ABSTRACT
The Water Framework Directive has as its objective the establishment of a framework for the protection of continental groundwater and surface, transitional, and coastal water. Additionally, this framework seeks to prevent further deterioration of these aquatic ecosystems, while protecting and improving their status.
Phytoplankton is one of the established biological indicators for determining the ecological status of water bodies. Of the other possible indicators that might also be employed, only biomass (chlorophyll a) has an established criterion pertinent to defining the ecological status, while composition and phytoplankton abundance have yet to be developed by the MED-GIG.
In the present work, a multimetric PHYMED index for ecological classification of coastal water bodies is developed, based on the composition, abundance, and biomass of the phytoplankton community.
For this purpose, data collected by the monitoring network of the Autonomous Region of Valencia from August 2005 to July 2008 were utilized. The counting of the phytoplankton communities was carried out via epiflourescent microscopy, thereby allowing differentiation and enumeration of a broad sample of organisms.
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 various parameters related to the composition and abundance of the phytoplankton community (the principal phytoplankton groups and their related variables), and the variations in content of chlorophyll a and total phosphorus (pressure indicators) in each coastal water body.
Based on the aforementioned analysis of pressures and impacts, and supplemented by a territorial analysis, reference conditions for the Autonomous Region of Valencia were determined to be the Sierra de Irta mountains (north of Castellón) for Type II-A (with moderate continental influence), and the Cape of San Antonio-Rock of Ifach (north of Alicante) for Type III (without continental influence).
After discarding those variables which did not readily allow a distinction between coastal water bodies to be discerned, or which presented a certain amount of variability in the reference conditions, four variables were selected to constitute the PHYMED index. These were chlorophyll a (total eukaryotes + cyanobacteria), picocyanobateria, prymnesiophyta (diatoms + cryptophyta), and the inverse percentage of primnesiophyta. 
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 total phosphorus (0,88 for Type II-A and 0,85 for Type III).
The PHYMED index classifies the ecological quality status of the Valencian water bodies 001, 002, 003, 004, 011, 012, 014 and 019 as “High”; 005, 007, 009, 010, 013, 015, and 018 as “Good”; and 008, 016, and 017 as “Moderate.”
The results obtained from this index were compared with those derived using chlorophyll a; with the multimetric PHYMED index, the existing deviations presently arising from the use of chlorophyll a as an ecological status indicator can be corrected.
Finally, a correlation is established between the approaches (chlorophyll a and PHYMED) and pressures (50th percentile and 90th percentile of total phosphorus). The pressures of the 50th percentile were statistically significant with both methods, while only the 90th percentile was significant using the PHYMED index.