Although there are few marshes along the Pacific coast, the rocky shores with cool water host kelp beds, which are formed by various species of algae that attach to hard substrate with a root-like system called a holdfast. Some kelp, particularly Macrosistus species, can grow many tens of meters in length up to the water surface, where their tops float and continue to grow. The plants are quite rubbery and can withstand significant wave action.
Kelp beds harbor extensive biological communities that include fish, sea otters, lobster, starfish, mollusks, abalones, and many other invertebrates. In addition, kelp beds absorb wave energy, helping to shelter beaches.