Alkalinity, pH, and pCO2 in the Laurentian Great Lakes: An initial view of seasonal and inter-annual trends

The effect of increasing temperature and pCO2 on experimental pelagic freshwater communities

“…Furthermore, increasing aquatic pCO 2 can cause the pH to decrease, which may slow growth rates of some zooplankton species, though this effect is often weaker than indirect, food quality effects (Urabe et al 2003; Meunier et al 2016). Freshwater zooplankton in particular have likely evolved to experience a wider range of pH concentrations than their marine counterparts due to the relatively high variability of pCO 2 within and across freshwater systems (Cole et al 1994; Minor and Brinkley 2022). For example, diel cycles of net autotrophy during the day and net heterotrophy at night can readily result in a change of one or more units of pH (Maberly 1996).…”

“…More fundamentally, while the rise of lake water temperatures worldwide is well documented (O'Reilly et al 2015), less information is available regarding long‐term trends of other lake properties shaping ecological processes. Although the few multidecade‐long time series of aquatic partial pressures of CO 2 (pCO 2 ) in lakes feature more examples of increasing than decreasing pCO 2 over time, many more studies would be needed to make any generalizations (Couturier et al 2022; Minor and Brinkley 2022). Unlike in marine systems, where aquatic pCO 2 is typically near equilibrium with atmospheric pCO 2 , freshwater systems are frequently in a state of disequilibrium (Cole et al 1994).…”

Total alkalinity measurement using an open‐source platform

“…This latter value is greater than the diel variability in p CO 2 observed in early summer 2001 in Lake Superior by Atilla et al (2011), greater than the annual variability of Earth's atmospheric p CO 2 , and greater than the mean daily difference between atmospheric and surface water p CO 2 in Lake Superior for large portions of the 5‐year period modeled by Bennington et al (2012). The uncertainty associated with measurements of pH and A T in the Great Lakes National Program Office biannual surveys of Laurentian Great Lakes is estimated as 0.2 pH units and 50 μ mol kg −1 (Minor and Brinkley 2022), which propagate to a p CO 2 uncertainty of ±163 μ atm. Uncertainty in measured inorganic carbon parameters including pH and A T has the potential to hinder carbon cycling studies and obscure biogeochemical observations of inland waters.…”

“…u(pCO 2 ) is indicated with contours as μ atm. The carbonate equilibrium constants of Cai et al (1998) were used based upon improved system consistency in over‐constrained measurements (Minor and Brinkley 2022). Code for this diagram is available in Data S1.…”

“…Uncertainty in calculated pCO 2 was propagated from uncertainty in DIC observed from measurements of reference materials and observed uncertainty in A T from this study. The carbonate equilibrium constants of Cai et al (1998) were used based upon improved system consistency in over-constrained measurements (Minor and Brinkley 2022).…”