Cell biovolume and carbon biomass of phytoplankton in degraded tropical estuaries in Northeastern Brazil

This study aimed to relate the seasonal and spatial variation of phytoplankton to environmental parameters in degraded tropical estuaries in Pernambuco, Northeastern Brazil. Phytoplankton samples and environmental parameters were collected at three stations, namely, Port Basin, Beberibe estuary, and Capibaribe estuary, during the low and high tides. Eighty-six taxa were identified; diatoms were the most diverse group with the highest cell density values, followed by cyanobacteria. The dominant species were Cylindrotheca closterium (Ehrenberg) Reimann & J.C. Lewin, Nitzschia longissima (Brébisson) Ralfs, and Planktothrix isothrix (Skuja) Komárek & Komárková. Mean biovolume during the studied period ranged from 1.615,3 to 67.423,5 μm3 and mean carbon biomass ranged from 104.5 to 29.397,1 pgC μm−3, with the highest values recorded during the rainy season. The species Coscinodiscus sp., Oscillatoria sp., Planktothrix isothrix, and Protoperidinium sp. were the most representative in biovolume. Precipitation and tides were the main factors controlling seasonal and spatial variability in parameters such as salinity, dissolved nutrients, and phytoplankton cell density. •Phytoplankton composition was characteristic of tropical regions in the south Atlantic.•Diatoms were important and contributed with the highest cell densities.•Cyanobacteria and diatoms were the main producers of biomass.•Seasonality was an important factor for changes in abiotic and biotic parameters.