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Sample records for zooplankton vertical migration

  1. Twilight vertical migrations of zooplankton in a Chilean fjord

    Science.gov (United States)

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

    2014-12-01

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

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

    Science.gov (United States)

    Berge, Jørgen; Cottier, Finlo; Varpe, Oystein; Renaud, Paul E; Falk-Petersen, Stig; Kwasniewski, Sawomir; Griffiths, Colin; Søreide, Janne E; Johnsen, Geir; Aubert, Anais; Bjærke, Oda; Hovinen, Johanna; Jung-Madsen, Signe; Tveit, Martha; Majaneva, Sanna

    2014-09-01

    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

  3. 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

  4. Seasonal and diel vertical migration of zooplankton in the High Arctic during the autumn midnight sun of 2008

    OpenAIRE

    Rabindranath, Ananda; Daase, Malin; Falk-petersen, Stig; Wold, Anette; Wallace, M. I.; Berge, Jørgen; Brierley, A. S.

    2011-01-01

    The diel vertical migration (DVM) of Calanus (Calanus finmarchicus, Calanus glacialis and Calanus hyperboreus) and Metridia longa was investigated in August 2008 at six locations to the north and northwest of Svalbard (Rijpfjorden, Ice, Marginal Ice Zone, Shelf break, Shelf and Kongsfjorden). Despite midnight sun conditions, a diel light cycle was clearly observed at all stations. We collected data on zooplankton vertical distribution using a Multi Plankton Sampler (200-?m mesh size) and an ...

  5. Towards a correct description of zooplankton feeding in models: Taking into account food-mediated unsynchronized vertical migration

    OpenAIRE

    Morozov, A.Yu.; Arashkevich, E. G.

    2009-01-01

    Abstract Complex nature of foraging behaviour of zooplankton makes it difficult to describe adequately zooplankton grazing in models with vertical space. In mean-field models (based on systems of PDEs or coupled ODEs), zooplankton feeding at a given depth is normally computed as the product of the local functional response and the zooplankton density at this depth. Such simplification is often at odds with field observations which show the absence of clear relationship between inta...

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

    Science.gov (United States)

    Kopacz, U.

    1994-06-01

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

  7. Diel vertical migration and spatial overlap between fish larvae and zooplankton in two tropical lakes, Brazil / Migração vertical diária e sobreposição espacial entre larvas de peixes e zooplâncton em dois lagos tropicais, Brasil

    Scientific Electronic Library Online (English)

    PHS., Picapedra; FA., Lansac-Tôha; A., Bialetzki.

    2015-05-01

    Full Text Available O efeito de larvas de peixes sobre a distribuição vertical dia-noite da comunidade zooplanctônica foi investigada em duas lagoas tropicais, lagoa Finado Raimundo e Pintado, Mato Grosso do Sul, Brasil. Foram realizadas amostragens noturnas e diurnas na região limnética de cada lagoa durante um períod [...] o de 10 meses consecutivos, entre abril de 2008 a janeiro de 2009. A comunidade zooplanctônica apresentou uma variada gama de respostas à pressão de predação exercida pelas larvas de peixes nos dois ambientes, enquanto que as larvas de peixes exibiram um padrão típico de migração vertical diária normal. Os resultados mostraram ainda, que a migração vertical diária é um comportamento importante para evitar a predação, uma vez que diminuiu a sobreposição espacial entre presa e seu predador em potencial, dando suporte a hipótese de que a migração vertical é um mecanismo de defesa contra a predação. Abstract in english The effect of fish larvae on the diel vertical migration of the zooplankton community was investigated in two tropical lakes, Finado Raimundo and Pintado lakes, Mato Grosso do Sul State, Brazil. Nocturnal and diurnal samplings were conducted in the limnetic region of each lake for 10 consecutive mon [...] ths from April 2008 to January 2009. The zooplankton community presented a wide range of responses to the predation pressure exerted by fish larvae in both environments, while fish larvae showed a typical pattern of normal diel vertical migration. Our results also demonstrated that the diel vertical migration is an important behaviour to avoid predation, since it reduces the spatial overlap between prey and potential predator, thus supporting the hypothesis that vertical migration is a defence mechanism against predation.

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

    Science.gov (United States)

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

    2014-08-01

    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.

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

    Directory of Open Access Journals (Sweden)

    Mahnoud Hassan Hanafi

    2012-06-01

    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.

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

    Directory of Open Access Journals (Sweden)

    Lampert Winfried

    2005-04-01

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

  11. Partial diel vertical migrations in pelagic fish.

    Science.gov (United States)

    Mehner, Thomas; Kasprzak, Peter

    2011-07-01

    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

  12. 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)

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

    Science.gov (United States)

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

    2011-07-01

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

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

    Science.gov (United States)

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

    2009-01-01

    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.

  15. Vertical migration in high Arctic waters during autumn 2004

    Science.gov (United States)

    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

    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.

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

    International Nuclear Information System (INIS)

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

  17. Dissipation Rate of Turbulent Kinetic Energy in Diel Vertical Migrations: Comparison of ANSYS Fluent Model to Measurements

    Science.gov (United States)

    Dean, Cayla; Soloviev, Alexander; Hirons, Amy; Frank, Tamara; Wood, Jon

    2015-04-01

    Recent studies suggest that diel vertical migrations of zooplankton may have an impact on ocean mixing, though details are not completely clear. A strong sound scattering layer of zooplankton undergoing diel vertical migrations was observed in Saanich Inlet, British Colombia, Canada by Kunze et al. (2006). In this study, a shipboard 200-kHz echosounder was used to track vertical motion of the sound scattering layer, and microstructure profiles were collected to observe turbulence. An increase of dissipation rate of turbulent kinetic energy by four to five orders of magnitude was measured during diel vertical migrations of zooplankton in one case (but not observed during other cases). A strong sound scattering layer undergoing diel vertical migration was also observed in the Straits of Florida via a bottom mounted acoustic Doppler current profiler at 244 m isobath. A 3-D non-hydrostatic computational fluid dynamics model with Lagrangian particle injections (a proxy for migrating zooplankton) via a discrete phase model was used to simulate the effect of diel vertical migrations on the turbulence for both Saanich Inlet and the Straits of Florida. The model was initialized with idealized (but based on observation) density and velocity profiles. Particles, with buoyancy adjusted to serve as a proxy for vertically swimming zooplankton, were injected to simulate diel vertical migration cycles. Results of models run with extreme concentrations of particles showed an increase in dissipation rate of turbulent kinetic energy of approximately five orders of magnitude over background turbulence during migration of particles in both Saanich Inlet and the Straits of Florida cases (though direct relation of the turbulence produced by buoyant particles and swimming organisms isn't straightforward). This increase was quantitatively consistent, with turbulence measurements by Kunze et al. (2006). When 10 times fewer particles were injected into the model, the effect on dissipation rate of turbulent kinetic energy was an order of magnitude smaller than that from the extreme concentration. At a concentration of particles 100 times smaller than the extreme concentration, there was no longer an observable effect. In the Straits of Florida, direct turbulence measurements were not available to make a quantitative comparison. However, a small, but statistically significant decrease in northward current velocity profiles during migration times were observed after averaging these profiles over 11 months. A small decrease of current velocity connected to the vertical migrations of particles was reproduced in the Straits of Florida model case. The deviations in the velocity profiles can be explained by the increase in turbulent mixing during vertical migration periods.

  18. Vertical migration of radionuclides in undisturbed soils

    International Nuclear Information System (INIS)

    Literature data on numerical values obtained for the parameters of the two most popular models for simulating the migration of radionuclides in undisturbed soils have been compiled and evaluated statistically. Parameters evaluated include D (dispersion coefficient) and v (effective convection velocity) of the Convection-Dispersion-Equation and migration rates derived from different approaches (compartment models, repeated measurements, CDE-approaches). Due to restrictions on the applicability of compartmental models, the convection-dispersion equation and its parameter values should be preferred. For temperate environments the data base is sufficiently strong, but for other environments (e.g. Tropics or Arctic) as well as for radionuclides other than caesium data on vertical migration are still scarce. (author)

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

    KAUST Repository

    Dypvik, Eivind

    2012-11-13

    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 (<10 individuals m?3 below 600 m). The skinnycheek lanternfish performed normal 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.

  20. Internal wave-mediated shading causes frequent vertical migrations in fishes

    KAUST Repository

    Kaartvedt, Stein

    2012-04-25

    We provide evidence that internal waves cause frequent vertical migrations (FVM) in fishes. Acoustic data from the Benguela Current revealed that pelagic scattering layers of fish below ~140 m moved in opposite phases to internal waves, ascending ~20 m towards the wave trough and descending from the wave crest. At the trough, the downward displacement of upper waters and the upward migration of fish created an overlapping zone. Near-bottom fish correspondingly left the benthic boundary zone at the wave trough, ascending into an acoustic scattering layer likely consisting of zooplankton and then descending to the benthic boundary zone at the wave crest. We suggest that this vertical fish migration is a response to fluctuations in light intensity of 3 to 4 orders of magnitude caused by shading from a turbid surface layer that had chlorophyll a values of 3 to 4 mg m?3 and varied in thickness from ~15 to 50 m at a temporal scale corresponding to the internal wave period (30 min). This migration frequency thus is much higher than that of the common and widespread light-associated diel vertical migration. Vertical movements affect prey encounters, growth, and survival. We hypothesize that FVM increase the likelihood of prey encounters and the time for safe visual foraging among planktivorous fish, thereby contributing to efficient trophic transfer in major upwelling areas.

  1. Bacteria dispersal by hitchhiking on zooplankton

    DEFF Research Database (Denmark)

    Grossart, Hans-Peter; Dziallas, Claudia

    2010-01-01

    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.

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

    DEFF Research Database (Denmark)

    Höffle, Hannes; Nash, Richard D.M.

    2013-01-01

    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

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

    Directory of Open Access Journals (Sweden)

    Erlei Cassiano Keppeler

    2004-06-01

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

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

    Scientific Electronic Library Online (English)

    Erlei Cassiano, Keppeler; Elsa Rodrigues, Hardy.

    2004-06-01

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

  5. Zooplankton patch dynamics: daily gap formation over abrupt topography

    Science.gov (United States)

    Genin, Amatzia; Greene, Charles; Haury, Loren; Wiebe, Peter; Gal, Gideon; Kaartvedt, Stein; Meir, Eli; Fey, Connie; Dawson, Jim

    1994-05-01

    Net tow and acoustic surveys of zooplankton distributions were made over and around Sixtymile Bank (110 km southwest of San Diego, California). Gaps devoid of vertically migrating zooplankton were formed every evening above the summit of the bank. Interactions between the migrating animals, their predators, physical advection and the local topography appear to determine the gap formation and dynamics. Gaps were transported downstream during the night and appeared to disintegrate slowly through vertical swimming behavior, current shear and mixing processes. Patch dynamics following gap formation, mediated by both ocean currents and animal behavior, should augment the spatial heterogeneity of zooplankton and affect marine food webs in areas where abrupt topography features are common.

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

    DEFF Research Database (Denmark)

    Kjellerup, Sanne; Dünweber, Michael

    2015-01-01

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

  7. Vertical instability and inclination excitation during planetary migration

    CERN Document Server

    Voyatzis, G; Tsiganis, K

    2014-01-01

    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....

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

    Science.gov (United States)

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

    2015-01-01

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

  9. 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)

    Glécia Trinta de Paula Freitas

    2012-06-01

    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.

  10. 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)

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

    2012-06-01

    Full Text Available 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.

  11. Meander migration in horizontally and vertically heterogeneous floodplains

    Science.gov (United States)

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

    2011-12-01

    This paper follows up the work by Motta et al. (2011b), who evaluated, using Monte Carlo simulations, the impact of horizontal floodplain heterogeneity on meander migration when considering hydraulic erosion, governed by the physical parameters critical shear stress and erodibility, as driving mechanism for migration. Similarly to what observed in a recent paper (Güneralp and Rhoads, 2011), which instead adopted the classic migration-coefficient approach, three governing parameters were identified that characterize the effect of floodplain heterogeneity on channel planform complexity, respectively quantifying the local randomness of soil resistance, the cross-valley increase of soil resistance, and the spatial scale of heterogeneity. Furthermore, using a physically- and process-based method for bank erosion instead of the migration-coefficient method, besides identifying and producing more complex planform shapes (Motta et al., 2011a,b), allows for considering the vertical soil heterogeneity, i.e., the presence of more than one material layer characterized by different erodibility and geotechnical properties. This paper illustrates the results of an ongoing effort to evaluate the effect of combined horizontal and vertical soil heterogeneity on meander migration. Test cases show the additional planform complexity generated by vertical heterogeneity when considering just hydraulic erosion, and when taking also into account mass failure mechanisms (namely, planar failure). The observation by Constantine et al. (2009) and Motta et al. (2011a) that mass failure mechanisms, although important, can be indirectly represented by modifying the parameters for hydraulic erosion to quantify rates of migration, may not be true for vertically heterogeneous floodplains. REFERENCES Constantine, C.R., Dunne, T., Hanson, G.J. 2009. Examining the physical meaning of the bank erosion coefficient used in meander migration modeling. Geomorphology 106 (3-4), 242-252. Güneralp, I., Rhoads, B.L., 2011. Influence of floodplain erosional heterogeneity on planform complexity of meandering rivers. Geophysal Research Letters 38, L14401. Motta, D., Abad, J.D., Langendoen, E.J., Garcia, M.H. 2011a. A simplified 2D model for meander migration with physically-based bank evolution. Geomorphology. In Press. Motta, D., Abad, J.D., Langendoen, E.J., Garcia, M.H. 2011b. Floodplain heterogeneity and meander migration, Proceedings of the River, Coastal and Estuarine Morphodynamics: RCEM2011 2011 Tsinghua University Press, Beijing.

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

    International Nuclear Information System (INIS)

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

  13. Turbulence and zooplankton production: insights from PROVESS

    DEFF Research Database (Denmark)

    Visser, Andre; Stips, A.

    2002-01-01

    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.

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

    Science.gov (United States)

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

    2014-12-01

    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 (day and night differences in pellet concentration and flux in the HI 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.

  15. Zooplankton and fisheries

    Digital Repository Service at National Institute of Oceanography (India)

    Goswami, S.C.

    1991-01-01

    is dominatEd. by herbivores. Zooplankton constitutes the main food item of several economic important animals. The pelagic fishes migrate in shoals to the feeding ground rich in food and hence zooplankton are used as indicators of rich potential fishing...

  16. Diatom vertical migration within land-fast Arctic sea ice

    Science.gov (United States)

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

    2014-11-01

    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.

  17. Diel vertical migration arising in a habitat selection game

    DEFF Research Database (Denmark)

    Sainmont, Julie; Thygesen, Uffe HØgsbro

    2013-01-01

    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

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

    Directory of Open Access Journals (Sweden)

    Chiarelle A.

    2006-11-01

    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.

  19. Distinctive stable isotope ratios in important zooplankton species in relation to estuarine salinity gradients: Potential tracer of fish migration

    Science.gov (United States)

    Suzuki, Keita W.; Kasai, Akihide; Isoda, Takane; Nakayama, Kouji; Tanaka, Masaru

    2008-07-01

    To assess the potential of stable isotope ratios as an indicator of fish migration within estuaries, stable isotope ratios in important zooplankton species were analyzed in relation to estuarine salinity gradients. Gut contents from migratory juveniles of the euryhaline marine fish Lateolabrax japonicus were examined along the Chikugo River estuary of the Ariake Sea, which has the most developed estuarine turbidity maximum (ETM) in Japan. Early juveniles in March and April preyed primarily on two copepod species; Sinocalanus sinensis at lower salinities and Acartia omorii at higher salinities. Late juveniles (standard length > 40 mm) at lower salinities preyed exclusively on the mysid Acanthomysis longirostris until July and complementarily on the decapod Acetes japonicus in August. These prey species were collected along the estuary during the spring-summer seasons of 2003 and 2004, and their carbon and nitrogen stable isotope ratios ( ?13C and ?15N) were evaluated. The ?13C values of prey species were distinct from each other and were primarily depleted within and in close proximity to the ETM (salinity < 10); S. sinensis (-26.6‰) < Acanthomysis longirostris (-23.3‰) < Acartia omorii (-21.1‰) < Acetes japonicus (-18.5‰). The overall gradient of ?13C with salinity occurred for all prey species and showed minor temporal fluctuations, while it was not directly influenced by the ?13C values in particulate organic matter along the estuary. In contrast to ?13C, the ?15N values of prey species did not exhibit any clear relationship with salinity. The present study demonstrated that ?13C has the potential for application as a tracer of fish migration into lower salinity areas including the ETM.

  20. Temporal variability of zooplankton biomass from ADCP backscatter time series data at the Bermuda Testbed Mooring site

    Science.gov (United States)

    Jiang, Songnian; Dickey, Tommy D.; Steinberg, Deborah K.; Madin, Laurence P.

    2007-04-01

    Temporal variability of acoustically estimated zooplankton biomass at the Bermuda Testbed Mooring (BTM) site in the Sargasso Sea (at 31°43'N, 64°10'W) is described for time scales from less than an hour to the seasonal cycle primarily using data obtained between August 1996 and November 2000, and from May 10 to November 13, 2003. Concurrent high frequency BTM observations of meteorological, physical, and bio-optical variables are used to interpret processes contributing to the zooplankton variability. Zooplankton biomass estimates are derived from regressions of backscatter intensity data measured with an upward looking 153-kHz acoustic Doppler current profiler (ADCP) and zooplankton net tow data collected near the BTM site as part of the Bermuda Atlantic Time-series Study (BATS). Our data show clear event-scale variations. Peaks are associated with annual spring blooms involving mixed layer shoaling and in some cases passages of mesoscale eddy features. Biomass peaks are often coincident with maxima seen in BTM chlorophyll fluorescence measurements (inferred phytoplankton biomass). Some storm events do not appear to manifest in significant perturbations of zooplankton distributions; however, Hurricane Fabian (2003) greatly impacted these distributions. Estimates of zooplankton biomass and relative vertical velocity show the vertical structure of daily migration patterns. Seasonal variations in migration patterns are also evident, with diel changes in zooplankton biomass most pronounced in spring and least pronounced in winter. In summary, our high temporal resolution time series of estimated zooplankton biomass in the open ocean provide information on scales inaccessible through conventional monthly ship-based sampling. These data have implications for upper ocean ecology and the vertical transport of carbon and nitrogen through the diel migration of zooplankton.

  1. 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

  2. Vertical migration of nuclides seeped from an uranium tailings impoundment

    International Nuclear Information System (INIS)

    After 31 year operation of an uranium tailings impoundment, sub-clayey samples beneath its bottom were taken for determining concentration distribution of U, Th and Ra seeped from the impoundment. For fitting nuclide migration, one dimensional convection-dispersion model of nuclide migration in groundwater was applied, and parameters were measured such as particle size of tailings, leaching factor of nuclides from tailings and distribution coefficients of nuclides in sub-clay. Results indicate that fine tailings are the main portion of tailings, and possess higher specific activities and lower leaching factor than coarse tailings. The sub-clay has a strong adsorption ability to nuclides, and distribution coefficients of U, Th and Ra are 62, 1.3 x 103 and 9.8 x 102 mL/g, respectively. The natural and man-made sub-clay layers beneath the impoundment can reduce effectively nuclides seepage and migration. (authors)

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

    OpenAIRE

    Sugiyama, Kazuyasu; Takemura, Fumio

    2010-01-01

    Deformation-induced lateral migration of a bubble slowly rising near a vertical plane wall in a stagnant liquid is numerically and theoretically investigated. In particular, our focus is set on a situation with a short clearance $c$ between the bubble interface and the wall. Motivated by the fact that numerically and experimentally measured migration velocities are considerably higher than the velocity estimated by the available analytical solution using the Fax\\'{e}n mirror...

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

    Directory of Open Access Journals (Sweden)

    M. Kitamura

    2013-08-01

    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.

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

    Directory of Open Access Journals (Sweden)

    M. Kitamura

    2013-04-01

    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.

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

    Science.gov (United States)

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

  7. 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)

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

    2012-04-01

    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.

  8. Spatial and temporal variability of zooplankton off New Caledonia (Southwestern Pacific) from acoustics and net measurements

    Science.gov (United States)

    Smeti, Houssem; Pagano, Marc; Menkes, Christophe; Lebourges-Dhaussy, Anne; Hunt, Brian P. V.; Allain, Valerie; Rodier, Martine; de Boissieu, Florian; Kestenare, Elodie; Sammari, Cherif

    2015-04-01

    Spatial and temporal distribution of zooplankton off New Caledonia in the eastern Coral Sea was studied during two multidisciplinary cruises in 2011, during the cool and the hot seasons. Acoustic measurements of zooplankton were made using a shipborne acoustic Doppler current profiler (S-ADCP), a scientific echosounder and a Tracor acoustic profiling system (TAPS). Relative backscatter from ADCP was converted to biomass estimates using zooplankton weights from net-samples collected during the cruises. Zooplankton biomass was estimated using four methods: weighing, digital imaging (ZooScan), ADCP and TAPS. Significant correlations were found between the different biomass estimators and between the backscatters of the ADCP and the echosounder. There was a consistent diel pattern in ADCP derived biomass and echosounder backscatter resulting from the diel vertical migration (DVM) of zooplankton. Higher DVM amplitudes were associated with higher abundance of small zooplankton and cold waters to the south of the study area, while lower DVM amplitudes in the north were associated with warmer waters and higher abundance of large organisms. Zooplankton was largely dominated by copepods (71-73%) among which calanoids prevailed (40-42%), with Paracalanus spp. as the dominant species (16-17%). Overall, zooplankton exhibited low abundance and biomass (mean night dry biomass of 4.7 ± 2.2 mg m3 during the cool season and 2.4 ± 0.4 mg m3 during the hot season) but high richness and diversity (Shannon index ˜4). Substantially enhanced biomass and abundance appeared to be episodically associated with mesoscale features contributing to shape a rather patchy zooplankton distribution.

  9. U, Th and 226Ra vertical migration in sub-clay from an uranium tailngs impoundment

    International Nuclear Information System (INIS)

    After 31 years operation of an uranium tailings impoundment, sub-clay samples beneath its bottom were taken for determining concentration distribution of U, Th and 226Ra migration from the impoundment. For study of nuclide migration, parameters were measured such as particle size of tailings, nuclide specific activities and leaching factors of tailings, and distribution coefficients of nuclides in sub-clay. One dimensional convection-dispersion model of nuclide migration was applied for fitting nuclide distribution in sub-clay. The result indicates that the sludge is the main component of tailings, and possess higher specific activities and lower leaching factor than coarse tailings. Sub-clay has a strong adsorption ability to nuclides, and the natural and man-made sub-clay layers beneath the impoundment bottom can effectively reduce nuclides seepage and vertical migration distance. Distribution coefficients of U, Th and 226Ra are 62, 1.3 x 103 and 9.8 x 102 mL/g, respectively. The vertical migration distances at which the concentrations of nuclides reduce to background level are 1.2 m for U and 0.2 m for Th and 226Ra. (authors)

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

    Science.gov (United States)

    Liu, Hui-Lian; Sun, Song

    2010-04-01

    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.

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

    KAUST Repository

    Prihartato, Perdana

    2014-12-01

    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.

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

    Science.gov (United States)

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

    2006-01-01

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

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

    International Nuclear Information System (INIS)

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

  14. Potential acidification impacts on zooplankton in CCS leakage scenarios.

    Science.gov (United States)

    Halsband, Claudia; Kurihara, Haruko

    2013-08-30

    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. PMID:23632089

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

    Scientific Electronic Library Online (English)

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

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

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

    Directory of Open Access Journals (Sweden)

    Ralf Schwamborn

    2008-01-01

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

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

    Science.gov (United States)

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

    2014-03-01

    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 krill appeared to undertake asynchronous migrations, with some krill always being present in near-bottom waters even though the entire population appeared to undertake DVM. PMID:24616550

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

    CERN Document Server

    Sugiyama, Kazuyasu

    2010-01-01

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

  19. Horizontal and vertical dynamics of zooplankton and larval fish communities during mid-summer in Disko Bay, West Greenland

    DEFF Research Database (Denmark)

    Munk, Peter; Nielsen, Torkel Gissel

    2015-01-01

    Disko Bay is a highly productive inlet at the border between high- and low-arctic sectors of west Greenland. The physical/chemical conditions in the bay have changed during recent decades, specifically during an inflow event in 1996–1997 that led to increased deep-water temperatures. To further understand the consequences of physical changes to the plankton community in the bay, we examine findings from a field study on mesozooplankton and fish larvae in the areas of Disko Bay and Disko Bank carried out in 1997. We sampled 31 stations over 5 days along four transects and assessed horizontal and vertical distribution patterns, community composition and plankton trophodynamics. Plankton abundance was enhanced near-coast and across the pycnocline, and communities differed between regions. Polar cod (Boreogadus saida) and the sandeel (Ammodytes sp.) were among the abundant fish larvae. Productivity/growth estimates of key species of copepods and fish larvae showed no apparent relationship to food availability; they reached weight specific values of ?6% day?1 for copepods and ?14% day?1 for fish larvae. Overall, we found a rich and dynamic plankton community, strongly influenced by the complex hydrography of the area. Thus, changes in physical characteristics of the bay could threaten the resilience of its ecosystem.

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

    KAUST Repository

    Vestheim, Hege

    2013-11-11

    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.

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

    CERN Document Server

    Bans, Alissa; Uribe, Ana

    2015-01-01

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

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

    Directory of Open Access Journals (Sweden)

    R. Bozzano

    2013-08-01

    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.

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

    OpenAIRE

    Sugiyama, Kazuyasu; Takemura, Fumio

    2008-01-01

    Deformation-induced lateral migration of a bubble slowly rising near a vertical plane wall in a stagnant liquid is numerically and theoretically investigated. In particular, our focus is set on a situation with a small clearance $c$ between the bubble interface and the wall. Motivated by the fact that experimentally measured migration velocity (Takemura et al. (2002, J. Fluid Mech. {\\bf 461}, 277)) is higher than the velocity estimated by the available analytical solution (M...

  4. Distribution of zooplankton biomass at three seamounts in the NE Atlantic

    Science.gov (United States)

    Martin, Bettina; Christiansen, Bernd

    2009-12-01

    During different seasons of the years 2003-2005 in the NE Atlantic, zooplankton were sampled with a MOCNESS (multiple opening/closing net and environmental sensing system, mesh size 333 ?m) above the slopes and summits of Seine, Sedlo and Ampère seamounts and at remote reference sites outside the influence of the seamounts (far field). Wet weights of different zooplankton size classes (2 cm) were measured. Night and day hauls were analysed in order to detect diel vertical migrations of the zooplankton, as well as a possible trapping effect due to the shallow topography. Biomass concentrations, independent of daytime, season and summit height, were reduced above the summits at all three seamounts compared to the slope and far-field sites. No trapping effect or retention of biomass was apparent above the seamounts. The vertical distribution patterns of the size class 0.5 cm were nearly absent above the summits of Seine and Ampère seamounts, but considerable numbers were found above the slopes and at the far-field sites. Possible explanations for the observed distribution patterns of zooplankton biomass and size classes are discussed, including retention and lateral advection due to the hydrography at the seamounts, as well as predation by resident seamount fish.

  5. Long-term acoustical observations of the mesopelagic fish Maurolicus muelleri reveal novel and varied vertical migration patterns

    KAUST Repository

    Staby, A

    2011-11-15

    We studied the temporal dynamics in the vertical distribution of Maurolicus muelleri scattering layers (SL) by examining continuous acoustic recordings over a 15 mo period in Masfjorden, Norway, complemented by intermittent sampling campaigns. The data revealed known patterns as normal diel vertical migration (DVM), midnight sinking between dusk and dawn, and periods without migrations, as well as novel behaviours consisting of early morning ascents, reverse diel vertical migrations, and interrupted ascents in the evening. During the first autumn of the study, adult fish modified their normal DVM behaviour by suspending their migration in the evening, yet ascending toward the surface in the later part of the night to reach upper layers during dawn. This behaviour was not observed during the second autumn of the study. By mid- to end of November (1st autumn), adult fish had suspended the nocturnal ascent entirely, and in the subsequent period until the end of January, a fraction of the population rather performed limited reverse migrations, slightly shifting their vertical distribution upwards during the first part of the day. From January to March 2008, fish interrupted their evening ascent at apparently random intervals and returned to deeper waters, instead of completing a full ascent to the surface. Our study underlines the value of long-term recordings, with the results suggesting that M. muelleri has the capability of changing its behaviour in response to ontogeny and internal state (satiation and hunger) as well as to external stimuli.

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

    OpenAIRE

    Hanazato, Takayuki; Oda, Shigeto

    2008-01-01

    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 in...

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

    International Nuclear Information System (INIS)

    The objective of this study was to identify the effect of lag time and residual water saturation on the vertical migration of Cryptosporidium parvum oocysts under transient flow conditions experienced across vegetated filter strips (VFS) receiving runoff from livestock areas. The vertical migration of C. parvum oocysts through unsaturated soils was studied in laboratory sand columns. Approximately 1x105 C. parvum oocysts and 1x105 carboxylated latex microspheres (4.5 ?m diameter, Polysciences, Inc.) were applied to the top of sand columns at the beginning of each run. Transient water applications to the top of the sand columns (73 cm per hour) simulated an unusually high rate of pond overflow to the inlet area of a VFS after a large storm event, followed by a lag period of either 4 or 48 hours and a repeated water application. Residual water saturation conditions, during the lag period, were controlled to either 2.9 or 12.6 percent by applying a mild vacuum to the bottom of the sand column. The oocysts and microspheres were enumerated along the sand column profile using epifluorescence microscopy. The median travel distance for oocysts was 8.7 ± 1.1 cm at 12.6 percent residual saturation versus 6.7 ± 0.8 cm for 2.9 percent residual saturation. Lag time did not have a statistically significant effect on median travel distance. The study indicates that surface applied C. parvum oocysts have limited mobility through a uniform unsaturated sand med through a uniform unsaturated sand medium experiencing high rates of transient water infiltration. (author)

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

    International Nuclear Information System (INIS)

    Vertical migration of pollutants through unsaturated zone is a complicated process and is affected by a number of factors like type of soil, its chemical properties, or organic matter content, in addition to climatic conditions and biological activity of microorganisms in soil. Soil properties that influence water movement through unsaturated zone are important for determining flow paths, reactions between soil and pollutants and the ultimate destination of these pollutants, and may improve the diagnosis of the potential pollution risk. Three soil cores were sampled to a depth up to 100 cm from cultivated clayey soil, sewage irrigated sandy soil and fertilized sandy soil. The samples were collected at intervals of 5 or 10 cm. The ?13C signature of the soil shifted significantly towards that of C3-type vegetation in soil cores. The general trend toward heavier 13C enrichment with depth could be due to isotopic fractionation occurring during decomposition of soil organic matters. Increased ?15N with depth in the soil cores suggests that microbial mineralization, denitrification, or volatilization processes caused the enriched ?15N signatures. Decreasing nitrogen percent and nitrate values with depth also help support the idea of microbiological processes. The results indicate that concentrations of major and trace elements varied widely among the different soil types and decreased with depths in the studied soil 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

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

    Science.gov (United States)

    Turner, Jefferson T.

    2015-01-01

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

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

    Science.gov (United States)

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

    2013-03-01

    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.

  11. Providing food for zooplankton in the aboratory

    International Nuclear Information System (INIS)

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

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

    Science.gov (United States)

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

    2014-08-01

    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.

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

    Directory of Open Access Journals (Sweden)

    Fasil Degefu

    2014-11-01

    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.

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

    Science.gov (United States)

    Fleischer, Guy W.; TeWinkel, Leslie M.

    1998-01-01

    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.

  15. Migrant biomass and respiratory carbon flux by zooplankton and micronekton in the subtropical northeast Atlantic Ocean (Canary Islands)

    Science.gov (United States)

    Ariza, A.; Garijo, J. C.; Landeira, J. M.; Bordes, F.; Hernández-León, S.

    2015-05-01

    Diel Vertical Migration (DVM) in marine ecosystems is performed by zooplankton and micronekton, promoting a poorly accounted export of carbon to the deep ocean. Major efforts have been made to estimate carbon export due to gravitational flux and to a lesser extent, to migrant zooplankton. However, migratory flux by micronekton has been largely neglected in this context, due to its time-consuming and difficult sampling. In this paper, we evaluated gravitational and migratory flux due to the respiration of zooplankton and micronekton in the northeast subtropical Atlantic Ocean (Canary Islands). Migratory flux was addressed by calculating the biomass of migrating components and measuring the electron transfer system (ETS) activity in zooplankton and dominant species representing micronekton (Euphausia gibboides, Sergia splendens and Lobianchia dofleini). Our results showed similar biomass in both components. The main taxa contributing to DVM within zooplankton were juvenile euphausiids, whereas micronekton were mainly dominated by fish, followed by adult euphausiids and decapods. The contribution to respiratory flux of zooplankton (3.4 ± 1.9 mg C m-2 d-1) was similar to that of micronekton (2.9 ± 1.0 mg C m-2 d-1). In summary, respiratory flux accounted for 53% (range 23-71) of the gravitational flux measured at 150 m depth (11.9 ± 5.8 mg C m-2 d-1). However, based on larger migratory ranges and gut clearance rates, micronekton are expected to be the dominant component that contributes to carbon export in deeper waters. Micronekton estimates in this paper as well as those in existing literature, although variable due to regional differences and difficulties in calculating their biomass, suggest that carbon fluxes driven by this community are important for future models of the biological carbon pump.

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

    DEFF Research Database (Denmark)

    Schultz, J.; Peck, M.A.

    2012-01-01

    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

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

    Czech Academy of Sciences Publication Activity Database

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

    2008-01-01

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

  18. 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)

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

    2006-04-01

    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.

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

    Science.gov (United States)

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

    2007-01-01

    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 .

  20. 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)

  1. Vertical Migration of Meloidogyne chitwoodi and M. hapla under Controlled Temperature.

    Science.gov (United States)

    Pinkerton, J N; Mojtahedi, H; Santo, G S; O'Bannon, J H

    1987-04-01

    Migratory ability of second-stage juveniles (J2) of two Meloidogyne chitwoodi races and a M. hapla population were compared in soil-filled columns at 12, 18, and 24 C. J2 of all populations migrated farthest at 18 C and least at 12 C. Nematode survival was significantly reduced (P = 0.05) at 24 C.M. chitwoodi J2 migrated further and in greater numbers than M. hapla J2 at all temperatures. A comparison with and without a host plant demonstrated no preferential migration toward the plant. Water percolation through the migration columns stimulated upward migration. PMID:19290123

  2. 137Cs vertical migration in a deciduous forest soil following the Fukushima Dai-ichi Nuclear Power Plant accident.

    Science.gov (United States)

    Nakanishi, Takahiro; Matsunaga, Takeshi; Koarashi, Jun; Atarashi-Andoh, Mariko

    2014-02-01

    The large amount of (137)Cs deposited on the forest floor because of the Fukushima Dai-ichi Nuclear Power Plant accident represents a major potential long-term source for mobile (137)Cs. To investigate (137)Cs mobility in forest soils, we investigated the vertical migration of (137)Cs 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 (137)Cs in the litter layer moved into the mineral soil within one year after the accident. On the other hand, the topsoil prevented migration of (137)Cs, and only 2% of (137)Cs 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 (137)Cs inventory. Therefore, the migration of (137)Cs by seepage water comprised only a very small part of the total (137)Cs inventory in the mineral soil, which was undetectable from the vertical distribution of (137)Cs in the soil profile. In the present and immediate future, most of the (137)Cs deposited on the forest floor will probably remain in the topsoil successively, although a small but certain amount of bioavailable (137)Cs exists in forest surface soil. PMID:24239654

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

    Science.gov (United States)

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

    2006-06-01

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

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

    DEFF Research Database (Denmark)

    Sainmont, Julie; Gislason, Astthor

    2014-01-01

    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.

  5. 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

  6. Assessment of brine migration risks along vertical pathways due to CO2 injection

    Science.gov (United States)

    Kissinger, Alexander; Class, Holger

    2015-04-01

    Global climate change, shortage of resources and the growing usage of renewable energy sources has lead to a growing demand for the utilization of subsurface systems. Among these competing uses are Carbon Capture and Storage (CCS), geothermal energy, nuclear waste disposal, 'renewable' methane or hydrogen storage as well as the ongoing production of fossil resources like oil, gas and coal. Additionally, these technologies may also create conflicts with essential public interests such as water supply. For example, the injection of CO2 into the subsurface causes an increase in pressure reaching far beyond the actual radius of influence of the CO2 plume, potentially leading to large amounts of displaced salt water. In this work we focus on the large scale impacts of CO2 storage on brine migration but the methodology and the obtained results may also apply to other fields like waste water disposal, where large amounts of fluid are injected into the subsurface. In contrast to modeling on the reservoir scale the spatial scale required for this work is much larger in both vertical and lateral direction, as the regional hydrogeology has to be considered. Structures such as fault zones, hydrogeological windows in the Rupelian clay or salt domes are considered as potential pathways for displaced fluids into shallow systems and their influence has to be taken into account. We put the focus of our investigations on the latter type of scenario, since there is still a poor understanding of the role that salt diapirs would play in CO2 storage projects. As there is hardly any field data available on this scale, we compare different levels of model complexity in order to identify the relevant processes for brine displacement and simplify the modeling process wherever possible, for example brine injection vs. CO2 injection, simplified geometries vs. the complex formation geometry and the role of salt induced density differences on flow. Further we investigate the impact of the displaced brine due to CO2 injection and compare it to the natural fluid exchange between shallow and deep aquifers in order to asses possible damage.

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

    DEFF Research Database (Denmark)

    Nilsson, Lars Anders Fredrik; Thygesen, Uffe HØgsbro

    2003-01-01

    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.

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

    Science.gov (United States)

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

    2009-10-01

    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.

  9. Vertical Migration of Meloidogyne chitwoodi and M. hapla under Controlled Temperature

    OpenAIRE

    Pinkerton, J. N.; Mojtahedi, H.; Santo, G. S.; O'Bannon, J. H.

    1987-01-01

    Migratory ability of second-stage juveniles (J2) of two Meloidogyne chitwoodi races and a M. hapla population were compared in soil-filled columns at 12, 18, and 24 C. J2 of all populations migrated farthest at 18 C and least at 12 C. Nematode survival was significantly reduced (P = 0.05) at 24 C.M. chitwoodi J2 migrated further and in greater numbers than M. hapla J2 at all temperatures. A comparison with and without a host plant demonstrated no preferential migration toward the plant. Water...

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

    Science.gov (United States)

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

    2015-02-01

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

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

    Science.gov (United States)

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

    2009-12-01

    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.

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

    Directory of Open Access Journals (Sweden)

    Carlos E. L. Esbérard

    2011-12-01

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

  13. Composición taxonómica del zooplancton superficial en el Pacífico colombiano (septiembre 2003) / Taxonomic composition of the surface zooplankton in the Colombian Pacific (September 2003)

    Scientific Electronic Library Online (English)

    Alan, Giraldo; Erica, Gutiérrez.

    2007-05-01

    Full Text Available Se realizó el análisis cualitativo y cuantitativo del zooplancton costero y oceánico del Pacífico colombiano para caracterizar la composición de la comunidad. La abundancia de zooplancton estuvo entre 7.900 y 100.500 ind·100 m-3. Se identificaron 26 grupos taxonómicos, siendo los copépodos los más a [...] bundantes, seguidos de los quetognatos. No se detectaron diferencias significativas en la abundancia de zooplancton entre la zona costera y oceánica. Similar patrón se observó entre las colectas diurnas y nocturnas. La ausencia de diferencias en la abundancia, tanto espacial (costa-océano) como temporalmente (circadiano), probablemente son el resultado del efecto del tipo de muestreo realizado (arrastre superficial), el cual no permitió visualizar adecuadamente el patrón general de migración vertical de los organismos zooplanctónicos Abstract in english A qualitative and quantitative analysis of coastal and oceanic zooplankton in the Colombian Pacific was carried out in order to characterize the composition of this community. Zooplankton abundance was between 7,900 and 100,500 ind·100 m-3. A total of 26 taxonomic groups were identified, with copepo [...] ds being the most abundant, followed by chaetognaths. No significant differences were detected between zooplankton abundance in coastal and oceanic zones. Similar patterns were observed for diurnal and nocturnal samplings. The lack of spatial (coastal-oceanic) and temporal (circadian) differences in abundance is probably a result of the type of sampling carried out (surface trawling), which did not allow adequate visualization of the general vertical migration pattern of the zooplanktonic organisms

  14. Composición taxonómica del zooplancton superficial en el Pacífico colombiano (septiembre 2003 Taxonomic composition of the surface zooplankton in the Colombian Pacific (September 2003

    Directory of Open Access Journals (Sweden)

    Alan Giraldo

    2007-05-01

    Full Text Available Se realizó el análisis cualitativo y cuantitativo del zooplancton costero y oceánico del Pacífico colombiano para caracterizar la composición de la comunidad. La abundancia de zooplancton estuvo entre 7.900 y 100.500 ind·100 m-3. Se identificaron 26 grupos taxonómicos, siendo los copépodos los más abundantes, seguidos de los quetognatos. No se detectaron diferencias significativas en la abundancia de zooplancton entre la zona costera y oceánica. Similar patrón se observó entre las colectas diurnas y nocturnas. La ausencia de diferencias en la abundancia, tanto espacial (costa-océano como temporalmente (circadiano, probablemente son el resultado del efecto del tipo de muestreo realizado (arrastre superficial, el cual no permitió visualizar adecuadamente el patrón general de migración vertical de los organismos zooplanctónicosA qualitative and quantitative analysis of coastal and oceanic zooplankton in the Colombian Pacific was carried out in order to characterize the composition of this community. Zooplankton abundance was between 7,900 and 100,500 ind·100 m-3. A total of 26 taxonomic groups were identified, with copepods being the most abundant, followed by chaetognaths. No significant differences were detected between zooplankton abundance in coastal and oceanic zones. Similar patterns were observed for diurnal and nocturnal samplings. The lack of spatial (coastal-oceanic and temporal (circadian differences in abundance is probably a result of the type of sampling carried out (surface trawling, which did not allow adequate visualization of the general vertical migration pattern of the zooplanktonic organisms

  15. Zooplankton from Lake Magelungen, Central Sweden 1960-1963

    Energy Technology Data Exchange (ETDEWEB)

    Almquist, Elisabeth

    1970-11-15

    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

  16. 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

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

    Scientific Electronic Library Online (English)

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

    2011-12-01

    Full Text Available Migration is defined as a seasonal and cyclic population movement observed in all animal classes and studied mainly in vertebrates. A considerable part of the knowledge on migration comes from birds, for which migration is an important aspect of their biology. In the case of bats, females usually 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.

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

    DEFF Research Database (Denmark)

    Boje, Jesper; Neuenfeldt, Stefan

    2014-01-01

    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

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

    International Nuclear Information System (INIS)

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

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

    Science.gov (United States)

    Malvandi, A.; Ganji, D. D.

    2015-02-01

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

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

    OpenAIRE

    Spinesi, Luca

    2005-01-01

    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...

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

    CERN Document Server

    Sugiyama, Kazuyasu

    2008-01-01

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

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

    CERN Document Server

    Uribe, Ana; Königl, Arieh

    2015-01-01

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

  4. Marine zooplankton studies in Brazil: a brief evaluation and perspectives

    Scientific Electronic Library Online (English)

    Rubens M., Lopes.

    2007-09-01

    Full Text Available 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.

  5. Marine zooplankton studies in Brazil: a brief evaluation and perspectives

    Directory of Open Access Journals (Sweden)

    Rubens M. Lopes

    2007-09-01

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

  6. Microplastic ingestion by zooplankton.

    Science.gov (United States)

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

    2013-06-18

    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

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

    Directory of Open Access Journals (Sweden)

    Takayuki HANAZATO

    2008-08-01

    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.

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

    Directory of Open Access Journals (Sweden)

    Sergio Palma

    2004-01-01

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

  9. Zooplankton body composition

    DEFF Research Database (Denmark)

    KiØrboe, Thomas

    2013-01-01

    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

  10. 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

    Directory of Open Access Journals (Sweden)

    Paul Kaufmann

    2011-09-01

    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

  11. 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)

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

    2011-09-01

    Full Text Available 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

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

    OpenAIRE

    Probst, Wolfgang Nikolaus; Eckmann, Reiner

    2009-01-01

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

  13. Zooplankton of West Madagascar

    Science.gov (United States)

    Bemiasa, John; Remanevy, Sitraka

    2014-05-01

    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 Madagascar.

  14. 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)

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

    2009-08-01

    Full Text Available 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

  15. Zooplankton - Study methods, importance and significant observations

    Digital Repository Service at National Institute of Oceanography (India)

    Gajbhiye, S.N.

    2002-01-01

    The intent of this section is to review briefly current knowledge of the structure and dynamics of the zooplankton and its ecology. Zooplankton are mysids of animal organisms that drift with currents. In an aquatic ecosystem zooplankton form...

  16. Changes in zooplankton habitat, behavior, and acoustic scattering characteristics across glider-resolved fronts in the Southern California Current System

    Science.gov (United States)

    Powell, Jesse R.; Ohman, Mark D.

    2015-05-01

    We report cross-frontal changes in the characteristics of plankton proxy variables measured by autonomous Spray ocean gliders operating within the Southern California Current System (SCCS). A comparison of conditions across the 154 positive frontal gradients (i.e., where density of the surface layer decreased in the offshore direction) identified from six years of continuous measurements showed that waters on the denser side of the fronts typically showed higher Chl-a fluorescence, shallower euphotic zones, and higher acoustic backscatter than waters on the less dense side. Transitions between these regions were relatively abrupt. For positive fronts the amplitude of Diel Vertical Migration (DVM), inferred from a 3-beam 750 kHz acoustic Doppler profiler, increased offshore of fronts and covaried with optical transparency of the water column. Average interbeam variability in acoustic backscatter also changed across many positive fronts within 3 depth strata (0-150 m, 150-400 m, and 400-500 m), revealing a front-related change in the acoustic scattering characteristics of the assemblages. The extent of vertical stratification of distinct scattering assemblages was also more pronounced offshore of positive fronts. Depth-stratified zooplankton samples collected by Mocness nets corroborated the autonomous measurements, showing copepod-dominated assemblages and decreased zooplankton body sizes offshore and euphausiid-dominated assemblages with larger median body sizes inshore of major frontal features.

  17. 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)

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

    Science.gov (United States)

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

    2005-01-01

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

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

    Science.gov (United States)

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

    2015-01-01

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

  20. Vertical Migrations and Feeding Rhythms of Acartia clausi and Pseudodiaptomus hessei (Copepoda: Calanoida) in a Tropical Lagoon (Ebrié, Côte d'Ivoire)

    Science.gov (United States)

    Kouassi, E.; Pagano, M.; Saint-Jean, L.; Arfi, R.; Bouvy, M.

    2001-06-01

    Diel changes in vertical distribution and gut pigment contents of Acartia clausi and Pseudodiaptomus hessei were studied during several 24-h time series performed between 1993 and 1997 in four sites of the Ebrié Lagoon (Côte d'Ivoire). The sites differed by their morphology and their hydrological structure and by the vertical distribution of chlorophyll biomass. Both species showed classical diel vertical migrations (DVM). Copepodites and adult stages of P. hessei were almost benthic during the day and evenly distributed through the water column at night. The amplitude of DVM of A. clausi increased from copepodites I-III to adults. Copepodites and adults of A. clausi increased significantly their gut fluorescence at night, whereas those of P. hessei showed no clear diel feeding rhythm (DFR). These results suggest that A. clausi feed mostly at night on phytoplanktonic particles and P. hessei feed mostly on benthic algal particles during the day and on sestonic particles at night. No relationship was observed between DFR and DVM because both patterns occurred when food was either vertically homogeneous or vertically stratified. The daily average gut fluorescence of A. clausi increased with ambient chlorophyll concentration until around 12-15 ?g l -1, whereas no relationship was found for P. hessei. The implication of these patterns on the adaptation capacities and the behaviour of the two species are discussed. The DVM of P. hessei should explain its rarity in the estuarine area. The comparison of our results with previous ones suggests an evolution of A. clausi DFR between 1981-1982 and 1996-1997, in relation to an intensification of eutrophication.

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

    OpenAIRE

    Chukwuka, K. S.; Uka, U. N.

    2007-01-01

    The effects of water hyacinth infestation on the distribution, abundance and species composition of zooplankton in Awba reservoir were investigated. Samples were collected in each of the sampling areas (water hyacinth infested and open water) by vertical zooplankton hauls using 64 um bolting silk net. The samples were immediately fixed in 4% formalin for preservation. The species composition of the zooplankton from the sampled areas consisted of 3 taxa, comprising of 6 species of Cladocera (M...

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

    Science.gov (United States)

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

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

    Science.gov (United States)

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

    2005-01-01

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

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

    International Nuclear Information System (INIS)

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

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

    International Nuclear Information System (INIS)

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

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

    Science.gov (United States)

    Probst, W N; Eckmann, R

    2009-01-01

    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

  7. 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)

    Hinrichsen, Hans-Harald; Peck, Myron A.

    2010-01-01

    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.

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

    Scientific Electronic Library Online (English)

    Rubén, Escribano.

    2006-10-01

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

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

    Energy Technology Data Exchange (ETDEWEB)

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

    2011-04-15

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

  10. 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.

  11. 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

  12. 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)

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

    2008-12-01

    Full Text Available 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.

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

    Science.gov (United States)

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

    2009-12-01

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

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

    Directory of Open Access Journals (Sweden)

    G. Economou

    2008-08-01

    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.

  15. 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

    OpenAIRE

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

    2010-01-01

    The aim of this work was to evaluate whether diel vertical migration of microcrustaceans from Lake Monte Alegre is related to invertebrate predators, namely larvae of Chaoborus brasiliensis. The hypothesis tested in the experiments was that the migratory behaviour of prey would depend on physical contact with Chaoborus brasiliensis larvae or with kairomones released by them. Two experiments were undertaken in the laboratory, with two treatments and three replicates each. Experiments were carr...

  16. Three-dimensional acoustic visualization of zooplankton patchiness

    Science.gov (United States)

    Greene, Charles H.; Wiebe, Peter H.; Pelkie, Chris; Benfield, Mark C.; Popp, Jacqueline M.

    Acoustic data were collected and visualized to characterize the 3-dimensional patchiness of zooplankton at a thermally stratified site on Georges Bank. The work was carried out as part of a field study conducted to examine the effects of springtime water-column stratification on the distributions of zooplankton and larval fish on the Bank. The acoustic data were acquired as the ship steamed a survey grid relative to the track of a surface drifter with a subsurface drogue. Although quite irregular in geographical coordinate space, the ship's track relative to the moving water closely matched the intended grid pattern once the drifter's movement in the tidal flow was taken into account. After changing coordinate systems to compensate for tidal advection, the acoustic data set was transformed from its curtain-like distribution in 3-dimensional space to a volumetric distribution. Two-dimensional point kriging was performed on the irregularly spaced data from each 2-m-thick depth stratum to produce a series of 2-dimensional, regularly spaced data grids. These data grids were then stacked to construct the 3-dimensional data grid required for volumetric visualization. A similar procedure was followed with the error variance values produced at each grid point through kriging to construct a 3-dimensional, volumetric distribution of the error variance. To examine zooplankton patchiness within the surveyed volume of water, isosurfaces corresponding to specific levels of acoustic backscatter were highlighted in the visualization. The 3-dimensional distribution of error variance was used to control the opacity of the isosurfaces to provide an objective, visual approach for displaying the statistical confidence one can have in the patches detected. In this survey, the ship steamed directly over a large, southwest- to northeast-oriented patch of zooplankton on at least three different passes. It also steamed over several smaller patches. The vertically compressed nature of the patches and their high degree of spatial heterogeneity in the horizontal plane are characteristic of the zooplankton distributions found in the deeper, seasonally stratified portions of Georges Bank.

  17. 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)

    Armando, Mujica; María L, Nava.

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

  18. Fish-mediated trait compensation in zooplankton

    DEFF Research Database (Denmark)

    Hylander, Samuel; Souza, M.S.

    2012-01-01

    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

  19. Trait-based approaches to zooplankton communities

    DEFF Research Database (Denmark)

    Lichtman, E.; Ohman, M.D.

    2013-01-01

    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

  20. Zooplankton

    Digital Repository Service at National Institute of Oceanography (India)

    Jyothibabu, R.; Madhu, N.V.

    2007-01-01

    microbes in the Sea; Marine Ecology Progress Series 10 257?263. Bhosle N. B. (2006) Butyltin compounds in biofilms and marine organisms from Dona Paula Bay west coast of India; In: Multiple dimensions of global environmental change (ed.) Sangeeta Sonak (New...

  1. Zooplankton distribution and behaviour in the Southern Ocean from surveys with a towed Optical Plankton Counter

    Science.gov (United States)

    Pollard, R. T.; Bathmann, U.; Dubischar, C.; Read, J. F.; Lucas, M.

    Spatial distributions of zooplankton with lengths between about 500 ?m and 8 mm are described from surveys in the vicinity of the Antarctic Polar Front in austral summer 1995/6 using an Optical Plankton Counter mounted on a towed profiling SeaSoar. The distributions, split into several logarithmically spaced size classes, are compared and related to the physical environment south of the Polar Front in the Antarctic Zone and within the Polar Frontal Zone. They also are compared with phytoplankton distributions determined from surface chlorophyll data. Both phytoplankton and zooplankton carbon densities are low in the Antarctic Zone (2-3 g C m -2), but rise to larger values in the Polar Frontal Zone (5-7 g C m -2 for zooplankton and a maximum of 6 g C m -2 at fronts for phytoplankton). Calibration of OPC derived zooplankton biovolume to carbon was achieved by comparison with dry weights from multinet samples deployed in conjunction with CTD casts. The net data showed that over 98% of zooplankton counts were copepods. Diel behaviour also was examined. Only larger copepods (over 2 mm long) displayed significant diel migration, and then only 10-20% of the standing stock; the majority remained deeper than about 100 m and their distribution patterns suggest that they may be retained aside from the main frontal jets by ageostrophic circulations associated with the front. Copepods shorter than 2 mm rose from depth over the month-long survey to become concentrated in the surface layer (the top 70-100 m). The largest copepods that could be resolved, with lengths of about 4-8 mm (possibly Rhincalanus gigas), displayed unexpected behaviour in tending to migrate to the top 0-10 m by day, descending to 40-50 m each night.

  2. Toxic effects of domestic sewage on zooplankton

    Digital Repository Service at National Institute of Oceanography (India)

    Gajbhiye, S.N.; Nair, V.R.; Desai, B.N.

    1987-01-01

    The toxic effects of raw domestic sewage on different groups of zooplank-ton, was tested in the laboratory for evaluating acute toxicity. 24 hr., LC-50 values for larvae of stomatopods, gastropods and chaetognaths (2-7% concentration) indicated...

  3. A Review: Potentiality of Zooplankton as Bioindicator

    OpenAIRE

    Zannatul Ferdous; A. K.M Muktadir

    2009-01-01

    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, temp...

  4. Future marine zooplankton research - a perspective

    DEFF Research Database (Denmark)

    Bathmann, U.; Bundy, M.H.

    2001-01-01

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

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

    OpenAIRE

    Acabado, Cristy S.; Campos, Wilfredo L.; Noblezada, Mary Mar P.; Estremadura, Dm G.

    2010-01-01

    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...

  6. Zooplankton ecology of the mangrove habitats of Goa

    Digital Repository Service at National Institute of Oceanography (India)

    Goswami, S.C.

    1992-01-01

    of its physico-chemical parameters, water depth, turbidity, tidal amplitude and organic matter. Zooplankton standing stock (biomass) values in mangroves were low as compared to contiguous estuarine and neritic biotopes. Micro-zooplankton, crustaceans...

  7. Zooplankton communities in the Krenceng Reservoair, Cilegon, Banten

    Directory of Open Access Journals (Sweden)

    Mufti P. Patria

    2005-11-01

    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.

  8. Zooplankton characteristics of the coastal ecosystem off Bombay, India

    Digital Repository Service at National Institute of Oceanography (India)

    Nair, V.R.; Ramaiah, Neelam

    1998-01-01

    The nearshore waters of Bombay sustain a rich and diverse zooplankton fauna. Continuous observations for a period of 15 months indicated a variation from 0.4 to 19.9 mg C.m sup(3) (av. 4.3 mg C.m sup(-3)) in zooplankton biomass. The zooplankton...

  9. A Review: Potentiality of Zooplankton as Bioindicator

    Directory of Open Access Journals (Sweden)

    Zannatul Ferdous

    2009-01-01

    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.

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

    Science.gov (United States)

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

    2014-11-01

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

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

    Directory of Open Access Journals (Sweden)

    K.S. Chukwuka

    2007-01-01

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

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

    Directory of Open Access Journals (Sweden)

    WJ. Minto

    2010-02-01

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

  13. 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)

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

    2010-02-01

    Full Text Available 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.

  14. The flow of nitrogen into the euphotic zone of the Baltic Proper as a result of the vertical migration of phytoplankton: An analysis of the long-term observations and ecohydrodynamic model simulation

    Science.gov (United States)

    Kowalewski, Marek

    2015-05-01

    The effect of the vertical migration (VM) of phytoplankton on the depletion of mineral nitrogen in the water layer intermediate between the thermocline and halocline during the summer thermal stratification of the Baltic Proper was investigated. The flux of nitrogen transported to the mixed layer from the intermediate layer beneath it was estimated on the basis of long-term observations (1970-2000) made in spring and summer at station BY15 in the Gotland Deep (central part of the Baltic Proper). The total nitrogen flux was estimated at ca 60 mmol m- 2 month- 1 in spring and at ca 4.7 mmol m- 2 month- 1 in summer. The total transport of nitrogen to the euphotic zone from April to August was estimated at 129 mmol m- 2 which, assuming the Redfield ratio to hold, corresponds to a new primary production of ca 10.3 gC m- 2. The deep chlorophyll maxima linked to the VM of phytoplankton may not be remotely sensed, which causes the level of primary production calculated on their basis to be somewhat underestimated. The ProDeMo ecohydrodynamic model was modified in such a way as to take account of the VM of dinoflagellates. Comparison of the model results with measured vertical distributions of mineral nitrogen enabled the choice of an appropriate numerical algorithm and confirmed the hypothesis that dinoflagellate VM may be responsible for the depletion of mineral nitrogen beneath the thermocline.

  15. Zooplankton assemblage of Oyun Reservoir, Offa, Nigeria

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    Moshood K Mustapha

    2009-12-01

    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.

  16. Experiments with vertically and laterally migrating subsurface explosions with applications to the geology of phreatomagmatic and hydrothermal explosion craters and diatremes

    Science.gov (United States)

    Valentine, Greg A.; Graettinger, Alison H.; Macorps, Élodie; Ross, Pierre-Simon; White, James D. L.; Döhring, Erika; Sonder, Ingo

    2015-03-01

    We present results of experiments that use small chemical explosive charges buried in layered aggregates to simulate the effects of subsurface hydrothermal and phreatomagmatic explosions at varying depths and lateral locations, extending earlier experimental results that changed explosion locations only along a vertical axis. The focus is on the resulting crater size and shape and subcrater structures. Final crater shapes tend to be roughly circular if subsurface explosion epicenters occur within each other's footprints (defined as the plan view area of reference crater produced by a single explosion of a given energy, as predicted by an empirical relationship). Craters are elongate if an epicenter lies somewhat beyond the footprint of the previous explosion, such that their footprints overlap, but if epicenters are too far apart, the footprints do not overlap and separate craters result. Explosions beneath crater walls formed by previous blasts tend to produce inclined (laterally directed) ejecta jets, while those beneath crater centers are vertically focused. Lateral shifting of explosion sites results in mixing of subcrater materials by development of multiple subvertical domains of otherwise pure materials, which progressively break down with repeated blasts, and by ejection and fallback of deeper-seated material that had experienced net upward displacement to very shallow levels by previous explosions. A variably developed collar of material that experienced net downward displacement surrounds the subvertical domains. The results demonstrate key processes related to mixing and ejection of materials from different depths during an eruptive episode at a maar-diatreme volcano as well as at other phreatomagmatic and hydrothermal explosion sites.

  17. Distribution and diversity of Zooplanktons in Madhya Pradesh, India

    Directory of Open Access Journals (Sweden)

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

    2013-03-01

    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.

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

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    Ahmet Nuri Tarkan

    2005-01-01

    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.

  19. Zooplankton composition in Dharamtar creek adjoining Bombay harbour

    Digital Repository Service at National Institute of Oceanography (India)

    Tiwari, L.R.; Nair, V.R.

    1993-01-01

    Dharamtar creek (Bombay, India) creek maintained rich zooplankton standing stock (av. 30.3 ml 100 m/3) with peak production during August-November. Zooplankton production rate for the entire system amounted to 10.32 mg C.100 m/3 d/1 with an annual...

  20. Metals in coastal zooplanktons - A coastal living resource hazard

    Digital Repository Service at National Institute of Oceanography (India)

    Paimpillil, J.S.; Joseph, T.; Rejomon, G.; Gerson, V.J.

    2010-01-01

    and euphausids. The trace metals were generally low in water column and in the zooplanktons, except in the vicinity of two major ports. The metal content trend in the zooplankton had a decreasing tendency as Fe>Zn>Mn>Cu>Ni>Co>Cd>Cr>Pb. The concentration factor...

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

    International Nuclear Information System (INIS)

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

  2. Upslope transport of near-bed zooplankton

    Science.gov (United States)

    Zimmer, Cheryl Ann

    2009-09-01

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

  3. Zooplankton assemblage of Oyun Reservoir, Offa, Nigeria

    Scientific Electronic Library Online (English)

    Moshood K, Mustapha.

    2009-12-01

    Full Text Available 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.

  4. 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)

    V. Raybaud

    2008-05-01

    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.

  5. Migration dynamics

    OpenAIRE

    Vergalli, Sergio; Moretto, Michele

    2002-01-01

    This paper tries to explain why most migration flows show some observable jumps in their processes, a phenomenon that seems to be sympathetic with the characteristic of irreversibility of migration. We present a real option model where the choice to migrate depends on both the differential wage between the host country and the country of origin, and on the probability of being fully integrated into the host country. The theoretical results show that the optimal migration decision of a single ...

  6. Zooplankton use of chemodetection to find and eat particles

    DEFF Research Database (Denmark)

    Jackson, G.A.; KiØrboe, Thomas

    2004-01-01

    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.

  7. Zooplankton data collected from THOMAS G. THOMPSON in TOGA Area of Pacific Ocean from zooplankton net casts; 30 January 1992 to 21 October 1992 (NODC Accession 9700054)

    National Oceanic and Atmospheric Administration, Department of Commerce — Zooplankton data were collected using zooplankton net casts in the TOGA Area of Pacific Ocean from THOMAS G. THOMPSON. Data were collected from 30 January 1992 to...

  8. Zooplankton species identities and other data collected from zooplankton net casts in the NE Atlantic Ocean from DISCOVERY; 12 November 1969 to 01 July 1988 (NODC Accession 9500097)

    National Oceanic and Atmospheric Administration, Department of Commerce — Zooplankton species identities and other data were collected by DISCOVERY using zooplankton net casts in the Northeast Atlantic Ocean. Data were collected from 12...

  9. Zooplankton data collected from zooplankton net by PERVENETS in the Bering Sea from 13 July 1959 to 12 August 1959 (NODC Accession 9500034)

    National Oceanic and Atmospheric Administration, Department of Commerce — Zooplankton data were collected by PERVENETS using zooplankton net casts in the Bering Sea. Data were collected from 13 July 1959 to 12 August 1959 by Pacific...

  10. Rostock zooplankton studies off West Africa

    Science.gov (United States)

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

    1995-03-01

    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.

  11. Bacterial diversity associated with freshwater zooplankton

    DEFF Research Database (Denmark)

    Grossart, Hans-Peter; Dziallas, Claudia

    2009-01-01

    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.

  12. A multivariate evaluation of environmental effects on zooplankton community structure in the western North Atlantic

    Science.gov (United States)

    Pepin, Pierre; Johnson, Catherine L.; Harvey, Michel; Casault, Benoit; Chassé, Joël; Colbourne, Eugene B.; Galbraith, Peter S.; Hebert, Dave; Lazin, Gordana; Maillet, Gary; Plourde, Stéphane; Starr, Michel

    2015-05-01

    We report on our analysis of zooplankton community structure in the western North Atlantic based on spring and fall monitoring surveys from 1999 to 2011 of three large marine ecosystems (LMEs; Newfoundland Shelf, Gulf of St. Lawrence and Scotian Shelf). We aimed to synthesize knowledge of the distribution of zooplankton communities and to evaluate their relationship to environmental conditions as either biogeographic constraints or smaller-scale ecosystems drivers or both. A combination of exploratory and constrained analyses helped identify the dominant roles of bathymetry, surface salinity and temperature, subsurface biogeochemical inventories of nitrate and chlorophyll a on the macroscale distribution of zooplankton. These variables highlight the potential influences of vertical habitat features, latitudinal and estuary-ocean gradients, deep-water intrusions, and differences in the seasonal succession on community structure at biogeographic scales. The spatial pattern in the residual field of the constrained analysis suggests that mesoscale features may play a role in shaping community structure within each of the LMEs and point to the limitation of analytical approaches based principally on water mass tracers applied over broad-scales. Interannual variations in key environmental drivers had inconsistent abilities in predicting changes in community composition across LMEs. Organisms that had the greatest influence on the delineation of communities were similar between spring and fall surveys and consisted of roughly a dozen dominant and ubiquitous taxa. Determining the influence of environmental variations on productivity of key secondary producers requires an approach focussed at the scale of individual LMEs in order to address the consequence of dissimilarities in the dominant trophic relationships or the response to remote forcing across the region.

  13. Improved Method for Determining Bacterial Filtration Rates in Zooplankton

    OpenAIRE

    Marvalin, Olivier; Lazarek, Stanislaw

    1988-01-01

    Filtration rates were determined for a natural population of zooplankton grazers (Bosmina longirostris [Müll.], Cyclops vicinus vicinus [Ulianine], Acanthodiaptomus denticornis [Wierz.], and Daphnia longispina [Müll.]) by using 3H-labeled bacteria as food for these organisms. There was a relationship between filtration rates of the major zooplankton grazers and the prevailing algal and bacterial composition in the lake water. Low filtration rates were obtained in the presence of colonial an...

  14. A Comparative Atlas of Zooplankton: Biological Patterns in the Oceans

    Science.gov (United States)

    Biggs, Douglas C.

    Large-scale biogeographic trends in the distribution of marine zooplankton are the subject of this work. As the subtitle of this book clarifies, it is an illustrated compendium of distributional patterns rather than a taxonomic atlas of invertebrate zoology. About half the work is devoted to Mercator projection maps of global distribution of various species of zooplankton and of chemical and physical properties of their environment. The other half is a treatise on plankton ecology as it relates to speciation.

  15. High Mortality of Red Sea Zooplankton under Ambient Solar Radiation

    OpenAIRE

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

    2014-01-01

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

  16. Vertical integration

    Energy Technology Data Exchange (ETDEWEB)

    Antill, N.

    1999-02-01

    This paper focuses on the trend in international energy companies towards vertical integration in the gas chain from wellhead to power generation, horizontal integration in refining and marketing businesses, and the search for larger projects with lower upstream costs. The shape of the petroleum industry in the next millennium, the creation of super-major oil companies, and the relationship between size and risk are discussed. The dynamics of vertical integration, present events and future developments are considered. (UK)

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

    DEFF Research Database (Denmark)

    Möller, Klas O.; St. John, Michael

    2012-01-01

    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

  18. Trace metal concentrations in marine zooplankton from the western Bay of Bengal

    Digital Repository Service at National Institute of Oceanography (India)

    Rejomon, G.; Balachandran, K.K.; Nair, M.; Joseph, T.

    2008-01-01

    -availabilities in seawater and hence an increased uptake of metals by zooplankton from coastal areas than offshore areas. The zooplankton species examined showed great accumulations of metals, with bioaccumulation factors in the range greater than 15,000 to 40...

  19. A study on the zooplankton of the Burhabalanga Estuary, Orissa Coast

    Digital Repository Service at National Institute of Oceanography (India)

    Ramaiah, Neelam; Chatterji, A.; Madhupratap, M.

    1996-01-01

    Annual variations in the zooplankton biomass and composition during 1991-92 were studied from the inshore, mouth and upstream regions of the Burhabalanga Estuary located in the Orissa Coast (India). Zooplankton biomass was maximum at all...

  20. Zooplankton of the southwest coast of India: abundance, composition, temporal and spatial variability in 1987

    Digital Repository Service at National Institute of Oceanography (India)

    Madhupratap, M.; Haridas, P.; Ramaiah, Neelam; Achuthankutty, C.T.

    1992-01-01

    During early southwest and northeast monsoon periods of 1967, zooplankton standing stocks and abundances were high all along the west coast of India. Swarms of zooplankton were common in the shelf areas resulting in a low diversity-high biomass...

  1. Migration chemistry

    International Nuclear Information System (INIS)

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

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

    Directory of Open Access Journals (Sweden)

    Luciana Gomes Barbosa

    2011-03-01

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

  3. 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)

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

    2011-03-01

    Full Text Available 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.

  4. Reaction of fresh water zooplankton community to chronic radiation exposure

    International Nuclear Information System (INIS)

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

  5. STUDIES ON ZOOPLANKTONS OF GODADA LAKE OF BULDHANA DISTRICT, (M. S. INDIA

    Directory of Open Access Journals (Sweden)

    Meena T. Nikam

    2012-05-01

    Full Text Available The plankton constitutes the basic food sources of any aquatic ecosystem, which supports fish and other aquatic animals. Zooplankton diversity is one of the most important ecological parameters in water quality assessment. Zooplanktons are good indicators of the changes in water quality because they are strongly affected by environmental conditions & respond quickly to changes in water quality. Zooplankton is the intermediate link between phytoplankton and fish. Hence qualitative and quantitative studies of zooplankton are of great importance.. In the present paper qualitative and quantitative studies of zooplanktons in Godada Lake of Buldhana district were carried out during February 2011 to January 2012.

  6. Detecting response patterns of zooplankton to environmental parameters in shallow freshwater wetlands: discovery of the role of macrophytes as microhabitat for epiphytic zooplankton

    Directory of Open Access Journals (Sweden)

    Jong-Yun Choi

    2015-05-01

    Full Text Available Freshwater macrophytes improve the structural heterogeneity of microhabitats in water, often providing an important habitat for zooplankton. Some studies have focused on the overall influence of macrophytes on zooplankton, but the effects of macrophyte in relation to different habitat characteristics of zooplankton (e.g., epiphytic and pelagic have not been intensively studied. We hypothesized that different habitat structures (i.e., macrophyte habitat would strongly affect zooplankton distribution. We investigated zooplankton density and diversity, macrophyte characteristics (dry weight and species number, and environmental parameters in 40 shallow wetlands in South Korea. Patterns in the data were analyzed using a self-organizing map (SOM, which extracts information through competitive and adaptive properties. A total of 20 variables (11 environmental parameters and 9 zooplankton groups were patterned onto the SOM. Based on a U-matrix, 3 clusters were identified from the model. Zooplankton assemblages were positively related to macrophyte characteristics (i.e., dry weight and species number. In particular, epiphytic species (i.e., epiphytic rotifers and cladocerans exhibited a clear relationship with macrophyte characteristics, while large biomass and greater numbers of macrophyte species supported high zooplankton assemblages. Consequently, habitat heterogeneity in the macrophyte bed was recognized as an important factor to determine zooplankton distribution, particularly in epiphytic species. The results indicate that macrophytes are critical for heterogeneity in lentic freshwater ecosystems, and the inclusion of diverse plant species in wetland construction or restoration schemes is expected to generate ecologically healthy food webs.

  7. 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)

  8. Zooplankton Diversity Of Dnyanganga Reservoir Near Khamgaon, Maharashtra

    Directory of Open Access Journals (Sweden)

    G. B. Kale

    2013-09-01

    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 .

  9. [Zooplankton in north branch waters of Changiiang Estuary].

    Science.gov (United States)

    Xu, Zhaoli

    2005-07-01

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

  10. Monarch Migration.

    Science.gov (United States)

    Williamson, Brad; Taylor, Orley

    1996-01-01

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

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

    Science.gov (United States)

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

    2012-02-01

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

  12. Reaction of fresh water zooplankton community to chronic radiation exposure

    Energy Technology Data Exchange (ETDEWEB)

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

    2014-07-01

    The characteristic features of ecological community as a whole and cenosis of zooplankton organisms as part of it determine the intensity of the processes of self-purification of water and the formation of a particular body of water. Identifying features of the structure and composition of the zooplankton community of aquatic ecosystems exposed to different levels of radiation exposure, it is necessary to identify patterns of changes in zooplankton and hydro-biocenosis as a whole. Industrial reservoirs, the storage of liquid low-level radioactive waste 'Mayak' for decades, have high radiation load. A large range of levels of radioactive contamination (total volume beta-activity in water varies from 2.2x10{sup 3} to 2.3x10{sup 7} Bq/l, total volume alpha-activity - from 2.6x10{sup -1} to 3.1x10{sup 3} Bq/l) provides a unique opportunity to study ecosystems in a number of reservoirs with increasing impact of radiation factor. We studied five reservoirs that were used as the storage of low-and intermediate-level liquid radioactive waste pond and one comparison water body. In parallel with zooplankton sampling water samples were collected for hydro-chemical analysis. 41 indicators were analysed in order to assess the water chemistry. To determine the content of radionuclides in the various components of the ecosystem samples were collected from water, bottom sediments and plankton. Sampling of zooplankton for the quantitative analysis was performed using the method of weighted average auto bathometer. Apshteyn's plankton net of the surface horizon was used for qualitative analysis of the species composition of zooplankton. Software package ERICA Assessment Tool 2012 was used for the calculation of the absorbed dose rate. Species diversity and biomass of zooplankton, the share of rotifers in the number of species, abundance and biomass decrease with the increase of the absorbed dose rate and salinity. The number of species in a sample decreases with the increase of the absorbed dose according to the S-shaped function. 5 % reduction in species diversity corresponds to 1.1x10{sup 2} mcGy/hr, 50 % reduction - 1.1x10{sup 3} mcGy/hr. Margalef's index and Shannon's index were 5% lower at 9.1x10{sup 2} mcGy/hr and 50% lower at 1.7x10{sup 3} mcGy/hr, that points to simplified communication in the plankton community. Quantitative indicators of zooplankton are less sensitive to changes in the aquatic environment under study than indicators of species richness and the complexity of relationships in the community. Document available in abstract form only. (authors)

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

    Directory of Open Access Journals (Sweden)

    Nuno Filipe Alves Correia de Melo

    2006-04-01

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

  14. Natural and cultivated zooplankton as food for halibut (Hippoglossus hippoglossus) larvae

    OpenAIRE

    Naas, Kjell Emil; Berg, Leif; Klungsøyr, Jarle; Pittman, Karin

    1987-01-01

    Natural zooplankton were pumped into a collector and size-fractionated. The zooplankton smaller than 350 ym were fed on a diatom dominated algal suspension cultured in 3 m deep out-door plastic bags. Halibut larvae were kept through the yolk sac stages in large temperature regulated bags, and when ready to start first feeding, they were offered both cultivated and natural zooplankton. The composition of fatty acids in growing larvae were analyzed to study the influence of dietary lipids.

  15. Taxonomy, distribution, and ecology of crustacean zooplankton in trough waters of Ankara (Turkey)

    OpenAIRE

    BA?AK, Elif; Aygen, Cem; Külköylüo?lu, Okan

    2014-01-01

    Troughs are one of the main components of villages in Turkey. They are constructed by converting springs or underground waters. Until now, there has been no extensive study investigating the composition and diversity of trough zooplankton species. In order to contribute knowledge on the zooplanktons in troughs, 142 troughs were randomly sampled from 17 districts in Ankara Province between 22 June and 3 July 2011. A total of 18 zooplanktons including 11 Copepoda and 7 Cladocera species were de...

  16. An overview of Southern Ocean zooplankton data: abundance, biomass, feeding and functional relationships

    OpenAIRE

    Atkinson, Angus; Ward, Peter; Hunt, B. P. V.; Pakhomov, E. A.; Hosie, G. W.

    2012-01-01

    There is an enormous amount of data on Southern Ocean (SO) zooplankton, mostly on their distribution with a minority addressing rate processes. This review aims to summarise these data and show where it resides, to assist SO food-web modellers or those with limited specialist knowledge of SO zooplankton. First, a brief overview is provided of the diversity and basic biology of SO zooplankton, with an emphasis on abundance, distribution and feeding. Second, advice is provided on the uses, stre...

  17. Spatial variations in zooplankton diversity in waters contaminated with composite effluents

    OpenAIRE

    Asitava CHATTERJEE; Chattopadhyay, Buddhadeb; Abhishek Roy GOSWAMI; Subhra Kumar MUKHOPADHYAY

    2007-01-01

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

  18. Heavy metals in zooplankton from the Southern Baltic.

    Science.gov (United States)

    Pempkowiak, J; Walkusz-Miotk, J; Be?dowski, J; Walkusz, W

    2006-03-01

    Samples of zooplankton and suspended matter were collected using a Bongo net (0.33/0.50 mm mesh net), and Nucleopore filters, respectively, from the Southern Baltic off Poland. Major classes of zooplankton, and selected heavy metals (Fe, Co, Ni, Mn, Pb, Cd, Cu, Zn, Cr) were determined in the collected samples. Concentrations of heavy metals in zooplankton were corrected for metals contributed by particulate matter adhering to zooplankton organisms. Heavy metals levels measured in nearshore samples (Bay of Gda?sk, Pomeranian Bay) were higher than those in the samples from the open sea. The only exception was cadmium exhibiting larger concentrations in the offshore as compared to the nearshore samples (0.8 vs. 1.3 microg/g d.w.). This was attributed to decreased concentrations, of both dissolved and particulate cadmium, caused by algal bloom. Larger concentrations of heavy metals in the Bay of Gda?sk in comparison with the Pomeranian Bay (e.g. Cd-1.3 vs. 0.8 microg/g, Cu-20.5 vs. 8.3 microg/g, Pb-12.9 vs. 1.2 microg/g, Cr-12.4 vs. 1.4 microg/g) were attributed to the direct discharge of the Vistula river to the Bay of Gda?sk, while the Pomeranian Bay receives the Odra river runoff indirectly, via the Szczecin Lagoon. The nonlinear estimation of the data set was used to evaluate concentrations of heavy metals in Copepoda and Cladocera. Copepoda proved to be enriched with heavy metals in comparison with Cladocera. PMID:16139327

  19. Flow disturbances generated by feeding and swimming zooplankton

    DEFF Research Database (Denmark)

    KiØrboe, Thomas; Jiang, Haisong

    2014-01-01

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

  20. Zooplankton Composition of Pulumur Stream (Tunceli-Turkey

    Directory of Open Access Journals (Sweden)

    Hilal Haykir

    2011-01-01

    Full Text Available This study was completed with periodical surveys in Pulumur stream between November 2009-October 2010 period. During the study, a total of 21 species (15 belonged to genus of Rotifera, 4 to Copepoda and 2 Cladocera were found in Pulumur stream. All of the zooplanktonic species have been detected for the first time in Pulumur stream. Also some water parameters (pH, dissolved oxygen, electrical conductivity and water temperature were measured during field trips.

  1. Studies on the zooplankton of the deep subalpine Lake Garda.

    Directory of Open Access Journals (Sweden)

    Luigi NASELLI-FLORES

    1999-02-01

    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.

  2. Considerations on the biochemical composition of some freshwater zooplankton species.

    Directory of Open Access Journals (Sweden)

    Nicoletta RICCARDI

    1999-02-01

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

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

    Directory of Open Access Journals (Sweden)

    Kuczy?ska-Kippen N.

    2013-07-01

    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.

  4. ZOOPLANKTON DIVERSITY OF GARGA RESERVOIR OF BOKARO, JHARKHAND, INDIA

    Directory of Open Access Journals (Sweden)

    Farhat Saba* and DN Sadhu

    2015-03-01

    Full Text Available The present study is on “Zooplankton diversity of Garga Reservoir of Bokaro District (Jharkhand”. The study was carried on from July’2012 to June’2013 at four selected sampling stations. Monthly variations and biodiversity indices of zooplanktons were observed. It revealed 11 different species of zooplanktons belonging to 4 different classes namely 3 rotifers, 4 cladocerans, 3 copepods and 1 ostracod. Among rotifers, Brachionus falacatus is abundant. Ceriodaphnia cornuta is predominant among cladocerans. Among copepods, numerical superiority was found in case of Nauplius. Ostracoda was represented by only one genus i.e. Stenocypris. Maximum percentage of Cladocera (34.89% and minimum percentage of Ostracoda (6.77% were observed. Margalef’s index (R1 and Menhinick index (R2 values (1.038 and 1.061 were found to be highest in April, 2013 and October, 2012 respectively. Lowest values (0.558 and 0.577 were found in July, 2012 and February, 2013. The Simpson’s index (n varied from 0.222 in April’13 to 0.667 in July’12. The Shannon index (H’ was found to be in the range of 0.451 in July’12 to 1.355 in April’13.

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

    Science.gov (United States)

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

    2014-11-01

    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.

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

    Directory of Open Access Journals (Sweden)

    A. N. Dede

    2015-01-01

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

  7. 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)

  8. Zooplankton data collected from zooplankton net casts from RESEARCHER I and other platforms in TOGA Area of Pacific Ocean; 16 March 1968 to 02 July 1970 (NODC Accession 9500141)

    National Oceanic and Atmospheric Administration, Department of Commerce — Zooplankton species identities and other data were collected using zooplankton casts in the TOGA Area of Pacific Ocean from RESEARCHER I and other platforms. Data...

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

    OpenAIRE

    Brun,Helene

    2007-01-01

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

  10. Zooplankton data collected from THOMAS G. THOMPSON in Arabian Sea; 01 January 1995 to 15 September 1995 (NODC Accession 9800071)

    National Oceanic and Atmospheric Administration, Department of Commerce — Zooplankton data were collected using zooplankton net casts in Arabian Sea from THOMAS G. THOMPSON. Data were collected from 01 January 1995 to 15 September 1995 by...

  11. Zooplankton data collected from THOMAS G. THOMPSON in Arabian Sea; 01 January 1995 to 15 September 1995 (NODC Accession 9800072)

    National Oceanic and Atmospheric Administration, Department of Commerce — Zooplankton data were collected using zooplankton net casts in Arabian Sea from THOMAS G. THOMPSON. Data were collected from 01 January 1995 to 15 September 1995 by...

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

    Directory of Open Access Journals (Sweden)

    Peter Anegg

    2014-07-01

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

  13. 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.

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

    Directory of Open Access Journals (Sweden)

    Hilal Bulut

    2014-01-01

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

  15. ZOOPLANKTON DENSITY OF LONI DAM WATER, KINWAT, DIST- NANDED, MAHARASHTRA (INDIA.

    Directory of Open Access Journals (Sweden)

    Maqdoom Mohiuddin

    2015-05-01

    Full Text Available In the present investigation was undertaken to study of the physicchemical parameters with relation to the zooplankton composition in Loni dam water. The physicchemical parameters of Loni Dam water were found favorable range for the growth of the zooplankton. The present investigation the three spots were selected for the study and named as Sites I, II and III respectively. The study carried out the one year during the June- 2012 to May-2013. The dominant trend in the zooplankton was Rotifera > Cladocera > Copepoda > Ostracoda and total count of zooplankton was 12 to 30 number/lit at Site- I, 11to 50 number/lit at Site- II and 13-43 number/lit at Site- III. The physicochemical parameters are favorable range for the growth of zooplankton and it may be beneficial for the fish culture.

  16. Effects of temperature on the metabolic stoichiometry of Arctic zooplankton

    Directory of Open Access Journals (Sweden)

    M. Alcaraz

    2013-02-01

    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 zooplankton carbon respiratory losses (hereafter CR and NH4-N and PO4-P excretion rates (hereafter NE and PE, respectively, but also to investigate whether these metabolic pathways responded similarly to temperature, and so how temperature could affect the stoichiometry of the metabolic products. Metabolic rates, normalised to per unit of zooplankton carbon biomass, increased with increasing temperature following the Arrhenius equation. However, the activation energy differed for the various metabolic processes considered. Respiration, CR, was the metabolic activity least affected by temperature, followed by NE and PE, and as a consequence the values of the CR : NE, CR : PE and NE : PE atomic quotients were inversely related to temperature. The effects of temperature on the stoichiometry of the excreted N and P products would contribute to modifying the nutrient pool available for phytoplankton and induce qualitative and quantitative shifts in the size, community structure and chemical composition of primary producers that could possibly translate to the whole Arctic marine food web.

  17. Effect of hydrodynamic cavitation on zooplankton: A tool for disinfection

    Digital Repository Service at National Institute of Oceanography (India)

    Sawant, S.S.; Anil, A.C.; Venkat, K.; Gaonkar, C.; Kolwalkar, J.; Khandeparker, L.; Desai, D.V.; Mahulkar, A.V.; Ranade, V.V.; Pandit, A.B.

    2008-01-01

    dimension of opening/ diameter of holes in orifice (m) D cell count in discharge water (post-cavitation) (m ?3 ) F constants in Eq. (6) g acceleration due to gravity (m/s 2 ) I cell count in intake water (pre-cavitation) (m ?3 ) k turbulent kinetic energy (m... Weber number X extent of killing of zooplankton Z potential head associated with incoming/outgoing mass (m) SUB density (kg/m 3 ) ESC surface tension (N/m) H9255 turbulence energy dissipation rate (m 2 /s 3 ) SYN viscosity of liquid (kg/m/s) Subscripts B...

  18. Water mite predation on zooplankton of a tropical lake

    OpenAIRE

    Cassano, C. R.; Castilho-noll, M. S. M.; Arcifa, M. S.

    2002-01-01

    Water mite (Krendowskia sp.) predation on zooplanktonic species from Lake Monte Alegre (São Paulo State, Brazil) was tested in laboratory experiments. One cladoceran, Daphnia gessneri, two copepods, Tropocyclops prasinus and Thermocyclops decipiens, and Chaoborus larvae III and IV were supplied as prey to adult mites. The cladoceran Ceriodaphnia cornuta was used in the experiment with mite nymphs. Only D.gessneri was preyed on by mites, at an average rate of 7 ind./mite/day, at 23-24ºC. Alt...

  19. Neustonic microplastic and zooplankton in the North Western Mediterranean Sea

    OpenAIRE

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

    2012-01-01

    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/m...

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

    Energy Technology Data Exchange (ETDEWEB)

    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

    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.

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

    Science.gov (United States)

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

    2008-07-01

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

  2. Temperature dependence of Arctic zooplankton metabolism and excretion stoichiometry

    Directory of Open Access Journals (Sweden)

    M. Alcaraz

    2012-06-01

    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.

  3. International Migration and Remittances

    OpenAIRE

    Dattatray Sitaram Bagade

    2012-01-01

    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...

  4. Migration and trade

    OpenAIRE

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

    2011-01-01

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

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

    Science.gov (United States)

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

    2014-07-01

    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.

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

    Directory of Open Access Journals (Sweden)

    Imoobe T.O.T.

    2009-01-01

    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.

  7. In different pressure an experimental study on migration of radon

    International Nuclear Information System (INIS)

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

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

    International Nuclear Information System (INIS)

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

  9. The possibilities of least-squares migration of internally scattered seismic energy

    KAUST Repository

    Aldawood, Ali

    2015-05-26

    Approximate images of the earth’s subsurface structures are usually obtained by migrating surface seismic data. Least-squares migration, under the single-scattering assumption, is used as an iterative linearized inversion scheme to suppress migration artifacts, deconvolve the source signature, mitigate the acquisition fingerprint, and enhance the spatial resolution of migrated images. The problem with least-squares migration of primaries, however, is that it may not be able to enhance events that are mainly illuminated by internal multiples, such as vertical and nearly vertical faults or salt flanks. To alleviate this problem, we adopted a linearized inversion framework to migrate internally scattered energy. We apply the least-squares migration of first-order internal multiples to image subsurface vertical fault planes. Tests on synthetic data demonstrated the ability of the proposed method to resolve vertical fault planes, which are poorly illuminated by the least-squares migration of primaries only. The proposed scheme is robust in the presence of white Gaussian observational noise and in the case of imaging the fault planes using inaccurate migration velocities. Our results suggested that the proposed least-squares imaging, under the double-scattering assumption, still retrieved the vertical fault planes when imaging the scattered data despite a slight defocusing of these events due to the presence of noise or velocity errors.

  10. A comparison of carbon-specific respiration rates in gelatinous and non-gelatinous zooplankton: A search for general rules in zooplankton metabolism

    Science.gov (United States)

    Schneider, G.

    1992-12-01

    Using 470 data from the literature the dry weight-specific respiration rates of gelatinous zooplankton (cnidarians, ctenophores and salps) and non-gelatinous zooplankton (mainly crustacea) were converted to carbon-specific values. The resulting carbon-specific respiration rates showed no significant differences between the two groups of zooplankton, indicating similar oxygen requirements per gram of carbon biomass. From this finding, it can be suggested that the differences in the rates of oxygen consumption measured in the two types of zooplankton in the sea can be explained by the carbon biomass ratio between gelatinous and non-gelatinous zooplankton. Furthermore, the low rate of metabolism of gelatinous species compared with that of non-gelatinous animals of the same volume can be attributed predominantly to the relatively low organic matter content in the former. It is recommended that all weight-specific metabolism rates be expressed using carbon as body mass unit (e.g. mg O2 gC-1 d-1) which enables more accurate comparisons between individuals exhibiting different dry weight/carbon ratios.

  11. Spatial patterns in the vertical structure of euphausiids in Gullmarsfjord, Sweden: Identifying influences on bilayer formation and distribution

    OpenAIRE

    Tarling, Geraint A; Cottier, Finlo R.; Everson, Inigo

    2014-01-01

    The formation of two vertically discrete layers (bilayers) at night-time is a commonly observed phenomenon in zooplankton and is regularly found in Gullmarsfjord, a fjord with a 50 m sill depth, deep basin and a three-layered water column. In an acoustic and net sampling survey in September 2003, night-time euphausiid layers occurred at 15 and 45 m, with the deeper layer containing relatively higher concentrations of adult Northern krill (Meganyctiphanes norvegica). The main night-time predat...

  12. Production of certain hydrolytic enzymes by psychrophilic bacteria from the Antarctic krill, zooplankton and seawater

    Digital Repository Service at National Institute of Oceanography (India)

    Ramaiah, N.

    1994-01-01

    . Presence of different enzymes was examined from about 500 of these strains. Bacterial numbers were the highest in the krill gut samples; moderate on zooplankton surfaces and low in water and the ice samples. Pseudomonas, Vibrio, Chromobacterium, Aeromonas...

  13. Studies on the associates and parasites of zooplankton from southwest and southeast coasts of India

    Digital Repository Service at National Institute of Oceanography (India)

    Santhakumari, V.

    1997-01-01

    Associates and parasites of zooplankton from southwest and southeast coasts of India were studied. Among the epizoic forms two species of ciliates infesting copepods were new records from Indian waters. Eight species of suctorians were found epizoic...

  14. Zooplankton ecology in the Mandovi-Zuari estuarine system of Goa, west coast of India

    Digital Repository Service at National Institute of Oceanography (India)

    Padmavati, G.; Goswami, S.C.

    1996-01-01

    .6%). Invertebrate larvae, luciferied shrimps, cladocerans and chaetognaths were the other common zooplankton groups. Distribution and abundance of majority of constituent groups and species were influenced by various hydrographical characteristics of the environment....

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

    International Nuclear Information System (INIS)

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

  16. Zooplankton of the lagoons of the Laccadives: diel patterns and emergence

    Digital Repository Service at National Institute of Oceanography (India)

    Madhupratap, M.; Achuthankutty, C.T; Nair, S.R.S.

    1991-01-01

    Zooplankton populations in the water column increased substantially at night in four lagoons of the Laccadives. Epibenthic forms emerging into the water column during night, as well as non-epibenthic forms such as calanoid and cyclopoid copepods...

  17. Zooplankton production, composition and diversity in the coastal waters of Goa

    Digital Repository Service at National Institute of Oceanography (India)

    Goswami, S.C.; Padmavati, G.

    1996-01-01

    enriched enriched environment during early postmonsoon months (October-November). Swarming of these zooplanktonic forms resulted in high biomass but low diversity community. Faunal and species diversity were enhanced with increase of carnivores...

  18. Elemental (C, H, N) composition of zooplankton from north Arabian Sea

    Digital Repository Service at National Institute of Oceanography (India)

    Matondkar, S.G.P.; Bhat, K.L.; Ansari, Z.A.; Parulekar, A.H.

    1995-01-01

    Zooplankton samples collected from north Arabian Sea during March 1992 were analysed for elemental (C,H,N) composition. Estimated carbon, hydrogen and nitrogen concentrations displayed variations among different groups but their ratios were nearly...

  19. Phytoplankton and zooplankton of some paddy-cum-prawn culture fields in and around Cochin

    Digital Repository Service at National Institute of Oceanography (India)

    Gopalakrishnan, T.C.; Devi, C.B.L.; Aravindakshan, P.N.; Nair, K.K.C.; Balasubramanian, T.; Kutty, M.K.

    1988-01-01

    The Phytoplankton and zooplankton from the paddy-cum-prawn culture fields from 4 areas in and around the Cochin backwaters were studied. Total Phytoplankton counts in the seasonal and perennial fields in all the areas showed good similarity...

  20. Microdistribution of zooplankton in the neustonic realm of the eastern Arabian Sea during southwest monsoon

    Digital Repository Service at National Institute of Oceanography (India)

    Achuthankutty, C.T.; Nair, S.R.S.; Nair, V.R.; Padmavati, G.; Madhupratap, M.

    1992-01-01

    During the southwest monsoon season of 1987, the zooplankton distributions in the neustonic realm (upper 50 cm) of the eastern Arabian Sea were studied and compared with those in the water column. The upper microlayer (upper 15 cm) had generally...

  1. Biomass and biochemical composition of zooplankton from northwest Bay of Bengal during January 1990

    Digital Repository Service at National Institute of Oceanography (India)

    Krishnakumari, L.; Goswami, S.C.

    1993-01-01

    Biomass, proximate composition, organic carbon and calorie content of assorted zooplankton from the surface waters were studied. Day and night stations revealed significant difference in biomass (displacement volume, dry wt and organic carbon...

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

    OpenAIRE

    E.N. Ezekiel; E.N. Ogamba and J.F.N. Abowei

    2011-01-01

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

  3. Accumulation of petroleum hydrocarbons in zooplankton of Banyas coastal waters (Syria)

    International Nuclear Information System (INIS)

    We present in this paper the distribution of petroleum hydrocarbons in seawater and their levels in zooplanktonic samples. Sampling operation was carried our between August 1995 and November 1996 in the coastal area of Banyas city (Eastern Mediterranean). Petroleum hydrocarbons concentrations were: ranged between non detectable values and 16.4 pill in seawater, and between non detectable values and 4304 ?/g dry weight in zooplanktonic samples

  4. Do phosphorus requirements for RNA limit genome size in crustacean zooplankton?

    OpenAIRE

    Hessen, Dag O.; Ventura, Marc; Elser, James J.

    2008-01-01

    As for most other organisms, genome size in zooplankton differs widely. This may have a range of consequences for growth rate, development, and life history strategies, yet the causes of this pronounced variability are not settled. Here we propose that small genome size may be an evolutionary consequence of phosphorus (P) allocation from DNA to RNA under P deficiency. To test this hypothesis we have compared the two major groups of zooplankton, copepods and cladocerans, that have overlapping ...

  5. The role of climate in shaping zooplankton communities of shallow lakes

    OpenAIRE

    Gyllström, Mikael; Hansson, Lars-Anders; Jeppesen, E; Garcia-Criado, F.; GROSS, E.; Irvine, K; Kairesalo, T; Kornijow, R.; Miracle, MR; Nykänen, M.; Noges, T.; Romo, S.; Stephen, D.; E. Van Donk; Moss, B.

    2005-01-01

    We analyzed data from 81 shallow European lakes, which were sampled with standardized methods, for combined effects of climatic, physical, and chemical features of food-web interactions, with a specific focus on zooplankton biomass and community structure. Multiple-regression analysis showed that total phosphorus (TP) generally was the most important predictor of zooplankton biomass and community structure. Climate was the next most important predictor and acted mainly through its effect on p...

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

    Directory of Open Access Journals (Sweden)

    Huseyin Guher

    2004-01-01

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

  7. Marriage, money and migration

    OpenAIRE

    A?stro?m, Johanna

    2009-01-01

    The thesis consists of a summary and four self-contained papers. Paper [I] examines the effects of interregional migration on gross earnings in married and cohabiting couples. In particular, we examine the link between education level and income gains. We find that pre-migration education level is a key determinant of migration and economic outcomes and is also a determinant of the effect of migration on income distribution within the household. The positive average effect on household earnin...

  8. Partitioning of polychlorinated biphenyls between Arctic seawater and size-fractionated zooplankton.

    Science.gov (United States)

    Sobek, Anna; Reigstad, Marit; Gustafsson, Orjan

    2006-07-01

    Concentrations of hydrophobic organic contaminants in zooplankton have been hypothesized to be governed by either near-equilibrium partitioning with surrounding water, growth dilution, or biomagnification. Concentrations of 17 polychlorinated biphenyls (PCBs) were measured in size-fractionated zooplankton, in phytoplankton (> 0.7 microm), and in the dissolved water phase (< 0.7 microm) in the surface water of the northern Barents Sea marginal ice zone east and north of Spitsbergen (Norway) and in the central Arctic Ocean at 89 degrees N. The linear partition model was used to indirectly assess if PCBs were equilibrated between water and the extractable organic matter (EOM) of zooplankton. As an independent test, the relation between the EOM-normalized partition coefficient (log K(EOM)) and trophic level (TL) of the zooplankton (based on delta 15N) was investigated. All log K-log K(OW) regressions were significant (n=18, p < 0.05, r2 = 0.65-0.95), being consistent with near-equilibrium partitioning and indirectly suggesting the absence of biomagnification. No correlation was found between log K(EOM) and TL, further supporting the apparent absence of biomagnification in zooplankton. One implication of these results is a reduced uncertainty in modeling of food web uptake, in which kinetic parameterizations of biodilution or biomagnification in zooplankton may be replaced by a simpler parameterization based on equilibrium partitioning. PMID:16833130

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

    Science.gov (United States)

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

    2008-04-01

    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

  10. Responses of phyto- and zooplankton communities to Prymnesium polylepis (Prymnesiales) bloom in the Baltic Sea.

    Science.gov (United States)

    Gorokhova, Elena; Hajdu, Susanna; Larsson, Ulf

    2014-01-01

    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

  11. Incorporation of nitrogen from N2 fixation into amino acids of zooplankton

    DEFF Research Database (Denmark)

    Loick-Wilde, Natalie; Dutz, Jörg

    2012-01-01

    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

  12. Migration and Adult Education

    Science.gov (United States)

    Gois, William

    2007-01-01

    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…

  13. More Myths of Migration.

    Science.gov (United States)

    Basch, Linda; Lerner, Gail

    1986-01-01

    Challenges "myths" about women and migration, including (1) the causes of migration are economic, not racism; (2) migrant women receive support from feminist groups and trade unions; (3) transnational corporations are positive forces in developing nations; (4) migration today has little impact on family life; and (5) most migrants cluster in…

  14. 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)

  15. Vertical axis wind turbines

    Science.gov (United States)

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

    2011-03-08

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

  16. Spatio-temporal Distribuution, Abundance and Species Composition of Zooplankton of Woji-okpoka Creek, Port Harcourt, Nigeria

    OpenAIRE

    Davies, Onome Augustina

    2009-01-01

    Woji-Okpoka Creek is situated in a strategic location in Port Harcourt, Rivers State, N igeria and itreceives domestic and industrial wastes from the Trans-amadi industrial Layout, main Port Harcourt abattoirand riverine communities. There is little information on the zooplankton of this creek. The study investigatedspecies composition, diversity, abundance and distribution of zooplankton as well as some physico-chemicalparameters that affect this organism. Zooplankton and surface water sampl...

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

    Directory of Open Access Journals (Sweden)

    V. N. Stolbunova

    2010-09-01

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

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

    OpenAIRE

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

    2011-01-01

    The aim of this study was to test the effects of natural free-floating plants on zooplankton distribution in a shallow subtropical lake. First, the hypothesis that free-floating plants have an effect on physico-chemicals, leading to a decrease on nutrient availability and influencing the phytoplankton biomass and zooplankton community was tested. Second, the hypothesis that free-floating plants act as a refuge for zooplankton was tested. Three microhabitats were selected: free-floating plants...

  19. Characterization of the zooplankton community, size composition, and distribution in relation to hydrography in the Japan/East Sea

    Science.gov (United States)

    Ashjian, Carin J.; Davis, Cabell S.; Gallager, Scott M.; Alatalo, Philip

    2005-06-01

    The Japan/East Sea (JES) may be thought of as a model or microcosm of larger oceanic systems where biogeographic boundaries juxtapose at highly dynamic boundaries. The northern and southern portions of the JES are hydrographically and biologically distinct, with the southern portion being more tropical/oligotrophic and the northern portion being more boreal/eutrophic. Regional zooplankton taxonomic and size compositions and abundance and the high-resolution vertical distribution of plankton, fluorescence, and coincident hydrography were described using the Video Plankton Recorder (VPR), equipped with high- and low-magnification cameras and environmental sensors and mounted on a vertically profiling towed vehicle, in the upper 80 m of the JES during the summer of 1999. A survey was conducted over both the northern and southern regions, including the Subpolar Front (SPF), that spanned 10-12° of latitude and longitude and covered an along track distance of 7000 km. Plankton also were collected at 15 selected stations using a ring net for silhouette analysis of taxa and size. Distributional patterns in abundance (#/liter) of plankton taxa from the VPR were quantified at sea in real time, identifying plankton automatically using a neural network classifier. The most abundant taxa identified were copepods, Oithona spp., Calanus spp., copepod nauplii, protozoa, and diatoms, with copepods the dominant taxon. The northern JES, southern JES, and North Korean Cold Current were distinct based on based on temperature-salinity properties. The hydrography was complex and characterized by multiple mesoscale features including currents and the meandering of the SPF. Different taxonomic and size compositions were observed in the three hydrographic regions. The vertical distributions of copepods and fluorescence were associated with hydrographic structure, especially at fronts. Plankton abundances varied with regional hydrographic region and environmental conditions, although strong associations were not always observed. The extremely dynamic nature of the JES may effectively mix the plankton and obscure strong gradients or differences between regions.

  20. Effect of errors in the migration velocity model of PS-converted waves on traveltime accuracy in prestack Kirchhoff time migration in weak anisotropic media

    OpenAIRE

    Dai, Heng; Li, Xiang

    2008-01-01

    We investigated the effect of errors in the migration-velocity model of PS-converted waves on the traveltime calculated in prestack Kirchhoff time migration in weak anisotropic media. The prestack-Kirchhoff-time-migration operator contains four parameters: the PS-converted-wave velocity, the vertical velocity ratio, the effective velocity ratio, and the anisotropic parameter. We derived four error factors that correspond to those parameters. Theoretical and numerical analyses of the error fac...

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

    Directory of Open Access Journals (Sweden)

    C. H. Hsieh

    2011-05-01

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

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

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

    Directory of Open Access Journals (Sweden)

    C. H. Hsieh

    2011-01-01

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

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

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

    Science.gov (United States)

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

    2013-01-01

    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, production patterns of zooplankton in John Day Reservoir. American Shad add to the planktivory exerted by other species like Neomysis mercedis to reduce the capacity of the reservoir to support other planktivorous fishes. The introduction of American Shad and other nonnative species will continue to alter the food web in John Day Reservoir, potentially affecting native fishes, including Pacific salmon Oncorhynchus spp.

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

    Directory of Open Access Journals (Sweden)

    Leonardo C. e Souza

    2011-06-01

    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.

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

    Directory of Open Access Journals (Sweden)

    Howaida Yehia ZAKARIA

    2007-12-01

    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.

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

    Scientific Electronic Library Online (English)

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

    2011-06-01

    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 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.

  7. Parasitic chytrids sustain zooplankton growth during inedible algal bloom

    Science.gov (United States)

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

    2014-01-01

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

  8. Zooplankton diversity across three Red Sea reefs using pyrosequencing

    KAUST Repository

    Pearman, John K.

    2014-07-30

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

  9. Fatty acid transformation in zooplankton: from seston to benthos

    DEFF Research Database (Denmark)

    Tiselius, Peter; Hansen, Benni Winding

    2012-01-01

    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.

  10. Vertical distribution and isotopic composition of living planktonic foraminifera in the western North Atlantic

    International Nuclear Information System (INIS)

    Thirteen species of planktonic foraminifera collected with vertically stratified zooplankton tows in the slope water, Gulf Stream cold core ring, and northern Sargasso Sea show significant differences in their vertical distributions in the upper 200 meters of these different hydrographic regimes. Gulf Stream cold core rings may be responsible for a southern displacement of the faunal boundary associated with the Gulf Stream when reconstructed from the deep-sea sediment record. Oxygen isotope analyses of seven species reveal that nonspinose species (algal symbiont-barren) apparently calcify in oxygen isotope equilibrium, whereas spinose species usually calcify out of oxygen isotope equilibrium by approximately -0.3 to -0.4 per mil in delta18O values. The isotope data indicate that foraminifera shells calcify in depth zones that are significantly narrower than the overall vertical distribution of a species would imply

  11. Migration and stratification

    OpenAIRE

    Jasso, Guillermina

    2011-01-01

    Migration and stratification are increasingly intertwined. One day soon it will be impossible to understand one without the other. Both focus on life chances. Stratification is about differential life chances - who gets what and why - and migration is about improving life chances - getting more of the good things of life. To examine the interconnections of migration and stratification, we address a mix of old and new questions, carrying out analyses newly enabled by a unique new data set on r...

  12. Doughnut In The Desert: Vertical Structure Of A Winter Production Pulse

    Science.gov (United States)

    Green, S. A.; Budd, J. W.; Kerfoot, W. C.

    2005-12-01

    SeaWiFS imagery has revealed a spatially complex, annually reoccurring pattern of chl a in the open waters of Southern Lake Michigan during late winter to early spring (March-April). The circular ring (doughnut) persists for weeks and occurs every year. A cross-lake survey in April 2001 confirmed the doughnut pattern and demonstrated that the gyre structure penetrated throughout the well-mixed water column. Spatial images suggest the feature may be related to the transport of phosphorus-rich coastal sediments which are entrained along gyre convergence zones and moved into the southern central region, enhancing deep-water production. Vertical reconstructions from two separate profiling instruments (CTD vertical casts, horizontal tows with an optical plankton counter) uncovered columnar patterns of Chl a, temperature, and other variables consistent with a spatially complex, rotating gyre structure. The horizontal surface patterns and vertical profiles suggest a heretofore unrecognized coupling between winter gyre formation, sediment resuspension, and deep-water productivity. The Chl a pattern is superimposed upon a spatially heterogeneous late-winter phytoplankton and zooplankton distribution pattern. The winter productivity pulse marked by the doughnut may explain how certain zooplankton species characteristic of the Great Lakes fauna can successfully over-winter through what was previously perceived as a very unproductive and resource-stressful period.

  13. Local and regional factors influencing zooplankton communities in the connected Kasseb Reservoir, Tunisia

    Scientific Electronic Library Online (English)

    Ikbel, Sellami; Jannet, Elloumi; Asma, Hamza; Mohammed Alaoui, Mhamdi; Habib, Ayadi.

    2011-04-01

    Full Text Available Associations between zooplankton community structure and abiotic (temperature, dissolved oxygen, turbidity, nutriments) and biotic factors (chlorophyll a and phytoplankton community) were examined, in Kasseb Reservoir, northern Tunisia. Samples were taken bimonthly from July to December 2002 at 3 sa [...] mpling stations (deepest station: Station 1, Brik River: Station 2 and M'Zaz Stama River: Station 3). From our results it is evident that zooplankton exhibit seasonally and spatially heterogeneous distribution. The highest density of zooplankton was recorded in September at a depth of 5 m (10.8 × 10³ ind·?-1). At Station 1 cyclopoid copepods (65% of total abundance) were the most abundant group followed by Cladocera (21% of total abundance). At Station 2 (93% of total abundance) and Station 3 (98% of total abundance) cyclopoid copepods were numerically dominant throughout the study period. Canonical correspondence analysis (CCA) was used to estimate the influence of abiotic and biotic factors in structuring the zooplankton assemblage. Zooplankton abundance was negatively correlated with turbidity (r= -0.381, P

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

    Directory of Open Access Journals (Sweden)

    Sharma, B.K.

    2012-12-01

    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.

  15. 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

  16. Zooplankton diversity of a sub-tropical reservoir of Mizoram, Northeast India

    Directory of Open Access Journals (Sweden)

    Sharma, B.K.

    2013-06-01

    Full Text Available This study on zooplankton diversity from the state of Mizoram of northeast India, based on plankton samples collected from Khawiva reservoir during November 2005-October 2007, recorded a total of 46 species. Zooplankton indicated monthly richness ranging between 19-36 and 25-34 species; registered 52.8-88.9 and 60.0-89.3% community similarities (vide Sørensen’s index; and comprised between 31.2±12.7 and 46.7±11.3% of net plankton abundance during two years, respectively. Copepoda and Rotifera, together, influenced zooplankton abundance. Rhizopoda and Cladocera showed limited importance while Nematoda and Ciliata recorded poor densities. Mesocyclops spp. > Keratella tropica are important taxa. Our results are characterized by moderate species diversity, high evenness and low dominance except in some months. Richness, abundance and species diversity followed no definite patterns of monthly variations. Individual abiotic parameters exerted limited influence on zooplankton richness and abundance, and on abundance of its constituent groups. The canonical correspondence analysis with fifteen abiotic parameters explained high cumulative variance (84.8% of zooplankton assemblages along axis 1 and 2 with importance of water temperature, rainfall, free carbon dioxide, conductivity and phosphate. Sladecek’s Q B/T quotient and Shannon’s diversity index reflected mesotrophic nature of Khawiva reservoir.

  17. A model to resolve organochlorine pharmacokinetics in migrating humpback whales.

    Science.gov (United States)

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

    2014-07-01

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

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

    DEFF Research Database (Denmark)

    Heath, M.; Brander, Keith

    1991-01-01

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

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

    International Nuclear Information System (INIS)

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

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

    DEFF Research Database (Denmark)

    Brönmark, Christer; Brodersen, Jakob

    2010-01-01

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

  1. Plankton distribution spectra: inter-size class variability and the relative slopes for phytoplankton and zooplankton

    Science.gov (United States)

    Martin, A. P.; Srokosz, M. A.

    2002-12-01

    Transects of a region of the North Atlantic, conducted in spring 1997, provide simultaneous measurements of a number of biophysical variables. These data are used to quantify the degree of spatial heterogeneity in the horizontal distributions of zooplankton, phytoplankton and potential temperature. More specifically, the spectral slope is calculated for the distribution of chlorophyll a, potential temperature and individual size-classes of zooplankton. A comparison of the estimated slopes provides the first evidence, from continuous measurements, that the gradient of zooplankton spectra may vary according to the size of the organism and, furthermore, that it may be steeper than that for phytoplankton both as an individual size class (500-1000 ?m) and as an ensemble (250-2000 ?m). The latter result is the exact opposite of conventional wisdom founded on previous observations. Our results highlight significant deficiencies in current models for plankton patchiness.

  2. 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

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

    Science.gov (United States)

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

    2006-01-01

    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.

  4. What Are Migration Networks?

    OpenAIRE

    Bauer, Thomas; Gang, Ira; Epstein, Gil

    2000-01-01

    Migration networks are usually captured by the number of people from the migrant?s country in the host region. Using Mexican migration data, we analyze the effects of the usual network variable and two additional origin-village-specific variables on migrants? location choice.

  5. Monarchs and Migration

    Science.gov (United States)

    0000-00-00

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

  6. Environmental change and migration.

    Czech Academy of Sciences Publication Activity Database

    Stojanov, Robert

    Santa Barbara, Calif : Praeger, 2012 - (Segal, U.; Elliot, D.), s. 55-89 ISBN 978-0-313-37807-2 R&D Projects: GA MŠk(CZ) ED1.1.00/02.0073 Institutional research plan: CEZ:AV0Z60870520 Keywords : migration processes * environmental change * climate change * environmental migrants * human migration Subject RIV: AO - Sociology, Demography

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

    OpenAIRE

    Sharma, B. K.; Sharma, S.

    2012-01-01

    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 sampl...

  8. Evaluation of sound extinction and echo interference in densely aggregated zooplankton

    Directory of Open Access Journals (Sweden)

    Natalia Gorska

    2000-09-01

    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.

  9. Vertical Line Test

    Science.gov (United States)

    2011-05-24

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

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

    International Nuclear Information System (INIS)

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

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

    Energy Technology Data Exchange (ETDEWEB)

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

    2014-07-01

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

  12. Vertical sleeve gastrectomy

    Science.gov (United States)

    ... or kidney Risks for vertical sleeve gastrectomy are: Gastritis (inflamed stomach lining), heartburn, or stomach ulcers Injury ... You may be asked to stop taking aspirin, ibuprofen (Advil, Motrin), vitamin E, warfarin (Coumadin), and any ...

  13. Prediction of uranium migration in granite media

    International Nuclear Information System (INIS)

    Choosing a preselected high level radioactive waste disposal site as study area, a hydrogeologic migration function is constructed. Several hydrogeologic parameters such as vertical dispersity, diffusion coefficient, flow velocity, simulated groundwater concentrations are discussed, and distribution coefficient of granites particles in the study area was measured by using batch method. Meanwhile the conditions after the uranium entered into the groundwater were simulated and predicted by using American hydrologic modeling software PHREEQC-II. The different roles of the various influential factors such as the pH values, dispersity and diffusion coefficient in the simulation are analyzed. The results show that pH values, dispersity and diffusion coefficient have an important influence on the nuclide migration in the groundwater of study area. (authors)

  14. Least-squares reverse-time migration of Cranfield VSP data for monitoring CO2 injection

    Science.gov (United States)

    TAN, S.; Huang, L.

    2012-12-01

    Cost-effective monitoring for carbon utilization and sequestration requires high-resolution imaging with a minimal amount of data. Least-squares reverse-time migration is a promising imaging method for this purpose. We apply least-squares reverse-time migration to a portion of the 3D vertical seismic profile data acquired at the Cranfield enhanced oil recovery field in Mississippi for monitoring CO2 injection. Conventional reverse-time migration of limited data suffers from significant image artifacts and a poor image resolution. Lease-squares reverse-time migration can reduce image artifacts and improves the image resolution. We demonstrate the significant improvements of least-squares reverse-time migration by comparing its migration images of the Cranfield VSP data with that obtained using the conventional reverse-time migration.

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

    Science.gov (United States)

    Li, Xiaoyu; Yu, Hongxian; Ma, Chengxue

    2014-11-01

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

  16. Determinants of Migration, Revisited

    OpenAIRE

    Alexander, Gigi; Foley, Maggie

    2014-01-01

    This empirical study investigates the impact on net state in-migration over the 2000-2003 period of a variety of economic and non-economic factors and thereby serves as a robustness test of previous studies. The empirical estimates indicate that the net state in-migration rate was an increasing function of median family income or expected median family income on the one hand and a decreasing function of the average cost of living. In addition, net state in-migration was an increasing function...

  17. Fiscal and migration competition

    OpenAIRE

    Razi?n, Assaf; Sadka, Efraim

    2010-01-01

    It is often argued that tax competition may lead to a 'race to the bottom'. This result may indeed hold in the case of factor mobility (such as capital). However, in this paper we emphasize the unique feature of labor migration, that may nullify the'race to the bottom' hypothesis. Labor migration is governed not only by net-of-tax factor rewards, but rather importantly also by the benefits that the welfare state provides. The paper analyzes fiscal competition with and without migration in a t...

  18. Forced Migration Projects

    Science.gov (United States)

    The Forced Migration Projects (FMP), operating under the auspices of the Open Society Institute (OSI), monitor developments in the Americas, the former Yugoslavia, and the former Soviet Union to identify the social, political, and economic conditions that cause the forced dislocations of people. This Website provides background information about the projects as well as full-text access to several FMP publications including The Forced Migration Monitor, a series of special reports on refugees and migration, recent news and articles on germane issues, and FM Alert, an electronic bulletin service. In addition, the site compiles a list of refugee-related links and hosts a discussion forum.

  19. Influence of wastewater on zooplankton communities in the Daugava River upstream and downstream of Daugavpils over the last 50 years

    Directory of Open Access Journals (Sweden)

    Deksne R.

    2011-11-01

    Full Text Available During expeditions to the section of the Daugava River from Surozha in Belarus to Dunava in Latvia in 2008, and during expeditions to the Kraslava-Dunava section in 2009, zooplankton were sampled. Quantitative characteristics, the relation of zooplankton taxonomic groups, the saprobity index and species diversity (Shannon-Wiener index were employed for the analysis of zooplankton community structure in the Daugava River. The results were compared with the Daugava zooplankton findings of the research carried out by Škute in 1962–1968 in similar sections of the river. Both in 1962–1963 and in 2005–2009, the base complex of the Daugava River zooplankton comprised cosmopolitan species; as for the diversity of species, the leading group of organisms was Rotifera. A tendency for decrease in the diversity of species was recorded. Relevant changes were recorded in the structure of taxa. The Daugava River is polluted by Daugavpils’ wastewater; however, the untoward influence of pollution on zooplankton is observed only in years and in seasons with low water level and discharge. Decrease in the amount of zooplankton occurs not only in the dominant species, but also in the decrease or even disappearance of oligosaprobes.

  20. 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 ...

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

    Science.gov (United States)

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

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

    Science.gov (United States)

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

    2014-11-01

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

  3. Zooplankton standing stock, community structure and diversity in the northern Arabian Sea

    Digital Repository Service at National Institute of Oceanography (India)

    Goswami, S.C; Srivastava, Y.

    1996-01-01

    station (lat. 22 degrees 07'N and long. 67 degrees 03'E) and was due to swarm of gammarid amphipods and shoal of sergestid shrimp Acetes johni. Herbivores dominated the zooplankton community and copepods were most abundant (36.9 to 71.7%). The other...

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

    Science.gov (United States)

    Luo, Jinhuo

    2013-10-01

    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

  5. Biochemical composition of zooplankton of Bombay High (oil platform) area in the Arabian Sea

    Digital Repository Service at National Institute of Oceanography (India)

    Bhat, K.L.; Wagh, A.B.

    1992-01-01

    Variations in the biochemical constituents and calorific values of zooplankton from an off-shore oil processing platform were estimated. Mean value of biomass was 0.35 ml.m/3 with relatively higher values during post-monsoon period. Copepods formed...

  6. DEGRADATION OF THE PERITROPHIC MEMBRANE OF FRESH-WATER ZOOPLANKTON FECAL PELLETS

    Science.gov (United States)

    Fecal pellets produced by Lake Michigan and Douglas Lake zooplankton in laboratory experiments were settled gently onto microscope slides in specially designed settling chambers. Permanent slides of settled pellets were made in triplicate 24, 48, 72, 96, 120, and 144 hours after ...

  7. Biochemical composition and caloric potential of zooplankton from Bay of Bengal

    Digital Repository Service at National Institute of Oceanography (India)

    Sreepada, R.A.; Rivonker, C.U.; Parulekar, A.H.

    1992-01-01

    .62, 4.95, 1.54, 0.43, 4.4 and 4.16 respectively on wet weight basis. A good correlation of caloric potential with protein and lipid indicated to a certain extent that protein and lipid act as metabolic reserves of the zooplankton in the area...

  8. Trace metal dynamics in zooplankton from the Bay of Bengal during summer monsoon

    Digital Repository Service at National Institute of Oceanography (India)

    Rejomon, G.; DineshKumar, P.K.; Nair, M.; Muraleedharan, K.R.

    2010-01-01

    of the northeast coast, and lowest concentrations in the open ocean warm gyre regions. The average trace metal concentrations (mu g g su(-1)) in coastal zooplankton (Fe, 44894.1 + or – 12198.2; Co, 46.2 + or – 4.6; Ni, 62.8 + or – 6.5; Cu, 84.9 + or – 6.7; Zn, 7546...

  9. Richness of Phytoplankton and Zooplankton in Water Streams at Jobolarangan Forest

    Directory of Open Access Journals (Sweden)

    WIRYANTO

    2001-07-01

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

  10. Heavy metals and zooplankton with special reference to Minamata (Japan) mercury pollution - A case study

    Digital Repository Service at National Institute of Oceanography (India)

    Gajbhiye, S.N.; Hirota, R.

    1993-01-01

    mercury was discharged about 30 years ago is still contaminated. Concentrations of total Hg in zooplankton decreased with increasing distance from the point of incident. Total Hg varied in the range of 0.037 to 5.40 mu g g/1 (dry) whereas methyl mercury...

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

    Directory of Open Access Journals (Sweden)

    Vesela Evtimova

    2014-04-01

    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.

  12. Relative abundance and diel variation of zooplankton from south west coast of India

    Digital Repository Service at National Institute of Oceanography (India)

    Santhakumari, V.; Peter, K.J.

    1993-01-01

    the traditional fishing grounds of Kerala Coast. Average biomass values ranged from 45-95 ml 100/m sup(-3). Increase in zooplankton at night was discernible at most of the stations and the highest biomass noticed was 131 ml 100/m sup(-3). Copepods formed the most...

  13. Changes in fish production effectivity in eutrophic fishponds of zooplankton structure.

    Czech Academy of Sciences Publication Activity Database

    Potužák, J.; H?da, J.; Pechar, Libor

    2007-01-01

    Ro?. 15, - (2007), s. 201-210. ISSN 0967-6120 R&D Projects: GA MŽP(CZ) SM/640/18/03; GA MŽP(CZ) SL/1/6/04 Institutional research plan: CEZ:AV0Z60870520 Keywords : fishponds * zooplankton * eutrophication * fish management * primary production Subject RIV: GL - Fishing Impact factor: 0.828, year: 2007

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

    Directory of Open Access Journals (Sweden)

    Ole-Petter Pedersen

    2010-09-01

    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.

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

    Directory of Open Access Journals (Sweden)

    Sharma, B.K.

    2011-10-01

    Full Text Available Plankton samples collected (November, 2002 – October, 2004 from Waithou and Utra pats, two floodplain lakesin Manipur state of northeast India, revealed species rich zooplankton (121 species with diverse nature of Rotifera (75 species.The individual pats exhibited rich species diversity (110 and 103 species and high monthly richness (68±7 and 61±8 speciesrespectively with higher community similarities. Zooplankton formed important quantitative component (56.0±4.3 % and55.1±5.1 % of net plankton of the two pats; Rotifera dominantly contributed to their abundance while Cladocera > Copepodawere sub-dominant groups. The richness and abundance showed significant variations between pats and between months andfollowed oscillating annual patterns in each pat except for peaks during winter. Zooplankton indicated higher species diversityand evenness, lower dominance, lack of quantitative importance of individual species, low densities and equitable abundance ofthe majority of species in both pats. The richness correlated inversely only with nitrate in Waithou pat and abundance positivelycorrelated with alkalinity only in Utra Pat. Canonical correspondence analysis (CCA with abiotic factors explained 55.6 % and61.8% cumulative variance of zooplankton assemblages of Waithou and Utra pats respectively along axis 1 and 2.

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

    Czech Academy of Sciences Publication Activity Database

    Stockdale, A.; Tipping, E.; Lofts, S.; Fott, J.; Garmo, Ø.; Hruška, Jakub; Keller, B.; Löfgren, S.; Maberlyh, S.; Majer, V.; Nierzwicki-Bauer, S. A.; Persson, G.; Schartau, A.; Thackeray, S. J.; Valois, A.; Vrba, Jaroslav; Walseng, B.; Yan, N.

    2014-01-01

    Ro?. 186, MAR (2014), s. 115-125. ISSN 0269-7491 R&D Projects: GA MŠk(CZ) ED1.1.00/02.0073; GA ?R GA206/07/1200 Institutional support: RVO:67179843 ; RVO:60077344 Keywords : chemical speciation * bioavailability * recovery * crustacean zooplankton * lakes Subject RIV: EH - Ecology, Behaviour Impact factor: 3.902, year: 2013

  17. Migration = cloning; aliasiing

    DEFF Research Database (Denmark)

    Hüttel, Hans; Kleist, Josva

    1999-01-01

    In Obliq, a lexically scoped, distributed, object-oriented programming language, object migration was suggested as the creation of a copy of an object’s state at the target site, followed by turning the object itself into an alias, also called surrogate, for the remote copy. We consider the creation of object surrogates as an abstraction of the abovementioned style of migration. We introduce Øjeblik, a distribution-free subset of Obliq, and provide three different configuration-style semantics, which only differ in the respective aliasing model. We show that two of the semantics, one of which matches Obliq’s implementation, render migration unsafe, while our new proposal for a third semantics is provably safe. Our work suggests a straightforward repair of Obliq’s aliasing model such that it allows programs to safely migrate objects.

  18. Migration and Place Attractiveness

    OpenAIRE

    Niedomysl, Thomas

    2006-01-01

    The thesis includes six self-contained papers that from various perspectives examine place attractiveness and migration in Sweden. Paper I provides an extensive overview of Swedish municipalities’ place marketing engagement to attract in-migrants, based on survey responses from 220 municipalities. The results suggest that, although this kind of marketing has become more prominent during the last few years, there is little evidence of any significant effects on migration flows. Paper II ad...

  19. Essays on international migration

    OpenAIRE

    Chowdhury, Mehdi Mahmud

    2011-01-01

    In recent time efforts are observed in re-evaluating the linkage between economic development and international migration. The thesis can be considered as an attempt to add something to those efforts. In this thesis we mainly analyse the effects of competition among the countries in international labour market and effects of migration on the research activities of firms. As appeared, these two issues so far have not received much attention of economic literature. We analyse the above men...

  20. Migration of Interplanetary Dust

    OpenAIRE

    Ipatov, S. I.; Mather, J. C.; Taylor, P. A.

    2003-01-01

    We numerically investigate the migration of dust particles with initial orbits close to those of the numbered asteroids, observed trans-Neptunian objects, and Comet Encke. The fraction of silicate asteroidal particles that collided with the Earth during their lifetime varied from 1.1% for 100 micron particles to 0.008% for 1 micron particles. Almost all asteroidal particles with diameter d>4 microns collided with the Sun. The peaks in the migrating asteroidal dust particles'...

  1. Migration and Culture

    OpenAIRE

    Epstein, Gil S.; Gang, Ira N.

    2010-01-01

    Culture is not new to the study of migration. It has lurked beneath the surface for some time, occasionally protruding openly into the discussion, usually under some pseudonym. The authors bring culture into the open. They are concerned with how culture manifests itself in the migration process for three groups of actors: the migrants, those remaining in the sending areas, and people already living in the recipient locations. The topics vary widely. What unites the authors is an understanding...

  2. MODERN MIGRATION POLICY OF RUSSIA

    Directory of Open Access Journals (Sweden)

    Kobylinsky S. V.

    2014-11-01

    Full Text Available Several peculiarities of the implementation of migration policy in the Russian Federation were considered in this article. We have shown main provisions on refugees and forced migrants from the Ukraine and labor migration. On the basis of the study we have suggested an improvement of migration legislation, in particular, creation of a single codex and migration police

  3. Migration and malaria.

    Science.gov (United States)

    Jitthai, Nigoon

    2013-01-01

    Migration is an important global issue as poorly managed migration can result in a diversity of problems, including an increase in the transmission of diseases such as malaria. There is evidence to suggest that malaria is no longer a forest-dependent disease and may largely be affected by population movements, mostly to agricultural areas. While internal and transnational migration has different legal implications in most countries, both types of migration occur for the same reasons; economic and/ or safety. Although migration in itself is not a definitive risk for malaria, several factors can put, migrants and local communities alike, in vulnerable situations. In particular, infrastructure and rural development, deforestation for logging and economic farming, political movements, and natural disasters are some of the major factors that push and pull people in and out of malaria-endemic areas. Therefore, understanding the changing socio-environmental situation as well as population movements and their associated risks for malaria infection, is critical for malaria control, containment, and elimination. Efforts to address these issues should include advocacy, mapping exercises and expanded/ strengthened surveillance to also include migrant health information systems. Malaria related information, prevention measures, and early diagnosis and appropriate treatment should be made easily accessible for migrants regardless of their migration status; not only to ensure that they are equipped with appropriate knowledge and devices to protect themselves, but also to ensure that they are properly diagnosed and treated, to prevent further transmission, and to ensure that they are captured by the surveillance system. PMID:24159832

  4. Stable oxygen and hydrogen isotope analyses of bowhead whale baleen as biochemical recorders of migration and arctic environmental change

    Science.gov (United States)

    deHart, Pieter A. P.; Picco, Candace M.

    2015-06-01

    An analysis of the stable isotopes of oxygen (?18O) and hydrogen (?D) was used to examine the linkage between sea ice concentration and the migration of western arctic bowhead whales (Balaena mysticetus; WABW). We compared ?18O and ?D variability along the length of WABW baleen with isotopic values of zooplankton prey from different WABW habitat, with published ?13C and ?15N data, and with historical sea ice records. Zooplankton signatures varied widely (?18O = -13‰-56‰; ?D = -220‰ to -75‰), with regional separation between winter (Bering Sea) and summer (eastern Beaufort Sea) habitats of WABW observable in ?D. The ?18O and ?D of WABW varied significantly along the length of baleen (?18O = 8-18‰; ?D = -180 to -80‰), confirming seasonal migration and reflecting distinct regional dietary variation in isotopes. WABW migration appears to have varied concomitant with temporal sea ice concentration (SIC) changes; in years with high SIC, the difference in ?D of WABW baleen between seasonal habitats was significantly greater than low SIC periods. This work shows that SIC is not only a determinant of habitat accessibility for WABW, but baleen may also be a record of historical SIC and Arctic climate.

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

    Directory of Open Access Journals (Sweden)

    Jafari Naser

    2011-01-01

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

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

    Science.gov (United States)

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

    2014-12-01

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

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

    DEFF Research Database (Denmark)

    Mitra, Aditee; Castellani, Claudia

    2014-01-01

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

  8. Verticality detecting device

    International Nuclear Information System (INIS)

    The device of the present invention is effective for the detection of verticality of fuel rods for a nuclear reactor. Namely, a lower fixed disk and an upper fixed disk are disposed with the surfaces to be used being opposed each other while having a gas of g = d + t, assuming as the outer diameter of a material to be tested as d and a verticality allowable value t. A voltage apply means for applying week voltage and a conduction detecting means for detecting the presence or absence of conduction between a material to be tested and the upper fixed disk are disposed between them. There is disposed a device for inserting a material to be tested, which allows the material to be tested to pass, while rotating, between the upper and the lower fixed disks. With such a constitution, when the verticality of the material to be tested is > t, the curved portion of the material to be tested is brought into contact with the upper fixed disk to flow weak current between them. The detection of the week current by the conduction detecting means enables determination whether the verticality of the material to be tested is greater or smaller than the allowable value. The device of the present invention enables automatic detection for the verticality of fuel rods, as a result, the detection can be improved, the labor and exposure dose can be reduced. (I.S.)

  9. Recent blooms of the dinoflagellate Ceratium in Albert Falls Dam (KZN): history, causes, spatial features and impacts on a reservoir ecosystem and its zooplankton

    Scientific Electronic Library Online (English)

    Rob C, Hart; Peter D, Wragg.

    2009-07-01

    Full Text Available A lake-wide bloom of the dinoflagellate Ceratium hirundinella, discovered in Albert Falls Dam in October 2006, exposed a significant ecological change indicative of reduced water quality in this historically mesotrophic reservoir. The spatial distribution of the bloom was examined synoptically in Oc [...] tober 2006 and January 2007; these surveys revealed generally higher dinoflagellate densities in inshore reaches of the lake, and especially in the discharge plume of the inflowing Mgeni River. Ceratium totally dominated the phytoplankton assemblage, accounting almost completely for coincident chlorophyll levels, which generally increased with depth to generate a 'deep' chlorophyll maximum. Vertical oxygen profiles during the bloom differed substantially from corresponding profiles during non-bloom conditions historically typical in this reservoir. Direct count data and ordination analysis using non-metric multidimensional scaling exposed marked changes in zooplankton community structure compared to seasonally congruent non-bloom conditions in other years. Changes included the effective replacement of Moina by Bosmina, substantial reductions in Daphnia and Ceriodaphnia, and smaller but definite increases in abundance especially of calanoid copepods, as well as cyclopoid copepods and of Chaoborus, although not all of these differences were apparent in both survey months. These compositional changes are attributable to intrinsic differences in feeding biology among taxa and their associated susceptibility to the altered food environment, which was commensurate with Ceratium's emergence. In addition, chydorid cladocerans appeared as a new (but spatially restricted) eutrophic bio-indicator component of the zooplankton, and the species diversity of cyclopoid copepods was enriched. The historical incidence of Ceratium in the lake since 1995 coincided with low NO3-N:TP values (used here as an N:P ratio proxy), particularly of inflow waters, and with broadly coincident values in the open lake. Ceratium was present but sparse in 1995, at average N:P ratios around 5.5. It disappeared in 1996 when the ratio increased radically to >10, and reappeared in 2004 after an erratic decline of the ratio to

  10. Migration of radionuclides following shallow land burial

    International Nuclear Information System (INIS)

    The site of a former nuclear laboratory and shallow land burial facility 25 km southwest of Chicago (USA) has been examined for radionuclide migration and residual radioactive materials. The radioactivity was produced during operations with the first nuclear reactors and associated research from 1943 to 1955. The chronology of events and details of the decommissioning procedures, including reactor burial, are described. Surface soil, surface water, soil borings drilled through and around the facility, and water from the dolomite aquifer and glacial till overburden were analyzed for a variety of radionuclides. The only nuclide found to have migrated out of the burial site is hydrogen-3, as tritiated water. This nuclide was detected in surface water, soil water, and nearby picnic wells. The concentrations in the wells show a seasonal fluctuation, from 0.1 nCi/t in the summer to 14 nCi/l in the recharging of the groundwater winter, that is attributed to by spring rains. Water migration rates in the glacial till and dolomite were estimated by several methods. The time of travel of water to the nearest well, 400 m from the facility, is estimated to be 58 months. The vertical and horizontal distribution of tritium in the glacial till was measured. The origin of the tritium, neutron-irradiated lithium, was established from measurements of the hydrogen isotopic ratios. Concentrations of other radionuclides in soil and water were normal, except for plutonium (at about twice fallout concentrations) in the first 2 m below the buried material. The solid-element nuclides have migrated very little. Exposure pathways and their associated doses, and procedures for retarding further migration are discUssed. (author)

  11. Globalization, Migration and Development

    Directory of Open Access Journals (Sweden)

    George, Susan

    2002-01-01

    Full Text Available EnglishMigration may become the most important branch of demography in the earlydecades of the new millennium in a rapidly globalizing world. This paper discusses the causes, costsand benefits of international migration to countries of the South and North, and key issues of commonconcern. International migration is as old as national boundaries, though its nature, volume,direction, causes and consequences have changed. The causes of migration are rooted in the rate ofpopulation growth and the proportion of youth in the population, their education and training,employment opportunities, income differentials in society, communication and transportationfacilities, political freedom and human rights and level of urbanization. Migration benefits the Souththrough remittances of migrants, improves the economic welfare of the population (particularly womenof South countries generally, increases investment, and leads to structural changes in the economy.However, emigration from the South has costs too, be they social or caused by factors such as braindrain. The North also benefits by migration through enhancement of economic growth, development ofnatural resources, improved employment prospects, social development and through exposure toimmigrants' new cultures and lifestyles. Migration also has costs to the North such as of immigrantintegration, a certain amount of destabilization of the economy, illegal immigration, and socialproblems of discrimination and exploitation. Issues common to both North and South include impact onprivate investment, trade, international cooperation, and sustainable development. Both North andSouth face a dilemma in seeking an appropriate balance between importing South's labour or itsproducts and exporting capital and technology from the North.FrenchLa migration est sans doute devenue la partie la plus importante de la démographie des premières décennies du nouveau millénaire dans un monde qui change rapidement. Ce document porte sur les causes, les coûts et les avantages de la migration internationale vers les pays du Sud et du Nord ainsi que sur les grandes préoccupations communes. La migration internationale existe depuis l'avènement des frontières nationales, bien que sa nature, son volume, sa direction ainsi que ses causes et conséquences aient changé. Les causes de la migration trouvent leur origine dans le taux de croissance d'une population, sa proportion de jeunes, leur niveau d'éducation et de formation, les occasions d'emploi, les écarts de revenu dans la société, les systèmes de communication et de transport, la liberté politique, les droits de la personne et le niveau d'urbanisation. La migration profite au Sud parce que les migrants envoient de l'argent, améliorant généralement le bien-être économique de la population (surtout celui des femmes des pays du Sud, augmentant les investissements et donne lieu à des changements structuraux de l'économie. Cependant, l'émigration du Sud a tout de même un prix, que ce soit social ou causé par des facteurs tels que l'exode des cerveaux. Le Nord profite aussi de la migration grâce à une meilleure croissance économique, l'exploitation de richesses naturelles, de meilleures possibilités d'emploi et le développement social par l'exposition aux nouvelles cultures et styles de vie des immigrants. La migration a aussi un prix pour le Nord tel que l'intégration des immigrants, une certaine déstabilisation de l'économie, l'immigration illégale ainsi que les problèmes sociaux relatifs à la discrimination et à l'exploitation. Les préoccupations communes au Sud et au Nord incluent les incidences sur les investissements privés, le commerce, la coopération internationale et le développement durable. Autant le Nord que le Sud doivent composer avec le dilemme de trouver l'équilibre entre l'importation de la main-d'œuvre du Sud.

  12. Zooplankton from a polluted river, Mula (India, with record of Brachionus rubens (Ehrenberg, 1838 epizoic on Moina macrocopa (Straus, 1820

    Directory of Open Access Journals (Sweden)

    Vanjare, A.I.

    2010-06-01

    Full Text Available Rotifera and Cladocera are free living zooplankton elements known to dominate freshwater habitats. Few rotifersare known to be parasitic and epizoic living in association with other organisms. Zooplankton from the polluted river Mula, Pune,Maharashtra was sampled from January to November 2009. Eighteen rotifers and ten cladocerans were recorded during the study.Samples revealed rotifer Brachionus rubens (Ehrenberg, 1838 epizoic on cladoceran Moina macrocopa (Straus, 1820, theoccurrence of which coincided with lower dissolved oxygen (DO content. The rotifers Asplanchnopus multiceps (Schrank,1793, Lacinularia elliptica (Shephard, 1897 and the cladoceran Kurzia longirostris (Daday, 1898 are new records to Maharashtrastate. The present study was an attempt to monitor a polluted habitat for zooplankton fauna. Detailed studies onorganically polluted eutrophic habitats could add new insights into zooplankton diversity and behaviour.

  13. Biometrics and international migration.

    Science.gov (United States)

    Redpath, Jillyanne

    2007-01-01

    This paper will focus on the impact of the rapid expansion in the use of biometric systems in migration management on the rights of individuals; it seeks to highlight legal issues for consideration in implementing such systems, taking as the starting point that the security interests of the state and the rights of the individual are not, and should not be, mutually exclusive. The first part of this paper briefly describes the type of biometric applications available, how biometric systems function, and those used in migration management. The second part examines the potential offered by biometrics for greater security in migration management, and focuses on developments in the use of biometrics as a result of September 11. The third part discusses the impact of the use of biometrics in the management of migration on the individual's right to privacy and ability to move freely and lawfully. The paper highlights the increasing need for domestic and international frameworks to govern the use of biometric applications in the migration/security context, and proposes a number of issues that such frameworks could address. PMID:17536151

  14. Colisión en dirección vertical

    Directory of Open Access Journals (Sweden)

    A Manzur

    2008-06-01

    Full Text Available Se presenta un experimento de demostración que ilustra una situación en la que las leyes de conservación del ímpetu y de la energía mecánica no se cumplen; sin embargo, su uso permite obtener una buena descripción cualitativa del resultado. El objetivo se logra al analizar la colisión vertical que se produce entre dos pelotas. Las pelotas con masas apropiadas se dejan caer, con la más liviana encima de la más masiva. Después de chocar con el suelo, la pelota inferior carece de movimiento vertical, mientras que la pelota de encima rebota hasta una altura mayor que la altura desde donde fueron soltadasThe demonstration experiment here presented illustrates a situation where the conservation laws of linear momentum and mechanical energy are not satisfied; however, their use allows a good qualitative description of the result observed. The objective is satisfactorily gotten by the analysis of the vertical collision between two balls. The balls with the appropriate masses are dropped, the small mass resting on top of the larger mass; after the collision between the bottom ball and the floor this ball does not have vertical motion, whereas the top ball rebounds up to a height higher than its original height

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

    Directory of Open Access Journals (Sweden)

    W. Ekau

    2010-05-01

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

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

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

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

    Directory of Open Access Journals (Sweden)

    W. Ekau

    2009-05-01

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

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

    This paper elucidates the role of DO for different taxa in the pelagic realm and the consequences of low oxygen for foodweb structure and system productivity.

  17. Long-term changes of the crustacean zooplankton community in Lake Mjøsa, the largest lake in Norway

    OpenAIRE

    Løvik, Jarl Eivind; Gösta KJELLBERG

    2003-01-01

    Lake Mjøsa has been subject to an accelerating eutrophication from the 1950s to the mid 1970s, but comprehensive nutrient reduction efforts caused marked reductions of phytoplankton production and biomass during the 1980s, a process that continued during the 1990s. Zooplankton biomass and species composition was considerably affected during the eutrophication and subsequent oligotrophication. Total crustacean zooplankton biomass decreased along with decreasing algal biomass during the 1980s a...

  18. Zooplankton from a polluted river, Mula (India), with record of Brachionus rubens (Ehrenberg, 1838) epizoic on Moina macrocopa (Straus, 1820)

    OpenAIRE

    Vanjare, A.I.; Padhye, S.M.; Pai, K

    2010-01-01

    Rotifera and Cladocera are free living zooplankton elements known to dominate freshwater habitats. Few rotifersare known to be parasitic and epizoic living in association with other organisms. Zooplankton from the polluted river Mula, Pune,Maharashtra was sampled from January to November 2009. Eighteen rotifers and ten cladocerans were recorded during the study.Samples revealed rotifer Brachionus rubens (Ehrenberg, 1838) epizoic on cladoceran Moina macrocopa (Straus, 1820), theoccurrence of w...

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

    Science.gov (United States)

    Lavaniegos, Bertha E.; Ohman, Mark D.

    2007-10-01

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

  20. Migration Information Source

    Science.gov (United States)

    As a publication of the Migration Policy Institute, the Migration Information Source "provides fresh thought, authoritative data from numerous global organizations and governments, and global analysis of international migration and refugee trends." Their well-organized homepage offers policy briefs, "Spotlight" features (including a recent one on Indian immigrants in the United States), and information about their ongoing projects. Policy makers and scholars will love the "Immigration Data Hub" area. Here they can get valuable data on state responses to immigrations, the top global destinations for Irish immigrants, as well as historical immigration data. Visitors can also use the "US in Focus" area to find out about specific immigration trends throughout the country, with a special focus on policy issues affecting states and urban areas. The site is rounded out by an RSS feed, a press room of recent news releases, and a glossary of terms.

  1. 210Po/210Pb dynamics in relation to zooplankton biomass and trophic conditions during an annual cycle in northwestern Mediterranean coastal waters

    International Nuclear Information System (INIS)

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

  2. Evaluation of factors related to increased zooplankton biomass and altered species composition following impoundment of a Newfoundland reservoir

    International Nuclear Information System (INIS)

    An 11-year study of the zooplankton community in Cat Arm Hydroelectric Reservoir in Newfoundland was conducted to assess long-term zooplankton community dynamics in a subarctic system. Zooplankton biomass and species compositions were monitored from 1983 to 1993. The monitoring program documented the trophic evolution of the Cat Arm system as it changed from a shallow lake with short water retention time to a deep reservoir with a much lower flushing rate. Zooplankton biomass increased approximately 19-fold in the oligotrophic hydroelectric reservoir following impoundment in 1984, relative to biomass in the preexisting lake. During the first three years of impoundment, there were no increases in either phytoplankton biomass or primary productivity. Natality of the dominant cladoceran (Daphnia catawba) did not increase. Summer water retention time increased from pre-impoundment levels of 4 days in 1983 to 338 days in 1993. The study showed that zooplankton biomass was greatly correlated with water retention time, and showed no major correlation with phytoplankton biomass, primary productivity, nutrient concentrations, pH, colour, or epilimnetic temperature. It was concluded that changes in the zooplankton community in the hydroelectric reservoir were a result of decreases in losses due to washout. 41 refs., 2 tabs., 6 figs

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

    Directory of Open Access Journals (Sweden)

    Vanessa Gazulha

    2011-08-01

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

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

    Energy Technology Data Exchange (ETDEWEB)

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

    1996-01-01

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

  5. Migration scenarii in extrasolar systems

    Directory of Open Access Journals (Sweden)

    Crida A.

    2011-02-01

    Full Text Available In this review talk, I present the theory of type I migration of small mass planets, and its latest developments that open the possibility of outward migration in the inner part of a protoplanetary disk. I also review the type II migration of giant planets, and mention the runaway, type III. Then, we focus on the migration of pairs of planets in resonance. The eccentricity of the planets raise, and possibly their mutual inclination as well. Also, the migration rate can be changed, and directed outward if the outer planet is the lighter. Last, we present a synthetic scenario of migration for the giant planets of our Solar System.

  6. Migration of seismic data

    International Nuclear Information System (INIS)

    Prospecting for oil and gas resources poses the problem of determining the geological structure of the earth's crust from indirect measurements. Seismic migration is an acoustic image reconstruction technique based on the inversion of the scalar wave equation. Extensive computation is necessary before reliable information can be extracted form large sets of recorded data. In this paper a collection of open-quotes industrialclose quotes migration techniques, each giving rise to a data parallel algorithm, is outlined. Computer simulations on synthetic seismic data illustrate the problem and the approach

  7. Is Migration Feminized?

    OpenAIRE

    Tokso?z, Gu?lay

    2012-01-01

    In the context of Turkey’s accession to the EU, the issue of potential migration from Turkey and its impact upon European labor markets became one of the concerns of the EU, considering Turkey’s growing population and young labor force. In 2011, half a century after the bi-lateral agreement between Turkey and Germany on labor recruitment in 1961, migration plays a key role in relations of Turkey with the EU and will even increase its significance – not necessarily for the next fifty ye...

  8. Migration, klima og sundhed

    DEFF Research Database (Denmark)

    Tellier, Siri; Carballo, Manuel

    2009-01-01

    Many tentative connections have been postulated between migration and climate. This article points to rural-urban migration, particularly into low elevation urban slums prone to flooding as an issue needing urgent attention by health professionals. It also notes the no-man's land in which environmental refugees find themselves and the consequences this may have. Finally, it points to the urgent need to reform health systems in both developing and developed countries to adapt to rapidly changing disease patterns and to become more responsive to them. Udgivelsesdato: 2009-Oct-26

  9. Unix Application Migration Guide

    CERN Document Server

    Microsoft. Redmond

    2003-01-01

    Drawing on the experience of Microsoft consultants working in the field, as well as external organizations that have migrated from UNIX to Microsoft® Windows®, this guide offers practical, prescriptive guidance on the issues you are likely to face when porting existing UNIX applications to the Windows operating system environment. Senior IT decision makers, network managers, and operations managers will get real-world guidance and best practices on planning and implementation issues to understand the different methods through which migration or co-existence can be accomplished. Also detailing

  10. What's driving migration?

    Science.gov (United States)

    Kane, H

    1995-01-01

    During the 1990s investment in prevention of international or internal migration declined, and crisis intervention increased. The budgets of the UN High Commissioner for Refugees and the UN Development Program remained about the same. The operating assumption is that war, persecution, famine, and environmental and social disintegration are inevitable. Future efforts should be directed to stabilizing populations through investment in sanitation, public health, preventive medicine, land tenure, environmental protection, and literacy. Forces pushing migration are likely to increase in the future. Forces include depletion of natural resources, income disparities, population pressure, and political disruption. The causes of migration are not constant. In the past, migration occurred during conquests, settlement, intermarriage, or religious conversion and was a collective movement. Current migration involves mass movement of individuals and the struggle to survive. There is new pressure to leave poor squatter settlements and the scarcities in land, water, and food. The slave trade between the 1500s and the 1800s linked continents, and only 2-3 million voluntarily crossed national borders. Involuntary migration began in the early 1800s when European feudal systems were in a decline, and people sought freedom. Official refugees, who satisfy the strict 1951 UN definition, increased from 15 million in 1980 to 23 million in 1990 but remained a small proportion of international migrants. Much of the mass movement occurs between developing countries. Migration to developed countries is accompanied by growing intolerance, which is misinformed. China practices a form of "population transfer" in Tibet in order to dilute Tibetan nationalism. Colonization of countries is a new less expensive form of control over territory. Eviction of minorities is another popular strategy in Iraq. Public works projects supported by foreign aid displace millions annually. War and civil conflicts have increased since the 1950s from 10 to 34. Of the 82 armed conflicts between 1988 and 1992, only 3 were between countries. Journalist Robert Kaplan suggests that future instability will occur due to heightened crime and fragmentation of government systems. The African continent has experienced very high migration. PMID:12288448

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

    International Nuclear Information System (INIS)

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

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

    Directory of Open Access Journals (Sweden)

    Hu He

    2014-02-01

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

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

    International Nuclear Information System (INIS)

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

  14. The International Organization for Migration in Global Migration Governance

    OpenAIRE

    Poulsen, Sofie Havn; Andersen, Lise

    2011-01-01

    This project focuses on the IOM, the notion of global governance of migration and the interaction between these two. The point of departure has been an attempt to grasp the current global approach to migration and comprehend whether, or to what degree, there is governance of migration issues taking place at a global level.

  15. Oceanic migration behaviour of tropical Pacific eels from Vanuatu

    DEFF Research Database (Denmark)

    Schabetsberger, R; Økland, F

    2013-01-01

    Information on oceanic migrations and spawning areas of tropical Pacific freshwater eels (genus Anguilla) is very limited. Lake Letas and its single outflowing river, Mbe Solomul on Gaua Island, Vanuatu, were surveyed for large migrating individuals. Twenty-four Anguilla marmorata (87 to 142 cm), 39 A. megastoma (50 to 131 cm), and 3 A. obscura (119 to 126 cm) were caught. Seven individuals were tagged with pop-up satellite transmitters and released offshore. One A. marmorata migrated 843 km towards the South Equatorial Current. The tag surfaced only 330 km from the point where the smallest leptocephalus has been captured so far. Tags on A. megastoma and A. obscura popped up within the archipelago. All 3 species exhibited pronounced diel vertical migrations. Eels descended from around 200 m nighttime depth, to 320 (A. obscura), 650 (A. marmorata), and 750 m (A. megastoma) during the day. A clear impact of the lunar cycle on the upper limit of migration depths was found in A. marmorata (full moon: 230 m, new moon: 170 m). These behaviours may be explained as a trade-off between predator avoidance and the necessity to maintain a sufficiently high metabolism for migration.

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

    Directory of Open Access Journals (Sweden)

    Alessandra PUGNETTI

    1999-08-01

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

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

    OpenAIRE

    Franz Lahnsteiner; Manfred Kletzl; Thomas Weismann

    2012-01-01

    Different feeding methods were tested for burbot, Lota lota, larvae. In small scale experiments with 300 larvae per treatment grinded artemia flakes, enriched artemia flakes, artemia flakes supplemented with dried algae (Chlorella sp., Spirulina sp.) and formulated microdiets consisting of different combinations of fishmeal, fish oil, soybean lecithin, casein, dextran, and artemia flakes were fed over a period of 30 days. These foods were compared to live zooplankton food collected from the n...

  18. Different tolerance of zooplankton communities to insecticide application depending on the species composition.

    OpenAIRE

    Masaki Sakamoto; Yoshinari Tanaka

    2013-01-01

    Natural zooplankton communities are composed of many different species at different trophic levels in the aquatic foodweb. Several researchers have reported that in mesocosm/enclosure experiments, larger cladocerans tend to be moresensitive to carbamate insecticides than smaller ones (Daphnia > Moina, Diaphanosoma > Bosmina). In contrast, resultsfrom individual-level laboratory tests have suggested that large cladoceran species are more tolerant than small species.To clarify this inconsistenc...

  19. Zooplankton community occurrence in an area influenced by uranium mine, Caldas, MG, Brazil

    International Nuclear Information System (INIS)

    The Ore Treatment Unit (UTM), situated on the Pocos de Caldas - MG Plateau, is Brazil's first venture in uranium ore mining and chemical treatment and it belongs to Brazilian Nuclear Industries today. At UTM, radioactive effluents are generated due to the mine's acid drainage processes (MAD). Thus, due to the lack of scientific information with emphasis on Zooplankton Communities in areas impacted by uranium mine and MAD, the current study aimed to evaluate parameters such as electrical conductivity, pH, total phosphorus, total nitrogen, sulfate, fluoride, uranium, thorium, manganese, zinc and aluminum, as well as richness and density of the zooplankton organism's, all in samples from the Pit Mine. The electrical conductivity values observed were elevated (1976 to 2760 ?S cm-1), while the pH values remained acidic (3.6 to 4.1). In respect to the SO4-2, elevated concentrations were observed (366.6 - 1832.0 mg L-1), as well as for F- (33.4 to 75.1 mg L-1). The U presented highest and lowest concentrations in Oct/08 and July/09, that is, 4.25 mg L-1 and 0.12 mg L-1, respectively. The Th concentrations remained constant (0.10 - 0.30 mg L-1). In respect to the Zooplankton Community low species richness and density were observed throughout the whole period. The low richness and density values of the zooplankton species can be related to the adverse environmental conditions, which are unfavorable to the development of this community: elevated values of electrical conductivity and acidic pH, both associated to the chemical composition of the effluent in natura. (author)

  20. Zooplankton diversity and its relation to various limnological parameters in the Arid region of Bikaner, Rajasthan

    OpenAIRE

    Shivani Sharma & Anu Kumar Sharma

    2013-01-01

    Aquatic ecosystems consist of physico-chemical factors and biotic factors. Physico-chemical factors are not alike in all water bodies; they change either due to natural or artificial processes. Zooplanktons are good indicators of the change in water quality because they are strongly affected by environmental conditions and respond quickly to changes in water quality. The present study was carried out for the period of fifteen months from January 2009 to March 2010. The study was carried out a...

  1. Crustacean zooplankton in Lake Constance from 1920 to 1995 : response to eutrophication and re-oligotrophication

    OpenAIRE

    Straile, Dietmar; Geller, Walter

    1998-01-01

    During the first three quarters of this century, the trophic state of Lake Constance changed from oligotrophic to meso-/eutrophic conditions. The response of crustaceans to the eutrophication process is studied by comparing biomasses of crustacean zooplankton from recent years, i.e. from 1979-1995, with data from the early 1920s (AUERBACH et a1. 1924, 1926) and the 1950s (MUCKLE & MUCKLEROTTENGATTER 1976). This comparison revealed a several-fold increase in crustacean biomass. The relative bi...

  2. Spatial variations in zooplankton diversity in waters contaminated with composite effluents

    Directory of Open Access Journals (Sweden)

    Asitava CHATTERJEE

    2007-08-01

    Full Text Available Zooplankton species are cosmopolitan in their clean freshwater habitat and are also found in industrial and municipal wastewaters. The present study records for the first time the aspects of zooplankton diversity in relation to physico-chemical environment of five selected sites of the East Calcutta wetlands, a Ramsar site of Kolkata city, India, heavily contaminated by industrial and municipal wastewaters. The study revealed the occurrence of 22 species of zooplankton, among these 3 species of Cladocera, 2 species of Copepoda, 15 species of Rotifera, and 2 species of Ostracoda were recorded. The copepod Mesocyclops leuckarti was found in all the five sites, rotifers Asplanchna brightwelli, Brachionus angularis, B. calyciflorus and Cladocera Ceriodaphnia cornuta were found in four sites; Moina micrura and Diaphanosoma sarsi were found at three sites. Site wise variation in dominance, diversity, evenness and richness were calculated. Site 1, a fish-pond that stabilized composite wastewater, showed the maximum species richness having 17 species, while Site 2, SWF wastewater carrying canal, showed only 4 species. The calculated Jack 1 values of Sites 1 to 5 were 21.78, 3.77, 18.63, 12.5 and 16.95 respectively. Shannon-Wiener species diversity index (H/ values were almost similar for all the three relatively less polluted sites viz, Site 1 (1.959, Site 4 (2.010, Site 5 (2.047. However, at highly polluted sites viz., 2 and 3, H/ value of 1.336 and 0.984 respectively, were calculated. Simpson’s Dominance index (Dsimp value was highest at Site 3 (0.618 indicating maximum dominance, whereas at Site 5 dominance was lowest (0.1680 and diversity was highest. We discuss the role of zooplankton in the amelioration of wastewater.

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

    OpenAIRE

    Vadadi-Fülöp, Cs.

    2009-01-01

    The spatial distribution and seasonal dynamics of zooplankton (Cladocera, Copepoda) were studied in the River Danube near Budapest, Hungary. The investigated river section was relatively poor in plankton, nauplii dominated. A total of 36 species was recorded of which Acanthocyclops robustus, Thermocyclops crassus, Bosmina longirostris were the most abundant. There was a downstream increase in copepod densities, however, no other remarkable differences could be observed between the profiles up...

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

    OpenAIRE

    Gorokhova, Elena; Hajdu, Susanna; Larsson, Ulf

    2014-01-01

    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 hypot...

  5. Zooplankton biomass and potential fishery resources of the EEZ of India

    Digital Repository Service at National Institute of Oceanography (India)

    Goswami, S.C.

    1996-01-01

    , Lakshadweep (Laccadive) and Andaman and Nicobar seas. Zooplankton biomass values ranged from 0.02 to 20.0 ml m sup(-3) (av. = 0.82 ml m sup(-3)); 0.01 to 5.3 ml m sup(-3) (av. = 0.22 ml m sup(-3)); 0.01 to 1.6 ml m sup(-3) (av. = 0.82 ml m sup(-3) and 0.2 to 0...

  6. Zooplankton standing stock assessment and fishery resources in the indian seas

    Digital Repository Service at National Institute of Oceanography (India)

    Goswami, S.C.; Sarupria, J.S.; Bhargava, R.M.S.

    1992-01-01

    of Bengal, Lakshadweep (Laccadive) Sea and Andaman Sea. The zooplankton biomass values fluctuated between 0.1 to 12 ml m sup(-3) (av. = 0.664 plus or minus 1.36 ml m sup(-3)), 0.1 to 8.0 ml m sup(-3) (av. = 0.355 plus or minus 0.761 ml m sup(-3)), 0.1 to 1...

  7. Responses of zooplankton to variation in elemental composition of algae: Regulation at individual and ecosystem levels

    OpenAIRE

    Darchambeau, Franc?ois

    2003-01-01

    The aim of this work was to improve our knowledge about the responses and adaptations of zooplankton, and especially Daphnia, when faced with food sources that are deficient in essential elements. First, we have modelled the constraints of feeding, digestion and growth in Daphnia. We have hypothesized that Daphnia possesses the intrinsic ability to initiate behavioural (i.e. filtration rate) and/or physiological (i.e. excretion rate of digestive enzymes) responses designed to cope with die...

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

    Directory of Open Access Journals (Sweden)

    E.N. Ezekiel

    2011-05-01

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

  9. Vertical pump vibrations

    International Nuclear Information System (INIS)

    With regard to their vibrational behaviour, vertical centrifugal pumps differ in many ways from other groups of machinery. Their particularities are characterized briefly, and the influence on the machine dynamics is shown. By means of examples from power plants and other industrial installations it is demonstrated, which types of vertical pump vibrations can occur, what kinds of measurements have to be performed to recognize causes for excessive vibrational amplitudes, and which remedies can be derived from this. A special problem arises when trying to categorize the actual vibrational intensity with regard to acceptability, as the use of the common technical standards can lead to misinterpretations in some respects. Finally, the possibilities of precalculation of the vibrational behaviour are shown with special regard to the gaining of th calculation input data. (orig.)

  10. Practical Data Migration

    CERN Document Server

    Morris, Johny

    2012-01-01

    This book is for executives and practitioners tasked with the movement of data from old systems to a new repository. It uses a series of steps guaranteed to get the reader from an empty new system to one that is working and backed by the user population. Using this proven methodology will vastly increase the chances of a successful migration.

  11. Net Migration Statistics

    Science.gov (United States)

    Bar chart of countries ranked by their net migration flow as of 2005. While the highest net in-flow is generally into large rich countries (USA, Spain, Germany etc.) Afghanistan had the second highest net inflow thanks to returning refugees.

  12. Migration pathways in soils

    International Nuclear Information System (INIS)

    This study looked at diffusive migration through three types of deformation; the projectile pathways, hydraulic fractures of the sediments and faults, and was divided into three experimental areas: autoradiography, the determination of diffusion coefficients and electron microscopy of model projectile pathways in clay. For the autoradiography, unstressed samples were exposed to two separate isotopes, Pm-147 (a possible model for Am behaviour) and the poorly sorbed iodide-125. The results indicated that there was no enhanced migration through deformed kaolin samples nor through fractured Great Meteor East (GME) sediment, although some was evident through the projectile pathways in GME and possibly through the GME sheared samples. The scanning electron microscopy of projectile pathways in clay showed that emplacement of a projectile appeared to have no effect on the orientation of particles at distances greater than two projectile radii from the centre of a projectile pathway. It showed that the particles were not simply aligned with the direction of motion of the projectile but that, the closer to the surface of a particular pathway, the closer the particles lay to their original orientation. This finding was of interest from two points of view: i) the ease of migration of a pollutant along the pathway, and ii) possible mechanisms of hole closure. It was concluded that, provided that there is no advective migration, the transport of radionuclides through sediments containing these defects would not be significantly more rapid than in undeformed sediments. (author)

  13. International Migration of Couples

    DEFF Research Database (Denmark)

    Munk, Martin D.; Junge, Martin

    2015-01-01

    We analyze emigration and return decisions of Danish couples. Our main questions are how emigration and return migration decisions depend on education, earnings, and the number and age of children. We use register data on full population from 1982 to 2006, focusing on opposite-gender couples in which the female is aged 23 to 37, and the male 25 to 39. We find that power couples in which both are highly educated are most likely to emigrate, but also most likely to return. Couples in which only the male is highly educated are more than twice as likely to emigrate as if only the female is highly edu-cated. Couples in which neither partner is highly educated are least likely to emigrate, but also have lowest return migration rates. This suggests that migration as brain circu-lation is most pronounced among the highly-educated. The probability of emigration is increasing in male earnings, but does not depend much on female earnings. Having children reduces the likelihood of emigration and the more so the older children are. Surprisingly, the return rates do not depend much on the number of children. Overall, our findings suggest that family migration patterns are still surprisingly traditional, re-sponding more to the male's job opportunities and education.

  14. Mexican Migration Project

    Science.gov (United States)

    The Mexican Migration Project's (MMP) interdisciplinary team of researchers collects and analyzes social and economic information on "the complex process of Mexican migration to the United States." This bilingual Website makes the project's work publicly available for research and education. Included are background information about the MMP, Facts & Figures on migration, and a section entitled Expressions, which provides oral histories and online artistic exhibits to promote an "understand[ing of] the emotional reality of migration." However, the core of the site is the extensive MMP Database, which contains general demographic and migratory data on over 7,000 households surveyed in 52 Mexican communities and data on more than 500 households surveyed in the US. Unix and PC Users may download the compressed (.zip) MMP data files in either ASCII (.dat) or SPSS portable (.exp) formats. Corresponding technical documentation is also available in .pdf format. The MMP is a binational research initiative co-directed by Jorge Durand, Professor of Social Anthropology at the University of Guadalajara, and Douglas S. Massey, Professor of Demography and Sociology at the University of Pennsylvania.

  15. Colisión en dirección vertical

    Scientific Electronic Library Online (English)

    A, Manzur.

    2008-06-01

    Full Text Available Se presenta un experimento de demostración que ilustra una situación en la que las leyes de conservación del ímpetu y de la energía mecánica no se cumplen; sin embargo, su uso permite obtener una buena descripción cualitativa del resultado. El objetivo se logra al analizar la colisión vertical que s [...] e produce entre dos pelotas. Las pelotas con masas apropiadas se dejan caer, con la más liviana encima de la más masiva. Después de chocar con el suelo, la pelota inferior carece de movimiento vertical, mientras que la pelota de encima rebota hasta una altura mayor que la altura desde donde fueron soltadas Abstract in english The demonstration experiment here presented illustrates a situation where the conservation laws of linear momentum and mechanical energy are not satisfied; however, their use allows a good qualitative description of the result observed. The objective is satisfactorily gotten by the analysis of the v [...] ertical collision between two balls. The balls with the appropriate masses are dropped, the small mass resting on top of the larger mass; after the collision between the bottom ball and the floor this ball does not have vertical motion, whereas the top ball rebounds up to a height higher than its original height

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

    Directory of Open Access Journals (Sweden)

    Thankhum Saron

    2013-04-01

    Full Text Available 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 influence, if any, of water quality of a river in sub-urban settings to the zooplankton population. Five sites were selected stretching from upstream before the river enter the urban area to the downstream as the river exit the urban area. Since the river is in suburb and for some special physical features the Iril river maintain a significant volume and there seems to be dilution effect and pollution of the river remain a lesser concern. Nevertheless, the study establishes possible influences of the change in water quality to plankton population

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

    Directory of Open Access Journals (Sweden)

    Ana Milstein

    1986-01-01

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

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

    Scientific Electronic Library Online (English)

    Ana, Milstein.

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

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

    Directory of Open Access Journals (Sweden)

    Franz Lahnsteiner

    2012-07-01

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

  20. Estimation of the toxicity of pollutants to marine phytoplanktonic and zooplanktonic organisms

    International Nuclear Information System (INIS)

    One of the basic components of the action plans sponsored by UNEP in the framework of the Regional Seas Programme is the assessment of the state of the marine environment and of its resources, and of the sources and trends of the pollution, and the impact of pollution on human health, marine ecosystems, and amenities. In order to ensure that the data obtained through this assessment can be compared on a world-wide basis and thus contribute to the Global Environment Monitoring System (GEMS) of UNEP, a set of Reference Methods and Guidelines for marine pollution studies are being developed as part of a programme of comprehensive technical support which includes the provision of expert advice, reference methods and materials, training and data quality assurance. This reference method describes procedures for estimating the toxicity of pollutants to marine phytoplankton and zooplankton. Procedures are given for estimating the media effective concentrations (EC50) of toxicants to phytoplankton, and the minimum algistatic concentration (MAC-5). For zooplankton, procedures are given for determining median lethal concentrations. Organisms are exposed to each of a range of concentrations of the test substance. For phytoplankton, the median effective concentration (EC50) is estimated in terms of the number of individuals surviving, the biomass of individuals surviving, or the chlorophyll content of the individuals surviving. For zooplankton, the media lethal concentration (LC50) is estimated by conventional log-probit analysis of the mortality data

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

    Directory of Open Access Journals (Sweden)

    Eliane Maria de Souza Nogueira

    2011-08-01

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

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

    Science.gov (United States)

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

    2014-04-01

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

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

    Directory of Open Access Journals (Sweden)

    Vadadi-Fülöp, Cs.

    2009-11-01

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

  4. Reprint of “Zooplankton biomass and electron transport system activity around the Balearic Islands (western Mediterranean)”

    Science.gov (United States)

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

    2014-10-01

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

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

    Science.gov (United States)

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

    2014-03-01

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

  6. Vertical distribution of radionuclides in soil

    International Nuclear Information System (INIS)

    Pedological profiles were opened at selected representative locations on different geomorphic types and in certain soil layers down to 3 m depth. The mechanical composition, hydro physical and chemical features were studied. The vertical distribution of naturally occurring radionuclides and 137 Cs was analyzed during 1988 and 1989. The parameter alpha of the exponential dependence of activity concentration vs. depth were calculated for the three soil types, as well as the activity concentration of 137 Cs at depths of 1 and 3 m. The extent of 137 Cs migration was evaluated at these depths and it is shown that the coefficient ? is proportional to the reciprocal of the time elapsed from the surface contamination. (author)

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

    International Nuclear Information System (INIS)

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

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

    Directory of Open Access Journals (Sweden)

    Stephanie E. Wilson

    2015-01-01

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

  9. Migrations in Slovenian geography textbooks

    Directory of Open Access Journals (Sweden)

    Jurij Senega?nik

    2013-12-01

    Full Text Available In Slovenia, the migrations are treated in almost all geographical textbooks for different levels of education. In the textbooks for the elementary school from the sixth to ninth grade, students acquire knowledge of the migrations by the inductive approach. Difficulty level of treatment and quantity of information are increasing by the age level. In the grammar school program a trail of gaining knowledge on migration is deductive. Most attention is dedicated to migrations in general geography textbooks. The textbooks for vocational and technical school programs deal with migrations to a lesser extent and with different approaches.

  10. Community structure of zooplankton in the main entrance of Bahía Magdalena, México during 1996

    Scientific Electronic Library Online (English)

    Jaime, Gómez-Gutiérrez; Ricardo, Palomares-García; Sergio, Hernández-Trujillo; Azucena, Carballido-Carranza.

    2001-06-01

    Full Text Available La estructura de la comunidad de zooplancton, incluyendo copépodos, eufáusidos, quetognatos y larvas de decápodos, fue monitoriada por seis ciclos circadianos usando muestras de redes Bongo (red de 500 mm de poro) de bahía Magdalena, en la costa suroeste de Baja California, México. Las muestras se o [...] btuvieron durante tres viajes oceanográficos (marzo, julio y diciembre de 1996) para describir los cambios en la estructura de la comunidad de zooplancton por toda la boca principal de la bahía Magdalena. La estructura de la comunidad de zooplancton mostró cambios fuertes con una relación cercana a las condiciones ambientales. Durante marzo, una columna de agua bien mezclada con baja temperatura y salinidad indicó una influencia del agua de la Corriente de California y de procesos de afloramiento local. Durante julio, la temperatura aumentó y se registró un ámbito de de salinidad amplio. La estratificación de la columna de agua fue intensa durante el verano, realzando la termoclina. Las temperatura y salinidad más altas fueron registradas en diciembre, relacionadas a la presencia de la Corriente Costera de Costa Rica (CRCC). La termoclina se hizo más profunda al aumentar la temperatura del agua. Una estructura de una comunidad templada típica con una riqueza específica baja denominada por Calanus pacificus, Nyctiphanes simplex y Acartia clausi y una biomasa de zooplancton alta (promedio 9.3 y 5.5 ml 1000 m-3 respectivamente) durante marzo y julio cambió a una estructura de una comunidad tropical más compleja con biomasa de zooplanton baja en diciembre (promedio 0.37 ml 1000 m-3). La boca de la bahía Magdalena tiene un intercambio vigoroso de agua causado por corrientes. La estructura de la comunidad de zooplancton no fue significantemente diferente entre la parte central de la bahía Magdalena y la plataforma continental afuera de la bahía en todos los meses. Los resultados sugieren una interacción de adentro hacia afuera más dinámica de los grupos de zooplancton que los antes pensado. Abstract in english The zooplankton community structure, including copepods, euphausiids, chaetognaths, and decapod larvae, was monitored during six circadian cycles using Bongo net (500 *m mesh net) samples from Bahía Magdalena, on the southwest coast of Baja California, México. Samples were obtained during three ocea [...] nographic surveys (March, July, and December 1996) to describe the changes in the zooplankton community structure throughout the main mouth of Bahía Magdalena. The zooplankton community structure showed strong changes with a close relation to environmental conditions. During March, a well-mixed water column with low temperature and salinity indicated an influence of the California Current water and local upwelling processes. During July, temperature increased a nd a wide salinity range was recorded. The stratification of the water column was intense during summer, enhancing the thermocline. The highest temperatures and salinity were recorded in December, related to the presence of the Costa Rica Coastal Current (CRCC). The thermocline deepened as water temperature increased. A typical temperate community structure with low specific richness dominated by Calanus pacificus, Nyctiphanes simplex, and Acartia clausi and high zooplankton biomass (average 9.3 and 5.5 ml 1000 m-3respectively) during March and July shifted to a more complex tropical community structure with a low zooplankton biomass in December (average 0.37 ml 1000 m-3). The mouth of Bahía Magdalena has a vigorous exchange of water caused by tidal currents. The zooplankton community structure was not significantly different between the central part of Bahía Magdalena and the continental shelf outside the bay for all months. The results suggest a more dynamic inside-outside interaction of zooplankton assemblages than first thought.

  11. Seasonal Migration of Meloidogyne chitwoodi and its Role in Potato Production

    OpenAIRE

    Mojtahedi, H.; Ingram, R. E.; Santo, G. S.; Pinkerton, J. N.; Reed, G. L.; Wilson, J. H.

    1991-01-01

    Seasonal vertical migration of Meloidogyne chitwoodi through soil and its impact on potato production in Washington and Oregon was studied. Nematode eggs and second-stage juveniles (J2) were placed at various depths (0-180 cm) in tubes filled with soil and buried vertically or in holes dug in potato fields. Tubes were removed at intervals over a 12-month period and soil was bioassayed on tomato roots. Upward migration began in the spring after water had percolated through the tubes. Nematodes...

  12. Particle fluxes in the deep Eastern Mediterranean basins: the role of ocean vertical velocities

    Directory of Open Access Journals (Sweden)

    L. Patara

    2008-08-01

    Full Text Available This paper analyzes the relationship between deep sedimentary fluxes and ocean current vertical velocities in an offshore area of the Ionian Sea, the deepest basin of the Eastern Mediterranean Sea. Sediment trap data are collected at 500 m and 2800 m depth in two successive moorings covering the period September 1999–May 2001. A tight coupling is observed between the upper and deep traps and the estimated particle sinking rates are higher than 200 m day?1. The current vertical velocity field is computed from a high resolution Ocean General Circulation Model simulation and from the wind stress curl. Current vertical velocities are larger and more variable than Ekman vertical velocities, yet the general patterns are alike. Current vertical velocities are generally smaller than 1 m day?1: we therefore exclude a direct effect of downward velocities in determining high sedimentation rates. However, we find that upward velocities in the subsurface layers of the water column are positively correlated with deep particle fluxes. We thus hypothesize that upwelling would produce an increase in upper ocean nutrient levels – thus stimulating primary production and grazing – a few weeks before an enhanced vertical flux is found in the sediment traps. By analyzing the delayed effects of ocean vertical velocities on deep particle fluxes we envisage a spectrum of particle sinking speeds ranging from about 100 m day?1 to more than 200 m day?1. High particle sedimentation rates may be attained by means of rapidly sinking fecal pellets produced by gelatinous macro-zooplankton. Other sedimentation mechanisms, such as dust deposition, are also considered in explaining large pulses of deep particle fluxes. The fast sinking rates estimated in this study might be an evidence of the efficiency of the biological pump in sequestering organic carbon from the surface layers of the deep Eastern Mediterranean basins.

  13. Dispersal and migration

    Directory of Open Access Journals (Sweden)

    Schwarz, C.

    2004-06-01

    Full Text Available Ringing of birds unveiled many aspects of avian migration and dispersal movements. However, there is even much more to be explored by the use of ringing and other marks. Dispersal is crucial in understanding the initial phase of migration in migrating birds as it is to understand patterns and processes of distribution and gene flow. So far, the analysis of migration was largely based on analysing spatial and temporal patters of recoveries of ringed birds. However, there are considerable biases and pitfalls in using recoveries due to spatial and temporal variation in reporting probabilities. Novel methods are required for future studies separating the confounding effects of spatial and temporal heterogeneity of recovery data and heterogeneity of the landscape as well. These novel approaches should aim a more intensive and novel use of the existing recovery data by taking advantage of, for instance, dynamic and multistate modeling, should elaborate schemes for future studies, and should also include other marks that allow a more rapid data collection, like telemetry, geolocation and global positioning systems, and chemical and molecular markers. The latter appear to be very useful in the delineating origin of birds and connectivity between breeding and non–breeding grounds. Many studies of migration are purely descriptive. However, King and Brooks (King & Brooks, 2004 examine if movement patterns of dolphins change after the introduction of a gillnet ban. Bayesian methods are an interesting approach to this problem as they provide a meaningful measure of the probability that such a change occurred rather than simple yes/no response that is often the result of classical statistical methods. However, the key difficulty of a general implementation of Bayesian methods is the complexity of the modelling —there is no general userfriendly package that is easily accessible to most scientists. Drake and Alisauskas (Drake & Alisauskas, 2004 examine the philopatric movement of geese using a classic multi–state design. Previous studies of philopaty often rely upon simple return rates —however, good mark–recapture studies do not need to assume equal detection probabilities in space and time. This is likely the most important contribution of multi–state modelling to the study of movement. As with many of these studies, the most pressing problem in the analysis is the explosion in the number of parameters and the need to choose parsimonious modelss to get good precision. Drake and Alisauska demonstrate that model choice still remains an art with a great deal of biological insight being very helpful in the task. There is still plenty of scope for novel methods to study migration. Traditionally, there has been a clear cut distinction between birds being labelled as “migrant” or “resident” on the basis of field observations and qualitative interpretations of patterns of ring–recoveries. However, there are intermediate species where only part of the population migrates (partial migrants or where different components of the population migrate to different extents (differential migrants. Siriwardena, Wernham and Baillie (Siriwardena et al., 2004 develop a novel method that produces a quantitative index of migratory tendency. The method uses distributions of ringing–to–recovery distances to classify individual species’ patterns of movement relative to those of other species. The areas between species’ cumulative distance distributions are used with multi–dimensional scaling to produce a similarity map among species. This map can be used to investigate the factors that affect the migratory strategies that species adopt, such as body size, territoriality and distribution, and in studies of their consequences for demographic parameters such as annual survival and the timing of breeding. The key assumption of the method is the similar recovery effort of species over space and time. It would be interesting to overlay maps of effort to try and remove any induced artefacts in the data. Differences in

  14. Diasporas, Migration & Identities

    Science.gov (United States)

    Funded with substantial monies provided by the Arts and Humanities Research Council in the United Kingdom, the Diasporas, Migrations & Identities research programme is designed "to research, discuss and present issues related to diasporas and migration, and their past and present impact on subjectivity and identity, culture and the imagination, place and space, emotion, politics and sociality." While the programme is no longer actively funded, visitors can view the fruits of their academic labors on this site in the "Publications" area. Visitors to this section can view their annual reports and their working papers. Scholars and others can make their way through ten working papers, which include the titles "Here we go-but where? The possibilities of diaspora in the field of sport" and "London's Chinatown: Diaspora, Identity and Belonging". The site also contains a "Links" area, which contains a healthy selection of external links to other like-minded research institutes and centers.

  15. The vertical transportation handbook

    CERN Document Server

    Strakosch, George R

    2010-01-01

    This new edition of a one-of-a-kind handbook provides an essential updating to keep the book current with technology and practice.  New coverage of topics such as machine-room-less systems and current operation and control procedures, ensures that this revision maintains its standing as the premier general reference on vertical transportation.  A team of new contributors has been assembled to shepherd the book into this new edition and provide the expertise to keep it up to date in future editions.  A new copublishing partnership with Elevator World Magazine ensures that the quality of the rev

  16. Vertical axis wind turbine

    International Nuclear Information System (INIS)

    In recent years, the interest in wind turbines with vertical axis noticeably increased. They have some important advantages: low cost, relatively simple structure, reliable packaging system of wind aggregate long period during which require no maintenance, low noise, independence of wind direction, etc.. The relatively low efficiency, however, makes them applicable mainly for small facilities. The work presents a methodology and software for approximately aerodynamic design of wind turbines of this type, and also analyzed the possibility of improving the efficiency of their workflow

  17. International Migration and Human Rights

    Science.gov (United States)

    The Global Migration Group (GMG) is an inter-agency group that is dedicated to encouraging the "adoption of more coherent, comprehensive and better coordinated approaches to the issue of international migration." Their number includes representatives from UNICEF, the World Bank and various regional commissions from the United Nations. In October 2008, they released this 144-page report in order to commemorate and reflect on the 60th anniversary of the Universal Declaration of Human Rights. The report is divided into seven sections, including those dealing with the legal framework of migration, globalization and migration trends, migration data, and a concluding chapter which discusses some of the most pressing issues facing different migrant groups around the world. The report also includes three very useful appendices which deal with the policy instruments used in regards to human migration and the adoption of key United Nations legal instruments involved with international migration.

  18. Zooplankton stable isotopes as integrators of bottom-up variability in coastal margins: A case study from the Strait of Georgia and adjacent coastal regions

    Science.gov (United States)

    El-Sabaawi, Rana; Trudel, Marc; Mazumder, Asit

    2013-08-01

    Understanding how environmental “bottom-up” conditions affect the production or survival of higher trophic levels is an integral component of ecosystem management. However, linking environmental conditions to higher trophic levels is difficult because of differences in turnover time. Carbon (?13C) and nitrogen (?15N) isotopes in animal tissues can elucidate these links because they can potentially integrate variability in nutrient concentrations, primary production, and food web structure on a time-scale that reflects the tissue turnover time of consumers. Here we assess environmental and trophic correlates of zooplankton stable isotopes in the Strait of Georgia and three adjacent coastal regions. Zooplankton stable isotopes show strong seasonal variability, and are typically highest in the summer. Regional ?15N signatures appear to be synchronized with the timing of production maxima in each region, and broadly reflect variability in nitrate and chlorophyll. In contrast zooplankton ?13C have relatively weak regional signatures. The environmental variables that best explain zooplankton stable isotopes vary between regions, and between seasons. On the west coast of Vancouver Island, zooplankton ?15N is significantly correlated with sea surface temperature throughout the year. In the Strait correlations between zooplankton stable isotopes and environmental variables are season-specific. In the spring, ?15N and ?13C are correlated with chlorophyll, zooplankton biomass and nitrate, but in the summer zooplankton ?15N is only weakly correlated with the biomass of carnivorous zooplankton. In both regions, between-year variability in zooplankton stable isotopes appears to reflect between-year variability in oceanographic conditions. A time-series of stable isotopes collected from a copepod (Neocalanus plumchrus) from the Strait of Georgia suggests that chlorophyll, nitrate and zooplankton biomass varied dramatically between 2001 and 2006, and sheds light on environmental conditions that accompanied that collapse of this important prey species. We discuss the implications of our findings for an ecosystem management approach to conservation.

  19. Changes of species composition, formation of quantitative structure and peculiarities of development of proto- and meta zooplankton under the impact of ecological factors in Lake Drukshiai

    International Nuclear Information System (INIS)

    According to 1993-95 research data, water temperature was found to be the most significant factor influencing the structure of zooplankton as well as seasonal development changes. Because of great amount of heated water discharged from Ignalina NPP, determining an increase of the temperature in all water layers and disappearance of the thermal zone below 10 degrees of Centigrade in deep water layers in summer, the species diversity of zooplankton decreased more than twice if compared with 1979-86. Cold-steno thermal species were the first to disappear. At the same time, warm-requiring and eurithermal species predominated. Natural seasonal rise of temperature (till 26.5 degrees of Centigrade) stimulated the development of some groups of meta zooplankton (Cladocera and Copepod a). The abundance of most species of Rotator ia decreased when the water temperature was over 15 degrees of Centigrade. The heated water discharged from Ignalina NPP caused structural changes of meta zooplankton, decrease of its biomass, decrease of the amount and biomass of proto zooplankton in this area. Because of heated water impact, the highest mortality of proto zooplankton was observed in summer. One maximum of quantitative development was characteristic of seasonal dynamics of zooplankton in Lake Drukshiai, while in water basins with natural thermal regime there are 2 seasonal maxima. Dependence of proto zooplankton on phytoplankton nd on Copepod a as well as dependence of meta zooplankton as well as dependence of meta zooplankton on phytoplankton were investigated. Data on spatial distribution of zooplankton in Lake Drukshiai indicate the eutrophication process in the southwestern part of the lake (because of increase of biogen s concentration). (author)

  20. Wetlands and Bird Migration

    Science.gov (United States)

    This activity demonstrates that coastal wetlands are an important factor to insure the success of bird migration. Students will discover that ponds, lakes and marshes provide food and shelter for traveling birds and, without the wetlands, birds would not have the energy to make the trek from areas as far south as Panama. They also learn that besides providing habitats for waterfowl, wetlands help relieve flooding, filter pollutants and are an integral part of the biosphere.

  1. Education, unemployment and migration

    OpenAIRE

    Eggert, Wolfgang; Krieger, Tim; Meier, Volker

    2009-01-01

    This paper studies a two-region model in which unemployment, education decisions and interregional migration are endogenous. The poorer region exhibits both lower wages and higher unemployment rates, and migrants to the richer region are disproportionally skilled. The brain drain from the poor to the rich region is accompanied by stronger incentives to acquire skills even for immobile workers. Regional shocks tend to affect both regions in a symmetric fashion, and skilled-biased technological...

  2. Essays on migration

    OpenAIRE

    Sarvimäki, Matti

    2009-01-01

    This dissertation consists of four empirical essays and an introductory chapter on the economics of migration. The first two essays study the longterm effects of relocating 11% of the Finnish population after the World War II. The first essay suggests that this shock set off a self-reinforcing process, where municipalities receiving the largest flows of displaced persons grew faster also in later periods. The second essay shows that being displaced increased long-term income of men, but had n...

  3. Functorial Data Migration

    CERN Document Server

    Spivak, David I

    2010-01-01

    In this paper we present a simple database definition language: that of categories and functors. A database schema is a category and a state is a set-valued functor. We show that morphisms of schemas induce three "data migration functors" that translate states from one schema to the other in canonical ways. Database states form a boolean topos of which the classical "relational algebra" is a fragment. These ideas thus create a new denotational semantics for database theory.

  4. Functorial Data Migration

    OpenAIRE

    Spivak, David I.

    2010-01-01

    In this paper we present a simple database definition language: that of categories and functors. A database schema is a small category and an instance is a set-valued functor on it. We show that morphisms of schemas induce three "data migration functors", which translate instances from one schema to the other in canonical ways. These functors parameterize projections, unions, and joins over all tables simultaneously and can be used in place of conjunctive and disjunctive que...

  5. Migration of uranium

    International Nuclear Information System (INIS)

    Uranium migration is treated as a process leading to mobilization and concentration of uranium in ore deposits. During the formation of global zonation, uranium migration contributed to the enrichment of this radioactive metal in the Earth's crust. The process of upper mantle and crust fractionation and differentiation is the first cycle of the mobilization process which led to uranium enrichment in rocks in some areas of the upper Earth's crust that could be considered as the primordial uranium provinces. Uranium migration is related to the structural history of sial Earth's crust and sial magmatism. During orogeny conditions could be created for development of progressive metamorphism and for magma generation. The latter is the best process for uranium mobilization. The effectiveness of this process depends on the composition of the primordial rocks and the intensity of the process. The importance of the magmatism for uranium mobilization is due to the magmatic differentiation. Selectively mobilized felsitic parts of the rocks migrate and form felsitic magmatic portions, which mobilize uranium. Solutions are the best uranium mobilization agents. Their generation starts with water separation from local permeable reservoirs and finishes with water dissociation from minerals during their dehydration. Such solutions could be endogenous or exogenous, depending on the igneous or sedimentary rocks which have been deformed. Some of the solutions can have mixed origin, if dethe solutions can have mixed origin, if deformed magmatic rocks contain exogenous water in pores and cracks and endogenous water in minerals. The mobilizing ability of the solutions depends on their energy, which could derive from their chemical compositions and from physical conditions of the geological environment. The movement of the mineralized solutions can be due to steam pressure and the pressure difference between the starting and the final point of the juvenile solutions, gravity for meteoric waters, convection in geoconvection cells, and water pressure in pressured hydrogeological systems. All these types of solution movement are considered, with emphasis on the more common ones. (author). 11 refs, 5 figs

  6. Irregular Migration in Egypt

    OpenAIRE

    NASSAR, Heba

    2008-01-01

    Egypt’s capital Cairo hosts one of the five largest urban refugee populations in the world. For this reason, our paper concentrates on the legal aspect of irregular migration, discussing the characteristics of these migrants as asylum seekers and refugees while also examining transit migrants. First, the paper tackles associated concepts and data issues, with reference to the existing literature and international standards. In the second part, an overview of the Middle East and Northern A...

  7. Migration, Trade and Unemployment

    OpenAIRE

    Heid, Benedikt; Larch , Mario

    2011-01-01

    A source of anxiety of policy makers and the public in general is the detrimental impact of trade and immigration on unemployment. The transitory restrictions for worker migration after the EU enlargements of 2004 and 2007 exemplify the supposed negative effect of immigration on labor markets. This paper aims to identify the effects of immigration alongside trade on unemployment controlling for the high correlation between immigration and goods flows in order to prevent an omitted variable bi...

  8. Migration of gall stones.

    OpenAIRE

    Taylor, T V; Armstrong, C. P.

    1987-01-01

    The factors influencing the migration of gall stones are ill understood. Altogether 331 patients undergoing cholecystectomy were studied prospectively. The diameters of the cystic and common bile ducts and of stones in the gall bladder and bile ducts were measured. Increasing pressure was applied to the freshly excised gall bladder in an attempt to evacuate stones through the cystic duct. Stones passed in 33 (60.0%) of patients with choledocholithiasis, 45 (67.2%) of patients with pancreatiti...

  9. Remittances and temporary migration

    OpenAIRE

    Dustmann, C.; Mestres, J

    2009-01-01

    In this paper we study the remittance behavior of immigrants and how it relates to temporary versus permanent migration plans. We use a unique data source that provides unusual detail on remittances and return plans, and follows the same household over time. Our data allows us also to distinguish between different purposes of remittances. We analyze the association between individual and household characteristics and the geographic location of the family as well as return plans...

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

    International Nuclear Information System (INIS)

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

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

    International Nuclear Information System (INIS)

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

  12. Preliminary assessment of the zooplankton community composition in a region under the influence of a uranium mine (Caldas, Southeastern Brazil)

    International Nuclear Information System (INIS)

    The Ore Treatment Unit consists of an open cast mine (CM), its mining waste areas, facilities for the physical treatment of the ore, and a chemical treatment plant for uranium extraction. At CM, the processes of acid drainage create effluents, which are treated by chemical processes and, thereafter, disposed of in Antas dam. The objective of the present study was to make an inventory of zooplanktonic and describe the physicochemical characteristics of site CM and at the site of treated effluents disposal (site 41), located at Antas dam. Water samples were collected in October/08 and January/09, in order to describe the abiotic variables and the zooplankton community. The average values of conductivity at sites CM and 41 were 2415 and 422 ?/cm2, respectively. Values of pH at site CM remained acid, whereas, at site 41 we recorded values near neutrality. The concentrations of total nutrients at both sampling sites were higher in the rainy season. Zooplankton species richness present at site CM was lower than at site 41, and there were only two identified species Bosmina sp and Keratella americana. At site 41 we recorded more species, mainly of the Rotifera. Among Cladocera, we identified two species, regarding Copepoda, the orders Cyclopoida and Calanoida were present. At site CM the density values were lower compared to site 41. The preliminary assessment of the zooplankton community showed lower values of species richness and density at site CM, what may be probably explained by the adverse environmental conditions for zooplankton community. (author)

  13. Short and long-term temporal variation of the zooplankton in a tropical estuary (Amazon region, Brazil

    Directory of Open Access Journals (Sweden)

    Kelli Garboza da Costa

    2008-08-01

    Full Text Available Nyctemeral and seasonal distribution of the zooplankton of the Taperaçu estuary and the effect of the hydrological parameters on the dynamics of these organisms were studied in March (rainy season and September 2005 (dry season. Zooplankton samplings were carried out during spring tides at 2-hours intervals during a 24 h period. Samples were collected with a plankton net of 120 ?m mesh size. Simultaneous temperature, salinity, pH and dissolved oxygen concentration measurements were accomplished at subsurface. The estuary presented a high seasonal variation in salinity (9.1-40.0 with regimes oscillating from mesohaline to polihaline/marine during the rainy and dry season, respectively. Temperature, pH and salinity were significantly higher during the dry season. A total of 50 taxa were identified, belonging to the following groups: Arthropoda, Sarcomastigophora, Cnidaria, Mollusca, Nematoda, Platyhelminthes, Bryozoa, Chordata, Annelida and Chaetognatha. Copepods dominated quantitatively the local zooplankton with 50% of the total organisms. Total zooplankton densities oscillated from 16,491 to 397,476 ind.m-3 during the dry and rainy season, respectively. Rainfall was the principal responsible for the hydrological parameters oscillations, mainly salinity, which influenced directly the population dynamics of the zooplankton of the Taperaçu estuary.

  14. Differences between Arctic and Atlantic fjord systems on bioaccumulation of persistent organic pollutants in zooplankton from Svalbard.

    Science.gov (United States)

    Hallanger, Ingeborg G; Ruus, Anders; Warner, Nicholas A; Herzke, Dorte; Evenset, Anita; Schøyen, Merete; Gabrielsen, Geir W; Borgå, Katrine

    2011-06-15

    Differences in bioaccumulation of persistent organic pollutants (POPs) between fjords characterized by different water masses were investigated by comparing POP concentrations, patterns and bioaccumulation factors (BAFs) in seven species of zooplankton from Liefdefjorden (Arctic water mass) and Kongsfjorden (Atlantic water mass), Svalbard, Norway. No difference in concentrations and patterns of POPs was observed in seawater and POM; however higher concentrations and BAFs for certain POPs were found in species of zooplankton from Kongsfjorden. The same species were sampled in both fjords and the differences in concentrations of POPs and BAFs were most likely due to fjord specific characteristics, such as ice cover and timing of snow/glacier melt. These confounding factors make it difficult to conclude on water mass (Arctic vs. Atlantic) specific differences and further to extrapolate these results to possible climate change effects on accumulation of POPs in zooplankton. The present study suggests that zooplankton do biomagnify POPs, which is important for understanding contaminant uptake and flux in zooplankton, though consciousness regarding the method of evaluation is important. PMID:21600630

  15. Behind the impact of introduced trout in high altitude lakes: adult, not juvenile fish are responsible of the selective predation on crustacean zooplankton

    Directory of Open Access Journals (Sweden)

    Rocco Tiberti

    2014-05-01

    Full Text Available Introduced fish seriously affect zooplankton communities in mountain lakes, often leading to the loss of large species. Selective predation is recognized to be the ultimate cause of such a strong impact. Here we describe the selection of zooplankton prey by analyzing the stomach contents of more than 300 brook trout (Salvelinus fontinalis inhabiting seven alpine lakes in the Gran Paradiso National Park (western Italian Alps. Our results show that planktivory is much more common in young fish, which feed on a larger number of taxa, but also adult fish maintain the ability to feed on zooplankton. There is a direct dependence between the length of zooplankton prey and the length of their fish predators, and adult, not juvenile fish are responsible of the selective predation on large crustacean zooplankton, which drive the impact of introduced fish throughout the entire zooplankton community. In some rare cases, large zooplankton populations develop in the presence of brook trout, and planktivory can become an important temporary resource for adult fish during the ice-free season. Thus, in the early stages of the establishment of non-native trout in alpine lakes, large-bodied zooplankton may represent an important food resource.

  16. International Migration Diversification: A New Perspective to Migration Management

    OpenAIRE

    Bulley, Cynthia A.; Peter Quartey

    2014-01-01

    Diversifying migration for development is an option that much has been discussed and yet little has been done in sending countries. The potential of international migration being harnessed for economic and social development have gained significant importance. Some initiatives have been discussed and launched to manage international migration. Some of these efforts are aimed at addressing the issue of containing the outflow and encouraging return of migrants to help with nation building. But ...

  17. Vertical plate motions in the West Siberian Basin

    Science.gov (United States)

    Vibe, Yulia; Clark, Stuart

    2015-04-01

    The West Siberian Basin is one of the world's largest sedimentary basins representing an important source of oil and gas. The Basin's history includes long periods of very slow subsidence coupled with periods of erosion and uplift. Despite that the Basin has been broadly explored the causes of these vertical motions are not yet understood. In this study we analyse the vertical motions by the means of backstripping. The new backstripping results refined by the paleo-water depth data give estimates of the subsidence and uplift rate. These results show a peculiar character of the vertical motions where the region of maximum subsidence migrated from the north to the south several times during the Basin's history. Such southward propagation of subsidence happened in the Late Jurassic, Aptian and in the Paleogene periods. The newly constrained local eustatic curve indicates that the Basin's vertical motions do not reflect the global sea level changes, but the more complicated tectonic processes. We put different data sets of the Basin's sediments and crust structure together with the new backstripping results in order to understand better the vertical motions and the processes underlying the irregular subsidence and uplift pattern of the West Siberian Basin

  18. Optimizing Total Migration Time in Virtual Machine Live Migration

    OpenAIRE

    Gustafsson, Erik

    2013-01-01

    The ability to migrate a virtual machine (VM) from one physical host to another is important in a number of cases such as power management, on-line maintenance, and load-balancing. The amount of memory used in VMs have been steadily increasing up to several gigabytes. Consequently, the time to migrate machines, the total migration time, has been increasing. The aim of this thesis is to reduce the total migration time. Previous work aimed at reducing the amount of time and disk space required ...

  19. Effects of experimental eutrophization on zooplankton community / Efeitos da eutrofização experimental sobre a comunidade zooplanctônica

    Scientific Electronic Library Online (English)

    Ana Maria Alves de, Medeiros; Cyntya Eustáquio de, Sousa; Maria Cristina, Crispim; Ana Karla Araújo, Montenegro.

    2013-06-01

    Full Text Available OBJETIVOS: O presente estudo avaliou os efeitos do aumento na concentração de nutrientes sobre a comunidade zooplanctônica, através de experimentos laboratoriais. MÉTODOS: Os experimentos foram realizados em laboratório, onde três estados tróficos foram simulados, a saber, mesotrófico, eutrófico e h [...] ipereutrófico. Cada tratamento foi replicado três vezes, e indivíduos de Brachionus urceolaris (10 indivíduos), Hexarthra mira (5) (Rotifera), Latonopsis sp. (10), Moina minuta (10) (Cladocera) e Thermocyclops sp. (5) (Copepoda) foram introduzidos em cada réplica. Durante o primeiro dia de experimento, e a cada sete dias de intervalo durante 14 dias (totalizando três amostragens), toda a água foi coletada de cada aquário e filtrada, para a determinação das densidades de cada espécie de zooplâncton. MANOVAs duas vias e ANOVAs de uma via foram empregadas para a determinação das variações nas densidades de zooplâncton entre os tratamentos e ao longo do período de estudo. Ainda, Modelos Lineares Generalizados (MLGs) foram empregados para avaliar como fatores ambientais que influenciaram a densidade do zooplâncton. A composição do fitoplâncton foi determinada no ínicio e no final do experimento. RESULTADOS: B. urceolaris e náuplios de copépodos, típicos de ambientes eutrofizados, apresentaram maiores densidades nos tratamentos eutrófico e hipereutrófico. Ainda, cianobactérias como Aphanothece sp. e Merismopedia sp. foram registradas nos tratamentos eutrófico e hipereutrófico, respectivamente. CONCLUSÕES: De maneira similar ao observado na natureza, o tratamento eutrófico apresentou maiores densidades de espécies do zooplâncton que se beneficiam do aumento na concentração de nutrientes. Respostas positivas ou negativas na dinâmica do zooplâncton fornecem uma ferramenta bioindicadora eficaz. Ainda, os resultados do presente estudo enfatizam a necessidade de implementar medidas reparadoras em ambientes aquáticos sujeitos a entradas constantes de nutrientes. Abstract in english AIMS: The present study evaluated the role that increased nutrient concentrations play on zooplankton community, by employing an experimental laboratory approach. METHODS: Experiments were conducted in the laboratory, where three trophic state conditions were simulated, namely, mesotrophic, eutrophi [...] c and hypereutrophic. Each treatment was replicated three times and individuals of Brachionus urceolaris (10 individuals), Hexarthra mira (5) (Rotifera), Latonopsis sp. (10), Moina minuta (10) (Cladocera) and Thermocyclops sp. (5) (Copepoda) were introduced to each replicate. On the first experiment day, and at 7-day intervals for a 14-day period (totaling three evaluations), all water content was collected from each container and filtered to determine the densities of each zooplankton species. Two-way MANOVA and one-way ANOVA designs were used to determine zooplankton density fluctuations among treatments and throughout the study period. Further, Generalized Linear Models (GLMs) were employed to assess how environmental factors affected zooplankton numbers. Phytoplankton composition was also determined in the beginning and in the end of the experiment. RESULTS: B. urceolaris and copepod nauplii, which are typical of eutrophic environments, showed higher densities on the eutrophic and hypereutrophic treatments. Furthermore, cyanobacteria such as Aphanothece sp. and Merismopedia sp. were recorded on the eutrophic and hypereutrophic treatments, respectively. CONCLUSIONS: Similarly to what is frequently observed in the wild, the eutrophic treatment showed higher densities of particular zooplankton species which are known to temporarily benefit from an increase in trophic concentrations. Positive or negative responses from zooplankton dynamics (but also phytoplankton species), provide an important bioindicator framework. Furthermore, results of the present study outline the need for implementing recovery measures on aquatic environments subject to constant nutrient inputs.

  20. Knowledge Vertices in XUNL

    Scientific Electronic Library Online (English)

    Ronaldo, Martins.

    2012-06-01

    Full Text Available This paper addresses some lexical issues in the development of XUNL - a knowledge representation language descendent from and alternative to the Universal Networking Language (UNL). We present the current structure and the role of Universal Words (UW) in UNL and claim that the syntax and the semanti [...] cs of UWs demand a thorough revision in order to accomplish the requirements of language, culture and human independency. We draw some guidelines for XUNL and argue that its vertices should be represented by Arabic numerals; should be equivalent to sets of synonyms; should consist of generative lexical roots; should correspond to the elementary particles of meaning; and should not bear any non-relational meaning.

  1. Estimation of positive sum-to-one constrained zooplankton grazing preferences with the DEnKF: a twin experiment

    Directory of Open Access Journals (Sweden)

    E. Simon

    2012-03-01

    Full Text Available We consider the estimation of the grazing preferences parameters of zooplankton in ocean ecosystem models with ensemble-based Kalman filters. These parameters are introduced to model the relative diet composition of zooplankton that consists of phytoplankton, small size-classes of zooplankton and detritus. They are positive values and their sum is equal to one. However, the sum-to-one constraint cannot be guaranteed by ensemble-based Kalman filters when parameters are bounded. Therefore, a reformulation of the parameterization is proposed. We investigate two types of variables transformations for the estimation of positive sum-to-one constrained parameters that lead to the estimation of new set of parameters with normal or bounded distributions. These transformations are illustrated and discussed with twin experiments performed with the 1-D coupled model GOTM-NORWECOM with Gaussian anamorphosis extensions of the deterministic ensemble Kalman filter (DEnKF.

  2. Estimation of positive sum-to-one constrained zooplankton grazing preferences with the DEnKF: a twin experiment

    Directory of Open Access Journals (Sweden)

    E. Simon

    2012-08-01

    Full Text Available We consider the estimation of the grazing preferences parameters of zooplankton in ocean ecosystem models with ensemble-based Kalman filters. These parameters are introduced to model the relative diet composition of zooplankton that consists of phytoplankton, small size-classes of zooplankton and detritus. They are positive values and their sum is equal to one. However, the sum-to-one constraint cannot be guaranteed by ensemble-based Kalman filters when parameters are bounded. Therefore, a reformulation of the parameterization is proposed. We investigate two types of variable transformations for the estimation of positive sum-to-one constrained parameters that lead to the estimation of a new set of parameters with normal or bounded distributions. These transformations are illustrated and discussed with twin experiments performed with the 1-D coupled model GOTM-NORWECOM with Gaussian anamorphosis extensions of the deterministic ensemble Kalman filter (DEnKF.

  3. Zooplankton as an early warning system of persistent organic pollutants contamination in a deep lake (lake Iseo, Northern Italy

    Directory of Open Access Journals (Sweden)

    Silvia Quadroni

    2012-07-01

    Full Text Available The lake Iseo has been recently contaminated by DDT residues, originated from the melting of a glacier that released the pollutants accumulated in the past. Because of this recent input, DDT residues concentrations rose more quickly in zooplankton than in fish during 2009. In autumn 2010 the ratio drastically dropped to one–two for all the compounds indicating that the glacial DDT load should have been ceased. The situation was different for PCBs that were released to a much lower extent from glaciers. The PCB 138 ratio between zooplankton and fish was always around one–two in both years. As the zooplankton response to pollution changes resulted particularly prompt, our research highlights the importance of this component as an early warning bioindicator of hydrophobic pollutants.

  4. Seasonal dynamics of crustacean zooplankton community structure in Erhai Lake, a plateau lake, with reference to phytoplankton and environmental factors

    Science.gov (United States)

    Yang, Wei; Deng, Daogui; Zhang, Sai; Hu, Cuilin

    2014-09-01

    The seasonal dynamics of a crustacean zooplankton community in Erhai Lake was investigated from May 2010 to April 2011. In total, 11 species were recorded, including six (6 genera) cladoceran and five (5 genera) copepod species. The crustacean zooplankton densities ranged from 24.3 to 155.4 ind./L. In winter and spring, the large-bodied cladoceran Daphnia galeata dominated the crustacean plankton community. In summer and autumn, when the colonial or filamentous algae dominated the phytoplankton communities, the small-bodied species (e.g. B osmina fatalis, Ceriodaphnia quadrangular, and Mesocyclops leuckarti) replaced the large-bodied ones. One-way ANOVA and redundancy analysis revealed that community structure was dependent upon total nitrogen, total phosphorus, water temperature, transparency, and the biomass of small algae. The variation in both phytoplankton structure and environmental variables were important factors in the seasonal succession of crustacean zooplankton structure in Erhai Lake.

  5. Migration experiments in Studsvik

    International Nuclear Information System (INIS)

    Field experiments (two-well pulse method) on the migration of Sr and Cs in a gneiss at Studsvik on the Swedish east coast as well as supporting laboratory measurements on sorption/migration have been performed. Interconnected fractures at about 100 m depth between boreholes were located and characterized. In the boreholes measurements of resistivity, spontaneous potential, pH, Eh, curvature, temperature, gamma radiation, and radon have been performed. The fracture zones were localized, using TV-logging, and the mineralogy of the water bearing fractures in a drill core from the area determined. The main fissure filling minerals were chlorite, calcite and smectite. The groundwater composition was analyzed and it was found that the water in some cases is oversaturated with respect to calcium carbonate. Temperatures up to 12 degreeC of the pumped water have been observed, corresponding to water originating from 200-400 m depth. In laboratory batch measurements it was found that the distribution coefficient for Studsvik gneiss and possible fissure filling minerals was 0.01-0.4 m3/kg. The sorption isotherm for the gneiss was almost linear, a Freundlich isotherm with the exponent 0.89 fits well to the data. In two field experiments, performed between different boreholes, retention factors for Sr of 17 and 30, respectively, were obtained. In laboratory column experiments, performed on crushed borehole material, the retention factor was 30-35, corresponding to a distribution coefficient of 0.006-0.008 m3/kg. For Cs, injected simultanously with the Sr, the retentionfactor is > 30. (No breakthrough after 5000 h.). In both the field experiments a minor amount of the Sr was migrating almost without retention (retention factor < 2). This effect was not observed for Cs, indicating that the process causing the fast transport of Sr is selective to Sr. (author)

  6. Population, desertification, and migration.

    Science.gov (United States)

    Westing, A H

    1994-01-01

    When an imbalance develops between population numbers and the carrying capacity of the land, the persons thereby displaced are referred to as environmental refugees. The utilization of the land beyond sustainability leads to land degradation and ultimately, desertification. The social and political impacts of long-term environmental migration can be distinguished: a) at the site of origin of the displaced persons by the residual population; b) at rural sites of destination within the nation between the new arrivals and preestablished populations; c) in the cities within the nation; d) in the nonindustrialized foreign countries; and e) in the industrialized foreign countries. In the event that an area which had previously been devoted to pastoralism is converted to agriculture, the displaced pastoralists might respond through armed rebellion. In some instances, the disenchanted urban squatters become a politically restive and even a destabilizing force, as occurred in Sudan in the 1980s, especially in Khartoum and Port Sudan. The foreign countries to which many of the displaced persons are migrating are subjected to increasing levels of migrant-induced economic, cultural, and political strains. The growing problems associated with south-to-north migration across the Mediterranean Sea have recently led France, Italy, Portugal, and Spain to enter into a consultative arrangement with Algeria, Libya, Mauritania, Morocco, and Tunisia. All foreign aid to the nonindustrialized countries that attempts to ameliorate the problem of desertification must adopt integrated approaches that: a) address population issues; b) support environmental education; c) provide for the protection of biodiversity; d) encourage participatory forms of local and national government; e) provide opportunities for income generation outside the livestock sector; and f) foster political security and facilitate ecogeographical (subregional) cooperation. PMID:12289925

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

    International Nuclear Information System (INIS)

    The detrimental effects of elevated intensities of mid-UV radiation (UVB), a result of stratospheric ozone depletion during the austral spring, on the primary producers of the Antarctic marine ecosystem have been well documented. Here we report that natural populations of Antarctic zooplankton also sustain significant DNA damage [measured as cyclobutane pyrimidine dimers (CPDs)] during periods of increased UVB flux. This is the first direct evidence that increased solar UVB may result in damage to marine organisms other than primary producers in Antarctica. The extent of DNA damage in pelagic icefish eggs correlated with daily incident UVB irradiance, reflecting the difference between acquisition and repair of CPDs. Patterns of DNA damage in fish larvae did not correlated with daily UVB flux, possibly due to different depth distributions and/or different capacities for DNA repair. Clearance of CPDs by Antarctic fish and krill was mediated primarily by the photoenzymatic repair system. Although repair rates were large for all species evaluated, they were apparently inadequate to prevent the transient accumulation of substantial CPD burdens. The capacity for DNA repair in Antarctic organisms was highest in those species whose early life history stages occupy the water column during periods of ozone depletion (austral spring) and lowest in fish species whose eggs and larvae are abundant during winter. Although the potential reduction in fitness of Antarctic zooplankton rtion 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

  8. Temperature and zooplankton size structure: climate control and basin-scale comparison in the North Pacific.

    Science.gov (United States)

    Chiba, Sanae; Batten, Sonia D; Yoshiki, Tomoko; Sasaki, Yuka; Sasaoka, Kosei; Sugisaki, Hiroya; Ichikawa, Tadafumi

    2015-02-01

    The global distribution of zooplankton community structure is known to follow latitudinal temperature gradients: larger species in cooler, higher latitudinal regions. However, interspecific relationships between temperature and size in zooplankton communities have not been fully examined in terms of temporal variation. To re-examine the relationship on a temporal scale and the effects of climate control thereon, we investigated the variation in copepod size structure in the eastern and western subarctic North Pacific in 2000-2011. This report presents the first basin-scale comparison of zooplankton community changes in the North Pacific based on a fully standardized data set obtained from the Continuous Plankton Recorder (CPR) survey. We found an increase in copepod community size (CCS) after 2006-2007 in the both regions because of the increased dominance of large cold-water species. Sea surface temperature varied in an east-west dipole manner, showing the typical Pacific Decadal Oscillation pattern: cooling in the east and warming in the west after 2006-2007. The observed positive correlation between CCS and sea surface temperature in the western North Pacific was inconsistent with the conventional interspecific temperature-size relationship. We explained this discrepancy by the geographical shift of the upper boundary of the thermal niche, the 9°C isotherm, of large cold-water species. In the eastern North Pacific, the boundary stretched northeast, to cover a large part of the sampling area after 2006-2007. In contrast, in the western North Pacific, the isotherm location hardly changed and the sampling area remained within its thermal niche throughout the study period, despite the warming that occurred. Our study suggests that while a climate-induced basin-scale cool-warm cycle can alter copepod community size and might subsequently impact the functions of the marine ecosystem in the North Pacific, the interspecific temperature-size relationship is not invariant and that understanding region-specific processes linking climate and ecosystem is indispensable. PMID:25750722

  9. Feeding and filtration rates of zooplankton (rotifers and cladocerans) fed toxic cyanobacterium (Microcystis aeruginosa).

    Science.gov (United States)

    Pérez-Morales, Alfredo; Sarma, S S S; Nandini, S

    2014-11-01

    Microcystis aeruginosa is generally dominant in many Mexican freshwater ecosystems interacting with zooplankton species. Hence, feeding and filtration rates were quantified for three cladoceran (Daphnia pulex, Moina micrura and Ceriodaphnia dubia) and three rotifer species (Brachionus calyciflorus, Brachionus rubens and Plationus patulus) using sonicated M. aeruginosa alone or mixed with Scenedesmus acutus in different proportions (25, 50 and 75%, based on cell density), offering a combined initial density of 100,000 cells·ml(-1). All the three cladoceran species ingested M. aeruginosa (100-300 cells ind(-1) min(-1)) when fed exclusively with cyanobacterium. When green alga offered as exclusive diet, the number of cells ingested by the tested cladocerans varied from 80 to 400 cells ind(-1) min(-1). Compared to cladocerans, rotifers in general consumed much lower quantity (< 200 cells ind(-1) min(-1)) of M. aeruginosa and S. acutus. The filtration rate for Daphnia pulex was inversely related to the proportion of green alga in the diet. For other tested cladocerans, no such clear trend was evident. In mixed treatments containing M. aeruginosa, the filtration rate of Daphnia was highest (about 220 ?l ind(-1) min(-1)) when the medium contained 75% of S. acutus. Among the rotifer species, P. patulus filtered highest volume (100 ?l ind(-1) min(-1) from mixed diets containing higher proportions (50 or 75%) of M. aeruginosa. Thus, there were species-specific differences in the filtration and feeding rates of zooplankton when offered mixed diets of green algae and toxic cyanobacteria. These probably explain the coexistence of different zooplankton species in Microcystis-dominant waterbodies. PMID:25522500

  10. Zooplankton associations and environmental factors in Ogunpa and Ona rivers, Nigeria

    Directory of Open Access Journals (Sweden)

    Gbemisola A. Akin-Oriola

    2003-06-01

    Full Text Available Zooplankton abundance, composition and environmental parameters were monitored in two tropical rivers over a twenty month period. The data was subjected to cluster, factor and correlation analysis to determine the grouping pattern of zooplankton and their relationship to environmental parameters. Environmental factors in Ogunpa and Ona rivers -included buffering capacity, trace metal ions, pH-temperature/ transparency- were primarily influenced by rainfall. The dominance of the Rotifera in both rivers was attributed to their short developmental rate and fish predation on larger zooplankton. Two groups of associations were identified in each river - a commonly occurring species group exhibiting strong homogenous correlation with environmental factors and a predominant group exhibiting weak correlation with environmental factors and whose abundance / composition may be defined by biotic factors.La abundancia, y composición del zooplancton, y parámetros ambientales fueron monitoreados en dos ríos tropicales durante un período de doce meses. Los datos fueron sometidos a análisis de agrupaciones, de factores y de correlación para determinar los patrones de agrupamiento del zooplancton y sus relaciones con parámetros ambientales. Los factores ambientales en los ríos Ogunpa y Ona, incluidos la capacidad tampón, iones metálicos traza, pH-temperatura/ transparencia, fueron influenciados principalmente por la lluvia. La dominancia de los Rotíferos en ambos ríos fue atribuida a su corta tasa de desarrollo y a la depredación del zooplancton grande por peces. Dos grupos de asociaciones fueron identificadas en cada río - la presencia de un grupo común de especies que exhiben una fuerte y homogénea correlación con factores ambientales y un grupo predominante que exhibe una débil correlación con factores ambientales y cuya abundancia / composición que podría estar definida por factores bióticos.

  11. Zooplankton associations and environmental factors in Ogunpa and Ona rivers, Nigeria

    Scientific Electronic Library Online (English)

    Gbemisola A., Akin-Oriola.

    2003-06-01

    Full Text Available La abundancia, y composición del zooplancton, y parámetros ambientales fueron monitoreados en dos ríos tropicales durante un período de doce meses. Los datos fueron sometidos a análisis de agrupaciones, de factores y de correlación para determinar los patrones de agrupamiento del zooplancton y sus r [...] elaciones con parámetros ambientales. Los factores ambientales en los ríos Ogunpa y Ona, incluidos la capacidad tampón, iones metálicos traza, pH-temperatura/ transparencia, fueron influenciados principalmente por la lluvia. La dominancia de los Rotíferos en ambos ríos fue atribuida a su corta tasa de desarrollo y a la depredación del zooplancton grande por peces. Dos grupos de asociaciones fueron identificadas en cada río - la presencia de un grupo común de especies que exhiben una fuerte y homogénea correlación con factores ambientales y un grupo predominante que exhibe una débil correlación con factores ambientales y cuya abundancia / composición que podría estar definida por factores bióticos. Abstract in english Zooplankton abundance, composition and environmental parameters were monitored in two tropical rivers over a twenty month period. The data was subjected to cluster, factor and correlation analysis to determine the grouping pattern of zooplankton and their relationship to environmental parameters. En [...] vironmental factors in Ogunpa and Ona rivers -included buffering capacity, trace metal ions, pH-temperature/ transparency- were primarily influenced by rainfall. The dominance of the Rotifera in both rivers was attributed to their short developmental rate and fish predation on larger zooplankton. Two groups of associations were identified in each river - a commonly occurring species group exhibiting strong homogenous correlation with environmental factors and a predominant group exhibiting weak correlation with environmental factors and whose abundance / composition may be defined by biotic factors.

  12. Migration and loving

    OpenAIRE

    Gevrek, Deniz

    2010-01-01

    This paper explores the relationship between anti-miscegenation laws, interracial marriage and black males' geographical distribution in the U.S. during and after the Great Migration. The U.S. Supreme Court decision in the case of Loving v. Virginia in 1967, which forced the last 16 Southern states to strike down their anti-miscegenation laws, creates a unique opportunity to explore the impact of an exogenous change in a state's laws regulating interracial marriages. Analyzing the U.S. Census...

  13. Climate and Human Migrations

    Science.gov (United States)

    Tom D. Dillehay (University of Kentucky; Department of Anthropology)

    2002-10-25

    Access to the article is free, however registration and sign-in are required. About 14,600 years ago, humans first appeared in south central Chile. But the arid regions of the Atacama desert in northern Chile were not populated for another 2000 years, and human occupation of this region subsequently remained intermittent. In his Perspective, Dillehay highlights the report of Núñez et al., whose integrative archaeological and paleoecological study shows that climate was the key factor in these human migrations. The study illustrates the power of an integrative approach to understanding the relation between human societies and climate change.

  14. Amenity migration and tourism.

    Czech Academy of Sciences Publication Activity Database

    Bartoš, Michael; Kušová, Drahomíra; T?šitel, Jan

    Tábor : University of South Bohemia ?eské Bud?jovice, University of Economics Bratislava, 2005 - (Hesková, M.; Šittler, E.; Dvo?ák, V.), s. 17-21 ISBN 80-7040-766-2. [Tourism, regional development and education. Sustainable development and tourism. Tábor (CZ), 12.05.2005-13.05.2005] Grant ostatní: EU(XE) European Union/'s Quality of Life and Management of Living Resources programme:QLK5-CT-2000-01211-SPRITE Institutional research plan: CEZ:AV0Z60870520 Keywords : sustainable tourism * amenity migration * regional development Subject RIV: AE - Management ; Administration

  15. Objectivity Data Migration

    OpenAIRE

    Nowak, Marcin; Nienartowicz, Krzysztof; Valassi, Andrea; Lubeck, Magnus; Geppert, Dirk

    2003-01-01

    In this article we describe the migration of event data collected by the COMPASS and HARP experiments at CERN. Together these experiments have over 300TB of physics data stored in Objectivity/DB that had to be transferred to a new data management system by the end of Q1 2003 and Q2 2003 respectively. To achieve this, data needed to be processed with a rate close to 100MB/s, employing 14 tape drives and a cluster of 30 Linux servers. The new persistency solution to accommodat...

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

    Directory of Open Access Journals (Sweden)

    P. Vandromme

    2010-12-01

    Full Text Available An integrated analysis of the pelagic ecosystems of the Ligurian Sea is performed combining time series of different zooplankton groups (small and large copepods, chaetognaths, appendicularians, pteropods, thaliaceans, decapods larvae, other crustaceans, other gelatinous and other zooplankton, chlorophyll-a and nutrients, seawater salinity, temperature and density and local weather at the Point B coastal station (Northern Ligurian Sea. From January 1995 to December 2005, a shift in most variables occurred ca. 2000. From 1995 to 2000 winters were wet and mild resulting in lower winter sea surface density. These years showed lower than average nutrients and zooplankton concentrations while phytoplankton biomass was higher. After 2000, winters were colder and dryer resulting in higher sea surface density. Nutrients and zooplankton showed higher concentrations while phytoplankton was lower than average. The ca. 2000 shift was observed for most zooplankton groups with a one year delay for certain groups. The observed patterns suggest that the pelagic ecosystem trophic state is mostly set by the winter forcing on the convection that upwells nutrients to the surface sustaining the spring bloom. However, low phytoplankton concentrations in higher nitrate and zooplankton conditions during the well mixed years suggest that phytoplankton is controlled by grazers. The proposed mechanisms of convection regimes hold for most of the time series, but specific years with contradicting patterns needed to be explained by other factors. The limitation of phytoplankton growth by the light availability in spring/summer was then proposed as a secondary driving force that can moderate or even reverse the winter forcing. Finally, the eleven years of observation did not reveal a clear link with the North Atlantic Oscillation, suggesting a more complex dynamics linking large scale climate to Ligurian Sea ecosystems or that the length of the plankton monitoring is not yet sufficient to detect those links.

  17. Particle fluxes in the deep Eastern Mediterranean basins: the role of ocean vertical velocities

    Directory of Open Access Journals (Sweden)

    L. Patara

    2009-03-01

    Full Text Available This paper analyzes the relationship between deep sedimentary fluxes and ocean current vertical velocities in an offshore area of the Ionian Sea, the deepest basin of the Eastern Mediterranean Sea. Sediment trap data are collected at 500 m and 2800 m depth in two successive moorings covering the period September 1999–May 2001. A tight coupling is observed between the upper and deep traps and the estimated particle sinking rates are more than 200 m day?1. The current vertical velocity field is computed from a 1/16°×1/16° Ocean General Circulation Model simulation and from the wind stress curl. Current vertical velocities are larger and more variable than Ekman vertical velocities, yet the general patterns are alike. Current vertical velocities are generally smaller than 1 m day?1: we therefore exclude a direct effect of downward velocities in determining high sedimentation rates. However we find that upward velocities in the subsurface layers of the water column are positively correlated with deep particle fluxes. We thus hypothesize that upwelling would produce an increase in upper ocean nutrient levels – thus stimulating primary production and grazing – a few weeks before an enhanced vertical flux is found in the sediment traps. High particle sedimentation rates may be attained by means of rapidly sinking fecal pellets produced by gelatinous macro-zooplankton. Other sedimentation mechanisms, such as dust deposition, are also considered in explaining large pulses of deep particle fluxes. The fast sinking rates estimated in this study might be an evidence of the efficiency of the biological pump in sequestering organic carbon from the surface layers of the deep Eastern Mediterranean basins.

  18. Families, children, migration and AIDS

    OpenAIRE

    Haour-Knipe, Mary

    2009-01-01

    Migration is very often a family affair, and often involves children, directly or indirectly. It may give rise to better quality of life for an entire family, or to bitter disappointment, and may also increase vulnerability to HIV and AIDS. This review, carried out for the Joint Learning Initiative on Children and AIDS, links the literature on “migration”, on “HIV and AIDS” and on “families”. Three themes are sketched: (1) As both HIV prevalence and circular migration increase, fo...

  19. Migration and the Demographic Shift

    OpenAIRE

    Zaiceva, Anzelika; Zimmermann, Klaus F.

    2014-01-01

    This chapter connects population aging with international migration. After documenting the trends for both, we review the supply-push and demand-pull determinants of migration, focusing particularly on the role of age and aging. We subsequently discuss the literature concerning the implications of migration in the context of aging for labor markets, health and public budgets including the political economy context. Although immigration is sometimes suggested as a solution for the aging proble...

  20. Social Union, Convergence and Migration

    OpenAIRE

    Sinn, Hans-werner; Ochel, Wolfgang

    2003-01-01

    The forces of the market and systems competition bring about economic and social convergence in Europe, and there is no need for social policies at the EU level. Social harmonization would distort migration flows and slow down the speed of economic convergence. National welfare states will be threatened by the free migration of people in Europe. The race to the bottom is a serious risk. However, to contain this risk, neither harmonization of welfare payments nor constraints on migration are n...

  1. Bayesian estimation in seismic migration

    OpenAIRE

    Pitas, I.; Venetsanopoulos, A.

    2010-01-01

    Seismic migration is a technique widely used in seismic oil exploration for wavefield reconstruction and for imaging the geometrical distribution of the reflection surfaces within the Earth from the seismic data recorded on the Earth surface. These data are usually corrupted by noise (white noise, surface waves, multiple reflections, etc.) that degrades the result of the migration. Another factor which influences the migration is the inadequate knowledge of the distribution of the acoustic wa...

  2. L-Lake zooplankton: L-Lake/Steel Creek Biological Monitoring Program, November 1985--December 1991

    Energy Technology Data Exchange (ETDEWEB)

    Bowers, J.A. [Westinghouse Savannah River Co., Aiken, SC (United States); Bowen, M. [Normandeau Associates, Inc., New Ellenton, SC (United States)

    1992-03-01

    The L- Lake Biological Monitoring Program was designed to meet environmental regulatory requirements associated with the restart of L-Reactor and address portions of Section 316(a) of the Clean Water Act, which requires an applicant for a discharge permit to provide scientific evidence that the discharge causes no significant impact on the indigenous ecosystem. The Department of Energy (DOE) must demonstrate that the discharge of L-Reactor affluent into L Lake will not inhibit the eventual establishment of a ``Balanced Biological Community`` (BBC) in at least 50% of the lake. This report details results of monitoring zooplankton populations in L-Lake.

  3. Growth of capelin in relation to zooplankton biomass in the Barents Sea

    OpenAIRE

    Gjøsæter, Harald; Skjoldal, Hein Rune; Hassel, Arne

    1995-01-01

    Growth of capelin in the Barents Sea stock has been found to vary considerably both between years and between different parts of the distribution area. The aim of this paper is to compare such growth variations with measured abundance of zooplankton within the capelin feeding area. In the period 1979-1984 a north-south transect in the Barents Sea was studied one to four times during summer. A negative relationship between the plankton biomass and the density of capelin along the section was e...

  4. Spring bloom dynamics and zooplankton biomass response on the US Northeast Continental Shelf

    Science.gov (United States)

    Friedland, Kevin D.; Leaf, Robert T.; Kane, Joe; Tommasi, Desiree; Asch, Rebecca G.; Rebuck, Nathan; Ji, Rubao; Large, Scott I.; Stock, Charles; Saba, Vincent S.

    2015-07-01

    The spring phytoplankton bloom on the US Northeast Continental Shelf is a feature of the ecosystem production cycle that varies annually in timing, spatial extent, and magnitude. To quantify this variability, we analyzed remotely-sensed ocean color data at two spatial scales, one based on ecologically defined sub-units of the ecosystem (production units) and the other on a regular grid (0.5°). Five units were defined: Gulf of Maine East and West, Georges Bank, and Middle Atlantic Bight North and South. The units averaged 47×103 km2 in size. The initiation and termination of the spring bloom were determined using change-point analysis with constraints on what was identified as a bloom based on climatological bloom patterns. A discrete spring bloom was detected in most years over much of the western Gulf of Maine production unit. However, bloom frequency declined in the eastern Gulf of Maine and transitioned to frequencies as low as 50% along the southern flank of the Georges Bank production unit. Detectable spring blooms were episodic in the Middle Atlantic Bight production units. In the western Gulf of Maine, bloom duration was inversely related to bloom start day; thus, early blooms tended to be longer lasting and larger magnitude blooms. We view this as a phenological mismatch between bloom timing and the "top-down" grazing pressure that terminates a bloom. Estimates of secondary production were available from plankton surveys that provided spring indices of zooplankton biovolume. Winter chlorophyll biomass had little effect on spring zooplankton biovolume, whereas spring chlorophyll biomass had mixed effects on biovolume. There was evidence of a "bottom up" response seen on Georges Bank where spring zooplankton biovolume was positively correlated with the concentration of chlorophyll. However, in the western Gulf of Maine, biovolume was uncorrelated with chlorophyll concentration, but was positively correlated with bloom start and negatively correlated with magnitude. This observation is consistent with both a "top-down" mechanism of control of the bloom and a "bottom-up" effect of bloom timing on zooplankton grazing. Our inability to form a consistent model of these relationships across adjacent systems underscores the need for further research.

  5. L-Lake zooplankton: L-Lake/Steel Creek Biological Monitoring Program, November 1985--December 1991

    International Nuclear Information System (INIS)

    The L- Lake Biological Monitoring Program was designed to meet environmental regulatory requirements associated with the restart of L-Reactor and address portions of Section 316(a) of the Clean Water Act, which requires an applicant for a discharge permit to provide scientific evidence that the discharge causes no significant impact on the indigenous ecosystem. The Department of Energy (DOE) must demonstrate that the discharge of L-Reactor affluent into L Lake will not inhibit the eventual establishment of a ''Balanced Biological Community'' (BBC) in at least 50% of the lake. This report details results of monitoring zooplankton populations in L-Lake

  6. Impact of climate change on zooplankton communities, seabird populations and arctic terrestrial ecosystem—A scenario

    Science.gov (United States)

    Stempniewicz, Lech; B?achowiak-Samo?yk, Katarzyna; W?s?awski, Jan M.

    2007-11-01

    Many arctic terrestrial ecosystems suffer from a permanent deficiency of nutrients. Marine birds that forage at sea and breed on land can transport organic matter from the sea to land, and thus help to initiate and sustain terrestrial ecosystems. This organic matter initiates the emergence of local tundra communities, increasing primary and secondary production and species diversity. Climate change will influence ocean circulation and the hydrologic regime, which will consequently lead to a restructuring of zooplankton communities between cold arctic waters, with a dominance of large zooplankton species, and Atlantic waters in which small species predominate. The dominance of large zooplankton favours plankton-eating seabirds, such as the little auk ( Alle alle), while the presence of small zooplankton redirects the food chain to plankton-eating fish, up through to fish-eating birds (e.g., guillemots Uria sp.). Thus, in regions where the two water masses compete for dominance, such as in the Barents Sea, plankton-eating birds should dominate the avifauna in cold periods and recess in warmer periods, when fish-eaters should prevail. Therefore under future anthropogenic climate scenarios, there could be serious consequences for the structure and functioning of the terrestrial part of arctic ecosystems, due in part to changes in the arctic marine avifauna. Large colonies of plankton-eating little auks are located on mild mountain slopes, usually a few kilometres from the shore, whereas colonies of fish-eating guillemots are situated on rocky cliffs at the coast. The impact of guillemots on the terrestrial ecosystems is therefore much smaller than for little auks because of the rapid washing-out to sea of the guano deposited on the seabird cliffs. These characteristics of seabird nesting sites dramatically limit the range of occurrence of ornithogenic soils, and the accompanying flora and fauna, to locations where talus-breeding species occur. As a result of climate warming favoring the increase of ichthyiofagous cliff-nesting seabirds, we can expect that large areas of ornithogenic tundra around the colonies of plankton-eating seabirds situated far from the sea may disappear, while areas of tundra in the vicinity of cliffs inhabited by fish-eating seabirds, with low total production and supporting few large herbivores, will likely increase, but only imperceptibly. This may lead to habitat fragmentation with negative consequences for populations of tundra-dependent birds and mammals, and the possibility of a substantial decrease in biodiversity of tundra plant and animal communities.

  7. The Impacts of Recently Established Fish Populations on Zooplankton Communities in a Desert Spring, and Potential Conflicts in Setting Conservation Goals

    Directory of Open Access Journals (Sweden)

    Sujan M. Henkanaththegedara

    2015-01-01

    Full Text Available Desert springs, which harbor diverse and endemic invertebrate assemblages, are often used as refuge habitats for protected fish species. Additionally, many of these springs have been colonized by invasive fish species. However, the potential impacts of recently established fish populations on invertebrate communities in desert springs have been relatively unexplored. We conducted a mesocosm experiment to assess the impact of both protected and invasive fish on community structure of spring-dwelling invertebrates focusing on zooplankton. Experimental populations of spring zooplankton communities were established and randomly assigned to one of three treatments, (1 invasive western mosquitofish (Gambusia affinis; (2 endangered Mohave tui chub (Siphateles bicolor mohavensis; and (3 fishless control. Final populations of zooplankton and fish were sampled, sorted, identified and counted. The treatment differences of zooplankton communities were analyzed by comparing the densities of six major zooplankton taxa. Further, we performed nonmetric multidimensional scaling (NMDS to visualize the patterns of zooplankton community assemblages. Four zooplankton taxa, crustacean nauplii, cladocera, calanoid and cyclopoid copepods had significantly lower densities in fish treatments compared to fishless control. Overall, invasive mosquitofish caused a 78.8% reduction in zooplankton density, while Mohave tui chub caused a 65.1% reduction. Both protected and invasive fish had similar effects on zooplankton except for cladocerans where tui chub caused a 60% reduction in density, whereas mosquitofish virtually eliminated cladocerans. The presence of fish also had a significant effect on zooplankton community structure due to population declines and local extirpations presumably due to fish predation. This work shows that conservation-translocations undertaken to conserve protected fish species may impact spring-dwelling invertebrate communities, and such impacts are similar to impacts due to colonization by invasive fish species.

  8. Passive partitioning of polychlorinated biphenyls between seawater and zooplankton, a study comparing observed field distributions to equilibrium sorption experiments.

    Science.gov (United States)

    Sobek, Anna; Cornelissen, Gerard; Tiselius, Peter; Gustafsson, Orjan

    2006-11-01

    From previous studies, it remains unclear whether polychlorinated biphenyls (PCBs) are biomagnified in zooplankton or if concentrations are simply governed by passive partitioning. In this study, in the Gullmar Fjord on the Swedish west coast, field-determined lipid-normalized partition coefficients (log Klip) were compared to equilibrium partition coefficients from laboratory sorption experiments with dead and preserved zooplankton. There was no significant difference between the linear regressions of log Klip-log Kow (analysis of covariance [ANCOVA], p 200 microm) were not statistically different from oc-normalized concentrations in phytoplankton (0.7-50 microm), which supports the absence of significant biomagnification. PMID:17144299

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

    Directory of Open Access Journals (Sweden)

    Richard A. VOLLENWEIDER

    2000-08-01

    Full Text Available The present comments resulted from a discussion I had with Dr. Riccardi about the validity of proxy estimates of protein, carbohydrate, and lipid in various zooplankton species of Northern Italian lakes (Riccardi & Mangoni 1999. For these estimates the authors used a calculation method proposed by Gnaiger & Bitterlich (1984; below referred to as G&B. The reason why I questioned the application of the unmodified G&B model to zooplankton was that carbohydrate in crustaceans is mostly present in form of chitin. The argumentation grow rapidly beyond a simple dispute about modes of calculation, leading to some more principle considerations about the limits of proxy estimates.

  10. Underground radionuclide migration

    International Nuclear Information System (INIS)

    The number 9 sub-report of the safety assesment studies of the disposal of radioactive waste in rock-salt formations concerns the calculation of radio-nuclide migration with groundwater. Calculations ar carried out in two phases. The first phase consists of calculation of the groundwater flow system under a great number of different hydrological boundary conditions, which possibly can be encountered in future. Variations in sea level and consequences of glaciations are included. Given a great number of possible groundwater flow systems, in the second phase radionuclide migration is calculated for a restricted number of representative situations. Transport of radionuclides with groundwater takes place, starting at a release point at the top (edge) of the rock salt formation until the landsurface, the bottom of a sea or an extraction-well for public water supply has been reached, at which places concentrations radionuclides have been computed as a function of time. Calculations continued till all concentrations had reached their maxima. Results form the input for biosphere dose-calculations, as reported in the number 10 sub-report. (author). 26 refs.; 43 figs.; 22 tabs

  11. Amenity migration as an example of the environmental migration.

    Czech Academy of Sciences Publication Activity Database

    Bartoš, Michael; Kušová, Drahomíra; T?šitel, Jan

    Newcastle upon Tyne : Cambridge Scholars Publishing, 2008, s. 58-75. ISBN 978-1-4438-0038-9 R&D Projects: GA ?R(CZ) GA403/07/0714 Institutional research plan: CEZ:AV0Z60870520 Keywords : amenity migration * environmental migration * local development Subject RIV: AO - Sociology, Demography

  12. Vertical Cable Seismic Survey for Hydrothermal Deposit

    Science.gov (United States)

    Asakawa, E.; Murakami, F.; Sekino, Y.; Okamoto, T.; Ishikawa, K.; Tsukahara, H.; Shimura, T.

    2012-04-01

    The vertical cable seismic is one of the reflection seismic methods. It uses hydrophone arrays vertically moored from the seafloor to record acoustic waves generated by surface, deep-towed or ocean bottom sources. Analyzing the reflections from the sub-seabed, we could look into the subsurface structure. This type of survey is generally called VCS (Vertical Cable Seismic). Because VCS is an efficient high-resolution 3D seismic survey method for a spatially-bounded area, we proposed the method for the hydrothermal deposit survey tool development program that the Ministry of Education, Culture, Sports, Science and Technology (MEXT) started in 2009. We are now developing a VCS system, including not only data acquisition hardware but data processing and analysis technique. Our first experiment of VCS surveys has been carried out in Lake Biwa, JAPAN in November 2009 for a feasibility study. Prestack depth migration is applied to the 3D VCS data to obtain a high quality 3D depth volume. Based on the results from the feasibility study, we have developed two autonomous recording VCS systems. After we carried out a trial experiment in the actual ocean at a water depth of about 400m and we carried out the second VCS survey at Iheya Knoll with a deep-towed source. In this survey, we could establish the procedures for the deployment/recovery of the system and could examine the locations and the fluctuations of the vertical cables at a water depth of around 1000m. The acquired VCS data clearly shows the reflections from the sub-seafloor. Through the experiment, we could confirm that our VCS system works well even in the severe circumstances around the locations of seafloor hydrothermal deposits. We have, however, also confirmed that the uncertainty in the locations of the source and of the hydrophones could lower the quality of subsurface image. It is, therefore, strongly necessary to develop a total survey system that assures a accurate positioning and a deployment techniques. We have carried out two field surveys in FY2011. One is a 3D survey with a boomer for a high-resolution surface source and the other one for an actual field survey in the Izena Cauldron an active hydrothermal area in the Okinawa Trough. Through these surveys, the VCS will become a practical exploration tool for the exploration of seafloor hydrothermal deposits.

  13. Software Engineering Challenges of Migration Projects

    OpenAIRE

    S.Geetha; Dr.Alagaramy

    2012-01-01

    Organisations often face the challenges of migration from legacy systems to new target systems. Such migration efforts represent a complex engineering problem. This paper describes migration planning, identifies influencing factors, outlines a set of migration planning activities and offers a set of guidelines for the migration planning

  14. Functions and Vertical Line Test

    Science.gov (United States)

    2011-01-17

    This lesson is designed to introduce students to the vertical line test for functions as well as practice plotting points and drawing simple functions. The lesson provides links to discussions and activities related to the vertical line test and functions as well as suggested ways to integrate them into the lesson.

  15. Vertical transmission of Kaposi's sarcoma.

    OpenAIRE

    McCarthy, G A; Kampmann, B.; V. Novelli; Miller, R.F.; Mercey, D. E.; Gibb, D

    1996-01-01

    AIDS related Kaposi's sarcoma is commonly seen in homosexual men, only occasionally in men and women with heterosexually acquired HIV, and extremely rarely in children. The case of an HIV infected mother and her vertically infected child who both developed visceral Kaposi's sarcoma is reported. It is proposed that the putative Kaposi's sarcoma agent may also be transmitted vertically.

  16. Vertical ovalness of glaucomatous cupping.

    Science.gov (United States)

    Gloster, J

    1975-01-01

    Slit-lamp examination and stereoscopic fundus photography were found to be helpful in differentiating between physiological and glaucomatous cupping of the disc. Vertical ovalness of any cup in the disc should raise the suspicion of glaucoma, and the magnitude of the vertical cup: disc ratio is of particular significance. PMID:1218184

  17. Measuring Growth with Vertical Scales

    Science.gov (United States)

    Briggs, Derek C.

    2013-01-01

    A vertical score scale is needed to measure growth across multiple tests in terms of absolute changes in magnitude. Since the warrant for subsequent growth interpretations depends upon the assumption that the scale has interval properties, the validation of a vertical scale would seem to require methods for distinguishing interval scales from…

  18. Vertical separation for TCF

    International Nuclear Information System (INIS)

    The authors studied an insertion for electrostatic separation of the electron and positron beams with the aims of: increasing luminosity by decreasing the minimum bunch spacing, matching the vertical dispersion function (not done in the Jowett lattice). The authors looked at three possibilities for the start of the insertion: a quadrupole doublet followed by the electrostatic separator (Jowett), a quadrupole doublet with the electrostatic separator between the two quadrupoles (Kamada), a separator followed by a quadrupole doublet. The third possibility was immediately discharged. Although possible for a B-factor with magnetic separation it is impractical for use with electrostatic separation because of the length and cross section of separator required. The Kamada scheme looked promising for getting very short inter-bunch spacing, but suffered from the disadvantage of requiring a very large ratio of beta functions at the Interaction Point (IP) (?x*/?y* = 100). (They would rather have a ?* ratio closer to 20 to 1). They decided to persue the doublet scheme to see whether it could match the performance of Kamada insertion. They assumed superconducting magnets could be used for the insertion quadrupoles, and they used as strong an electrostatic field for the separator as Kamada

  19. Vertical guidance of shearers

    International Nuclear Information System (INIS)

    Mining Engineers have always been aware of the basic need to avoid contamination of the mined product, by controlling the cutting horizon at the coal face. The ability to maintain the optimum cutting horizon results in more effective roof control and ensures a safer and more efficient working environment, for men and machinery. The cost of treatment in the surface coal preparation plant is reduced. Transportation through the total mine system of material finally destined for the spoil heap is minimised. A reduction in product contamination is achieved and makes more effective use of the mine capacity. These benefits make possible significant improvements in productivity and financial returns. Exploitation of micro computer based systems has enabled the successful development of equipment which employs sensors to detect the very low natural gamma radiation from roof strata; to determine and allow control of the position of the cut relative to the roof and floor. This paper reviews the experience gained by the National Coal Board, particularly in South Yorkshire Area, with the vertical steering of ranging drum shearers. It outlines the benefits and considers the future for this technology and its contribution to total coal face automation

  20. Trade Liberalisation and Vertical Integration

    DEFF Research Database (Denmark)

    Bache, Peter Arendorf; Laugesen, Anders

    2013-01-01

    We build a three-country model of international trade in final and intermediate goods and study the relation between different types of trade liberalisation and vertical integration. Firms are heterogeneous with respect to both productivity and factor intensity as observed in data. Final-good producers face decisions on exporting, vertical integration of intermediate-input production, and whether the intermediate-input production should be offshored to a low-wage country. We find that due to firm-level complementarities, the shares of final-good producers that pursue either vertical integration, offshoring, or exporting are all increasing when intermediate- or final-goods trade is liberalised and when the cost of vertical integration is reduced. At the same time, one will observe individual firms that shift away from either vertical integration, offshoring, or exporting. All these results hold for a class of productivity distributions to which the Pareto distribution belongs.

  1. Imazethapyr and imazapic, bispyribac-sodium and penoxsulam: zooplankton and dissipation in subtropical rice paddy water.

    Science.gov (United States)

    Reimche, Geovane B; Machado, Sérgio L O; Oliveira, Maria Angélica; Zanella, Renato; Dressler, Valderi Luiz; Flores, Erico M M; Gonçalves, Fábio F; Donato, Filipe F; Nunes, Matheus A G

    2015-05-01

    Herbicides are very effective at eliminating weed and are largely used in rice paddy around the world, playing a fundamental role in maximizing yield. Therefore, considering the flooded environment of rice paddies, it is necessary to understand the side effects on non-target species. Field experiment studies were carried out during two rice growing seasons in order to address how the commonly-used herbicides imazethapyr and imazapic, bispyribac-sodium and penoxsulam, used at recommended dosage, affect water quality and the non-target zooplankton community using outdoor rice field microcosm set-up. The shortest (4.9 days) and longest (12.2 days) herbicide half-life mean, estimated of the dissipation rate (k) is shown for imazethapyr and bispyribac-sodium, respectively. Some water quality parameters (pH, conductivity, hardness, BOD5, boron, potassium, magnesium, phosphorus and chlorides) achieved slightly higher values at the herbicide treatment. Zooplankton community usually quickly recovered from the tested herbicide impact. Generally, herbicides led to an increase of cladocera, copepods and nauplius population, while rotifer population decreased, with recovery at the end of the experiment (88 days after herbicide treatment). PMID:25659307

  2. The use of zooplankton in a biomonitoring program to detect lake acidification and recovery

    Energy Technology Data Exchange (ETDEWEB)

    Marmorek, D.R.; Korman, J. (ESSA Environmental and Social Systems Analysts Ltd., Vancouver, BC (Canada))

    1993-08-01

    A detailed review of the zooplankton literature found strong evidence that lake acidification consistently causes declines in crustacean and rotifer species richness, the relative abundance of cyclopoids and daphnids, and the relative abundance of 16 particular zooplankton species. Five species were found to consistently increase as lake pH declines. Inconsistent effects were observed on crustacean biomass and mean organism size. Biomonitoring response variables recommended to detect incipient community changes included the relative abundance of pH sensitive species, overall crustacean and rotifer community composition plotted in abundance ordination space, crustacean and rotifer species richness, and the relative abundance of acid tolerant species. If acidification effects have been detected using the above response variables, then more detailed monitoring to understand the functional characteristics of affected systems (e.g. crustacean biomass, rotifer biomass and/or overall community size spectra) is appropriate. A lake selection procedure is recommended to maximize the number of systems containing sensitive species, and ensure a set of reference systems whose acidity is unlikely to change significantly. 48 refs., 4 tabs.

  3. Development of zooplankton culture subsystem for a closed ecological recirculating aquaculture system (CERAS)

    Science.gov (United States)

    Omori, Katsunori; Oguchi, Mitsuo; Takeuchi, Toshio

    2006-01-01

    Ten parthenogenetic females of Moina macrocopa were placed in small cells with different flow conditions. The cells were opened after three-days of cultivation, and the water fleas in each cell were counted. It appeared that M. macrocopa were cultured effectively in a relatively slow current, 10 cm/min., but the population growth was not significantly influenced by the difference in flow direction. Subsequent, filtration efficiencies of filters with various pore sizes were compared. Four available porous hollow-fiber membrane modules, ACP-1010, AHP-1010, PSP-103, and PMP-102 (Asahi-Kasei Corp.), were tested. The module with the larger pore size initially filtered a greater amount of water but clogged up sooner. ACP-1010, which has the smallest pores, was considered to be suitable to filter condensed algal water due to its durability and stable filtration. An improved zooplankton culture device (IZCD) was designed and constructed based on these examinations. IZCD is a 13.2L airtight device characterized by a short and thick rearing tank and alternate filtration with paired fine hollow-fiber membrane modules. It must be tested and revised to be used in research into the optimal conditions for a zooplankton culture in a closed environment.

  4. ZOOPLANCTON EN LA LARVICULTURA DE PECES NEOTROPICALES / ZOOPLANKTON IN LARVICULTURE OF NEOTROPICAL FISHES

    Scientific Electronic Library Online (English)

    Martha, Prieto G; Victor, Atencio G.

    2008-05-01

    Full Text Available La larvicultura de peces neotropicales altriciales presenta limitaciones para el manejo de la primera alimentación dado el pobre desarrollo del tracto digestivo y capacidad natatoria. La alimentación de la larva debe considerar el tamaño, densidad y calidad de la presa ofrecida. Este documento revis [...] a a la luz de recientes trabajos la incidencia del zooplancton en la larvicultura de peces, aborda la importancia de la larvicultura en el proceso piscícola, la importancia del zooplancton como alimento y las alternativas en el manejo de cladóceros, copépodos y rotíferos para la alimentación de larvas de especies neotropicales. Abstract in english Because of the poor development of digestive system and swimming capability of young fish, larviculture of altricial neotropical fish presents for the management of the initial feeding. The feeding of the larvae must consider the size, density and quality of the prey offered. This document reviews t [...] he incidence of zooplankton in fish larvicultura, approaches the importance of larviculture in fish rearing, the importance of zooplankton as prey, and alternatives in the handling of cladocerans, copepods and rotifers for the feeding of larvae of neotropical fishes.

  5. Physicochemistry and zooplankton of two karstic sinkholes in the Yucatan Peninsula, Mexico

    Directory of Open Access Journals (Sweden)

    Adrian Cervantes-Martinez

    2014-02-01

    Full Text Available The planktonic communities composed of rotifers and crustaceans of two tropical karstic lakes in the Yucatan Peninsula, Mexico, with similar origin but different trophic state were analyzed. Both systems, the meso-eutrophic (El Padre and oligotrophic (Minicenote were considered as monomictic lakes. The abundance, temporal distribution of species, richness and diversity were measured and discussed in relation to the influence of abiotic factors and the presence of a natural predator. These analyses indicated that these tropical systems were not homogenous for several of these measures at both spatial scales and during the annual cycle analyzed, despite their reduced temperature variation compared to temperate lakes. The results indicated that the dynamics in the zooplankton community were related to the environmental factors, the opportunistic species (with maximum densities related to resource maxima, and the exploitative competition between the dominant herbivorous species. Independently of the trophic condition, the abundance, richness, and diversity were lower during the mixing period. During the annual cycle studied in the meso-eutrophic system, the key environmental parameters related to plankton abundance were pH and temperature whereas in the oligotrophic system, oxygen concentration was important. In both lakes, richness and diversity were related to conductivity, although in the oligotrophic lake the relation was negative whereas in the meso-eutrophic lake it was positive. No relationship was found between the abundance of the studied predator (Chaoborus sp. and the changes in the abundance, diversity and richness of zooplankton in the systems.

  6. Spatiotemporal dynamics in a reaction–diffusion toxic-phytoplankton–zooplankton model

    International Nuclear Information System (INIS)

    In this paper, we investigate the complex dynamics of a spatial toxic-phytoplankton–zooplankton model with Holling type-II functional response. Through a detailed analytical study of the reaction–diffusion model, we obtain some conditions for local and global stability and for diffusive instability with zero-flux boundary conditions of a positive equilibrium. On the basis of these results, we present the evolutionary processes of pattern formation that involve organism distribution and the interaction of a spatially distributed population with local diffusion. Then, novel numerical evidence of the time evolution of patterns controlled by diffusion and environmental carrying capability in the model are presented, and it is found that the model dynamics exhibits complex pattern replication. Additional studies reveal that pattern formation in the spatially extended model depends on the choice of the initial conditions. These results indicate that the interaction between toxin-producing phytoplankton and zooplankton in marine environments may be partly driven by the forces of diffusion or the environmental carrying capability. (paper)

  7. Migrating foreign body from hypopharynx.

    DEFF Research Database (Denmark)

    Mowinckel, Marius Storm; Charabi, Birgitte Wittenborg

    2014-01-01

    In this case report we present a 20-month-old girl with a migrating foreign body, a "smiley" sticker, that migrated from hypopharynx to surrounding tissue and created an abscess with a fistula, one year after ingestion. The foreign body was removed without difficulty under general anaesthesia, and the patient was discharged after few days with peroral antibiotics.

  8. Africa: Setting for Human Migration

    Science.gov (United States)

    Buuba, Babacar Diop

    2007-01-01

    Analysis of African migrations can help to understand prehistoric, historical, ancient modern and contemporaneous migrations. Movements of populations were and continue to be so intense that, for some analysts, they constitute one of the dominant trends of the history and destiny of the very old continent. African and non-African states, whether…

  9. Migration, Diaspora et développement humain

    OpenAIRE

    Bouoiyour, Jamal

    2006-01-01

    This contribution aims to provide some understanding of migration issues in the case of Morocco. This is to recall the various initiatives taken by the Moroccan authorities to strengthen ties between Morocco and migrants. An analysis of the evolution of remittances and their impact on the economy is proposed. Similarly, we address the problem of migration of highly skilled labor in the Moroccan case.

  10. The economics of circular migration

    OpenAIRE

    Constant, Amelie F.; Nottmeyer, Olga; Zimmermann, Klaus F.

    2012-01-01

    Circular migration receives increasing attention due to its empirical relevance and as a policy concept to manage labor flows. This review discusses the advantages and disadvantages of circular movements for all parties. It studies the characteristics of circular movers worldwide and investigates the consequences of restrictive migration policies. Recent policy initiatives that aim to manage circular labor movement are also analyzed.

  11. Cyanobacteria bloom: selective filter for zooplankton? / Floração de cianobactéria: filtro seletivo para zooplâncton?

    Scientific Electronic Library Online (English)

    NAST, Mello; PM, Maia-Barbosa.

    2015-03-01

    Full Text Available O reservatório de Ibirité é um ambiente urbano, eutrófico com periódicas ocorrências de florações de cianobactérias. O padrão de mistura deste reservatório é monomítico quente, permanecendo estratificado a maior parte do ano, circulando na estação seca (inverno). Durante o ciclo hidrológico de outub [...] ro/07 a outubro/08, ocorreram quatro cenários com condições ambientais distintas, que influenciaram na estruturação da comunidade zooplanctônica, conforme observado em estudo prévio. As mudanças na estrutura da comunidade zooplanctônica entre os cenários foram estudadas objetivando analisar a estabilidade e persistência desta comunidade. O coeficiente de correlação de Spearman foi utilizado para medir a estabilidade; a persistência foi considerada por meio de uma análise de agrupamento; e as mudanças na composição da comunidade foram estimadas através do índice de diversidade ? temporal. A comunidade foi estável, considerando os padrões de distribuição da abundância, somente na transição entre os cenários 1 e 2 (n=30; r= 0,71; p=0,00001), nos quais não foram observadas florações de cianobactérias. A persistência do zooplâncton entre os cenários foi baixa, apresentando composições de espécies distintas. As maiores variações na composição das espécies, estimadas através dos valores de diversidade ? temporal, foram nas transições entre os cenários 3-0 (1,45) e 0-1 (1,05), e o menor valor na transição entre os cenários 1-2 (0,57). Os resultados do presente trabalho sugerem que as florações de cianobactérias no reservatório de Ibirité estariam funcionando como “filtros seletivos”, ou seja, distúrbios com capacidade suficiente para alterar a estrutura da comunidade zooplanctônica. Abstract in english The Ibirité reservoir is an urban and eutrophic environment, with regular occurrences of cyanobacteria blooms. The reservoir is warm monomict and remains stratified most of the year, circulating in the dry season (winter). During the hydrological cycle of October/07 to October/08 there were four sce [...] narios with different environmental conditions, which influenced the structure of the zooplankton community, as confirmed in a previous study. Changes in the zooplankton community structure between the scenarios were studied, aiming at analyzing the stability and persistence of this community. The Spearman’s coefficient of correlation was used to measure the stability; the persistence was evaluated through a cluster analysis and changes in community composition were estimated by the "temporal" ? diversity index. Considering the distribution patterns of abundance, the community was stable only in the transition between scenarios 1 and 2 (n = 30, r = 0.71, p = 0.00001), when there were no cyanobacteria blooms. The persistence of zooplankton between the scenarios was low, showing a distinct species composition for each scenario. The highest variations in species composition, observed by the values of temporal ? diversity index, were the transitions between scenarios 3-0 (1.45) and 0-1 (1.05), and the lowest variations occurred in the transition between scenarios 1-2 (0.57). The results suggest that the cyanobacteria blooms at Ibirité reservoir are be acting as "selective filters", and are, thus, disturbances with sufficient ability to change the structure of the zooplankton community. Keywords Urban Reservoir, zooplankton, bloom of cyanobacteria, stability, persistence.

  12. Radionuclide Migration: Prediction Experience

    International Nuclear Information System (INIS)

    Many different methods of calculating radionuclide migration (transfer) with groundwater-from very simple handmade calculations to use of sophisticated computer models, - exist and are in use. There is no doubt whether we can solve a particular problem in this area; the question is how can we find means of doing this in a fast, precise and economical way. According to practical experience of MosSIA 'Radon' specialists it is useful at the first stage to assess the degree to which various parameters affect the final result. Then the relevance of modeling parameters is usually assessed. SUE MosSIA 'Radon' has applied this complex approach to assessing possible radionuclide transfer from the long term storage facilities located within one of the sites in Moscow. Questions of model verification, computer realization, the analysis of obtained results, a role and a place of these calculations in safety assessment and safety case are beyond the scope of this paper. (authors)

  13. Chandra Contaminant Migration Model

    Science.gov (United States)

    Swartz, Douglas A.; O'Dell, Steve L.

    2014-01-01

    High volatility cleans OBFs and low volatility produces a high build-up at OBF centers; only a narrow (factor of 2 or less) volatility range produces the observed spatial pattern. Simulations predict less accumulation above outer S-array CCDs; this may explain, in part, gratings/imaging C/MnL discrepancies. Simulations produce a change in center accumulation due solely to DH heater ON/OFF temperature change; but a 2nd contaminant and perhaps a change in source rate is also required. Emissivity E may depend on thickness; another model parameter. Additional physics, e.g., surface migration, is not warranted at this time. At t approx. 14 yrs, model produced 0.22 grams of contaminant, 0.085 grams remaining within ACIS cavity; 7 percent (6mg) on OBFs.

  14. Objectivity Data Migration

    CERN Document Server

    Nowak, M; Valassi, Andrea; Lubeck, M; Geppert, D; Geppert, Dirk

    2003-01-01

    In this article we describe the migration of event data collected by the COMPASS and HARP experiments at CERN. Together these experiments have over 300TB of physics data stored in Objectivity/DB that had to be transferred to a new data management system by the end of Q1 2003 and Q2 2003 respectively. To achieve this, data needed to be processed with a rate close to 100MB/s, employing 14 tape drives and a cluster of 30 Linux servers. The new persistency solution to accommodate the data is built upon relational databases for metadata storage and standard "flat" files for the event data. The databases contain collections of 109 events and allow generic queries or direct navigational access to the data, preserving the original C++ user API. The central data repository at CERN is implemented using several Oracle9i servers on Linux and the CERN Mass Storage System CASTOR.

  15. Anomalous dynamics of cell migration

    CERN Document Server

    Dieterich, Peter; Preuss, Roland; Schwab, Albrecht; 10.1073/pnas.0707603105

    2009-01-01

    Cell movement, for example during embryogenesis or tumor metastasis, is a complex dynamical process resulting from an intricate interplay of multiple components of the cellular migration machinery. At first sight, the paths of migrating cells resemble those of thermally driven Brownian particles. However, cell migration is an active biological process putting a characterization in terms of normal Brownian motion into question. By analyzing the trajectories of wildtype and mutated epithelial (MDCK-F) cells we show experimentally that anomalous dynamics characterizes cell migration. A superdiffusive increase of the mean squared displacement, non-Gaussian spatial probability distributions, and power-law decays of the velocity autocorrelations are the basis for this interpretation. Almost all results can be explained with a fractional Klein- Kramers equation allowing the quantitative classification of cell migration by a few parameters. Thereby it discloses the influence and relative importance of individual comp...

  16. Neural Crest Cell Migration

    Science.gov (United States)

    PhD Jack D Thatcher (West Virginia School of Osteopathic Medicine Structural Biology)

    2010-11-29

    This simple FlashTM animation depicts migration of neural crest cells throughout the mesoderm of the neurulating germ disc. For context it opens with a cross section of the germ disc showing the neural crests at the dorsal end of the neural tube. It then turns to a lateral view, which allows users to observe neural crest cells separating from the crests and migrating into the mesoderm along the neural tube or epidermis. A back button allows users to jump to previous scenes, a rate button allows them to toggle between fast and slow modes, and a text button allows them to toggle explanatory text on and off. Instructions for opening animation with Windows system. 1. Double click the icon for the SWF. 2. A dialog box may pop up that begins with the statement "Windows cannot open this file:" If this box does not appear proceed to step 4. If it does choose "Select the program from a list," then click OK. 3. Another dialog box will pop up that lists different programs. Make sure " Internet Explorer" is selected, then click OK. 4. A Window for Internet Explorer will pop up. Beneath the toolbars at the top of the window a yellow bar will appear that reads "To help protect your security, Internet Explorer has restricted this webpage from running scripts or Active X controls that could access your computer. Click here for options..." Pass the cursor over this yellow bar and click the right mouse button. 5. A dialog box will pop up. Left click the option "Allow Blocked Content." 6. Another dialog box will appear labeled "Security Warning" asking you to confirm that you want to run the content. Click "Yes." 7. The Flash animation will appear in the Internet Explorer Window. 8. Left click anywhere in the animation to advance the display. 9. Read instructions provided by the animation for additional controls such as navigation buttons.

  17. Development of Vertical Cable Seismic System

    Science.gov (United States)

    Asakawa, E.; Murakami, F.; Sekino, Y.; Okamoto, T.; Ishikawa, K.; Tsukahara, H.; Shimura, T.

    2011-12-01

    In 2009, Ministry of Education, Culture, Sports, Science and Technology(MEXT) started the survey system development for Hydrothermal deposit. We proposed the Vertical Cable Seismic (VCS), the reflection seismic survey with vertical cable above seabottom. VCS has the following advantages for hydrothermal deposit survey. (1) VCS is an efficient high-resolution 3D seismic survey in limited area. (2) It achieves high-resolution image because the sensors are closely located to the target. (3) It avoids the coupling problems between sensor and seabottom that cause serious damage of seismic data quality. (4) Because of autonomous recording system on sea floor, various types of marine source are applicable with VCS such as sea-surface source (GI gun etc.) , deep-towed or ocean bottom source. Our first experiment of 2D/3D VCS surveys has been carried out in Lake Biwa, JAPAN, in November 2009. The 2D VCS data processing follows the walk-away VSP, including wave field separation and depth migration. Seismic Interferometry technique is also applied. The results give much clearer image than the conventional surface seismic. Prestack depth migration is applied to 3D data to obtain good quality 3D depth volume. Seismic Interferometry technique is applied to obtain the high resolution image in the very shallow zone. Based on the feasibility study, we have developed the autonomous recording VCS system and carried out the trial experiment in actual ocean at the water depth of about 400m to establish the procedures of deployment/recovery and to examine the VC position or fluctuation at seabottom. The result shows that the VC position is estimated with sufficient accuracy and very little fluctuation is observed. Institute of Industrial Science, the University of Tokyo took the research cruise NT11-02 on JAMSTEC R/V Natsushima in February, 2011. In the cruise NT11-02, JGI carried out the second VCS survey using the autonomous VCS recording system with the deep towed source provided by Institute of Industrial Science, the University of Tokyo. It generates high frequency acoustic waves around 1kHz. The acquired VCS data clearly shows the reflections and currently being processed for imaging the subsurface structure.

  18. Responses of zooplankton in lufenuron-stressed experimental ditches in the presence or absence of uncontaminated refuges.

    Science.gov (United States)

    López-Mancisidor, Patricia; Van den Brink, Paul J; Crum, Steven J H; Maund, Steve J; Carbonell, Gregoria; Brock, Theo C M

    2008-06-01

    Outdoor experimental ditches were used to evaluate the influence of untreated refuges on the recovery of zooplankton communities following treatment with the fast-dissipating insecticide lufenuron. Each experimental ditch was divided into three sections of the same surface area. The treatments differed in the proportion of ditch (0, 33, 67, and 100% of the surface area) to which the insecticide was applied at the same nominal treatment (3 mug/L). During the first week postapplication, a barrier was placed between treated and untreated ditch sections. The untreated sections were included to provide a source of organisms for recovery of affected zooplankton populations in the treated sections of the ditch after the removal of the barrier. Cyclopoida were the most affected by lufenuron treatment, followed by Daphnia gr. galeata. These and other direct effects of treatment on larvae of the phantom midge Chaoborus spp. resulted in clear indirect effects on populations of Calanoida, Ceriodaphnia, and Rotifera. Overall, faster recovery of the zooplankton community was observed in the treated sections of ditches that were sprayed for a smaller proportion of their surface area. Nevertheless, individual zooplankton populations showed considerable differences in rate of recovery. Cyclopoida showed a relatively slow rate of recovery even in the partially treated ditches. Daphnia gr. galeata recovered more rapidly in treated ditch sections in the presence of unsprayed ditch sections, illustrating the potential influence of unexposed refuges. Furthermore, the presence of refuges most likely dampened the magnitude and duration of indirect effects in the ditches treated with lufenuron. PMID:18466038

  19. Zooplankton biomass and abundance of Antarctic krill Euphausia superba DANA in Indian Ocean sector of the southern ocean

    Digital Repository Service at National Institute of Oceanography (India)

    Ingole, B.S.; Parulekar, A.H.

    1993-01-01

    Zooplankton sampling was carried out during the first six Indian Scientific Expeditions to Antarctica (1981-1987) to estimate krill abundance in the Indian sector of the Southern Ocean (between 35 to 70 degrees S and 10 to 52 degrees E). This study...

  20. Observations on phytoplankton pigments, zooplankton and physico-chemical parameters in surface waters from southern Indian Ocean and Antarctic region

    Digital Repository Service at National Institute of Oceanography (India)

    JiyalalRam, M.; Goswami, S.C.

    1993-01-01

    and phaeopigments. Copepods, euphausiids, decapods, polychaetes and chaetognaths were the major constituents of zooplankton community. The salinity values varied from 34.06 to 36.14 x 10/3. Temperature fluctuations of the seawater were pronounced (-0.5 to 29.5?C...

  1. Trophic structure and levels of selected metals in the zooplankton community of Thane-Bassein Creek, Bombay

    Digital Repository Service at National Institute of Oceanography (India)

    Nair, V.R.; Krishnamurti, A.J.; Gajbhiye, S.N.

    1999-01-01

    -83% to total zooplankton population. Decapods were relatively more in the outer (av. 11%) as compared to interior zone (av. 7%). Population density of carnivores were 2-4 times more in the polluted interior segment. Among the different metals studied Cu and Zn...

  2. Zooplankton around Marion and Prince Edward Islands; 24 March 1976 to 25 November 1976 (NODC Accession 0000940)

    National Oceanic and Atmospheric Administration, Department of Commerce — Samples of zooplankton taken at 12 stations around Marion and Prince Edward Islands (47oS - 35oE) in March 1976 from the 'Marion-Dufresne' and at 2 stations in the...

  3. Composition and abundance of zooplankton in the limnetic zone of seven reservoirs of the Paranapanema River, Brazil

    Directory of Open Access Journals (Sweden)

    SAMPAIO E. V.

    2002-01-01

    Full Text Available The species composition and abundance of the zooplankton community of seven reservoirs of the Paranapanema River, located between 22º37'-23º11'S and 48º55'-50º32'W, were analysed over four periods, in the year of 1979. The zooplankton community was composed of 76 species of Rotifera, 26 species of Cladocera and 7 species of Copepoda. For a large part of the period under study the Rotifera were dominant, followed by Copepoda. The Piraju and Salto Grande reservoirs, which occupy intermediate positions in the cascade of reservoirs, were richest in species, most of them belonging to Rotifera and Cladocera. In the reservoirs Rio Pari and Rio Novo, lateral to the cascade of reservoirs, a lower species richness was observed, although higher densities of organisms were found than in the other reservoirs located in the main river body. Different rotifer species occurred in succession, being abundant in different periods, with no defined pattern. Among the copepods, Thermocyclops decipiens predominated in the majority of the reservoirs. Ceriodaphnia cornuta was the most abundant cladoceran in the intermediate reservoirs of the cascade, and Daphnia gessneri, Bosminopsis deitersi and Moina minuta, in the reservoirs lateral to the cascade. The most frequent zooplankton species were Notodiaptomus conifer, Thermocyclops decipiens, Ceriodaphnia cornuta cornuta and C. cornuta rigaudi, Daphnia gessneri, Bosmina hagmanni, Keratella cochlearis and Polyarthra vulgaris. Some relationships were found between the trophic state of the reservoirs and the zooplankton community.

  4. Diversity and composition of zooplankton in rice fields during a crop cycle at Pathum Thani province, Thailand

    Directory of Open Access Journals (Sweden)

    Supenya Chittapun

    2009-08-01

    Full Text Available A study of zooplankton communities in three rice fields (RF1, RF2 and RF3 at Pathum Thani province was carried out from August to November 2005. A total of 88 taxa were identified. Of these, 74 belonged to Rotifera, 11 were Cladocera and 3 were Copepoda. The highest number of zooplankton species was recorded in RF1 (75 species, followed by RF2 (55 species and RF3 (51 species. The highest average H’ was registered in RF2 (1.83, followed by RF3 (1.59 and RF1 (1.52. The highest average zooplankton abundance was reported from RF3 (22,630.7 indL-1, followed by RF2 (1,756.8 indL-1 and RF1 (1,519.5 indL-1. The main zooplankton components in the three areas were nauplii, rotifers and Cladocera. Cladoceraplayed a major role in structuring rotifer communities in rice fields.

  5. Restoring lakes by using artificial plant beds: habitat selection of zooplankton in a clear and a turbid shallow lake

    DEFF Research Database (Denmark)

    Schou, Majbritt Overgård; Risholt, Casper

    2009-01-01

    1. Return of large-bodied zooplankton populations is of key importance for creating a shift from a turbid to a clear-water state in shallow lakes after a nutrient loading reduction. In temperate lakes, recovery is promoted by submerged macrophytes which function as a daytime refuge for large zooplankton. However, recovery of macrophytes is often delayed and use of artificial plant beds (APB) has been suggested as a tool to enhance zooplankton refuges, thereby reinforcing the shift to a clear-water state and, eventually, colonisation of natural plants. 2. To further evaluate the potential of APB in lake restoration, we followed the day–night habitat choices of zooplankton throughout summer in a clear and a turbid lake. Observations were made in the pelagic and littoral zones and in APB in the littoral representing three different plant densities (coverage 0%, 40% and 80%). 3. In the clear lake, the zooplankton (primarily Daphnia) were mainly found in the pelagic area in spring, but from mid-May they were particularly abundant in the APB and almost exclusively so in mid-June and July, where they appeared in extremely high densities during day (up to 2600 ind. L?1). During night Daphnia densities were overall more equally distributed between the five habitats. Ceriodaphnia was proportionally more abundant in the APB during most of the season. Cyclopoids were more abundant in the high APB during day but were equally distributed between the five habitats during night. 4. In the turbid lake, however, no clear aggregation was observed in the APB for either of the pelagic genera (Daphnia and Bosmina). This may reflect a higher refuge effect in the open water due to the higher turbidity, reduced ability to orient to plant beds and a significantly higher fish density (mainly of roach, Rutilus rutilus, and perch, Perca fluviatilis) in the plant beds than in the clear lake. Chydorus was found in much higher proportions among the plants, while cyclopoids, particularly the pelagic Cyclops vicinus, dominated in the pelagic during day and in the pelagic and high density plants during night. 5. Our results suggest that water clarity is decisive for the habitat choice of large-bodied zooplankton and that introduction of APB as a restoration measure to enhance zooplankton survival is only a useful tool when water clarity increases following loading reduction. Our results indicate that dense APB will be the most efficient.

  6. Lake Roosevelt Fisheries Evaluation Program, Part B; Limnology, Primary Production, and Zooplankton in Lake Roosevelt, Washington, 1998 Annual Report.

    Energy Technology Data Exchange (ETDEWEB)

    Shields, John; Spotts, Jim; Underwood, Keith

    2002-11-01

    The Lake Roosevelt Fisheries Evaluation Program is the result of a merger between two projects, the Lake Roosevelt Monitoring Program (BPA No. 8806300) and the Lake Roosevelt Data Collection Project (BPA No. 9404300). These projects were merged in 1996 to continue work historically completed under the separate projects, and is now referred to as the Lake Roosevelt Fisheries Evaluation Program. The 1998 Annual Report, Part B. Limnology, Primary Production, and Zooplankton in Lake Roosevelt, Washington examined the limnology, primary production, and zooplankton at eleven locations throughout the reservoir. The 1998 research protocol required a continuation of the more complete examination of limnological parameters in Lake Roosevelt that began in 1997. Phytoplankton and periphyton speciation, phytoplankton and periphyton chlorophyll a analysis, complete zooplankton biomass analysis by taxonomic group, and an increased number of limnologic parameters (TDG, TDS, etc.) were examined and compared with 1997 results. Total dissolved gas levels were greatly reduced in 1998, compared with 1997, likely resulting from the relatively normal water year experienced in 1998. Mean water temperatures were similar to what was observed in past years, with a maximum of 22.7 C and a minimum of 2.6 C. Oxygen concentrations were also relatively normal, with a maximum of 16.6 mg/L, and a minimum of 0.9 mg/L. Phytoplankton in Lake Roosevelt was primarily composed of microplankton (29.6%), Cryptophyceae (21.7%), and Bacillriophyceae (17.0 %). Mean total phytoplankton chlorophyll a maximum concentration occurred in May (3.53 mg/m{sup 3}), and the minimum in January (0.39 mg/m{sup 3}). Phytoplankton chlorophyll a concentrations appear to be influenced by hydro-operations and temperature. Trophic status as indicated by phytoplankton chlorophyll a concentrations place Lake Roosevelt in the oligomesotrophic range. Periphyton colonization rates and biovolume were significantly greater at a depth of 1.5 m (5 ft) when compared with a 4.6 m (15 ft) depth, and during the shorter incubation periods (two and four weeks). Mean zooplankton densities were greatest for Copepoda (88 %), then Daphnia spp. (10%) and other Cladocera (2.1%), while the zooplankton biomass assessment indicated Daphnia spp. had the greatest biomass (53.6%), then Copepoda (44.0%) and other Cladocera (2.5%). Mean overall zooplankton densities were the lowest observed since 1991. The cause was unclear, but may have been an artifact of human error. It seems unlikely that hydro-operations played a significant part in the reduction of zooplankton in light of the relatively friendly water year of 1998.

  7. Inservice testing of vertical pumps

    International Nuclear Information System (INIS)

    This paper focuses on the problems that may occur with vertical pumps while inservice tests are conducted in accordance with existing American Society of Mechanical Engineers Code, Section XI, standards. The vertical pump types discussed include single stage, multistage, free surface, and canned mixed flow pumps. Primary emphasis is placed on the hydraulic performance of the pump and the internal and external factors to the pump that impact hydraulic performance. In addition, the paper considers the mechanical design features that can affect the mechanical performance of vertical pumps. The conclusion shows how two recommended changes in the Code standards may increase the quality of the pump's operational readiness assessment during its service life

  8. Dominance shift of zooplankton species composition in the central Strait of Georgia, British Columbia during 1997 Cambio en el zooplancton dominante del estrecho de Georgia, British Columbia durante 1997

    Directory of Open Access Journals (Sweden)

    Martha J. Haro-Garay

    2008-08-01

    Full Text Available A multivariate analysis of the zooplankton was completed during the 1997 annual cycle in the central Strait of Georgia, Canada. Sampling was conducted monthly in a single location (49° 15' 0" N, 123° 44' 9" W. The study used the species as environment descriptors, and examined possible patterns of species associations. Principal components analysis showed two groups of species coinciding with changes in vertical salinity structure arising from two phases of the Fraser River runoff. Group I was dominant during fall-winter to early spring related to low-runoff season. Group II was dominant during late spring to summer, and related to high-runoff season. Notable results were the scarcity of Neocalanus plumchrus and Euphausia pacifica, typically dominant species of zooplankton, coincident with river runoff levels lower than previous years and with an early phytoplankton bloom. We speculate that these results are a consequence of El Niño 1997 event, combined with the climate change expressed as a decreased freshwater runoff. Low abundance of Neocalanus plumchrus and Euphausia pacifica affected the zooplankton biomass. Consequently, substitute dominant P. pacifica and Cyphocaris challengeriprobable play an important role in trophic dynamics while N. plumchrus and E. pacifica are scarce. Both amphipods feed on small zooplankters that feed on nanoplankton, concentrating food energy and biomass from small zooplankters. This suggests that P. pacifica and C. challengeri are an important link in the trophic ecology of the Strait of Georgia. In conclusion, shifts in zooplankton species dominance highly likely have an effect on juvenile zooplanktivorous salmon specie.Se realizó un análisis multivariado del zooplancton de la parte central del estrecho de Georgia, Canadá durante 1997, con muestreos mensuales en una localidad (49° 15' 0" N, 123° 44' 9" W. Las especies se usaron como descriptores del ambiente para examinar posibles patrones de asociación. Mediante análisis de componentes principales se encontraron dos grupos coincidentes con cambios en la estructura vertical de la salinidad inducidos por las fases de flujo intensa y débil del Río Fraser. El grupo I estuvo presente de septiembre a marzo durante la fase de flujo débil del río. El grupo II durante la fase de flujo intensa de mayo a julio. Fue notoria la escasez de Neocalanus plumchrus y Euphausia pacifica, especies dominantes típicas, coincidente con niveles de flujo del Río Fraser inferiores a años previos, y con un florecimiento de fitoplancton temprano. Se especula que estos resultados son consecuencia de El Niño 1997, combinado con cambio climático expresado en la baja descarga del río. La baja abundancia de Neocalanus plumchrus y Euphausia pacifica afectó la biomasa zooplanctónica, en su lugar dominaron Parathemisto pacifica y Cyphocaris challengerique depredan al zooplancton pequeño que se alimenta de nanoplancton, concentrando la energía y biomasa del zooplancton pequeño. Esto sugiere que Parathemisto pacifica y Cyphocaris challengeri son un elemento de enlace importante en la ecología trófica del Estrecho de Georgia cuando N. plumchrus y E. pacifica son escasas. Se concluye que los cambios en la dominancia de especies muy probablemente tienen efecto sobre el salmón juvenil y los peces zooplanctófagos.

  9. The migration of bensulfurron-methyl in soil

    International Nuclear Information System (INIS)

    The migration of 14C-bensulfuron-methyl in 6 soils by means of soil TLC was studied. The Rf values in the tested soil were in range of 0.11 to 0.80 and the herbicide was slightly mobile in red earth from Anhui. Mobile in yellow fluvo-aquatic soil from Jiangsu and middle mobile in red earth from Jiangxi, red earth from Hunan and yellow brown earth from Nanjing. By leaching with large area of soil column, the dynamics of leaching of 3 kinds of soil column under the simulated rain was determined and it is clear that the rain fall needed by a vertical 10 cm fall of bensulfuron-methyl in yellow fluvo-aquatic soil is 82 mm; in the yellow brown earth, 240 mm of rainfall reached leaching rate of 56.55%; but in red earth with rain fall of 622 mm, the leaching rate is only 23.51%. The migration of bensulfuron-methyl has close relationship with soil pH and clay content. With the increase of pH, its migration increases and is easy to be leached. Bensulfuron-methyl is not easy to migrate with water, so its pollution to ground water is almost none

  10. Preliminary assessment of the zooplankton community composition in a region under the influence of a uranium mine (Caldas, Southeastern Brazil)

    Energy Technology Data Exchange (ETDEWEB)

    Ferrari, Carla Rolim; Roque, Claudio Vitor; Ronqui, Leilane B.; Campos, Michelle B.; Rodgher, Suzelei; Nascimento, Marcos Roberto Lopes; Azevedo, Heliana de [Pocos de Caldas Laboratory, Brazilian Nuclear Energy Commission, MG (Brazil)], e-mail: carlarolimferrari@yahoo.com.br, e-mail: cvroque@cnen.gov.br, e-mail: pmarcos@cnen.gov.br, e-mail: leilanebio@yahoo.com.br, e-mail: michelle_borato@hotmail.com, e-mail: surodgher@uol.com.br, e-mail: hazevedo@cnen.gov.br; Wisniewski, Maria Jose dos Santos [Federal University of Alfenas (UNIFAL-MG), MG (Brazil). Lab. of Limnology], e-mail: czw@uol.com.br

    2009-07-01

    The Ore Treatment Unit consists of an open cast mine (CM), its mining waste areas, facilities for the physical treatment of the ore, and a chemical treatment plant for uranium extraction. At CM, the processes of acid drainage create effluents, which are treated by chemical processes and, thereafter, disposed of in Antas dam. The objective of the present study was to make an inventory of zooplanktonic and describe the physicochemical characteristics of site CM and at the site of treated effluents disposal (site 41), located at Antas dam. Water samples were collected in October/08 and January/09, in order to describe the abiotic variables and the zooplankton community. The average values of conductivity at sites CM and 41 were 2415 and 422 {mu}/cm{sup 2}, respectively. Values of pH at site CM remained acid, whereas, at site 41 we recorded values near neutrality. The concentrations of total nutrients at both sampling sites were higher in the rainy season. Zooplankton species richness present at site CM was lower than at site 41, and there were only two identified species Bosmina sp and Keratella americana. At site 41 we recorded more species, mainly of the Rotifera. Among Cladocera, we identified two species, regarding Copepoda, the orders Cyclopoida and Calanoida were present. At site CM the density values were lower compared to site 41. The preliminary assessment of the zooplankton community showed lower values of species richness and density at site CM, what may be probably explained by the adverse environmental conditions for zooplankton community. (author)

  11. Long-term changes of the crustacean zooplankton community in Lake Mjøsa, the largest lake in Norway

    Directory of Open Access Journals (Sweden)

    Jarl Eivind LØVIK

    2003-08-01

    Full Text Available Lake Mjøsa has been subject to an accelerating eutrophication from the 1950s to the mid 1970s, but comprehensive nutrient reduction efforts caused marked reductions of phytoplankton production and biomass during the 1980s, a process that continued during the 1990s. Zooplankton biomass and species composition was considerably affected during the eutrophication and subsequent oligotrophication. Total crustacean zooplankton biomass decreased along with decreasing algal biomass during the 1980s and 1990s. The seasonal means of zooplankton biomass were positively correlated with seasonal means of phytoplankton biovolume and chlorophyll-a, indicating a primarily bottom up regulation of the zooplankton biomass. Several herbivorous and omnivorous zooplankton species (Daphnia galeata, Bosmina longispina, Limnocalanus macrurus and Cyclops lacustris were probably negatively affected by reduced algal biomass, whereas other species (Holopedium gibberum and Thermocyclops oithonoides/Mesocyclops leuckarti seemed to be positively affected. H. gibberum disappeared in the 1960s, but reappeared in the 1980s after the significant reduction in algal biomass and primary production. The temporal trend of T. oithonoides/M. leuckarti indicated a strong competition with cladocerans (mainly B. longispina and D. galeata in periods with high algal biomass. Early warming of the lake could also have promoted a biomass increase of T. oithonoides/M. leuckarti in later years, although the mean epilimnion temperature did not correlate with seasonal mean biomass of these species. The seasonal mean biomass of Eudiaptomus gracilis, the dominant calanoid, showed substantial fluctuations with 6-7 years between tops, but a decreasing trend during the 1990s. However, there were no significant correlations between this species and any of the environmental variables. The study indicated that dominant cladocerans (D. galeata and B. longispina are decisive for the success of cisco (Coregonus albula, one of the most important planktivorous fish species, as also described by earlier studies. However it also demonstrated top down control on cladocerans in years with especially large stocks of cisco.

  12. Zooplankton community of Parnaíba River, Northeastern Brazil / Comunidade zooplanctônica do Rio Parnaíba, Nordeste, Brasil

    Scientific Electronic Library Online (English)

    Ludmilla Cavalcanti Antunes, Lucena; Thaís Xavier de, Melo; Elvio Sergio Figueredo, Medeiros.

    2015-03-01

    Full Text Available Resumo Objetivo: O objetivo do presente estudo é apresentar uma lista de espécies de zooplâncton (Rotifera, Cladocera e Copepoda) do Rio Parnaíba, NE, Brasil, com comentários sobre a sua distribuição ao longo do rio e entre estações do ano. Métodos O zooplâncton foi amostrado usando uma rede de plâ [...] ncton (60 µm) e concentrado em um volume de 80 mL para ser levado ao laboratório. As amostragens ocorreram durante o período seco (Outubro 2010) e chuvoso (Abril 2011) e foram restritas a áreas marginais com profundidades entre 80 e 150 cm. Resultados Um total de 132 espécies foi registrado, sendo que durante a estação seca foram registradas 82 espécies e durante a estação chuvosa foram registradas 102 espécies. Rotifera representou 66,7% das espécies coletadas, seguido por Cladocera com 26,5% e Copepoda com 6,8%. Conclusões A riqueza de espécies coletada foi alta quando comparada com outros sistemas lóticos brasileiros. No contexto atual de transposição de águas e manejo de fluxo hidrológico nos rios do Nordeste, o presente estudo ressalta a importância do Rio Parnaíba e sua variação sazonal para a conservação da biodiversidade do semiárido brasileiro. Abstract in english Aim: The objective of the present work is to present a list of species of zooplankton (Rotifera, Cladocera and Copepoda) from the Parnaíba River. Additionally, we provide comments on their distribution along the river, and between dry and wet seasons. Methods Zooplankton was collected with a plankt [...] on net (60 µm mesh) and concentrated into a volume of 80 mL for further analysis, during the dry (October 2010) and wet (April 2011) seasons. Sampling was restricted to the marginal areas at depths between 80 and 150 cm. Results A total of 132 species was recorded among the three zooplankton groups studied. During the dry season a total of 82 species was registered and 102 species was registered for the wet season. Rotifera contributed with 66.7% of the species, followed by Cladocera (26.5%) and Copepoda (6.8%). Conclusions The richness of species observed was high compared to other large rivers in Brazil. In the context of current policies for water management and river diversions in northeastern Brazil, the present study highlights the importance of this river system for biodiversity conservation.

  13. "Global Migration Patterns" Lesson Plan

    Science.gov (United States)

    The United States has often been referred to as a "nation of immigrants." While immigration has historically been the country's foundation, immigration continues to shape the structure and composition of the population. The majority of migrants move in response to economic pressures, but some migrants—called refugees—move because of fear. Recognizing their story is also an important part of understanding international migration. The objectives of this course are to understand immigration to the United States, to identify major international migration streams, to evaluate the i