Data from: Cardiorespiratory adjustments to chronic environmental warming improves hypoxia tolerance in European perch

Aquatic hypoxia will become increasingly prevalent in the future as a
result of eutrophication combined with climate warming. While short-term
warming typically constrains fish hypoxia tolerance, many fishes cope with
warming by adjusting physiological traits through thermal acclimation.
Yet, little is known about how such adjustments affect tolerance to
hypoxia. We examined European perch (Perca fluviatilis) from the Biotest
enclosure (23°C, Biotest population), a unique ∼1 km2 ecosystem
artificially warmed by cooling water from a nuclear power plant, and an
adjacent reference site (16–18°C, reference population). Specifically, we
evaluated how acute and chronic warming affect routine oxygen consumption
rate (Ṁ O2, routine) and cardiovascular performance in acute hypoxia,
alongside assessment of the thermal acclimation of the aerobic
contribution to hypoxia tolerance (critical O2 tension for Ṁ O2, routine:
Pcrit) and absolute hypoxia tolerance (O2 tension at loss of equilibrium;
PLOE). Chronic adjustments (possibly across lifetime or generations)
alleviated energetic costs of warming in Biotest perch by depressing Ṁ
O2, routine and cardiac output, and by increasing blood O2 carrying
capacity relative to reference perch acutely warmed to 23°C. These
adjustments were associated with improved maintenance of cardiovascular
function and Ṁ O2, routine in hypoxia (i.e. reduced Pcrit). However,
while Pcrit was only partially thermally compensated in Biotest perch,
they had superior absolute hypoxia tolerance (i.e. lowest PLOE) relative
to reference perch irrespective of temperature. We show that European
perch can thermally adjust physiological traits to safeguard and even
improve hypoxia tolerance during chronic environmental warming. This
points to cautious optimism that eurythermal fish species may be resilient
to the imposition of impaired hypoxia tolerance with climate warming.