Harmful algal blooms

Abstract

Phytoplankton or micro-algae play a vital role as primary producers in all aquatic habitats, but when their population overwhelms other forms of aquatic life, an environmental and economic impact is likely. Very prominent in coastal waters, this population increase or bloom formation generally discolours the surface waters to red, pink, brown, or white. It was red, when such an instance was first reported, and hence the phenomenon carried the name 'red tide' and is now also popularly called as harmful algal bloom. Bloom formation is a natural process and it enhances biological productivity, but turns worrisome when caused by toxic species, leading to massive fish mortalities and hazards to human health. Incidences of'red tide' are increasing in the Indian seas, particularly along the west coast. Reports on discolouration of waters accompanied by fish mortalities and nauseating stench sickening the people along coastal stretches are quite common. Incidences of paralytic shellfish poisoning are also hitting newspaper headlines. We summarize here some such instances that occurred along the west coast of India, and illustrate how these tiny microscopic forms suddenly grow into a disproportionate mass to draw global concern.