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Mangroves as a Source of Greenhouse Gases to the Atmosphere and Alkalinity and Dissolved Carbon to the Coastal Ocean: A Case Study From the Everglades National Park, Florida
Author(s) -
Reithmaier Gloria M. S.,
Ho David T.,
Johnston Scott G.,
Maher Damien T.
Publication year - 2020
Publication title -
journal of geophysical research: biogeosciences
Language(s) - English
Resource type - Journals
eISSN - 2169-8961
pISSN - 2169-8953
DOI - 10.1029/2020jg005812
Subject(s) - alkalinity , dissolved organic carbon , mangrove , greenhouse gas , environmental science , carbon dioxide , carbon sink , environmental chemistry , total inorganic carbon , carbon fibers , sink (geography) , total organic carbon , hydrology (agriculture) , chemistry , oceanography , ecology , climate change , geology , geography , materials science , cartography , geotechnical engineering , organic chemistry , composite number , composite material , biology
Most research evaluating the potential of mangroves as a sink for atmospheric carbon has focused on carbon burial in sediments. However, the few studies that have quantified lateral exchange of carbon and alkalinity indicate that the dissolved carbon and alkalinity export may be several‐fold more important than burial. This study aims to investigate rates and drivers of alkalinity, dissolved carbon, and greenhouse gas fluxes of the mangrove‐dominated Shark River estuary located in the Everglades National Park in Florida, USA. Spatial surveys and 29‐hr time series were conducted to assess total alkalinity (TAlk), organic alkalinity (OAlk), dissolved inorganic carbon (DIC), dissolved organic carbon (DOC), carbon dioxide (CO 2 ), methane (CH 4 ), and nitrous oxide (N 2 O) dynamics. Dissolved carbon and greenhouse gas concentrations were coupled to porewater input, which was examined using radon‐222. Shark River was a source of CO 2 (92 mmol/m 2 /day), CH 4 (56 μmol/m 2 /day), and N 2 O (2 μmol/m 2 /day) to the atmosphere. Dissolved carbon export (DIC = 142 mmol/m 2 /day, DOC = 39 mmol/m 2 /day, normalized to mangrove area) was several‐fold higher than previously reported carbon burial rates in the study area (~28 mmol/m 2 /day). The majority of the DIC was exported as TAlk (97 mmol/m 2 /day), which remains dissolved in the ocean for millennia and, therefore, represents a long‐term sink for atmospheric carbon. By integrating our results with previous studies, we argue that alkalinity, dissolved carbon, and greenhouse gas fluxes should be considered in future blue carbon budgets.