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

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Zooplankton populations which perform diel vertical migration (DVM) only spend the night in surface water layers but migrate downwards into the lower water layers during the day. The intention of this study was to investigate effects of DVM of Daphnia on phytoplankton dynamics and Daphnia life history parameters in a lake. I conducted field and laboratory experiments in which I compared ‘migration’ with ‘no-migration’ situations. It is generally assumed that phytoplankton communities ...

Reichwaldt, Elke S.

2004-01-01

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Evidences of zooplankton vertical migration in stocked and never-stocked alpine lakes in Gran Paradiso National Park (Italy)  

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Zooplankton vertical migration was described in four high altitude lakes in Gran Paradiso National Park (Northern Italy) during 2008 summertime. The authors succeeded in describing the vertical distribution of 6 species: diel vertical migrations were observed in the case of adult crustacean species (Cyclops gr. abyssorum, Arctodiaptomus alpinus and Daphnia gr. longispina), whereas the remaining rotifer species (Keratella quadrata, Polyarthra gr. dolichoptera and Synchaeta gr. stylata-pectinat...

Tiberti, Rocco; Barbieri, Mattia

2011-01-01

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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

2012-01-01

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

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

2009-01-01

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

Directory of Open Access Journals (Sweden)

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

Cuilin Hu

2014-02-01

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

Scientific Electronic Library Online (English)

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

Pedro, Apablaza; Sergio, Palma.

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Coarse-scale horizontal patchiness and vertical migration of zooplankton in Gulf Stream warm-core ring 82-H  

Science.gov (United States)

A 1-m 2 MOCNESS with 20 nets was used to make a series of tows in Gulf Stream meander/ring 82-H (September/October 1982) including two 0-100 m undulating "towyos". One towyo, made at dusk in the core of 82-H (of Sargasso Sea/Gulf Stream origin) permitted study of the effect of diel migration on the spatial variability of copepod and euphausiid species abundance, and species composition in a region of low physical variability. The other towyo taken across a front on the outer edge of 82-H (a mixture of Gulf Stream, Shelf and Slope Water), allowed comparison of spatial variability of the same biological properties in a region of strong physical variability. A sharp transition in euphausiid species composition occurred in the ring core after sunset as dielly migrating euphausiids moved into the surface waters. A similar, but less extreme change took place in copepod species composition because a smaller proportion of these migrated. All copepod migrants also entered surface waters after sunset with species living deeper in the water column during the day arriving in the surface waters later than those living shallower. ENRIGHT's (1977, Limnology and Oceanography, 22, 856-872) hypothesis for the metabolic advantages available through diel vertical migration does not account for the observed behavior of the migrating copepods and euphausiids at this time and place. Estimated swimming speeds (typically 50-200 m h -1) of migrating copepods and euphausiids were similar in spite of large differences in body size between the two groups. Variations in species composition were substantially larger at the edge of the ring where species proportions changed radically in concert with changes in water-mass properties. There were also large differences in species composition between the samples from the ring core and the front which equaled those which occurred across the front. Hydrographic differences were stronger than diel changes due to migration for copepods but not for euphausiids. Streamers of surface water which originated within the frontal region and spiraled into the ring core could provide colonizers of many species not present at the time of ring formation.

Wiebe, Peter H.; Copley, Nancy J.; Boyd, Steven H.

1992-03-01

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

Directory of Open Access Journals (Sweden)

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

Pedro Apablaza

2006-11-01

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

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

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

2004-01-01

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Old and new perspectives on zooplankton and vertical particle flux  

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Our understanding of the relationships between zooplankton and vertical flux of particles in the North Atlantic has matured over the last half century. Evolving from the simple concept of 11 grazing inhibits sedimentation", the relationship gained additional system-dependent quantitative as well as qualitative dimensions. The "zooplankton" and mediated processes such as production of feces are now recognized to be diverse and pivotal components influencing the distribution of o...

Noji, Thomas; Rey, Francisco

1996-01-01

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Plankton vertical migrations - Implications for the pelagic ecosystem  

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

Haupt, Florian

2011-01-01

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

Directory of Open Access Journals (Sweden)

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

Mahnoud Hassan Hanafi

2012-06-01

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

Directory of Open Access Journals (Sweden)

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

Lampert Winfried

2005-04-01

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Vertical distribution and diel patterns of zooplankton abundance and biomass at Conch Reef, Florida Keys (USA)  

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Zooplankton play an important role in the trophic dynamics of coral reef ecosystems. Detailed vertical and temporal distribution and biomass of zooplankton were evaluated at four heights off the bottom and at six times throughout the diel cycle over a coral reef in the Florida Keys (USA). Zooplankton abundance averaged 4396 ± 1949 SD individuals m?3, but temporal and spatial distributions varied for individual zooplankton taxa by time of day and by height off the bottom. Copepods comprised...

Heidelberg, Karla B.; O Neil, Keri L.; Bythell, John C.; Sebens, Kenneth P.

2010-01-01

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

International Nuclear Information System (INIS)

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

2007-03-01

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How internal waves influence the vertical distribution of zooplankton  

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1. We present data with a high spatio-temporal resolution from a 72-h field survey in Bautzen Reservoir (Saxony, Germany). The aims of this survey were to observe hydrophysical processes during a period of unstable stratification in spring and investigate the effect of wind-induced internal waves on the vertical distribution of zooplankton. 2. Wind velocities up to 10 m s)1 caused a strong downwelling event of warm water at the sampling site and led to the generation of internal waves with...

Rinke, Karsten; Hu?bner, Ina; Petzoldt, Thomas; Rolinski, Susanne; Ko?nig-rinke, Marie; Post, Johannes; Lorke, Andreas; Benndorf, Ju?rgen

2007-01-01

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Trade-offs in the vertical distribution of zooplankton: ideal free distribution with costs?  

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Zooplankton vertical migratory patterns are a classic example of optimal habitat choice. We hypothesize that zooplankton distribute themselves vertically in the water column according to an ideal free distribution (IFD) with costs such as to optimize their fitness. In lakes with a deep-water chlorophyll maximum, zooplankton are faced with a trade-off, either experiencing high food (high reproductive potential) but low temperature (slow development) in the hypolimnion or high temperature and l...

Lampert, Winfried; Mccauley, Edward; Manly, Bryan F. J.

2003-01-01

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

Digital Repository Infrastructure Vision for European Research (DRIVER)

Abstract Background In lakes with a deep-water algal maximum, herbivorous zooplankton are faced with a trade-off between high temperature but low food availability in the surface layers and low temperature but sufficient food in deep layers. It has been suggested that zooplankton (Daphnia) faced with this trade-off distribute vertically according to an "Ideal Free Distribution (IFD) with Costs". An experiment has been designed to test the density (competition) depend...

Lampert Winfried

2005-01-01

20

Flow regime associated with vertical secondary migration  

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Secondary migration is defined as the movement of hydrocarbons through relatively permeable rocks from source to trap: a two-phase flow within a porous medium. Depending on the geometry and capillary pressure distributions of carrier beds, secondary migration has both vertical and lateral components. The present paper focuses on that part of the migration where the movement is mainly vertical. Its objective is to propose a description of the dynamics governing the vertical part of secondary m...

Vasseur, Guy; Xiaorong, Luo; Yan, Jianzhao; Loggia, Didier; Toussaint, Renaud; Schmittbuhl, Jean

2013-01-01

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

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

Erlei Cassiano Keppeler; Elsa Rodrigues Hardy

2004-01-01

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

International Nuclear Information System (INIS)

This paper gives the results of research to explain the role played by marine plankton metabolism in the vertical oceanic transport of the alpha-emitting nuclides. The common Mediterranean euphausiid, Meganyctiphanes norvegica, was selected as the typical zooplanktonic species that is the focus of this work. Measurements of "2"3"9 "2"4"0Pu, "2"3"8U, "2"3"2Th, and "2"1"0Po 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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Opposing diel migration of fish and zooplankton in the littoral zone of a large lake  

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Backscatter data from an acoustic Doppler current profiler are analyzed to provide simultaneous estimates of relative concentration of Daphnia and relative abundance of young-of-the-year perch in the vicinity of an artificial reef in the littoral zone of Lake Constance. These long-term (3 months) and highresolution (1 h) observations demonstrate the existence of opposing diel migration patterns in fish and zooplankton. According to the data, the migration pattern constrains feeding of young-o...

Lorke, Andreas; Weber, Arnd; Hofmann, Hilmar; Peeters, Frank

2008-01-01

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

DEFF Research Database (Denmark)

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

Höffle, Hannes; Nash, Richard D.M.

2013-01-01

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

Directory of Open Access Journals (Sweden)

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

Erlei Cassiano Keppeler

2004-06-01

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

Scientific Electronic Library Online (English)

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

Keppeler, Erlei Cassiano; Hardy, Elsa Rodrigues.

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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

28

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

Science.gov (United States)

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

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

2012-01-01

29

Bacteria dispersal by hitchhiking on zooplankton  

Digital Repository Infrastructure Vision for European Research (DRIVER)

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 dispers...

Grossart, Hans-peter; Dziallas, Claudia; Leunert, Franziska; Tang, Kam W.

2010-01-01

30

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

DEFF Research Database (Denmark)

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

Hylander, Samuel; Jephson, T.

2011-01-01

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

Scientific Electronic Library Online (English)

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

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

32

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

Directory of Open Access Journals (Sweden)

Full Text Available AIM: Carneiro reservoir is an aquatic environment used for net cage aquaculture activities, located in the semi-arid region of northeastern Brazil. Vertical distribution was evaluated in order to determine the effects of organic enrichment induced by aquaculture on zooplankton movements. METHODS: three replicate samples were collected during midday and midnight at each of three depths along the water column (i.e. surface: 0 m; middle: 2 m and bottom: 4 m at two sites (near and far from the net cages. Samples were collected using a 3 L volume capacity Van Dorn bottle. The collected individuals were preserved in a 4% formaldehyde solution saturated with sugar and, later, identified and counted on a Sedgwick-Rafter chamber under a microscope, considering a minimum of 100 individuals per subsample. RESULTS: higher species richness and density were observed at the N station (nearby the net cages compared to the F station (distant from the net cages. With few exceptions, Rotifer species did not exhibit typical vertical migration patterns, concentrating at bottom depths during daytime and at intermediate depths during nighttime. Brachionus dolabratus and Hexarthra mira were the only species to show reverse vertical migration at the N station, in opposition to patterns of the cyclopoid copepod Termocyclops crassus. Furthermore, vertical migration patterns were not clear for Cladocera and Copepoda species nearby the net cages, but were rather clear at the F station. CONCLUSIONS: the presence of fish net cages increased zooplankton species richness (mostly rotifers and density. Vertical movements were more pronounced at sites distant from net cages, suggesting that the increased food availability reduced the need for the typical vertical movements during daytime at sites nearby the net cages.OBJETIVO: O açude do Carneiro é um ambiente aquático utilizado para atividades de aquicultura em tanques-rede, localizado na região semi-árida do nordeste do Brasil. A distribuição vertical foi avaliada com a finalidade de determinar os efeitos do enriquecimento orgânico induzido pela aquicultura nos movimentos do zooplâncton. MÉTODOS: três réplicas amostrais foram coletadas à meia noite (0:00 horas e ao meio dia (12:00 horas em cada uma de três profundidades da coluna d'água (i.e. superfície: 0 m; meio: 2 m e fundo: 4 m em duas áreas (próximo e distante dos tanques-rede. As amostras foram coletadas utilizando uma garrafa de Van Dorn com 3 L de capacidade volumétrica. Os indivíduos coletados foram preservados em uma solução de formol a 4% saturada com açúcar e, posteriormente, identificados e quantificados com uma câmara de contagem Sedgwick-Rafter sob microscópio, considerando um mínimo de 100 indivíduos por subamostra. RESULTADOS: a riqueza de espécies e a densidade foram maiores na estação N (próxima aos tanques-rede quando comparadas com a estação F (distante dos tanques-rede. Com poucas exceções, espécies de Rotifera não exibiram padrões típicos de migração vertical, concentrando-se nas camadas mais profundas durante o dia e nas camadas intermediárias durante a noite. Brachionus dolabratus e Hexarthra mira foram as únicas espécies que mostraram padrões de migração vertical inversos na estação N, em oposição aos padrões do copépodo ciclopóide Termocyclops crassus. Além disso, padrões de migração vertical não foram claros para as espécies de Cladocera e Copepoda próximos aos tanques-rede, mas foram evidentes na estação F. CONCLUSÕES: a presença de tanques-rede para peixes aumentou a riqueza de espécies (a maioria rotíferos e a densidade de zooplâncton. Movimentos verticais foram mais pronunciados nos locais distantes dos tanques-rede, sugerindo que o aumento da disponibilidade de alimento reduziu a necessidade dos movimentos verticais típicos durante o dia, nos locais próximos aos tanques-rede.

Glécia Trinta de Paula Freitas

2012-06-01

33

Turbulence and zooplankton production: insights from PROVESS  

DEFF Research Database (Denmark)

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

Visser, Andre

2002-01-01

34

Effects of diel vertical migration on ephippia production in Daphnia  

Digital Repository Infrastructure Vision for European Research (DRIVER)

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

Alekseev, Victor

2004-01-01

35

Vertical instability and inclination excitation during planetary migration  

CERN Document Server

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

Voyatzis, G; Tsiganis, K

2014-01-01

36

Meander migration in horizontally and vertically heterogeneous floodplains  

Science.gov (United States)

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

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

2011-12-01

37

Vertical migration of tritium in soil-plant system  

International Nuclear Information System (INIS)

The results of experiences on studying vertical migration, distribution in soil and tritium intake in the HTO form in plants at various methods of their irrigation (surface and subsoil) are presented. Tritium distribution at the soil profile depth depended on the method of irrigation. At surface irrigation radiator concentration has grown with the depth, at subsoil irrigation as a rule, lowered with depth. The analysis of vegetable material has shown that HTO content in free water (given off at +105 deg) constitutes 0,03 and 0,4% of found quantity, respectively at subsoil and surface irrigation. It is concluded that vertical migration, character of distribution in soil and HTO implantation into plants depend on intensity relation of ascending and descending currents of moisture created when using variuos methods of soil irrigation

1985-05-01

38

Vertical migration of 85Sr, 137Cs and 131I in various arable and undisturbed soils  

International Nuclear Information System (INIS)

The vertical migration of 85Sr, 137Cs and 131I in some arable and undisturbed single-contaminated soils was studied by gamma-spectrometry measurements under lysimetric laboratory conditions during irrigation of the soil profiles with wet atmospheric precipitation for about one year, except 131I. A new simple exponential compartment (box) model was derived, which makes it possible to calculate the migration rate constants and migration rates in the individual soil layers (vertical sections) as well as the total vertical migration rate constants and total vertical migration rates of radionuclides in the bulk soil horizon. The relaxation times of radionuclides in respective soil horizons can also be evaluated. (author)

2003-08-01

39

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

Digital Repository Infrastructure Vision for European Research (DRIVER)

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

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

2012-01-01

40

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

Science.gov (United States)

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

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

2008-01-01

 
 
 
 
41

Diel vertical migration arising in a habitat selection game  

DEFF Research Database (Denmark)

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

Sainmont, Julie; Thygesen, Uffe Høgsbro

2013-01-01

42

Vertical migration of 137Cs in the South Caspian soil  

International Nuclear Information System (INIS)

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

2012-01-01

43

Diurnal variation of zooplankton in Bhoj Wetland, Bhopal, India  

Directory of Open Access Journals (Sweden)

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

Najeeb Ahmad Bhat

2013-09-01

44

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

Directory of Open Access Journals (Sweden)

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

Chiarelle A.

2006-11-01

45

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

Scientific Electronic Library Online (English)

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

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

46

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

Directory of Open Access Journals (Sweden)

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

RODRIGO RAMOS-JILIBERTO

2001-09-01

47

Potential acidification impacts on zooplankton in CCS leakage scenarios  

International Nuclear Information System (INIS)

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

2013-08-30

48

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

Directory of Open Access Journals (Sweden)

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

M. Kitamura

2013-04-01

49

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

Directory of Open Access Journals (Sweden)

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

M. Kitamura

2013-08-01

50

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

Science.gov (United States)

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

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

2013-08-01

51

Vertical migration of 85Sr, 137Cs and 131I in various arable and undisturbed soils  

International Nuclear Information System (INIS)

Vertical migration of 85Sr, 137Cs and 131I in some arable and undisturbed single-contaminated soils was studied by gamma-spectrometry measurements in lysimetric laboratory conditions applying irrigation of the soil profiles with wet atmospheric precipitation for about one year (except radioiodine). A new simple exponential compartment (box) model was derived, allowing us to calculate the migration rate constants and migration rates in the individual soil layers (vertical sections) as well as the total vertical migration rate constants and total vertical migration rates of radionuclides in the bulk soil horizon. The data from the time dependence of the depth activity distribution (radionuclide concentration along the vertical soil profile) were used to test the model. The migration rate constants and migration rates were found to be affected by the contaminating radionuclides as well as by the site, type and depth of the soil. The relaxation times of the radionuclides in the soil horizons were calculated. The effects on the rate parameters of the permanent grass cover and the zeolite applied onto the arable soil surfaces were also investigated

2002-03-01

52

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.

2006-12-01

53

Vertical migration of radionuclides in undisturbed grassland soils  

Energy Technology Data Exchange (ETDEWEB)

Literature data on numerical values obtained for the parameters of the two most popular models for simulating the migration of radionuclides in undisturbed soils have been compiled and evaluated statistically. Due to restrictions on the applicability of compartmental models, the convection-dispersion equation and its parameter values should be preferred. For radiocaesium, recommended values are derived for its effective convection velocity and dispersion coefficient. Data deficiencies still exist for radionuclides other than caesium and for soils of non-temperate environments.

Kirchner, Gerald [BfS Federal Office for Radiation Protection, D-38201 Salzgitter (Germany); Strebl, Friederike [Austrian Research Centers GmbH (ARC), Department of Radiation Safety and Applications, A-2444 Seibersdorf (Austria)], E-mail: friederike.strebl@arcs.ac.at; Bossew, Peter [Institute for Environment and Sustainability, DG Joint Research Centre, European Commission, I-21020 Ispra (Italy); Ehlken, Sabine [Klinikum Bremen-Mitte, D-28177 Bremen (Germany); Gerzabek, Martin H. [University of Natural Resources and Applied Life Sciences Vienna, Peter-Jordan-Strasse 82b, A-1190 Vienna (Austria)

2009-09-15

54

Zooplankton Distribution in Four Western Norwegian Fjords  

Science.gov (United States)

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

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

2000-01-01

55

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

Science.gov (United States)

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

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

2002-12-01

56

Studies on Horizontal and Vertical Migration of 90Sr in Soil Systems  

International Nuclear Information System (INIS)

Here are presented results of studies on vertical and horizontal migration of strontium 90Sr isotope in soil systems of Bug river valleys. Mean radioactivity of strontium in these soils was 26.15 ± 22.2 Bq/kg. Atmospheric precipitation of strontium on this area was 0.35 kBq/m2/cm. Radioactivity in soil profiles ranged from 17 to 130 Bq/m2/cm and the isotope was detected even at 30 cm depth. Some tendency to vertical migration of strontium towards the river was noticed. Obtained results were compared with concentrations of calcium and strontium in the soil. Any clear influence of these elements on the migration of strontium 90Sr was noticed. (author)

2002-01-01

57

The role of zooplankton in the pelagic-benthic coupling of the Southern Ocean  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Zooplankton contributes in different ways to pelagic-benthic coupling: Their faecal material is a major route of energy flow and the vertical migrations of many species as well as the production of pelagic larvae by benthic organisms represent different paths to link the two subsystems. Antarctic particle fluxes have been shown to be highly variable in size and composition within a given region and even at the same site from year to year. There are also differences throughout the water column...

Schnack-schiel, Sigrid B.; Isla, Enrique

2005-01-01

58

Effect of Zooplankton Community Structure on Particle Flux and Nutrient Cycling at the Bermuda Atlantic Time-series Study (BATS) Site  

Science.gov (United States)

The structure of zooplankton communities has a significant impact on vertical transport and cycling of elements in the sea. Zooplankton play an integral role in the flux of material out of the euphotic zone at BATS via active transport by vertical migrators and by production of rapidly sinking fecal pellets. Zooplankton biomass in the upper 200 m at BATS is on average 1.7 times higher at night than day due to vertical migration. Migrating zooplankton actively transport a substantial amount of dissolved inorganic and organic carbon and nitrogen to deep water at BATS (via respiration and excretion), which can be significant relative to the passive flux of sinking particles. Active transport of C is equal to a mean of 8% (maximum 39%), and N equal to a mean of 13% (maximum 164%) of the gravitational vertical export of particulate organic C and N, respectively, measured with sediment traps at 150 m. Substantial excretion of dissolved organic material by migrators (mean of 24% of total C and 32% of total N metabolized) could be important to the microbial community at depth. Dissolved material exported by zooplankton is usually not at a Redfield C:N ratio of 6.6, contributing to non-Redfield remineralization patterns seen at depth. Changes in the zooplankton community can also dramatically affect the composition and sedimentation rate of fecal pellets, and thus the export of organic material. However, zooplankton biomass alone is not necessarily a good predictor of flux; the species composition of the resident community may at times more considerably affect export of organic material to the deep ocean. For example, there is a positive but weak relationship between monthly zooplankton biomass and organic C flux at BATS. Analysis of the bloom dynamics of salps (large gelatinous zooplankton) over the ten-year time series at BATS indicates salps graze on average 4% of the primary production, but fecal flux from salps can constitute on average 33% (maximum over 10-fold) of the sediment trap flux. An effort is underway to analyze the species composition of the BATS zooplankton time series in order to better understand how diel, seasonal and interannual changes in the taxa affect biogeochemical cycles in the Sargasso Sea.

Steinberg, D. K.; Madin, L. P.

2001-12-01

59

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

Digital Repository Infrastructure Vision for European Research (DRIVER)

Eutrophic temperate and sub-tropical lakes often exhibit a marked vertical structure during the warm season that involves important spatial differences of physical, chemical and biological variables. Therefore, zooplankton is exposed to a highly heterogeneous environment in the vertical dimension. In this work, We analyze the depth-distribution of the cladoceran Daphnia ambigua in the eutrophic, monomictic lake El Plateado at midday and midnight, along with its relationship with the vertical ...

RODRIGO RAMOS-JILIBERTO; Zu?n?iga, Luis R.

2001-01-01

60

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

Scientific Electronic Library Online (English)

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

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

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

Directory of Open Access Journals (Sweden)

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

Ralf Schwamborn

2008-01-01

62

Vertical distribution, feeding and migration behaviour of the myctophiid Benthosema glaciale in Masfjorden, western Norway  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Abstract This study addresses the mesopelagic fish, Benthosema glaciale focusing on feeding, vertical distributions and diel migration pattern. During a cruise with the vessel ?Trygve Braarud? to Masfjorden, ~50 km north of Bergen (60?52?30 N, 5?24?70 E) from the 2nd to the 6th October 2006 fish were sampled by oblique and horizontal trawls. A bottom deployed 38 kHz split beam echosounder, placed at 400 m depth, provided continuous acoustic data on both...

2007-01-01

63

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

Digital Repository Infrastructure Vision for European Research (DRIVER)

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

2010-01-01

64

Vertical migration of three coastal species of chaetognaths in the western Mediterranean Sea  

Digital Repository Infrastructure Vision for European Research (DRIVER)

[EN] Chaetognaths present at a 24-h station located off the Ebro River delta in the western Mediterranean basin were studied. No vertical migratory behaviour related to the light cycle was observed in the total chaetognaths as a whole, but the behaviour of the individual species present in the area, Sagitta enflata, S. setosa and S. minima, did present differences. S. enflata migrated through the water column during the day, whereas S. setosa and S. minima did not exhibit any appreciable diff...

Andre?u, Pilar

1992-01-01

65

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

66

Assessing the use of magnetic methods to monitor vertical migration of metal pollutants in soil  

Science.gov (United States)

In order to assess the use of magnetic methods to study and improve our understanding of the vertical migration behavior of metal pollutants in natural soil, a controlled experiment was performed during August-December 2009, near Belle River, Ontario. The soil is Quaternary in age, consisting primarily of glacial till (Tavistock Till) overlain by localized alluvium deposits of very recent origin. Groundcover vegetation is minimal, consisting only of various grasses. Eighteen PVC tubes (8” wide, 16” long) were inserted vertically into the ground as test capsules, in order to avoid contaminating the surrounding area. Magnetite powder (5µm) was distributed on the surface of the soil inside nine of the tubes (10 grams of magnetite/tube) to simulate anthropogenic contamination, while the others were used as controls. Magnetic Susceptibility (MS) measurements were used for both ongoing surface monitoring and pre- and post-treatment vertical migration assessment. The initial surface MS values in the contaminated tubes were one to two orders of magnitude larger than in the uncontaminated tubes. While the surficial MS remained fairly stable in uncontaminated soil, decreases of 15-60 % were observed in contaminated soil tubes. Susceptibility profiles from soil cores in the contaminated tubes show that the concentration of iron containing particles is highest at depths between 2-7 cm. Energy Dispersive Spectroscopy (EDS) analysis on layers with an enhanced magnetic signal showed high weight% of iron and oxygen, indicating the presence of iron minerals. Scanning Electron Microscopy (SEM) showed that the magnetite powder and the particles from the contaminated tubes had similar morphologies. These results suggest that the magnetite migrated downwards into the soil over the five month period, probably as a result of rainwater infiltration and vertical migration. Some of the soil profiles showed a small enhancement of magnetic signal at 17-18 cm, and SEM-EDS analysis shows that these zones often contained high levels of Ti and Fe, and are perhaps related either to some form of natural barrier in the soil or to an agricultural effect. The results allow us to assess downward migration rates within this soil, and show that such short-term investigations can provide valuable information on the migration behavior of the metal pollutants, and the potential depth of soil contamination.

Sapkota, B.; Cioppa, M. T.

2010-12-01

67

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

2002-03-01

68

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

Science.gov (United States)

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

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

2014-02-01

69

Vertical migration of 134Cs bearing soil particles in arid soils: implications for plutonium redistribution  

International Nuclear Information System (INIS)

Vertical migration of plutonium in soils at the Waste Isolation Pilot Plant (WIPP) and the Rocky Flats Environmental Technology Site (RFETS) was evaluated based on observed 134Cs migration in soil column experiments. After applying 134Cs-labeled soil particles to the surfaces of large, undisturbed soil cores collected from each site, resulting soil columns were subjected to experimental cycles of irrigation plus drying (treatment columns) or to cycles of irrigation only (control columns). Mean losses of 134Cs inventory from soil surfaces were 3.1 ± 0.6% cycle-1 and 0.7 ± 0.6% cycle-1 respectively for RFETS treatment and control columns. WIPP columns had mean respective losses of 1.3 ± 1.2% cycle-1 and 0.5 ± 0.2% cycle-1. Bulk transport of labeled soil particles through soil cracks was an important process in RFETS soils, accounting for 64-86% of total 134Cs migration. Colloidal transport processes governed migration in WIPP soils

2006-01-01

70

The Effects of Radial Migration on the Vertical Structure of Galactic Discs  

CERN Document Server

We present evidence that isolated growing discs, subject to internal spiral perturbations, thicken due to both heating \\emph{and} radial migration. We show this by demonstrating that the thickness and vertical velocity dispersions of coeval stars depend on their age as well as the change in their radii. While the disc thickens due to internal processes, we find that this induces only a minor amount of flaring. We further demonstrate the consequences of such thickening on the structural properties of stellar populations and find that they qualitatively agree with recent studies of the Milky Way disc.

Roskar, Rok; Loebman, Sarah R

2012-01-01

71

Diel vertical migration of phytoplankton and heterotrophic flagellates in the Gulf of Riga  

Science.gov (United States)

Vertical distribution of a phototrophic ciliate ( Mesodinium rubrum), autotrophic dinoflagellates ( Peridiniella catenata, Heterocapsa rotundata, Dinophysis acuminata), a cryptomonad ( Teleaulax sp.), a filamentous cyanobacterium ( Aphanizomenon flos-aquae), a non-motile chlorophyte ( Monoraphidium sp.) and two heterotrophic dinoflagellates were studied during two diel periods in spring (May 1-2 and 27-28, 1995) and summer (June 26-27 and July 6-7, 1994) in the southern part of the Gulf of Riga, the Baltic Sea. The two seasons, corresponding to the vernal bloom and summer stage, differed considerably with respect to phytoplankton community, hydrography and vertical distribution of the species. In spring the cells stayed in the upper mixed layer above a strong thermocline at 12-15 m depth, and changes in the vertical distribution were related to surface avoidance in the middle of the day. By using correspondence analysis, the vertical distribution of all the motile species were shown to differ significantly from the non-motile Monoraphidium, but not from each other. The vertical migration was reflected in a higher variability in the depth distribution patterns of the motile species, compared to Monoraphidium. In summer 1994, Aphanizomenon, Dinophysis and Teleaulax showed similar depth distribution patterns during the first period, but different from Mesodinium and the heterotrophic dinoflagellates, while during the second period all the autotrophic species had a species specific depth distribution pattern. Me. rubrum revealed a considerably different depth distribution between the two seasons, characterised by surface accumulation in spring and relatively uniform depth distribution over the whole sampling range (0-30 m) in summer. The results demonstrate different vertical niche separation strategies between species.

Olli, Kalle

1999-12-01

72

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

Digital Repository Infrastructure Vision for European Research (DRIVER)

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

Weikert, H.; Koppelmann, R.

1993-01-01

73

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

Science.gov (United States)

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

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

2014-01-01

74

Vertical migration of Norwegian spring-spawning herring larvae in relation to predator and prey distribution  

DEFF Research Database (Denmark)

A diel vertical migration (DVM) pattern of Norwegian spring spawning herring (Clupea harengus) larvae was investigated during 19 and 20 April 2009. Factors influencing DVM included physical and biological properties of the water column. Data on larvae, prey and predators were collected with a depth-stratified multisampling device, inshore of Sklinna bank, close to the Norwegian coast, while light conditions were calculated using a Matlabâ?  algorithm. A type I DVM pattern (i.e. deep during daytime, shallow at night) was observed for herring larvae, mainly occurring above the thermocline. No sizedependent differences were observed for larval vertical positioning. The highest overlap in depth distribution with their main prey was observed during daytime, when larvae were distributed deeper in the water column. From acoustics and macroplankton trawl data, a type I DVM was also observed for krill, although their concentrations were relatively low in the area. Cumulative predatorprey overlap plots suggest that krillmost likely forage on copepods and smaller organisms. During the day, larvae concentrate near the thermocline to feed, while they move towards the surface at dusk, possibly to use the remaining light to continuing feeding. During the night, when light levels were too low to feed, larvae spread out in the water column above the thermocline. This migration pattern reduces the overlap between larvae and potential predators such as krill, which also move higher up during nighttime. It is suggested that the pattern of herring larvae DVM is a behavioural response to active pursuit of prey

Ferreira, Ana Sofia; Stenevik, Erling Kre

2012-01-01

75

Vertical Migrations of a Deep-Sea Fish and Its Prey  

Science.gov (United States)

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

Afonso, Pedro; McGinty, Niall; Graca, Goncalo; Fontes, Jorge; Inacio, Monica; Totland, Atle; Menezes, Gui

2014-01-01

76

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

Science.gov (United States)

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

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

2014-10-01

77

Bias in acoustic biomass estimates of Euphausia superba due to diel vertical migration  

Science.gov (United States)

The diel vertical migration (DVM) of Antarctic krill ( Euphausia superba) can greatly bias the results of qualitative and quantitative hydroacoustic surveys which are conducted with a down-looking sonar and irrespective of the time of day. To demonstrate and quantify these negative biases on both the estimates of biomass distribution and abundance, a time-depth-density analysis was performed. Data were collected, as part of the United States Antarctic Marine Living Resources Program (AMLR), in the vicinities of Elephant Island, Antarctica, during the austral summers of 1992 and 1993. Five surveys were conducted in 1992; two covered a 105 by 105 n.mi. area centered on Elephant Island, two encompassed a 60 by 35 n.mi. area immediately to the north of the Island, and one covered a 1 n.mi. 2 area centered on a large krill swarm to the west of Seal Island. The 1993 data include repetitions of the two small-area and two large-area surveys. Average krill volume densities were calculated for each hour as well as for three daily periods: day, twilight and night. These data were normalized and presented as a probability of daily average density. With spectral analysis to identify the frequencies of migration, a four-term periodic function was fitted to the probability density function of average daily biomass versus local apparent time. This function was transformed to create a temporal compensation function (TCF) for upwardly adjusting acoustic biomass estimates. The TCF was then applied to the original 1992 survey data; the resulting biomass estimates are an average of 49.5% higher than those calculated disregarding biases due to diel vertical migration. The effect of DVM on the estimates of krill distribution are illustrated by a comparison of compensated and uncompensated density maps of two 1992 surveys. Through this technique, high density kril areas are revealed where uncompensated maps indicated low densities.

Demer, David A.; Hewitt, Roger P.

1995-04-01

78

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

79

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

DEFF Research Database (Denmark)

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

Schultz, J.; Peck, M.A.

2012-01-01

80

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

International Nuclear Information System (INIS)

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

1980-01-01

 
 
 
 
81

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

82

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

International Nuclear Information System (INIS)

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

1986-01-01

83

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

84

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

International Nuclear Information System (INIS)

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

2002-06-01

85

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

Digital Repository Infrastructure Vision for European Research (DRIVER)

Diel vertical migration (DVM) of larvae of the phantom midge Chaoborus flavicans (Diptera: Chaoboridae) inhabiting a fishless pond and a fish-abundant lake (Lake Nakanuma) was studied in the field and in the laboratory. In the fishless pond, dissolved oxygen concentration and water temperature were homogeneously distributed in the vertical profiles and Chaoborus larvae did not show DVM. In contrast, there was thermal stratification and an anoxic layer in Lake Nakanuma, and 2nd, 3rd and 4th in...

Oda, Shigeto; Hanazato, Takayuki

2008-01-01

86

Krill diel vertical migration fine dynamics, nocturnal overturns, and their roles for aggregation in stratified flows (vol 65, pg 574, 2008)  

Digital Repository Infrastructure Vision for European Research (DRIVER)

A set of high-resolution observations on short-term dynamics of krill diel vertical migrations (DVM) in the St. Lawrence Estuary are presented here, including vertical mass transfer measurements from multifrequency echo sounding coupled with stratified net sampling and tracers of individual vertical movements from stomach pigments over a 72 h period. The data set is supplemented by vertical migration speeds and biomass diel patterns from ADCP (acoustic Doppler current profiler) time series la...

Sourisseau, Marc; Simard, Y.; Saucier, F. J.

2009-01-01

87

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

2007-01-01

88

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

International Nuclear Information System (INIS)

Vertical migration of pollutants through unsaturated zone is a complicated process and is affected by a number of factors like type of soil, its chemical properties, or organic matter content, in addition to climatic conditions and biological activity of microorganisms in soil. Soil properties that influence water movement through unsaturated zone are important for determining flow paths, reactions between soil and pollutants and the ultimate destination of these pollutants, and may improve the diagnosis of the potential pollution risk. Three soil cores were sampled to a depth up to 100 cm from cultivated clayey soil, sewage irrigated sandy soil and fertilized sandy soil. The samples were collected at intervals of 5 or 10 cm. The ?13C signature of the soil shifted significantly towards that of C3-type vegetation in soil cores. The general trend toward heavier 13C enrichment with depth could be due to isotopic fractionation occurring during decomposition of soil organic matters. Increased ?15N with depth in the soil cores suggests that microbial mineralization, denitrification, or volatilization processes caused the enriched ?15N signatures. Decreasing nitrogen percent and nitrate values with depth also help support the idea of microbiological processes. The results indicate that concentrations of major and trace elements varied widely among the different soil types and decreased with depths in the studied soil profile. The accumulation pattern for these elements in the soil profiles follows the order: Co < Ni < Mo < Ag < Sr < V < Cu < Cr < Zn < Mn < B < Mg < Al < Fe. The relationships between element concentrations against ph and organic matter contents show antithetical relationships and suggest evidence that these elements arise from anthropogenic input. The results of this study show that there exists risk for the environment due to notable migration of pollutants through the unsaturated zone and that the migrations were also observed to be highly correlated with sandy soil as well as organic matter content rather than ph values

2012-01-01

89

Risks of increased UV-B radiation for zooplankton  

International Nuclear Information System (INIS)

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

1994-03-01

90

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

91

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

Directory of Open Access Journals (Sweden)

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

Jaromír SE?A

2010-08-01

92

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

93

Distribution of zooplankton populations within and adjacent to a thermal plume  

International Nuclear Information System (INIS)

Zooplankton distributions in the 1-m stratum differed between ambient waters and the thermal plume of the Donald C. Cook Nuclear Power Plant. Zooplankton were most abundant in the warmest waters of the plume with the region of high densities extending over an approximate area of 0.2 to 0.3 km"2. Water temperature was not a reliable indicator of alterations in zooplankton populations. Alterations were primarily due to upward vertical displacment of deep-living zooplankton. Large horizontal variability in zooplankton densities and use of conventional sampling procedures (vertically hauled nets, widely spaced stations) prevent traditionally designed monitoring programs from detecting such alterations. Zooplankton may experience indirect mortality losses in the plume if transfer of deep-living zooplankton to the surface layers makes them more visible to visual-feeding fish predators, and turbulences in the plume reduce zooplankters' ability to detect and avoid such predators. (auth)

1981-01-01

94

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

Digital Repository Infrastructure Vision for European Research (DRIVER)

Migration is defined as a seasonal and cyclic population movement observed in all animal classes and studied mainly in vertebrates. A considerable part of the knowledge on migration comes from birds, for which migration is an important aspect of their biology. In the case of bats, females usually migrate larger distances than males in some species. The present study analyzes the seasonal occurrence of Pygoderma bilabiatum (Wagner, 1843) at different elevations, in order to test for a pattern ...

2011-01-01

95

Zooplankton from Lake Magelungen, Central Sweden 1960-1963  

Energy Technology Data Exchange (ETDEWEB)

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

Almquist, Elisabeth

1970-11-15

96

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

Science.gov (United States)

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

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

2014-01-01

97

Individual-based simulation of diel vertical migration of Daphnia : a synthesis of proximate and ultimate factors  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Diel vertical migration (DVM) of Daphnia is a well-studied inducible defence mechanism against predation by fish. Our study is anchored in constructing an individual-based model of DVM in order to bring established knowledge about essential key processes into a synthesis. For that purpose, we combined information about both proximate and ultimate factors of DVM with the intention to unify published results from these historically separated lines of research. The model consists of three submod...

Rinke, Karsten; Petzoldt, Thomas

2008-01-01

98

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

Science.gov (United States)

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

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

2007-01-01

99

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

International Nuclear Information System (INIS)

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

2014-01-01

100

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

Digital Repository Infrastructure Vision for European Research (DRIVER)

The objective of this study was to quantify and to model zooplankton transport with emphasis on decapod crustacean larvae. Sampling was carried out at three depths with a plankton pump coupled to a 300-/¿m mesh. Current data were obtained with an ADCP. Our data showed the existence of vertically and horizontally heterogeneous current and transport fields. We identified 27 groups of Decapoda (larvae of Sergestidae, Porcellanidae, Upogebiidae, Cari dea, Brachyura). Most of the species and larv...

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

2008-01-01

 
 
 
 
101

Vertical migration of plutonium-239 + -240, americium-241 and caesium-137 fallout in a forest soil under spruce  

International Nuclear Information System (INIS)

The vertical activity distributions of fallout 238Pu, 239+240Pu, 241Am, 134Cs and 137Cs in a forest soil (Hapludult) were determined at several locations in a spruce stand separately according to their origin (global fallout or Chernobyl fallout). To determine the rate of migration of these radionuclides in each soil horizon, the observed depth profiles of the radionuclides were evaluated with a compartment model. In the top organic horizons (LOf1 and Of2), the migration rates for all radionuclides from both sources were above 0.5 cm per year. In the Oh horizon the migration rates observed for global fallout Pu, Am and Cs were similar (0.2-0.4 cm per year). Compared with Pu, however, the mobility of Am is slightly, but statistically significantly, enhanced. The highest rate in this layer was found for Chernobyl-derived radiocaesium (2 cm per year). In the layers of the mineral horizon (depth 0-2,2-5 and 5-10 cm) the observed migration rates were very similar for global fallout Pu (0.08-0.7 cm per year) and Am (0.1-2 cm per year). In comparison, the migration rate of global fallout radiocaesium was about half in each layer. The highest rate was observed again for Chernobyl-derived radiocaesium (0.5-3 cm per year). (author)

1992-03-01

102

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

103

Microplastic ingestion by zooplankton.  

Science.gov (United States)

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

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

2013-06-18

104

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

International Nuclear Information System (INIS)

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

2014-02-01

105

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

DEFF Research Database (Denmark)

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

Nilsson, Lars Anders Fredrik; Thygesen, Uffe Høgsbro

2003-01-01

106

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

Science.gov (United States)

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

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

2009-10-01

107

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

2009-06-01

108

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

Science.gov (United States)

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

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

2006-05-01

109

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

Directory of Open Access Journals (Sweden)

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

Carlos E. L. Esbérard

2011-12-01

110

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

Scientific Electronic Library Online (English)

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

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

111

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

Science.gov (United States)

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

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

2012-01-01

112

Zooplankton of West Madagascar  

Science.gov (United States)

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

Bemiasa, John; Remanevy, Sitraka

2014-05-01

113

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.

2011-02-01

114

Diel vertical migration of major fish-species in Lake Victoria, East Africa  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Understanding of migration patterns is essential in the interpretation of hydro-acoustic stock assessment data of partly demersal partly pelagic fish stocks. In this paper we provide this kind of information for some species that were common in the Mwanza Gulf of Lake Victoria in the 1980s, before and after the upsurge of introduced Nile perch (Lates niloticus). Detritivorous haplochromines and Nile tilapia (Oreochromis niloticus), both stay near the bottom during day and night. Feeding seems...

2004-01-01

115

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

Digital Repository Infrastructure Vision for European Research (DRIVER)

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

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

2009-01-01

116

Distribution and diel vertical migration of Eurasian perch (Perca fluviatilis L.) during winter  

Digital Repository Infrastructure Vision for European Research (DRIVER)

The distribution and migration patterns of overwintering perch were studied by hydroacoustics and gill netting in Lake Constance, central Europe. In autumn, perch left the littoral and moved to deeper waters for overwintering. They lived at temperatures below 6°C for about six months. In January, perch were present between the 42 and 69 m depth contours. Their distribution then shifted to increasingly shallower depths by 0.25 m per day, and they returned to the littoral in early May where ad...

1996-01-01

117

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

Digital Repository Infrastructure Vision for European Research (DRIVER)

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

Spinesi, Luca

2005-01-01

118

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

Directory of Open Access Journals (Sweden)

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

Sergio Palma

2004-01-01

119

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

Scientific Electronic Library Online (English)

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

Sergio, Palma; Pedro, Apablaza.

120

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

2008-12-01

 
 
 
 
121

Migration.  

Science.gov (United States)

The note explains the different definitions of immigration, emigration, and net migration, and how they all differ from each other. It shows patterns of population change since 1970, the reasons for this change, and how they arrived at the figures they go...

C. A. Young

1977-01-01

122

Do littoral macrophytes influence crustacean zooplankton  

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

Geraldes, Ana Maria; Boavida, Maria Jose?

2004-01-01

123

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

124

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

Directory of Open Access Journals (Sweden)

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

Takayuki HANAZATO

2008-08-01

125

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

Scientific Electronic Library Online (English)

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

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

126

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

127

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

Science.gov (United States)

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

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

2005-01-01

128

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

Digital Repository Infrastructure Vision for European Research (DRIVER)

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

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

2009-01-01

129

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

Digital Repository Infrastructure Vision for European Research (DRIVER)

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

2001-01-01

130

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

International Nuclear Information System (INIS)

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

2014-01-20

131

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

Digital Repository Infrastructure Vision for European Research (DRIVER)

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 bivalve...

Ahmet Nuri Tarkan; Inibilir, Melek I.; Ali Serhan Tarkan

2005-01-01

132

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

Digital Repository Infrastructure Vision for European Research (DRIVER)

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

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

2007-01-01

133

Start feeding of salmonids with lake zooplankton  

Digital Repository Infrastructure Vision for European Research (DRIVER)

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

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

1982-01-01

134

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

Science.gov (United States)

Diel vertical migration and feeding on phytoplankton by adult female Calanus pacificus, Metridia lucens and Pseudocalanus newmani were simultaneously measured near the end of a phytoplankton bloom. Almost the entire Calanus population migrated out of the deep layer (108-50 m) at night but only about 30% came to the surface (25-0 m). Feeding occurred only at night and was equally high in the surface and intermediate layers, in spite of much higher food concentrations in the surface. Like Calanus, the entire Metridia population was found in the deep layer during the day but unlike Calanus, 20-50% remained in the deep layer at night and most migratory Metridia were collected from the surface layer. Metridia feeding at night was highest in the surface layer but significant feeding also occurred in both the intermediate and deep layers. Migratory behavior of Pseudocalanus was weak, with the proportion of the population in the surface layer increasing from slightly <10% during the day to approx 30% at night. Feeding occurred in both surface and intermediate layers throughout the 24 h but was greater in both layers at night. The different migratory patterns are discussed in the context of our current understanding of the contributions of predator avoidance and feeding to diel vertical migration.

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

1998-06-01

135

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

Directory of Open Access Journals (Sweden)

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

Neda Fazeli

2013-12-01

136

Distribution and abundance of zooplankton populations in Crater Lake, Oregon  

Science.gov (United States)

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

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

2007-01-01

137

Stable Isotope and Signature Fatty Acid Analyses Suggest Reef Manta Rays Feed on Demersal Zooplankton  

Science.gov (United States)

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

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

2013-01-01

138

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

139

ZOOPLANKTON AS A FOOD SOURCE  

Science.gov (United States)

While thousands of zooplankton species could potentially serve as food for larval stages of cultured fish and crustaceans, the aquaculturists practical choice of a reproducible live food ratio is quite limited. In practice, rotifers and brine shrimp are the most commonly used zoo...

140

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

International Nuclear Information System (INIS)

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

2005-01-01

 
 
 
 
141

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

142

On the use of vertically averaged models to simulate CO2 migration in a layered saline aquifer  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Geologic and flow characteristics such as permeability and porosity, capillary pressure, geologic structure, and thickness all influence and affect CO2 plume distribution to varying degrees. These parameters do not necessarily act independently. Depending on the variations in these parameters one may dominate the shape and size of the plume. In this master thesis, we consider the long-term fate and migration of a large CO2 plume that takes place in a heterogeneous (two-layer) sloping saline ...

El-faour, Basil Fayez

2010-01-01

143

Dissolved and fecal pellet carbon and nitrogen release by zooplankton in tropical waters  

Science.gov (United States)

Carbon (C) and nitrogen (N) release by tropical zooplankton (mostly copepods) and micronekton (euphausiids, pelagic red crabs, and salps) was investigated near VERTEX particle traps at 18°N, 108°W (in 1981) and 15°40'N, 107°30'W (in 1982). The objective was to assess the significance of fecal pellet release relative to respiratory and dissolved excretory release of C and N and relative to primary production in the same waters. For small (salps, using respiratory—excretory data from the literature and our own observations of fecal pellet production. Either the literature data were not applicable to our salps, or the salps had a more lipid-based metabolism. Reasonably balanced C and N loss budgets were computed for the small and large zooplankton. Daily fecal pellet C egestion represented only 2 to 3% of both large and small zooplankton body C content, and daily fecal pellet N egestion was <2% of zooplankton body N. Likewise, daily fecal pellet production by small and large zooplankton together accounted for <2% of the daily primary C and N production in the top 100 m of water; that is, 'new' primary production would have had to replace losses of <2% per day to balance fecal pellet losses from large and small zooplankton, presuming all fecal pellets sank below 100 m without being eaten or remineralized. However, the estimate of total C flux through 120 m (from particle trap data) was only 4.4% of primary production, so the fecal pellet flux from small and large zooplankton could have accounted for up to 41% of the total flux. From corollary data, it was estimated that the total vertical C flux could result almost entirely from combined fecal pellet production by the existing zooplankton and micronekton concentrations. The vast majority of the primary C production (95.6%) was supported by respired and dissolved excreted compounds plus any atmospheric inputs.

Small, Lawrence F.; Fowler, Scott W.; Moore, Stanley A.; LaRosa, Jacques

1983-12-01

144

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

International Nuclear Information System (INIS)

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

2002-10-01

145

Vorticity and mixing induced by the barotropic M 2 tidal current and zooplankton biomass distribution in the Gulf of California  

Science.gov (United States)

Vertical mixing and biological processes in the Gulf of California were analyzed using calculated relative vorticity fields induced by the barotropic M 2 tide and zooplankton biomass distribution. M 2 tidal currents contribute significantly to the general circulation observed in the upper gulf. The results revealed zones with high vertical and horizontal values of relative vorticity in regions where temperature anomalies and water exchange take place. The horizontal component of the vorticity vector is considerable in areas of the upper gulf, where high vertical shear of the velocity was estimated. Patterns of the horizontal component of the vorticity, the Simpson-Hunter criterion and the chlorophyll concentration showed similarities. The interaction of tidal flow with the complex bathymetry is the main source of vorticity and mixing in the gulf. The vertical component of the relative vorticity reaches positive values in regions where cyclonic circulation has been reported. A total of 35 groups of zooplankton were identified in the gulf; Copepoda, Chaetognatha, and Euphausiacea were the three major groups. High zooplankton biomasses in the archipelago region of the gulf were associated with topographic effect, which induces strong shear velocities, creating vertical mixing and increasing the supply of nutrients to the surface layers, which in turn induces high chlorophyll concentration or phytoplankton and thereby supports the zooplankton biomass. The zooplankton biomass was closely related to high values of the horizontal component of relative vorticity.

Salas-de-León, David Alberto; Carbajal, Noel; Monreal-Gómez, Maria Adela; Gil-Zurita, Antonio

2011-08-01

146

Zooplankton of Munzur River (Tunceli, Turkey  

Directory of Open Access Journals (Sweden)

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

Serap Saler

2011-01-01

147

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

International Nuclear Information System (INIS)

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

2005-01-01

148

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

Energy Technology Data Exchange (ETDEWEB)

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

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

2008-12-15

149

Microscale nutrient patches produced by zooplankton  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Both track autoradiography and grain-density autoradiography show that individual zooplankton create miniature patches of dissolved nutrients and that algae exploit those regions to absorb phosphate. The patches are short lived and can be dispersed artificially by small-scale turbulence. Our data support a simple model of encounters between algae and nutrient plumes produced by swimming zooplankton.

Lehman, John T.; Scavia, Donald

1982-01-01

150

Calvert Cliffs zooplankton entrainment study. Final report  

International Nuclear Information System (INIS)

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

1980-01-01

151

Calvert Cliffs zooplankton entrainment study. Final report  

Energy Technology Data Exchange (ETDEWEB)

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.

Bradley, B.P.

1980-01-01

152

Zooplankton data report: Winter MIZEX, 1987  

Energy Technology Data Exchange (ETDEWEB)

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

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

1988-12-01

153

Effects of ultraviolet radiation on pigmentation, photoenzymatic repair, behavior, and community ecology of zooplankton.  

Science.gov (United States)

In this report, we provide a perspective on how zooplankton are able to respond to present and future levels of ultraviolet (UV) radiation, a threat that has been present throughout evolutionary time. To cope with this threat, zooplankton have evolved several adaptations including behavioral responses, repair systems, and accumulation of photoprotective compounds. Common photoprotective compounds include melanins and carotenoids, which are true pigments, but also mycosporine-like amino acids (MAAs) and several other substances, and different taxa use different blends of these compounds. It is not only the level of UV radiation, however, that determines the amount of photoprotective compounds incorporated by the zooplankton, but also other environmental factors, such as predation and supply rate of the compounds. Furthermore, compared to taxa that are less pigmented, those taxa with ample pigmentation are generally less likely to exhibit diel migration. The photoenzymatic repair of UV damages seems to be more efficient at intermediate temperature than at low and high temperatures, suggesting that it is less useful at high and low latitudes, where UV radiation is often extremely high. While predicted future increases in UV radiation are expected to substantially affect many processes, recent studies show that most zooplankton taxa are well adapted to cope with such increases, either by UV avoidance behavior or by incorporation of photoprotective compounds. Hence, we conclude that future increase in UV radiation will have only moderate direct effects on zooplankton biomass and community dynamics. PMID:19707615

Hansson, Lars-Anders; Hylander, Samuel

2009-09-01

154

Vertical migration of aggregated aerobic and anaerobic ammonium oxidizers enhances oxygen uptake in a stagnant water layer.  

Science.gov (United States)

Ammonium can be removed as dinitrogen gas by cooperating aerobic and anaerobic ammonium-oxidizing bacteria (AerAOB and AnAOB). The goal of this study was to verify putative mutual benefits for aggregated AerAOB and AnAOB in a stagnant freshwater environment. In an ammonium fed water column, the biological oxygen consumption rate was, on average, 76 kg O(2) ha(-1) day(-1). As the oxygen transfer rate of an abiotic control column was only 17 kg O(2) ha(-1) day(-1), biomass activity enhanced the oxygen transfer. Increasing the AnAOB gas production increased the oxygen consumption rate with more than 50% as a result of enhanced vertical movement of the biomass. The coupled decrease in dissolved oxygen concentration increased the diffusional oxygen transfer from the atmosphere in the water. Physically preventing the biomass from rising to the upper water layer instantaneously decreased oxygen and ammonium consumption and even led to the occurrence of some sulfate reduction. Floating of the biomass was further confirmed to be beneficial, as this allowed for the development of a higher AerAOB and AnAOB activity, compared to settled biomass. Overall, the results support mutual benefits for aggregated AerAOB and AnAOB, derived from the biomass uplifting effect of AnAOB gas production. PMID:17401560

Vlaeminck, Siegfried E; Dierick, Katleen; Boon, Nico; Verstraete, Willy

2007-07-01

155

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

DEFF Research Database (Denmark)

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

Wieland, Kai

1997-01-01

156

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

Directory of Open Access Journals (Sweden)

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

G. Economou

2008-08-01

157

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

Directory of Open Access Journals (Sweden)

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

G. Economou

2008-01-01

158

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

Energy Technology Data Exchange (ETDEWEB)

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

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

2011-04-15

159

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

International Nuclear Information System (INIS)

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

2011-04-15

160

Fish-mediated trait compensation in zooplankton  

DEFF Research Database (Denmark)

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

Hylander, Samuel; Souza, M.S.

2012-01-01

 
 
 
 
161

Zooplankton of Munzur River (Tunceli, Turkey)  

Digital Repository Infrastructure Vision for European Research (DRIVER)

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

Serap Saler

2011-01-01

162

FUNCTIONAL BIOASSAYS UTILIZING ZOOPLANKTON: A COMPARISON  

Science.gov (United States)

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

163

Zooplankton abundance in relation to state and type of intrusions onto the southeastern United States shelf during summer  

Energy Technology Data Exchange (ETDEWEB)

The vertical distribution of zooplankton on the continental shelf of northeastern Florida was determined in and around upwelling events and related to concentrations of particulate matter. Doliolida and the cladoceran Penilia avirostris were significantly more abundant in upwelled water < 22/sup 0/C and the cyclopoid genus Oncaea more abundant at warmer temperatures. The abundance of doliolida, Oithona and Oncaea in intrusions and the thermocline was significantly higher in older than in recently upwelled waters. The vertical sequences of the abundance of zooplankton and particulate matter (2-114 ..mu..m ESD) were identical. Zooplankton maxima co-occurred primarily with maxima in phytoplankton biomass (chlorophyll a) and only partly with primary productivity. 27 references, 16 figures, 6 tables.

Paffenhoefer, G.A.; Wester, B.T.; Nicholas, W.D.

1984-01-01

164

Lake acidification: Effects on crustacean zooplankton populations  

Energy Technology Data Exchange (ETDEWEB)

The ranked acid sensitivities of six common crustacean zooplankton taxa were determined from a multilake field survey in Ontario and from laboratory bioassays. The two approaches gave the same ranking (from most to least sensitive): Daphnia galeata mendotae, Daphnia retrocurva, and Skistodiaptomus oregonensis > Diaphanosoma birgei > Mesocyclops edax > Bosmina longirostris. This finding suggests that acidification has caused the widespread damage which has been documented for the zooplankton of Ontario and northeastern US lakes. 24 refs., 3 figs., 2 tabs.

Havens, K.E. (Kent State Univ., OH (United States)); Yan, N.D. (Ontario Ministry of the Environment, Dorset (Canada)); Keller, W. (Ontario Ministry of the Environment, Sudbury (Canada))

1993-08-01

165

Zooplankton assemblage of Oyun Reservoir, Offa, Nigeria  

Digital Repository Infrastructure Vision for European Research (DRIVER)

The influence of physico-chemical properties of Oyun Reservoir, Offa, Nigeria (a shallow tropical African reservoir) on its zooplankton composition and abundance were investigated at three stations for two years between January 2002 and December 2003. Diversity is not high: only three groups of zooplankton were found: Rotifera with eight genera; and Cladocera and Copepoda with three genera each. Rotifera dominated numerically (71.02%), followed by Cladocera (16.45%) and Copepoda (12.53%). The...

Mustapha, Moshood K.

2009-01-01

166

A Review: Potentiality of Zooplankton as Bioindicator  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Problem statement: This review tended to summarize some recent research on zooplankton as bioindicator in India and some other countries of the world. Approach: These researches were mainly on fresh water bodies. Results: Qualitative as well as quantitative analysis were done by Shannon diversity index (H'), Evenness index (J), Species Richness index (S) and Saprobic index. In most of the cases zooplankton population size was correlated with biotic and abiotic parameters ...

Zannatul Ferdous; Muktadir, A. K. M.

2009-01-01

167

Neustonic microplastic and zooplankton in the North Western Mediterranean Sea.  

Science.gov (United States)

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

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

2012-04-01

168

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

Science.gov (United States)

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

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

2013-12-01

169

Zooplankton communities in the Krenceng Reservoair, Cilegon, Banten  

Directory of Open Access Journals (Sweden)

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

Mufti P. Patria

2005-11-01

170

LIMNETIC ZOOPLANKTON OF LAKES IN KATMAI NATIONAL MONUMENT, ALASKA  

Science.gov (United States)

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

171

Size-structured risk assessments govern Daphnia migration  

Digital Repository Infrastructure Vision for European Research (DRIVER)

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

Hansson, Lars-anders; Hylander, Samuel

2009-01-01

172

UV radiation and freshwater zooplankton: damage, protection and recovery  

Digital Repository Infrastructure Vision for European Research (DRIVER)

While many laboratory and field studies show that zooplankton are negatively affected when exposed to high intensities of ultraviolet radiation (UVR), most studies also indicate that zooplankton are well adapted to cope with large variations in their UVR exposure in the pelagic zone of lakes. The response mechanisms of zooplankton are diverse and efficient and may explain the success and richness of freshwater zooplankton in optically variable waters. While no single behavioural or physiologi...

Rautio, Milla; Tartarotti, Barbara

2010-01-01

173

Elemental concentration of zooplankton and their particulate products  

International Nuclear Information System (INIS)

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

1974-06-00

174

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

175

A Review: Potentiality of Zooplankton as Bioindicator  

Directory of Open Access Journals (Sweden)

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

Zannatul Ferdous

2009-01-01

176

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

Scientific Electronic Library Online (English)

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

Mujica, Armando; Nava, María L.

177

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

Digital Repository Infrastructure Vision for European Research (DRIVER)

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

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

2010-01-01

178

ZOOPLANKTON OCCURANCE DURING MONSOON SEASON FROM EKRUK TANK, SOLAPUR  

Directory of Open Access Journals (Sweden)

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

M. R. Gurav , K. R. Rao

2014-06-01

179

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

International Nuclear Information System (INIS)

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

1977-04-14

180

Zooplankton assemblage of Oyun Reservoir, Offa, Nigeria  

Directory of Open Access Journals (Sweden)

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

Moshood K Mustapha

2009-12-01

 
 
 
 
181

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

182

Power-plant-related estuarine zooplankton studies  

International Nuclear Information System (INIS)

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

1979-01-29

183

Power-plant-related estuarine zooplankton studies  

Energy Technology Data Exchange (ETDEWEB)

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

Sage, L.E.; Olson, M.M.

1981-01-01

184

ZOOPLANKTON IN EAST COAST OF PENINSULAR MALAYSIA  

Directory of Open Access Journals (Sweden)

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.

N. IWASAKI

2006-12-01

185

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

Energy Technology Data Exchange (ETDEWEB)

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

Smith, S.L.

1982-01-01

186

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

International Nuclear Information System (INIS)

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

1992-05-15

187

Preliminary study of the effect of pumped-storage plant operation on zooplankton  

Energy Technology Data Exchange (ETDEWEB)

The hydromechanical effect of hydroelectric stations on zooplankton is customarily regarded as a constantly acting and comparatively harmless factor, since its destruction is inevitable when water masses are passed through hydroelectric stations, but its capacity for restoration is high (i.e., destruction of the zooplankton of the forebay is compensated by its production in the after bay). It is not known how correct such an opinion is, or what is the true balance of losses and reproduction of zooplankton in the forebays and after bays of hydroelectric stations. However, hydroelectric plants of a new type, pumped-storage plants, have been constructed in recent years and others are planned for the Dnieper reservoirs. The operational principle and purpose of these plants is that they employ special vertical turbine-electric pumps that pump water at night from the reservoirs into pumped-storage facilities at high levels, and then release this water during daytime peaks through pipes to the turbines that generate additional electric power. Such pumped-storage plants are planned, in particular, as part of the Danube-Dnieper water economy complex and for some reservoirs in the North European regions of the USSR.

Tseyeb, Y.Y.; Zhdanova, G.A.

1980-01-01

188

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

Energy Technology Data Exchange (ETDEWEB)

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

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

2005-07-01

189

Size-structured risk assessments govern Daphnia migration.  

Science.gov (United States)

One of the more fascinating phenomena in nature is animal mass migrations and in oceans and freshwaters, diel variations in depth distribution of zooplankton are a phenomenon that has intrigued scientists for more than a century. In our study, we show that zooplankton are able to assess the threat level of ultraviolet radiation and adjust their depth distribution to this level at a very fine tuned scale. Moreover, predation risk induces a size-structured depth separation, such that small individuals, which we show are less vulnerable to predation than larger, make a risk assessment and continue feeding in surface waters during day, offering a competitive release from down-migrating larger animals. Hence, we mechanistically show that such simple organisms as invertebrate zooplankton are able to make individual, size-specific decisions regarding how to compromise between threats from both predators and UV radiation, and adjust their diel migratory patterns accordingly. PMID:18812291

Hansson, Lars-Anders; Hylander, Samuel

2009-01-22

190

Selective uptake of 55Fe from seawater by zooplankton  

International Nuclear Information System (INIS)

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

1978-01-01

191

Temperature effects on phytoplankton diversity — The zooplankton link  

Science.gov (United States)

Recent climate warming is expected to affect phytoplankton biomass and diversity in marine ecosystems. Temperature can act directly on phytoplankton (e.g. rendering physiological processes) or indirectly due to changes in zooplankton grazing activity. We tested experimentally the impact of increased temperature on natural phytoplankton and zooplankton communities using indoor mesocosms and combined the results from different experimental years applying a meta-analytic approach. We divided our analysis into three bloom phases to define the strength of temperature and zooplankton impacts on phytoplankton in different stages of bloom development. Within the constraints of an experiment, our results suggest that increased temperature and zooplankton grazing have similar effects on phytoplankton diversity, which are most apparent in the post-bloom phase, when zooplankton abundances reach the highest values. Moreover, we observed changes in zooplankton composition in response to warming and initial conditions, which can additionally affect phytoplankton diversity, because changing feeding preferences of zooplankton can affect phytoplankton community structure. We conclude that phytoplankton diversity is indirectly affected by temperature in the post-bloom phase through changing zooplankton composition and grazing activities. Before and during the bloom, however, these effects seem to be overruled by temperature enhanced bottom-up processes such as phytoplankton nutrient uptake.

Lewandowska, Aleksandra M.; Hillebrand, Helmut; Lengfellner, Kathrin; Sommer, Ulrich

2014-01-01

192

Thermal stress studies on selected zooplankton species and an isopod  

Energy Technology Data Exchange (ETDEWEB)

Laboratory determination of temperature stress levels and assessment of their ecological consequences was carried out for selected zooplankton species to develop data for ecological impact associated with industrial use of natural water for cooling. An included literature search revealed substantial fish and benthos data, but little on stress temperature effects on zooplankton. Information was gathered on two cladocerans, four copepods and an isopod.

Bunting, D.L.; Cheper, N.J.

1980-06-01

193

COMPARISONS OF ZOOPLANKTON COMMUNITY SIZE STRUCTURE IN THE GREAT LAKES  

Science.gov (United States)

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

194

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

Directory of Open Access Journals (Sweden)

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

WJ. Minto

2010-02-01

195

Effects of a synthetic oil on zooplankton community structure  

Energy Technology Data Exchange (ETDEWEB)

This study assessed the effects of a coal-derived oil on the structure of zooplankton communities of laboratory pond microcosms and outdoor experimental ponds. Several measures of community structure and multivariate statistical techniques were used to reveal changes in the patterns of zooplankton community structure caused by the perturbation. From these results the basic ecological mechanisms responsible for maintenance of zooplankton community structure were inferred. The comparison of the field, laboratory microcosm, and laboratory bioassay results for the effects of oil provided an empirical basis for predicting pollutant effects on aquatic ecosystems. The responses of the microcosm and pond zooplankton communities to oil treatment were quite similar. Changes in cladoceran densities were the most sensitive indicators of stress in the zooplankton communities. Copepods were slightly less sensitive, and rotifers were least sensitive to oil treatment.

Hook, L.A.

1988-01-01

196

Zooplankton assemblage of Oyun Reservoir, Offa, Nigeria  

Scientific Electronic Library Online (English)

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

Mustapha, Moshood K.

197

Mesoscale distribution and community composition of zooplankton in the Mozambique Channel  

Science.gov (United States)

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

Huggett, Jenny A.

2014-02-01

198

Zooplankton response to biogas slurry in carp ponds  

Energy Technology Data Exchange (ETDEWEB)

Biogas slurry (BGS) applied at 52.1 litres ha{sup -1} day{sup -1} (6.4% dry matter) resulted in a significant increase in total zooplankton over the control. Addition of supplementary feed, comprised of rice bran (3 parts) and groundnut oil-cake (1 part, dry w/w basis), further increased total zooplankton production. Differences in zooplankton densities among treatments were due to corresponding differences in green algae. The application of biogas slurry, however, did not change the community structure of zooplankton. Generally, copepods remained the single largest group in all the treatments, including the control, although their per cent contribution to total zooplankton showed a distinct decline with an increase in nutrient enrichment. Rotifers, on the other hand, increased their per cent contribution to total zooplankton with a increase in nutrient enrichment. Cladocerans were poorly represented in all the treatments. Highest production of total zooplankton in biogas slurry plus supplementary feed-treated tanks resulted in maximum fish yield in these tests. (author).

Sehgal, H.S.; Kaur, K.; Sehgal, G.K. (Punjab Agricultural Univ., Ludhiana (IN). Dept. of Zoology)

1992-01-01

199

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

International Nuclear Information System (INIS)

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

1993-09-01

200

Effect of various intake designs on zooplankton entrainment  

Energy Technology Data Exchange (ETDEWEB)

Field studies were conducted at the intakes of three Tennessee Valley Authority electric power plants to determine whether intake design is a feasible means of mitigating effects on zooplankton by minimizing the quantity entrained. Three intake designs were evaluated: one with a shallow skimmer wall, one with a deep skimmer wall, and one with no skimmer wall. Several studies indicated possible differences between day and night in the quantity of zooplankton entrained. None of these studies indicated that the intake designs studied minimized the quantity of zooplankton entrained because the quantities in the intake canals were similar to the quantities in the source water body.

Dycus, D.L.

1983-03-01

 
 
 
 
201

Assessment of thermal discharges on zooplankton in Conowingo Pond, Pennsylvania  

Energy Technology Data Exchange (ETDEWEB)

Natural variations must be distinguished from those due to facility operation in any attempt to assess accurately the impacts of power station thermal discharges on zooplankton communities in receiving waters. Covariance analysis proved helpful in separating natural variations from those due to operation of the Peach Bottom Atomic Power Station in Conowingo Pond, on the lower Susquehanna River, Pa. The covariance technique overcame problems associated with other assessment techniques. Multiple regression analysis indicated that an increase in zooplankton production, particularly in winter, would result from thermal discharges. Zooplankton population in Conowingo Pond showed great resiliency. (1 diagram, 5 graphs, 1 map, 13 references, 5 tables)

Mathur, D.; Robbins, T.W.; Purdy, E.J.

1980-06-01

202

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

International Nuclear Information System (INIS)

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

1986-01-01

203

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

Energy Technology Data Exchange (ETDEWEB)

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

Napp, J.M.

1986-01-01

204

Revisiting the role of zooplankton in pelagic ecosystems  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Preface of the 38th International Liège Colloquium on Ocean Dynamics (Liège, Belgium, 8–12 May 2006) : Revisiting the role of zooplankton in pelagic ecosystems. Issue of JMS edited by Jean-Henri Hecq and Anne Goffart.

Hecq, Jean-henri; Goffart, Anne

2009-01-01

205

GUIDELINES FOR ZOOPLANKTON SAMPLING IN QUANTITATIVE BASELINE AND MONITORING PROGRAMS  

Science.gov (United States)

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

206

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....

207

Body size and food size in freshwater zooplankton  

Digital Repository Infrastructure Vision for European Research (DRIVER)

We used double-label liquid scintillation techniques to measure the efficiencies with which eight different-sized zooplankton species ingested four cell types relative to a standard cell type (Chlamydomonas). Efficiency ratios (ERs: clearance rate on cell type X ÷ clearance rate on Chlamydomonas) on the three ultraplankton (<5 ?m in diameter) cells (a coccoid bacterium and the algae Synechococcus and Nannochloris) varied greatly among zooplankton species but were not correlated with zooplan...

Bogdan, Kenneth G.; Gilbert, John J.

1984-01-01

208

On autumn zooplankton of Semipalatinsk test site water-bodies  

International Nuclear Information System (INIS)

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

2000-01-01

209

Interactions between Predation and Resources Shape Zooplankton Population Dynamics  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Identifying the relative importance of predation and resources in population dynamics has a long tradition in ecology, while interactions between them have been studied less intensively. In order to disentangle the effects of predation by juvenile fish, algal resource availability and their interactive effects on zooplankton population dynamics, we conducted an enclosure experiment where zooplankton were exposed to a gradient of predation of roach (Rutilus rutilus) at different algal concentr...

Nicolle, Alice; Hansson, Lars-anders; Brodersen, Jakob; Nilsson, P. Anders; Brönmark, Christer

2011-01-01

210

Improved Method for Determining Bacterial Filtration Rates in Zooplankton  

Digital Repository Infrastructure Vision for European Research (DRIVER)

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

Marvalin, Olivier; Lazarek, Stanislaw

1988-01-01

211

Procedures involved in radioecological studies with marine zooplankton  

International Nuclear Information System (INIS)

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

1975-01-01

212

Zooplankton use of chemodetection to find and eat particles  

Digital Repository Infrastructure Vision for European Research (DRIVER)

The ability of raptorial zooplankton to find large particles such as marine aggregates is crucial to their use of the particles as food and to the fate of the particles. Kiorboe & Thygesen (2001) developed a numerical approach to describe particle detection by chemosensory zooplankton. In this paper, we develop and test a simplified mathematical description of the process and explore the ecological implications of chemosensory particle detection. Our results suggest that chemosensory particle...

Jackson, G. A.; Kiørboe, Thomas

2008-01-01

213

A Comparative Atlas of Zooplankton: Biological Patterns in the Oceans  

Science.gov (United States)

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

Biggs, Douglas C.

214

Zooplankton data report: the Marginal Ice Zone Experiment MIZEX, 1984  

Energy Technology Data Exchange (ETDEWEB)

The Marginal Ice Zone Experiment (MIZEX 84) concentrated on atmospheric, oceanic, and ice interactions in the Fram Strait region of the Greenland Sea, specifically the effect of the retreating ice margin on the productivity in the area and the use of zooplanktonic species as indicators of Arctic and North Atlantic water masses. The data in this report are the quantitative analyses of zooplankton collected while aboard the research vessel Polarstern.

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

1986-03-01

215

Interactions between predation and resources shape zooplankton population dynamics.  

Science.gov (United States)

Identifying the relative importance of predation and resources in population dynamics has a long tradition in ecology, while interactions between them have been studied less intensively. In order to disentangle the effects of predation by juvenile fish, algal resource availability and their interactive effects on zooplankton population dynamics, we conducted an enclosure experiment where zooplankton were exposed to a gradient of predation of roach (Rutilus rutilus) at different algal concentrations. We show that zooplankton populations collapse under high predation pressure irrespective of resource availability, confirming that juvenile fish are able to severely reduce zooplankton prey when occurring in high densities. At lower predation pressure, however, the effect of predation depended on algal resource availability since high algal resource supply buffered against predation. Hence, we suggest that interactions between mass-hatching of fish, and the strong fluctuations in algal resources in spring have the potential to regulate zooplankton population dynamics. In a broader perspective, increasing spring temperatures due to global warming will most likely affect the timing of these processes and have consequences for the spring and summer zooplankton dynamics. PMID:21304980

Nicolle, Alice; Hansson, Lars-Anders; Brodersen, Jakob; Nilsson, P Anders; Brönmark, Christer

2011-01-01

216

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

Science.gov (United States)

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

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

2013-12-01

217

Fluxes of biogenic carbon in the Southern Ocean: roles of large microphagous zooplankton1  

Science.gov (United States)

The Southern Ocean is an extreme environment, where waters are permanently cold, a seasonal ice cover extends over large areas, and the solar energy available for photosynthesis is severely restricted, either by vertical mixing to considerable depths or, especially south of the Antarctic Circle, by prolonged seasonal periods of low or no irradiance. Such conditions would normally lead to low productivity and a water column dominated by recycling processes involving microbial components of pelagic communities but this does not seem to be the case in the Southern Ocean, where there is efficient export to large apex predators and deep waters. This paper investigates the role of large microphagous zooplankton (salps, krill, and some large copepods) in the partitioning of biogenic carbon among the pools of short- and long-lived organic carbon and sequestered biogenic carbon. Large microphagous zooplankton are able to ingest microbial-sized particles and thus repackage small, non-sinking particles into both metazoan biomass and large, rapidly sinking faeces. Given the wide spatio-temporal extent of microbial trophic pathways in the Southern Ocean, large zooplankton that are omnivorous or able to ingest small food particles have a competitive advantage over herbivorous zooplankton. Krill efficiently transfer carbon to a wide array of apex predators and their faecal pellets are exported to depth during occasional brief sedimentation episodes in spring time. Salps may be a significant link towards some fish (directly) and other apex predators (indirectly) and, at some locations (especially in offshore waters) and time, they may account for most of the downward flux of biogenic carbon. Large copepods are a trophic link towards fish and at least one whale species, and their grazing activity generally impedes the export of organic particles to depth. As a result, biogenic carbon is channelled mainly towards apex predators and episodically into the deep ocean. Without these original interactions, Antarctic waters might well be dominated by microbial components and recycling processes instead of active export from the generally small primary producers towards large apex predators.

Le Fèvre, Jacques; Legendre, Louis; Rivkin, Richard B.

1998-11-01

218

Return migration.  

Science.gov (United States)

The author reviews the findings of the growing literature on return migration. Topics covered include typologies of return migrants, reasons for return, adaptation and readjustment of returnees, and the impact of return migration on the migrants' home societies. The focus of the study is on international return migration, migration to Northern Europe and northeastern North America, and return migration to the southern and eastern fringes of Europe and the Caribbean PMID:12264425

Gmelch, G

1980-01-01

219

Planet Migration  

Digital Repository Infrastructure Vision for European Research (DRIVER)

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

Lubow, Stephen H.; Ida, Shigeru

2010-01-01

220

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

 
 
 
 
221

The Underwater Vision Profiler 5: An advanced instrument for high spatial resolution studies of particle size spectra and zooplankton  

Digital Repository Infrastructure Vision for European Research (DRIVER)

The Underwater Vision Profiler (UVP) was developed to quantify the vertical distribution of macroscopic particles and zooplankton > 100 mu m in size. The smaller size limit is fixed by optical resolution, whereas the larger size limit is determined by the volume of water illuminated per image. The new fifth generation instrument (UVP5) is compact (30 kg in air) and operates either as a stand-alone instrument with an independent power supply for use on a mooring or free-drifting array, or as a...

Picheral, Marc; Guidi, Lionel; Stemmann, Lars; Karl, David M.; Iddaoud, Ghizlaine; Gorsky, Gabriel

2010-01-01

222

Nitrogen isotopic ratios in fecal pellets produced by marine zooplankton  

Energy Technology Data Exchange (ETDEWEB)

At each site and in every season studied, zooplankton in the upper ocean produced fecal pellets that were 1.3% lower in {delta}{sup 15}N than their body tissue but 2.2% higher than their apparent food source. {sup 14}N-containing molecules are evidently preferentially assimilated in zooplankton intestinal tracts, though other isotopic effects must account for the enrichment in {sup 15}N of these organisms relative to their food. These results also show zooplankton to be important modifiers of nitrogen isotopic ratios for marine particulate matter. {delta}{sup 15}N values for sinking particles and fecal pellets are similar, supporting the perspective that macrozooplankton are important factors in producing and processing particles that sink into the ocean's interior and sediments. In contrast, the relationship in {delta}{sup 15}N between fecal pellets and suspended particles in the euphotic zone is more variable. It appears that zooplankton select food particles of varying {delta}{sup 15}N from the suspended particle pool. These results suggest that both zooplankton feeding behavior and their digestive chemistry are important in determining the composition of sinking particulate matter in the ocean with respect to the suspended particle source in the euphotic zone.

Altabet, M.A. (Woods Hole Oceanographic Institution, MA (USA)); Small, L.F. (Oregon State Univ., Corvallis (USA))

1990-01-01

223

Zooplankton-phytoplankton interactions simulated by combining distinct modeling approaches in the Norwegian Sea  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Calanus finmarchicus is the dominant herbivorous mesozooplankton in the Norwegian Sea and has the potential for impacting strongly on the population dynamics of phytoplankton. We have developed a novel individual based Calanus model with simulated evolution of behavioural traits, including vertical migration strategies and timing of ontogenetic migrations. The results show that the simulated Calanus population is able to remain viable in the Norwegian Sea basin over hundreds of years and evol...

2007-01-01

224

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

Digital Repository Infrastructure Vision for European Research (DRIVER)

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

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

2012-01-01

225

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

Digital Repository Infrastructure Vision for European Research (DRIVER)

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

Md. Towhid Ibna Alam; Md. Anwar Kabir

2003-01-01

226

Effects of experimental acidification on zooplankton population and community dynamics  

Energy Technology Data Exchange (ETDEWEB)

Experimental evidence is provided of indirect ecological changes occurring through alterations in both competitive and predatory interactions within zooplankton communities during acidification. Acidification experiments were conducted on zooplankton in 16-m[sup 3] enclosures suspended in a Precambrian Shield lake in central Ontario in order to identify mechanisms of community change. Changes in abundance, body size, egg ratio, and lipid status in zooplankton populations reflected changes in biotic interactions during acidification to pH between 5.0 and 6.0. Abundance of small cladocerans (especially Bosmina longirostris) increased following acidification despite increases in abundance or dominance of their cyclopoid predators. Increased reproduction of Bosmina, in the absence of detectable changes in edible phytoplankton biomass, suggests that this was due to competitive release from larger cladoceran species that did not survive acidification. 45 refs., 3 figs., 7 tabs.

Locke, A.; Sprules, W.G. (Toronto Univ., Mississauga, ON (Canada))

1993-01-01

227

Zooplankton abundance and diversity in Lake Bracciano, Latium, Italy  

Directory of Open Access Journals (Sweden)

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

Fiorenza G. MARGARITORA

2002-08-01

228

Locomotor adaptations of some gelatinous zooplankton.  

Science.gov (United States)

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

Bone, Q

1985-01-01

229

Release of Dissolved Amino Acids by Marine Zooplankton.  

Science.gov (United States)

Marine net zooplankton release dissolved amino acids into the water. Release rates are positively correlated with temperature and can be estimated by the equation: Release rate, (milligrams of alpha-amino nitrogen per gram dry weight of zooplankton per day) = 1.0 x temperature ( degrees C) -5.9. Release rates appeared to be independent of the taxonomic composition of the test samples, which were variously dominated by copepods, salps, chaetognaths, coelenterates, or radiolarians. These amino acids constitute an important source of dissolved organic matter in the sea. PMID:17829748

Johannes, R E; Webb, K L

1965-10-01

230

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

231

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.

2008-08-01

232

FORAGE FISH AND ZOOPLANKTON COMMUNITY COMPOSITION IN WESTERN LAKE SUPERIOR  

Science.gov (United States)

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

233

Phytoplankton and zooplankton of the Lednicke rybniky fishponds  

International Nuclear Information System (INIS)

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

2003-06-01

234

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

Science.gov (United States)

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

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

2009-01-01

235

Effect of various intake designs on zooplankton entrainment  

Energy Technology Data Exchange (ETDEWEB)

Field studies were conducted at the intakes of three Tennessee Valley Authority electric power plants to determine whether intake design is a feasible means of mitigating effects on zooplankton by minimizing the quantity entrained. Three intake designs were evaluated: one with a shallow skimmer wall, one with a deep skimmer wall, and one with no skimmer wall. Many sample sets from these studies were highly variable because of inadequate sample replication, thus precluding the use of statistical tests on some of the data. Where possible, an analysis of variance and a Student, Newman, Keuls multiple range test were computed and tested at the 0.05 level. Several studies indicated possible differences between day and night in the quantity of zooplankton entrained. The greater quantities entrained at night were related to a greater abundance in the source water body at night rather than to intake design. These results indicate that time-of-day differences might be used to mitigate effects on zooplankton at some intakes if the intake could be operated to require less cooling water when concentrations were greatest. None of these studies indicated that the intake designs studied minimized the quantity of zooplankton entrained because the quantities in the intake canals were similar to the quantities in the source water body.

Dycus, D.L.

1983-03-01

236

Zooplankton Diversity Of Dnyanganga Reservoir Near Khamgaon, Maharashtra  

Directory of Open Access Journals (Sweden)

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

G. B. Kale

2013-09-01

237

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

Science.gov (United States)

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

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

2005-01-01

238

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

Directory of Open Access Journals (Sweden)

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

Bowszys M.

2014-03-01

239

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

Science.gov (United States)

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

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

2008-08-01

240

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

Directory of Open Access Journals (Sweden)

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

TUDOR Mihaela

2009-09-01

 
 
 
 
241

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

242

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

243

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

244

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

Science.gov (United States)

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

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

2012-02-01

245

210Po and 210Pb in zooplankton fecal pellets  

International Nuclear Information System (INIS)

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

1978-01-01

246

Estimation of zooplankton mortality caused by an Arctic glacier outflow  

Directory of Open Access Journals (Sweden)

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

Marek J. Zaj±czkowski

2001-09-01

247

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

Energy Technology Data Exchange (ETDEWEB)

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

Day, K.E.

1986-01-01

248

Zooplankton Composition of Pulumur Stream (Tunceli-Turkey  

Directory of Open Access Journals (Sweden)

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

Hilal Haykir

2011-01-01

249

Zooplankton Composition of Pulumur Stream (Tunceli-Turkey)  

Digital Repository Infrastructure Vision for European Research (DRIVER)

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

2011-01-01

250

High dispersal capacity of cladoceran zooplankton in newly found communities  

Digital Repository Infrastructure Vision for European Research (DRIVER)

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

Louette, G.; Meester, L.

2008-01-01

251

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

2008-02-01

252

Next Generation Sequencing Reveals the Hidden Diversity of Zooplankton Assemblages  

Science.gov (United States)

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

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

2013-01-01

253

Bacteria of the ?-Subclass Proteobacteria Associated with Zooplankton in Chesapeake Bay  

Digital Repository Infrastructure Vision for European Research (DRIVER)

The seasonal abundance of ?-subclass Proteobacteria, Vibrio-Photobacterium, Vibrio cholerae-Vibrio mimicus, Vibrio cincinnatiensis, and Vibrio vulnificus in the Choptank River of Chesapeake Bay associated with zooplankton was monitored from April to December 1996. Large (>202-?m) and small (64- to 202-?m) size classes of zooplankton were collected, and the bacteria associated with each of the zooplankton size classes were enumerated by fluorescent oligonucleotide direct count. Large popula...

2002-01-01

254

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

International Nuclear Information System (INIS)

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

1994-01-01

255

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

Directory of Open Access Journals (Sweden)

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

Md. Towhid Ibna Alam

2003-01-01

256

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

Digital Repository Infrastructure Vision for European Research (DRIVER)

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

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

2013-01-01

257

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

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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 structur...

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

2001-01-01

258

Stable carbon isotope signatures of zooplankton in some reservoirs in Korea  

Digital Repository Infrastructure Vision for European Research (DRIVER)

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

2013-01-01

259

Zooplankton chitobiase activity as an endpoint of pharmaceutical effect.  

Science.gov (United States)

Numerous human and veterinary pharmaceuticals are constantly entering surface waters, despite little understanding of their potential impacts on aquatic ecosystems. To address this concern, an attempt to create a simple, reproducible, inexpensive, and sublethal toxicity bioassay for freshwater zooplankton was initiated. The approach was centered on characterizing the response of a zooplankton enzyme, chitobiase, to the presence of a toxicant. The aim of the present research was to develop a reproducible laboratory-based assay for Daphnia magna chitobiase activity and to screen four commonly prescribed pharmaceuticals using that assay. The four pharmaceuticals tested for potential effects on D. magna chitobiase activity were atorvastatin, lovastatin, fluoxetine, and sertraline. We were able to detect exposure-associated differences in chitobiase activity at concentrations of 0.1 mug/L fluoxetine after 24 and 72 hours of exposure. Differences were also detected for the other compounds. The response of chitobiase was found to be promising as an assay to measure sublethal effects in D. magna and perhaps other zooplankton species. PMID:17972005

Richards, S M; Kelly, S E; Hanson, M L

2008-05-01

260

Considerations on the biochemical composition of some freshwater zooplankton species.  

Directory of Open Access Journals (Sweden)

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

Nicoletta RICCARDI

1999-02-01

 
 
 
 
261

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

262

Studies on the zooplankton of the deep subalpine Lake Garda.  

Directory of Open Access Journals (Sweden)

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

Luigi NASELLI-FLORES

1999-02-01

263

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

Scientific Electronic Library Online (English)

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

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

264

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

Directory of Open Access Journals (Sweden)

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

Nishida Mutsumi

2009-09-01

265

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

International Nuclear Information System (INIS)

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

2013-01-01

266

Dominance shift of zooplankton species composition in the central Strait of Georgia, British Columbia during 1997 Cambio en el zooplancton dominante del estrecho de Georgia, British Columbia durante 1997  

Digital Repository Infrastructure Vision for European Research (DRIVER)

A multivariate analysis of the zooplankton was completed during the 1997 annual cycle in the central Strait of Georgia, Canada. Sampling was conducted monthly in a single location (49° 15' 0" N, 123° 44' 9" W). The study used the species as environment descriptors, and examined possible patterns of species associations. Principal components analysis showed two groups of species coinciding with changes in vertical salinity structure arising from two phases of the Fraser River runoff. Group I...

Haro-garay, Martha J.; Leonardo Huato Soberanis

2008-01-01

267

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

Science.gov (United States)

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

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

1982-07-01

268

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

Science.gov (United States)

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

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

2011-01-01

269

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

Science.gov (United States)

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

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

2008-01-01

270

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

Science.gov (United States)

Hydroacoustics can be used to assess zooplankton populations, however, backscatter must be scaled to be biologically meaningful. In this study, we used a general model to correlate site-specific hydroacoustic backscatter with zooplankton dry weight biomass estimated from net tows. The relationship between zooplankton dry weight and backscatter was significant (p zooplankton dry weight biomass, we used geostatistics to analyze the mean and variance, and ordinary kriging to create spatial zooplankton distribution maps. The mean zooplankton dry weight biomass estimates from plankton net tows and hydroacoustics were not significantly different (p = 0.19) but the hydroacoustic data had a significantly lower coefficient of variation (p zooplankton distribution illustrated spatial trends in zooplankton dry weight biomass that were not discernable from the overall means.

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

2006-01-01

271

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

Digital Repository Infrastructure Vision for European Research (DRIVER)

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

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

2006-01-01

272

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

Directory of Open Access Journals (Sweden)

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

D. N. Veerendra

2012-12-01

273

[Limnetic zooplankton run-off a high-head dam and their fate in a river with high current velocity (case of the Krasnoiarsk hydroelectric power station on the Yenisei river].  

Science.gov (United States)

The vertical distribution of net zooplankton in head-water of Krasnoyarsk hydroelectric power station and its horizontal distribution in the tail-water were studied during two years in winter and summer seasons. In order to distinguish living and dead individuals the special staining was used. It was revealed that on average 77% of living plankton pass through high-head dam with deep water scoop to the tailwater. While passing through dam aggregates some individuals of the reservoir plankton are traumatized and die, that results in some increase of portion of dead individuals in the tail water near dam (from 3 to 6%). Alive zooplankton passed through the dam aggregates is eliminated under the Upper Yenisei highly turbulent conditions. There is approximately 10% of it in 32 km from the dam if compare with biomass in 20-40 m layer of reservoir, the portion of dead increases to 11%. The biomass of zooplankton suspended in the water column of the tail-water sometimes increases (till > 1 g/m3) due to large Copepoda Heteroscope borealis, which inhabits near-bottom and near-shore river zones and can be found in the central part of the river during reproductive period. Limnetic zooplankton from the reservoir cannot be considered as important food for planktivores in the tail-water. PMID:15032067

Dubovskaia, O P; Gladyshev, M I; Makhutova, O N

2004-01-01

274

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

Science.gov (United States)

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

275

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

Science.gov (United States)

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

276

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

Science.gov (United States)

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

277

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

International Nuclear Information System (INIS)

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

2012-02-01

278

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

Science.gov (United States)

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

279

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

280

Neustonic microplastic and zooplankton in the North Western Mediterranean Sea  

Digital Repository Infrastructure Vision for European Research (DRIVER)

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

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

2012-01-01

 
 
 
 
281

Antarctic zooplankton metabolism: carbon requirements and ammonium excretion of salps and crustacean zooplankton in the vicinity of the Bransfield Strait during January 1994  

Science.gov (United States)

Metabolic rates (oxygen consumption and ammonia excretion) of zooplankton were determined during the austral summer (January 1994), in the eastern Bransfield Strait. The study area comprised four distinct hydrographic zones: the ice edge on the western Weddell Sea, the waters of Weddell Sea origin, the southern part of the Weddell-Scotia Confluence, and the waters of Bellingshausen origin. The objectives were to estimate the fraction of primary production accounted for by the metabolism of salps and crustacean zooplankton, as well as the contribution of their excretion to the nitrogen demand of phytoplankton. Biomass-specific respiration and excretion rates of zooplankton were measured simultaneously by incubation methods at in situ temperatures. Zooplankton biomass was measured as organic C on aliquots of samples taken between 0 and 200 m. Primary production was measured by 14C incorporation, using photosynthesis-irradiance relationships. Primary production ranged from 179 to 1612 mg C m -2 day -1. Salps were the most abundant zooplankton group, located mainly in the northern part of the study area, where they excluded other zooplankters. Their biomass ranged from 115 to 2930 mg C m -2 (0-200 m). On average, their metabolic carbon requirements represented about 5% of primary production per day, and their excretion of ammonia contributed 10% of daily phytoplankton nitrogen demand. Crustacean zooplankton were of minor importance in the study area, except at the ice edge and areas of recently melted ice. Their biomass ranged from 14.5 to 494 mg C m -2 and they required on average 0.9% of daily primary production, while ammonia excretion accounted for around 0.4% of the phytoplankton nitrogen demand. During this cruise, salps were the most important zooplankton group from the point of view of the transfer of biogenic carbon and nitrogen recycling. However, the control exerted by zooplankton on primary producers was overall modest, and most of the phytoplankton carbon probably sedimented out of the water column.

Alcaraz, M.; Saiz, E.; Fernandez, J. A.; Trepat, I.; Figueiras, F.; Calbet, A.; Bautista, B.

1998-11-01

282

Zooplankton size selection relative to gill raker spacing in rainbow trout  

Science.gov (United States)

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

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

2005-01-01

283

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

284

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

Science.gov (United States)

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

285

Temporal and spatial distribution of microcrustacean zooplankton in relation to turbidity and other environmental factors in a large tropical lake (L. Tana, Ethiopia)  

Digital Repository Infrastructure Vision for European Research (DRIVER)

The spatial and seasonal distribution of microcrustacean zooplankton of Lake Tana (Ethiopia) was monthly studied for 2 years. Concurrently, various environmental parameters were measured and related to zooplankton distribution. Canonical Correspondence Analysis (CCA) was used to estimate the influence of abiotic factors and chlorophyll a content in structuring the zooplankton assemblage. Among the environmental factors, zooplankton abundance correlated most strongly with turbidity. Turbidity ...

Dejen, E.; Vijverberg, J.; Nagelkerke, L. A. J.; Sibbing, F. A.

2004-01-01

286

Migration of shallow seismic reflection data  

Energy Technology Data Exchange (ETDEWEB)

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

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

1994-03-01

287

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

Digital Repository Infrastructure Vision for European Research (DRIVER)

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

2007-01-01

288

Zooplankton size and distribution within mesoscale structures in the Mozambique Channel: A comparative approach using the TAPS acoustic profiler, a multiple net sampler and ZooScan image analysis  

Science.gov (United States)

Two surveys were conducted in the Mozambique Channel in November 2009 and April/May 2010 to study the influence of mesoscale eddies on the zooplanktonic component of the ecosystem. Three complementary methods were used to sample zooplankton: (1) hydro-acoustics with a TAPS™ multi-frequency zooplankton profiler; (2) in situ biological sampling using a Multinet with samples processed via the classical settled biovolume technique; (3) ZooScan image analysis which determines biovolume, size and taxonomic composition. This approach presented an ideal opportunity to compare the results of these different methods which highlighted a large overlap in their detectable size range. Each method favoured a particular size fraction of the population, i.e. TAPS for the microzooplankton (3 mm ESR). In the case of the 2009 cruise, a well-established cyclone-anticyclone dipole was sampled, with results clearly indicating a higher concentration of zooplankton in the cyclonic eddy compared to the anticyclonic counterpart. The TAPS also detected high surface (0-22 m) concentrations of what appeared to be microzooplankton or marine snow in the cyclone. In 2010, the eddy field was less defined and more spatially variable compared to that in 2009. Two cyclonic and anticyclonic features were sampled during the cruise, each with different life histories and levels of stability. Results were inconsistent compared to those of 2009 and dependent on the size component of the population, with both cyclonic and anticyclonic features capable of having higher planktonic biomass. Differences in species composition between these mesoscale features were not too different and mainly a matter of relative biovolume. Less well formed eddy fields, particularly in the mid-Mozambique Channel, therefore appear to result in indistinct vertical and horizontal zooplankton distribution patterns.

Lebourges-Dhaussy, A.; Huggett, J.; Ockhuis, S.; Roudaut, G.; Josse, E.; Verheye, H.

2014-02-01

289

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

Directory of Open Access Journals (Sweden)

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

Imoobe T.O.T.

2009-01-01

290

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

Science.gov (United States)

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

Rios-Jara, E.

1998-06-01

291

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

292

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

Directory of Open Access Journals (Sweden)

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

M. Arun Kumar

2013-09-01

293

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

Directory of Open Access Journals (Sweden)

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

Che Abd Rahim Mohamed

2005-01-01

294

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

International Nuclear Information System (INIS)

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

2011-08-01

295

Evaluation of a system to automatically sample zooplankton from the discharge of dams  

Energy Technology Data Exchange (ETDEWEB)

Automatic plankton samplers installed at two dams on the Connecticut River continuously monitored crustacean zooplankton from October 1977 through 1979 and allowed a significant reduction in man-hours involved in an extensive sampling program. Automatic samplers efficiently sampled most species and size classes of crustacean zooplankton in a similar, but not consistently identical manner as a commonly used towed-net plankton sampler. The smallest sized zooplankton were captured more efficiently than the largest. Mesh selection and sampler avoidance exerted different influences on automatic samplers and towed nets. Future use of the samplers and direct comparison of results to results obtained by other methods was supported.

Rosen, R.A.

1982-02-01

296

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

International Nuclear Information System (INIS)

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

1992-01-01

297

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

Energy Technology Data Exchange (ETDEWEB)

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

Schmidt, S.; Reyss, J.L.; Buat-Menard, P. (Centre National de la Recherche Scientifique (CNRS), 91 - Gif-sur-Yvette (France). Centre des Faibles Radioactivites); Nival, P.; Baker, M.

1992-01-01

298

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

Science.gov (United States)

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

Schneider, G.

1992-12-01

299

Radial Migration in Galactic Thick Discs  

CERN Document Server

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

300

International Migration and Remittances  

Directory of Open Access Journals (Sweden)

Full Text Available Human migration is a physical movement by human beings from one geographical areato another geographical area. Migration is internal as well as external. At theinternational level, no universally accepted definition for “Migrant” exists. The UniteNations defines “migration as an individual who has resided in a foreign country formore than one year irrespective of the causes, voluntary or involuntary, and the means,regular or irregular, used migrate”. Key terms of migrations is documented migration,economic migration, irregular migration, skilled migration, temporary workersmigration, internally displaced persons (IDP migration, refugee, stateless person, etc. .

Dattatray Sitaram Bagade

2012-08-01

 
 
 
 
301

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

Directory of Open Access Journals (Sweden)

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

TÖRÖK Liliana

2007-10-01

302

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

Directory of Open Access Journals (Sweden)

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

Wendel Keller

2013-10-01

303

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

International Nuclear Information System (INIS)

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

2002-02-01

304

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

Science.gov (United States)

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

305

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

International Nuclear Information System (INIS)

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

1999-07-01

306

Predation control of zooplankton dynamics : a review of observations and models  

Digital Repository Infrastructure Vision for European Research (DRIVER)

We performed a literature review to examine to what degree the zooplankton dynamics in different regional marine ecosystems across the Atlantic Ocean is driven by predation mortality and how the latter is addressed in available modelling approaches. In general, we found that predation on zooplankton plays an important role in all the six considered ecosystems, but the impacts are differently strong and occur at different spatial and temporal scales. In ecosystems with extreme environmental co...

Daewel, Ute; Hjollo, Solfrid Saetre; Huret, Martin; Ji, Rubao; Maar, Marie; Niiranen, Susa; Travers-trolet, Morgane; Peck, Myron A.; Wolfshaar, Karen E.

2014-01-01

307

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

Digital Repository Infrastructure Vision for European Research (DRIVER)

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

Huseyin Guher; Timur Kirgiz; Belgin Camur; Utku Guner

2004-01-01

308

Zooplankton of Tikehau atoll (Tuamotu archipelago) and its relationship to particulate matter  

Digital Repository Infrastructure Vision for European Research (DRIVER)

The standing stock and taxonomic composition of zooplankton (> 200 microns) were monitored in the lagoon of Tikehau atoll from April 1985 to April 1986. These data were supplemented by two 10 d studies on the variability, structure and functioning of the pelagic ecosystem. The biomass of animals > 2000 comprised 50% of the total biomass of all organisms from 35 to >2000 microns. The zooplankton populations were characterized by successive blooms of copepods, larvaceans, pteropods and salps, p...

Le Borgne, Robert; Blanchot, Jean; Charpy, Loi?c

1989-01-01

309

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

Digital Repository Infrastructure Vision for European Research (DRIVER)

We examined monthly changes in crustacean zooplankton community composition during the initial colonisation period of a newly constructed pond (LWL pond), and in the littoral zone of an adjacent lake (Ramsey lake). In addition, four unconnected constructed ponds aged ?20 years with established zooplankton communities were sampled and compared to the LWL pond. The species richness of both LWL pond and Ramsey lake increased over the ice-free season, although ...

Chantal Audet; Shannon MacPhee; Wendel Keller

2013-01-01

310

Seasonal Distribution of Zooplankton in Mahanadi Estuary (Odisha), East Coast of India: A Taxonomical Approach  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Study of coastal and estuarine water is important as they act as a medium of exchange of materials between land and ocean. Mahanadi estuarine system forms the largest system of its kind in Odisha. Zooplankton, the secondary producers plays a vital role in the hydrobiology and food chain regulation. The zooplankton diversity of Mahanadi estuary (Odisha) was investigated during postmonsoon (December 2009), premonsoon (April 2010) and monsoon (July 2010). Important hydrographical parameter...

Srichandan, S.; Panda, C. R.; Rout, N. C.

2013-01-01

311

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

Digital Repository Infrastructure Vision for European Research (DRIVER)

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 pre...

2002-01-01

312

Relation between th-234 scavenging and zooplankton biomass in mediterranean surface waters  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Dissolved and particulate Th-234 activities were determined and phyto- and zooplankton biomass were periodically measured 8 miles off Nice (Mediterranean Sea) during spring 1987. The results show a strong variability of Th-234 distribution on short time scales in northwestern Mediterranean surface waters. The good correlation observed between the zooplankton biomass and the rate of Th-234 export to deep water in particulate form is in agreement with the assumption that the residence time of p...

1992-01-01

313

Distribution and Abundance of Gelatinous Zooplankton along Tamil Nadu Coastal Waters  

Digital Repository Infrastructure Vision for European Research (DRIVER)

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

2013-01-01

314

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

Digital Repository Infrastructure Vision for European Research (DRIVER)

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

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

2013-01-01

315

Sources of variability in zooplankton feeding experiments: The importance of accurate determination of algal growth rates  

Digital Repository Infrastructure Vision for European Research (DRIVER)

[EN] The multiplicative models used to determine zooplankton feeding rates lead to increased uncertainty of the estimated grazing rate through the propagation of experimental error. The quantification of algal growth rates in control jars constitutes one of the main sources of error, which can account for most of the observed residual variability in zooplankton experimental data. This effect increases with increasing growth rate. Increasing the number of control jars and improving other metho...

Saiz, Enric

1993-01-01

316

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

Digital Repository Infrastructure Vision for European Research (DRIVER)

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 a...

Souza, Leonardo C. E.; Branco, Christina W. C.; Patrícia Domingos; Bonecker, Se?rgio L. C.

2011-01-01

317

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

Digital Repository Infrastructure Vision for European Research (DRIVER)

Trophic transfer of Hg across lakes within a region has been related to multiple environmental factors, but the nature of these relationships across distinct basins within individual large lakes is unknown. We investigated Hg bioaccumulation in zooplankton in basins of differing trophic status in Lake Champlain (Vermont, USA) to determine the strongest predictors of Hg bioaccumulation. Zooplankton were sampled in Malletts Bay (oligotrophic) and Missisquoi Bay (eutrophic) in 2005–2008. Zoopl...

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

2012-01-01

318

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

Digital Repository Infrastructure Vision for European Research (DRIVER)

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

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

2007-01-01

319

Induced pigmentation in zooplankton: a trade-off between threats from predation and ultraviolet radiation  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Ultraviolet (UV) radiation is harmful to all life, and the ongoing depletion of the ozone layer is likely to affect interactions among both terrestrial and aquatic organisms. Some organisms have evolved adaptations to reduce radiation damage, such as the various types of protective pigmentation of freshwater zooplankton. However, strong pigmentation also increases vulnerability to visually hunting predators. Hence, where both UV radiation and predation are intense, zooplankton may be sandwich...

Hansson, Lars-anders

2000-01-01

320

Induced pigmentation in zooplankton: a trade-off between threats from predation and ultraviolet radiation.  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Ultraviolet (UV) radiation is harmful to all life, and the ongoing depletion of the ozone layer is likely to affect interactions among both terrestrial and aquatic organisms. Some organisms have evolved adaptations to reduce radiation damage, such as the various types of protective pigmentation of freshwater zooplankton. However, strong pigmentation also increases vulnerability to visually hunting predators. Hence, where both UV radiation and predation are intense, zooplankton may be sandwich...

Hansson, L. A.

2000-01-01

 
 
 
 
321

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

Energy Technology Data Exchange (ETDEWEB)

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

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

2008-06-10

322

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

Science.gov (United States)

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

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

2009-01-01

323

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

Science.gov (United States)

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

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

2014-01-01

324

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

Science.gov (United States)

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

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

2012-01-01

325

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. ...

326

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

Energy Technology Data Exchange (ETDEWEB)

Zooplankton mortalities resulting from passage through the Donald C. Cook Nuclear Plant (southeastern Lake Michigan) were studied over an 8-year (1975-1982) period. The power plant operated at a low ..delta..T (<12/sup 0/C) and discharge water temperatures did not exceed 35/sup 0/C (except September 1978). While zooplankton mortalities were significantly greater in discharge than intake waters, differences were small, averaging <3%. There was no evidence of additional delayed effects on zooplankton mortality following plant passage. There was no relationship between zooplankton mortalities and temperature (..delta..T, discharge water temperature). Mechanical stresses appeared to be the major cause of zooplankton mortality. The authors hypothesize that fish predation, rather than power plant operation, probably was the major source of zooplankton mortality in inshore waters during much of the year.

Evans, M.S.; Warren, G.J.; Page, D.I.

1986-06-01

327

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

International Nuclear Information System (INIS)

Zooplankton mortalities resulting from passage through the Donald C. Cook Nuclear Plant (southeastern Lake Michigan) were studied over an 8-year (1975-1982) period. The power plant operated at a low ?T (<12"0C) and discharge water temperatures did not exceed 35"0C (except September 1978). While zooplankton mortalities were significantly greater in discharge than intake waters, differences were small, averaging <3%. There was no evidence of additional delayed effects on zooplankton mortality following plant passage. There was no relationship between zooplankton mortalities and temperature (?T, discharge water temperature). Mechanical stresses appeared to be the major cause of zooplankton mortality. The authors hypothesize that fish predation, rather than power plant operation, probably was the major source of zooplankton mortality in inshore waters during much of the year. (author)

1986-01-01

328

Seasonal variations of species composition and abundance of zooplankton in Ehoma Lake, a floodplain lake in Nigeria  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Ehoma Lake is among the important breeding sites of the major fishes in the Mid-Cross River, Nigeria. The juveniles of these fishes are solely dependent on zooplankton, which has not been studied previously. I studied monthly the lake’s physico-chemical variables and zooplankton composition in three stations (littoral, sub-littoral and pelagic) from March 2005 to August 2006. Sixty-seven zooplankton species (42 rotifers, 19 cladocerans and 6 copepods) were identified. Daphnia obtusa Kurz, K...

Okogwu, Okechukwu I.

2010-01-01

329

Zooplankton abundance and distribution around on a seamount in the Andaman Sea, Thailand, measured with acoustic methods and biological sampling  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Studies of abundance and distribution of zooplankton with acoustic instruments is new methodology in Thailand. In order to evaluate if the zooplankton could be detected and measured, a specific area around a seamount in the Andaman Sea was selected for comparative measurements zooplankton with acoustics and with biological sampling. The survey was conducted with the Andaman Sea Fisheries Research and Development Center vessel RV Pramong 4" in 3 cruises during the southwest monsoon perio...

Jithlang, Issarapon

2011-01-01

330

Zooplankton abundance and distribution around on a seamount in the Andaman Sea, Thailand, measured with acoustic methods and biological sampling  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Studies of abundance and distribution of zooplankton with acoustic instruments is new methodology in Thailand. In order to evaluate if the zooplankton could be detected and measured, a specific area around a seamount in the Andaman Sea was selected for comparative measurements zooplankton with acoustics and with biological sampling. The survey was conducted with the Andaman Sea Fisheries Research and Development Center vessel RV Pramong 4" in 3 cruises during the southwest monsoon period fro...

Jithlang, Issarapon

2011-01-01

331

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

332

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

Directory of Open Access Journals (Sweden)

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

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

C. H. Hsieh

2011-05-01

333

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

Directory of Open Access Journals (Sweden)

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

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

C. H. Hsieh

2011-01-01

334

Seasonal Distribution of Zooplankton in Mahanadi Estuary (Odisha, East Coast of India: A Taxonomical Approach  

Directory of Open Access Journals (Sweden)

Full Text Available Study of coastal and estuarine water is important as they act as a medium of exchange of materials between land and ocean. Mahanadi estuarine system forms the largest system of its kind in Odisha. Zooplankton, the secondary producers plays a vital role in the hydrobiology and food chain regulation. The zooplankton diversity of Mahanadi estuary (Odisha was investigated during postmonsoon (December 2009, premonsoon (April 2010 and monsoon (July 2010. Important hydrographical parameters such as water temperature, salinity, pH and dissolved oxygen, NO2 (nitrite, NO3 (nitrate, NH4 (ammonia, TN (total nitrogen, PO4 (phosphate, TP (total phosphorous and SiO4 (silicate were measured during the present study along with the study of the qualitative and quantitative aspects of zooplankton. Zooplankton population dominated by copepod at all the stations in all the seasons except during low tide of premonsoon season where caridean larvae were dominant. In total, 86 species of zooplankton, mostly belonging to Crustacea, Chaetognatha, Mollusca, Polychaeta, Cnidaria, Ctenophora, Protozoa, Larvacea among the holoplankton and 16 different types of larval forms were encountered. The population density ranged from 52 to 885 org. m-3 with highest density during high tide of post-monsoon i.e., 885 org. m-3. The copepods like Subeucalanus mucronatus, Subeucalanus subcrassus, Sapphirina maculosa, Sapphirina auronitens are recorded for the first time from marine and estuarine ecosystem of Odisha. Presence of 16 different crustacean dominated larval forms signifies the conduciveness of estuary during the whole period for breeding and spawning of shell fishes in the estuary. During the present study, zooplankton population density was positively related with zooplankton biomass.

C. R. Panda

2013-01-01

335

Parasitic chytrids sustain zooplankton growth during inedible algal bloom  

Science.gov (United States)

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

Rasconi, Serena; Grami, Boutheina; Niquil, Nathalie; Jobard, Marlene; Sime-Ngando, Telesphore

2014-01-01

336

Fatty acid transformation in zooplankton: from seston to benthos  

DEFF Research Database (Denmark)

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

Tiselius, Peter; Hansen, Benni Winding

2012-01-01

337

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

International Nuclear Information System (INIS)

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

1998-11-15

338

Prediction of response of zooplankton biomass to climatic and oceanic changes  

Energy Technology Data Exchange (ETDEWEB)

This paper examines the long-term variation in zooplankton biomass in response to climatic and oceanic changes, using a neural network as a nonlinear multivariate analysis method. Zooplankton data collected from 1951 to 1990 off the shore of northeastern Japan were analyzed. We considered patterns of the Kuroshio and the Oyashio, sea surface temperature, and meteorological parameters as environmental factors that affect zooplankton biomass. Back propagation neural networks were trained to generate mapping functions between environmental variables and zooplankton biomass. The performance of the network models was tested by varying the numbers of input and hidden units. Changes in zooplankton biomass could be predicted from environmental conditions. The neural network yielded predictions with smaller errors than those of predictions determined by linear multiple regression. The sensitivity analysis of networks was used to extract predictive knowledge. The air pressure, sea surface temperature, and some indices of atmospheric circulation were the primary factors for predictions. The patterns of the Kuroshio and the Oyashio demonstrated different effects among sea areas.

Aoki, Ichiro [Department of Aquatic Bioscience, Graduate School of Agricultural and Life Sciences, University of Tokyo, Yayoi, Bunkyo, Tokyo (Japan); Komatsu, Teruhisa [Ocean Research Institute, University of Tokyo, Minamidai, Nakano, Tokyo (Japan); Hwang, Kangseok [National Fisheries Research and Development Agency, Shirang-ri, Kijang, Pusan (Korea, Republic of)

1999-08-17

339

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

Energy Technology Data Exchange (ETDEWEB)

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

Jeffree, R.A. [Australian Nuclear Science and Technology Organisation (ANSTO), Lucas Heights, NSW (Australia). Environment Division

1998-12-31

340

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

Science.gov (United States)

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

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

2014-01-01

 
 
 
 
341

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

Energy Technology Data Exchange (ETDEWEB)

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

Havens, K.E.; Decosta, J.

1987-04-01

342

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

Directory of Open Access Journals (Sweden)

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

Susana B. José de Paggi

2013-10-01

343

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

Directory of Open Access Journals (Sweden)

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

Sharma, B.K.

2012-12-01

344

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

2011-03-01

345

"2"1"0Po uptake by zooplankton during a one year cycle in relation to trophic conditions in Monaco Bay  

International Nuclear Information System (INIS)

Former evidence showed that in oligotrophic waters in French Polynesia there is an inverse correlation between zooplankton biomass and zooplankton "2"1"0Po concentration. To study the same phenomenon in a more seasonal environment, monthly samples of zooplankton, water, fecal pellets, and particulate organic matter were obtained in Monaco monthly and analyzed for "2"1"0Po content

1999-07-01

346

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

347

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

DEFF Research Database (Denmark)

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

Frost, Jessica R.; Denda, Anneke

2011-01-01

348

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

349

Cyanobacteria dominance influences resource use efficiency and community turnover in phytoplankton and zooplankton communities.  

Science.gov (United States)

Freshwater biodiversity loss potentially disrupts ecosystem services related to water quality and may negatively impact ecosystem functioning and temporal community turnover. We analysed a data set containing phytoplankton and zooplankton community data from 131 lakes through 9 years in an agricultural region to test predictions that plankton communities with low biodiversity are less efficient in their use of limiting resources and display greater community turnover (measured as community dissimilarity). Phytoplankton resource use efficiency (RUE = biomass per unit resource) was negatively related to phytoplankton evenness (measured as Pielou's evenness), whereas zooplankton RUE was positively related to phytoplankton evenness. Phytoplankton and zooplankton RUE were high and low, respectively, when Cyanobacteria, especially Microcystis sp., dominated. Phytoplankton communities displayed slower community turnover rates when dominated by few genera. Our findings, which counter findings of many terrestrial studies, suggest that Cyanobacteria dominance may play important roles in ecosystem functioning and community turnover in nutrient-enriched lakes. PMID:24467318

Filstrup, Christopher T; Hillebrand, Helmut; Heathcote, Adam J; Harpole, W Stanley; Downing, John A

2014-04-01

350

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

International Nuclear Information System (INIS)

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

2014-03-01

351

Spring-time zooplankton size structure over the continental shelf of the Bay of Biscay  

Science.gov (United States)

Linking lower to higher trophic levels requires a special focus on the pivotal role played by mid-trophic levels, i.e. the zooplankton. One of the most relevant information on zooplankton in term of fluxes of matter lies in its size structure. We present here an extensive dataset of size measurements covering part of the western European shelf and slope, from the Galician coast to the Ushant front, during springs from 2005 to 2012. Zooplankton size spectra were estimated using both measurements carried out in situ by the Laser-Optical Plankton Counter (LOPC, 816 records) and WP2 net (200 ?m mesh size) samples scanned following the ZooScan methodology and image analysis (a total of 89 samples were analyzed). The LOPC counts and sizes all particles in the range 100 to 2000 ?m of spherical equivalent diameter (ESD) whereas the WP2/ZooScan allows the counting, sizing and identification of zooplankton from ~400 ?m ESD. The difference between the LOPC (all particles) and the WP2/ZooScan (zooplankton only) is assumed to provide the size distribution of non-living particles whose descriptors are further related to a set of explanatory variables (including physical, biological and geographic descriptors). A statistical correction based on these explanatory variables is then applied to LOPC measurements to removed the part due to non-living particles and estimate zooplankton size spectra. This extensive data set provides a new look at regional and inter-annual variability of the pelagic ecosystem of the Bay of Biscay.

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

2013-11-01

352

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

Digital Repository Infrastructure Vision for European Research (DRIVER)

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

Riemann, Bo

1985-01-01

353

Climate warming and the decline of zooplankton in the California current  

Energy Technology Data Exchange (ETDEWEB)

Since 1951, the biomass of macrozooplankton in waters off southern California has decreased by 80 percent. During the same period, the surface layer warmed-by more than 1.5{degrees}C in some places-and the temperature differences across the thermocline increased. Increased stratification resulted in less lifting of the thermocline by wind-driven upwelling. A shallower source of upwelled waters provided less inorganic nutrient for new biological production and hence supported a smaller zooplankton population. Continued warming could lead to further decline of zooplankton. 10 refs., 5 figs.

Roemmich, D.; McGowan, J. [Univ. of California, San Diego, CA (United States)

1995-03-03

354

Evaluation of sound extinction and echo interference in densely aggregated zooplankton  

Directory of Open Access Journals (Sweden)

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

Natalia Gorska

2000-09-01

355

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

Science.gov (United States)

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

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

356

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

357

Effects of ultraviolet-B radiation on phytoplankton - zooplankton interactions = [Effecten van ultraviolet-B straling op interacties tussen fytoplankton en zooplankton  

Digital Repository Infrastructure Vision for European Research (DRIVER)

The decrease in stratospheric ozone concentration has received wide attention because the ozone layer protects the earth from harmful ultraviolet-B radiation (UVB, 280-320 nm). UVB radiation is harmful for organisms, and therefore scientific research into how UVB radiation affects organisms and ecosystems receives great interest. This thesis describes the effects of UVB radiation on interactions between phytoplankton (algae) and zooplankton (waterfleas) in freshwater ecosystems.The underlying...

1999-01-01

358

Model migration schedules incorporating student migration peaks  

Directory of Open Access Journals (Sweden)

Full Text Available This paper proposes an extension of the standard parameterised model migration schedule to account for highly age-concentrated student migration. Many age profiles of regional migration are characterised by sudden 'spiked' increases in migration intensities in the late teenage years, which are related to leaving school, and, in particular, to entry into higher education. The standard model schedule does not appear to be effective in describing the pattern at these ages. This paper therefore proposes an extension of the standard model through the addition of a student curve. The paper also describes a relatively simple Microsoft Excel-based fitting procedure. By way of illustration, both student peak and standard model schedules are fitted to the age patterns of internal migration for two Australian regions that experience substantial student migration. The student peak schedule is shown to provide an improved model of these migration age profiles. Illustrative population projections are presented to demonstrate the differences that result when model migration schedules with and without student peaks are used.

Tom Wilson

2010-07-01

359

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

360

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

 
 
 
 
361

Richness of Phytoplankton and Zooplankton in Water Streams at Jobolarangan Forest  

Directory of Open Access Journals (Sweden)

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

WIRYANTO

2001-07-01

362

Predator-induced morphological defenses in marine zooplankton: a larval case study.  

Science.gov (United States)

While there are numerous reports of predator-induced morphological defenses for freshwater zooplankton, freshwater larvae, and benthic marine animals, a literature search revealed no reports of predator-induced morphological defenses for marine zooplankton. Rarity of predator-induced morphological defenses in marine zooplankton would imply a difference in predation risks compared to those experienced by freshwater organisms and benthic marine adults, whereas the presence of such plasticity in defenses would imply that risks are modified by developmental responses. This study reports a predator-induced change in defenses and vulnerability of a marine planktonic larva. Specifically, when reared in the presence of zoea larvae of Cancer spp., veliger larvae of the intertidal snail Littorina scutulata developed significantly smaller shell apertures and rounder shells than did cohort veligers reared in the absence of predator cues. Pairwise predation trials demonstrated that veligers reared with caged zoeas throughout development had greater survival than predator-naive veligers during short-term exposure to zoeas. The development of predator-induced morphological defenses by some marine larvae introduces a range of testable hypotheses on developmental plasticity that reduces vulnerability of planktonic larvae and other marine zooplankton to predators. PMID:17536718

Vaughn, Dawn

2007-04-01

363

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.

Agamaliyev F.Q

2013-01-01

364

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

International Nuclear Information System (INIS)

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

1977-05-01

365

Contrasting zooplankton communities (Arctic vs. Atlantic in the European Arctic Marginal Ice Zone  

Directory of Open Access Journals (Sweden)

Full Text Available Relationships between the zooplankton community and various environmental factors (salinity, temperature, sampling depth and bottom depth were established in the European Arctic Marginal Ice Zone (MIZ using multivariate statistics. Three main zooplankton communities were identified: an Atlantic Shallow Community (AtSC, an Arctic Shallow Community (ArSC and a Deep Water Community (DWC. All species belonging to AtSC and ArSC were pooled and their relative abundances in the total zooplankton calculated with respect to a particular layer (surface, mid and deep strata, regions (the Barents Sea, Fram Strait and the waters off northern Svalbard, years (1999 or 2003 and seasons (spring or autumn. Mapping of the proportions of Arctic and Atlantic species led to the conclusion that zooplankton from the MIZs do not exactly follow complementary water masses, although the general pattern of AtSC and ArSC dominance accords with the physical oceanography of the study area (AtW and ArW respectively. The mid layer proved to be a better predictor of mesozooplankton distribution than the unstable conditions near the surface.

Katarzyna B?achowiak-Samo?yk

2008-09-01

366

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

2011-09-01

367

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

Science.gov (United States)

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

368

Zooplankton feeding ecology and the experimental acidification of Little Rock Lake  

International Nuclear Information System (INIS)

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

1988-01-01

369

Zooplankton feeding ecology and the experimental acidification of Little Rock Lake  

Energy Technology Data Exchange (ETDEWEB)

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

Sierszen, M.E.

1988-01-01

370

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

371

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

Directory of Open Access Journals (Sweden)

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

Ole-Petter Pedersen

2010-09-01

372

Effects of acid and cadmium on improved zooplankton in a Canadian shield lake  

Energy Technology Data Exchange (ETDEWEB)

The effects of plankton invertebrate populations of added acid and of cadmium were monitored in seven 1.5 x 10/sup 5/ L impoundments placed over sediments in a lake being artificially acidified. Two enclosures were acidified to pH 5 and pH 4 and immediate effects on the zooplankton community studied. 1, 3, 10, and 30 ..mu..g cadmium/L were added to each of four enclosures in 1977 and residual effects of 1-10 ..mu..g Cd/L on the zooplankton community studied in 1978. The system containing 30 ..mu..g Cd/L was acidified to pH 4 in 1978 and effects on the zooplankton monitored. The biomass of the control impoundment was dominated by Diaptomus minutus. In all but one manipulated system the average total biomass was lower than in the control. The zooplankton biomass of manipulated systems were dominated by Tropocyclops prasinus mexicanus, Bosmina longirostris or rotifers. 14 references, 6 figures, 3 tables.

Lawrence, S.G.

1980-01-01

373

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

Science.gov (United States)

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

374

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

Science.gov (United States)

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

375

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

Science.gov (United States)

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

376

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

Science.gov (United States)

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

377

Relative abundance of resident versus oceanic zooplankton over an interisland reef  

International Nuclear Information System (INIS)

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

1979-02-01

378

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

International Nuclear Information System (INIS)

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

1987-01-01

379

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

2007-01-01

380

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

 
 
 
 
381

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

Directory of Open Access Journals (Sweden)

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

Vesela Evtimova

2014-04-01

382

The Lake Ontario zooplankton community before (1987-1991) and after (2001-2005) invasion-induced ecosystem change  

Science.gov (United States)

We assessed changes in Lake Ontario zooplankton biomass, production, and community composition before (1987–1991) and after (2001–2005) invasion-induced ecosystem changes. The ecosystem changes were associated with establishment of invasive dreissenid mussels and invasive predatory cladocerans (Bythotrephes and Cercopagis). Whole-lake total epilimnetic plus metalimnetic zooplankton production declined by approximately half from 42.45 (g dry wt?m?2? year?1) during 1987–1991 to 21.91 (g dry wt?m?2? year?1) in 2003 and averaged 21.01 (g dry wt?m?2? year?1) during 2001–2005. Analysis of two independent data sets indicates that the mean biomass and biomass proportion of cyclopoid copepods declined while the same measures increased for the invasive predatory cladocerans. Changes in means and proportions of all other zooplankton groups were not consistent between the data sets. Cyclopoid copepod biomass and production declined by factors ranging from 3.6 to 5.7. Invasive predatory cladoceran biomass averaged from 5.0% to 8.0% of the total zooplankton biomass. The zooplankton community was otherwise resilient to the invasion-induced disruption as zooplankton species richness and diversity were unaffected. Zooplankton production was likely reduced by declines in primary productivity but may have declined further due to increased predation by alewives and invasive predatory cladocerans. Shifts in zooplankton community structure were consistent with increased predation pressure on cyclopoid copepods by alewives and invasive predatory cladocerans. Predicted declines in the proportion of small cladocerans were not evident. This study represents the first direct comparison of changes in Lake Ontario zooplankton production before and after the invasion-induced disruption and will be important to food web-scale investigations of invasion effects.

Stewart, T. J.; Johannsson, O. E.; Holeck, K.; Sprules, W. G.; O'Gorman, R.

2010-01-01

383

Role of predation by zooplankton in transport and fate of protozoan (oo)cysts in granular activated carbon filtration.  

Science.gov (United States)

The significance of zooplankton in the transport and fate of pathogenic organisms in drinking water is poorly understood, although many hints of the role of predation in the persistence of microorganisms through water treatment processes can be found in literature. The objective of this study was to assess the impact of predation by natural zooplankton on the transport and fate of protozoan (oo)cysts in granular activated carbon (GAC) filtration process. UV-irradiated unlabelled Cryptosporidium parvum and Giardia lamblia (oo)cysts were seeded into two pilot-scale GAC filtration columns operated under full-scale conditions. In a two-week period after seeding, a reduction of free (oo)cysts retained in the filter bed was observed. Zooplankton was isolated from the filter bed and effluent water on a 30 microm net before and during the two-week period after seeding; it was enumerated and identified. Rotifers, which are potential predators of (oo)cysts, accounted for the major part of the isolated zooplankton. Analytical methods were developed to detect (oo)cysts internalized in natural zooplankton isolated from the filter bed and effluent water. Sample sonication was optimized to disrupt zooplankton organisms and release internalized microorganisms. (Oo)cysts released from zooplankton after sonication were isolated by IMS and stained (EasyStain) for microscopic counting. Both Cryptosporidium and Giardia (oo)cysts were detected in association with zooplankton in the filter bed samples as well as in the effluent of GAC filters. The results of this study suggest that predation by zooplankton can play a role in the remobilization of persistent pathogens such as Cryptosporidium and Giardia (oo)cysts retained in GAC filter beds, and consequently in the transmission of these pathogens in drinking water. PMID:19853879

Bichai, Françoise; Barbeau, Benoit; Dullemont, Yolanda; Hijnen, Wim

2010-02-01

384

Population and International Migration.  

Science.gov (United States)

International migration is a conspicous form of population interaction between richer and poorer countries. The paper makes an assessment of the dimensions of past and present day migration, its determinants, the effects on sending countries, costs and be...

G. Swamy

1985-01-01

385

Migration and revolution  

Directory of Open Access Journals (Sweden)

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

Nando Sigona

2012-06-01

386

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

387

Marriage, money and migration  

Digital Repository Infrastructure Vision for European Research (DRIVER)

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

2009-01-01

388

Essays on temporary migration  

Digital Repository Infrastructure Vision for European Research (DRIVER)

My thesis dissertation focuses on the temporariness of migration, its diverse effects as well as on migration selection. The first paper, A Dynamic Model of Return Migration analyzes the decision process underlying return migration using a dynamic model. We explain how migrants