RESUMO
The limnological features and the phytoplankton community of the Cachoeira Dourada reservoir were analyzed in December 2006, May 2007 and November 2007. Temporal changes in the taxonomic composition, density, diversity and dominance of species were analyzed in relation to climatic factors and the physical and chemical characteristics of the water. A positive correlation was found between some of the physical and chemical variables and the phytoplankton community. According to the CCA, variables such as the extent of the euphotic zone, temperature, pH, nitrogen and phosphorus concentrations directly affected the phytoplankton dynamics. Organisms belonging to the class Cyanophyceae were the most representative in all the sampling periods, comprising the functional groups K, S1, M and H. Hydrodynamics and seasonal fluctuations of environmental factors were the driving forces determining the composition and abundance of the algal assemblages. Despite the prevalence of Cyanobacteria, the reservoir is still oligotrophic. The absence of blooms and the relatively low population abundances indicated that the quality of the reservoir's water still lies within the limits required for its multiples uses.
Assuntos
Biodiversidade , Biomassa , Fitoplâncton/classificação , Brasil , Monitoramento Ambiental , Densidade Demográfica , Estações do AnoRESUMO
The limnological features and the phytoplankton community of the Cachoeira Dourada reservoir were analyzed in December 2006, May 2007 and November 2007. Temporal changes in the taxonomic composition, density, diversity and dominance of species were analyzed in relation to climatic factors and the physical and chemical characteristics of the water. A positive correlation was found between some of the physical and chemical variables and the phytoplankton community. According to the CCA, variables such as the extent of the euphotic zone, temperature, pH, nitrogen and phosphorus concentrations directly affected the phytoplankton dynamics. Organisms belonging to the class Cyanophyceae were the most representative in all the sampling periods, comprising the functional groups K, S1, M and H. Hydrodynamics and seasonal fluctuations of environmental factors were the driving forces determining the composition and abundance of the algal assemblages. Despite the prevalence of Cyanobacteria, the reservoir is still oligotrophic. The absence of blooms and the relatively low population abundances indicated that the quality of the reservoir's water still lies within the limits required for its multiples uses.
As características limnológicas e a comunidade fitoplanctônica do reservatório de Cachoeira Dourada foram analisadas nos meses de dezembro de 2006, maio de 2007 e novembro de 2007. As flutuações temporais na composição taxonômica, densidade, diversidade e dominância de espécies foram analisadas em relação aos fatores climáticos e às variáveis físicas e químicas da água. Uma correlação positiva foi encontrada entre algumas das variáveis físicas e químicas analisadas e a comunidade fitoplanctônica. De acordo com a CCA, variáveis como a extensão da zona eufótica, temperatura, pH, nitrogênio e fósforo influenciaram diretamente na dinâmica do fitoplâncton. Organismos pertencentes à classe Cyanophyceae foram as mais representativas em todos os períodos amostrais, abrangendo os grupos funcionais K, S1, M e H. A hidrodinâmica e a variação sazonal dos fatores ambientais foram as forças determinantes da composição e abundância das assembleias de algas. Apesar do predomínio de cianobactérias, o ambiente do reservatório ainda é oligotrófico. A ausência de florações e as abundâncias populacionais relativamente baixas indicaram que a qualidade da água do reservatório continua se mantendo dentro dos limites estipulados para seus usos múltiplos.