Last updated July 18, 2018 at 12:22 pm
Antarctic ecosystems could be more vulnerable than suspected to global warming.
A bed of kelp from one of the islands in the Southern Ocean. Picture: Ceridwen Fraser
The unexpected discovery of southern bull kelp on an Antarctic beach has revealed how vulnerable Antarctica is to ecological changes driven by climate change and the impacts of pollution.
The kelp travelled 20,000 kilometres, passing through what were thought to be impenetrable polar currents and winds, to complete the longest known biological rafting event ever recorded.
However, ocean modelling by Australian scientists trying to understand how this journey occurred has highlighted that it may not have been a rare event. Kelp and all manner of floating pollution is likely to be reaching Antarctic shores.
“This finding shows us that living plants and animals can reach Antarctica across the ocean, with temperate and sub-Antarctic marine species probably bombarding Antarctic coastlines all the time,” said lead author Dr Ceridwen Fraser, from the Australian National University.
“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.”
The Australian component of the international project brought together researchers from ANU, the University of NSW and the ARC Centre of Excellence for Climate Extremes (CLEx).
Storms help change the game
The oceanographic analysis was led by Fraser and CLEx’s Dr Adele Morrison, who says strong westerly winds and surface currents are expected to drive floating objects north and away from Antarctica but this all changes when the disruptive influence of Antarctic storms is factored in.
“Once we incorporated wave-driven surface motion, which is especially pronounced during storms, suddenly some of these biological rafts were able to fetch up on the Antarctic coastline,” she said.
This has important implications for the science of ocean drift that is used to track plastics, aeroplane crash debris and other floating material across our seas.
Further evidence that kelps regularly travel into Antarctic waters came from the Antarctic Circumnavigation Expedition, which observed kelps off the Antarctic Peninsula and East Antarctica.
“These findings could change the way we model oceanic surface movement,” said CLEX’s Dr Andy Hogg. “If this wave-driven surface motion – known as Stokes drift – influences the movement of particles around Antarctica, it could be important for other stormy seas too.”
DNA samples taken from the kelp revealed that one specimen drifted all the way from the Kerguelen Islands and another from South Georgia.
“These are astonishing voyages, but worrying too,” Fraser said. “They show that Antarctic ecosystems could be more vulnerable to global warming than we had suspected,”
“Parts of Antarctica are among the fastest warming places on Earth. 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 paper published in Nature Climate Change.
