Summary of Abstract Submission

Abstract Submission No. IO50-03-0016PresentationOral

EFFECT OF ANTHROPOGENIC INPUTS ON NITROGEN AND CARBON UPTAKE RATES IN THE COASTAL ARABIAN SEA

Sanjeev Kumar*1, Bhavya P.S.1

1 Physical Research Laboratory, Ahmedabad 380009, India

ABSTRACT :

Coastal regions are vulnerable ecosystems due to increased nutrient loading from anthropogenic activities. Anthropogenic inputs cause these coastal systems to shift drastically from N limited to N surplus leading to eutrophication, a major threat to most of the estuaries and coastal waters around the world. Our understanding of the effects of anthropogenic inputs in the coastal Arabian Sea vis--vis biogeochemical transformation rates remains inadequate. Experiments were conducted to quantify rates of NO3-, NH4+, and C uptake along with N2 fixation rates in the coastal Arabian Sea along two transects, viz. off Cochin and Mangalore using stable isotopes tracer technique. In general, N and C uptake rates in the nearshore waters of the Cochin transect were significantly higher than that observed for the Mangalore transect, indicating the influence of direct N loading from the Cochin estuary on the uptake rates of the coastal Arabian Sea. Also, the uptake rates at nearshore station were significantly higher than stations farther from the coast. Despite high dissolved inorganic nitrogen concentrations, considerable N2 fixation rates were observed in the coastal waters. NH4+ was the preferred substrate for phytoplankton growth indicating the significance of regenerative processes in primary production.