Salt Marsh Values: Retrospection from the end of the Century

Abstract

Two of the greatest problems in coastal waters are eutrophicaton and rapid decline in populations of important fish species. Salt marshes are important in combating both these problems. A paradigm for salt marsh function: marshes import inorganic nutrients and export organic nutrients and, as a result, grow fish. As ground and tidal water flow through salt-water wetlands, plants, bacteria and algae produce or transform the organic matter of the food chain that supports fish and shellfish populations. While salt marshes modify the principal plant nutrients, N and P, some of the pathways result in removal of nutrients from biologically active systems. Nitrogen is removed primarily either by being trapped in refractory organic matter that contributes to marsh maintenance through accretion or through loss to the atmosphere (as N₂) by denitrification. Salt marshes along the Atlantic coast of the United States have changed during the past century; the number of hectares has declined and the nutrient loading per hectare has increased. We examine data on the correlation between fish catch and various marsh features from Long Island, New York in 1880. We review research on the ways salt marshes reduce both the level and rate of eutrophication of coastal waters by intercepting nitrate in discharging groundwater. Finally, we consider how these functions have changed with the decrease in area of salt marshes along the Atlantic coast from Georgia to Maine.