An international study to comprehend and predict the likely impact of ocean acidification on shellfish and other marine organisms living in seas, from the tropics to the poles, has been published this week in the journal Global Change Biology.
Ocean acidification is occurring because some of the increased carbon dioxide humans are adding to the atmosphere dissolves in the ocean and reacts with water to produce an acid.
The results suggest that increased acidity is affecting the size and weight of shells and skeletons, and the trend is widespread across marine species. These animals are an important food source for marine predators such as tropical seabirds and seals as well as being a valuable ingredient in human food production. Consequently, these changes are likely to affect humans and the ocean’s large animals.
UK scientists from the British Antarctic Survey (BAS) and the National Oceanography Centre (NOC), together with colleagues from Australia’s James Cook and Melbourne Universities and the National University of Singapore, investigated the natural variation in shell thickness and skeletal size in four types of marine creatures living in 12 different environments from the tropics to the Polar Regions. Their aim was to get a clearer understanding of similarities and differences between species, and to make better predictions of how these animals might respond to increasing acidity in the oceans.
The effort required by clams, sea snails and other shellfish to extract calcium carbonate from seawater to build their shells and skeletons varies from place to place in the world’s oceans. A number of factors, including temperature and pressure, affect the availability of calcium carbonate for species that produce carbonate skeletons.
There is already evidence that ocean acidification is affecting the ability of some marine species to grow, especially during their early life stages, and there is mounting concern about whether or not these species can evolve or adapt to cope with increases in acidity in the coming decades.
This study shows, over evolutionary time, animals have adapted to living in environments where calcium carbonate is relatively difficult to obtain by forming lighter skeletons. Carbon dioxide from fossil fuel combustion is altering seawater chemistry in the same way, in a process called ocean acidification and this is making it harder for marine animals to make shells and skeletons.
Polar sea urchin from the Antarctic, Sterechinus neumayeri (Photo: Sue-Ann Watson)
Polar sea snail from the Arctic, Buccinum glaciale (Photo: Sue-Ann Watson)
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