Sanctuary Integrated Monitoring Network
National Marine Sanctuaries

Kelp Forests

Kelp Forests_ map
Figure 1. Zones of kelp forests within the Monterey Bay, Gulf of the Farallones, and Cordell Bank National Marine Sanctuaries. [View Larger]
Kelp forests provide important structural features and ecosystem function to coastal marine communities. The physical structure of kelp provides vertical habitat similar to trees on land; it is used by numerous fishes and invertebrates.

Two species account for the bulk of physical structure and kelp biomass in the northern California region: bull kelp, Nereocystis luetkeana, and giant kelp, Macrocystis pyrifera.

Bull kelp, which tolerates high wave action, is typical along exposed rocky shores, whereas giant kelp is abundant in all areas except the most exposed sites. Bull kelp is an annual, and giant kelp is a perennial but rarely lives longer than two to three years. Both species recruit in late spring and early summer.

In addition to the canopy-forming species, there are several kelp species (e.g., Pterygophora californica, Laminaria spp.) that form an understory below giant and bull kelp. This understory adds a tremendous amount of biomass to the kelp forest and provides additional habitat for fishes and invertebrates.

Kelp forests extend from just beyond the breaking waves to depths of usually less than 25 meters throughout most of the Monterey Bay National Marine Sanctuary's nearshore waters. No kelp forests exist in the Gulf of the Farallones or Cordell Bank sanctuaries.

Kelp Canopy Maxima Interactive Map

Kelp data for the California coastline were collected from aerial surveys in the following years: 1989, 1999, 2002-2006, and 2008-2009. This interactive map includes this dataset, which is a merge of all 9 years of kelp data to represent the canopy maxima.


The thousands of invertebrate species that live in kelp forests help make this system rich and diverse.
Canopy of Giant kelp (Macrocystis pyrifera) overhead a research diver off the coast of Big Sur. The diver is counting canopy fishes.

A lingcod (<em>Ophiodon elongatus</em>) resting on a rocky ledge in Carmel Bay. This photo was taken during a series of subtidal surveys for the Reef Environmental Education Foundation (REEF).

Giant kelp and other algae support large populations of benthic invertebrates, which in turn attract higher-order predators. Some common invertebrate species associated with kelp forests include the ochre sea star, Pisaster ochraceus, purple urchin, Strongylocentrotus purpuratus, and the California sea cucumber, Parastichopus californicus.

Kelp forests are considered an important nursery habitat for nearshore rockfishes and serve as a primary foraging area for many southern sea otters, Enhydra lutris nereis.


Within the three northern California sanctuaries, kelp forest monitoring efforts currently take place in the Monterey Bay sanctuary only; neither the Gulf of the Farallones nor the Cordell Bank sanctuary has monitoring efforts focused on this habitat.

Examples of related monitoring projects: