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.

Nitrogen exchange between a portion of vegetated salt marsh and the adjoining creek

“…As in the present study (Fig. 8), both Lee (1979) and Wolaver et al ( 1983) found a correlation between uptake by the marsh and nutrient concentrations in the flooding water. These past studies and present results suggest that the seasonal pattern of inorganic nitrogen import is more dependent on the concentration of nutrients in water flooding the marsh than on the seasonal demand of primary producers in the marsh.…”

“…The net result was a loss of nitrogen from the marsh to the creek dominated by dissolved organic nitrogen export during inundation and drainage (Table 2). Previous exchange studies on the marsh surface indicated similar results for inorganic nitrogen (Lee 1979;Wolaver et al 1983), but seasonal patterns of exchange did vary among sites. A Virginia mesohaline marsh (Wolaver et al 1983) had peak imports of inorganic nitrogen during early spring and fall, apparently related to elevated concentrations of inorganic nitrogen flooding the marsh because of increased agricultural activities.…”

“…The rate of rainfall (2.25 cm over 1.28 h) during the 20 November 1983 sampling was two times higher than any other rain sampling (Table 4). Others have also reported rainstorms causing episodic exports of particulate carbon from marshes during low tide (Chalmers et al 1985;Wolaver and Spurrier 1988).…”

“…Biogeochemical cycling in each of these subsystems is probably quite diverse, and their separate roles in controlling overall import-export characteristics have received little attention. A few studies have attempted to identify and quantify exchanges between the vegetated portion of the marsh and the adjacent tidal creeks (Agosta 1985;Jordan and Correll 1985;Lee 1979;Welsh 1980;Wolaver et al 1983).…”

Shifts in seston characteristics after inundation of a European coastal salt marsh

“…It has been found that these episodic events may result in a pulse of POM suspended in the marsh runoff (Chalmers et al 1985;Wolaver and Spurrier 1988). Roman and Daiber (1989) noticed the presence of plant fragments in the ebbtide water under these circumstances and attributed it to vigorous flushing and erosion of the marsh surface.…”