Aquatic macroinvertebrates in an irregularly flooded salt marsh: diversity and seasonal variation

The aquatic macroinvertebrate community structure in a coastal Virginia salt marsh was investigated. Sixteen samples were taken weekly from 2 different sites on Smith Island, Virginia, from April to mid-October 1982. Bimonthly samples were taken during the months of March and November, due to low density of organisms and reduced growth rates at these times. A total of 46 macroinvertebrate taxa (including larvae of Aedes sollicitans, Culicoides furens, Chrysops spp. and Tabanus spp.) were collected, with 17 occurring in at least 5% of the samples, indicating a relatively diverse fauna. Temporal changes in the macroinvertebrate community could not be attributed to the wide fluctuations observed in the physical environment except during extremes. Seasonal changes in the community were attributed to cycling due to individual life cycles of the resident organisms and drying and flooding of the marsh. Species diversity remained high throughout the summer months and was only reduced drastically during drought periods. Fast recolonization of prey species resulted in higher densities at the site with most severe conditions (highest frequency of drying). This was thought to be due to predator elimination caused by drying.