Southern carbon sinks on the rise

Polar carbon sinks may be increasing say researchers from the British Antarctic Survey (BAS) who have studied collections of a marine bryozoa dating back to a 1901 expedition to the South Pole

Researchers studied the population of Cellarinella nutti – a twig-like filter-feeding invertebrate – and discovered that they were growing steadily from 1901 to 1990, when their growth more than doubled.

The rapid growth of C. nutti coincides with an increase in regional production of phytoplankton which relies on carbon dioxide in the water for sustenance. The carbon in the algae is taken up by the bryozoans where it is incorporated into the skeleton and other tissues. Their skeleton is ideal for studies of this type are they preserved a clear macroscopic environmental record via tree-like growth rings. As the bryozoans grow, parts break off and are buried into the seabed.

“Thus the amount of carbon being buried on the seabed is increasing,” said David Barnes of the BAS. “This is one of the first few pieces of evidence that life in Antarctica has recently changed drastically.”

He says the shift is most likely the result of ozone losses, which have led to an increase in wind speeds over the last 10 years. This clears ice and drives greater circulation of surface waters – which causes a boon in phytoplankton.

“If we are right, this is a rare example of animals responding to one global phenomenon, the ozone hole, and affecting another, the greenhouse effect,” Barnes said.

It is not yet clear how big an impact the changes in C. nutti might have, but Barnes suspects it might be quite small.

“Nevertheless, we think that the combination of ice shelf losses and sea ice losses due to climate change and the effect of ozone loss-induced wind speeds offers some hope for much-needed carbon sequestration to the seabed in the Southern Ocean,” Barnes said. “There are few other places in the world where global and regional changes could actually lead to more carbon being removed from the system.”