A recent study shows how ocean life and pollution can find their way to Antarctica’s shores.
New research indicates that Antarctica’s distinctive ecosystems may be in danger due to the introduction of foreign marine species and pollution from land areas in the Southern Hemisphere.
Published today in Global Change Biology, a collaborative study from researchers at UNSW Sydney, ANU, University of Otago, and the University of South Florida reveals that floating objects can access Antarctic waters from more locations than previously understood.
“With the rising quantity of plastics and other human debris in the ocean, there are more possibilities for marine life to reach Antarctica,” explains lead author Dr. Hannah Dawson, who conducted this research as part of her PhD at UNSW and is currently with the University of Tasmania.
Foreign species, including various small marine invertebrates, may make their way to Antarctica by hitching a ride on floating debris such as kelp, driftwood, pumice, and plastic. Earlier studies suggested these organisms only traveled from isolated and uninhabited islands in the Southern Ocean, but the latest findings show they can also come from all southern continents.
“Although we knew that kelp could float to Antarctica from nearby sub-Antarctic islands like Macquarie and Kerguelen, our research indicates that floating debris can originate from much farther north, including areas like South America, New Zealand, Australia, and South Africa,” states Dr. Dawson.
Co-author Professor Crid Fraser from the University of Otago mentions that kelp could significantly impact Antarctica’s marine ecosystem.
“Southern bull kelp and giant kelp can grow over 10 meters long and form forest-like habitats that can transport numerous small organisms during their long trips to Antarctica,” she highlights.
“If they establish themselves in Antarctica, it could lead to drastic changes in the local marine ecosystems.”
Southern Ocean Modelling
Utilizing surface current and wave data from 1997 to 2015, the team analyzed how debris from various Southern Hemisphere land sources moves toward Antarctica, offering new insights into marine dispersal frequencies and routes.
“We were able to determine how often these rafting events occur by simulating dispersal paths over 19 years with varying oceanographic conditions,” explains ANU co-author Dr. Adele Morrison.
“Our findings indicated that floating objects reached the Antarctic coastline in every simulated year, suggesting a persistent influx of anything that can float, whether it’s kelp or a plastic bottle.”
Dr. Dawson compares the modeling to the childhood game ‘Poohsticks’ from Winnie the Pooh.
“Think of releasing a stick into a river and then running downstream to see where it ends up—this is similar to our modeling process, but we simulate ocean currents instead of a river,” she describes.
“We released millions of virtual particles, symbolizing debris, from different land masses, and then we modeled their trajectories over 19 years based on predicted surface ocean currents and waves. Afterward, we were able to see where they would likely end up.
“The quickest journey to the Antarctic coastline took about nine months from Macquarie Island, which is located south of New Zealand. Conversely, particles released from South America had the longest trips on average,” she mentions.
Warmer Waters
The study also identifies which parts of the Antarctic shoreline are especially vulnerable to the arrival of foreign species.
“Most drifting objects tend to arrive at the Antarctic Peninsula’s tip, which has relatively warm ocean temperatures and often remains ice-free. These conditions make it a prime location for non-native species to initially establish themselves,” remarks UNSW Scientia Professor Matthew England, a co-author of the study.
The recent sharp decrease in Antarctic sea ice heightens concerns about these rafting connections.
“Sea ice naturally acts as a barrier that prevents many non-native species from successfully establishing around Antarctica,” explains Dr. Dawson.
“If the ongoing decline in Antarctic sea ice continues, living organisms floating on the surface or attached to debris may find it easier to colonize the continent, which could lead to significant effects on local ecosystems.”
