Three studies, published in Nature Climate Change on August 25, have highlighted the need for more research on how oceans, and ocean fauna, are responding to anthropogenic climate change.
The oceans absorb more than a quarter of carbon dioxide in the atmosphere, which dissolves in the water to form carbonic acid. This way, the oceans act as a carbon dioxide sink. However, as the amount of greenhouse gas increases in the atmosphere, so does the amount of carbonic acid in the waters, leading to ocean acidification (OA).
The studies have found varying levels of adaptability among different organisms. Scientists from the Helmholtz Centre for Polar and Marine Research have found that corals and echinoderms (like starfish) face endangerment and extinction, respectively, by 2100.
Their findings are more pertinent because they are based on the same emission scenarios used by the Intergovernmental Panel on Climate Change (IPCC) to prepare its Fifth Assessment Report, due out in September.
Corals spend their entire life in one place and cannot efficiently compensate for higher acidity as they lack the necessary physiological mechanisms.
These organisms also secrete calcium carbonate to create the most productive ecosystems known: coral reefs. Higher OA and warmer climes could interfere with the formation of reefs, with the scientists believing they could face extinction by the end of the century.
On the other hand, marine biologists led by researchers from Plymouth University, England, have found that certain sea worms have developed genetic responses to climate change — a first. These researchers studied the response of polychaete worms living around the carbon dioxide-rich volcanic vents off the southern coast of Italy to higher levels of carbonic acid.
Dr. Maria-Cristina Gambi, of the Naples Zoological Station and one of the study's researchers, noted, “The nereid polychaete worms showed a differentiated genotype, found exclusively within the acidic area, demonstrating a true local adaptation to such conditions,” in an email.
This implies that, through evolution, the DNA of the nereid family of polychaete worms has been altered to give the worm a trait – increased physiological plasticity – to help tackle higher OA. However, Dr. Gambi is not yet sure how this change in the genetic makeup will manifest.
This is the first time that this kind of genetic adaptation has been showed by a complex animal species (a metazoan invertebrate) in response to climate change.
In fact, the third study, out of the Max Planck Institute for Meteorology, Hamburg, showed that OA could also reduce the amount of biogenic emissions of sulphur compounds like dimethylsulphide.
Though not a greenhouse gas, dimethylsulphide cools the atmosphere by reducing the amount of solar energy reaching Earth’s surface. If its concentration is diminished, it could result in ocean acidification directly adding to global warming.