Lake James L, Serbst Jonathan R, Kuhn Anne, Charpentier Michael, Smucker Nathan J
US Environmental Protection Agency, Office of Research and Development, 27 Tarzwell Drive, Narragansett, RI 02882, USA.
General Dynamics Information Technology, 27 Tarzwell Drive, Narragansett, RI 02882, USA.
Water (Basel). 2022 Nov 16;14(22):1-12. doi: 10.3390/w14223712.
Excessive inputs of nitrogen from anthropogenic activities in watersheds can cause detrimental effects to aquatic ecosystems, but these effects can be difficult to determine based solely on nitrogen concentrations because of their temporal variability and the need to link human activities to ecological responses. Here, we (1) tested the use of stable isotopes of nitrogen (δN) and carbon (δC) in benthic organic matter (BOM) as proxies for isotope ratios of filter feeding bivalves in lakes and estuaries, which can be used as indicators but are harder to sample and often spatially sparse, and (2) evaluated if stable isotope ratios in benthic organic matter could be used to assess impacts from anthropogenic land development of watersheds. The δN in BOM isolated from surficial sediment (δN) was significantly correlated with δN in filter feeding unionid mussels ( δN) from lakes and with hard-shell clams ( δN) from estuaries. In lakes, δC was significantly correlated with δC, but δC was not significantly correlated with δC in estuaries. Values of δN and δN were significantly and positively correlated with increasing amounts of impervious surface, urban land cover, and human populations in watersheds surrounding lakes. In estuaries, δN was only significantly and positively correlated with greater percent impervious surface in the watersheds. Correlations of δC in lakes and estuaries, δC, and δC with land use and human population were mostly non-significant or weak. Overall, these results show that δN can serve as a proxy for δN of filter feeding bivalves in lakes and estuaries and is useful for assessing anthropogenic impacts on aquatic systems and resources. Our study area was limited in size, but our results support further studies to test the application of this sediment stable isotope-based technique for assessing and ranking aquatic resources across broad geographical areas.
流域内人为活动产生的过量氮输入会对水生生态系统造成有害影响，但由于其时间变异性以及将人类活动与生态响应联系起来的必要性，仅基于氮浓度很难确定这些影响。在此，我们（1）测试了将底栖有机物（BOM）中氮（δN）和碳（δC）的稳定同位素用作湖泊和河口滤食性双壳类动物同位素比值的替代指标，滤食性双壳类动物虽可作为指标，但采样难度较大且空间分布往往稀疏；（2）评估了底栖有机物中的稳定同位素比值是否可用于评估流域人为土地开发的影响。从表层沉积物中分离出的BOM中的δN与湖泊中滤食性珠蚌的δN以及河口硬壳蛤的δN显著相关。在湖泊中，δC与δC显著相关，但在河口，δC与δC不显著相关。湖泊周边流域中，δN和δN的值与不透水表面、城市土地覆盖和人口数量的增加显著正相关。在河口，δN仅与流域中更大比例的不透水表面显著正相关。湖泊和河口的δC、δC以及δC与土地利用和人口的相关性大多不显著或较弱。总体而言，这些结果表明，δN可作为湖泊和河口滤食性双壳类动物δN的替代指标，有助于评估人为活动对水生系统和资源的影响。我们的研究区域面积有限，但我们的结果支持进一步研究，以测试这种基于沉积物稳定同位素的技术在广泛地理区域评估和排名水生资源方面的应用。
