Water quality in Europe is an important subject, treated by the WFD (Water Framework Directive). To assess the ecological status of water bodies in Europe, each country must develop biological indices. The phytoplankton lake index (IPLAC) is the tool developed in France to provide an assessment of the quality of water bodies according to French phytoplankton communities surveyed. Statistical models have been, for the vast majority, drawn from data from French water bodies and were designed with the goal to match the best features of French territory. For this, the development of this index was dependent on phytoplankton elements specific to this territory. It needs and respects the phytoplankton sampling protocol developed in France (Laplace-Treyture & al., 2009 ). IPLAC is the weighted average of the MBA (total Algal Biomasse Metric) and the MCS (Specific Composition Metric). The result is expressed in EQR.