Metabolic responses of the Nereid polychaete, Alitta succinea, to hypoxia at two different temperatures

Coastal hypoxia has detrimental effects to community ecology, degrading community structure and diminishing benthic function. Benthic function is largely driven by infauna bioturbation, which facilitates life-supporting processes by increasing the quality of marine sediments for nearly all biota. These infauna-mediated processes are diminished by coastal hypoxia. However, some infauna have been documented to exhibit metabolic plasticity to low oxygen allowing them to maintain some form of benthic function. Of particular interest to this study is the Nereid polychaete Alitta succinea. Stopflow respirometry was used to assess the hypoxic tolerance of A. succinea, by quantifying resting metabolic rate (VO2 ), critical oxygen saturation (i.e. the oxygen level below which worms could not maintain aerobic metabolism), and the oxyregulation ability at an acclimation temperature (25 °C) and after an acute temperature increase (to 30 °C). The acute Q10 during normoxia was 4.6, though this effect of temperature on VO2 was completely muted during hypoxia with a Q10 of 1. Compared among other polychaetes, A. succinea was the most efficient at oxyregulation, resulting in low critical oxygen saturation levels of 16% and 10% at 25 and 30 °C, respectively. Finally, there was a significant effect of hypoxia on the mass metabolism relationship of A. succinea. Oxygen consumption rates were significantly higher during hypoxia only for smaller A. succinea, suggesting a physiological size selection for hypoxia response. These findings demonstrate the significant effect of hypoxia on A. succinea metabolism, but also provide the metabolic justification for survival of this infaunal worm during severe hypoxia.