Tiny marine creatures transporting carbon to seafloor

Colonies of tiny Antarctic marine creatures are thriving in response to a reduction in sea-ice cover, according to new research. A British Antarctic Survey (BAS) report suggests the filter-feeding bryozoans may be responsible for transporting millions of tonnes of carbon from the atmosphere to polar sea beds.

Their research was published on Monday (September 21) in the Cell Press journal Current Biology.

A British Antarctic Survey (BAS) investigation study into biological change on the seabeds of six continental shelf areas around Antarctica analysed bryozoan skeletons collected during ship-borne research cruises. Data was gathered over at least 20 years of research cruises, the most recent of which was on board the RRS James Clark Ross, using a custom built high-resolution camera lander.

Study author Dr David Barnes said charting the growth of bryozoans was easy. Pointing to rings on the skeletons he said “all of the growth between those two rings are how much it has grown that year. So if we collect it in 2008 we can see that this part here and this part here has been grown in 2008, and this ring here and there in 2007, and so on all the way back; and we can look back in time, you can see it as a little time machine recording information about our planet.”

Barnes’s study showed that broyzoans on west Antarctic seabeds have greatly increased the amount of carbon being transported to the seabed and that this is linked to decreasing sea ice.

He said: “This lives in the shallows and the shallows of the west Antarctic peninsula adjacent to Rothera research station and one of the fasting changing seas in the world – both because it’s getting very warm and the sea ice is gradually retreating along the peninsula – and that’s important to this little guy because it feeds on the algae that’s in the water column and as the sea ice retreats along the peninsula and there is less and less time and space each year, so it occupies less area and it occupies it for less time, that means there’s more time for the algae to grow and more algae for this animal to eat.”

Barnes says bryozoans now take up 75,000 tonnes of carbon more than they did 20 years ago. He believes his study results are an important step towards improving understanding of the impact of environmental change in Antarctica.

Carbon being transported to polar sea beds is equivalent to tens of thousands of hectares of tropical rain-forest, said Barnes. He added that changes to marine life in Antarctica’s continental shelf areas may help evaluate the role of lifeforms in carbon draw-down.

One unexpected find was that the world’s first High Seas Marine Protected Area (MPA), the southern continental shelf of the South Orkney Islands, was identified as the area where the bryozoans were thriving most. An international, BAS-led scientific cruise there early next year should help researchers discover why.

The research was funded by the Natural Environment Research Council (NERC), the Darwin Initiative (DEFRA) and the Pew Charitable Trusts. (Reuters)