Distribution Characteristics and Dynamics of Marine Hydrogen in the Eastern Indian Ocean

The ocean serves as a significant contributor of atmospheric Hydrogen (H2) with indirect greenhouse effects. However, uncertainties persist regarding internal production and consumption processes of marine H2, as well as controlling factors. Our study examined the spatial distribution and source-sink dynamics of marine H2 in the Eastern Indian Ocean. H2 concentrations in surface seawater exhibited a range of 2.95-21.96 nmol L-1. High concentrations of H2 were observed in the anoxic water in the Bay of Bengal. Rates of H2 photo-production and microbial consumption in surface seawater ranged from 1.80 to 17.78 nmol L-1 h-1 and 1.02-9.18 nmol L-1 h-1, respectively. When considering the entire mixed layer, photo-production contribute to approximately 31%-43% of the total H2 removal, with cyanobacteria potentially serving as another source in the mixed layer. Compared with the sea-to-air exchange, microbial consumption was the primary removal pathway of H2 in seawater.