Organic carbon fluxes between a high marsh and estuary, and the inapplicability of the Outwelling Hypothesis

Tidal fluxes of total (TOC), dissolved (DOC) and suspended particulate (POC) organic carbon were measured between a high, Sarcocornia-Chenolea salt marsh and Kariega estuary, South Africa.Fluxes were measured over 42 tides, through four (7 to 14 d) sampling periods.The marsh showed an annual export of TOC of + l 6 g C m-2 yr.', with 80% of this occurring in dissolved form.The export was equivalent to 6% of the aerial macrophyte production of the marsh.In both absolute terms, and relative to macrophyte production, the fluxes were simllar to those reported for hlgh elevation, Spartina patens and Distichlis spicata marshes on the east coast of the USA.They were, however, an order of magnitude smaller than for most low, Spartina dlterniflora marshes.A carbon budget developed for the Kariega marsh showed that respiration (mainly by the sediments and to a lesser extent by resident crabs) accounted for 7 0 % of marsh production, leaving 30% for burial or export to the estuary.We speculate that the small export was a funct~on of the high elevation of the marsh, and that the Outwelling Hypothesis may be less applicable to high than low marshes.