MÃE-BÁ LAGOON IN ESPIRITO SANTO STATE, BRAZIL: AN ECOSYSTEM WITH POTENTIAL FOR A CYANOBACTERIAL BLOOM?

Abstract

Herein we present the results of a three-year study in the Mãe-Bá lagoon (Espírito Santo State, Brazil) aimed to evaluate the structure and dynamics of local communities of phytoplankton and periphytic cyanobacteria, in an attempt to identify potentially toxic species and to evaluate whether this lagoon has the potential to experience a cyanobacterial bloom. Limnological and environmental variables were measured over dry and rainy seasons from four different sampling sites. High densities of cyanobacteria were registered, and the composition and number of taxa tended to be homogeneous over the temporal and spatial scales, while the density of cyanobacteria tended to vary. Highest densities of cyanobacteria were recorded from sampling site 1 at the north dam and sampling site 2 near the Mãe-Bá village, and during the dry seasons. Synechococcus spp., Synechocystis aquatilis, S. diplococca, Pseudanabaena catenata, P. papillaterminata, Limnothrix redekei, Planktolyngbya limnetica, and Microcystis sp. were the dominant taxa at both sampling sites. All these organisms contain strains known to produce toxic compounds. Factors promoting cyanobacterial growth in the Mãe-Bá lagoon were temperature, pH and nutrient concentration, while the main limiting resource to cyanobacterial blooms was phosphate. Based on our findings, the Mãe-Bá lagoon can be considered a ecosystem at risk of toxic cyanobacterial blooms.