Claris N. Sunjo , Eliot A. Atekwana , Hendratta N. Ali , Henry M. Agbogun , Isaac K. Njilah
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引用次数: 0
Abstract
Tidal creeks are conduits for tide-driven processing and exchange of water and dissolved inorganic carbon (DIC) between the open estuary and mangrove forests. Yet, the sources of DIC, and the role of tidal creeks in the cycling of DIC and its transport to the open water of mangrove estuaries is poorly understood. This study was conducted in a tidal creek in the freshwater tidal zone at the land-estuary boundary of a tropical mangrove estuary. We made 177 measurements of salinity and 80 measurements of geogenic solutes (silica, Ca, Mg), DIC components (partial pressure of CO2 (pCO2), alkalinity and total DIC) and stable isotopes of water (δ18O and δD) and DIC (δ13CDIC). We aimed to determine the sources and the timing of water input into the tidal creek, how the different water sources control input of DIC, and how DIC is cycled through semidiurnal mixed tides and over a diel cycle. The salinity-δ18O relationship indicates two sources of water, while the relationships for salinity-DO, salinity-solute, and salinity-DIC implicated submarine groundwater discharge (SGD) as the source providing the DIC processed and transported to the open estuary. Normalized water level vs. salinity reveals that SGD sourced DIC dominates the water column during tidal ebbing and halfway through tidal flooding. In contrast, freshwater from the open estuary mainly dilutes the solutes and DIC from halfway during tidal flooding to peak high tide. The photocycle, heterotrophic and autotrophic processes are unable to explain the more than 5 times greater than atmospheric pCO2 recorded during the daytime and at low tide. These findings demonstrate that SGD is a significant DIC source in tidal creeks at the land-estuary transition zone which indicate the important role of SGD in the cycling of carbon in the freshwater tidal zones of mangrove estuaries.
期刊介绍:
Marine Chemistry is an international medium for the publication of original studies and occasional reviews in the field of chemistry in the marine environment, with emphasis on the dynamic approach. The journal endeavours to cover all aspects, from chemical processes to theoretical and experimental work, and, by providing a central channel of communication, to speed the flow of information in this relatively new and rapidly expanding discipline.