Do life patterns differ between two Scotia Arc localities? A preliminary investigation of three erect Antarctic bryozoan species

Abstract

Erect bryozoans are extremely abundant and diverse in polar waters and individual species may span a wide range in latitude and bathymetry. A number of aspects of lifestyle, including polypide recycling, embryo production, distribution, growth form and epibiosis were compared in three species of erect byozoans. These were collected from two locations; Signy Island (60°S) and Rothera Point, Adelaide Island (68°S) and a variety of depths. All three species were in similar stages of polypide cycling within and between the two sites. In the species Isosecuriflustra rubefacta and Nematoflustra flagellata the rate of brown body production (polypide generations) was slower at Signy Island than at Rothera Point. There was little difference between localities (within species) in the pattern of embryo production and no change in embryo size with depth. Embryos of I. rubefacta, however, were significantly larger at Rothera Point than at Signy Island. The proportion of the community occupied by each species changed with depth, but all three species occurred in shallower water at Rothera Point than at Signy Island. Fouling by epibionts decreased with increasing depth and from Signy Island to Rothera Point, both in terms of per cent cover and number of colonizing taxa. Possible trends with depth and latitude are compared with other studies involving bryozoans. The literature on Antarctic benthic taxa, in general, is also considered to determine whether trends within the Bryozoa are reflected in other groups.