Temporal variation in phytoplankton community in a freshwater coastal lake of southern Brazil

Abstract

AIM: The aim of the present study was to study the vertical variation in phytoplankton community in a subtropical coastal lake and to verify the temporal variation of this community following variation in temperature and dissolved nitrogen and phosphorus. METHODS: Sampling of phytoplankton and abiotic variables were performed monthly from June/2009 to January/2011 at four depths from the central part of Peri Lake. The data were analyzed using analysis of variance, correlation and canonical correspondence analysis. RESULTS: Vertical variation in the phytoplankton community and limnological data did not occur but temporal variation was found. The lake was limited by light and nutrients and this light limitation selected the Cyanobacteria species from Sn and S1 functional groups. Phytoplankton community was composed of five groups, with 31 freshwater taxa, in which Cyanobacteria was the most important with 87.7% of total density and Chlorophyta with 11.8%. Cylindrospermopsis raciborskii was dominant during almost the whole study period because when temperature and phosphorus increased and wind speed decreased Limnothrix sp. density was boosted. Different species of Cyanobacteria filamentous showed correlation with variables in different ways, indicating that some species can co-exist, each of them having distinct niches or can compete by the same resource. CONCLUSION: The phytoplankton presented periodicity driven by annual change in water temperature and nutrients availability. Peri Lake's features allow for the occurrence of a vertically homogeneous water column and the dominance of cyanobacterial functional groups adapted to low underwater light and nutrients deficiency

Keywords

• lago subtropical
• Cyanobacteria
• Cylindrospermopsis raciborskii
• nutrientes
• variação temporal