Updated chemical oceanography data from the Hakai Institute on Quadra Island, BC

Figure 1: Sea surface temperature (SST; °C), sea surface salinity (SSS), CO2 partial pressure (pCO2; µatm), and the saturation state of aragonite (Ωarag) from December 18, 2014 to July 3, 2015. Ωarag was calculated using three regional alkalinity-salinity relationships: those reported by Wootton and Pfister [2012; blue] and Ianson et al. [2003; magenta], and one constructed from the data reported by Murray et al. [2015; red]. Ωarag from the Murray et al. [2015] relationship falls in the middle of values calculated from the other two relationships; the data used for this relationship span a broader salinity range, were collected over two annual cycles, and are in closer proximity to Quadra Island. Owing to these reasons, this relationship is believed to currently be the best suited for this dataset. Blue and black horizontal lines in the Ωarag panel mark conditions that are stressful for early life stages of some bivalve species, and conditions that are corrosive for aragonite. Data shown are 5-min averages of 2-sec data. All questions regarding these data should be directly to Wiley Evans at wiley.evans@hakai.org.

Figure 2: Relationship between pCO2 and Ωarag with color as pHT. Note that seawater conditions are never acidic (i.e. pHT < 7) even though at times (i.e. winter) seawater is corrosive to aragonite (Figure 1). From the data collected thus far, Ωarag can vary by nearly 0.4 units over nearly constant pCO2 and pHT conditions. For instance, at a pCO2 of 250 µatm and pHT near 8.15, Ωarag ranges from 1.8 to 2.2. Also note that the lowest pH conditions do not coincide with the lowest saturation states. These intricacies of the carbonate system are why pHT alone fails to track carbonate system variability in complex coastal settings. All questions regarding these data should be directly to Wiley Evans at wiley.evans@hakai.org.