Occurrence of red tide caused by Karenia mikimotoi (toxic dinoflagellate) in the Southwest coast of India

Abstract

Intense brownish discoloration was observed in the surface waters of Cochin barmouth on 21st October 2009, which found to extend a few kilometers in the coastal waters. Continuous monitoring was carried out in the region for a period of 5 days (21st to 25th October 2009) and generated data on changes in water quality and phytoplankton community associated with the bloom. Relatively high level of inorganic nutrients (ammonia 0.5-9.7 mu M, nitrate 1.3-2.9 mu M, phosphate 1-2.3 mu M, silicate 23.5-39.9 mu M) and chlorophyll a (av. 56.8 + or -23.7 mg m sup(-3)) concentration were observed during the bloom period. Microscopic analysis revealed that the discoloration was caused by an unarmored toxic dinoflagellate, Karenia mikimotoi Miyake & Kominami ex Oda (Karenia, Gymnodiniaceae) belongs to Gymnodiniales, which cause massive fish mortality by releasing hemolytic compounds.