Paper Reviewed
Midway, S.R., Hasler, C.T., Wagner, T. and Suski, C.D. 2017. Predation of freshwater fish in environments with elevated carbon dioxide. Marine and Freshwater Research 68: 1585-1592.

Writing as background for their study, Midway et al. (2017) write that "freshwater CO2 is expected to increase in some systems in the future," possibly in part due to rising atmospheric CO2 concentrations. However, they note that "future changes in pCO2 will vary widely on the basis of several environmental factors, including terrestrial primary productivity, substrate and biological respiration." And they add that pCO2 in freshwater may become more variable as a result of changing precipitation patterns and management activities. Consequently, it is anticipated that the biota of many freshwater ecosystems will be exposed to higher and more variable pCO2 in the future, a development referred to as freshwater acidification. However, unlike its marine equivalent (ocean acidification), little is known about how freshwater acidification might impact organisms in non-marine environments.

Hoping to provide some enlightenment in this regard, Midway et al. investigated the impact of CO2 exposure on the predator-prey relationship between two freshwater fishes. Largemouth bass (Micropterus salmoides) was the examined predator and fathead minnow (Pimephales promelas) the studied prey. For their analysis, the four scientists exposed the bass to three pCO2 treatment levels (ambient, low and high, corresponding to ~500, 4500 and 9000 µatm) for a period of four days, after which they introduced fathead minnows and measured multiple parameters relating to predatory response, including if the prey was consumed, time to consumption, number of total and failed strikes and time between multiple strikes.

Results of the analysis revealed, in the words of the authors, that "the ability of M. salmoides to capture and consume prey was not altered despite exposure to elevated pCO2." Such absence of a change in feeding behavior, they add, "may be due to [M. salmoides] being exposed to elevated pCO2 during their evolutionary history and, potentially, because they have a more robust physiological response to high concentrations of CO2." Thus, freshwater acidification appears to be a non-concern in terms of future prey consumption by largemouth bass.