Establishing an Anthropogenic Nitrogen Baseline Using Native American Shell Middens
Establishing an Anthropogenic Nitrogen Baseline Using Native American Shell Middens
复制标题
利用美洲原住民贝丘建立人为氮基线
DOI：
10.3389/fmars.2016.00079
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发表时间：
2016
影响因子：
3.7
通讯作者：
A. Humphries
中科院分区：
文献类型：
--
作者：
A. Oczkowski;Thomas Gumbley;B. Carter;R. Carmichael;A. Humphries
罗德岛州的纳拉甘西特湾200多年来一直受到人为营养物质的严重影响。最近改善水质的努力使这个点源河口的污水氮(N)负荷减少了一半以上。考虑到海湾肥沃的时间比监测项目实施的时间更长，我们试图更深入地了解系统中的氮动态是如何历史变化的。为此，我们测量了早在3000BP到现在的蛤壳中的N稳定同位素(δ15N)值。在一段时间内，他们将美洲原住民助产士的样本与当地从博物馆、考古公司和研究生论文项目中收集的样本进行了比较。总体而言，纳拉甘西特湾蛤壳中的δ15N值随着时间的推移而显著增加，反映了已知的人为营养丰富模式。定居前的中壳δ15N值显著低于欧洲接触后。虽然从15世纪末到2005年的贝壳之间没有统计上的差异，但2005年和2015年的贝壳之间存在显著差异，我们将其归因于与最近的污水处理升级相关的污水中较高的δ15N值。相比之下，罗德岛南部海岸贝壳的δ15N值随着时间的推移保持不变；虽然受到人类活动的影响，但这些地区不直接受到点源污水排放的影响。总体而言，我们的结果表明，这种用于测量蛤壳中δ15N值的同位素技术提供了有用的洞察，了解了几千年来沿海生态系统中N的动态变化，为管理者制定N减少目标时提供了重要的历史信息。
Narragansett Bay, Rhode Island, has been heavily influenced by anthropogenic nutrients for more than 200 years. Recent efforts to improve water quality have cut sewage nitrogen (N) loads to this point source estuary by more than half. Given that the bay has been heavily fertilized for longer than monitoring programs have been in place, we sought additional insight into how N dynamics in the system have historically changed. To do this, we measured the N stable isotope (δ15N) values in clam shells from as early as 3000 BP to the present. Samples from Native American middens were compared with those collected locally from museums, an archaeological company, and graduate student thesis projects, during a range of time periods. Overall, δ15N values in clam shells from Narragansett Bay have increased significantly over time, reflecting known patterns of anthropogenic nutrient enrichment. Pre-colonization midden shell δ15N values were significantly lower than those post-European contact. While there were no statistical differences among shells dated from the late 15th Century to 2005, there was a significant difference between 2005 and 2015 shells, which we attribute to the higher δ15N values in the effluent associated with recent sewage treatment upgrades. In contrast, the δ15N values of shells from the southern Rhode Island coast remained constant through time; while influenced by human activities, these areas are not directly influenced by point-source sewage discharge. Overall, our results show that this isotope technique for measuring δ15N values in clam shells provides useful insight into how N dynamics in coastal ecosystems have changed during thousands of years, providing managers vital historical information when setting goals for N reduction.