UMR CNRS 5805 EPOC, Université Bordeaux 1, Place du Docteur Peyneau, 33120 Arcachon, France.
Ecotoxicology. 2012 Jul;21(5):1403-14. doi: 10.1007/s10646-012-0894-3. Epub 2012 Apr 4.
Metal wastes can significantly disturb aquatic communities, particularly photosynthetic organisms, the main primary producers in freshwater running ecosystems. In this study, biofilms and diatoms were used as bioindicators to characterize the kinetics of biofilm recovery. An experimental decontamination study was conducted under laboratory conditions, after biofilm colonisation at a site subject to discharge of industrial metals (Zn and Cd) and in parallel at an upstream site, metal-free, considered as a control. After 24 days of colonisation, biofilms were translocated and maintained in the laboratory for 56 days under clean conditions (control and decontamination) or metal contamination. Various tests were conducted from the community level--measures of metal bioaccumulation, cell densities and taxonomic investigations, to the individual level--measures of teratological forms. After 56 days of decontamination, Zn and Cd concentrations in decontaminated biofilms showed a sharp decline, respectively ranging from 6.7 ± 2 to 4 ± 2.5 mg Zn g⁻¹ DW and from 207.6 ± 24.5 to 45.4 ± 9.9 μg Cd g⁻¹ DW. However, at the end of the experiment bioaccumulations remained significantly higher than concentrations in control biofilms. Despite a diatom evolution in biofilm assemblages, taxonomic inventories did not demonstrate a complete restoration of diatom communities in biofilms under decontamination conditions compared with controls, since metal-resistant species initially present after colonisation at the contaminated site, such as Eolimna minima, persisted in high abundance in decontaminated biofilms. Biofilms kept under metal pressure showed very high bioaccumulation capacities and a sharp decline of species diversity which allowed identification of some resistant species. Regarding these first results on the behaviour of diatom biofilms under experimental decontamination conditions, improvement of the natural hydrosystem's chemical state appears quickly, but an eventual return to good ecological status appears delayed, with the persistence of metal-tolerant species even after 56 days.
金属废物会对水生群落造成严重干扰，尤其是对淡水流水生态系统中的主要初级生产者——光合作用生物。在本研究中，生物膜和硅藻被用作生物标志物来描述生物膜恢复的动力学。在实验室条件下进行了一项实验性去污研究，在一个受到工业金属（锌和镉）排放影响的地点进行生物膜定植，并在一个上游无金属的地点进行平行定植，作为对照。在 24 天的定植后，生物膜被转移并在实验室中保持 56 天，在清洁条件（对照和去污）或金属污染下。从群落水平——金属生物积累、细胞密度和分类学调查，到个体水平——畸形形式的测量，进行了各种测试。去污 56 天后，去污生物膜中的 Zn 和 Cd 浓度急剧下降，分别从 6.7±2 到 4±2.5 mg Zn g⁻¹ DW 和 207.6±24.5 到 45.4±9.9 μg Cd g⁻¹ DW。然而，在实验结束时，生物积累仍然明显高于对照生物膜中的浓度。尽管生物膜群落中的硅藻发生了演变，但分类学清查并没有表明在去污条件下生物膜中的硅藻群落能够完全恢复到对照水平，因为在受污染地点定植后最初存在的金属抗性物种，如 Eolimna minima，在去污生物膜中仍以高丰度存在。在金属压力下保持的生物膜表现出非常高的生物积累能力和物种多样性的急剧下降，这使得一些抗性物种得以识别。关于这些在实验性去污条件下硅藻生物膜行为的初步结果，水生态系统化学状态的改善很快，但生态状况的最终恢复似乎被延迟，即使在 56 天后，仍有金属耐受物种存在。
