Managing nonpoint sources of nutrients and sediments is the primary challenge for improving conditions in the Susquehanna-Chesapeake basin. Aquatic macroinvertebrates are widely used indicators of stream ecological integrity, but the relationship between nutrient runoff and macroinvertebrate response remains indistinct. Logistical and financial hurdles hinder collection of high-resolution empirical nutrient data, but landscape-based models like the Soil and Water Assessment Tool (SWAT) offer a more practical approach. Nutrient runoff was simulated with SWAT for a small, upland, agricultural Pennsylvania watershed. Three levels of ecological assessment were used to interpret SWAT results. Macroinvertebrate communities (intensive) were sampled at 14 sites and described using an Index of Biotic Integrity (IBI). Biological integrity was moderately degraded in many reaches. The Stream-Wetland-Riparian (SWR) Index (rapid) and landscape metrics (remote) also indicated prevalent agricultural stressors. Baseflow nitrate grab samples, collected once per season, showed no significant relationship with IBI score. Thirty spatiotemporal scales of nutrient data were extracted from SWAT for phosphorus, nitrate, and organic nitrogen. Best subsets regression was performed on IBI scores using SWAT, land cover, and SWR variables. Results were significant (p < .001) with high R2 values (84.8 and 86.2), signifying a negative relationship between instream nutrient concentration and IBI score. This study demonstrates the viability of SWAT as an alternative to in-field nutrient sampling, the value of spatiotemporal scale in model outputs, and the importance of site condition variables in relating nutrients to stream ecological health.

中文翻译：

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源水流条件和养分径流：将特警与宾夕法尼亚州农业流域的经验生态措施联系起来

管理营养物和沉积物的非点源是改善萨斯奎汉纳-切萨皮克盆地条件的主要挑战。水生大型无脊椎动物是河流生态完整性的广泛使用指标，但养分径流与大型无脊椎动物反应之间的关系仍不清楚。后勤和财务障碍阻碍了高分辨率经验养分数据的收集，但土壤和水评估工具 (SWAT) 等基于景观的模型提供了更实用的方法。使用 SWAT 模拟宾夕法尼亚州一个小型高地农业流域的养分径流。三个级别的生态评估用于解释特警结果。大型无脊椎动物群落（密集型）在 14 个地点取样，并使用生物完整性指数 (IBI) 进行描述。许多河段的生物完整性中度下降。河流-湿地-河岸 (SWR) 指数（快速）和景观指标（远程）也表明普遍存在农业压力因素。每个季节收集一次的基流硝酸盐抓取样本与 IBI 得分没有显着关系。从 SWAT 中提取了 30 个时空尺度的磷、硝酸盐和有机氮营养数据。使用 SWAT、土地覆盖和 SWR 变量对 IBI 分数进行最佳子集回归。结果显着 (p < .001)，具有高 R2 值（84.8 和 86.2），表明河内养分浓度与 IBI 分数之间呈负相关。这项研究证明了 SWAT 作为田间养分采样的替代方案的可行性，模型输出中时空尺度的价值，