AUTHOR=Sun Yafei , Wang Guizhi , Weng Yubin , Li Qing , Zhang Fei , Jiang Weizhen , Dai Guiyuan , Lin Wen , Sun Shengyao , Jiang Yiyong , Zhang Yuanjing 

TITLE=Submarine groundwater discharge in Dongshan Bay, China: A master regulator of nutrients in spring and potential national significance of small bays

JOURNAL=Frontiers in Marine Science

VOLUME=Volume 10 - 2023

YEAR=2023

URL=https://www.frontiersin.org/journals/marine-science/articles/10.3389/fmars.2023.1164589

DOI=10.3389/fmars.2023.1164589

ISSN=2296-7745

ABSTRACT=We revealed that submarine groundwater discharge (SGD) predominately regulated nutrients distributions and fueled algal growth in Dongshan Bay, China based on mapping and time-series observations of Ra isotopes and nutrients, a case study of small bays (< 500 km2). On the bay-wide scale, the SGD rate was estimated to be 0.048 ± 0.022 m d-1 and contributed over 95% of the nutrients. At the time-series site where the bay-wide highest Ra activities in the bottom water marked an SGD hotspot with an average rate an order of magnitude greater, the maximum chlorophyll concentration co-occurred, suggesting that SGD may support the algal bloom. The ever most significant positive correlations between 228Ra and nutrients throughout the water column (P < 0.01, R2 > 0.90 except for soluble reactive phosphorus in the surface) suggested predominance of SGD in controlling nutrient distributions in the bay. Extrapolated to a national scale, the SGD-carried nutrient fluxes in small bays were 1.5 times as much as those in large bays (> 2000 km2). Thus, SGD-carried nutrients in small bays merit immediate attention in environmental monitoring and management.