Assessment of ecological quality status using macrobenthic faunal diversity as tools in anthropogenically disturbed Ennore estuary, Tamil Nadu, India

Abstract

Anthropogenic pressure in coastal and estuarine environments remains a global concern, due to increased threats to the environment and biodiversity. Ennore estuary receives industrial effluent and sewage discharge from the surrounding urban areas and Manali industrial complex. The present study examined the Ecological Quality Status (EcoQS) of the Ennore estuary using indices like Shannon–Wiener index (H’), AZTI marine biotic index (AMBI) and the multivariate AMBI (M-AMBI). A total of 25 taxa were recorded and Polychaeta (86.9%) and Chironomidae (11.7%) were the dominant groups. The abundance ranged from 124 ± 56 to 11933 ± 5173 ind. m−2. The species richness and diversity were very low and abundance was high in mid-estuary with the dominance of opportunistic and tolerant polychaete species. Shannon diversity index showed that EcoQS of estuary is in the poor to bad category. The results of AMBI values reveal high proportion of the benthic ecosystem is heavily disturbed (64.5%) whereas; M-AMBI exhibited the EcoQS as poor (19.8%) and moderate (13.5%). Ecological groups confirm that opportunistic (EGIV; 79.2%; EGV; 1.1%) and tolerant (EGIII; 16.9%) groups were dominant indicating the stress-tolerant species are able to proliferate in such environment. Nevertheless, ecological quality status is slightly good during monsoon due to frequent flush out by rainwater runoff. The ecological health status of the Ennore estuary could be restored by ensuring enough water flow between the estuary and coastal water through frequent dredging of sandbars at the mouth.