Carbon transport between a euhaline vegetated marsh in South Carolina and the adjacent tidal creek: contributions via tidal inundation, runoff and seepage

Abstract

Exchange of organic carbon (DOC and POC) between a euhaline vegetated marsh and an adjacent tidal creek (North Inlet, South Carolina) was studled on 40 tidal cycles between 15 Apr 1983 and 19 Jun 1984. A flume was utilized to evaluate the role of the vegetated marsh in processing carbon during tidal inundation and a drainage weir was used to measure export from the marsh via runoff and seepage during low tide exposure (including storm events). Mean flood water DOC concentrations varied seasonally from 3.1 to 18.6 ppm. Maximum concentrations were observed in late w n t e r and early spring, and were associated with freshwater discharge from the adjacent forest. There was a stahstically insignificant (a = 0.05) DOC import to the vegetated marsh during tidal inundation of 2.9 g C m-' yr-l. Mean flood water POC concentrations varied seasonally between 0.7 and 4.6 ppm with the highest values observed during the summer The vegetated marsh was a sink for POC during tidal inundation except when storm events occurred on the ebb tide. There was a statistically significant (a = 0.05) import of POC to the vegetated marsh of 83.3 g C m-2 yr-' with the largest removal rate observed when the tidal water resided on the low marsh (tall Spartina alterniflora) Exports of DOC and POC from the marsh via runoff and seepage d u r ~ n g low tide exposure (including rain events) were 36.2 g C m-' yr-l and 30.6 g C m-' yr-' The annual net exchange (inports-exports) of carbon between the marsh and the adjacent tidal creek suggests thls system is a sink for POC and a source for DOC, the total organic carbon exchange being negligible. This study implies the vegetated marsh may not be the source of carbon which was found to outwell from this and other marsh-estuarine systems.