TY - JOUR
T1 - Carbon dynamics and inconstant porewater input in a mangrove tidal creek over contrasting seasons and tidal amplitudes
AU - Taillardat, Pierre
AU - Ziegler, Alan D.
AU - Friess, Daniel A.
AU - Widory, David
AU - Truong Van, Vinh
AU - David, Frank
AU - Thành-Nho, Nguyễn
AU - Marchand, Cyril
N1 - Publisher Copyright:
© 2018 Elsevier Ltd
PY - 2018/9/15
Y1 - 2018/9/15
N2 - Constraining the contribution of mangrove-derived carbon in tidal creeks is fundamental to understanding the fate of mangrove primary production and the role of mangroves as coastal carbon sinks. Porewater measurements and 24-h time series in a mangrove tidal creek were conducted during the dry and wet season, and over contrasting tidal ranges at the Can Gio Biosphere Reserve, Vietnam. Surface water carbon concentrations (dissolved organic carbon (DOC), dissolved inorganic carbon (DIC), partial pressure of carbon dioxide (pCO2)) and their respective δ13C values were correlated with radon, suggesting that porewater input drives mangrove-derived carbon in the tidal creek. Based on three complementary mixing models, porewater input contributed to about 30% of the water volume and 46% to 100% of DOC and DIC pools in the tidal creek at low tide, with variabilities between seasons and tidal amplitudes. The creek carbon pool was 88% DIC, 6% DOC, and 6% particulate organic carbon (POC). The pCO2 values during the wet season (2973–16,495 μatm) were on average 5-fold higher than during the dry season (584–2946 μatm). This was explained by a potential greater mineralization attributed to higher organic matter availability and residual humidity that stimulate bacterial activity, and by a potential tidal dilution changing the pCO2/DIC ratio as suggested by the Revelle factor. Consequently, average CO2 evasion from the creek was estimated at 327–427 mmolC m−2 d−1 during the wet season and 92–213 mmolC m−2 d−1 during the dry season, using two independent approaches. Tidal amplitude seemed to influence porewater input and its carbon loads, with a higher contribution during frequent and high tidal amplitudes (symmetric). However, the highest input occurred in a tidal cycle which was preceded by tidal cycle of low amplitude (asymmetric). We explain this ambiguity by the influence of both, rapid water turnover intensifying porewater exchange, and long water residence time enhancing carbon load in porewater.
AB - Constraining the contribution of mangrove-derived carbon in tidal creeks is fundamental to understanding the fate of mangrove primary production and the role of mangroves as coastal carbon sinks. Porewater measurements and 24-h time series in a mangrove tidal creek were conducted during the dry and wet season, and over contrasting tidal ranges at the Can Gio Biosphere Reserve, Vietnam. Surface water carbon concentrations (dissolved organic carbon (DOC), dissolved inorganic carbon (DIC), partial pressure of carbon dioxide (pCO2)) and their respective δ13C values were correlated with radon, suggesting that porewater input drives mangrove-derived carbon in the tidal creek. Based on three complementary mixing models, porewater input contributed to about 30% of the water volume and 46% to 100% of DOC and DIC pools in the tidal creek at low tide, with variabilities between seasons and tidal amplitudes. The creek carbon pool was 88% DIC, 6% DOC, and 6% particulate organic carbon (POC). The pCO2 values during the wet season (2973–16,495 μatm) were on average 5-fold higher than during the dry season (584–2946 μatm). This was explained by a potential greater mineralization attributed to higher organic matter availability and residual humidity that stimulate bacterial activity, and by a potential tidal dilution changing the pCO2/DIC ratio as suggested by the Revelle factor. Consequently, average CO2 evasion from the creek was estimated at 327–427 mmolC m−2 d−1 during the wet season and 92–213 mmolC m−2 d−1 during the dry season, using two independent approaches. Tidal amplitude seemed to influence porewater input and its carbon loads, with a higher contribution during frequent and high tidal amplitudes (symmetric). However, the highest input occurred in a tidal cycle which was preceded by tidal cycle of low amplitude (asymmetric). We explain this ambiguity by the influence of both, rapid water turnover intensifying porewater exchange, and long water residence time enhancing carbon load in porewater.
KW - CO efflux
KW - Dissolved carbon
KW - Mixing model
KW - Porewater input
KW - Stable isotopes
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U2 - 10.1016/j.gca.2018.06.012
DO - 10.1016/j.gca.2018.06.012
M3 - Article
AN - SCOPUS:85049322242
SN - 0016-7037
VL - 237
SP - 32
EP - 48
JO - Geochimica et Cosmochimica Acta
JF - Geochimica et Cosmochimica Acta
ER -