Distribution of ostracode assemblages along the nearshore and offshore areas of Malabar coast, Kerala (west coast of India)

Abstract

Sixty-one ostracode species have been identified in 76 sediment samples from 28 nearshore and 48 offshore locations off Malabar Coast, Kerala. Q mode cluster analysis of the ostracode assemblages of the nearshore sediments indicates that the entire nearshore assemblages can be classified into two clusters – cluster I – Kumbla (A₁) – Hosdurg (B₁) and Mattul (D₁) blocks and Cluster II – Payyannur (C₁) – Cannanore (E₁) – Telicherry (F1) blocks. This clustering is probably due to the differences in the depositional environment. The influence of estuarine environment is predominant in the cluster I due to the mixing of freshwater from the surrounding land masses. Several backwaters are observed in the areas covered by this cluster. Cluster analysis of offshore assemblages indicate that the entire offshore off Malabar coast can be divided into two clusters, cluster I – Kumbla (A₂) and Bekal (B₂), cluster II – Neeleswaram (C₂), Payyannur (D₂) and Payangoti (E₂) blocks. The presence of shallow water ostracode species in cluster I which lived in nearshore sand and silty sand substrate under the influence of subtropical water currents are inferred and further indicated by the fossil molluscan assemblages. Q-mode cluster analysis and details of physical and ecological parameters suggest that there is a substantial influence of substrate, organic matter and salinity in the distribution, diversity and abundance of the ostracode. Based on this, the Malabar coast of Kerala is significantly classified as a marine ecosystem/environment category.