Ecological implications and roles of cyanobacteria (cyanophyta) in food security – A review

Abstract

Cyanobacteria (Cyanophyta), commonly called blue green algae, are prokaryotes that inhabit a wide variety of habitats as free living, epiphytic, symbiotic or parasitic plants. They form a component of the base of the aquatic food chain, and their photosynthetic activity aerates the habitat. Hence, they are of great importance in aquaculture. Spirulina and Nostoc commune are sources of single cell proteins, edible to man. Nitrogen fixing forms (Anabaena, Nostoc, etc) increase the nitrogen content of the habitat and supply nitrates in symbiotic relationships where they enhance the nutritive quality of the host plant, which could be used as green manure, fodder, and fish feed. Some act as bio-fertilizers, a fact that can be utilized effectively in improving plant nutrition, especially in rice and wheat production. As producers of growth hormones, they improve yield of rice (e.g. Phormidium tenue). Consequently they are essential in rice based economies. Some are capable of producing antibiotics (Microcystis, Nostoc and Scytonema). Cyanobacteria prevent soil erosion; help in soil water retention, sodium removal and act as the first colonizers in land reclamation. Blooms of some species release toxins and lead to anoxia in the habitat to the detriment of biota. Phormidium is known to reduce the quality of brine. Some of these Cyanobacteria have been observed in Nigerian environment. There is therefore the need to harness them or combat the obnoxious forms. Control of blooms is expensive hence the need for research into their biological control.