Acidifying Arctic Ocean threatens food web: study

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This article was published 5/12/2013 (1328 days ago), so information in it may no longer be current.

SCIENTISTS huddled in a sea-ice camp on the Arctic Ocean have produced new evidence climate change could be threatening the food web in the Far North.

The researchers found shrimp-like creatures eaten by everything from fish to whales are likely to react poorly to increasingly acidic water caused by high levels of carbon dioxide in the atmosphere.

"There were certainly possibilities for these animals to be affected," said Ceri Lewis of the University of Exeter, lead author of a paper published this week in the Proceedings of the National Academy of Sciences. "They're one of the key components of the Arctic food web."

Lewis and her colleagues spent months at a time on the sea ice off Ellef Ringes Island, which is west of Ellesmere Island and just south of the magnetic North Pole.

They were studying the effect of pH levels on different types of the tiny crustaceans called copepods. They found some stayed at one depth, while others moved up and down, which exposed them to different pH levels.

The levels are a measure of acidity or alkalinity. The lower the pH, the more acidic a substance.

They took samples of copepods and exposed them to sea water in which the acidity had been increased to levels expected in about 100 years.

"We're putting animals in a time machine and transporting them 100 years into the future," said Lewis.

The copepods that stayed at one depth didn't do well at all.

"They were really suffering," Lewis said.

Even the ones that swam up and down and were accustomed to different pH levels were noticeably harmed. Their young, it seems, don't move around and aren't as adaptable.

"We did see mortalities," said Lewis. "They were quite sensitive."

Lewis cautioned her experiment amounted to "shock treatment" for the copepods. In real life, the tiny creatures will have a century to get used to a more acidic environment. But, she said, 100 years isn't very long.

"In terms of evolutionary adaptation, that's not very much."

The stakes are high. The Arctic Ocean is acidifying faster than any other on Earth and all oceans are gradually losing pH. Copepods are one of the foundations of the marine ecosystem.

It's been two years since Lewis folded away her tent, rolled up her sleeping bag and left the Ellef Ringes ice camp, so memories of the hardships are gradually fading.

"It hurt my fingers a lot on the days where I worked with sea water at -40, but you forget that quickly and you just remember how beautiful it was," she said. "It was a really tough two months doing the work but you forget that bit and just remember all the amazing moments.

"I fell in love with the Arctic. My colleagues are desperately trying to get some money together to come back. But I don't think it will be an ice camp.

"Unfortunately."

-- The Canadian Press