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

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 CO 2 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 CO 2 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 DOC, 8.1 ± 6.2 TgC yr −1 DIC, and 0.7 ± 0.6 Tmol yr −1 TA. Small catchments (

Bibliographic Information