[IIOE2-EP41] Dinitrogen Fixation in the Indian Ocean: an interbasin and seasonal comparison (DINDE)
Lead Investigator :
- Mar Benavides, Mediterranean Institute of Oceanography (MIO), Campus de Luminy Batiment Mediterranee
13288 Marseille cedex 09, France
Other Key participants (s):
- Arvind Singh,Physical Research Laboratory (PRL), India
- Sophie Bonnet,Mediterranean Institute of Oceanography (MIO), France
Period of Project: September 2020 - August 2023
Brief description of the Project:
Biological dinitrogen (N2) fixation by specialized prokaryotes so-called diazotrophs is the main contributor to reactive nitrogen stocks in the ocean, fueling the marine food chain and promoting CO2 sequestration. As compared to other oceanic basins, the magnitude and controls of N2 fixation in the Indian Ocean remain unknown and excluded from global ocean nitrogen budgets.
The Indian Ocean is separated by the Indian subcontinent into the Arabian Sea (west) and the Bay of Bengal (east). The biogeochemistry of the region is controlled by the Asian monsoon system, which has different effects on the Arabian Sea than in the Bay of Bengal. Hence, marine biogeochemical studies in the Indian Ocean need to consider the interbasin and the inter-season variability. The goal of DINDE (Dinitrogen Fixation in the Indian Ocean: an interbasin and seasonal comparison) is to decipher the role of N2 fixation in the two sub-basins of the Indian Ocean, focusing on the two most unknown seasons: winter monsoon and intermonsoon. DINDE will examine the magnitude of N2 fixation rates according to environmental variability, untangling the diversity of local diazotroph assemblages and their metabolic controls. Moreover, DINDE will isolate strains with the aim of discovering diazotroph species unique to the Indian Ocean. DINDE will integrate the second International Indian Ocean Expedition (IIOE-2), a novel international effort to study the oceanography of the Indian Ocean. The in situ work will be performed during four oceanographic cruises (two per basin in each target season,two in German vessels and two in Indian vessels). The project will be carried out by the French and Indian collaborating PIs, a PhD student and an assistant. Sample analyses will be shared among the two labs according to their expertise and equipment.
As the Indian Ocean is warming faster than any other basin in the world's oceans, quantifying its N2 fixation capacity and understanding its biogeochemical dynamics emerges as a priority in current oceanographic research. DINDE lays the ground for a new collaboration between Indian and France, opening new research avenues in the most unknown oceanic basin.
Region of study:
The goal of DINDE is to decipher the role of diazotrophy in the two sub-basins of the IO between seasons. Since the great majority of the previous N2 fixation related oceanographic cruises were performed during the summer monsoon, we will focus on the northeast monsoon and intermonsoon seasons. Sampling will take place in the frame of the IIOE-2 German oceanographic cruises complemented by cruises in Indian oceanographic vessels. The cruises are programmed to cover a winter monsoon and an intermonsoon seasons in both the Arabian Sea and the Bay of Bengal as follows:
- Cruise 1: Winter monsoon Arabian Sea cruise (German cruise BIOCAN-IIOE2)
- Cruise 2: Intermonsoon Arabian Sea cruise (Indian cruise tentatively on FORV Sagar Sampada)
- Cruise 3: Winter monsoon Bay of Bengal cruise (German cruise BIOCAT-IIOE2)
- Cruise 4: Intermonsoon Bay of Bengal cruise (Indian cruise tentatively on FORV Sagar Sampada)