Department of Aquatic Sciences and Assessment, Swedish University of Agricultural Sciences, Uppsala, Sweden.
Environment and Climate Change Canada, National Hydrology Research Centre, Saskatoon, SK, Canada.
Environ Pollut. 2023 Nov 15;337:122598. doi: 10.1016/j.envpol.2023.122598. Epub 2023 Sep 21.
Rivers are often exposed to multiple stressors, such as nutrients and contaminants, whose impacts on the river food webs may not be distinguished by sole assessment of biological community structures. We examined the benthic algal assemblages and the fatty acids (FA) of benthic macroinvertebrates in the lower Athabasca River in Canada, aiming to assess the changes in algal support and nutritional quality of the benthic food web in response to cumulative exposure to natural bitumen, municipal sewage discharge (hereafter, "sewage"), and oil sands mining ("mining"). Data show that the decline in water quality (increases in nutrient concentrations and total suspended solids) was associated with decreases in benthic diatom abundance, and was driven mainly by sewage-induced nutrient enrichment. Responses in nutritional quality of benthic macroinvertebrates, indicated by their polyunsaturated FA (PUFA) concentrations, were taxon- and stressor-specific. Nutritional quality of the larval dragonfly predator, Ophiogomphus, decreased nonlinearly with decreasing benthic diatom abundance and was lowest at the sewage-affected sites, although exposure to natural bitumen also resulted in reduced Ophiogomphus PUFA concentrations. In contrast, the PUFA concentrations of mayfly grazers/collector-gatherers were not affected by natural bitumen exposure, and were higher at the sewage and sewage+mining sites. The PUFA concentrations of the shredder Pteronarcys larvae did not change with cumulative exposure to the stressors. Sediment metal and polycyclic aromatic compound concentrations were not associated with the macroinvertebrate FA changes. Overall, we provide evidence that sewage induced reduction in trophic support by PUFA-rich diatoms, and was the predominant driver of the observed changes in FA composition and nutritional quality of the benthic macroinvertebrates. Fatty-acid metrics are useful to untangle effects of concurrent stressors, but the assessment outcomes depend on the functional feeding guilds used. A food-web perspective using multiple trophic levels and feeding guilds supports a more holistic assessment of the stressor impacts.
河流经常受到多种胁迫因素的影响，如营养物质和污染物，这些因素对河流食物网的影响可能无法仅通过对生物群落结构的单一评估来区分。我们检查了加拿大亚巴斯卡河下游的底栖藻类组合和底栖大型无脊椎动物的脂肪酸 (FA)，旨在评估藻类支持和底栖食物网营养质量的变化，以响应对天然沥青、城市污水排放（以下简称“污水”）和油砂开采（“开采”）的累积暴露。数据表明，水质下降（营养物浓度和总悬浮固体增加）与底栖硅藻丰度下降有关，主要是由污水引起的营养物富化所致。底栖大型无脊椎动物营养质量的变化，由其多不饱和 FA（PUFA）浓度表示，是分类群和胁迫因素特异性的。幼虫蜻蜓捕食者 Ophiogomphus 的营养质量呈非线性下降，与底栖硅藻丰度下降呈负相关，在受污水影响的地点最低，尽管暴露于天然沥青也导致 Ophiogomphus PUFA 浓度降低。相比之下，蜉蝣食草动物/集食者的食草动物/集食者的 FA 浓度不受天然沥青暴露的影响，并且在污水和污水+开采地点更高。碎屑 Pteronarcys 幼虫的 PUFA 浓度随胁迫因素的累积暴露而没有变化。沉积物金属和多环芳烃化合物浓度与大型无脊椎动物 FA 变化无关。总体而言，我们提供的证据表明，污水诱导了富多不饱和脂肪酸的硅藻对营养的支持减少，这是观察到的 FA 组成和底栖大型无脊椎动物营养质量变化的主要驱动因素。脂肪酸指标可用于理清并发胁迫因素的影响，但评估结果取决于所使用的功能摄食群。使用多个营养级和摄食群的食物网视角支持对胁迫影响进行更全面的评估。
