Salt-marsh benthic invertebrates: Small-scale patterns of distribution and abundance

Monitoring of small-scale distribution patterns of benthic invertebrates has demonstrated distinct trends in faunal abundances with position relative to individual culms of saltmarsh cordgrass,Spartina alterniflora, at Tar Landing Bay Marsh, near Morehead City, North Carolina. Samples containing culms ofSpartina yielded significantly higher abundances (at least three times) than did samples without them. Among common species, onlyNereis succinea did not show this effect. Matrix-arranged and randomly placed sets of samples have confirmed a positive relationship between cross-sectional area of culms in a sample (at the sediment-water interface) and contained numbers of macrofauna, juvenile macrofauna and meiofauna. These patterns occurred despite a decreased volume of sediment in samples containing culms. Heightened abundances of benthic invertebrates associated with structural elements at the sediment-water interface may result from either nonrandom recruitment (either active via recruit selectivity or passive through hydrogeographic effects of culms) or differential post-recruitment mortality (resulting from inhibition of epibenthic predators or from variable habitat quality).