Rafts of seaweed can ferry marine life across the otherwise impenetrable currents surrounding Antarctica, a new study shows.
And while Antarctic conditions are currently too chilly for the stowaways to live, global warming could eventually make it habitable for them.
Researchers from Australian National University and the University of Cape Town, South Africa tracked species movements from the South Atlantic and Indian Oceans in 2008, 2013 and 2014.
They found two species of kelp helped worms, snails, crustaceans and other seaweeds cross the Antarctic Polar Front, a barrier of jets and flows that separates Antarctic and sub-Antarctic waters to the north.
“We’ve been focusing a lot on minimising plants and animals being accidentally carried into the Antarctic by humans,” says lead author and Australian National University biologist Ceridwen Fraser.
“This research shows that some species can also get into the region without our help.”
The kelp culprits, Macrocystis pyrifera and Durvillaea antarctica, are large, buoyant species that grow in sub-Antarctic waters. They create large floating “rafts” that can travel hundreds of kilometres with a host of marine invertebrates on board.
When they hit the Antarctic Polar Front, most kelp remains behind the barrier, pushed back north by jets. But small sections snap off and get caught in eddies propelling them, and the foreign sea life aboard, southward into Antarctic waters.
So why aren’t we seeing signs of this foreign life in Antartic waters already?
In short, it’s too cold for them to survive.
But that may change soon enough, Fraser says: “The Antarctic is one of the world’s fastest-warming regions, and the consequences of new species establishing there could lead to drastic ecosystem changes.”
The work was published in Ecography.
Phil Ritchie is a Melbourne-based journalist.
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