Composition of sedimentary organic matter in Thrissur Kole wetland, Southwest India

Abstract

Spatio-temporal distribution dynamics of various biochemical components in Thrissur Kole wetland were analysed to assess the quality of organic matter (OM) and trophic status. Thrissur Kole wetland forms the part of the Vembanad wetland system, located in the southwest coast of India. Surface sediment samples were collected from sixteen sites during non-monsoon (February 2019) and monsoon (August 2019) seasons. Concentration of biochemical parameters displayed a trend as follows: total carbohydrates > total protein > tannin & lignin > total lipids. Observed chlorophyll pigment concentration in sediments was as follows: Chla > Chlb > Chlc (in both seasons). Intermediate values of C/N ratios indicated a mixed origin of OM. Majority of stations exhibited lower values of protein to carbohydrate ratios which revealed the occurrence of aged sedimentary OM. Lower values of lipid to carbohydrate ratio indicated lower nutritional value of the organic content. The lower content of labile OM, low biopolymeric carbon to total organic carbon ratio and low algal contribution to the biopolymeric carbon suggested that a bulk fraction of OM exist as refractory. Trophic state of the wetland system was evaluated as hypertrophic, based on protein and carbohydrate content, biopolymeric carbon and algal contribution to biopolymeric carbon.