Sun Danqing, Ibánhez Juan Severino Pino, Zhang Jing, Zhang Guosen, Jiang Shan
State Key Laboratory of Estuarine and Coastal Research, East China Normal University, Shanghai 200241, China.
Instituto de Investigacións Mariñas, Consejo Superior de Investigaciones Científicas (IIM-CSIC), Eduardo Cabello 6, 36208 Vigo, Spain.
Sci Total Environ. 2024 May 10;924:171473. doi: 10.1016/j.scitotenv.2024.171473. Epub 2024 Mar 6.
Seasonal field surveys (April 2018 to February 2019) were conducted in a subterranean estuary (STE) seepage face in Sanggou Bay (China) aiming to explore the transport and reactivity of phosphorus (P) and biogeochemical linkages with the cycling of nitrogen (N) prior to discharge. Porewater dissolved inorganic phosphorus (DIP) and dissolved organic phosphorus (DOP) together with different fractions of sedimentary P were analyzed in the upper, middle and lower intertidal covering the top 20 cm of sediment (1-4 cm, 5-8 cm, 9-12 cm, 13-16 cm and 17-20 cm depth). The accumulation of sedimentary organic P stimulated the growth of phosphate-solubilizing microorganisms and led to porewater DOP enrichment during spring. During summer, total P (TP), porewater DIP and DOP concentrations decreased, potentially due to enhanced mineralization driven by high ambient temperature. From autumn to winter, pelagic organic matter into the STE lowered, triggering a drop of TP standing stocks. Compared with the significant seasonality, sedimentary P storage was statistically identical along the intertidal. Such spatial homogeneity likely results from the rebalance driven by P adsorption dynamics and pelagic organic matter delivered by tide and wave setup. The vertical distribution of DIP, DOP, and sedimentary TP were linked to nitrate transformations. In the sediment layer with active mineralization and nitrification, concentrations of DOP, sedimentary redox and clay P increased. In the layer with active nitrate removal (2-5 cm depth), both DIP and DOP concentrations decreased. The sedimentary loosely-bound and organic P were also lower there. Notably, a substantial quantity of soluble P seeped out, acting as an important contributor to the dissolved P pool of the receiving waters. The spatial and temporal overlap of high concentrations of N and P in STEs adds variabilities and uncertainties in P out-drainage fluxes and nutrient stoichiometry balances, which should draw attention from coastal researchers and stakeholders.
2018年4月至2019年2月期间，在中国桑沟湾的一个地下河口渗出面进行了季节性野外调查，旨在探究磷（P）的迁移和反应性以及排放前与氮（N）循环的生物地球化学联系。对潮间带上部、中部和下部覆盖沉积物顶部20厘米（深度为1-4厘米、5-8厘米、9-12厘米、13-16厘米和17-20厘米）的孔隙水溶解无机磷（DIP）、溶解有机磷（DOP）以及不同形态的沉积磷进行了分析。春季，沉积有机磷的积累刺激了溶磷微生物的生长，并导致孔隙水DOP富集。夏季，总磷（TP）、孔隙水DIP和DOP浓度下降，这可能是由于高温驱动的矿化作用增强所致。从秋季到冬季，进入地下河口的浮游有机物减少，导致TP存量下降。与显著的季节性相比，潮间带沉积物中磷的储存量在统计学上是相同的。这种空间均匀性可能是由磷吸附动力学以及潮汐和波浪作用带来的浮游有机物驱动的再平衡导致的。DIP、DOP和沉积TP的垂直分布与硝酸盐转化有关。在具有活跃矿化和硝化作用的沉积层中，DOP、沉积氧化还原和黏土磷的浓度增加。在具有活跃硝酸盐去除作用的层（深度为2-5厘米）中，DIP和DOP浓度均下降。那里的沉积松散结合态磷和有机磷也较低。值得注意的是，大量可溶性磷渗出，成为接收水体溶解磷库的重要贡献者。地下河口高浓度N和P的时空重叠增加了磷排放通量和营养盐化学计量平衡的变异性和不确定性，这应引起沿海研究人员和利益相关者的关注。
