Seasonal variation in the distribution of mollusks
in relation to environmental parameters was studied at four
mangrove stations on the Pondicherry coast during September
2008-August 2009. A total of 37 species of molluscs were
recorded, among them 16 species of bivalves belonging to 7
families and 12 Genera, and 21 species of gastropods belonging
to 14 families and 19 Genera, with the Cereithedia cingulata
being the dominant group. An increase of species density and
diversity in the Post monsoon season was observed, with the
highest values for both indexes at stations 1 and 2, and the
lowest at stations 3 and 4 fine where the sand assemblage was
dominated by a few gastropods. Pollution indicator species
Cassidula nucleus, Melampus ceylonicus, Sphaerassiminea minuta
were found only in highly polluted regions near stations 3 and
4; they were totally absent in moderately polluted areas near
stations 1 and 2. From a stepwise multivariate analysis of the
different environmental parameters regarding molluscan density,
it was found that in all 10 parameters govern the density variation
of benthic mollusks in Pondicherry mangroves and that the
organic matter of sediment and sulphide, DO, and salinity were
the highly significant ones
