The largest seaweed, giant kelp ( Macrocystis ) is the fastest growing and most prolific of all plants found on earth. Growing from the seafloor and extending along the ocean surface in lush canopies, giant kelp provides an extensive vertical habitat in a largely two-dimensional seascape. It is the foundation for one of the most species-rich, productive, and widely distributed ecological communities in the world. Schiel and Foster's scholarly review...