Herbivory is a widespread biotic interaction with important ecological and evolutionary implications. Benthic marine systems show greater producer consumption than any other aquatic or terrestrial environment. Marine algae and plants have a variety of defensive mechanisms such as structural, chemical, and nutritional traits with the capacity to reduce herbivore consumption. These mechanisms can function simultaneously. Here, we quantified consumption by juvenile Diadema africanum and Paracentrotus lividus on 15 algal species (1) to investigate the relative contribution of algal nutritional, chemical, and structural traits to the patterns of consumption and (2) to assess whether this relative contribution varies as a function of herbivore species. Differences in consumption were found between sea urchins; however, changes differed across algal and herbivore species.There was no clear relationship between the nutritional contents and consumption rates on the studied species of algae. The structure and chemical defenses of algae species played an important role in the feeding behavior of the studied herbivores. Our results suggest that multiple defensive traits may be necessary to deter herbivores in the field.