Oxygen supply capacity breathes new life into critical oxygen partial pressure (Pcrit)

Details

• Journal Title:
  Journal of Experimental Biology
• Personal Author:
  Seibel, Brad A. ; Andres, Alyssa ; Birk, Matthew A. ; Burns, Alexandra L. ; Shaw, C. Tracy ; Timpe, Alexander W. ; Welsh, Christina J.
• NOAA Program & Office:
  OAR (Oceanic and Atmospheric Research) ; NOS (National Ocean Service)
• Description:
  The critical oxygen partial pressure (Pcrit), typically defined as the PO2 below which an animal's metabolic rate (MR) is unsustainable, is widely interpreted as a measure of hypoxia tolerance. Here, Pcrit is defined as the PO2 at which physiological oxygen supply (α0) reaches its maximum capacity (α; µmol O2 g−1 h−1 kPa−1). α is a species- and temperature-specific constant describing the oxygen dependency of the maximum metabolic rate (MMR=PO2×α) or, equivalently, the MR dependence of Pcrit (Pcrit=MR/α). We describe the α-method, in which the MR is monitored as oxygen declines and, for each measurement period, is divided by the corresponding PO2 to provide the concurrent oxygen supply (α0=MR/PO2). The highest α0 value (or, more conservatively, the mean of the three highest values) is designated as α. The same value of α is reached at Pcrit for any MR regardless of previous or subsequent metabolic activity. The MR need not be constant (regulated), standardized or exhibit a clear breakpoint at Pcrit for accurate determination of α. The α-method has several advantages over Pcrit determination and non-linear analyses, including: (1) less ambiguity and greater accuracy, (2) fewer constraints in respirometry methodology and analysis, and (3) greater predictive power and ecological and physiological insight. Across the species evaluated here, α values are correlated with MR, but not Pcrit. Rather than an index of hypoxia tolerance, Pcrit is a reflection of α, which evolves to support maximum energy demands and aerobic scope at the prevailing temperature and oxygen level.
• Source:
  Journal of Experimental Biology, 224(8)
• DOI:
  https://doi.org/10.1242/jeb.242210
• ISSN:
  0022-0949 ; 1477-9145
• Format:
  PDF
• Publisher:
  The Company of Biologists
• Document Type:
  Journal Article
• Funding:
  Grant no. NA17OAR4310081 ; Grant no. NA18NOS4780167
• Rights Information:
  Other
• Compliance:
  Library
• Main Document Checksum:
  urn:sha-512:da9272d3f7285788c665ebe9a1695b5b111afc4e9f7e30ae360c3f966e35c7e77e8adce19f989d8375bfca22831ae5b0b9d8d74a03406eb1de512411adf8ed79
• Download URL:
  https://repository.library.noaa.gov/view/noaa/65125/noaa_65125_DS1.pdf
• File Type:
  [PDF - 756.98 KB ]