Dinoflagellate Bloom of Karenia mikimotoi along the Southeast Arabian Sea, Bordering Western India

A harmful algal bloom (HAB) occurred along the southeast Arabian Sea, bordering Western India, during September to November 2004. This bloom was unique in the region in terms of its large spatial extent, and the trend was weakened towards November. Mass mortality of fish, emanation of noxious odour, and respiratory problems among the children on the coastal stretch were noticed. The phytoplankton species Gymnodiniium, class Dinophyceae bloom accounted for 98% of the standing crop. The bloom Karenia mikimotoi showed a maximum density of 19.37×104 cells L−1 and 18.94×104 cells L−1 at nearshore and offshore, respectively. The remotely sensed chlorophyll a (Chl a) data from seaWiFS, sea surface temperature (SST) from advanced very high resolution radiometer (AVHRR), rainfall from tropical rainfall measuring Mission (TRMM), and Sea winds from QuickSCAT reflected the bloom due to Karenia mikimotoi, suggesting the advection process at the coastal waters. The release of toxins specifically the neurotoxic shellfish poisoning (NSP) and azaspiracid shellfish poisoning (AZP) from the bloom was assessed by chemical and mouse bioassay of the extract from mussel Perna indica, showing negative results. These indicate that asphyxiation and abnormal mucus secreted by the K. mikimotoi led to clogging of gills that accentuated the mass fish kills