Evidence for a marine molluscan fauna beneath ice shelves in the Lazarev and Weddell seas, Antarctica, from shells of Adamussium colbecki and Nacella (Patinigera) cf. concinna

Abstract

Only one living specimen of Adamussium colbecki was found amongst the shells of this species collected in the Lazarev and Weddell Seas, and those of the limpet Nacella cf. concinna from three locations in the southern Weddell Sea. In order to explain this peculiarity four hypotheses are discussed. The possibility that the shells belong to living deep-water populations is in contradiction to the high number of trawl samples taken in the area and the abundance of empty shell material. ¹⁴C dates show the shells are recent, thus excluding the possibility that the shells belong to autochthonous fossil populations exposed on the seafloor. Lateral transport of living specimens or shells over long distances by marine currents or by ice is unlikely due to their state of preservation and the water circulation pattern. The most likely explanation is that the shells are allochthonous, transported only over short distances by marine currents from adjacent areas underneath floating ice shelves where both species have living populations.