Marea Roja

In communities on the central coast of Venezuela, massive poisonings occur that cause fish mortality and effects on the health of people and domestic animals. To understand the dynamics of these phenomena, it is necessary to know the community structure of phytoplankton during events. With the support of the community, samples of phytoplankton were collected during three massive poisonings that occurred in 2010, 2014, and 2015. And also, physicochemical variables of the water were determined. As a result, a diverse community was obtained with the presence of diatoms, dinoflagellates, cyanobacteria, and euglenophytes with significant differences in the composition in each event. However, in the three massive poisonings, an overgrowth of dinoflagellates of the genus Ostreopsis coincides, accompanied by the euglenophyte Eutreptiella gymnastica, which are widely known for their toxic effects on algal blooms when they reach densities greater than 1,000 cell/liter. When comparing these conditions with those in which there is no intoxication, it can be seen that the proportion of the density of Ostreopsis spp with respect to the rest of the dinoflagellates exceeds 50%, which could serve as an indicator during harmful algal blooms of these species.