SOUTH AFRICAN PELAGIC GOOSE BARNACLES (CIRRIPEDIA, THORACICA): SUBSTRATUM PREFERENCES AND INFLUENCE OF PLASTIC DEBRIS ON ABUNDANCE AND DISTRIBUTION

Twenty-two South African shores were surveyed for stranded debris colonized by goose barnacles. The most frequently colonized substrata were kelp (Ecklonia maxima) and plastic, comprising 33.1 and 29.0% of total colonized items, respectively. Four goose barnacle species showed significant preferences for specific substrata: Dosima fascicularis for feathers; Lepas anserifera for rubber sandals; L. pectinata for the shells of dead cephalopods Spirula spirula; and L. testudinata for kelp E. maxima. The other species, L. anatifera and L. australis, did not show significant preference for specific substrata. All species frequently attached to plastic debris. Object size and species were significantly related (P < 0.0001), with D. fascicularis and L. pectinata colonizing relatively smaller objects than other species. Colony size differed significantly between species (P < 0.0001), with D. fascicularis and L. pectinata occurring in relatively smaller colonies and L. testudinata being the only species to regularly occur in colonies >= 1000 individuals. We conclude that the nature and abundance of available substrata greatly influences the abundance and distribution of goose barnacles, and the increasing abundance of plastic is drastically increasing their opportunities to colonize and disperse within the southern African region.