POWRE: Nitrogen Cycling in a Lagoonal Land Margin Ecosystem: Importance of Dissolved Organic Nitrogen

9805928 麦格拉瑟里河口和浅泻湖是陆地和海洋生态系统之间的纽带，接受大量的外部营养物和有机物输入。沿海流域的过量无机养分负荷与初级生产力的增加以及接收水域生境结构和营养动态的变化直接相关。相比之下，人们对近岸系统中有机养分的循环和生物利用度知之甚少，尽管这些系统的有机养分输入有时可能高于无机负荷。该 POWRE 奖项重点关注溶解有机氮 (DON)，它是沿海浅水区氮循环的潜在重要组成部分。沿海泻湖和海湾构成了大多数大陆陆地边缘生态系统的主要类型，但通过这些系统保留和运输营养物质所受到的关注远远少于大河口。这些系统之间氮循环过程的一个主要区别是底栖初级生产者对浅沿海泻湖和海湾的养分转化的巨大影响。沉积物-水界面上的交换在泻湖系统的养分循环中发挥着关键作用，因为水柱混合良好，并且相对于较大的沉积物表面积而言体积较小。将结合现场观察、实验室实验和数值模拟来检验有关有机物负荷、呕吐毒素通量和底栖植物之间相互作用的假设。这些结果将有助于我们预测不同负荷模式对沿海泻湖系统的影响，以及为减少浅海沿海系统富营养化影响而采取的可能缓解措施的有效性。

9805928 McGlathery Estuaries and shallow lagoons are the link between terrestrial and oceanic ecosystems and receive considerable external inputs of nutrients and organic matter. Excess inorganic nutrient loading from coastal watersheds has been directly related to increases in primary production and to changes in habitat structure and trophic dynamics in receiving waters. By comparison, little is known about the cycling and bioavailability of organic nutrients in nearshore systems, even though organic nutrient inputs to these systems can sometimes be higher than inorganic loadings. This POWRE award focuses on dissolved organic nitrogen (DON) as a potentially important component of the nitrogen cycle in shallow coastal waters. Coastal lagoons and bays constitute a major type of land margin ecosystem on most continents, but the retention and transport of nutrients through these systems have received far less attention than in large estuaries. A major difference in the nitrogen cycling processes between these systems is the large influence that benthic primary producers have on nutrient transformations in shallow coastal lagoons and bays. Exchanges across the sediment-water interface play a key role in nutrient cycling in lagoonal systems because the water column is well-mixed and small in volume relative to the large sediment surface area. A combination of field observations, laboratory experiments and numerical modeling will be used to test hypotheses regarding interactions between and among organic matter load, flux of DON, and benthic plants. The results will aid our ability to predict both the consequences of different loading regimes to coastal lagoonal systems and the effectiveness of possible mitigation efforts to reduce the effects of eutrophication in shallow coastal systems.