Letter from Antarctica: Hunting ocean acidification at the South Pole

By Dr Donna Roberts

Onboard the Aurora Australis

11.30 am, 6 January 2012

It’s day one of the Mawson Centenary Cruise to Commonwealth Bay in Antarctica, and while all other expeditioners are lying low adjusting to the swell of the Southern Ocean, Team Acid has begun searching for shelled zooplankton – the tiny creatures at the bottom of the food chain and those most at risk of changing ocean chemistry or ‘ocean acidification’.

If there is evidence to be found of the effects of chemical change on marine biological systems, Team Acid is looking in the right spot.

Not only do the world’s oceans play a crucial role in capturing CO2 (they currently capture a quarter of our emissions each year), the polar oceans capture a disproportionate share of this because of the so-called ‘champagne effect’.

Dr Donna Roberts on the Mawson Centenary Cruise to Commonwealth Bay in Antarctica. The Aurora Australis icebreaker is 94 m long and weighs 3900 tonnes.

Just like a bottle of champagne in the fridge stays fizzy longer than a bottle of champagne at room temperature, so the polar oceans absorb more CO2 than temperate and tropical regions.

However this great environmental service played by the oceans comes at a cost to marine life.

Ocean acidification, sometimes referred to as ‘the evil twin of climate change’, decreases the availability of carbonate ions for shell-forming and skeleton-building organisms known as calcifiers.

On this voyage Team Acid is collecting, across the waters from southern Australia to Antarctica, samples of animals that make shells from carbonate.

This will enable us to establish a baseline record of Southern Ocean shell makers which will be invaluable for future comparative studies of the impacts of acidification in the Southern Ocean.

The team is made up of myself and two enthusiastic volunteers – Dr Delphine Dissard, a research scientist from the University of Western Australia, and Kelly Strzepek, a research student from the Australian National University (also known for her fabulous collection of entertaining beanies).

Our search has hit the jackpot, netting pteropods (marine snails often referred to as ‘sea butterflies’) and foraminifera (single-celled shell makers) which we will take home so we can study their shells in detail.

Team Acid - Dr Delphine Dissard, Dr Donna Roberts and Kelly Strzepek

We have also chanced upon different macro specimens in each trawl, including a large pyro soma (a bit like a giant worm) that had everyone enthralled and, due to the fact that all the biologists on board are microbiologists, took a day to identify.

Our study of the tiny, shelled creatures from the bottom of the food chain at the bottom of the world is particularly important because, ultimately, impacts on polar calcifiers will have impacts on higher levels of the food chain and across latitudinal boundaries.

Polar calcifiers are important food sources for marine predators including salmon, mackerel, herring, cod and baleen whales in the Arctic, and krill, fur seals, Adelie penguins and whales in the Antarctic.

Loss or reduction in habitat of these ‘potato chips of the sea’ is likely to have serious consequences for the wider ocean community.

Perhaps closer to most people’s hearts (or stomachs) is the likely impacts of ocean acidification on fish. Some of the richest and most heavily exploited fishing areas in the world are located in high-latitude seas.

Dr Roberts examines the peteropods which the team has collected. They will study the shells for signs of ocean acidification.

More than half the total current US fishery landings – a $4-billion-per-year industry – are derived from Alaskan waters.

The Southern Ocean currently supports krill and Patagonian toothfish fisheries.

Under current global emission scenarios ocean acidification is likely to severely affect the waters that support these industries before the end of this century.

Team Acid is focusing on the little things to illuminate some of the biggest issues facing the planet, particularly the increasingly worrying picture of impacts on Southern Ocean plankton in a high CO2 world.

Dr Donna Roberts is Ocean Acidification project leader at the Antarctic Climate & Ecosystems Cooperative Research Centre (ACE CRC), Hobart, Australia.

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