Seagrasses can enhance carbonate sediment dissolution on diel timescales through oxidation of the rhizosphere and production of acidic exudates of dissolved organic matter (DOM). Carbonates can also associate with DOM either from biogenesis or later adsorption. However, the impact of mineral dissolution on the release of carbonate-associated DOM and on surface water DOM quantity and quality is unclear. We analyzed sub-daily changes in EEMS-PARAFAC components (excitation-emission matrices with parallel factor analysis), fluorescence, and absorbance properties of surface waters over adjacent low- and high-density (LD and HD) Thalassia testudinum seagrass meadows in Florida Bay, United States. We compared fluorescent DOM characteristics of seagrass leaves, acidified (dissolved) sediment leachates, and surface water samples collected from the HD and LD sites with surface water from a nearby mangrove island. The HD site was higher in humic-like PARAFAC components, specific ultraviolet absorbance, and humification index. We did not observe changes in EEMs indices or PARAFAC components with cumulative photosynthetically active radiation, indicating that photodegradation was unlikely to contribute to temporal variability in DOM. Similarities among DOM optical properties from acidified sediment leachates and surface waters at both sites suggest the importance of carbonate dissolution/reprecipitation for DOM cycling, while seagrass leaf leachates were markedly dissimilar to surface waters. We observed similarities among the acidified sediment leachate, surface water, and porewater elsewhere in Florida Bay, indicating dynamic coupling between these DOM pools. From this short study, Florida Bay DOM cycling appears to be more sensitive to carbonate dissolution than to additional photodegradation or authigenic seagrass leaching.

中文翻译：

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碳酸盐相关有机物是亚热带海草草甸中可检测的溶解有机物源

海草可以通过根际的氧化和溶解有机物质 (DOM) 的酸性渗出物的产生，在日尺度上增强碳酸盐沉积物的溶解。碳酸盐也可以通过生物发生或后期吸附与 DOM 相关联。然而，矿物溶解对碳酸盐伴生 DOM 释放和地表水 DOM 数量和质量的影响尚不清楚。我们分析了佛罗里达湾相邻低密度和高密度（LD 和 HD） Thalassia testudinum 海草草甸的 EEMS-PARAFAC 分量（具有平行因子分析的激发-发射矩阵）、荧光和吸收特性的次日变化， 美国。我们比较了海草叶、酸化（溶解）沉积物渗滤液、从 HD 和 LD 站点收集的地表水样本以及来自附近红树林岛的地表水。HD 部位的腐殖质样 PARAFAC 成分、特定紫外线吸收率和腐殖化指数较高。我们没有观察到 EEMs 指数或 PARAFAC 成分与累积光合有效辐射的变化，表明光降解不太可能导致 DOM 的时间变化。两个地点的酸化沉积物渗滤液和地表水的 DOM 光学特性之间的相似性表明碳酸盐溶解/再沉淀对 DOM 循环的重要性，而海草叶渗滤液与地表水明显不同。我们观察到佛罗里达湾其他地方的酸化沉积物渗滤液、地表水和孔隙水之间的相似性，指示这些 DOM 池之间的动态耦合。从这项简短的研究中，佛罗里达湾 DOM 循环似乎对碳酸盐溶解比对额外的光降解或自生海草浸出更敏感。