Impact of Short- and Long-Term Exposure to Elevated Seawater Pco2 on Metabolic Rate and Hypoxia Tolerance in Octopus rubescens

Abstract

Much of the CO2 released by human activity into the atmosphere is dissolving into the oceans, making them more acidic. In this study we provide the first data on the short- and long-term impacts of ocean acidification on octopuses. We measured routine metabolic rate (RMR) of Octopus rubescens at elevated CO2 pressure (Pco2) with no prior acclimation and 1 or 5 wk of acclimation and critical oxygen pressure (Pcrit) after 5 wk of acclimation. Our results show that with no prior acclimation, octopuses had significantly higher RMRs in 1,500-μatm Pco2 environments than octopuses in 700- or 360-μatm environments. However, after both 1 and 5 wk of acclimation there was no significant difference in RMRs between octopuses at differing Pco2, indicating that octopuses acclimated rapidly to elevated Pco2. In octopuses acclimated for 5 wk at 1,500 μatm Pco2, we observed impaired hypoxia tolerance, as demonstrated by a significantly higher Pcrit than those acclimated to 700 μatm Pco2. Our findings suggest that O. rubescens experiences short-term stress in elevated Pco2 but is able to acclimate over time. However, while this species may be able to acclimate to near-term ocean acidification, compounding environmental effects of acidification and hypoxia may present a physiological challenge for this species.