Ocean Acidification does Not Limit Squid Metabolism via Blood Oxygen Supply

Matthew A. Birk, Erin L. McLean, Brad A. Seibel

Research output: Contribution to journalArticlepeer-review

Abstract

<p> Ocean acidification is hypothesized to limit the performance of squid owing to their exceptional oxygen demand and pH sensitivity of blood&ndash;oxygen binding, which may reduce oxygen supply in acidified waters. The critical oxygen partial pressure ( <em> P </em> <sub> crit </sub> ), the <em> P </em> O <sub> 2 </sub> below which oxygen supply cannot match basal demand, is a commonly reported index of hypoxia tolerance. Any CO <sub> 2 </sub> -induced reduction in oxygen supply should be apparent as an increase in <em> P </em> <sub> crit </sub> . In this study, we assessed the effects of CO <sub> 2 </sub> (46&ndash;143&emsp14;Pa; 455&ndash;1410&emsp14;&mu;atm) on the metabolic rate and <em> P </em> <sub> crit </sub> of two squid species &ndash; <em> Dosidicus gigas </em> and <em> Doryteuthis pealeii </em> &ndash; through manipulative experiments. We also developed a model, with inputs for hemocyanin pH sensitivity, blood <em> P </em> CO <sub> 2 </sub> and buffering capacity, that simulates blood oxygen supply under varying seawater CO <sub> 2 </sub> partial pressures. We compare model outputs with measured <em> P </em> <sub> crit </sub> in squid. Using blood&ndash;O <sub> 2 </sub> parameters from the literature for model inputs, we estimated that, in the absence of blood acid&ndash;base regulation, an increase in seawater <em> P </em> CO <sub> 2 </sub> to 100&emsp14;Pa (&asymp;1000&emsp14;&mu;atm) would result in a maximum drop in arterial hemocyanin&ndash;O <sub> 2 </sub> saturation by 1.6% at normoxia and a <em> P </em> <sub> crit </sub> increase of &asymp;0.5&emsp14;kPa. Our live-animal experiments support this supposition, as CO <sub> 2 </sub> had no effect on measured metabolic rate or <em> P </em> <sub> crit </sub> in either squid species.</p>
Original languageAmerican English
JournalJournal of Experimental Biology
Volume221
DOIs
StatePublished - Oct 1 2018

Keywords

  • Acid–base balance
  • Blood–O2 binding
  • Hypercapnia
  • Cephalopod
  • Hypoxia tolerance
  • Dosidicus

Disciplines

  • Life Sciences

Cite this