Molluscs and biodegradable pollution in rivers: proposal for a scale of sensitivity of species

Malacological surveys and physico-shemical water analysis have been carried out at one hundred and sixty stations in France, distributed accross 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 to this type of pollution is presented.