Suboxic waters of the eastern Arabian Sea shelter secondary chlorophyll maximum dominated by heterotrophic dinoflagellate Pronoctiluca spp. (order Noctilucales).

In the present study, we investigated the dinoflagellate assemblages in the upper water column (< 150-m depth), focusing on the suboxic waters of the eastern Arabian Sea (EAS) along 68°E from 8°N to 21°N during the southwest monsoon 2020 (SWM-2020). Dinoflagellate abundance was higher in the upper water column (0-80-m depth, mean ± SD = 411 ± 903 cells L) compared to deeper waters (80-150-m depth, mean ± SD = 128 ± 216 cells L). Among 11 identified taxonomic dinoflagellate orders, Peridinales were predominant in the upper waters column (71%, mean ± SD = 285 ± 858 cells L).

Biogeochemical cycling of iodine in the Bay of Bengal: A comparison with the Arabian Sea.

Iodine is a redox-sensitive element and a potential oxidant for the respiration of organic matter. Here we report the spatial variation of dissolved iodine in the Bay of Bengal (BoB) oxygen minimum zone (OMZ) and compare it with that of the Arabian Sea (AS). Subsurface iodide peaks were observed in the upper boundary of the OMZ, representing 20 to 70 % of the total iodine budget in the BoB.

Seasonally varying biogeochemical regime around the coral habitats off central west coast of India.

The Western Indian Continental Shelf (WICS) experiences upwelling during the Southwest Monsoon (SWM), leading to deoxygenation and acidification of subsurface waters. The region has patchy growth of corals, e.g.

Contrasting patterns in pH variability in the Arabian Sea and Bay of Bengal.

Continuous understanding of the ongoing ocean acidification (OA) is essential for predicting the future impact of OA on marine ecosystems. Here we report the results of open ocean time-series measurements (19 cruises) of seawater pH in total hydrogen ion scale (pH) and associated parameters in the Arabian Sea (AS) and the Bay of Bengal (BoB). During southwest monsoon (SWM), the pH within the 30 to 100 m water column shows the maximum difference between the two basins with BoB pH being lower (up to ~0.

Response of oceanic subsurface chlorophyll maxima to environmental drivers in the Northern Indian Ocean.

Subsurface Chlorophyll Maxima (SCM) contributes a significant proportion to depth-integrated ocean primary production, making it important to understand its spatiotemporal variability in changing environmental conditions. Based on field observations and in situ data, we studied SCM characteristics in four distinct environmental settings across Northern Indian Ocean: SEAS-south eastern Arabian Sea (coastal upwelling zone), SAS-Southern Arabian Sea (Arabian Sea mini warm pool-ASMWP), SBOB-Southern Bay of Bengal (presence of mesoscale eddies) and ANS-Andaman Sea (region of active volcanoes). SCM displayed significant spatial variability: Z (SCM depth) ranged between 25 and 88 m (mean = 59.