Aquatic Pollution and Coastal Management

Unit 3 : Agricultural wastes and eutrophication

3.15.Algal blooms in Indian waters
The red tide is not an unknown phenomenon in Indian waters. Until 1973, sporadic blooms of Noctiluca scintilans, Trichodesmium erythraeum, Rhizosolenia sp., etc. have been reported, but none were of HAB type. However, since 1981, cases of paralytic shellfish poisoning (PSP) from coastal Tamil Nadu, Karnataka and Maharashtra were reported with adverse effects. In 1981, PSP resulted in the hospitalization of 85 people and death of three persons due to the consumption of bloom-affected mussel Meretrix casta in Tamil Nadu. A similar incidence took place in Mangalore in 1983, but in both the cases causative species were not identified. In 1996, Gymnodinium catenatum, a potent PSP species both as planktonic cells and cysts in sediment, in the coastal waters of Karnataka (off Mangalore) was reported, but the low number of cells had no toxic effect. In September 1997, an outbreak of PSP was reported in three villages of Kerala, resulting in the death of seven persons and hospitalization of over 500, following consumption of mussel, Perna indica. During a reconnaissance cruise in 2001, on the coastal vessel Sagar Shukti, a toxic algal bloom by hitherto unreported dinoflagellate Cochlodinium polykrikoides was reported by the NIO team. Though this species is a fish-killer in Korea, the cause for fish mortality noticed off Goa could not be confirmed. These few examples underline the unpredictable nature of the bloom and perhaps answer the query regarding whether India should really worry about the blooms.