[IIOE2-EP12] Dust Stimulated Nitrogen Fixation in the Arabian Sea- an assessment of HNLC region hypothesis (DUSTNIF)

Lead Investigator and other key participant (s):

  1. Dr. Arvind Singh, PRL, Ahmedabad, India.

Period of Project: 2016-2020

Brief description of the Project:

The oceans act as a major sink for anthropogenic CO2 through primary production. Though the Arabian Sea (area ~6.2 × 106 km2) covers only about 1% of the global ocean surface but contributes up to 5% of the global marine primary production2, partly due to high influx of ‘new’ nitrogen via diazotrophic N2 fixation. Iron, whose main source in the ocean is atmospheric transport of dust, is an essential nutrient for sustaining N2 fixation. Despite being in the vicinity of the Thar desert on the east and the Arabia desert on the west, the Arabian Sea has been recently hypothesized to be an HNLC (high nutrient low chlorophyll) region (Naqvi et al., Biogeosciences, 2010).

One of the most spectacular biological phenomena is the occurrence of annual spring Trichodesmium blooms in the Arabian Sea. There is a north-south gradient in dust deposition. We hypothesize (i) that this gradient plays a major role in Trichodesmium distribution, and (ii) the HNLC region could be limited just to the south Arabian Sea. In order to test our hypotheses, this project aims a comprehensive study of N2 fixation rates, chemical characterization of the dust and sea water, primary production and community structure analysis along the three transacts in the Arabian Sea during April 2017 onboard FORV Sagar Sampada (cruise already allotted) and on a couple of cruises in coming years.

This project is being initiated as an Early Career Scientists Network endeavour.

Region of study

Arabian Sea, Bay of Bengal