Estudo da estrutura da comunidade zooplanctônica e sua relação com as cianobactérias em três reservatórios do médio rio Tietê, SP / Zooplankton structure and its relationships with cyanobacteria in three reservoirs of middle Tietê river, São Paulo State, Brazil
Laira Lúcia Damasceno de Oliveira
DATA DE PUBLICAÇÃO
Cyanobacteria blooms are increasingly being detected in São Paulo state reservoirs, particularly in those of middle Tietê river basin. The presence of cyanobacteria can cause deterioration of water quality in these systems due to its potential toxicity to the aquatic biota, and also risks to human health. The aim of the present srtudy was to analyse the structure of the zooplankton community in three reservoirs placed in middle Tietê river basin, SP (Barra Bonita, Bariri and Ibitinga) and its relationships with blooms of cyanobacteria, with emphasis on its toxic effects upon the daphnid Ceriodaphnia silvestrii, a native species. Sampling was carried out in June and September 2008 and January and May 2009. Measurements of several physical, chemical and biological parameters were carried out in each reservoir. Samples of cyanobacteria blooms were taken with phytoplankton nets and properly kept for posterior analysis of species composition, cyanotoxin quantification and also for acute toxicity testing. It was found that zooplankton communities in the reservoirs are dominated by rotifers and copepods in most of the water layers sampled. The cyclopoid copepods were more abundant than calanoid ones with great representativiness of the young forms (nauplii and copepodids). The Cladocera species Bosmina longirostris and some species of Rotifera as Brachionus calyciflorus were frequent in all reservoirs, indicating that they might have strategies to cope with the cyanobacteria bloom toxicity. Microcystin LR concentrations were detected in all samples of blooms from Middle Tietê River reservoirs with concentrations varying from 18,2 to 100 müg/ L. Acute toxicity tests revealed that raw extracts from cyanobacteria scums were toxic to the daphnid Ceriodaphnia silvestrii, causing immobilization of natatory movements even at low LR microcystin concentrations, thus negatively affecting the aquatic biota.
cladocera bioassays ecologia do zooplâncton ecotoxicology ensaios com cladocera cyanobacteria tiete reservoirs zooplankton ecology toxicidade de microcistinas reservatórios do tietê microcystin toxicity ecotoxicologia cianobactérias
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