NOAA Research Ties Dissolving Shells off US West Coast to CO2 Emissions

Most people aren't familiar with pteropods. but they're very familiar with the fish that eat it. Commercially valuable fish such as salmon, sablefish, and rock sole all consume the pteropod. However, National Oceanic and Atmospheric Administration (NOAA) and partner scientists have linked the concentration of human-caused carbon dioxide in waters off the U.S. Pacific coast to the dissolving of pterapod shells.

"This is the first time we've been able to tease out the percentage of human-caused carbon dioxide from natural carbon dioxide along a large portion of the West Coast and link it directly to pteropod shell dissolution," shared Richard Feely. A NOAA senior scientist, he led the research that was published in Estuarine, Coastal and Shelf Science. "Our research shows that humans are increasing the acidification of U.S. West Coast coastal waters, making it more difficult for marine species to build strong shells."

The pteropod is a sea snail the size of the head of a pin. Native to the Pacific Ocean, the pterapod has been the focus of research in recent years because of the possible harmful effects of CO2 in seawater. The way pterapod shells are affected by CO2 could be an indicator of ocean acidification affecting the larger marine ecosystem.

Feely and his team used several decades of measurements from the Pacific Ocean taken through the U.S. Global Ocean Carbon and Repeat Hydrography Program and new data from four NOAA West Coast research cruises conducted between 2007 and 2013. By utilizing a method to estimate additional CO2 from human-caused emissions since the start of the Industrial Era as compared to CO2 from natural sources, the researchers found that concentrations of human-caused CO2 are greatest in shallow waters where the atmosphere gives up large amounts of its CO2 to the sea.

Once researchers created a detailed map of the human-generated CO2 concentrations, they looked at how pteropod shells fared in areas with varying seawater CO2 concentrations. They found more than 50 percent of pteropod shells collected from coastal waters with the high CO2 concentrations were severely dissolved. An estimated 10 to 35 percent of pteropods from offshore waters showed shell damage when examined under a scanning electron microscope.

"We estimate that since pre-industrial times, pteropod shell dissolution has increased 20 to 25 percent on average in waters along the U.S. West Coast," said Nina Bednaršek, a NOAA postdoctoral research associate from the University of Washington. "This new research suggests we need a better understanding of how changes in pteropods may be affecting other species in the food chain."