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Large Porewater-Derived Carbon Outwelling Across Mangrove Seascapes Revealed by Radium Isotopes4.44 MB
Published (Version of record)CC BY-NC V4.0, Open Access
Published (Version of record)CC BY-NC V4.0, Open
Journal article
Large Porewater‐Derived Carbon Outwelling Across Mangrove Seascapes Revealed by Radium Isotopes
Journal of geophysical research. Oceans, Vol.129(9)
09/2024
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Abstract
Mangrove-dominated coastlines have high carbon sequestration capacity, but it remains unclear whether tidally outwelled carbon is transformed within the coastal ocean or exported offshore. Here, we used radium isotopes (224Ra and 223Ra) to investigate carbon outwelling in two mangrove seascapes in Brazil across multiple spatial scales. We sampled porewaters to define the source composition, mangrove creek waters to resolve tidal cycles, and cross-shelf transects to trace outwelling in coastal seascapes. Radium isotopes were positively correlated with dissolved inorganic (DIC), organic (DOC) and particulate organic (POC) carbon across the seascapes. DIC was the primary form of carbon (mean ± SD), representing 85% of the total carbon pool as bicarbonate (75 ± 11%), carbonate (6 ± 5%), and CO2 (4 ± 9%). DOC and POC accounted for 10 ± 6% and 5 ± 6% of total carbon, respectively. Although mangrove waters emitted CO2 to the atmosphere (38–143 mmol m−2 d−1), both bays and continental shelves were a CO2 sink (−2.5 to −0.5 mmol m−2 d−1) associated to chlorophyll-a enrichments (r2 = 0.86). Total carbon outwelled from mangroves were 3–4 times higher than soil carbon burial at both mangrove sites. Bicarbonate export (27–72 mmol m−2 d−1) to the continental shelf was the major fate of carbon outwelling, more than doubling the perceived capacity of mangrove soil to sequester carbon. Hence, disregarding outwelling as a blue carbon sink mechanism would lead to underestimated assessments of how mangroves capture CO2 and help to mitigate climate change.
Details
- Title
- Large Porewater‐Derived Carbon Outwelling Across Mangrove Seascapes Revealed by Radium Isotopes
- Creators
- Alex Cabral - University of GothenburgGloria M. S. Reithmaier - University of GothenburgYvonne Y. Y. Yau - University of GothenburgLuiz C. Cotovicz - Leibniz Institute for Baltic Sea ResearchJoão Barreira - Universidade Federal FluminenseBárbara Viana - Universidade Federal de Santa CatarinaJuliana Hayden - Universidade Federal de Santa CatarinaSteven Bouillon - KU LeuvenNilva Brandini - Universidade Federal FluminenseVanessa Hatje - Universidade Federal da BahiaCarlos E. de Rezende - State University of Norte FluminenseAlessandra L. Fonseca - Universidade Federal de Santa CatarinaIsaac R. Santos - University of Gothenburg
- Publication Details
- Journal of geophysical research. Oceans, Vol.129(9)
- Publisher
- Wiley-Blackwell Publishing, Inc.
- Grant note
- Vetenskapsrådet. Grant Numbers: 2019-03930, 2020-00457
- Identifiers
- 991013219713102368
- Copyright
- © 2024 The Author(s). This is an open access article under the terms of the Creative Commons Attribution-NonCommercial License.
- Academic Unit
- Faculty of Science and Engineering
- Language
- English
- Resource Type
- Journal article