Studies on the Littoral Seaweed Epifauna of St Croix Island 2. Composition and Summer Standing Stock

The fauna associated with the littoral seaweeds of St Croix Island has been investigated in terms of numbers and biomass (grams and kilojoules). The seaweeds support an abundant and diverse epifauna dominated by crustaceans, nematodes, annelids, molluscs and mites. The summer standing stock of epifauna from the seaweeds occurring in three different metre wide vertical strips of shore was determined and found to tota 2,1— 4,6 x 10⁶ individuals (equivalent to 85—117 g dry mass or 1,2— 1,7 x 10³ kJ). The nature of the seaweed microenvironment influences the epifauna and algal turfs and tufted seaweeds supported more epifauna than seaweeds with flattened thalli. A model depicting feeding relationships and the role of seaweed epifauna in the littoral zone is given and suggests that epifauna feed on detritus, plankton, algae or other epifauna and are in turn preyed upon, selectively or non selectively, by littoral macrofauna and transient predators.