Freshwater molluscs and biodegradable pollution of watercourses: scale of sensitivity of species, genera and families

Abstract

Malacological surveys and physico-chemical water analysis have been carried out at one hundred and sixty stations in France, distributed across five major catchment areas. The relationships between six of the variables: dissolved oxygen, BOD5, ammonia nitrogen, nitrites, Kjeldhal nitrogen and orthophosphates can be considered as indicators of biodegradable pollution and the populations of forty eight species of molluscs have been studied using correspondence analysis. A scale of sensitivity of these species to this type of pollution is presented here. Using these results as a basis, and introducing of supplementary elements in the analysis, we have been able to formulate a scale of sensitivity of mollusc genera and families. A quantification of information lost when using genus or family-level rather than species-level identification was carried out. The results obtained showed that the genus-level identification can constitute an acceptable compromise for using molluscs as water quality indicators in biomonitoring.