Kelp's 20,000km Antarctic journey: our last wilderness isn't so remote after all. / Supplied
Antarctica might seem an icy wilderness cut off from the human world and its pollution - but a remarkable new discovery shows the frozen continent is not as isolated as we might think.
Scientists have been astonished to observe how kelp made it 20,000km from some remote islands in the Southern Indian Ocean to Antarctica's pristine shores.
While their just-published study remarkably revealed the longest known case of "biological rafting", it also threw up some worrying prospects.
Drifting plastics, and even new species, might be able to travel to the unspoilt environment more easily than thought as the climate warmed.
Until now, the barriers created by polar winds and currents were considered to be impenetrable.
But DNA samples taken from the kelp confirmed they'd floated all the way from the Kerguelen Islands, across a route that must have been tens of thousands of kilometres long.
While strong westerly winds and surface currents were thought to drive floating objects north and away from Antarctica, this all changed when the disruptive influence of Antarctic storms were factored in.
Using cutting-edge modelling techniques, the team began to see how large waves arising during storms could help kelp rafts to reach the continent.
Once they incorporated wave-driven surface motion, which was especially pronounced during storms, some of these biological rafts were found to be able to fetch up on the Antarctic coastline.
Southern bull kelp growing on subantarctic Marion Island. It doesn't currently grow in Antarctica, and could drastically change ecosystems if it's able to establish there. Photo / Ceridwen Fraser
The research stood to change the way scientists thought about Southern Ocean oceanography, where storms could play a big role moving drifting material.
The findings also had important implications for the science of ocean drift that was used to track plastics, aeroplane crash debris and other floating material across our seas.
"The results suggest that Antarctica won't be immune from drifting plastics that are increasingly a problem in the world's marine ecosystems," said study co-author Professor Jon Waters, of the University of Otago's Zoology Department.
"It also highlights the potential for new species to colonise Antarctica as the climate warms."
The study's lead author, former Otago PhD student Dr Ceridwen Fraser, added the findings showed living plants and animals could reach Antarctica across the ocean, with temperate and sub-Antarctic marine species probably bombarding Antarctic coastlines all the time.
A seal swims among southern bull kelp on subantarctic Marion Island. Photo / Ceridwen Fraser
"We always thought Antarctic plants and animals were distinct because they were isolated, but this research suggests these differences are almost entirely due to environmental extremes, not isolation," said Fraser, now based at Australian National University.
The new research also showed Antarctica's ecosystems could be more vulnerable to global warming than previously suspected.
"Parts of Antarctica are among the fastest warming places on Earth," Fraser said.
"If plants and animals get to Antarctica fairly frequently by floating across the ocean, they will be able to establish themselves as soon as the local environment becomes hospitable enough."
The study built on a previous Marsden Fund-supported project led by Waters together with Fraser.
It also comes months after scientists confirmed small particles of plastic, often invisible to the naked eye and measuring less than 5mm, in the waters around Antarctica.
