In the seasonally hypoxic semi-enclosed Omura Bay, Japan, regression equations estimating year-round nutrient [NO₃ + NO₂, NH₄, PO₄, Si(OH)₄] concentrations in pore water were successfully constructed based on water temperature and the concentration of biogenic elements in surface sediments, except for NH₄ and PO₄ concentrations in summer when the hypoxic water mass develops. Core incubation studies revealed that pore water NH₄ and PO₄ concentrations under anaerobic conditions increased 1.4–2.2 and 1.8–2.1 times, respectively, above levels estimated with the regression equations. These were in good agreement with the values observed in the field during summer. The gradient in nutrient concentrations between the measured values in the overlying water column and the estimated values in the pore water revealed that spatial fluctuations in nutrient fluxes at the sediment–water interface across the Omura Bay ranged from 1.5 to 2 times, reaching up to 3–4 times in the summer. Annual nutrient fluxes from the sediment (690–780 ton-N year⁻¹ for DIN, 77–85 ton-P year⁻¹ for DIP, and c.a. 4700 ton-Si year⁻¹ for DSi) were comparable to those from terrestrial areas. Accurate estimation of internal loadings is essential to properly evaluate residual nutrients and organic matter in the water column and their effect on aquatic ecosystems.

中文翻译：

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日本季节性缺氧大村湾沉积物养分通量的时空变化估算

在日本季节性缺氧的半封闭大村湾，根据水温和水温，成功建立了估算全年孔隙水中养分[NO ₃  + NO ₂，NH ₄，PO ₄，Si（OH）₄ ]浓度的回归方程。缺氧水团在夏季发展时，除了NH ₄和PO ₄浓度外，表面沉积物中生物元素的浓度。核心孵育研究表明，孔隙水NH ₄和PO ₄在厌氧条件下的浓度分别比通过回归方程估算的水平高1.4-2.2倍和1.8-2.1倍。这些与夏季实地观察到的值非常吻合。上覆水柱测量值与孔隙水估算值之间养分浓度的梯度表明，大村湾整个沉积物-水界面养分通量的空间波动范围是1.5至2倍，最高可达3倍。夏季–4次。从沉积物年度养分通量（690-780吨-N年^-1为DIN，77-85吨-P年^-1用于DIP，和Ca4700吨硅年^-1DSi）的数据与陆地地区的数据相当。内部负荷的准确估算对于正确评估水柱中的残留养分和有机物及其对水生生态系统的影响至关重要。