Significantly, this study examined the abundance and diversity of meiofauna in relation to environmental parameters across four selected stations along the Thoothukudi coast from October 2023 to March 2024. These stations were selected based on pollution gradients, with Station 1 serving as a reference site and Stations 2–4 being influenced by anthropogenic activities. The analysis focused on meiofaunal groups, including nematodes, copepods, polychaetes and foraminifera, alongside environmental variables; such as temperature, salinity, pH, dissolved oxygen and sediment organic carbon. The results revealed significant spatial and temporal variations, with nematodes dominating all stations (70–260 individuals per sample) but showing reduced abundance in the polluted Station 2 (25–130 individuals per sample), likely due to elevated temperatures (29–32°C) from thermal effluent discharge. Copepods exhibited a marked decline, underscoring their sensitivity to pollution. Key environmental stress markers included lower pH levels (7.6–8.5), indicating progressive acidification, while dissolved oxygen (3.4–4.5 ml/l) and organic carbon content (0.138–0.911 mgC/g) correlated strongly with shifts in meiofaunal assemblages. The findings highlight severe meiofaunal stress near sewage outfalls, particularly in Punnakayal, emphasizing the urgent need for long-term monitoring and targeted mitigation strategies to address coastal degradation in the region.

Meiofauna, Thoothukudi coast, Environmental stress, Nematodes, Coastal pollution