Kelp Rafts Are Bringing Invaders to Antarctica

[Judi Lynn]

Animals have long rafted around the planet, but the southern continent was considered too remote, too isolated, and too cold for that to be a problem—until now.

by Brian Owens
February 26, 2020 | 600 words, about 3 minutes

Antarctica is, for the most part, cut off from the rest of the planet by swirling ocean currents, raging winds, and frigid temperatures. The continent’s physical isolation has long been thought to have kept it well protected from invasions of nonnative species. But the discovery of living creatures on kelp rafts in Antarctic waters—including some known to be invasive in other cold regions—shows that the physical barriers are not insurmountable and invasions could become more common as the climate warms.

Though inhospitable to most life, Antarctica is not immune to introduced species. Most, such as the flightless midges that have infested Signy Island, have been inadvertently brought in by humans. And while rafting in on kelp had previously been identified as a way for nonnative species to arrive, it was considered unlikely given the breadth of the Southern Ocean and the weather and ocean current patterns that tend to push such rafts north.

Huw Griffiths, a marine biologist with the British Antarctic Survey, and his colleagues, however, recently collected more than a dozen kelp rafts from the Southern Ocean and the beaches of Antarctic islands. The rafts, which were made of kelp species that are not native to Antarctica, were transporting thousands of other species. Some, such as goose barnacles (Lepas australis), are not a threat because they only live in the open ocean. But others, having somehow survived the long and harrowing journey, could make a new home on Antarctica.

One species the scientists found, a tiny colonial animal known as a bryozoan, is particularly worrying. It is known to be a harmful invader in other cold water regions. If it made the jump from a raft to a native kelp, it would encrust the seaweed, cutting off its access to sunlight with potentially devastating consequences. “The local kelp is a major part of the ecosystem, and it may not have defenses against this bryozoan,” says Griffiths.

More:
https://www.hakaimagazine.com/news/kelp-rafts-are-bringing-invaders-to-antarctica/