Effects of Inner Shelf Environment on the Distribution of Recent Ostracoda from the Southern Part of Gulf of Mannar, SE Coast of India

Abstract

To understand the impact on temporal variation of inner shelf environments of the southern part of Gulf of Mannar on the distribution of Ostracoda, a systematic collection of sediment and bottom water samples were made at 28 stations. Seven samples each were collected along four traverses, from off the coast of Tuticorin, Sippikulam, Mookaiyur and Volinokkam, for three seasons, representing Pre-monsoon, Post monsoon/winter and Summer. Thus the collections amounted to a total of 84 samples. A total of 48 species belonging to 36 genera, 18 families, 5 super families and 2 suborders of Podocopida have been identified. The bottom water parameters viz. temperature, salinity, dissolved oxygen and sediment parameters viz. calcium carbonate, organic matter content and sand, silt & clay ratio have been studied for three different seasonal collections along with the population distribution of the Ostracoda.  Temporal variation of temperature, salinity and dissolved oxygen content of the bottom water shows a positive correlation with the distribution of Ostracoda. Spatially, higher CaCO3 content and moderate organic matter content are associated with a higher population of Ostracoda. Temporally, the conditions prevailed during April (summer) accounts for higher population.  The siltysand type of substrate is found to be an accommodative substrate for higher population.