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

[Departement_IRSTEA]Eaux [TR1_IRSTEA]BELCA ; International audience ; Diatoms play a key role in the functioning of streams, and their sensitivty 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 qual ty monitoring programs, the effects of metals on diatom commun ties have been studied in many polluted watersheds as well as in laboratory experiments, underlying their high potential for metal contamination assessment. Here, we review the response of diatoms to metal pollution from individual level (e.g. size, growth form, and morphological abnormalities) to community structure (replacement of sensitive species by tolerant ones). These potential effects are then tested using a large multi-country database combining diatom and metal information. Metal contamination proved to be a strong driver of the community structure, and enabled for the identification of tolerant species like Cocconeis placentula var. euglypta, Eolimna minima , Fragilaria gracilis, Nitzschia sociabilis, Pinnularia parvulissima, and Surirella angusta. Among the traits 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.