Oxygen supply to the heart has been hypothesized to limit cardiac performance and whole animal acute thermal tolerance (CT_max) in fish. We tested these hypotheses by continuously measuring venous oxygen tension (Pvo₂) and cardiovascular variables in vivo during acute warming in European perch (Perca fluviatilis) from a reference area during summer (18°C) and a chronically heated area (Biotest enclosure) that receives warm effluent water from a nuclear power plant and is normally 5–10°C above ambient (24°C at the time of experiments). While CT_max was 2.2°C higher in Biotest compared with reference perch, the peaks in cardiac output and heart rate prior to CT_max occurred at statistically similar Pvo₂ values (2.3–4.0 kPa), suggesting that cardiac failure occurred at a common critical Pvo₂ threshold. Environmental hyperoxia (200% air saturation) increased Pvo₂ across temperatures in reference fish, but heart rate still declined at a similar temperature. CT_max of reference fish increased slightly (by 0.9°C) in hyperoxia, but remained significantly lower than in Biotest fish despite an improved cardiac output due to an elevated stroke volume. Thus, while cardiac oxygen supply appears critical to elevate stroke volume at high temperatures, oxygen limitation may not explain the bradycardia and arrhythmia that occur prior to CT_max. Acute thermal tolerance and its thermal plasticity can, therefore, only be partially attributed to cardiac failure from myocardial oxygen limitations, and likely involves limiting factors on multiple organizational levels.

Item Type:	Refereed Article
Keywords:	climate change, thermal distribution
Research Division:	Biological Sciences
Research Group:	Zoology
Research Field:	Animal physiological ecology
Objective Division:	Environmental Management
Objective Group:	Coastal and estuarine systems and management
Objective Field:	Coastal or estuarine biodiversity
UTAS Author:	Clark, TD (Dr Timothy Clark)
ID Code:	112356
Year Published:	2016
Web of Science® Times Cited:	42
Deposited By:	Office of the DVC-Research
Deposited On:	2016-11-04
Last Modified:	2017-06-20
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