Phytoplankton diel variation and vertical distribution in two Amazonian floodplain lakes (Batata Lake and Mussurá Lake, Pará-Brasil) with different mixing regimes

Abstract

Both phytoplankton diel variation and vertical distribution were studied in two clear water Amazonian floodplain lakes (Batata and Mussurá) during the high water hydrological period. Small chlorococales, especially Chlorella homosphaera SKUJA in both Batata and Mussurá lakes, Cryptomonas marsonii SKUJA, Cryptomonas pyrenoidifera GEITLER and Mougeotia delicata BECK, in Batata Lake, and C. marsonii, Cryptomonas curvata EHRENBERG and Chromulina gyrans STEIN in Mussurá Lake were the most representative algal populations. Reduced phytoplankton densities were found in Batata Lake, with a stratified vertical distribution during the day and tendency to a more even distribution from the end of night time to sunrise. On the other hand, the highest phytoplankton densities were observed in Mussurá Lake, being concentrated mainly in superficial layers (0-3 meters) during a 24-hour cycle. In both lakes, higher concentrations were found during the middle of the day. Hydrological and hydrographical conditions may be the reason for such different behaviour between Batata Lake and Mussurá Lake. © MPI für Limnologie, AG Tropenökologie, Plön; INPA, Manaus.