Environmental Conditions off Karaikal, South-East Coast of India, as Deciphered from Recent Benthic Foraminiferal Distributions

Abstract

Bottom water and sediment samples collected from off Karaikal, Arasalar River mouth and further upstream revealed that the environmental conditions control the distribution of benthic foraminiferal populations. In the offshore region, although Ammonia beccarii dominates the assemblage, depth of the water column seems to play a significant role in controlling the distribution of taxa constituting the assemblage. Within the depth range of sampling, a general increase in total populations of this species is observed. The nearshore stations are characterized by relatively higher total populations of such species as Spiroloculina orbis, Pararotalia nipponica and Elphidium crispum, all of which typically inhabit shallow waters on the east coast of India. Both living and total populations of all the species put together show a definite increase with depth of the water column; the maximum living and total populations have been counted to be 36 and 328, respectively. In proximity to the Arasalar River mouth also, A. beccarii predominates the assemblage which, however, is similar to those recorded from estuaries in the Indian region. The assemblage recorded from the upstream samples with relatively increased DO content but decreased salinities is still dominated by the same species, but its associated taxa are characteristic of euhaline to meso-polyhaline environmental conditions. The present study reiterates the need for examining modern benthic foraminiferal distributions and the assemblages therein from diverse environments, in order to facilitate better interpretation of fossil assemblages.

Keywords Foraminifera , Distribution ,Environment ,Karaikal , SE coast of  India