Dissolved oxygen and oxygen minimum zone in the southern abyssal region of the East Vietnam Sea

Phan Minh Thu1,2,*, Bui Hong Long1, Nguyen Minh Hieu1, Nguyen Nhu Trung3
Received: 3 September 2020; Accepted: 26 November 2020
©2020 Vietnam Academy of Science and Technology (VAST)
 

Abstract
Based on data from the cruise in the period of August-October 2019, reanalysis data of WOD-2018 and station Bio-agro0348 (2014-2016), the paper showed the current situation and spatial variation of content of dissolved oxygen (DO) in the southern abyssal region of the East Vietnam Sea. The concentration of DO ranges from 2.48-6.25 mg/L or 1.86-4.70 mL/L. In the surface layer, the DO fluctuated strongly, but in deep water layers the DO had the same trend, and formed the minimum oxygen zone (OMZ). This OMZ was distributed at water layer ranging from 450 m to 1,200-1,300 m, with a thickness ranging from 650-850 m. The variation of the OMZ depended on the hydrodynamic regime and special weather conditions. Based on the distribution of DO, the water column was able to form four zones: oxygen-rich surface zone, reducing DO zone, OMZ and oxygen-rich bottom zone. Variation of DO in deep zones may affect the formation of Fe-Mn crust and nodules in the study area. Finally, this article is the first finding of DO content in the southern abyssal region of the East Vietnam Sea.
Keywords: Dissolved oxygen, oxygen minimum zone (OMZ), the East Vietnam Sea