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article imageChanging oceans affecting calcification of marine organisms

By Karen Graham     Jul 24, 2014 in Science
The ocean is home to many creatures, and all of them take their sustenance from this environment. One group of organisms use the ocean's calcium to create their shells and exoskeletons. These are the calcifiers, the mollusks, corals and starfish.
There are good reasons to be concerned about the ocean's calcifiers. Recent studies have focused on these organisms and the impact that acidification of the world's oceans will have on them. The June issue of Biological Bulletin, published by the Marine Biological Laboratory, discusses the challenges faced by these sea creatures in light of the changing composition of the seas worldwide.
Our oceans are becoming warmer and more acidic because of rising atmospheric carbon dioxide loads. This, in turn is threatening the very survival of calcifying organisms because of the reduced saturation of carbonates needed for calcification. The ability to calcify came about independently with many sea creatures during the Cambrian era. Then, calcium levels in the oceans were much higher than they are today. The use of calcium carbonate was helpful in creating biodiversity, resulting in the vast numbers of calcifiers we see today.
It is important to remember that the oceans have an important role in protecting the Earth. Oceans cover 71 percent of the Earth's surface. Saltwater makes up 97 percent of all the water on the planet, with only 2 percent ice and just 1 percent being freshwater. The oceans act as a heat repository, absorbing, storing and then slowly releasing heat back into the atmosphere. It buffers the climate near the land, and eventually over the whole planet.
The ocean is also the Earth's largest carbon dioxide reservoir. The oceans contain 50 percent more carbon dioxide than the atmosphere. So as more and more man-made carbon dioxide has entered the atmosphere, more and more has also entered the oceans. All that excess CO2 has created an unwanted result, acidification of the ocean waters. What happens is nothing more than a chemical reaction. As CO2 dissolves in the ocean, acidity rises. Researchers say that by the end of the Industrial Revolution, the acidity of the ocean had risen 30 percent. By the end of this century, the oceans could be 150 percent more acidic.
A NOAA (PMEL) moored autonomous CO 2 buoy used for measuring CO 2 concentration and ocean acidificat...
A NOAA (PMEL) moored autonomous CO 2 buoy used for measuring CO 2 concentration and ocean acidification studies. Shown is the Moored Autonomous pCO2 (MAP-CO2) Buoy for ocean acidification research. Buoy engineered and deployed by NOAA.
Co-editors of the study, Maria Byrne of the University of Sydney; and Gretchen Hofmann of the University of California-Santa Barbara wrote, "Today, modern calcifiers face a new and rapidly escalating crisis caused by warming and acidification of the oceans with a reduction in the availability of carbonate minerals, a change driven by the increase in atmospheric CO2 due to anthropogenic emissions and industrialization. The CO2 itself can also directly cause metabolic stress."
Contributing editors to the journal addressed metabolic stress in a variety of calcifiers under different degrees of stress. Janice Lough and Neal Cantin of the Australian Institute of Marine Science chose to study data on coral reefs and the impact of environmental stressors on them. At the same time, Philippe Dubois (Université Libre de Bruxelles) discussed the observed changes in sea urchin exoskeletons.
Other researchers studied lesser known organisms, particularly bryozoans, a type of invertebrate filter-feeder, and how the creation of certain niche-habitats affected their sensitivity to fluctuating calcium levels. Some researchers studied the affect of ocean acidification on predator-prey interactions, while other studied acidification's impact on oysters.
A colony of the modern marine bryozoan Flustra foliacea.
A colony of the modern marine bryozoan Flustra foliacea.
Hans Hillewaert
The contributors were able to identify some key gaps in the still evolving field of marine global change biology. Publishing these papers in Biological Bulletin is a way to share these research topics with scientists around the world, putting global emphasis on the problem of seawater acidification and other threats to our oceans.
More about Oceans, Marine, carbonate, Calcium, Acidification
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