Valve movement of three species of North American freshwater mussels exposed to elevated carbon dioxide

Abstract

Freshwater mussels are at-risk taxa and may be exposed to high levels of carbon dioxide (CO₂) because of the potential use of CO₂ to control the movement of invasive aquatic fish species. One potential behavioral response to a change in the partial pressure of CO₂ (pCO₂) may be altered valve movement. In this study, three species of mussels were fitted with modified sensors and exposed to two regimes of pCO₂ to define thresholds of impaired valve movement. The first experiment demonstrated that Pyganodon grandis were much more tolerant to rising pCO₂ relative to Lampsilis siliquoidea (acute closure at ∼200,000 μatm in comparison to ∼80,000 μatm). The second experiment consisted of monitoring mussels for 6 days and exposing them to elevated pCO₂ (∼70,000 μatm) over a 2-day period. During exposure to high pCO₂, Lampsilis cardium were open for nearly the entire high pCO₂ period. Conversely, P. grandis were closed for most of the period following exposure to high pCO₂. For L. siliquoidea, the number of closures decreased nearly 40-fold during high pCO₂. The valve movement responses observed suggest species differences, and exposure to elevated pCO₂ requires a reactive response.

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