Are mangrove carbon exports old or modern? A multiple radio- and stable isotope analysis

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dc.contributor.authorMaher, DTen_AU
dc.contributor.authorCall, Men_AU
dc.contributor.authorSantos, IRen_AU
dc.contributor.authorSanders, CJen_AU
dc.contributor.authorSchulz, KGen_AU
dc.contributor.authorJenkinson, Aen_AU
dc.contributor.authorJacobsen, GEen_AU
dc.date.accessioned2022-08-30T22:48:21Zen_AU
dc.date.available2022-08-30T22:48:21Zen_AU
dc.date.issued2015-07-09en_AU
dc.date.statistics2022-01-12en_AU
dc.description.abstractAround half of the carbon fixed by mangroves globally is unaccounted for in current carbon budgets. Much of the "missing" carbon may be associated with the underground respiration of organic matter which is exported via groundwater flow. In mangrove systems, crabs burrows and macropores created by dead roots may expose buried carbon to changes in redox conditions, and potentially lead to the remineralisation and export of old carbon (100's to 1 000's of years old). This has important implications for the global "blue carbon" stocks in mangroves. To assess whether old or modern carbon is exported, we measured Δ14C-DlC concentrations in a mangrove creek hourly over a tidal cycle. In addition we measured groundwater radiogenic geochemical tracers (223Ra 224Ra, 226Ra and 222 Rn), along with continuous measurements of δ13C-C02 using a cavity ring down spectrometer. There was significant export of DIC from the mangrove system that had a δ13C value matching mangrove organic matter. The export was driven by underground carbon respiration and subsequent export via groundwater as determined via radiogenic tracers. Interestingly, the age of the exported DIC as determined by a mixing and mass balance model of measured Δ14c-DIC values, was 100's of years old, suggesting that the timescale used to estimate long term carbon burial in mangroves should be longer than what is currently used (typically buried carbon > 30 years old is considered 'Ipermanent"). The results also suggests that there might be at least two distinct pathways for carbon export from mangroves - 1 ) Remineralisation of 'Young" shallow surface organic matter which is lost directly to the atmosphere as C02 within the mangrove forest, and 2) Remineralisation of "old" buried carbon which is exported via lateral groundwater export to the coastal ocean. Measuring these pathways in conjunction will help to adequately constrain carbon budgets and determine the long term burial capacity of mangroves.en_AU
dc.description.sponsorshipAustralian Nuclear Science and Technology Organisation (ANSTO)en_AU
dc.identifier.citationMaher, D., Call, M., Santos, I., Sanders, C., Schulz, K., Jenkinson, A., & Jacobsen, G. (2015). Are mangrove carbon exports old or modern? A multiple radio- and stable isotope analysis. Presentation to the 13th Australasian Environment Isotope Conference (AEIC), Sydney, 8-10th July 2015. In 13th Australasian Environmental Isotope Conference, Sydney, Australia, 8-10th July 2015, Programme and Abstracts, (pp. 72).en_AU
dc.identifier.conferenceenddate10 July 2015en_AU
dc.identifier.conferencename13th Australasian Environment Isotope Conference (AEIC)en_AU
dc.identifier.conferenceplaceSydney, Australiaen_AU
dc.identifier.conferencestartdate8 July 2015en_AU
dc.identifier.pagination72en_AU
dc.identifier.urihttps://apo.ansto.gov.au/dspace/handle/10238/13692en_AU
dc.language.isoenen_AU
dc.publisherUniversity of New South Wales and Australian Nuclear Science and Technology Organisationen_AU
dc.subjectMangrovesen_AU
dc.subjectCarbonen_AU
dc.subjectStable isotopesen_AU
dc.subjectRadioisotopesen_AU
dc.subjectMangrovesen_AU
dc.subjectGround wateren_AU
dc.subjectCarbon 14en_AU
dc.titleAre mangrove carbon exports old or modern? A multiple radio- and stable isotope analysisen_AU
dc.typeConference Presentationen_AU
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