Tesis 3074: Abstract.
The EU Water Framework Directive (2000/60/EC), henceforth referred to as WFD, has as its aim the establishment of a framework for the protection of European inland surface waters, ground waters and transitional and coastal waters, so as to prevent their further deterioration and to protect and improve the overall state of European aquatic ecosystems.
The final goal of the WFD is to achieve a good ecological status for these aquatic ecosystems by 2015. To this end, it is necessary to first characterize and identify the ecological quality of the water bodies by means of indicator elements of ecological quality, be they biological, physiochemical or hydromorphological. Another key activity is to conduct an intercalibration exercise that ensures correlation of the ecological-class thresholds for the different indicator elements of ecological quality vis-à-vis the ecosystem changes being characterized for different locations.
One of the biological indicators established by the WFD to determine the ecological state of coastal water bodies is phytoplankton. Within this group are two principal aspects: 
•	Phytoplankton composition
•	Phytoplankton biomass (chlorophyll a), the focus this dissertation.
The present dissertation seeks to adequately structure the preliminary and essential conceptual model with which to establish the pertinent criteria for defining the typologies of the different Mediterranean water bodies, the reference zones and the thresholds for ecological-status classifications, using chlorophyll a as a quality indicator parameter.
First, the dissertation analyzes the implications for a sampling network when determining a system’s trophic state with chlorophyll a as an indicator parameter. As part of the intercalibration exercise, instituted in accordance with the guidelines of the WFD and addressed specifically to the Spanish Mediterranean, the nearshore:inshore conversion factor derived from the values of the 90th percentile of chlorophyll a was set at 0.5 (inshore is defined as the coastline, nearshore as the line situated 1500 m from the coast). The findings within the Comunidad Valencia reveal the presence of a negative gradient in the concentrations of chlorophyll a as distance from the coast increases. Moreover, this decrease is more pronounced in the areas closest to the coast, where a nearly exponential falloff is observed. To account for this, a conversion factor of .31 was subsequently calculated for the Comunidad Valenciana data. Therefore, the distribution of sampling networks should be conditioned by the extension of the eutrophic zone and the application of a pre-established value for the entire Western Mediterranean is not expedient.
Second, a methodology is developed herein to establish the typology of the coastal waters of the Comunidad Valenciana. The aforementioned intercalibration exercise proposes that mean annual salinity be used as a parameter in defining Mediterranean pelagic water types as a function of the level of continental influence. This utilization of mean annual salinity leads to qualitative changes to the typology of various bodies of water from year to year; however, the characterization is contingent upon utilizing the 90th percentile of chlorophyll a from a five-year span of data. This supposes serious problems for the viability of chlorophyll a as an ecological indicator. To obviate this incongruence, a global territorial analysis was carried out, followed by a statistical analysis based on hierarchical classifications. Both utilized monthly data collected over the course of a two-year monitoring program. The findings of these two analyses coincide in that, in the Comunidad Valenciana, San Antonio Cape represents a dividing line where waters under a moderate continental influence are situated to the north, while waters without a continental influence lie to the south.
Third, this dissertation examines the group of problems associated with employing chlorophyll a concentrations in the WFD’s coastal pelagic characterization of water bodies under a continental influence. In addition, the necessity of differentiating between the direct and indirect influence of continental inputs is likewise studied. It is easy to arrive at erroneous decisions when ecologically characterizing an area with chlorophyll a as an indicator. This can be attributed to not only the temporal variations of chlorophyll a in each area, but also to the location of the sampling point itself and the season during which the sampling is conducted. In light of the results, it became necessary to develop a method that would allow for the characterization of a zone, but which simultaneously excluded the interference generated by a direct continental influence. Consequently, a salinity threshold was established to define zones affected by direct continental discharges (near field, where the nutrients exhibit a behavior inversely related to that of salinity). This threshold was determined using a factor analysis of various physiochemical and biological parameters (salinity, dissolved inorganic nitrogen, total phosphorus, orthosilic acid and chlorophyll a) derived from samplings of plumes, beaches and the two in combination. This factor analysis concluded that the salinity cutoff point (the point at which the behavior of nutrients and salinity is independent) is 37.5g/kg.
Finally, addressed in detail are the problems derived from establishing the ecological quality of different water bodies with only a single metric. As mentioned earlier, the intercalibration exercise, initiated specifically for the Spanish Mediterranean in accordance with WFD guidelines, establishes that the determination of a trophic state should be based on the 90th percentile of monthly concentrations of chlorophyll a collected in samples over a five-year period. For this reason, a new focus was developed incorporating other metrics that account for the inherent variability of a system. The selection of reference zones was made only after a thorough analysis of pressures and impacts: it was not based on a single parameter. Once the reference zones are selected for the water-body classification, a contrastive methodology is proposed which takes into consideration the degree of deviation an ecosystem can tolerate.