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Abstract. Discharge of groundwater and associated chemical compounds into coastal karstic regions, which are abundant in the Mediterranean basin, is envisaged to be significant. In this study, we evaluate the groundwater discharge and its nutrient load to the open karstic site of Badum (Castelló, East Spain). Salinity profiles evidenced that groundwater discharge from coastal brackish springs causes a buoyant fresher layer, as identified with thermal infrared images. Chemical tracers (radium isotopes, dissolved inorganic silicate and seawater major elements) have been used to determine a brackish groundwater proportion in coastal waters of 36% in

Abstract. Discharge of groundwater and associated chemical compounds into coastal karstic regions, which are abundant in the Mediterranean basin, is envisaged to be significant. In this study, we evaluate the groundwater discharge and its nutrient load to the open karstic site of Badum (Castelló, East Spain). Salinity profiles evidenced that groundwater discharge from coastal brackish springs causes a buoyant fresher layer, as identified with thermal infrared images. Chemical tracers (radium isotopes, dissolved inorganic silicate and seawater major elements) have been used to determine a brackish groundwater proportion in coastal waters of 36% in October 2006 and 44% in June 2007. Based on a radium-derived residence time of 2.7 days in October 2006 and 2.0 days in June 2007, total SGD fluxes have been estimated in 71 500 and 187 000 m3 d−1, respectively, with fresh-SGD contributions representing 71% and 85%. The calculated SGD-associated nutrient fluxes, most likely of natural origin, were 1500 and 8300 μmol m−2 d−1 of DIN and 19 and 40 μmol m−2 d−1 of DIP in October 2006 and June 2007, respectively. These inputs may actually lead to or enhance P limitation, thereby altering the structure of biological communities in the area.

Consecutively to the global sea-level rise, coastal landscapes significantly changed during the Early Holocene. We explored how coastal mutations have affected ancient human systems in the western Mediterranean. The Pego-Oliva basin (Spain) provides a thick sediment sequence located in proximity to two well-studied Mesolithic and Neolithic archaeological sites. Based on 16 sediment cores, sedimentological analyses, 14 C dates, and integration of previous works, we reconstructed the architecture of the sedimentary facies and the chronology of deposition for the last 9500 years. From 9500 to 8200 cal. BP, the stepwise inland migration of the coastline is characterised by the deposition of peat layers at distinct depths indicating four phases of barrier-lagoon systems development. The marine transgression caused the disappearance of the lagoon at 8200 cal. BP, and reached a maximum inland position at 7300 cal. BP. Since 5800 cal. BP, sea-level stabilisation induced coastal progradation and barrier-lagoon system construction. Five marine flooding phases dated at 9500, 9100-9000, 8750-8650, 8450-8200, and 8100-7300 cal. BP match Atlantic meltwater pulses. Comparison to archaeology shows that the long-lasting Mesolithic occupation corresponds to the presence of coastal offering easily exploitable local intertidal resources. In contrast, during the Late Mesolithic, we observe a lagoon contraction and the reduction of lagoon bivalves size arguing for a decrease in resource productivity. This changes in the lagoon ecosystems negatively impacted to Late Mesolithic populations leading to a less intense occupation of this area. Therefore, the 700 years' temporal hiatus between the last hunter-gatherers and the first farmers occupying this area is explained by the disappearance of the formerly exploited biotopes because of sea-level rise, a situation that may have been aggravated by coincidence of the 8200 cal. BP climate event. The maximal sea transgression corresponded to a shift from intertidal to infralittoral species between the Impressa/Precardial and the Postcardial Neolithic, indicating a good adaptation to changing environments at that time. However, comparison between Late Mesolithic to Early Neolithic suggests that communities with different cultural baggage have had a different perception of the same environment. By the past perspective, it emphasises that perception of the ecosystem value as a benefit or constraint, and of the risks associated with sea-level rise, relies first on the local and regional scales adaptive capacity of society to global changes.

Seven borehole cores were analysed to reconstruct the Pleistocene evolution of the Pego-Oliva Basin (Mediterranean coast, Iberian Peninsula). A total of 295 samples were recovered for amino acid racemization (AAR) dating, and 77 samples for sedimentological, palaeontological and biomarker determination, with two objectives: (1) to establish a chronological framework (especially for Middle Pleistocene); and (2) to obtain data on the palaeoenvironment.AAR proved that the record covers approximately 650 ka in which no important hiatuses occurred, although minor ones cannot be discarded. AAR provided valuable information on differential subsidence rates, and Marine Isotope Stages (MISs) 15–1 were identified.Litho- and biofacies allowed the identification of distinct palaeoenvironments through time, with the constant presence of a marsh/lagoonal environment with brackish or saline water with continental or marine influence. Remains of marine molluscs allowed the determination of periods of highstand sea level. Biomarkers indicated a constant input from terrestrial plants, and allowed definitions of periods with variable water mass and environmental moisture. As in other Mediterranean littoral areas, facies with a marine influence occurred mainly during odd MISs, indicating periods of highstand sea level. In contrast, alluvial-fan progradation and continental brackish wetlands developed during even MISs.

In this contribution, we describe the formation and evolution of the upconing process in a Mediterranean coastal aquifer. The study area has experienced severe salinization over the last 40 years because of intensive exploitation of groundwater. We used historical and current records of piezometric levels and chloride concentrations to trace the development of the salinization of the aquifer. We defined the 3D shape of the saline wedge from the spatial distribution of chloride concentrations and vertical well logs of electrical conductivity using monitoring network data. Upconing first appeared in the early 90s and has continued until the present day. In this study, we examined the intensity of the upconing process. Dry periods and the associated increases in pumping caused the advance of seawater intrusion. The sharp reduction in groundwater withdrawals over the last 10 years has caused the saline wedge to move backwards, although the ongoing pumping and the climate conditions mean that this retreat is quite slow.

Over 40 years, the detrital aquifer of the Plana de Castellón (Spanish Mediterranean coast) has been subjected to seawater intrusion because of long dry periods combined with intensive groundwater exploitation. Against this backdrop, a managed artificial recharge (MAR) scheme was implemented to improve the groundwater quality. The large difference between the electrical conductivity (EC) of the ambient groundwater (brackish water due to marine intrusion) and the recharge water (freshwater) meant that there was a strong contrast between the resistivities of the brackish water saturated zone and the freshwater saturated zone. Electrical resistivity tomography (ERT) can be used for surveying similar settings to evaluate the effectiveness of artificial recharge schemes. By integrating geophysical data with lithological information, EC logs from boreholes, and hydrochemical data, we can interpret electrical resistivity (ER) with groundwater EC values and so identify freshwater saturated zones. Using this approach, ERT images provided a high-resolution spatial characterization and an accurate picture of the shape and extent of the recharge plume of the MAR site. After 5 months of injection, a freshwater plume with an EC of 400-600 μS/cm had formed that extended 400 m in the W-E direction, 250 m in the N-S direction, and to a depth of 40 m below piezometric level. This study also provides correlations between ER values with different lithologies and groundwater EC values that can be used to support other studies.