Estuarine canal estate waters: Hotspots of CO 2 outgassing driven by enhanced groundwater discharge?
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Marine Chemistry, ISSN: 0304-4203, Vol: 167, Page: 82-92
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- Repository URL:
- https://epubs.scu.edu.au/esm_pubs/2424; https://works.bepress.com/isaac_santos/60; https://works.bepress.com/damien_maher/22
- Earth and Planetary Sciences; Chemistry; Environmental Science; Coastal hydrology; permeable sediments; floodplain; greenhouse gases; Moreton Bay; mangrove; 040200; Environmental Sciences
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Increased water-to-air carbon dioxide fluxes are a potentially important, but as yet unquantified, consequence of canal estate developments in estuaries surrounded by coastal wetlands. We used detailed p CO 2 and radon ( 222 Rn, a submarine groundwater discharge tracer) surveys to investigate whether water-to-air CO 2 fluxes were enhanced in residential canal systems, and whether groundwater exchange may drive p CO 2 distribution. Observations were performed along 300 km of canals, rivers, estuaries, and coastal embayments from the Gold Coast (Queensland, Australia), one of the largest estuarine canal systems globally. Overall, residential canal estate waters were supersaturated in CO 2 with p CO 2 ranging from 372 to 3639 μatm and 434 to 3080 μatm in the dry and wet season surveys, respectively. p CO 2 usually increased in areas of reduced connectivity (i.e., poorly flushed dead end canals). A stronger correlation between 222 Rn and p CO 2 than between dissolved oxygen and p CO 2 implied that groundwater seepage (not pelagic respiration) was the major driver p CO 2 supersaturation within the canal system. Average area-weighted water-to-air CO 2 fluxes within canals were 34 and 67 mmol C m −2 d −1 during the dry and wet seasons respectively. When upscaled to the entire Gold Coast estuarine system, residential canal contributed 46% and 56% of the total flux of CO 2 to the atmosphere during the dry and wet seasons, respectively. These results imply that areas that were previous atmospheric carbon sinks (i.e. coastal wetlands) have become sources of CO 2 to the atmosphere since the development of residential canal estates.