Florações de Algas Nocivas E Seus Efeitos Ambientais

Abstract

The term harmful algal blooms (HABs) include both toxin-producing species, which can contaminate top consumers through biomagnification, and high biomass' producers, that can lead to dissolved oxygen depletion in the water column and, thereby, rise mortality rates in the marine environment, producing toxins or not; as well as those that can cause inflammatory effects and mechanical damage to fish and invertebrates. In particular, synthesis of toxins (internally stocked or released in the medium) is taken as a strategy of the phytoplankton to reduce the effects of potential competitors and predators. Of more than 5000 known species of phytoplankton, only 6% can be harmful and less than 2% produces toxins. Originally natural phenomena common to various regions on our planet, HABs show an increase in their extent and persistence, related to antropogenic impact responsible for coastal water eutrophication, organisms' transport through ballast water, increase of aquaculture and climate changes associated to the increase in industrial activities for the last two centuries. Once each species shows different adaptative strategies and acts in distinct ways in response to environmental change, it is argued that better investigations will be those that can identify and quantify the specific adaptations of HABs-causing species that are able to lead to their selection, particularly to several hydrodynamic and ecological conditions. Thus, the present work intends to present a summary of the most important aspects linked to the developmentof these blooms and, mainly, report some cases about the impact of their occurrence on coastal communities.