Irstea, UR MALY, 5 rue de la Doua, BP 32108, F-69616, Villeurbanne Cedex, France.
Irstea, UR MALY, 5 rue de la Doua, BP 32108, F-69616, Villeurbanne Cedex, France.
Water Res. 2017 Jul 1;118:131-140. doi: 10.1016/j.watres.2017.04.031. Epub 2017 Apr 18.
Bioaccumulated concentrations of toxic elements in biomonitor invertebrate species have already been used to successfully link metal bioavailability and impairments of stream macroinvertebrate communities at the scale of the watershed. However, implementing this empirical comparative approach at a greater spatial scale remains a challenge due to the diversity of biogeographical contexts encompassed by regional and national scales. We showed in previous studies that the use of standard organisms caged permits the use of a common biomonitor over a far greater geographical range, while limiting the influence of confounding factors on levels of bioavailable contamination. In this study, levels of Cd, Hg, Ni and Pb contamination assessed by active biomonitoring with caged Gammarus fossarum were compared to abundances of on-site gammarids on 94 sites in France. Based on this national dataset of in situ bioassays, we first re-determined bioavailable background assessment concentrations (BBACs), i.e. concentrations measured in caged G. fossarum indicating a significant bioavailable contamination, which we had previously defined at a regional scale for these four metallic elements. On-site gammarid abundances were retrieved from monitoring programs implemented by French water agencies for the evaluation of ecological status for the European Water Framework Directive. These abundances were corrected for the influence of stream physico-chemical typology in order to permit a reliable comparison of gammarid densities between sites at the national scale. Clear trends of degradation of gammarid densities with increasing levels of bioaccumulated concentrations were identified for three of the four elements (Cd, Ni and Pb). Threshold concentrations in caged organisms above which the numbers of free-ranging gammarids were abnormally low - namely bioavailable ecological assessment concentrations (BEACs) - were determined. The reliability and validity of the BEACs, their comparison with BBACs and their usefulness in terms of prioritisation of contaminants, sites in freshwater management, are discussed.
生物监测无脊椎动物体内有毒元素的生物累积浓度已被成功用于将金属生物有效性与流域尺度上溪流大型无脊椎动物群落的损害联系起来。然而，由于区域和国家尺度所涵盖的生物地理背景多样性，在更大的空间尺度上实施这种经验比较方法仍然是一个挑战。在之前的研究中，我们表明，使用标准笼养生物可以在更大的地理范围内使用通用的生物监测器，同时限制混杂因素对生物可利用污染水平的影响。在这项研究中，通过笼养食蚊鱼进行主动生物监测评估的 Cd、Hg、Ni 和 Pb 污染水平与法国 94 个地点现场食蚊鱼的丰度进行了比较。基于这个国家现场生物测定数据集，我们首先重新确定了生物可用背景评估浓度（BBACs），即食蚊鱼体内测量到的表明存在显著生物可用污染的浓度，这些浓度我们之前曾在区域尺度上为这四种金属元素定义过。现场食蚊鱼的丰度是从法国水机构为评估欧洲水框架指令的生态状况而实施的监测计划中获取的。为了能够在国家尺度上可靠比较不同地点的食蚊鱼密度，对这些丰度进行了溪流理化类型影响的校正。对于其中三种元素（Cd、Ni 和 Pb），随着生物累积浓度的增加，食蚊鱼密度下降的趋势非常明显。在笼养生物中确定了高于这些元素的生物可用生态评估浓度（BEACs）的浓度阈值，在这些浓度阈值之上，自由游动的食蚊鱼数量异常低。讨论了 BEACs 的可靠性和有效性、它们与 BBACs 的比较及其在优先考虑污染物、淡水管理中的地点方面的有用性。
