Silicate as the Probable Causative Agent for the Periodic Blooms in the Coastal Waters of South Andaman Sea

Abstract

Periodic algal blooms of three diatom species such as Coscinodiscus centralis, Rhizosolenia alata andRhizosolenia imbricata were observedduringSeptember 2011, December 2011 and March 2012 in the coastal waters of South Andaman Sea at Junglighat bay area (11° 39 N and 92° 43 E). The blooms were intense, with Coscinodiscus at aconcentration of 89,000 cells mL-1(contributing 85 to 98% to the total phytoplanktonpopulation), Rhizosolenia alataat a concentration of 13,000 cellsmL-1(86-93%) and Rhizosolenia imbricata at aconcentration of 19,000 cells. mL-1(91-99%). Nutrients, most importantly nitrate and silicate have emerged as the key factors controlling phytoplankton growth in this area.