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‣ Efeitos do cobre e cromo na comunidade zooplanctônica : um estudo experimental em mesocosmos; Effects of copper and chromium on the zooplankton community : a mesocosms experimental study

Gusmão, Luiz Felipe Mendes de
Fonte: Biblioteca Digitais de Teses e Dissertações da USP Publicador: Biblioteca Digitais de Teses e Dissertações da USP
Tipo: Dissertação de Mestrado Formato: application/pdf
Publicado em 28/07/2004 Português
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O crescente desenvolvimento industrial e urbano tem acarretado a introdução de grandes quantidades de metais nos ecossistemas aquáticos, expondo, potencialmente, sua biota e toda a cadeia alimentar que dela se origina à contaminação por esses elementos. Muitos estudos sobre o comportamento dos metais no meio aquático vêm sendo desenvolvidos, pois os metais representam um problema ambiental por sua persistência no ambiente e não biodegradabilidade. No entanto, pouco se conhece sobre seus efeitos ecológicos na estrutura e função das comunidades aquáticas. O presente trabalho, neste sentido, visa contribuir para um melhor conhecimento desses efeitos sobre a comunidade zooplanctônica em experimentos de campo que reproduzem, com maior fidelidade, o ecossistema. O objetivo deste trabalho foi avaliar os efeitos dos metais cromo e cobre sobre a estrutura da comunidade zooplanctônica de espécies holo-zooplanctônicas em experimentos de mesocosmos realizados na Represa do Lobo-Broa (CHREA/USP). Os mesocosmos constituíram-se de três cercados de filme de PVC transparente, com volume aproximado de 5000 litros, em contato com o sedimento de fundo. Um mesocosmos foi mantido como controle, não sendo contaminado, e os outros dois foram contaminados inicialmente com as concentrações máximas permitidas pelo CONAMA/86 para o cobre (20µg/L) e cromo (40µg/L). O experimento foi realizado de 28 de Março a 30 de Abril de 2002...

‣ Zooplâncton em córregos sob diferentes usos da terra na bacia do Rio Preto (Distrito Federal e Goiás); Zooplankton of streams under different land uses in RiomPreto watershed (Federal District and state of Goiás, Brazil)

Oliveira, Clarissa Barbosa de
Fonte: Biblioteca Digitais de Teses e Dissertações da USP Publicador: Biblioteca Digitais de Teses e Dissertações da USP
Tipo: Dissertação de Mestrado Formato: application/pdf
Publicado em 27/11/2009 Português
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O zooplâncton possui grande sensibilidade ambiental e responde rapidamente a alterações ambientais com alterações na abundância e riqueza de organismos. Ainda se conhece muito pouco sobre os organismos aquáticos do Cerrado, assim como há poucos estudos sobre o zooplâncton de ambientes lóticos no Brasil. Esse trabalho teve como objetivo caracterizar dois córregos da bacia do Rio Preto, médio São Francisco, pela avaliação de comunidades zooplanctônicas e suas relações com características físicas, químicas e biológicas da água, comparando córregos em áreas de vegetação nativa conservada e sob influência de áreas agrícolas. Foram amostradas duas sub-bacias do Rio Preto, localizadas em área de Cerrado (DF e GO) durante quatro semanas nos períodos seco e chuvoso. Em dois pontos de amostragem por córrego, foram coletadas amostras de zooplâncton e de água. Variáveis físicas e químicas da água e a concentração de a clorofila a foram determinadas. Os dois córregos apresentaram tendência de aumento de íons no período chuvoso. O córrego Estanislau (em área agrícola) apresentou maiores concentrações de nitrato, sódio, cloreto e clorofila a em relação ao córrego Pindaíba (em área de vegetação nativa). O zooplâncton se caracterizou por densidades muito baixas e alta riqueza de espécies...

‣ Temporary fragmentation of a marginal lake and its effects on zooplankton community structure and organization

Nadai, R.; Henry, R.
Fonte: Instituto Internacional de Ecologia Publicador: Instituto Internacional de Ecologia
Tipo: Artigo de Revista Científica Formato: 819-835
Português
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Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP); Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES); Processo FAPESP: 97/04999-8; Uma lagoa lateral a um rio (Lagoa do Coqueiral marginal ao Rio Paranapanema na zona de sua desembocadura na Represa de Jurumirim, São Paulo, Brasil) apresentou segmentação em quatro corpos de água pequenos e isolados entre si quando, durante um período prolongado de seca, ocorreu ruptura da associação entre os dois ambientes. O objetivo deste trabalho foi comparar as modificações temporais na estrutura da comunidade zooplanctônica (abundância total, riqueza e diversidade de espécies) nestes quatro corpos de água. em dois períodos - um, na fase de isolamento do lago em relação ao rio, e outro, na fase de restauração da conectividade hidrológica - foram efetuadas amostragens do zooplâncton e medidas de fatores abióticos. Um efeito de concentração na abundância do zooplâncton foi registrado com o avançar da seca, contudo sem alterações significativas na riqueza e diversidade de espécies. Com o pulso de inundação pelo curso de água, uma redução na densidade total do zooplâncton ocorreu na lagoa por efeito de diluição e um aumento substancial na riqueza e diversidade específica foi registrado. O influxo lateral de água do rio para o ambiente lacustre atua como fator de distúrbio na estrutura da comunidade zooplanctônica...

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

Gazulha,Vanessa; Montú,Mônica; Marques,David da Motta; Bonecker,Claúdia Costa
Fonte: Instituto de Tecnologia do Paraná - Tecpar Publicador: Instituto de Tecnologia do Paraná - Tecpar
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/08/2011 Português
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The aim of this study was to test the effects of natural free-floating plants on zooplankton distribution in a shallow subtropical lake. First, the hypothesis that free-floating plants have an effect on physico-chemicals, leading to a decrease on nutrient availability and influencing the phytoplankton biomass and zooplankton community was tested. Second, the hypothesis that free-floating plants act as a refuge for zooplankton was tested. Three microhabitats were selected: free-floating plants, littoral area and open water. Results demonstrated that the effects of different microhabitats on phytoplankton biomass and physico-chemicals were not significant, indicating a weak influence of the plants. Zooplankton densities were higher in free-floating plants and littoral area, although the effect of microhabitats was weak for most of the predominant genera. The absence of free-floating plant effects on phytoplankton and physico-chemicals showed that it was not a factor influencing the microcrustacean distribution in the microhabitats. Low differences in densities of zooplankton among microhabitats and low abundance of large-bodied cladocerans led to reject the hypothesis that free-floating plants act as a refuge for zooplankton.

‣ The nutritional status of zooplankton in a tropical reservoir: effects of food quality and community structure

Pinto-Coelho,R. M.; Giani,A.; Morais-Jr.,C. A.; Carvalho-Jr.,E. R.; Bezerra-Neto,J. F.
Fonte: Instituto Internacional de Ecologia Publicador: Instituto Internacional de Ecologia
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/05/2005 Português
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The temporal variability of energetic reserves of zooplankton in the eutrophic Pampulha reservoir was investigated during two successive annual cycles. The effects of dominance of large filter-feeding cladocerans (Daphnia) and the occurrence of massive blooms of the cyanobacteria Microcystis on the energetic reserves of zooplankton were tested. This study showed that phytoplankton composition has a greater effect on energetic reserves of zooplankton. Some associations between lipid levels and the specific composition of zooplankton were also found. This study also demonstrated that the elementary composition of phosphorus in zooplankton can be used as an estimator of the nutritional status of zooplankton.

‣ Temporary fragmentation of a marginal lake and its effects on zooplankton community structure and organization

Nadai,R.; Henry,R.
Fonte: Instituto Internacional de Ecologia Publicador: Instituto Internacional de Ecologia
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/08/2009 Português
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A river lateral lake (Coqueiral Lake marginal to Paranapanema River in its mouth zone into Jurumirim Reservoir, São Paulo, Brazil) presented fragmentation into four small isolated bodies of water during a prolonged drought period, disrupting the link with the river. The aim of this work was to compare the temporal modifications on zooplankton community structure (total abundance, species richness, and diversity) in the four water bodies. Zooplankton samplings and abiotic factor measurements were made in two periods - during isolation phase of the lake in relation to river and after re-establishment of hydrologic connectivity. A concentration effect on zooplankton abundance was recorded with drought progression, but without significant modifications in species richness and diversity. When the river inundation pulse occurred, a reduction in total zooplankton density was observed due to the dilution effect and a significant increase in species richness and diversity was recorded. Lateral water influx from the river to the lacustrine environment acts as a temporary disturbance factor on the zooplankton community structure. Zooplankton species composition presented some modifications between the two periods. Zooplankton organism drift in water from the river to the lake...

‣ Effects of liming and development of Curimbatá (Prochilodus lineatus) larvae on the abundance of zooplankton in fish ponds

Paes,Thécia Alfenas Silva Valente; Paes,José Mauro Valente; Rojas,Nilton Eduardo Torres; Rocha,Odete; Wisniewski,Maria José dos Santos
Fonte: Associação Brasileira de Limnologia Publicador: Associação Brasileira de Limnologia
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/12/2011 Português
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AIM: We aimed to evaluate the influence of the correction of the water alkalinity in the fish ponds on the density of zooplankton under a period they were stocked with larvae of Prochilodus lineatus, a neotropical fish called "Curimbatá". METHODS: We used a factorial design completely randomized. In one plot (2 ponds) there was no correction of the alkalinity of the water (20 mg CaCO3.L-1) and in two others, this variable was adjusted weekly to values around 30 and 60 mg CaCO3.L-1 ¹, with two replicates each. Zooplankton was sampled weekly and the experiment lasted 63 days. RESULTS: Significant differences in the density of the zooplankton over time (F = 6.78, p < 0.05) were found and there was a sharp decrease in zooplankton density from first to second week, and successive small increases in density from the fourth week until the end of the experiment. When considering the entire study period, alkalinity correction 60 mg CaCO3.L-1 resulted in higher density of zooplankton. Great changes in zooplankton composition occurred. Rotifera were dominant at the beginning of the experiment and Cladocera and Copepoda in the later weeks possibly due to an interplay of dilution by rain and fish predation in the initial part of the experiment and due to both alkalinity correction and predation by both fish and predatory copepods from the fourth week until the end. CONCLUSION: The experiment corroborated the hypothesis that correction of water alkalinity in ponds does favor zooplankton development but also highlighted biotic and abiotic interaction of factors operating simultaneously.

‣ The effect of Bythotrephes longimanus on the size structure of zooplankton communities in Muskoka Lakes, Ontario, Canada

Pokorny, Johanna
Fonte: Quens University Publicador: Quens University
Tipo: Tese de Doutorado Formato: 8392704 bytes; application/msword
Português
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Bythotrephes longimanus, an exotic zooplanktivore introduced to the Laurentian Great Lakes in the 1980s, alters indigenous aquatic ecosystems as it continues to disperse to surrounding inland lakes. The zooplankton community size-structure of 311 lakes in Muskoka, Ontario, Canada, were used to examine the impact of Bythotrephes longimanus, as well as the abiotic and biotic variables that determine zooplankton size structure. Total zooplankton density and weighted mean size were not significantly lower in invaded lakes, however, biomass was. The lack of change in density in conjunction with the significantly lower biomass in invaded lakes suggested a predominance of small zooplankton, which was further supported by Principal Component Analysis (PCA), and diverges from previous research where Bythotrephes predation suppressed smaller zooplankton populations. Overall, however, the PCAs of density and biomass suggested no difference between the variation in the invaded versus the uninvaded lakes. Redundancy Analyses (RDA) indicated that the variables that explained significant portions of variation in both density and biomass were total phosphorus, dissolved organic carbon, pH and lake morphometry. These variables were important in determining overall zooplankton community structure...

‣ Evidence against portage length and reproductive mode as predictors of canoe-mediated dispersal for crustacean zooplankton

Stasko, Ashley
Fonte: Quens University Publicador: Quens University
Tipo: Tese de Doutorado
Português
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Understanding the role of dispersal in determining the distribution of crustacean zooplankton is an important step in predicting recovery trajectories in damaged aquatic systems. Recreational canoes have been identified as a potential vector for the dispersal of zooplankton among lakes. This study investigated the effect of portage length (time out of water) and reproductive mode on the ability of zooplankton from George Lake, Killarney Provincial Park, Ontario, to survive transport by canoe and subsequently establish a viable population. Zooplankton were rinsed from canoe hulls after simulated portages that lasted 5, 10, 15, 20, or 30 min and were then incubated in artificial ponds for six weeks. There were no significant differences between portage length treatments for final pond richness, Simpson’s diversity, or % asexual individuals. There was considerable variation in community composition between replicate ponds within each treatment, as well as among initial canoe hull abundances. Sida crystallina and Bosmina sp. were by far the most common and dominant species in experimental ponds despite being rare in George Lake. This suggests that canoe dispersal of viable adult zooplankton does occur, and that it may be more frequent for some species than for others. However...

‣ Assessing the chemical and biological recovery of lakes in Killarney Park from regional acid deposition from 1972 to 2011: the recovery of acid-damaged crustacean zooplankton communities.

Steele, Samantha
Fonte: Quens University Publicador: Quens University
Tipo: Tese de Doutorado
Português
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Acidification of aquatic ecosystems has resulted in severe habitat destruction and loss of biodiversity, regionally and globally. Near Sudbury, Ontario, Canada lakes in Killarney Park were highly acidified by the large-scale Sudbury metal smelter emissions of sulfur dioxide and nitrogen oxides, in the 1960s. Fortunately due to the steady decline in emissions, pH increases in these acid-damaged lakes has been observed. This study was undertaken to determine the extent of chemical and biological recovery of lakes in Killarney Park from 1972 to 2011. We assessed the relative importance of environmental variables in shaping the structure of zooplankton communities. Forty-three lakes were sampled to characterize environmental conditions and zooplankton community structure. We compared historic data from a 1972 survey to the data collected in the 2011 survey from the identical lakes; analyses were conducted to compare pH, zooplankton abundance, diversity, richness, and community composition. Chemical recovery was observed with a significant increase in pH from 1972 to 2011. However, our analyses revealed that minimal biological recovery was observed from 1972 to 2011; there was no significant increase in Shannon-Weiner diversity, total abundance or the presence of acid-sensitive zooplankton species...

‣ Community structure and algal feeding preferences of zooplankton in Myponga and South Para Reservoirs.

Ismail, Azma Hanim
Fonte: Universidade de Adelaide Publicador: Universidade de Adelaide
Tipo: Tese de Doutorado
Publicado em //2012 Português
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Zooplankton community structure was studied monthly in Myponga and South Para Reservoirs in South Australia from January 2008 to June 2009. Myponga Reservoir is a highly managed reservoir with prolong artificial mixing while South Para Reservoir is non-managed and has less human perturbation. The total number of taxa in Myponga and South Para Reservoirs were 16 and 20 respectively. Cladocera was the dominant taxonomic group in relation to the total number of taxa but in terms of total density, Copepoda were the numerically dominant group in both reservoirs. The most frequently occurring Cladocera were Ceriodaphnia cf. quadrangula, Ceriodaphnia cornuta and Bosmina meridionalis while Asplanchna priodonta was the predominant Rotifera throughout the study. Copepoda were dominated by Calamoecia ampulla and Microcyclops sp., making up the largest portion of total zooplankton density. Differences with regard to species richness were due to the sole occurrence of Polyarthra dolichoptera, Keratella slacki, Anuraeopsis fissa and Pompholyx complanata in South Para Reservoir. Observations showed relatively consistent species diversity and density throughout the study in Myponga Reservoir except for low densities during summer for Cladocera and Copepoda groups while seasonal variations in zooplankton composition and abundance are features of South Para Reservoir. Shallow locations have greater zooplankton densities compared to deep locations in both reservoirs. Nevertheless...

‣ Ecological interactions between zooplankton and photosynthetic bacteria in Crawford Lake, Ontario

Mazumder, A.
Fonte: Brock University Publicador: Brock University
Tipo: Electronic Thesis or Dissertation
Português
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The present study was carried out to test the hypothesis that photosynthetic bacteria contribute a large portion of the food of filter feeding zooplankton populations in Crawford Lake, Ontario. The temporal and spatial variations of both groups of organisms are strongly dependent on one another. 14 By using C-Iabelled photosynthetic bacteria. the ingestion and clearance rates of Daphnia pulex, ~. rosea, and Keratella spp were estimated during summer and fall of 1982. These quantitative estimations of zooplankton ingestion and clearence rates on photosynthetic bacteria comprised an original addition to the literature. Photosynthetic bacteria comprised a substantial portion of the diet of all four dominant zooplankton species. The evidence for this is based on the ingestion and clearance rates of the dominant zooplankton species. Ingestion rates of D. pulex and D. rosea ranged 5 5 -1 -1 - -- 5 - -- 5 from 8.3X10 -1 to 14.6XlO -1 cells.ind. hr and 8.1X10 to 13.9X10 cells.ind. hr • Their clearance rates ranged from 0.400 to 1.000 -1 -1 -1 -1 ml.ind. hr. and 0.380 to 0.930 ml.ind. hr • The ingestion and clearance -1 -1 -1 -1 rates of Keratella spp were 600 cell.ind. hr and 0.40 ul.ind. hr respectively. Clearance rates were inversely proportional to the concentration of food cells and directly proportional to the body size of the animals. It is believed that despite the very short reg~neration times of photosynthetic bacteria (3-8 hours) their population densities were controlled in part by the feeding rates of the dominant zooplankton in Crawford Lake. By considering the regeneration times of photosynthetic bacteria and the population clearance rates of zooplankton...

‣ Responses of zooplankton community structure and ecosystem function to the invasion of an invertebrate predator, Bythotrephes longimanus

Strecker, Angela Lee
Fonte: Quens University Publicador: Quens University
Tipo: Tese de Doutorado Formato: 1841060 bytes; application/pdf
Português
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Freshwater ecosystems face unprecedented levels of human-induced stresses and it is expected that the invasion of non-indigenous species will cause the greatest loss of biodiversity in lakes and rivers worldwide. Bythotrephes longimanus is a predatory invertebrate that invaded North America in the early 1980s, first being detected in the Great Lakes, and then moving to a number of inland lakes in Ontario and the northern United States. Using experimental and survey-based approaches, I tested several hypotheses concerning the effects of Bythotrephes on native zooplankton community structure and function. My results indicate that Bythotrephes reduces total abundance, biomass, and richness of zooplankton, especially cladoceran taxa, throughout the ice-free season. As a result of high predation pressure by the invader, total seasonal and epilimnetic zooplankton production was also substantially reduced in invaded lakes, which may have important consequences for the transfer of energy to fish and other taxa that feed on zooplankton. Interestingly, there was some evidence that zooplankton shifted their reproduction in time and space to avoid Bythotrephes, which may buffer the effects of the invader on food web functioning. Other measures of ecosystem function were relatively unaffected by the invasion of Bythotrephes. In addition...

‣ Análise da estrutura e transporte do zooplâncton no estuário do Rio Caravelas (Bahia-Brasil) através do uso do zooscan; Spatial-temporal dynamics of zooplankton in the Caravelas river estuary (Bahia, Brazil)

Cabral, Camila Rodrigues
Fonte: Universidade Federal do Rio Grande do Norte; BR; UFRN; Programa de Pós-Graduação em Bioecologia Aquática; Bioecologia Aquática Publicador: Universidade Federal do Rio Grande do Norte; BR; UFRN; Programa de Pós-Graduação em Bioecologia Aquática; Bioecologia Aquática
Tipo: Dissertação Formato: application/pdf
Português
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Spatial-temporal dynamics of zooplankton in the Caravelas river estuary (Bahia, Brazil). The survey was conducted in order to describe the zooplankton community of the estuary Caravelas (Bahia, Brazil), to quantify and relate the patterns of horizontal and vertical transport with the type of tide (neap and spring) and tidal phase (flood and ebb). Zooplankton samples were collected with the aid of a suction pump (300L), filtered in plankton nets (300μm) and fixed in saline formalin 4%. Samples were collected at a fixed point (A1), near the mouth of the estuary, with samples taken at neap tides and spring tides during the dry and rainy seasons. Samples were collected for 13 hours, at intervals of 1 hour in 3 depths: surface, middle and bottom. Simultaneous collection of biological, we measured the current velocity, temperature and salinity of the water through CTD. In the laboratory, samples were selected for analysis in estereomicroscope, with 25 groups identified, with Copepoda getting the highest number of species. The 168 samples obtained from temporal samples were subsampled and processed on equipment ZooScan, with the aid of software ZooProcess at the end were generated 458.997 vingnettes. 8 taxa were identified automatically...

‣ Influencia del nivel hídrico y de la macrofitia en los patrones espaciales y temporales del zooplancton de una laguna de inundación; Influence of water level and macrophytes in the spatial and temporal patterns of zooplankton in a floodplain lake

Chaparro, Griselda Noemí
Fonte: Facultad de Ciencias Exactas y Naturales. Universidad de Buenos Aires Publicador: Facultad de Ciencias Exactas y Naturales. Universidad de Buenos Aires
Tipo: info:eu-repo/semantics/doctoralThesis; tesis doctoral; info:eu-repo/semantics/publishedVersion Formato: application/pdf
Publicado em //2013 Português
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En este estudio se analizaron los efectos combinados de las variaciones hidrométricas y de la macrofitia en la dinámica temporal y espacial del zooplancton de una laguna de inundación (Laguna Grande, Reserva Natural Otamendi, Buenos Aires). Las variaciones marcadas de nivel hídrico determinaron condiciones ambientales contrastantes en la laguna que afectaron los atributos del zooplancton. El período extraordinario de aguas bajas comprendido en este estudio se caracterizó por una columna de agua muy corta, salinidades elevadas, floraciones de cianobacterias potencialmente tóxicas y una mínima heterogeneidad ambiental. Estas condiciones conformaron un ambiente estresante para el zooplancton reflejado en el hacinamiento de los organismos, la prevalencia de la reproducción sexual, la baja diversidad y la composición del ensamble, que estuvo restringido a las especies eurihalinas tolerantes. Los pulsos hídricos registrados posteriormente provocaron cambios hacia condiciones más favorables y un mayor desarrollo de los ensambles de macrófitas con distintas formas de vida que promovió la diversidad del zooplancton. Los efectos de los pulsos sobre la abundancia de las comunidades biológicas (plancton y macrófitas) dependieron del momento del año en que éstos ocurrieron...

‣ Physical control of zooplankton communities in the Catalan Sea

Alcaraz, Miquel; Calbet, Albert; Estrada, Marta; Marrasé, Cèlia; Saiz, Enric; Trepat, Isabel
Fonte: Elsevier Publicador: Elsevier
Tipo: Artículo Formato: 283613 bytes; application/pdf
Português
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19 pages, 10 figures, 7 tables.-- Printed version published in issue Aug-Sep 2007.-- Issue title: "Ecological Functioning of the Iberian Seas: A synthesis of GLOBEC Research in Spain and Portugal".; The study of the response of planktonic systems to environmental variability, and particularly to differences in the intensity and frequency of mechanical energy inputs, one of the leading objectives of GLOBEC, has been an important part of the research developed in the Spanish Mediterranean over the last decades. In this review we will discuss the research conducted at different space and time scales, intended to cope with the broad space and time variability scales of plankton. The time- and space scales considered range from small- (i.e., from seconds and mm, affecting zooplankton at individual level) to meso- (weeks and tens of km) and large scales (i.e., seasonal changes in the density structure of the water column). The discussion includes laboratory research using visual observation techniques at individual level, the use of experimental micro- and mesocosms, as well as data obtained by sampling natural systems during oceanographic cruises. At the smaller scales, mechanical energy inputs produce turbulent water movements that enhance the encounter probability between zooplankton and their prey...

‣ Spatial patterns reveal strong abiotic and biotic drivers of zooplankton community composition in Lake My´vatn, Iceland

Bartrons, Mireia; Einarsson, Árni; Nobre, Regina L G; Herren, Cristina M.; Webert, Kyle C.; Brucet, Sandra; Ólafsdóttir, Sólveig R.; Ives, Anthony R.
Fonte: Universidade Autônoma de Barcelona Publicador: Universidade Autônoma de Barcelona
Tipo: Artigo de Revista Científica Formato: application/pdf
Publicado em //2015 Português
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Spatial patterns in the abundance of species are determined by local abiotic and biotic conditions, and by the movement of individuals among localities. For species distributed among discrete habitat "islands", such as zooplankton distributed among lakes, local conditions within lakes often dominate low movement rates among lakes to determine the composition of communities. Here, we ask whether the same abiotic and biotic environmental conditions can generate spatial patterns in the distribution of zooplankton within a lake where there are high horizontal movement rates. We conducted three spatial surveys of zooplankton communities in Lake Mývatn, Iceland, a moderately sized (37 km2) shallow lake with a high outflow rate. The pelagic zooplankton community showed strong spatial structure (spatial autocorrelation), with species composition varying with spatial variation in chlorophyll-a, the abundance of Anabaena (cyanobacteria), lake depth, light extinction coefficient, and temperature. These factors are known from other studies to be strong drivers of among-lake variation in freshwater zooplankton communities. However, in contrast with among-lake studies, fish (stickleback) abundance had no measureable effect on the abundance or species composition of the zooplankton community...

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

Okogwu,Okechukwu. I
Fonte: Revista de Biología Tropical Publicador: Revista de Biología Tropical
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/03/2010 Português
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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, Keratella valga Ehrenberg, Keratella ticinensis Callerrio, Keratella hiemalis Carlin, Brachionus dimidiatus Bryce and Lecane candida Hauer and Murray are new records for Nigeria. The dominant zooplankters were Diaphanosoma excisum Kurz and Moina micrura Kurz. There was an inverse relationship between species richness and abundance. Richness was highest in the dry season while peak zooplankton abundance was recorded in the rainy season. Zooplankton abundance and species richness decreased progressively from the littoral to the pelagic station while the Shannon-Weaver diversity index varied from 0.68 to 1.28 without a clear seasonal trend. There is a succession pattern: rotifers that are dominant in the dry season are replaced by cladocerans in the rainy season. This succession was greatly influenced by seasonal flooding of the lake. As no previous information on the zooplankton of the lake is available...

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

Gómez-Gutiérrez,Jaime; Palomares-García,Ricardo; Hernández-Trujillo,Sergio; Carballido-Carranza,Azucena
Fonte: Revista de Biología Tropical Publicador: Revista de Biología Tropical
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/06/2001 Português
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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 structure showed strong changes with a close relation to environmental conditions. During March, a well-mixed water column with low temperature and salinity indicated an influence of the California Current water and local upwelling processes. During July, temperature increased a nd a wide salinity range was recorded. The stratification of the water column was intense during summer, enhancing the thermocline. The highest temperatures and salinity were recorded in December, related to the presence of the Costa Rica Coastal Current (CRCC). The thermocline deepened as water temperature increased. A typical temperate community structure with low specific richness dominated by Calanus pacificus, Nyctiphanes simplex, and Acartia clausi and high zooplankton biomass (average 9.3 and 5.5 ml 1000 m-3respectively) during March and July shifted to a more complex tropical community structure with a low zooplankton biomass in December (average 0.37 ml 1000 m-3). The mouth of Bahía Magdalena has a vigorous exchange of water caused by tidal currents. The zooplankton community structure was not significantly different between the central part of Bahía Magdalena and the continental shelf outside the bay for all months. The results suggest a more dynamic inside-outside interaction of zooplankton assemblages than first thought.

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

Sellami,Ikbel; Elloumi,Jannet; Hamza,Asma; Mhamdi,Mohammed Alaoui; Ayadi,Habib
Fonte: Water SA Publicador: Water SA
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/04/2011 Português
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Associations between zooplankton community structure and abiotic (temperature, dissolved oxygen, turbidity, nutriments) and biotic factors (chlorophyll a and phytoplankton community) were examined, in Kasseb Reservoir, northern Tunisia. Samples were taken bimonthly from July to December 2002 at 3 sampling stations (deepest station: Station 1, Brik River: Station 2 and M'Zaz Stama River: Station 3). From our results it is evident that zooplankton exhibit seasonally and spatially heterogeneous distribution. The highest density of zooplankton was recorded in September at a depth of 5 m (10.8 × 10³ ind·ℓ-1). At Station 1 cyclopoid copepods (65% of total abundance) were the most abundant group followed by Cladocera (21% of total abundance). At Station 2 (93% of total abundance) and Station 3 (98% of total abundance) cyclopoid copepods were numerically dominant throughout the study period. Canonical correspondence analysis (CCA) was used to estimate the influence of abiotic and biotic factors in structuring the zooplankton assemblage. Zooplankton abundance was negatively correlated with turbidity (r= -0.381, P <0.05). The results also suggest that both local (environmental parameters, competition, and predation) and regional (hydrologic connections and dispersal) factors have a significant effect on both species richness and community structure of zooplankton in Kasseb Reservoir. The presence of zooplankton species con sidered to be indicators of eutrophic status confirmed the high trophic levels of Kasseb Reservoir.