Roberts Andrew D, Besser John, Hundley Josh, Mosby David E, Rosenberger Amanda, Bouska Kristen L, Simmons Bryan R, McMurray Stephen E, Faiman Scott, Lueckenhoff Leslie
U.S. Fish and Wildlife Service, Ecological Services, 101 Park Deville Drive, Suite A, Columbia, MO, USA.
Columbia Environmental Research Center, U.S. Geological Survey, 4200 E New Haven Rd, Columbia, MO 65201, USA.
Sci Total Environ. 2023 Jun 10;876:162743. doi: 10.1016/j.scitotenv.2023.162743. Epub 2023 Mar 11.
The Big River in southeast Missouri drains the largest historical lead mining area in the United States. Ongoing releases of metal contaminated sediments into this river are well documented and are suspected of suppressing freshwater mussel populations. We characterized the spatial extent of metal contaminated sediments and evaluated its relationship with mussel populations in the Big River. Mussels and sediments were collected at 34 sites with potential metal effects and 3 reference sites. Analysis of sediment samples showed that lead (Pb) and zinc (Zn) concentrations were 1.5 to 65 times greater than background concentrations in the reach extending 168 km downstream from Pb mining releases. Mussel abundance decreased acutely downstream from these releases where sediment Pb concentrations were highest and increased gradually as Pb sediment concentrations attenuated downstream. We compared current species richness with historical survey data from three reference rivers with similar physical habitat characteristics and human effects, but without Pb-contaminated sediment. Big River species richness was on average about one-half that expected based on reference stream populations and was 70-75 % lower in reaches with high median Pb concentrations. Sediment Zn and cadmium, and particularly Pb, had significant negative correlations with species richness and abundance. The association of sediment Pb concentrations with mussel community metrics in otherwise high-quality habitat indicates that Pb toxicity is likely responsible for depressed mussel populations observed within the Big River. We used concentration-response regressions of mussel density verses sediment Pb to determine that the Big River mussel community is adversely affected when sediment Pb concentrations are above 166 ppm, the concentration associated with 50 % decreases in mussel density. Based on this assessment of metals concentrations sediment and mussel fauna, our findings indicate that sediment in approximately 140 km of the Big River with suitable habitat has a toxic effect to mussels.
密苏里州东南部的大河排水区域是美国历史上最大的铅矿区。有充分记录表明，金属污染沉积物持续排入这条河流，并且怀疑这抑制了淡水贻贝的数量。我们对金属污染沉积物的空间范围进行了特征描述，并评估了其与大河中贻贝数量的关系。在34个可能受金属影响的地点和3个参考地点采集了贻贝和沉积物样本。沉积物样本分析表明，在从铅矿开采排放点向下游延伸168公里的河段中，铅（Pb）和锌（Zn）的浓度比背景浓度高1.5至65倍。在这些排放点下游，贻贝数量急剧减少，那里沉积物中的铅浓度最高，随着下游铅沉积物浓度的降低，贻贝数量逐渐增加。我们将当前的物种丰富度与来自三条具有相似物理栖息地特征和人类影响但没有铅污染沉积物的参考河流的历史调查数据进行了比较。大河的物种丰富度平均约为基于参考河流种群预期值的一半，在铅浓度中位数较高的河段中低70 - 75%。沉积物中的锌和镉，特别是铅，与物种丰富度和数量呈显著负相关。在其他方面高质量栖息地中，沉积物铅浓度与贻贝群落指标之间的关联表明，铅毒性可能是导致大河中观察到的贻贝数量减少的原因。我们使用贻贝密度与沉积物铅的浓度 - 反应回归来确定，当沉积物铅浓度高于166 ppm时，大河贻贝群落会受到不利影响，该浓度与贻贝密度降低50%相关。基于对金属浓度沉积物和贻贝动物群的评估，我们的研究结果表明，大河中约140公里具有适宜栖息地的沉积物对贻贝具有毒性作用。
