Abstract
Carbonate chemistry variability is often poorly characterized in coastal regions and patterns of covariation with other biologically important variables such as temperature, oxygen concentration, and salinity are rarely evaluated. This absence of information hampers the design and interpretation of ocean acidification experiments that aim to characterize biological responses to future pCO2 levels relative to contemporary conditions. Here, we analyzed a large carbonate chemistry data set from Puget Sound, a fjord estuary on the U.S. west coast, and included measurements from three seasons (winter, summer, and fall). pCO2 exceeded the 2008–2011 mean atmospheric level (392 µatm) at all depths and seasons sampled except for the near-surface waters (< 10 m) in the summer. Further, undersaturated conditions with respect to the biogenic carbonate mineral aragonite were widespread (Ωar<1). We show that pCO2 values were relatively uniform throughout the water column and across regions in winter, enriched in subsurface waters in summer, and in the fall some values exceeded 2500 µatm in near-surface waters. Carbonate chemistry covaried to differing levels with temperature and oxygen depending primarily on season and secondarily on region. Salinity, which varied little (27 to 31), was weakly correlated with carbonate chemistry. We illustrate potential high-frequency changes in carbonate chemistry, temperature, and oxygen conditions experienced simultaneously by organisms in Puget Sound that undergo diel vertical migrations under present-day conditions. We used simple calculations to estimate future pCO2 and Ωar values experienced by diel vertical migrators based on an increase in atmospheric CO2. Given the potential for non-linear interactions between pCO2 and other abiotic variables on physiological and ecological processes, our results provide a basis for identifying control conditions in ocean acidification experiments for this region, but also highlight the wide range of carbonate chemistry conditions organisms may currently experience in this and similar coastal ecosystems.
Highlights
Global surface ocean pH levels have decreased by approximately 0.1 units since the Industrial Revolution and will potentially decline an additional 0.3 to 0.4 units over the century due to anthropogenic CO2 emissions [1,2,3,4]
Recognition of the potential disparity between conditions considered ‘‘controls’’ in ocean acidification’’ (OA) experiments and actual carbonate chemistry conditions experienced by organisms in the habitats they occupy has been highlighted in a suite of recent publications [9,10,18,19,20]
We considered a scenario in which the present-day anthropogenic dissolved inorganic carbon (DIC) load in Puget Sound (,30 mmol kg21; [26]) was quadrupled to 120 mmol kg21
Summary
Global surface ocean pH levels have decreased by approximately 0.1 units since the Industrial Revolution and will potentially decline an additional 0.3 to 0.4 units over the century due to anthropogenic CO2 emissions [1,2,3,4]. This change in ocean chemistry, termed ‘‘ocean acidification’’ (OA), results in a reduction in the saturation state of carbonate minerals such as calcite and aragonite, elevates pCO2, and lowers pH [5]. There is increasing awareness that researchers should attempt to simulate control conditions that correspond to carbonate chemistry conditions experienced by organisms in natural habitats and interpret experimental outcomes [21,22]
Sign-in/Register to view highlights & summary Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
