Estimation of inherent optical properties of saline stretches of vembanad lake

Abstract: Vembanad Lake is the second largest lagoon in India and the largest lake in the state of Kerala. In the west, the lake joins to Arabian Sea through two inlets at Kochi andAzhikode. The highly populated coastal zones in and around the lake, resorts, house boats,agricultural field and industries on the banks of the lake directly or indirectly exploit the lakeresources ultimately results in contamination of the water body by many ways. This workinvestigates the possible synoptic view on the seasonal variability of inherent opticalproperties of Vembanad Lake. The water sample collectionwas undertaken in 20 days interval from three stations of Lake for three different seasons;pre-monsoon, monsoon and post-monsoon respectively during the period of April 2018 to January 2019.It was found thatdetritus material play a vital role in determining the optical properties of the lake at 440nm.Chl-a was observed in the range of 1.2 to 13.0 mgm-3 with an average of 7.9 mgm-3,with post-monsoon having the highest value.An inverse relationship was observed between salinity and CDOM during the entire study period andconfirms river driven dischargeas the major source of CDOM.SCDOMvalue ranged from 0.0097to 0.02163nm-1 with an average value of 0.01645nm-1.High value of aph was found during the premonsoon season and a significant relationship betweenaph and chl-a was observed during the post monsoon season. Comparison of insituchl-a data with remote sensing data collected from satellite sentinel 2A and 2B indicated a significant relationship during the study period. In Barmouth region, primary productivity data showed a significant relationship with chl-a andaph with r2values of 0.6542 and 0.8663 respectively.The outcome of the study points a variation in inherent optical properties that indicates the change in water mass and constituents of Vembanad Lake.