Hitchhiking crabs on tourist ships could put the squeeze on Antarctic wildlife

Invasive species such as crabs and mussels "hitching a lift" to the Antarctic on tourist ships pose threat to wildlife, a Cambridge University study has found.

Scientists examined the routes of ships travelling to and from the ice continent, with tourist, research and supply ships often travelling between the Arctic and Antarctic – carrying species from one pole to the other.

The US ship Gould at Antarctica

Credit: Lloyd Peck

They found 1,581 global ports with links to Antarctica, all of which could be a source of potentially damaging non-native species.

The Antarctic has no native shallow-water crabs or mussels, species that are widespread elsewhere in the world and could pose a threat to other animals if imported.

Mussels, barnacles and algae can grow on the hulls of ships – a phenomenon known as "biofouling" – while European shore crabs have been found living on ships that travel large distances around the globe.

Stalked and acorn barnacles, green algae and caprellid amphipods on a ship that visited Antarctica

Credit: Arlie McCarthy

Antarctic wildlife is especially vulnerable to predators like crabs, which "crush" their prey and are not currently found on the continent. Mussel beds could also crowd out native species such as sponges, limpets and sea anemones.

Arlie McCarthy, lead author, a researcher in the University of Cambridge’s Department of Zoology and the British Antarctic Survey, said the knock-on effects could lead to a decline in krill, which the continent’s already endangered mammals and birds rely on for food.

"Krill is so important for the pelagic community, for penguins, seals and whales,” she said. “We don’t know new invasive species won’t have an impact.”

Bryozoans, stalked barnacles and acorn barnacles in a ship's water discharge outlet

Credit: Arlie McCarthy

Professor David Aldridge, co-author and also of the University of Cambridge, said: "Invasive, non-native species are one of the biggest threats to Antarctica’s biodiversity. Its native species have been isolated for the last 15 to 30 million years.

"They may also have economic impacts, via the disruption of fisheries."

Professor Lloyd Peck, another co-author and a researcher at the British Antarctic Survey, said: "Biosecurity measures to protect Antarctica, such as cleaning ships’ hulls, are currently focused on a small group of recognised ‘gateway ports’.

"With these new findings, we call for improved biosecurity protocols and environmental protection measures to protect Antarctic waters from non-native species, particularly as ocean temperatures continue to rise due to climate change."

The study, published in the journal Proceedings of the National Academy of Sciences, also warned that the currently "pristine" Antarctic could become more hospitable to life from other oceans because of climate change.

Global warming is happening more quickly at the poles than in more equatorial climates, with the Antarctic thought to be warming three times faster than the global average.

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