Coastal wetlands and salt marsh areas perform a wide range of ecosystem services including shoreline stabilization, sediment and nutrient retention, high primary and secondary production, fisheries resources, habitat and food resources for terrestrial, aquatic and marine fauna, coastal water quality buffering, biomass and biodiversity reservation and recreation and tourism amenities. Consequently, these ecosystems not only show a high natural value, but also a high natural heritage value. Coastal wetlands and marsh areas may present an extraordinary value from a scientific or conservational point of view, from their natural beauty, and they may be the habitat of threatened species.
La Pletera salt marshes is a protected area located in the north of the mouth of the Ter River (NE Spain), in a region dominated by agricultural and tourism activities. These marshes are composed of wetlands and some coastal lagoons that were affected by the incomplete construction of an urban development in 1987. This area has been the focus of two Life+ projects, whose aim was to restore this area, to recover its ecological functionality, and to protect a threatened fish species (Aphanius iberus). Within these projects, a creation of a lagoon was undertaken in 2002; and in a second phase, between 2016 and 2017, four new lagoons were created.
In this area, a study to determine the importance of groundwater in these coastal lagoons has been conducted. On the one hand, hydrochemical and isotopic analyses were conducted to build hydrogeological and evaporation models. On the other one, the one-dimension model General Lake Model was used to assess the water balance and salinity dynamics in the two natural lagoons, and in the new one created in 2002.
Results show that during dry seasons groundwater maintains these ecosystems, with a 15-80% of the water in the lagoons. The salinity in La Pletera lagoons depended on the mixing of fresh and sea water mainly occurring within the aquifer, and evaporation. In addition, the GLM provided us a comprehensive understanding of the hydrological dynamics, and allow us to detect that during Summer the lagoons lost water through outflows, but at the beginning of Autumn this water, saltier than the sea, returned to the lagoons in the first cyclonic storm periods.
Consequently, this study highlights the importance of groundwater as hydrogeological heritage, due to its role in the maintenance of the biological heritage, as well as its interest from the scientific and educational point of view.
 Menció, et al. (2017), DOI: 10.1016/j.jhydrol.2017.07.034
 Casamitjana, X., Menció, A., Quintana, X., Soler, D., Compte, J., Martinoy, M., Pascual, J. (2019, under revision). The salinity regime of the coastal lagoons in La Pletera Salt Marshes. Journal of Hydrology.
Fundings: CGL2016-76024-R (MINECO) and EC LIFE 13 NAT/ES/001001 projects.