Bioindication and macrophytic indices, tools for assessing and diagnosing the quality of watercourses

Abstract

The bioindication concept, applied to the aquatic vegetation compartment, is covering different approaches, coming from those usually developed through phytosociological and phytoecological methods. They are based on studies about relationships between species forming recognizable units, called syntaxons, or between each species and its environmental factors, linked to its presence and behaviour in the site. In the eighties, needs were precisely oriented to the development of synthetic indices, allowing to quantify eutrophication phenomena. In France, this topic had allowed to boost macrophytes studies, considering their evaluation as a necessary tool for managing aquatic habitats. Some more operational approaches were then pushed up, as functional approaches, in order to analyze the environmental functioning through the populations behaviour, or the study about reference phytocenosis, which are giving standards for comparison to local floristic surveys. In 2001, a synthesis realised by the GIS Macrophytes has allowed to get a view-point about all these approaches, tested or developed in France. Aquatic phytoecological studies led to the publication of a biocenotic index, the IBMR (Biological Macrophytes Index in Rivers). This index is normalised in France from 2003, and is now officially adopted for rivers macrophytes sampling through monitoring networks. These methods have been indeed overtaken, as well as others hydrobiological approaches, by implementation of the European Water Framework Directive in 2000. To meet the new requirements proceeding from the application of this European regulation, works for adaptation and development are intensely set up, as well in using acquired knowledge in phytoecology, than in generating new actual questions, at which the world of science must give pragmatic responses. For that, the new trend and the densification of national monitoring networks, will allow in return to get homogeneous data on a large scale, what have not be done already, in opening new prospects.