I found two articles today about different animals that could enter the Antarctic environment if warming continues. One is the shark, which currently do not enter the Antarctic waters because they are still too cold for sharks. It is predicted that within the next 100 years the Antarctic waters could become warm enough for sharks. This could pose a major threat to sea life in the Antarctic because most of the creatures remain slow moving and soft bodied like those creatures in the Ancient Seas. Read more about sharks invading Antarctica in this article.
A second animal that is invading due to global warming is the crab. With warmer waters in the Antarctic they will be able to live there without fear of magnesium poisoning. Again they will easily prey on the sea life in Antarctica because the species here do not have the defenses similar species that have evolved in habitats already with crabs have. Read more about the crab invasion here.
Both species would pose a threat to the biodiversity in the Antarctic.