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High CO 2 evasion during floods in an A ustralian subtropical estuary downstream from a modified acidic floodplain wetland
Author(s) -
Ruiz-Halpern Sergio,
Maher Damien T.,
Santos Isaac R.,
Eyre Bradley D.
Publication year - 2015
Publication title -
limnology and oceanography
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.7
H-Index - 197
eISSN - 1939-5590
pISSN - 0024-3590
DOI - 10.1002/lno.10004
Subject(s) - estuary , tributary , hydrology (agriculture) , environmental science , wetland , salinity , floodplain , surface runoff , groundwater , discharge , groundwater discharge , oceanography , ecology , aquifer , geology , drainage basin , groundwater flow , biology , geotechnical engineering , cartography , geography
Dissolved CO 2 dynamics associated with flooding and postflood recovery were investigated in the lower estuary of the Richmond River and a tributary draining an acidic wetland. Heavy rains (up to 133 mm d −1 ) resulted in large discharge volumes (up to 250 × 10 6 m 3 d −1 ) flushing the estuary in less than a day. Maximum values of the partial pressure of CO 2 ( PCO 2, 2006 Pa or 19,801 μ atm) occurred during the postflood recovery period. HighPCO 2values were related to the transport of floodplain metabolic products via surface runoff and groundwater as well as the low pH (4.22) of waters draining a modified wetland with coastal acid sulphate soils. Aerobic respiration alone could not explain the high concentrations of CO 2 in the estuary and an area of low buffering developed in the 0–20 salinity range.PCO 2was correlated with freshwater discharge in the Richmond River main channel ( R 2 = 0.82; p < 0.05; n = 9) but not in the acidified tributary ( R 2 = 0.17; p > 0.05; n = 7). Air‐water fluxes of CO 2 were at the high end of the range for aquatic systems (maximum 1413 mmol C m −2 d −1 , mean 252 mmol C m −2 d −1 ). This study highlights the large spatiotemporal variability ofPCO 2, the importance of episodic flooding events, the role of adjacent modified acidic wetlands, and the role of groundwater discharge as a source of CO 2 to estuaries. Global estimates of CO 2 air‐water fluxes in estuaries may be under estimated due to the lack of high‐resolution data to capture short‐term episodic events (e.g., flooding), in tropical and subtropical areas.