German researchers see “ominous change” in increasing CO2 levels
By Summit Voice
FRISCO — There’s no question that the rapid acidification of the oceans will disrupt ecosystems and perhaps even wipe out some of the most sensitive species, including some shellfish.
British Antarctic Survey researchers last year showed how corrosive waters in the southern Ocean is destroying sea snail shells. Other studies suggest mussel beds in the Pacific Northwest may also be feeling the impacts, as the oceans absorb and process anthropogenic greenhouse gases.
As the atmospheric carbon dioxide dissolves in water, it forms carbonic acid and causes the pH value of the oceans to drop, posing challenges for many species that live on the cusp of a delicate chemical balance.
Biologists at the Alfred Wegener Institute, Helmholtz Centre for Polar and Marine Research recently assessed the extent of what they called an “ominous change,” finding that the impacts are widespread, yet with very different effects on various species.
The study, published Aug. 25 in Nature Climate Change, compiled and analysed all available data on the reaction of marine animals to ocean acidification from five taxa: Corals, crustaceans, molluscs, vertebrates such as fishes and echinoderms such as starfish und sea urchins.
“Our study showed that all animal groups we considered are affected negatively by higher carbon dioxide concentrations. Corals, echinoderms and molluscs above all react very sensitively to a decline in the pH value”, said Dr. Astrid Wittmann.
Some echinoderms such as brittle stars have lower prospects of survival in carbon dioxide values predicted for the year 2100. By contrast, only higher concentrations of carbon dioxide would appear to have an impact on crustaceans such as the Atlantic spider crab or edible crab. However, the sensitivity of the animals to a declining pH value may increase if the sea temperature rises simultaneously.
In general, species rooted in place, like coral, are considered more sensitive, while mobile species can balance any initial fall in the pH value very well in their blood.
But there are exceptions. In their larval stage, fish are quite sensitive to ocean acidification.
“Not all effects we are currently measuring are decisive for the destiny of a species possibly in the long term”, said Prof. Hans-Otto Pörtner. “We compared our results with the widespread deaths of species around 250 and 55 million years ago when CO2 concentrations were also elevated … we discovered similar sensitivities in the same animal taxa,” Pörtner said. The spread of the corals and the size of the reefs slumped drastically 55 million years ago whilst fish exhibited a great adaptive capacity and were able to further extend their dominance.”
The study is part of the framework for the Fifth Assessment Report of the Intergovernmental Panel on Climate Change. It is the first IPCC report to extensively document the consequences of climate change on the ecosystems of the oceans. The report will be published at the end of March 2014 and is prepared by the so-called second working group, which assesses how climate change impacts socio-economic and ecological systems.