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 ？cells？L？1 and ？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. 1. Introduction There is a concern for HABs due to their deleterious effects on marine resources, such as death of marine mammals, birds, and sea turtles. It causes food web disruption and adversely affects local and regional economies [1]. Several international organizations have focused on HABs, the factors responsible for the events, potential toxicity, and impact. Hydrographic parameters such as current, temperature, and salinity fronts have contributed to the formation of HABs [2]. Additionally, shallow shelves with seasonal changes in hydrographic feature influence the initiation, growth, and transport of blooms, [3] and climatic conditions also affect the occurrence of these features [4]. The role of nutrients in the evolution of HABs has finally been documented [5–7]. Wind patterns, moreover, contribute to periodic coastal upwelling and downwelling potentially influencing onshore and offshore movements of bloom. Further, current intrusion [8–10], thermal fronts concentrate and transport bloom populations [11–15], and their role in toxic bloom formation have been investigated using satellite images [16]. To observe widely and quantify the HABs are much difficult for the entire coast due to its spread in spatiotemporal variation during