Prospects for golden tides in the East China Sea under climate change: Changes in water temperature and Sargassum horneri in Jeju Island, Korea

Abstract

The East China Sea have been reported as one of most rapidly warming regions of the world. Macroalgal blooms have been increasingly observed in the East China Sea and the Yellow Sea. Massive golden tides caused by Sargassum horneri after the 2010s covered the East China Sea extensively. This study was conducted to understand population dynamics of S. horneri in Jeju Island, Korea and to predict the golden tides affected by climate change. The warming trend of seawater temperature in Jeju was especially higher in winter than in summer. Populations of S. horneri had repeatedly clear annual life cycles during experimental period from November 2017 to August 2022. The growth of S. horneri reflected seasonal and annual patterns in seawater temperature. Density of the population recruited in 2017 were significantly higher than those of after 2019. Specific growth of S. horneri yearly changed by the lowest water temperature. The highest growth rate and thallus height of S. horneri occurred at a water temperature of approximately 15℃ in 2018 and 2022, but it no showed similar elongation and thallus height in 2020-2021 when the lowest water temperatures exceeded 15℃. In 2022, although fast growth of S. horneri occurred individually due to the low winter water temperature, the biomass per unit area was lowered due to the lowest population density. This suggests that long-term increases in seawater temperature can alter overall population maintenance patterns. These results aim that the extent of S. horneri population may vary depending on the water temperature, and indicate that the distribution and pattern of golden tides in the East China Sea may change due to climate change.