First research cruise to study ocean acidification in European waters
In the summer of 2011, the first research cruise specifically designed to study ocean acidification in European waters was conducted, with 24 scientists from eight different UK institutes aboard the RRS Discovery. During this 35 day cruise, 21 of those scientists focused their research on the impact of ocean acidification on the pelagic zone (seawater that is not close to the bottom or near to the shore), looking at the impact of the changing chemistry on marine organisms and ecosystems in the water column, the cycling of carbon and nutrients in the sea and how the sea interacts with the atmosphere to influence climate.
Three of the scientists had their attention focused on some out-of-sight animals which may also be threatened by changing ocean chemistry – the enigmatic cold-water coral species Lophelia pertusa. To many in the UK, the thought of coral reefs in UK waters is surprising, with images of tropical corals in their bright colours springing to mind. But, off the Hebridean island of Mingulay extensive reefs are formed from cold-water corals, which support a variety of fish life and invertebrate species.
Laura Wicks, Sebastian Hennige and Murray Roberts from Heriot-Watt University, Edinburgh, are part of the UK Ocean Acidification Benthic Research Consortium. Aboard RRS Discovery they carefully sampled the corals from the Mingulay Reef Complex to use in a series of experiments on board.
Currently, little is known about how these animals function, for example their food preferences, and how they cope with changes in the water temperature in which they live. As such the cruise represented a unique opportunity for the scientists to study how freshly-sampled corals responded to changes in their diet, temperature, and perhaps most importantly the changing chemistry of the water in which they live.
Increasing acidity in the oceans linked to increased carbon dioxide in the atmosphere could seriously damage marine creatures, like cold-water corals, which need calcium carbonate (CaCO3) to build their skeletons. Once absorbed in seawater, carbon dioxide forms carbonic acid and lowers ocean pH, which makes carbonate less available and thus makes it harder for corals to build their skeletons. Understanding how corals respond to the future chemistry of the oceans, and whether they can still grow, feed and reproduce are important knowledge gaps which these scientists are addressing.
Laura and Sebastian subjected the corals they collected to a range of environmental conditions, including increased temperatures and enhanced CO2 levels and measured their metabolic and growth response. Now they are back on dry land, the sample processing from those experiments begins, with results expected in the next few months.Additionally, corals were collected to take part in a long-term experiment in a purpose built mesocosm system at Heriot Watt University.
For 18 months, these corals will be subject to a range of temperature and CO2 levels, and their growth and metabolism monitored. This will help us to understand whether corals have the ability to acclimate to new conditions. The chemistry and temperature of the oceans are changing rapidly; only by understanding how animals respond to such changes will we be able to make predictions on the future for cold-water corals and the communities they support.