ORGANIC-CARBON FLUXES BETWEEN A HIGH MARSH AND ESTUARY, AND THE INAPPLICABILITY OF THE OUTWELLING HYPOTHESIS

Tidal fluxes of total (TOC), dissolved (DOG) and suspended particulate (POC) organic carbon were measured between a high, Sarcocornia- Cheno lea salt marsh and Kariega estuary, South Africa. Fluxes were measured over 42 tides, through four (7 to 14 d) sampling periods. The marsh s howed an annual export of TOC of +16 gC m(-2) yr(-1), with 80% of this occurring in dissolved form. The export was equivalent to 6% of the a erial macrophyte production of the marsh. In both absolute terms, and relative to macrophyte production, the fluxes were similar to those re ported for high elevation, Spartina patens and Distichlis spicata mars hes on the east coast of the USA. They were, however, an order of magn itude smaller than for most tow, Spartina alterniflora marshes. A carb on budget developed for the Kariega marsh showed that respiration (mai nly by the sediments and to a lesser extent by resident crabs) account ed for 70% of marsh production, leaving 30% for burial or export to th e estuary. We speculate that the small export was a function of the hi gh elevation of the marsh, and that the Outwelling Hypothesis may be l ess applicable to high than low marshes.