A novel method for determination of aragonite saturation state on the continental shelf of central Oregon using multi‐parameter relationships with hydrographic data

We developed a multiple linear regression model to robustly determine aragonite saturation state (Ω arag ) from observations of temperature and oxygen (R 2 = 0.987, RMS error 0.053), using data collected in the Pacific Northwest region in late May 2007. The seasonal evolution of Ω arag near central Oregon was evaluated by applying the regression model to a monthly (winter)/bi‐weekly (summer) water‐column hydrographic time‐series collected over the shelf and slope in 2007. The Ω arag predicted by the regression model was less than 1, the thermodynamic calcification/dissolution threshold, over shelf/slope bottom waters throughout the entire 2007 upwelling season (May–November), with the Ω arag = 1 horizon shoaling to 30 m by late summer. The persistence of water with Ω arag < 1 on the continental shelf has not been previously noted and could have notable ecological consequences for benthic and pelagic calcifying organisms such as mussels, oysters, abalone, echinoderms, and pteropods.