An Isotopic Tracer Experiment at the Ecosystem Scale

需要提高对河口氮循环的理解，以帮助解释氮输入的人为变化如何影响海岸系统。我们提出通过向帕克河-梅岛河口（美国国家科学基金会资助的陆地边缘生态系统研究（LMER）项目）上游添加富含15n的溶解无机氮，对河口氮动力学的概念模型和数值模型进行实验测试。以前在森林流域、湖泊和河流中进行的全系统标记实验已经证明了添加示踪剂方法的可行性、有效性和成本效益。在帕克河-梅岛湾河口，对添加的氮示踪剂的分布进行密集测量，将得出水、食物网成分和沉积物中氮的通量和停留时间的估计。15N添加实验将为测试和完善复杂的河口N流模型提供信息，否则很难验证。该产品将大大提高对河流盐沼河口氮的运输，转化和命运的理解。

Peterson Improved understanding of the nitrogen cycle in estuaries is needed to help explain how anthropogenic changes in nitrogen inputs are affecting coastal systems. We propose to experimentally test conceptual and numerical models of nitrogen dynamics in an estuary by adding 15N-enriched dissolved inorganic nitrogen to the upper reaches of the Parker River-Plum Island Estuary, the site of and ongoing NSF-funded Land Margin Ecosystem Research (LMER) program. Previous whole system labeling experiments in forested watersheds, lakes and rivers have demonstrated there feasibility, power and cost effectiveness of the tracer addition approach. In the Parker River-Plum Island Sound estuary, intensive measurements of the distribution of the added nitrogen tracer will yield estimates of fluxes and residence times of nitrogen in water, food web components and sediments. The 15N addition experiment will provide information to test and refine complex models estuarine N flow that are otherwise very difficult to validate. The product will be greatly improved understanding of the transport, transformation, and fate of nitrogen in riverine saltmarsh estuaries.