ECOLOGY OF CYANOBACTERIA: CAUSES AND CONSEQUENCES OF BLOOMS

Abstract

revista vol 13 nº 2.indd

Cyanobacteria form a group of prokaryotic microorganisms of aquatic ecosystems that are important primary producers and are usually responsible for blooms in freshwater habitats. This manuscript reviews the available literature on the factors promoting cyanobacterial blooms and their consequences. Such factors include light, temperature, stability of the water column, pH, nutrients, and grazing. Cyanobacteria can efficiently absorb light using phycobiliproteins, and develop better in neutral to alkaline water. Elevated temperatures can promote thermal stratification, estabilising the water column and triggering bloom formation. Nitrogen and phosphorus are the main nutrients required by cyanobacteria, which are also responsible for eutrophication, thus influencing the magnitude, duration and composition of blooms. Many species of cyanobacteria are unpalatable and grazing pressure can be reduced because of their large size, mucilage and even toxins. Cyanobacterial blooms, which often culminate in unsightly foul-smelling water, may harm the environment, affecting local food webs, nutrient cycling, biodiversity and human health. Several natural and anthropogenic factors can control the blooms, such as sedimentation, hydrology and nutrient balance. Furthermore, blooms can be minimized or eliminated by application of algaecides, vertical mixing, reduction in water retention and biomanipulation. Further detailed investigations must be carried out in order to properly manage aquatic ecosystems and prevent and/or effectively control cyanobacterial blooms.