@article{fdi:010088809,
  title = {{A} novel high-resolution in situ tool for studying carbon biogeochemical processes in aquatic systems : the lake {A}iguebelette case study},
  author = {{G}rilli, {R}. and {D}elsontro, {T}. and {G}arnier, {J}. and {J}acob, {F}r{\'e}d{\'e}ric and {N}emery, {J}.},
  editor = {},
  language = {{ENG}},
  abstract = {{L}akes and reservoirs are a significant source of atmospheric methane ({CH}4), with emissions comparable to the largest global {CH}4 emitters. {U}nderstanding the processes leading to such significant emissions from aquatic systems is therefore of primary importance for producing accurate projections of emissions in a changing climate. {I}n this work, we present the first deployment of a novel membrane inlet laser spectrometer ({MILS}) for fast simultaneous detection of dissolved {CH}4, ethane ({C}2{H}6) and the stable carbon isotope of methane (delta 13{CH}4). {D}uring a 1-day field campaign, we performed 2{D} mapping of surface water of {L}ake {A}iguebelette ({F}rance). {A}verage dissolved {CH}4 concentrations and delta 13{CH}4 were 391.9 +/- 156.3 nmol {L}-1 and -67.3 +/- 3.4 parts per thousand in the littoral area and 169.8 +/- 26.6 nmol {L}-1 and -61.5 +/- 3.6 parts per thousand in the pelagic area. {T}he dissolved {CH}4 concentration in the pelagic zone was 50 times larger than the concentration expected at equilibrium with the atmosphere, confirming an oversaturation of dissolved {CH}4 in surface waters over shallow and deep areas. {T}he results suggest the presence of {CH}4 sources less enriched in 13{C} in the littoral zone (presumably the littoral sediments). {T}he {CH}4 pool became more enriched in 13{C} with distance from shore, suggesting that oxidation prevailed over epilimnetic {CH}4 production and it was further confirmed by an isotopic mass balance technique with the high-resolution data. {T}his new in situ fast response sensor allows one to obtain unique high-resolution and high-spatial coverage data sets within a limited amount of survey time. {T}his tool will be useful in the future for studying processes governing {CH}4 dynamics in aquatic systems. {H}igh-resolution mapping of surface methane and its isotopic signature enables accurate characterization of aquatic systems and discrimination of biochemical processes at work. {A}t {L}ake {A}iguebelette, this new in situ tool allowed us to conclude that methane present at the surface comes mainly from shallow littoral areas, where sediments, which are a source of methane, are closer to the surface. {D}uring lateral transport of water masses from the littoral zone, the change in isotopic signature reveals that methane oxidation prevails over local in situ production. {C}omparison with previous studies validates the importance of high-resolution measurements (particularly to capture the high variability in the littoral zone) and showed that smaller lakes experience stronger methane isotopic signature changes for a given methane concentration variation. {T}his can be explained by the fact that the smaller lake has a larger littoral-to-total surface area. {T}his new tool will be useful in the nearby future to study the processes governing {CH}4 dynamics in aquatic systems. {F}ast in situ measurements of dissolved methane and its stable carbon isotope{H}igh-spatial resolution mapping of dissolved methane and its stable carbon isotope{I}mproved production/oxidation process identification over discrete sampling},
  keywords = {in situ measurements ; dissolved methane ; isotopic measurements ; biogeochemical process ; limnology ; {FRANCE}},
  booktitle = {},
  journal = {{J}ournal of {G}eophysical {R}esearch : {B}iogeosciences},
  volume = {128},
  numero = {12},
  pages = {e2022{JG}007200 [17 p.]},
  ISSN = {2169-8953},
  year = {2023},
  DOI = {10.1029/2022jg007200},
  URL = {https://www.documentation.ird.fr/hor/fdi:010088809},
}