Groundwater and nutrient discharge through karstic coastal springs (Castelló, Spain)

Abstract

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.

Quantification of submarine/intertidal groundwater discharge and nutrient loading from a lowland karst catchment

“…Globally, the majority of SGD has been found to occur as recirculated seawater (Burnett et al, 2006). However, in karstic regions, which frequently exhibit high permeability and reduced surface drainage capabilities, SGD is primarily composed of terrestrial freshwater (Garcia-Solsona et al, 2010b;Weinstein et al, 2011). SGD has been acknowledged as a significant source of nutrients to coastal waters (Slomp and Van Cappellen, 2004;Paytan et al, 2006;Garcia-Solsona et al, 2010a;Einsiedl, 2012;Rodellas et al, 2014) as well as being a source of trace metals and contaminants (Boehm et al, 2004;Windom et al, 2006;Beck et al, 2007); as such, SGD has become a topic of substantial research interest (Moore, 2010).…”

Submarine groundwater discharge as a major source of nutrients to the Mediterranean Sea

“…) may be also found in entirely fresh groundwater springs [e.g., Badum (29), Sa Nau (30)], and fresh groundwater may be mixed with saline waters before inflowing to the sea, the 228 Ra approach followed in this study is likely capturing most of the fresh groundwater inputs. In any case, such underestimation would not compromise the range of total SGD calculated here.…”

Submarine Groundwater Discharge at a Single Spot Location: Evaluation of Different Detection Approaches

“…Also the isotope ratios determined along the transect are in the same range as observed at Cabbé (Figure 6). If SGD at Cabbé were a source of radium one would expect decreasing The lack of radium enrichment in the groundwater discharging at Cabbé is in contrast to several other SGD studies in the Mediterranean Sea where radium has been successfully applied as SGD tracer [38][39][40]. We explain the lack of radium in the discharging groundwater to be due to two main reasons: (1) The SGD site studied is hydraulically connected to a major karst aquifer.…”