Summary of Abstract Submission

Abstract Submission No. IO50-08-0017PresentationPoster

OPTICAL CHARACTERIZATION OF THE METABOLICALLY PRODUCED COLOURED DISSOLVED ORGANIC MATTER (CDOM) AND FLUORESCENT DISSOLVED ORGANIC MATTER (FDOM) IN A LARGE BRACKISH WATER LAGOON.

G. Chiranjeevulu*1, Nittala S. Sarma**1, P. Venkatesh1, B. Charan Kumar**1, A.V. Raman1

1 Andhra University, India

ABSTRACT :

Colored dissolved organic matter (CDOM) and fluorescent DOM (FDOM) were measured for a year on monthly samples in the Chilka lagoon, Asia¿s largest brackish water lagoon in order to identify and quantify the DOM sources and sinks. The CDOM was at its peak at the time of peak terrestrial flux (September) and also at the time of peak in situ input when the flow was lean (March), attributed to phytoplankton production and heterotropic metabolism. The northern part of the lagoon which is the entry point for CDOM-rich river water has higher CDOM during the year. The active flow (AF) and Lean flow (LF) conditions are distinguished by CDOM, its spectral slope and the humic fluorophores. CDOM was conservative with salinity in both the AF and LF seasons. Dissolved organic carbon (DOC) was significantly correlated with CDOM during LF. Four fluorescence components namely three humic-like and one protein-like were noticed. The fluorophores¿ intensities were high during LF compared with AF attributed to FDOM liberation by higher bacterial metabolism. The tryptophan (T) fluorophore is positively correlated with dissolved organic nitrogen (DON) in both seasons indicate that the T peak is proxy for DON. This study reveals that (i) Chilka lagoon is a highly fluorescent lagoon compared with other aquatic bodies like the coastal waters of Bay of Bengal and Indian estuaries, and (ii) CDOM is helpful to investigate the ecosystem changes involving the major components i.e., terrestrial influx, seagrass and macrophyte weed communities, phytoplankton and bacterial metabolism.