One health and contaminated estuarine ecosystems: a critical review of the status of Thane Creek, Mumbai, India

Estuaries are critical components in the environmental risk assessment of anthropogenic contamination. They funnel the emissions from upstream terrestrial catchments and are often within historically established population and industrial centers. They are sensitive and biodiverse and increasingly acknowledged be subject to increasing risks and hazards from urban development and climate change. To understand these effects, regular monitoring is essential but needs to be appropriate to allow impact assessment and direct long-term mitigation strategies, building resilience under the advancing impacts of climate change. A One Health approach to environmental assessment is needed to counter the emergence of global public health threats, such as antimicrobial resistance (AMR) supporting the interaction between estuarine ecology, humans and the environment. We focus on Thane Creek, Mumbai, India as a critical case being recently designated a RAMSAR site and India’s only urban RAMSAR wetland. The necessity of a robust environmental monitoring system for regulatory policy development reflects impacts from historic and emerging pollution sources. It is a particularly sensitive environment, and one of the largest creeks in Asia, with ecosystem function identified to be highly vulnerable to the impacts of climate change. Rapid urbanization, causing alterations to creek geometry over relatively short timescales, has impinged on wetland habitats. Data from governmental monitoring and previous studies of environmental quality in Thane Creek are compared to data for other Indian estuaries. Overall, there is evidence of contamination from sources including domestic sewage and nearby industries, which may have chronic impacts on the ecosystem. Dissolved oxygen was lower, biochemical oxygen demand higher, and coliform counts similar in Thane Creek compared to other estuaries. The influence of tidal dynamics and sediment movement is likely to develop seasonal variation in AMR within water and sediments with potential impact on a rich and diverse ecology, especially for migratory birds. Subsets of organic contaminants and potentially toxic elements are currently monitored infrequently in water but have been found enriched in the creek’s sediments. These key geochemical parameters are likely to have significant impacts on environmental health and highlight the need for wider assessment of environmental stressors and the development of more robust estuarine health indicators. Given both the ecological and geographical sensitivity of the region focusing on one health is a more appropriate monitoring strategy to address the emerging ecosystem challenges.