Oreaster reticulatus was studied in eight populations inhabiting shallow-water grassbeds and/or sand bottoms off Carriacou and Union Island in the Grenadines, and off St. Croix in the U.S. Virgin Islands (Caribbean). The sea star is fundamentally an omnivorous, microphagous substratum grazer: grassblades and/or surface sediments are accumulated beneath the disc by tube feet, and associated micro-organisms and detritus are ingested and digested by extraoral eversion of the cardiac stomach. Substratum grazing involves minimal foraging effort; however, the low concentration of particulate food resources necessitates frequent feeding. O. reticulatus also has a limited capacity for herbivory and can hydrolyze soluble algal cell contents. Opportunistic predation and scavenging of macrofauna may provide an important nutritional supplement, although capturable prey or carrion are generally unavailable or inaccessible to the sea star. Marked differences in individual size, storage and reproductive capacity among neighboring populations of O. reticulatus are attributed to differences in the quality and/or quantity of food resources. Intraspecific competition may limit productivity, particularly in isolated sand patches containing dense and extremely aggregated populations.

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