Fig. 3. Effect of elevated CO₂ on the movement levels of squid.

Mean number of line crosses (± standard error) in 5-minute trials for squid exposed to control (447 µatm), moderate (626 µatm), or high (956 µatm) CO₂. Mean movement includes individuals that were at rest throughout the trial (zero line crosses) in light grey (left y-axis) and excludes individuals at rest in dark grey (right y-axis). Sample sizes are displayed above the bars.