Spatial variations in recent ostracode assemblages and bottom environments in Trincomalee Bay, northeast coast of Sri Lanka

Abstract

Trincomalee Bay lies on the northeast coast of Sri Lanka and has alarge semienclosed opening toward the Bay of Bengal. We focus onrecent ostracode assemblages, which have not yet been studied in thisbay. As a result, at least 36 ostracode taxa were identified fromsurface sediments in the bay. Many of them are typical tropicalwaterspecies that have been reported from inner bays and shallow marineareas around the coast of the IndoPacific region. We compared thespecies composition of ostracodes in the study area with that inadjacent seas. The result clearly showed that ostracode assemblagesfrom Sri Lanka have strong connection with those along the coast of theIndian subcontinent. Moreover we evaluated the bottom environment inTrincomalee Bay on the basis of statistical analyses of ostracodeassemblages combined with grain size, and total organic carbon（TOC）and total nitrogen contents. The results showed that the TOC content isrelated to grain size and is relatively high in the inner part of InnerHarbor and Koddiyar Bay, where finegrained sediments are distributed.The result showed that the ostracode distribution in Trincomalee Bay isdepend on natural environmental factors such as water depth, grainsize, TOC contents of sediments, and water salinity.