Fifteen years of marsh flumes: a review of marsh-water column interactions in southeastern USA estuaries

A number of major estuarine studies conducted in the 1960s and '70s addressed the "outwelling hypothesis' by quantifying nutrient and material fluxes between marsh basins and adjacent estuaries or coastal oceans. Although many past and contemporary reviewers of this literature refer to these fluxes as "marsh-estuarine exchanges', none directly quantified interactions between marshes and the inundating water column. Among a large number of process-oriented ecosystem studies conducted in estuaries since that time, several investigators have used flumes to measure marsh-water column interactions. Marsh flume studies conducted at eight sites in the southeastern US are represented, including Louisiana, Georgia, South Carolina, and Virginia. Brackish and salt marshes are represented, from a range of tidal regimes, estuarine types, and stages of ecological maturity. Predicted tidal range was signifiantly related to fluxes of inorganic nutrients, dissolved and particulate organics, and inorganic sediments. Nutrient and organic matter fluxes were positively related to tidal range, with a switch from export (negative flux) to uptake consistently occurring at about 1 m of tidal range. When the flume flux data was divided into geologically young and old marshes, similar patterns of relationships to tidally range were found but the slopes from younger marshes were consistently 1.5 to 3 times greater than those from older marshes. -from Author