Abstract
In the semiarid region, the reservoirs perform important role for the regional development, which results in the increase of the anthropogenic pressure, causing changes in the water quality. The knowledge of the zooplankton structure supplies basic information for the ecology, zoology, limnology and biogeography of these organisms. The objective of this study was to characterize the plankton microcrustaceans assemblage (Copepoda and Cladocera) in the Pedra Dam Reservoir (PDR) in two distinct periods (rainy and dry/2003). The samplings were carried out in four station of the PDR, using plankton net (70µm of mesh), by vertical hauls from the bottom until the surface, and preserved in formaldehyde 4%. A total of 12 species of microcrustaceans were identified. The dominant species were Notodiaptomus iheringi and Daphnia gessneri. Adult density ranged from 4303 to 7423 ind.m-3 in January and from 669 to 7272 ind.m-3 in July. Shannon diversity index varied from 1.90 bits.ind-1 in July to 2.71 bits.ind-1 in January. Higher densities of individuals, diversity index and equitability were found during rainy season. The structure of the microcrustaceans assemblage differed between rainy and dry seasons and was significantly correlated with the physical and chemical water variables.
Highlights
Os reservatórios são ecossistemas artificiais que apresentam características limnológicas intermediárias entre rios e lagos e que estão sujeitos a forças naturais e antrópicas (TUNDISI, 1990)
Uma abordagem detalhada da Análise de Componentes Principais com os dados físicos e químicos da água no reservatório Barragem da Pedra, durante o período de 2003, foi realizada por Sonoda e Simões
The structure of the microcrustaceans assemblage differed between rainy and dry seasons and was significantly correlated with the physical and chemical water variables
Summary
A bacia hidrográfica do rio de Contas compreende uma área de 55.334 km do Estado da Bahia, localizada no Planalto Sul-Baiano e parte meridional da Chapada Diamantina, onde se encontram as suas nascentes, e desemboca no Oceano Atlântico, em Itacaré (BRASIL, 1999). Apesar de sua extensa bacia de recepção, o rio de Contas apresenta pequeno volume de água, pois a maior parte de seu alto e médio curso encontra-se na região do sertão semi-árido. O rio de Contas apresenta 19 barramentos ao longo do seu curso; destes, destaca-se o reservatório Barragem de Pedra (13o52’11’’/40o14’10’’) com uma área de 101 km e um volume de aproximadamente 1.640 x 106 m3 (MULLER, 1995). As amostragens foram realizadas em quatro pontos ao longo do reservatório Barragem de Pedra (Figura 1), em meio às regiões lacustre e transição, em duas campanhas: uma no período de chuva (21 e 22 de janeiro de 2003) e outra no período de seca (14 e 15 de julho de 2003)
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