Cyanobacteria in freshwater benthic environments

Cyanobacteria are widespread in freshwater benthic environments, which include wetlands, lake littoral zones, streams and rivers. This chapter outlines the major constraints on cyanobacteria in these environments. Environmental and ecological factors that determine the diversity and biomass of cyanobacteria in the freshwater benthos include physical disturbance in the form of turbulent energy and wetting/drying cycles, temperature, light, nutrients and grazing. Nutrients are particularly important, because their concentrations can control cyanobacteria within and among benthic habitats, and cyanobacteria can reciprocally influence nutrient availability via nitrogen fixation and phosphorus co-precipitation by calcareous species. Top-down control via grazing may also help to explain diverse patterns of cyanobacterial abundance, because of the interactions which occur between the cyanobacteria and their predators. Anthropogenic activities sometimes have a pronounced effect on the environmental conditions that control cyanobacterial diversity and abundance in these habitats and the resulting functional changes in the communities can result in a loss of important ecosystem services provided by these organisms