Ocean Acidification Occurring at Unprecedented Rates

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Ocean acidification is the process of decreasing pH in the Earth’s oceans. This is mainly due to the absorption of carbon dioxide emitted by humans. As CO₂ dissolves in seawater, hydrogen ion concentrations increase, thus lowering the ocean pH. Oceans are currently absorbing about a quarter of all CO₂ that is released into the air and with the increasing acidity of these marine environments come many concerns about the future of these ecosystems.

This week, at the Third International Symposium on the Ocean in a High-CO₂ World in Monterey, California, Dr. Daniela Schmidt of the University of Bristol’s School of Earth Sciences warns us that the current rates of ocean acidification are unlike any other in the Earth’s history.

Dr Schmidt said: “Ocean acidification has happened before, sometimes with large consequences for marine ecosystems. But within the last 300 million years, never has the rate of ocean acidification been comparable to the ongoing acidification.”

When ocean acidification occurred in the past, it was noted that species responded to “the warming, acidification, change in nutrient input and loss of oxygen — the same processes that we now see in our oceans.” However, according to Dr Schmidt “the geological record also shows changes in species distribution, changes in species composition, changes in calcification and growth and in a few cases extinction.”

Dr Claudine Hauri, an oceanographer from the University of Alaska Fairbanks also agreed with the increased rate of change, stating: “The chemistry of these waters is changing at such a rapid pace that organisms now experience conditions that are different from what they have experienced in the past. And within about 20 or 30 years, the chemistry again will be different from that of even today.”

By studying the long-term evidence of ocean acidification and their associated biotic responses through the geological record, researchers studied the trends of acidification in these ocean ecosystems. Evidence shows that elevated atmospheric CO₂, global warming, and ocean acidification has occurred over the past 300 million years of Earth’s history. However, increased rates of change will have had a significant impact on marine life, especially for calcifiers such as corals and mollusks that construct their shells and skeletons from calcium carbonate.

Although similarities exist, no past event can serve as a model for future projections due to the unprecedented releases of anthropogenic CO₂.

Read more at the University of Bristol.

CO2 in ocean image via Shutterstock.