Presence of microcystin during events of algal blooms in Araruama Lagoon

Abstract

Algal blooms are phenomena produced by anthropogenic activities, despite the possible natural causes. In Araruama Lagoon, blooms occurred in 2005 and in subsequent years, causing profound changes in phytoplankton communities. These episodes triggered events of extensive fish mortality associated with low levels of dissolved oxygen. Another adverse effect associated with blooms is the production of harmful toxins such as phycotoxins produced by eukaryotic microalgae and cyanotoxins produced by cyanobacteria. Samples of fish (mullet and menhaden) and seston showed levels of microcystin by enzyme-linked immunosorbent assay (ELISA), also a seston sample (São Pedro d'Aldeia on 08/22/2007), in a period not related to fish mortality, showed cells which contained genes encoding microcystin synthetase, an enzyme responsible for the synthesis of microcystin. The succession of microalgae with the concomitant presence of potentially toxic cyanobacteria draws attention to the risk of chronic exposure by the population that uses fish as their main protein source.

Keywords

• Cianobactérias. Florações. Toxinas.