Holocene development of the fauna of Lake Boeckella, northern Antarctic Peninsula

The origins of the freshwater fauna that inhabits Antarctic lakes are poorly known. The species present today could be relict species that have survived Quaternary glaciations on the continent, or Holocene migrants from more temperate regions. One approach to investigating these questions is to study faunal microfossils in lake sediment. This approach was applied to a 293 cm sediment core from Lake Boeckella, located at the northern tip of the Antarctic Peninsula. The microfossils indicated that most of the metazoan species that occur in the lake today have been present since soon after the lake's formation c. 5.5 ka ago. In particular, the centropagid copepod Boeckella poppei (Mrazek) has been present throughout the lake's history, suggesting a local source for this species. The development of biodiversity in the lake with time was in general more consistent with local (Antarctic) rather than distant (South American) sources, though an alternative explanation is that dispersal to Antarctica was more efficient in the mid-Holocene. Evidence of dispersal from extra-continental sites comes from the scattered occurrence throughout the core of Eubosmina chilensis (Daday), a South American species that does not reach the Antarctic or the sub-Antarctic islands at present, and which failed to establish a permanent population in the lake.