Field evidence that shrimp predation regulates meiofauna.

The grass shrimp Palaemonetes pugio, a suspected predator/disturber on meiofauna, and other large natant forms (>2 mm) were selectively excluded from microecosystem tanks for nine months during which time replicability between the tanks was established. Subsequently, shrimp were reintroduced into one of the four tanks via an aquarium and the meiofauna populations monitored in the "shrimp" and control tanks. In the presence of the predator/disturber, total meiofauna, nematode, oligochaete, and polychaete densities were significantly lower than in control tanks. In the presence of the predator/disturber, total meiofauna, nematode, oligochaete, and polychaete densities were significantly lower than in control tanks. Shrimp predation/disturbance significantly reduced meiofauna abundance in this salt marsh habitat but it did not alter the species diversity of the dominant taxon. The meiobenthos displayed characteristics common to other biologically regulated assemblages and our data provide the first field evidence of macrofaunal control of meiofauna community structure.