Spatial and seasonal distribution of Ostracoda in a lagoonal environment along the northeastern coast of India: Implications to assess coastal ecology and paleoenvironment

Abstract

Variable seasonal interaction of both fresh and marine waters in lagoon ecosystems generally creates salinity gradients, which significantly impact the microhabitat of the benthos. This study assessed the spatial-seasonal abundance and diversity of ostracods along the salinity gradient of Chilika Lagoon (India) by seasonally collecting substrate sediment from twenty-two fixed stations along with the environmental parameters of lagoon-bottom water in Asia's largest brackish water lagoon. The samples were analyzed for living and dead ostracod species abundance, diversity and correlated with environmental parameters. The river mouth proximal region having sandy silt substrate under low energy conditions and high total organic carbon, had a higher abundance of low salinity tolerant ostracod species. The interior region of the lagoon showed a high abundance and diversity of variable salinity tolerant brackish water species, with a high proportion of dead specimens. In the region proximal to the sea mouth that is influenced by high energy conditions and sandy substrate, ostracod abundance and diversity are low, and only a few very high salinity tolerant ostracod species are found. Canonical correspondence analysis in addition to environmental preferences of living ostracod species and articulated valve abundance suggest environment-specific ostracod assemblages, consistent with the traditional use of ostracod species as a proxy to reconstruct paleo coastal ecology and paleoenvironment.