Ice retreat can transform wildlife in arctic seas

The ice loss in the polar seas can have far-reaching consequences for the ecosystem there – and therefore also for fisheries. Scientists have concluded this from analysis of ancient DNA from the seabed, the Alfred Wegener Institute (AWI) in Bremerhaven reported on Monday. A team led by Ulrike Herzschuh looked back some 20,000 years to the last Ice Age.

Deposits that have accumulated on the seabed over thousands of years and have now been brought to the surface were examined. The research team found DNA from representatives of 167 families of marine animals whose habitat is the ice or open water. “We were surprised ourselves that there was information about the entire ecosystem in these ancient sediments,” explains Herzschuh. They presented their findings in the scientific journal “Nature Communications”.

She found that diatoms and other algae in or under the sea ice were typical of the colder phases of the last Ice Age. These are small oxygen producers that copepods use as food. These, in turn, were eaten by fish from the cod family, such as Pacific cod, Alaska pollock, and arctic cod.

In contrast, in warmer eras without ice, there were far fewer diatoms and copepods, but more cyanobacteria. On the seafloor, seagrass meadows have spread into sheltered bays, and instead of cod, more salmon and Pacific herring swam in the Bering Sea.

The team also expects similar changes in a warmer and largely ice-free future. Catching some popular edible fish such as pollack and cod might not be worth the effort in the Bering Sea, it was said. On the other hand, pink salmon and Pacific herring could be advancing further north.

The researchers also expect that under ice-free conditions, the planktonic communities will transport less carbon into the depths and deposit it in the sediments. The oceans may then no longer be able to store as much carbon dioxide, further fueling climate change, it was said. (sda/afp/oee)