Cyanobacterial Blooms and Their Implications in the Changing Environment

Cyanobacteria are the most ancient phytoplankton that first appeared at least 2.5 billion years ago and have a prolonged evolutionary history. They can form impenetrable and toxic blooms in aquatic ecosystems such as freshwater and marine environments. Cyanobacterial blooms produce cyanotoxins that endanger ecosystem functioning and deteriorate water quality used for recreation, drinking, and in fisheries, thus, adversely affecting human health and the economy. Some bloom-producing genera are Aphanizomenon, Planktothrix, Cylindrospermopsis, Nodularia, Trichodesmium, Dolichospermum, and Microcystis. They increase turbidity and suppress submerged aquatic vegetation. Due to the microbial bloom-mediated environmental degradation, oxygen scarcity might occur, inducing hypoxia and anoxia, and resulting in the death of fish and benthic invertebrates. Several cyanotoxins cause many diseases related to digestion, liver, and neurological disorders when ingested by birds and mammals, including humans. Global changes resulting from human impacts like eutrophication, rising CO2 levels, and global warming are major driving forces for the enhancement of cyanobacterial blooms in many aquatic systems worldwide. Various management strategies such as nutrient load reduction, hydrodynamic changes, and chemical and biological controls have been used to reduce bloom occurrence and proliferation of cyanobacteria. In this chapter, we have discussed the approaches regarding the understanding of how global changes affect cyanobacterial blooms and also suggested effective prediction and management strategies.