Climate change is acknowledged as a major threat to marine ecosystems, but the effect of temperature on
species interactions remains poorly understood. We quantified the effects of long-term warming on
plant-herbivore interactions of a dominant seagrass, Zostera muelleri. Growth, herbivory and tolerance
to damage were compared between a meadow warmed by the thermal plume from a power station
for 30 years (2–3 C above background temperatures) and three control locations. Leaf growth rates
and tissue loss were spatially variable but unrelated to temperature regimes. Natural herbivory was generally
low. Simulated herbivory experiments showed that the tolerance of Z. muelleri to defoliation did
not differ between warm and unimpacted meadows, with damaged and undamaged plants maintaining
similar growth rates irrespective of temperature. These results suggest that the ability of temperate Z.
muelleri to tolerate herbivory is not strongly influenced by warming, and this species may be relatively
resilient to future environmental change.