The bay of Bengal is one of the four hypoxic zones, followed by a significant decrease in surface dissolved oxygen.Dissolved oxygen is a necessary condition for the survival of organisms.As the bay of Bengal region is affected by tropical cyclones, the strong mixing and upwelling caused by them will cause vertical movement of subsurface water bodies.At present, most studies focus on the effects of tropical cyclones on dissolved oxygen in coastal and surface waters, but how to affect the distribution of dissolved oxygen in deep subsurface waters has not been fully studied.

The study used biological Argo buoys and multivariate satellite remote sensing data to study the effects of tropical cyclones on dissolved oxygen in the subsurface layer (20-200 m) of the low-oxygen region in the bay of Bengal from 2013 to 2018.The results reveal three different types of dissolved oxygen responses.The first type occurred in the area of strong mixing and downdraft caused by the passing of tropical cyclone Hudhud, mainly manifested as the increase of dissolved oxygen in the subsurface layer (37-70 m).The second response mainly occurs in the strong uplift area caused by the passage of tropical cyclones Hudhud, Five, Marrutha and Mora. The common characteristic is that the tropical cyclone moves slowly.The third response occurred mainly after the passage of Vardah, a faster-moving tropical cyclone.The distribution characteristics are that dissolved oxygen decreases in the shallow subsurface layer (18-39 m), increases in the deeper subsurface layer (40-79 m), and decreases in the deep layer (80-150 m).The vertical distribution of three layers of dissolved oxygen is mainly caused by the strong mixing and upwelling caused by tropical cyclones.The three different types of responses are mainly determined by the tropical cyclone's wind speed, velocity and Ekman suction.In addition, it is also affected by shallow oxygen thermocline, mesoscale vortex and biochemical interaction.This study is of great significance for further analysis and assessment of the effects of tropical cyclones on the low oxygen areas in the bay of Bengal.

Tang danling's team has been studying the Marine ecological effects of "wind pump" for a long time. At present, the team undertakes the key project of national natural science foundation of China, "Marine phytoplankton particle size distribution and related ecological factors' response to typhoons -- based on remote sensing and field observation data".The result is a collaboration between the research team and the Canadian scientists and co-funded by the national natural science foundation of China (NSF key project no. 41430968) and the youth fund (no. 41806146).The full text links to:

https://www.sciencedirect.com/science/article/pii/S0048969718352768.

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