For the category transitional waters was carried out a study in 2005 which dealt with the definition of a framework and develop an evaluation score for the Flemish transitional waters (the biological elements phytoplankton, benthos and macrophytes). All Flemish transitional water bodies, which - except for three artificial - any change were indicated strong need for the WFD by the end of 2009 to determine the maximum and good ecological potential by evaluating all relevant biological quality elements and the supporting elements.