Sea ice loss in Arctic causing ecosystem changes: study
Last year's record loss of Arctic sea ice is already causing big changes for plants and animals that scientists are just starting to understand, according to newly published research.
"It takes only one season to change how a deep-sea system functions," said Antje Boetius, who was the head scientist aboard a German research vessel that sailed through the High Arctic last summer.
That voyage of the Polarstern, owned by Germany's Alfred Wegener Institute, couldn't have come at a more interesting time.
In 2012, scientists measured Arctic sea ice at its lowest level in 33 years of satellite records. Where the Polarstern originally planned to work, "there was not even an ice cube for us," said Boetius.
The Polarstern had to travel more than 400 kilometres farther north to find enough ice to begin its planned research on algae called Melosira arctica that normally grow under the ice in thick, ropy strands up to five metres long. Few animals eat Melosira, but many live in it and Boetius compares it to a kind of coral reef.
The Polarstern scientists wanted to find out if Melosira was benefiting from thinner ice that allows more light to pass through. They also wanted to check anecdotal reports that suggested Melosira mats were disappearing.
Researchers found both assertions were correct, but not in the way they expected.
"We were surprised that we saw (Melosira mats) everywhere, but they had fallen to the deep sea," said Boetius.
"We found their remnants. It looked like someone had pulled out hair. Something had happened to them."
The scientists checked the sea floor as far down as 4.4 kilometres and that's where they found the algae.
Boetius suggests Melosira benefits from spring sunshine filtering through the thinner ice. Later in the season, when the sea gets too warm and too diluted by meltwater, the algae simply drop off.
But in the energy-poor Arctic ocean, the transfer of that much organic material from one level to another is having profound consequences.
In just one season, the numbers of sea cucumbers and brittle stars on the sea floor have exploded. Bacteria have bloomed to the point where they have used all the available oxygen in the water in some areas of the ocean bottom.
"We saw the first anoxic spots forming in the deep sea," Boetius said. "That can change life dramatically."
As for what the loss of Melosira mats means for surface sea life, Boetius concedes they just don't know.
She said the lack of any other organisms feeding on the dead Melosira, as well as the presence of plenty of oxygen in sea-floor sediments, convinces her that what the Polarstern observed is a very recent development.
She maintained that the Polarstern research, published Thursday in the prestigious journal Science, constitutes a lesson for those who still imagine the Arctic as an unchanging expanse of ice, snow and water.
"Will this be the future Arctic that we have just acquired the first evidence of? This we cannot answer.
"We are really at the point where we look and see changes that we cannot even model, or that we really cannot explain."
The radical changes in the High Arctic seas after just one season are a warning to those planning to exploit the area's resources, or use it as a shipping corridor, Boetius said.
"We are thinking of uses without even documenting how the Arctic functions."