Extended Data Fig. 3: Temperature sensitivity of processes that govern the O2 supply.
a, The rate of diffusive flux across the boundary layer increases with temperature in proportion to Scn, where the Schmidt number (Sc) is the ratio of seawater viscosity (υ) to O2 diffusivity (κ). Typical values of the exponent, n, are −1/2, −2/3 and −1, depending on the underlying model of boundary layer renewal23. In all cases, the empirically derived curves (solid) are well approximated by an Arrhenius function (dashed) with corresponding activation energy parameters (that is, Es) ranging from 0.21 eV (for n = −1/2; blue) to 0.27 eV (for n = −2/3; green) and 0.42 eV (for n = −1; red). b, Experimental measurements of rates of the ventilation (solid) and circulation (dashed) of animals. Rates at multiple temperatures are from published studies of six species, including three annelids24 (Nereis virens, blue; Nereis succinea, brown; and Nereis diversicolor, gold; all with n = 6 independent experiments) and three chordates (Lepornis macrochirus26, red; Oncorhynchus mykiss51, green; Leiopotherupon unicolor25, cyan; all with n = 7 independent experiments). c, For each species, the temperature sensitivity of each rate is determined by fitting to an Arrhenius function above and below 20 °C, the approximate thermal midpoint of all data. Histograms of activation energy in each temperature range (insets) are significantly different (two-sample Kolmogorov–Smirnov test; P = 5× 10−4) for warm conditions (Es = 0.04 ± 0.18 (mean ± s.d.)) and cool waters (Es = 0.55 ± 0.15 (mean ± s.d.)). d, Distributions of Eo computed from experimental data at temperatures at or above 15 °C (red bars) are higher than for the same parameter computed using only temperatures at or below 15 °C (blue bars). For species for which at least two Pcrit values were available both above and below Tref, the difference between Eo for warm and cold temperatures (green bars) is always greater than zero, and has a mean value (0.55 eV) similar to the change in temperature dependence of ventilation and circulation rates across cold and warm temperatures (green bars in c).
