Spatial variations in zooplankton diversity in waters contaminated with composite effluents  

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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

207

Zooplankton in the Schelde estuary, Belgium and the Netherlands: long-term trends in spring populations  

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A compilation of available data in between 1967 and 2002 on spring zooplankton abundance was made for the brackish and the freshwater zone of the Schelde estuary. The general picture is a significant increase of 1–2 orders of magnitude in abundance for Rotifera, Copepoda and Branchiopoda (mainly Cladocera) in the freshwater zone, while zooplankton abundance in the brackishwater zone remained more constant. Possible natural and management related causes for this increase in zooplankton abund...

Tackx, Micky; Aze?mar, Fre?de?ric; Boule?treau, Ste?phanie; Pauw, Niels; Bakker, Kees; Sautour, Benoit; Gasparini, Ste?phane; Soetaert, Karline; Damme, Stefan; Meire, Patrick

2005-01-01

208

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.)

209

STUDY ON ZOOPLANKTON FAUNA AND SEASONAL VARIATION IN BHIMA RIVER NEAR GURSALE VILLAGE, DIST: SOLAPUR, (MAHARASHTRA.  

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Full Text Available During present investigation total 18 Zooplankton species were recorded fromBhima river near Gursale village Taluka Pandharpur, Dist. Solapur (M.S from Jan. 2014 toDec.2014. Which consist of 9 Species belong to Rotifera, 5 species belong to Cladocera, 4 species belong to Copepoda, The Rotifera was the most dominant group throughout the Studyperiod. The number of Zooplankton was highest in summer followed by winter and lowest inMonsoon Season. The Zooplankton variation were observed as follows Rotifera > Copepod >Cladocera in Study Period. All Three zooplankton groups were observing in throughout studyperiod.

A. N. Dede

2015-01-01

210

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

211

Vertical mammaplasty.  

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Current criticisms regarding vertical mammaplasty include problems with poor immediate postoperative appearance, nipple-areola complex malposition, and excessive lower pole length. These problems can be avoided by proper patient selection, by utilizing correct concepts of skin design, and by observing correct glandular resection and closure concepts. Vertical mammaplasty also can result in other problems, such as hypertrophic circumareolar scars and lower pole deformities, including notching, boxy shape, infra-areolar depression, and flatness. These problems are also largely avoidable by using correct technique. Several basic concepts described previously have not proven necessary to achieve good results. Abandoning some of these principles has contributed to the ability to establish an aesthetically ideal breast shape intraoperatively as well as to a decrease in morbidity. This includes eliminating liposuction as a major integral component of the procedure, eliminating suturing the gland to the pectoralis muscle, not undermining the lower pole skin, and avoiding overly wide skin resection and tight wound closure that produces significant lower pole distortion in the early postoperative period. An important concept that has proven reliable is to use a "closed" design that does not predetermine the areolar opening whenever circumstances permit. When this is not possible, a modification that utilizes the smallest possible circumference as an open design is better than a large "mosque." These alternatives allow greater flexibility in determining final nipple position and also reduce the risk of hypertrophic circumareolar scars. Important glandular resection concepts include creating pillars that are attached to both the skin and the chest wall; making them of adequate dimension to avoid postoperative lower pole shape problems, such as flattening; resecting closer to the skin lateral to the pillars to avoid a boxy breast shape; and using a drain both to assist in accurately determining the endpoint of resection and to avoid postoperative seromas. Key closure concepts include approximation of the superior surfaces of the pillars at their base to maintain vertical height and thereby prevent lower pole flattening; approximation of the inferior surfaces of the pillars to the base of the breast to prevent notching; and proper management of the vertical incision by restricting the purse-string suture effect to only the inferior portion of the incision, where there may be skin excess present. Inclusion of these concepts leads to predictable and improved aesthetic results in vertical mammaplasty. This allows full realization of the purported advantages of vertical mammaplasty and allows this method to be utilized with a level of confidence similar to that seen with inverted-T techniques. PMID:15793463

Hidalgo, David A

2005-04-01

212

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.

2005-11-04

213

Vertical Village  

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Vertical village är ett tätt kvarter på östermalm med sammanlänkande trappor och gator som tar dig upp i stadsrummet, en förlängning av staden upp över takåsarna med vidsträckt utsikt. Längs din väg upp mellan gator och gränder nns liv och rörelse. För att skapa denna o-entlighet krävs en öppen byggnad med god förankring till marknivån men istället för ett traditionellt kvarter med o-entlig verksamhet i markplan valde jag att lyfta det o-entliga rummet över takåsarna me...

Svensson, Staffan

2012-01-01

214

Vertical distribution of phytoplankton functional groups in a tropical shallow lake: driving forces on a diel scale Distribuição vertical de grupos funcionais fitoplanctônicos em um lago tropical raso: forças direcionadoras em escala nictemeral  

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AIM: This study analyzed the vertical distribution of phytoplankton functional groups in two diel cycles in a warm monomictic shallow tropical lake; METHODS: Sampling of the abiotic variables, phytoplankton and zooplankton communities was performed at intervals of 3 hours over 24 hours in vertical profiles, in the stratification (February) and circulation (July) periods; RESULTS: The high thermal stability and the partial atelomixis favored the coexistence of functional groups that are sensit...

Luciana Gomes Barbosa; Paulina Maria Maia Barbosa; Francisco Antonio Rodrigues Barbosa

2011-01-01

215

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  

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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

216

ZOOPLANKTON DIVERSITY AND ITS RELATIONSHIP WITH PHYSICO-CHEMICAL PARAMETERS IN MANI RESERVOIR OF WESTERN GHATS, INDIA  

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Studies on relationship between zooplankton abundance and water quality parameter in Mani reservoir were made between January 2008 and December 2008.in the urrent investigation, impact of different physico-chemical parameters on zooplankton population was found. Ten genera of zooplankton were identified. The relationship between zooplankton and water quality parameters was varied from place to place depending upon the condition of the reservoir water.

Veerendra, D. N.; Thirumala, S.; Manjunatha, H.; Aravinda, H. B.

2012-01-01

217

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...

218

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...

219

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.

220

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...

 
 
 
 
221

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...

222

Zooplankton community patterns in the Chukchi Sea during summer 2004  

Science.gov (United States)

Zooplankton were sampled in the Chukchi Sea along three transects between Alaska and Russia, plus four high-speed transects across the axis of Herald Valley in August of 2004. A total of 50 holoplanktonic species, along with a prominent assemblage of meroplankton were encountered; most were of Pacific Ocean origin. Copepods represented the most diverse group with 23 species, and contributed the bulk (3100 ind. m -3, 30 mg dry weight m -3) of the total holozooplankton community abundance (3500 ind. m -3) and biomass (42 mg DW m -3) at most stations. Meroplanktonic larvae were, on average, almost as abundant (2260 ind. m -3) as the holozooplankton. Copepods were dominated numerically by four species of Pseudocalanus, Oithona similis, and the neritic copepods Acartia longiremis and Centropages abdominalis. The larger-bodied copepods, Calanus glacialis/ marshallae and three Neocalanus species, equalled or exceeded the biomass of Pseudocalanus, followed by contributions from Metridia pacifica and Eucalanus bungii. Considerable abundance (256 ind. m -3) and biomass (42 mg DW m -3) of the larvacean Oikopleura vanhoeffeni was observed throughout the sampling area. The chaetognath Parasagitta elegans (4.8 mg DW m -3) and a diverse assemblage of cnidarians (˜1.2 mg DW m -3) comprised the dominant predators. Six major assemblages of zooplankton were identified, and each was closely tied to physical properties of water masses: Euryhaline species in the warm fresh Alaska Coastal Current, a Bering Sea assemblage of both shelf and oceanic species in cool salty Bering Sea Water, a transitional group between these two, a neritic Bering Sea assemblage in cold salty Bering Winter Water, and a small cluster of Arctic Shelf species in cold, fresh Resident Chukchi Water. Ongoing climate change may alter the boundaries, extent of penetration, size spectra, and productivities of these communities, thus warranting regular monitoring of the zooplankton communities of this gateway into the Arctic.

Hopcroft, Russell R.; Kosobokova, Ksenia N.; Pinchuk, Alexei I.

2010-01-01

223

Cladoceran zooplankton abundance under clear and snow-covered ice  

Science.gov (United States)

We described the distribution of cladoceran zooplankton under the ice in a natural, glacial lake. Local light availability apparently altered the spatial distribution of cladocerans. Light levels measured under snow-covered areas (0.178 lux) were an order of magnitude less than those measured at the same depth under clear ice (1.750 lux). Cladoceran density under snow-covered areas was significantly higher (Bosmina spp.=3.34/L; Daphnia spp.=0.61/L) than cladoceran abundance under clear ice (Bosmina spp.=0.91/L; Daphnia spp.=0.19/L).

DeBates, T.J.; Chipps, S.R.; Ward, M.C.; Werlin, K.B.; Lorenzen, P.B.

2003-01-01

224

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

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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

225

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 (similarityhabits 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

226

Influence de la luminosité nocturne et de la turbidité sur le comportement vertical de migration de la civelle d'anguille (Anguilla anguilla L. dans l'estuaire de l'Adour  

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Compte tenu des observations effectuées, le schéma migratoire vertical de l'espèce peut être modélisé de la manière suivante : l'interaction entre la luminosité nocturne et la turbidité influence les déplacements de civelles dans la colonne d'eau en relation avec leur comportement lucifuge. Plus la lumière nocturne qui pénètre dans la colonne d'eau est importante et plus les civelles migrent en profondeur.

DE CASAMAJOR M. N.

1999-07-01

227

The directional measurement and calculation of radon migration coefficient  

International Nuclear Information System (INIS)

A directional measurement device has been designed to determine the radon migration in the ideal condition. Both horizontal and vertical migration of radon are studied. The horizontal migration coefficient of radon is 0.024 cm2·s-1, which is much less than 0.1 cm2·s-1, the diffusion coefficient of radon in the air given by the references. The vertical migration coefficient of radon is 0.182 cm2·s-1, which is considerably greater than the diffusion coefficient of radon in the air. (authors)

228

Temperature dependence of Arctic zooplankton metabolism and excretion stoichiometry  

Science.gov (United States)

We assessed the relationship between zooplankton metabolism (respiration and inorganic N and P excretion) and "in situ" temperature through a grid of stations representing a range of natural temperature variation during the ATOS-Arctic cruise (July 2007). The objective was to explore not only the direct effects of temperature on O2 consumption and NH4-N and PO4-P excretion, but also to investigate the possible relationships between temperature and the stoichiometry of the metabolic products. Zooplankton metabolic rates increased according to the rising temperature conditions, following the Arrhenius equation. However, the activation energy differed for the various metabolic processes considered. Respiration was the metabolic activity less affected by temperature, followed by NH4-N and PO4-P excretion, and as a consequence the values of the C : N, C : P and N : P quotients of the metabolic products were inversely related to temperature. The effects of temperature on the stoichiometry of the excretion products would contribute to modify the nutrient pool available for phytoplankton and induce qualitative and quantitative shifts in the characteristics of primary producers that could possibly translate into the whole Arctic marine food web.

Alcaraz, M.; Almeda, R.; Saiz, E.; Calbet, A.; Duarte, C. M.; Agustí, S.; Santiago, R.; Alonso, A.

2012-06-01

229

Vertical fluid flow, fractures, redox and sedimentary magnetization  

Energy Technology Data Exchange (ETDEWEB)

Magnetization along fault planes has been observed through high resolution aeromagnetic (HRAM) surveys. In an effort to explain this magnetization, a model has been proposed involving vertical flow of fluids along fractures and faults. Regional hydrodynamic studies of the Alberta Basin show that there is potential for vertical fluid flow. In areas where fractures or faults allow vertical fluid migration, fluids and rocks with contrasting redox potentials co-mingle leading to conditions for the possible deposition of magnetic minerals. Paleozoic cores in NE Alberta were studied. Results showed that there was vertical migration of sulfate rich waters in the presence of hydrocarbons from the oxidizing environment of the Elk Point Group into overlying reduced marine shales and carbonates of the Beaverhill Lake Group. This vertical fluid migration has initiated the low temperature formation of exotic mineral species.

Abercrombie, H.J.; Peirce, J.W.

1997-09-01

230

Short-term variation in zooplankton community from Daya Bay with outbreaks of Penilia avirostris  

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Full Text Available The zooplankton community structure in bays fluctuates as a result of anthropogenic activities in such waters. We focused on the short-term variability of a zooplankton community and compared its differences at the outflow of a nuclear power plant (ONPP, in a marine cage-culture area (MCCA and in unpolluted waters (UW in the south-west part of Daya Bay from 28 April to 1 June 2001. Environmental factors and zooplankton abundance differed significantly among stations at ONPP, MCCA and UW: high temperatures and a high zooplankton abundance occurred at ONPP, while a high chlorophyll a concentration and a low zooplankton abundance prevailed in MCCA. Statistical analysis revealed that the zooplankton diversity and abundance could be reduced by the activity of the marine cage-culture in a short time. Penilia avirostris made up an important component of the zooplankton in the study area, its abundance ranging widely from 16 to 7267 indiv. m-3 from April to June and peaking at the ONPP outflow. The outbreak of P. avirostris probably resulted from the combined effects of favourable water temperature, food concentration and its parthenogenetic behaviour.

Kaizhi Li

2014-06-01

231

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

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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

232

Spatial and Temporal Variations in the Zooplankton Community of Phosphorescent Bay, Puerto Rico  

Science.gov (United States)

Nocturnal variations of zooplankton abundance and hydrographic conditions were examined at three locations (centre, north shore and south shore) in Phosphorescent Bay, Puerto Rico, from May 1992 through April 1993. Seven taxa accounted for approximately 96% of the annual mean zooplankton abundance: Oithonaspp. (43·5%), Acartia tonsa(31·5%), copepod nauplii (8·8%), Paracalanusspp.(6·7%), gastropod veligers (2·5%), larvaceans (1·7%) and Pseudo-diaptomus cokeri(1·6%). Copepods dominated numerically throughout the year and comprised 94·3% of total zooplankton. Higher abundance of zooplankton (mean±1 SD=252 259±176 797 individuals m -3) was associated with cool water temperatures (24·9-27·4 °C) and dry conditions (0·3-2·9 cm precipitation/month) which prevailed between December and March relative to the period between April and November (warm/wet season) (mean±1 SD=59 773±26 861 individuals m -3), when temperature and precipitation were higher (27·3-30·3 °C, 3·1-20·6 cm month -1). Fluctuations of zooplankton populations, particularly copepods, followed progressive increments in chlorophyll aconcentrations. This abundance pattern was consistent at the three sampling stations. Zooplankton abundance was higher on the north shore of the bay. The taxonomic composition of zooplankton was similar at the sampling stations studied.

Rios-Jara, E.

1998-06-01

233

Cs-137 migration in soil near NPPs  

International Nuclear Information System (INIS)

A convective-diffusion model has been employed for describing Cs-137 migration in soil. The migration parameters were determined by comparing the calculated vertical distribution profiles with the experimental ones. The migration parameters dependence on the soil state has been studied. Cs-137 penetration rate was found to be function of the soil type, surface state, soil wetness and orography. The obtained values are presented. A method is suggested for revealing the soil surface contamination by Cs-137 produced during NPP operation with distinguishing it from the global contamination background. For this purpose Cs-137 content in the upper 5 mm soil layer is estimated

234

How zooplankton feed: mechanisms, traits and trade-offs.  

Science.gov (United States)

Zooplankton is a morphologically and taxonomically diverse group and includes organisms that vary in size by many orders of magnitude, but they are all faced with the common problem of collecting food from a very dilute suspension. In order to maintain a viable population in the face of mortality, zooplankton in the ocean have to clear daily a volume of ambient water for prey particles that is equivalent to about 10(6) times their own body volume. While most size-specific vital rates and mortality rates decline with size, the clearance requirement is largely size-independent because food availability also declines with size. There is a limited number of solutions to the problem of concentrating dilute prey from a sticky medium: passive and active ambush feeding; feeding-current feeding, where the prey is either intercepted directly, retained on a filter, or individually perceived and extracted from the feeding current; cruise feeding; and colonization of large particles and marine snow aggregates. The basic mechanics of these food-collection mechanisms are described, and it is shown that their efficiencies are inherently different and that each of these mechanisms becomes less efficient with increasing size. Mechanisms that compensate for this decline in efficiency are described, including inflation of feeding structures and development of vision. Each feeding mode has implications beyond feeding in terms of risk of encountering predators and chance of meeting mates, and they partly target different types of prey. The main dichotomy is between (inefficient) ambush feeding on motile prey and the more efficient active feeding modes; a secondary dichotomy is between (efficient) hovering and (less efficient) cruising feeding modes. The efficiencies of the various feeding modes are traded off against feeding-mode-dependent metabolic expenses, predation risks, and mating chances. The optimality of feeding strategies, evaluated as the ratio of gain over risk, varies with the environment, and may explain both size-dependent and spatio-temporal differences in distributions of various feeding types as well as other aspects of the biology of zooplankton (mating behaviour, predator defence strategies). PMID:20682007

Kiørboe, Thomas

2011-05-01

235

Concentrations of 210Po and 210Pb in Zooplankton at Pulau Redang, Terengganu, Malaysia  

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Full Text Available Zooplankton samples collected from eight stations around Pulau Redang, Terengganu, Malaysia were use for measure the concentration activities of 210Po and 210Pb using Alpha Spectrometry. Mean activity in zooplankton tissue for 210Po [364.67?21.00 Bq kg 1 (dry wt.] was much greater than 210Pb [93.67?6.83 Bq kg 1 (dry wt.] with ranging ratio of 210Po/210Pb from 3.46 to 4.71. These fluctuated may be related to the feeding habits of zooplankton and daily biological processes occurred in water column.

Che Abd Rahim Mohamed

2005-01-01

236

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

Digital Repository Infrastructure Vision for European Research (DRIVER)

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 re...

Ana María Gagneten

2002-01-01

237

Effects of zooplankton herbivory on biomarker proxy records  

Science.gov (United States)

The stable carbon isotopic compositions of cholesterol, generally the most dominant sterol in the copepod Temora, bears the ?13C "signature" of its dietary precursor sterol when fed on Isochrysis galbana and Rhodomonas sp. The ?13C of cholesterol in the faecal pellets released from Temora longicornis fed on Rhodomonas sp. is identical to the ?13C of the sterols in the diet, indicating that no significant carbon isotopic fractionation effects occur when the copepod modifies eukaryotic precursor sterols to cholesterol. Furthermore, the ratio of long-chain alkenones and their stable carbon isotopic compositions in I. galbana were identical to those egested in faecal material. Thus Zooplankton herbivory does not invalidate the use of these alkenones as a proxy for sea surface temperature and pCO2.

Grice, Kliti; Klein Breteler, Wim C. M.; Schouten, Stefan; Grossi, Vincent; de Leeuw, Jan W.; Sinninghe Damsté, Jaap S.

1998-12-01

238

The analysis of the records of zooplankton species from the Danube Delta Biosphere Reserve  

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Full Text Available Based on informations from various bibliographical references, the authors present the list of 945 zooplankton species ever recorded in the Danube Delta Biosphere Reserve. There are also remarks related tothe taxonomical position of some species.

TÖRÖK Liliana

2007-10-01

239

Astaxanthin in the calanoid copepod Calanus helgolandicus: dynamics of esterfication and vertical distribution in the German Bight, North Sea.  

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Zooplankton synthesise astaxanthin, a carotenoid pigment believed to protect against high-energy irradiance, from precursors in their diet. Different patterns of astaxanthin vertical distribution would be expected from the benefits of photoprotection, the costs of visual predation and the availability of food. Despite a highly resolved sampling approach (4 m depth intervals), no clear pattern of vertical distribution or correlation with chlorophyll a concentrations was found for Calanus helgo...

Sommer, Frank; Agurto, Cristian; Henriksen, Peter; Kioerboe, Thomas

2006-01-01

240

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

 
 
 
 
241

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

242

The Impact of Fish Predation and Cyanobacteria on Zooplankton Size Structure in 96 Subtropical Lakes  

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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 zooplan...

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

2013-01-01

243

Zooplankton diversity analysis through single-gene sequencing of a community sample  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Abstract Background Oceans cover more than 70% of the earth's surface and are critical for the homeostasis of the environment. Among the components of the ocean ecosystem, zooplankton play vital roles in energy and matter transfer through the system. Despite their importance, understanding of zooplankton biodiversity is limited because of their fragile nature, small body size, and the large number of species from various taxonomic phyla. Here we present the results of single-...

Nishida Mutsumi; Hashiguchi Yasuyuki; Machida Ryuji J; Nishida Shuhei

2009-01-01

244

Species composition, abundance and distribution of zooplankton in a tropical eutrophic lake: Lake Catemaco, México  

Digital Repository Infrastructure Vision for European Research (DRIVER)

From April 1992 to May 1993, zooplankton samples were collected monthly by means of horizontal tows in nine sites of the lake. Prior to the towing, temperature of surface water, transparency (Secchi), pH and dissolved oxygen were evaluated. A total of 31 zooplankton forms, including 14 species of rotifers, three copepods, five cladocerans and one ostracod, as well as protozoans (mainly vorticellids and ciliates), were detected. Rotifers were the dominant organisms, mainly Brachionus havanaens...

Roberto E Torres-Orozco B; Zanatta, Sandra A.

1998-01-01

245

A Study on Zooplankton Organisms Community Structures of Lake Terkos (Istanbul-Turkey  

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Full Text Available This research has been conducted to determine seasonal changes of zooplanktonic organisms (Rotifera, Cladocera, Copepoda in the lake Terkos. Zooplankton samples have been collected in five different stations in monthly periods between April 2000-March 2001. As a result, 1992556 ind m-3 was found in lake Terkos and it is made up of 1177334 ind m-3 Rotifera (59.1%, 117583 ind m-3 Cladocera (5.9% and 697639 ind m-3 Copepoda (35%

Huseyin Guher

2004-01-01

246

Distribution and Abundance of Gelatinous Zooplankton along Tamil Nadu Coastal Waters  

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The distribution and abundance of the gelatinous zooplankton namely hydromedusae, scyphomedusae, siphonophore, ctenophore, salps, doliolids, appendicularians and chaetognaths were investigated in two seasons at seven stations in East Tamil Nadu coast, India. The occurrences of gelatinous zooplankton were observed to be more in summer than in winter. However, the composition of different species in each group varied from all the stations and seasons. Apart from the individual variation i...

Prasanna Kumar, C.; Sampath Kumar, P.; Iyyapparajanarasimapallavan, G.; Jalal, K. C. A.; Kamaruzzaman, B. Y.; Akbar John, B.

2013-01-01

247

Zooplankton diversity of two floodplain lakes (pats) of Manipur, northeast India  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Plankton samples collected (November, 2002 – October, 2004) from Waithou and Utra pats, two floodplain lakesin Manipur state of northeast India, revealed species rich zooplankton (121 species) with diverse nature of Rotifera (75 species).The individual pats exhibited rich species diversity (110 and 103 species) and high monthly richness (68±7 and 61±8 species)respectively with higher community similarities. Zooplankton formed important quantitative component (56.0±4.3 % and55.1±5.1 %) o...

Sharma, B. K.

2011-01-01

248

The Distribution and Seasonality of Zooplankton in Sombreiro River, Niger Delta, Nigeria  

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The distribution and seasonality of zooplankton in Sombreiro River of the, Niger Delta area in Nigeria was studied for a period of two years (August, 2007-July, 2009). All the zooplankton species occurred in all the stations except Mysis sp that was not recorded in station 4 (Odiemudie). Also all the stations recorded seventeen species (17) each except station 4 (Odiemudie) that had sixteen (16) species. Five species of Cladocera occurred in all the stations and were fairly distributed. In st...

Ezekiel, E. N.; Abowei, E. N. Ogamba And J. F. N.

2011-01-01

249

Predicting zooplankton response to environmental changes in a temperate estuarine ecosystem  

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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

250

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

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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

251

Zooplankton and diatoms of temporary and permanent freshwater pans in the Mpumalanga Highveld region, South Africa  

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This paper provides a description of the zooplankton and epiphytic diatom communities of permanent and temporary freshwater pans in the Mpumalanga Highveld region of South Africa. Few studies have investigated the biota of pans in this area, which is seriously threatened by mining and agricultural development. Nineteen pan sites within a 20 km radius covering a wide range of water chemistries were sampled once for zooplankton, epiphytic diatoms and water physico-chemical data in 2009. Collect...

Riato, Luisa; Ginkel, Carin; Taylor, Jonathan C.

2014-01-01

252

Abundance and diversity of zooplankton in semi intensive prawn (Macrobrachium rosenbergii) farm.  

Science.gov (United States)

The present study was carried out on the seasonal abundance and diversity of zooplankton in a semi- intensive prawn farm of Bagerhat district from July to December, 2008. Plankton samples were collected by conical shaped monofilament nylon net (Plankton net) and Lugol's solution was used for preservation. The zooplankton abundance was influenced by physico-chemical factors. During the study period 11 genera of zooplankton under 5 orders were recorded from the study ponds namely Copepoda, Rotifera, Cladocera, Ostracoda and Crustacean Larvae. Among all groups copepod was the dominant order. The percentages of Copepoda, Rotifera, Cladocera, Ostracoda and Crustacean Larvae in semi-intensive culture system were 54%, 28%, 12%, 4% and 2% respectively. But the genera Brachionus under the order of Rotifer was dominant among all other genera. Cyclops and Helidiaptomus under the order of Copepod were the 2nd dominant genera. Numbers of zooplankton species were recorded to be the highest in summer season and minimum at early winter season. Highest number of zooplankton found at the month of October. Total zooplankton shows significant positive relationship with water temperature ((r?=?+0.384), Dissolve Oxygen(r?=?+0.113), pH(r?=?+0.320), Free CO2 (r?=?+0.319), Alkalinity(r?=?+0.269), Hardness (r?=?+0.402) and negative relationship with Salinity(r?=?-0.486), Transparency(r?=?-0.693). The findings of the present study will help to improve the management strategies of shrimp culture system. PMID:23667823

Shil, Jadobendro; Ghosh, Alokesh Kumar; Rahaman, S M Bazlur

2013-12-01

253

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

254

Examining shifts in zooplankton community as a response of environmental change in Lakes  

Science.gov (United States)

We examined 20 years of zooplankton samples from Harp Lake for shifts in zooplankton variability following invasion by zooplankton predator Bythotrephes longimanus, using organism body size—as measured at high resolution by Laser Optical Plankton Counter (LOPC)—as the primary metric of investigation. A period of transitory high variability in the 2yr post-invasion was observed for both body size compositional variability and aggregate variability metrics, with both measures of variability shifting from low or intermediate to high variability immediately following invasion, before shifting again to intermediate variability, 2 yr post-invasion. Aggregate and compositional variability dynamics were also considered in combination over the study period, revealing that the period of transitory high variability coincided with a shift from a community-wide stasis variability pattern to one of asynchrony, before a shift back to stasis 2 yr post-invasion. These dynamics were related to changes in the significant zooplankton species within the Harp Lake community over the pre- and post- invasion periods, and are likely to be indicative of changes in the stability in the zooplankton community following invasion by Bythotrephes. The dual consideration of aggregate and compositional variability as measured by LOPC was found to provide a valuable means to assess the ecological effects of biological invasion on zooplankton communities as a whole, extending our knowledge of the effects of invasion beyond that already revealed through more traditional taxonomic investigation.

Ghadouani, Anas; Mines, Conor; Legendre, Pierre; Yan, Norman

2014-05-01

255

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

256

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

Digital Repository Infrastructure Vision for European Research (DRIVER)

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

257

Zooplankton as a food resource of juvenile fish in the littoral shallows of the Ry-binsk reservoir  

Directory of Open Access Journals (Sweden)

Full Text Available Species composition, dominant species and quantitative characteristics of zooplankton in different habitats of the littoral shallow part of the Rybinsk Reservoir were studied at the end of august 2009. In the structure of zooplankton community 75 taxa have been found among which crustaceans are prevailed. The most of them belong to littoral forms. The highest values of abundance and biomass of zooplankton and density accumulation of young fish are recorded in mouth parts of rivers inflowing the reservoir.

V. N. Stolbunova

2010-09-01

258

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

259

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

260

Springtime zooplankton size structure over the continental shelf of the Bay of Biscay  

Science.gov (United States)

Linking lower and higher trophic levels requires special focus on the essential role played by mid-trophic levels, i.e., the zooplankton. One of the most relevant pieces of information regarding zooplankton in terms of flux of energy lies in its size structure. In this study, an extensive data set of size measurements is presented, covering parts of the western European continental shelf and slope, from the Galician coast to the Ushant front, during the springs from 2005 to 2012. Zooplankton size spectra were estimated using measurements carried out in situ with the Laser Optical Plankton Counter (LOPC) and with an image analysis of WP2 net samples (200 ?m mesh size) performed following the ZooScan methodology. The LOPC counts and sizes particles within 100-2000 ?m of spherical equivalent diameter (ESD), whereas the WP2/ZooScan allows for counting, sizing and identification of zooplankton from ~ 400 ?m ESD. The difference between the LOPC (all particles) and the WP2/ZooScan (zooplankton only) was assumed to provide the size distribution of non-living particles, whose descriptors were related to a set of explanatory variables (including physical, biological and geographic descriptors). A statistical correction based on these explanatory variables was further applied to the LOPC size distribution in order to remove the non-living particles part, and therefore estimate the size distribution of zooplankton. This extensive data set provides relevant information about the zooplankton size distribution variability, productivity and trophic transfer efficiency in the pelagic ecosystem of the Bay of Biscay at a regional and interannual scale.

Vandromme, P.; Nogueira, E.; Huret, M.; Lopez-Urrutia, Á.; González-Nuevo González, G.; Sourisseau, M.; Petitgas, P.

2014-10-01

 
 
 
 
261

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

262

Parasitic Chytrids sustain zooplankton growth during inedible algal bloom  

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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

263

Zooplankton of Lake Orta after liming: an eleven years study  

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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

264

Trophic transfer of cyanobacterial toxins from zooplankton to planktivores: consequences for pike larvae and mysid shrimps.  

Science.gov (United States)

The aim of this study was to evaluate the potentially harmful effects of zooplankton preexposed to cyanobacteria on two planktivorous animals: a fish larva (pike, Esox lucius) and a mysid shrimp (Neomysis integer). The planktivores were fed zooplankton from a natural community that had been preexposed to cell-free extract or to purified toxin (nodularin) of the cyanobacterium Nodularia spumigena, and the growth, feeding, and pellet production of the planktivores, as well as the toxin content of the pellets, were measured. In addition, radiolabeled nodularin ((3)H-dihydronodularin) was used in separate experiments to measure the vector transfer of nodularin from zooplankton to their predators. During 11-day exposures, dissolved nodularin was transferred to pike larvae and N. integer via zooplankton at very low rates of accumulation. Treatment with N. spumigena extract decreased the ingestion and feces production rates of pike larvae. With purified nodularin alone, no such effect could be observed. No effect on molting cycle length, fecal pellet production, C:N ratio, or growth of N. integer was detected. The results suggest that dissolved cyanobacterial toxins released during bloom decay can have a negative impact on feeding and, hence, on the growth of fish larvae via zooplankton, even without direct contact between cyanobacteria and the fish. PMID:15892036

Karjalainen, Miina; Reinikainen, Marko; Spoof, Lisa; Meriluoto, Jussi A O; Sivonen, Kaarina; Viitasalo, Markku

2005-06-01

265

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

266

Zooplankton Atlas of the Southern Ocean: The SCAR SO-CPR Survey (1991-2008)  

Science.gov (United States)

The SCAR Southern Ocean Continuous Plankton Recorder (SO-CPR) Survey produces one of the largest and most accessed zooplankton data sets in the world. These data serve as a reference for other Southern Ocean monitoring programmes such as those run by the Commission for the Conservation of Antarctic Marine Living Resources (CCAMLR) and the developing Southern Ocean Observing System (SOOS). It has been instrumental in providing baseline data on zooplankton composition, communities, and distribution patterns on the ocean basin scale. The SO-CPR Survey is publishing the first detailed geographical atlas of the near-surface Southern Ocean zooplankton. This atlas is based on 22,553 CPR samples collected from 1991 to 2008 from voyages operated by Australia, Japan, Germany, New Zealand, USA and Russia. The Atlas documents the distribution and abundance of the 50 most abundant zooplankton taxa amongst the 200+ taxa sampled. The maps are printed in alphabetical order of the genera within each taxon and nomenclature is based on the Register of Antarctic Marine Species (RAMS) developed by the SCAR Marine Biodiversity Information Network (SCAR-MarBIN). The SO-CPR Atlas will operate as a ready reference to researchers interested in the distribution of zooplankton in the Southern Ocean, for example knowing the distribution of grazers in relation to phytoplankton production or the availability of prey for higher predators.

McLeod, David J.; Hosie, Graham W.; Kitchener, John A.; Takahashi, Kunio T.; Hunt, Brian P. V.

2010-08-01

267

Inter-annual variability of a zooplankton community: the importance of summer concentrated rainfall in a regulated river ecosystem  

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Full Text Available We monitored the zooplankton community dynamics of a regulated river system (the Nakdong River in South Korea,in an effort to characterize the relationship between basin rainfall quantity and changes in zooplankton communitystructure. The river studied herein has four multipurpose dams upstream and one estuarine barrage at the river mouth,resulting in intensive flow regulation. We hypothesized that flow regulation would effect zooplankton community structurechanges not only within the summer period of concentrated rainfall, but also during the subsequent seasons. Fieldmonitoring was conducted on a weekly basis (1999 to 2009 at the study site (27 km upstream from the estuary dam.The studied years were divided into two groups: rainy years with annual rainfall greater than total average annual rainfall,and dry years (years with lower than average annual rainfall. The zooplankton community data was also dividedinto two groups according to year and community structural characteristics. The summer density of zooplankton waslow during the summer concentrated rainfall period. In the autumn, zooplankton density was statistically related toriver flow (r2 = 0.30, P < 0.05, N = 11, which was affected by the summer concentrated rainfall (r2 = 0.31, P < 0.05, N = 11.Furthermore, autumn zooplankton density was positively related to that observed in the summer (r2 = 0.53, P < 0.05, N= 11. Therefore, it can be concluded that summer concentrated rainfall can affect the following seasons’ zooplanktondensities caused by dam flow control, and the potential growth rate of zooplankton

Jong-Yun Choi

2011-03-01

268

Hydroacoustic estimation of zooplankton biomass at two shoal complexes in the Apostle Islands Region of Lake Superior  

Science.gov (United States)

Hydroacoustics can be used to assess zooplankton populations, however, backscatter must be scaled to be biologically meaningful. In this study, we used a general model to correlate site-specific hydroacoustic backscatter with zooplankton dry weight biomass estimated from net tows. The relationship between zooplankton dry weight and backscatter was significant (p < 0.001 ) and explained 76% of the variability in the dry weight data. We applied this regression to hydroacoustic data collected monthly in 2003 and 2004 at two shoals in the Apostle Island Region of Lake Superior. After applying the regression model to convert hydroacoustic backscatter to zooplankton dry weight biomass, we used geostatistics to analyze the mean and variance, and ordinary kriging to create spatial zooplankton distribution maps. The mean zooplankton dry weight biomass estimates from plankton net tows and hydroacoustics were not significantly different (p = 0.19) but the hydroacoustic data had a significantly lower coefficient of variation (p < 0.001). The maps of zooplankton distribution illustrated spatial trends in zooplankton dry weight biomass that were not discernable from the overall means.

Holbrook, B.V.; Hrabik, T.R.; Branstrator, D.K.; Yule, D.L.; Stockwell, J.D.

2006-01-01

269

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

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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

270

Hydrography and zooplankton off the central Oregon coast during the 1997-1998 El Nino event  

Energy Technology Data Exchange (ETDEWEB)

Hydrography and zooplankton were monitored at several ocean stations off the coast of Oregon to compare 1997 ocean conditions with conditions observed in the 1970s. It was shown that in the early spring of 1997, the Oregon upwelling zone began in a normal fashion and was followed by an increase in zooplankton production. In May, zooplankton numbers declined and continued to do so throughout the summer. The study, which also included sea surface temperature monitoring, showed that the sea surface temperature on the shelf was warmer by one degree than previous El Nino events. It was suggested that the warming in 1997 was due to onshore advection of warm offshore waters. The issue of how atmospheric pressure patterns and equatorial events influence coastal upwelling off the coast of Oregon was also explored. 1 tab., 3 figs.

Peterson, W.T.; Emmett, B.; Jacobson, K. [NOAA, NMFS, NWFSC, Hatfield Marine Science Center, Newport, OR (United States); Schiewe, M.; Casillas, E. [NOAA, NWFSC Northwest Fisheries Science Center, Seattle, WA (United States)

1998-12-31

271

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

272

Size-related response of zooplankton to hydroclimatic variability and water-quality in an organically polluted estuary of the Basque coast (Bay of Biscay)  

Science.gov (United States)

Seasonal, interannual and spatial variabilities were analysed for the > 100 ?m and > 200 ?m zooplankton assemblages in the estuary of Bilbao throughout 1997-2000, and related to hydroclimatic and water-quality factors. Seasonal and interannual patterns of abundance differed between assemblages, and only the abundance of the > 100 ?m zooplankton was correlated with temperature. The large-sized zooplankton decreased more drastically than the small-sized zooplankton with decreasing salinity, and showed highest correlations with dissolved oxygen and water transparency. Seasonal changes were the major variability mode of zooplankton composition in both assemblages. Interannual changes associated to phytoplankton biomass and temperature were more evident in the small-sized zooplankton, whilst spatial differences related to oxygen depletion were more evident in the large-sized zooplankton. This indicates that small zooplankton was more sensitive to climate-related factors, while large zooplankton was more sensitive to water quality. Small copepods, cirriped larvae, appendicularians and Noctiluca were the main taxa responsible for the interannual variations in the > 100 ?m assemblage. In the > 200 ?m assemblage, large copepods were the main zooplankton responsible for the spatial variability related to oxygen depletion. Cnidarians and cladocerans responded mainly to decreases in salinity, and polychaete larvae were found to be unaffected by the decrease in dissolved oxygen and salinity. Results suggest that size-related differential responses of zooplankton should be considered when zooplankton monitoring is performed to assess the effect of climate forcing and pollution in coastal and estuarine environments.

Intxausti, Lander; Villate, Fernando; Uriarte, Ibon; Iriarte, Arantza; Ameztoy, Iban

2012-06-01

273

Evaluation of sound extinction and echo interference in densely aggregated zooplankton  

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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

274

Potential Importance of Fish Predation and Zooplankton Grazing on Natural Populations of Freshwater Bacteria †  

Digital Repository Infrastructure Vision for European Research (DRIVER)

The rates of ingestion of natural bacterial assemblages by natural populations of zooplankton (>50 ?m in size) were measured during a 19-day period in eutrophic Frederiksborg Slotssø, Denmark, as well as in experimental enclosures (containing 5.3 m3 of lake water). The fish and nutrients of the enclosures were manipulated. In enclosures without fish, large increases in ingestion by zooplankton >140 ?m in size were found (up to 3 ?g of C liter?1 h?1), compared with values less than 0.3...

Riemann, Bo

1985-01-01

275

Migration and revolution  

Directory of Open Access Journals (Sweden)

Full Text Available The Arab Spring has not radically transformed migration patterns in the Mediterranean, and the label ‘migration crisis’ does not do justice to the composite and stratified reality.

Nando Sigona

2012-06-01

276

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)

277

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

Energy Technology Data Exchange (ETDEWEB)

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 {sup 90}Sr in water was 2.8 kBq/l, {sup 137}Cs - 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/m{sup 3} (given the mean and standard deviation), in 2012 - 26.0±0.9 million individuals/m{sup 3}. 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)

Osipova, O.; Pryakhin, E. [Urals Research Center for Radiation Medicine - URCRM (Russian Federation); Ivanov, I. [FSUE Mayak PA (Russian Federation)

2014-07-01

278

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

279

Lymphocyte migration studies  

Digital Repository Infrastructure Vision for European Research (DRIVER)

For maintenance of immunity and tolerance, the organs and tissues of the organism are connected by migrating lymphoid cells. Understanding lymphocyte migration is essential for many disorders and diseases - especially in the mucosa-lined organs. Detailed analyses of migrating lymphocytes have been performed in many species, especially in laboratory animals. However, important experiments in lymphocyte migration have been carried out in large animals, for example sheep, cattle and pigs. These ...

Bimczok, Diane; Rothko?tter, Hermann

2006-01-01

280

Impacts of hypoxia on the structure and processes in the pelagic community (zooplankton, macro-invertebrates and fish)  

Science.gov (United States)

Dissolved oxygen (DO) concentration in the water column is an environmental parameter that is crucial for the successful development of many pelagic organisms. Hypoxia tolerance and threshold values are species- and stage-specific and can vary enormously. While some fish species may suffer from oxygen values of less than 3 ml L-1 and show impact on growth, development and behaviour, other organisms such as euphausiids may survive DO levels as low as 0.1 ml L-1. A change in the average or the minimum or maximum DO in an area may have significant impacts on the survival of certain species and hence on the species composition in the ecosystem with consequent changes in trophic pathways and productivity. Evidence of the deleterious effects of oxygen depletion on species of the pelagic realm is scarce, particularly in terms of the effect of low oxygen on development, recruitment and patterns of migration and distribution. While planktonic organisms have to cope with different DOs and find adaptive mechanisms, nektonic species may avoid areas of inconvenient DO and develop adapted migrational strategies. Planktonic organisms may only be able to escape vertically, above or beneath the Oxygen Minimum Zone (OMZ). In shallow areas only the surface layer can serve as a refuge, in deep waters many organisms have developed vertical migration strategies to use, pass and cope with the OMZ. This paper elucidates the role of DO for different taxa in the pelagic realm and the consequences of low oxygen for foodweb structure and system productivity.

Ekau, W.; Auel, H.; Pörtner, H.-O.; Gilbert, D.

2009-05-01

 
 
 
 
281

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

282

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

283

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

284

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

Digital Repository Infrastructure Vision for European Research (DRIVER)

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; Ivan Pandourski; Apostol Apostolov

2014-01-01

285

Richness of Phytoplankton and Zooplankton in Water Streams at Jobolarangan Forest  

Directory of Open Access Journals (Sweden)

Full Text Available Plankton is components of aquatic ecosystem. Phytoplankton play as primary producers, zooplankton play an important role in the higher order in the transfer of energy primary producers, the alga, to the higher order consumers such as aquatic insects, larval fish, and some adult fish. Streams of Jobolarangan forest may show phytoplankton and zooplankton that unique. The objectives of this research were to know diversity of phytoplankton and zooplankton and to determined their density. Plankton were sampled using 25-30 ?m mesh net, in three location of streams, i.e.: Parkiran (1773 m asl., Mrutu (1875 m asl., and Air Terjun (1600 m asl.. Samples were examined under light microscope for identification, and determined their density/L. Richness of phytoplankton in streams at Jobolarangan forest composed by family of Chlorophyceae, Euglenophyceae (Algae, and Bacillariophyceae. Zooplanktons that were found order of rotifer, cladoceras, and copepods. Allochtonous productivity, low nutrient level, low light level, and flowing water condition caused density of plankton/L in stream at Jobolarangan was low, i.e. 0,064 to 0,232.

WIRYANTO

2001-07-01

286

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

287

Superior odontoid migration in the Klippel–Feil patient  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Klippel-Feil syndrome (KFS) is an uncommon condition noted primarily as congenital fusion of two or more cervical vertebrae. Superior odontoid migration (SOM) has been noted in various skeletal deformities and entails an upward/vertical migration of the odontoid process into the foramen magnum with depression of the cranium. Excessive SOM could potentially threaten neurologic integrity. Risk factors associated with the amount of SOM in the KFS patient are based on conjecture and have not been...

Samartzis, Dino; Kalluri, Prakasam; Herman, Jean; Lubicky, John P.; Shen, Francis H.

2007-01-01

288

Long distance dispersal of zooplankton endemic to isolated mountaintops--an example of an ecological process operating on an evolutionary time scale.  

Science.gov (United States)

Recent findings suggest a convergence of time scales between ecological and evolutionary processes which is usually explained in terms of rapid micro evolution resulting in evolution on ecological time scales. A similar convergence, however, can also emerge when slow ecological processes take place on evolutionary time scales. A good example of such a slow ecological process is the colonization of remote aquatic habitats by passively dispersed zooplankton. Using variation at the protein coding mitochondrial COI gene, we investigated the balance between mutation and migration as drivers of genetic diversity in two Branchipodopsis fairy shrimp species (Crustacea, Anostraca) endemic to remote temporary rock pool clusters at the summit of isolated mountaintops in central South Africa. We showed that both species colonized the region almost simultaneously c. 0.8 My ago, but exhibit contrasting patterns of regional genetic diversity and demographic history. The haplotype network of the common B. cf. wolfi showed clear evidence of 11 long distance dispersal events (up to 140 km) with five haplotypes that are shared among distant inselbergs, as well as some more spatially isolated derivates. Similar patterns were not observed for B. drakensbergensis presumably since this rarer species experienced a genetic bottleneck. We conclude that the observed genetic patterns reflect rare historic colonization events rather than frequent ongoing gene flow. Moreover, the high regional haplotype diversity combined with a high degree of haplotype endemicity indicates that evolutionary- (mutation) and ecological (migration) processes in this system operate on similar time scales. PMID:22102865

Vanschoenwinkel, Bram; Mergeay, Joachim; Pinceel, Tom; Waterkeyn, Aline; Vandewaerde, Hanne; Seaman, Maitland; Brendonck, Luc

2011-01-01

289

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

290

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

291

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

292

Zooplankton diversity and physico-chemical conditions in three perennial ponds of Virudhunagar district, Tamilnadu.  

Science.gov (United States)

Plankton diversity and physico-chemical parameters are an important criterion for evaluating the suitability of water for irrigation and drinking purposes. In this study we tried to assess the zooplankton species richness, diversity and evenness and to predict the state of three perennial ponds according to physico-chemical parameters. A total of 47 taxa were recorded: 24 rotifers, 9 copepods, 8 cladocerans, 4 ostracods and 2 protozoans. More number of zooplankton species were recorded in Chinnapperkovil pond (47 species) followed by Nallanchettipatti (39 species) and Kadabamkulam pond (24 species). Among the rotifers, Branchionus sp. is abundant. Diaphanosoma sp. predominant among the cladocerans. Among copepods, numerical superiority was found in the case of Mesocyclopes sp. Cypris sp. repeated abundance among ostracoda. Present study revealed that zooplankton species richness (R1 and R2) was comparatively higher (R1: 4.39; R2: 2.13) in Chinnapperkovil pond. The species diversity was higher in the Chinnapperkovil pond (H': 2.53; N1: 15.05; N2: 15.75) as compared to other ponds. The water samples were analyzed for temperature, pH, electrical conductivity alkalinity salinity, phosphate, hardness, dissolved oxygen and biological oxygen demand. Higher value of physico-chemical parameters and zooplankton diversity were recorded in Chinnapperkovil pond as compared to other ponds. The zooplankton population shows positive significant correlation with physico-chemical parameters like, temperature, alkalinity phosphate, hardness and biological oxygen demand, whereas negatively correlated with rainfall and salinity. The study revealed that the presence of certain species like, Monostyla sp., Keratella sp., Lapadella sp., Leydigia sp., Moinodaphnia sp., Diaptomus sp., Diaphanosoma sp., Mesocyclopes sp., Cypris sp. and Brachionus sp. is considered to be biological indicator for eutrophication. PMID:21046994

Rajagopal, T; Thangamani, A; Sevarkodiyone, S P; Sekar, M; Archunan, G

2010-05-01

293

Analysis of southeast Australian zooplankton observations of 1938-42 using synoptic oceanographic conditions  

Science.gov (United States)

The research vessel Warreen obtained 1742 planktonic samples along the continental shelf and slope of southeast Australia from 1938-42, representing the earliest spatially and temporally resolved zooplankton data from Australian marine waters. In this paper, Warreen observations along the southeast Australian seaboard from 28°S to 38°S are interpreted based on synoptic meteorological and oceanographic conditions and ocean climatologies. Meteorological conditions are based on the NOAA-CIRES 20th Century Reanalysis Project; oceanographic conditions use Warreen hydrological observations, and the ocean climatology is the CSIRO Atlas of Regional Seas. The Warreen observations were undertaken in waters on average 0.45 °C cooler than the climatological average, and included the longest duration El Niño of the 20th century. In northern New South Wales (NSW), week time-scale events dominate zooplankton response. In August 1940 an unusual winter upwelling event occurred in northern NSW driven by a stronger than average East Australian Current (EAC) and anomalous northerly winds that resulted in high salp and larvacean abundance. In January 1941 a strong upwelling event between 28° and 33°S resulted in a filament of upwelled water being advected south and alongshore, which was low in zooplankton biovolume. In southern NSW a seasonal cycle in physical and planktonic characteristics is observed. In January 1941 the poleward extension of the EAC was strong, advecting more tropical tunicate species southward. Zooplankton abundance and distribution on the continental shelf and slope are more dependent on weekly to monthly timescales on local oceanographic and meteorological conditions than continental-scale interannual trends. The interpretation of historical zooplankton observations of the waters off southeast Australia for the purpose of quantifying anthropogenic impacts will be improved with the use of regional hindcasts of synoptic ocean and atmospheric weather that can explain some of the physically forced natural variability.

Baird, Mark E.; Everett, Jason D.; Suthers, Iain M.

2011-03-01

294

Synthetic seismic monitoring using reverse-time migration and Kirchhoff migration for CO2 sequestration in Korea  

Science.gov (United States)

During last two decades, CO2 sequestration in the subsurface has been extensively studied and progressed as a direct tool to reduce CO2 emission. Commercial projects such as Sleipner, In Salah and Weyburn that inject more than one million tons of CO2 per year are operated actively as well as test projects such as Ketzin to study the behavior of CO2 and the monitoring techniques. Korea also began the CCS (CO2 capture and storage) project. One of the prospects for CO2 sequestration in Korea is the southwestern continental margin of Ulleung basin. To monitor the behavior of CO2 underground for the evaluation of stability and safety, several geophysical monitoring techniques should be applied. Among various geophysical monitoring techniques, seismic survey is considered as the most effective tool. To verify CO2 migration in the subsurface more effectively, seismic numerical simulation is an essential process. Furthermore, the efficiency of the seismic migration techniques should be investigated for various cases because numerical seismic simulation and migration test help us accurately interpret CO2 migration. In this study, we apply the reverse-time migration and Kirchhoff migration to synthetic seismic monitoring data generated for the simplified model based on the geological structures of Ulleung basin in Korea. Synthetic seismic monitoring data are generated for various cases of CO2 migration in the subsurface. From the seismic migration images, we can investigate CO2 diffusion patterns indirectly. From seismic monitoring simulation, it is noted that while the reverse-time migration generates clear subsurface images when subsurface structures are steeply dipping, Kirchhoff migration has an advantage in imaging horizontal-layered structures such as depositional sediments appearing in the continental shelf. The reverse-time migration and Kirchhoff migration present reliable subsurface images for the potential site characterized by stratigraphical traps. In case of vertical CO2 migration at injection point, the reverse time migration yields better images than Kirchhoff migration does. On the other hand, Kirchhoff migration images horizontal CO2 migration clearer than the reverse time migration does. From these results, we can conclude that the reverse-time migration and Kirchhoff migration can complement with each other to describe the behavior of CO2 in the subsurface. Acknowledgement This work was financially supported by the Brain Korea 21 project of Energy Systems Engineering, the "Development of Technology for CO2 Marine Geological Storage" program funded by the Ministry of Land, Transport and Maritime Affairs (MLTM) of Korea and the Korea CCS R&D Center (KCRC) grant funded by the Korea government (Ministry of Education, Science and Technology) (No. 2012-0008926).

Kim, W.; Kim, Y.; Min, D.; Oh, J.; Huh, C.; Kang, S.

2012-12-01

295

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

296

Feminization of migrations?  

Directory of Open Access Journals (Sweden)

Full Text Available Women have always taken part in migrations, but their presence varied depending on their origins, on the labour market situation both in the areas of origin and in the target areas, as well as the migration policies in the immigration areas. Their presence was not always visible and did not attract as much scholarly and political attention as today. What happened, how can one explain such an interest lately, whereas only few years ago the subject was marginal, in the shadow of the "mainstream - malestream", i.e. migration as a phenomenon which focuses on geographic mobility of men, while women are not considered as equal protagonists, they either follow or remain at home. Could the so called "feminization" of migration explain the great and sudden interest for women and gender in migrations? This text critically examines the notion of "feminization" considered today as one of the main dimensions of global migration flows. Drawing on trends both globally and in specific countries, it shows that "feminization" is neither a new nor a sudden trend and entails variations depending on the origins, level of development and maturity of migration flows. In some groups men were primo-migrants and with a gradual feminization the flows reach a balanced sex ratio. There where women migrated first, or became numerically predominant, one observs the opposite trend: a "masculinization". Some authors rightly refer to "gender transition", the term which covers both trends. It is argued in the conclusion that the visibility and growing interest for women in migration and, more recently, for a gender perspective in migration, is not only due to the changing migration patterns and profile of migrants but also to the renewal of theoretical perspectives in migration and gender studies in a context that largely facilitated that renewal. The focus of our attention today on specific aspects of migration is triggered not only by genuine changes in migration trends, but it is also a result of a long process of visibilisation in the academic production on migration, women and gender. These trends may have existed earlier in the migration history but had remained in the shadow of categories defining, recording and analyzing migration.

Morokvaši? Mirjana

2010-01-01

297

Zooplankton functional groups on the continental shelf of the yellow sea  

Science.gov (United States)

Zooplankton plays a vital role in marine ecosystems. Variations in the zooplankton species composition, biomass, and secondary production will change the structure and function of the ecosystem. How to describe this process and make it easier to be modeled in the Yellow Sea ecosystem is the main purpose of this paper. The zooplankton functional groups approach, which is considered a good method of linking the structure of food webs and the energy flow in the ecosystems, is used to describe the main contributors of secondary produciton of the Yellow Sea ecosystem. The zooplankton can be classified into six functional groups: giant crustaceans, large copepods, small copepods, chaetognaths, medusae, and salps. The giant crustaceans, large copepods, and small copepods groups, which are the main food resources for fish, are defined depending on the size spectrum. Medusae and chaetognaths are the two gelatinous carnivorous groups, which compete with fish for food. The salps group, acting as passive filter-feeders, competes with other species feeding on phytoplankton, but their energy could not be efficiently transferred to higher trophic levels. From the viewpoint of biomass, which is the basis of the food web, and feeding activities, the contributions of each functional group to the ecosystem were evaluated; the seasonal variations, geographical distribution patterns, and species composition of each functional group were analyzed. The average zooplankton biomass was 2.1 g dry wt m -2 in spring, to which the giant crustaceans, large copepods, and small copepods contributed 19, 44, and 26%, respectively. High biomasses of the large copepods and small copepods were distributed at the coastal waters, while the giant crustaceans were mainly located at offshore area. In summer, the mean biomass was 3.1 g dry wt m -2, which was mostly contributed by the giant crustaceans (73%), and high biomasses of the giant crustaceans, large copepods, and small copepods were all distributed in the central part of the Yellow Sea. During autumn, the mean biomass was 1.8 g dry wt m -2, which was similarly constituted by the giant crustaceans, large copepods, and small copepods (36, 33, and 23%, respectively), and high biomasses of the giant crustaceans and large copepods occurred in the central part of the Yellow Sea, while the small copepods were mainly located at offshore stations. The giant crustaceans and large copepods dominated the zooplankton biomass (2.9 g dry wt m -2) in winter, contributing respectively 57 and 27%, and they, as well as the small copepods, were all mainly located in the central part of the Yellow Sea. The chaetognaths group was mainly located in the northern part of the Yellow Sea during all seasons, but contributed less to the biomass compared with the other groups. The medusae and salps groups were distributed unevenly, with sporadic dynamics, mainly along the coastline and at the northern part of the Yellow Sea. No more than 10 species belonging to the respective functional groups dominated the zooplankton biomass and controlled the dynamics of the zooplankton community. The clear picture of the seasonal and spatial variations of each zooplankton functional group makes the complicated Yellow Sea ecosystem easier to be understood and modeled.

Sun, Song; Huo, Yuanzi; Yang, Bo

2010-06-01

298

Zooplankton community structure, biomass and role in carbon fluxes during the second half of a phytoplankton bloom in the eastern sector of the Kerguelen Shelf (January February 2005)  

Science.gov (United States)

During the KEOPS survey, zooplankton was sampled with vertical tows to estimate zooplankton stock and to study its composition and size structure both using traditional taxonomic identification and Optical Plankton Counter (OPC). Mesozooplankton OPC-biomass derived from OPC size spectra and integrated over 200 m was variable with average values about 10 g C m -2 along transects A and B and at the fixed station KERFIX, and only ˜5 g C m -2 along transect C. Stations in the most oceanic area (A11, B11, and C11) presented biomass values 3 times lower than the mean value of their respective transects, highlighting a clear decrease of the biomass beyond the shelf. The mesozooplankton community was dominated by copepods, particularly by large- and medium-size calanoids and small Oithonidae. Large numbers of different copepodites stages and nauplii were found, as well as exuviae, indicating that individuals were in active growing phase over the whole area. Euphausiids, chaetognaths, appendicularians, amphipods, polychaetes, ostracods and salps were found as well. Two reference stations, A3 located in the middle of the bloom on the shelf and C11 in the oceanic waters, were visited several times during the cruise. No particular temporal variations, neither in biomass nor in community structure, were observed, but differences in integrated biomass (average biomass at A3: 10.6 g C m -2; at C11: 2.8 g C m -2) between oceanic and shelf stations clearly show an enhanced secondary production on the shelf. Additional measurements at some stations were performed in order to quantify ingestion (gut contents) and respiration rates on key species and size groups. Gut pigment contents were higher during the first half of the survey at both stations, showing clear temporal changes probably linked to the prey field, with lower values always reported in the oceanic waters compared to the shelf. Values of respiration and ingestion rates extrapolated from OPC size spectra using published allometric relationships are discussed.

Carlotti, François; Thibault-Botha, Delphine; Nowaczyk, Antoine; Lefèvre, Dominique

2008-03-01

299

Densidad, biomasa y composición del zooplancton, en el estrato superficial de la cuenca de Cariaco, Venezuela / Density, biomass and composition of zooplankton, in the surface layer of the Cariaco basin, Venezuela  

Scientific Electronic Library Online (English)

Full Text Available SciELO Chile | Language: Spanish Abstract in spanish Con la finalidad de entender los procesos que determinan los cambios en la composición y abundancia del zooplancton en la estación de series de tiempo CARIACO (`Carbon Retention in a Colored Ocean'), se estudió la densidad, biomasa y composición del zooplancton durante el periodo noviembre 2002-ener [...] o 2004. Se midió in situ la salinidad, temperatura y concentración de oxígeno disuelto. Se estimó la biomasa fitoplanctónica (Chl a), la biomasa (peso seco) y densidad zooplanctónica. Se realizaron calados oblicuos bimensuales con una red Bongo en los intervalos 0-30, 30-70 y 70-100 m. Los máximos valores de biomasa (0,039 mg m-3 peso seco) y densidad zooplanctónica (582 ind. m-3) para las tres capas se midieron en el período de surgencia costera. Por otra parte, los valores más bajos para esta variables (0,007 mg m-3 and 7 ind. m-3, respectivamente) se registraron en mayo de 2003. En general, los mayores valores se detectaron en la capa 30-70 m, a pesar de que la variabilidad temporal en los estratos fue similar. La comunidad zooplanctónica estuvo dominada por copépodos, cladóceros y apendicularias. Los resultados reflejaron una amplia variabilidad temporal en la composición y abundancia de la comunidad zooplanctónica, a pesar de que la estación está ubicada en un área tropical, debido al efecto de la surgencia costera estacional. Abstract in english In order to understand the processes that determine changes in zooplankton abundance and composition in the CARIACO (Carbon Retention in a Colored Ocean) Time Series Station, zooplankton biomass, composition and density were studied aboard the O/V Hermano Ginés from November 2002 to January 2003. Sa [...] linity, temperature and dissolved oxygen were measured in situ. Zooplankton samples were collected by vertical tows using a Bongo net (mesh size 333 and 555 mm) at a speed of 2 knots at the intervals 0-30, 30-70, and 70-100 m. Chlorophyll (chl a), zooplankton biomass (dry mass) and density were estimated. The maximum values of biomass (0.039 mg m-3 dry mass) and zooplankton density (582 ind. m-3) for the three strata were measured during the upwelling period. On the other hand, the lower values for these variables (0.030 mL m-3, 0.007 mg m-3 and 7 ind. m-3, respectively) were recorded in May 2003. In general, the greatest values were detected within the 30 to 70 m range. Even though, the variability of the different strata was similar. The zooplankton community was dominated by copepods, cladocerans and appendicularians. The results showed a great temporal variability en zooplankton biomass and composition in spite of the fact that the station is located in a tropical area due to the effect of seasonal coastal upwelling.

Brightdoom, Márquez; José, Díaz-Ramos; Luis, Troccoli; Baumar, Marín; Ramón, Varela.

2009-12-01

300

Migration in Burkina Faso  

Digital Repository Infrastructure Vision for European Research (DRIVER)

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

 
 
 
 
301

Biological processes in the water column of the South Atlantic Bight: zooplankton responses. Progress report, June 1985-June 1986  

Energy Technology Data Exchange (ETDEWEB)

The effects of wind forcing on water displacement from the near- to the offshore environment of the southeastern continental shelf are discussed. This report presents information on zooplankton abundance and distribution in relation to hydrographic variables. 7 figs. (ACR)

Paffenhoefer, G.A.

1985-12-20

302

Climate-mediated changes in zooplankton community structure for the eastern Bering Sea  

Science.gov (United States)

Zooplankton are critical to energy transfer between higher and lower trophic levels in the eastern Bering Sea ecosystem. Previous studies from the southeastern Bering Sea shelf documented substantial differences in zooplankton taxa in the Middle and Inner Shelf Domains between warm and cold years. Our investigation expands this analysis into the northern Bering Sea and the south Outer Domain, looking at zooplankton community structure during a period of climate-mediated, large-scale change. Elevated air temperatures in the early 2000s resulted in regional warming and low sea-ice extent in the southern shelf whereas the late 2000s were characterized by cold winters, extensive spring sea ice, and a well-developed pool of cold water over the entire Middle Domain. The abundance of large zooplankton taxa such as Calanus spp. (C. marshallae and C. glacialis), and Parasagitta elegans, increased from warm to cold periods, while the abundance of gelatinous zooplankton (Cnidaria) and small taxa decreased. Biomass followed the same trends as abundance, except that the biomass of small taxa in the southeastern Bering Sea remained constant due to changes in abundance of small copepod taxa (increases in Acartia spp. and Pseudocalanus spp. and decreases in Oithona spp.). Statistically significant changes in zooplankton community structure and individual species were greatest in the Middle Domain, but were evident in all shelf domains, and in both the northern and southern portions of the eastern shelf. Changes in community structure did not occur abruptly during the transition from warm to cold, but seemed to begin gradually and build as the influence of the sea ice and cold water temperatures persisted. The change occurred one year earlier in the northern than the southern Middle Shelf. These and previous observations demonstrate that lower trophic levels within the eastern Bering Sea respond to climate-mediated changes on a variety of time scales, including those shorter than the commonly accepted quasi-decadal time periods. This lack of resilience or inertia at the lowest trophic levels affects production at higher trophic levels and must be considered in management strategy evaluations of living marine resources.

Eisner, Lisa B.; Napp, Jeffrey M.; Mier, Kathryn L.; Pinchuk, Alexei I.; Andrews, Alexander G.

2014-11-01

303

Coherence of long-term variations of zooplankton in two sectors of the California Current System  

Science.gov (United States)

We analyzed long-term (56-year) variations in springtime biomass of the zooplankton of the California Current System from two primary regions sampled by CalCOFI: Southern California (SC) and Central California (CC) waters. All organisms were enumerated from the plankton samples and converted to organic carbon biomass using length-carbon relationships, then aggregated into 19 major taxa. Planktonic copepods dominate the carbon biomass in both SC (59%) and CC (46%), followed by euphausiids (18% and 25% of mean biomass in SC and CC, respectively). Pelagic tunicates, especially salps and doliolids, constituted a higher fraction of the biomass in CC (13%) than in SC (5%). There was no long-term trend detectable in total zooplankton carbon biomass, in marked contrast to a decline in zooplankton displacement volume in both regions. The difference between these biomass metrics is accounted for by a long-term decline in pelagic tunicates (particularly salps), which have a relatively high ratio of biovolume:carbon. The decline in pelagic tunicates was accompanied by a long-term increase in water column density stratification. No other taxa showed a decline over the duration of the study, apart from salps and pyrosomes in SC and doliolids in CC. Some zooplankton taxa showed compensatory increases over the same time period (ostracods, large decapods, and calycophoran siphonophores in both SC and CC; appendicularians and polychaetes in SC). Two tests for ecosystem shifts, a sequential algorithm and the cumulative sum of anomalies (CuSum) approach, failed to detect changes in 1976-1977 in total carbon biomass, displacement volume, or most individual major taxa, suggesting that aggregated biomass is an insensitive indicator of climate forcing. In contrast, both techniques revealed a cluster of step-like changes associated with the La Niña of 1999. The major El Niño’s in the past half century have consistently depressed total zooplankton biomass and biomass of many major taxa in both SC and CC, although such effects are transitory. Much, but not all, of the interannual variability in zooplankton is shared between the Southern and Central California sectors of the California Current System.

Lavaniegos, Bertha E.; Ohman, Mark D.

2007-10-01

304

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

305

Aquaporins and cell migration.  

Science.gov (United States)

Aquaporin (AQP) water channels are expressed primarily in cell plasma membranes. In this paper, we review recent evidence that AQPs facilitate cell migration. AQP-dependent cell migration has been found in a variety of cell types in vitro and in mice in vivo. AQP1 deletion reduces endothelial cell migration, limiting tumor angiogenesis and growth. AQP4 deletion slows the migration of reactive astrocytes, impairing glial scarring after brain stab injury. AQP1-expressing tumor cells have enhanced metastatic potential and local infiltration. Impaired cell migration has also been seen in AQP1-deficient proximal tubule epithelial cells, and AQP3-deficient corneal epithelial cells, enterocytes, and skin keratinocytes. The mechanisms by which AQPs enhance cell migration are under investigation. We propose that, as a consequence of actin polymerization/depolymerization and transmembrane ionic fluxes, the cytoplasm adjacent to the leading edge of migrating cells undergoes rapid changes in osmolality. AQPs could thus facilitate osmotic water flow across the plasma membrane in cell protrusions that form during migration. AQP-dependent cell migration has potentially broad implications in angiogenesis, tumor metastasis, wound healing, glial scarring, and other events requiring rapid, directed cell movement. AQP inhibitors may thus have therapeutic potential in modulating these events, such as slowing tumor growth and spread, and reducing glial scarring after injury to allow neuronal regeneration. PMID:17968585

Papadopoulos, M C; Saadoun, S; Verkman, A S

2008-07-01

306

Prävention irregulärer Migration  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Technische Zusammenarbeit mit den Grenzorganen der Auswanderungsländer, massenmediale Vermittlung realitätsgetreuer Informationen über die Einwanderungsländer und Entwicklungsprojekte mit Rückkehrern sind die Hauptschienen der Prävention irregulärer Migration.

Niederberger, Josef Martin; Wichmann, Nicole

2007-01-01

307

Demography of zooplankton (Anuraeopsis fissa, Brachionus rubens and Moina macrocopa) fed Chlorella vulgaris and Scenedesmus acutus cultured on different media  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Generally zooplankton growth is often limited by the quality of their algal diet. A cheaper common practice in aquaculture, is to culture algae with fertilizers; however, the demography of zooplankton when fed these algae has not yet been evaluated. We studied the population growth and life table demography of the rotifers Anuraeopsis fissa and Brachionus rubens, and the cladoceran Moina macrocopa. For this, the algae Scenedesmus acutus or Chlorella vulgaris were cultured on defined (BoldR...

Jesús Morales-Ventura; Nandini, S.; Sarma, S. S. S.; Maria Elena Castellanos-Páez

2012-01-01

308

The role of light for fish-zooplankton-phytoplankton interactions during winter in shallow lakes – a climate change perspective  

Digital Repository Infrastructure Vision for European Research (DRIVER)

1. Variations in the light regime can affect the availability and quality of food for zooplankton grazers as well as their exposure to fish predation. In northern lakes light is particularly low in winter and, with increasing warming, the northern limit of some present-day plankton communities may move further north and the plankton will thus receive less winter light. 2. We followed the changes in the biomass and community structure of zooplankton and phytoplankton in a cle...

Bramm, M. E.; Lassen, M. K.; Liboriussen, L.; Richardson, K.; Ventura, Marc; Jeppesen, Erik

2009-01-01

309

Hierarchical Analysis of Zooplankton Assemblages over Semidiel Pattern in the Lagoon of Kavaratti Atoll, Lakshadweep Archipelago, India  

Digital Repository Infrastructure Vision for European Research (DRIVER)

A hierarchical analysis of data concerning the zooplankton assemblages over a semidiel pattern werepresented in the inside waters of Kavaratti lagoon. Gastropod larvae dominated in all time intervals throughoutthe study. The dendrogram matrix clearly indicated the community interrelation ships expressed by thisunivalve molluscan group over semidiel pattern towards other groups of zooplanktons aggregated in thecollections. Copepod varieties form a single separate cluster and showed its presenc...

Jean Jose, J.; Baiju, P. Udayakumar V. J. Ajimon R. Shibu K. Narendra Babu R. S.

2010-01-01

310

Distribution of zooplankton populations in marennes-oleron bay (france), structure and grazing impact of copepod communities  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Zooplankton distribution in Marennes-Oleron Bay (France) varies during the year and is essentially determined by seasonal rhythms. The whole set of zooplanktonic taxa can be divided into three groups: the first bearing oceanic affinities; the second with estuarine tendencies; and the third more intermediate. Important water flows inhibit the establishment in a specific zone of an autochthonous community (this community is reduced to such species as Acartia discaudata, Acartia grani and Euterp...

Sautour, B.; Castel, Jerome

1993-01-01

311

Zooplankton communities fluctuations from 1995 to 2005 in the Bay of Villefranche-sur-Mer (Northern Ligurian Sea, France)  

Digital Repository Infrastructure Vision for European Research (DRIVER)

An integrated analysis of the pelagic ecosystems of the Ligurian Sea is performed combining time series of different zooplankton groups (small and large copepods, chaetognaths, appendicularians, pteropods, thaliaceans, decapods larvae, other crustaceans, other gelatinous and other zooplankton), chlorophyll-a and nutrients, seawater salinity, temperature and density and local weather at the Point B coastal station (Northern Ligurian Sea). From January 1995 to December 2005, ...

Vandromme, P.; Stemmann, L.; Berline, L.; Gasparini, S.; Mousseau, L.; Prejger, F.; Passafiume, O.; -m Guarini, J.; Gorsky, G.

2010-01-01

312

Diatom and crustacean zooplankton communities, their seasonal variability and representation in the sediments of subarctic Lake Saanajärvi  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Present and past diatom and crustacean zooplankton communities of subarctic Lake Saanajärvi in Finnish Lapland were studied with special emphasis on their representation in the sediment surface. Two years monitoring of the present state of the lake revealed it to be ultraoligotrophic with a biomass peak during autumn overturn. Chrysophytes and diatoms were the most abundant phytoplankton groups, with four species forming the main bulk of the crustacean zooplankton community. The comparison o...

Rautio, Milla; Korhola, Atte; Sorvari, Sanna

2000-01-01

313

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

314

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 SciELO Brazil | Language: English Abstract in english 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

315

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

316

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

317

The El Niño event and its influence on the zooplankton off Peru  

Science.gov (United States)

The Zooplankton groups in general, and the copepoda group in particular, were determined and quantified. Changes were observed in their latitudinal distribution in the area between 6°00' and 12°38'S and up to 270 n. mi (513 km) off the coast during January and February 1983. The biomass fluctuated between 3 and 18 mL m-2, where the highest values are given by organisms typical of subtropical surface waters such as giltheads, appendicularians, and oceanic copepods. Because of the tropicalizing effect of the study area, a density decrease of larval stages of Zooplankton typical for the area was observed, while prawn larval stages, unusual for the area, were found. Furthermore, there is a significant increase of carnivorous and omnivorous genera of the Copepoda group, such as Centropages, Candacia, Euchaeta, and Labidocera, all identified as predators of anchovy and sardine larvae.

Carrasco, S.; Santander, H.

1987-12-01

318

Distribution and Abundance of Gelatinous Zooplankton along Tamil Nadu Coastal Waters  

Directory of Open Access Journals (Sweden)

Full Text Available The distribution and abundance of the gelatinous zooplankton namely hydromedusae, scyphomedusae, siphonophore, ctenophore, salps, doliolids, appendicularians and chaetognaths were investigated in two seasons at seven stations in East Tamil Nadu coast, India. The occurrences of gelatinous zooplankton were observed to be more in summer than in winter. However, the composition of different species in each group varied from all the stations and seasons. Apart from the individual variation in seasonal distribution, most of the species appeared to be cosmopolitan in the Indian waters. A total of 34 species from summer and 17 species from winter were recorded during the present study. The hydromedusae were dominant in both the seasons of the study period. Ephyrae of the scyphomedusae were also noticed in both the seasons.

C. Prasanna Kumar

2013-01-01

319

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

320

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

 
 
 
 
321

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

Energy Technology Data Exchange (ETDEWEB)

The goal of the Fall Removal Experiment 1987 was to determine the processes affecting the dependent and fate of low salinity coastal water and of biological material therein during fall when winds are mainly south-to westward. Five zooplankton taxa, Acartia tonsa, (A. tonsa) Paracalanus species (sp), Temora turbinata (T. turbinata), Oncaea sp, and Sagitta enflata were examined. Data on the distribution of all five taxa were presented, and distribution over time was also studied. The abundance of A. tonsa decreased tenfold over the 13 day sampling period, Paracalanus varied twofold and T. Turbinata showed little variability. The A. tonsa decrease was postulated to result from food abundance or predation, although the possible role of size distribution, water displacement and chlorophyll distribution will be examined in the future. A possible role of turbulence in zooplankton abundance is being examined. 8 refs., 5 figs.

1990-02-07

322

Impact of perfluorooctanoic acid on the structure of the zooplankton community in indoor microcosms.  

Science.gov (United States)

There is presently, a substantial amount of information being gathered concerning the environmental risk associated with the perfluorooctanoic acid (PFOA) compound. The aim of this paper was to determine a 35 day community no observable effect concentration (NOEC(community)) or lowest observable effect concentration (LOEC) for freshwater zooplankton exposed to PFOA during a study in 30 l indoor aquatic microcosms. Some significant (P richness > or = Cyclops canthocamptus staphylinus > Cyclops diaptomus>total zooplankton > or = Rotifera sp. The long term ecological significance of these temporal fluctuations could not be determined in this study, however, the overall study cessation analysis showed that the structure of the ecosystem was changed from a more diverse community dominated by larger species towards a less diverse community dominated by smaller more and robust species (P < 0.05). Additional chronic toxicity testing should also be addressed since these compounds are so persistent and recalcitrant. PMID:12560171

Sanderson, Hans; Boudreau, Timothy M; Mabury, Scott A; Solomon, Keith R

2003-02-12

323

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

324

Endoscopic removal of a migrating polyester band using argon plasma coagulation.  

Science.gov (United States)

A case is reported of a 40-year-old woman with a past history of bariatric surgery with vertical banding gastroplasty. Migrating band was observed during upper GI endoscopy performed for pyrosis. Before undergoing another bariatric intervention, migrated band had to be removed. This procedure was successfully performed endoscopically using argon plasma coagulation. No complication occurred. This case highlights that migrated band could be easily and safely removed without the need of specific or dedicated endoscopic tool. PMID:23273494

Musquer, Nicolas; Letessier, Eric; Le Rhun, Marc; Coron, Emmanuel

2013-06-01

325

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

326

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

327

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.

328

Open water zooplankton communities in North African wetland lakes:the CASSARINA Project  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Zooplankton (Copepoda, Cladocera, Ostracoda, Rotifera and Diptera larvae) in nine North African lakes was collected from open water areas over twenty months during 1997/99. The results were used to monitor changes in the pelagic micro-invertebrate fauna of these sites with the purpose of exploring diversity structure and regional species occurrences. The studied sites formed three distinct groups based on hydrology and water quality criteria: (i) acid water with no marine connection (Megene C...

Ramdani, Mohammed; Elkhiati, Najat; Flower, Roger J.; Birks, Hilary H.; Krai?em, Mejdidine M.; Fathi, Adel A.; Patrick, Simon T.

2001-01-01

329

Spatio-temporal variability of zooplankton community structure and trophic processes off central Peru  

Digital Repository Infrastructure Vision for European Research (DRIVER)

The coastal upwelling ecosystems of the Humboldt Current are characterized by high biological production. This productivity originates in the lower trophic levels in response to the fertilization of the surface layers with nutrients that are brought to upper layers through wind-driven processes. Phytoplankton is mainly consumed mainly by zooplankton, which in turn is preyed on by small pelagic fishes. These groups of organisms are subject to large perturbations due to intrannual (seasonal) an...

Criales Hernandez, Maria Isabel

2009-01-01

330

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

Digital Repository Infrastructure Vision for European Research (DRIVER)

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

331

The effects of seston lipids on zooplankton fatty acid composition in Lake Washington, Washington, USA.  

Science.gov (United States)

We collected suspended particulate matter (seston) and zooplankton samples from Lake Washington in Seattle, Washington, U.S.A., over a 10-month period to investigate the effects of food availability on zooplankton fatty acid (FA) composition. The percentage of nutritionally critical omega3 polyunsaturated fatty acids (PUFA) in the seston varied from 8% of the FA pool in midsummer to 30% during the spring diatom bloom. Zooplankton accumulated much higher percentages omega3 PUFA than was available in the seston. In particular, cladocerans preferentially accumulated eicosapentaenoic acid (EPA, 20:5omega3), copepods accumulated docosahexaenoic acid (DHA, 22:6omega3), and both copepods and cladocerans accumulated 18 carbon chain omega3 PUFAs (C18 omega3). By comparison, the FA of zooplanktivorous juvenile sockeye salmon (Oncorhynchus nerka) were strongly dominated by EPA (12.5% +/- 2.1%) and DHA (28.2% +/- 8.7%). The saturated fatty acid and the arachidonic acid (ARA, 20:4omega6) composition of Diaptomus ashlandi was strongly (r2 = 0.76) and moderately (r2 = 0.54) correlated with the prevalence of these FAs in the seston. Furthermore, the DHA content of Diaptomus was moderately correlated with the seston's DHA content (r2 = 0.45) and very strongly correlated with seston EPA (r2 = 0.89). Since EPA was the most prevalent PUFA in the seston and DHA was the most prevalent PUFA in Diaptomus, these results suggest that Diaptomus may synthesize DHA from the EPA in their food. In general, zooplankton species in Lake Washington were strongly enriched with those FA molecules that are most physiologically important for fish nutrition (i.e., ARA, EPA, and DHA), indicating a clear mechanism by which changes in seston composition influence fisheries ecology. PMID:20380207

Ravet, Joseph L; Brett, Michael T; Arhonditsis, George B

2010-01-01

332

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

333

Eclipse effects on field crops and marine zooplankton: the 29 March 2006 Total Solar Eclipse  

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Some effects in the biosphere from the Total Solar Eclipse of 29 March 2006 were investigated in field crops and marine zooplankton. Taking into account the decisive role of light on plant life and productivity, measurements of photosynthesis and stomatal behaviour were conducted on seven important field-grown cereal and leguminous crops. A drop in photosynthetic rates, by more than a factor of 5 in some cases, was observed, and the minimum values of photosynthetic rates ranged between 3.13 a...

Economou, G.; Christou, E. D.; Giannakourou, A.; Gerasopoulos, E.; Georgopoulos, D.; Kotoulas, V.; Lyra, D.; Tsakalis, N.; Tziortzou, M.; Vahamidis, P.; Papathanassiou, E.; Karamanos, A.

2008-01-01

334

Spatial variations in zooplankton diversity in waters contaminated with composite effluents  

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Full Text Available 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 of Cladocera, 2 species of Copepoda, 15 species of Rotifera, and 2 species of Ostracoda were recorded. The copepod Mesocyclops leuckarti was found in all the five sites, rotifers Asplanchna brightwelli, Brachionus angularis, B. calyciflorus and Cladocera Ceriodaphnia cornuta were found in four sites; Moina micrura and Diaphanosoma sarsi were found at three sites. Site wise variation in dominance, diversity, evenness and richness were calculated. Site 1, a fish-pond that stabilized composite wastewater, showed the maximum species richness having 17 species, while Site 2, SWF wastewater carrying canal, showed only 4 species. The calculated Jack 1 values of Sites 1 to 5 were 21.78, 3.77, 18.63, 12.5 and 16.95 respectively. Shannon-Wiener species diversity index (H/ values were almost similar for all the three relatively less polluted sites viz, Site 1 (1.959, Site 4 (2.010, Site 5 (2.047. However, at highly polluted sites viz., 2 and 3, H/ value of 1.336 and 0.984 respectively, were calculated. Simpson’s Dominance index (Dsimp value was highest at Site 3 (0.618 indicating maximum dominance, whereas at Site 5 dominance was lowest (0.1680 and diversity was highest. We discuss the role of zooplankton in the amelioration of wastewater.

Asitava CHATTERJEE

2007-08-01

335

Migration of health workers.  

Science.gov (United States)

The discussion and debate stimulated by these papers focused across a range of issues but there were four main areas of questioning: "measuring" and monitoring migration (issues related to comparability, completeness and accuracy of data sets on human resources); the impact of migration of health workers on health systems; the motivations of individual health workers to migrate (the "push" and "pull" factors) and the effect of policies designed either to reduce migration (e.g "self ufficiency") or to stimulate it (e.g active international recruitment). It was recognised that there was a critical need to examine migratory flows within the broader context of all health care labour market dynamics within a country, that increasing migration of health workers was an inevitable consequence of globalisation, and that there was a critical need to improve monitoring so as to better inform policy formulation and policy testing in this area. PMID:18561695

Buchan, James

2008-01-01

336

Composition, density and biomass of zooplankton in culture ponds of Litopenaeus vannamei (DECAPODA: PENAEIDAE in southern Brazil. Composition, density and biomass of zooplankton in culture ponds of Litopenaeus vannamei (DECAPODA: PENAEIDAE in southern Brazil.  

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Full Text Available Litopenaeus vannamei is the most cultivated shrimp species in Brazil, being fed basically on high protein formulated diets. However, some studies have shown that the natural zooplankton found in shrimp ponds can be part of the diet of this crustacean. In this study, the zooplankton composition, density and biomass were evaluated for two shrimp ponds from a shrimp farm in the Patos Lagoon estuary, in southern Brazil (32°00’S, 51°59’W between 11/09/2005 and 01/20/2006. The two ponds were sampled over three consecutive months using a zooplankton net of 150 cm total length, 30 cm mouth diameter and 140 µm nylon mesh size. All the zooplankton samples were preserved in formaldehyde solution at a final concentration of 4% and transported to the laboratory, where the composition, density and biomass (wet and dry weight were assessed. Copepoda and Cladocera were the most frequent groups, while the most abundant species were Acartia tonsa, Pseudodiaptomus richardi and Moina micrura,species commonly found in the Patos Lagoon Estuary. The density values obtained in the ponds were higher than those usually found in the estuary during periods of maximum production, reaching 278 org.L-1 in 11/18/2005 (pond 1, and 277 org.L-1 in 12/08/2005 (pond 2, suggesting that the zooplankton grow well in the shrimp ponds. Zooplankton biomass in the ponds was also relatively high, ranging from 0.15 to 13.28 g.m-3 of wet weight and 0.01 to 2.72 g.m-3 of dry weight, following the same tendency of density. These results clearly indicate that the natural zooplankton occurring in the shrimp ponds represents a potential food source for the shrimp larvae and juveniles during the first months of culture. Litopenaeus vannamei is the most cultivated shrimp species in Brazil, being fed basically on high protein formulated diets. However, some studies have shown that the natural zooplankton found in shrimp ponds can be part of the diet of this crustacean. In this study, the zooplankton composition, density and biomass were evaluated for two shrimp ponds from a shrimp farm in the Patos Lagoon estuary, in southern Brazil (32°00’S, 51°59’W between 11/09/2005 and 01/20/2006. The two ponds were sampled over three consecutive months using a zooplankton net of 150 cm total length, 30 cm mouth diameter and 140 µm nylon mesh size. All the zooplankton samples were preserved in formaldehyde solution at a final concentration of 4% and transported to the laboratory, where the composition, density and biomass (wet and dry weight were assessed. Copepoda and Cladocera were the most frequent groups, while the most abundant species were Acartia tonsa, Pseudodiaptomus richardi and Moina micrura,species commonly found in the Patos Lagoon Estuary. The density values obtained in the ponds were higher than those usually found in the estuary during periods of maximum production, reaching 278 org.L-1 in 11/18/2005 (pond 1, and 277 org.L-1 in 12/08/2005 (pond 2, suggesting that the zooplankton grow well in the shrimp ponds. Zooplankton biomass in the ponds was also relatively high, ranging from 0.15 to 13.28 g.m-3 of wet weight and 0.01 to 2.72 g.m-3 of dry weight, following the same tendency of density. These results clearly indicate that the natural zooplankton occurring in the shrimp ponds represents a potential food source for the shrimp larvae and juveniles during the first months of culture.

A. P. Cardozo

2007-04-01

337

Zooplankton biomass and electron transport system activity around the Balearic Islands (western Mediterranean)  

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Measuring electron transport system (ETS) activity in zooplankton provides an index of respiration, theoretically, the potential respiration rate. We apply the ETS technique to estimate potential respiration and carbon demand from the zooplankton community in the upper 200 m of the water column near the Balearic Islands. The investigation was focused on two areas with different oceanographic conditions: the Balearic and Algerian subbasins. It compared the biomass, potential respiration and specific potential respiration of different size fractions (53-200, 200-500, > 500 ?m) in both areas. In these regions the largest contribution to respiration was found in the larger sizes. The specific respiration (per unit biomass) was greater in smaller fractions, indicating that they have a more active metabolism. Both biomass and potential respiration increased in the Algerian subbasin and for both regions biomass and potential respiration were greater in shallow waters over the continental shelf (law as a tool to investigate the relationships between these two variables, we found that the exponential relation coefficient (b) was less than 0.75, indicating that the respiration was depressed (shifted down). In cultures and in eutrophic ocean waters (upwelling areas) b normally is greater than 0.75, consequently we intuit that the low value of b over the Balearic and Algerian subbasins indicates that the zooplankton is not well fed and that they are living under oligotrophic stress.

Herrera, A.; Gómez, M.; Packard, T. T.; Fernández de Puelles, M. L.

2014-03-01

338

Biodiversity and community structure of zooplankton in the Sub-basin of Rio Poxim, Sergipe, Brazil  

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Full Text Available The zooplankton of aquatic environments is composed mostly of protozoans, rotifers, cladocerans and copepods, which play an important role in the food chain, transferring mass and energy from primary producers to higher trophic levels. This work was prepared with the objective of contributing to the knowledge of zooplankton biodiversity that occurs in the Sub-basin of Rio Poxim. Water samples were taken at monthly intervals at four sampling stations located along the sub-basin in the period August 2009 to July 2010. To obtain the zooplankton community, 100 L of water were filtered on nylon net with an aperture of 50 mm. Were identified 72 taxa distributed in the following taxonomic categories Rotifera, Protozoa, Porifera, Nematoda, Anellida, Cladocera, Copepoda, Ostracoda, Isopoda and Insecta. In terms of species richness, the phylum Rotifera followed by the Protoctista were the most relevant with forty and fifteen taxa, respectively. The most representative taxa in numerical terms were Arcella vulgaris, Notholca sp. Rotary sp. and nematodes. Regarding the community diversity index, the community was characterized as low diversity, but the taxa were distributed evenly in all monitoring points.

Eliane Maria de Souza Nogueira

2011-08-01

339

Evidence of microplastics in samples of zooplankton from Portuguese coastal waters.  

Science.gov (United States)

Records of high concentrations of plastic and microplastic marine debris floating in the ocean have led to investigate the presence of microplastics in samples of zooplankton from Portuguese coastal waters. Zooplankton samples collected at four offshore sites, in surveys conducted between 2002 and 2008, with three different sampling methods, were used in this preliminary study. A total of 152 samples were processed and microplastics were identified in 93 of them, corresponding to 61% of the total. Costa Vicentina, followed by Lisboa, were the regions with higher microplastic concentrations (0.036 and 0.033 no. m?³) and abundances (0.07 and 0.06 cm³ m?³), respectively. Microplastic: zooplankton ratios were also higher in these two regions, which is probably related to the proximity of densely populated areas and inputs from the Tejo and Sado river estuaries. Microplastics polymers were identified using Micro Fourier Transformed Infrared Spectroscopy (?-FTIR), as polyethylene (PE), polypropylene (PP) and polyacrylates (PA). The present work is the first report on the composition of microplastic particles collected with plankton nets in Portuguese coastal waters. Plankton surveys from regular monitoring campaigns conducted worldwide may be used to monitor plastic particles in the oceans and constitute an important and low cost tool to address marine litter within the scope of the Marine Strategy Framework Directive (2008/56/EC). PMID:24461782

Frias, J P G L; Otero, V; Sobral, P

2014-04-01

340

A multivariate approach to environmental-zooplankton relationships in Maldonado Bay (Uruguay  

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Full Text Available Environment-zooplankton relationships were analysed in Maldonado Bay (Uruguay, an estuarine area between the River Plate and the Atlantic Ocean. This was done through Principal Component Analysis. Most of the environment variability is accounted for, primarily, by the outflow of the River Plate and the inflow of coastal waters which change through the annual cycle, and in the second place by surface water conditions. On the other hand, most of the zooplankton variability is accounted for by 17 taxa abundant in April and February and by one dominant species present only from May to August. A second source of zooplanktonic variability is due to species which occurred in fall only The main observed variabili ty occurred on an annual scale. On it, variations on smaller scales overlap: from one day to another, between Maldonado Bay and the adjacent waters of the River Plate. The main factors involved were different at each scale. The Bay is relatively isolated from adjacent waters, but the degree of isolation varies throughout the year. The influence of coastal water is greater and occurs first outside the Bay. Biological processes may develop under different conditions in the Bay and in the adjacent waters of the River Plate.

Ana Milstein

1986-01-01

 
 
 
 
341

Changes in the nearshore and offshore zooplankton communities in Lake Ontario: 1981-88  

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We examined trends and factors influencing changes in nearshore and offshore zooplankton abundance and composition in Lake Ontario between 1981 and 1988. In the nearshore (southshore and eastern basin), zooplankton abundance decreased and shifts occurred in the relative abundances of Bosmina longirostris and Daphnia retrocurva (eastern basin) and Daphnia retrocurva and Daphnia galeata mendotae (southshore). These changes could have resulted from increased vertebrate predation or reduced food resources which intensified the effects of predation. In the offshore, the first appearance (FA) of the larger, less common cladoceran species occurred earlier in the season as of 1985. FA was correlated with cumulative epilimnetic temperature (CET) and the catch per unit effort (CPUE) of alewife (Alosa pseudoharengus) a?Y165 mm caught in U.S. waters in the spring. In 1987, when CET was high and CPUE of alewife a?Y165 mm was low, large populations of these cladocerans developed in June and July. Bythotrephes cederstroemi, a recent invader in the Great Lakes, was abundant only in 1987 when the CPUE of alewife was lowest. Changes in zooplankton abundance, development, and composition along the nearshore-offshore gradient reflected effects of temperature, habitat, and planktivory on the community.

Johannsson, Ora E.; Mills, Edward L.; O'Gorman, Robert

1991-01-01

342

Fatty acid profiling reveals seasonal and spatial shifts in zooplankton diet in a temperate estuary  

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Fatty acids composition of copepod and cladoceran species and their possible food sources was investigated in the Mondego estuary (southern Europe) in order to explain the seasonal variation of the small copepods Acartia clausi, Acartia tonsa, Copidodiaptomus numidicus, Temora longicornis and the freshwater cladoceran Daphnia longispina. A total of 12 zooplankton species (7 marine, 2 estuarine and 3 freshwater species) were studied. A multivariate analysis revealed a clear seasonal distribution of zooplankton species in terms of fatty acids composition and abundance, with winter and spring zooplankton species showing maximal concentrations and diversity of total fatty acids. These findings underline the role of lipids as storage during the colder seasons in a highly variable environment like an estuary. Estuarine and freshwater species showed a more diverse array of saturated and unsaturated fatty acids rather than marine species, except for Centropages typicus. Fatty acids markers of trophic position indicated the presence of two trophic levels: copepod species were primarily omnivorous, whereas cladocerans showed to be herbivorous. Our results suggest that feeding patterns of plankton change spatially and temporally, reflecting the shifts in dominance between diatoms and flagellates as well as between dinoflagellates/diatoms and small animals.

Gonçalves, A. M. M.; Azeiteiro, U. M.; Pardal, M. A.; De Troch, M.

2012-08-01

343

Rearing of Burbot, Lota lota (Pisces, Teleostei, Larvae with Zooplankton and Formulated Microdiets  

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Full Text Available Different feeding methods were tested for burbot, Lota lota, larvae. In small scale experiments with 300 larvae per treatment grinded artemia flakes, enriched artemia flakes, artemia flakes supplemented with dried algae (Chlorella sp., Spirulina sp. and formulated microdiets consisting of different combinations of fishmeal, fish oil, soybean lecithin, casein, dextran, and artemia flakes were fed over a period of 30 days. These foods were compared to live zooplankton food collected from the nature. After 30 days, only feeding with live zooplankton resulted in high survival rates > 80%. No survival was observed with artificial microdiets. The 15 d survival of larvae was significantly lowest with agar agar bound microparticles and with formulated diets containing > 7% soya lecithin and > 3 % fish oil. The live zooplankton feeding method was also tested in a large scale experiment with 25,000 larvae per tank for a period of 100 d. After 100 d the larvae survival rate was > 65 %, and the body length had increased for circa 6-fold.

Franz Lahnsteiner

2012-07-01

344

Zooplankton (Cladocera, Copepoda dynamics in the River Danube upstream and downstream of Budapest, Hungary  

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Full Text Available The spatial distribution and seasonal dynamics of zooplankton (Cladocera, Copepoda were studied in the River Danube near Budapest, Hungary. The investigated river section was relatively poor in plankton, nauplii dominated. A total of 36 species was recorded of which Acanthocyclops robustus, Thermocyclops crassus, Bosmina longirostris were the most abundant. There was a downstream increase in copepod densities, however, no other remarkable differences could be observed between the profiles upstream and downstream of the capital. Generally, the streamline was characterized by lower densities and lower number of taxa as compared to the river bank; nevertheless, there were differences between the left and the right banks both upstream or downstream as well. Seasonal dynamics was defined by a marked late winter–spring aspect and abundance peaks were found to be characteristic for Danube with high densities in May–June and August–September. Examining the relationship between zooplankton density and the hydrological regime, it can be concluded that zooplankton production in the main channel is of minor importance, rather floodplain areas and adjacent water bodies seem to be important sources of plankton biomass.

Vadadi-Fülöp, Cs.

2009-11-01

345

Indices of zooplankton community as valuable tools in assessing the trophic state and water quality of eutrophic lakes: long term study of Lake Võrtsjärv  

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On the basis of long-term (1964-2011) research, we tested the hypothesis that the zooplankton community has a highly indicative value in assessing the ecosystem and trophic state of water bodies. Basing on the results of our study and taking into account relevant data from numerous zooplankton studies, we can conclude that the zooplankton measures deserving to be used as indicators in the monitoring of Lake Võrtsjärv (and other similar eutrophic water bodies) could be the following: i) i...

Juta Haberman; Marina Haldna

2014-01-01

346

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

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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 li...

Mo?ller, Klas O.; Saint John, Michael; Temming, Axel; Floeter, Jens; Sell, Anne F.; Herrmann, Jens Peter; Mo?llmann, Christian

2012-01-01

347

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

348

Impacts of hypoxia on the structure and processes in pelagic communities (zooplankton, macro-invertebrates and fish)  

Science.gov (United States)

Dissolved oxygen (DO) concentration in the water column is an environmental parameter that is crucial for the successful development of many pelagic organisms. Hypoxia tolerance and threshold values are species- and stage-specific and can vary enormously. While some fish species may suffer from oxygen values of less than 3 mL O2 L-1 through impacted growth, development and behaviour, other organisms such as euphausiids may survive DO levels as low as 0.1 mL O2 L-1. A change in the average or the range of DO may have significant impacts on the survival of certain species and hence on the species composition in the ecosystem with consequent changes in trophic pathways and productivity. Evidence for the deleterious effects of oxygen depletion on pelagic species is scarce, particularly in terms of the effect of low oxygen on development, recruitment and patterns of migration and distribution. While planktonic organisms have to cope with variable DOs and exploit adaptive mechanisms, nektonic species may avoid areas of unfavourable DO and develop adapted migration strategies. Planktonic organisms may only be able to escape vertically, above or beneath the Oxygen Minimum Zone (OMZ). In shallow areas only the surface layer can serve as a refuge, but in deep waters many organisms have developed vertical migration strategies to use, pass through and cope with the OMZ. This paper elucidates the role of DO for different taxa in the pelagic realm and the consequences of low oxygen for foodweb structure and system productivity. We describe processes in two contrasting systems, the semi-enclosed Baltic Sea and the coastal upwelling system of the Benguela Current to demonstrate the consequences of increasing hypoxia on ecosystem functioning and services.

Ekau, W.; Auel, H.; Pörtner, H.-O.; Gilbert, D.

2010-05-01

349

Impacts of hypoxia on the structure and processes in pelagic communities (zooplankton, macro-invertebrates and fish  

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Full Text Available Dissolved oxygen (DO concentration in the water column is an environmental parameter that is crucial for the successful development of many pelagic organisms. Hypoxia tolerance and threshold values are species- and stage-specific and can vary enormously. While some fish species may suffer from oxygen values of less than 3 mL O2 L?1 through impacted growth, development and behaviour, other organisms such as euphausiids may survive DO levels as low as 0.1 mL O2 L?1. A change in the average or the range of DO may have significant impacts on the survival of certain species and hence on the species composition in the ecosystem with consequent changes in trophic pathways and productivity.

Evidence for the deleterious effects of oxygen depletion on pelagic species is scarce, particularly in terms of the effect of low oxygen on development, recruitment and patterns of migration and distribution. While planktonic organisms have to cope with variable DOs and exploit adaptive mechanisms, nektonic species may avoid areas of unfavourable DO and develop adapted migration strategies. Planktonic organisms may only be able to escape vertically, above or beneath the Oxygen Minimum Zone (OMZ. In shallow areas only the surface layer can serve as a refuge, but in deep waters many organisms have developed vertical migration strategies to use, pass through and cope with the OMZ.

This paper elucidates the role of DO for different taxa in the pelagic realm and the consequences of low oxygen for foodweb structure and system productivity. We describe processes in two contrasting systems, the semi-enclosed Baltic Sea and the coastal upwelling system of the Benguela Current to demonstrate the consequences of increasing hypoxia on ecosystem functioning and services.

W. Ekau

2010-05-01

350

Culture optimization for the emergent zooplanktonic model organism Oikopleura dioica  

Science.gov (United States)

The pan-global marine appendicularian, Oikopleura dioica, shows considerable promise as a candidate model organism for cross-disciplinary research ranging from chordate genetics and evolution to molecular ecology research. This urochordate, has a simplified anatomical organization, remains transparent throughout an exceptionally short life cycle of less than 1 week and exhibits high fecundity. At 70 Mb, the compact, sequenced genome ranks among the smallest known metazoan genomes, with both gene regulatory and intronic regions highly reduced in size. The organism occupies an important trophic role in marine ecosystems and is a significant contributor to global vertical carbon flux. Among the short list of bona fide biological model organisms, all share the property that they are amenable to long-term maintenance in laboratory cultures. Here, we tested diet regimes, spawn densities and dilutions and seawater treatment, leading to optimization of a detailed culture protocol that permits sustainable long-term maintenance of O. dioica, allowing continuous, uninterrupted production of source material for experimentation. The culture protocol can be quickly adapted in both coastal and inland laboratories and should promote rapid development of the many original research perspectives the animal offers. PMID:19461862

Bouquet, Jean-Marie; Spriet, Endy; Troedsson, Christofer; Otterå, Helen; Chourrout, Daniel; Thompson, Eric M.

2009-01-01

351

The paradox of pelagic food webs in the northern Bering Sea—II. Zooplankton communities  

Science.gov (United States)

Anadyr Water, a "river" of oceanic water originating over the continental slope of the Bering Sea, transports oceanic zooplankton onto the shallow northern shelf and into the Chukchi Sea through western Bering Strait. The oceanic copepods Neocalanus cristatus, N. plumchrus, Eucalanus bungii and Metridia pacifica dominated the biomass of herbivorous zooplankton in Anadyr Water on the Bering-Chukchi shelf, averaging about 5 g m -2 (dry weight) in midsummer and 2 g m -2 in later summer of 1985 and 1986. The biomass of copepods was at times augmented considerably by that of a larvacean, Oikopleura spp. Oceanic water was replaced to the east, and often overlain by, lighter water formed on the continental shelf. The oceanic species were not present in waters of shelf origin, where Calanus marshallae was the major herbivore, averaging about 1 g m -2 in summer 1985, but only 0.2-0.5 g m -2 in 1986. In the low salinity, nearshore water, C. marshallae was uncommon and Pseudocalanus spp. and Acartia longiremis predominated. A preliminary estimate indicated that in the order of 1.8 × 10 12g C of boreal zooplankton were carried into the Chukchi Sea during summer 1985. On average, the grazers were unable to control prodigious diatom growth that resulted from concentrated nutrients also carried by Anadyr Water into the area. In contrast, the smaller biomass of grazers in the shelf community, away from the region of high diatom biomass, might have had a much greater influence over the standing stock of phytoplankton following the spring bloom, and, at times, could have consumed the daily primary production. The highly productive pelagic food web of oceanic origin in the north does not have close coupling between primary producers and zooplankton, or between zooplankton and their predators, and contrasts with the oceanic community in the southeastern Bering Sea, where the same species of herbivores apparently have a much greater effect on phytoplankton biomass, and provide an efficient transfer of the available fixed energy to upper trophic levels in pelagic food webs.

Springer, Alan M.; McRoy, C. Peter; Turco, Kathy R.

1989-04-01

352

Impacts of zooplankton composition and algal enrichment on the accumulation of mercury in an experimental freshwater food web  

Energy Technology Data Exchange (ETDEWEB)

There is a well documented accumulation of mercury in fish to concentrations of concern for human consumption. Variation in fish Hg burden between lakes is often high and may result from differences in Hg transfer through lower levels of the food web where mercury is bioconcentrated to phytoplankton and transferred to herbivorous zooplankton. Prior research derived patterns of mercury accumulation in freshwater invertebrates from field collected animals. This study provides results from controlled mesocosm experiments comparing the effects of zooplankton composition, algal abundance, and the chemical speciation of mercury on the ability of zooplankton to accumulate mercury from phytoplankton and transfer that mercury to planktivores. Experiments were conducted in 550-L mesocosms across a gradient of algal densities manipulated by inorganic nutrient additions. Enriched, stable isotopes of organic (CH{sub 3} {sup 200}HgCl) and inorganic ({sup 201}HgCl{sub 2}) mercury were added to mesocosms and their concentrations measured in water, seston, and three common zooplankton species. After 2 weeks, monomethylmercury (MMHg) concentrations were two to three times lower in the two copepod species, Leptodiaptomus minutus and Mesocyclops edax than in the cladoceran, Daphnia mendotae. All three zooplankton species had higher MMHg concentrations in mesocosms with low versus high initial algal abundance. However, despite higher concentrations of inorganic mercury (Hg{sub I}) in seston from low nutrient mesocosms, there were no significant differences in the Hg{sub I} accumulated by zooplankton across nutrient treatments. Bioaccumulation factors for MMHg in the plankton were similar to those calculated for plankton in natural lakes and a four-compartment (aqueous, seston, macrozooplankton, and periphyton/sediments) mass balance model after 21 days accounted for {approx}18% of the CH{sub 3} {sup 200}Hg and {approx}33% of the {sup 201}Hg added. Results from our experiments corroborate results from field studies and suggest the importance of particular zooplankton herbivores (e.g., Daphnia) in the transfer of Hg to higher trophic levels in aquatic food webs.

Pickhardt, Paul C. [Department of Biological Sciences, Dartmouth College, Hanover, NH 03755 (United States)]. E-mail: paul.pickhardt@stonybrook.edu; Folt, Carol L. [Department of Biological Sciences, Dartmouth College, Hanover, NH 03755 (United States); Chen, Celia Y. [Department of Biological Sciences, Dartmouth College, Hanover, NH 03755 (United States); Klaue, Bjoern [Department of Geological Sciences, University of Michigan, Ann Arbor, MI 48109 (United States); Blum, Joel D. [Department of Geological Sciences, University of Michigan, Ann Arbor, MI 48109 (United States)

2005-03-01

353

Impacts of zooplankton composition and algal enrichment on the accumulation of mercury in an experimental freshwater food web  

International Nuclear Information System (INIS)

There is a well documented accumulation of mercury in fish to concentrations of concern for human consumption. Variation in fish Hg burden between lakes is often high and may result from differences in Hg transfer through lower levels of the food web where mercury is bioconcentrated to phytoplankton and transferred to herbivorous zooplankton. Prior research derived patterns of mercury accumulation in freshwater invertebrates from field collected animals. This study provides results from controlled mesocosm experiments comparing the effects of zooplankton composition, algal abundance, and the chemical speciation of mercury on the ability of zooplankton to accumulate mercury from phytoplankton and transfer that mercury to planktivores. Experiments were conducted in 550-L mesocosms across a gradient of algal densities manipulated by inorganic nutrient additions. Enriched, stable isotopes of organic (CH3 200HgCl) and inorganic (201HgCl2) mercury were added to mesocosms and their concentrations measured in water, seston, and three common zooplankton species. After 2 weeks, monomethylmercury (MMHg) concentrations were two to three times lower in the two copepod species, Leptodiaptomus minutus and Mesocyclops edax than in the cladoceran, Daphnia mendotae. All three zooplankton species had higher MMHg concentrations in mesocosms with low versus high initial algal abundance. However, despite higher concentrations of inorganic mercuryhigher concentrations of inorganic mercury (HgI) in seston from low nutrient mesocosms, there were no significant differences in the HgI accumulated by zooplankton across nutrient treatments. Bioaccumulation factors for MMHg in the plankton were similar to those calculated for plankton in natural lakes and a four-compartment (aqueous, seston, macrozooplankton, and periphyton/sediments) mass balance model after 21 days accounted for ?18% of the CH3 200Hg and ?33% of the 201Hg added. Results from our experiments corroborate results from field studies and suggest the importance of particular zooplankton herbivores (e.g., Daphnia) in the transfer of Hg to higher trophic levels in aquatic food webs

354

Meso- and macro-zooplankton community structure of the Amundsen Sea Polynya, Antarctica (Summer 2010–2011  

Directory of Open Access Journals (Sweden)

Full Text Available Abstract The Amundsen Sea Polynya (ASP has, on average, the highest productivity per unit area in Antarctic waters. To investigate community structure and the role that zooplankton may play in utilizing this productivity, animals were collected at six stations inside and outside the ASP using paired “day-night” tows with a 1 m2 MOCNESS. Stations were selected according to productivity based on satellite imagery, distance from the ice edge, and depth of the water column. Depths sampled were stratified from the surface to ? 50–100 m above the seafloor. Macrozooplankton were also collected at four stations located in different parts of the ASP using a 2 m2 Metro Net for krill surface trawls (0–120 m. The most abundant groups of zooplankton were copepods, ostracods, and euphausiids. Zooplankton biovolume (0.001 to 1.22 ml m-3 and abundance (0.21 to 97.5 individuals m-3 varied throughout all depth levels, with a midsurface maximum trend at ? 60–100 m. A segregation of increasing zooplankton trophic position with depth was observed in the MOCNESS tows. In general, zooplankton abundance was low above the mixed layer depth, a result attributed to a thick layer of the unpalatable colonial haptophyte, Phaeocystis antarctica. Abundances of the ice krill, Euphausia crystallarophias, however, were highest near the edge of the ice sheet within the ASP and larvae:adult ratios correlated with temperature above a depth of 60 m. Total zooplankton abundance correlated positively with chlorophyll a above 150 m, but negative correlations observed for biovolume vs. the proportion of P. antarctica in the phytoplankton estimated from pigment ratios (19’hexanoyloxyfucoxanthin:fucoxanthin again pointed to avoidance of P. antarctica. Quantifying zooplankton community structure, abundance, and biovolume (biomass in this highly productive polynya helps shed light on how carbon may be transferred to higher trophic levels and to depth in a region undergoing rapid warming.

Stephanie E. Wilson

2015-01-01

355

Glossary: migration and health.  

Science.gov (United States)

The literature on migration and health is quite heterogeneous in how migrants are labelled and how the relation between migration and health is conceptualised. A narrative review has been carried out. This glossary presents the most commonly used terms in the field of migration and health, along with synonyms and related concepts, and discusses the suitability of their use in epidemiological studies. The terminology used in migrant health is ambiguous in many cases. Studies on migrant health should avoid layman terms and strive to use internationally defined concepts. PMID:21282138

Urquia, Marcelo L; Gagnon, Anita J

2011-05-01

356

VSP migration: Synthetic and field examples  

International Nuclear Information System (INIS)

Imaging theory is developed for data gathered from vertical seismic profile (VSP) or offset VSP's. Wavefield extrapolation is performed by the raytracing method. The process is not diplimited and results are applicable to arbitrary VSP acquisition geometries in straight or deviated boreholes. Algorithms are presented to isolate the primary reflectivity seismic image when insufficient source illumination and data redundancy exist, a condition which is prevalent in VSP data sets. Synthetic as well as field data examples are demonstrated with application of VSP migration. In the synthetic examples migration results for one- and two-dimensional velocity variations and straight and deviated boreholes are shown. Field examples consist of a shear wave VSP recorded in Kansas and multioffset P-wave VSP's recorded in south-central Texas. The speed with which this process can be achieved should show significant advantage over finite difference types of wave field extrapolators. Regular geophone or source spacing is not required

357

Radial migration and its effects on the thin and thick disks  

CERN Document Server

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 scalelength), in little radial heating and no appreciable changes to the vertical or radial structure of the disk. Our results suggest that the radial displacements are driven by Sellwood & Binney's corotation scattering process and 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 resp...

Vera-Ciro, Carlos; Navarro, Julio; Abadi, Mario

2014-01-01

358

Migration og etnicitet  

DEFF Research Database (Denmark)

Migration og etnicitet er aktuelle og forbundne fænomener, idet migration øger berøringsfladerne mellem befolkningsgrupper. Etniciteter formes i takt med at grænser drages imellem disse grupper. Imod moderniserings-teoriernes forventning forsvandt etnicitet ikke som en traditionel eller oprindelig måde at skabe tilhørsforhold på; globalt set fremstår vor tid istedet som en "migrationens tidsalder", der tilsyneladende også er en tidsalder, hvor kulturelle særtræk, i form af etnicitet, udgør vigtige linjer, hvorefter grupper skilller sig ud fra hinanden. Både migration og etnicitet bringer fokus på nationalstaten, dens suverænitet og kapaciteten hos dens institutioner til henholdsvis at regulere bevægelser over statsgrænser og til at definere de former for fællesskab, som præger de enkelte samfund. I sociologien har man tidligere primært koncentreret sig om studier af migrationsprocessen som den finder sted i modtagerlandet, men nyere perspektiver på migration, som begreber om medborgerskab, transnationalisme og diaspora er eksponenter for, søger udover den nationalstatslige ramme og inddrager konsekvenserne af migrationen for afsenderlande.

Christiansen, Connie CarØe

2004-01-01

359

Po-210 and Pb-210 concentration factors for zooplankton and faecal pellets in the oligotrophic South-West Pacific  

International Nuclear Information System (INIS)

In a previous study on zooplankton sampled from very low productivity waters of French Polynesia, their Po-210 concentrations were found to be unexpectedly elevated, compared to values measured in marine zooplankton from various other geographical regions of the world. For the French Polynesian samples their Po-210 concentrations also increased appreciably as their biomass declined. A simple conceptual and mathematical model, that incorporated the established role of zooplankton faecal pellets in the removal of Po-210 and particle-reactive radionuclides and stable metals from the water column, could capture the shape of this empirical relationship between Po-210 concentration and their biomass and also explained the biomass-related mechanism that increases Po-210 concentrations in zooplankton. Similarly, a field investigation in the Timor Sea showed that a range of particle-reactive elements showed elevated water concentrations as particle removal rates, as inferred from Th-234: U-238 disequilibria, reduced in the euphotic zone. However, in these previous studies simultaneous in situ measurements of a range of parameters valuable in assessment of the role of zooplankton in the biogeochemical cycling of particle-reactive elements like Po-210 and Pb-210 were not made. Here we report preliminary results of a field study, that was undertaken in the oligotrophic waters of the South-West Pacific between New Caledonia and Fiji, where we simultaneously measured a) zooplankton we simultaneously measured a) zooplankton biomass and their faecal pellet production rates; b) Po-210 and its progenitor Pb-210 in water, zooplankton and their faecal pellets; and c) particle flux rates using U-238:Th-234 disequilibria, to further assess the role of zooplankton in Po-210 and Pb- 210 biogeochemistry in the euphotic zone of oligotrophic systems. Zooplankton sampled from the oceanic region of the South-West Pacific between Fiji and New Caledonia had biomasses ranging from 0.1 to 7.1 mgDW/m3, with a median value of 3.6 and mean of 2.65 mgDW/m3. Their faecal pellet production rates were measured on board and varied between 1.82.10-4-3.78.10-3 g dry faecal pellet. g dry zooplankton-1. hour-1, median ). Their measured Po-210 and Pb-210 concentrations were 830-2655 Bq.KgDW-1 and 44- 617Bq. KgDW-1, respectively. Po-210 and Pb-210 concentrations in zooplankton varied between 565-1736 Bq.Kg dry weight-1 and 47-551 Bq.Kg dry weight-1, respectively. Po-210 concentration factors that only varied between 1.3-3.3. 105 were elevated compared to the IAEA recommended value of 3.104 based on previous values. Similarly, Pb-210 concentration factors ranging from 0.9-9.1. 104, were considerably elevated compared to the IAEA recommended value of 1.103, indicating the presence of a further concentrating mechanism. Our results for Po-210 and Pb-210 show a consistency with published values, in that the concentration factor for Po-210 is elevated relative to Pb-210, but contrast with previous reported values in both being elevated by about an order of magnitude. Their comparably elevated concentrations in faecal pellets suggest that enhanced concentrations in zooplankton are a reflection of the heightened concentrations in their dietary phytoplankton

360

Po-210 and Pb-210 concentration factors for zooplankton and faecal pellets in the oligotrophic South-West Pacific  

International Nuclear Information System (INIS)

In a previous study on zooplankton sampled from very low productivity waters of French Polynesia, their Po-210 concentrations were found to be unexpectedly elevated, compared to values measured in marine zooplankton from various other geographical regions of the world. For the French Polynesian samples their Po-210 concentrations also increased appreciably as their biomass declined. A simple conceptual and mathematical model, that incorporated the established role of zooplankton faecal pellets in the removal of Po-210 and particle-reactive radionuclides and stable metals from the water column, could capture the shape of this empirical relationship between Po-210 concentration and their biomass and also explained the biomass-related mechanism that increases Po-210 concentrations in zooplankton. Similarly, a field investigation in the Timor Sea showed that a range of particle-reactive elements showed elevated water concentrations as particle removal rates, as inferred from Th-234: U-238 disequilibria, reduced in the euphotic zone. However, in these previous studies simultaneous in situ measurements of a range of parameters valuable in assessment of the role of zooplankton in the biogeochemical cycling of particle-reactive elements like Po-210 and Pb-210 were not made. Here we report preliminary results of a field study, that was undertaken in the oligotrophic waters of the South-West Pacific between New Caledonia and Fiji, where we simultaneously measured a) zooplankton we simultaneously measured a) zooplankton biomass and their faecal pellet production rates, b) Po-210 and its progenitor Pb-210 in water, zooplankton and their faecal pellets and c) particle flux rates using U-238:Th-234 disequilibria, to further assess the role of zooplankton in Po-210 and Pb-210 biogeochemistry in the euphotic zone of oligotrophic systems. Zooplankton sampled from the oceanic region of the SW Pacific between Fiji and New Caledonia had biomasses ranging from 0.1 to 7.1 mg dw/m3, with a median value of 3.6 and mean of 2.65 mg dw/m3. Their faecal pellet production rates were measured on board and varied between 1.82.10-4-3.78.10-3 g dry faecal pellet. g dry zooplankton-1. hour-1. Their measured Po-210 and Pb-210 concentrations were 830-2655 Bq kg dw-1 and 44-617 Bq kg dw-1, respectively. Po-210 and Pb-210 concentrations in zooplankton varied between 565-1736 Bq kg dw-1 and 47-551 Bq kg dw-1, respectively. Po-210 concentration factors that only varied between 1.3-3.3. 105 were elevated compared to the IAEA recommended value of 3.104 based on previous values. Similarly, Pb-210 concentration factors ranging from 0.9-9.1. 104, were considerably elevated compared to the IAEA recommended value of 1.103, indicating the presence of a further concentrating mechanism. Our results for Po-210 and Pb-210 show a consistency with published values in that the concentration factor for Po-210 is elevated relative to Pb-210, but contrast with previous reported values in both being elevated by about an order of magnitude. Their comparably elevated concentrations in faecal pellets suggest that enhanced concentrations in zooplankton are a reflection of the heightened concentrations in their dietary phytoplankton