Small wetland-fringed estuaries deliver disproportionately large carbon loads to the ocean

IF 3.8 1区 地球科学 Q1 LIMNOLOGY
Gloria M. S. Reithmaier, Damien T. Maher, Ceylena Holloway, Rogger E. Correa, Isaac R. Santos
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Abstract

Previous estimates of dissolved carbon export from estuaries focused on larger systems in the Northern Hemisphere, with little data for smaller tropical estuaries often fringed by intertidal wetlands. We investigated lateral export (outwelling) and transformation rates of dissolved organic carbon (DOC), dissolved inorganic carbon (DIC), and total alkalinity (TA) as well as CO2 emissions from 18 diverse Australian estuaries. Most estuaries acted as net sources for DOC (72%), DIC (83%), and TA (50%). On average, estuaries exported 120 ± 55 and 344 ± 150 mmol m−2 catchment yr−1 DOC and DIC, respectively. Estuarine CO2 emissions (33 ± 20 mmol m−2 estuary d−1) equalled 13% ± 16% of the dissolved lateral carbon export. Carbon export positively correlated with runoff, rain, and intertidal wetland cover, and negatively correlated with estuary and catchment area. Mangroves and saltmarshes cover < 1% of all catchments but can contribute 46% ± 11% of the DOC and 67% ± 13% of the DIC exported to the ocean. Upscaling our observations, Australian estuaries export 2.8 ± 2.2 TgC yr−1 DOC, 8.1 ± 6.2 TgC yr−1 DIC, and 0.7 ± 0.6 Tmol yr−1 TA. Small catchments (< 10 ha) making up 70% of all estuaries and accounting for 18% of the total freshwater flow provided 27% to the total dissolved carbon export. Overall, small tropical estuaries fringed by highly productive intertidal wetlands are hotspots of carbon exports and should be considered in marine carbon budgets.

Abstract Image

小型湿地河口向海洋排放的碳负荷过大
以前对河口溶解碳输出的估算主要集中在北半球较大的系统,而对通常被潮间带湿地环绕的较小热带河口的数据则很少。我们调查了澳大利亚 18 个不同河口的溶解有机碳(DOC)、溶解无机碳(DIC)和总碱度(TA)的横向输出(外流)和转化率以及二氧化碳排放量。大多数河口都是溶解有机碳(72%)、溶解无机碳(83%)和总碱度(50%)的净来源。平均而言,河口输出的 DOC 和 DIC 分别为 120 ± 55 和 344 ± 150 mmol m-2 流域年-1。河口二氧化碳排放量(33 ± 20 mmol m-2 河口年-1)相当于溶解侧碳排放量的 13% ± 16%。碳输出与径流、降雨和潮间带湿地覆盖呈正相关,与河口和集水区呈负相关。红树林和盐沼覆盖了所有集水区的 1%,但却贡献了 46% ± 11% 的 DOC 和 67% ± 13% 的 DIC 排放到海洋中。根据我们的观测结果,澳大利亚河口每年输出 2.8 ± 2.2 TgC 的 DOC、8.1 ± 6.2 TgC 的 DIC 和 0.7 ± 0.6 Tmol 的 TA。小型集水区(< 10公顷)占所有河口的70%,占淡水总流量的18%,提供了27%的溶解碳输出总量。总体而言,由高产潮间带湿地环绕的小型热带河口是碳输出的热点地区,应在海洋碳预算中予以考虑。
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来源期刊
Limnology and Oceanography
Limnology and Oceanography 地学-海洋学
CiteScore
8.80
自引率
6.70%
发文量
254
审稿时长
3 months
期刊介绍: Limnology and Oceanography (L&O; print ISSN 0024-3590, online ISSN 1939-5590) publishes original articles, including scholarly reviews, about all aspects of limnology and oceanography. The journal''s unifying theme is the understanding of aquatic systems. Submissions are judged on the originality of their data, interpretations, and ideas, and on the degree to which they can be generalized beyond the particular aquatic system examined. Laboratory and modeling studies must demonstrate relevance to field environments; typically this means that they are bolstered by substantial "real-world" data. Few purely theoretical or purely empirical papers are accepted for review.
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