Delineating ecosystem structure and trophic organization to evaluate the health status of a tropical coastal region in the neighbourhood of Mumbai megacity

The Mumbai metropolitan region has undergone rapid urbanization and economic expansion in recent years. Ensuring the sustainability of artisanal fishers' livelihoods and safeguarding coastal ecosystems poses a significant challenge to the city's overall sustainability. This study examines the ecological structure to ascertain how anthropogenic stressors affect ecological functioning of Mumbai coastal waters (MCW). Ecopath with Ecosim (version 6.6.8) was employed to construct a mass-balanced trophic model for the MCW. This model delineated 20 distinct groups, including seven types of Teleost fishes, eight Invertebrate groups, Elasmobranchs (cartilaginous fish), Birds, Zooplankton, Phytoplankton, and Detritus. At trophic hierarchy's base were detritus and primary producers (trophic level = 1), while highest trophic level was occupied by Elasmobranchs (trophic level = 4.40). Energy transfer efficiency within the ecosystem varied significantly across different categories. Ecotrophic efficiency ranged from 0.062 for detritus to 0.997 for filter feeders, with consumer groups often surpassing 0.80. Both primary producers and detritus exhibited average transfer efficiencies of 31.76% and 33.56%, respectively. A combination of indicators collectively indicated that the MCW ecosystem was in an early and immature stage of development. These indicators encompassed net system production (2735.077 t km-2y-1), ratio of total primary production to total biomass (26.88), ratio of total biomass to total system throughput (0.013), recycling index (Finn's cycling index = 1.23%), the system's omnivory index (0.47), and the connectance index (0.342%). Moreover, the ascendancy (36.06%) and overhead (67.94%) results indicated the ecosystem's stability and resilience against disturbances. Total eco-exergy was calculated at 45645.1 g m- 2, with a specific eco-exergy of 100.3 g m- 2. These indices offer valuable insights into the energy and structure of the ecosystem. This study emphasizes the need for diverse ecological and fishery regulations. Additionally, it stresses the importance of fostering conversations around strategic conservation planning and building the capacity to execute these plans effectively.