The fate of copepod populations in the Paranapanema River (São Paulo, Brazil), downstream from the Jurumirim dam
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Data
2002-12-01
Autores
Mitsuka, Patricia Maria [UNESP]
Henry, Raoul [UNESP]
Título da Revista
ISSN da Revista
Título de Volume
Editor
Brazilian Archives of Biology and Technology
Resumo
As mudanças longitudinais na estrutura das populações de copépodos foram examinadas durante as estações seca e chuvosa num trecho de 42 km do Rio Paranapanema, a jusante da Represa de Jurumirim. Amostras foram coletadas na zona `lacustre da represa próxima à barragem e também em 12 estações situadas na região lateral e no meio do canal do Rio Paranapanema, a jusante da barragem. As seguintes espécies de Cyclopoida foram encontradas nos locais: Thermocyclops decipiens, Thermocyclops minutus, Tropocyclops sp Paracyclops sp., e Mesocyclops sp., e de Calanoida: Argyrodiaptomus furcatus, Notodiaptomus iheringi e Notodiaptomus conifer. Na represa, a abundância de copépodos durante as estações seca e chuvosa correspondeu a 41 e 51% do zooplâncton total, respectivamente. Esta diferença pode ser relacionada às variações de precipitação e nivel de água, e especialmente à influência de variáveis como temperatura da água, concentrações de oxigênio dissolvido e clorofila-a. Nenhuma diferença significativa nas densidades de organismos foi encontrada entre amostras de zooplâncton coletadas na região lateral e no meio do rio. em relação à variação longitudinal no trecho do Rio Paranapanema, uma diminuição significativa na densidade e o desaparecimento de algumas espécies foram registradas a partir de 11 km da barragem durante a estação seca. Nas estações localizadas a partir de 32 km da barragem, uma redução drástica na abundância de copépodos foi observada no período chuvoso. Estas observações podem estar associadas não somente à mudança ambiental de condições lênticas para lóticas, mas também à combinação de certos fatores como velocidade da correnteza, vazão de água e precipitação.
The longitudinal changes in the structure of copepod populations were examined during the dry and rainy seasons in a 42 km stretch of the Paranapanema River downstream from the dam of the Jurumirim Reservoir. Samples were taken in the lacustrine zone of the reservoir near the dam, and also at 12 stations distributed in the middle and the lateral regions of the channel of the Paranapanema River downstream from the dam. The following species of Cyclopoida were found at the sites: Thermocyclops decipiens, Thermocyclops minutus, Paracyclops sp., Tropocyclops sp and Mesocyclops sp., and of Calanoida: Argyrodiaptomus furcatus, Notodiaptomus iheringi and Notodiaptomus conifer. In the reservoir sampling station, the copepod abundance during the dry and rainy seasons corresponded to 41 and 51% of the total zooplankton, respectively. This difference could be related to the rainfall and water level variations, and especially to the influence of variables such as water temperature, dissolved oxygen and chlorophyll-a contents. No significant differences in organism numbers were recorded among samples of zooplankton taken in the middle and near-bank parts of the river. In relation to longitudinal variation in the Paranapanema River stretch, a significant decrease in density and disappearance of some species were recorded 11km downstream of the dam during the dry season. At the stations 32km from the dam, a drastic reduction in copepod abundance was observed in the rainy season. These observations could be linked not only to environmental changes from lentic to lotic conditions, but also to the combination of certain factors such as current velocity, water outflow of the reservoir, and rainfall.
The longitudinal changes in the structure of copepod populations were examined during the dry and rainy seasons in a 42 km stretch of the Paranapanema River downstream from the dam of the Jurumirim Reservoir. Samples were taken in the lacustrine zone of the reservoir near the dam, and also at 12 stations distributed in the middle and the lateral regions of the channel of the Paranapanema River downstream from the dam. The following species of Cyclopoida were found at the sites: Thermocyclops decipiens, Thermocyclops minutus, Paracyclops sp., Tropocyclops sp and Mesocyclops sp., and of Calanoida: Argyrodiaptomus furcatus, Notodiaptomus iheringi and Notodiaptomus conifer. In the reservoir sampling station, the copepod abundance during the dry and rainy seasons corresponded to 41 and 51% of the total zooplankton, respectively. This difference could be related to the rainfall and water level variations, and especially to the influence of variables such as water temperature, dissolved oxygen and chlorophyll-a contents. No significant differences in organism numbers were recorded among samples of zooplankton taken in the middle and near-bank parts of the river. In relation to longitudinal variation in the Paranapanema River stretch, a significant decrease in density and disappearance of some species were recorded 11km downstream of the dam during the dry season. At the stations 32km from the dam, a drastic reduction in copepod abundance was observed in the rainy season. These observations could be linked not only to environmental changes from lentic to lotic conditions, but also to the combination of certain factors such as current velocity, water outflow of the reservoir, and rainfall.
Descrição
Palavras-chave
Downstream, reservoir, copepod, abundance
Como citar
Brazilian Archives of Biology and Technology. Brazilian Archives of Biology and Technology, v. 45, n. 4, p. 479-490, 2002.