## 4 Discussion
The response of the biological indicators to the pressures assessed by the LUPLES method was studied by the BQE, defined in the WFD, which is already intercalibrated and used at the European level [62; 63], using the normalized values (EQR) to allow the comparison of the assessed impact, regardless the metric used. Eutrophication pressure levels determined by the LUPLES method correlated significantly with the chl-\(a\) concentration, defined as one of the main metrics for the BQE-phytoplankton, used for ecological quality assessment [13; 64]. Organic enrichment pressures also corelated significantly with the chl-\(a\) concentration, which suggested a proper estimation of the defined pressure, as the decomposition of organic matter provides inorganic nutrients which enhances phytoplankton growth [65]. The pollution pressures defined by the LUPLES also showed negative significant effects on benthic invertebrate assemblages. The structure and composition of the communities of these organisms have been widely studied as indicators of the ecological status of waterbodies [66; 67], representing good indicators of the effects of eutrophication on the ecological quality of the waterbody [14], organic enrichment [68], toxic pollution [16], and acidification [15]. In our case, the results for benthic invertebrates also validated our hypothesis, with a significant negative response of the four water quality pressure types to the normalized data, based on benthic invertebrate indicators. Contrarily to phytoplankton and benthic invertebrates, no statistically significant relationship between pollution pressure level and macrophytes was found, although a negative trend was apparent. We would expect a reduction in macrophye coverage with increases in the eutrophication pressure level [69], although there are more sensitive or more tolerant taxa already defined as indicators by the WFD [70]. Depending on the nature of the macrophye indices, based on abundance, richness, or a combination of both, they could be more or less sensitive to the assessed pollution pressures. Macrophyytes, however, are also used as indicators of the impacts caused by hydrological and morphological pressures, and their coverage is used as a metric of the ecological status for the BQE \"other aquatic flora\" [43]. Considering the relevance of the hydro-morphology of the waterbody for the status of macrophye communities [19], the identification of hydrological and morphological pressures is key for ecological status assessments [63]. This is even more important in Mediterranean waterbodies due to the higher levels of hydrological stress [43]. The LUPLES method proposes the assessment of these two types of pressures separately, by estimating the direct alterations on the water fluxes in the catchment, as well as by alterations of the waterbody shoreline and banks. Hydrological alterations, assessed by the LUPLES method, were correlated negatively with the percentage of submerged macrophytes, meanwhile, morphological alterations correlated negatively with helpbytes coverage. Although our results generally showed statistically significant correlations between the pressure levels assessed by the LUPLES method and the metric values, in some cases some statistics were weak (i.e., even if \(p\)-values showed statistically significant relationships, the percentage of variance explained was not very high). This could be explained by several factors. First, the data were obtained from raw databases, where the values of the metrics of the different member states are stored. We assumed that they were obtained using similar or comparable methods (the so-called \"intercalated methods\" according to the WFD terminology). On the other hand, they correspond to historical series, which, for the data used, were collected between 2004-2013. The pressures assessed were estimated at a fixed time point, based on the 2012 maps, since the available information on the metrics was not so abundant as to be suitable to make correlations in different time periods.