DINÂMICA SAZONAL DO FITOPLÂNCTON DO PARQUE ESTADUAL DO CHARAPUCU (AFUÁ, ARQUIPÉLAGO DO MARAJÓ, PARÁ, BRASIL)

This work was conducted in the Charapucu State Park, a pioneer to the archipelago of Marajo 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, redox potential, nitrate, total phosphorus and chlorophyll-a. Keywords: Diversity; Plankton; Zygnematophyceae; Amazon.