Ecological quality assessment of anthropogenically active coastal areas around Sri Vijaya Puram (Port Blair) using biotic indices: A framework for coastal conservation.

This study evaluates the ecological quality status (EcoQS) of intertidal habitats around Sri Vijaya Puram (Port Blair), where coastal ecosystems are increasingly impacted by urban expansion, sewage discharge, harbour operations, and tourism-related pressures. Using a multi-index approach, we applied four marine biotic indices such as AMBI, M-AMBI, BENTIX, and BOPA, alongside the Shannon-Wiener diversity index to assess EcoQS across six anthropogenically influenced sites over two years. The results revealed pronounced spatial variations in EcoQS. Sites which are mainly influenced by sewage discharges and organic enrichment (Phoenix Bay), exhibited moderate EcoQS, while regions influenced by mangrove and seagrass ecosystems showed good, albeit unbalanced, ecological quality. An increase in species diversity was observed, driven by the proliferation of opportunistic and tolerant species. The study demonstrated the adaptability of the multivariate AMBI (M-AMBI) in detecting pollution gradients even in the absence of pristine reference conditions, highlighting its utility in data-limited tropical island systems. It also evaluated the performance of temperate-derived marine biotic indices (MBIs) under tropical environmental settings, confirming their relevance with appropriate contextual adjustments. The findings revealed EcoQS in island systems like Port Blair is driven more by site-specific anthropogenic pressures, such as sewage discharge, solid waste and harbour activities, than by seasonal environmental variability. These results emphasise the value of integrating multiple biotic indices to improve the sensitivity and accuracy of EcoQS assessments in tropical ecosystems and support the development of a robust, multi-index framework for long-term ecological monitoring and coastal management.