Green Lauri, Magel Caitlin, Brown Cheryl
Current Address: Bloomsburg University, 400 East Second Street, Bloomsburg, PA, 17815.
U.S. Environmental Protection Agency 2111 SE Marine Science Center Drive, Newport, OR, 97366.
Reg Stud Mar Sci. 2021 Jun;45:1-15. doi: 10.1016/j.rsma.2021.101851.
Eutrophication remains a threat to coastal habitats and water quality worldwide. The U.S. Clean Water Act resulted in reductions of nutrient loading from point sources but management of nonpoint sources (NPS) of nutrients remains challenging despite efforts over at least three decades. The hydrological factors, best management practices (BMPs) and regulatory mechanisms that target nutrient NPS and improve coastal ecosystem function are poorly understood. We identified three case study sites in the U.S. with sufficient NPS management and monitoring history to quantify changes in estuarine habitat and water quality following BMP implementation and regulation targeting nutrient NPS. Utilizing publicly available data, we compared sites that are geographically distant and hydrologically distinct. We found that BMPs targeting NPS loads from surface waters into Roberts Bay (Florida) and Newport Bay (California) significantly reduced nutrient concentrations and harmful algal blooms within ~20 years. Improvements occurred despite concurrent human population growth within both watersheds. Conversely, we found that the majority of BMPs implemented within the Peconic Estuary (New York) watershed targeted surface waters despite a dominance of nitrogen inputs (97%) from groundwater and atmospheric sources. Declines in habitat and water quality in Peconic Estuary may be due to a failure to control the dominant nutrient sources and the long residence time of nitrogen in groundwater. Compared to surface water, reducing groundwater and atmospheric nutrients face greater technical and financial challenges. Improvements to Peconic Estuary may occur with further reductions in surface water inputs and as nutrients leach out of the groundwater. Although the effectiveness of specific NPS BMPs has been examined at small spatial scales, our study is the first to quantify improvements at a watershed scale. We showed that successful NPS management pathways are those which targeted the dominant sources of nutrients to coastal ecosystems and applied multiple BMPs within watersheds.
富营养化仍然是全球沿海栖息地和水质面临的一大威胁。美国的《清洁水法》使得点源营养物负荷有所减少，但尽管经过了至少三十年的努力，非点源营养物的管理仍然颇具挑战。对于针对非点源营养物并改善沿海生态系统功能的水文因素、最佳管理措施（BMPs）及监管机制，人们了解甚少。我们在美国确定了三个案例研究地点，这些地点有足够的非点源管理和监测历史，以便量化在实施针对非点源营养物的最佳管理措施及监管之后河口栖息地和水质的变化。利用公开可得的数据，我们比较了地理位置遥远且水文特征不同的地点。我们发现，针对从地表水排入罗伯茨湾（佛罗里达州）和纽波特湾（加利福尼亚州）的非点源负荷实施的最佳管理措施在约20年内显著降低了营养物浓度和有害藻华。尽管两个流域内的人口同时在增长，但仍实现了改善。相反，我们发现，佩科尼克河口（纽约州）流域内实施的大多数最佳管理措施都以地表水为目标，尽管氮输入的97%来自地下水和大气源。佩科尼克河口栖息地和水质的下降可能是由于未能控制主要营养源以及氮在地下水中的停留时间较长。与地表水相比，减少地下水和大气中的营养物面临更大的技术和资金挑战。随着地表水输入的进一步减少以及营养物从地下水中渗出，佩科尼克河口可能会出现改善。尽管已在小空间尺度上研究了特定非点源最佳管理措施的有效性，但我们的研究是首次在流域尺度上量化改善情况。我们表明，成功的非点源管理途径是那些针对沿海生态系统主要营养源并在流域内应用多种最佳管理措施的途径。
