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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. [ABSTRACT FROM AUTHOR]

River-estuarine ecosystems are under severe anthropogenic threat due to resource exploitation, transportation, sewage/industrial discharges, and pollutants from surrounding areas. Monitoring the water quality and biological communities is essential for assessing ecosystem health and sustainability. Present study integrated the ecological community data along with water quality analysis to understand the impact of anthropogenic pressures on benthic macroinvertebrates. Samples were collected from 10 locations (comprising of both rural and urban areas) for Benthic macroinvertebrates, physico-chemical and microbiological parameters along the lower stretch of the Bhagirathi-Hooghly river-estuarine (BHE) system during the post-monsoon seasons of 2020, 2021, and 2022. During the entire study period, a total of 5730 individuals from 54 families in 19 orders of 3 phylum of macroinvertebrate were recorded. Among them Thiaridae (27.1%) and Chironomidae (22.8%) were found to be the most abundant families. Based on the water quality data Cluster analysis and nMDS indicated two distinct groups of locations: Group-I with rural settings and Group-II with urban settings. Alpha diversity metrics showed higher diversity (2.817) and evenness (0.744) in rural locations (Group-I) compared to urban locations (Group-II). The overall saprobic score of the macroinvebrate data revealed Group-I (5.09) to be in good condition, while Group-II (4.95) showed moderately polluted conditions. Redundancy analysis (RDA) highlighted the correlation of pollution-tolerant species (Chironomidae, Culicidae) with high organic loads i.e., biochemical oxygen demand (BOD), chemical oxygen demand (COD) in Group-II. In contrast, Group-I locations exhibited positive correlations with Dissolved Oxygen (DO) and supported less pollution-tolerant organisms (Coenagrionidae, Dytiscidae). The study emphasizes the importance of integrated analysis of ecological community data and water quality parameters to assess the health status of river-estuarine ecosystems. [Display omitted] • Macroinvertebrate diversity declines in downstream of BHE system due to pollution. • Pollution-tolerant species dominate in urban areas, reflecting pollution impact. • Saprobic index revealed Gr-I is less polluted than Gr-II locations. • RDA reveals pollution's role in shaping macroinvertebrate distribution. [ABSTRACT FROM AUTHOR]

A trophic model was constructed for the Poonthura Estuary, a small, anthropogenically impacted estuary along the south-western coast of India. An Ecopath with Ecosim based trophic modelling approach, based on observations made between 2016 and 2020, revealed that the Poonthura Estuary had a low total system throughput (3044.2 t km-2 year-1), low ascendancy (15%), high Finn's cycling index (17.9%), low primary production/total biomass (5.2 t km-2 year-1), high mean transfer efficiency (12.4%), and low eco-exergy (14,455.46 gm detritus equivalent m-2). These values indicated that the estuary is an immature, less organized, and unhealthy system. The evaluation of Ecological Network Analysis, and ecosystem health indices revealed that the ecological structure and functioning of the estuary are impaired to a large extent from multiple anthropogenic stressors. The Poonthura Estuary trophic model revealed the total primary production/respiration value as 0.46, indicative of the massive pollution that the system is subjected to, particularly from organic sources. Small benthic carnivores were the most important keystone groups recorded from the Poonthura Estuary, despite their low biomass. The comparison of ecological indices of Poonthura Estuary, with those recorded for other small estuaries from various geographical locations, suggested dissimilar trophic functioning and food web structures from estuaries with similar physical features. Our study is a pioneering step to reveal the ecosystem status and functioning of small, anthropogenically disturbed estuaries, besides offering theoretical and scientific basis for the management, supervision and restoration of the Poonthura Estuary as well as other small estuaries, around the world. [Display omitted] • An Ecopath with Ecosim based trophic modelling approach, was undertaken at a small, severely polluted, anthropogenically impacted estuary. • The food web structure of Poonthura Estuary in southern India reveals that the ecosystem is immature and has a less-organized food web. • The ecosystem health indices revealed that the ecological structure and functioning of the Poonthura Estuary are impaired from multiple anthropogenic stressors. • The comparison of ecological indices of Poonthura Estuary, and other small estuaries suggested dissimilar trophic functioning and food web structures. [ABSTRACT FROM AUTHOR]

The present study aimed to investigate the water quality characteristics and the ecological indicators of wastewater of white legged shrimp Penaeus vannamei ponds along the Southeast coast of India. The wastewater samples were collected from 15 shrimp farms covering 11 districts located along the coastal line of Tamil Nadu and Puducherry, India. By adopting standard methods, the collected samples were subjected to analyses of physico-chemical and biological characteristics, especially the microbial load and metal and plankton composition. The nitrate-nitrogen, ammonia-nitrogen, THB, TCB, and Cu concentrations of the samples were found to exceed the permissible limit as recommended by WHO, USEPA, CPCB, and CAA. Principal component analysis and canonical correspondence analysis have suggested that the phosphate, nitrate, silicate, ammonia, and total phosphorus are the important chemical factors. The generated data would be of interest to farmers for their shrimp crop management vis-à-vis culture pond wastewater treatment. • Penaeus vannamei cultured wastewaters significantly contribute to nutrients pollution. • This study covers 1076 km coastal area consisting 15 farms in 11 districts from tow states. • Higher level of NO 3 , NH 3 , THB, TCB, Cu detected in wastewater than the permissible limit • Plankton diversity was triggered by higher loading of nutrients. • PCA and CCA suggest that total nitrogen plays vital role in wastewater. [ABSTRACT FROM AUTHOR]