Diversity and Distribution of Meiofauna along the Chennai Coast and Their Role as Pollution Indicators (using the N/C ratio)

Meiofaunal assemblages play a crucial role in maintaining sediment ecosystems and environmental health. Therefore, their diversity and distribution serve as valuable indicators of the ecological well-being of their niche. The current study aims to investigate meiofaunal diversity along the Chennai coast and evaluate the efficiency of the nematode/copepod (N/C) ratio as a pollution indicator. Sediment samples were collected from 8 sites across four stations along the Chennai coast: Marina Beach, Edward Elliot’s Beach, Foreshore Estate Beach, and Kasimedu Beach. Meiofaunal diversity (up to the phyla level) was assessed, and diversity indices—including Simpson’s index (D), Shannon–Wiener index (H’), and Evenness index (E’)—were calculated along with the N/C ratio. Analysis of a total of 160 ml of extract from the sediment samples revealed the presence of 14 major phyla from 3,267 specimens. Nematodes dominated the meiofaunal community (62%), followed by harpacticoid copepods (20%). Other identified phyla included isopods (4%), polychaetes (2%), foraminifera (2%), acari (2%), ostracods (2%), oligochaetes (2%), and cyclopoids (1%). A small fraction (3%) comprised miscellaneous phyla such as amphipods, archiannelids, pycnogonids, rotifers, and sipunculans. A notable trend of higher meiofaunal count in the upper sediment strata (0–5 cm) compared to deeper sediment strata (5–10 cm) was observed. This indicates the importance of surface microhabitats. The findings of the study suggest a clear relationship between pollution levels, meiofaunal assemblage, and ecosystem health, with the most polluted sites having lower taxonomic evenness and greater dominance of pollution-resistant phyla. Additionally, heavy metal analysis for Copper, Chromium, Cadmium, and Zinc was performed on seawater samples from eight sites as part of the broader environmental assessment.