Due to their ubiquitous occurrence and taxonomic diversity, diatoms have become widely used for monitoring the environmental conditions in freshwater. Metal contaminations affect water quality and may lead to shifts in diatom community structure as well as individuals’ morphology. In the present study the characteristics of periphytic biofilms were analysed in situ (Riou-Mort watershed, South West France), and under experimental conditions. The metals (cadmium and zinc) caused a replacement of sensitive diatom species (Cyclotella meneghiniana, Navicula gregaria, Navicula veneta) by more tolerant ones (Eolimna minima especially), but also induced a reduction in size of some individuals, and / or an apparition of valve abnormailites. Not only metals but also other factors such as nutrient concentrations, affected diatom responses by favouring biomass production and modifying diatom community structure towards a dominance of saprophilous species. It was also demonstrated that the organic matrix acts like a barrier against deleterious effects of metals on diatom assemblages. Benthic communities proved to be great potential indicators of metal pollutions, and this work provides a basis for constructing a diatom-based index of presumptive metal contamination.
More information available at http://archives.disvu.u-bordeaux1.fr/pdf/2006/MORIN_SOIZIC_2006.pdf