Researchers studying OA impact on ocean health

Two scientists at Columbia University in New York are leading research projects to examine how climate change is affecting the health of the global ocean, which covers 70 percent of the planet Earth.

Their concern is that the ocean is becoming more acidic due to the rising concentration of carbon dioxide in Earth’s atmosphere, about 30 percent of which is absorbed by the ocean. While this process helps to minimize global warming the dissolution of carbon dioxide in the ocean leads to formation of carbonic acid, which makes seawater more acidic. It is this “ocean acidification” that makes it harder for calcifying organisms such as corals, mollusk and some plankton to build their shells and skeletons.

The team at Columbia’s Lamont-Doherty Earth Observatory includes marine geochemist Barbel Honisch, and paleoclimate scientist Brad Linsley.

The current pH of the ocean is about 8.1, representing a 25 percent increase in acidity over the past 200 years. As the amount of carbon dioxide in the atmosphere rises, researchers expect seawater acidity to increase another 25 percent by the end of the 21st century.

Honisch is currently studying how seawater chemistry changes through time. She is analyzing their shells of tiny plankton organisms called foraminifera that were preserved I deep sea sediments during this and other time periods, which are recovered from the sea floor by deep-ocean drilling.

Honisch is hoping to quantify changes in the ocean that occurred due to past climate shifts, and to determine whether and how marine organisms adapted to these changing conditions.

Linsley, meanwhile, is reconstructing past climate using corals and sediments to learn how changes in global temperatures, ocean salinity, and atmospheric hydrology carried in the past. Corals are very sensitive to temperature changes and when ocean temperatures rise even one degree Celsius, corals are stressed out and algae are expelled from the corals.

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