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Despite increasing evidence that herbivory on seagrasses can be substantial in nearshore systems, there is only scarce experimental data on the direct quantification of seagrass removal by herbivores. To help fill this gap, and to evaluate the hypothesis that herbivory on the Mediterranean seagrass Posidonia oceanica (L.) Delile is generally low, we assessed the patterns of grazing pressure variability and its effects on seagrass in an undisturbed meadow in the NW Mediterranean. We quantified herbivore density and grazing pressure through both direct (tethering experiment) and indirect (through marks of herbivore attacks) measurements. Although grazing varied greatly both temporally and spatially, our results show that whereas consumption by the sea urchin Paracentrotus lividus is relatively minor, P. oceanica is intensely grazed by the fish Sarpa salpa in summer. During this period, fish are very abundant at …