Multi-species algal balls and potentially imprisoned fauna: an unusual benthic assemblage

Abstract

Unattached algae which form balls are normally reported as being composed of a single species. We report both monospecific algal balls and multispecies assemblages with up to four species providing major structural components from the Caribbean at Los Roques Archipelago, Venezuela. Many of the multispecies balls possessed a cavity surrounded by thick walls of sediment-impregnated algal filaments. Cavity volume was positively related to the length of algal balls. The hollow algal balls were remarkable in that they often contained, and likely imprisoned, a variety of invertebrates, including several species of polychaetes, sipunculans, molluscs, and crustaceans. Relationships between cavity volume and either number or volume of fauna were non-significant. Faunal associates, if in fact imprisoned, are likely to benefit from reduced predation but may be subject to limited food supply, crowding, oxygen deprivation, and limited reproductive opportunities.