Antarctic Lacustrine Copepods: Scattered Remnants of an Ancient Fauna and Recent Marine Invaders
Swadling, KM and Gibson, JAE, Antarctic Lacustrine Copepods: Scattered Remnants of an Ancient Fauna and Recent Marine Invaders, Copepods: Diversity, Habitat and Behaviour, Nova Science Publishers, L Seuront (ed), Halifax, pp. 77-100. ISBN 978-1631178467 (2014) [Research Book Chapter]
The Antarctic continent is home to myriad lakes, ranging from freshwater to hypersaline environments. These lakes provide habitat for low trophic level organisms and are often dominated by bacteria and protists. However, in some of the lakes copepods and other invertebrates have managed to thrive. At least eight species of copepods have been identified, with the possibility of several more being present. While the number of copepod species is not high, their ability to adapt to the Antarctic environment is reflected in their behavior, life history strategies and physiology. Calanoid copepods have been observed in both marine-derived and freshwater lakes, while cyclopoids are presently identified only from freshwater lakes and harpacticoids from saline lakes. Evidence compiled from both continental and peninsular Antarctica suggests that some of the copepods, notably Gladioferens antarcticus and Boeckella poppei that inhabit the freshwater lakes, could well have been in situ prior to the Last Glacial Maximum and possibly for much longer. This evidence has led to the conclusion that, with respect to Antarctic freshwater zoogeography, "vicariance rather than dispersal may yet prove to be the most parsimonious and reasonable explanation". However, it is also possible for the freshwater habitats that dispersal has played a significant role, particularly in the colonization of lakes along the Antarctic Peninsula by copepods from South America during the Holocene. Populations of marine-derived copepods are found living in saline lakes, particularly in oases along the margins of East Antarctica. The populations have been present for many thousands of years, following isolation of the lakes from the ocean via isostatic rebound approximately 5000 years BP. The animals were either passively trapped in newly-forming lakes that arose as a result of a decrease in the local sea level, or they were transported via sea spray and/or by animal vectors. Physiological traits such as broad salinity and/or temperature tolerance have promoted the establishment of copepod populations in Antarctic lakes. The family Centropagidae has been particularly successful in colonizing the freshwater lakes, with three species currently known. Members of this family are often common in coastal, estuarine and freshwaters of other continents and are known for their euryhalinity. Similarly, the most successful saline species, Paralabidocera antarctica, is a member of the Acartiidae, a family that is often numerically dominant in estuarine and coastal waters in temperate and tropical regions throughout the world. It is not yet understood how these populations will respond to relatively rapid environmental change.