Delineating the Aquifer Role in the Anthropogenic Fingerprint on the Groundwater-Dependent Ecosystem of the Biguglia Lagoon (Corsica, France)

Abstract

The Biguglia lagoon is the largest wetland of Corsica Island and is located immediately south to the densely urbanized city of Bastia. A part of the ecological preservation of the lagoon is based on the quantity and the quality of the freshwater supply coming from groundwater flows unfortunately still underestimated and misunderstood. To evaluate the role of the groundwater connexion to the lagoon hydrological behaviour, different hydrogeological investigations were carried out with a multi-tracer geochemical approach (major ions, trace elements, δ¹⁸O, δD and ³H). Main results show a clear impact of the surrounding anthropogenic activities on the groundwater quality of the alluvial plain of the Biguglia lagoon. The presence of old groundwater dated with ³H indicates a current pollution of the groundwater due to former agricultural practice. The impact of the vegetable production, which is a recent land activity, is not yet visible. However, decennial residence times of groundwater indicate in the near future, a potential threat to the drinking water supply quality as well as to the lagoon water quality by the current agricultural activities, and particularly by nitrates. In the end, a resilience analyse was led considering the groundwater as a main node of the lagoon socio-ecologic system. This transdisciplinary approach has underlined a dynamic global system, where the link between the different social influences is clearly expressed in the groundwater quality. Taking into account the groundwater resilience factors is then one of the key issues for the global management of Mediterranean lagoons.