Abstract. Hypersaline 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) are being buried at rates averaging 21 (± 6), 1.7 (± 0.3), and 1.4 (± 0.3) g m⁻² y⁻¹, respectively, during the previous century in three contrasting HTFs 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 CO₂ influx and emission estimates found during the dry and wet season in the Brazilian HTF, the only site with seasonal CO₂ fluxes measurements, the OC sedimentary profiles over several decades suggests efficient OC burial at all sites. Indeed, the stable isotopes of OC and TN (δ¹³C and δ¹⁵N) along with C : 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 nutrient sink and suggest that coastal HTF ecosystems could be included in the emerging blue carbon framework.

中文翻译：

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高盐滩涂作为重要的蓝色碳系统：来自三个生态系统的案例研究

摘要。高盐滩涂（HTFs）是沿海生态系统，淡水短缺通常发生在红树林上带附近的干旱或半干旱地区，没有重要的河流贡献。在这里，我们估计有机碳（OC），总氮（TN）和总磷（TP）被掩埋的速率平均为21（±6），1.7（±0.3）和1.4（±0.3）g m ^-2  y ^-1在上个世纪，分别采用了三种截然不同的HTF系统，一种在巴西（富营养），另一种在澳大利亚（贫营养）。尽管这些比率低于附近的红树林，盐沼和海草系统的比率，但是考虑到它们的广泛覆盖范围，HTF作为OC，TN和TP汇的重要性可能很高。尽管在巴西HTF（唯一的季节性CO ₂通量测量站点）的干旱和潮湿季节发现了空气-盐下层CO ₂净流入量与排放估算值之间的短期测量变化，但几十年来的OC沉积特征表明有效的OC在所有地点埋葬。事实上，稳定OC和TN（的同位素δ ¹³ C和δ ¹⁵N）以及C：N比率表明，微藻类底栖动物是这些HTF中掩埋OC的主要来源。我们的发现强调了以前未量化的碳以及养分汇，并表明沿海HTF生态系统可以包括在新兴的蓝色碳框架中。