## 3 Results and Discussion
### Delimitation of Coastal Lakes
#### 3.4.2 Coastal Lagoons--Vixan  
The space classified as lake in Vixan covered an area of 18 ha. However, it must be emphasized that delimitation of the lake proved difficult in relation to the separation from the coastline. Between the lake and the sea, there is a strip of land of length 300 m occupied by a transition plain with a drainage channel, associated with a salt marsh dominated by _Juncus maritimus_, _Juncus acutus_, and _Scripus maritimus_ (Figure 4). This category continues at the back of the dune system, which hampers delimitation of the area. The main criteria used for habitat delimitation was the identification of hydrophyte vegetation as a dominant formation. Regarding the environmental units, most of the area was occupied by reed bed (54.9%), while open water occupied 18.8%. In addition, an area of salt marsh occurred at the front part (26.3%). In relation to the surface area of alluvial forest that appears in the official cartography, its inclusion was ruled out, because the extension was negligible and limited to a few specimens of _Alnus glutinosa_ and _Salix atrocinerea_ that did not constitute a continuous forest. Unlike the proposed classification, PDRN divided the Vix\(\check{\text{\text{\text{\text{\text{\text{\text{\text{a}}}}}}}}\)n lake into three main habitats: coastal lagoon (94.7% of the area), calcareous fens with _Cladium mariscus_ and _Carcin davallianae_ (54.7%) and alluvial forest (45.7%). The proportions of each of these habitats indicate an important degree of overlap between units. For instance, the area registered as alluvial forest was simultaneously identified as coastal lagoon and calcareous fens. Figure 5 shows this habitat overlapping at the back of the lake. In this respect, the alluvial forest was not relevant in Vix\(\check{\text{\text{\text{\text{\text{\text{a}}}}}}}\)n (Figure 4). The disperse trees occurred in the distal zone and occupied a surface area (based on their canopy) of 395 m\({}^{2}\), i.e., much smaller than the 76,000 m\({}^{2}\) registered in the PDRN. The small area occupied, and their lack of continuity indicated that this unit should be removed and that the zone designated as alluvial forest should be re-designated as reed bed, because the species associated with this habitat predominate in this lake zone. The habitat designation in the front part of the lake differed from the official cartography. In the PDRN, a zone of calcareous fens (7210) appears in this area. This habitat is associated with water margins, flowing, or standing in hygroturb calcareous soils, with communities dominated by _Cladium mariscus_. Recent studies [34] have shown that the substrate of the zone is acidic or even very acidic (pH 4-6). This finding is incompatible with the term \"calcareous\" that defines and characterizes this habitat. Habitat 7210 is considered by some authors as mixed habitat, defined by the characteristics of the physical environment (substrate) and the vegetation. Several environmental agencies consider that, although the presence of plant cover with a particular structural characteristic is very important in the habitat definition, this should be developed in a marshy area and on calcareous soils [42; 43]. Figure 4: Coastal lagoon of Vix\(\check{\text{\text{\text{\text{\text{a}}}}}}\)n. (**a,b**) represent the temporal evolution of environmental units in 1989 and 2017, respectively. On the lagoon back appear two categories, reedbed and crops, because this part is occupied for reedbeds and the local inhabitants using the zone for their crops. (**c**) shows TRI classification, in black, values below mean and in white the values above mean. (**d**) Official cartography representing the distribution of habitats from Annex I of Habitats Directive. The red line in all cases represent the extent marked for the lagoon by our analysis (IGN [20]; Xunta de Galicia (c)).