Cyanobacteria Economic Importance:
Cyanobacteria have both useful and harmful activities-
Useful Activities of Cyanobacteria:
(1) Cyanobacteria are the earliest photosynthesizers. These have changed the earth’s anaerobic atmosphere into aerobic atmosphere.
(2) Spirulina is cultivated in ponds and tanks as a protein-rich food for fish and other animals. It is also used as an important source of human food. Nostoc balls of terrestrial species are used as feed by Chinese and South Americans.
(3) Some cyanobacteria like Nostoc and Anabaena increase soil fertility by fixing the free nitrogen of the atmosphere. These days, farmers inoculate rice fields with flakes of cyanobacteria to increase the yield.
(4) Cyanobacteria help in reclaiming barren soils and make them productive by increasing nitrogen, phosphorous, organic content and water-holding capacity of the soil. Examples- Anabaena, Aulosira, Sytonema, etc.
(5) Some forms such as Tolypothrix and Anabaena prevent soil erosion and help in soil conservation.
(6) Some cyanobacteria in a symbiotic relationship act as pioneers in plant succession.
(7) Anabaena and Aulosira do not allow mosquito larvae in their vicinity. These can be inoculated in village ponds to check the growth of mosquitoes.
Harmful Activities of Cyanobacteria:
(1) Some cyanobacteria produce toxins that are harmful to fishes and other aquatic animals. Such water is equally toxic to humans.
(2) Profuse growth of some cyanobacteria deplete the oxygen content of water bodies, thereby resulting in the death of aquatic animals.
(3) Some species of cyanobacteria spoil the textiles, cordage and tents.
(4) Some cyanobacteria grow on the walls and roof of buildings during the rainy season causing discolouration, leakage and corrosion of plaster and buildings.
(5) Lynbya causes skin diseases.
(6) Some cyanobacteria, for example- Oscillatoria, grow in municipal water reservoirs. They clog the water filters and spoil the colour and taste by giving a foul odour and fishy taste to water.
