HERBIVORY ON THE SEAGRASS CYMODOCEA-NODOSA (UCRIA) ASCHERSON IN CONTRASTING SPANISH MEDITERRANEAN HABITATS

We assess the magnitude and variability of herbivory (i.e. leaf consum ption and sloughing caused by herbivore bites) on the seagrass Cymodoc ea nodosa along the Spanish Mediterranean coast and test the hypothesi s that this is higher in meadows growing in sheltered bays than in exp osed, 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 gre at variation in the fraction of leaf production lost by herbivores, wh ich ranged from <1 to about 50%. Most (75%) of the populations, howeve r, supported modest losses of leaf production (<10%). A significant fr action (30%) of the variance in herbivory was explained by meadow expo sure, 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, inc reases notably from exposed to sheltered meadows in the Spanish Medite rranean and point to the importance of considering the degree of expos ure when addressing herbivory on other seagrass species.