Suivi des macroalgues subtidales de la façade Manche-Atlantique - Rapport final - Convention 2010 - Action 5

A new assessment method was developped by the Marine Biology laboratory of Concarneau to evaluate the ecological status of coastal waters for Channel and Atlantic coastlines using rocky bottom subtidal macroalgae as a biological indicator. Studied parameters are algal belts depth limits, density of structuring algae, algal biodiversity, algal composition and Laminaria hyperborea epiphytism. This protocol was developped using an existing dataset from Brittany Rebent survey program. Some adaptations were necessary to implement this assessment method to the 44 Water Framework Directive (WFD) survey sites along Channel and Atlantic coastlines. Each parameter is evaluated according to specific rating tables and then the quality index is calculated for each survey site. The Ecological Quality Ratio (EQR) of a survey site is determined by the ratio of its quality index and the reference quality index. This method was applied on 35 water masses and results shows that 9 of them do not respect WFD requirements for ecological quality.