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1

Arctic complexity: a case study on diel vertical migration of zooplankton  

Science.gov (United States)

Diel vertical migration (DVM) of zooplankton is a global phenomenon, characteristic of both marine and limnic environments. At high latitudes, patterns of DVM have been documented, but rather little knowledge exists regarding which species perform this ecologically important behaviour. Also, in the Arctic, the vertically migrating components of the zooplankton community are usually regarded as a single sound scattering layer (SSL) performing synchronized patterns of migration directly controlled by ambient light. Here, we present evidence for hitherto unknown complexity of Arctic marine systems, where zooplankton form multiple aggregations through the water column seen via acoustics as distinct SSLs. We show that while the initiation of DVM during the autumnal equinox is light mediated, the vertical positioning of the migrants during day is linked more to the thermal characteristics of water masses than to irradiance. During night, phytoplankton biomass is shown to be the most important factor determining the vertical positioning of all migrating taxa. Further, we develop a novel way of representing acoustic data in the form of a Sound Image (SI) that enables a direct comparison of the relative importance of each potential scatterer based upon the theoretical contribution of their backscatter. Based on our comparison of locations with contrasting hydrography, we conclude that a continued warming of the Arctic is likely to result in more complex ecotones across the Arctic marine system. PMID:25221372

Berge, J?rgen; Cottier, Finlo; Varpe, ?ystein; Renaud, Paul E.; Falk-Petersen, Stig; Kwasniewski, Sawomir; Griffiths, Colin; S?reide, Janne E.; Johnsen, Geir; Aubert, Anais; Bjaerke, Oda; Hovinen, Johanna; Jung-Madsen, Signe; Tveit, Martha; Majaneva, Sanna

2014-01-01

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Diel vertical migration and distribution of zooplankton in a tropical Brazilian reservoir  

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Full Text Available Diel vertical migration of zooplankton is a strategy usually employed to reduce the risk of predation, and it can also be associated with the environmental day/night shifts, particularly of light and temperature. The aim of this study was to identify the diel patterns of zooplankton vertical migration and their relationship to the environmental variables in a shallow reservoir in northeastern Brazil. Water samples were taken at a single five-meter depth sampling station (Subsurface, 50% Io, 1% Io and Bottom at four-hour intervals over a period of 24 hours. Two Cladocera species (Moina minuta and Diaphanosoma spinulosum and one Copepoda species (Notodiaptomus cearensis showed similar patterns of nocturnal migration, staying at the bottom during the day and rising toward the surface in the afternoon and during the night. Brachionus falcatus and Hexarthra mira (Rotifera showed no patterns of vertical migration and their vertical distributions were relatively homogenous. Environmental variables were poorly correlated to the species distribution, suggesting that other mechanisms may be responsible of inducing vertical migration.

Ana M. A. da Silva

2009-03-01

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Towards resolving the paradox of enrichment: the impact of zooplankton vertical migrations on plankton systems stability.  

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Eutrophication, often resulting from human activity, is a serious threat to aquatic communities. Theoretical analysis of this phenomenon, based on conceptual mathematical models, leads to controversial predictions known as Rosenzweig's paradox of enrichment. At the same time, field observations demonstrate that real plankton communities exhibit various mechanisms of self-regulation which can buffer negative effects of enrichment. In this paper, we study potential effects of zooplankton vertical migration on stability of plankton systems functioning. We consider an intrinsically unstable plankton model, which is characterized by an unlimited phytoplankton multiplication and population oscillations of increasing amplitude, and investigate whether vertical migrations of zooplankton can stabilize such a system at low plankton densities. By means of developing two different models accounting for different ecological situations, e.g. deep waters and shallow waters, we show that vertical migrations of zooplankton can result in stabilization of eutrophic plankton systems. Thus, we show that this mechanism, rarely taken into account in models of plankton dynamics, may be important for resolving the paradox of enrichment in plankton communities. PMID:17624371

Morozov, Andrew Yu; Petrovskii, Sergei V; Nezlin, Nikolay P

2007-10-01

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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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Seasonal variation of diel vertical migration of zooplankton from ADCP backscatter time series data in the Lazarev Sea, Antarctica  

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Ten-month time series of mean volume backscattering strength (MVBS) and vertical velocity obtained from three moored acoustic Doppler current profilers (ADCPs) deployed from February until December 2005 at 64°S, 66.5°S and 69°S along the Greenwich Meridian were used to analyse the diel vertical zooplankton migration (DVM) and its seasonality and regional variability in the Lazarev Sea. The estimated MVBS exhibited distinct patterns of DVM at all three mooring sites. Between February and October, the timing of the DVM and the residence time of zooplankton at depth were clearly governed by the day-night rhythm. Mean daily cycles of the ADCP-derived vertical velocity were calculated for successive months and showed maximum ascent and descent velocities of 16 and -15 mm s -1. However, a change of the MVBS pattern occurred in late spring/early austral summer (October/November), when the zooplankton communities ceased their synchronous vertical migration at all three mooring sites. Elevated MVBS values were then concentrated in the uppermost layers (feeding.

Cisewski, Boris; Strass, Volker H.; Rhein, Monika; Krägefsky, Sören

2010-01-01

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

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Full Text Available To study the proximal factors inducing diel vertical migration (DVM in large and small zooplankton species in a plateau lake in China, we investigated the DVM of crustacean zooplankton in lake Erhai bimonthly from November 2009 to September 2010. We hypothesized that the factors affecting DVM behaviour in different-sized zooplankton were different. A linear regression was used to assess the relationships between environmental variables and the vertical distribution of zooplankton. All crustacean zooplankton exhibited normal DVM patterns (down during the day, up at night across sampling months. The weighted mean depth (WMD of all zooplankton did not show a significant correlation with the WMD of the dominant phytoplankton and chlorophyll-a. However, a negative relationship was observed between the distribution of zooplankton and water temperature in January, March, and July 2010, but the relationship was relatively weak (R2 between 0.1 and 0.4. The vertical distribution of zooplankton was primarily affected by water transparency (P0.05, whereas the factors inducing DVM behaviour differed between large and small zooplankton. Predation avoidance and phototactic behaviour may be the dominant factors influencing DVM of large species, whereas only phototaxis contributed to the migratory behaviour of small species.

Cuilin Hu

2014-02-01

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

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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  

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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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Diel changes in the near-surface biomass of zooplankton and the carbon content of vertical migrants  

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Zooplankton biomass and the carbon content of vertical migrants were measured in the NE Atlantic (36.5°N, 19.2°W) between 11 and 18 July 1996 as part of the Plankton Reactivity in the Marine Environment (PRIME) programme. The increase in zooplankton biomass near the surface (0-100 m) at night compared to during the day suggested that diel vertical migration was an important feature at this site. For three species of vertically migrant copepods, Pleuromamma pisekii, P. gracilis and P. abdominalis, the carbon content of individuals collected at dusk was significantly less than for individuals collected at dawn, with this reduction being 6.2, 7.3 and 14.8%, respectively. This dawn-dusk reduction in carbon content is consistent with the diel pattern of feeding and fasting exhibited by vertical migrants and supports the suggestion that migrating zooplankton will cause an active export of carbon from the surface layers.

Hays, Graeme C.; Harris, Roger P.; Head, Robert N.

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Partial diel vertical migrations in pelagic fish.  

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1. Field studies on diel vertical migration (DVM) usually report uniform behaviour with population-wide ascents and descents during crepuscular periods. This contrasts partial seasonal migrations of many animal populations, where individuals choose either the resident or the migrant strategy depending on population density, feeding opportunity and predation risk in the resident and migrant habitats. 2. We tested whether DVM of freshwater zooplanktivorous fish (Coregonus spp.) resembles partial migrations. Twenty-eight hydroacoustic surveys were performed in the deep Lake Stechlin (Germany) between 2000 and 2010, with samplings encompassing all months between March and December. Zooplankton samples were simultaneously taken in epilimnetic and hypolimnetic layers. Fish obtained from depth-stratified samplings by a midwater trawl were used to test for individual differences between residents and migrants. 3. We show for the first time that DVMs of freshwater fish resemble patterns of partial migrations often found in seasonal environments. Across all samplings, 7-33% of fish did not ascend at dusk, but exhibited the resident strategy. The proportion or residents increased at low zooplankton feeding rates in the daytime habitat and during months when the temperature difference between daytime and night-time habitats was minor. 4. Slightly larger size and higher caloric density of migrants over residents in one of the coexisting Coregonus species suggested that individual differences contributed to the migration strategy performed. However, these results were based on one sample only, and extrapolation to the entire data set is not possible. 5. Our results are indirect evidence that the balance between migrants and residents may primarily depend on the trade-off between feeding gains and metabolic and predation costs of migration. However, the results also suggest that the global fitness consequences for the resident and migrant strategies may not be identical, rendering the importance of individual traits in the 'decision to migrate' likely. PMID:21366565

Mehner, Thomas; Kasprzak, Peter

2011-07-01

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

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

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

2009-01-01

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

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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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Vertical distribution of zooplankton and active flux across an anticyclonic eddy in the Canary Island waters  

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The vertical distribution (0-900 m) of zooplankton biomass and indices of feeding (gut fluorescence, GF) and metabolism (electron transfer system, ETS) were studied across an anticyclonic eddy south of Gran Canaria Island (Canary Islands). Two dense layers of organisms were clearly observed during the day, one above 200 m and the other at about 500 m, coincident with the deep scattering layer (DSL). The biomass displacement due to interzonal migrants in the euphotic zone was more than 2-fold higher than that previously reported for the southern area of this archipelago. The gut flux estimated (0.14-0.44 mgC m -2 d -1) was similar to the values previously found in the Canaries. The respiratory flux outside the eddy (1.85 mgC m -2 d -1) was in the lower range of values reported for this area. Inside the eddy, migrant biomass and respiration rates were 2- and 4- fold higher than in the surrounding waters. Active flux mediated by diel vertical migrants inside the eddy (8.28 mgC m -2 d -1) was up to 53% of the passive carbon flux to the mesopelagic zone (15.8 mgC m -2 d -1). It is, therefore, suggested that the anticyclonic eddy enhanced both migration from deep waters and active flux.

Yebra, L.; Almeida, C.; Hernández-León, S.

2005-01-01

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Vertical migration in high Arctic waters during autumn 2004  

Science.gov (United States)

The diel vertical migration (DVM) of zooplankton and pelagic fish in the southern Arctic Ocean (82°N) and in Rijpfjorden (Svalbard, Nordaustlandet, 80°N) was investigated in autumn 2004, when there were distinct differences in light conditions between day and night. We collected data on zooplankton and fish distribution using plankton nets, trawls, and an echo sounder together with data on environmental parameters including sea-ice distribution, hydrography, and in situ fluorescence in the water column. In Rijpfjorden, the Arctic phytoplankton bloom had culminated several weeks prior to the present study and all three Calanus species had migrated down to depths for over wintering and did not show any changes in vertical distribution. However, in the Arctic Ocean pack ice at 82°N, Calanus hyperboreus, was found in high abundances (up to 65 ind. m -3) actively feeding on the Arctic bloom in September. They performed a classic DVM, feeding in the upper 50 m during the night and descending to depths below 50 m during the day. In Rijpfjorden, distinct DVM patterns were observed among the amphipod Themisto libellula, adult and juvenile stages of the pteropod Limacina helicina, and polar cod. Polar cod in Rijpfjorden fed on Calanus spp. and on L. helicina. We conclude that animals display DVM in the Arctic during autumn if they need to feed in food-rich surface waters.

Falk-Petersen, Stig; Leu, Eva; Berge, Jørgen; Kwasniewski, Slawomir; Nygård, Henrik; Røstad, Anders; Keskinen, Essi; Thormar, Jonas; von Quillfeldt, Cecilie; Wold, Anette; Gulliksen, Bjørn

2008-10-01

16

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

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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

18

Enhancement of anammox by the excretion of diel vertical migrators.  

Science.gov (United States)

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

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

2014-11-01

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

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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

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Vertical migration and diel feeding periodicity of the skinnycheek lanternfish (Benthosema pterotum) in the Red Sea  

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The vertical migration and diel feeding periodicity of the skinnycheek lanternfish (Benthosema pterotum) were studied by use of a hull-mounted 38 kHz echo sounder, ROV-deployments and net-sampling at two locations (?24°48?N, ?36°15?E and ?21°27?N, ?38°5?E) in the central Red Sea. The mesopelagic zone of the Red Sea represents an unusual environment with very high temperatures (?22 °C) and low zooplankton concentrations (diel vertical migration from ?500 to 750 m during daytime to the epipelagic zone (upper ?200 m) at night. A strict feeding periodicity occurred; with the skinnycheek lanternfish foraging on zooplankton throughout the night, while rapidly digesting the preceding nocturnal meal in the warm mesopelagic region. We hypothesize that the constrained epipelagic distribution of zooplankton and the unusual warm waters of the Red Sea force the whole population to ascend and feed in epipelagic waters every night, as the prey-ration eaten each night is fully digested at mesopelagic depths during daytime.

Dypvik, Eivind; Kaartvedt, Stein

2013-02-01

 
 
 
 
21

Diel vertical migration: Ecological controls and impacts on the biological pump in a one-dimensional ocean model  

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vertical migration (DVM) of zooplankton and micronekton is widespread in the ocean and forms a fundamental component of the biological pump, but is generally overlooked in global models of the Earth system. We develop a parameterization of DVM in the ocean and integrate it with a size-structured NPZD model. We assess the model's ability to recreate ecosystem and DVM patterns at three well-observed Pacific sites, ALOHA, K2, and EQPAC, and use it to estimate the impact of DVM on marine ecosystems and biogeochemical dynamics. Our model includes the following: (1) a representation of migration dynamics in response to food availability and light intensity; (2) a representation of the digestive and metabolic processes that decouple zooplankton feeding from excretion, egestion, and respiration; and (3) a light-dependent parameterization of visual predation on zooplankton. The model captures the first-order patterns in plankton biomass and productivity across the biomes, including the biomass of migrating organisms. We estimate that realistic migratory populations sustain active fluxes to the mesopelagic zone equivalent to between 15% and 40% of the particle export and contribute up to half of the total respiration within the layers affected by migration. The localized active transport has important consequences for the cycling of oxygen, nutrients, and carbon. We highlight the importance of decoupling zooplankton feeding and respiration and excretion with depth for capturing the impact of migration on the redistribution of carbon and nutrients in the upper ocean.

Bianchi, Daniele; Stock, Charles; Galbraith, Eric D.; Sarmiento, Jorge L.

2013-04-01

22

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; Munk, Peter

2013-01-01

23

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

24

Vertical migration of the Chernobyl originated uranium in soil profile  

International Nuclear Information System (INIS)

In this work the results of studies devoted to vertical migration of various physical-chemical forms of uranium in soil profile are presented. The migration rate of uranium for different soil types is provided. (authors)

25

Distribution, annual cycle, and vertical migration of acoustically derived biomass in the Arabian Sea during 1994 1995  

Science.gov (United States)

The distinguishing characteristic that sets the Arabian Sea apart from other oceanic regions is the regular oscillation of monsoonal atmospheric conditions that produces predictable periods of upwelling or convective mixing, with associated biological response, during the Southwest and Northeast monsoons, respectively. This oscillation is also evident in cycles of standing stocks of zooplankton and micronekton. The vertical distribution and spatial pattern of zooplankton and micronekton biomass were estimated using an acoustic Doppler current profiler along a 1000-km transect extending from the continental shelf of Oman to the central Arabian Sea during ten cruises on the R/V Thomas G. Thompson (November 1994-December 1995). The influence of the Southwest Monsoon, and accompanying upwelling and enhanced acoustically derived biomass, was the dominant feature in the spatial-temporal distributions of both zooplankton and micronekton near the Omani coast. The diel vertical migration of predators (myctophids, pelagic crabs), and the seasonal changes in the strength of this signal, was the most significant pattern observed in the vertical distribution of biomass and imparted a strong day-night signal to the integrated upper water-column biomass. Significant differences in the magnitude of integrated upper water-column biomass, both zooplankton (day) and migrator-zooplankton (night), were seen between inshore and offshore of the atmospheric Findlater Jet. A station located in the central Arabian Sea demonstrated seasonal changes in biomass over the year, despite being quite far from the influence of the monsoonal oscillations. Predation pressure was greater offshore of the Findlater Jet than in the region inshore of the Jet or in the central Arabian Sea. The pelagic community of the Arabian Sea may have evolved life history strategies to coincide with the predictable monsoonal cycle.

Ashjian, Carin J.; Smith, Sharon L.; Flagg, Charles N.; Idrisi, Nasseer

26

Evidence of Diel Vertical Migration in Mnemiopsis leidyi  

Digital Repository Infrastructure Vision for European Research (DRIVER)

The vertical distribution and migration of plankton organisms may have a large impact on their horizontal dispersal and distribution, and consequently on trophic interactions. In this study we used video-net profiling to describe the fine scale vertical distribution of Mnemiopsis leidyi in the Kattegat and Baltic Proper. Potential diel vertical migration was also investigated by frequent filming during a 24-hour cycle at two contrasting locations with respect to salinity stratification. The v...

Haraldsson, Matilda; Ba?mstedt, Ulf; Tiselius, Peter; Titelman, Josefin; Aksnes, Dag L.

2014-01-01

27

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

International Nuclear Information System (INIS)

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

28

Climate induced glacial meltwater turbidity affect vertical position and community composition of phytoplankton and zooplankton  

DEFF Research Database (Denmark)

Receding glaciers are among the most obvious changes caused by global warming, and glacial meltwater entering lakes generally forms plumes of particles. By taking vertical samples along a horizontal gradient from such a particle source, we found that photosynthetically active radiation (PAR) and ultraviolet radiation (UVR) attenuated 20–25% faster close to the inflow of suspended particles compared with the more transparent part of the gradient. All sampled stations had a deep chlorophyll a (Chl a) maximum at 15–20 m which was more distinct in the transparent part of the horizontal gradient. Picocyanobacteria increased in abundance in more transparent water and their numbers were tightly correlated with the intensity of the deep Chl a maxima. Motile species of phytoplankton had a deeper depth distribution in transparent versus less transparent water. Yet other species, like Chrysochromulina parva, that can withstand high PAR intensities and low nutrient concentrations, increased in abundance as the water became more transparent. Also copepods increased in abundance, indicating that they are more successful in transparent water. We conclude that sediment input into lakes creates horizontal gradients in PAR and UVR attenuation which strongly affect both distribution and behavior of phyto- and zooplankton. The input of glacial flour creates a subhabitat that can function as a refuge for species that are sensitive to high PAR and UVR exposure. When the glacier has vanished, this habitat may disappear. During the melting period, with heavy sediment input, we predict that competitive species in transparent waters, like Chrysocromulina, picocyanobacteria and copepods, will become less common. The deep Chl a maxima is also likely to become less developed. Hence, glacier melting will probably have profound effects on both species composition and behavior of several planktonic taxa with potential effects on the food web

Hylander, Samuel; Jephson, T.

2011-01-01

29

Evidence of diel vertical migration in Mnemiopsis leidyi.  

Science.gov (United States)

The vertical distribution and migration of plankton organisms may have a large impact on their horizontal dispersal and distribution, and consequently on trophic interactions. In this study we used video-net profiling to describe the fine scale vertical distribution of Mnemiopsis leidyi in the Kattegat and Baltic Proper. Potential diel vertical migration was also investigated by frequent filming during a 24-hour cycle at two contrasting locations with respect to salinity stratification. The video profiles revealed a pronounced diel vertical migration at one of the locations. However, only the small and medium size classes migrated, on average 0.85 m h(-1), corresponding to a total migration distance of 10 m during 12 h. Larger individuals (with well developed lobes, approx. >27 mm) stay on average in the same depth interval at all times. Biophysical data suggest that migrating individuals likely responded to light, and avoided irradiance levels higher than approx. 10 µmol quanta m(-2) s(-1). We suggest that strong stratification caused by low surface salinity seemed to prohibit vertical migration. PMID:24466162

Haraldsson, Matilda; Båmstedt, Ulf; Tiselius, Peter; Titelman, Josefin; Aksnes, Dag L

2014-01-01

30

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

31

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  

Directory of Open Access Journals (Sweden)

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

Glécia Trinta de Paula Freitas

2012-06-01

32

Diel vertical migration and feeding rhythm of copepods under sea ice at Saroma-ko Lagoon  

Science.gov (United States)

Diel vertical migration and feeding rhythm of copepods were investigated in Saroma-ko Lagoon, Japan, one of the southernmost areas covered by seasonal sea ice in the Northern Hemisphere. Copepods were collected under sea ice every 4 h for 24 h at five depths (0, 1, 3, 6 and 9 m from the under-surface of the sea ice) to examine their density and ingestion rate. Distinct changes in the vertical distribution and ingestion rate of copepods were observed at dusk, when they migrated upward from the near-bottom layer to the food-abundant sub-ice layer. However, most copepods left the food-abundant sub-ice layer by midnight and reached near bottom again before sunrise. The ingestion rates of copepods increased after sunset throughout the water column as in areas without ice cover. The ingestion rates at the food-poor near-bottom layer were higher than those during the day in the food-abundant sub-ice layer. The estimated grazing rate by zooplankton, predominately copepods, was between 0.056 and 0.08% of the chlorophyll standing stock in the water column per day. This estimate is lower than that observed under Arctic sea ice, due to the lower biomass of copepods under sea ice at Saroma-ko Lagoon.

Saito, Hiroaki; Hattori, Hiroshi

1997-02-01

33

The distribution and vertical flux of fecal pellets from large zooplankton in Monterey bay and coastal California  

Science.gov (United States)

We sampled zooplankton and fecal pellets in the upper 200 m of Monterey Bay and nearby coastal regions in California, USA. On several occasions, we observed high concentrations of large pellets that appeared to be produced during night-time by dielly migrating euphausiids. High concentrations of pellets were found in near-surface waters only when euphausiids co-occurred with high concentrations of large (>10 ?m) phytoplankton. Peak concentrations of pellets at mid-depth (100 or 150 m) during the day were consistent with the calculated sinking speeds of pellets produced near the surface at night. At these high flux locations (HI group), pellet concentrations declined below mid-depth. In contrast, at locations where the phytoplankton assemblage was dominated by small phytoplankton cells (profiles were mostly due to sinking of dielly-pulsed inputs in the surface layer, and that small zooplankton (Oithona, Oncaea), heterotrophic dinoflagellates, and bacterial activity probably caused some pellet degradation or consumption below 100 m. We estimated that consumption of sinking pellets by large copepods was insignificant. High fluxes of pellets were episodic because they required both high concentrations of large phytoplankton and large stocks of euphausiids. Under these conditions, flux events overwhelmed retention mechanisms, resulting in large exports of organic matter from the upper 200 m.

Dagg, Michael J.; Jackson, George A.; Checkley, David M.

2014-12-01

34

Turbulence and zooplankton production: insights from PROVESS  

DEFF Research Database (Denmark)

Zooplankton are directly influenced by turbulence in both a passive and an active manner. Passively, zooplankton are at the mercy of turbulence in how it affects their vertical mixing, encounter rate, detection abilities and feeding current efficiency. Many zooplankton species, however, are actively able to mitigate the effects of turbulence by modifying their behaviour, e.g. vertical migration, prey switching and habituation to hydromechanical stimuli. Both theoretical treatments of these processes and field observations from the northern North Sea are examined. Field observations show that some copepod species actively migrate to avoid high turbulence levels in surface waters. Furthermore, observations show a negative relationship between turbulence and zooplankton ingestion rates. This supports the paradigm of a dome-shaped response for zooplankton production with environmental turbulence. A theoretical treatment shows that the reaction distance, R, for an ambush-feeding copepod feeding on swimming organisms follows R alpha epsilon(-1/6) where epsilon is the turbulent dissipation rate, a result that shows close agreement with previously reported experimental results. (C) 2002 Elsevier Science B.V. All rights reserved.

Visser, Andre

2002-01-01

35

Vertical instability and inclination excitation during planetary migration  

CERN Document Server

We consider a two-planet system, which migrates under the influence of dissipative forces that mimic the effects of gas-driven (Type II) migration. It has been shown that, in the planar case, migration leads to resonant capture after an evolution that forces the system to follow families of periodic orbits. Starting with planets that differ slightly from a coplanar configuration, capture can, also, occur and, additionally, excitation of planetary inclinations has been observed in some cases. We show that excitation of inclinations occurs, when the planar families of periodic orbits, which are followed during the initial stages of planetary migration, become vertically unstable. At these points, {\\em vertical critical orbits} may give rise to generating stable families of $3D$ periodic orbits, which drive the evolution of the migrating planets to non-coplanar motion. We have computed and present here the vertical critical orbits of the $2/1$ and $3/1$ resonances, for various values of the planetary mass ratio....

Voyatzis, G; Tsiganis, K

2014-01-01

36

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

37

Zooplankton and the oceanography of the eastern tropical Pacific: A review  

Science.gov (United States)

We review the spatial and temporal patterns of zooplankton in the eastern tropical Pacific Ocean and relationships with oceanographic factors that affect zooplankton distribution, abundance and trophic relationships. Large-scale spatial patterns of some zooplankton groups show broad coincidence with surface water masses, circulation, and upwelling regions, in agreement with an ecological and dynamic partitioning of the pelagic ecosystem. The papers reviewed and a new compilation of zooplankton volume data at large-scale show that abundance patterns of zooplankton biomass have their highest values in the upwelling regions, including the Gulf of Tehuantepec, the Costa Rica Dome, the equatorial cold tongue, and the coast of Peru. Some of the first studies of zooplankton vertical distribution were done in this region, and a general review of the topic is presented. The possible physiological implications of vertical migration in zooplankton and the main hypotheses are described, with remarks on the importance of the oxygen minimum zone (OMZ) as a barrier to both the vertical distribution and migration of zooplankton in the region. Recent results, using multiple-net gear, show that vertical distribution is more complex than previously thought. There are some well-adapted species that do live and migrate within the OMZ. Temporal patterns are reviewed and summarized with historical data. Seasonal variations in zooplankton biomass follow productivity cycles in upwelling areas. No zooplankton time series exist to resolve ENSO effects in oceanic regions, but some El Niño events have had effects in the Peru Current ecosystem. Multidecadal periods of up to 50 years show a shift from a warm sardine regime with a low zooplankton biomass to a cool anchovy regime in the eastern Pacific with higher zooplankton biomasses. However, zooplankton volume off Peru has remained at low values since the 1972 El Niño, a trend opposite to that of anchoveta biomass since 1984. Studies of trophic relations emphasize the difference in the productivity cycle in the eastern tropical Pacific compared to temperate or polar ecosystems, with no particular peaks in the stocks of either zooplankton or phytoplankton. Productivity is more dependent on local events like coastal upwelling or water circulation, especially in the equatorial countercurrent and around the equatorial cool-tongue. Micrograzers are very important in the tropics as are predatory mesozooplankton. Up to 70% of the daily primary productivity is consumed by microzooplankton, which thus regulates the phytoplankton stocks. Micrograzers are an important link between primary producers, including bacteria, and mesozooplankton, constituting up to 80% of mesozooplankton food. Oceanography affects zooplankton trophic relationships through spatial-temporal effects on primary productivity and on the distributions of metabolic factors, food organisms, and predators. This paper is part of a comprehensive review of the oceanography of the eastern tropical Pacific.

Fernández-Álamo, María Ana; Färber-Lorda, Jaime

2006-05-01

38

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

39

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

40

Diatom vertical migration within land-fast Arctic sea ice  

Science.gov (United States)

Light levels inside first-year, landfast sea ice were experimentally altered by manipulating overlying snow depths. Irradiance available for ice algae growing near the ice-bottom, and under the ice, was highly dependent on snow depths ranging from 0 to > 30 cm. Importantly, algal vertical distributions also changed under different irradiances. Under thick snow (low light), the majority of algae were found several cm above the ice-seawater interface, while progressively more were found nearer the interface at locations with thinner overlying snow (higher light). Short-term field experiments suggested that ice algae were able to reposition themselves within the ice column within 3 days after manipulating snow depths. Laboratory gliding rate measurements of a cultured ice diatom suggested that it is capable of daily cm-scale movement. Vertical migration may help ice diatoms balance opposing light and nutrient resource gradients, similar to strategies used by some benthic and pelagic algae. Moreover, when ice algae congregate near the ice-seawater interface, they may be especially susceptible to loss from the ice environment. Vertical repositioning in response to changing light dynamics may be a mechanism to optimize between vertically-opposing environmental factors and help explain the connection between melting snow cover and export of biomass from sea ice.

Aumack, C. F.; Juhl, A. R.; Krembs, C.

2014-11-01

 
 
 
 
41

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

42

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  

Digital Repository Infrastructure Vision for European Research (DRIVER)

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

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

2012-01-01

43

Elastic iterative migration of offset vertical seismic profile (VSP) data  

Energy Technology Data Exchange (ETDEWEB)

An iterative elastic migration/inversion scheme is presented and tested on synthetic offset vertical seismic profile (VSP) data. The imaging scheme i rooted in inversion theory and is based on full elastic two-way extrapolation in two dimensions. The wavefield extrapolation is implemented using an efficient high-order finite difference technique. Both P and S waves reflections contribute to the depth images for the density parameter and the shear modulus, whereas mainly P waves contribute to the bulk modulus image. These images and the background model are updated in each iteration using the correlation of the forward modeled elastic field with the backpropagated residual field. A k[sub x] - k[sub z] filter is applied to the images in order to remove low wavenumber components and artifacts due to the limited recording aperture. Experiments on synthetic data show that smooth initial models give better images than initial models having sharp interfaces. Furthermore, increasing the number of iterations or the number of shot positions improve the image quality. Images based on both P and S waves give better near well resolution than images based on acoustic energy only for large offset VSP data. A deviated well geometry give better images than a vertical well geometry. 11 refs., 15 figs., 1 tab.

Mittet, R.; Helgesen, J.

1992-06-01

44

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

45

Diurnal variation of zooplankton in Bhoj Wetland, Bhopal, India  

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Full Text Available The diurnal dynamics of the vertical distribution of zooplankton was studied in Bhoj Wetland, Bhopal. Vertical distribution of the zooplankton community in general showed a clear diurnal variation in the water column of a typical stratified lake. Zooplankton concentration was found to be high at the surface layer during night hours with peak abundance around the middle of the night and another peak was observed just before sunrise, followed by a rapid nadir after sunrise. Zooplankton can offset the loss of daytime foraging opportunity by moving up into the water column to graze at night, when predation by visual predators is greatly reduced and it can be also attributed to light intensity which is responsible for vertical migration during the twenty four hour cycles. Among different classes, cladocerans and the copepod showed nocturnal migration conversely rotifers, had a relatively uniform distribution throughout the water column Out of the twenty three species, Bosmina species and Cyclops species ascended at night and descended during day hours, however, Keratella cochlearis showed uniformity in distribution throughout the water column during the study.

Najeeb Ahmad Bhat

2013-09-01

46

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

47

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

48

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

Directory of Open Access Journals (Sweden)

Full Text Available The magnitude of the 9.0 Tohoku earthquake and the ensuing tsunami on 11 March 2011, inflicted heavy damage on the Fukushima Dai-ichi nuclear power plant (FNPP1. Fission products were emitted, falling over a broad range in the Northern Hemisphere, and water contaminated with radionuclides leaked into the ocean. In this study, we described the horizontal distribution of the Fukushima-derived radiocesium in zooplankton and in seawater in the western North Pacific Ocean (500–2100 km from the FNPP1 10 months after the accident. 134Cs and 137Cs were detected in zooplankton and seawater from all the stations. Because of its short half-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

49

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

Directory of Open Access Journals (Sweden)

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

M. Kitamura

2013-04-01

50

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

Science.gov (United States)

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.

Kitamura, M.; Kumamoto, Y.; Kawakami, H.; Cruz, E. C.; Fujikura, K.

2013-08-01

51

The effects of Najas marina on the zooplankton species composition and water chemistry in a small, shallow lake (Fehér-tó, Fert?-Hanság National Park, Hungary  

Directory of Open Access Journals (Sweden)

Full Text Available Horizontal distribution and diurnal migration of zooplankton as well as a few water chemistry parameters were investigated in the clear-water and the turbid state of the extremely shallow Lake Fehér (Hungary between 1998-2001. Significant horizontal and diel differences were recorded in the density and composition of zooplankton assemblages as well as a few water chemical parameters between the turbid and clear-water state of lake. In the turbid state copepods dominanted zooplankton assemblages developed with low density and species richness and the cladoceran zooplankton consisted of mainly pelagic species with low abundance values. During the presence of Najas marina the zooplankton community was dominated by cladocerans and the ratio of the macrophyta-associated species was high. In case of few cladoceran species significant diel density differences developed between the macrophyte bed and the above macrophyte-free water column however macrophyta-associated species did not show diel vertical migration. Based on the result of diurnal monitoring the importance of DHM (diel horizontal migration was irrelevant in the uniform and dense Najas beds and zooplankton appear to migrate vertically rather than horizontally.

Kiss, A.

2006-12-01

52

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

53

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

Directory of Open Access Journals (Sweden)

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

A. Forest

2012-04-01

54

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

Directory of Open Access Journals (Sweden)

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

A. Forest

2011-11-01

55

Seasonal response of zooplankton to monsoonal reversals in the Arabian Sea  

Science.gov (United States)

The US JGOFS Arabian Sea Process Study was designed to provide a seasonally and spatially resolved carbon budget for a basin exhibiting some of the highest and lowest concentrations of plant biomass in the world's ocean. During the US JGOFS Process Study in the Arabian Sea (September 1994-January 1996), the absolute maximum in biomass of epipelagic zooplankton in the entire study was observed during the Southwest Monsoon season inshore of the Findlater Jet in the area of upwelling. The greatest contrast between high and low biomass in the study area also was observed during the Southwest Monsoon, as was the strongest onshore-offshore gradient in biomass. Lowest biomass throughout the study was observed at the most offshore station (S15), outside the direct influence of the monsoon forcing. The greatest day/night contrasts in biomass were observed nearshore in all seasons, with nighttime biomass exceeding daytime in the Northeast Monsoon season, but daytime exceeding nighttime in the Southwest Monsoon season. The diel vertical migration patterns in general reversed between the monsoons at all stations in the southern part of the study area. Virtually, no diel vertical migration of zooplankton took place in any season at the station with strong, persistent subsurface suboxic conditions (N7), suggesting that these conditions suppress migration. Based on the distribution of biomass, we hypothesize that inshore of the Findlater Jet, zooplankton grazing on phytoplankton is the dominant pathway of carbon transformation during both monsoon seasons, whereas offshore the zooplankton feed primarily on microplankton or are carnivorous, conditions that result in reduction of the carbon flux mediated by the zooplankton. Predation by mesopelagic fish, primarily myctophids, may equal daily growth of zooplankton inshore of the Findlater Jet during all seasons. This suggests that the food web inshore of the Findlater Jet is well integrated, may have evolved during past periods of intensified upwelling, and has a distinctly annual cycle.

Smith, Sharon; Roman, Michael; Prusova, Irina; Wishner, Karen; Gowing, Marcia; Codispoti, L. A.; Barber, Richard; Marra, John; Flagg, Charles

56

Equivalent offset migration for VSP's and data acquired with vertical receiver arrays  

Energy Technology Data Exchange (ETDEWEB)

The equivalent offset method (EOM) of prestack migration is extended to include data that is acquired with vertical receiver arrays. Summing of input data directly to the vertical-array common scatterpoint gather (VCSP) is maintained with a single time shift (static) for each input trace. The EOM method is a Kirchhoff prestack migration that initially forms common scatter point (CSP) gathers. Application of Kirchhoff NMO then stacking of these gathers includes the amplitude scaling and filtering of Kirchhoff migrations. An essential feature of the equivalent offset method is the reduction of the double square-root equation into the hyperbolic form of the travel time equation. A number of raypath configurations were considered to define the value of the vertical two way travel time from the scatter point to the surface and velocity. CSP gathers with velocities and time similar to conventional processing is shown. The CREWES Blackfoot 3-D VSP data was preprocessed with the sources at a flat datum. The EOM of prestack migration was applied to VCSP data, and prestack migration gathers permit accurate velocities to be determined. 3 refs.

Bancroft, J.C.; Xu Yong (Calgary Univ., Calgary, AB, (Canada))

1999-01-01

57

Equivalent offset migration for VSP`s and data acquired with vertical receiver arrays  

Energy Technology Data Exchange (ETDEWEB)

The equivalent offset method (EOM) of prestack migration is extended to include data that is acquired with vertical receiver arrays. Summing of input data directly to the vertical-array common scatterpoint gather (VCSP) is maintained with a single time shift (static) for each input trace. The EOM method is a Kirchhoff prestack migration that initially forms common scatter point (CSP) gathers. Application of Kirchhoff NMO then stacking of these gathers includes the amplitude scaling and filtering of Kirchhoff migrations. An essential feature of the equivalent offset method is the reduction of the double square-root equation into the hyperbolic form of the travel time equation. A number of raypath configurations were considered to define the value of the vertical two way travel time from the scatter point to the surface and velocity. CSP gathers with velocities and time similar to conventional processing is shown. The CREWES Blackfoot 3-D VSP data was preprocessed with the sources at a flat datum. The EOM of prestack migration was applied to VCSP data, and prestack migration gathers permit accurate velocities to be determined. 3 refs.

Bancroft, J.C.; Xu Yong [Calgary Univ., Calgary, AB, (Canada)

1999-11-01

58

Mechanism of vertical migration of Am 241 in peaty-gley soil  

International Nuclear Information System (INIS)

Nowadays soil in the Chernobyl zone has become a source from which radionuclides can come to other objects of biosphere. The vertical migration determines distribution of the radionuclides in the soil. For research of vertical migration of Am 241 in soil the distribution of the radionuclide in granulometric fractions of the soil particles was measured, humus was extracted from the soil with the help of a sodium pyrophosphate solution by the accelerated method of Kononova and Beltchikova. For an estimation of a share of a mobile form of radionuclide the soil was dissolved in ammonium acetate solution. The conclusion is made, that nowadays significant part of Am 241 is strongly fixed on a mineral matrix of the soil and migrates together with the soil particles

59

Intensification of open-ocean oxygen depletion by vertically migrating animals  

Science.gov (United States)

Throughout the ocean, countless small animals swim to depth in the daytime, presumably to seek refuge from large predators. These animals return to the surface at night to feed. This substantial diel vertical migration can result in the transfer of significant amounts of carbon and nutrients from the surface to depth. However, its consequences on ocean chemistry at the global scale have remained uncertain. Here, we determine the depths of these diel migrations in the global ocean using a global array of backscatter data from acoustic Doppler current profilers, collected between 1990 and 2011. We show that the depth of diel migration follows coherent large-scale patterns. We find that migration depth is greater where subsurface oxygen concentrations are high, such that seawater oxygen concentration is the best single predictor of migration depth at the global scale. In oxygen minimum zone areas, migratory animals generally descend as far as the upper margins of the low-oxygen waters. Using an ocean biogeochemical model coupled to a general circulation model, we show that by focusing oxygen consumption in poorly ventilated regions of the upper ocean, diel vertical migration intensifies oxygen depletion in the upper margin of oxygen minimum zones. We suggest that future changes in the extent of oxygen minimum zones could alter the migratory depths of marine organisms, with consequences for marine biogeochemistry, food webs and fisheries.

Bianchi, Daniele; Galbraith, Eric D.; Carozza, David A.; Mislan, K. A. S.; Stock, Charles A.

2013-07-01

60

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.)

 
 
 
 
61

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.

62

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

63

Vertical migration studies of 137Cs from nuclear weapons fallout and the Chernobyl accident  

International Nuclear Information System (INIS)

The vertical migration of 137Cs originating from nuclear weapons fallout (NWF) and the Chernobyl accident has been studied at 33 sampling sites in western Sweden. An attempt to describe the present depth distribution with a solution to the convection-diffusion equation (CDE) with a pulse-like fallout event as the initial condition was made. A sum of two CDEs describing the NWF and Chernobyl debris was fitted to the actual depth profiles measured by soil sampling. The fitted depth profiles were used to correct in situ measurements for the actual depth distribution, showing good agreement with the accumulated activities in soil samples. As expected, the vertical migration was very slow and most caesium was still present in the upper soil layers. The ranges of the apparent convection velocity, v, and apparent diffusion coefficient, D, were between 0 and 0.35 cm/year and 0.06 and 2.63 cm2/year, respectively

64

Diel vertical distribution and migration of a euphausiid Euphausia pacifica in the Southern Yellow Sea  

Science.gov (United States)

Stage-specific differences in the diel vertical distribution and migration of a euphausiid, Euphausia pacifica, were studied at a single station (E2, 70 m water depth) in the South Yellow Sea, by sampling with a conical closing net from five discrete strata, every 3 h, for 24 h, on 2-3 May 2001. Environmental data were collected simultaneously with the net sampling. Results showed that eggs contributed a large proportion of the numerical abundance of the Euphausia pacifica population throughout the investigation. They were mainly distributed below 20 m depth, and concentrated in the 30-50 m strata throughout the day and night. Nauplius stage I (NI) was distributed below 10 m, and seldom occurred in the upper 10 m. Nauplius stage II (NII) and Metanauplius stage (MN) extended their distribution to nearly the whole water column; however, the MN resided somewhat shallower than NII. The majority of calyptopis stages I to III (CI to CIII ) and early furcilia stages I to III (FI to FIII) were restricted to the upper 30 m throughout the day. The weighted mean depth tended to increase as the stage progressed from stage FI onward. Calyptopis stages showed a weak or moderate diel vertical migration behavior, and the onset of an obvious diel vertical migration took place in FII stage. The amplitude of the diel vertical migration varied with developmental stages. Stages after FIV were often absent from samples during the investigation, but from the limited available data, DVM occurred from stages FIV-VI and female adults. However, the male adults showed a somewhat different migration behavior. In summary, an ontogenetic migration pattern is obvious from this high-frequency sampling: spawning took place at 20-50 m depth, hatched nauplii sank a little, metanauplius began moving toward the surface, and calyptopis larvae reached the uppermost layer. Furcilia larvae began DVM and deepened their daytime residence depth with age. The vertical distribution of Euphausia pacifica seemed to relate to temperature and chlorophyll a.

Liu, Hui-Lian; Sun, Song

2010-04-01

65

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

66

Vertical migration of Haemonchus contortus third stage larvae on Brachiaria decumbens grass.  

Science.gov (United States)

The present study aimed at evaluating the vertical migration of Haemonchus contortus third stage larvae (L3) on Brachiaria decumbens grass, as well as at verifying whether larval numbers on pasture varies over the day due to climatic conditions. Feces containing H. contortus L3 were deposited on the soil in the middle of herbage which was initially 30 cm high. Seven days later, samples of different herbage strata (0-10, 10-20 and >20 cm), remaining feces and a layer of approximately 1cm soil were collected. Tests were carried out in four periods: September 2006, December 2006, March 2007, and June 2007. Samples were collected at sunrise, mid-day, sunset, and mid-night. The humidity and temperature conditions observed in different months influenced larval migration from the feces to the grass. In September, December and March, it rained after fecal deposition on pasture, which favored migration of larvae from the feces to the herbage. Conversely, in June 2007, when there was no rainfall after fecal deposition and temperatures were lower, L3 were mainly recovered from feces. As regards the vertical migration of larvae, the numbers of H. contortus L3 in the forage strata remained relatively constant over the day. This indicates there is not a determined period in which sheep on pasture are at higher risk of infection. Finally, in all collection periods a considerable amount of third stage larvae was observed on the herbage top, which is the first plant part consumed by sheep. PMID:18824304

Silva, B F; Amarante, M R V; Kadri, S M; Carrijo-Mauad, J R; Amarante, A F T

2008-11-25

67

Diel vertical migration behaviour of the Northern krill (Meganyctiphanes norvegica Sars).  

Science.gov (United States)

The prototype of Meganyctiphanes norvegica diel vertical migration (DVM) behaviour comprises ascent around dusk, feeding near the surface at night, and descent at dawn, explained as a trade-off between feeding and predator avoidance in an environment where both food and risk of predation is highest near surface. Light is the proximate cue, and daytime distribution is deeper in clear waters and sunny weather and nocturnal distributions deeper in moonlight. However, both internal state and external factors further affect and modify the diel migration pattern. While Meganyctiphanes migrates in synchrony to the surface at sunset, part of the population may descend soon after the ascent with individuals re-entering upper layers throughout the night. This has been explained with hungry individuals being prone to take larger risks and hence stay shallower, while satiated individuals seek shelter at depth. Females migrate closer to the surface than males of equivalent size, possibly due to their greater demand for energy to fuel egg production. Freshly moulted M. norvegica remain at depth throughout the diel cycle. This has been related to the fact that that krill do not feed during moulting, to reduced swimming capacity, and as a mechanism to avoid cannibalism whilst in a vulnerable condition. In some locations large parts of the population remain at depth at night. Such behaviour may incur access to demersal food sources, provide avoidance of predators, or can be a means to avoid horizontal transport to adjacent, unfavourable areas. Environmental gradients can arrest migrations of M. norvegica, yet the effect of physics is not always distinguished from associated biological properties, like subsurface maxima of phytoplankton located at pycnocline boundaries. Deeper nocturnal distribution when predators were abundant has been reported, and krill may adjust their distribution upwards when exposed to deep-living predators. Instantaneous escape to approaching predators is a common component of the anti-predator repertoire of Meganyctiphanes. Occasionally reported schooling behaviour that overrides normal DVM behaviour may serve anti-predation purposes, as well as being related to reproduction. M. norvegica can remain within confined areas, often defined by the bottom topography, even when exposed to strong currents. Behaviourally mediated retention may be accomplished by vertical migration in depth-stratified flows, but evidence for active use of DVM for the purpose of retention is so far circumstantial among M. norvegica. In several instances, large aggregations of krill that repeatedly occur in the same location appear to be accidental consequences of krill vertical migration behaviour interacting with the mean circulation and bottom topography, rather than representing active retention behaviour. PMID:20955895

Kaartvedt, Stein

2010-01-01

68

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

69

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

International Nuclear Information System (INIS)

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

70

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

71

Temporal variations of zooplankton biomass in the Ligurian Sea inferred from long time series of ADCP data  

Science.gov (United States)

Three years of 300 kHz acoustic doppler current profiler data collected in the central Ligurian Sea are analysed to investigate the variability of the zooplankton biomass and the diel vertical migration in the upper thermocline. After a pre-processing phase aimed at avoiding the slant range attenuation, hourly volume backscattering strength time series are obtained. Despite the lack of concurrent net samples collection, different migration patterns are identified and their temporal variability examined by means of time-frequency analysis. The effect of changes in the environmental condition is also investigated. The highest zooplankton biomasses are observed in April-May just after the peak of surface primary production in March-April. The main migration pattern found here points to a "nocturnal" migration, with zooplankton organisms occurring deeper in the water column during the day and shallower at night. Also, twilight migration is highlighted during this study. The largest migrations are recorded in November-December, corresponding to lowest backscattering strength values and they are likely attributable to larger and more active organisms (i.e. euphausiids and mesopelagic fish). The results suggest further applications of the available historical acoustic doppler current profiler time series.

Bozzano, R.; Fanelli, E.; Pensieri, S.; Picco, P.; Schiano, M. E.

2014-02-01

72

Temporal variations of zooplankton biomass in the Ligurian Sea inferred from long time series of ADCP data  

Directory of Open Access Journals (Sweden)

Full Text Available Three years of 300 kHz ADCP data collected in the central Ligurian Sea are analyzed to investigate the variability of the zooplankton biomass and the Diel Vertical Migrations (DVM in the upper thermocline. After a pre-processing aimed at avoiding the slant range attenuation, hourly volume backscattering strength time series are obtained. Despite the lack of concurrent net samples collection, different migration patterns are identified and their temporal variability examined by means of time-frequency analysis. The effect of changes in the environmental condition is also investigated. Highest zooplankton biomasses are observed in April–May just after the peak of surface primary production in March–April. The main migration pattern points to a "nocturnal" migration with zooplankton organisms occurring deeper in the water column during the day and shallower at night. Also twilight migration is highlighted during this study. The largest migrations are recorded in November–December, corresponding to lowest backscattering strength values and are likely attributable to larger and more active organisms (i.e. euphausiids and mesopelagic fish. The results suggest further applications of the historical ADCP time series available.

R. Bozzano

2013-08-01

73

Vertical structural patterns of deep-living zooplankton in the ne atlantic, the levantine sea and the red-sea - a comparison  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Full-depth profiles of zooplankton numerical abundance and major taxa composition are presented with special attention to the dominant copepod fauna, for directly comparable data sets from sites to a depth of 4 300 m in the Levantine and Red Seas, which are also compared with the deep mid-latitude NE Atlantic. Copepods showed highest proportions of calanoids, cyclopoids sensu lato and harpacticoids in the 333 mum net subsurface samples from the Atlantic. Among the calanoids as the predominant...

Weikert, H.; Koppelmann, R.

1993-01-01

74

Vertical diel migration and feeding of Euphausia vallentini within southern Chilean fjords  

Science.gov (United States)

E. vallentini is a circumpolar vertical migrator in the open ocean that enters the Chilean fjords through the sills to become the most common and abundant euphausiid. The diel migratory and feeding patterns of this species are studied in this distinct, enclosed and bathymetrically variable environment. The main goal was to determine the ability of E. vallentini to alter its vertical diel range in order to avoid shallow depths, or to maintain its depth migratory range and take advantage of benthic environment during daytime. Multiple opening closing nets sampled the water column in several basins along the Strait of Magellan. Fluorometrically determined stomach pigments along with on board experiments of evacuation rates allowed estimation of ingestion and consumption rates. Samples of stomach content were microscopically examined to compare day and night diet. E. vallentini migrated between the surface at night and 100-200 m in daytime. Surface night dwellers had higher chlorophyll stomach content than deep daytime dwellers. Diet composition changed from dinoflagellates and tintinnids at night, to a polychaeths-dominated diet in daytime. Stomach content, ingestion rates and consumption rates of phytoplankton were higher at night than in daytime, and accounted for an impact of 0.17% upon phytoplankton biomass. Changes of diet of E. vallentini imply unique adaptations to take advantage of both pelagic and demersal environments, which could explain its high abundance and high frequency of encounter within the southern Chilean fjords.

Hamame, Madeleine; Antezana, Tarsicio

2010-04-01

75

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

76

Inventory and vertical migration of 137Cs in Spanish mainland soils  

International Nuclear Information System (INIS)

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

77

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

Dutz, Jörg

2012-01-01

78

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

79

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

80

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

Science.gov (United States)

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

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

2014-08-01

 
 
 
 
81

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

International Nuclear Information System (INIS)

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

82

Zooplankton time series from the Strait of Georgia: Results from year-round sampling at deep water locations, 1990-2010  

Science.gov (United States)

We have compiled and archived a large fraction of the zooplankton data collected from the Strait of Georgia during the past 50 years. Although the full dataset is very heterogeneous and gappy, sampling since 1990 has been consistent and frequent enough to examine interannual variability of the full zooplankton community. In this paper we focus on deep tows at mid-Strait deep-water locations, where vertical-migratory zooplankton can be captured at all times of day and all seasons. Average zooplankton dryweight biomass is high (?9 g m-2) and varies seasonally between a winter minimum (?4 g m-2) and a broad late-spring to autumn maximum (10-11 g m-2). Much of the biomass in all seasons consists of large crustaceans (copepods, euphausiids and amphipods with oceanic and subarctic zoogeographic affinities) that undergo strong diurnal or seasonal vertical migrations. Their interannual variability is very strong: about an order of magnitude within most zooplankton categories, and nearly two orders of magnitude for euphausiids, large copepods, and chaetognaths. Most (73%) of the interannual variability is accounted for by three principal components. The dominant mode (36%) is a low-frequency decadal fluctuation shared by most zooplankton taxa: declining from 1990 to 1995, increasing to a maximum ?1999-2002, declining to a second minimum in 2005-2007, and then recovering to near-average levels by 2010. This zooplankton signal correlates positively with the North Pacific Gyre Oscillation (NPGO) climate index, negatively with temperature anomalies throughout the water column, and positively (but less consistently) with survival anomalies of Strait of Georgia salmon and herring. Proximal causal mechanisms are less certain, but probably include estuarine advective exchange with outer coast populations, and timing match-mismatch within the Strait.

Mackas, David; Galbraith, Moira; Faust, Deborah; Masson, Diane; Young, Kelly; Shaw, William; Romaine, Stephen; Trudel, Marc; Dower, John; Campbell, Rob; Sastri, Akash; Bornhold Pechter, Elizabeth A.; Pakhomov, Evgeny; El-Sabaawi, Rana

2013-08-01

83

Diel vertical migrations and feeding behavior of the mysid Rhopalophthalmus africana (Crustacea: Mysidacea) in a tropical lagoon (Ebrié, Côte d'Ivoire)  

Science.gov (United States)

Time-series sampling, gut content analysis, gut fluorescence measurements, and experiments on feeding, respiration and ammonia excretion were performed at a fixed station (4.5 m depth) on four occasions (from 1990 to 1997) to evaluate the impact of mysids on phytoplankton and zooplankton in a tropical brackish lagoon. Rhopalophthalmus africana, the dominant species, exhibited marked upward migrations at night. Grazing experiments showed that R. africana did not consume sestonic particles in most cases. Predation experiments showed that R. africana actively consumed zooplankton and selected prey according to their size and/or their abundance. The predation rate increased linearly with increasing prey concentration and did not taper at highest prey concentration. A low metabolic oxygen to nitrogen ratio (O/N, 5-13 at:at) reinforced the assumption of a relatively permanent carnivory. Nocturnal increase in gut fullness suggests night-time feeding, but relatively high gut fluorescence during the day, resulting mainly from a fluorimetric tracing of animal prey, suggested also a diurnal ingestion of zooplankton items concentrated near the bottom. The daily grazing impact of R. africana on phytoplankton was very low (0.14% of the in situ chlorophyll concentration), whereas its daily nutrient recycling through excretion (8-15% of the in situ NH 4 concentration) was rather high. The predation impact (33-154% of the zooplankton production) was high and suggests an important role of mysids to explain the low zooplankton/phytoplankton biomass ratio and the low transfer efficiency observed within the food chain of the western part of Ebrié Lagoon.

Kouassi, Ernest; Pagano, Marc; Saint-Jean, Lucien; Sorbe, Jean Claude

2006-04-01

84

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

Directory of Open Access Journals (Sweden)

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

Jaromír SE?A

2010-08-01

85

Buoyancy characteristics of the bloater (Coregonus hoyi) in relation to patterns of vertical migration and acoustic backscattering  

Science.gov (United States)

Acoustic studies in Lake Michigan found that bloaters (Coregonus hoyi) were less reflective per size than the other major pelagic species. This difference in in situ acoustic backscattering could indicate that the deep-water bloaters have compressed swimbladders for much of their vertical range with related implications on buoyancy. To test this hypothesis, the buoyancy characteristics of bloaters were determined with fish placed in a cage that was lowered to bottom and monitored with an underwater camera. We found bloaters were positively buoyant near surface, neutrally buoyant at intermediate strata, and negatively buoyant near bottom. This pattern was consistent for the range of depths bloaters occur. The depth of neutral buoyancy (near the 50-n strata) corresponds with the maximum extent of vertical migration for bloaters observed in acoustic surveys. Fish below this depth would be negatively buoyant which supports our contention that bloaters deeper in the water column have compressed swimbladders. Understanding the buoyancy characteristics of pelagic fishes will help to predict the effects of vertical migration on target strength measurement and confirms the use of acoustics as a tool to identify and quantify the ecological phenomenon of vertical migration.

Fleischer, Guy W.; TeWinkel, Leslie M.

1998-01-01

86

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

87

Distribution of zooplankton populations within and adjacent to a thermal plume  

International Nuclear Information System (INIS)

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

88

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

89

Vertically migrating micronekton and macrozooplankton communities around Guam and the Northern Mariana Islands  

Science.gov (United States)

The distribution, biomass, and assemblages of vertically migrating micronekton/macrozooplankton were studied in relation to oceanographic conditions around Guam and the adjacent Northern Mariana Islands during Spring 2010, using 3-m2 Isaacs-Kidd Midwater Trawl (IKMT). The study area was located within the oligotrophic waters of the westward flowing North Equatorial Current (NEC). However, southern stations of the survey were situated close to the northern boundary of the more productive North Equatorial Countercurrent (NECC), where we observed the highest biomass, abundance, species richness, and diversity of pelagic organisms. Overall, we recorded 85 species from 20 families of mostly mesopelagic species in the area, with lanternfishes (Myctophidae—40 species) and dragonfishes (Stomiidae—18 species) being the most taxonomically diverse groups. Three genera of mesopelagic shrimps, Sergestes, Janicella and Sergia, dominated the decapod crustacean component of the micronekton community numerically and by biomass, while the contribution from cephalopods was relatively minor. Assemblages of major micronekton/macrozooplankton groups, based on biomass and abundance showed principal changes with latitude. However, the classification and ordination analysis, based on taxonomically resolved taxa (fishes and decapod shrimps), indicated additional zonal variation, with areas east and west of the island chain showing different community structure. The mean total micronekton biomass for the area near the productive boundary region between the NEC and NECC was 5.8 mg/m3, with a mean biomass of 1.2 mg/m3 obtained for stations in the oligotrophic NEC area. The corresponding biomass of mesopelagic fishes was 0.88 mg/m3 and 0.24 mg/m3 for these two areas, respectively. We reviewed and compared the available information on the quantitative distribution of midwater fish biomass in the western tropical Pacific and outlined major patterns of variation in the equatorial Pacific in general.

Suntsov, Andrey; Domokos, Réka

2013-01-01

90

Research of the vertical soil profiles migration of the Chernobyl origin men-made radionuclides in Polesija  

International Nuclear Information System (INIS)

The research of migration of Chernobyl origin radionuclides was carried out in vertical soil profiles of the 'Ryzhyj les' waste disposal area within 5 km Ch NPP zone. The 1122-soil samples were selected during 2000-2001 years. The ?-, ?- and X-emanation of these samples were studies after corresponding preparation. The 134,137Cs, 154,155Eu, 241Am and 238+239+240Pu isotopes were identified. The (90Sr + 90Y) isotopes were identified in equilibrium as a result of the research of the 'non thin' layers samples ?-spectra. The 238+239+240Pu isotopes were determined by Lx-emanation spectroscopy of U and Np. The migration of 134,137Cs, 154,155Eu, 90Sr, 241Am isotopes was observed to the depth up down 30 cm, and the 238+239+240Pu migration was observed to depth of 10/15 cm. The obtained data is discussed

91

Study on the rate of plutonium vertical migration in various soil types of Lublin region (Eastern Poland)  

International Nuclear Information System (INIS)

Soil contamination level with 239+240Pu of Lublin region was determined using the alpha spectrometric method. Results were compared with similar data from the study performed 15 year earlier. Decrease in total 239+240Pu concentration and reducing quantity of Chernobyl fraction (up to almost negligible value of 1 %) has been observed in upper soil layer. Determination of 239+240Pu concentration in soil profile layers allows calculating a vertical migration velocity of plutonium applying a compartment migration model. It was found that 239+240Pu migration rate varies depending on soil type from 0.29 cm year-1 in Podsols to 0.58 cm year-1 in Fluvisols with mean value of 0.5 cm year-1. (author)

92

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

93

Zooplankton from Lake Magelungen, Central Sweden 1960-1963  

International Nuclear Information System (INIS)

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

94

Zooplankton metabolism and carbon demand at two seamounts in the NE Atlantic  

Science.gov (United States)

Zooplankton metabolic rates, determined from electron transfer system (ETS) activity, were studied at two seamounts (Seine: 34°N, 14°W, summit depth ˜170 m; Sedlo: 40°N, 27°W, summit depth ˜750 m) in the northeast (NE) Atlantic during three cruises in November 2003, April 2004 and July 2004. ETS activity and respiratory carbon demand were measured for samples taken at seamount and open-ocean locations in order to probe the hypothesis of locally enhanced seamount productivity. ETS activity and biomass revealed no consistent diel patterns of feeding activity and vertical migration at Seine and Sedlo Seamounts. Spatial differences of biomass-specific ETS activity were observed at both seamounts and coincided with differences in food abundance and quality. At Seine Seamount in April 2004, biomass-specific ETS activity was on average higher at the seamount locations compared to the open ocean, though the enhancement was of a lower magnitude than spatial and temporal variability and had no apparent influence on zooplankton respiratory carbon demand or biomass. A persistent pattern of reduced zooplankton biomass above the summit location at Seine Seamount in April 2004 and July 2004 resulted in a local reduction of respiratory carbon demand. At Sedlo Seamount in November 2003, large spatial differences in biomass-specific ETS activity observed at the seamount locations resulted in a large range of respiratory carbon demand at the seamount, but were not reflected in zooplankton biomass. The depth-integrated (0-150 m) median respiratory carbon demand of the zooplankton community estimated from day and night hauls was 2.1 mg C m -2 d -1 at Seine Seamount (range: 0.3-6.3) and 2.9 mg C m -2 d -1 at Sedlo Seamount (range: 1.6-12.0). The sporadic nature and low magnitude of locally higher zooplankton respiration rates at the seamounts, which did not result in locally higher zooplankton standing stock biomass, lead us to reject the hypothesis that locally enhanced seamount productivity provides an autochthonous food supply to the resident faunas at Seine and Sedlo Seamounts. Instead, we conclude that the faunas at both seamounts are more likely supported by advection of food from the surrounding ocean.

Hirch, S.; Martin, B.; Christiansen, B.

2009-12-01

95

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

96

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

97

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

DEFF Research Database (Denmark)

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

Nilsson, Lars Anders Fredrik; Thygesen, Uffe HØgsbro

2003-01-01

98

Spatial distribution and vertical migrations of fish larvae communities off Northwestern Iberia sampled with LHPR and Bongo nets  

Science.gov (United States)

The spatial distribution and diel vertical migration of fish larvae were studied in relation to the environmental conditions off NW Iberia during May 2002. Larvae from 23 families were identified, the most abundant were the Clupeidae, Gobiidae, Callionymidae, Blenniidae, Sparidae and Labridae. Sardina pilchardus was the most abundant species, mean concentrations 1 order of magnitude higher than the other fish larvae species. Larval horizontal distribution was mainly related to upwelling-driven circulation, resulting in an offshore increase of larval abundance while the vertical distribution was closely associated to the Western Iberia Buoyant Plume. Despite this general trend, taxon-specific relationships between the distribution of larvae and environmental variables were observed, and temperature was an important regressor explaining the distribution of most taxa. A comparison between ichthyoplankton samples collected alternatively with the LHPR and Bongo nets resulted in captures of larvae ?1 order of magnitude higher for the LHPR, probably related to its higher towing speed. The spatial distribution and relative composition of larvae were also different for both nets, although the most frequent/abundant groups were the same. A fixed station sampled for 69-h showed diel vertical migrations performed by the larvae, with the highest larval concentrations occurring at surface layers during the night and most larvae being found in the neuston layer only during that period.

Garrido, Susana; Santos, A. Miguel P.; dos Santos, Antonina; Ré, Pedro

2009-10-01

99

Shoreward advection of phytoplankton and vertical re-distribution of zooplankton by episodic near-bottom water pulses on an insular shelf: Oahu, Hawaii  

Science.gov (United States)

Shoreward pulses of cold, high salinity, phytoplankton-rich bottom water represent short time scale changes in nearshore hydrography and biological community structure off the leeward coast of Oahu, Hawaii. A three-week mooring deployment in Spring 2009 revealed that 'cold pulses' occurred over all phases of the semidiurnal surface tide, but that a statistically greater proportion occurred at low slack tide, when the typically along-shore flow rotated and briefly exhibited a more dominant onshore component. Cold pulses were more frequent and propagated farther shoreward when background water-column stratification increased. Targeted shipboard sampling of a cold pulse in Spring 2010 revealed that chlorophyll fluorescence within the cold pulse was 7 standard deviations higher than the 11-h mean outside the cold pulse, phytoplankton concentrations (cells mL-1) were up to a factor of 3 higher within the cold pulse, and phytoplankton entrained within the cold pulse were adapted to habitats with lower light levels and higher nutrient concentrations compared to ambient waters. Analysis of multi-frequency acoustic data collected during two shipboard surveys in 2009 and 2010 indicated that acoustic scattering during cold pulses was predominantly biological, dominated by 1.0-1.5 mm spheroid fluid-like scatterers, both in the waters above the cold pulse and in a strong-scattering feature at the cold-pulse interface. These aggregations of larger organisms at the cold-pulse interface did not appear to migrate downwards into the phytoplankton-rich water during the active passage of the cold pulse. Observations of similar temperature events throughout the tropical Pacific, combined with our multidisciplinary findings, suggest that pulsed deliveries of phytoplankton-rich water to nearshore habitats may be regular occurrences throughout the North Pacific Subtropical Gyre.

Sevadjian, J. C.; McManus, M. A.; Benoit-Bird, K. J.; Selph, K. E.

2012-12-01

100

Marine zooplankton studies in Brazil: a brief evaluation and perspectives  

Scientific Electronic Library Online (English)

Full Text Available SciELO Brazil | Language: English Abstract in portuguese 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 me [...] nos 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. Abstract in english 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 i [...] nitial 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.

Rubens M., Lopes.

 
 
 
 
101

Investigation of Vertical Migration of Pollutants through the Unsaturated Zone Using Stable Isotopes and Trace Elements  

International Nuclear Information System (INIS)

reased with depths in the studied soil profile. The accumulation pattern for these elements in the soil profiles follows the order: Co < Ni < Mo < Ag < Sr < V < Cu < Cr < Zn < Mn < B < Mg < Al < Fe. The relationships between element concentrations against ph and organic matter contents show antithetical relationships and suggest evidence that these elements arise from anthropogenic input. The results of this study show that there exists risk for the environment due to notable migration of pollutants through the unsaturated zone and that the migrations were also observed to be highly correlated with sandy soil as well as organic matter content rather than ph values

102

Mathematical model of 137Cs vertical migration in a forest soil  

International Nuclear Information System (INIS)

A detailed simulation model for prediction of the magnitude and direction of radionuclide migration in forest soils is described. The mathematical model has been constructed to simulate 137Cs dynamics in the soddy podzolic soils of a mixed forest system (predominantly oak with some birch and pine) in the 30-km zone around the Chernobyl Nuclear Power Plant (ChNPP). Field data gathered by the Radioecology Laboratory of Moscow State University were used both for parameterization of the model and also for validation. Some problems encountered in the mathematical modeling of 137Cs migration in these ecosystems are discussed. (Author)

103

Vertical Migration of Radionuclides in Soils on the Chernobyl Nuclear Power Plant (ChNPP) Exclusion Zone (1987-2007)  

Science.gov (United States)

In 1986-1987, a set of experimental sites for studies of vertical migration of radionuclides released from the ChNPP was established in the ChNPP Exclusion Zone for various fallout plumes. The sites were selected considering local terrain and geo-chemical conditions, as well as physical and chemical characteristics of the fallout. The experimental sites included grasslands, and pre-Chernobyl cultivated meadows and croplands. Vertical migration of radionuclides in the ChNPP Exclusion Zone grasslands was evaluated. Parameters of 137Cs, 90Sr, and 239,240Pu transfer were calculated and the periods during which these radionuclides reach their ecological half-life in the upper 5 cm soil layer were estimated. Migration capabilities of these radionuclides in the grassland soils tend to decrease as follows: 90Sr >137Cs ? 239,240Pu. A significant retardation of the 137Cs vertical migration was shown in the grasslands long after the Chernobyl accident. During the 21st year after the fallout, average Tecol values for 137Cs (the period of time it takes in the environment for 137Cs to reach half the value of its original concentration in the upper 5 cm soil layer, regardless of physical decay) are as follows: 180 - 320 years for grassland containing automorphous mineral soils of a light granulometric composition; and 90 - 100 years for grassland containing hydromorphous organogenic soils. These values are significantly higher than those estimated for the period of 6-9 years after the fallout: 60 - 150 years and 11 - 20 years, respectively. The absolute 137Cs Tecol values are by factors of 3-7 higher than 137Cs radiological decay values long after the accident. Changes in the exposure dose resulting from the soil deposited 137Cs only depend on its radiological decay. This factor should necessarily be considered for development of predictive assessments, including dose exposures for the hypothetical population in case of their re-evacuation to the exclusion areas. The obtained results have to be considered for predictive assessments, including those for dose exposures for the hypothetical population in case of their re-evacuation to the exclusion areas if implementation and/or planning of remediation activities at the ChNPP Exclusion Zone are considered reasonable and appropriate.

Jannik, G. T.; Ivanov, Y. A.; Kashparov, V. A.; Levchuk, S. E.; Bondarkov, M. D.; Maksymenko, A. M.; Farfan, E. B.; Marra, J. C.

2009-12-01

104

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.

105

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

106

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

107

Metabolic physiology of the Humboldt squid, Dosidicus gigas: Implications for vertical migration in a pronounced oxygen minimum zone  

Science.gov (United States)

The Humboldt (or jumbo) squid, Dosidicus gigas, is an active predator endemic to the Eastern Pacific that undergoes diel vertical migrations into a pronounced oxygen minimum layer (OML). Here, we investigate the physiological mechanisms that facilitate these migrations and assess the associated costs and benefits. Exposure to hypoxic conditions equivalent to those found in the OML (?10 ?M O 2 at 10 °C) led to a significant reduction in the squid’s routine metabolic rate (RMR), from 8.9 to 1.6 ?mol O 2 g -1 h -1 ( p RMR increased significantly with temperature ( p < 0.05), from 8.9 (at 10 °C) to 49.85 ?mol O 2 g -1 h -1 (at 25 °C) which yielded a Q10 of 2.0 between 10 and 20 °C and 7.9 between 20 and 25 °C ( p < 0.05). These results suggest that 25 °C, although within the normal surface temperature range in the Gulf of California, is outside this species’ normal temperature range. By following the scattering layer into oxygen-enriched shallow water at night, D. gigas may repay any oxygen debt accumulated during the daytime. The dive to deeper water may minimize exposure to stressful surface temperatures when most prey have migrated to depth during the daytime. The physiological and ecological strategies demonstrated here may have facilitated the recent range expansion of this species into northern waters where expanding hypoxic zones prohibit competing top predators.

Rosa, Rui; Seibel, Brad A.

2010-07-01

108

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

International Nuclear Information System (INIS)

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

109

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

110

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

111

Vertical and Horizontal Innovation : Effects of Globalization and Migration on Inequality, Growth and Human Capital Accumulation  

Digital Repository Infrastructure Vision for European Research (DRIVER)

In this paper I consider two symmetric countries/regions which trade in final goods. In each country is active the manufacturing sector and both vertical and horizontal innovation conduced by individuals with heterogenous ability. I show that a more globalized world, as represented by lower iceberg-type transportation cost, spurs human capital accumulation, and widens skill premium within each country. However, it may be the case that globalization reduces the per-capita output growth rate of...

Spinesi, Luca

2005-01-01

112

Periodic swarms of the salp Salpa aspera in the Slope Water off the NE United States: Biovolume, vertical migration, grazing, and vertical flux  

Science.gov (United States)

Sampling during four summers over a twenty-seven year period has documented dense populations of Salpa aspera in the Slope Water south of New England, northeastern United States. The salps demonstrated a strong pattern of diel vertical migration, moving to depth (mostly 600-800 m) during the day and aggregating in the epipelagic (feeding experiments indicated that both the aggregate and solitary stages filtered water at rates ranging from 0.5 to 6lh-1ml-1 biovolume. Maximum displacement volumes of salps measured were 5.7lm-2 in 1986 and 1.6lm-2 in 1993. Depending on the year, the sampled salp populations were calculated to clear between 8 and 74% of the upper 50 m during each 8 h night. Total fecal output for the same populations was estimated to be between 5 and 91mgCm-2night-1. These results, and other observations, suggest this region is a salp "hot spot", with swarms of S. aspera developing seasonally on a frequent basis.

Madin, L. P.; Kremer, P.; Wiebe, P. H.; Purcell, J. E.; Horgan, E. H.; Nemazie, D. A.

2006-05-01

113

Diel vertical migration of European hake Merluccius merluccius and associated temperature histories: insights from a pilot data-storage tagging (DST) experiment.  

Science.gov (United States)

A pioneering experiment of archival tagging of European hake Merluccius merluccius provided evidence of a diel vertical migration pattern which was analysed using an automatic method, developed and validated through time-frequency analyses. Frequent vertical movements across the thermocline were observed and fish experienced rapid temperature changes >7° C. These tagging-recapture data also suggested a homing behaviour to feeding grounds. PMID:22803732

De Pontual, H; Jolivet, A; Bertignac, M; Fablet, R

2012-07-01

114

Vertical migration of phototrophic bacterial populations in a hypersaline microbial mat from Salins-de-Giraud (Camargue, France).  

Science.gov (United States)

The spatio-temporal distribution of phototrophic communities of the hypersaline photosynthetic Camarguc microbial mat (Salins-de-Giraud, France) was investigated over a diel cycle by combining microscopic and molecular approaches. Microcoleus chthonoplastes and Halomicronema excentricum, the dominant cyanobacteria of this oxyphotrophic community, were observed with confocal laser scanning microscopy to determine their biomass profiles. Both bacteria have similar vertical distributions, varying from a homogenous distribution through the mat during the night, to a specific localization in the upper oxic zone of 1.5 mm during the day. Terminal restriction fragment length polymorphism of PCR-amplified pufM gene fragments revealed three groups of anoxyphototrophic populations, which varied according to the two opposite periods of the diel cycle under study. They were either specifically detected in only one period, or homogenously distributed through the mat in all periods, or located in specific zones of the mat depending on the period considered. Oxygen concentrations, pH and biomass of the major filamentous cyanobacteria were the determinative factors in the distribution of these anoxyphototrophs across the mat. Thus, vertical migration, cell-cell aggregate formation and metabolic switches were the most evident defence of the photosynthetic populations against the adverse effects of sulfide and oxygen fluxes during a diel cycle. PMID:16907751

Fourçans, Aude; Solé, Antoni; Diestra, Ella; Ranchou-Peyruse, Anthony; Esteve, Isabel; Caumette, Pierre; Duran, Robert

2006-09-01

115

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.

116

Seasonally dynamic diel vertical migrations of Mysis diluviana, coregonine fishes, and siscowet lake trout in the pelagia of western Lake Superior  

Science.gov (United States)

Diel vertical migrations are common among many aquatic species and are often associated with changing light levels. The underlying mechanisms are generally attributed to optimizing foraging efficiency or growth rates and avoiding predation risk (?). The objectives of this study were to (1) assess seasonal and interannual changes in vertical migration patterns of three trophic levels in the Lake Superior pelagic food web and (2) examine the mechanisms underlying the observed variability by using models of foraging, growth, and ?. Our results suggest that the opossum shrimp Mysis diluviana, kiyi Coregonus kiyi, and siscowet lake trout Salvelinus namaycush migrate concurrently during each season, but spring migrations are less extensive than summer and fall migrations. In comparison with M. diluviana, kiyis, and siscowets, the migrations by ciscoes C. artedi were not as deep in the water column during the day, regardless of season. Foraging potential and ? probably drive the movement patterns of M. diluviana, while our modeling results indicate that movements by kiyis and ciscoes are related to foraging opportunity and growth potential and receive a lesser influence from ?. The siscowet is an abundant apex predator in the pelagia of Lake Superior and probably undertakes vertical migrations in the water column to optimize foraging efficiency and growth. The concurrent vertical movement patterns of most species are likely to facilitate nutrient transport in this exceedingly oligotrophic ecosystem, and they demonstrate strong linkages between predators and prey. Fishery management strategies should use an ecosystem approach and should consider how altering the densities of long-lived top predators produces cascading effects on the nutrient cycling and energy flow in lower trophic levels.

Ahrenstorff, Tyler D.; Hrabik, Thomas R.; Stockwell, Jason D.; Yule, Daniel L.; Sass, Greg G.

2011-01-01

117

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

Science.gov (United States)

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

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

1996-06-01

118

Zooplankton intermittency and turbulence  

Science.gov (United States)

Planktonic organisms usually live in a turbulent world. Since marine turbulence is characterized by very high Reynolds numbers, it possesses very intermittent fluctuations which in turn affect marine life. We consider here such influence on zooplankton on 2 aspects. First we consider zooplankton motion in the lab. Many copepods display swimming abilities. More and more species have been recently recorded using normal or high speed cameras, and many trajectories have been extracted from these movies and are now available for analysis. These trajectories can be complex, stochastic, with random switching from low velocity to high velocity events and even jumps. These complex trajectories show that an adequate modeling is necessary to understand and characterize them. Here we review the results published in the literature on copepod trajectories. We discuss the random walk, Levy walk modeling and introduce also multifractal random walks. We discuss the way to discriminate between these different walks using experimental data. Stochastic simulations will be performed to illustrate the different families. Second, we consider zooplankton contact rates in the framework of intermittent turbulence. Intermittency may have influence on plankton contact rates. We consider the Particle Stokes number of copepods, in a intermediate dissipation range affected by intermittent fluctuations. We show that they may display preferential concentration effects, and we consider the influence on contact rates of this effect in the intermediate dissipation range.

Schmitt, François G.

2010-05-01

119

Biomass Atlas of Net Zooplankton in the Northeastern Pacific Ocean, 1956-1964.  

Science.gov (United States)

The collection of zooplankton samples in the northeast Pacific Ocean was carried out as during oceanographic and exploratory fishing surveys. Samples were collected from vertical hauls and horizontal tows with a NORPAC net; other samples were collected wi...

R. J. LeBrasseur

1965-01-01

120

Distribución vertical de la biomasa zooplanctónica y densidad ictioplanctónica durante un ciclo anual en la plataforma continental del sur del Golfo de México / Vertical distribution of zooplankton biomass and ichthyoplankton density during an annual cycle on the continental shelf of the southern Gulf of Mexico  

Scientific Electronic Library Online (English)

Full Text Available SciELO Chile | Language: Spanish Abstract in spanish Se analizó estacionalmente la biomasa zooplanctónica (BZ) y la densidad ictioplanctónica (DI) en la columna de agua sobre la plataforma continental del sur del Golfo de México, para determinar sus patrones de distribución vertical y establecer si existe una relación entre ambos componentes. Se muest [...] rearon cinco niveles de profundidad: 0-6 m, 6-12 m, 12-18 m, 45-55 m y 95-105 m. El patrón de distribución vertical de la BZ y de la DI fue similar en todas las épocas de muestreo, con la mayor concentración de organismos en los niveles superficiales y la más baja en los niveles más profundos. Estos resultados sugieren que la columna de agua en el área de estudio puede estar dividida en una capa superficial (0 a 18 m) y una capa profunda (45 a 100 m) y que las diferencias estacionales pueden ser atribuidas a los procesos de mezcla. Esta diferencia entre las capas superficiales y las profundas ocurre porque, en general, las capas superficiales de la columna de agua son las más productivas. La relación entre la BZ y la DI fue positiva y significativa (ANCOVA, P Abstract in english Seasonal zooplankton biomass (ZB) and ichthyoplankton density (ID) in the water column on the continental shelf of the southern Gulf of Mexico were analyzed to determine their vertical distribution patterns and assess if there is a relationship between both components. Five depth levels were sampled [...] : 0-6, 6-12, 12-18, 45-55 and 95-105 m. The vertical distribution patterns of ZB and ID were similar for all sampling seasons, with the greatest concentration of organisms in the upper levels and the lowest at deeper levels. These results suggest that the water column in the study area may be divided into a surface layer (0-18 m) and a deep layer (45-100 m), and seasonal differences may be attributed to mixing processes. The difference between the surface and the deep layers occurs because, in general, the upper layer is the most productive sector of the water column. The relationship between ZB and ID in the water column was positive and significant (ANCOVA, P

María de la Luz, Espinosa-Fuentes; César, Flores-Coto; Laura, Sanvicente-Añorve; Faustino, Zavala-García.

2009-08-01

 
 
 
 
121

Zooplankton of West Madagascar  

Science.gov (United States)

During six week survey (August - October 2009) in Western and Northern coast of Madagascar, the R/V 'Dr. Fridtjof Nansen' has carried out a study of the pelagic ecosystem. In collaboration with Agulhas & Somali Current Large Marine Ecosystems project (ASCLME) and South West Indian Ocean Fisheries Project (SWIOFP), the aim of the survey was to establish the physical, chemical and biological characteristics of the Western Madagascar shelf region as a whole. Zooplankton samples were collected with Hydrobios Multinet at all environmental stations ranging from 200 m depth to the surface. The Multinet was equipped with 5 nets for depth-stratified sampling. The nets were fitted with 180 µm mesh size and the water flow through the nets was measured. The Multinet was deployed and retrieved at a rate of ~ 1.5 m per second and was obliquely hauled. The five nets were triggered at the pre-selected depth intervals 0-25m, 25-50m, 50-80m, 80-120m and 120-200m. All samples were stored in marked bottles and preserved with buffered formaldehyde of 4% for further analysis. As results,the zooplankton abundance was influenced by physico-chemical factors. During the study period 34 Family of zooplankton were identified which are dominated by Copepoda (58,69%) followed by Radiolaria (12,06%), Appendicularia (6,47%), Sagitta (5,11%), Larvae (4,57%), Ostracoda (3,13%), pelagic Foraminifera (2,15%). Family of zooplankton with abundance <1% were also recorded, namely Salpidae (0,94%), Euphausiacea (0,44%), Tintinnidae (0,39%), Annélidae Polychètes (0,34%), Mysidacea (0,21%), Ptéropodae (0,13%). Highest number of zooplankton were found at the depth below the maximum of fluorescence during the day. Copepods distribution depends on site and depth. During this study, the number of identified species is always superior to 50 for all sampling sites. The findings of the present study will help to improve the scientific knowledge of the marine ecosystem of the west coast of Madagascar.

Bemiasa, John; Remanevy, Sitraka

2014-05-01

122

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

123

PAR and UV effects on vertical migration and photosynthesis in Euglena gracilis.  

Science.gov (United States)

Recently it was shown that the unicellular flagellate Euglena gracilis changes the sign of gravitaxis from negative to positive upon excessive radiation. This sign change persists in a cell culture for hours even if subsequently transferred to dim light. To test the ecological relevance of this behavior, a vertical column experiment was performed (max. depth 65 cm) to test distribution, photosynthetic efficiency and motility in different horizons of the column (surface, 20, 40 and 65 cm). One column was covered with a UV cut-off filter, which transmits photosynthetically active radiation (PAR) only, the other with a filter which transmits PAR and UV. The columns were irradiated with a solar simulator (PAR 162 W m(-2), UV-A 32.6 W m(-2), UV-B 1.9 W m(-2)). The experiment was conducted for 10 days, normally with a light/dim light cycle of 12 h:12 h, but in some cases the light regime was changed (dim light instead of full radiation). Under irradiation the largest fraction of cells was found at the bottom of the column. The cell density decreased toward the surface. Photosynthetic efficiency, determined with a pulse amplitude modulated fluorometer, was negligible at the surface and increased toward the bottom. While the cell suspension showed a positive gravitaxis at the bottom, the cells in the 40 cm horizon were bimodally oriented (about the same percentage of cells swimming upward and downward, respectively). At 20 cm and at the surface the cells showed negative gravitaxis. Positive gravitaxis was more pronounced in the UV + PAR samples. At the surface and in the 20 and 40 cm horizons photosynthetic efficiency was better in the PAR-only samples than in the PAR + UV samples. At the bottom photosynthetic efficiency was similar in both light treatments. The data suggest that high light reverses gravitaxis of the cells, so that they move downward in the water column. At the bottom the light intensity is lower (attenuation of the water column and self shading of the cells) and the cells recover. After recovery the cells swim upward again until the negative gravitaxis is reversed again. PMID:17645652

Richter, Peter; Helbling, Walter; Streb, Christine; Häder, Donat-P

2007-01-01

124

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

125

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  

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Full Text Available 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 after 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 locationINTRODUÇÃO: 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 natural 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

Paul Kaufmann

2011-09-01

126

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

127

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

128

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.

129

Vertical movements of Atlantic salmon postsmolts relative to measures of salinity and water temperature during the first phase of the marine migration  

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The migratory behaviour of hatchery-reared Atlantic salmon, Salmo salar L., post-smolts during the first phase of the marine migration was examined to assess their susceptibility to salmon lice, Lepeophtheirus salmonis (Krøyer), infestations. Swimming depths of eight post-smolts relative to the measured salinity and temperature were monitored for an average of 11.4 h following release outside the mouth of the River Eio using depth sensitive acoustic transmitters. Vertical salinity and temper...

Davidsen, Jan Grimsrud; Plantalech Manel-la, Nuria; Thorstad, E. B.; Økland, F.; Sivertsga?rd, Rolf; Mckinley, R. S.; Finstad, B.

2009-01-01

130

Effects of nitrate on the diurnal vertical migration, carbon to nitrogen ratio, and the photosynthetic capacity of the dinoflagellate Gymnodinium splendens  

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A non-thecate dinoflagellate, Gymnodinium splendens, was studied in a 12 d laboratory experiment in 2.0 x 0.25 m containers in which light, temperature, and nutrients could be manipulated. Under a 12 h light:12 h dark cycle, the dinoflagellates exhibited diurnal vertical migrations, swimming downward before the dark period began and upward before the end of the dark period. This vertical migration probably involved geotaxis and a diel rhythm, as well as light-mediated behavior. The vertical distribution of nitrate affected the behavior and physiology of the dinoflagellate. When nitrate was present throughout the container, the organisms resembled those in exponential batch culture both in C:N ratios and photosynthetic capacity (P/sub max/); moreover, they migrated to the surface during the day. In contrast, when nitrate was depleted, C:N ratios increased, P/sub max/ decreased, and the organisms formed a subsurface layer at a depth corresponding to the light level at which photosynthesis saturated. When nitrate was present only at the bottom of the tank, C:N ratios of the population decreased until similar to those of nutrient-saturated cells and P/sub max/ increased; however, the dinoflagellates behaved the same as nutient-depleted cells, forming a subsurface layer during the light period. Field measurements revealed a migratory subsurface chlorophyll maximum layer dominated by G. splendens. It was just above the nitracline during the day, and in the nitracline during the night, which concurs with our laboratory observations.

Cullen, J.J.; Horrigan, S.G.

1981-01-01

131

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

International Nuclear Information System (INIS)

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

132

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

Science.gov (United States)

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

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

2005-01-01

133

Sobre a migração vertical diária do plâncton ao largo de Santos, Estado de São Paulo, Brasil On the diurnal vertical migration of plankton off the coast of Santos, São Paulo State, Brazil  

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Full Text Available Várias estações foram ocupadas ao largo de Santos, durante os anos de 1960, 1961 e 1962, com a finalidade do estudo da migração vertical diária do plâncton, assim como sua relação com os parâmetros temperatura, salinidade e massas de água. Os quadros gerais do movimento vertical variaram nas diferentes datas. Demonstrou-se que a luz nem sempre pôde ser considerada como o principal fator envolvido na migração. A termoclina atuou como um fator limitando o movimento em apenas uma, das cinco estações onde esteve presente. Em estações onde ocorreram massas de água de diferentes limites de salinidade, a migração dos zooplanctontes ocorreu em geral acima ou abaixo da região de encontro dessas massas de água, independente da presença ou não de termoclina. Concluiu-se que, na região onde os estudos foram feitos, a migração diária do plâncton se apresenta bastante diversificada e não pode ser diretamente relacionada a diferentes épocas do ano ou condições oceanográficas predominantes na região. Este fato deve ser levado em conta em futuros estudos de distribuição e ecologia na região, assim como, nos resultados obtidos nos estudos de indicadores planctônicos.Several stations were occupied off the coast of Santos, with the purpose of studying the diurnal vertical migration of plankton. The results showed that in the region, the patterns of migration of net plankton are quite diversified and they cannot be related to differ ent seasons or oceanographie parameters.

Gloria Soares Moreira

1976-01-01

134

Diel vertical migration and feeding in adult female Calanus pacificus, Metridia lucens and Pseudocalanus newmani during a spring bloom in Dabob Bay, a fjord in Washington USA  

Science.gov (United States)

Diel vertical migration and feeding on phytoplankton by adult female Calanus pacificus, Metridia lucens and Pseudocalanus newmani were simultaneously measured near the end of a phytoplankton bloom. Almost the entire Calanus population migrated out of the deep layer (108-50 m) at night but only about 30% came to the surface (25-0 m). Feeding occurred only at night and was equally high in the surface and intermediate layers, in spite of much higher food concentrations in the surface. Like Calanus, the entire Metridia population was found in the deep layer during the day but unlike Calanus, 20-50% remained in the deep layer at night and most migratory Metridia were collected from the surface layer. Metridia feeding at night was highest in the surface layer but significant feeding also occurred in both the intermediate and deep layers. Migratory behavior of Pseudocalanus was weak, with the proportion of the population in the surface layer increasing from slightly Feeding occurred in both surface and intermediate layers throughout the 24 h but was greater in both layers at night. The different migratory patterns are discussed in the context of our current understanding of the contributions of predator avoidance and feeding to diel vertical migration.

Dagg, M. J.; Frost, B. W.; Newton, J.

1998-06-01

135

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

136

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

Scientific Electronic Library Online (English)

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

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

2004-05-01

137

Distribution and abundance of zooplankton populations in Crater Lake, Oregon  

Science.gov (United States)

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

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

2007-01-01

138

Investigation of vertical migration of 54Mn, 58Co, 63Ni, and 55Fe in the soil-water-plants system  

International Nuclear Information System (INIS)

The work studied the vertical migration of radionuclides 54Mn, 55Fe, 58Co, and 63Ni in coriander, fennel, and onion, which are widely used in food of Tajikistan's population. The results showed that these radionuclides accumulate only in these plants' roots. It is connected with formation of complex forms of isotopes of 54Mn, 55Fe, 58Co, and 63Ni with organic part of soil. A size of such a complex considerably increases a capillary of the plant, which makes impossible its proliferation into stalks and other parts of a plant by the way of self-diffusion. (author)

139

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

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

Neda Fazeli

2013-12-01

140

Distribution and vertical dynamics of planktonic communities at Sofala Bank, Mozambique  

Science.gov (United States)

Coastal ecosystem processes are largely influenced by the interaction of different factors operating at various temporal and spatial scales, specifically those responsible for primary production patterns that modulate zooplankton and subsequent trophic levels. Hydrological processes, such as tidal cycles and coastal currents, nutrients availability, phytoplankton groups (studied through algal pigment signatures analysed by HPLC), and zooplankton abundance and distribution were investigated at the Sofala Bank (Mozambique), with special emphasis on their horizontal distribution and vertical dynamics (48 h). Horizontal distribution has shown inshore-offshore gradients in all analysed parameters, as well as inshore waters intrusion probably related to Zambezi River delta runoff. Tidal currents were responsible for major hydrological vertical variations and for horizontal and vertical advection of phytoplankton biomass in the surface and deepest layers, respectively. Nutrient concentrations were typical from oligotrophic regions, and nutrient ratios were strongly influenced by depleted nitrate + nitrite concentrations, indicating low estuarine discharges typical from the dry season. The very low N:P ratio obtained suggests strong nitrogen limitation to phytoplankton communities, supporting the low phytoplankton abundance observed. Both phytoplankton pigments and zooplankton were found mainly near the bottom (40 m depth), despite the latter displayed vertical migrations triggered by light variations. Phytoplankton community was dominated by microflagellates, specifically prymnesiophyceans, and behaved as a whole, except Cyanobacteria that displayed vertical distribution movements different from other phytoplankton groups, being mainly concentrated at mid-water column depths (10-20 m). This investigation enhances physico-chemical phenomena and their importance determining the planktonic communities vertical dynamics at Sofala Bank, a tropical coastal ecosystem of the Western Indian Ocean where planktonic dynamics are still poorly described and understood.

Leal, M. C.; Sá, C.; Nordez, S.; Brotas, V.; Paula, J.

2009-10-01

 
 
 
 
141

Melatonin signaling controls circadian swimming behavior in marine zooplankton.  

Science.gov (United States)

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

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

2014-09-25

142

Vertical migration of leachate pollutants in clayey soils beneath an uncontrolled landfill at Huainan, China: a field and theoretical investigation.  

Science.gov (United States)

To assess the extent of leachate migration, continuous samples of clayey soils (about 9m) were obtained beneath a 17-year old uncontrolled landfill in southeastern China. The soil samples were sub sectioned and analyzed to determine the concentrations of chloride, sodium and COD in the pore water. Total nitrogen and soil organic matter content of the soil samples were also determined. Leachate-derived chloride was detected in the clayey soil to a maximum depth of 9m. Sodium and COD were found to migrate into the soils to depths of 3-4m due to the attenuation of solutes by the soil organic matter and clay minerals at the shallow soils. The estimated migration depths for the chloride are 3m in the case of pure diffusion. Advection and mechanical dispersion were found to be more important than molecular diffusion for this site with an 8m high leachate mound. By comparing the results obtained by the mathematical modeling for layered advection-dispersion problem with the measured concentration profiles, the ranges of the effective diffusion coefficient, retardation factor and dispersivity of the soils were estimated. Better fits are obtained by employing an artificial effective interface about 1m above the observed interface. The clayey soils showed a relatively high attenuation capacity for COD with the estimated retardation factor of 5. PMID:24144934

Zhan, T L T; Guan, C; Xie, H J; Chen, Y M

2014-02-01

143

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

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

Rubén Escribano

2006-10-01

144

Zooplankton and forage fish species off Peru: Large-scale bottom-up forcing and local-scale depletion  

Science.gov (United States)

The Humboldt Current System, like all upwelling systems, has dramatic quantities of plankton-feeding fish, which suggested that their population dynamics may ‘drive’ or ‘control’ ecosystem dynamics. With this in mind we analysed the relationship between forage fish populations and their main prey, zooplankton populations. Our study combined a zooplankton sampling program (1961-2005) with simultaneous acoustic observations on fish from 40 pelagic surveys (1983-2005) conducted by the Peruvian Marine Research Institute (IMARPE) and landing statistics for anchoveta ( Engraulis ringens) and sardine ( Sardinops sagax) along the Peruvian coast from 1961 to 2005. The multi-year trend of anchoveta population abundance varied consistently with zooplankton biovolume trend, suggesting bottom-up control on anchovy at the population scale (since oceanographic conditions and phytoplankton production support the changes in zooplankton abundance). For a finer-scale analysis (km) we statistically modelled zooplankton biovolume as a function of geographical (latitude and distance from the 200-m isobath), environmental (sea surface temperature), temporal (year, month and time-of-day) and biological (acoustic anchovy and sardine biomass within 5 km of each zooplankton sample) covariates over all survey using both classification and regression trees (CART) and generalized additive models (GAM). CART showed local anchoveta density to have the strongest effect on zooplankton biovolume, with significantly reduced levels of biovolume for higher neighbourhood anchoveta biomass. Additionally, zooplankton biovolume was higher offshore than on the shelf. GAM results corroborated the CART findings, also showing a clear diel effect on zooplankton biovolume, probably due to diel migration or daytime net avoidance. Apparently, the observed multi-year population scale bottom-up control is not inconsistent with local depletion of zooplankton when anchoveta are locally abundant, since the latter effect was observed over a wide range of overall anchoveta abundance.

Ayón, Patricia; Swartzman, Gordon; Bertrand, Arnaud; Gutiérrez, Mariano; Bertrand, Sophie

2008-10-01

145

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

146

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

DEFF Research Database (Denmark)

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

Huwer, Bastian

2010-01-01

147

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

148

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

149

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

Energy Technology Data Exchange (ETDEWEB)

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

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

2008-12-15

150

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.

151

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

Science.gov (United States)

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 (100kDa-0.2?m) and small (3-30kDa) organic colloids whilst at Eskmeals, U was mainly in the small colloidal and truly dissolved fractions. Especially below 10cm 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(IV) reduction resulted in the release of both Mn(II) and U(VI) into the truly dissolved phase. PMID:21345483

Graham, Margaret C; Oliver, Ian W; MacKenzie, Angus B; Ellam, Robert M; Farmer, John G

2011-04-15

152

Downward carbon transport by diel vertical migration of the copepods Metridia pacifica and Metridia okhotensis in the Oyashio region of the western subarctic Pacific Ocean  

Science.gov (United States)

Seasonal change in the downward carbon transport due to respiration and mortality through diel vertical migration (DVM) of the calanoid copepods Metridia pacifica and Metridia okhotensis was estimated in the Oyashio region, western subarctic Pacific during six cruises from June 2001 to June 2002. M. pacifica (C4, C5 and adult females) was an active migratory species throughout the year though its DVM amplitude varied among seasons and stages. The mean distribution depths of adult females during the daytime were positively related with the illumination level in the water column, being shallowest in April and deepest in January. M. okhotensis generally showed less-extensive migrations than M. pacifica. Therefore, together with their lower abundance, this species is considered to be a less-important mechanism of downward transport of carbon except for April when their DVM was more active and descended deeper than M. pacifica, which remained in the upper 150 m even during the daytime. The mean migrating biomass of the two Metridia species was 558 mg C m -2 d -1 and was high during summer to winter (263-1676 mg C m -2 d -1) and low during spring (59-63 mg C m -2 d -1). Total downward flux through DVM fluctuated between 1.0 and 20.0 mg C m -2 d -1 with an annual mean of 8.0 mg C m -2 d -1. Contribution of the respiratory flux was greater than the mortality flux and accounted for 64-98% of total migratory flux throughout the year except for January when contribution of both fluxes was equal. Overall the annual carbon transport by DVM of Metridia spp. was estimated as 3.0 g C m -2 year -1, corresponding to 15% of the annual total POC flux at 150 m at the study site, suggesting that DVM is a significant process for carbon export in the subarctic region as well as that in tropical and subtropical oceanic regions. Since DVM in M. pacifica is more active during the non-bloom season when the gravitational flux of particulate matter is low, this species plays an important role in driving the biological pump in the subarctic Pacific during summer to winter.

Takahashi, Kazutaka; Kuwata, Akira; Sugisaki, Hiroya; Uchikawa, Kazuhisa; Saito, Hiroaki

2009-10-01

153

Estimates of zooplankton abundance and size distribution with the Optical Plankton Counter (OPC)  

DEFF Research Database (Denmark)

The capability of the Optical Plankton Count er (OPC) to examine the abundance and size distribution of zooplankton was tested in Storfjorden, Norway, in June 1993. Selected material obtained from net sampling was measured with a laboratory version of the OPC and compared with microscope analysis in order to identify main species in the in situ size frequency distributions obtained by the submersible version of the OPC. Differences in the particle concentration between shallow and deep water layers were clearly resolved by the submersible OPC, but the high diversity of the zooplankton community and widely overlapping size ranges prevented a detailed analysis of the fine scale vertical distribution and the horizontal variability of abundance for distinct species. These results are used to discuss the limitations of the OPC for rapid and continuous surveying of spatial distribution and abundance of zooplankton

Wieland, Kai

1997-01-01

154

A Comparison of Zooplankton Assemblages in a Coastal Upwelling and Offshore Station in East Sulu Sea  

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Full Text Available Partially enclosed marine basins often display characteristic pelagic faunal compositions reflecting their distinctive hydrographic conditions. Seasonal upwelling along the northern coast of the Zamboanga Peninsula in East Sulu Sea results to the high fisheries production in the area likely by enhancing local plankton abundance. Zooplankton in this area were investigated during the Joint PhilEx oceanographic cruise on board the R/V Melville in December 2007. Data on the abundance and vertical distribution of major groups of zooplankton were analyzed and compared between two sets of MOCNESS samples collected from a coastal upwelling station and the other from an offshore station. Eighty four (84 zooplankton taxa belonging to 20 major groups were identified in the coastal station, while ninety five (95 taxa under 28 major groups were found in the offshore station. The total zooplankton density was much higher in the coastal station (98.9 ind./m3 than in the offshore station (47.5 ind./m3. Copepods dominated in both stations, comprising up to 70% of the total zooplankton. No distinct variation in the abundance, composition and distribution of zooplankton with depth was observed except in 150 – 200 m depth stratum in the coastal station wherein a dramatic increase in the abundance of copepods, ostracods and chaetognaths was noted. In the offshore station, the crustaceans also showed a drastic increase in abundance in the 50 – 100 m depths. These appear to be related to the thermocline in both stations, where typically higher upper layer primary productivity can support dense communities of zooplankton.

Cristy S Acabado

2010-12-01

155

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

156

Fish-mediated trait compensation in zooplankton  

DEFF Research Database (Denmark)

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

Hylander, Samuel

2012-01-01

157

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

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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

158

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

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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

159

Day-Night Vertical Distribution and Feeding Patterns of Fourth Instar ofChaoborus Larvae in a Neotropical Reservoir (Socuy Reservoir, Venezuela)  

Science.gov (United States)

The day-night vertical distribution, diel feeding activity and diet of fourth instar of Chaoborus larvae were analyzed in lacustrine zone of a neotropical reservoir which shows seasonally contrasting hypolimnetic oxygen conditions. Larvae stayed in sediment and water bottom during day and ascended to surface during night. Results indicate that feeding activity is limited mainly to the plankton population. Phytoplankton, rotifers or remains of Chaoborus larvae were not found in crops. With the exception of ostracods, all crustacean prey available in the zooplankton occurred in the guts. Ceriodaphnia cornuta and Moina micrura were the most frequent food items (about 75% of occurrence frequency) and were positively selected. The remainder crustacean zooplankton taxa were negatively selected by larvae. The most intense feeding activity in larvae occurred near midnight and sunrise, in dates when the hypolimnion was anoxic. When oxygen was available on the bottom, a higher and not changing diel feeding activity was detected. Our results indicate that vertical migration may promote a spatial separation between larvae and zooplankton, and feeding activity of larvae occurred only when both overlapped.

López, Carlos; Zoppi de Roa, Evelyn

2005-05-01

160

Horizontal migration of Acartia pacifica Steuer (copepoda) in response to UV-radiation.  

Science.gov (United States)

It is known that zooplankton migrate vertically to avoid UV-radiation (UVR, 280-400nm), but little is known if such avoidance happens horizontally. Here, we showed that the copepod Acartia pacifica avoided UV irradiated fields horizontally. Exposure of A. pacifica to PAR or PAR+UV-A for 30min did not make any difference in the horizontal distribution of the individuals. However, addition of UV-B radiation, that is PAR+UV-A+B, resulted in uneven distributions among the treatments, with significant less individuals compared to the PAR or PAR+UV-A treatments. More carotenoids and UV-absorbing compounds were found in the A. pacifica individuals that chose to stay under the radiation treatments with UV. It is concluded that A. pacifica can migrate horizontally to avoid UV-related harms and those contains more protective compounds were less sensitive to UVR. PMID:20696590

Ma, Z; Zengling, M A; Li, W; Wei, L I; Gao, K; Kunshan, G A O

2010-12-01

 
 
 
 
161

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.

162

FUNCTIONAL BIOASSAYS UTILIZING ZOOPLANKTON: A COMPARISON  

Science.gov (United States)

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

163

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

164

Kinds and Abundance of Zooplankton Collected by the USCG Icebreaker Glacier in the Eastern Chukchi Sea, September-October 1970.  

Science.gov (United States)

Zooplankton samples were taken at 39 oceanographic stations in the eastern Chukchi Sea in September and October 1970. Sampling was done by vertical tows from near bottom to the surface with a 0.5-m diameter No. 0(0.57mm) mesh NorPac standard plankton net....

B. L. Wing

1974-01-01

165

Zooplankton biomass, advection and production on the northern Gulf of Alaska shelf from simulations and field observations  

Science.gov (United States)

Interpretation of zooplankton field observations on the Gulf of Alaska (GOA) shelf is complicated by the complex physical environment of currents, eddies and meanders which mix oceanic and coastal water masses to varying degrees. We therefore developed a lower trophic level model embedded in an ocean circulation model to examine the effects of wind, runoff and temperature on transport, biomass and production of microzooplankton and copepods on the northern GOA shelf and adjacent ocean. Mean microzooplankton biomass varied from 10-90 and 10-50 mg C m- 3 in the upper 50 m for field measurements and simulations respectively. Mean simulated and measured copepod biomass in the upper 100 m was about 1-40 g C m- 3. Field data indicated that Neocalanus biomass was negatively correlated with salinity in May. Simulations indicated that the negative correlation was due to elevated primary and secondary production on the shelf relative to the adjacent ocean. Floats programmed to simulate the ontogenetic vertical migrations of Neocalanus indicated that ~ 10 to 50% of Neocalanus originating near the shelf break spend at least some time on the shelf, depending on location. Residence time of floats on the shelf was affected primarily by wind, secondarily by runoff. Primary and secondary production in the simulations were highly correlated (r > 0.9). Simulated secondary production was 10-90 g C m- 2 y- 1, with highest values in Lower Cook Inlet, around Kodiak and west of Kodiak.

Coyle, K. O.; Gibson, G. A.; Hedstrom, K.; Hermann, A. J.; Hopcroft, R. R.

2013-12-01

166

Zooplankton Community Composition in Nearshore Waters of Southern Lake Michigan.  

Science.gov (United States)

Zooplankton samples collected in 1977 in the nearshore waters of southern Lake Michigan (0.4 km from shore) were analyzed to provide a bench mark on zooplankton community composition for comparison with future studies. Species composition, abundance, and ...

J. E. Gannon, F. J. Bricker, K. S. Bricker

1983-01-01

167

Zooplankton communities in the Krenceng Reservoair, Cilegon, Banten  

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Full Text Available This research was carried out to know the structure of zooplankton communities and relations between the phytoplankton and zooplankton in the Krenceng Reservoair, Cilegon. The zooplankton abundance with used Sedwigck Rafter Counting Method, diversity and evenness were counted. Relations between zooplankton and the environmental factors as well as its relations to phytoplankton calculated with regression. The results showed that are 13 species of the zooplankton found which including in three classes with the highest abundance on Novembers 2002 and March 2003 of the Rotifera. The analysis of regression pointed out that the environmental factors such: pH, BOD5, nitrate, CO2 and abundance of phytoplankton influence the abundance zooplankton in November. While in March, the abundance of zooplankton is influenced by brigthtness, nitrate, orthophosphates and C organic. The abundance of phytoplankton influenced positively by the abundance of zooplankton.

Mufti P. Patria

2005-11-01

168

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...

169

Elemental concentration of zooplankton and their particulate products  

International Nuclear Information System (INIS)

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

170

Vertical habitat partitioning by large calanoid copepods in the oceanic subarctic Pacific during Spring  

Science.gov (United States)

The copepods Neocalanus plumchrus, N. flemingeri, N. cristatus, and Eucalanus bungii dominate the net zooplankton throughout the subarctic Pacific Ocean. All four species have an extensive seasonal ontogenetic vertical migration, completing most or all of their feeding and somatic growth in spring and early summer. We used stratified tows with MOCNESS and BIONESS instrumented net systems to resolve their upper ocean vertical distributions in May and June of 1984, 1987 and 1988. In each year the feeding copepodite stages of all four species were concentrated above the permanent halocline (roughly from 0 to 150m). However, the four species showed strong vertical species zonation and segregation within this layer. We consistently found a near-surface pair ( N. plumchrus and N. flemingeri) and a subsurface pair ( N. cristatus and E. bungii). The boundary between these groups shifts vertically, but was sharply defined and was very often coincident with a weak and transient thermocline marking the base of the layer actively mixed by surface wind and wave energy. Diel vertical migration was very limited during our sampling periods. The data suggest that the vertical distribution patterns of the copepods could be set by responses to the local intensity of turbulent mixing in the watercolumn. N. plumchrus and N. flemingeri occupied a stratum characterized by strong turbulence. N. cristatus and E. bungii occupied a stratum that was a local minimum in turbulence profiles. The depth of the boundary between the species pairs was deeper when winds and surface energy inputs were strong. The vertical partition pattern may also be determined by a difference in feeding strategy between the species pairs. N. plumchrus and N. flemingeri may feed on the enhanced protozoan population of the mixed layer, while N. cristatus and E. bungii feed on particle aggregates settling from above.

Mackas, David L.; Sefton, Hugh; Miller, Charles B.; Raich, Anne

171

A Review: Potentiality of Zooplankton as Bioindicator  

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

Zannatul Ferdous

2009-01-01

172

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.

173

Zooplankton van het Veerse Meer in 1987 (Zooplankton of the Veerse Lake in 1987),  

Science.gov (United States)

Fourteen zooplankton groups were found in Lake Veere. In 1987 6 groups dominated in numbers as well as in biomass: Rotifera, Polychaeta (larvae of Polydora spp.), Copepoda, Cirripedia (larvae of Balanus spp.), Bivalvia (larvae) and Gastropoda (larvae). Sm...

N. J. P. Revis, C. Bakker

1988-01-01

174

ZOOPLANKTON OCCURANCE DURING MONSOON SEASON FROM EKRUK TANK, SOLAPUR  

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

M. R. Gurav , K. R. Rao

2014-06-01

175

SENSITIVITY OF ZOOPLANKTON INDICATORS IN REGIONAL MONITORING  

Science.gov (United States)

This study describes an approach for assessing and selecting ecological indicators for regional monitoring of northeastern US lakes. We analyze the components of variance for indicators of zooplankton richness and abundance in the context of the spatial and temporal sampling des...

176

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

International Nuclear Information System (INIS)

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

177

Zooplankton assemblage of Oyun Reservoir, Offa, Nigeria  

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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

178

Acoustic scattering from zooplankton and micronekton in relation to a whale feeding site near Georges Bank and Cape Cod  

Science.gov (United States)

This research was part of the South Channel Ocean Productivity Experiment (SCOPEX), a multidisciplinary study to investigate the biological and physical processes associated with the very high annual springtime abundance of right whales ( Eubalaena glacialis) in the Great South Channel off New England. Right whales appear to gather there in the spring because of the increased abundance of aggregations of their principal prey, the copepod Calanus finmarchicus. Observations of hydroacoustic scattering were made in relation to the hydrography, whale distributions, and other biological measurements in the vicinity of the Great South Channel during May 1986, March, April and May of 1988, and May and June of 1989. Copepods were detected (at 200 kHz) as a near-surface layer with strong diel changes. In 1989, a second frequency (120 kHz) was used to discriminate between copepod layers (which the 120 kHz detected only weakly) and other targets (which both frequencies detected). Acoustically distinct layers of zooplankton and micronekton were observed, which were often correlated in time and space with the copepod layers. Quantitative estimates derived from the acoustic data indicate that the abundance of zooplankton varied from 1-5 g wet weight m -3 to 18-25 g wet weight m -3 which correlates well with the abundances observed from MOCNESS tows. The acoustic data revealed a complex diel migration of two layers in addition to the copepods. Euphausiids (predominantly Meganyctiphanes sp.) were found in a layer above the bottom, and a mid-water layer may have been due to sand lance ( Ammodytes americanus). The observed biological phenomena appeared to be related to the complex hydrography of the region. A surface thermal front existed at the northern entrance to the channel in 1988 and 1989, with colder vertically mixed water to the south and warmer stratified water to the north. A Fast Fourier Transform analysis for spectral composition and autocovariance shows (a) strong contrasts in the spectral density across one frontal feature (predominantly a salinity front) as opposed to away from the front, and (b) significant differences between those areas where a whale moved more rapidly (presumably searching for food) and where it spent more time (presumably or observably feeding). The behavior of whales, in particular the right whale, can be shown to be related to the spatial scales and abundance of their prey by the use of hydroacoustic estimates of target distribution and abundance.

MacAulay, Michael C.; Wishner, Karen F.; Daly, Kendra L.

179

Power-plant-related estuarine zooplankton studies  

International Nuclear Information System (INIS)

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

180

Distribution and diversity of Zooplanktons in Madhya Pradesh, India  

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

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

2013-03-01

 
 
 
 
181

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

182

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

Science.gov (United States)

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

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

2012-05-01

183

Abundance, Species Composition and Spatial Distribution of Zooplankton in Lake Hashengie of Tigray, Northern Ethiopia  

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Full Text Available Zooplanktons are an important link between phytoplankton primary production and consumers at the higher levels of the trophic cascade (i.e., secondary consumers. Furthermore, they may impact the pathways of energy flow and matter circulation in freshwater ecosystems. To this end this research was conducted to investigate the abundance and spatial distribution, production of Zooplankton in Lake Hashegie. Species composition, abundance and spatial distribution of crustacean zooplankton were studied in Lake Hashengie from late September 2010 to early June 2011. A total of 15 species were recorded, with copepod specie being numerically dominant. Variation in abundance was extremely high, ranging from 8 individuals liter for cladoceran to more than 1000 individuals liter for copepods. There was no significant difference in the distribution of rotifer species between inshore and offshore regions (t-test, n = 12 p = 0.25. Crustacean species richness was low, with only five cladoceran and three copepod species occurring in the open water. Daphnia magna and Daphnia galeata dominated the cladoceran community, whereas thermocyclops was the dominant copepod. Variation in the spatial distribution of crustacean species was neither observed horizontally between inshore and offshore areas nor vertically in the highly turbid and wind exposed to deeper part of the lake. On the other hand crustacean varied significantly in size and number between inshore and offshore areas (Anova test, n = 231, p<0.002. Adult crustaceans dominated offshore, whereas juveniles were more abundant inshore, suggesting a predominantly littoral selective predation on large and adult crustaceans by fish.

Tsegazeabe H. Haileselasie

2012-07-01

184

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

185

Size-structured risk assessments govern Daphnia migration.  

Science.gov (United States)

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 individuals, which we show are less vulnerable to predation than larger, make a risk assessment and continue feeding in surface waters during day, offering a competitive release from down-migrating larger animals. Hence, we mechanistically show that such simple organisms as invertebrate zooplankton are able to make individual, size-specific decisions regarding how to compromise between threats from both predators and UV radiation, and adjust their diel migratory patterns accordingly. PMID:18812291

Hansson, Lars-Anders; Hylander, Samuel

2009-01-22

186

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

Directory of Open Access Journals (Sweden)

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

187

Selective uptake of 55Fe from seawater by zooplankton  

International Nuclear Information System (INIS)

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

188

COMPARISONS OF ZOOPLANKTON COMMUNITY SIZE STRUCTURE IN THE GREAT LAKES  

Science.gov (United States)

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

189

Zooplankton assemblage of Oyun Reservoir, Offa, Nigeria  

Scientific Electronic Library Online (English)

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

Moshood K, Mustapha.

190

Studies on zooplankton of Lago Paione Superiore  

Directory of Open Access Journals (Sweden)

Full Text Available We report here the results of a three year study on the zooplankton of Lago Paione Superiore, an acid sensitive lake above the tree line in the Italian Alps. The research was carried out within MOLAR, an EC-founded Project on “Measuring and Modeling the dynamic response of remote mountain lakes ecosystems to environmental change”. This study comes after a series of investigations on the effects of acidification, in which we documented the changes occurred with decreasing water pHs, by comparing the recent situation with that in the literature of the 40s, and reconstructed the beginning of anthropogenic disturbance through an analysis of the past cladocera assemblages archived in the lake sediments. A characteristic pattern in seasonal periodicity is a transition from a community dominated by small zooplankton (August to a community where the large particle-feeder Daphnia longispina dominates. This is a typical pattern observed in fishless, copepod-cladocera lakes. Regardless from which food is able to exploit, Daphnia population of Lago Paione Superiore is composed by well-fed organisms, visually rich in lipids, able to produce more than one generation/ year of parthenogenetic females at density levels which are rather high in an oligotrophic high mountain lake.

Patrizia COMOLI

1999-08-01

191

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

192

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

193

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 were sampled with vertical WP-II hauls (200 ?m mesh-size and large mesozooplankton, macrozooplankton and micronekton with a BIONESS multinet sampler (500 ?m 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 intense, was associated with changes in zooplankton community composition. Among copepods, the abundance of Calocalanus, Euchaeta, Heterorhabdus, Mesocalanus, Nannocalanus, Neocalanus, Pleuromammaand 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. The Shannon diversity index, Pielou evenness and species richness were used to describe temporal variations of large copepod (>500 ?m diversity. The 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 a replacement of the zooplankton population.

V. Raybaud

2008-12-01

194

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

Directory of Open Access Journals (Sweden)

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

V. Raybaud

2008-05-01

195

Zooplankton use of chemodetection to find and eat particles  

DEFF Research Database (Denmark)

The ability of raptorial zooplankton to find large particles such as marine aggregates is crucial to their use of the particles as food and to the fate of the particles. Kiorboe & Thygesen (2001) developed a numerical approach to describe particle detection by chemosensory zooplankton. In this paper, we develop and test a simplified mathematical description of the process and explore the ecological implications of chemosensory particle detection. Our results suggest that chemosensory particle detection can be more efficient than hydrodynamic detection. The exact extent depends greatly on the sensitivity of chemodetection in zooplankton, a process that has not been well studied experimentally.

Jackson, G.A.; KiØrboe, Thomas

2004-01-01

196

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

197

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

198

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

Science.gov (United States)

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

199

GUIDELINES FOR ZOOPLANKTON SAMPLING IN QUANTITATIVE BASELINE AND MONITORING PROGRAMS  

Science.gov (United States)

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

200

Procedures involved in radioecological studies with marine zooplankton  

International Nuclear Information System (INIS)

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

 
 
 
 
201

Promotion of harmful algal blooms by zooplankton predatory activity  

Digital Repository Infrastructure Vision for European Research (DRIVER)

The relationship between algae and their zooplanktonic predators typically involves consumption of nutrients by algae, grazing of the algae by zooplankton which in turn enhances predator biomass, controls algal growth and regenerates nutrients. Eutrophication raises nutrient levels, but does not simply increase normal predator–prey activity; rather, harmful algal bloom (HAB) events develop often with serious ecological and aesthetic implications. Generally, HAB species are outwardly poor co...

Mitra, Aditee; Flynn, Kevin J.

2006-01-01

202

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

203

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

Energy Technology Data Exchange (ETDEWEB)

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

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

1980-04-01

204

Planet Migration  

CERN Document Server

Planet migration is the process by which a planet's orbital radius changes in time. The main agent for causing gas giant planet migration is the gravitational interaction of the young planet with the gaseous disk from which it forms. We describe the migration rates resulting from these interactions based on a simple model for disk properties. These migration rates are higher than is reasonable for planet survival. We discuss some proposed models for which the migration rates are lower. There are major uncertainties in migration rates due to a lack of knowledge about the detailed physical properties of disks. We also describe some additional forms of migration.

Lubow, Stephen H

2010-01-01

205

Planet Migration  

Science.gov (United States)

Planet migration is the process by which a planet's orbital radius changes in time. The main agent for causing gas giant planet migration is the gravitational interaction of the young planet with the gaseous disk from which it forms. We describe the migration rates resulting from these interactions based on a simple model for disk properties. These migration rates are higher than is reasonable for planet survival. We discuss some proposed models for which the migration rates are lower. There are major uncertainties in migration rates due to a lack of knowledge about the detailed physical properties of disks. We also describe some additional forms of migration.

Lubow, S. H.; Ida, S.

206

Planet Migration  

Digital Repository Infrastructure Vision for European Research (DRIVER)

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

Lubow, Stephen H.; Ida, Shigeru

2010-01-01

207

Model of optimal current feeding in zooplankton  

DEFF Research Database (Denmark)

Zooplankton feeding formulations in plankton models have exclusively focused on the relation between food concentration and ingestion, with respiration and excretion being treated separately, despite experimental evidence for strong links among these processes. We present an optimal current-feeding model linking ingestion, respiration, and assimilation efficiency to foraging activity. The Ivlev model is a special case of our optimal current-feeding model, which applies to static feeding behaviour. We validate our model with experimental data for copepods, ciliates, and dinoflagellates. Parameter estimates suggest that phylogenetic grouping is more important than predator size in determining feeding behaviour. Respiratory costs of foraging, e.g. for generating a feeding current, may be much larger than previously thought, are larger in smaller organisms, and might explain the independent development of feeding thresholds in different micro- and mesozooplankton groups. Both preferential feeding on, and lower feeding thresholds for, larger food particles are predicted to derive from greater capture efficiency owing to enhanced detectability of larger particles. The relation between feeding threshold and prey size appears to depend on feeding strategy but not on predator size, as a common relationship seems to apply for current feeders (ciliates and copepods) spanning a vast size range. Our model exhibits an inverse relationship between ingestion and assimilation efficiency, reducing the contribution of copepods to export of organic matter relative to remineralisation at low food concentrations. Export ratio variations previously thought to require strong shifts in community composition can be generated by changes in feeding behaviour predicted by our model.

Pahlow, M; Prowe, A.E. Friederike

2010-01-01

208

Modified residual migration of seismic data  

Energy Technology Data Exchange (ETDEWEB)

A method is described for migrating seismic events in the presence of a vertically- and laterally-varying velocity field, each said event being characterized by a raw input time, comprising: (a) scanning the true migration velocity field within an area of survey to define the minima of a true velocity function vs. time within the migration velocity field and defining a first stage function of migration velocity vs. time that is less than but approaches the minima of said true velocity field; (b) migrating at least one seismic event over a first migration pass with the aid of a preselected migration algorithm using a first migration velocity selected from said first stage function of velocity vs. time using as an argument, the raw input time of said at least one seismic event; (c) selecting a second velocity from said first stage function of migration velocity vs. time and selecting a true migration velocity from the true migration velocity function using as an argument the migrated time of said at least one seismic event; (d) defining a dip-dependent residual migration velocity as the square root of the difference between the squares of the selected true migration velocity and said selected second velocity; and (e) re-migrating the migrated seismic event using the residual migration velocity in conjunction with a desired migration algorithm.

Beasley, C.J.; Klotz, R.; Permata, T.

1993-08-03

209

Migration of shallow marine seismic data  

Energy Technology Data Exchange (ETDEWEB)

I applied the f-k migration using the phase shift method in the frequency domain to shallow marine seismic data. I tested a simple model which has different dips and velocities to analyze the migration effect. I used different velocities for the migration of the shallow marine seismic data acquired off Pohang and estimated the horizontal and vertical movement assuming a velocity and measuring the dip angle and two-way travel time from the folding structure in the seismic section. Proper migration velocity was determined not to over migrate. The migration effect of dip structure was small, even if the dip looks steep in the seismic section because the dip was exaggerated vertically. The migration of complex structure was conducted successfully. The diffraction was removed well and the irregular boundary and structure below the boundary appeared clearly after migration. (author). 9 refs., 9 figs.

Lee, Ho Young [Korea Institute of Geology Mining and Materials, Taejon (Korea, Republic of)

1996-06-30

210

Influence of mesoscale anticyclonic eddies on zooplankton distribution south of the western Aleutian Islands during summer  

Science.gov (United States)

Mesoscale anticyclonic eddies have been observed south of the Aleutian Islands located between the Bering Sea and the subarctic Pacific. Eddies farther east, in the Gulf of Alaska, are known to transport coastal water and coastal zooplankton to offshore open ocean. The impacts of mesoscale anticyclonic eddies formed south of the western Aleutian Islands (Aleutian eddies) on the zooplankton community are not fully understood. In the present study, we describe zooplankton population structures within an Aleutian eddy and outside the eddy during July 2010. Our field study was conducted at seven stations along 51°15?N from 171°21?E to 174°38?E (western line) and at four stations along 50°40?N from 176°24?E to 178°44?E (eastern line) on 7-8 July 2010. At each station, environmental data (temperature, salinity and fluorescence were measured by CTD/XCTD. Zooplankton samples were collected by vertical tow of 150 m depth to the surface using 100 ?m mesh size plankton net. Based on the sea level anomaly (SLA), the western line crossed an anticyclonic eddy but the eastern line did not cross the eddy (Fig. 1). This Aleutian eddy was formed south of Attu Island (52°54?N, 172°54?E) in mid-February 2010, and it moved southeastward in the next five months. The SLA near the eddy center, representing the strength of the eddy, continuously increased, and the area oscillated at one to two month periods overlain on a general increase from ~7,000 to ~18,000 km2. Large oceanic copepods, Neocalanus cristatus, Eucalanus bungii and Metridia pacifica were more abundant inside the eddy than the outside. Inside the eddy, the life stage distribution of N. cristatus was advanced than that outside, and Neocalanus spp. had accumulated more lipids. These conditions probably reflect the greater primary production in the eddy, production enhanced by nutrients advected into the eddy. Since the Aleutian eddy was formed in offshore waters and/or eddy-eddy interaction occurred after its formation, it contained mostly oceanic copepods. The sufficient food condition in the eddy presumably induced higher growth and survival rates of these oceanic copepods, resulting in the greater abundance, advanced development stages and greater lipid accumulation. Fig. 1. Sea level anomaly along the sampling lines on 7 July 2010 south of the western Aleutian Islands.

Saito, R.; Yamaguchi, A.; Yasuda, I.; Ueno, H.; Ishiyama, H.; Imai, I.

2013-12-01

211

Use Limnetic Zooplankton Sampling in Assessments of Fish Community Structure in Minnesota Bass-Panfish Lakes.  

Science.gov (United States)

Zooplankton and fish were sampled in 42 bass-panfish lakes over a two year period to determine if zooplankton sampling coupled with standard fish population assessments could be a useful fisheries management tool. Correlation analysis was used to identify...

J. E. Westerlund, P. C. Jacobson, H. K. Van Offelen, J. K. Hirsch

1998-01-01

212

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

213

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 ½of 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; Agusti, Susana; Carreja, Beatriz; Duarte, Carlos M.

2014-01-01

214

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 ½of 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

215

Impacts of ontogenetically migrating copepods on downward carbon flux in the western subarctic Pacific Ocean  

Science.gov (United States)

To evaluate the impacts of ontogenetically (seasonally) migrating copepods on carbon transport to the mesopelagic zone, we investigated depth distribution, population structure, and feeding activity of the ontogentic copepod community in the western subarctic Pacific Ocean from day-night pairs of zooplankton samples down to 1000 m during the VERtical Transport In the Global Ocean (VERTIGO) program. Over the 31 July-16 August 2005 study period, the biomass of Neocalanus cristatus and Neocalanus plumchrus predominated in the near surface waters, while Neocalanus flemingeri was already dormant at depth. We observed a strong diel migration for Metridia pacifica, and a seasonal downward migration for Eucalanus bungii. Based on gut pigment analysis, ingestion rate of the copepod community was 214-375 mg C m -2 day -1, which was equal to 26-37% of the concurrent primary production. However, comparison of grazing estimated from gut pigments to calculated carbon demand of the copepod community indicates that phytoplankton comprised 37-59% of the ingested carbon. Thus, the copepod community appears to have also relied on detritus and microzooplankton for their nutrition, likely because primary production during this time was dominated by picophytoplankton too small to be grazed by these large copepods. Fecal pellet flux by the copepod community was estimated to account for 141-223% of the sedimentary particulate organic carbon (POC) flux at 150 m, suggesting considerable fragmentation and consumption of pellets in the upper layers. Fecal pellets alone were adequate to meet copepod carbon demand in the surface 0-150 m layer. Active carbon flux by diel migration of M. pacifica (respiration, egestion, and mortality) was 4-17 mg C m -2 day -1, equal to 6-44% of sedimentary POC flux at 150 m. Active carbon flux by N. flemingeri ontogenetic migration (i.e., respiration and mortality at depth) contributed 246 mg C m -2 year -1, equal to 9% of sedimentary POC flux at 1000 m. The imminent downward migration of N. cristatus and N. plumchrus would lead to an additional ontogenetic carbon flux on the order of 1719 mg C m -2 year -1. Copepod fecal pellet transport and active transport by diel and ontogenetic migration are thus important carbon fluxes during a season dominated by small phytoplankton, and ontogenetic migrants in the subarctic Pacific Ocean play a relatively more important role in active carbon flux compared with other open-ocean regions.

Kobari, Toru; Steinberg, Deborah K.; Ueda, Ai; Tsuda, Atsushi; Silver, Mary W.; Kitamura, Minoru

2008-07-01

216

International Migration  

Science.gov (United States)

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

217

Evolutionary adaptation of marine zooplankton to global change.  

Science.gov (United States)

Predicting the response of the biota to global change remains a formidable endeavor. Zooplankton face challenges related to global warming, ocean acidification, the proliferation of toxic algal blooms, and increasing pollution, eutrophication, and hypoxia. They can respond to these changes by phenotypic plasticity or genetic adaptation. Using the concept of the evolution of reaction norms, I address how adaptive responses can be unequivocally discerned from phenotypic plasticity. To date, relatively few zooplankton studies have been designed for such a purpose. As case studies, I review the evidence for zooplankton adaptation to toxic algal blooms, hypoxia, and climate change. Predicting the response of zooplankton to global change requires new information to determine (a) the trade-offs and costs of adaptation, (b) the rates of evolution versus environmental change, (c) the consequences of adaptation to stochastic or cyclic (toxic algal blooms, coastal hypoxia) versus directional (temperature, acidification, open ocean hypoxia) environmental change, and (d) the interaction of selective pressures, and evolutionary and ecological processes, in promoting or hindering adaptation. PMID:22809192

Dam, Hans G

2013-01-01

218

Lake St. Clair zooplankton: Evidence for post-dreissena changes  

Science.gov (United States)

We surveyed the zooplankton of Lake St. Clair at 12 sites over ten dates from May to October 2000. Mean zooplankton density by site and date was 168.6 individuals/L, with Dreissena spp. veligers the most abundant taxon at 122.7 individuals/L. Rotifers, copepods, and cladocerans were far lower in mean abundance than in the early 1970s (rotifers, 20.9/L; copepods, 18.1/L; and cladocerans, 6.8/L). Species richness of zooplankton taxa in 2000 was 147, which was virtually unchanged from that of the first reported survey in 1894. Overall, the decline in abundance was greatest for rotifers (-90%) and about equal for cladocerans (-69%) and copepods (-66%). The decrease in abundance of Daphnia spp. was especially dramatic in Canadian waters. The decline in the southeastern region was significant for all three major groups of zooplankton, whereas in the northwestern region the decline was significant only for rotifers. From June to August 2000, Lake St. Clair open waters were numerically dominated by Dreissena spp. veligers, with a reduced abundance of rotifers and crustaceans compared to pre-Dreissena spp. surveys. Mean nutrient concentrations were not different from the 1970s, but Secchi depth (greater) and chlorophyll a concentration (lower) were. Disproportionate reduction in rotifer abundance is consistent with hypotheses implicating direct consumption by settled Dreissena spp. Reduction of crustaceans is likely due to more complex interactions including removal of nauplii as well as resource competition for phytoplankton.

David, K. A.; Davis, B. M.; Hunter, R. D.

2009-01-01

219

Phytoplankton and zooplankton of the Lednicke rybniky fishponds  

International Nuclear Information System (INIS)

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

220

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...

 
 
 
 
221

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)

222

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

223

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

224

Correlates of Zooplankton Beta Diversity in Tropical Lake Systems  

Science.gov (United States)

The changes in species composition between habitat patches (beta diversity) are likely related to a number of factors, including environmental heterogeneity, connectivity, disturbance and productivity. Here, we used data from aquatic environments in five Brazilian regions over two years and two seasons (rainy and dry seasons or high and low water level periods in floodplain lakes) in each year to test hypotheses underlying zooplankton beta diversity variation. The regions present different levels of hydrological connectivity, where three regions present lakes that are permanent and connected with the main river, while the water bodies of the other two regions consist of permanent lakes and temporary ponds, with no hydrological connections between them. We tested for relationships between zooplankton beta diversity and environmental heterogeneity, spatial extent, hydrological connectivity, seasonality, disturbance and productivity. Negative relationships were detected between zooplankton beta diversity and both hydrological connectivity and disturbance (periodic dry-outs). Hydrological connectivity is likely to affect beta diversity by facilitating dispersal between habitats. In addition, the harsh environmental filter imposed by disturbance selected for only a small portion of the species from the regional pool that were able to cope with periodic dry-outs (e.g., those with a high production of resting eggs). In summary, this study suggests that faunal exchange and disturbance play important roles in structuring local zooplankton communities. PMID:25330034

Lopes, Paloma M.; Bini, Luis M.; Declerck, Steven A. J.; Farjalla, Vinicius F.; Vieira, Ludgero C. G.; Bonecker, Claudia C.; Lansac-Toha, Fabio A.; Esteves, Francisco A.; Bozelli, Reinaldo L.

2014-01-01

225

Comparison between zooplankton data collected by the Continuous Plankton Recorder survey in the English Channel and by WP-2 nets at station L4, Plymouth (UK)  

Science.gov (United States)

Zooplankton sampling has been carried out by the Continuous Plankton Recorder (CPR) survey since the 1930s enabling the study of long-term changes in plankton populations, the elucidation of seasonal patterns of abundance, and more recently providing zooplankton biomass estimates for ecosystem models. Data for zooplankton abundance collected by CPR tows in the Western English Channel (between 1988 and 1998) were compared to vertically integrated samples collected from station L4 off Plymouth, UK. Comparisons were made for locally abundant copepods (including Acartia, Calanus, Para/ Pseudocalanus, Centropages, Oithona and Temora) collected by CPR and WP-2 nets. All dominant species recorded at L4 were also common to the CPR data. However, the position of the taxa in the two datasets was not equivalent. Seasonal cycles revealed by CPR data were significantly similar to those recorded throughout the water column at L4 for most taxa. However, absolute levels of abundance differed for the two datasets: abundances were underestimated by CPR samples when compared to those of vertically integrated samples by a factor of between 2 and 35, with the exception of Centropages. The differing mesh sizes (200 and 270 ?m) of the WP-2 net and CPR mesh could only partially explain these differences in abundance, implying that the behaviour of individual taxa and their depth in the water column also influenced the abundance recorded.

John, Eurgain H.; Batten, Sonia D.; Harris, Roger P.; Hays, Graeme C.

2001-12-01

226

Changes in fecal pellet characteristics with depth as indicators of zooplankton repackaging of particles in the mesopelagic zone of the subtropical and subarctic North Pacific Ocean  

Science.gov (United States)

We investigated how fecal pellet characteristics change with depth in order to quantify the extent of particle repackaging by mesopelagic zooplankton in two contrasting open-ocean systems. Material from neutrally buoyant sediment traps deployed in the summer of 2004 and 2005 at 150, 300, and 500 m was analyzed from both a mesotrophic (Japanese time-series station K2) and an oligotrophic (Hawaii Ocean Time series—HOT station ALOHA) environment in the Pacific Ocean as part of the VERtical Transport In the Global Ocean (VERTIGO) project. We quantified changes in the flux, size, shape, and color of particles recognizable as zooplankton fecal pellets to determine how these parameters varied with depth and location. Flux of K2 fecal pellet particulate organic carbon (POC) at 150 and 300 m was four to five times higher than at ALOHA, and at all depths, fecal pellets were two to five times larger at K2, reflective of the disparate zooplankton community structure at the two sites. At K2, the proportion of POC flux that consisted of fecal pellets generally decreased with depth from 20% at 150 m to 5% at 500 m, whereas at ALOHA this proportion increased with depth (and was more variable) from 14% to 35%. This difference in the fecal fraction of POC with increasing depth is hypothesized to be due to differences in the extent of zooplankton-mediated fragmentation (coprohexy) and in zooplankton community structure between the two locations. Both regions provided indications of sinking particle repackaging and zooplankton carnivory in the mesopelagic. At ALOHA, this was reflected in a significant increase in the mean flux of larvacean fecal pellets from 150 to 500 m of 3-46 ?g C m -2 d -1, respectively, and at K2 a large peak in larvacean mean pellet flux at 300 m of 3.1 mg C m -2 d -1. Peaks in red pellets produced by carnivores occurred at 300 m at K2, and a variety of other fecal pellet classes showed significant changes in their distribution with depth. There was also evidence of substantially higher pellet fragmentation at K2 with nearly double the ratio of broken:intact pellets at 150 and 300 m (mean of 67% and 64%, respectively) than at ALOHA where the proportion of broken pellets remained constant with depth (mean 35%). Variations in zooplankton size and community structure within the mesopelagic zone can thus differentially alter the transfer efficiency of sinking POC.

Wilson, Stephanie E.; Steinberg, Deborah K.; Buesseler, Ken O.

2008-07-01

227

The Effect of Radial Migration on Galactic Disks  

Science.gov (United States)

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

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

2014-10-01

228

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

Science.gov (United States)

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

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

2008-08-01

229

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

Science.gov (United States)

Four groups of larval razorback sucker, an endangered fish, were exposed to selenium-laden zooplankton and survival, growth, and whole-body residues were measured. Studies were conducted with 5, 10, 24, and 28-day-old larvae fed zooplankton collected from six sites adjacent to the Green River, Utah. Water where zooplankton were collected had selenium concentrations ranging from zooplankton ranged from 2.3 to 91 ??g/g dry weight. Static renewal tests were conducted for 20 to 25 days using reference water with selenium concentrations of zooplankton containing 12 ??g/g selenium. Whole-body concentrations of selenium ranged from 3.7 to 14.3 ??g/g in fish fed zooplankton from the reference site (Sheppard Bottom pond 1) up to 94 ??g/g in fish fed zooplankton from North Roadside Pond. Limited information prior to the studies suggested that the Sheppard pond 1 site was relatively clean and suitable as a reference treatment; however, the nearly complete mortality of larvae and elevated concentrations of selenium in larvae and selenium and other elements in zooplankton indicated that this site was contaminated with selenium and other elements. Selenium concentrations in whole-body larvae and in zooplankton from all sites were close to or greater than toxic thresholds where adverse effects occur in fish. Delayed mortality occurred in larvae fed the two highest selenium concentrations in zooplankton and was thought due to an interaction with other elements. ?? 2004 Elsevier Inc. All rights reserved.

Hamilton, S. J.; Buhl, K. J.; Bullard, F. A.; McDonald, S. F.

2005-01-01

230

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

Science.gov (United States)

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

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

2013-01-01

231

Influence of the late winter bloom on migrant zooplankton metabolism and its implications on export fluxes  

Science.gov (United States)

Studies on carbon active fluxes due to diel migrants are scarce and critical for carbon flux models and biogeochemical estimates. We studied the temporal variability and vertical distribution of biomass, indices of feeding and respiration of the zooplanktonic community north off the Canary Islands during the end of the late winter bloom, in order to assess vertical carbon fluxes in this area. Biomass distribution during the day presented two dense layers of organisms at 0-200 m and around 500 m, whereas at night, most of the biomass concentrated in the epipelagic layer. The gut pigment flux (0.05-0.18 mgC·m - 2 ·d - 1 ) represented 0.22% of the estimated passive export flux (POC flux) while potential ingestion represented 3.91% of the POC (1.24-3.40 mgC·m - 2 ·d - 1 ). The active respiratory flux (0.50-1.36 mgC·m - 2 ·d - 1 ) was only 1.57% of the POC flux. The total carbon flux mediated by diel migrants (respiration plus potential ingestion) ranged between 3.37 and 9.22% of the POC flux; which is three-fold higher than calculating ingestion fluxes from gut pigments. Our results suggest that the fluxes by diel migrants play a small role in the downward flux of carbon in the open ocean during the post-bloom period.

Putzeys, S.; Yebra, L.; Almeida, C.; Bécognée, P.; Hernández-León, S.

2011-12-01

232

Coprophagy in copepods and in a natural zooplankton community  

DEFF Research Database (Denmark)

Sediment trap studies have revealed that often only a minor fraction of the zooplankton fecal pellet production leave the upper ocean, and it has been suggested that copepod grazing on pellets (coprophagy) is the reason for this. A simple model is here used to estimate rate of coprophagy from lab and field observations. In the lab Acartia tonsa and Temora longicornis have coprophagous behavior and clear fecal pellets at a rate of 10-15 ml/female/d. Observations of fecal pellet production, sedimentation, and abundance collected during a 10-d late summer study in the North Sea revealed that less than 5 % of the fecal pellet production in the upper 50 m was lost as flux below 50 m depth. Estimates of coprophagy rates showed, however, that the zooplankton community > 200 um could account for only a few percent of the fecal pellet loss. Thus, plankton organisms < 200 ?m must be responsible for the degradation of the fecal pellets

Poulsen, Louise K.; KiØrboe, Thomas

233

210Po and 210Pb in zooplankton fecal pellets  

International Nuclear Information System (INIS)

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

234

Effects of nonylphenol on zooplankton in aquatic microcosms.  

Science.gov (United States)

We investigated the effects of the endocrine disruptor nonylphenol (NP) on the zooplankton assemblages of 230 L aquatic microcosms during a four-week preapplication period, a six-week NP treatment via controlled release, and a six-week postapplication period. Zooplankton assemblage change, investigated by ordination principal response curves (PRC), was due to lower abundances of copepoda, rotifera, and cladocera. The most sensitive groups/taxa were copepoda larvae, followed by the rotifers Synchaeta spp., Polyarthra spp., and the cladocerans Daphnia longispina and Chydorus sphaericus. The mean no-observed-effect concentrations for the community (NOEC(community)) was 30 microg/L. Cladocera densities recovered during the postapplication period at all but the highest NP concentrations (maximum 120 microg/L); copepod densities did not recover at the three highest concentrations (maximum 96-120 microg/L). PMID:14587915

Severin, Gabriele E; Welzl, Gerhard; Jüttner, Ingrid; Pfister, Gerd; Schramm, Karl-Werner

2003-11-01

235

Estimation of zooplankton mortality caused by an Arctic glacier outflow  

Directory of Open Access Journals (Sweden)

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

Marek J. Zaj±czkowski

2001-09-01

236

Next Generation Sequencing Reveals the Hidden Diversity of Zooplankton Assemblages  

Science.gov (United States)

Background Zooplankton play an important role in our oceans, in biogeochemical cycling and providing a food source for commercially important fish larvae. However, difficulties in correctly identifying zooplankton hinder our understanding of their roles in marine ecosystem functioning, and can prevent detection of long term changes in their community structure. The advent of massively parallel next generation sequencing technology allows DNA sequence data to be recovered directly from whole community samples. Here we assess the ability of such sequencing to quantify richness and diversity of a mixed zooplankton assemblage from a productive time series site in the Western English Channel. Methodology/Principle Findings Plankton net hauls (200 µm) were taken at the Western Channel Observatory station L4 in September 2010 and January 2011. These samples were analysed by microscopy and metagenetic analysis of the 18S nuclear small subunit ribosomal RNA gene using the 454 pyrosequencing platform. Following quality control a total of 419,041 sequences were obtained for all samples. The sequences clustered into 205 operational taxonomic units using a 97% similarity cut-off. Allocation of taxonomy by comparison with the National Centre for Biotechnology Information database identified 135 OTUs to species level, 11 to genus level and 1 to order, <2.5% of sequences were classified as unknowns. By comparison a skilled microscopic analyst was able to routinely enumerate only 58 taxonomic groups. Conclusions Metagenetics reveals a previously hidden taxonomic richness, especially for Copepoda and hard-to-identify meroplankton such as Bivalvia, Gastropoda and Polychaeta. It also reveals rare species and parasites. We conclude that Next Generation Sequencing of 18S amplicons is a powerful tool for elucidating the true diversity and species richness of zooplankton communities. While this approach allows for broad diversity assessments of plankton it may become increasingly attractive in future if sequence reference libraries of accurately identified individuals are better populated. PMID:24244737

Harmer, Rachel A.; Somerfield, Paul J.; Atkinson, Angus

2013-01-01

237

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

238

A stochastic analysis for a phytoplankton-zooplankton model  

International Nuclear Information System (INIS)

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

239

Studies on the zooplankton of the deep subalpine Lake Garda.  

Digital Repository Infrastructure Vision for European Research (DRIVER)

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

Naselli-flores, Luigi; Salmaso, Nico

1999-01-01

240

High dispersal capacity of cladoceran zooplankton in newly found communities  

Digital Repository Infrastructure Vision for European Research (DRIVER)

The relative importance of local and regional factors to community buildup is a key question in community ecology. Dispersal capacity is an important regional determinant but is very difficult to assess. Instead, measuring colonization rates in newly created habitats can provide a reasonable approximation of dispersal capacities. We monitored cladoceran zooplankton colonization rates in 25 newly dug and isolated pools. During the first 15 months, an average of 4.2 cladoceran species coloni...

Louette, G.; Meester, L.

2008-01-01

 
 
 
 
241

Increased zooplankton PAH concentrations across hydrographic fronts in the East China Sea.  

Science.gov (United States)

The Changjiang has transported large quantities of polycyclic aromatic hydrocarbons (PAHs) to the East China Sea (ECS), but information of these pollutants in zooplankton is limited. To understand PAHs pollution in zooplankton in the ECS, total concentrations of PAHs in zooplankton from surface waters were measured. Values of PAHs ranged from 2 to 3500 ng m(-3) in the ECS, with highest PAHs levels located at the salinity front between the Changjiang Diluted Water (CDW) and the mid-shelf waters. In contrast, concentrations of zooplankton PAHs in the mid-shelf and outer-shelf waters were significantly lower (2-23 ng m(-3)) than those in the CDW. These results demonstrate that PAHs are conspicuously accumulated in zooplankton at the salinity front between the CDW and the mid-shelf waters. These higher levels of PAHs in zooplankton at the salinity front may be further biomagnified in marine organisms of higher trophic levels through their feeding activities. PMID:24775063

Hung, Chin-Chang; Ko, Fung-Chi; Gong, Gwo-Ching; Chen, Kuo-Shu; Wu, Jian-Ming; Chiang, Hsin-Lun; Peng, Sen-Chueh; Santschi, Peter H

2014-06-15

242

Studies on the zooplankton of the deep subalpine Lake Garda.  

Directory of Open Access Journals (Sweden)

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

Luigi NASELLI-FLORES

1999-02-01

243

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

Directory of Open Access Journals (Sweden)

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

Kuczy?ska-Kippen N.

2013-07-01

244

Diversity, Distribution and Abundance of Zooplanktonic Larvae in Pakistani Waters  

Directory of Open Access Journals (Sweden)

Full Text Available Zooplanktonic larvae are very important and at knowing the patterns of diversity, distribution and abundance on the coast of Pakistan offer a wide variety of zooplanktonic larvae. Thirty six species belonging to 7 major phyla, 3 minor phyla and 11 orders have been recorded conducted from September 2001 and December 2002. Two hundred and ninety three samples were collected from Sonmiani and Korangi Creek at sixteen stations in Pakistani waters. Oblique tows from 5 m above bottom to the surface were made for 10 min with 333 um mesh paired nets and for 1-3 min with a 110 ?m mesh net. Temperature and salinity at the surface and near bottom were recorded at each station. The dominant zooplanktonic larvae groups reached their maximum abundance during summer June-August and also produced secondary peaks in fall October or winter December. A few species had numerical maxima in the spring (March and April. It is concluded from the results that the Pakistani waters Northern Arabian Sea sustains a high faunal range and a wide range of habital selection mainly depending upon their feeding habits and other behavior.

Farzana Yousuf

2006-01-01

245

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

246

Relationship Between Zooplankton Abundance and Physico-Chemical Parameters in Sundarban Ecosystem During Monsoon  

Directory of Open Access Journals (Sweden)

Full Text Available Studies on relationship between zooplankton abundance and physico-chemical parameters in Sundarban mangrove ecosystem during monsoon were made for a period of July, 2001. In the present study, impact of different physico-chemical parameters on zooplankton population was found. The relationship between zooplankton and water quality parameters was varied from place to place depending upon the condition of the water body.

Md. Towhid Ibna Alam

2003-01-01

247

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

International Nuclear Information System (INIS)

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

248

Spatial pattern of zooplankton diversity in Lianjiang River, Guangdong Province, China  

Directory of Open Access Journals (Sweden)

Full Text Available Twelve dams have been built along the Lianjiang River, the largest tributary of the Beijiang River in Guangdong Province, China. To understand the spatial distribution of zooplankton diversity developing after the establishment of these dams and cascades, and also the effects that these dams have had on zooplankton community structure, a study was conducted on the aquatic ecosystem in October 2007. Twelve sampling sites (S1–S12 along the main stream of Lianjiang River were established to study the composition of different groups of zooplankton and dominant species, the spatial distribution of abundance, biomass, diversity index of zooplankton as well as the zooplankton community, and relationships with environmental factors. Records showed that there were 76 species of zooplankton, which included 19 species of protozoa, 25 species of rotifer, 17 species of cladocera and 15 species of copepoda. Species numbers of zooplankton were greatest in sites S2 to S4, and lowest in S5. The dominant species were Stentor polymorphrus, Brachionus calyciflorus, Bosmina longirostris and Ectocyclops phaleratus, and significant differences in the distribution of dominant species existed between sampling points. Abundance of zooplankton fluctuated between 921.00 and 2,160.35 individuals/L, with highest abundance occurring in S5 and lowest in S1. Biomass of zooplankton fluctuated between 0.198 and 0.699 mg/L, with the highest value occurring in S5 and the lowest in S1. Generally, the values of Margalef species richness index, Shannon-Wiener diversity index and Pielou Evenness index of different zooplankton groups showed higher in upstream and lower in middle and downstream. PCA analysis showed a significant association between zooplankton community and environmental factors such as ammonia nitrogen, permanganate index, pH and transparence. We concluded that significant differences in ecological factors between habitats, such as nutrients, caused by cascade development, were the key factors determining the spatial distribution of zooplankton diversity in the Lianjiang river.

Yuan Gao

2013-11-01

249

Operation Migration  

Science.gov (United States)

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

250

Medical migration.  

Science.gov (United States)

The issue of professional migration, however emotional it may have become, ought not to be regarded in moralizing terms. The history of western medicine is the history of migrating physicians. A doctor who moves from a locality to another to take up a new assignment there cannot be said to have "abandoned his patients". This emotional bond has become the victim of specialization and of depersonalization of medical services and not of medical migration, brain drain or otherwise. The primary reason for medical migration is not financial; the desire to migrate usually begins with the desire to learn. Professionals crave in the first line for professional satisfaction. The migration of medical manpower cannot be stopped with administrative measures and will not be stopped by exhortations and appeals, moralization and condemnations. Brain drain is a global phenomenon and has always been so. A country which loses its professionals, its doctors, should examine the social relationships within the profession and should investigate whether the opportunities for deriving professional satisfaction from everyday work exist or whether these have been thwarted by the hierarchy, conservatism, cronyism and the general lack of comprehension of what good medical care is about. PMID:11593497

Loefler, I J

2001-10-01

251

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

Directory of Open Access Journals (Sweden)

Full Text Available 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-gene zooplankton community analysis using a method that determines a large number of mitochondrial COI gene sequences from a bulk zooplankton sample. This approach will enable us to estimate the species richness of almost the entire zooplankton community. Results A sample was collected from a depth of 721 m to the surface in the western equatorial Pacific off Pohnpei Island, Micronesia, with a plankton net equipped with a 2-m2 mouth opening. A total of 1,336 mitochondrial COI gene sequences were determined from the cDNA library made from the sample. From the determined sequences, the occurrence of 189 species of zooplankton was estimated. BLASTN search results showed high degrees of similarity (>98% between the query and database for 10 species, including holozooplankton and merozooplankton. Conclusion In conjunction with the Census of Marine Zooplankton and Barcode of Life projects, single-gene zooplankton community analysis will be a powerful tool for estimating the species richness of zooplankton communities.

Nishida Mutsumi

2009-09-01

252

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

International Nuclear Information System (INIS)

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

253

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

254

Vertical transport of steroid alcohols and ketones measured in a sediment trap experiment in the equatorial Atlantic Ocean  

Science.gov (United States)

The vertical flux and free steroid alcohol (sterol) and ketone composition of particulate material was determined using sediment traps deployed at 389, 988, 3755 and 5068 m at a station in the equatorial North Atlantic, PARFLUX E. Cholest-5-en-3?-ol (cholesterol) was found to be the dominant sterol in all the traps. This compound had a maximum flux at 988 m, accounting for more than 90% of the sterols at this depth. Inputs from mesopelagic Zooplankton populations living in or migrating to depths between the 389 and 988 m traps appear to be responsible for this distribution. The deeper two traps exhibited an increased flux of phytosterols relative to cholesterol, probably due to (a) the incorporation of labile phytoplankton remains in fecal pellets and rapid transport into the deep sea and (b) differential dissolution of heterogeneous large particles. A maximum of 5-22% of the sterols produced in the euphotic zone were present in the 389 m trap. This value drops to less than 1% for the 5068 m trap, 200 m above the sediment surface. In general steroid ketone fluxes gradually decreased with depth. ?4-Stenones were found in greater abundance than their saturated counterparts. Cholest-4-en-3-one was the major steroid ketone detected in all the traps. A five-fold increase with depth in the cholest-4-en-3-one to cholesterol ratio is most likely due to microbial oxidation of sterols to steroid ketones, or higher ?4-stenone inputs relative to sterols from organisms.

Gagosian, Robert B.; Smith, Steven O.; Nigrelli, Gale E.

1982-07-01

255

Planktivory in the changing Lake Huron zooplankton community: Bythotrephes consumption exceeds that of Mysis and fish  

Science.gov (United States)

Oligotrophic lakes are generally dominated by calanoid copepods because of their competitive advantage over cladocerans at low prey densities. Planktivory also can alter zooplankton community structure. We sought to understand the role of planktivory in driving recent changes to the zooplankton community of Lake Huron, a large oligotrophic lake on the border of Canada and the United States. We tested the hypothesis that excessive predation by fish (rainbow smelt Osmerus mordax, bloater Coregonus hoyi) and invertebrates (Mysis relicta, Bythotrephes longimanus) had driven observed declines in cladoceran and cyclopoid copepod biomass between 2002 and 2007. We used a field sampling and bioenergetics modelling approach to generate estimates of daily consumption by planktivores at two 91-m depth sites in northern Lake Huron, U.S.A., for each month, May-October 2007. Daily consumption was compared to daily zooplankton production. Bythotrephes was the dominant planktivore and estimated to have eaten 78% of all zooplankton consumed. Bythotrephes consumption exceeded total zooplankton production between July and October. Mysis consumed 19% of all the zooplankton consumed and exceeded zooplankton production in October. Consumption by fish was relatively unimportant - eating only 3% of all zooplankton consumed. Because Bythotrephes was so important, we explored other consumption estimation methods that predict lower Bythotrephes consumption. Under this scenario, Mysis was the most important planktivore, and Bythotrephes consumption exceeded zooplankton production only in August. Our results provide no support for the hypothesis that excessive fish consumption directly contributed to the decline of cladocerans and cyclopoid copepods in Lake Huron. Rather, they highlight the importance of invertebrate planktivores in structuring zooplankton communities, especially for those foods webs that have both Bythotrephes and Mysis. Together, these species occupy the epi-, meta- and hypolimnion, leaving limited refuge for zooplankton prey. Published 2011. This article is a US Government work and is in the public domain in the USA.

Bunnell, D. B.; Davis, B. M.; Warner, D. M.; Chriscinske, M. A.; Roseman, E. F.

2011-01-01

256

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 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 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

257

Spatial and Temporal Variability of Zooplankton Thin Layers: The Effects of Composition and Orientation on Acoustic Detection of Layers.  

Science.gov (United States)

Our primary long-term objective is to better understand the physical and biological mechanisms of formation and maintenance of thin layers of zooplankton. Because zooplankton can be strong sound scatterers, acoustic instruments are effective at detecting ...

A. Lavery, C. Ashjian, D. Fratantoni, M. Sutor, P. Wiebe

2008-01-01

258

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

Directory of Open Access Journals (Sweden)

Full Text Available 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.

D. N. Veerendra

2012-12-01

259

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

Directory of Open Access Journals (Sweden)

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

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

L. Mousseau

2009-01-01

260

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

Science.gov (United States)

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

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

2008-01-01

 
 
 
 
261

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

Science.gov (United States)

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

262

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...

263

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...

264

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.

265

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

266

Neustonic microplastic and zooplankton in the North Western Mediterranean Sea  

Digital Repository Infrastructure Vision for European Research (DRIVER)

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

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

2012-01-01

267

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  

Directory of Open Access Journals (Sweden)

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

268

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

International Nuclear Information System (INIS)

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

269

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

Science.gov (United States)

Four groups of larval razorback sucker, an endangered fish, were exposed to selenium-laden zooplankton and survival, growth, and whole-body residues were measured. Studies were conducted with 5, 10, 24, and 28-day-old larvae fed zooplankton collected from six sites adjacent to the Green River, Utah. Water where zooplankton were collected had selenium concentrations ranging from <0.4 to 78 ??g/L, and concentrations in zooplankton ranged from 2.3 to 91 ??g/g dry weight. Static renewal tests were conducted for 20 to 25 days using reference water with selenium concentrations of <1.1 ??g/L. In all studies, 80-100% mortality occurred in 15-20 days. In the 28-day-old larvae, fish weight was significantly reduced 25% in larvae fed zooplankton containing 12 ??g/g selenium. Whole-body concentrations of selenium ranged from 3.7 to 14.3 ??g/g in fish fed zooplankton from the reference site (Sheppard Bottom pond 1) up to 94 ??g/g in fish fed zooplankton from North Roadside Pond. Limited information prior to the studies suggested that the Sheppard pond 1 site was relatively clean and suitable as a reference treatment; however, the nearly complete mortality of larvae and elevated concentrations of selenium in larvae and selenium and other elements in zooplankton indicated that this site was contaminated with selenium and other elements. Selenium concentrations in whole-body larvae and in zooplankton from all sites were close to or greater than toxic thresholds where adverse effects occur in fish. Delayed mortality occurred in larvae fed the two highest selenium concentrations in zooplankton and was thought due to an interaction with other elements. ?? 2004 Elsevier Inc. All rights reserved.

Hamilton, S.J.; Buhl, K.J.; Bullard, F.A.; McDonald, S.F.

2005-01-01

270

Zooplankton size selection relative to gill raker spacing in rainbow trout  

Science.gov (United States)

Rainbow trout Oncorhynchus mykiss are one of the most widely stocked salmonids worldwide, often based on the assumption that they will effectively utilize abundant invertebrate food resources. We evaluated the potential for feeding morphology to affect prey selection by rainbow trout using a combination of laboratory feeding experiments and field observations in Flaming Gorge Reservoir, Utah-Wyoming. For rainbow trout collected from the reservoir, inter-gill raker spacing averaged 1.09 mm and there was low variation among fish overall (SD = 0.28). Ninety-seven percent of all zooplankton observed in the diets of rainbow trout collected in the reservoir were larger than the interraker spacing, while only 29% of the zooplankton found in the environment were larger than the interraker spacing. Over the size range of rainbow trout evaluated here (200-475 mm), interraker spacing increased moderately with increasing fish length; however, the size of zooplankton found in the diet did not increase with increasing fish length. In laboratory experiments, rainbow trout consumed the largest zooplankton available; the mean size of zooplankton observed in the diets was significantly larger than the mean size of zooplankton available. Electivity indices for both laboratory and field observations indicated strong selection for larger-sized zooplankton. The size threshold at which electivity switched from selection against smaller-sized zooplankton to selection for larger-sized zooplankton closely corresponded to the mean interraker spacing for both groups (???1-1.2 mm). The combination of results observed here indicates that rainbow trout morphology limits the retention of different-sized zooplankton prey and reinforces the importance of understanding how effectively rainbow trout can utilize the type and sizes of different prey available in a given system. These considerations may improve our ability to predict the potential for growth and survival of rainbow trout within and among different systems. ?? Copyright by the American Fisheries Society 2005.

Budy, P.; Haddix, T.; Schneidervin, R.

2005-01-01

271

Migration of shallow seismic reflection data  

Energy Technology Data Exchange (ETDEWEB)

The authors present an analysis of migration effects on seismic reflection images of very shallow targets such as those that are common objectives of engineering, groundwater, and environmental investigations. They use an example of seismic reflection data from depths of 5 to 15 m that show negligible effect from migration, despite the apparent steep dip on the seismic section. Their analysis of the question of when to migrate shallow reflection data indicates it is critical to take into account the highly variable near-surface velocities and the vertical exaggeration on the seismic section. A simple set of calculations is developed as well as a flow chart based on the migrator's equation'' that can predict whether migration of an arbitrary shallow seismic section is advisable. Because shallow reflection data are often processed on personal computers, unnecessary migration of a large data set can be prohibitively time-consuming and wasteful.

Black, R.A.; Steeples, D.W. (Univ. of Kansas, Lawrence, KS (United States). Dept. of Geology); Miller, R.D. (Kansas Geological Survey, Lawrence, KS (United States))

1994-03-01

272

Promotion of harmful algal blooms by zooplankton predatory activity.  

Science.gov (United States)

The relationship between algae and their zooplanktonic predators typically involves consumption of nutrients by algae, grazing of the algae by zooplankton which in turn enhances predator biomass, controls algal growth and regenerates nutrients. Eutrophication raises nutrient levels, but does not simply increase normal predator-prey activity; rather, harmful algal bloom (HAB) events develop often with serious ecological and aesthetic implications. Generally, HAB species are outwardly poor competitors for nutrients, while their development of grazing deterrents during nutrient stress ostensibly occurs too late, after the nutrients have largely been consumed already by fast-growing non-HAB species. A new mechanism is presented to explain HAB dynamics under these circumstances. Using a multi-nutrient predator-prey model, it is demonstrated that these blooms can develop through the self-propagating failure of normal predator-prey activity, resulting in the transfer of nutrients into HAB growth at the expense of competing algal species. Rate limitation of this transfer provides a continual level of nutrient stress that results in HAB species exhibiting grazing deterrents protecting them from top-down control. This process is self-stabilizing as long as nutrient demand exceeds supply, maintaining the unpalatable status of HABs; such events are most likely under eutrophic conditions with skewed nutrient ratios. PMID:17148360

Mitra, Aditee; Flynn, Kevin J

2006-06-22

273

Effects of the ``Amoco Cadiz'' oil spill on zooplankton  

Science.gov (United States)

A survey of zooplankton physiology on the northern coast of Brittany (France) was carried out over a one-year period by comparing two estuarine areas, one oil-polluted area (Aber Benoit) following the oil spill by the tanker “Amoco Cadiz” and one non-oil-polluted area (Rade de Brest). A new approach to an ecological survey was made by describing trophic relationships using analysis of digestive enzyme equipment (amylase and trypsin) of zooplankton organisms, mesoplankton populations and some selected species. These measurements allowed determination of (a) groups of populations with homogeneous trophic and faunistic characteristics and (b) groups of species with homogeneous trophic characteristics. The study of the appearance of these groups over a one-year period revealed the succession of populations and their adaptation to the environment on the basis of biochemical analysis. These phenomena observed in the compared areas showed marked differences in the most polluted areas during the productive spring period. Specific treatment of the data using unusual correlations between digestive enzymes is discussed in terms of the immediate effect on the whole population and on a copepod ( Anomalocera patersoni) living in the upper 10 cm.

Samain, J. F.; Moal, J.; Coum, A.; Le Coz, J. R.; Daniel, J. Y.

1980-03-01

274

Promotion of harmful algal blooms by zooplankton predatory activity  

Science.gov (United States)

The relationship between algae and their zooplanktonic predators typically involves consumption of nutrients by algae, grazing of the algae by zooplankton which in turn enhances predator biomass, controls algal growth and regenerates nutrients. Eutrophication raises nutrient levels, but does not simply increase normal predator–prey activity; rather, harmful algal bloom (HAB) events develop often with serious ecological and aesthetic implications. Generally, HAB species are outwardly poor competitors for nutrients, while their development of grazing deterrents during nutrient stress ostensibly occurs too late, after the nutrients have largely been consumed already by fast-growing non-HAB species. A new mechanism is presented to explain HAB dynamics under these circumstances. Using a multi-nutrient predator–prey model, it is demonstrated that these blooms can develop through the self-propagating failure of normal predator–prey activity, resulting in the transfer of nutrients into HAB growth at the expense of competing algal species. Rate limitation of this transfer provides a continual level of nutrient stress that results in HAB species exhibiting grazing deterrents protecting them from top-down control. This process is self-stabilizing as long as nutrient demand exceeds supply, maintaining the unpalatable status of HABs; such events are most likely under eutrophic conditions with skewed nutrient ratios. PMID:17148360

Mitra, Aditee; Flynn, Kevin J

2006-01-01

275

Temperature dependence of Arctic zooplankton metabolism and excretion stoichiometry  

Directory of Open Access Journals (Sweden)

Full Text Available 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.

M. Alcaraz

2012-06-01

276

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)

277

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

Science.gov (United States)

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

278

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

Directory of Open Access Journals (Sweden)

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

279

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

Directory of Open Access Journals (Sweden)

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

Imoobe T.O.T.

2009-01-01

280

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

Science.gov (United States)

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

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

2014-07-01

 
 
 
 
281

Biochemical composition and calorific value of zooplankton from the coastal waters of South Andaman  

Directory of Open Access Journals (Sweden)

Full Text Available Estimation of biochemical composition of zooplankton is important in understanding their metabolism, nutritive value and energy transfer which are relevant to the marine ecosystem. Zooplankton biomass and their biochemical composition were estimated from the coastal waters of South Andaman during October 2011 to September 2012. The dry weight biomass and chlorophyll a discerned a positive correlation (p is less than 0.05; one-way ANOVA in two stations. Protein formed the major fraction of the organic constituents. Seasonal variation in the protein content of zooplankton was observed. Carbohydrate was the minor component and ranged from 1.1-12.2% ( Mean= 3.4+-1.1 in terms of dry weight. Neither lipid nor carbohydrate appeared to be significant source of energy for these organisms. Caloric value obtained in this study ranged from 1.35 to 2.72 kcal/g dry weight ( Mean=1.8+-0.2. Relatively higher values were attributed to the dominance of calanoid copepods in the zooplankton population almost throughout the year. Zooplankton did not show an extensive lipid storage suggesting that protein may serve as metabolic reserve. It is therefore evident that zooplankton can be utilized as nutritional live feed for the cultivable species of fish and prawn in aquaculture farms. The variations in biochemical composition of zooplankton are influenced by species composition and feeding activities of zooplankton, which is in accordance with the previous studies. This study is the first report on Biochemical Composition and Calorific Value of Zooplankton from the coastal waters of Port Blair, South Andaman.

M. Arun Kumar

2013-09-01

282

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

International Nuclear Information System (INIS)

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

283

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

Directory of Open Access Journals (Sweden)

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

284

International migration - OECD  

...International migration &ndash OECD, Migration at the Development Centre Data and research on international migration including migration stocks and flows, immigrants ..., Can migration contribute to economic progress? Work of the Development Centre on Migration and Development demonstrates the gains from increased international labour ... international migration, migration stocks, migrant flows, immigrants, labour market, integration, discrimination, migration,labour mobility,development, globalisation,policy ...coherence,remittances,centre International migration - OECD Français Follow us E-mail Alerts Blogs OECD Home About Countries Topics Statistics Newsroom OECD Home › International ...

285

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

Science.gov (United States)

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

286

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

International Nuclear Information System (INIS)

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

287

Colonization of constructed ponds by crustacean zooplankton: local and regional influences  

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Full Text Available We examined monthly changes in crustacean zooplankton community composition during the initial colonisation period of a newly constructed pond (LWL pond, and in the littoral zone of an adjacent lake (Ramsey lake. In addition, four unconnected constructed ponds aged ?20 years with established zooplankton communities were sampled and compared to the LWL pond. The species richness of both LWL pond and Ramsey lake increased over the ice-free season, although Ramsey lake always had more species. Almost half of all species sampled occurred in both pond and lake. None of the zooplankton communities in the ponds used in the spatial analysis resembled communities of the LWL pond or one another. Taken together, these results indicate a lack of dispersal limitation, which suggests that differing local habitat factors had a strong influence in structuring the zooplankton communities.

Wendel Keller

2013-10-01

288

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

Directory of Open Access Journals (Sweden)

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

289

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

Digital Repository Infrastructure Vision for European Research (DRIVER)

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.

To?ro?k, Liliana; Radu, Adina

2007-01-01

290

Environmental assessment of spatial distribution of zooplankton community in Lake Manzalah, Egypt  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Lake Manzalah is the largest of the four Nile Delta lakes in Egypt. It provides more than 50% of the total inland fisheries of the country. During the last two decades the Lake has been exposed to multiple changes mainly due to local human activities. Monthly zooplankton samples were collected during an integrated environmental monitoring program within the MELMARINA Project that extended from July 2003 to September 2004 to study the distribution and occurrence of zooplankton community in Lak...

Zakaria, Howaida Yehia; Hussien Ahmed, Mahmoud; Flower, Roger

2007-01-01

291

Seasonal Variation of Zooplankton Population with Reference to Water Quality of Iril River in Imphal  

Digital Repository Infrastructure Vision for European Research (DRIVER)

The zooplankton population of Iril river of Imphal valley of Manipur was investigated with reference to water quality. The fish biodiversity potential of the river remain intake despite the sub-urban exposure of the river. Since plankton play a great food chain role for fish community, knowing the population of zooplankton as secondary resource is needed. Deterioration of water quality in urban area remain, in most cases, a basic feature. The present investigation endeavour to establish the ...

Thankhum Saron; Bijen Meitei

2013-01-01

292

Secondary Productivity of Pelagic Zooplankton in Lake Paldang and Lake Cheongpyeong  

Digital Repository Infrastructure Vision for European Research (DRIVER)

We estimated monthly and annual secondary productivity of pelagic zooplankton in Lake Paldang and Lake Cheongpyong. Secondary productivity was calculated by combining estimated zooplankton biomass and biomass-specific productivity for each site and depth from March to November 2008. In addition to somatic production, we measured production of eggs and exuviae for three dominant species: Daphnia galeata, Bosmina longirostris, Cyclops sp. In terms of biomass, B. longirostris was dominant in Lak...

Jisoon Kang; Sungbae Joo; Sungjin Nam; Garam Jeong; Dongwoo Yang; Hae-Kyung Park; Sangkyu Park

2009-01-01

293

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

Digital Repository Infrastructure Vision for European Research (DRIVER)

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. Zoopl...

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

2012-01-01

294

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

Digital Repository Infrastructure Vision for European Research (DRIVER)

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

295

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

296

The effects of juvenile American shad planktivory on zooplankton production in Columbia River food webs  

Science.gov (United States)

Columbia River reservoirs support a large population of nonnative American Shad Alosa sapidissima that consume the zooplankton that native fishes also rely on. We hypothesized that the unprecedented biomass of juvenile American Shad in John Day Reservoir is capable of altering the zooplankton community if these fish consume a large portion of the zooplankton production. We derived taxon-specific estimates of zooplankton production using field data and a production model from the literature. Empirical daily ration was estimated for American Shad and expanded to population-level consumption using abundance and biomass data from hydroacoustic surveys. Daphnia spp. production was high in early summer but declined to near zero by September as shad abundance increased. American Shad sequentially consumed Daphnia spp., copepods, and Bosmina spp., which tracked the production trends of these taxa. American Shad evacuation rates ranged from 0.09 to 0.24/h, and daily rations ranged from 0.008 to 0.045 g·g?1·d?1 (dry weight) over all years. We observed peak American Shad biomass (45.2 kg/ha) in 1994, and daily consumption (1.6 kg/ha) approached 30% (5.3 kg/ha) of zooplankton production. On average, American Shad consumed 23.6% of the available zooplankton production (range, food web in John Day Reservoir, potentially affecting native fishes, including Pacific salmon Oncorhynchus spp.

Haskell, Craig A.; Tiffan, Kenneth F.; Rondorf, Dennis W.

2013-01-01

297

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

Directory of Open Access Journals (Sweden)

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

Choi Jong-Yun

2014-01-01

298

Terrestrial carbon is a resource, but not a subsidy, for lake zooplankton  

Science.gov (United States)

Inputs of terrestrial organic carbon (t-OC) into lakes are often considered a resource subsidy for aquatic consumer production. Although there is evidence that terrestrial carbon can be incorporated into the tissues of aquatic consumers, its ability to enhance consumer production has been debated. Our research aims to evaluate the net effect of t-OC input on zooplankton. We used a survey of zooplankton production and resource use in ten lakes along a naturally occurring gradient of t-OC concentration to address these questions. Total and group-specific zooplankton production was negatively related to t-OC. Residual variation in zooplankton production that was not explained by t-OC was negatively related to terrestrial resource use (allochthony) by zooplankton. These results challenge the designation of terrestrial carbon as a resource subsidy; rather, the negative effect of reduced light penetration on the amount of suitable habitat and the low resource quality of t-OC appear to diminish zooplankton production. Our findings suggest that ongoing continental-scale increases in t-OC concentrations of lakes will likely have negative impacts on the productivity of aquatic food webs.

Kelly, Patrick T.; Solomon, Christopher T.; Weidel, Brian C.; Jones, Stuart E.

2014-01-01

299

Zooplankton assemblages in eutrophic reservoirs of the Brazilian semi-arid.  

Science.gov (United States)

Species composition, density, and temporal dynamics of zooplankton were studied in six reservoirs in a semi-arid region in tropical northeastern Brazil (Rio Grande do Norte state). All the reservoirs are highly eutrophic, with high contents of total nitrogen (minimum of 1200 µg.L(-1)) and total phosphorus (minimum of 10 µg.L(-1)), and extremely high algal biomass was registered (surpassing 20 µg Chl a.L(-1)). All the reservoirs showed an enduring condition of high turbidity and phytoplankton assemblages dominated by cyanobacteria. Zooplankton also showed quantitative patterns suggestive of eutrophic conditions, expressed by high densities, mainly in Passagem das Traíras and Sabugi reservoirs. A spatial differentiation in the composition of the zooplankton community was registered. Rotifers (especially Keratella tropica, Brachionus havanensis, and Keratella americana) were the dominant forms in the zooplankton community of Itans, Passagem das Traíras, and Sabugi reservoirs, while calanoid copepods (mainly Notodiaptomus cearensis) dominated in the Armando Ribeiro, Gargalheiras, and Parelhas systems. The existence of novel relationships in zooplankton community composition in eutrophic reservoirs in this tropical semi-arid region must be considered in designating zooplankton indicators of eutrophic conditions. PMID:23644787

Eskinazi-Sant'Anna, E M; Menezes, R; Costa, I S; Araújo, M; Panosso, R; Attayde, J L

2013-02-01

300

Development of Baltic Sea zooplankton in the presence of a toxic cyanobacterium: a mesocosm approach  

DEFF Research Database (Denmark)

Cyanobacteria blooms are common in the Baltic Sea and are considered to be a poor food source and sometimes toxic to zooplankton. Most experiments demonstrating harmful effects have been short-term incubations with monocultures or simple mixtures of food. In this study, a mesocosm approach was used to examine zooplankton responses over generation timescales. A toxic strain of the cyanobacterium Nodularia spumigena was added to bag enclosures of ambient water. The initial mesozooplankton concentration was either reduced by prescreening the water or enriched with locally caught zooplankton. Experiments ran for 15 days, long enough to monitor reproductive success and development of the next mesozooplankton generations. There was no major harmful effect on the zooplankton assemblage, even though the concentration of the toxin nodularin was in the upper range of field observations. The copepod Eurytemora affinis, rotifers Synchaeta spp. and the cladoceran Bosmina longispina maritima were able to develop and reproduce successfully in the presence of N. spumigena. The only species showing impaired recruitment was the copepod Acartia bifilosa. The general lack of population level effects from N. spumigena in this study can be reconciled with previous observations of adverse effects. Cyanobacteria alone may be poor food and toxic to zooplankton, but in the mesocosms a rich assemblage of microbiota developed, similar to that associated with blooms in the field. We suggest that, in the context of otherwise food-depleted summer situations in the open Baltic Sea, zooplankton can derive benefit from cyanobacteria bloom assemblages.

Schmidt, Katrin; Koski, Marja

2002-01-01

 
 
 
 
301

Zooplankton assemblages in montane lakes and ponds of Mount Rainier National Park, Washington State, USA  

Science.gov (United States)

Water quality and zooplankton samples were collected during the ice-free periods between 1988 and 2005 from 103 oligotrophic montane lakes and ponds located in low forest to alpine vegetation zones in Mount Rainier National Park, Washington State, USA. Collectively, 45 rotifer and 44 crustacean taxa were identified. Most of the numerically dominant taxa appeared to have wide niche breadths. The average number of taxa per lake decreased with elevation and generally increased as maximum lake depths increased (especially for rotifers). With one exception, fish presence/absence did not explain the taxonomic compositions of crustacean zooplankton assemblages. Many rotifer species were common members of zooplankton assemblages in montane lakes and ponds in western North America, whereas the crustacean taxa were common to some areas of the west, but not others. Constraints of the environmental variables did not appear to provide strong gradients to separate the distributions of most zooplankton species. This suggests that interspecific competitive interactions and stochastic processes regulate the taxonomic structures of the zooplankton assemblages at the landscape level. Crustacean species that had broad niche breadths were associated with different rotifer taxa across the environmental gradients. Studies of zooplankton assemblages need to address both crustacean and rotifer taxa, not one or the other.

Larson, G. L.; Hoffman, R.; McIntire, C. D.; Lienkaemper, G.; Samora, B.

2009-01-01

302

Terrestrial carbon is a resource, but not a subsidy, for lake zooplankton.  

Science.gov (United States)

Inputs of terrestrial organic carbon (t-OC) into lakes are often considered a resource subsidy for aquatic consumer production. Although there is evidence that terrestrial carbon can be incorporated into the tissues of aquatic consumers, its ability to enhance consumer production has been debated. Our research aims to evaluate the net effect of t-OC input on zooplankton. We used a survey of zooplankton production and resource use in ten lakes along a naturally occurring gradient of t-OC concentration to address these questions. Total and group-specific zooplankton production was negatively related to t-OC. Residual variation in zooplankton production that was not explained by t-OC was negatively related to terrestrial resource use (allochthony) by zooplankton. These results challenge the designation of terrestrial carbon as a resource subsidy; rather, the negative effect of reduced light penetration on the amount of suitable habitat and the low resource quality of t-OC appear to diminish zooplankton production. Our findings suggest that ongoing continental-scale increases in t-OC concentrations of lakes will likely have negative impacts on the productivity of aquatic food webs. PMID:25000755

Kelly, Patrick T; Solomon, Christopher T; Weidel, Brian C; Jones, Stuart E

2014-05-01

303

Responses of Phyto- and Zooplankton Communities to Prymnesium polylepis (Prymnesiales) Bloom in the Baltic Sea  

Science.gov (United States)

A large bloom of Prymnesium polylepis occurred in the Baltic Sea during the winter 2007 – spring 2008. Based on numerous reports of strong allelopathic effects on phytoplankton exerted by P. polylepis and its toxicity to grazers, we hypothesized that during this period negative correlations will be observed between P. polylepis and (1) main phytoplankton groups contributing to the spring bloom (i.e., diatoms and dinoflagellates), and (2) zooplankton growth and abundance. To test these hypotheses, we analyzed inter-annual variability in phytoplankton and zooplankton dynamics as well as growth indices (RNA?DNA ratio) in dominant zooplankton in relation to the Prymnesium abundance and biomass. Contrary to the hypothesized relationships, no measurable negative responses to P. polylepis were observed for either the total phytoplankton stocks or the zooplankton community. The only negative response, possibly associated with P. polylepis occurrence, was significantly lower abundance of dinoflagellates both during and after the bloom in 2008. Moreover, contrary to the expected negative effects, there were significantly higher total phytoplankton abundance as well as significantly higher winter abundance and winter-spring RNA?DNA ratio in dominant zooplankton species in 2008, indicating that P. polylepis bloom coincided with favourable feeding conditions for zooplankton. Thus, primary consumers, and consequently also zooplanktivores (e.g., larval fish and mysids), may benefit from haptophyte blooms, particularly in winter, when phytoplankton is scarce. PMID:25393031

Gorokhova, Elena; Hajdu, Susanna; Larsson, Ulf

2014-01-01

304

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

Dutz, Jörg

2012-01-01

305

Microcystin production by Microcystis aeruginosa exposed to different stages of herbivorous zooplankton.  

Science.gov (United States)

Microcystin (MC) production by four monoclonal Microcystis aeruginosa strains was evaluated in response to infochemicals (indirect exposure) released from different stages of herbivorous zooplankton (neonate/juvenile and adult Daphnia magna and Moina macrocopa). The intracellular MC and extracellular MC concentrations were significantly different among the control and treatments with zooplankton culture media filtrates (p<0.05), and in most cases MC production was significantly higher (p<0.05) in strains exposed to infochemicals released from adult zooplankton rather than those of neonate/juvenile zooplankton in four strains of M. aeruginosa. Compared to intracellular MC (385.0-5598.6microg g(-1)DW), very low concentrations of extracellular MC (9.9-737.6microg ml(-1)) were released, but both showed similar temporal patterns over the course of the experiment. This result might be attributed to the fact that adult zooplankton produced more infochemical signals than equal numbers of smaller juveniles and neonates. It is the first study to provide evidence that MC production might be impacted by infochemicals released from different stages of zooplankton, mediated with physiological characteristics, body size, and feeding habits. PMID:18243271

Jang, Min-Ho; Ha, Kyong; Takamura, Noriko

2008-04-01

306

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

Science.gov (United States)

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

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

2012-01-01

307

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

International Nuclear Information System (INIS)

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

308

Model migration schedules incorporating student migration peaks  

Digital Repository Infrastructure Vision for European Research (DRIVER)

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

Tom Wilson

2010-01-01

309

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

310

A 15-month study of zooplankton ingestion by farmed mussels ( Mytilus edulis) in Bantry Bay, Southwest Ireland  

Science.gov (United States)

There is a growing body of evidence to suggest that bivalve molluscs routinely ingest zooplankton. To elucidate further these observations, a 15-month study of zooplankton ingestion by farmed mussels was conducted using mussel long-lines in Bantry Bay, Ireland. Stomach content analysis of the mussels showed that there was evidence of zooplankton ingestion throughout the sampling period, but that highest mean numbers of zooplankters were ingested by mussels in the spring and summer months. Various zooplankton species were present in mussel stomachs. Harpacticoid copepods were found more often in stomach contents than calanoid copepods, probably due to their proximity to the bivalves' inhalent siphons. Barnacle cyprids featured in large numbers in stomach contents, but only for a period of 3 months which broadly corresponded with their pelagic phase. Sizes of ingested zooplankton ranged from 126 ?m to 6 mm, but more of the smaller zooplankters (e.g. crustacean nauplii) were ingested. When lengths of ingested copepods were compared with those found in plankton net samples, it was found that the net-sampled copepods were significantly larger than those found in mussel stomachs, suggesting that mussels select for smaller categories within the zooplankton available to them. Soft bodied zooplankton was rarely found in mussel stomachs but their absence may be due to rapid digestion or they may have been destroyed in the preservation process. Ingestion of zooplankton by bivalves is discussed in the context of the impacts mussel farms have on resident zooplankton populations.

Lehane, Clare; Davenport, John

2006-05-01

311

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

312

Parasitic Chytrids sustain zooplankton growth during inedible algal bloom  

Directory of Open Access Journals (Sweden)

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

SerenaRasconi

2014-05-01

313

Environmental assessment of spatial distribution of zooplankton community in Lake Manzalah, Egypt  

Directory of Open Access Journals (Sweden)

Full Text Available Lake Manzalah is the largest of the four Nile Delta lakes in Egypt. It provides more than 50% of the total inland fisheries of the country. During the last two decades the Lake has been exposed to multiple changes mainly due to local human activities. Monthly zooplankton samples were collected during an integrated environmental monitoring program within the MELMARINA Project that extended from July 2003 to September 2004 to study the distribution and occurrence of zooplankton community in Lake Manzalah. Results showed that, the average zooplankton standing crop was 1277 x 103 individuals m-3 . Spring was the most productive season (2127 x 103 individuals m-3 representing 41.65% to the total zooplankton counts. Five groups dominated zooplankton community; Rotifera, Copepoda, Ostracoda, Protozoa and Cladocera. The meroplanktonic larvae of Polychaeta, Cirripedia, Mysidacea and Gastropoda as well as free living nematods were rarely recorded. Rotifera contributed 81.89% to the total zooplankton community. They were represented by 38 species belonging to 19 genera dominated by genus Brachionus (86.65% of the total Rotifera followed by genus Keratella (8.68%. Keratella species has been indicated as an indicator of pollution. Copepoda (including their larval stages was the second group in order of abundance forming about 14.28% of the total zooplankton counts and represented by seven species. Acanthocyclops americanus was the dominant species. The productivity of Lake Manzalah decreased from 1979 to become highly eutrophic lake during the present study, but with higher production than the other Egyptian lakes. Management is needed to stabilize the Manzalah lake ecosystem in a way that promotes the sustainability of the system.

Howaida Yehia ZAKARIA

2007-12-01

314

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

315

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

316

Predation by jellyfish on large and emergent zooplankton: Implications for benthic pelagic coupling  

Science.gov (United States)

Stable carbon isotopes were used to determine the contribution of emergent demersal zooplankton to the diet of the scyphozoan jellyfish Catostylus mosaicus at Smiths Lake, New South Wales, Australia. A preliminary study in 2004 indicated that there was no difference in the ?13C of ectodermal tissue and mesoglea of the medusae. In 2005, medusae and zooplankton present during the day and night were sampled and isotopic signatures were modelled using IsoSource. Modelling indicated that: (1) mollusc veligers and copepods sampled during the day contributed jellyfish; (2) copepods sampled at night contributed up to 25%; and (3) the large, emergent decapod Lucifer sp. contributed 88-94%. We hypothesised, therefore, that medusae derive most of their carbon from emergent species of zooplankton. In 2006, sampling done in 2005 was repeated three times over a period of 4 weeks to measure short-term temporal variation in isotopic signatures of medusae and zooplankton, and emergent demersal zooplankton was specifically sampled using emergence traps. Short-term temporal variation in isotopic signatures was observed for some taxa, however, actual variations were small (jellyfish, and that the maximum possible contribution of daytime copepods and molluscs was only 22%. Jellyfish apparently derive most of their carbon from emergent zooplankton and by capturing small numbers of relatively large taxa, such as Lucifer sp. or mysid shrimp. Small but abundantly captured zooplankton (such as mollusc veligers) contribute only minor amounts of carbon. Jellyfish have a major role in the transfer of carbon between benthic and pelagic food webs in coastal systems.

Pitt, Kylie A.; Clement, Anne-Laure; Connolly, Rod M.; Thibault-Botha, Delphine

2008-03-01

317

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

318

Migration patterns in India.  

Science.gov (United States)

"The chief objective of the present paper is to comprehend the broad spatial patterns of internal migrations in India." Aspects considered include data constraints, the magnitude of internal migration, interstate migration, migration to rural and to urban destinations, spatial patterns, and areas of origin and destination. PMID:12179044

Smita; Chandna, R C

1991-01-01

319

Preliminary study on the occurrence and risk arising from bacteria internalized in zooplankton in drinking water.  

Science.gov (United States)

In this study, an environmental sampling campaign was conducted to detect internalized E. coli and C. jejuni bacteria in zooplankton and amoebae samples collected at various stages of three water treatment plants in Amsterdam, the Netherlands. Eight sampling locations were selected and sampling was performed twice, at a two-week interval, at each location. Chlorination was used to inactivate free (external) bacteria in the concentrated zooplankton samples and sonication was used to disrupt zooplankton organisms in order to release and recover internalized bacteria. Zooplankton enumeration was performed by microscopy. No internalized E. coli or C. jejuni bacteria were recovered from all of the samples analyzed. The occurrence of internalized E. coli or C. jejuni bacteria in drinking water was estimated to be lower than one internalized bacteria in 10? zooplankton organisms, as derived from the detection limit of the sampling campaign. By using the QMRA approach and the Beta-Poisson model, a risk of infection of less than 9.2E-6 and 5.9E-5 was estimated for internalized E. coli and C. jejuni in drinking water, respectively. This study remains preliminary due to the limited number of samples taken at each location. PMID:21245561

Bichai, F; Hijnen, W; Baars, Eric; Rosielle, M; Dullemont, Y; Barbeau, B

2011-01-01

320

Some ecological implications of a neem (azadirachtin) insecticide disturbance to zooplankton communities in forest pond enclosures.  

Science.gov (United States)

A neem-based insecticide, Neemix 4.5, was applied to forest pond enclosures at concentrations of 10, 17, and 28 microg l(-1) azadirachtin (the active ingredient). At these test concentrations, significant, concentration-dependent reductions in numbers of adult copepods were observed, but immature copepod and cladoceran populations were unaffected. There was no evidence of recovery of adult copepods within the sampling season (May to October). The ecological significance of this disturbance to the zooplankton community was examined by determining biomass as a measure of food availability for higher predators, plankton community respiration, dissolved oxygen (DO) concentrations, and conductivity as functional indicators of ecosystem stress, and zooplankton food web stability as a measure of effects on trophic structure. The selective removal or reduction of adult copepods was sufficient to measurably reduce total zooplankton biomass for several weeks mid-season. During the period of maximal impact (about 4-9 weeks after the applications), total plankton community respiration was significantly reduced, and this appeared to contribute to significant, concentration-dependent increases in dissolved oxygen and decreases in conductivity among treated enclosures. The reductions in adult copepods resulted in negative effects on zooplankton food web stability through eliminations of a trophic link and reduced interactions and connectance. Comparing the results here to those from a previous study with tebufenozide, which was selectively toxic to cladocerans and had little effect on food web stability, indicates that differential sensitivity among taxa can influence the ecological significance of pesticide effects on zooplankton communities. PMID:15063074

Kreutzweiser, David P; Sutton, Trent M; Back, Richard C; Pangle, Kevin L; Thompson, Dean G

2004-04-28

 
 
 
 
321

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

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

Susana B. José de Paggi

2013-10-01

322

Diversity of zooplankton in a tropical floodplain lake of the Brahmaputra river basin, Assam (Northeast India  

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Full Text Available The zooplankton diversity of a floodplain lake of the Brahmaputra river basin of lower Assam is analyzed on the bases of net plankton samples collected from the littoral (station 1 and semi-limnetic (station 2 regions during January–December 2010. The species-rich zooplankton (143 species hypothesized environmental heterogeneity of this wetland. They showed high monthly richness (81 ± 11 and 72 ± 11 species and recorded 44.7–79.3% and 46.7–89.7% community similarities at two sampling stations, respectively. Zooplankton formed 55.5 ± 10.9 % and 63.9 ± 9.6 % of net plankton abundance. Rotifera > Cladocera mainly influenced their richness and density variations. Copepoda is a sub-dominant quantitative group while Mesocyclops spp., Asplanchna priodonta, Chydorus sphaericus, Bosmina longirostris and Sinantherina socialis are relatively important taxa. High species diversity and low densities of majority of species are hypothesized to fine niche portioning amongst different species in combination with high micro- and macro-scale habitat heterogeneity. The zooplankton is characterized by high equitability and low dominance. Individual abiotic factors recorded limited influence on richness and abundance. Canonical correspondence analysis with ten abiotic factors explained 56.0 % and 55.8 % cumulative variance of zooplankton assemblages along axis 1 and 2. The CCA affirmed micro-environmental differences between the sampling stations.

Sharma, B.K.

2012-12-01

323

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

International Nuclear Information System (INIS)

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

324

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

Science.gov (United States)

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

Zuo, Shengpeng; Wan, Kun; Ma, Sumin

2015-01-01

325

Spatiotemporal statistical analyses reveal predator-driven zooplankton fluctuations in the Barents Sea  

Science.gov (United States)

There is limited statistical support for top-down effects on plankton in oceanic ecosystems. We quantify the combined effects of key planktivorous fish, invertebrates and climate on mesozooplankton dynamics in the Barents Sea. Zooplankton biomass was measured during Russian and Norwegian surveys in April-May and June-July 1959-1990 and August-early October (1981) 1984-2010. We found that zooplankton biomass in the central and northern Barents Sea in August-October showed pronounced multi-year fluctuations that were strongly negatively correlated with the total biomass of planktivorous fish. Fish predation explained >50% of the interannual variability in the biomass of medium-sized and large mesozooplankton in these parts of the Barents Sea and the predation effects remained significant while accounting for effects of climate variables. Spatiotemporal statistical analyses for different zooplankton size fractions supported the interpretation of top-down control, predominantly from capelin, on the zooplankton. In the southwestern Barents Sea the fluctuations were less pronounced and uncorrelated to total biomass of planktivorous fish, suggesting weaker top-down control by fish in this region, characterised by higher productivity and higher diversity of the predators. We suggest that predator-driven zooplankton fluctuations may play an important role in the ecosystem dynamics of the Barents Sea and potentially other Arcto-boreal shelves.

Stige, Leif Christian; Dalpadado, Padmini; Orlova, Emma; Boulay, Anne-Cécile; Durant, Joël M.; Ottersen, Geir; Stenseth, Nils Chr.

2014-01-01

326

Phosphorus release of metazoan zooplankton in two bays with different trophic status in Lake Taihu (China  

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Full Text Available The contribution of metazoan zooplankton to internal phosphorus (P cycling was investigated in Meiliang and Wuli Bays of Lake Taihu, a eutrophic, shallow lake in China by determining biomass and biomass specific P release rates. The zooplankton community of eutrophic Meiliang Bay was dominated by cladocerans, particularly Daphnia spp. and copepods, while dominant groups in hypereutrophic Wuli Bay included rotifers, copepods, and cladocerans. Release rates of PO43--P ranged from 0.20 to 0.57 mg·g (dry weight-1·h-1 in Meiliang Bay and 0.20 to 0.76 mg·g-1·h-1 in Wuli Bay. In most cases, P release rates were higher in Wuli Bay than Meiliang Bay. Phosphorus fluxes from zooplankton excretion varied from 5.34 to 57.41 mg·m-2·d-1 in Meiliang Bay and 8.20 to 70.02 mg·m-2·d-1 in Wuli Bay. Since P released by zooplankton in this study was in a form available to phytoplankton, zooplankton may represent a significant source of P contributing to high phytoplankton biomass in Lake Taihu.

Ning J.

2013-06-01

327

The role of aluminium contamination in determining phytoplankton and zooplankton responses to acidification  

Energy Technology Data Exchange (ETDEWEB)

A bioassay was performed at neutral pH Lake O'Woods, West Virginia using in situ enclosures. Replicated enclosures were either untreated controls, acidified to pH 4.7, or acidified and spiked with 300 microg L/sup -1/ Al. Algal and zooplankton responses to the treatments were compared to determine whether the impacts of acidification are influenced by Al concentration. With acidification, chlorophyll a concentration increased but zooplankton abundance did not change. The phytoplankton became dominated by the dinoflagellate Peridinium inconspicuum, while in the control, diatoms, euglenophytes and chlorophytes were dominant. Acidification did not result in succession in the zooplankton because all of the dominant species at the start of the experiment were acid tolerant. Aluminium addition resulted in reduced chlorophyll a concentration and zooplankton abundance. The same phytoplankton and zooplankton became dominant in the acid and acid plus Al treatments. This suggests a linkage between the ability to tolerate elevated H/sup +/ and elevated Al levels. 38 refs.

Havens, K.E.; Decosta, J.

1987-04-01

328

Water quality and zooplankton in tanks with larvae of Brycon Orbignyanus (Valenciennes, 1949).  

Science.gov (United States)

Due to the importance of water variables conditions and available food in the development and survival of fish larvae, the current research evaluates the effects of two different food treatments (ration + zooplankton and only zooplankton) and water quality in tanks with Brycon orbignyanus larvae. Total water transparency (45 cm) has been mainly associated with short residence time, continuous water flow and shallowness. Dissolved oxygen ranged between 1.32 and 7.00 mg.L(-1) in tanks with ration + zooplankton and between 1.82 and 7.60 mg.L(-1) in tanks with only zooplankton treatments. Nutrients were directly affected by the addition of ration in water, with the exception of nitrite. Ten Rotifera species were found represented by high densities, ranging between 8.7 x 10(5) and 1.3 x 10(6) org.m(-3), throughout the experimental period (January to March/1996). Cladocera had the lowest density in the four tanks under analysis and ranged between 4.7 x 10(4) and 2.1 x 10(5) org.m(-3) for the six species. Diaphanosoma birgei has been classified as the most frequent species. Since ration + zooplankton produced better larvae yield, this treatment is recommended for Brycon orbignyanus larvae. PMID:18470380

Sipaúba-Tavares, L H; Alvarez, E J da S; Braga, F M de S

2008-02-01

329

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

330

International Migration and Remittances  

Digital Repository Infrastructure Vision for European Research (DRIVER)

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

Dattatray Sitaram Bagade

2012-01-01

331

Zooplankton community structure of the sea surface microlayer near nuclear power plants and marine fish culture zones in Daya Bay  

Science.gov (United States)

The authors' surveys in May June 1999 (two cruises) at six sampling stations near nuclear power plants (NPP) and marine fish culture zones in Daya Bay, Guangdong, revealed species composition, densities and body-size of the sea surface microlayer (SM) zooplankton (>35 ?m). Results showed that protozoans and copepod nauplii were the predominant components, accounting for 65.40% to 95.56% of total zooplankton in abundance. The size-frequency distributions showed that the frequency of micro-zooplankton (0.02 0.2 mm) reached 0.8235. The SM zooplankton community structure revealed in the present study was quite different from that revealed by investigations in the 1980s in Daya Bay. Difference of sampling method has important influence on the obtained zooplankton community structure. SM zooplankton consisted of micro- and mesozooplankton (0.2 2.0 mm), with micro-zooplankton being predominant. Some possible cause-effect relations between the zooplankton community structure and mariculture, nuclear power plants cooling systems and sampling method are discussed.

Yang, Yu-Feng; Wang, Zhao-Ding; Pan, Ming-Xiang; Jiao, Nian-Zhi

2002-06-01

332

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

333

An index of biotic integrity based on the summer polyhaline zooplankton community of the Chesapeake Bay.  

Science.gov (United States)

A zooplankton index of biotic integrity was developed for the polyhaline waters of the Chesapeake Bay using data from a long-term environmental assessment program in which both zooplankton and water quality were regularly monitored. Summer (July to September) sampling events were classified as either coming from impaired or reference (least-impaired) conditions based on water quality conditions. Seventeen zooplankton community metrics were evaluated under these criteria and nine were chosen for a composite index. These were the Simpson diversity index, and abundance of barnacle larvae, rotifers, cladocerans, copepods, total mesozooplankton, and predators. The composite index of biotic integrity correctly classified about 94% of the impaired samples and about 82% of the reference samples. Average classification efficiency was 88%. This index appears to be an effective measure of eutrophication for the summer polyhaline waters of the Chesapeake Bay ecosystem. PMID:16709431

Carpenter, K E; Johnson, J M; Buchanan, C

2006-09-01

334

Distribution and trophic links of gelatinous zooplankton on Dogger Bank, North Sea  

DEFF Research Database (Denmark)

The ecology of small, gelatinous zooplankton is not integrated into management of Dogger Bank (54° 00? N, 3° 25? E to 55° 35? N, 2° 20? E). In pursuit of this goal, gelatinous zooplankton and their potential prey were sampled along a transect across the bank on June 10–16, 2007. Eleven species of small medusae and ctenophores were collected, with six abundant taxa occurring in greater numbers below the thermocline and in the shallower, southeastern portion of the bank. There were no statistically significant diel changes in distribution. In contrast, potential prey were distributed more evenly across the bank and throughout the water column. Isotopic analyses revealed that gelatinous zooplankton fed on both smaller (100–300 ?m) and larger (>300 ?m) mesozooplankton, but also potentially on each other. These ecological insights suggest that small medusae and ctenophores should be integrated into sustainable management of Dogger Bank.

Frost, Jessica R.; Denda, Anneke

2011-01-01

335

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

336

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

International Nuclear Information System (INIS)

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

337

Food habits of Juvenile American Shad and dynamics of zooplankton in the lower Columbia River  

Science.gov (United States)

As many as 2.4 million adult American shad annually pass John Day Dam, Columbia River to spawn upriver, yet food web interactions of juvenile shad rearing in John Day Reservoir are unexplored. We collected zooplankton and conducted mid-water trawls in McNary (June-July) and John Day reservoirs (August-November) from 1994 through 1996 during the outmigration of subyearling American shad and Chinook salmon. Juvenile American shad were abundant and represented over 98% of the trawl catch in late summer. The five major taxa collected in zooplankton tows were Bosmina longirostris, Daphnia, cyclopoid cope-pods, rotifers, and calanoid copepods. We evaluated total crustacean zooplankton abundance and Daphnia biomass in relation to water temperature, flow, depth, diel period, and cross-sectional location using multiple regression. Differences in zooplankton abundance were largely due to differences in water temperature and flow. Spatial variation in total zooplankton abundance was observed in McNary Reservoir, but not in John Day Reservoir. Juvenile American shad generally fed on numerically abundant prey, despite being less preferred than larger bodied zooplankton. A decrease in cladoceran abundance and size in August coupled with large percentages of Daphnia in juvenile American shad stomachs indicated heavy planktivory. Smaller juvenile American shad primarily fed on Daphnia in August, but switched to more evasive copepods as the mean size of fish increased and Daphnia abundance declined. Because Daphnia are particularly important prey items for subyearling Chinook salmon in mainstem reservoirs in mid to late summer, alterations in the cladoceran food base is of concern for the management of outmigrating salmonids and other Columbia River fishes. ?? 2006 by the Northwest Scientific Association. All rights reserved.

Haskell, C. A.; Tiffan, K. F.; Rondorf, D. W.

2006-01-01

338

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

Science.gov (United States)

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

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

2014-11-15

339

Carbon intake by zooplankton. Importance and role of zooplankton grazing in the Indian sector of the Southern Ocean  

Science.gov (United States)

Ingestion by mesozooplankton and micronekton was monitored during two of the ANTARES cruises in the Indian sector of the Southern Ocean in spring and summer. The composition of the mesozooplankton populations varied in space and with season. Copepods always dominated in number and biomass, but salps and pteropods were present in the northern part of the transect in summer. Five species of large copepod ( Calanus simillimus, Calanoides acutus, Rhincalanus gigas, Calanus propinquus and Metridia gerlachei) dominated the biomass with a North-South gradient. Smaller species ( Oithona spp., Ctenocalanus citer, Clausocalanus laticeps) were also present. Biomass showed a definite trend with highest levels towards the polar front zone and permanent open-ocean area. Feeding activity was monitored either for the total population (summer) or specific individuals (spring). In summer, depending on the area considered, grazing rates by mesozooplankton appeared to have a significant impact on phytoplankton primary production. In the northern part of the transect (polar front zone or PFZ), salps and to a minor extent pteropods and copepods contributed mostly to the feeding pressure. Maximum intensity was observed in the Coastal Antarctic Zone (CCSZ) where Euphausia superba (adults and calyptopis larvae) could ingest more than 100% of the daily primary production. In spring, the impact of copepods dominated the zooplankton community. Small calanoids and young stages of large species of copepods rather than adult stages were the dominant contributors to grazing pressure. In summer, respiration rates of the dominant copepod species showed that energy expenditure exceeded by far chlorophyll ingestion. This is generally interpreted as the consequence of ingestion of alternate non-chlorophyll food source. The inverse correlation between the biomass of microzooplankton and the area of maximum difference between grazing and respiration confirmed that in summer the protozoans are strongly controlled by the copepod community.

Mayzaud, P.; Tirelli, V.; Errhif, A.; Labat, J. P.; Razouls, S.; Perissinotto, R.

340

Zooplankton diversity and abundance of mangrove ecosystem of Kali estuary, Karwar, west coast of India  

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Full Text Available The present study conducted at the mangrove ecosystem of Kali estuary. Samples were collected from the three fixed stations for the period of thirteen months from January 2008 to January 2009 at regular monthly interval to identify and quantify the abundance, taxonomy and relative ratio of phytoplankton and zooplankton. In the present study of species diversity of zooplankton groups in the mangrove area, composed of twelve groups comprising fifty two species major share comes from the copepods which comprises about seventeen species. Protozoa taxa comprised by five species, coelenterata and cladocera by two species each, ctenophore comprised by single species whereas the larval forms comprised by fourteen species.

V. Kumar

2013-09-01

 
 
 
 
341

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

342

Zooplankton from OTEC sites in the Gulf of Mexico and the Caribbean  

Energy Technology Data Exchange (ETDEWEB)

The spatial and temporal variations in the abundance of major classes of zooplankton were measured using standard methods, between June and October 1978, at two OTEC sites in the Gulf of Mexico and in the Caribbean near Puerto Rico. The usual oceanic patterns were found with highest numbers near the surface, especially at night, and lowest numbers at 800 to 1000 m. Absolute numbers varied considerably from site to site. As expected, copepods (usually divided between calanoids and cyclopoids) dominated the zooplankton at all sites.

Commins, M.L.; Horne, A.J.

1979-06-01

343

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

344

Migration and Adult Education  

Science.gov (United States)

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

Gois, William

2007-01-01

345

Signatures of currency vertices  

CERN Document Server

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

Holme, Petter

2008-01-01

346

Contrasting patterns of allochthony among three major groups of crustacean zooplankton in boreal and temperate lakes.  

Science.gov (United States)

The importance of terrestrial-derived organic matter for lake zooplankton communities remains debated, partly because little is known about the basic pathways by which allochthonous carbon is transferred to zooplankton, and whether these vary among the major taxonomic and functional groups. We quantified allochthony of three zooplankton groups (Cladocera, Calanoida, and Cyclopoida) across 18 lakes in Quebec, spanning broad gradients of dissolved organic matter (DOM) and lake trophy, using a multi-isotope (delta2H + delta13C), multi-source (terrestrial, phytoplanktonic, benthic) approach. All three zooplankton groups had significant levels of allochthony, but differed greatly in their respective patterns across lakes. Allochthony in Calanoida and Cyclopoida was linked to detrital food chains based on particulate organic matter (POM) and on DOM, respectively, whereas in Cladocera it appeared related to both pathways; not surprisingly this latter group had the highest mean allochthony (0.31; compared to 0.18 in Cyclopoida and 0.16 in Calanoida). This study highlights the complexity of the pathways of delivery and transfer of terrestrial organic matter in freshwaters, and underscores the role that microbial food webs play in this transfer. PMID:25163126

Berggren, Martin; Ziegler, Susan E; St-Gelais, Nicolas F; Beisner, Beatrix E; Del Giorgio, Paul A

2014-07-01

347

Phytoplankton-zooplankton dynamics in periodic environments taking into account eutrophication.  

Science.gov (United States)

In this paper, we derive and analyze a mathematical model for the interactions between phytoplankton and zooplankton in a periodic environment, in which the growth rate and the intrinsic carrying-capacity of phytoplankton are changing with respect to time and nutrient concentration. A threshold value: "Predator's average growth rate" is introduced and it is proved that the phytoplankton-zooplankton ecosystem is permanent (both populations survive cronically) and possesses a periodic solution if and only if the value is positive. We use TP (Total Phosphorus) concentration to mark the degree of eutrophication. Based on experimental data, we fit the growth rate function and the environmental carrying capacity function with temperature and nutrient concentration as independent variables. Using measured data of temperature on water bodies we fit a periodic temperature function of time, and this leads the growth rate and intrinsic carrying-capacity of phytoplankton to be periodic functions of time. Thus we establish a periodic system with TP concentration as parameter. The simulation results reveal a high diversity of population levels of the ecosystem that are mainly sensitive to TP concentration and the death-rate of zooplankton. It illustrates that the eruption of algal bloom is mainly resulted from the increasing of nutrient concentration while zooplankton only plays a role to alleviate the scale of algal bloom, which might be used to explain the mechanism of algal bloom occurrence in many natural waters. What is more, our results provide a better understanding of the traditional manipulation method. PMID:23791607

Luo, Jinhuo

2013-10-01

348

Role of food partitioning in structuring the zooplankton community in mountain lakes.  

Science.gov (United States)

Trophic-niche differentiation is often cited as a main factor in structuring zooplankton assemblages, although field evidence for this is rarely presented. The study was based on a survey of 29 Pyrenean lakes with altitudes ranging between 1,875 and 2,990 m carried out during July and August 2000. Because of the oligotrophic nature of these lakes, we aimed to confirm that food partitioning is a major factor in shaping zooplankton assemblages. We analysed the amino acid composition of six cladocera and seven copepod species. A discriminant analysis showed that each species could be distinguished according to its amino acid composition. A negative relationship between amino acid differentiation and co-occurrence among the cladocera and cyclopoid copepod was observed. In contrast, calanoids did not show any relationship and were characterised by a high amino acid differentiation between species. As the differences in the amino acid composition among zooplankton species indicate distinct food sources, the relationship found indicates that trophic-niche differentiation plays a key role in determining the assemblage of these zooplankton communities. Therefore exploitative competition, either at present or in the past by driving co-evolutionary histories, has been a significant factor in structuring the cladocera and cyclopoid communities in these oligotrophic lakes. PMID:12827488

Guisande, C; Bartumeus, F; Ventura, M; Catalan, J

2003-08-01

349

Community-level disruptions among zooplankton of pond mesocosms treated with a neem (azadirachtin) insecticide.  

Science.gov (United States)

A natural, plant-derived insecticide, neem, is being evaluated as an alternative insect pest control product for forestry in Canada. As part of the process to investigate the environmental safety of neem-based insecticides, a mesocosm experiment was conducted to assess the effects of neem on natural zooplankton communities. Replicate (n=5), shallow (azadirachtin. Zooplankton communities were quantitatively sampled over a 4-month experimental period in treated and control enclosures, and water samples were collected to track azadirachtin concentrations. Concentrations in water declined linearly with estimated DT(50) values of 25-29 days. Trends in abundance over time among populations of cladocerans, copepods, and rotifers were found to differ significantly among treatments. At the two highest test concentrations, adverse effects were obvious with significant reductions in several cladoceran species, and near elimination of the three major copepod species present. More subtle effects at the two lowest test concentrations were determined by comparing the community structure of enclosures across treatment levels and over time through an analytical process based on the multivariate statistical software, PRIMER. Significant effects on community structure were detected at both of these lower concentrations, including the expected environmental concentration of 0.035 mg/l azadirachtin. Differential responses among species (some increases, some decreases) caused detectable disruptions in community structure among zooplankton of treated enclosures. Perturbations to zooplankton communities were sufficient to cause measurable differences in system-level metabolism (midday dissolved oxygen concentrations) at all but the lowest test concentration. PMID:11856575

Kreutzweiser, David P; Back, Richard C; Sutton, Trent M; Thompson, Dean G; Scarr, Taylor A

2002-03-01

350

Zooplankton feeding ecology and the experimental acidification of Little Rock Lake  

International Nuclear Information System (INIS)

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

351

Restructuring of a zooplankton community by perturbation from a wind-forced coastal jet  

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Full Text Available The impact of transient wind events on an established zooplankton community was observed during a field survey in a coastal region off northern Norway in May 2002. A transient wind event induced a coastal jet/filament intrusion of warm, saline water into our survey area where a semi-permanent eddy was present. There was an abrupt change in zooplankton community structure within 4-7 days of the wind event, with a change in the size structure, an increase in lower size classes less than 1 mm in equivalent spherical diameter (ESD and a decrease in larger size classes greater than 1.5 mm in ESD. The slope of zooplankton biovolume spectra changed from -0.6 to -0.8, consistent with the size shifting towards smaller size classes. This study shows that even well established zooplankton communities are susceptible to restructuring during transient wind events, and in particular when wind forcing induces horizontal currents or filaments.

Ole-Petter Pedersen

2010-09-01

352

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

Science.gov (United States)

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

353

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

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

Vesela Evtimova

2014-04-01

354

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

International Nuclear Information System (INIS)

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

355

Solar UVB-induced DNA damage and photoenzymatic DNA repair in antarctic zooplankton  

International Nuclear Information System (INIS)

tion in fitness of Antarctic zooplankton resulting from DNA damage is unknown, we suggest that increased solar UV may reduce recruitment and adversely affect trophic transfer of productivity by affecting heterotrophic species as well as primary producers. 54 refs., 4 figs., 2 tabs

356

Zooplankton fauna and seasonal changes of Zarrineh river and its constructed dams; West Azarbaijan, Iran  

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Full Text Available This study was carried out to determine the diversity and density of zooplankton population of Zarrine river and its constructed dams to develop the aquaculture activities in the region regarding their key role on fish larvae feeding. The sample collection was conducted monthly during 2008 to 2009. In each site 30 liters of water were filtered with a 55 µ mesh size plankton net and one liter of obtained extract was fixed with 4% formalin and its zooplankton fauna counted and identified.. The results showed that zooplankton fauna from different parts of Zarrine river included 3 major groups: Rotatoria, Cladocera and Copepoda. These groups comprised of 24 genera and 40 species. According to the species number, among the studied groups Rotatoria, Cladocera and Copepoda had the higher number of species, with 12 genera and 24 species, 7 genera and 10 species, 5 genera and 6 species , respectively. Seasonal studies showed that spring, autumn, winter and summer included 52%, 20 %, 16 %, and 12 % of zooplankton population, respectively.

Agamaliyev F.Q

2013-01-01