Marshalonis Daniel, Larson Chad
United States Environmental Protection Agency, Region 10, 1200 6th Ave, Seattle, WA 98101, USA.
Washington State Department of Ecology, Environmental Assessment Program, 300 Desmond Drive SE, Lacey, WA 98503, USA.
Ecol Indic. 2018 Oct;93:365-378. doi: 10.1016/j.ecolind.2018.04.060.
Determining the causes of biological impairment in urban stream settings presents unique challenges because there are many potential stressors associated with human development. A rigorous, scientifically based process is more likely to identify influential stressors that can be reduced to improve stream condition. We used the U.S. Environmental Protection Agency's (U.S. EPA) CADDIS (Causal Analysis/Decision Information System) stressor identification process to assess eight candidate causes in the urban Soos Creek Basin in Washington State. The eight candidate causes capable of negatively affecting the abundance and diversity of benthic macroinvertebrates are: flow alteration, increased fine sediments, reduced habitat complexity, elevated water temperature, low dissolved oxygen, elevated nutrients, increased ionic concentration, and toxic pollutants. We assembled multiple lines of evidence, as well as the consistency of that evidence and agreement with other assessments. We evaluated the influence of natural and cumulative anthropogenic stressors on macroinvertebrate communities by comparing various chemical, physical, and biological measures at sites in the Soos Creek Basin with regional reference sites. Of the stressors evaluated, flow alteration, increased fine sediments, and loss of habitat complexity were the most probable causes of biological impairment, with multiple biological metrics responding predictably across levels of impairment. Key findings from this study include: the use of specific community alterations as evidence in causal assessment, demonstration of links in a complete causal pathway, and the use of multiple models to show which pathway is likely stronger. In addition to the value to the specific case, the analyses increased our understanding of the responses of stream invertebrate communities in urban environments. Ultimately, demonstrating the utility of causal assessment in a practical situation provides greater confidence that mitigation efforts aimed at improving biological health of urban stream communities will have detectable desired effects while also providing a baseline from which the effectiveness of management practices can be evaluated.
确定城市溪流环境中生物受损的原因面临着独特的挑战，因为与人类发展相关的潜在压力源众多。一个严谨、基于科学的过程更有可能识别出那些可以减少以改善溪流状况的有影响力的压力源。我们使用了美国环境保护局（U.S. EPA）的CADDIS（因果分析/决策信息系统）压力源识别过程，来评估华盛顿州城市苏斯溪流域的八个候选原因。这八个能够对底栖大型无脊椎动物的丰度和多样性产生负面影响的候选原因是：水流改变、细颗粒沉积物增加、栖息地复杂性降低、水温升高、溶解氧降低、营养物质升高、离子浓度增加和有毒污染物。我们收集了多条证据线索，以及这些证据的一致性和与其他评估的一致性。我们通过比较苏斯溪流域各地点与区域参考地点的各种化学、物理和生物指标，评估了自然和累积人为压力源对大型无脊椎动物群落的影响。在所评估的压力源中，水流改变、细颗粒沉积物增加和栖息地复杂性丧失是生物受损最可能的原因，多个生物指标在不同受损水平上呈现出可预测的反应。这项研究的主要发现包括：在因果评估中使用特定的群落变化作为证据、在完整的因果途径中证明联系，以及使用多个模型来表明哪条途径可能更强。除了对具体案例的价值外，这些分析还增进了我们对城市环境中溪流无脊椎动物群落反应的理解。最终，在实际情况中证明因果评估的效用，能让人们更有信心地认为，旨在改善城市溪流群落生物健康的缓解措施将产生可检测到的预期效果，同时还提供了一个可据此评估管理措施有效性的基线。
