TY - JOUR
T1 - Submarine karstic springs as a source of nutrients and bioactive trace metals for the oligotrophic Northwest Mediterranean Sea
AU - Tamborski, Joseph
AU - van Beek, Pieter
AU - Conan, Pascal
AU - Pujo-Pay, Mireille
AU - Odobel, Charlene
AU - Ghiglione, Jean François
AU - Seidel, Jean Luc
AU - Arfib, Bruno
AU - Diego-Feliu, Marc
AU - Garcia-Orellana, Jordi
AU - Szafran, Armand
AU - Souhaut, Marc
N1 - Funding Information:
This study was funded by the MED-SGD project funded by ANR ; France ( ANR-15-CE01-0004 ; PI: Pieter van Beek). The postdoctoral fellowship of Joseph Tamborski is supported by FEDER funded by Europe and Région Occitanie Pyrénées-Méditerranée (SELECT project; PIs: Pieter van Beek and Marc Souhaut). Jordi Garcia Orellana wants to thank the support of the Generalitat de Catalunya to MERS ( 2018 SGR-1588 ). This work is contributing to the ICTA ‘Unit of Excellence’ (MinECo, MDM2015-0552). This work benefited from the Port-Miou in-situ observatory within the framework of the KARST observatory network ( www.sokarst.org ) initiative from the INSU/CNRS. Rainfall data are provided by Météo-France. We thank the captain and crew of RV Antédon II for help during sampling at sea, including Simon Bejannin and Emilie Le Roy at LEGOS. We thank Dorian Guillemain, Nagib Bhairy, Deny Malengros and Christian Grenz at MIO for providing the CTD data. We thank Remi Freydier at AETE-ISO Platform, OSU-OREME/Université de Montpellier, for performing trace element analyses and Olivier Crispi at LOMIC, Banyuls-sur-Mer.
Publisher Copyright:
© 2020 Elsevier B.V.
Copyright:
Copyright 2020 Elsevier B.V., All rights reserved.
PY - 2020/8/25
Y1 - 2020/8/25
N2 - Groundwater springs in karstified carbonate aquifers are known to transport carbon, nutrients and trace elements to the coastal ocean. The biogeochemical significance of submarine karstic springs and their impact on coastal primary production are often difficult to quantify. We investigated several karstic springs, including the first-order Port-Miou spring, in an urbanized watershed that is also severely impacted by sewage effluent (Calanques of Marseille-Cassis, France). Karstic springs were elevated in major nutrients and bioactive trace metals over Mediterranean seawater, with relatively low concentration ranges. Groundwater NO3 − was likely derived from atmosphere-aquifer interactions, while DOC:DON ratios reveal that NO2 − and NH4 + was autochthonously produced during mixing between karst groundwater and seawater. Submarine groundwater discharge (SGD) during March 2018 (wet season, baseflow conditions) was 6.7 ± 2.0 m3 s−1 for the entire investigated coastline, determined from simultaneous 224Ra and 226Ra mass balances. The contribution of groundwater PO4 3−, the major limiting nutrient of the Mediterranean Sea, sustained only 1% of primary production adjacent to sewage outfall, but between 7 and 100% of the local primary production in areas that were not impacted by sewage. Groundwater and seawater Fe:DIN and Fe:DIP ratios suggest that Fe was not a limiting micro-nutrient during the period of study, where bioactive trace metal fluxes were dominated by sewage and atmospheric deposition, although excess Fe from groundwater may locally enhance N fixation. Groundwater solute fluxes may easily vary by a factor of two or more over time because karst aquifers are sensitive to precipitation, as is the case of the regional carbonate karstified aquifer of Port-Miou, highlighting the critical importance of properly characterizing nutrient and trace metal inputs in these coastal environments.
AB - Groundwater springs in karstified carbonate aquifers are known to transport carbon, nutrients and trace elements to the coastal ocean. The biogeochemical significance of submarine karstic springs and their impact on coastal primary production are often difficult to quantify. We investigated several karstic springs, including the first-order Port-Miou spring, in an urbanized watershed that is also severely impacted by sewage effluent (Calanques of Marseille-Cassis, France). Karstic springs were elevated in major nutrients and bioactive trace metals over Mediterranean seawater, with relatively low concentration ranges. Groundwater NO3 − was likely derived from atmosphere-aquifer interactions, while DOC:DON ratios reveal that NO2 − and NH4 + was autochthonously produced during mixing between karst groundwater and seawater. Submarine groundwater discharge (SGD) during March 2018 (wet season, baseflow conditions) was 6.7 ± 2.0 m3 s−1 for the entire investigated coastline, determined from simultaneous 224Ra and 226Ra mass balances. The contribution of groundwater PO4 3−, the major limiting nutrient of the Mediterranean Sea, sustained only 1% of primary production adjacent to sewage outfall, but between 7 and 100% of the local primary production in areas that were not impacted by sewage. Groundwater and seawater Fe:DIN and Fe:DIP ratios suggest that Fe was not a limiting micro-nutrient during the period of study, where bioactive trace metal fluxes were dominated by sewage and atmospheric deposition, although excess Fe from groundwater may locally enhance N fixation. Groundwater solute fluxes may easily vary by a factor of two or more over time because karst aquifers are sensitive to precipitation, as is the case of the regional carbonate karstified aquifer of Port-Miou, highlighting the critical importance of properly characterizing nutrient and trace metal inputs in these coastal environments.
KW - GEOTRACES
KW - Karst
KW - Nutrients
KW - Radium isotopes
KW - Springs
KW - Submarine groundwater discharge
UR - https://www.scopus.com/pages/publications/85084504133
U2 - 10.1016/j.scitotenv.2020.139106
DO - 10.1016/j.scitotenv.2020.139106
M3 - Artículo
C2 - 32422479
AN - SCOPUS:85084504133
SN - 0048-9697
VL - 732
JO - Science of the Total Environment
JF - Science of the Total Environment
M1 - 139106
ER -