ECOSYSTEM GRADING BASED ON SELECTED WATER QUALITY PARAMETERS FOR A CHOSEN COASTAL VILLAGE IN THE VEMBANAD LAKE SYSTEM, KERALA, INDIA

The coastal ecosystems are impacted by anthropogenic activities and habitat of most of the estuarine resident and migratory fauna are getting degraded. The studies conducted by Central Marine Fisheries Research Institute (CMFRI), during the past two decades have shown that the water quality in the industrial area of Vembanad Lake is being affected. The present study aimed at monitoring and grading the aquatic ecosystems of Mulavukad, a coastal village in the Vembanad Lake system so that suitable site specific micro level environment management plan could be developed for solving the issues of environmental degradation and to improve the resource status and effective utilization of aquatic systems.

Samples were collected from 43 locations covering different usage categories viz. open estuary, shrimp farms (operational and non operational), inland water bodies, canals running through populated areas and mangroves. Water quality was assessed based on selected physical, chemical, biological and microbiological indicators using standard methods during post-monsoon (October-December 2017). The data set for evaluation of the ecosystem was selected from these water quality parameters based on PCA analysis. The selected parameters were scored using linear scoring function and these scores were combined into a normalized ecosystem index reflecting the system's overall health. The ecosystems were categorized as poor, fair, moderate and good based on <25^th, 25^th - 50^th, 50^th - 75^th and >75^th percentile values of the normalized ecosystem index obtained in the study area.

Ecosystem grading based on the index revealed that 35% of the estuarine region and 50% of active shrimp farms surveyed were in 'Good' condition (Fig. 1 and 2). Around 33% of abandoned farms have good production potential in terms of water quality. Mangroves showed only fair water quality in 75% of the stations due to the presence of coliform bacteria (Fig.3), inland waters being good in 16.67% stations (Fig.4) and canals with good water quality being 12.5%.