A pilot study of sampling, using monthly marine flights over spatially distributed stations, was conducted with the aim to characterize the carbonate system in Puget Sound over a full year-long period. Surface waters of Puget Sound were found to be under-saturated with respect to aragonite during October–March, and super-saturated during April–September. Highest pCO₂ and lowest pH occurred during the corrosive October–March period. Lowest pCO₂ and highest pH occurred during the super-saturated April–September period. The monthly variations in pCO₂ , pH, and aragonite saturation state closely followed the variations in monthly average chlorophyll a. Super-saturated conditions during April–September are likely strongly influenced by photosynthetic uptake of CO2 during the phytoplankton growing season. The relationship between phytoplankton production, the carbonate system, and aragonite saturation state suggests that long-term trends in eutrophication processes may contribute to trends in ocean acidification in Puget Sound.

Pelletier G., Roberts M., Keyzers M. & Alin S.R., 2018. Seasonal variation in aragonite saturation in surface waters of Puget Sound – a pilot study. Elementa: Science of the Anthropocene 6 (1): 5. doi:10.1525/elementa.270. Article.