Kelp Is Undertaking Epic Voyages To Reach Antarctica And We Finally Know How

Durvillaea kelp in the surf. Ceridwen Fraser

When you're going on a scientific research mission to one of the most remote places on Earth, taking the right equipment matters. Yet when one researcher forgot some of his intended luggage, he made a more important discovery than he would ever have expected, contradicting the long-standing belief that Antarctica is largely biologically isolated from the rest of the world. Initially oceanographers struggled to understand how kelp could travel so far against the prevailing wind and currents, carrying other organisms with it, but modeling has now revealed the crucial role of storms.

Antarctica is surrounded by the circumpolar current, an endless loop of water pushing ever-eastward, driven by the powerful southern winds and unobstructed by land, other than being forced through the narrow gap between the Antarctic Peninsula and Tierra del Fuego. Although whales and seabirds can power across this obstacle, few other life forms can do so, keeping the frozen continent almost biologically isolated from the rest of the planet.

At least that is what was believed, until the Universidad de Concepción's Dr Erasmo Macaya, unable to do the work he had come to King George Island to do, spent a lot of time walking along the beaches looking at seaweed. Macaya noticed that some of the kelp didn't look like it should be there. The oceans off Antarctica, cold as they are, do support some kelp species, but Macaya's finds were Durvillaea antarctica, which somewhat ironically does not normally live close to the continent with which it shares its name.

Durvillaea on the beach. Ceridwen Fraser

Macaya got in touch with several other researchers, including Dr Ceridwen Fraser of the Australian National University (ANU), who had already been studying Durvillaea. Analysis of the specimens' genetics revealed one frond had come from South Georgia, and the other from the Kerguelen Islands.

Although South Georgia is quite close to the Antarctic Peninsula, the kelp must have either traveled directly against the prevailing currents or nearly circumnavigated the globe, a journey of 20,000 kilometers (12,400 miles) – the longest rafting voyage ever recorded.

Relationship of Durvillaea from different locations (a), the likely routes (b), and a photo of the kelp on King George Island (c). Fraser et al/Nature Climate Change

It is common for kelp rafts to carry entire ecosystems aboard them, with generations of some microbes living and dying near the stem in the course of a journey. Fraser told IFLScience these kelp bore only barnacles, but where there are two rafts there must be others, and some may have passengers.

The discovery turns expectations of Antarctica's future on their head. Currently, the frozen continent is too cold for lifeforms from elsewhere on the planet to flourish there, but rapid warming in certain parts is changing this. Previously many biologists expected the circumpolar current would shield Antarctica from invading species, but now it seems likely that many will soon come to inhabit the place.

Fraser and Macaya consulted Dr Adele Morrison, also of ANU, about how it was possible for species that cannot swim to make this voyage. “Strong westerly winds and surface currents are expected to drive floating objects north and away from Antarctica, but when the disruptive influence of Antarctic storms is factored in, that all changes,” Morrison said in a statement

Morrison's modeling in Nature Climate Change showed the storms create a random effect, dispersing kelp fronds that start a journey together. “Suddenly some of these biological rafts were able to fetch up on the Antarctic coastline,” Morrison said. 

The work explains not only the presence of kelp in Antarctica, but microplastics on the same beaches. Fraser told IFLScience these plastics are now being found in quantities too large to be explained by lazy tourists, and must also be crossing from areas to the north, polluting even this wild part of the planet.

Australian National University 

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