@article{fdi:010083805,
  title = {{C}arbon dynamics driven by seawater recirculation and groundwater discharge along a forest-dune-beach continuum of a high-energy meso-macro-tidal sandy coast},
  author = {{C}harbonnier, {C}. and {A}nschutz, {P}. and {A}bril, {G}. and {M}ucci, {A}. and {D}eirmendjian, {L}oris and {P}oirier, {D}. and {B}ujan, {S}. and {L}ecroart, {P}.},
  editor = {},
  language = {{ENG}},
  abstract = {{H}igh-energy tidal beaches are exposed to strong physical forcings. {T}he submarine groundwater discharge ({SGD}) that occurs in intertidal sandy sediments includes both terrestrial, fresh groundwater flow and seawater recirculation, and plays a significant role in regulating biogeochemical cycles in some coastal zones. {I}n this transition zone between land and sea, complex biogeochemical reactions alter the chemical composition of pore waters that discharge to the coastal ocean. {R}ecent studies highlight that {SGD} can be a significant source of carbon to the coastal ocean but very few have investigated {SGD} in high-energy environments. {W}e have characterized the dissolved carbon dynamics in such a high-energy environment ({T}ruc {V}ert {B}each, {SW} {F}rance) through pore-water sampling in key compartments of the {SGD} system. {D}issolved organic carbon ({DOC}), p{H}, total alkalinity ({TA}), and the isotopic composition of dissolved inorganic carbon (delta {C}-13-{DIC}) were measured in pore waters sampled at regular intervals between 2011 and 2014 in the intertidal zone of the beach, the mixing zone of the subterranean estuary ({STE}), and the freshwater aquifer upstream from the beach. {R}esults reveal that {SGD} exports dissolved carbon mostly as {DIC} to the {A}quitaine coast, some of which originates from the aerobic respiration of marine organic matter within the beach aquifer. {T}his is highlighted by the reverse spatial trend of {DOC}, which is consumed, and {DIC}, which is produced. {S}aline pore waters expelled from the beach through tidally-driven recirculation of seawater provide about 4400 tons of carbon per year to the coastal zone of the 240-km long {A}quitaine sandy coast. {T}errestrial groundwater, characterized by high p{CO}(2) values, is also a significant contributor to the {DIC} flux to the coastal ocean (16,200 tons per year). {T}his flux is abated by {CO}2 evasion in the upper beach, at the onset of the salinity gradient in the {STE}, and within the surficial freshwater aquifer along the forest-beach transect below the coastal foredune. {A}ccordingly, the {DIC}:{TA} ratio evolves to below 1, suggesting that this {SGD} increases the buffer capacity of coastal seawater against acidification. {T}his study demonstrates that high-energy beaches are active vectors of {DIC} from the land to the coastal ocean as well as significant sources of {CO}2 to the atmosphere, and must therefore be taken into consideration in {SGD} carbon budgets.},
  keywords = {{T}idal beach ; {S}ubmarine groundwater discharge ; {S}ubterranean estuary ; {A}erobic benthic respiration ; {CO}2 degassing ; {A}quitaine coast ; {FRANCE} ; {AQUITAINE} ; {ATLANTIQUE} ; {TRUC} {VERT} {PLAGE}},
  booktitle = {},
  journal = {{G}eochimica et {C}osmochimica {A}cta},
  volume = {317},
  numero = {},
  pages = {18--38},
  ISSN = {0016-7037},
  year = {2022},
  DOI = {10.1016/j.gca.2021.10.021},
  URL = {https://www.documentation.ird.fr/hor/fdi:010083805},
}