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Near-empty tanks at simulated ‘high tide’, seabed submerged.


MORE INFORMATION


UKOA is funded jointly by NERC, the Department for Environment, Food and Rural Affairs (Defra) and the Department of Energy and Climate Change (DECC). www.oceanacidification.org.uk Email: Kelvin Boot – kelota@pml.ac.uk


The main partners in the benthic consortium include: Plymouth Marine Laboratory, Marine Biological Association of the UK, Scottish Association for Marine Science, Centre for Environment, Fisheries & Aquaculture Science, and the Universities of Aberdeen, St Andrews, Bangor, Heriot-Watt (with Glasgow), Hull, Plymouth and Southampton.


Whilst collecting material for most of the experiments was relatively straightforward, the cold water coral studies could not begin until the first UKOA research cruise in 2011, led by the National Oceanography Centre. One of its first tasks was to visit the cold-water coral reefs off north west Scotland. The aim is to understand the impact


Water tanks at Aberdeen.


to varying sea water pH according to projections of future atmospheric CO2 levels. These experiments have produced apparently contradictory results, with some organisms seeming to thrive in lower ocean pH while others show apparently negative effects. We need to know much more about what these effects might be, when they might happen and how they might be balanced by the organisms. Steve Widdicombe sums up the


challenge: ‘We need to understand how animals divide their energy between things like shell growth, reproduction and other activities when faced with environmental stresses like ocean acidification and rising temperatures. Different animals will do it differently – some might be able to access the energy they need to adapt; many more might not.’ The problem calls for longer-term


studies that can overlap experiments on a number of generations of animals, and look across a whole community or habitat. The consortium has developed a series


of unique experimental environments which closely reflect conditions in three coastal seafloor habitats: soft sediments; calcareous biogenic habitats – areas like cold-water coral reefs and coral-like algae called maerl; and the rocky intertidal zone.


of ocean acidification and warming on the biogeochemistry of benthic habitats, and on the health of their organisms, and to assess how much those organisms can adapt to change. Rather than look at isolated species, the results will help predict the impact of future CO2 changes on whole communities, and on the biodiversity and functioning of coastal habitats.


Time and tide For these experiments to be worth their salt, they must be consistent across the consortium. So, each institute observes its particular marine environment under the same variations in CO2 levels – 380 parts per million (ppm), 750ppm and 1000ppm – and under the same changes in temperatures, which follow seasonal variation as well as simulating a possible future increase of 4°C, following IPCC projected scenarios. They must also reproduce real-world


conditions as closely as possible. So PML keeps rocky shore species – including dog whelk, top shell, barnacle, sea urchin and seaweed – in a temperature-controlled room where light levels parallel those of the outside world. Because the tides are a major influence


on the behaviour of rocky shore animals, the researchers have built large cantilevered tanks that gradually fill with water so their occupants emerge and submerge as the local tides fall and rise.


Attention to detail is crucial. Mirroring


the real world as closely as possible makes it more likely that any changes seen in these experiments are down to the variations in CO2 and temperature alone. One experiment at Oceanlab at the


University of Aberdeen will look for changes in the behaviour of cockles, brittlestars and ragworms by observing bioturbation – the way these creatures mix sediment (for example, by burrowing in or ingesting it) and how this affects the exchange of chemicals between sediment and water. By using brightly-coloured sediment particles and putting a bromide tracer in the sea water, the researchers can follow how the particles are being moved around, and measure the amount and rate of sea water moving through the creatures’ burrows. It’s not just the range of experiments


that is unusual. ‘We are all using the same techniques for analysing the calcium-carbonate system in different environments, over a longer period – 18 months – than has been done before – this is a world first!’ Widdecombe explains. ‘Having a coordinated approach means other people can look at our data and relate our experimental responses to theirs.’ He expects the consortium’s


experiments to begin producing results within three months, but the real interest will come with longer-term observations of a year and beyond. Ocean acidification is a relatively new


field, and while it is beginning to gain attention from scientists, policy-makers and the public, we still have a great deal to learn. The UKOA programme will clear up many doubts about its consequences. It will begin providing the concrete evidence that we need to mitigate and adapt to the changes, before it’s too late. n


PLANET EARTH Autumn 2011 13


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