Consistency in diatom response to metal-contaminated environments ; Patrons de réponse des diatomées en environnements contaminés par les métaux

[Departement_IRSTEA]Eaux [TR1_IRSTEA]BELCA ; International audience ; Diatoms play a key role in the functioning of streams, and their sensitivity to many environmental factors has led to the development of numerous diatom-based indices used in water quality assessment. Although diatom-based monitoring of metal contamination is not currently included in water quality monitoring programs, the effects of metals on diatom communities have been studied in many polluted watersheds as well as in laboratory experiments, underlying their high potential for metal contamination assessment. Here, we built large database of river diatoms (comprising more than 600 taxa) that were exposed to various loads of heavy metals in the water was investigated. The samples were collected during field surveys carried out in 6 different countries (France, Spain, Switzerland, Canada, Vietnam, China). After taxonomy harmonization, the patterns in diatom community structure were investigated for 202 samples, all collected from hard substrates in rivers with circumneutral water pH. As the sites were contaminated by a mixture of different metals (mainly Al, As, Cd, Cr, Cu, Fe, Hg, Ni, Pb, Zn) with various loads, metal concentrations were converted into a single score after Clements et al. (2000) in order to classify sites according to potential metal toxicity. Metal contamination proved to be a strong driver of the community structure, and enabled for the identification of tolerant species like Eolimna minima, Surirella angusta, Cocconeis placentula var. euglypta or Pinnularia parvulissima. Traits were also tested: diatom cell size and the occurrence of diatom deformities were found to be good indicators of high metal contamination. This work provides a basis for further use of diatoms as indicators of metal pollution Clements WH, Carlisle DM, Lazorchak JM, Johnson PC, 2000. Heavy metals structure benthic communities in Colorado mountain streams.