Benthic diatom monitoring and assessment of freshwater environments: Standard methods and future challenges
Bioindication diatomique et évaluation de la qualité des eaux douces : méthodes standard et challenges futurs
Résumé
Since biofilms integrate the environmental effects of water chemistry, along with the physical and geomorphological characteristics of rivers and lakes, they have been widely applied in biomonitoring. In particular, diatoms are extensively used as reliable environmental indicators. Diatoms are microscopic, unicellular brown algae, which often dominate the algal biomass of biofilms. The shape and morphology of the siliceous skeleton, the frustules, unique to each taxon are used for taxonomical identification. The floras are diverse, in relation to their geographical location (climate, geology, relief) and to the quality of the aquatic environments they inhabit. Indeed, species are sensitive to the water physicochemical parameters and their presence/abundance is therefore correlated to water quality. Diatom sensitivity or tolerance towards different environmental parameters has long been studied and used to implement bioassessment methods. Such methods evolved from indices of saprobity designed first for European streams, to developments of various diatom indicators worldwide, able to highlight different types of pollution (pH, salinity, nutrients, toxicants). The objective of this chapter is to provide scientists and water managers with a broad overview of diatom tools helpful to monitor the ecological status of freshwater environments. We describe the applicability range and the limitations of the main existing methods, metrics (indices, traits) and types of surveys used, as well as the challenges faced by scientists to improve routine biomonitoring.