Effects of different oxygen regimes on ecological performance and bioenergetics of a coastal marine bioturbator, the soft shell clam Mya arenaria

Benthic species are exposed to oxygen fluctuations that can affect their performance and survival. Physiological effects and ecological consequences of fluctuating oxygen are not well understood in marine bioturbators such as the soft-shell clam Mya arenaria. We explored the effects of different oxygen regimes (21 days of exposure to constant hypoxia (-4.1 kPa PO2), cyclic hypoxia (-2.1--10.4 kPa PO2) or normoxia (-21 kPa PO2)) on energy metabolism, oxidative stress and ecological behaviors (bioirrigation and bioturbation) of M. arenaria. Constant hypoxia and post-hypoxic re-covery in cyclic hypoxia led to oxidative injury of proteins and lipids, respectively. Clams acclimated to constant hyp-oxia maintained aerobic capacity similar to the normoxic clams. In contrast, clams acclimated to cyclic hypoxia suppressed aerobic metabolism and activated anaerobiosis during hypoxia, and strongly upregulated aerobic metabo-lism during recovery. Constant hypoxia led to decreased lipid content, whereas in cyclic hypoxia proteins and glycogen accumulated during recovery and were broken down during the hypoxic phase. Digging of clams was impaired by con-stant and cyclic hypoxia, and bioirrigation was also suppressed under constant hypoxia. Overall, cyclic hypoxia ap-pears less stressful for M. arenaria due to the metabolic flexibility that ensures recovery during reoxygenation and mitigates the negative effects of hypoxia, whereas constant hypoxia leads to depletion of energy reserves and impairs ecological functions of M. arenaria potentially leading to negative ecological consequences in benthic ecosystems.

Automated summary

This study explored the effects of different oxygen regimes on the energy metabolism, oxidative stress, and ecological behaviors of the soft-shell clam Mya arenaria. The results showed that cyclic hypoxia is less stressful for M. arenaria compared to constant hypoxia, as it promotes metabolic flexibility and recovery during reoxygenation. Constant hypoxia, on the other hand, leads to depletion of energy reserves and impairs ecological functions of M. arenaria.