Cardiorespiratory responses in an Antarctic fish suggest limited capacity for thermal acclimation

Abstract

Polar fishes are at high risk from increasing seawater temperatures.

Antarctic emerald rockcod have the capacity to compensate for warming when uncoupled from CO2‐acidification

“…Elevated f V and f H likely increased O 2 supply to facilitate the increased metabolic costs under elevated temperature and P CO 2 with of fish significantly increasing with elevated temperature. The Antarctic notothen Notothenia coriiceps exhibited a similar cardiorespiratory response to juvenile T. bernacchii in this study when exposed to warming (5°C) for 6 weeks (Egginton & Campbell, ) with f H remaining elevated across acclimation time and thus showing no compensation for increased temperature. Conversely, adult T. bernacchii acclimated for 2 weeks at 2°C had no change in f H or f V compared to control conditions at −1°C (Jayasundara et al., ), suggesting cardiorespiratory responses to warming may have stage‐specific limitations.…”

“…Simulated models project that the duration of low pH events in winter may increase in McMurdo Sound, thus exposing marine organisms to deleterious levels of pH for longer periods (Kapsenberg, Kelley, Shaw, Martz, & Hofmann, ). There are numerous studies investigating the effects of high temperature on the physiology of adult Antarctic fishes (Beers & Jayasundara, ; Bilyk & DeVries, ; Egginton & Campbell, ; Peck, Morley, Richard, & Clark, ; Sandersfeld, Davison, Lamare, Knust, & Richter, ; Sandersfeld, Mark, & Knust, ; Seebacher, Davison, Lowe, & Franklin, ; Somero & Hochachka, ; Weinstein & Somero, ); however, there are considerably fewer studies focused on how Antarctic fishes may respond to elevated P CO 2 , and the effects of elevated P CO 2 and temperature concurrently, with the focus on adult fishes (Enzor, Hunter, & Place, ; Enzor & Place, ; Enzor, Zippay, & Place, ; Strobel, Graeve, Pörtner, & Mark, ; Strobel, Leo, Pörtner, & Mark, ; Strobel et al., ) and only one study on an early life stage (i.e., embryos, Flynn, Bjelde, Miller, & Todgham, ). Since sensitivity to environmental stressors can vary across ontogeny (Hamdoun & Epel, ; Pörtner & Peck, ), we cannot predict species vulnerability to ocean changes of elevated P CO 2 and temperature by only evaluating sensitivity to change in adults.…”

“…Antarctic fishes have evolved under a stable, cold environment for millions of years (Eastman, ) and as a result are predicted to be highly sensitive to changes in ocean conditions, particularly ocean warming. Studies assessing the physiological impacts of warming on Antarctic fishes in the Nototheniidae family have shown changes to cardiorespiratory and metabolic performance (Egginton & Campbell, ; Enzor et al., , ; Franklin, Davison, & Seebacher, ; Jayasundara, Healy, & Somero, ; Seebacher et al., ); however, the degree of vulnerability and acclimation capacity may be species‐specific (Egginton & Campbell, ; Franklin et al., ; Jayasundara et al., ; Robinson & Davison, ,b; Seebacher et al., ). For example, studies of the emerald rockcod, Trematomus bernacchii , a dominant benthic species by biomass in the Ross Sea (Vacchi, La Mesa, & Greco, ), have demonstrated impacts of warming across several levels of organization, including limitations in cardiac performance (Jayasundara et al., ), sustained elevated metabolic costs (Enzor et al., , ), aerobic to anaerobic fuel switching (Enzor et al., ; Jayasundara et al., ), mitochondria break temperatures (Weinstein & Somero, ), a twofold increase in brain oxygen (O 2 ) consumption (Somero & DeVries, ), and up to an 85% reduction in growth (Sandersfeld et al., ).…”

The temperature dependence of electrical excitability in fish hearts

“…The AP responses of polar stenotherms and tropical eurytherms to thermal acclimation are poorly elucidated, and therefore thermal plasticity of cardiac excitation in these species remains to be shown. In polar stenotherms, the capacity of cardiac function to acclimate to changes in temperature is more limited (Podrabsky and Somero, 2006;Franklin et al, 2007;Bilyk and DeVries, 2011;Egginton and Campbell, 2016); therefore, it can be anticipated that the thermal plasticity of excitability in these species is also modest.…”

Exploring nature's natural knockouts:In vivocardiorespiratory performance of Antarctic fishes during acute warming

“…Comparisons could then be made with cardiorespiratory regulatory capacity of Hb + nototheniids (e.g. Axelsson et al, 1992Axelsson et al, , 1994Franklin et al, 2007;Campbell et al, 2009;Egginton and Campbell, 2016).…”