Estuaries often experience multiple water quality impairments including nitrogen enrichment and elevated fecal pollution. These pollutant sources are often linked and difficult to characterize, especially in multiple use watersheds, hindering the identification of effective mitigation steps. Tillamook Bay (Oregon, USA) has a mixed-use watershed including many potential nutrient and fecal bacteria sources due to agricultural activities, human development, and local wildlife populations. In this study, microbial source tracking, watershed modeling, and stable isotope analysis were combined to understand sources of watershed nitrogen and fecal bacteria to receiving waters. Tributaries of Tillamook Bay were sampled approximately monthly from June 2016 to May 2017 at 16 sites. Paired measurements of host-associated qPCR-based genetic markers targeting human (HF183/BacR287 and HumM2), ruminant (Rum2Bac), cattle (CowM2 and CowM3), canine (DG3), and avian (GFD) fecal pollution sources and nitrate stable isotope (δ¹⁵N-NO₃) were compared to each other and to watershed modeled contributions. Ruminant and cattle-associated genetic markers were detected at a high frequency across sites, with the Rum2Bac marker detected in 94% of samples collected across sites and concentrations significantly correlated with E. coli levels. Cattle and ruminant genetic marker concentrations increased downstream in four out of five tributaries, mirroring δ¹⁵N-NO₃ spatial trends during the wet season, suggesting a similar source and delivery for these co-pollutants. Although agricultural inputs are the dominant source of both fecal contamination and nitrogen to this system, human-associated genetic markers and elevated nutrient levels (NH₄⁺ and PO₄^-3) were observed at two sites in proximity to a wastewater treatment facility on the Trask River. Elevated δ¹⁵N-NO₃ and HF183/BacR287 levels in the same samples further corroborate a wastewater impact at these Trask River sites. Results support the utility of using a combined pollutant tracking approach when evaluating nutrient and fecal pollution in agriculturally intensive watersheds.

中文翻译：

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农业流域中营养物和微生物来源耦合追踪的综合方法


河口经常会出现多种水质损害，包括氮富集和粪便污染加剧。这些污染源通常是相互关联的且难以表征的，尤其是在多用途流域中，阻碍了确定有效的缓解措施。蒂拉穆克湾（美国俄勒冈州）有一个混合用途流域，由于农业活动、人类发展和当地野生动物种群，包括许多潜在的营养和粪便细菌来源。在这项研究中，将微生物来源追踪、流域建模和稳定同位素分析相结合，以了解流域氮和粪便细菌到接收水域的来源。从 2016 年 6 月到 2017 年 5 月，大约每月在 16 个地点对蒂拉穆克湾的支流进行采样。针对人 （HF183/BacR287 和 HumM2）、反刍动物 （Rum2Bac）、牛 （CowM2 和 CowM3）、犬 （DG3） 和禽 （GFD） 粪便污染源和硝酸盐稳定同位素 （δ¹⁵N-NO₃） 的基于宿主相关 qPCR 的遗传标记的配对测量彼此比较，并与流域建模的贡献进行比较。反刍动物和牛相关遗传标记物在各个地点的检测频率很高，在跨站点收集的样本中检测到 Rum2Bac 标记物的 94%，浓度与大肠杆菌水平显著相关。牛和反刍动物遗传标记浓度在 5 条支流中 4 条支流的下游增加，反映了雨季δ¹⁵N-NO₃ 空间趋势，表明这些共污染物的来源和传递相似。 尽管农业投入是该系统粪便污染和氮的主要来源，但在特拉斯克河废水处理设施附近的两个地点观察到人类相关的遗传标记和升高的营养水平（NH₄⁺ 和 PO ^4-3）。相同样品中^{δ 15}N-NO₃ 和 HF183/BacR287 水平升高进一步证实了这些 Trask River 站点的废水影响。结果支持在评估农业密集型流域的营养物和粪便污染时使用联合污染物跟踪方法的实用性。