From October 7 to November 7, the U.S. Geological Survey, the National Oceanic and Atmospheric Administration (NOAA), and the Global Foundation for Ocean Exploration (GFOE) are exploring deep-sea corals, sponges, and fish habitat off the U.S. West Coast. While the expedition is underway, let us serve as your terminology tour guides to the unusual and sometimes hard-to-pronounce words that dwell in the depths of deep-ocean science.

The WaterWord:  Aragonite

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Definition: Just like we need calcium for our bones and teeth, many marine organisms rely on calcium – in the form of calcium carbonate – for their skeletons and shells. In the ocean, there are two mineral forms of calcium carbonate: calcite and aragonite. Both warm- and cold-water scleractinian corals, including the deep-sea Lophelia pertusa, produce their skeletons using aragonite.

Etymology: Aragon – from the part of Spain where the mineral was first identified; -ite, a suffix used to create a noun denoting a rock or mineral.

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Use/Significance in the Earth Science Community: As the ocean absorbs more and more atmospheric carbon dioxide, seawater becomes more acidic and the availability of the biologically important carbonate ions decreases. Less carbonate ions makes it difficult for corals and shelled organisms to build their calcium carbonate structure. When the saturation state (i.e., the tendency to dissolve) of aragonite is less than 1, aragonite can dissolve, which could have implications for deep-sea organisms that rely on the mineral to build and maintain their skeletons and shells.

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U.S. Geological Survey Use: On the EXPRESS 2019 expedition, USGS scientists are collecting water samples daily using bottles attached to a CTD, or Conductivity, Temperature, and Depth recorder. The data collected from these water samples will provide insight into aragonite saturation state in areas surrounding deep-sea corals and will be incorporated into models that can help predict where deepwater corals are located.

Keep up with the deep-sea findings on the Cruise Log and social media: Facebook and Twitter.