Tidally driven submarine groundwater discharge to a marine aquaculture embayment: Insights from radium and dissolved silicon

For understanding the significance of tidal pumping for driving submarine groundwater discharge (SGD), two time series observations were conducted over tidal cycles in typical mariculture areas of Sanmen Bay, China. Based on ²²⁴Ra and dissolved silicon (DSi), the tide-driven SGD fluxes showed significant negative correlations with tidal height, and were 16.4 ± 5.6 cm d⁻¹ and 21.7 ± 13.9 cm d⁻¹ at two coastal sites of the Sanmen Bay, highlighting the potential of DSi in SGD calculation when coastal waters are on short time scales. Furthermore, nutrient fluxes through tidally influenced SGD were estimated to be 11.5–26.5 mmol m⁻² d⁻¹ for dissolved inorganic nitrogen, 0.06–0.34 mmol m⁻² d⁻¹ for dissolved inorganic phosphorus and 11.5–32.1 mmol m⁻² d⁻¹ for DSi, which were higher than those from surface loadings, revealing that tide-driven SGD with large amounts of nutrient and high N:P ratios may significantly contribute to the development of marine aquaculture.