The past 25 years of research on algal-herbivore interactions have witnessed remarkable advances in our understanding of algal defenses and the chemical and morphological mechanisms that algae use to protect themselves from being consumed by their herbivores (Hay and Fenical 1988; Paul 1992; Steinberg 1992; Paul et al. 2001; Paul and Puglisi 2004; Paul et al. 2006; see Chaps. 2–6). In particular, we have a tremendous amount of information on the diversity, concentrations, and distributions of algal secondary metabolites within and across seaweed individuals, and in many cases, which of these algal compounds deter particular herbivores (Cronin 2001; Van Alstyne et al. 2001; Amsler and Fairhead 2006).