The record ice lows in the Arctic last year created a ripple effect all the way to the seafloor, with significant ramifications for plants, marine diversity and the local carbon cycle.
Artcitc algae in an ice cave. Photo by Stephanie Fitzgerald
That finding came yesterday from a scientific team that traveled through the central Arctic and discovered large amounts of algae hanging from sea ice and dwelling on the sea bottom like green carpets. The research suggests that the effects of declining ice levels because of warming can spread through the marine ecosystem much faster than previously thought, the scientists said.
It also provides evidence that ice thinning is promoting algal growth by increasing available sunlight, according to the study.
"It looks like we may be in a new phase of the Arctic," said Antje Boetius, a scientist at the Alfred Wegener Institute for Polar and Marine Research in Germany and an author of the research, published yesterday in Science.
The new research resulted from a two-and-a-half-month journey in late summer on the icebreaker Polarstern. When news hit of the unprecedented ice loss, the team shifted its course north to survey a broader area than originally planned, said Boetius.
Using advanced cameras, the team peered more than 2 miles below the surface before discovering patches of algae ranging from 1 to 50 centimeters (20 inches) in diameter. In some spots, the organisms, Melosira arctica, covered 10 percent of the seafloor. The species appeared in all surveyed spots, indicating a wide range, she said.
"We were totally surprised to see that the seafloor had turned green in parts," said Boetius. Normally, the floor would be a barren, beige brown color. Because Melosira arctica typically have an ice habitat, the researchers concluded the algae had dislodged and sunk to depth as a result of the unprecedented ice loss.
Rapidly changing ecosystem
After looking through records, "we found no prior evidence this had happened before," said Boetius.
While it is too early to know whether the phenomenon will repeat itself, large amounts of algae have the potential to disrupt the local ecosystem by altering the feeding behavior of algae-dependent animals, said Boetius.
Algal communities also may shift the concentrations of nutrients in water, a dynamic that could in theory hamper the functioning of plant life at the surface dependent on nutrients, she said. That is a "hot debate," she said.
Previously, scientists knew of the existence of ice algae but did not understand details of their behavior outside of coastal regions, or in areas of thinning ice. It was unknown that algae could sink all the way to the lightless seafloor and live there for a period of time, said Boetius.
Currently, sea cucumbers and starfish are the main consumers of the algae, but that could quickly change if the blooms occur again, she said.
"If this keeps happening, we could have different types of deep-sea life. Some animals may go extinct. Others may thrive," she said. Organisms that need a lot of oxygen in some spots could run into problems, she said in one example.
That could happen in the long term because algae-loving bacteria in the deep sea use up oxygen, much in the same way that people do in a closed room, said Boetius. Additionally, algae could disrupt the ability of the Arctic region to absorb carbon, although the effect likely would be local, not global, said Boetius.
Implications for food chains
"It's too early to know what will happen," she said. It is extremely important to conduct additional research, considering that such dramatic changes happened in one summer, she said.
"My worry is if we don't speed up our research, we may have a whole new type of ocean and we have not been observing it," she said.
The work builds on a Science study last year finding a large bloom of phytoplankton underneath ice in the Chukchi Sea. Previously, many believed that sea ice would block sunlight and not allow such growth.
The new results "are certainly consistent with the massive under ice bloom we discovered in the Chukchi Sea," said Kevin Arrigo, a professor at Stanford University who led the earlier research.
Zach Brown, a doctorate candidate at Stanford University who has studied Arctic phytoplankton and did not participate in the new study, said the paper was "good and significant." It is likely there will be a completely ice-free Arctic ocean by the mid-21st century, a situation that could export all Melosira arctica to the ocean depths, since it will have no ice to cling to.
"This will certainly have implications for the food webs in these regions -- both for upper-ocean species as well as benthic critters feeding on the bottom," he said.
Reprinted from ClimateWire with permission from Environment & Energy Publishing, LLC. 202-628-6500. E&E Publishing is the leading source for comprehensive, daily coverage of environmental and energy issues. Click here to start a free trial to E&E's information services.
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