BIOINDICATION USING VEGETATION OF THREE REGULATED RIVERS UNDER AGRO-INDUSTRIAL PRESSURE IN WESTERN FRANCE

Abstract

The longitudinal changes of richness and composition of aquatic plants have been studied from headwaters to the fifth stream order in three near-by rivers or Western Brittany (France), the Orne, Sélune and Rance. All rivers were regulated years ago with dams located on the lower third of the studies river stretches. A shifting evolution of the macrophyte richness was revealed in a previous study along the river continuum, related 10 habitat heterogeneity. influences of regulated sectors and geological changes. Nutrient enrichment and organic pollution influences were the main secondary gradients. On this basis we improved a methodology to complete a biotic index used in Europe for water trophy assessment, following the European water frame work directive the IBMR based on aquatic plant survey: a validation with classical statistical tests and a comparison to a canonical analysis were performed. Finally this approach permitted to make a proposition of adaptation of the index to the Local particularities of each three high anthropised rivers