Epibiotic communities on sublittoral macroinvertebrates at Signy Island, Antarctica

Abstract

The epibiotic communities on locally abundant macroinvertebrates, in particular the brachiopodLiothyrella uvaand the limpetNacella concinna, were examined from depths between 0 and 50 m at Signy Island, Antarctica. The percentage cover by epibionts onLiothyrellaincreased from <20% on the smallest individuals to >50% on the largest, and decreased slightly with depth. The percentage cover ofNacellaby epibionts increased with size of individual over an approximately similar range of values, but in contrast withLiothyrellaincreased greatly with depth. Cheilostome bryozoans and annelids of the genusSpirorbisformed >90% (by area) of the colonists onLiothyrellaand 30–60% onNacella, the coralline algaLithothamnionand sponges making up the remainder. The bryozoans, which generally dominated the epibiotic communities, comprised complex associations of species which could be described as either generalists, host-specific epibiotic, low specificity epibiotic or locally abundant background species. Positive associations of both occurrence and abundance were found between some of the bryozoans living epibiotically on the brachiopodLiothyrella. The overgrowth interactions recorded, between the three main epibiotic faunal taxa; sponges, bryozoans and annelids, were essentially hierarchical. Sponges usually overgrew Bryozoa, and Bryozoa overgrewSpirorbisas well as occasion-ally smothering small brachiopods. In four adultLiothyrelladeath may have been caused by the epibiotic bryozoanArachnopusia inchoatagrowing over the gape, so preventing feeding and/or respiration.