Studies of biotic interactions of algae that involve chemical defenses or signals are currently vibrant, active components of both marine ecological and phycological research. This field is rapidly growing, not only by delving deeper into relatively well-known aspects such as secondary metabolite defenses of tropical and temperate macroalgae to herbivores but also by broadening such work into new habitats and by expanding the field to include many other aspects of the chemical interactions of algae with other organisms or with their environments. This book has attempted to span the breadth of algal chemical ecology from the perspective of basic ecology. To keep it of manageable length, its scope is restricted primarily to ecological aspects of the field and in doing so, it is unfortunate that a great deal of excellent work in applied areas of algal chemical ecology could not be included. Likewise, algal natural products chemistry is not emphasized in most chapters but the book begins with an introduction to the chemistry of algal defenses that is intended as a primer on natural products chemistry for algal ecologists. In addition, although intended to be broad, it could not be so comprehensively and consequently each author was asked to highlight new areas of research and simply refer a reader to previously published reviews where appropriate.