SGER: Dispersal of Planktonic Invertebrate Larvae and the Biogeography of the Antarctic Benthos

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AbstractOPP99-10164P.I. Rudolf ScheltemaBecause of the extreme isolation of Antarctica since the early Oligocene one can expect to encounter a unique invertebrate fauna with a high degree of endemism. Yet, some benthic taxa include from 20 to 50 percent non-endemic species. To account for such species it has been proposed that an intermittent reciprocal exchange must occur between the antiboreal populations of South America and the Antarctic continent. One possible means by which the geographical distribution can be maintained and genetic exchange may be accomplished is by the passive dispersal of planktonic larvae. To show that such dispersal is actually accomplished it must be demonstrated that (1) larvae of sublittoral species actually are found within the Drake passage and that such larvae belong to species that occur both in the antiboreal South American and Antarctic faunas and (2) that a hydrographic mechanism exists that can explain how the passive transport of larvae may occur between the two continents. The proposed research will address these two requirements by making transects of plankton samples across the Drake passage and by examining the possibility of cross frontal exchange of larvae at the subantarctic and polar fronts of the Antarctic circumpolar current as well as the possible transport of larvae in mesoscale rings. The outcome may suggest species that in the future may profitably be examined using molecular techniques, comparing individuals from bottom populations of South America and Antarctica. The study necessarily must be of a very preliminary nature since the occurrence of planktonic larvae of sublittoral benthic species in the Drake Passage has never before been examined.