Background

The European Water Framework Directive (WFD) has been implemented to achieve a good ecological status in European water bodies requiring macrophyte community assessment as one of the biological quality elements (BQEs). While in several lakes in Schleswig-Holstein (Germany) different BQEs improved within recent years, no recovery of macrophyte communities in some lakes could be achieved, despite the reduction of nutrient input and eutrophication. Due to the fact that no impairment of phytoplankton could be observed, toxic stress due to sediment contamination was hypothesized as a possible limiting factor of macrophyte community recovery.

Results

Sediment toxicity was investigated by performing an extensive chemical screening of sediment contamination and a risk assessment based on toxic unit (TU) summation, using equilibrium water concentrations and algal toxicity as surrogates for lacking data on macrophyte toxicity. Possible indirect risks via toxic pressure on grazer were assessed via TUs based on crustaceans. The study revealed algal TUs of more than one order of magnitude below chronic toxicity thresholds in lakes with high and good status of the macrophyte community and increasing concentrations and frequency of exceedance of toxicity thresholds for lakes with moderate-to-bad status. The antifouling biocides irgarol and diuron were identified as major risk drivers. In addition, PAHs and glyphosate could not be ruled out to contribute to toxic pressure on macrophytes. Despite exceedance of toxicity thresholds for crustaceans, no connection of the ecological status of the macrophyte communities with toxic risks to grazers could be observed.

Conclusions

Our study suggests that in a multiple pressure situation the toxic pressure created due to the contamination of sediments with antifouling biocides is one of the limiting factors for the recovery of macrophyte communities in impaired lakes of Schleswig-Holstein. This finding is in agreement with a Europe-wide survey on almost 47,000 sites suggesting that no good ecological status can be observed at sites with contamination exceeding toxicity thresholds. Similar to the survey, our study indicates additional stressors preventing the achievement of a good quality status of the lake ecosystems.

中文翻译：

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防污杀生物剂是石勒苏益格-荷尔斯泰因州湖泊大型植物群落恢复的限制因素之一

背景

实施欧洲水框架指令（WFD）是为了在需要大型植物群落评估作为生物质量要素（BQE）之一的欧洲水体中达到良好的生态状态。尽管近年来在石勒苏益格-荷尔斯泰因州（德国）的几个湖泊中，不同的BQE有所改善，但尽管减少了养分投入和富营养化，但某些湖泊的大型植物群落并未恢复。由于没有观察到浮游植物受损的事实，因此推测由于沉积物污染引起的毒性胁迫是大型植物群落恢复的可能限制因素。

结果

通过对沉积物污染进行广泛的化学筛选和基于毒性单位（TU）总和的风险评估，使用了平衡水浓度和藻类毒性作为缺乏大植物毒性数据的替代物，对沉积物毒性进行了研究。通过基于甲壳类动物的TU评估了由于放牧者的毒性压力而可能产生的间接风险。该研究表明，在具有高水平和良好状态的大型植物群落的湖泊中，藻类TUs低于慢性毒性阈值一个数量级以上，而对于中度至不良状态的湖泊，其毒性阈值的浓度和频率不断增加。防污杀虫剂irgarol和diuron被确定为主要的风险驱动因素。此外，不能排除多环芳烃和草甘膦对大型植物产生毒性压力。

结论

我们的研究表明，在多重压力情况下，由于防污杀菌剂对沉积物的污染而产生的毒性压力是石勒苏益格-荷尔斯泰因州受损湖泊中大型植物群落恢复的限制因素之一。这一发现与欧洲范围内对近47,000个站点的调查一致，表明在污染超过毒性阈值的站点无法观察到良好的生态状况。与调查相似，我们的研究表明，其他压力因素阻碍了湖泊生态系统的良好质量状况的实现。