Data from: The influence of carbon dioxide accumulation on integrative physiological recovery timelines in diving odontocetes

Substantial research has examined the use and limits of oxygen (O2) stores
by marine mammals during exercise (e.g., diving and foraging). In
comparison, far less is known about the system-wide effects of carbon
dioxide (CO2) accumulation during submergence and subsequent depletion
while breathing at the surface. Traditionally, the primary emphasis of
surface recovery periods in diving marine mammals has focused on the time
required to restore O2 stores. This is despite suggestions that CO2
readjustment may be the limiting factor determining when diving can
resume. Here, we conduct a comparative assessment of post-exercise
recovery timelines for both O2 and CO2 in two odontocetes, bottlenose
dolphins (Tursiops truncatus) and beluga whales (Delphinapterus leucas),
following varying repetitions of sequential submerged swims. We identified
select system-wide impacts associated with changes in onboard O2 and CO2
levels and explored the integrated recovery dynamics of respiratory and
blood gases, blood pH, ventilation, and peripheral vasodilation. We found
that for both species, respiratory O2 and CO2 levels returned to resting
levels within 3 to 8 minutes following submerged exercise, depending on
the species. In comparison, blood O2 and CO2 concentrations required
longer durations (< 10–15 min) to return to resting levels. Blood
acidity, best explained by changes in pCO2, remained elevated throughout
the 10-15 min recovery period, possibly serving as the bottleneck for
complete recovery. Post-exercise changes in ventilatory and vascular
patterns were also observed, likely driven by increasing blood acidity
associated with increased swim effort and CO2 accumulation. The magnitude
of these responses differed between the species. Given the sensitivity of
mammalian systems to minor variations in CO2 and its influence on
acid-base balance and respiratory function, this metabolite appears to
play a dominant role in cetacean dive recovery. Documenting this role will
be increasingly relevant as we try to understand the short- and long-term
impacts of anthropogenic disturbance on wild cetacean populations as they
avoid human activities on and in the seas.