NIFS announced that the hypoxic water mass that occurred in coastal areas of the South Sea in early June of this year disappeared completely with the last occurrence in the Jinhae Bay on October 25. 

*A hypoxic water mass is a body of water with extremely low dissolved oxygen (DO) levels, typically defined as less than 3 milligrams per liter, which threatens aquatic life. It most commonly occurs during summer, driven by a combination of high water temperatures and a significant temperature gap between the surface and bottom layers. 

Since the first finding of hypoxic water masses in coastal areas of the South Sea in the Jinhae Bay on June 10, their occurrence expanded to Gyeongnam (June 12-19), the Gamangman Gulf, Jeonnam (June 18), and the Cheonsu Bay, Chungnam (July 7). In the Cheonsu Bay, they occurred this year, following the one in 2024 that occurred in six years since 2018. 

This year, the accumulated rainfall was the 74 percent level of the average year (as of October 16, 1,530mm), causing hypoxic water masses to form in the depths of around 2-3m which was shallower than 6-7m of average year. The duration in the western part of Jinhae Bay was also 138 days, shorter by 44 days than 182 days of last year. 

The president of NIFS (Mr. Choi, Yong-seok) said, “There has been increasing variability in the pattern of hypoxic water mass occurrence due to climate change cross the globe. Therefore, it is critical to understand the variability pattern of hypoxic water mass occurrence in the summer of the southern coast every year.” The president also said, “NIFS will work on the real-time monitoring of the occurrence range and intensity as well as prompt information provision to fishermen for mitigating the damages to aquaculture organisms.”