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The California Current System is thought to be particularly vulnerable to ocean acidification, yet pH remains chronically undersampled along this coast, limiting our ability to assess the impacts of ocean acidification. To address this observational gap, we integrated the Deep-Sea-DuraFET, a solid-state pH sensor, onto a Spray underwater glider. Over the course of a year starting in April 2019, we conducted seven missions in central California that spanned 161 glider days and >1600 dives to a maximum depth of 1000 m. The sensor accuracy was estimated to be ± 0.01 based on comparisons to discrete samples taken alongside the glider (n = 105), and the precision was ± 0.0016. CO2 partial pressure, dissolved inorganic carbon, and aragonite saturation state could be estimated from the pH data with uncertainty better than ± 2.5%, ± 8 μmol kg-1, and ± 2%, respectively. The sensor was stable to ± 0.01 for the first 9 months but exhibited a drift of 0.015 during the last mission. The drift was correctable using a piecewise linear regression based on a reference pH field at 450 m estimated from published global empirical algorithms. These algorithms require accurate O2 as inputs; thus, protocols for a simple predeployment air calibration that achieved accuracy of better than 1% were implemented. The glider observations revealed upwelling of undersaturated waters with respect to aragonite to within 5 m below the surface near Monterey Bay. These observations highlight the importance of persistent observations through autonomous platforms in highly dynamic coastal environments. [ABSTRACT FROM AUTHOR]

Whiting events, or waters with high concentrations of fine-grained calcium carbonate, have been previously reported in southwest Florida using three years of observations from the Moderate Resolution Imaging Spectroradiometer. Here, the initial case study has been expanded to 13 years (2003–2015) with a statistical analysis that includes environmental data to document and understand longer term temporal and spatial variability of whiting occurrence in the same region. Annual mean whiting coverage (km2) peaked in 2011 and 2012, with the highest daily coverage in 2008 (126.0 km2). Over the time series, whiting events showed spatial variability based on distance from shore. Whiting seasonality also varied within the extended time series. Multivariate linear and non-linear regressions between mean whiting coverage (km2) and several environmental variables (wind speed, sea surface temperature, precipitation, and nearby river discharge) were performed over the entire study region as well as subregions based on spatial division from the coast line. Statistically significant correlations have been found with sea surface temperature and river discharge in subregions. These findings suggest that although observing spatial and temporal patterns of whiting events is possible with modern satellites, understanding the mechanisms regulating their initiation and maintenance is more difficult. [ABSTRACT FROM AUTHOR]