Interactions Between Antarctic and Sub-Antarctic Marine, Freshwater and Terrestrial Organisms

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The various studies carried out since the beginning of the BIOMASS (Biological Investigations of Marine Antarctic Systems and Stocks) programme have revealed the complexity of interactions between Antarctic marine organisms, with krill (Euphausiacea) as a key group. On the one hand, the interactions between whales, seals, fish, birds, and krill, and, on the other hand, the interactions between krill and phytoplankton have been carefully described. However, several interactions have not been sufficiently stressed, more particularly those responsible for the impacts of terrestrial and freshwater ecosystems on marine organisms and vice versa. Certain recent studies have shown that the terrestrial micro-flora play an important role in Antarctica as well as in the Sub-Antarctic islands, due to a substantial influx of run-off water. Similarly, the terrestrial micro-fauna is linked with the coastal marine micro-fauna; coastal birds, such as terns and penguins, and seals, such as the Elephant Seal, Mirounga leonina, playing important roles in coastal ecosystems. It is necessary to emphasize the role played by seabirds which introduce significant quantities of nutrients into terrestrial ecosystems: it has been demonstrated that in one Sub-Antarctic island this amounts to about 56 kg ha−1 yr −1 of N alone. The role of seals which breed on land and feed at sea is also important, because they constitute a link between terrestrial micro-organisms and marine fauna. One type of interaction has not yet been studied in detail, and requires research: it is the role of parasites which need 2 or more hosts, invertebrate and vertebrate. Finally, there is the role of man whose presence on land and whose exploitation of whales, fish, krill, and other crustaceans can modify the natural dynamic equilibrium of the interactions between terrestrial, freshwater and marine ecosystems.