Kelp
Kelps are large brown algae seaweeds that make up the order Laminariales. There are about 30 different genera.
Kelp forest
Multiple kelp species often co-exist within a forest; the term understory canopy refers to the stipitate and prostrate kelps. For example, a "Macrocystis" canopy may extend many meters above the seafloor towards the ocean surface, while an understory of the kelps "Eisenia" and "Pterygophora" reaches upward only a few meters. Beneath these kelps, a benthic assemblage of foliose red algae may occur. The dense vertical infrastructure with overlying canopy forms a system of microenvironments similar to those observed in a terrestrial forest, with a sunny canopy region, a partially shaded middle, and darkened seafloor. Each guild has associated organisms, which vary in their levels of dependence on the habitat, and the assemblage of these organisms can vary with kelp morphologies. For example, in California, "Macrocystis pyrifera" forests, the nudibranch "Melibe leonina", and skeleton shrimp "Caprella californica" are closely associated with surface canopies; the kelp perch "Brachyistius frenatus", rockfish "Sebastes" spp., and many other fishes are found within the stipitate understory; brittle stars and turban snails "Tegula" spp. are closely associated with the kelp holdfast, while various herbivores, such as sea urchins and abalone, live under the prostrate canopy; many seastars, hydroids, and benthic fishes live among the benthic assemblages; solitary corals, various gastropods, and echinoderms live over the encrusting coralline algae. In addition, pelagic fishes and marine mammals are loosely associated with kelp forests, usually interacting near the edges as they visit to feed on resident organisms.