Summary of Abstract Submission

Abstract Submission No. IO50-03-0037PresentationPoster

NITROGEN CYCLING ALONG THE WESTERN CONTINENTAL SHELF OF INDIA DURING SEASONAL ANOXIA : A STABLE ISOTOPIC APPROACH

Pratirupa Bardhan*1, S.W.A. Naqvi1, S.G. Karapurkar1, A.K. Pratihary1

1 CSIR-National Institute of Oceanography, India

ABSTRACT :

The western continental shelf of India (WCSI) experiences coastal upwelling and severe oxygen deficiency during summer and autumn. Carbon and nitrogen isotopic composition (δ13C and δ15N) of suspended particulate matter and dual isotopic composition (δ15N and δ18O) of dissolved nitrate were measured in shelf waters from Calicut to Mumbai during the late upwelling phase in September-October, 2011. The aim of the study was to trace the source end-members and to determine the fate of anthropogenic N in the world┐s largest naturally-formed coastal oxygen-deficient system. Results reveal distinct marine isotopic signatures in the organic matter in spite of the huge terrestrial load entering the system. Previous measurements in waters affected by high N loss had yielded unexpectedly low δ15N-NO3- (~5┐). A comparison with these data and a re-evaluation of the N-loss fractionation factor are made in this study.