Figure 5.

Exposure to low-pH seawater can attenuate the antipredator behaviour of herbivorous snails (T. funebralis) that inhabit tidepools, altering their grazing patterns and thus the way in which cascading, top–down effects of sea-star predators operate in the system. Under ambient conditions (pH ~ 7.9 on the total scale) in mesocosm experiments, snails exit the water when they sense the presence of sea-star predators (L. hexactis; yellow triangle) or dissolved cue from them (blue–green square); this flight response provides a spatial refuge from predation and reduces the grazing pressure of snails on macroalgae. However, under low-pH conditions (pH ~ 6.9, expected in isolated tidepool waters during nighttime low tides under OA), snails spend more time in the water in the presence of sea stars, increasing their access to and consumption of macroalgae relative to when they are in ambient seawater. Error bars represent 95% confidence intervals. Figure modified from Jellison and Gaylord (2019).