PHYMED: An ecological classification system for the Water Framework Directive based on phytoplankton community composition

Abstract

The European Water Framework Directive (WFD) has as its objective the establishment of a framework for the protection of continental, groundwater and surface, transitional, and coastal water. The phytoplankton is one of the biological quality elements established for determining the ecological status within the Directive. Phytoplankton biomass, composition and abundance, together with frequency of blooms, are the metrics to be assessed according to the WFD. For the Mediterranean coastal water only biomass (chlorophyll a) has been intercalibrated by the Mediterranean Geographical Intercalibration Group. In the present contribution, a multimetric index PHYMED for ecological classification of coastal water bodies in Valencia Region is developed based on biomass and phytoplankton community composition. First, a conceptual model was established to develop a system of indicators based on the composition of the phytoplankton community. Formulating the model required a preliminary analysis of the existing correlations between the parameters related to the phytoplankton community composition and the variations in the pressure indicators in each coastal water body. After discarding those variables which did not readily allow a distinction between coastal water bodies to be discerned four phytoplankton variables were selected to constitute the PHYMED index. Reference conditions were determined based on the analysis of pressures and impacts and supplemented by a thorough territorial analysis. To verify that this index responded well to the varying ranges in pressure, a statistically significant correlation was confirmed to exist between the index and the phosphorus values. The results obtained from this index were compared with those derived using chlorophyll a finding that the existing deviations presently arising from the use of chlorophyll a as an ecological status indicator can be corrected with the proposed multimetric index. © 2011 Elsevier Ltd. All rights reserved.