Carbon Isotopic Composition of Suspended Particulate Matter and Dissolved Inorganic Carbon in the Cochin Estuary during Post-Monsoon

Detailed measurements of carbon (C) isotopic composition in dissolved inorganic (δ ¹³C_DIC) and particulate organic (δ ¹³C_POC) fractions were conducted at 18 stations in the Cochin estuary during the post-monsoon season. In general, C biogeochemistry of different regions of the Cochin estuary appears to be regulated by different sources and processes. The northern zone of the estuary appears to be influenced primarily by mixing of sea water enriched in ¹³C_POC and ¹³C_DIC, and river run-off depleted in the same. In contrast, the southern zone of the estuary was found to be greatly influenced by local terrestrial sources. Relatively depleted ¹³C_POC in the freshwater Vembanad lake compared to the main estuary suggests inputs from terrestrial sources along with in situ productivity.