Fig. 1: Relationships among species traits that govern the temperature-dependent vulnerability to hypoxia of marine animals. | Nature

Fig. 1: Relationships among species traits that govern the temperature-dependent vulnerability to hypoxia of marine animals.

From: Metabolic trait diversity shapes marine biogeography

Fig. 1

a, Curves of constant  Metabolic Index (Φ) trace the \({p}_{{{\rm{O}}}_{2}}\) required to satisfy the O2 demand of species for resting (blue) or active (red) metabolic rates. be, The resting curve of each species is defined by a hypoxia vulnerability (Vh) and its temperature sensitivity (Eo), each of which reflect separate traits for O2 supply and demand (b, d) and their covariation (c, e). Active curves, which are increased from the resting curve by sustained activity (SMS), require a correspondingly higher Φ (Φcrit) (Fig. 4). The intersection of Φ curves with atmospheric \({p}_{{{\rm{O}}}_{2}}\) define the upper thermal limits of aerobic metabolism (ATmax) (Fig. 5). b, c, Hypoxia vulnerability (Vh; atm) and O2 demand at rest (b; αD; μmol O2 h−1 g−3/4, log10 scale) vary widely among species but are uncorrelated because the metabolic rate and the efficacy of the O2 supply (c; αS; μmol O2 h−1 g−3/4 atm−1) are strongly correlated (Extended Data Table 1). d, The temperature dependence of the hypoxia vulnerability (Eo; eV) is shifted to lower values than that of resting metabolic rate (Ed; eV) because the O2 supply accelerates with temperature (that is, Es = Ed − Eo > 0), partially compensating the thermal rise in metabolic demand. e, The relationship between Eo and Ed (dotted line; slope < 1) (Extended Data Table 1) suggests that species with a stronger metabolic response to temperature also exhibit stronger compensatory O2 supply mechanisms (Extended Data Fig. 2b). Values of Es are within the range predicted for diffusion (yellow shading) and empirically estimated from rates of the ventilation and circulation of animals in cool waters (blue shading; 0.55 ± 0.15 eV (mean ± s.d.) and warm waters (red shading; 0.04 ± 0.18 eV (mean ± s.d.)) (Extended Data Fig. 3). c, e, Data (points and error bars, or centred dot, if the error bars are shorter than marker) are mean ± s.e.m. for species with n > 2 temperature values. See Supplementary Table 1 for the number of independent experiments for each species, and Extended Data Table 1 for statistics on the two-sided t-tests of the trait correlations.

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