Ocean Acidification Exacerbated by Coastal Upwelling: Monitoring of CO2 and O2 on the California Shelf, and Studies of Their Effects on Red Sea Urchins, California Mussels and Abalone

This project explores the effects of ocean acidification on shell-building organisms such as abalone and sea urchins, as observed through field measurements at an upwelling center off California and through laboratory experiments designed to simulate low-oxygen, corrosive conditions that may be experienced during periods of upwelling. In work to date, scientists have deployed a moored infrared detector 10 kilometers off Trinidad Head in Humboldt County that continuously measures surface ocean and atmospheric carbon dioxide concentrations from which estimates of surface ocean pH can be calculated. Sensors at the mooring are also recording water temperatures, salinity and oxygen concentrations. Water samples are being collected from the R/V Coral Sea about 15 times a year at the mooring and along a transect west of it to groundtruth the sensor data and document a broader view of the when, where and how long corrosive, low-oxygen waters persist in the region. With partial support from the National Science Foundation, scientists have designed and are now operating a temperature controlled, flowthrough gas equilibrium tank system for conducting manipulation experiments on shell-building species that may be most vulnerable to changes in seawater carbonate chemistry. In soon-to-be published experiments, scientists have documented changes in shell thickness and growth rates in young abalone exposed to acidic and then normal water conditions, mimicking the conditions experienced by organisms during upwelling, when nutrient-rich, low-oxygen, acidic waters are brought from depth to the surface. In the project's final year, scientists will study the effects of low-oxygen, low-pH conditions on the gene expression patterns of red sea urchins to more fully understand the consequence of upwelled water on these commercially important species. Results will be shared with resource managers, abalone farmers, sea urchin fishermen and other interested parties.