LTREB: Nutrients and climate as drivers of carbon sequestration and ecosystem metabolism in a shallow coastal ecosystem during recovery from nitrogen pollution

氮污染是对沿海海湾生态完整性的最大威胁之一，导致美国三分之二的海湾生态系统退化。东海岸大部分地区都有浅海海湾，特别容易受到过量氮的影响，这可能导致藻华、溶解氧低和高栖息地质量海草的丧失。这项研究将检查浅水湾的恢复，因为氮的输入大大减少，而其他营养物质和污染物的输入没有任何伴随的变化，这可能是美国第一个这样的研究。该地点位于科德角（MA）的西法尔茅斯港，在过去的15年里，由于污水处理厂污染了地下水，导致水质差和栖息地退化，该地点的氮输入水平很高。氮污染现在已经被清理干净，因此进入港口的氮输入将比过去减少三分之一。迄今为止，相对较少的沿海海湾从过量的氮输入中恢复过来，因此本研究将提供有关栖息地质量恢复速度和恢复程度的信息，这对更好地管理和保护这些宝贵的沿海资源至关重要。虽然大多数海岸科学家认为氮是海岸富营养化的主要原因，但这一观点仍存在争议。这项研究将提供重要的见解，不仅是氮是否是控制养分，而且如果是，为什么。一种假设是，从较深的沿海水域大量净进口磷有助于维持氮的限制。如果是这样的话，净磷进口量应该会随着初级生产（以及由此产生的对磷的需求）的下降而下降。该研究还将探索碳储量与生态系统净产量的关系，验证低氮投入将使生态系统向更大的异养转变的假设。港口是否会通过进口超过净呼吸量的碳来继续储存碳？这些问题将通过测量从溶解氧和pH值、海草范围和生物量元素组成的变化中产生的初级生产和生态系统呼吸速率，以及通过测量港口和马萨诸塞州Buzzards湾更深的邻近沿海水域之间的氮、磷和碳交换来解决。结果将与12年来在高氮负荷期间采集的数据进行比较，从而提供系统回收轨迹的有力图片。

Nitrogen pollution is one of the largest threats to the ecological integrity of coastal bays, leading to the degradation of two-thirds of these systems in the US. Shallow coastal bays are found along much of the east coast, and are particularly vulnerable to the effects of excess nitrogen, which can lead to algal blooms, low dissolved oxygen, and loss of high-habitat quality seagrasses. This research will examine the recovery of a shallow bay as nitrogen inputs are greatly reduced without any concomitant change in inputs of other nutrients and pollutants, making it perhaps the first such study in the US. The site, West Falmouth Harbor on Cape Cod (MA), has received high levels of nitrogen inputs for the past 15 years, due to contamination of incoming groundwater by a sewage treatment plant, causing poor water quality and habitat degradation. The nitrogen contamination has now been cleaned up, and so nitrogen inputs entering the harbor will be 3-fold less than in the past. To date, relatively few coastal bays have recovered from excessive nitrogen inputs, so this study will provide information on the rate of recovery and extent of restoration of habitat quality that is critical to better manage and protect these valuable coastal resources. While most coastal scientists believe nitrogen is the primary cause of coastal eutrophication, this remains debated. This study will provide important insights as to not only whether nitrogen is the controlling nutrient, but if so, why. One hypothesis is that a large net import of phosphorus from deeper coastal water helps maintain N limitation. If so, net phosphorus import should decline as primary production (and resultant demand for phosphorus) declines. The research will also explore the relationship of carbon storage to net ecosystem production, testing the hypothesis that lower nitrogen inputs will shift the ecosystem towards greater heterotrophy. Will the harbor continue to store carbon, by importing more carbon than the net amount respired? These questions will be addressed by measuring rates of primary production and ecosystem respiration from diel changes in dissolved oxygen and pH, seagrass extent and biomass elemental composition, and by measuring the exchanges of nitrogen, phosphorus, and carbon between the harbor and the deeper adjacent coastal waters of Buzzards Bay, MA. Results will be compared with 12 years of data taken during the high nitrogen loading period, and will thus provide a strong picture of the recovery trajectory of the system.