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1

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 differential losses can produce substantial errors in the results, it was necessary to process the samples on the boat immediately after collection, without preservation.

1985-01-01

2

Zooplankton grazing in a eutrophic lake: implications of diel vertical migration. [Scenedesmus; Eudiaptomus; Daphnia; Ceriodaphnia; Synechococcus  

Energy Technology Data Exchange (ETDEWEB)

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 ..mu..m) was labeled with /sup 32/P; a larger green alga (Scenedesmus, 4-15 ..mu..m) was labeled with /sup 14/C. 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 differential losses can produce substantial errors in the results, it was necessary to process the samples on the boat immediately after collection, without preservation.

Lampert, W.; Taylor, B.E.

1985-02-01

3

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

UK PubMed Central (United Kingdom)

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

Gutierrez MF; Gagneten AM; Paggi JC

2012-01-01

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

Science.gov (United States)

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

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

2011-08-14

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

Scientific Electronic Library Online (English)

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

Apablaza, Pedro; Palma, Sergio

2006-11-01

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

Directory of Open Access Journals (Sweden)

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

Pedro Apablaza; Sergio Palma

2006-01-01

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

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

Mohamed Moussa Dorgham; Mohsen Mohamed Elsherbiny; Mahnoud Hassan Hanafi

2012-01-01

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

Science.gov (United States)

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

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

2009-01-01

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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 239 240Pu, 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

1978-04-28

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

Science.gov (United States)

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

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

2013-04-01

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

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

Erlei Cassiano Keppeler; Elsa Rodrigues Hardy

2004-01-01

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Bacteria dispersal by hitchhiking on zooplankton  

DEFF Research Database (Denmark)

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

Grossart, Hans-Peter; Dziallas, Claudia

2010-01-01

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

Science.gov (United States)

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 (Red Sea force the whole population to ascend and feed in epipelagic waters every night, as the prey-ration eaten each night is fully digested at mesopelagic depths during daytime.

Dypvik, Eivind; Kaartvedt, Stein

2013-02-01

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Centropages behaviour: Swimming and vertical migration  

Science.gov (United States)

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

Alcaraz, Miguel; Saiz, Enric; Calbet, Albert

2007-02-01

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Effects of diel vertical migration on ephippia production in Daphnia  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Fish presence in experimentally simulated temperature conditions (limno-towers) led to diel vertical migration and resulted in a decrease of ephippia production in Daphnia pulicaria. Diel fluctuation of food, temperature and day length similar to those experienced by migrating Daphnia were tested in...

Victor ALEKSEEV

16

Diel vertical migration in deep sea plankton is finely tuned to latitudinal and seasonal day length.  

UK PubMed Central (United Kingdom)

Diel vertical migration (DVM) is a ubiquitous phenomenon in marine and freshwater plankton communities. Most commonly, plankton migrate to surface waters at dusk and return to deeper waters at dawn. Up until recently, it was thought that DVM was triggered by a relative change in visible light intensity. However, evidence has shown that DVM also occurs in the deep sea where no direct and background sunlight penetrates. To identify whether such DVM is associated with latitudinal and seasonal day light variation, one and a half years of recorded acoustic data, a measure of zooplankton abundance and movement, were examined. Acoustic Doppler current profilers, moored at eight different sub-tropical latitudes in the North-Atlantic Ocean, measured in the vertical range of 500-1600 m. DVM was observed to follow day length variation with a change in season and latitude at all depths. DVM followed the rhythm of local sunrise and sunset precisely between 500 and 650 m. It continued below 650 m, where the deepest penetrable irradiance level are <10?? times their near-surface values, but plankton shortened their time at depth by up to about 63% at 1600 m. This suggests light was no longer a cue for DVM. This trend stayed consistent both across latitudes and between the different seasons. It is hypothesized that another mechanism, rather than light, viz. a precise biochemical clock could maintain the solar diurnal and seasonal rhythms in deep sea plankton motions. In accordance with this hypothesis, the deepest plankton were consistently the first to migrate upwards.

van Haren H; Compton TJ

2013-01-01

17

Optimal foraging and diel vertical migration in a life history model  

DEFF Research Database (Denmark)

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

Sainmont, Julie; Andersen, Ken Haste

18

Diurnal variation of zooplankton in Bhoj Wetland, Bhopal, India  

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

Najeeb Ahmad Bhat; Ashwani Wanganeo; Parvaiz Ahmad Bhat, et al.

2013-01-01

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

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

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

2013-01-01

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

Science.gov (United States)

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

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

2013-08-01

 
 
 
 
21

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

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

Kiss, A.

2006-01-01

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The influence of the Chaoborus brasiliensis (Theobald, 1901) (Diptera, Chaoboridae) larvae in the zooplankton vertical distribution at Nado Lagoon, Belo Horizonte, state of Minas Gerais, Brazil A influência da larva de Chaoborus brasiliensis (Theobald, 1901) (Diptera, Chaoboridae) na distribuição vertical da comunidade zooplanctônica da lagoa do Nado, Belo Horizonte, Estado de Minas Gerais  

Directory of Open Access Journals (Sweden)

Full Text Available The effects of Chaoborus brasiliensis (Diptera, Chaoboridae), an invertebrate predator, on the zooplankton spatial distribution in a shallow tropical reservoir, Nado Lagoon, were investigated in this work. The habitat overlap degree, i.e., the overlap in the vertical distribution of predator and potential preys was measured during diel vertical migration (DVM). The study focused the reservoir predominant taxa (defined as the most frequent and abundant species). Several organisms showed DVM (Brachionus falcatus, B. caudatus, B. angularis, Moina micrura and Thermocyclops minutus), while in others this behavior was not clear, or even not detected (Keratella cochlearis, K. tropica, K. bostoniensis and T minutus nauplii). The conclusion was that C. brasiliensis influenced directly most zooplankters spatial distribution in this reservoir, and DVM was important to reduce spatial overlapping with the predator. Furthermore, the study showed that such behaviors change significantly along the season cycle.Foi analisado o efeito do predador invertebrado, Chaoborus brasiliensis (Diptera, Chaoboridae), sobre a distribuição espacial dos táxons predominantes da comunidade zooplanctônica de um reservatório tropical raso, lagoa do Nado, explorando as mudanças na sobreposição espacial entre predador e presas durante a migração vertical diária. A comunidade zooplanctônica apresentou uma variada gama de respostas à pressão de predação exercida pelas larvas de Chaoborus. Diversos táxons exibiram MVD (Brachionus falcatus, B. caudatus, B. angularis, Moina micrura, Thermocyclops minutus) e outros em que esse comportamento não foi tão nítido ou não foi detectado (K. cochlearis, K. tropica, K. bostoniensis e náuplios de T. minutus). A maioria dos táxons estudados tiveram a sua distribuição vertical associada à presença desse predador invertebrado, e a migração vertical diária dessas espécies foi importante na redução da sobreposição espacial com o predador. Além disso, o estudo demonstrou que esses padrões experimentam consideráveis mudanças ao longo do ciclo sazonal.

José Fernandes Bezerra Neto; Ricardo Motta Pinto-Coelho

2002-01-01

23

Vertical migration of iodine, technetium and neptunium in peat  

International Nuclear Information System (INIS)

The upward migration of iodine, technetium and neptunium in two naturally occurring peat blocks was measured. One block was taken from a floating sphagnum bog, and the other from a reed-sedge fen. Iodine showed a little retardation compared to tritium tracer, but neptunium was significantly retarded, and technetium never reached the surface at all.

1986-01-01

24

Potential acidification impacts on zooplankton in CCS leakage scenarios.  

Science.gov (United States)

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

Halsband, Claudia; Kurihara, Haruko

2013-04-28

25

Potential acidification impacts on zooplankton in CCS leakage scenarios.  

UK PubMed Central (United Kingdom)

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.

Halsband C; Kurihara H

2013-08-01

26

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

Directory of Open Access Journals (Sweden)

Full Text Available The size distribution and mean spatial trends of large particles (>100 ?m, in equivalent spherical diameter, ESD) and mesozooplankton were investigated across the Mackenzie Shelf (southeast Beaufort Sea, Arctic Ocean) in July–August 2009. Our main objective was to combine results from an Underwater Vision Profiler 5 (UVP5) and traditional net tows (200 ?m mesh size) to characterize the structural diversity and functioning of the Arctic shelf-basin ecosystem and to assess the large-scale correspondence between the two methodological approaches. The core dataset comprised 154 UVP5 profiles and 29 net tows conducted in the shelf (1000 m) regions of the study area. The mean abundance of total particles and zooplankton in the upper water column (a (chl a) concentration, with maximum values between 30 and 70 m depth. Based on the size-spectra derived from the UVP5 dataset, living organisms (0.1–10 mm ESD) accounted for an increasingly large proportion of total particle abundance (from 0.1 % to >50 %) when progressing offshore and as the ESD of particles was increasing. Both the UVP5 and net tows determined that copepods dominated the zooplankton community (~78–94 % by numbers) and that appendicularians were generally the second most abundant group (~1–11 %). The vertical distribution patterns of copepods and appendicularians indicated a close association between primary production and the main grazers. Manual taxonomic counts and ZooScan image analyses shed further light on the size-structure and composition of the copepod community – which was dominated at ~95 % by a guild of 10 typical taxa. The size distributions of copepods, as evaluated with the 3 methods (manual counts, ZooScan and UVP5), showed consistent patterns co-varying in the same order of magnitude over the upper size range (>1 mm ESD). Copepods 1 mm ESD. Our results illustrate that the combination of traditional sampling methods and automated imaging techniques is a powerful approach that enabled us to conclude on the prevalence of a relatively high productivity regime and dominant herbivorous food web over the shelf when compared with the low-productive recycling system detected offshore.

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

2012-01-01

27

Quantitative parameters of radionuclide vertical migration in the soils on different meadow types  

International Nuclear Information System (INIS)

[en] The two-component convective-different model was used for determination of vertical migration parameters of 90Cs and 137Cs in meadow ecosystems and dependence from meadow type and soil properties was shown. The migration coefficients decrease in the order: peatland lowland meadows flood plain meadows dry meadows. The ecological half-life in the root zone ranges from 55 to 143 y for dry meadows and from 15 to 21 y for peatlands. Refs. 23, tabs. 4

1996-01-01

28

Intensification of open-ocean oxygen depletion by vertically migrating animals  

Science.gov (United States)

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

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

2013-07-01

29

Mechanism of phototaxis in marine zooplankton.  

UK PubMed Central (United Kingdom)

The simplest animal eyes are eyespots composed of two cells only: a photoreceptor and a shading pigment cell. They resemble Darwin's 'proto-eyes', considered to be the first eyes to appear in animal evolution. Eyespots cannot form images but enable the animal to sense the direction of light. They are characteristic for the zooplankton larvae of marine invertebrates and are thought to mediate larval swimming towards the light. Phototaxis of invertebrate larvae contributes to the vertical migration of marine plankton, which is thought to represent the biggest biomass transport on Earth. Yet, despite its ecological and evolutionary importance, the mechanism by which eyespots regulate phototaxis is poorly understood. Here we show how simple eyespots in marine zooplankton mediate phototactic swimming, using the marine annelid Platynereis dumerilii as a model. We find that the selective illumination of one eyespot changes the beating of adjacent cilia by direct cholinergic innervation resulting in locally reduced water flow. Computer simulations of larval swimming show that these local effects are sufficient to direct the helical swimming trajectories towards the light. The computer model also shows that axial rotation of the larval body is essential for phototaxis and that helical swimming increases the precision of navigation. These results provide, to our knowledge, the first mechanistic understanding of phototaxis in a marine zooplankton larva and show how simple eyespots regulate it. We propose that the underlying direct coupling of light sensing and ciliary locomotor control was a principal feature of the proto-eye and an important landmark in the evolution of animal eyes.

Jékely G; Colombelli J; Hausen H; Guy K; Stelzer E; Nédélec F; Arendt D

2008-11-01

30

Mechanism of phototaxis in marine zooplankton.  

Science.gov (United States)

The simplest animal eyes are eyespots composed of two cells only: a photoreceptor and a shading pigment cell. They resemble Darwin's 'proto-eyes', considered to be the first eyes to appear in animal evolution. Eyespots cannot form images but enable the animal to sense the direction of light. They are characteristic for the zooplankton larvae of marine invertebrates and are thought to mediate larval swimming towards the light. Phototaxis of invertebrate larvae contributes to the vertical migration of marine plankton, which is thought to represent the biggest biomass transport on Earth. Yet, despite its ecological and evolutionary importance, the mechanism by which eyespots regulate phototaxis is poorly understood. Here we show how simple eyespots in marine zooplankton mediate phototactic swimming, using the marine annelid Platynereis dumerilii as a model. We find that the selective illumination of one eyespot changes the beating of adjacent cilia by direct cholinergic innervation resulting in locally reduced water flow. Computer simulations of larval swimming show that these local effects are sufficient to direct the helical swimming trajectories towards the light. The computer model also shows that axial rotation of the larval body is essential for phototaxis and that helical swimming increases the precision of navigation. These results provide, to our knowledge, the first mechanistic understanding of phototaxis in a marine zooplankton larva and show how simple eyespots regulate it. We propose that the underlying direct coupling of light sensing and ciliary locomotor control was a principal feature of the proto-eye and an important landmark in the evolution of animal eyes. PMID:19020621

Jékely, Gáspár; Colombelli, Julien; Hausen, Harald; Guy, Keren; Stelzer, Ernst; Nédélec, François; Arendt, Detlev

2008-11-20

31

Mathematical modeling of cascading migration in a tri-trophic food-chain system.  

UK PubMed Central (United Kingdom)

Diel vertical migration is a behavioral antipredator defense that is shaped by a trade-off between higher predation risk in surface waters and reduced growth in deeper waters. The strength of migration of zooplankton increases with a rise in the abundance of predators and their exudates (kairomone). Recent studies span multiple trophic levels, which lead to the concept of coupled vertical migration. The migrations that occur at one trophic level can affect the vertical migration of the next lower trophic level, and so on, throughout the food chain. This is called cascading migration. In this paper, we introduce cascading migration in a well-known model (Hastings and Powell, Ecology 73:896-903, 1991). We represent the dynamics of the system as proposed by Hastings and Powell as a phytoplankton-zooplankton-fish (prey-middle predator-top predator) model where fish affect the migrations of zooplankton, which in turn affect the migrations of motile phytoplankton. The system under cascading migration enhances system stability and population coexistence. It is also observed that for a higher rate of cascading migration, the system shows chaotic behavior. We conclude that the observations of Hastings and Powell remain true if the cascading migration rate is high enough.

Samanta S; Chowdhury T; Chattopadhyay J

2013-06-01

32

Mathematical modeling of cascading migration in a tri-trophic food-chain system.  

Science.gov (United States)

Diel vertical migration is a behavioral antipredator defense that is shaped by a trade-off between higher predation risk in surface waters and reduced growth in deeper waters. The strength of migration of zooplankton increases with a rise in the abundance of predators and their exudates (kairomone). Recent studies span multiple trophic levels, which lead to the concept of coupled vertical migration. The migrations that occur at one trophic level can affect the vertical migration of the next lower trophic level, and so on, throughout the food chain. This is called cascading migration. In this paper, we introduce cascading migration in a well-known model (Hastings and Powell, Ecology 73:896-903, 1991). We represent the dynamics of the system as proposed by Hastings and Powell as a phytoplankton-zooplankton-fish (prey-middle predator-top predator) model where fish affect the migrations of zooplankton, which in turn affect the migrations of motile phytoplankton. The system under cascading migration enhances system stability and population coexistence. It is also observed that for a higher rate of cascading migration, the system shows chaotic behavior. We conclude that the observations of Hastings and Powell remain true if the cascading migration rate is high enough. PMID:23860921

Samanta, S; Chowdhury, T; Chattopadhyay, J

2013-04-07

33

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

Energy Technology Data Exchange (ETDEWEB)

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

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

1981-01-01

34

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

UK PubMed Central (United Kingdom)

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

Sotton B; Guillard J; Anneville O; Maréchal M; Savichtcheva O; Domaizon I

2013-07-01

35

Numerical studies of the influence of food ingestion on phytoplankton and zooplankton biomasses  

Directory of Open Access Journals (Sweden)

Full Text Available This paper presents the numerical simulations of the influence of food ingestion by a herbivorous copepod on phytoplankton and zooplankton biomasses (PZB) in the sea. The numerical studies were carried out using the phytoplankton-zooplankton-nutrient-detritus PhyZooNuDe biological upper layer model. This takes account both of fully developed primary production and regeneration mechanisms and of daily migration of zooplankton. In this model the zooplankton is treated not as a 'biomass' but as organisms having definite patterns of growth, reproduction and mortality. Assuming also that {Zoop} is composed ofi cohorts of copepods with weights Wi and numbers Zi, then {Zoop} = WiZi. The PhyZooNuDe model consists of three coupled, partial second-order differential equations of the diffusion type for phytoplankton, zooplankton and nutrients, and one ordinary first-order differential equation for the benthic detritus pool, together with initial and boundary conditions. The calculations were made during 90 days (April, May and June) for the study area P1 (Gdansk Deep) in an area 0z<=20 m with a vertical space step of 0.1 m and a time step of 300 s. The simulation given here demonstrated the importance of food ingestion by zooplankton in that it can alter the nature of the interactions of plants and herbivores. The analysis of these numerical studies indicate that the maximal ingestion rate and the half-saturation constant for grazing strongly affect the magnitude of the spring bloom and the cyanobacterial bloom, and also the total zooplankton biomass.

Lidia Dzierzbicka-G³owacka

2002-01-01

36

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

Science.gov (United States)

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

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

2005-10-21

37

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

Energy Technology Data Exchange (ETDEWEB)

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

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

2006-07-01

38

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

UK PubMed Central (United Kingdom)

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.

McClellan Y; August RA; Gosz JR; Gann S; Parmenter RR; Windsor M

2006-01-01

39

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

Science.gov (United States)

Three years of 300 kHz 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.

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

2013-08-01

40

Deriving regional vertical fluid migration rates offshore southwestern Taiwan using bottom-simulating reflectors  

Science.gov (United States)

Fluid migration rates are important parameters for understanding the structural characteristics and evolution of the crustal tectonics and hydrocarbon exploration. However, they are difficult to measure on the seafloor. Densely sampled temperature measurements might shed light on our study of the fluid migration rates. In this study, we first use reflection seismic data to derive geothermal gradient patterns at different sub-seafloor depths, then calculated 1D vertical fluid flow models by analyzing the Péclet numbers in the offshore regions of SW Taiwan. We found Péclet numbers ranging from 2 to 5, implying that vertical fluid flow velocities are between 6 and 44 cm/year. Assumed a homogenous permeable layer and no lateral variation of the temperature fields, we analyzed possible errors caused by depth-dependent thermal conductivity and velocity-depth function. They probably cause less than 2 cm/year of errors in the estimated vertical fluid flow rate. In terms of regional fluid flow patterns, we found higher fluid flow rates near the toe of the trench, and a dramatic increase in fluid flow rate when the continental slope of the Chinese passive margin enters into the trench, and reduced fluid flow rates in the hinterland. We propose that this is a new and potentially useful method to derive regional fluid flow rate models for studying geochemical and biological processes in shallow seafloor sediments and the regional hydrological budget.

Chen, Liwen; Chi, Wu-Cheng; Liu, Char-Shine; Shyu, Chun-Tien; Wang, Yunshuen; Lu, Char-Yu

2012-12-01

 
 
 
 
41

Development of vertical-looking radar technology for monitoring insect migration.  

UK PubMed Central (United Kingdom)

The development of vertical-looking radar (VLR) has allowed long-term monitoring of the altitudinal and temporal dynamics of high-flying insect populations to be a practical proposition for the first time. The system also provides a unique insight into the behaviour of migrating insects. A new analysis routine for estimating body mass of over-flying insects is described. Procedures for calculating the maximum range of detection for insects of different sizes and the volume of air sensed by the VLR have also been developed. Sample data of diurnal patterns of activity, temporal variation of abundance and density-height profiles of aerial insect populations are presented.

Chapman JW; Smith AD; Woiwod IP; Reynolds DR; Riley JR

2002-08-01

42

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

1973-01-01

43

A New Trait-Based Auto-Emergent Model for Zooplankton and Confrontation with Size-Structured Observations from the Bay of Biscay  

Science.gov (United States)

Zooplankton plays a significant role in marine ecosystems bridging the gap between primary producers and top consumers and interacting with the particle flux through complex dynamics. Scarcity of data and complexity of observing zooplankton make it difficult to integrate it in biogeochemical models where it is most often formulated in a simpler manner, i.e. classic box models with usually two compartments (micro and meso/macro zooplankton). Recent advances in automatic sizing, counting and identification allow better estimates of the dynamics and distribution of zooplankton, notably through the measurement of its size structure, and for zooplankton size matter. Most zooplankton physiological rates as well as predator:prey interactions can be significantly relied to individuals size through allometric relations. Such size-dependency was used in recent models. Yet, these models were neither confronted to observations nor integrated in 3D biogeochemical models. Here we propose a newly developed model of zooplankton dynamics based on size-dependent allometric relations but which allows various diet types regardless of the size. A size and a degree of herbivory is randomly drawn for each zooplankton species generated within the model (up to 400 here, limited by actual computational costs). By generating random degree of herbivory zooplankton species of same size could have various diet (from herbivore to carnivore). Other parameters leading to various reproductive strategies or vertical migration could also be drawn randomly (not tested here). The zooplankton model is coupled to the 3D biogeochemical model MARS3D on a test case representing a simplified view of the Bay of Biscay (i.e., continental shelf, estuary, tides). The model shows auto-emergent properties with the selection of size/diet most adapted to local conditions (here offshore vs. coastal, estuary…). Then, patterns of the modeled size-structure of the zooplankton are confronted to the ones observed during Spring-time cruises in the Bay of Biscay. The usefulness of the proposed zooplankton model for large scale biogeochemical models is further discussed.

Vandromme, Pieter; Sourisseau, Marc; Huret, Martin

2013-04-01

44

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

Energy Technology Data Exchange (ETDEWEB)

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

Timoshin, S.S.; Berezhnova, N.I.

1986-01-01

45

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

Energy Technology Data Exchange (ETDEWEB)

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

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

2002-06-15

46

Vertical migration and motility responses in three marine phytoplankton species exposed to solar radiation.  

Science.gov (United States)

Diurnal vertical migration in the water column and the impact of solar radiation on motility were investigated in three marine phytoplankton species: Tetraselmis suecica, Dunaliella salina and Gymnodinium chlorophorum. Cells were exposed to solar radiation either in ultraviolet radiation (UVR, 280-400 nm) transparent Plexiglas tubes (45 cm length, 10 cm diameter) or in quartz tubes under three radiation treatments: PAB (280-700 nm), PA (320-700 nm) and P (400-700 nm). The three species displayed different behavior after exposure to solar radiation. Tetraselmis suecica was insensitive to UVR and under high solar radiation levels, cells accumulated preferentially near the surface. Exposure experiments did not indicate any significant changes in swimming speed nor in the percentage of motile cells after 5 h of exposure. On the other hand, D. salina was sensitive to UV-B displaying a significant decrease in swimming speed and percentage of motile cells after 2-3 h of exposure. Moreover, D. salina cells migrated deep in the water column when irradiance was high. The response of G. chlorophorum was in between that of the other two species tested, with a slight (but significant) decrease in swimming speed and percentage of motile cells in all radiation treatments after 5 h of exposure. While G. chlorophorum cells were more or less homogenously distributed in the water column, a slight (but significant) avoidance response to high radiation was observed at local noon, with cells migrating deep in the water column. Our data clearly indicate that these sub-lethal effects of solar radiation are species-specific and they might have important implications for the aquatic ecosystem. PMID:17645651

Richter, Peter R; Häder, Donat-P; Gonçalves, Rodrigo J; Marcoval, M Alejandra; Villafañe, Virginia E; Helbling, E Walter

47

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

1970-01-01

48

Chemotaxis increases vertical migration and apparent transverse dispersion of bacteria in a bench-scale microcosm.  

Science.gov (United States)

The success of in situ bioremediation is often limited by the inability to bring bacteria in contact with the pollutant, which they will degrade. A bench-scale model aquifer was used to evaluate the impact of chemotaxis on the migration of bacteria toward the source of a chemical pollutant. The model was packed with sand and aqueous media was pumped across horizontally, simulating groundwater flow in a homogenous aquifer. A vertical gradient in chemoattractant was created by either a continuous injection of sodium benzoate or a pulse injection of sodium acetate. A pulse of chemotactic Pseudomonas putida F1 or a non-chemotactic mutant of the same species was injected below the attractant. The eluent was sampled at the microcosm outlet to generate vertical concentration profiles of the bacteria and chemoattractant. Moment analysis was used to determine the center and variance of the bacterial profiles. The center of the chemotactic bacterial population was located at an average of 0.74 ± 0.07 cm closer to the level at which the chemoattractant was injected than its non-chemotactic mutant in benzoate experiments (P < 0.015) and 0.4 ± 0.2 cm closer in acetate experiments (P < 0.05). The transverse dispersivity of the chemotactic bacteria was 4 ± 1 × 10(-3) cm higher in benzoate experiments than the transverse dispersivity of the non-chemotactic mutant and 1 ± 2 × 10(-3) cm higher in acetate experiments. These results underscore the contribution of chemotaxis to improve transport of bacteria to contaminant sources, potentially enhancing the effectiveness of in situ bioremediation. PMID:21495010

Strobel, Kathryn L; McGowan, Sara; Bauer, Robert D; Griebler, Christian; Liu, Jun; Ford, Roseanne M

2011-04-27

49

Chemotaxis increases vertical migration and apparent transverse dispersion of bacteria in a bench-scale microcosm.  

UK PubMed Central (United Kingdom)

The success of in situ bioremediation is often limited by the inability to bring bacteria in contact with the pollutant, which they will degrade. A bench-scale model aquifer was used to evaluate the impact of chemotaxis on the migration of bacteria toward the source of a chemical pollutant. The model was packed with sand and aqueous media was pumped across horizontally, simulating groundwater flow in a homogenous aquifer. A vertical gradient in chemoattractant was created by either a continuous injection of sodium benzoate or a pulse injection of sodium acetate. A pulse of chemotactic Pseudomonas putida F1 or a non-chemotactic mutant of the same species was injected below the attractant. The eluent was sampled at the microcosm outlet to generate vertical concentration profiles of the bacteria and chemoattractant. Moment analysis was used to determine the center and variance of the bacterial profiles. The center of the chemotactic bacterial population was located at an average of 0.74 ± 0.07 cm closer to the level at which the chemoattractant was injected than its non-chemotactic mutant in benzoate experiments (P < 0.015) and 0.4 ± 0.2 cm closer in acetate experiments (P < 0.05). The transverse dispersivity of the chemotactic bacteria was 4 ± 1 × 10(-3) cm higher in benzoate experiments than the transverse dispersivity of the non-chemotactic mutant and 1 ± 2 × 10(-3) cm higher in acetate experiments. These results underscore the contribution of chemotaxis to improve transport of bacteria to contaminant sources, potentially enhancing the effectiveness of in situ bioremediation.

Strobel KL; McGowan S; Bauer RD; Griebler C; Liu J; Ford RM

2011-09-01

50

Horizontal and Vertical Migration Patterns of Phormidium corallyticum and Beggiatoa spp. Associated with Black-Band Disease of Corals  

UK PubMed Central (United Kingdom)

An in situ field study of the motility patterns exhibited by Phormidium corallyticum and Beggiatoa spp. in black-band disease of corals was conducted over a 5-day period. Measurements were made at a spatial resolution of 50 &mgr;m to document the horizontal migration of black-band across living coral tissue, while vertical migrations within the band were documented by observation and macrophotography of the black-band surface. It was determined that horizontal migration occurred both day and night, with the fastest movements by the front of the band during the day and the back of the band at night. Beggiatoa would rise to the band surface at night, and would often remain above the cyanobacterial population during extended periods of illumination the following day. The migration patterns are discussed in terms of motility cues and microbial physiology.

Richardson LL

1996-11-01

51

Horizontal and Vertical Migration Patterns of Phormidium corallyticum and Beggiatoa spp. Associated with Black-Band Disease of Corals  

Science.gov (United States)

An in situ field study of the motility patterns exhibited by Phormidium corallyticum and Beggiatoa spp. in black-band disease of corals was conducted over a 5-day period. Measurements were made at a spatial resolution of 50 &mgr;m to document the horizontal migration of black-band across living coral tissue, while vertical migrations within the band were documented by observation and macrophotography of the black-band surface. It was determined that horizontal migration occurred both day and night, with the fastest movements by the front of the band during the day and the back of the band at night. Beggiatoa would rise to the band surface at night, and would often remain above the cyanobacterial population during extended periods of illumination the following day. The migration patterns are discussed in terms of motility cues and microbial physiology. PMID:8849426

Richardson

1996-11-01

52

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

Energy Technology Data Exchange (ETDEWEB)

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

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

2011-10-01

53

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

International Nuclear Information System (INIS)

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

2004-01-01

54

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

International Nuclear Information System (INIS)

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

2011-10-01

55

Microplastic ingestion by zooplankton.  

UK PubMed Central (United Kingdom)

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.

Cole M; Lindeque P; Fileman E; Halsband C; Goodhead R; Moger J; Galloway TS

2013-06-01

56

Microplastic ingestion by zooplankton.  

Science.gov (United States)

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

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

2013-06-06

57

Marine zooplankton studies in Brazil: a brief evaluation and perspectives  

Directory of Open Access Journals (Sweden)

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

Rubens M. Lopes

2007-01-01

58

Marine zooplankton studies in Brazil: a brief evaluation and perspectives  

Scientific Electronic Library Online (English)

Full Text Available Abstract in portuguese As pesquisas sobre o zooplâncton marinho no Brasil têm sido primariamente descritivas, com a maioria dos estudos enfocando a análise da estrutura da comunidade e assuntos relacionados. A composição e a distribuição espacial de muitos grupos taxonômicos encontram-se bem estudadas, embora os táxons menos abundantes e de menores dimensões, assimcomo os estágios iniciais do ciclo de vida da maioria das espécies, tenham recebido pouca atenção. Alguns táxons nume (more) ricamenteimportantes 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 initial stages of almost all species have received little attention. Some numerically important taxa such as heterotrophic protists, ctenophores, acoel turbellarians and ostraco (more) ds 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.

Lopes, Rubens M.

2007-09-01

59

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

Energy Technology Data Exchange (ETDEWEB)

The spatial distribution and vertical migration of global fallout {sup 137}Cs were studied in soils from South Patagonia at the austral region of South America in semi-natural and natural environments located between 50-54 deg. S and 68-74 deg. W. The {sup 137}Cs areal activity density varied from 222 to 858 Bq m{sup -2}, and was found to be significantly positively correlated (p<0.001) with the mean annual precipitation rate. The fraction of the total activity density observed in steppe grass varied from <0.03% to 0.12% (median <0.07%) and is considerably lower than the results obtained at the South Shetland Islands (median 8%) and in other temperate environments in south-central Chile (median 0.2%). The median of the convection velocity v{sub s} of {sup 137}Cs in the soil in such polar isotundra climate has been determined to be 0.056 cm y{sup -1}. This value is higher than v{sub s} determined under polar climate (-0.012 cm y{sup -1}) and is near to the upper limit of v{sub s}-values determined in temperate environments from Chile (0.019 cm y{sup -1}). The median value of the diffusion coefficient D{sub s} (0.048 cm{sup 2} y{sup -1}) is similar to D{sub s} observed in an Antarctic region (0.043 cm{sup 2} y{sup -1}) and lower than D{sub s} in temperate regions of Chile (1.24 cm{sup 2} y{sup -1}). About 35 years after the highest depositions, {sup 137}Cs had penetrated to a depth of 6-14 cm in the Patagonian soils and can be expected to remain in the rooting zone of grass for many decades. Nevertheless, because of its low transfer to steppe grass observed at this region, the radioecological sensitivity of this ecosystem with respect to fallout radiocesium seems to be lower than in other polar regions.

Schuller, P. E-mail: pschulle@uach.cl; Bunzl, K.; Voigt, G.; Ellies, A.; Castillo, A

2004-07-01

60

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

Science.gov (United States)

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

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

2012-12-01

 
 
 
 
61

Zooplankton body composition  

DEFF Research Database (Denmark)

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

KiØrboe, Thomas

2013-01-01

62

Effect of plant trichomes on the vertical migration of Haemonchus contortus infective larvae on five tropical forages.  

Science.gov (United States)

The influence of trichomes on vertical migration and survival of Haemonchus contortus infective larvae (L3) on different forages was investigated. Four different forages showing different distributions of trichomes (Brachiaria brizantha cv. Marandu, Brachiaria brizantha cv. Xaraes, Andropogon gayanus, and Stylosanthes spp.), and one forage species without trichomes (Panicum maximum cv. Tanzania), were used. Forages cut at the post-grazing height were contaminated with faeces containing L3. Samples of different grass strata (0-10, 10-20, >20 cm) and faeces were collected for L3 quantification once per week over four weeks. In all forages studied, the highest L3 recovery occurred seven days after contamination, with the lowest recovery on A. gayanus. In general, larvae were found on all forages' strata. However, most of the larvae were at the lower stratum. There was no influence of trichomes on migration and survival of H. contortus L3 on the forages. PMID:18975119

Oliveira, Aruaque L F; Costa, Ciniro; Rodella, Roberto A; Silva, Bruna F; Amarante, Alessandro F T

2008-10-31

63

Effect of plant trichomes on the vertical migration of Haemonchus contortus infective larvae on five tropical forages.  

UK PubMed Central (United Kingdom)

The influence of trichomes on vertical migration and survival of Haemonchus contortus infective larvae (L3) on different forages was investigated. Four different forages showing different distributions of trichomes (Brachiaria brizantha cv. Marandu, Brachiaria brizantha cv. Xaraes, Andropogon gayanus, and Stylosanthes spp.), and one forage species without trichomes (Panicum maximum cv. Tanzania), were used. Forages cut at the post-grazing height were contaminated with faeces containing L3. Samples of different grass strata (0-10, 10-20, >20 cm) and faeces were collected for L3 quantification once per week over four weeks. In all forages studied, the highest L3 recovery occurred seven days after contamination, with the lowest recovery on A. gayanus. In general, larvae were found on all forages' strata. However, most of the larvae were at the lower stratum. There was no influence of trichomes on migration and survival of H. contortus L3 on the forages.

Oliveira AL; Costa C; Rodella RA; Silva BF; Amarante AF

2009-06-01

64

Pre-stack reverse-time migration for elastic waves with application to synthetic offset vertical seismic profiles  

Energy Technology Data Exchange (ETDEWEB)

A pre-stack migration algorithm for elastic waves in two-dimensional variable-velocity media is developed, implemented, and tested. The algorithm operates in the time-space domain and is based on reverse-time finite-difference extrapolation of elastic waves. The algorithm is explained and demonstrated in the context of imaging of elastic vertical seismic profile data, but is applicable to any source-recorder geometry. Synthetic test examples include a point diffractor, laterally homogeneous layers, and the flank of a salt dome.

Sun, R.; McMechan, G.A.

1986-03-01

65

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

Scientific Electronic Library Online (English)

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

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

2011-12-01

66

The effect of variable turbulent intensities on the distribution of zooplankton in the shallow, large Lake Balaton (Hungary) L’effet d’intensités de turbulence variables sur la distribution du zooplancton dans le Balaton (Hongrie), grand lac peu profond  

Directory of Open Access Journals (Sweden)

Full Text Available The influence of current velocity on zooplankton organisms is manifold. Moderate current velocity is beneficial for zooplankton, but through various mechanisms too high a current velocity can have detrimental effects. We examined how current velocity acts on zooplankton in Lake Balaton at different levels and found a highly significant, negative relation between current velocity and the density of zooplankton assemblages. Of the studied assemblages, Daphnia galeata  ×  cucullata and Eudiaptomus gracilis exhibited the greatest sensitivity to the degree of current velocity. During calm weather, when the water surface was calm too, nocturnal migration was observed for both Daphnia galeata  ×  cucullata and Eudiaptomus gracilis. We demonstrated that the vertical migration of these two species started before the storm as the usual nocturnal migration, but during the storm the regular pattern was confused. L’influence de la vitesse du courant sur les organismes zooplanctoniques est variée. Une vitesse de courant modérée est bénéfique au zooplancton, mais par des mécanismes divers un courant fort peut avoir également des effets néfastes. Nous avons étudié comment la vitesse du courant agit sur le zooplancton dans le lac Balaton à différents niveaux et avons trouvé une relation significativement négative entre la vitesse du courant et la densité des assemblages zooplanctoniques. Parmi les espèces étudiées, Daphnia galeata  ×  cucullata et Eudiaptomus gracilis montrent la plus forte sensibilité à la vitesse du courant. Par temps calme, quand la surface de l’eau est plate, une migration nocturne est observée aussi bien pour Daphnia galeata  ×  cucullata que pour Eudiaptomus gracilis. Nous avons montré que la migration verticale de ces deux espèces démarre avant la tempête comme la migration nocturne usuelle, mais pendant la tempête le schéma habituel est brouillé.

Baranyai E.; G.-Tóth L.; Vári A.; Homonnay Z.G.

2011-01-01

67

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

Science.gov (United States)

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

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

2012-01-01

68

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

International Nuclear Information System (INIS)

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

2008-01-01

69

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

International Nuclear Information System (INIS)

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

2009-11-19

70

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

Energy Technology Data Exchange (ETDEWEB)

Total inventories and depth distributions of atomic weapons testing fallout {sup 137}Cs 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 <0.5 cm/year were calculated. Modeling the {sup 137}Cs transport by the convection-dispersion equation yielded a better accordance with the measured depth distributions than the application of a compartmental model.

Schuller, Paulina; Ellies, Achim [Universidad Austral de Chile, Valdivia (Chile); Kirchner, Gerald [University of Bremen, Bremen (Germany)

1997-01-27

71

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

Scientific Electronic Library Online (English)

Full Text Available Abstract in spanish Se analizó estacionalmente la biomasa zooplanctónica (BZ) y la densidad ictioplanctónica (DI) en la columna de agua sobre la plataforma continental del sur del Golfo de México, para determinar sus patrones de distribución vertical y establecer si existe una relación entre ambos componentes. Se muestrearon 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 (more) 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 t (more) he 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

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

2009-08-01

72

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

Science.gov (United States)

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

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

2012-06-15

73

Interpretation of the vertical structure and seasonal variation of the diurnal migrating tide from the troposphere to the lower mesosphere  

Science.gov (United States)

The latitudinal-vertical structure and the seasonal variation of the diurnal migrating tide (DW1) from the troposphere to the lower mesosphere are investigated, using reanalysis data from the Modern Era Retrospective analysis for Research and Applications (MERRA) and a linear tidal model. The observed latitude-altitude structure of DW1 is well represented by the four lowest-order classical Hough modes each of which shows its own unique vertical propagation characteristics. The tropospheric profile of DW1 temperature in the tropics is found to be mainly controlled by the first symmetric propagating Hough mode. The constant phase in the troposphere is due to the small static stability in the troposphere. The amplitude from the stratosphere to the lower mesosphere maximizes at solstices. This is caused by a major contribution from the anti-symmetric propagating Hough mode. It is found that this seasonal variation is not explained by that of diabatic heating. Using a linear model, we found that background zonal wind is important for the seasonality. Also, using a modified mode-coupling approach, we interpret that in addition to primary tides generated by diabatic heating, secondary tides generated by meridional advection of background zonal momentum have a large contribution to the DW1, creating the above mentioned seasonal variation from the stratosphere to the lower mesosphere in the tropics. We suggest that both excitation and propagation characteristics can be physically interpreted in terms of the superposition of independent classical Hough modes. That is, each Hough mode is excited by diabatic heating and secondarily by mechanical forcing, and then propagates following its own vertical propagation characteristics.

Sakazaki, Takatoshi; Fujiwara, Masatomo; Zhang, Xiaoli

2013-04-01

74

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

Energy Technology Data Exchange (ETDEWEB)

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

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

2004-05-01

75

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)

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

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

2011-01-01

76

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

Scientific Electronic Library Online (English)

Full Text Available Abstract in portuguese INTRODUÇÃO: Na cirurgia plástica, uma constante preocupação é a cicatriz pós-operatória. É muito importante para o cirurgião conhecer a evolução natural da cicatriz. A cicatriz de abdominoplastia tem a tendência natural de subir com o passar do tempo. Neste estudo, calculou-se a migração vertical natural da cicatriz pós-abdominoplastia, avaliando o efeito da fixação do retalho abdominal inferior na prevenção dessa ascensão. MÉTODO: Estudo prospectivo (more) 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 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 condu (more) cted 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

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

2011-09-01

77

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

Energy Technology Data Exchange (ETDEWEB)

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

Shestopalov, V.M.; Bublyas, V.N.; Gudzenko, V.V.; Onishchenko, I.P.; Borodavko, I.V.; Boguslavsky, A.S.

1995-12-31

78

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

Energy Technology Data Exchange (ETDEWEB)

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

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

1981-01-01

79

Latitudinal patterns of polychlorinated biphenyls (PCBs) in zooplankton (organochlorine contamination)  

Energy Technology Data Exchange (ETDEWEB)

Concentrations of polychlorinated biphenyls (PCBs) in freshwater biota from southern Canada to the Arctic were assessed. High levels of organochlorine pollutants have been observed in the Canadian Arctic. These pollutants migrate from urban to pristine areas via volatilization and deposition processes. The global fractionation model predicts that semi-volatile compounds will predominate at high latitudes and that proportions of less volatile organochlorine pollutants will be greater in the south than in the north. The study addressed the utility of three operationally-defined zooplankton size fractions as biomonitors, the effect of the food web structure on PCB concentrations in these fractions, and seasonal variability of PCB concentrations in zooplankton from two temperate lakes and one arctic lake.

Koenig, B.G.

1997-12-31

80

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

Scientific Electronic Library Online (English)

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

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

2004-05-01

 
 
 
 
81

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

Directory of Open Access Journals (Sweden)

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

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

2004-01-01

82

Spatial structure of the zooplankton community in the coastal upwelling system off central-southern Chile in spring 2004 as assessed by automated image analysis  

Science.gov (United States)

Size spectra of the mesozooplankton community was studied under the influence of coastal upwelling during austral spring 2004 in the coastal upwelling zone off central-southern Chile. Size spectra were derived from the ZooImage analysis of digitalized zooplankton samples obtained from the upper 200 m during a survey carried out under active upwelling (November 2004). An upwelling filament extended up to 180 km offshore, and the upper boundary of the oxygen minimum zone (1 mL O2 L-1) varied between 20 m (nearshore) and 300 m depth (oceanic). The community descriptors (slope of the size spectra, size class index, abundance of size classes) were derived from the size spectra. Stepwise multiple regression analysis found significant correlations between these descriptors and oceanographic variables (temperature, dissolved oxygen, chlorophyll-a, OMZ depth). These data suggest an upwelling-dependent zooplankton distribution characterized by aggregations in a mid-shelf zone, where the log-normalized size spectra become flatter due to an increased abundance of larger size classes (>3 mm). In contrast, the inshore and offshore zones were dominated by small (OMZ depth near 200 m. These spatial patterns and slopes of the size spectra however, were subjected to a significant day vs. night effect mostly explained by the diel vertical migration of the euphausiid Euphausia mucronata. This migration can descend below 200 m during the daylight, causing the larger size classes to disappear from the size spectrum and resulting in a steeper slope. Time-dependent effects must, therefore, be considered when examining the spatial patterns of zooplankton in coastal upwelling zones.

Manríquez, Karen; Escribano, Ruben; Riquelme-Bugueño, Ramiro

2012-01-01

83

Can Vertical Migrations of Dinoflagellates Explain Observed Bioluminescence Patterns During an Upwelling Event in Monterey Bay, California.  

Science.gov (United States)

UUVs surveys showed that bioluminescent dinoflagellates from the northern part of the Monterey Bay, CA were able to avoid advection by southward flowing currents along the entrance to the Bay. We investigate if modeling dinoflagellates' vertical swimming ...

B. Penta I. Shulman M. A. Moline S. Anderson S. H. Haddock

2012-01-01

84

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

Scientific Electronic Library Online (English)

Full Text Available Abstract in spanish El zooplancton de la zona de surgencia costera en el Pacífico Sur Oriental se encuentra afecto a una zona de mínimo de oxígeno muy somera (ZMO). En el presente trabajo, se resume la información disponible de las especies del zooplancton que interactuan con la ZMO en la región de surgencia del norte de Chile. Los datos provienen desde los cruceros MinOx y ZOMEI realizados en marzo del 2000 y octubre del 2005, respectivamente a bordo del R/V Vidal Gormáz de la Armada (more) 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 cruise carried out in March 2000 and the ZOMEI cruise perfomed in October 2005, both onboard the R/V Vidal Gormaz of the Chilean navy. Nineteen species of copepods and 10 of euph (more) ausiids 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.

Escribano, Rubén

2006-10-01

85

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

Directory of Open Access Journals (Sweden)

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

Rubén Escribano

2006-01-01

86

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

Energy Technology Data Exchange (ETDEWEB)

In this paper the inventory of {sup 90}Sr in 34 points distributed along the Spanish peninsular territory is presented. Obtained values range between 173 Bq/m{sup 2} and 2047 Bq/m{sup 2}. From these data set and those {sup 137}Cs data obtained in a previous work the {sup 137}Cs/{sup 90}Sr activity ratio has been established, laying this value between 0.9 and 3.6. Also the migration depth of both radionuclides has been analysed obtaining for {sup 137}Cs an average value 57% lower than that obtained for {sup 90}Sr. Additionally, this paper presents the results obtained in 11 sampling points in which the activity vertical profile has been measured. These profiles have been analysed to state the behaviour of strontium in soils and after, by using a convective-diffusive model, the parameters of the model which governs the vertical migration of {sup 90}Sr in the soil, v (apparent convection velocity) and D (apparent diffusion coefficient) have been evaluated. Mean values obtained are 0.20 cm/year and 3.67 cm{sup 2}/year, respectively. - Highlights: > Measured {sup 90}Sr activity in Spanish mainland, being within a range of [173, 2047] Bq/m{sup 2}, with a mean value of 793 Bq/m{sup 2}. > Compared the migration capacity of {sup 137}Cs and {sup 90}Sr in the same soils. > {sup 90}Sr shows a unique behaviour tendency in soil. > The parameters which govern the applied model have been obtained for the analysed profiles. > Analysed those parameters' values also reflects this unique tendency.

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

2011-11-15

87

Calvert Cliffs zooplankton entrainment study. Final report  

International Nuclear Information System (INIS)

[en] 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

1980-01-01

88

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

Directory of Open Access Journals (Sweden)

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

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

2010-01-01

89

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

DEFF Research Database (Denmark)

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

Hinrichsen, Hans-Harald; Peck, Myron A.

2010-01-01

90

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

Directory of Open Access Journals (Sweden)

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

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

2008-01-01

91

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

Directory of Open Access Journals (Sweden)

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

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

2008-01-01

92

Trait-based approaches to zooplankton communities  

DEFF Research Database (Denmark)

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

Lichtman, E.; Ohman, M.D.

2013-01-01

93

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

UK PubMed Central (United Kingdom)

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

Chien YC; Wu SC; Chen WC; Chou CC

2013-04-01

94

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

Science.gov (United States)

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

Sager, Manfred; Unterfrauner, Hans

2013-04-01

95

Spatial distribution and vertical migration of (137)Cs in soils of Belgrade (Serbia) 25 years after the Chernobyl accident.  

Science.gov (United States)

In this study, the specific activity of (137)Cs was determined by gamma-ray spectrometry in 72 surface soil samples and 11 soil profiles collected from the territory of Belgrade 25 years after the Chernobyl accident. Based on the data obtained the external effective gamma dose rates due to (137)Cs were assessed and geographically mapped. The influence of pedogenic factors (pH, specific electrical conductivity, cation exchange capacity, organic matter content, soil particle size and carbonate content) on the spatial and vertical distribution of (137)Cs in soil was estimated through Pearson correlations. The specific activity of (137)Cs in surface soil samples ranged from 1.00 to 180 Bq kg(-1), with a mean value of 29.9 Bq kg(-1), while in soil profiles they ranged from 0.90 to 58.0 Bq kg(-1), with a mean value of 15.3 Bq kg(-1). The mean external effective gamma dose at 1 m above the ground due to (137)Cs in the soil was calculated to be 1.96 nSv h(-1). Geographic mapping of the external effective gamma dose rates originating from (137)Cs revealed much higher dose rates in southern parts of Belgrade city and around the confluence of the Sava and Danube. Negative Pearson correlation coefficients were found between pH, cation exchange capacity and (137)Cs specific activity in surface soil. There were positive correlations between organic matter and (137)Cs specific activity in surface soil; and between specific electrical conductivity, organic matter, silt content and (137)Cs specific activity in soil profiles. PMID:23681090

Petrovi?, Jelena; ?uji?, Mirjana; ?or?evi?, Milan; Dragovi?, Ranko; Gaji?, Boško; Miljani?, Š?epan; Dragovi?, Snežana

2013-06-01

96

Spatial distribution and vertical migration of (137)Cs in soils of Belgrade (Serbia) 25 years after the Chernobyl accident.  

UK PubMed Central (United Kingdom)

In this study, the specific activity of (137)Cs was determined by gamma-ray spectrometry in 72 surface soil samples and 11 soil profiles collected from the territory of Belgrade 25 years after the Chernobyl accident. Based on the data obtained the external effective gamma dose rates due to (137)Cs were assessed and geographically mapped. The influence of pedogenic factors (pH, specific electrical conductivity, cation exchange capacity, organic matter content, soil particle size and carbonate content) on the spatial and vertical distribution of (137)Cs in soil was estimated through Pearson correlations. The specific activity of (137)Cs in surface soil samples ranged from 1.00 to 180 Bq kg(-1), with a mean value of 29.9 Bq kg(-1), while in soil profiles they ranged from 0.90 to 58.0 Bq kg(-1), with a mean value of 15.3 Bq kg(-1). The mean external effective gamma dose at 1 m above the ground due to (137)Cs in the soil was calculated to be 1.96 nSv h(-1). Geographic mapping of the external effective gamma dose rates originating from (137)Cs revealed much higher dose rates in southern parts of Belgrade city and around the confluence of the Sava and Danube. Negative Pearson correlation coefficients were found between pH, cation exchange capacity and (137)Cs specific activity in surface soil. There were positive correlations between organic matter and (137)Cs specific activity in surface soil; and between specific electrical conductivity, organic matter, silt content and (137)Cs specific activity in soil profiles.

Petrovi? J; ?uji? M; ?or?evi? M; Dragovi? R; Gaji? B; Miljani? Š; Dragovi? S

2013-06-01

97

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

UK PubMed Central (United Kingdom)

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

Ma Z; Zengling MA; Li W; Wei LI; Gao K; Kunshan GA

2010-12-01

98

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

Science.gov (United States)

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

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

2010-08-08

99

Future marine zooplankton research - a perspective  

DEFF Research Database (Denmark)

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

Bathmann, U.; Bundy, M.H.

2001-01-01

100

Neustonic microplastic and zooplankton in the North Western Mediterranean Sea.  

Science.gov (United States)

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

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

2012-02-09

 
 
 
 
101

Neustonic microplastic and zooplankton in the North Western Mediterranean Sea.  

UK PubMed Central (United Kingdom)

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

Collignon A; Hecq JH; Glagani F; Voisin P; Collard F; Goffart A

2012-04-01

102

Migração vertical das larvas de Chaoborus brasiliensis (Theobald, 1901) (Diptera, Chaoboridae) em um reservatório tropical: lagoa do Nado, Belo Horizonte, Estado de Minas Gerais Vertical migration of Chaoborus brasiliensis (Diptera, Chaoboridae) larvae in Nado Lagoon, a tropical reservoir in Belo Horizonte, state of Minas Gerais, Brazil  

Directory of Open Access Journals (Sweden)

Full Text Available Inúmeros trabalhos têm mostrado que a larva de Chaoborus desenvolve migração vertical diária, buscando evitar a predação por peixes, e que a amplitude da migração vertical cresce com o estágio larval. Neste estudo, monitorou-se a distribuição vertical de Chaoborus brasiliensis durante o dia e à noite de outubro/99 a setembro/00, em um reservatório raso, a lagoa do Nado. A profundidade média em que cada estádio foi encontrado foi estimada durante o dia e à noite e comparada à amplitude da migração entre eles. Adicionalmente, buscou-se determinar se a distribuição vertical de C. brasiliensis estava relacionada com a concentração crítica de oxigênio, 1,0mg.l-1. Não foram encontradas diferenças significativas entre a amplitude da migração vertical diária entre os estádios. A profundidade média em que os estádios eram encontrados durante o dia e à noite mostrou-se positivamente correlacionada com a profundidade da concentração crítica de oxigênio. Tal fato suporta a hipótese de que a migração vertical seja um mecanismo de defesa contra a predação por peixes, considerando que as larvas desse díptero usam a camada anóxica como refúgio contra os peixes predadores.Many investigations have shown that Chaoborus larvae develop diel vertical migration (DVM) to avoid fish predation and that this migration's amplitude is often associated with the instar stage. In this study, the Chaoborus brasiliensis vertical distribution was monitored in a shallow reservoir (Nado Lagoon, Belo Horizonte, Brazil), during the diel cycle, from October 1999 to September 2000. The mean depth in which each stage was found was estimated day and night and compared to their migration amplitude. No association was found between instar phase and DVM amplitude. Nevertheless, a clear association was found between the dissolved oxygen critical concentration and the amplitude of Chaoborus DVM. 1.0 mg.1(-1) was considered the concentration below which fish cannot survive. This finding gives support to the hypothesis that vertical migration is a defense mechanism against predation, since the larvae use the anoxic layer as a refuge against fish predation.

José Fernandes Bezerra Neto; Ricardo Motta Pinto-Coelho

2002-01-01

103

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

DEFF Research Database (Denmark)

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

Cazzanelli, Matteo; Perlt, Trine Warming

2008-01-01

104

Measurixg methods of marine zooplankton biomacc  

UK PubMed Central (United Kingdom)

The determination of the zooplankton biomass is the most essential part of the research on marine ecology .There are a wide variety of biomass measurements.According to the principles of these methods?four types can be classified:body-sized counting estimation?volumetric?gravi metric?biothe mical analysis .Furthermore?the advantages and disadvantages of various methods were also discussed.

ZUO Tao; WANG Rong

2003-01-01

105

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

DEFF Research Database (Denmark)

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

Visser, Andre; Mariani, Patrizio

2009-01-01

106

Habitat structure determines resource use by zooplankton in temperate lakes.  

UK PubMed Central (United Kingdom)

While the importance of terrestrial linkages to aquatic ecosystems is well appreciated, the degree of terrestrial support of aquatic consumers remains debated. Estimates of terrestrial contributions to lake zooplankton have omitted a key food source, phytoplankton produced below the mixed layer. We used carbon and nitrogen stable isotope data from 25 Pacific Northwest lakes to assess the relative importance of particulate organic matter (POM) from the mixed layer, below the mixed layer and terrestrial detritus to zooplankton. Zooplankton and deep POM were depleted in ¹³C relative to mixed layer POM in lakes that can support deep primary production. A Bayesian stable isotope mixing model estimated that terrestrial detritus contributed <5% to zooplankton production, and confirms the role of lake optical and thermal properties; deep POM accounted for up to 80% of zooplankton production in the clearest lakes. These results suggest terrestrial support of lake zooplankton production is trivial.

Francis TB; Schindler DE; Holtgrieve GW; Larson ER; Scheuerell MD; Semmens BX; Ward EJ

2011-04-01

107

Habitat structure determines resource use by zooplankton in temperate lakes.  

Science.gov (United States)

While the importance of terrestrial linkages to aquatic ecosystems is well appreciated, the degree of terrestrial support of aquatic consumers remains debated. Estimates of terrestrial contributions to lake zooplankton have omitted a key food source, phytoplankton produced below the mixed layer. We used carbon and nitrogen stable isotope data from 25 Pacific Northwest lakes to assess the relative importance of particulate organic matter (POM) from the mixed layer, below the mixed layer and terrestrial detritus to zooplankton. Zooplankton and deep POM were depleted in ¹³C relative to mixed layer POM in lakes that can support deep primary production. A Bayesian stable isotope mixing model estimated that terrestrial detritus contributed <5% to zooplankton production, and confirms the role of lake optical and thermal properties; deep POM accounted for up to 80% of zooplankton production in the clearest lakes. These results suggest terrestrial support of lake zooplankton production is trivial. PMID:21314881

Francis, Tessa B; Schindler, Daniel E; Holtgrieve, Gordon W; Larson, Eric R; Scheuerell, Mark D; Semmens, Brice X; Ward, Eric J

2011-02-14

108

Distribution and diversity of Zooplanktons in Madhya Pradesh, India  

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

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

2013-01-01

109

ZOOPLANKTON IN EAST COAST OF PENINSULAR MALAYSIA  

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Full Text Available An ecological study of zooplankton was carried out as part of a three year oceanographic study of South China Sea from 2002 to 2005. Field samplings were conducted to determine the density and distribution of zooplankton in the East Coast of Peninsular Malaysia which include Terengganu, Pahang and Johor coastal area. Samples were collected from a total of 105 stations within 19 transects laid 60km to open sea. The highest density was found at Terengganu coast, and the lowest was at Pahang coast. In Terengganu, Harpacticoida was the most dominant group with highest number found in transect laid from Kuala Terengganu water and was followed by Calanoida with highest number in transect laid near Merang seaward to Redang Island. The dominance of Calanoida and Harpaticoida was also shown in Pahang and Johor waters. In Pahang, Calanoida was found in highest density at the northern transect laid nearest to Terengganu water. It was followed by Harpaticoida with high density along the study area before sharply decrease in transect nearest to Johor. In Johor, Calanoida was highest in density at transect near to Pulau Babi Besar in Mersing water while highest density of Harpacticoida was found in Kota Tinggi water. Other groups including Cyclopoida, Cladocera, Ostracoda, Mysidacea, Ctenophora and Chaetognatha were found in small abundance along the study area. This study indicates high biodiversity of zooplankton in Malaysian water of South China Sea.

K. ZALEHA; B. M. SATHIYA; N. IWASAKI

2006-01-01

110

Zooplankton assemblage of Oyun Reservoir, Offa, Nigeria  

Scientific Electronic Library Online (English)

Full Text Available Abstract in spanish La influencia de las propiedades fisicoquímicas del Reservorio Oyun, Offa, Nigeria (un embalse tropical somero) sobre la composición y abundancia del zooplancton fue investigada en tres estaciones entre enero de 2002 y diciembre de 2003. La diversidad no resultó muy alta con tres grupos de 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 zooplanct (more) on 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 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 C (more) opepoda (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.

Mustapha, Moshood K

2009-12-01

111

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

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

Tsegazeabe H. Haileselasie; Mekonen Teferi; Tadesse Dejenie; Kiros Welegerima; Tsegaluel Abay; Solomon A. Hiluf; Kokob Girmay

2012-01-01

112

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

Science.gov (United States)

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

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

2009-04-01

113

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

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

Ahmet Nuri Tarkan; Melek I inibilir; Ali Serhan Tarkan

2005-01-01

114

Simple, inexpensive apparatus for rotating bottles during zooplankton feeding experiments  

Energy Technology Data Exchange (ETDEWEB)

By using the bearing in the hub of bicycle wheels to support the weight of jars containing zooplankton and experiment food, a small laboratory stirring motor can be used to slowly rotate several kilograms of jars for zooplankton feeding experiments. This apparatus is quickly assembled from easily obtainable parts at almost no cost.

McCarthy, J.F.

1983-01-01

115

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

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

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

2011-01-01

116

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

Directory of Open Access Journals (Sweden)

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

WJ. Minto; MS. Arcifa; A. Perticarrari

2010-01-01

117

Shrimp pond zooplankton dynamics and the efficiency of sampling effort.  

UK PubMed Central (United Kingdom)

The abundance and species composition of zooplankton assemblages were examined in a commercial Penaeus monodon (Fabricius) aquaculture pond in subtropical Australia. Numbers and biomass of zooplankton in the surface tows (142 micrometer mesh) varied from 2080 L?¹ (2466 micrograms L?¹) to < 1 L?¹ (15 micrograms L?¹). Peak zooplankton abundance and biomass occurred at the beginning of the shrimp farm season. The small copepod Oithona australis Nishida was dominant during these peaks in abundance although other species were common, including small, low-salinity copepods in the first year and larger marine copepods in the second year. Irrespective of taxa or size, zooplankton abundance declined rapidly after the stocking of P. monodon postlarvae, indicating high levels of non-selective predation. For the remainder of the grow-out season, mean zooplankton abundance was below 1 L?¹ in the first season and below 3 L?¹ in the second season. The factors that maintain the abundance of these zooplankton assemblages at these relatively low levels are poorly understood but may include a deterioration pond water quality. At these lower levels of abundance, the copepods Acartia pacifica Steuer and Acartia sinjiensis Mori were relatively common during the middle phase of the production season, with barnacle nauplii increasing in abundance during the later stages of the grow-out season. Analysis of fixed effects showed that there were significant differences in total zooplankton abundance between farm production seasons and occasion within season, and time (day or night). Analysis of random effects demonstrated that the dominant source of variation, in total zooplankton abundance, was day-to-day changes within sampling occasions. The complexity of temporal and spatial patterns in the abundance, distribution and composition of zooplankton assemblages in shrimp ponds presents significant challenges in designing sampling programmes that accurately quantify temporal or spatial trends. Our results have shown that sampling for more than four consecutive days, at more than one site, is necessary to accurately assess such trends.

Preston NP; Coman FE; Fry VM

2003-04-01

118

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

Science.gov (United States)

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

119

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

Energy Technology Data Exchange (ETDEWEB)

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

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

1980-04-01

120

Marine Fauna of the Aegean Sea. Surface Zooplankton from the North Aegean Sea.  

Science.gov (United States)

A systematic survey of the surface zooplankton from the whole Aegean Sea and some data on the zooplankton from different depths in the South Aegean is presented. Regular sampling of plankton and gathering of oceanographic data from several seasonal statio...

V. G. Kiortsis

1969-01-01

 
 
 
 
121

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

Energy Technology Data Exchange (ETDEWEB)

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

Lambert, R.M.

1989-01-01

122

DNA barcoding and its application to marine zooplankton ecology  

Directory of Open Access Journals (Sweden)

Full Text Available As the main components of marine biota, zooplankton play vital roles in the marine biodiversity, trophic relationships and ecosystem dynamics. However, morphological identification of zooplankton is time-consuming and even impossible for some taxa, especially for pelagic larvae. Diversity of marine zooplankton is believed to be underestimated. DNA Barcodes (short DNA sequences for species recognition and discrimination) provide powerful tools for rapid species identification and are quickly applied in marine zooplanktonecological researches. Here we give a general introduction on the concept, advantages, and limitations of DNA barcoding. We review the multiple applications of DNA barcodes (mainly focused on the mitochondrial cytochrome c oxidase subunit I (mtCOI) gene) in the marine zooplankton ecological researches, which include rapid species identification, cryptic species reveal, trophic relationship analysis, invasive species monitoring, historical range expansion, population genetic and biogeographic analysis. We anticipate that DNA barcoding techniques will be increasingly used by marine ecologists. With the DNA barcode reference libraries completing and new high-throughput tools such as next generation sequencing developing, DNA barcoding will provides more information that, not only for species identification and discovery, but also help to improve our understanding of zooplankton biodiversity and their functions in marine ecosystems.

Chaolun Li; Minxiao Wang; Fangping Cheng; Song Sun

2011-01-01

123

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

DEFF Research Database (Denmark)

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

Möller, Klas O.; St. John, Michael

2012-01-01

124

Effects of toxic substances on zooplankton populations: a Great Lakes perspective  

Energy Technology Data Exchange (ETDEWEB)

The chapter discusses how toxic substances can affect zooplankton, both at the species and community level, modifying factors affecting toxicity, the effects of various environmental pertubations, including toxic substances, on Great Lakes zooplankton, and the role of zooplankton in the transport, persistence, and biomagnification of toxic substances.

Evans, M.S.; McNaught, D.

1988-01-01

125

Zooplankton abundance and diversity in Lake Bracciano, Latium, Italy  

Directory of Open Access Journals (Sweden)

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

Ornella FERRARA; Daria VAGAGGINI; Fiorenza G. MARGARITORA

2002-01-01

126

Estimating the grazing impact of marine micro-zooplankton  

Energy Technology Data Exchange (ETDEWEB)

This paper describes a dilution technique for estimating the micro-zooplankton grazing impact on natural communities of marine phytoplankton. Experiments performed in coastal waters off Washington, USA yield estimates of micro-zooplankton impact equivalent to 6 to 24% of phytoplankton standing biomass and 17 to 52% of production per day. Indirect evidence suggests that most of this impact is due to the feeding of copepod nauplii and tintinnids; in contrast, non-loricate ciliates, comprising 80 to 90% of numerical abundance, appeared to contribute little to phytoplankton mortality.

Landry, M.R.; Hassett, R.P.

1982-01-01

127

Simplified zooplankton-net cod-end  

Energy Technology Data Exchange (ETDEWEB)

A simplified plankton-net cod-end has been field-tested in the tropical Atlantic Ocean and has proved to be both easy to use and effective in reducing the time needed to complete a net-station. The model tested was attached to a 75 cm net of 202 um mesh hauled vertically, but modifications to suit other needs are slight.

Duncan, C.P.

1980-12-01

128

Migration of shallow marine seismic data  

Energy Technology Data Exchange (ETDEWEB)

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

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

1996-06-30

129

Considerations on the biochemical composition of some freshwater zooplankton species.  

Digital Repository Infrastructure Vision for European Research (DRIVER)

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, ...

Nicoletta RICCARDI; Monica MANGONI

130

Transfer of seston to zooplankton in marine ecosystems  

Digital Repository Infrastructure Vision for European Research (DRIVER)

When considering zooplankton feeding as one of the pathways involved in the transfer of substances in marine ecosystems, it is important to study the composition and size distribution of the seston: firstly, the elements in which one is interested may be associated with different types and sizes of ...

Tackx, M.

131

Zooplankton Diversity Of Dnyanganga Reservoir Near Khamgaon, Maharashtra  

Directory of Open Access Journals (Sweden)

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

G. B. Kale

2013-01-01

132

Light scattering by selected zooplankton from the Gulf of Aqaba.  

UK PubMed Central (United Kingdom)

Light scattering by zooplankton was investigated as a major factor undermining transparency camouflage in these pelagic animals. Zooplankton of differing transparencies--including the hyperiid amphipod Anchylomera blossevillei, an unknown gammarid amphipod species, the brine shrimp Artemia salina, the euphausiid shrimp Euphausia diomedeae, the isopod Gnathia sp., the copepods Pontella karachiensis, Rhincalanus sp. and Sapphirina sp., the chaetognath Sagitta elegans and an enteropneust tornaria larva--were illuminated dorsally with white light (400-700 nm). Spectral measurements of direct transmittance as well as relative scattered radiances at angles of 30 degrees , 90 degrees , 150 degrees and 180 degrees from the light source were taken. The animals sampled had transparencies between 1.5% and 75%. For all species, the highest recorded relative scattered radiance was at 30 degrees , with radiances reaching 38% of the incident radiance for the amphipod A. blossevillei. Scattering patterns were also found to be species-specific for most animals. Relative scattered radiances were used to estimate sighting distances at different depths. These calculations predict that all of the examined zooplankton are brighter than the background radiance when viewed horizontally, or from diagonally above or below at shallow depths. Thus, in contrast to greater depths, the best strategy for detecting transparent zooplankton in the epipelagic environment may be to search for them from above while looking diagonally downwards, looking horizontally or looking from below diagonally upwards. Looking directly upwards proved to be more beneficial than the other viewing angles only when the viewed animal was at depths greater than 40 m.

Gagnon YL; Shashar N; Warrant EJ; Johnsen SJ

2007-11-01

133

Comparative spring distribution of zooplankton in three macrotidal European estuaries  

Digital Repository Infrastructure Vision for European Research (DRIVER)

The zooplankton of three european estuaries (Ems, Gironde and Westerschelde) was investigated during spring 1992 by means of samples taken along the salinity gradient. The three estuaries are comparable in terms of total area, flushing time and salinity gradient but differ by their level of eutrophi...

Sautour, B.; Castel, J.

134

Neustonic microplastic and zooplankton in the North Western Mediterranean Sea  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Neustonic microplastic and zooplankton abundance was determined in the North Western Mediterranean Sea during a summer cruise between July 9th and August 6th 2010, with a break between July 22th and 25th due to a strong wind event. Ninety percent of the 40 stations contained microplastic particles ...

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

135

Bird Migration  

Science.gov (United States)

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

136

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

Science.gov (United States)

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

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

2013-01-01

137

Influence de la luminosité nocturne et de la turbidité sur le comportement vertical de migration de la civelle d'anguille (Anguilla anguilla L.) dans l'estuaire de l'Adour Influence of night brightness and turbidity on the vertical migratory behaviour of glass-eels (Anguilla Anguilla L.) in the Adour estuary  

Directory of Open Access Journals (Sweden)

Full Text Available Les mouvements migratoires des civelles en fonction des conditions environnementales sont étudiés à partir d'une campagne d'échantillonnage dans l'estuaire de l'Adour au cours de la saison 1997/1998. Cette campagne se déroule la nuit, pendant le flot, à 10 km en amont de la limite transversale de la mer, sur un secteur de 12 km, situé dans la zone de propagation de la marée. Les densités de civelles sont estimées à partir du poids capturé dans des filets à mailles fines par unité de volume d'eau filtré dans différents secteurs (5 stations, 3 traits de tamis par station et 2 prélèvements par trait de tamis en surface et en profondeur). Entre novembre et mars, les arrivées de civelles forment une courbe en cloche avec un pic de migration en janvier. Le flux de civelles transite dans cette zone, en surface et en profondeur, mais préférentiellement en profondeur si l'intensité de la lumière nocturne (phase lunaire) est forte et la turbidité de l'eau faible. La situation lunaire et la turbidité modifient le comportement des individus ainsi que leur accessibilité à la pêcherie. Compte tenu des observations effectuées, le schéma migratoire vertical de l'espèce peut être modélisé de la manière suivante : l'interaction entre la luminosité nocturne et la turbidité influence les déplacements de civelles dans la colonne d'eau en relation avec leur comportement lucifuge. Plus la lumière nocturne qui pénètre dans la colonne d'eau est importante et plus les civelles migrent en profondeur. Glass-eels migratory movements according to environmental conditions were studied on Adour estuary during the 1997/1998 catch season. These observations took place at night, during flood tide, 10 kilometres upstream the sea transversal limit, on a sector of 12 kilometres in length where we observed the propagation of tide. Glass-eels densities (in g per 100 m3) were estimated with fine mesh nets on 5 sampling stations. On each station, 3 longitudinal transects were sampled simultaneously in surface and close to the bottom. Catch abundance between November and March followed a dome shape tendency with a pick in January. Movements into the water column were induced by moonlight intensity. Glass-eels migrate mainly close to the bottom when turbidity is low and moonlight intensity is high. Moon phases and turbidity induced modifications in glass-eels behaviour and catchability by the fishery. According to these observations, a modelisation of vertical migratory scheme of glass-eels in that estuary can be proposed : high moonlight intensity and low turbidity induced abundance of glass-eels mainly close to the bottom ; low moonlight intensity and/or high turbidity induced dispersion of glass-eels throughout the water column.

DE CASAMAJOR M. N.; BRU N.; PROUZET P.

2008-01-01

138

International Migration  

Science.gov (United States)

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

139

Estimation of zooplankton mortality caused by an Arctic glacier outflow  

Directory of Open Access Journals (Sweden)

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

Marek J. Zaj±czkowski; Joanna Lege¿ynska

2001-01-01

140

Zooplankton distribution as related to summer hydrographic conditions in Onslow Bay, North Carolina  

Energy Technology Data Exchange (ETDEWEB)

Zooplankton concentration and composition was related to hydrographic parameters in Onslow Bay, NC. During summer the hydrography of Onslow Bay is often characterized by the presence of nutrient-rich Gulf Stream waters. These originate from greater depths of the Gulf Stream, intrude at subsurface depths, frequently strand in the Bay and have high concentrations of particulate matter and chlorophyll a. Since such water masses can maintain their integrity for up to one month, temporal changes in phyto- and zooplankton communities may be followed. This paper describes the concentration, composition and distribution of abundant zooplankton taxa from summer 1976. Zooplankton distribution was affected by hydrography. Zooplankton biomass and composition indicate relatively high production of and low predation rates on zooplankton in intruded waters.

Paffenhoefer, G.A.

1980-01-01

 
 
 
 
141

Zooplankton distribution as related to summer hydrographic conditions in Onslow Bay, North Carolina  

Energy Technology Data Exchange (ETDEWEB)

Zooplankton concentration and composition were related to hydrographic parameters in Onslow Bay, NC. During summer the hydrography of Onslow Bay is often characterized by the presence of nutrient-rich Gulf Stream waters. These originate from greater depths of the Gulf Stream, intrude at subsurface depths, frequently strand in the Bay and have high concentrations of particulate matter and chlorophyll a. Since such water masses can maintain their integrity for up to one month, temporal changes in phyto- and zooplankton communities may be followed. Researchers describe the concentration, composition and distribution of abundant zooplankton taxa from summer 1976. Zooplankton distribution was affected by hydrography as, for example, Oncaeidae and Corycaeidae were significantly more abundant in intrusions than in the upper mixed layer. Zooplankton biomass and composition indicate relatively high production of and low predation rates on zooplankton in intruded waters.

Paffenhoefer, G.A.

1980-01-01

142

Zooplankton distribution as related to summer hydrographic conditions in Onslow Bay, North Carolina  

Energy Technology Data Exchange (ETDEWEB)

Zooplankton concentration and composition was related to hydrographic parameters in Onslow Bay, NC. During summer the hydrography of Onslow Bay is often characterized by the presence of nutrient-rich Gulf Stream waters. These originate from greater depths of the Gulf Stream, intrude at subsurface depths, frequently strand in the Bay and have high concentrations of particulate matter and chlorophyll a. Since such water masses can maintain their integrity for up to one month, temporal changes in phyto- and zooplankton communities may be followed. Researchers describe the concentration, composition and distribution of abundant zooplankton taxa from summer 1976. Zooplankton distribution was affected by hydrography as, for example, Oncaeidae and Corycaeidae were significantly more abundant in intrusions than in the upper mixed layer. Zooplankton biomass and composition indicate relatively high production of and low predation rates on zooplankton in intruded waters.

Paffenhoefer, G.A.

1980-01-01

143

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

UK PubMed Central (United Kingdom)

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.

Chen C; Kamman N; Williams J; Bugge D; Taylor V; Jackson B; Miller E

2012-02-01

144

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

Science.gov (United States)

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

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

2011-10-11

145

Dynamics of radiation situation on the territory of Belarus and migration of radionuclides in different types of soils after Chernobyl catastrophe  

International Nuclear Information System (INIS)

A vertical migration of radionuclides Cs, Sr and Pu in soils (in upper 5 cm) of Belarus is given. Influence of genetic parameters of soil for vertical migration of radionuclides is introduced. The main factor of the velocity for radionuclides migration is super humidity. A forecast of vertical migration of radionuclides is made for the year 2016. (author)

2000-01-01

146

A stochastic analysis for a phytoplankton-zooplankton model  

International Nuclear Information System (INIS)

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

2008-01-01

147

Diversity, Distribution and Abundance of Zooplanktonic Larvae in Pakistani Waters  

Directory of Open Access Journals (Sweden)

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

Farzana Yousuf; Kiran Wasee

2006-01-01

148

Considerations on the biochemical composition of some freshwater zooplankton species.  

Directory of Open Access Journals (Sweden)

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

Nicoletta RICCARDI; Monica MANGONI

1999-01-01

149

Environmental factors affecting methyl mercury accumulation in zooplankton  

Energy Technology Data Exchange (ETDEWEB)

The relationship between environmental factors and methyl mercury accumulation in filter-feeding macrozooplankton was investigated in an effort to obtain an integrated measure of the bioavailability of methyl mercury in the water column. Since macrozooplankton are an important food source for fish, the factors that affect their bioaccumulation of mercury are directly relevant to the contamination of fish. Methyl mercury accumulation in zooplankton collected from 24 lakes in south-central Ontario ranged from 19 to 448 ng.g dry mass{sup -}1{sup ,} and was highest in acidic brown-water lakes. Water color and pH were found to be the best predictors of methyl mercury levels, being positively correlated with water color and inversely correlated with pH. There was a positive correlation with drainage ratio and per cent wetland in the catchment. Zooplankton methyl mercury levels were also well correlated with mercury concentrations in smallmouth bass and largemouth bass, confirming that zooplankton is a good indicator of mercury bioavailability at the base of the food chain. 67 refs., 3 tabs., 4 figs.

Westcott, K.; Kaiff, J. [McGill Univ., Montreal, PQ (Canada). Dept. of Biology

1996-10-01

150

Effects of temperature on the metabolic stoichiometry of Arctic zooplankton  

Directory of Open Access Journals (Sweden)

Full Text Available We assessed the relationship between zooplankton metabolism (respiration and inorganic N and P excretion) and "in situ" temperature through a grid of stations representing a range of natural temperature variation during the ATOS-Arctic cruise (July 2007). The objective was to explore not only the direct effects of temperature on 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.

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

2013-01-01

151

Studies on the zooplankton of the deep subalpine Lake Garda.  

Directory of Open Access Journals (Sweden)

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

Nico SALMASO; Luigi NASELLI-FLORES

1999-01-01

152

Mercury biomagnification in marine zooplankton food webs in Hudson Bay.  

UK PubMed Central (United Kingdom)

While much research has been carried out on mercury in large marine mammals and associated food webs in northern regions, comparatively less has been conducted on lower trophic levels including zooplankton and the subsequent transfer to predators, which marks the entry of mercury into northern marine food webs. We present here the first database for mercury uptake and transfer exclusively within zooplankton food webs in northern marine waters. We have investigated both total (THg) and monomethylmercury (MMHg) concentrations, and isotopic signatures (?(15)N and ?(13)C) in individual zooplankton taxa collected over a period of eight years (2003-2010) from across Hudson Bay (including Hudson Strait and Foxe Basin) as part of research icebreaker cruises. ?(15)N values ranged from 3.4 to 14.0‰, implying trophic levels ranging from 1 to 4, and THg concentrations ranged from 5 to 242 ng g(-1) dw. Food web linkages were identified within the data set, and mercury biomagnification was evident both with THg and MMHg concentrations increasing from prey to predator, and with trophic magnification factors (TMFs). Total mercury and MMHg transfer in a unique prey-predator linkage (Limacina helicina-Clione limacina) are investigated and discussed with regard to known physiological and biochemical characteristics. The results suggest that exposure to mercury at higher trophic levels including humans can be affected by processes at the bottom of Arctic marine food webs.

Foster KL; Stern GA; Pazerniuk MA; Hickie B; Walkusz W; Wang F; Macdonald RW

2012-12-01

153

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

Directory of Open Access Journals (Sweden)

Full Text Available Abstract Background Oceans cover more than 70% of the earth's surface and are critical for the homeostasis of the environment. Among the components of the ocean ecosystem, zooplankton play vital roles in energy and matter transfer through the system. Despite their importance, understanding of zooplankton biodiversity is limited because of their fragile nature, small body size, and the large number of species from various taxonomic phyla. Here we present the results of single-gene zooplankton community analysis using a method that determines a large number of mitochondrial COI gene sequences from a bulk zooplankton sample. This approach will enable us to estimate the species richness of almost the entire zooplankton community. Results A sample was collected from a depth of 721 m to the surface in the western equatorial Pacific off Pohnpei Island, Micronesia, with a plankton net equipped with a 2-m2 mouth opening. A total of 1,336 mitochondrial COI gene sequences were determined from the cDNA library made from the sample. From the determined sequences, the occurrence of 189 species of zooplankton was estimated. BLASTN search results showed high degrees of similarity (>98%) between the query and database for 10 species, including holozooplankton and merozooplankton. Conclusion In conjunction with the Census of Marine Zooplankton and Barcode of Life projects, single-gene zooplankton community analysis will be a powerful tool for estimating the species richness of zooplankton communities.

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

2009-01-01

154

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

Scientific Electronic Library Online (English)

Full Text Available Abstract in portuguese OBJETIVO: Analisar a distribuição vertical dos grupos funcionais fitoplanctônicos em dois ciclos nictemerais em um lago tropical monomítico raso; MÉTODOS: As amostragens das variáveis abióticas, comunidades fitoplanctônica e zooplanctônica foram realizadas a intervalos de 3 horas ao longo de 24 horas em perfis verticais, nos períodos de estratificação (fevereiro) e de circulação (julho); RESULTADOS: A elevada estabilidade térmica e a atelomixia parcial favo (more) receram 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 profiles, in the stratification (February) and circulation (July) periods; RESULTS: The high thermal stability and the partial atelomixis favored the coexistence of functional g (more) roups 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.

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

2011-03-01

155

Significance of zooplankton fecal pellet for particulate matter movement in the ocean. Kaiyo no busshitsu junkan ni okeru fecal pellet no yakuwari  

Energy Technology Data Exchange (ETDEWEB)

This paper introduces roles and features of zooplankton fecal pellet, a representative large-size particle for particulate matter movement in the ocean. Particles precipitating from the ocean surface to depths comprise remains of zooplanktons and phytoplanktons, fecal pellets, and soil particles, generically called the marine snow. The precipitating speeds of marine snow coagulates at site were 1 m/day for those with a size of 4 mm to 5 mm and 36 m /day for those of 1 mm to 2.5 mm, faster in the smaller particles. Coccolithophorid in phytoplanktons among the fecal pellet components has coccolith with its cell surface comprising CaCO{sub 3}. Identifying its behavior is very important to clarify the carbon circulation. The existence of Thaliacea species of zooplankton living in the surface water layer involves largely in transporting CaCO{sub 3} into ocean depths through its intake of coccolithophorid and excretion as the fecal pellet. A close correlation is observed between vertical change in the fecal pellets and flux of total carbon amount. 45 refs., 4 figs., 2 tabs.

Tanaka, Y. (Geological Survey of Japan, Tsukuba (Japan))

1992-04-01

156

Bird Migration  

Science.gov (United States)

The first Web site (1) from Sony Picture Classics presents the official home page for "Winged Migration," the new, Academy-award nominated documentary from director Jacques Perrin that follows the epic migrations of birds worldwide using innovative techniques to capture amazing migration footage. Visitors to this site will find a trailer for the film, bird watching Web links, production notes, information on related environmental issues, and a very cool interactive feature showing bird migration routes. Not surprisingly, the Migratory Bird Center at the Smithsonian National Zoological Park offers a mountain of information on bird migration, including a Bird of the Month page (2). BirdSource, a partnership of the National Audubon Society and the Cornell Lab of Ornithology, offers this online introduction to bird migration (3), including an interactive map and case studies representing the different categories of bird movement. The next Web site is the home page for the International Center for the Study of Bird Migration located in Israel, a country on the flight path of approximately 500 million migrating birds (4). The Center offers a number of real time information features, including data from satellite transmitters, nest cameras, and more. Be warned: the birdcalls that randomly emanate from your computer speakers with this Web site are kind of spooky. The BBC Science Shack, part of Open University, provides the following Web page (5), offering a brief explanation of how migrating birds know where to go. The next Web site is part of the Web companion to the PBS NOVA documentary "Night Creatures of the Kalahari." Visitors will find an interesting account of nighttime bird migration based on the research of Cornell ornithologist Bill Evans (6). The site also includes audio clips of eleven migrating bird species. Next comes the Web site for Operation Migration, the nonprofit organization famous for pioneering the use of ultra-light aircraft to teach whooping cranes a safe migration route (7). Visitors can track the progress of the latest group of cranes, who have recently left their winter habitat to make their way back to Wisconsin. And finally, visitors can find some of the best places to watch birds, migrating or otherwise, at this straightforward Web site from Birder.com (8).

Sohmer, Rachel.

2003-01-01

157

Bythotrephes invasion elevates trophic position of zooplankton and fish: implications for contaminant biomagnification  

UK PubMed Central (United Kingdom)

We estimated the effects of Bythotrephes longimanus invasion on the trophic position (TP) of zooplankton communities and lake herring, Coregonus artedi. Temporal changes in lacustrine zooplankton communities following Bythotrephes invasion were contrasted with non-invaded reference lakes, and along with published information on zooplankton and herring diets, formed the basis of estimated changes in TP. The TP of zooplankton communities and lake herring increased significantly following the invasion of Bythotrephes, whereas TP in reference lakes decreased (zooplankton) or did not change significantly (lake herring) over a similar time frame. Elevated TP following Bythotrephes invasion was most prominent in lakes that also supported the glacial relict, Mysis diluvania, suggesting a possible synergistic interaction between these two species on zooplankton community composition. Our analysis indicated that elevated TPs of zooplankton communities and lake herring are not simply due to the presence of Bythotrephes, but rather reflect changes in the zooplankton community induced by Bythotrephes; namely, a major reduction in the proportion of herbivorous cladoceran biomass and a concomitant increase in the proportion of omnivorous and/or predatory copepod biomass in invaded lakes. We demonstrated that increases in TP of the magnitude reported here can lead to substantial increases in fish contaminant concentrations. In light of these results, we discuss potential mechanisms that may be responsible for the disconnect between empirical and theoretical evidence that mid-trophic level species invasions (e.g., Bythotrephes) elevate contaminant burdens of consumer species, and provide testable hypotheses to evaluate these mechanisms.

Rennie MichaelD; Strecker AngelaL; Palmer MichelleE

2011-11-01

158

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

Digital Repository Infrastructure Vision for European Research (DRIVER)

Zooplankton samples collected from eight stations around Pulau Redang, Terengganu, Malaysia were use for measure the concentration activities of 210Po and 210Pb using Alpha Spectrometry. Mean activity in zooplankton tissue for 210Po [364.67?21.00 Bq kg 1 (...

Che Abd Rahim Mohamed; Phang Feong Kuan

159

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

Digital Repository Infrastructure Vision for European Research (DRIVER)

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 r...

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

160

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

International Nuclear Information System (INIS)

[en] 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 across basins and to inter-annual variation in algal density.

2012-01-01

 
 
 
 
161

Vertical Farm  

Science.gov (United States)

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

2005-11-04

162

Migration Ecology  

Science.gov (United States)

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

Alerstam, Thomas

2008-01-15

163

Operation Migration  

Science.gov (United States)

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

164

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.)

1992-01-01

165

Temperature dependence of Arctic zooplankton metabolism and excretion stoichiometry  

Directory of Open Access Journals (Sweden)

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

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

2012-01-01

166

Zooplankton feeding on the nuisance flagellate Gonyostomum semen.  

UK PubMed Central (United Kingdom)

The large bloom-forming flagellate Gonyostomum semen has been hypothesized to be inedible to naturally occurring zooplankton due to its large cell size and ejection of long slimy threads (trichocysts) induced by physical stimulation. In a grazing experiment using radiolabelled algae and zooplankton collected from lakes with recurring blooms of G. semen and lakes that rarely experience blooms, we found that Eudiaptomus gracilis and Holopedium gibberum fed on G. semen at high rates, whereas Daphnia cristata and Ceriodaphnia spp. did not. Grazing rates of E. gracilis were similar between bloom-lakes and lakes with low biomass of G. semen, indicating that the ability to feed on G. semen was not a result of local adaptation. The high grazing rates of two of the taxa in our experiment imply that some of the nutrients and energy taken up by G. semen can be transferred directly to higher trophic levels, although the predominance of small cladocerans during blooms may limit the importance of G. semen as a food resource. Based on grazing rates and previous observations on abundances of E. gracilis and H. gibberum, we conclude that there is a potential for grazer control of G. semen and discuss why blooms of G. semen still occur.

Johansson KS; Vrede T; Lebret K; Johnson RK

2013-01-01

167

Promotion of harmful algal blooms by zooplankton predatory activity.  

UK PubMed Central (United Kingdom)

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

Mitra A; Flynn KJ

2006-06-01

168

Promotion of harmful algal blooms by zooplankton predatory activity.  

Science.gov (United States)

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

Mitra, Aditee; Flynn, Kevin J

2006-06-22

169

Concentration of chemical elements by zooplankton of the White Sea  

Science.gov (United States)

A technique of net sampling of zooplankton at night in the Kandalaksha and Dvinskii Bays and during the full tide in the Onezhskii Bay of the White Sea allowed us to obtain "clean" samples without considerable admixtures of terrigenous suspension. The absence of elements-indicators of the terrigenous suspension (Al, Ti, and Zr) in the EDX spectra allows concluding that the ash composition of the tested samples is defined by the constitutional elements comprising the organic matter and integument (chitin, shells) of planktonic organisms. A quantitative assessment of the accumulation of a large group of chemical elements (approximately 40) by zooplankton based on a complex of modern physical methods of analysis is presented. The values of the coefficient of the biological accumulation of the elements (Kb) calculated for the organic matter and the enrichment factors (EF) relative to the Clarke concentrations in the shale are in general determined by the mobility of the chemical elements in the aqueous solution, which is confirmed by the calculated chemical speciation of the elements in the inorganic subsystem of the surface waters of Onezhskii Bay.

Leonova, G. A.; Bobrov, V. A.; Bogush, A. A.; Bychinskii, V. A.

2013-02-01

170

Vertical optimetry  

International Nuclear Information System (INIS)

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

2002-04-30

171

Profitability of vertical integration  

Energy Technology Data Exchange (ETDEWEB)

This paper examines the profitability of vertical integration using alternate indices of vertical integration. Results suggest that the profitability-vertical integration relation is highly sensitive to the specification of the vertical integration measure used. 4 references, 1 table.

Maddigan, R.J.; Zaima, J.K.

1985-09-01

172

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

Directory of Open Access Journals (Sweden)

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

Imoobe T.O.T.; Adeyinka M.L.

2009-01-01

173

A comparison of zooplankton sampling methods in evaluating copper sulfate toxicity in outdoor microcosms  

Energy Technology Data Exchange (ETDEWEB)

Six outdoor microcosms (2m{sup 3}) were used to determine copper sulfate effects on epibenthic and planktonic zooplankton community structure. Microcosms were treated three times with CuSO{sub 4} at 0, 50, 100, 200, 350, 550 {mu}g Cu/L, respectively. Zooplankton was sampled biweekly from July through October 1993. Epibenthic zooplankton was collected with an inverted funnel trap, whereas planktonic zooplankton was sampled with an integrated water column sampler. Samples were sieved through a 35 {mu}m mesh and organisms preserved with 1% Lugol`s solution and later identified to genus or species level. Both communities initially decreased in total abundance at high copper rates. However, recovery started shortly after the final Cu application. Species richness was lowest at high copper concentrations, particularly in the epi-benthic community. Epibenthic zooplankton diversity decreased at high copper rates, whereas planktonic zooplankton diversity did not. Epi-benthic zooplankton may be a sensitive indicator of chemical stress and therefore be used to assess the bioavailability of sediment-bound xenobiotics.

Hellenbrandt, S.; La Point, T.W. [Clemson Univ., Pendleton, SC (United States); Shaw, J.L.; Marshall, S.J. [Zeneca Ag Products, Whitakers, NC (United States); Ratte, H.T. [Technical Univ. of Aachen (Germany)

1994-12-31

174

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

Directory of Open Access Journals (Sweden)

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

M. Arun Kumar; G. Padmavati; I. Anandavelu, et al.

2013-01-01

175

Effect of Dreissena mussels on the distribution of zooplankton as exemplified by the Main Kakhovka Canal  

Energy Technology Data Exchange (ETDEWEB)

In summer the abundance of zooplankton in the Main Kakhovka Canal varied in the range of 1,500-18,500 indiv.m{sup -3}, with a biomass of 15-240 mg m{sup -3}. From the upper reach of the canal to the end, the zooplankton become less diverse and there is a decrease in both abundance and biomass. In the initial sections of the canal, copepods predominated, owing to their considerable influxes from other sources, i.e., Kakhovka Reservoir. Whereas in the second half of the canal, the dominant complexes of zooplankton changed and consisted primarily of cladocerans and Dreissena veligers. With high abundance of Dreissena polymorpha (Pallas) and D. bugensis (Andrusov) (mean biomass was 4.2 kg m{sup -2}), with the maximum ca. 17.8 kg m{sup -2}, mussels had a significant effect on the spatial distribution of planktonic invertebrates. In different areas of the canal the measurable quantitive replenishment of zooplankton was proceeded by planktonic larvae of Dreissena. Being active filterers, Dreissena mollusks undermine food resources of filter-feeding zooplankton by accelerating sedimentation of suspended matter, including organic substances, by a factor of 1.4-3.0. Dreissena can control zooplankton density by consumption of some of the species. With predominating rotifers and juveniles cladocerans in the plankton, the total abundance of zooplankton influenced by Dreissena bugensis had decreased by 53% after 12 h, whereas the amount of dominant species, Euchlanis dilatata and Bosmina longirostris, had declined respectively by 92% and 64%. Dreissena individuals 14-18 mm long, are the predominant size group of mussels in the Main Kakhovka Canal and can filter off planktonic invertebrates with body lengths between 20 and 400 m. Zooplankton species of such size can pass through the bronchial siphon of Dreissena and so they are vulnerable to consumption by mussels. There is an inverse relationship between the biomass of zooplankton and the biomass of adult Dreissena mussels.

Grigorovich, I.A.; Shevtsova, L.V. [National Ukrainian Academy of Sciences, Kiev (Ukraine)

1995-06-01

176

Monarch Migration.  

Science.gov (United States)

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

Williamson, Brad; Taylor, Orley

1996-01-01

177

Migration & Modernity  

Digital Repository Infrastructure Vision for European Research (DRIVER)

The main objective of this essay is to analyze the challenges caused by today's modern phenomenon of change in our society and to discuss it in relationship to the process of migration. In doing so I focus on questions like, "what does it really mean when a person becomes a migrant and what does it ...

Budathoki, Aakash

178

Zooplankton, Water Temperature, and Salinities in the Columbia River Estuary, December 1971 through December 1972.  

Science.gov (United States)

Sampling was conducted at seven stations in the Columbia River estuary throughout 1972 to provide baseline information on species diversity, relative abundance, and seasonal occurrence of zooplankton, as well as ambient water temperatures and salinities. ...

D. A. Misitano

1974-01-01

179

SEASONAL ZOOPLANKTON VARIATION IN NAGARTAS DAM NEAR PARTUR DIST. JALNA (M.S) INDIA  

Directory of Open Access Journals (Sweden)

Full Text Available In the present work, we provide quantitative information on the seasonal variations of zooplankton and selected physico-chemical variables a large man-made reservoir in the Jalna district. In the study period we have recorded 24 species of which, 10 species belongs to rotifera, 6 species belongs to cladocera, 5 species belongs to copepoda and 3 species of ostracoda. Among zooplankton, particularly rotifera was the dominant group throughout the study period and highest count was recorded in the summer season while low incidence was observed in southwest monsoon season. Zooplankton community is also correlated with physicochemical parameters. The results indicate that the distribution and density of zooplankton species influenced by physical and chemical factors of the environment.

Pramod P Gaike; K. B. Shejule

2012-01-01

180

Zooplankton and epibenthic fauna in shrimp ponds: factors influencing assemblage dynamics.  

UK PubMed Central (United Kingdom)

The assemblage composition, biomass and dynamics of zooplankton and epibenthos were examined in a commercial shrimp (penaeid prawn) pond in subtropical Australia. Physicochemical characteristics of the pond water were measured concurrently. Numbers and biomass of zooplankton in the surface tows (140 micromolar mesh) varied from 111.7 ind. L?¹ (324 micrograms L?¹) to 8.3 ind. L?¹ (44.2 micrograms L?¹). Immediately after the ponds were stocked with shrimp postlarvae there was a rapid decline in zooplankton numbers, particularly the dominant larger copepods. We attributed this to predation by the shrimp postlarvae. Subsequent peaks in zooplankton numbers were principally due to barnacle nauplii. Changes in abundance and biomass of the zooplankton assemblage were not correlated with physicochemical characteristics. Epibenthic faunal abundance in the beam trawls (1 mm mesh) peaked at 14 ind. m?² and the biomass at 0.8 g m?². Unlike zooplankton, the peaks in abundance of epibenthos did not correspond to the peaks in biomass. This was due to the large differences in the size of the dominant taxa across the season. Sergestids (Acetes sibogae) and amphipods were the most abundant taxa in beam trawl samples, with amphipods abundance increasing towards the end of the growout. Negative correlations were found between epibenthos abundance and pH and temperature. These relationships were strongly influenced by the high abundances of amphipods and may reflect an effect on the growth of macroalgae in the pond rather than a direct effect on the epibenthos. No correlations were found between epibenthic fauna biomass and physicochemical parameters. Abundances of epibenthic fauna were not related to zooplankton densities, indicating that this source of food was not likely to be a limiting factor. Neither the pond water exchange regime nor moon phase could explain changes in abundances of zooplankton or epibenthos assemblages. Zooplankton clearly contribute to the nutrition of shrimp postlarvae immediately after stocking. The establishment of an abundant assemblage of zooplankton before stocking shrimp postlarvae would appear to be beneficial, if not essential. Later in the season, zooplankton and epibenthos apparently contribute little to shrimp biomass. Owing to their relatively low biomass, the consumption of shrimp feeds by epibenthos is likely to be insignificant compared with that of the shrimp.

Coman FE; Connolly RM; Preston NP

2003-04-01

 
 
 
 
181

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

UK PubMed Central (United Kingdom)

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

Eskinazi-Sant'Anna EM; Menezes R; Costa IS; Araújo M; Panosso R; Attayde JL

2013-02-01

182

Preliminary studies on the association between zooplankton and the stramenopilan fungi, aplanochytrids.  

UK PubMed Central (United Kingdom)

The relationship of the marine heterokont stramenopilan protists, the aplanochytrids, with the zooplankton was studied in coastal waters. The aplanochytrids were fed to the zooplankton specimens and observed for grazing by two different approaches: [1] using fluorescently-labeled prey approach and [2] using internal transcribed spacer-based molecular probe and in situ hybridization approach. The aplanochytrid cells were detected in the guts as well as fecal pellets of the zooplankton, thus serving as prey to them. Aplanochytrids were consistently isolated from zooplankton specimens. The isolates did not produce a wide array of enzymes, implicating that they may not play a major role in degradation of zooplankton exoskeleton. They were found to produce only protease considerably and sometimes lipase too. The amplified rDNA restriction analysis showed similar patterns, suggesting that most of the isolates might be same strains of Aplanochytrium spp. The existence of aplanochytrids with the zooplankton in marine waters points towards their probable association either as predator-prey or as commensalistic rather than saprophytic type of association.

Damare VS; Damare S; Ramanujam P; Meena RM; Raghukumar S

2013-05-01

183

Radial Migration in Galactic Thick Discs  

CERN Multimedia

We present a study of the extent to which the Sellwood & Binney radial migration of stars is affected by their vertical motion about the midplane. We use both controlled simulations in which only a single spiral mode is excited, as well as slightly more realistic cases with multiple spiral patterns and a bar. We find that rms angular momentum changes are reduced by vertical motion, but rather gradually, and the maximum changes are almost as large for thick disc stars as for those in a thin disc. We find that particles in simulations in which a bar forms suffer slightly larger angular momentum changes than in comparable cases with no bar, but the cumulative effect of multiple spiral events still dominates. We have determined that vertical action, and not vertical energy, is conserved on average during radial migration.

Solway, Michael; Schoenrich, Ralph

2012-01-01

184

Neuronal Migration Disorders  

Science.gov (United States)

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

185

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

Science.gov (United States)

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

Lehane, Clare; Davenport, John

2006-05-01

186

Vertical sleeve gastrectomy  

Science.gov (United States)

Gastrectomy - sleeve; Gastrectomy - greater curvature; Gastrectomy - parietal; Gastric reduction; Vertical gastroplasty ... to lose weight through diet and exercise. Vertical sleeve gastrectomy is not a "quick fix" for obesity. ...

187

Cs-137 migration in soil near NPPs  

International Nuclear Information System (INIS)

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

1984-01-01

188

Correlations between trace metal concentrations (Cd, Cu, Pb, Zn) in seawater and zooplankton organisms (Copepoda) of the Arctic and Atlantic Ocean. Wechselbeziehungen zwischen Spurenmetallkonzentrationen (Cd, Cu, Pb, Zn) im Meerwasser und in Zooplanktonorganismen (Copepoda) der Arktis und des Atlantiks  

Energy Technology Data Exchange (ETDEWEB)

Due to the significant amounts of heavy metals (Cd, Pb, Cu, Zn) in the ocean, their horizontal and vertical distributions, and more importantly, their uptake by zooplankton, organisms are essential to the understanding of heavy metal cycling in the ocean. In order to further the understanding of the heavy metal cycle, four experiments based from the research vessel 'RV Polarstern' in two different oceans were completed. During April 1989 and May 1990, samples of the water and the zooplankton were obtained from the eastern Atlantic Ocean at the surface and selected depths. Additionally, samples from sea ice and melt water from a glacier, as well as from the surface and selected depths, were obtained in the Arctic Ocean during June 1989 and July 1990. Dissolved trace metal concentrations in a water sample were obtained from liquid-liquid extractions followed by Atomic Absorption Spectroscopy (AAS) analysis. The trace metal concentrations in zooplankton organisms were obtained by freeze drying the organisms followed by acid digestion. The resulting sample was analyzed using AAS. (orig.).

Pohl, C.

1992-01-01

189

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

Scientific Electronic Library Online (English)

Full Text Available Abstract in english Zooplankton may be regarded as a sensitive tool for monitoring environmental variations in coastal lagoons due to their ability to immediately react to changes in the water column trophic features and salinity levels. As a coastal lagoon with a broad history of anthropic influence, Rodrigo de 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 d (more) e 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.

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

2011-06-01

190

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

Directory of Open Access Journals (Sweden)

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

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

2011-01-01

191

Zooplankton of Lake Orta after liming: an eleven years study  

Directory of Open Access Journals (Sweden)

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

Carla BONACINA; Andrea PASTERIS

2001-01-01

192

Regional zooplankton dispersal provides spatial insurance for ecosystem function.  

UK PubMed Central (United Kingdom)

Changing environmental conditions are affecting diversity and ecosystem function globally. Theory suggests that dispersal from a regional species pool may buffer against changes in local community diversity and ecosystem function after a disturbance through the establishment of functionally redundant tolerant species. The spatial insurance provided by dispersal may decrease through time after environmental change as the local community monopolizes resources and reduces community invasibility. To test for evidence of the spatial insurance hypothesis and to determine the role dispersal timing plays in this response we conducted a field experiment using crustacean zooplankton communities in a subarctic region that is expected to be highly impacted by climate change - Churchill, Canada. Three experiments were conducted where nutrients, salt, and dispersal were manipulated. The three experiments differed in time-since-disturbance that the dispersers were added. We found that coarse measures of diversity (i.e. species richness, evenness, and Shannon-Weiner diversity) were generally resistant to large magnitude disturbances, and that dispersal had the most impact on diversity when dispersers were added shortly after disturbance. Ecosystem functioning (chl-a) was degraded in disturbed communities, but dispersal recovered ecosystem function to undisturbed levels. This spatial insurance for ecosystem function was mediated through changes in community composition and the relative abundance of functional groups. Results suggest that regional diversity and habitat connectivity will be important in the future to maintain ecosystem function by introducing functionally redundant species to promote compensatory dynamics.

Symons CC; Arnott SE

2013-05-01

193

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

Scientific Electronic Library Online (English)

Full Text Available Abstract in english 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 sampling 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 spa (more) tially 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

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

2011-04-01

194

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

Directory of Open Access Journals (Sweden)

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

Yamila S. Battauz; Susana B. José de Paggi; Juan C. Paggi; Marcelo Romano; Ignacio Barberis

2013-01-01

195

Seasonal fluctuations of DDTs and PCBs in zooplankton and fish of Lake Maggiore (Northern Italy).  

UK PubMed Central (United Kingdom)

Concentrations of DDTs and PCBs were determined in the zooplankton and in three different fish species (shad, whitefish and roach) collected seasonally during 2009 and 2010 in three sites in Lake Maggiore, a south-alpine lake that has been contaminated by DDT since 1996. As previously observed in 2008, even during 2009 DDTs concentrations were higher in zooplankton than in fish, probably due to the very unstable situation of the lake still influenced by local inputs. The situation changed in 2010, when all DDT compounds increased in fish to levels much higher than those measured in zooplankton. Biomagnification was statistically demonstrated for pp'DDE in all the three fish species, indicating a probable signal of recovery of the lake. Although with respect to total PCBs we observed that the contamination levels varied across time periods and across fish species, biomagnification was evident from zooplankton to fish both in 2009 and in 2010. As concern individual PCBs, biomagnification from zooplankton to all three fish species was significant for PCB 153 and PCB 138.

Bettinetti R; Quadroni S; Manca M; Piscia R; Volta P; Guzzella L; Roscioli C; Galassi S

2012-07-01

196

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

Directory of Open Access Journals (Sweden)

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.

Sharma, B.K.; Pachuau, L.

2013-01-01

197

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

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

Sharma, B.K.; Sharma, S.

2012-01-01

198

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

Digital Repository Infrastructure Vision for European Research (DRIVER)

Litopenaeus vannamei is the most cultivated shrimp species in Brazil, being fed basically on high protein formulated diets. However, some studies have shown that the natural zooplankton found in shrimp ponds can be part of the diet of this crustacean. In this study, the zooplankton composition, dens...

A. P. Cardozo; J. G. F. Bersano; W. J. A. Amaral

199

Miracle of Winged Migration  

Science.gov (United States)

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

Tenenbaum, David

2007-12-31

200

Migration of Birds  

Science.gov (United States)

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

Lincoln, Frederick C.; Peterson, Steven R.; Zimmerman, John L.

2008-01-03

 
 
 
 
201

The scale of divergence: a phylogenetic appraisal of intercontinental allopatric speciation in a passively dispersed freshwater zooplankton genus.  

UK PubMed Central (United Kingdom)

Molecular studies have enlightened our understanding of freshwater zooplankton biogeography, yet questions remain regarding the scale and commonality of geographic speciation. Here, we present a mtDNA-based phylogenetic hypothesis for 92 Daphnia species from all seven continents, with a focus on North and South America, Europe, and Australia, and use it to explore the frequency, scale, and geographical orientation of allopatric divergence events. Allopatric speciation can conservatively account for at least 42% of cladogenetic events among the species included in our study; most of these involve intercontinental splits. Closely related species pairs are concentrated in the circumarctic region and between northern and southern continents, aligned with bird migration routes, suggesting recent dispersal. By contrast, deeper phylogenetic patterns are consistent with vicariance scenarios linked to continental fragmentation. The possible reasons for the puzzling persistence of these ancient patterns in light of the eroding force of dispersal are considered. Our results demonstrate the high frequency and complex pattern of allopatric speciation in this ancient, passively dispersed genus.

Adamowicz SJ; Petrusek A; Colbourne JK; Hebert PD; Witt JD

2009-03-01

202

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

Directory of Open Access Journals (Sweden)

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

Jong-Yun Choi; Kwang-Seuk Jeong; Geung-Hwan La; Hyun-Woo Kim; Kwang-Hyun Chang; Gea-Jae Joo

2011-01-01

203

[Biochemical composition of crustacean zooplankton and their grazing on phytoplankton and ciliated protozoans in a recently founded reservoir (Sahela, Morocco].  

UK PubMed Central (United Kingdom)

In order to assess the impact of crustacean zooplankton on phytoplankton and protozoan ciliates in the Sahela reservoir under semi-arid climate, we conducted experiments during the period from July to December 1999 at the deepest point in the lake (15 m). Samplings and measurements were carried out in diffusion chambers submerged in situ over a period of 7 h without (control chambers) and with (experimental chambers) crustacean zooplankton. During these experiments, counts were conducted on phytoplankton and ciliates to determine the abundance and the mortality of these organisms due to zooplankton in each diffusion chambers at t = 0 and t = 7 h of incubation. The study showed that the growth rates of phytoplankton and ciliates populations varied between 0.02 and 0.05 h-1 and from 0.01 to 0.07 h-1, respectively. The mortality caused by zooplankton grazing fluctuated from 0.07 to 0.2 h-1 of phytoplankton and from 0.01 to 0.2 h-1 of ciliates. These mortalities were significantly and positively correlated with the growth rates (r = 0.8; p < 0.02; n = 9). Moreover, the heavy predation by the crustacean zooplankton was exerted on small-sized phytoplankton and ciliates and we demonstrated the relationships between protozoans and zooplankton for the transfer of matter and energy in aquatic food webs. Furthermore, the crustacean zooplankton metabolism was different, whether zooplankton was present in diffusion chambers or in the lake.

Derraz K; Elalami R; Atiki I; Mhamdi MA

2003-08-01

204

Preliminary data concerning zooplankton and zoobenthos communities of the Lower Mures River from the Lunca Muresului National Park (Arad County)  

Directory of Open Access Journals (Sweden)

Full Text Available The present paper represents an inventory of aquatic fauna from the lower Mures River, downstream of Arad, in the Lunca Muresului National Park. Zooplanktonic microcrustaceans and zoobenthonic communities were considered for the study. The samples were taken in the year 2004, using the qualitative sampling equipment not only for zooplankton but also for zoobenthos communities.

Karina BATTES; Claudia PAVELESCU

2006-01-01

205

[Biochemical composition of crustacean zooplankton and their grazing on phytoplankton and ciliated protozoans in a recently founded reservoir (Sahela, Morocco].  

Science.gov (United States)

In order to assess the impact of crustacean zooplankton on phytoplankton and protozoan ciliates in the Sahela reservoir under semi-arid climate, we conducted experiments during the period from July to December 1999 at the deepest point in the lake (15 m). Samplings and measurements were carried out in diffusion chambers submerged in situ over a period of 7 h without (control chambers) and with (experimental chambers) crustacean zooplankton. During these experiments, counts were conducted on phytoplankton and ciliates to determine the abundance and the mortality of these organisms due to zooplankton in each diffusion chambers at t = 0 and t = 7 h of incubation. The study showed that the growth rates of phytoplankton and ciliates populations varied between 0.02 and 0.05 h-1 and from 0.01 to 0.07 h-1, respectively. The mortality caused by zooplankton grazing fluctuated from 0.07 to 0.2 h-1 of phytoplankton and from 0.01 to 0.2 h-1 of ciliates. These mortalities were significantly and positively correlated with the growth rates (r = 0.8; p < 0.02; n = 9). Moreover, the heavy predation by the crustacean zooplankton was exerted on small-sized phytoplankton and ciliates and we demonstrated the relationships between protozoans and zooplankton for the transfer of matter and energy in aquatic food webs. Furthermore, the crustacean zooplankton metabolism was different, whether zooplankton was present in diffusion chambers or in the lake. PMID:14608696

Derraz, Khalid; Elalami, Rachid; Atiki, Ilham; Mhamdi, Mohamed Alaoui

2003-08-01

206

Environmental toxicology: population modeling of cod larvae shows high sensitivity to loss of zooplankton prey.  

UK PubMed Central (United Kingdom)

Two factors determine whether pollution is likely to affect a population indirectly through loss of prey: firstly, the sensitivity of the prey to the pollutants, and secondly, the sensitivity of the predator population to loss of prey at the given life stage. We here apply a statistical recruitment model for Northeast Arctic cod to evaluate the sensitivity of cod cohorts to loss of zooplankton prey, for example following an oil spill. The calculations show that cod cohorts are highly sensitive to possible zooplankton biomass reductions in the distribution area of the cod larvae, and point to a need for more knowledge about oil-effects on zooplankton. Our study illustrates how knowledge about population dynamics may guide which indirect effects to consider in environmental impact studies.

Stige LC; Ottersen G; Hjermann DØ; Dalpadado P; Jensen LK; Stenseth NC

2011-02-01

207

Recovery of crustacean zooplankton communities from acid and metal contamination: comparing manipulated and reference lakes  

Energy Technology Data Exchange (ETDEWEB)

The changes that have taken place over the past 15 years in the crustacean zooplankton communities of three CaCO{sub 3} and Ca(OH){sub 2} contaminated lakes were studied. The three experimental lakes are located near Sudbury, Ontario, an area damaged by SO{sub 2} and metal emissions from copper and nickel smelters. The limed experimental lakes were compared with temporal and spatial reference lakes to determine long-term recovery of crustacean zooplankton communities from acid and metal contamination. Data on the recovery of zooplankton from disturbances was provided. The value of reference lakes for studies of recovery was demonstrated. Univariate versus multivariate indicators of recovery were compared. It was determined that multivariate analysis was well suited to determining the extent of recovery, and the extent to which the pace of recovery was regulated by the severity of acid and metal contamination. 100 refs., 10 tabs., 13 figs.

Yan, N.D.; Somers, K.M.; Pawson, T.W.; Girard, R.E. [Ontario Ministry of Environment and Energy, Dorset, ON (Canada). Dorset Research Centre; Keller, W. [Cooperative Freshwater Ecology Unit, Toronto, ON (Canada)

1996-06-01

208

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

Energy Technology Data Exchange (ETDEWEB)

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

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

1998-12-31

209

Evaluation of sound extinction and echo interference in densely aggregated zooplankton  

Directory of Open Access Journals (Sweden)

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

Natalia Gorska

2000-01-01

210

Verticale Drainage (Vertical Drainage).  

Science.gov (United States)

The report covers vertical draining systems which serve to accelerate consolidation. Thereby the vertical drainage system serves a dual purpose of accelerating the primary settlement process and increasing stability during and directly after raising. The ...

1993-01-01

211

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

DEFF Research Database (Denmark)

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

Jacobsen, Lene; Perrow, M.R.

1997-01-01

212

Seasonal variations in zooplankton abundances in the Iturbide reservoir (Isidro Fabela, State of Mexico, Mexico).  

Science.gov (United States)

This studywas undertaken to quantify the seasonal variations of zooplankton (rotifers, cladocerans and copepods) and selected physico-chemical variables (temperature, pH, conductivity, Secchi disc transparency, dissolved oxygen, ammonia, nitrate and phosphate concentrations) in the Iturbide dam. Monthly zooplankton samples (50 l filtered through 50 microm mesh, in duplicates from each of the 4 stations) were collected from February 2008 to January 2009. Simultaneously physico-chemical variables were measured. The zooplankton samples were fixed in 4% formalin in the field. In general, the temperature ranged from 9 to 16 degrees C, rarely exceeding 20 degrees C. Secchi transparency was nearly 100% since the reservoir was shallow (sulcata were the dominant rotifers during the study period. On an annual average, rotifer density ranged between 50-200 ind.(-1). Among crustaceans Chydorus brevilabris and Macrothrix triserialis were most abundant. The maximal density of these cladocerans was about 50 ind. l(-1). Copepods were much lower in numbers (< 20 ind. l(-1)). In general the density of zooplankton was higher during summer months (April to July) than during winter. Shannon-Wiener diversity index varied from 1.0 to 4.3 depending on the site and the sampling period. Based on the data of Secchi transparency and nutrient concentrations, the Iturbide reservoir appeared to be mesotrophic. PMID:22315826

Sarma, S S S; Osnaya-Espinosa, Lidia Rosario; Aguilar-Acosta, Claudia Romina; Nandini, S

2011-07-01

213

Species composition and diversity of zooplankton in tidal creeks of the Chongming Dongtan intertidal flat  

Directory of Open Access Journals (Sweden)

Full Text Available In order to reveal the diversity of zooplankton in tidal creeks of the Chongming Dongtan intertidal flat, we sampled zooplankton at 18 stations in six tidal creeks during four seasons from April to December in 2008. The species composition, dominant species, community structure, and species diversity were recorded. A total of 44 species, belonging to 6 taxa, were identified. Among them, Copepoda were dominant, accounting for 79.5% of the total recorded species. There were nine dominant species. Sinocalanus tenellus was the most dominant species in spring, Schmackeria poplesia in summer, Schmackeria poplesia and Sinocalanus sinensis in autumn, and Sinocalanus sinensis and Limnoithona etraspina in winter. Shannon-Wiener indices (H?) were higher in summer and winter, species richness indices (d) were higher in summer and autumn, and Pielou evenness indices (J?) peaked in winter. Compared with data from North Channel and the North Branch of the Yangtze River Estuary, only six common species were found, demonstrating significantly different species composition. The ecological characteristics of zooplankton were also related to tide; species diversity was slightly higher during flood tide than ebb tide. In addition, the dominant species were different during flood and ebb tide. Environmental factors, such as salinity, temperature, runoff, and tidal current influenced the temporal and spatial distributions of zooplankton in tidal creeks.

Qiang Li; Chuanguang An; Qiang Ma; Linlin Xu; Yunlong Zhao

2010-01-01

214

Recreational boats as a vector of secondary spread for aquatic invasive species and native crustacean zooplankton  

UK PubMed Central (United Kingdom)

Recreational boats in tow between lakes are a known vector of the spread of aquatic invading species (AIS), but we have no test of the hypothesis that recreational boats are also a vector of secondary spread of AIS among freshwater ecosystems via in-water transport i.e., while boating between interconnected waterways. In this study, we surveyed recreational boaters travelling into Lake Simcoe (44°25?N, 79°20?W), Ontario, Canada, on their recreational activities, boat maintenance, and travel destinations, measured the degree of vessel fouling, and sampled all standing water and attached macrophytes associated with their vessels. A total of 321 zooplankton individuals comprising 15 different species were collected from the standing water in vessels, including veligers of the invasive zebra mussel Dreissena. The volume of water collected within the vessels significantly increased the number of zooplankton transported. Zooplankton species from pelagic habitats or with planktonic life stages were collected more frequently than species that occupy littoral or benthic habitats, likely reflecting the recreational activities of boaters. Patterns of boater activities, movements and hygiene habits, suggest recreational boating in the Lake Simcoe region is contributing to the spread of native and invasive species into nearby waterways. Our study validates the widespread assumption that recreational boats are an important in-water vector for the secondary spread of both native and invasive zooplankton species. Future management strategies to reduce the spread of AIS should be aimed at increasing awareness of boater hygiene practices, particularly the frequent draining of standing water.

Kelly NE; Wantola K; Weisz E; Yan ND

2013-03-01

215

[Spatial niches of dominant zooplankton species in Sanmen Bay, Zhejiang Province of East China].  

UK PubMed Central (United Kingdom)

Ecological niche has close relations with inter-species competition and resources utilization, and thus, can be used as an indicator to symbolize the resources utilization capability of certain groups of related species. In this paper, the niche breadth and overlap of the dominant zooplankton species in the Sanmen Bay of Zhejiang were determined by Shannon's formula and Petraitis index, respectively, and the differentiation of the niche was studied by canonical correspondence analysis (CCA), aiming to approach the distribution features of coastal zooplankton and related affecting factors in the Bay. In the study area, some coastal species such as Zonosagitta bedoti, Centropages dorsispinatus, and brachyuran larvae had wider niche breadth than the pelagic species such as Flaccisagitta enflata and Pseudeuphausia sinica, and the species of different groups with prey-predator relation had a greater niche overlap than those of the same groups without this relation. The CCA analysis showed that the spatial distribution of the zooplankton was more affected by water temperature, salinity, and chlorophyll a content rather than nutrients. The spatial niche of the zooplankton species was correlated with their living habit, inter-species competition, and prey- predator relationship.

Xu XQ; Zeng JN; Chen QZ; Liu JJ; Du P; Wang GZ

2013-03-01

216

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

Directory of Open Access Journals (Sweden)

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

Mohsenpour Azari A; Agamaliyev F.Q

2013-01-01

217

New and rare taxa of freshwater zooplankton in the fauna of Yugoslavia  

Directory of Open Access Journals (Sweden)

Full Text Available Analysis of the faunistic composition of Zooplankton in two reservoirs for watersupply nearby Kragujevac indicated a relatively great diversity. Qualitative analysis of Zooplankton composition in the Grošnica reservoir demonstrated the presence of 105 laxa, whereas somewhat fewer taxa (99) were recorded in the Gruža reservoir. Most of the taxa recorded in both reservoirs are cosmopolitan organisms. Small number of recorded taxa have been rarely registered in the territory of Serbia till present. The following species from the group of Rotatoria can be mentioned as being probably found for the first time in waters of our country: Dicranophorus rostralus, Philodina aadicomis and Trichocerca jenningsi. All three of these species were recorded only in the Grošnica reservoir. Only inspection of the complete literature on Zooplankton in our country could confirm with certainty that the Grošnica reservoir is the first record of these three species in the territory of Serbia. However, even such data as our represents a contribution to the knowledge on diversity of the Zooplankton fauna of Serbia.

Ostoji? Aleksandar M.

2002-01-01

218

Seasonal composition and population density of zooplankton in Lake Timsah, Suez Canal, Egypt:  

Directory of Open Access Journals (Sweden)

Full Text Available Zooplankton composition and abundance were investigated seasonally at ten sites in Lake Timsah and the adjacent, connected western lagoon in relation to the physico-chemical conditions. A total of 42 taxa (including larval stages) were identified, among them 21 species of copepods, 6 rotifers, 5 cladocerans, 1 chaetognath and 1 urochordate. Copepods represented the predominant component (77.7% of the total community), followed by rotifers, molluscs, cladocerans and (9.2, 4.7 and 3.9% respectively), while other groups collectively formed about 4.5% of the total zooplankton population. Summer was the most productive season with an average count of 40 864 individuals m-3. The dominant copepod species were Paracalanus crassirostris and Oithona nana representing 28.3 and 24.3% of the total zooplankton respectively. The total zooplankton count, including copepods, and its dominant species showed significant positive correlations with temperature, pH and total phytoplankton density. However, negative correlations were detected between densities of rotifers, and salinity and dissolved oxygen.

Mohsen M. El-Sherbiny; Ali M. Al-Aidaroos; Ali Gab-Alla

2011-01-01

219

Diversity, Abundance and Seasonal Dynamic of Zooplankton Community in a South-Saharan Reservoir (Burkina Faso)  

Directory of Open Access Journals (Sweden)

Full Text Available From May 2004 to April 2005, the zooplankton of the Loumbila reservoir was subject to a 14 days periodicity follow-up. This study attempt to describe the diversity, abundance and seasonal dynamic of zooplankton community in a south-saharian reservoir. Plankton community was sampled with horizontal tows of a plankton net of 100 ?m mesh size. The samples analysis permitted to identify 7 species of Cladocera and 2 species of the Copepoda. The overall Rotifers observed belong to 14 genera. The Cochran`s Q-test together with various methods of variance analyses and the Redundancy Analysis (RDA) allowed to highlight the seasonal dynamics of zooplankton settlement. The most significant factor in this dynamics is water movement i.e., water gain or loss in the reservoir. This factor evolves together with some physicochemical parameters favourable to plankton development and simultaneously opposes some other unfavourable factors such as high conductivity. Crustaceans are more sensitive to the season impacts than Rotifers. Besides this seasonal variability the zooplankton community of Loumbila reservoir also shows variability according to depth.

Adama Oueda; Wendengoudi Guenda; Andre T. Kabre; Frederic Zongo; Gustave B. Kabre

2007-01-01

220

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

Directory of Open Access Journals (Sweden)

Full Text Available 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 at three desert water ponds around Bikaner. The objective of the study was to quantify the relative importance of local environmental conditions and diversity of the principal zooplankton species with in sampling site. Limnological parameters were investigated for temperature, pH, EC, dissolved oxygen, free CO2, hardness and alkalinity. Among cations (Ca++, Mg++, Na+, K+) and anions (CO3-- , HCO3-, Cl-, SO4--, PO4--, SiO2--, NO3--) were observed. They were within tolerable range. Even under harsh and hostile environmental conditions of desert a variety of zooplanktonic faunal species was found which are typically adapted for the given conditions of existence, it constituted total of 63 genera of zooplankton of which Protozoa constituted (20 taxa) followed by Crustacea (14 taxa), Rotifera (12 taxa), Insecta (11 taxa), Oligochaeta (3 taxa), Turbellaria, Hirudinea and Acari (1 taxa each) were recorded in decreasing order.

Shivani Sharma & Anu Kumar Sharma

2013-01-01

 
 
 
 
221

Impact of wildfire and clear-cutting in the boreal forest on methyl mercury in zooplankton  

Energy Technology Data Exchange (ETDEWEB)

The effects of forest logging and wildfire on methylmercury (MeHg) concentrations in bulk zooplankton collected in 38 oligotrophic lakes located in the boreal forest were compared. Mean MeHG concentrations were found to be significantly higher in zooplankton collected in lakes with recently logged watersheds than in lakes with recently burned or undisturbed watersheds. Using multiple regression analysis, it was calculated that when all the lakes were included, 43 per cent of the variability in MeHg levels were the result of four variables, namely dissolved organic carbon, pH, dissolved oxygen and immature zooplankton biomass. Regression calculated for each group of lakes explained less (for the reference lakes) or more (for the logged and burned lakes) of the variability in MeHg than did the general model. Dissolved organic carbon was the only variable common to all models, which is an indication of the importance of watershed processes in the transfer of humic matter bound Hg to lakes. Higher levels of dissolved carbon in these lakes would influence mechanisms associated with microbial methylation and with light-mediated demethylation. By way of contrast, forest fires, which also constitute major perturbation in boreal forests, show no comparable linkage to increased MeHg in zooplankton. 32 refs., 4 tabs., 2 figs.

Garcia, E.; Carignan, R. [Montreal Univ., Dept. de sciences biologiques, PQ (Canada)

1999-02-01

222

The link between environmental variation and evolutionary shifts in dormancy in zooplankton.  

UK PubMed Central (United Kingdom)

Sex and dormancy are intertwined in organisms that engage in asexual and sexual reproduction. The transition between asexual and sexual reproduction typically results in a dormant stage that provides a mechanism for persisting under harsh environmental conditions. For example, many zooplankton engage in sexual reproduction when environmental conditions deteriorate and produce resting eggs that remain viable for decades. It has long been assumed that observed variation in the timing and magnitude of investment into a dormant stage among populations or species reflects local environmental conditions. Yet, the importance of dormancy for the persistence of a given population can differ dramatically among habitats (i.e., permanent vs. seasonal ponds). As a result, environmental conditions may exert selection on the propensity for zooplankton to engage in sexual reproduction and enter dormancy in natural populations. Here, I highlight a growing body of research illustrating an important link between environmental conditions and divergent reproductive strategies in zooplankton. I specifically: (1) review the environmental cues that initiate a transition between asexual and sexual reproduction in zooplankton and (2) describe recent work demonstrating an evolutionary consequence of ecological selective pressures, such as predation and habitat predictability, on variation in the extent to which organisms engage in sex and enter dormancy. Such results have implications for the genetics and ecology of these organisms.

Walsh MR

2013-10-01

223

Effect of Advection on Variations in Zooplankton at a Single Location Near Cabo Nazca, Peru.  

Science.gov (United States)

Temporal variations in the biomass and species composition of zooplankton at a single midshelf station in an upwelling area off Peru can be explained to a large extent by onshore-offshore advection in the upper 20 m of the water column. During periods of ...

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

1980-01-01

224

Protein expression from zooplankton communities in a metal contaminated NW mediterranean coastal ecosystem.  

UK PubMed Central (United Kingdom)

Bidimensional and monodimensional polyacrylamide gel electrophoresis were used to study protein expression from zooplankton collected in thirteen stations of Toulon Bay (NW Mediterranean). In this ecosystem, Little Bay showed higher trace metal concentrations (13.5-23.8 nM for Cu, 0.73-1.24 nM for Pb, 27.8-58.7 nM for Zn) than Large Bay (Cu 2.2-15.6 nM; Pb 0.19-0.78 nM; Zn 9.0-38.8 nM). Trace metals positively correlated (p < 0.05) with expression of four zooplankton proteins (MW in kDa/pI: 25.0/5.6; 48.8/4.1; 38.2/4.4; 38.3/5.8) and with biomass of Oithona nana, predominant copepod in Little Bay. Sequencing by LC-MS/MS putatively provided zooplankton identity of these proteins: they were cytoskeleton actin, except one protein that was the chaperone calreticulin. We suggest that actin and calreticulin could be regarded as zooplankton markers of metal stress and be involved in a possible tolerance of O. nana to contamination, contributing to its development in a marine perturbed ecosystem.

Jean N; Dumont E; Durrieu G; Balliau T; Jamet JL; Personnic S; Garnier C

2012-09-01

225

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

Science.gov (United States)

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

Luo, Jinhuo

2013-06-20

226

A sampler-incubator for studying zooplankton grazing and phytoplankton production.  

Digital Repository Infrastructure Vision for European Research (DRIVER)

A new instrument to quantify the zooplankton grazing on phytoplankton and the phytoplankton growth is described. This instrument consists of two cylindrical chambers and a mechanical system for shutting, by a messenger both the chambers simultaneously. With this instrument the grazing may be evaluat...

Oscar RAVERA; Silvia SCOTTO

227

Isotopic fractionation and trophic position of zooplankton species in the Upper Paraná River floodplain.  

Science.gov (United States)

This study aimed to evaluate the isotopic fractionation and trophic position of three zooplankton species (Notodiaptomus amazonicus, Moina minuta and Bosmina hagmanni) in the Upper Paraná River floodplain. We predict that phytoplankton is the main food resource used by these species. Three zooplankton samples and three phytoplankton samples were taken from each sampling site, with three to four samples collected for each species. The number of individuals for samples varied according to the body size: from 100 to 130 individuals for Notodiaptomus amazonicus; 150 to 200 for Moina minuta; and from 250 to 300 for Bosmina hagmanni. The isotopic values for ?13C and ?15N were determined using mass spectrophotometer. The isotopic fractionation of 13C was performed according to the relationship ? = ?13C zooplankton - ?13C phytoplankton. To determine the possible trophic position of these species, we used the expression TL = (?15N zooplankton - ?15N phytoplankton)/?+ 1. The species showed high variation in isotopic fractionation and in trophic position in the different environments. We verified that the species use other food resources in addition to phytoplankton. The elucidation and understanding of the trophic position of the organisms based on stable isotopic analysis offers complementary information to traditional techniques. This analysis helps explain the flow of matter and energy in the food chain of floodplain aquatic environments as well as trace the trophic relationships involved in the ecological roles and strategies of distinct species. PMID:21437401

Santana, A R A; Benedito, E; Ducatti, C; Lansac-Tôha, F A

2011-02-01

228

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

Directory of Open Access Journals (Sweden)

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 species)respectively 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.

Sharma, B.K.

2011-01-01

229

The role of climate in shaping zooplankton communities of shallow lakes  

Digital Repository Infrastructure Vision for European Research (DRIVER)

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 to...

Gyllström, Mikael; Hansson, Lars-Anders; Jeppesen, Erik; Garcia-Criado, Francisco; Gross, Elisabeth; Irvine, Kenneth

230

Vertical axis wind turbines  

Science.gov (United States)

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

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

2011-03-08

231

Studies on ecological adaptation model of Calnus sinicus and Paracalanus parvus piplation vertical migraton in the Bohai Sea  

UK PubMed Central (United Kingdom)

Optimal population ecological adaptation model is used to demonstrate the vertical migration of Ca lanus sinicus and Paracalanus parvus population of Bohai Sea ecosystem.Life cycle, generation time, fecundity, and egg production quantity are the main factors to detenn ine these two species' vertical migration. For a Ca lanus sinicus-type life history, fitness is maximized by diurnal vertical m igrations. When advection risk in surface waters is low and by spending less time in the upperwaters as the velocity increases. For a Paracalanus parvus-type life history, vertical migration is occurred when advection increases.

Han Xifu; Wang Rong; Wang Junping

2001-01-01

232

Vertical distribution and isotopic composition of living planktonic foraminifera in the Western north atlantic.  

UK PubMed Central (United Kingdom)

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 delta(18)O 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.

Fairbanks RG; Wiebe PH; Bé AW

1980-01-01

233

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

Energy Technology Data Exchange (ETDEWEB)

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 delta/sup 18/O 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.

Fairbanks, R.G. (Columbia Univ., Palisades, NY); Wiebe, P.H.; Be, A.W.H.

1980-01-04

234

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

1980-01-04

235

Extracoelenteric zooplankton feeding is a key mechanism of nutrient acquisition for the scleractinian coral Galaxea fascicularis.  

Science.gov (United States)

Internal and external feeding on zooplankton may provide scleractinian corals with important nutrients. However, the latter process has never been properly quantified. To quantify the dynamics of zooplankton capture, digestion and release for a scleractinian coral, we performed detailed video analyses of Galaxea fascicularis feeding on Artemia nauplii. A highly dynamic process of prey capture, digestion and release was observed. A single G. fascicularis polyp (N=3) captured 558±67 and released 383±75 Artemia nauplii over a 6 h interval. On average, 98.6% of prey captured was not ingested. Instead, prey items were clustered into aggregates that were digested externally by mesenterial filaments. In addition, we employed carbon, nitrogen and phosphorus analysis of zooplankton before and after digestion by G. fascicularis colonies (N=6). For total organic carbon, 43.1% (0.298±0.148 ?g Artemia(-1)) was lost after 6 h of digestion. For total organic nitrogen, total organic phosphorus and orthophosphate (PO(4)(3-)), these values were 51.3% (0.059±0.028 ?g Artemia(-1)), 50.9% (0.009±0.004 ?g Artemia(-1)) and 84.6% (0.0019±0.0008 ?g Artemia(-1)), respectively. For extracoelenteric zooplankton feeding alone, total estimated nutrient inputs for G. fascicularis colonies were 76.5±0.0 ?g organic carbon, 15.2±0.0 ?g organic nitrogen, 2.3±0.2 ?g organic phosphorus and 0.5±0.8 ?g inorganic phosphorus per cm(2) coral tissue per day. These values exceed calculations based on intracoelenteric feeding by up to two orders of magnitude. Our results demonstrate that extracoelenteric zooplankton feeding is a key mechanism of nutrient acquisition for a scleractinian coral. These results are of importance to coral aquaculture and our understanding of benthic-pelagic coupling on coral reefs. PMID:21957098

Wijgerde, Tim; Diantari, Rara; Lewaru, Muhammad Wahyudin; Verreth, Johan A J; Osinga, Ronald

2011-10-15

236

Extracoelenteric zooplankton feeding is a key mechanism of nutrient acquisition for the scleractinian coral Galaxea fascicularis.  

UK PubMed Central (United Kingdom)

Internal and external feeding on zooplankton may provide scleractinian corals with important nutrients. However, the latter process has never been properly quantified. To quantify the dynamics of zooplankton capture, digestion and release for a scleractinian coral, we performed detailed video analyses of Galaxea fascicularis feeding on Artemia nauplii. A highly dynamic process of prey capture, digestion and release was observed. A single G. fascicularis polyp (N=3) captured 558±67 and released 383±75 Artemia nauplii over a 6 h interval. On average, 98.6% of prey captured was not ingested. Instead, prey items were clustered into aggregates that were digested externally by mesenterial filaments. In addition, we employed carbon, nitrogen and phosphorus analysis of zooplankton before and after digestion by G. fascicularis colonies (N=6). For total organic carbon, 43.1% (0.298±0.148 ?g Artemia(-1)) was lost after 6 h of digestion. For total organic nitrogen, total organic phosphorus and orthophosphate (PO(4)(3-)), these values were 51.3% (0.059±0.028 ?g Artemia(-1)), 50.9% (0.009±0.004 ?g Artemia(-1)) and 84.6% (0.0019±0.0008 ?g Artemia(-1)), respectively. For extracoelenteric zooplankton feeding alone, total estimated nutrient inputs for G. fascicularis colonies were 76.5±0.0 ?g organic carbon, 15.2±0.0 ?g organic nitrogen, 2.3±0.2 ?g organic phosphorus and 0.5±0.8 ?g inorganic phosphorus per cm(2) coral tissue per day. These values exceed calculations based on intracoelenteric feeding by up to two orders of magnitude. Our results demonstrate that extracoelenteric zooplankton feeding is a key mechanism of nutrient acquisition for a scleractinian coral. These results are of importance to coral aquaculture and our understanding of benthic-pelagic coupling on coral reefs.

Wijgerde T; Diantari R; Lewaru MW; Verreth JA; Osinga R

2011-10-01

237

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

Directory of Open Access Journals (Sweden)

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

Jafari Naser; Nabavi Mohamad Saiad; Akhavan Moslem

2011-01-01

238

[Vertical distribution of radiolarians and their role in epipelagic communities of the West Pacific rise and the Gulf of California  

UK PubMed Central (United Kingdom)

Vertical distribution of different groups of radiolarians and mesozooplankton (I = 0.2-3.0 mm) and the contribution of radiolarians to total biomass of bathometer-sampled zooplankton were studied in the epipelagic West Pacific Rise and the Gulf of California during 49th cruise of R/V "Akademik Mstislav Keldysh" (September-October, 2003). The production of the symbiotic algae of acantharians and colonial radiolarians as well as their contribution to the total primary production were evaluated. The proportion of all radiolarian groups in the total zooplankton biomass was shown to range from 1.4 to 11.5%. The contribution of zooxanthellae to the total primary production was not great in the studied region and equaled 0.1-1.2 and 0.3-0.7% for colonial radiolarians and acantharians, respectively.

Zas'ko DN; Rusanov II

2005-05-01

239

[Vertical distribution of radiolarians and their role in epipelagic communities of the West Pacific rise and the Gulf of California].  

Science.gov (United States)

Vertical distribution of different groups of radiolarians and mesozooplankton (I = 0.2-3.0 mm) and the contribution of radiolarians to total biomass of bathometer-sampled zooplankton were studied in the epipelagic West Pacific Rise and the Gulf of California during 49th cruise of R/V "Akademik Mstislav Keldysh" (September-October, 2003). The production of the symbiotic algae of acantharians and colonial radiolarians as well as their contribution to the total primary production were evaluated. The proportion of all radiolarian groups in the total zooplankton biomass was shown to range from 1.4 to 11.5%. The contribution of zooxanthellae to the total primary production was not great in the studied region and equaled 0.1-1.2 and 0.3-0.7% for colonial radiolarians and acantharians, respectively. PMID:16004268

Zas'ko, D N; Rusanov, I I

240

Signatures of currency vertices  

CERN Document Server

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

Holme, Petter

2008-01-01

 
 
 
 
241

Signatures of Currency Vertices  

Science.gov (United States)

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

Holme, Petter

2009-03-01

242

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

Scientific Electronic Library Online (English)

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

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

2009-12-01

243

STUDIES ON ZOOPLANKTON DIVERSITY IN RELATION TO WATER QUALITY OF AMBE GHOSALE LAKE OF THANE CITY, (MS) INDIA  

Directory of Open Access Journals (Sweden)

Full Text Available Zooplanktons are known to dominate freshwater habitats. Zooplankton studied from the Ambe Ghosale Lake, Thane city of Maharashtra state was studied during January to December 2011. Fifteen Rotifers and twelve cladocerans and six Copepods were recorded during the study. In this study, we found that organisms like nauplii and rotifers predominated even among the cladocerans. We also found that zooplankton community of the lake of this system was characterized by species already known in similar environments. The climate, the presence of suspended solids, the consequent decreased availability of food, and the progressive water quality gradient towards eutrophication were the main factors governing the composition and structure of the zooplankton community and the climate was one of the main factors controlling population size in this community.

Nimbalkar R K, V N Kamtikar1, S S Shinde1, and M S Wadikar2

2013-01-01

244

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

Science.gov (United States)

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

245

Methods of Separate Collection of Marine Phyto- and Zooplankton (O Metodike Razdelnogo Sbora Morskogo Fito- I Zooplanktona).  

Science.gov (United States)

The method of separating phytoplankton from zooplankton by screening the samples through two sieves and fixing them for subsequent analysis was developed by the author. The sampling and processing made during the Vityaz' and Akademik Berg expeditions in 1...

G. K. Barashkov

1969-01-01

246

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

UK PubMed Central (United Kingdom)

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

Havens KE

2002-04-01

247

Spatial heterogeneity of zooplankton abundance and diversity in the Saudi coastal waters of the Southern Red Sea  

Science.gov (United States)

The horizontal distribution, abundance and diversity of zooplankton has been studied at 50 stations along the Saudi coastal waters of the southern Red Sea (27 stations around Farasan archipelago, 9 around Al-Qunfodah and 14 around Al-Lith) during March-April 2011 using a plankton net of 150 µm. The zooplankton standing crop fluctuated between 1058 and 25787 individuals/m3 with an average of 5231 individuals/m3. Zooplankton was dominated by holoplanktonic forms that representing 80.26 % of total zooplankton, while meroplanktonic constituting 19.74% and dominated by mollusc larvae. Copepods appeared to be the predominant component, formed an average of 69.69 % of the total zooplankton count followed by chaetognaths and urochordates (4.5 and 4.1% of total zooplankton respectively). A total of 100 copepods species in addition to several species of other planktonic groups (cladocerans, chaetognaths, urochordates) were recorded in the study area. The copepod diversity decreased northward (94, 69 and 62 species at Farasan, Al-Qunfodah and Al-Lith respectively). In general, adult cyclopoid copepods dominated the zooplankton community in term of abundance and species number (19.55 %, 65 species) with dominance of Oncaea media, Oithona similis and Farranula carinata followed by adult calanoid copepods (19.38%, 35 species) with dominance of Paracalanus aculeatus, Clausocalanus minor, Acartia (Acanthacartia) fossae and Centropages orsinii. Harapacticoids densities were low in abundance, represented only by 5 species and dominated mainly by Euterpina acutifronis. Some copepod species decreased northward: Acartia amboinensis, Canthocalanus pauper, Labidocera acuta, Corycaeus flaccus, C. typicus, C. agilis, C. catus, C. giesbrechti, C. latus, C. furcifer and Euterpina acutifronis, while others increased northward (Acartia fossae, Undinula vulgaris and Centropages orsinii). Among copepod orders, Monstrilloida and Siphonostomatoida were observed only in southern area (Farasan archipelago). Keywords: Zooplankton, copepods, abundance, diversity, Red Sea, Saudi Arabia.

Al-Aidaroos, Ali; El-Sherbiny, Mohsen; Mantha, Gopikrishna

2013-04-01

248

Migration and revolution  

Directory of Open Access Journals (Sweden)

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

Hein de Haas; Nando Sigona

2012-01-01

249

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

Scientific Electronic Library Online (English)

Full Text Available Abstract in english The aim of this study was to test the effects of natural free-floating plants on zooplankton distribution in a shallow subtropical lake. First, the hypothesis that free-floating plants have an effect on physico-chemicals, leading to a decrease on nutrient availability and influencing the 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: (more) 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.

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

2011-08-01

250

Biodiversity of zooplankton communities in the Upper Parana River floodplain: interannual variation from long-term studies.  

UK PubMed Central (United Kingdom)

We investigated the effect of interannual variation of hydrosedimentological regime and connectivity on the zooplankton biodiversity in the Upper Paraná River floodplain. Zooplankton samplings were undertaken between 2000 and 2007, in different environments of the floodplain, including connected and isolated floodplain lakes, backwaters, rivers and channels. The zooplankton included 541 species. Rotifers showed the highest species richness and abundance. Among the zooplankton species, 71 represent new occurrence records for the floodplain. The species accumulation curve showed a continuous increase in gamma diversity, demonstrating the importance of long-term research for accurate knowledge of biodiversity in heterogeneous and dynamic ecosystems, such as the floodplains. Interannual beta diversity among studied years indicated a lesser alteration in community composition in 2001, when a long limnophase period was observed. In most of the environments, the highest species richness values were related to the greatest flooding amplitudes. Flooding amplitude, which is associated with connectivity, favors faunal exchange amongst the environments and between the pelagic and littoral zones. This explains the occurrence of both planktonic and non-planktonic species within the community. On the other hand, mean zooplankton abundance values were higher when a long isolation period occurred. Differences between the potamophase and limnophase amplitude associated with connectivity among the environments were the most important factors for the structure and dynamics of the zooplankton community in the Upper Paraná River floodplain.

Lansac-Tôha FA; Bonecker CC; Velho LF; Simões NR; Dias JD; Alves GM; Takahashi EM

2009-06-01

251

Macroeconomic influences on migration.  

UK PubMed Central (United Kingdom)

"The changing composition and magnitude of internal migration flows are of critical importance in determining the potential economic growth of a region. Yet, there can be little doubt that the business cycle has a significant influence on migration flows and propensities. This paper explores the effects of macroeconomic events on migration [within Canada] through an examination of the extent of the influence of the national and regional business cycle on the in-, out- and net-migration rates." (SUMMARY IN FRE AND GER)

Milne WJ

1993-01-01

252

Dimensions in cell migration.  

UK PubMed Central (United Kingdom)

The importance of cell migration for both normal physiological functions and disease processes has been clear for the past 50 years. Although investigations of two-dimensional (2D) migration in regular tissue culture have elucidated many important molecular mechanisms, recent evidence suggests that cell migration depends profoundly on the dimensionality of the extracellular matrix (ECM). Here we review a number of evolving concepts revealed when cell migration is examined in different dimensions.

Doyle AD; Petrie RJ; Kutys ML; Yamada KM

2013-10-01

253

Dimensions in cell migration.  

Science.gov (United States)

The importance of cell migration for both normal physiological functions and disease processes has been clear for the past 50 years. Although investigations of two-dimensional (2D) migration in regular tissue culture have elucidated many important molecular mechanisms, recent evidence suggests that cell migration depends profoundly on the dimensionality of the extracellular matrix (ECM). Here we review a number of evolving concepts revealed when cell migration is examined in different dimensions. PMID:23850350

Doyle, Andrew D; Petrie, Ryan J; Kutys, Matthew L; Yamada, Kenneth M

2013-07-10

254

Migration and Adult Education  

Science.gov (United States)

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

Gois, William

2007-01-01

255

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

Energy Technology Data Exchange (ETDEWEB)

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

Paffenhofer, G.A.

1992-09-25

256

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

Energy Technology Data Exchange (ETDEWEB)

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

Paffenhofer, G.A.

1992-09-25

257

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.

1995-01-01

258

Seasonal variations in zooplankton abundances in the Iturbide reservoir (Isidro Fabela, State of Mexico, Mexico).  

UK PubMed Central (United Kingdom)

This studywas undertaken to quantify the seasonal variations of zooplankton (rotifers, cladocerans and copepods) and selected physico-chemical variables (temperature, pH, conductivity, Secchi disc transparency, dissolved oxygen, ammonia, nitrate and phosphate concentrations) in the Iturbide dam. Monthly zooplankton samples (50 l filtered through 50 microm mesh, in duplicates from each of the 4 stations) were collected from February 2008 to January 2009. Simultaneously physico-chemical variables were measured. The zooplankton samples were fixed in 4% formalin in the field. In general, the temperature ranged from 9 to 16 degrees C, rarely exceeding 20 degrees C. Secchi transparency was nearly 100% since the reservoir was shallow (< 2 m) even during the rainy seasons. Dissolved oxygen was generally high, 13-18 mg l(-1). Nitrate levels (10 to 170 microg l(-1)) were low while phosphates were relatively high (9 to 35 microg l(-1)). The Iturbide reservoir was dominated by rotifer species. We encountered in all, 55 taxa of rotifers, 9 cladocerans and 2 copepods. The rotifer families Trichocercidae and Notommatidae had the highest number of species (7 each) followed by Colurellidae and Lecanidae (6 and 5 species, respectively). Trichocerca elongata, Ascomorpha ovalis, K. americana, K. cochlearis, Lepadella patella and Pompholyx sulcata were the dominant rotifers during the study period. On an annual average, rotifer density ranged between 50-200 ind.(-1). Among crustaceans Chydorus brevilabris and Macrothrix triserialis were most abundant. The maximal density of these cladocerans was about 50 ind. l(-1). Copepods were much lower in numbers (< 20 ind. l(-1)). In general the density of zooplankton was higher during summer months (April to July) than during winter. Shannon-Wiener diversity index varied from 1.0 to 4.3 depending on the site and the sampling period. Based on the data of Secchi transparency and nutrient concentrations, the Iturbide reservoir appeared to be mesotrophic.

Sarma SS; Osnaya-Espinosa LR; Aguilar-Acosta CR; Nandini S

2011-07-01

259

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

Directory of Open Access Journals (Sweden)

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

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

2011-01-01

260

Stability and bifurcation in a two harmful phytoplankton-zooplankton system  

International Nuclear Information System (INIS)

In this paper, a mathematical model consisting of two harmful phytoplankton and zooplankton with discrete time delays is considered. We prove that a sequence of Hopf bifurcations occur at the interior equilibrium as the delay increases. Meanwhile, the phenomenon of stability switches is found under certain conditions. The direction of the Hopf bifurcations and the stability of the bifurcating periodic solutions are determined by using the theory of normal form and center manifold. Numerical simulations are given to support the theoretical results.

2009-02-15

 
 
 
 
261

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

Directory of Open Access Journals (Sweden)

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

Cristiana CALLIERI; Alessandra PUGNETTI; Marina MANCA

1999-01-01

262

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

Directory of Open Access Journals (Sweden)

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

A. P. Cardozo; J. G. F. Bersano; W. J. A. Amaral

2007-01-01

263

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

Directory of Open Access Journals (Sweden)

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

Franz Lahnsteiner; Manfred Kletzl; Thomas Weismann

2012-01-01

264

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

1989-01-01

265

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

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

Vadadi-Fülöp, Cs.

2009-01-01

266

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

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

Ana Paula Sousa Pereira; Anderson Nascimento do Vasco; Fábio Brandão Britto; Arisvaldo Vieira Méllo Júnior; Eliane Maria de Souza Nogueira

2011-01-01

267

Zooplankton community resilience and aquatic environmental stability on aquaculture practices: a study using net cages.  

Science.gov (United States)

Fish farming in net cages causes changes in environmental conditions. We evaluated the resilience of zooplankton concerning this activity in Rosana Reservoir (Paranapanema River, PR-SP). Samples were taken near the net cages installed at distances upstream and downstream, before and after net cage installation. The resilience was estimated by the decrease in the groups' abundance after installing the net cages. The zooplankton community was represented by 106 species. The most abundant species were Synchaeta pectinata, S. oblonga, Conochilus coenobasis, Polyarthra dolichoptera and C. unicornis (Rotifera), Ceriodaphnia cornuta, Moina minuta, Bosmina hagmanni and C. silvestrii (Cladocera) and Notodiaptomus amazonicus (Copepoda). The resilience of microcrustaceans was affected in the growing points as this activity left the production environment for longer, delaying the natural ability of community responses. Microcrustaceans groups, mainly calanoid and cyclopoid copepods, had a different return rate. The net cage installation acted as a stress factor on the zooplankton community. Management strategies that cause fewer risks to the organisms and maximize energy flow may help in maintaining system stability. PMID:22437379

Dias, J D; Simões, N R; Bonecker, C C

2012-02-01

268

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

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Full Text Available 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 inconsistency, we conducted a microcosm experiment using model zooplankton communities withdifferent species compositions, where animals were exposed to lethal (near to the 24 h LC50, concentration estimatedto kill 50% of individuals within 24-h for the small cladoceran Bosmina) and lower, sublethal concentrations of carbaryl.In the experiment, population densities of the small cladocerans (Bosmina and Bosminopsis) decreased subsequent tothe applications of chemical, but no impacts were observed on the large cladoceran Daphnia. Our results supported thereports of previous individual level toxicity tests, and indicated that the sensitivity of zooplankton to the insecticide wasunchanged by biological interactions but the response of population can be modified by compensation of populationthrough hatching from resting eggs and/or the persistence of insecticide in the systems.

Masaki Sakamoto; Yoshinari Tanaka

2013-01-01

269

Effect of planktivores, zooplankton, and macrobenthos on material flow in a small lake  

International Nuclear Information System (INIS)

Planktivores, zooplankton grazers, and macrobenthos were studied to determine how changes in animal community structure may alter the flow of material in Dunham Pond, CT. Chaoborus and chironomid larvae were studied to determine how they affect the flux of matter across the sediment/water interface. This was done by incubating undisturbed cores in situ and relating changes in water chemistry to larval density. The log-transformed flux rates of iron, manganese, and phosphorus were linearly related to larval biomass. Functional groups may be successfully used to predict rates of material flow. Changes in the mass of macroinvertebrates affect the flux rates of redox-active substances across the sediment/water interface. The use of population densities and feeding characteristics to estimate trophic transfer in Dunham Pond indicate that (1) visual planktivory by larval perch may result in overutilization of prey, (2) ambush planktivory by univoltine Chaoborus appears to under utilize prey, and (3) zooplankton grazing tracks net primary productivity, regardless of zooplankton community structure. Animal groups cycle 30-100% of the phosphorus required for 14C productivity in Dunham Pond

1985-01-01

270

Biotic Spectrum of Chando Lake in Context of Ecological Status and Zooplankton Diversity  

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Full Text Available Covering an area of approximate 650 ha, Chando Lake is located in South East of Basti, (U.P.). No precise study regarding its hydrobiology has been conducted. Hence, present study has been undertaken to observe its ecological status and zooplankton diversity from June 2010 to May 2012. The early mean flow in this lake relied on rains and the mean annual rain fall was recorded to be 1094 cm with in 51 average rainy days. The average value of the temperature was recorded to be 28.46°C, pH 7.38, transparency 58.52 cm, DO 6024 mg/L, free CO2 3.70 mg/L, TDS 1 52.20 mg/L, total hardness 153.69 mg/L , total alkalinity 272.44 mg/L , Nitrate 7.11 mg/L, phosphate 0.83 mg/L and chloride 34.63 mg/L. In the present study 23 species of zooplankton were noticed out of which six species belong to cladocerans, six species of copepods, four species of protozoans and seven species of rotiferans. The study of zooplankton species diversity and abundance with respect to biotic factors may assist in future planning for the management of intensive fish culture in this vast lake.

Anuradha Shukla; J.P. Shukla; M. Mishra

2012-01-01

271

Anisotropy processing in vertically inhomogeneous media  

Energy Technology Data Exchange (ETDEWEB)

Alkhalifah and Tsvankin show that P-wave normal-moveout (NMO) velocity for horizontal and dipping reflectors, as well as time migration, in transversely isotropic (TI) media with a vertical symmetry axis depends just on the zero-dip NMO velocity [V{sub nmo} (0)], and a parameters {eta} that is a combination of Thomsen`s parameters. Their inversion procedure makes it possible to obtain 71 and reconstruct the NMO velocity as a function of ray parameter using moveout velocities for two different dips. This means that inversion of dip-dependent information allows one to perform all time-processing in TI media using only surface P-wave data. The layered TI media NMO equation for dipping reflectors provides the basis for extending TI velocity analysis to vertically inhomogeneous media. The multi-layered NMO equation is based on a root-mean-square (rms) average of modified interval velocities corresponding to a single ray parameter, that of the dipping event. Therefore, modified interval velocity values can be extracted from the stacking velocities using a Dixtype differentiation procedure. In addition, the 77 inversion is performed simultaneously with the interval velocity evaluation in each layer. Time migration, like DMO, depends on two parameters in vertically inhomogeneous media, namely the NMO velocity and {eta}, both of which can vary with depth. Therefore, the NMO velocity and 77 estimated using the dip dependency of P-wave moveout velocity can be used in a TI time migration. An application of anisotropic processing to seismic data from offshore Africa demonstrates the importance of considering anisotropy, especially as it pertains to focusing dipping events.

Alkhalifah, T.

1995-12-31

272

Vertical axis windmills  

Energy Technology Data Exchange (ETDEWEB)

The wind motor contains a vertical shaft on supports. On its upper end there is a cross on whose ends blades are hinged with circular bar profile. Vertical stands are also attached to the ends of the cross. They are connected in the lower part with floating ring-shaped body. This body is placed in the ring-shaped reservoir filled with liquid. This method creates a floating support for the rotating rotor. The rotation is transmitted from the vertical shaft to the generator through a reducer.

Spicer, R.S.W.

1984-05-10

273

Interactions Between Benthic Predators and Zooplanktonic Prey are Affected by Turbulent Waves.  

UK PubMed Central (United Kingdom)

Predators capture prey in complex and variable environments. In the ocean, bottom-dwelling (benthic) organisms are subjected to water currents, waves, and turbulent eddies. For benthic predators that feed on small animals carried in the water (zooplankton), flow not only delivers prey, but can also shape predator-prey interactions. Benthic passive suspension feeders collect prey delivered by movement of ambient water onto capture-surfaces, whereas motile benthic predators, such as burrow-dwelling fish, dart out to catch passing zooplankton. How does the flow of ambient water affect these contrasting modes of predation by benthic zooplanktivores? We studied the effects of turbulent, wavy flow on the encounter, capture, and retention of motile zooplanktonic prey (copepods, Acartia spp.) by passive benthic suspension feeders (sea anemones, Anthopleura elegantissima). Predator-prey interactions were video-recorded in a wave-generating flume under two regimes of oscillating flow with different peak wave velocities and levels of turbulent kinetic energy ("weak" and "strong" waves). Rates of encounter (number of prey passing through a sea anemone's capture zone per time), capture (prey contacting and sticking to tentacles per time), and retention (prey retained on tentacles, without struggling free or washing off, per time) were measured at both strengths of waves. Strong waves enhanced encounter rates both for dead copepods and for actively swimming copepods, but there was so much variability in the behavior of the live prey that the effect of wave strength on encounter rates was not significant. Trapping efficiency (number of prey retained per number encountered) was the same in both flow regimes because, although fewer prey executed maneuvers to escape capture in strong waves, more of the captured prey was washed off the predators' tentacles. Although peak water velocities and turbulence of waves did not affect feeding rates of passive suspension-feeding sea anemones, increases in these aspects of flow have been shown to enhance feeding rates and efficiency of motile benthic fish that lunge out of their burrows to catch zooplankton. Faster, more turbulent flow interferes with the ability of prey to detect predators and execute escape maneuvers, and thus enhances capture rates both for passive suspension-feeding predators and for actively swimming predators. However, prey captured in the mouths of fish are not washed away by ambient flow, whereas prey captured on the tentacles of suspension feeders can be swept off before they are ingested. Therefore, the effects of flowing water on predation on zooplankton by benthic animals depend on the feeding mode of the predator.

Robinson HE; Finelli CM; Koehl MA

2013-08-01

274

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

Directory of Open Access Journals (Sweden)

Full Text Available 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 oceanographic 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.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 obtuvieron 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.

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

2001-01-01

275

Micromachined electrostatic vertical actuator  

Energy Technology Data Exchange (ETDEWEB)

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

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

1999-10-19

276

Hybrid vertical cavity laser  

DEFF Research Database (Denmark)

A new hybrid vertical cavity laser structure for silicon photonics is suggested and numerically investigated. It incorporates a silicon subwavelength grating as a mirror and a lateral output coupler to a silicon ridge waveguide.

Chung, Il-Sug; MØrk, Jesper

2010-01-01

277

Observations of copepod feeding and vertical distribution under natural turbulent conditions in the North Sea  

DEFF Research Database (Denmark)

We present results of simultaneous measurements of turbulent- dissipation rate, zooplankton vertical distribution and copepod gut pigments in the northern North Sea. Analysis shows that some, but not all, copepods (by species, sex and stage) exhibit significant dependence on turbulence in respect to Vertical distribution and feeding rate. Oithona similis (female and copepodite stages) exhibits an avoidance of the surface layer when turbulence is strong there. For the range of turbulence (10(-7) to 10(-3) m(2) s(-3)) and ambient chlorophyll concentration (0.5-0.8 mug l(-1)) encountered, Calanus spp. and Metridia lucens exhibited a significant negative response in feeding-rate index with increasing turbulence. Centropages typicus and Pseudocalanus spp, also exhibited a negative response but of less significance.

Visser, Andre; Saito, H.

2001-01-01

278

Vertical distribution of natural radionuclides in soils  

Directory of Open Access Journals (Sweden)

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

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

2012-01-01

279

Vertical distribution of natural radionuclides in soils  

Science.gov (United States)

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

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

2012-04-01

280

SLS Vertical emittance tuning  

CERN Document Server

To establish ultra-small vertical emittances (<1 pm.rad at 2.86 GeV) is one important aim of future linear collider damping ring optimization studies (In January 2011, the EU-project TIARA (Test Infrastructure and Accelerator Research Area)1 started with contributions from the SLS as part of the SVET (SLS Vertical Emittance Tuning) work package WP6 [1].) at the SLS.[...

Böge, M; Milas, N.; Streun, A.; Liuzzo, S.M.

2011-01-01

 
 
 
 
281

The vertical conveyor belt  

Energy Technology Data Exchange (ETDEWEB)

LTA Process Engineering have developed the high angle conveying (HAC) system which can transport material at steep angles, and vertically. Two ordinary conveyor belts - one using spring-loaded idlers - hug the material between them to eliminate relative movement between material and belts and avoid damage to materials which are vulnerable to handling. Materials can be lifted vertically to more than 350 metres. Only extremely mobile or liquid-bearing material is not suited to the sandwich belt HAC system. 1 fig.

1992-03-01

282

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

Directory of Open Access Journals (Sweden)

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.

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

2009-01-01

283

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

Directory of Open Access Journals (Sweden)

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

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

2010-01-01

284

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

International Nuclear Information System (INIS)

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

1991-01-01

285

Migration Policy Institute  

Science.gov (United States)

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

286

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

Directory of Open Access Journals (Sweden)

Full Text Available Present and past diatom and crustacean zooplankton communities of subarctic Lake Saanajärvi in Finnish Lapland were studied with special emphasis on their representation in the sediment surface. Two years monitoring of the present state of the lake revealed it to be ultraoligotrophic with a biomass peak during autumn overturn. Chrysophytes and diatoms were the most abundant phytoplankton groups, with four species forming the main bulk of the crustacean zooplankton community. The comparison of the present plankton community with the species composition in the sediment surface showed that only some plankton groups are suitable for paleolimnological studies. The value of diatoms for paleolimnological studies was supported by the observation that all of the species recorded from various habitats in the lake were detectable in the sediment. In addition, some species (e.g. Cyclotella glomerata) that limnological sampling had not detected were found in the sediment record. Similarly, the zooplankton class Chydoridae and Daphnia hyalina species were equally or better represented in the sediment than in the water column. On the other hand, the sediment trap and core evidence of the whole crustacean zooplankton community suggested many zooplankton species have little or no significance in paleolimnological studies. For example the two dominant copepod species, Eudiaptomus graciloides and Cyclops abyssorum, were not detectable in sediment trap samples. These findings indicate that only a small fraction of the living biota are preserved in the sediments, and this should be taken into account when drawing conclusions based on the detection of just one such species group.

Milla RAUTIO; Sanna SORVARI; Atte KORHOLA

2000-01-01

287

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 speciehness and density at site CM, what may be probably explained by the adverse environmental conditions for zooplankton community. (author)

2009-10-02

288

Horizontal collectors for landfill gas collection and migration control  

Energy Technology Data Exchange (ETDEWEB)

Landfill owners and operators are forever challenged with properly managing landfill gas (LFG). Collecting this LFG has evolved into an art, as well as a science. Technical expertise and sheer creativity complementary skills required to successfully manage both LFG collection and migration. The vertical LFG collection well has been an essential component for landfill owners and operators for over three decades. They have proved troublesome, however, for active landfill owners who attempt to collect LFG from the midst of an active site-the vertical wells prove more a {open_quotes}target{close_quotes} for refuse collection vehicles disposing their load, than for effective, long term LFG collection. Active and inactive/closed landfill owners must also contend with LFG migration at or near the refuse boundary. Multiple vertical LFG wells must be used to control LFG migration and surface emissions. Vertical LFG wells do work, but at significant expense of the landfill owner. In the past 10 years, the use of horizontal LFG wells or collectors has gained momentum, both for effectiveness and cost. The City of Los Angeles, Bureau of Sanitation operates one active Class III landfill and manages five closed Class III landfills. At Lopez Canyon Landfill (active), horizontal LFG collection wells were installed as early as 1987, for LFG collection. At Toyon Canyon Landfill (closed), horizontal collection wells were installed in 1992 and 1994 for LFG migration and surface emissions control.

Dobrowski, J.G. [Constantin Pano, Los Angeles, CA (United States)

1995-08-01

289

Al thermo-migration for the formation of deep junctions  

Energy Technology Data Exchange (ETDEWEB)

An alternative method for creating total vertical junction insulation of power devices is presented. It involves the thermo-migration of melted Al/Si. The method is first theoretically presented. Physical and electrical results are then given showing the efficiency of the method in terms of surface consumption and voltage handling capability. The issue of manufacturability is finally addressed. (authors) 8 refs.

Dilhac, J.M.; Cornibert, L.; Ganibal, C.

1998-06-01

290

Oil migration conditions within the Tatar arch and Melekesskiy depression  

Energy Technology Data Exchange (ETDEWEB)

Within the Tatar arch and the Melekesskiy depression, there were and are conditions for vertical migration of oil from the Devonian deposits into the overlying rocks of the Carboniferous and Permian. This explains the close qualities of oil in the region. The oil pools could be found in any level where there are the necessary conditions for their preservation.

Kafichev, V.G.

1984-01-01

291

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

International Nuclear Information System (INIS)

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

2008-01-01

292

The effect of variable turbulent intensities on the distribution of zooplankton in the shallow, large Lake Balaton (Hungary) L’effet d’intensités de turbulence variables sur la distribution du zooplancton dans le Balaton (Hongrie), grand lac peu profond  

Digital Repository Infrastructure Vision for European Research (DRIVER)

The influence of current velocity on zooplankton organisms is manifold. Moderate current velocity is beneficial for zooplankton, but through various mechanisms too high a current velocity can have detrimental effects. We examined how current velocity acts on zooplankton in Lake Balaton at diffe...

Baranyai E.; G.-Tóth L.; Vári A.; Homonnay Z.G.

293

Changes in zooplankton communities along a mercury contamination gradient in a coastal lagoon (Ria de Aveiro, Portugal).  

Science.gov (United States)

The main objective of this paper was to evaluate the impact of mercury on the zooplankton communities' structure and functioning and their bioaccumulation patterns along a contamination gradient in a temperate coastal lagoon. Our results demonstrated that total abundance was not negatively affected by Hg contamination, since the most contaminated areas presented the highest values, being the copepod Acartia tonsa the dominant species, which means that it is a very well adapted and tolerant species to mercury. Nevertheless, negative effects were observed in terms of species diversity, since the most contaminated areas presented the lowest values of species richness, evenness and heterogeneity. Moreover, the spatial mercury gradient was reflected on the bioaccumulation patterns of the zooplankton communities. This reinforces the idea that zooplankton can be considered as an important vehicle of mercury transfer through the food pelagic web since it constitutes a primordial food resource for several commercial fish species. PMID:24064374

Cardoso, Patrícia Gonçalves; Marques, Sónia Cotrim; D'Ambrosio, Mariaelena; Pereira, Eduarda; Duarte, Armando Costa; Azeiteiro, Ulisses Miranda; Pardal, Miguel Ângelo

2013-09-21

294

Comparative study of the zooplankton composition of six lacustrine ecosystems in Central Brazil during the dry season  

Directory of Open Access Journals (Sweden)

Full Text Available Zooplankton community from six lacustrine ecosystems located in Federal District (Central Brazil) was studied based on samples collected during the dry season (July to September). A total of 71 taxa were recorded: 44 rotifers, 17 cladocerans and 10 copepods. The highest number of zooplankton species was recorded in oligotrophic Bonita Pond (32 species) and the lowest number in hypertrophic waste stabilisation ponds (7 species). This tendency of decreasing the diversity with increasing trophic level was consistent with a cluster analysis of the samples based on Sorensen index of similarity. From the overall similarity dendrogram, two groups of ecosystems were distinguished: one containing the natural ponds Bonita and Formosa and the other comprising the reservoirs Santa Maria, Descoberto and Paranoá. The role of morphometric features in determining the zooplankton community in such lacustrine ecosystems was also discussed.

STARLING F. L. do R. M.

2000-01-01

295

Analyzing the trophic link between the mesopelagic microbial loop and zooplankton from observed depth profiles of bacteria and protozoa  

Science.gov (United States)

It is widely recognized that organic carbon exported to the ocean aphotic layer is significantly consumed by heterotrophic organisms such as bacteria and zooplankton in the mesopelagic layer. However, very little is known for the trophic link between bacteria and zooplankton or the function of the microbial loop in this layer. In the northwestern Mediterranean, recent studies have shown that viruses, bacteria, heterotrophic nanoflagellates, and ciliates distribute down to 2000 m with group-specific depth-dependent decreases, and that bacterial production decreases with depth down to 1000 m. Here we show that such data can be analyzed using a simple steady-state food chain model to quantify the carbon flow from bacteria to zooplankton over the mesopelagic layer. The model indicates that bacterial mortality by viruses is similar to or 1.5 times greater than that by heterotrophic nanoflagellates, and that heterotrophic nanoflagellates transfer little of bacterial production to higher trophic levels.

Tanaka, T.; Rassoulzadegan, F.; Thingstad, T. F.

296

Changes in zooplankton communities along a mercury contamination gradient in a coastal lagoon (Ria de Aveiro, Portugal).  

UK PubMed Central (United Kingdom)

The main objective of this paper was to evaluate the impact of mercury on the zooplankton communities' structure and functioning and their bioaccumulation patterns along a contamination gradient in a temperate coastal lagoon. Our results demonstrated that total abundance was not negatively affected by Hg contamination, since the most contaminated areas presented the highest values, being the copepod Acartia tonsa the dominant species, which means that it is a very well adapted and tolerant species to mercury. Nevertheless, negative effects were observed in terms of species diversity, since the most contaminated areas presented the lowest values of species richness, evenness and heterogeneity. Moreover, the spatial mercury gradient was reflected on the bioaccumulation patterns of the zooplankton communities. This reinforces the idea that zooplankton can be considered as an important vehicle of mercury transfer through the food pelagic web since it constitutes a primordial food resource for several commercial fish species.

Cardoso PG; Marques SC; D'Ambrosio M; Pereira E; Duarte AC; Azeiteiro UM; Pardal MA

2013-09-01

297

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

International Nuclear Information System (INIS)

[en] 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 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

2004-01-01

298

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

International Nuclear Information System (INIS)

[en] 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 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

2006-01-01

299

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)

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.

Roberta Bettinetti; Letizia Garibaldi; Barbara Leoni; Silvia Quadroni; Silvana Galassi

2012-01-01

300

Analyzing the trophic link between the mesopelagic microbial loop and zooplankton from observed depth profiles of bacteria and protozoa  

Directory of Open Access Journals (Sweden)

Full Text Available It is widely recognized that organic carbon exported to the ocean aphotic layer is significantly consumed by heterotrophic organisms such as bacteria and zooplankton in the mesopelagic layer. However, very little is known for the trophic link between bacteria and zooplankton or the function of the microbial loop in this layer. In the northwestern Mediterranean, recent studies have shown that viruses, bacteria, heterotrophic nanoflagellates, and ciliates distribute down to 2000 m with group-specific depth-dependent decreases, and that bacterial production decreases with depth down to 1000 m. Here we show that such data can be analyzed using a simple steady-state food chain model to quantify the carbon flow from bacteria to zooplankton over the mesopelagic layer. The model indicates that bacterial mortality by viruses is similar to or 1.5 times greater than that by heterotrophic nanoflagellates, and that heterotrophic nanoflagellates transfer little of bacterial production to higher trophic levels.

T. Tanaka; F. Rassoulzadegan; T. F. Thingstad

2005-01-01

 
 
 
 
301

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

Directory of Open Access Journals (Sweden)

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.

Gbemisola A. Akin-Oriola

2003-01-01

302

Microtubules in Cell Migration.  

UK PubMed Central (United Kingdom)

Migration is a polarized cellular process that opposes a protrusive front edge to a retracting trailing edge. From the front to the rear, actin-mediated forces sequentially promote cell protrusion, adhesion, contraction, and retraction. Over the past decade, microtubules have revealed their pivotal role in cell migration. Through their roles in cell mechanics, intracellular trafficking, and signaling, microtubules participate in all essential events leading to cell migration. The front-rear polarization of microtubule functions relies on the asymmetric regulation of microtubule dynamics and stability; the asymmetric distribution of microtubule-associated protein complexes; and finally, the orientation of the microtubule network along the axis of migration. Microtubule network polarity controls the establishment and maintenance of the spatial and temporal coordination of migration events and is therefore the key to persistent directed migration. This review summarizes our current understanding of the functions of microtubules in persistent cell migration and of the migration-associated signals that promote microtubule network polarization. Expected final online publication date for the Annual Review of Cell and Developmental Biology Volume 29 is October 06, 2013. Please see http://www.annualreviews.org/catalog/pubdates.aspx for revised estimates.

Etienne-Manneville S

2013-07-01

303

The Migration Game  

Science.gov (United States)

This site features an interactive Migration Game created by the Migratory Bird Center at the Smithsonian National Zoological Park. In it, you can help Wanda the Wood Thrush travel from her winter home in Costa Rica to her summer home in Maryland by answering questions regarding migration in general and specific migratory habits of the wood thrush.

2008-01-01

304

Migration Networks in Senegal  

Digital Repository Infrastructure Vision for European Research (DRIVER)

This paper investigates the importance and role of migration networks in Senegal using a new nationally representative survey conducted in 2006-2007. Using a sample of 1707 Senegalese households I explore potentially differential effects of networks on international migration depending on their char...

Chort, Isabelle

305

Experimental evidence of the effect of nutrient enrichment on the zooplankton in a Brazilian coastal lagoon  

Directory of Open Access Journals (Sweden)

Full Text Available Non-treated sewage disposal is one of the main impacts to which Imboassica Lagoon has been subjected. The aim of this study was to evaluate the effect of a potential increase in the artificial enrichment on the environmental conditions and zooplankton of this system. To this end, an experimental study was conducted in mesocosms where nutrients were added daily. Bacterial numbers, chlorophyll-a, and picoplanktonic cyanobacteria densities showed an increase with the availability of nutrients. Bacterio- and phytoplankton seemed to be regulated by the rotifers Brachionus rotundiformis and Hexarthra brandorffi.

KOZLOWSKY-SUZUKI B.; BOZELLI R. L.

2002-01-01

306

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

1992-01-01

307

[Non-predatory mortality of the crustacean zooplankton and its possible causes (a literature review)  

UK PubMed Central (United Kingdom)

General mortality (death rate, d) in natural populations of the crustacean zooplankton is calculated as difference between birth rate (b) and population growth rate (r). The mortality includes both predatory (consumptive) and non-predatory (non-consumptive), or "natural", deaths of individuals due to senescence, diseases and parasites, starvation, limiting physical and chemical factors of anthropogenic or natural origin. Modem methods of evaluation of non-predatory mortality of the plankton crustaceans, including direct method based on live/dead sorting by special staining of samples and measurements of sedimentation rate of dead individuals using a sedimentation trap are briefly characterized. Possible causes of non-predatory mortality of crustacean are examined based on different (mainly fresh) temperate water bodies. The possible causes are classified as: physical conditions including temperature, wind effects, ultraviolet radiation, water turbidity, current velocity; chemical conditions including concentration of dissolved oxygen, pH value, water toxicity of both anthropogenic (due to pollutant inflow) and natural (due to cyanobacterial bloom and ingestion of some toxic diatoms by copepods) origin; parasites and epibionts; bottom-up factors or food limitation including quantity and quality of food, the former as content of carbon (energy) and the latter as content of essential compounds in food. It is concluded that, for the populations of crustacean herbivorous zooplankton, the biotic factors appeared to be more important and more probable causes of non-predatory mortality than the abiotic ones, under conditions of non-acid water bodies of the temperate zone when the current speed is less than critical one (0.25 m/c) and in absence of the anthropogenic toxicants. These factors are primarily a food poor quality due to low content of phosphorus, nitrogen, polyunsaturated fatty acids of omega3 family and others, as well as microparasites causing infections and, to a lesser extent (just in blooming water bodies), natural toxicity of cyanobacteria. Non-optimal for the zooplankton physical and chemical factors, as causes of non-predatory mortality of plankton crustaceans, appeared to be less important because of their acting episodically in time locally in space, so the zooplankton is able to avoid their effects and to regenerate fast.

Dubovskaia OP

2009-03-01

308

A sampler-incubator for studying zooplankton grazing and phytoplankton production.  

Directory of Open Access Journals (Sweden)

Full Text Available A new instrument to quantify the zooplankton grazing on phytoplankton and the phytoplankton growth is described. This instrument consists of two cylindrical chambers and a mechanical system for shutting, by a messenger both the chambers simultaneously. With this instrument the grazing may be evaluated by counting the algal cells at the beginning and the end of the experiment as well as by the radioisotope technique. This instrument combines the advantages of others used to the same aim by other authors; e.g. Gliwicz (1968), Haney (1971), Hart & Christmas (1984). As an example, the results of two experiments are reported.

Oscar RAVERA; Silvia SCOTTO

1999-01-01

309

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

Energy Technology Data Exchange (ETDEWEB)

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.

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

1992-03-01

310

Vertical cable seismic applications  

Energy Technology Data Exchange (ETDEWEB)

In November 1995, Texaco Inc. and PGS formed an alliance for commercializing a new method to acquire 3-D marine seismic. The venture offers vertical cable seismic (VCS) data acquisitions and processing. The 3-D technique was developed by Texaco at its exploration and production technology center in Houston. The vertical cables yield high-resolution 3-D data which is acquired in a truly 3-D sense as opposed to conventional acquisition using a series of 2-D lines. Positioning of arrays is well defined, which results in complete and accurate data analysis.

Havig, S.O. [Petroleum Geo-Services AS, Houston, TX (United States); Krail, P.M. [Texaco, Inc., Houston, TX (United States)

1996-05-01

311

A vertical cephalometric analysis.  

UK PubMed Central (United Kingdom)

Correctly assessing open-bite malocclusions has remained problematic because clinicians have not had entirely reliable methods of determining the exact amount of skeletal and dental contributions to the problem. A new cephalometric technique, the vertical cephalometric analysis, offers orthodontists a system that precisely identifies the percentage of skeletal and dentoalveolar components that open-bite patients have. The vertical cephalometric analysis offers a discriminating diagnostic method for evaluating, diagnosing, and treatment planning for patients with open bite. This technique will allow clinicians to classify patients with accuracy, as well as to establish prognoses and select therapies.

Alió Sanz JJ; Iglesias Conde C

2007-01-01

312

Tomography wave equation migration  

Energy Technology Data Exchange (ETDEWEB)

With the aid of both the 2-D Fourier transform theory and the CT technique-projection and reconstruction principle in image processing, the author uses scaler wave equation to develop CT migration formulas-projection and reconstruction expressions for seismic data processing. Applying the formulas to the migration of a horizontal seismic stack section, the author can obtain a conventional migration section, or a migration section without noise or with interpolated traces. This method is available to migrate the horizontal stack section which has low S/N ratio or unequal group intervals. It has advantages such as high S/N ratio, no boundary reflection effect and so forth. The theoretical and real data processing results obtained using this method are shown in this paper.

Huaxiang, M.

1990-01-01

313

Migration and Environmental Hazards.  

UK PubMed Central (United Kingdom)

Losses due to natural hazards (e.g., earthquakes, hurricanes) and technological hazards (e.g., nuclear waste facilities, chemical spills) are both on the rise. One response to hazard-related losses is migration, with this paper offering a review of research examining the association between migration and environmental hazards. Using examples from both developed and developing regional contexts, the overview demonstrates that the association between migration and environmental hazards varies by setting, hazard types, and household characteristics. In many cases, however, results demonstrate that environmental factors play a role in shaping migration decisions, particularly among those most vulnerable. Research also suggests that risk perception acts as a mediating factor. Classic migration theory is reviewed to offer a foundation for examination of these associations.

Hunter LM

2005-03-01

314

Dissociated vertical deviation  

Directory of Open Access Journals (Sweden)

Full Text Available Dissociated vertical deviation (DVD) is a common type of squint usually seen during the course of infantile esotropia. It is characterised by an increased angle of hyperdeviation of the nonfixating eye while patient is in the visual inattention state. The treatment of DVD is surgical. This condition must be well-defined and differentiated from overaction of the inferior oblique muscle.

?brahim ERBA?CI; K?vanç GÜNGÖR; Necdet BEK?R

2002-01-01

315

Colisión en dirección vertical  

Scientific Electronic Library Online (English)

Full Text Available Abstract in spanish 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 in (more) ferior 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 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 (more) 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

Manzur, A

2008-06-01

316

Asymmetric Vertical Integration  

Digital Repository Infrastructure Vision for European Research (DRIVER)

We examine vertical backward integration in a reducedform model of successive oligopolies. Our key findings are: (i) There may be asymmetric equilibria where some firms integrate and others remain separated, even if firms are symmetric initially; (ii) Efficient firms are more likely to integrate ver...

Buehler, Stefan; Schmutzler, Armin

317

Asymmetric vertical integration  

Digital Repository Infrastructure Vision for European Research (DRIVER)

We examine vertical backward integration in a reduced-form model of successive oligopolies. Our key findings are: (i) There may be asymmetric equilibria where some firms integrate and others remain separated, even if firms are symmetric initially; (ii) Efficient firms are more likely to integrate ve...

Buehler, Stefan; Schmutzler, Armin

318

Cyclic vertical deviation.  

Digital Repository Infrastructure Vision for European Research (DRIVER)

A 34-year-old Caucasian woman underwent craniofacial surgery for fronto-orbital fibrous dysplasia. She developed vertical diplopia for 10 months after surgery, which then disappeared for 1 month. The deviation returned with a circadian pattern, 24 hours of hypertropia and exotropia with diplopia alt...

Metz, H S; Searl, S S

319

VSP migration: Synthetic and field examples  

International Nuclear Information System (INIS)

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

1987-01-01

320

Spatiotemporal dynamics in a reaction–diffusion toxic-phytoplankton–zooplankton model  

Science.gov (United States)

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.

Rao, Feng

2013-08-01

 
 
 
 
321

Metabolic Theory of Ecology and diversity of continental zooplankton in Brazil  

Directory of Open Access Journals (Sweden)

Full Text Available Several ecological hypotheses try to explain geographical patterns in biodiversity. The Metabolic Theory of Ecology (MTE) predicts that temperature is the main determinant of richness patterns for ectothermic organisms and that the relationship between richness (lnS) and temperature (1/kT) is a linear relationship with angular coefficient (b) near -0.65. This study tested the MTE for continental zooplankton diversity in 63 lakes in Brazil. Copepoda, Cladocera and Rotifera, as well as the three groups combined, showed different patterns from that predicted by MTE, with b values equal to 0.871, 0.516, 0.720 and 0.901, respectively. Temperature explains 12.7% of the richness of Copepoda, 5.3% of Cladocera, 6.7% of Rotifera, and 11.4% of all zooplankton groups together. Several studies have shown that the MTE does not apply to many terrestrial groups, perhaps because the model does not consider variances generated by other factors such as environmental spatial range, body size and other variables. The present study confirms this point of view, expanding it to continental aquatic invertebrates as well. macroecology; biodiversity; Copepoda; Cladocera; Rotífera; temperature gradients

Olívia Penatti Pinese; Fernanda Aparecida da Silva Cassemiro; José Fernando Pinese; José Alexandre Felizola Diniz-Filho

2011-01-01

322

Estimating release rates of phosphorus from zooplankton: model and experimental verification  

Energy Technology Data Exchange (ETDEWEB)

The flux of phosphorus in a zooplankton-phytoplankton system is described by a simple compartment model, with differential equations for grazing, growth and reproduction of animals, and release and recycling of P. The mean release rates from zooplankton for a given period are derived for cases restricted to animals feeding on algae at densities above the incipient limiting food concentration. The model is used to analyze short term incubation experiments with Daphnia pulex feeding on Scenedesmus sp. and Daphnia longispina feeding on Rhodomonas lacustris in dim light. When food organisms were saturated with P. total release rates were in the range 1.1-1.5 ..mu..g P (mg dry wt)/sup -1/h/sup -1/ in accordance with a maximal excretion rate of 0.8 ..mu..g P (mg dry wt)/sup -1/h)/sup 1/ predicted by the model of Peters. Phosphorus-starved phytoplankton, containing less P, gave much lower release rates, about 0.05 ..mu..g P (mg dry wt)/sup -1/h/sup -1/, only 10% of the excretion rate predicted by the model of Peters.

1985-07-01

323

Associations of cyanobacterial toxin, nodularin, with environmental factors and zooplankton in the Baltic Sea.  

Science.gov (United States)

Concentrations of a cyanobacterial toxin, nodularin, were measured in the Baltic Sea in 1998 and 1999. Statistical associations of nodularin concentrations with environmental factors were tested by multiple regression analysis. To reveal the toxin-producing organism, colonies of Aphanizomenon and filaments of Nodularia were picked and analyzed for peptide toxins. It was also investigated whether there was an association with zooplankton and Nodularia. All the measured seston samples contained nodularin, but other toxins were not detected by the HPLC analysis. In both years, the highest nodularin concentrations were found at the surface water layer. The nodularin concentrations were positively correlated with silicate concentrations in water. High concentrations of silica in surface water may indicate recent upwelling, which in turn renders surface water rich in nutrients. This upwelling is likely to intensify cyanobacterial growth and toxin production, which may explain this rather unexpected result. The picked Aphanizomenon colonies did not contain nodularin and the dissolved nodularin concentrations were below detection limit. Thus it was concluded that most of the nodularin was bound to Nodularia cells. The abundances of zooplankton (copepods, rotifers, and cladocerans) were unrelated to Nodularia, but were positively associated with Aphanizomenon. PMID:14681737

Repka, S; Meyerhöfer, M; von Bröckel, K; Sivonen, K

2003-12-23

324

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.

325

Migration of cells in the rat corneal epithelium  

Energy Technology Data Exchange (ETDEWEB)

The migration of cells in the rat corneal epithelium was studied using continuous labelling with tritiated thymidine ({sup 3}H)TdR, during a 24 h period. Most mitoses resulted in 2 new basal cells. Cells leaving the basal cell layer moved vertically to the surface in all areas of the corneal epithelium. The first labelled cells reached the surface 3 days after the first injection of ({sup 3}H)TdR. No stream of cells from the conjunctiva to the cornea in the limbal areas was observed, and no centripetal migration of epithelial cells in the cornea could be observed. After a cell has lost its attachment to the basement membrane, it is committed to be exfoliated in a few days without undergoing mitosis. Thus the slow centripetal migration of epithelial cells and the exchange of centrally located cells, as indicated by clinical findings and experimental studies, can only be explained by migration of basal cells. (author).

Haaskjold, E.; Bjerknes, E. (Institute of Pathology, University of Oslo, Rikshospitalet (Norway)); Bjerknes, R. (Institute of Informatics, University of Oslo, Blindern, Oslo (Norway))

1989-01-01

326

Migration of cells in the rat corneal epithelium  

International Nuclear Information System (INIS)

The migration of cells in the rat corneal epithelium was studied using continuous labelling with tritiated thymidine [3H]TdR, during a 24 h period. Most mitoses resulted in 2 new basal cells. Cells leaving the basal cell layer moved vertically to the surface in all areas of the corneal epithelium. The first labelled cells reached the surface 3 days after the first injection of [3H]TdR. No stream of cells from the conjunctiva to the cornea in the limbal areas was observed, and no centripetal migration of epithelial cells in the cornea could be observed. After a cell has lost its attachment to the basement membrane, it is committed to be exfoliated in a few days without undergoing mitosis. Thus the slow centripetal migration of epithelial cells and the exchange of centrally located cells, as indicated by clinical findings and experimental studies, can only be explained by migration of basal cells. (author).

1989-01-01

327

Signs of Migration  

Science.gov (United States)

Students research and examine the practical and instinctual characteristics of the migration patterns of many different animal species. The will also work in groups to illustrate their research and make presentations.

Kqed

2007-08-30

328

International Organization for Migration  

Science.gov (United States)

The International Organization for Migration (IOM) is an intergovernmental body "committed to the principle that humane and orderly migration benefits migrants and society." IOM currently has 69 member states and 48 observer states worldwide. In addition, numerous international governmental organizations and non-governmental organizations hold observer status with IOM, assisting in the study, development, and enactment of migration policies. The IOM Website offers a wealth of information on the organization and its initiatives. The site posts official IOM news releases and statements and provides access to IOM publications including books, surveys, studies, journals, newsletters, and informational updates. IOM also hosts MIGRATION WEB, a searchable and browseable gateway to a bevy of information resources on the Internet.

329

Migration = cloning; aliasiing  

DEFF Research Database (Denmark)

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.

Hüttel, Hans; Kleist, Josva

1999-01-01

330

Migration og etnicitet  

DEFF Research Database (Denmark)

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

Christiansen, Connie CarØe

2004-01-01

331

Defining lifestyle migration  

Directory of Open Access Journals (Sweden)

Full Text Available This paper seeks to provide a conceptual framework for studying migration to the Algarve by Northern Europeans. ‘Lifestyle migration’ is suggested as a generic term for this trend, which is part of a recent but flourishing global social phenomenon. I also point to the glaring gap in the literature as far as empirical studies based in the Algarve are concerned, and make suggestions for a research agenda.

Kate Torkington

2010-01-01

332

Migration and Narration  

Directory of Open Access Journals (Sweden)

Full Text Available The following article aims to work out the main narrative techniques of “telling migration”. The conclusions drawn on the subject of migration and narration are based on a one-year field work study, combining participant observation with interviewing. This study took place in New Zealand concentrating on German immigrants between 1936 and 1996. The main source for my analysis given in this paper is provided by 102 people I interviewed. The texts of these biographically-focussed interviews allowed me to work not only on an ethnographical history of migration but also to gain insights into peoples’ experiences, and over and above that, to learn what kind of stories and techniques of storytelling emigration creates. The book focuses on a comparatively wide time frame of sixty years (Boenisch- Brednich 2001). This makes it possible to analyse very different periods of migration and groups of migrants, contrasting social categories as well as exploring differences in education, milieu, age and gender. Furthermore, it becomes obvious that although all migrants were leaving Germany and arriving in New Zealand, they experienced what were in effect very different countries through time – different Germanys, different New Zealands. To work out the changing reasons for migrating (work migration, refuge, global lifestyle, etc.) inside western societies is a major theme the book is aiming for. A second approach is to investigate migration from the perspective of focussing on everyday life, an investigation on the basis of personal experiences, such as “work, housing, food, celebrations, social life”. A special focus is set on the analysing of “mental narratives” as key stories, examples, comparatives etc. The central questions of this project were: What kind of strategies do people use to cope with a major changes in their biography, as constituted by emigration? What does integration really mean and how does it work for different groups? What kind of collective and individual stories does migration create? In which ways does retroperspection work as a technique for creating autobiographies in oral transmission?

Brigitte Boenisch-Brednich

2002-01-01

333

Vertically brushing electric toothbrush  

UK PubMed Central (United Kingdom)

The vertically brushing electric toothbrush includes toothbrush handle, toothbrush head, speed varying gear set, link rod unit and toothbrush head driving pull rod. The speed varying gear set is provided with eccentric shaft to convert rotation motion into linear reciprocation of the toothbrush head driving pull rod the toothbrush head has squared column in the back to penetrate the hole in the toothbrush handle for loose fitting with the toothbrush head driving pull rod and one guide shaft perpendicular to the axis of the toothbrush handle is fixed onto the toothbrush handle via the guide hole to make the toothbrush head reciprocate linearly along the guide shaft. The electric toothbrush of the present invention has the bristles brush vertically along the tooth gap to eliminate dirt.

BANGJUN HUANG

334

INTEGRATED VERTICAL PLANTING MODULE  

UK PubMed Central (United Kingdom)

The invention includes a box with a water inlet on top, drainage outlets in the bottom, and multiple nursing cells horizontally and vertically arranged inside. The nursing cells are permanently linked inside the box. Each nursing cell has reservoir grooves in the bottom, and light and air circulation cells around all sides. A slit is placed on adjacent walls of nursing cells in each row, and also in each column, thereby connecting two adjacent nursing cells. The planting module is integrated, ready for use without any assembly required. Light and air circulation cells around nursing cells provide sufficient sunlight for growth of the plants inside. Reservoir grooves in the cell bottom can better keep moisture and nutrients inside. Horizontal and vertical slits in the cell walls provide even and rapid distribution for water that enters the module.

ZHAO FEIYUN; ZHAO LIN

335

INTEGRATED VERTICAL GREENING MODULE  

UK PubMed Central (United Kingdom)

The invention includes a box with a water inlet on top, drainage outlets in the bottom, and multiple nursing cells horizontally and vertically arranged inside. The nursing cells are permanently linked inside the box. Each nursing cell has reservoir grooves in the bottom, and light and air circulation cells around all sides. A slit is placed on adjacent walls of nursing cells in each row, and also in each column, thereby connecting two adjacent nursing cells. The planting module is integrated, ready for use without any assembly required. Light and air circulation cells around nursing cells provide sufficient sunlight for growth of the plants inside. Reservoir grooves in the cell bottom can better keep moisture and nutrients inside. Horizontal and vertical slits in the cell walls provide even and rapid distribution for water that enters the module.

ZHAO FEIYUN; ZHAO LIN

336

Oryctes rhinoceros vertical trap  

UK PubMed Central (United Kingdom)

The utility model discloses an oryctes rhinoceros vertical trap which comprises a rain-proofing frame [1], a crisscross pest gear plate [2] and a pest catcher [3], wherein, the rain-proofing frame comprises a mobile ring [11], a funnel cover [12] and a support [13] the mobile ring [11] is fixed on the top end of the funnel cover [12] the funnel cover is fixed on the support the crisscross pest gear plate [2] is a baffle with a crisscross cross section the pest catcher [3] is a container with spillway holes [31] around. The oryctes rhinoceros vertical trap has the advantages of simple structure, convenient manufacturing, good pest catching effect and convenient use, traps the oryctes rhinoceros with the tropism of adult oryctes rhinoceros to the synthetic pheromone, and can be widely applied to coconut growing areas and palm botanical garden districts.

SHANCHUN HUANG; WEIQUAN QIN; ZILONG MA; CHAOXU LI; KEMING LI; ZHAOJUN LU

337

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

Digital Repository Infrastructure Vision for European Research (DRIVER)

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 co...

Jarl Eivind LØVIK; Gösta KJELLBERG

338

Composition and abundance of zooplankton in the limnetic zone of seven reservoirs of the Paranapanema River, Brazil.  

Science.gov (United States)

The species composition and abundance of the zooplankton community of seven reservoirs of the Paranapanema River, located between 22 degrees 37'-23 degrees 11'S and 48 degrees 55'-50 degrees 32'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. PMID:12530191

Sampaio, E V; Rocha, O; Matsumura-Tundisi, T; Tundisi, J G

2002-11-05

339

Composition and abundance of zooplankton in the limnetic zone of seven reservoirs of the Paranapanema River, Brazil  

Directory of Open Access Journals (Sweden)

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.

SAMPAIO E. V.; ROCHA O.; MATSUMURA-TUNDISI T.; TUNDISI J. G.

2002-01-01

340

Sources of suspended organic matter and selective feeding by zooplankton in an estuarine mangrove ecosystem, as traced by stable isotopes  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Between January 1995 and August 1996, suspended matter and zooplankton were sampled at different locations in a mangrove ecosystem located in the Gautami Godavari Estuary and adjacent Kakinada Bay (Andhra Pradesh, India). Suspended matter was sampled at 13 different stations, and was found to have a...

Bouillon, S.; Mohan, P.C.; Sreenivas, N.; Dehairs, F.A.

 
 
 
 
341

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

Digital Repository Infrastructure Vision for European Research (DRIVER)

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 d...

Roberta Bettinetti; Letizia Garibaldi; Barbara Leoni; Silvia Quadroni; Silvana Galassi

342

Reduction in labile copper in the 7-day Ceriodaphnia dubia toxicity test due to the interaction with zooplankton food.  

Science.gov (United States)

Due to the increased popularity of zooplankton toxicity tests, it is important to investigate potential confounding factors. Though zooplankton food has been studied extensively to meet the nutritional needs of the zooplankton, less research has been done on whether food addition reduces the toxicity of metals in the tested sample. This investigation combines toxicity tests and metal speciation analysis to determine whether the EPA recommended food of YCT (yeast, cerophyll, and trout chow) and Pseudokirchneriella subcapitata (formerly Selenastrum capricornutum) reduces copper toxicity by decreasing the concentration of labile copper. Toxicity tests were performed with Ceriodaphnia dubia on culture water spiked with 0, 787, and 1574 nM copper with five different food levels. A Chelex-100 cation exchange resin and a graphite furnace-atomic absorption spectrophotometer were used in conjunction with the toxicity tests to measure the amount of labile copper in the culture water. At the EPA recommended food dosage, the C. dubia food has a chelating capacity of approximately 500 nM Cu. For both concentrations of spiked culture water, the toxicity to C. dubia was reduced with increasing food level, which seemed to be both from a decrease in labile copper concentration and an increase in the nutritional condition of the zooplankton. PMID:15234169

Hauri, James F; Horne, Alex J

2004-08-01

343

Responses of zooplankton in lufenuron-stressed experimental ditches in the presence or absence of uncontaminated refuges.  

UK PubMed Central (United Kingdom)

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.

López-Mancisidor P; Van den Brink PJ; Crum SJ; Maund SJ; Carbonell G; Brock TC

2008-06-01

344

Responses of Zooplankton in Lufenuron-Stressed Experimental Ditches in the Presence or Absence of Uncontaminated Refuges.  

UK PubMed Central (United Kingdom)

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 post application 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.

López-Mancisidor P; Van den Brink P; Crum S; Maund S; Carbonell G; Brock T

2008-01-01

345

Responses of zooplankton in lufenuron-stressed experimental ditches in the presence or absence of uncontaminated refuges.  

Science.gov (United States)

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

López-Mancisidor, Patricia; Van den Brink, Paul J; Crum, Steven J H; Maund, Steve J; Carbonell, Gregoria; Brock, Theo C M

2008-01-22

346

A comparison of growth rate of halibut larvae (Hippoglossus hippoglossus L.) fed wild zooplankton and enriched Artemia  

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Halibut larvae at an age of 267 day degrees post hatching, were reared through first feeding, outdoors in 100 l plastic bags. There were three feeding regimes: wild zooplankton, Artemia enriched on the algae Isochrysis galbana and Artemia enriched with "Super Selco". The larval growth was ...

Skjolddal, Lillian; Harboe, Torstein; Næss, Tore Håkon; Naas, Kjell Emil; Rabben, Håvard

347

Migration Type III  

Science.gov (United States)

Migration type IIIMigration of objects embedded in disks (and the accompanying eccentricity evolution) is becoming a major theme in planetary system formation.The underlying physics can be distilled into the notion of disk-planet coupling via Lindblad resonances, which launch waves, sometimes spectacular spiral shock waves in gas disks. The wave pattern exchanges angular momentum with the planet. That causes (i) migration, (ii) eccentricity evolution, and (iii) gap opening by sufficiently massive planets.A competing source of disk-planet interaction, the corotationaltorques, are much less conspicuous (corotation does not produce easilydetectable waves, as galaxy observers can attest) and have often been missed in the analysis of planet migration. If spiral waves are like waves at Goleta beach, then the corotation acts more like a stealthy riptide. Corotationalflows lie at the basis of a new, surprisingly rapid, mode of migration (type III),superseding the standard type II migration (with a gap), and revising the speed of type I migration (without a gap). The talk will contain results obtained at KITP, e.g., an analytical derivation of da/dt in type III motion. It will be illustrated by videos of high-resolution numerical simulations obtained with different implementations of the Piecewise Parabolic Method hydrodynamics.

Artymowicz, Pawel

2004-03-01

348

Lake Roosevelt Fisheries Evaluation Program, Part B; Limnology, Primary Production, and Zooplankton in Lake Roosevelt, Washington, 1998 Annual Report.  

Energy Technology Data Exchange (ETDEWEB)

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.

Shields, John; Spotts, Jim; Underwood, Keith

2002-11-01

349

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

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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.

Jarl Eivind LØVIK; Gösta KJELLBERG

2003-01-01

350

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

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Full Text Available 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 samples were collected monthly from May2004 – April 2006 at low and high tides from ten stations according to APHA methods. These were analysedfor temperature, turbidity, transparency, salinity, dissolved oxygen (DO), biological oxygen demand (BOD),pH and nutrients. Zooplankton was identified microscopically. Species diversity was calculated using standardindices. Data was analysed using analysis of variance, Duncan multiple range and descriptive statistics.Zooplankton demonstrated significant temporal variation (P<0.05). A total of 85 species dominated bycopepods (43.4%) were identified. Diversity indices for copepods were: 1.0±0.03 (Margalef) and 0.5±0.02(Shannon). Water temperature 28.6±0.06cC, turbidity 3.6±0.32 NTU and transparency 0.7±0.01m showedsignificant temporal variations (P<0.05). Water chemical parameters were: salinity, 14.4±4.67‰; DO,5.0±0.10mg/l; BOD, 3.3±0.09mg/l and alkalinity, 84.1±1.41mg/l. Phosphate and ammonia exceeded FEPA andUSEPA acceptable levels for natural aquatic bodies. Phosphate demonstrated significant spatial variation(P<0.05). The presence of dominant copepods indicates an environment under stress. The domestic andindustrial effluents should be recycled or and treated instead of being discharged into this creek.

Davies, Onome Augustina

2009-01-01

351

Globalization, Migration and Development  

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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 women)of 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.

George, Susan; Samuel, John

2002-01-01

352

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)

1980-03-14

353

Occlusal vertical dimension in prosthodontics.  

UK PubMed Central (United Kingdom)

Occlusal vertical dimension is important in all aspects of prosthodontics. Unfortunately, there is no scientific method of determining the correct occlusal vertical dimension. The amount of interocclusal rest space (IRS) is a rough guide since muscle tone, which determines the space, is variable. IRS varies greatly from one patient to the next. It will automatically be correct when the occlusal vertical dimension is correct. IRS should not be interfered with regardless of its size. Many techniques have been used for determining occlusal vertical dimension in dentulous and edentulous patients. Regardless of the technique, the occlusal vertical dimension must be determined carefully by the dentist for a successful prosthesis.

Chou TM; Moore DJ; Young LJ Jr; Glaros AG; Chou JI

1996-05-01

354

Vertical distribution of radionuclides in soil  

International Nuclear Information System (INIS)

[en] 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)

1990-01-01

355

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

Directory of Open Access Journals (Sweden)

Full Text Available From April 1992 to May 1993, zooplankton samples were collected monthly by means of horizontal tows in nine sites of the lake. Prior to the towing, temperature of surface water, transparency (Secchi), pH and dissolved oxygen were evaluated. A total of 31 zooplankton forms, including 14 species of rotifers, three copepods, five cladocerans and one ostracod, as well as protozoans (mainly vorticellids and ciliates), were detected. Rotifers were the dominant organisms, mainly Brachionus havanaensis (27.6 ind l-¹), B. angularis (6.9 ind l-¹), Keratella cochlearis (4.9 ind l-¹), Conochilus unicornis (10.8 ind l-¹) and C. dossuarius (3.1 ind l-¹). Within crustaceans, higher densities were shown by larvae (nauplii and copepodites) of calanoid (16.8 ind l-¹) and cyclopoid (15.6 ind l-¹) copepods, as well as Arctodiaptomus dorsalis (2 ind l-¹), Mesocyclops edax (0.5 ind l-¹), and the cladocerans Bosmina longirostris (1.6 ind l-¹) and Diaphanosoma brachyurum (0.5 ind l-¹). Densities were low, probably because of a high predation pressure imposed by fishes. A gradual increase in total zooplankton density related with a progressive diminution of transparency was observed throughout the sampling period. Zooplankton densities in the stations located at the central part of the lake were higher when compared with those at a more peripheral position. Time variation in rotifer's relative abundance was directly related to temperature fluctuations. The low density and diversity values, the small size of the zooplankters, the presence of an important number of indicator species, and the calanoid copepods: other planktonic crustaceans low ratio, are all indicators of eutrophy. Evidences suggest that the eutrophication process of Lake Catemaco is still progressing rapidly.Entre abril de 1992 y mayo de 1993, se realizaron mensualmente recolectas subsuperficiales de zooplancton, con red, en nueve localidades del lago, en donde también se determinaron la temperatura superficial, la visibilidad del disco de Secchi, el pH y la concentración de oxígeno disuelto. Entre las 31 formas de plancton detectadas en las distintas submuestras se registraron 14 especies de rotíferos, tres de copépodos, cinco de cladóceros y un ostrácodo, además de protozoarios, principalmente vorticélidos y ciliados. Los rotíferos fueron los organismos más abundantes; Brachionus havanaensis fue la especie dominante, seguida por Conochilus unicornis, Brachionus angularis, Keratella cochlearis y Conochilus dossuarius. Entre los copépodos destacaron Arctodiaptomus dorsalis y Mesocyclops edax, además de sus nauplios y copepoditos, y entre los cladóceros Diaphanosoma brachyurum, Bosmina longirostris, y Bosminopsis sp. Las densidades observadas en los grupos dominantes del zooplancton fueron bajas; sin embargo, a lo largo del período de estudio se observó un incremento paulatino en la densidad zooplantónica total, relacionado con una disminución progresiva de la visibilidad del disco de Secchi. Las densidades más altas se detectaron en los sitios más alejados de la costa. Las variaciones estacionales en la abundancia relativa de los rotíferos estuvieron estrechamente relacionadas con las fluctuaciones de la temperatura. Los bajos valores de densidad y diversidad, el pequeño tamaño de los zooplancters, la presencia de un importante número de especies indicadoras y la baja razón copepodos calanoides: otros crustáceos planctónicos, son todos indicadores de condiciones eutróficas. Además, existen evidencias de que el proceso de eutrofización del lago está avanzando aceleradamente.

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

1998-01-01

356

Size and dry weight of main zooplankton species in Bariri reservoir (SP, Brazil).  

Science.gov (United States)

In order to generate a database for secondary production studies in the São Paulo State (Brazil) reservoirs, the size and dry weight of 13 sooplankton species from Bariri reservoir (middle Tietê River) were determined. Diameter and dry weight of eggs from some cladoceran and copepod species were also determined. Sizes varied from 108.6 microm (Keratella tropica) to 2488.6 microm (females of Argyrodiaptomus azevedoi), while dry weights varied between 0.025 microg (K. tropica) and 51.250 microg (females of A. azevedoi). Egg diameters varied between 75.0 microm (Mesocyclops ogunnus) and 171.8 microm (Ceriodaphnia silvestrii), while egg dry-weights varied between 0.074 microg (Acanthocyclops robustus) and 0.865 microg (Bosmina hagmanni). Size and dry weight distribution of the zooplanktonic organisms was not linear in the bariri reservoir. PMID:18476312

González, E J; Matsumura-Tundisi, T; Tundisi, J G

2008-02-01

357

Zooplankton of an urban stretch, Itapecerica river, Divinópolis, Minas Gerais, Brazil  

Directory of Open Access Journals (Sweden)

Full Text Available The aim of this project was to study the zooplanktonic composition of the Itapecerica river in its 29kmurban section across the city of Divinópolis, state of Minas Gerais. Eight sampling points were established within thissection, six in lotic and two in lentic waters. Samples were taken monthly from March/2002 to February/2003 totalizing84 samples. A plankton net with a mesh opening size of 35 ?m was utilized for sampling. Temperature, pH, dissolvedoxygen and electrical conductivity measurements were also taken during sampling. 101 taxa were registered, of which35 were Protozoa, 52 Rotifera, 10 Cladocera and four Copepoda. The number of taxa was considered high whencompared to similar studies. Among the richest group, rotifers, the most expressed genera were Lecane and Brachionus.This study recorded the first appearance of the exotic species Kellicottia bostoniensis (Rousselet 1908) for the sub-basinof Itapecerica river.

Ferraz, H. D. A.; Landa, G. G.; Paprocki, H.

2009-01-01

358

The distribution of micro zooplankton in the lagoon environments; La distribuzione del microzooplancton negli ambienti lagunari  

Energy Technology Data Exchange (ETDEWEB)

The aim of this work is to verify the possible use of micro zooplankton as a biological indicator in aquatic environments. In particular, studies carried out in lagoon environments are reported, relatively to the Venice lagoon and the Pontine coastal lakes (Italy). New methodologies to assess the micro plankton component are developed and tested, particularly the concentration and count steps. The use of the same methodologies to assess nano plankton component, as biological indicator. are reported. [Italian] Nel presente lavoro viene analizzata la possibilita' di utilizzare il microzooplancton quale indicatore biologico negli ambienti acquatici (mmarini, acquadulcicoli, salmastri). In particolare, vengono riportati gli studi effettuati dall'ENEA (National Agency for New Technology, Energy and the Environment) su tale componente in ambienti lagunari, con riferimento alla laguna di Venezia e alle lagune pontine.

Grenni, P.; Creo, C. [ENEA, Centro Ricerche Casaccia, Rome (Italy). Dipt. Ambiente

1998-07-01

359

Biomass estimates of freshwater zooplankton from length-carbon regression equations  

Directory of Open Access Journals (Sweden)

Full Text Available We present length/carbon regression equations of zooplankton species collected from Lake Maggiore (N. Italy) during 1992. The results are discussed in terms of the environmental factors, e.g. food availability, predation, controlling biomass production of particle- feeders and predators in the pelagic system of lakes. The marked seasonality in the length-standardized carbon content of Daphnia, and its time-specific trend suggest that from spring onward food availability for Daphnia population may be regarded as a simple decay function. Seasonality does not affect the carbon content/unit length of the two predator Cladocera Leptodora kindtii and Bythotrephes longimanus. Predation is probably the most important regulating factor for the seasonal dynamics of their carbon biomass. The existence of a constant factor to convert the diameter of Conochilus colonies into carbon seems reasonable for an organism whose population comes on quickly and just as quickly disappears.

Marina MANCA; Patrizia COMOLI

2000-01-01

360

Species assemblages of zooplanktonic crustaceans in mountain shallow ponds of Chile (Parque Cañi)  

Scientific Electronic Library Online (English)

Full Text Available Abstract in english Even though the Chilean lakes are characterized by their oligotrophy, a transition from oligotrophy to mesotrophy, due human intervention, has been reported in some lakes. Nevertheless, there are still some pristine and unpolluted small lakes and ponds in mountain zones, free of human intervention and surrounded by native forests. Nine unpolluted, oligotrophic and pristine water bodies located in Cañi Park, a mountain zone with altitudes between 1000 to 1500 m a.s.l and (more) forests where Nothofagus dombeyi, N. pumilio and Araucaria araucana predominate, were studied. For each sampled lake, zooplankton was collected and environmental parameters were obtained (conductivity, total dissolved solids, and chlorophyll concentration). A null model of species co-occurrence was applied to determine randomness in species associations. All sites revealed low species richness (

Ríos, Patricio De los; Roa, Guido

2010-02-01

 
 
 
 
361

The vertical transportation handbook  

CERN Multimedia

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

Strakosch, George R

2010-01-01

362

Vertical Motion Simulator  

Science.gov (United States)

The Vertical Motion Simulator (VMS), at the NASA Ames Research Center, is an advanced flight simulation facility. This Web site provides thorough descriptions of all of the VMS systems. The VMS is a full immersion environment, complete with customizable cockpit, controls, and instrumentation to give the appearance of any aerospace vehicle. One of its most intriguing characteristics is "out-the-window graphics." This allows the pilot to see computer generated imagery of real locations, so virtually everything is identical to the actual flying experience. Even aircraft that are still in the design stage can be simulated on the VMS.

363

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

2012-01-01

364

Vertical junction solar cell  

Energy Technology Data Exchange (ETDEWEB)

This patent describes an improved vertical junction solar cell. It comprises: a silicon semiconductor body having a front surface; parallel grooves formed ins aid front surface of the body and disposed normal to the front surface, the grooves defining a corresponding walls each having a top surface and side surfaces and groove bottoms between adjacent ones of the walls at least one photoro Haic junction extending along the side and top surface of the walls; and focusing coverslide means for focusing incident light impinging the solar cell onto the top surfaces of the walls and away from the groove bottoms to thereby reduce radiation degradation of the solar cell.

Warfield, D.B.

1992-03-24

365

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 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.

1997-01-01

366

The construction of Cs 137 migration practical model in soil-plant system by using technology of geographic information system  

International Nuclear Information System (INIS)

[en] This work describes the construction of Cs 137 migration model in soil-plant system with taking into consideration factors of physical dissociation, sorption and fixation of Cs 137 in soil, vertical migration and transport factor into plant by using geographic information system

2002-01-01

367

A Generic Process Migration Algorithm  

Directory of Open Access Journals (Sweden)

Full Text Available Process migration has been advocated as a means of improving multicomputer configuration performance. The optimized migration algorithm utilized in migration event has direct effect on the efficiency and deployment of the process migration system. However, every design has preference factors results in concentration on specific aspect of the migration algorithm. There is no generic migration algorithm which could satisfy all circumstances with almost reasonable costs. This paper reviews the major issues which constitute the developer concerns when implementing a process migration algorithm. This examination indicates the existence of similarity in all process migration algorithms. A new migration algorithm is given and compared to the other algorithms. This algorithm attempts to integrate the significant features of the existing algorithms to form a generic algorithm.

Amirreza Zarrabi

2012-01-01

368

Vertical Protocol Composition  

DEFF Research Database (Denmark)

The security of key exchange and secure channel protocols, such as TLS, has been studied intensively. However, only few works have considered what happens when the established keys are actually used—to run some protocol securely over the established “channel”. We call this a vertical protocol composition, and it is truly commonplace in today’s communication with the diversity of VPNs and secure browser sessions. In fact, it is normal that we have several layers of secure channels: For instance, on top of a VPN-connection, a browser may establish another secure channel (possibly with a different end point). Even using the same protocol several times in such a stack of channels is not unusual: An application may very well establish another TLS channel over an established one. We call this selfcomposition. In fact, there is nothing that tells us that all these compositions are sound, i.e., that the combination cannot introduce attacks that the individual protocols in isolation do not have. In this work, we provea composability result in the symbolic model that allows for arbitrary vertical composition (including self-composition). It holds for protocols from any suite of channel and application protocols that fulfills a number of sufficient preconditions. These preconditions are satisfied for many practically relevant protocols such as TLS.

Groß, Thomas; Mödersheim, Sebastian Alexander

2011-01-01

369

Vertical heat exchanger  

International Nuclear Information System (INIS)

The design is described in detail of a vertical heat exchanger with two separate vertical capillary tube bundles and with heating steam condensation in the inter-tube space of the tube bundles. The design features a number of advantages, such as: the heat exchanger allows the supply of condensate from a higher heating degree; the inner structure separates the top and the bottom tube bundles thus preventing the condensate from running down to the bottom bundle; the inner structure and the jacket form the inlet steam chamber from which the heating steam is evenly distributed to both tube bundles; the assembly of the heat exchanger is easy because the inner structure is welded in the jacket as a whole and the tube bundles are inserted from both sides. It is also advantageous that the condensate produced on the individual bundles can be separated and the condensate level in the collector can be controlled in service and discharged from the heat exchanger through the discharge pipe. The heat exchanger is usable for both conventional and nuclear power generation. (A.K.). 3 figs

1983-08-31

370

forced-migration-history  

Science.gov (United States)

This new, UK-based, moderated mailing list serves as a forum for discussions on population displacements in 20th-century European history, "and to explore the inter-relationship of forced migration/resettlement/repatriation with nationalism, state formation and the construction of social identities." While the moderators believe that most of the subscribers will be involved in migration studies, history, geography, demography, and anthropology or sociology, scholars from other fields and different geographical and historical time periods are most welcome. Users will find archived messages and subscription information at the site.

371

Migration, klima og sundhed  

DEFF Research Database (Denmark)

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

Tellier, Siri; Carballo, Manuel

2009-01-01

372

Unix Application Migration Guide  

CERN Document Server

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

Microsoft. Redmond

2003-01-01

373

BROWNS FERRY BIOTHERMAL RESEARCH SERIES. II. EFFECTS OF TEMPERATURE ON BLUEGILL AND WALLEYE, AND PERIPHYTON, MACROINVERTEBRATE, AND ZOOPLANKTON COMMUNITIES IN EXPERIMENTAL ECOSYSTEMS  

Science.gov (United States)

Effects of long-term, March-September 1977, temperature elevations on aquatic communities in 12 outdoor experimental channels were evaluated. Macroinvertebrates, periphyton, and zooplankton colonized the channels naturally from the water supplied from Wheeler Reservoir, Tennessee...

374

Zooplankton assemblages in eutrophic reservoirs of the Brazilian semi-arid/ Assembléias zooplanctônicas em reservatórios eutróficos do semiárido brasileiro  

Scientific Electronic Library Online (English)

Full Text Available Abstract in portuguese A composição de espécies, a densidade e a dinâmica temporal do zooplâncton foram estudadas em seis reservatórios de uma região semiárida no nordeste do Brasil (Estado do Rio Grande do Norte). Todos os reservatórios estão altamente eutróficos, com altas concentrações de nitrogênio total (mínimo de 1.200 µg.L-1) e fósforo total (mínimo de 10 µg.L-1), e biomassa algal extremamente alta (muitas vezes, superando 20 µg.L-1 de Chl a). Todos os reservatórios (more) apresentaram alta turbidez e assembleias fitoplanctônicas dominadas por cianobactérias. O zooplâncton também apresentou padrões quantitativos sugestivos de condições eutróficas, expressas por altas densidades, principalmente nos Reservatórios Passagem das Traíras e Sabugi. Foi registrada uma diferenciação espacial na composição da comunidade zooplanctônica. Rotíferos (especialmente Keratella tropica, Brachionus havanensis e Keratella americana) foram as formas dominantes na comunidade zooplanctônica dos Reservatórios Itans, Passagem das Traíras e Sabugi, enquanto copépodos Calanoida (principalmente Notodiaptomus cearensis) dominaram nos Reservatórios Armando Ribeiro Gonçalves, Gargalheiras e Parelhas. A existência de novas relações na composição da comunidade zooplanctônica em reservatórios eutróficos dessa região semiárida tropical deve ser considerada no estabelecimento de indicadores zooplanctônicos de condições eutróficas. Abstract in english Species composition, density, and temporal dynamics of zooplankton were studied in six reservoirs in a semi-arid region in tropical northeastern Brazil (Rio Grande do Norte state). All the reservoirs are highly eutrophic, with high contents of total nitrogen (minimum of 1200 µg.L-1) and total phosphorus (minimum of 10 µg.L-1), and extremely high algal biomass was registered (surpassing 20 µg Chl a.L-1). All the reservoirs showed an enduring condition of high turbidity (more) and phytoplankton assemblages dominated by cyanobacteria. Zooplankton also showed quantitative patterns suggestive of eutrophic conditions, expressed by high densities, mainly in Passagem das Traíras and Sabugi reservoirs. A spatial differentiation in the composition of the zooplankton community was registered. Rotifers (especially Keratella tropica, Brachionus havanensis, and Keratella americana) were the dominant forms in the zooplankton community of Itans, Passagem das Traíras, and Sabugi reservoirs, while calanoid copepods (mainly Notodiaptomus cearensis) dominated in the Armando Ribeiro, Gargalheiras, and Parelhas systems. The existence of novel relationships in zooplankton community composition in eutrophic reservoirs in this tropical semi-arid region must be considered in designating zooplankton indicators of eutrophic conditions.

Eskinazi-Sant'Anna, EM.; Menezes, R.; Costa, IS.; Araújo, M.; Panosso, R.; Attayde, JL.

2013-02-01

375

Migration scenarii in extrasolar systems  

Directory of Open Access Journals (Sweden)

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