FN Archimer Export Format
PT J
TI Nutrient Fluxes Associated With Submarine Groundwater Discharge From Karstic Coastal Aquifers (Côte Bleue, French Mediterranean Coastline)
BT 
AF Bejannin, Simon
   Tamborski, Joseph James
   van Beek, Pieter
   Souhaut, Marc
   Stieglitz, Thomas
   Radakovitch, Olivier
   Claude, Christelle
   Conan, Pascal
   Pujo-Pay, Mireille
   Crispi, Olivier
   Le Roy, Emilie
   Estournel, Claude
AS 1:1;2:1;3:1;4:1;5:2;6:2,3;7:2;8:4;9:4;10:4;11:1;12:1;
FF 1:;2:;3:;4:;5:;6:;7:;8:;9:;10:;11:;12:;
C1 LEGOS, Laboratoire d'Etudes en Géophysique et Océanographie Spatiales UMR 5566 (Université de Toulouse, CNES, CNRS, IRD, UPS), Observatoire Midi Pyrénées, Toulouse, France
   Aix-Marseille Univ, CNRS, IRD, INRA, Coll France, CEREGE, Aix-en-Provence, France
   IRSN (Institut de Radioprotection et de Sûreté Nucléaire), PSE-ENV/SRTE/LRTA, Saint-Paul-Lez-Durance, France
   Laboratoire d'Océanographie Biologique, Sorbonne Université, UPMC, CNRS, UMR 7621, Laboratoire Arago, Banyuls-sur-Mer, France
C2 LEGOS, FRANCE
   UNIV AIX MARSEILLE, FRANCE
   IRSN, FRANCE
   UNIV SORBONNE, FRANCE
IF 5.411
TC 10
UR https://archimer.ifremer.fr/doc/00610/72171/70945.pdf
   https://archimer.ifremer.fr/doc/00610/72171/70946.jpeg
   https://archimer.ifremer.fr/doc/00610/72171/70947.jpeg
   https://archimer.ifremer.fr/doc/00610/72171/70948.xlsx
LA English
DT Article
BO Antedon II
DE ;submarine groundwater discharge;Mediterranean sea;radium isotopes;thermal infrared remote sensing;nutrient fluxes;GEOTRACES
AB Determination of submarine groundwater discharge (SGD) from karstic coastal aquifers is important to constrain hydrological and biogeochemical cycles. However, SGD quantification using commonly employed geochemical methods can be difficult to constrain under the presence of large riverine inputs, and is further complicated by the determination of the karstic groundwater endmember. Here, we investigated a coastal region where groundwater discharges from a karstic aquifer system using airborne thermal infrared mapping and geochemical sampling conducted along offshore transects. We report radium data (223Ra, 224Ra, 228Ra) that we used to derive fluxes (water, nutrients) associated with terrestrial groundwater discharge and/or seawater circulation through the nearshore permeable sediments and coastal aquifer. Field work was conducted at different periods of the year to study the temporal variability of the chemical fluxes. Offshore transects of 223Ra and 224Ra were used to derive horizontal eddy diffusivity coefficients that were subsequently combined with surface water nutrient gradients (NO2− + NO3−, DSi) to determine the net nutrient fluxes from SGD. The estimated DSi and (NO2− + NO3−) fluxes are 6.2 ± 5.0 *103 and 4.0 ± 2.0 *103 mol d−1 per km of coastline, respectively. We attempted to further constrain these SGD fluxes by combining horizontal eddy diffusivity and 228Ra gradients. However, SGD endmember selection in this area (terrestrial groundwater discharge vs. porewater) adds further uncertainty to the flux calculation and thus prevented us from calculating a reliable flux using this latter method. Additionally, the relatively long half-life of 228Ra (5.75 y) makes it sensitive to specific circulation patterns in this coastal region, including sporadic intrusions of Rhône river waters that impact both the 228Ra and nutrient surface water distributions. We show that SGD nutrient fluxes locally reach up to 20 times the nutrient fluxes from a small river (Huveaune River). On a regional scale, DSi fluxes driven by SGD vary between 0.1 and 1.4% of the DSi inputs of the Rhône River, while the (NO2− + NO3−) fluxes driven by SGD on this 22 km long coastline are between 0.1 and 0.3% of the Rhône River inputs, the largest river that discharges into the Mediterranean Sea. Interestingly, the nutrient fluxes reported here are similar in magnitude compared with the fluxes quantified along the sandy beach of La Franqui, in the western Gulf of Lions (Tamborski et al., 2018), despite the different lithology of the two areas (karst systems vs. unconsolidated sediment). 
PY 2020
PD FEB
SO Frontiers In Environmental Science
SN 2296-665X
PU Frontiers Media SA
VL 7
IS 205
UT 000518696300001
DI 10.3389/fenvs.2019.00205
ID 72171
ER

EF