POSTER Session 1

Massive cyclone-induced changes in Phytoplankton Community Structure, Biomass and Productivity captured at sea and from space during the Indo-US EKAMSAT-2023

The pre-monsoon month of May in the Arabian Sea is a period of acute oligotrophy especially the southeast region, which comes under the influence of an annually recurring warm pool. The water column at this time of the year is unusually warm, highly stratified and nutrient impoverished, and small cell cyanobacteria dominate the base of the food chain. With the transition to the summer monsoon and the onset of the southwest monsoonal winds mark, the stratified layer, gradually erodes, resulting in the injection of cooler, nutrient-rich waters from depth into the euphotic zone, and the replacement of surface cyanobacterial populations by diatoms. Despite the importance of this air-sea interactive process for the Arabian Sea food web, ocean biogeochemistry and pelagic coastal fisheries, there are very few contemporary studies that have captured the transition of the Arabian Sea ecosystem from its oligotrophic to mesotrophic state. The pilot Indo-US EKAMSAT study undertaken in early June 2023 was an excellent opportunity to fill this important knowledge gap. The unanticipated passage of Cyclone Biparjoy in the eastern Arabian Sea hastened this process, proving to be an excellent analog for understanding how the Arabian Sea ecosystem responds to monsoonal wind forcing. This presentation uses outputs from a physical model to detail the abrupt shift in phytoplankton communities, their biomass and net primary productivity that was captured from both shipboard and satellite bio-optical datasets.

Joaquim I. Goes, Lamont Doherty Earth Observatory, Columbia University, USA, https://orcid.org/0000-0002-9785-6985

Antonio Mannino, NASA Goddard Space Flight Center, USA

Sergio deRada, Naval Research Laboratory, Stennis Space Center, USA

Sherwin Lardner, Naval Research Laboratory, Stennis Space Center, USA

Helga do Rosario Gomes, Lamont Doherty Earth Observatory, Columbia University, USA

Jinghui Wu, Lamont Doherty Earth Observatory, Columbia University, USA

Charles Kovach, NOAA National Environmental Satellite, Data, and Information Service (NESDIS), USA

Rohan Menezes, Darmouth College, USA

Laura Zoffoli, Institute of Marine Science, Italian National Research Council, Italy

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