Effects of variable oxygen regimes on mitochondrial bioenergetics and reactive oxygen species production in a marine bivalve, <i>Mya arenaria</i>

ABSTRACT Estuarine and coastal benthic organisms often experience fluctuations in oxygen levels that can negatively impact their mitochondrial function aerobic metabolism. To study these impacts, we exposed a common sediment-dwelling bivalve, the soft-shell clam Mya arenaria, for 21 days to chronic hypoxia (PO2 ∼4.1 kPa), cyclic ∼12.7–1.9 kPa, mean 5.7 kPa) or normoxia ∼21.1 kPa). pH was manipulated mimic covariation CO2/pH hypoxic zones. Mitochondrial respiration, including proton leak, capacity oxidative phosphorylation (OXPHOS), maximum activity of electron transport system (ETS), reactive species (ROS) production, affinity cytochrome c oxidase (CCO) were assessed. Acclimation constant did not affect studied traits except modest decrease OXPHOS coupling efficiency. Cyclic had no effect on ETS capacity, but increased leak lowered Furthermore, mitochondria clams acclimated higher rates ROS generation compared with hypoxia. CCO upregulated under hypoxia, change. These findings indicate long-term has stronger M. arenaria than might lead impaired ATP synthesis, costs maintenance stress. changes populations Baltic Sea increasing pressure.