Community structure ofthe macrobenthos associated with seagrass of the Indian River estuary, Florida

Effects of predation on community structure of the macrobenthos associated with dense stands of Halodule wrightii in the Indian River estuary of east central Florida were studied using cages. The three study sites represented a stress gradient of temperature, salinity and tide. Major changes, as affected by caging, were measured byspecies diversity, species evenness and species richness, showing opposite effects at the sites representing two extremes of the environmental stress gradient. At the site characterized by a physically unstable and unpredictable environment, the increases of several species within the cage were in accord with predator-prey theory. At the other extreme, where the environment was more physically stable and predictable, increases in diversity of caged macrofauna were inconsistent with current hypotheses of biological interactions affecting community structure.