Herbivory on the seagrass Cymodocea nodosa (Ucria) ascherson in contrasting Spanish Mediterranean habitats

We assess the magnitude and variability of herbivory (i.e. leaf consumption and sloughing caused by herbivore bites) on the seagrass Cymodocea nodosa along the Spanish Mediterranean coast and test the hypothesis that this is higher in meadows growing in sheltered bays than in exposed, open zones. Total leaf loss by herbivores varied by about three orders of magnitude along the Spanish Mediterranean coast, from < 1 to 130 mg DW shoot^-1 yr^-1. These differences were paralleled by a great variation in the fraction of leaf production lost by herbivores, which ranged from < 1 to about 50%. Most (75%) of the populations, however, supported modest losses of leaf production (< 10%). A significant fraction (30%) of the variance in herbivory was explained by meadow exposure, the meadows growing in sheltered bays suffering about five times the losses encountered in open sites. These results suggest that the trophic importance of C. nodosa as a food resource for herbivores, and the role of herbivores on the control of the seagrass production, increases notably from exposed to sheltered meadows in the Spanish Mediterranean and point to the importance of considering the degree of exposure when addressing herbivory on other seagrass species.