Dynamics and Feeding Activity of High-Density Aggregations of Oreaster reticulatus (Echinodermata: Asteroidea) in a Sand Patch Habitat

Abstract

Aggregations of Oreaster reticulatus (L.) in a large sand paich amid an offshore seagrass bed (Syringodium filiforme) off St. Croix (US Virgin Islands) were characterized by protracted fronts of high density (2-7 individuaIs m-2). Fronts migrated across the sand patch at approximately 7 m d-1 and were refracted and deflected at the grassbed border. Intensive microphagous feeding effected a 2-fold turnover of surface sediments in the area covered by a front during 24 h, resulting in a marked decrease in chlorophyll concentration. Conspicuously mounded feeding sites were uniformly dispersed in the wake of the fronts. Overlap among feeding sites was high indicating intraspecific competition for food.