## 4 Discussion
Other sites with high eutrophication pressure levels, with LUPLES method values between 10 and 20, were located in highly altered catchments, with a percentage of agriculture coverage above 50 or even 75% of the total area, such as Etang de Canet, Stagno di Cabras, Valli residue del comprensorio di Comacchio, Biviere di Gela or Stagno di Corru S'Ittiri. Generally, all the studied coastal lagoons presented a eutrophication pressure level above 10, which is in agreement with the general degradation of the coastal systems [56]. The specific pollutants pressure level presented quite similar results, especially in terms of the relationship between agriculture and the use of nutrients and chemical compounds as fertilizers or pesticides [57]. For the organic enrichment pressure level, Albufera de Valencia was the only site with a value above 20, i.e., a high pressure level. Apart from the organic matter that can originate from agriculture [38], the Albufera catchment is highly populated, with urban uses representing an important source of pressures [3]. The acidification pressure level correlated significantly with some of these metrics, however, since this pressure was estimated to be low in all the studied sites, this may be considered as a spurious correlation that is mostly due to covariation. Further refinement of the specific assessment algorithms for this type of pressure seems to be necessary in order to refine our method. Subsequent analyses, such as genetic programming, will allow us to refine the method for this type of pressure, and indeed, the rest of the pressure types in future work, with validations using additional sites and data sources [25]. Pressure levels estimated by land use in the catchment area could be translated into changes in some ecological parameters on the waterbody, which could also imply reductions in their ecological status [12]. The levels of pressures estimated by the LUPLES is coherent with the impacts measured by the ecological status indicators on the waterbodies, showing a degreasing ecological status in response to increased levels of pressures, as we have shown in our study, which validates the method developed. One of the ecosystem pressure responses estimated by our method, was the positive correlation between the estimated pressure levels and the concentrations of nitrogen and phosphorus. These significant correlations demonstrated the relationship that exists between land use in the catchments and the level of eutrophication pressure, as reported in previous studies [10]. Another effect of the increased pressure on the status of the waterbody was the response of metabolic activity as a measure of ecosystem functioning, especially induced by eutrophication and organic enrichment [58; 59]. A positive correlation between the eutrophication pressure level and the dissolved oxygen concentration (DO) was found, in accordance with the expected response of the ecosystem by the proliferation of photosynthetic organisms [60]. Contrarily, a negative correlation of DO with the organic enrichment pressure level was found, as the increases in organic matter availability can promote exacerbated growth of heterotrophic organisms, thus enhancing oxygen-consuming organic matter degradative metabolism, namely, respiration [61]. The impacts on biological communities also showed clear responses to the pressure levels estimated by the LUPLES method. Sites with high pressure levels where those with poorer values of indicators of bad ecological status (such as chl-\(a\) concentration), also showing lower values of indicators of good ecological status (such as the benthic invertebrate EQR), which indicates the clear relationship between the pressures quantified by our method and their associated impacts on the biological communities.