Hypersaline tidal flats as important “blue carbon” systems: a case study from three ecosystems

Brown, Dylan R.; Marotta, Humberto; Peixoto, Roberta B.; Enrich-Prast, Alex; Barroso, Glenda C.; Soares, Mario L. G.; Machado, Wilson; Pérez, Alexander; Smoak, Joseph M.; Sanders, Luciana M.; Conrad, Stephen; Sippo, James Z.; Santos, Isaac R.; Maher, Damien T.; Sanders, Christian J.

page2528Hypersaline tidal flats (HTFs) are coastal ecosystems with freshwater deficits often occurring in arid or semi-arid regions near mangrove supratidal zones with no major fluvial contributions. Here, we estimate that organic carbon (OC), total nitrogen (TN) and total phosphorus (TP) were buried at rates averaging 21 (inline-formula±6), 1.7 (inline-formula±0.3) and 1.4 (inline-formula±0.3) inline-formula M4inlinescrollmathml unit normal g nobreak0.125em normal m - normal 2 nobreak0.125em normal yr - normal 1 50pt15ptsvg-formulamathimgd56bb1a870d4b5859c1aa633400a5bee bg-18-2527-2021-ie00001.svg50pt15ptbg-18-2527-2021-ie00001.png , respectively, during the previous century in three contrasting HTF systems, one in Brazil (eutrophic) and two in Australia (oligotrophic). Although these rates are lower than those from nearby mangrove, saltmarsh and seagrass systems, the importance of HTFs as sinks for OC, TN and TP may be significant given their extensive coverage. Despite the measured short-term variability between net air–saltpan inline-formulaCO2 influx and emission estimates found during the dry and wet season in the Brazilian HTF, the only site with seasonal inline-formulaCO2 flux measurements, the OC sedimentary profiles over several decades suggest efficient OC burial at all sites. Indeed, the stable isotopes of OC and TN (inline-formulaδ13C and inline-formulaδ15N) along with inline-formulaC:N ratios show that microphytobenthos are the major source of the buried OC in these HTFs. Our findings highlight a previously unquantified carbon as well as a nutrient sink and suggest that coastal HTF ecosystems could be included in the emerging blue carbon framework.

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Brown, Dylan R. / Marotta, Humberto / Peixoto, Roberta B. / et al: Hypersaline tidal flats as important “blue carbon” systems: a case study from three ecosystems. 2021. Copernicus Publications.

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