The effects of marsh edge and surface elevation on the distribution of salt marsh infauna and prey availability for nekton predators

Abstract

The relative importance of edge and elevation on infaunal distribution patterns within an intertidal collecting infauna on the nonvegetated intertidal and within the marsh at tina Iterniflora salt marsh was examined by distances of one, three., five., and ten meters from the marsh edge. During most of the year,, densities of most polychaetes and crustaceans within marsh vegetation were highest one meter from the marsh edge compared with densities farther from the marsh e ' dge. Distributions of surface-dwelling infauna had the strongest relationship with marsh edge; whereas, some subsurface feeders were not affected by proximity to edge. Multivariate analysis of covariance suggested that densities of overall infauna were consistently related to marsh edge throughout the year even after accounting for elevation effects. The relationship between infaunal abundance and surface elevation was Significant only during the early spring, mid-summer, and late fall. These data suggest that edge effects influence infaunal distributions more than elevation within the salt marsh. The relative value of the marsh surface and associated intertidal infaunal populations to predators was examined in two laboratory experiments (in May and August,, 1995). Growth comparisons were made of several common marsh etfferus),, and gulf killffish ( undulus dis that were allowed to forage for two weeks on sediments from three different microhabitats: nonvegetated intertidal, marsh one meter from the edge, and marsh ten meters from the edge. Growth rates were not significantly different among microhabitats, but in each experiment, growth rates were less than those reported in the literature for wild populations. Thus, predator growth appeared to be food-hmited in experimental chambers, and growth rates were not an accurate