EPIBIONT FORAMINIFERA OF SERTELLA-FRIGIDA (WATERS) (BRYOZOA, CHEILOSTOMATA) FROM TERRANOVA BAY, ROSS SEA, ANTARCTICA

Several arenaceous and calcareous foraminifera epibionts of Sertella f rigida (Waters) (Bryozoa, Cheilostomata), collected in Terranova Bay d uring the 1989-90 Italian Antarctic expedition, were studied. Arenaceo us species, such as Psammosphaera fusca Schulze f. adhaerescens Rhumbl er, Haplophragmoides canariensis d'Orbigny, Portatrochammina antarctic a (Parr), and Trochammina arctica Hedley, Hurdle and Burdett, are a co nspicuous component of the epifaunal community. The calcareous foramin ifers encrusting S. frigida are mostly represented by Cibicides refulg ens Montfort and Rosalina globularis d'Orbigny. Foraminifera were foun d only in the basal part of the bryozoan colonies. The presence of man y juveniles provided evidence that foraminifers were reproducing at th e time of sampling. Psammosphaera fusca f. adhaerescens was found excl usively inside the zooids of S. frigida. The large number of individua ls associated with the bryozoan suggest that P. fusca f. adhaerescens finds optimum conditions (shelter, food, and grains for shell building ) for growth inside the zooids of S. frigida. The other species occurr ed most commonly adhered to the trabeculae or to the zooid orifices of S. frigida. An elevated position offers a better chance to catch food particles from the overlying water column. Foraminifers could benefit also from bryozoan feeding currents. The availability of resuspended organic material could provide a more consistent source of food in a h ighly seasonal oligotrophic environment.