U.S. Geological Survey, Oregon Water Science Center, 2130 SW 5th Ave, Portland, OR 97201, USA.
U.S. Geological Survey, Washington Water Science Center, 934 Broadway, Suite 300, Tacoma, WA 98402, USA.
Sci Total Environ. 2019 Apr 10;660:1472-1485. doi: 10.1016/j.scitotenv.2018.12.240. Epub 2018 Dec 28.
During 2014, the U.S. Geological Survey (USGS) National Water-Quality Assessment (NAWQA) project assessed stream quality in 75 streams across an urban disturbance gradient within the Piedmont ecoregion of southeastern United States. Our objectives were to identify primary instream stressors affecting algal, macroinvertebrate and fish assemblages in wadeable streams. Biotic communities were surveyed once at each site, and various instream stressors were measured during a 4-week index period preceding the ecological sampling. The measured stressors included nutrients; contaminants in water, passive samplers, and sediment; instream habitat; and flow variability. All nine boosted regression tree models - three for each of algae, invertebrates, and fish - had cross-validation R (CV R) values of 0.41 or above, and an invertebrate model had the highest CV R of 0.65. At least one contaminant metric was important in every model, and minimum daytime dissolved oxygen (DO), nutrients, and flow alteration were important explanatory variables in many of the models. Physical habitat metrics such as sediment substrate were only moderately important. Flow alteration metrics were useful factors in eight of the nine models. Total phosphorus, acetanilide herbicides and flow (time since last peak) were important in all three algal models, whereas insecticide metrics (especially those representing fipronil and imidacloprid) were dominant in the invertebrate models. DO values below approximately 7 mg/L corresponded to a strong decrease in sensitive taxa or an increase in tolerant taxa. DO also showed strong interactions with other variables, particularly contaminants and sediment, where the combined effect of low DO and elevated contaminants increased the impact on the biota more than each variable individually. Contaminants and flow alteration were strongly correlated to urbanization, indicating the importance of urbanization to ecological stream condition in the region.
2014 年，美国地质调查局（USGS）国家水质评估（NAWQA）项目评估了美国东南部皮埃蒙特生态区的 75 条溪流，这些溪流位于城市干扰梯度范围内。我们的目标是确定影响可涉水溪流中藻类、大型无脊椎动物和鱼类群落的主要溪流胁迫因素。在每个地点进行了一次生物群落调查，并在生态采样前的 4 周索引期内测量了各种溪流胁迫因素。测量的胁迫因素包括营养物；水、被动采样器和沉积物中的污染物；溪流栖息地；以及流量变化。所有九个提升回归树模型-藻类、无脊椎动物和鱼类各三个-的交叉验证 R（CV R）值均为 0.41 或更高，并且无脊椎动物模型的 CV R 值最高，为 0.65。至少有一个污染物指标在每个模型中都很重要，最低日白天溶解氧（DO）、营养物和流量变化是许多模型中的重要解释变量。物理栖息地指标如沉积物基质仅具有中等重要性。流量变化指标在九个模型中的八个中是有用的因素。总磷、乙酰苯胺类除草剂和流量（上次峰值后的时间）在所有三个藻类模型中都很重要，而杀虫剂指标（尤其是那些代表氟虫腈和噻虫啉的指标）在无脊椎动物模型中占主导地位。DO 值低于约 7mg/L 对应于敏感类群的强烈减少或耐受类群的增加。DO 还与其他变量（尤其是污染物和沉积物）之间存在强烈的相互作用，其中低 DO 和升高的污染物的综合效应对生物群的影响大于每个变量单独的影响。污染物和流量变化与城市化强烈相关，表明城市化对该地区生态溪流状况的重要性。
