RESUMO: Este trabalho foi realizado no Parque Estadual do Charapucu, sendo pioneiro para o arquipélago do Marajó e teve como objetivo conhecer a diversidade do fitoplâncton correlacionada com os fatores físico-químicos da água dos rios que margeiam e cortam este Parque. Para o estudo das variáveis físico-químicas, quali-quantitativo do fitoplâncton e para determinação da clorofila-a foram coletadas amostras nos meses de maio e outubro de 2013, representando os períodos de maior (mês chuvoso) e menor (mês seco) precipitação pluviométrica, respectivamente. Foram identificadas 164 espécies com o predomínio da classe Zygnematophyceae em riqueza. Os táxons Aulacoseira granulata, Aulacoseira spp., Coscinodiscus sp., Cryptomonas ovata, Eudorina elegans, Eunotia spp., Eunotia pectinalis, Mougeotia sp., Paralia sulcata, Pseudanabaena spp., Pseudanabaena mucicola, Surirella spp., Thalassionema nitzshioides e Ulotrix spp. se destacaram em termos de freqüência e abundância. A maioria das variáveis físico-químicas e biológicas apresentou variação ao longo do estudo sendo reguladas por flutuações de precipitação pluviométrica e pelas características típicas das águas brancas e pretas. A densidade foi mais elevada durante o período seco em águas brancas e a clorofila-a variou apenas sazonalmente, sendo os maiores valores registrados no mês seco. As correlações mostraram que a dinâmica da comunidade fitoplanctônica foi influenciada principalmente pelas variáveis temperatura, pH, condutividade elétrica, sólidos totais dissolvidos, potencial de oxi-redução, nitrato, fósforo total e clorofila-a. Palavras-chave: Diversidade,ABSTRACT: This work was conducted in the Charapucu State Park, a pioneer to the archipelago of Marajó and aimed to understand the diversity of phytoplankton correlated with physical-chemical factors of the water of the rivers that border and cut this park. To study the physical and chemical variables, qualitative and quantitative phytoplankton and determination of chlorophyll-a samples were collected in May and October 2013, representing the periods of highest (rainy month) and lower (dry month) rainfall. 164 species were identified, with the predominance of Zygnematophyceae class in ofrichness. The taxa Aulacoseira granulata, Aulacoseira spp., Coscinodiscus sp., Cryptomonas ovata, Eudorina elegans, Eunotia spp., Eunotia pectinalis, Mougeotia sp., Paralia sulcata, Pseudanabaena spp. Pseudanabaena mucicola, Surirella spp. Thalassionema nitzshioides and Ulotrix spp. were the most frequent and abundant. Most physical and biological variables showed variation throughout the study period being regulated by rainfall fluctuations and the typical characteristics of white and black waters. The density was significantly higher during the dry season and in white waters. The chlorophyll-a varied seasonally and the highest values were recorded in the dry months. The correlations showed that the phytoplankton community was mainly influenced by the variables temperature, pH, electrical conductivity, total dissolved solids, redo...

Composição, riqueza e índices ecológicos do fitoplâncton do lago Bolonha (Belém, Pará) Composition, richness and ecological index of phytoplankton of lake Bolonha (Belém, Pará

The infl uence of environmental variables on planktonic biodiversity is widely known. However, the absence of information about the cyanobacterial community in tropical estuarine regions motivated this work, whose objective was to investigate the spatio-temporal variation of cyanobacterial density related to physicochemical factors in a Brazilian Amazonian estuary. For the qualitative and quantitative study of cyanobacteria and physicochemical variables, samples were collected in April/ July/2009 and April/August/2010. We identifi ed 31 species of the orders Chroococcales, Oscillatoriales and Nostocales. Species of the genera Aphanocapsa, Dolichospermum, Komvophoron, Microcystis, Pseudanabaena and Merismopedia were frequent and abundant throughout the study period. Some of the found genera have already been described as potential toxin producers. The dynamics of cyanobacteria were temporal, the highest densities occurred in 2010 (average= 1080.86 ± 702.86 cells.mL -1 ) mainly infl uenced by the high values of pH, temperature, electrical conductivity, total dissolved solids, ammonium nitrogen which led cyanobacteria to present different responses in terms of richness, density and diversity between the years.

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