Monsoon regime in the Indian Ocean and zooplankton variability

Abstract

The monsoonal effects on zooplankton lead to characteristic zoogeographic patterns in the open ocean and coastal waters. The evaluation of zooplankton variability in the Indian Ocean is presented in three sections: the open ocean, coastal waters and the estuaries in order to show how the monsoon exerts its influence on zooplankton from different types of environment. In the open ocean, the semi-annually reversing system of currents exert profound influence on the shifting of zooplankton populations and its diversity and this is reflected in the relative abundance of total zooplankton biomass. In the coastal waters, the monsoonal effect is more during the SW monsoon (June to November) when freshwater influx from rivers and estuaries lower the salinity along the coast to 30-34.5 ppt and the time lag involved in the north to south or reverse pattern of movement of species along with associated factors responsible for such variability calls for detailed investigation. In estuaries, the monsoon exerts stress on estuarine fauna by bringing about a drastic change in salinity