Calcifying organisms, under threat from a combination of ocean warming and acidification

Newswise: Calcifying organisms, under threat from a combination of ocean warming and acidification

A bryozoan, at 32m depth at Signy Island, Antarctica. Credit: David Barnes, British Antarctic Survey

A new study led by the Institut de Ciències del Mar (ICM-CSIC), with colleagues from the British Antarctic Survey, the Institute of Oceanology, the Polish Academy of Sciences and the University of Gdańsk have also participated has revealed that global warming and ocean acidification threaten marine organisms that build their skeletons and shells with calcium carbonate (chalk) such as corals, bryozoans, molluscs, sea urchins or crustaceans.

The work, recently published in the journal Ecography, focuses on organisms with calcium carbonate skeletons from around Antarctica in the Southern Ocean. Calcium carbonate is more soluble in more acidic waters which contain more carbon dioxide (CO2), such as the colder waters of the polar regions, making it harder for these creatures to build their skeletons.

Bryozoans, key for understanding the global change impacts on calcifying organisms

To carry out the study, researchers analysed the skeleton of a group of marine creatures called bryozoans (commonly known as moss animals), which are small filter-feeding invertebrates that live on the seafloor and can create complex habitats that enhance biodiversity.

In this sense, the expert explains that the bryozoan skeletons are made of the two main types of calcium carbonate, calcite or aragonite, but they can also incorporate magnesium, which can make the skeletons more vulnerable to acidification.

Through mineralogical analyses, researchers identified the different types of minerals and determined the levels of magnesium found in Antarctic bryozoan skeletons, creating the largest dataset for Southern Ocean bryozoans ever produced. Then, they included these mineral signatures with existing data from almost 500 species found in the Southern Hemisphere and compared the distribution of the different mineral types and levels of magnesium in their skeletons with the temperature of the seawater that they lived in.

Instituto de Ciencias del Mar, News Wise, 28 November 2022. Press release.

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