RESUMEN

The tropical estuaries are characterized with high biological production and also impacted by anthropogenic activities. Describing these estuaries in terms of ecological data and trophic dynamics to reveal the ecological impacts is gaining attention recently. In this study, the ecological structure is analyzed for a heavily impacted small macrotidal tropical estuary, Ulhas river estuary (URE), situated near Mumbai megacity in the western coast of India, to delineate the impact of anthropogenic stressors on the ecosystem functioning. The URE is being exploited for sand and fisheries resources, and also faces risks from anthropogenic activities. The ecological data of URE were compiled for 2017-18 together with the most relevant literature estimates to construct an ecosystem model. A trophic organization in 20 functional groups was identified for URE using Ecopath modeling approach. The functional groups identified in the food web ranged from detritus and primary producers (trophic level (TL) = 1) to large pelagics (TL = 4.14). Detritivory: herbivory ratio (1.35) indicated that the detritus chain is dominant over the primary producer's chain. The total system throughput (TST) was estimated as 16 736.2 t km-2year-1. The indices such as net system production (NSP = 1 398.781 t km-2 year-1), total primary production/total biomass (TPP/TB = 25.17), biomass/total system throughput (TB/TST = 0.01), recycling index (Finn's Cycling Index = 13.94%), system omnivory index (0.3), relative ascendency (25.6%), and system overhead (74.4%) classified URE as an immature system. The eco-exergy index (30748.54 gm detritus equivalent m-2) showed that the ecosystem is a moderately stable and relatively less organized network. The estuarine fish community index (EFCI) yielded a value of 38 indicating the poor health status of the fish community in URE. The study delivers a comprehensive understanding of the ecosystem setting in URE and characterizes the prevailing condition. The ecological indicators analyzed here point towards a medium to a high level of impact in URE due to anthropogenic activities.

Asunto(s)

Ecosistema , Estuarios , Animales , Explotaciones Pesqueras , Estado de Salud , India

RESUMEN

The pollution due to marine debris is a serious environmental threat in many parts of the world. The abundance of marine debris, composition and its distribution over the seafloor along north-east coast of Arabian coast was studied through trawl based swept method. Experimental fishing was conducted fortnightly using shrimp bottom trawl and collected debris was categorized as per standard protocols. A total of 1077 pieces of debris (11.7 kg dry weight) were collected from 25 hauls. The average number and weight of debris were 943 items/km2 and 10.2 kg/km2 respectively. The estimated total marine debris along this coast was 379 t (dry weight). Plastic-based debris contributed maximum (87.1%) to the total debris collected in numbers and among this, plastic bags and food wrappers were dominant. Debris produced by shoreline/recreational activities comprised the major source of debris (88.6%) along this coast. This study provides the evidence that the effective use of available fishing trawlers and co-management practices ("Make fishers friend") can help to remove the seabed debris. The base data generated through this study would facilitate region-based effective control and management of plastic debris pollution.