Distribution and structure of shallow subterranean aquatic arthropod communities in the parklands of Washington, D.C.

Abstract

Over 150 sites in the parklands of southeast Washington, D.C., were examined for the presence of inhabitants of seepage springs and associated groundwater habitats—the hypotelminorheic. Three species predominated—the isopod Caecidotea kenki and the amphipods Crangonyx shoemakeri and Stygobromus tenuis sensu lato. C. shoemakeri and Stygobromus rarely occurred together, in part because of different habitat preferences. Based on stepwise logistic regression, Stygobromus preferred cooler water with lower specific conductance, and Crangonyx preferred warmer waters. Seven environmental parameters—temperature, temperature deviation from average, radon, specific conductance, DO, pH, and depth of clay layer—could not distinguish between inhabited and uninhabited sites, suggesting that most sites studied are potential habitats. Nearest neighbour analysis of Stygobromus sites showed them to be significantly farther apart than either Caecidotea or Crangonyx sites, suggesting that they are limited in dispersal ability. Overall, all three species appear to form meta-populations, and so the protection of all sites, not just currently occupied sites, is important.