Marine research: Hitchhiking to Antarctica

In recent years, non-native species have repeatedly been found in Antarctic waters. These include springtails, mites, bryozoans and barnacles. Isolated grass species have also taken root. These organisms probably arrived on the ice continent via ships or garbage floating in the water.

If the species become invasive, they endanger the Antarctic ecosystem – as does the rubbish itself that washes up from countries in the southern hemisphere. All of this has been known for several years. Now a new study published in the specialist magazine »Global Change Biology« was published, however, that these floating objects that make it into the waters of Antarctica come from many more places than previously assumed.

While it was previously known that seaweed could form a kind of raft and reach Antarctica from sub-Antarctic islands such as the Macquarie and Kerguelen Islands, the current study shows »that floating objects can reach Antarctica from much further north. including South America, New Zealand, Australia and South Africa,” said lead author Hannah Dawson, who led the research as part of her doctoral thesis at the University of New South Wales (UNSW) in Sydney and is now at the University of Tasmania.

Seaweed acts as a raft

According to Dawson, more and more plastic and more waste in the oceans are leading to more and more living organisms reaching Antarctica. Because the creatures basically hitchhike on the garbage to Antarctica. They make use of all floating objects – seaweed and driftwood as well as pumice stone and plastic.

The seaweed itself can cause enormous damage to the Antarctic marine ecosystem, as co-author Crid Fraser from the University of Otago in New Zealand, who was also involved in the study, explained. The seaweed is “very large – often over ten meters long” and forms “a forest-like habitat” for many small animals that travel to Antarctica on it like a raft. “If they colonize Antarctica, the marine ecosystems there could change dramatically,” warned the researcher.

Antarctic Peninsula first affected

For the study, the team worked with modeled surface current and wave data from 1997 to 2015, tracking floating debris from various land sources. The researchers found that foreign objects reached the Antarctic coast in each of the simulated years – seaweed as well as plastic bottles. The “fastest” objects were on the move for almost nine months. They started their journey from Macquarie Island, an island south of New Zealand that is part of Australia. Objects from South America, on the other hand, had the longest journey.

As part of their research, the scientists also found out which regions of the Antarctic coast are most at risk from the arrival of non-native species. A particularly large number of objects reach the tip of the Antarctic Peninsula, a region with relatively warm sea temperatures and often ice-free conditions. “These factors make it a likely area where non-native species will first establish themselves,” said UNSW’s Matthew England, another author of the study. This trend has been further reinforced in recent years by the dramatic decline in Antarctic sea ice. Sea ice acts as a barrier for many non-native species to successfully colonize Antarctica, said lead author Dawson.

Climate change is making the situation worse

If Antarctic sea ice continues to decline, creatures that float on the surface or are attached to floating objects will find it easier to colonize the continent. According to the researchers, this in turn will have a major impact on the ecosystems there. In a warming world, Antarctica is one of the few refuges for slow-growing, cold-water species. If alien species successfully establish themselves in the cold polar waters, they could compete with native species and dramatically change the ecosystems there.

Similar to Antarctica, other remote places also suffer from washed-up garbage. It was only in January that the Cocos Islands, which are located in the Indian Ocean and belong to Australia, reported that they were virtually drowning in garbage.