Algae, Brown Algae, Brown Algae: Brown Seaweeds: Phaeophyta, California, Channel Islands, United States, giant kelp: Macrocrystis integrifolia

Rainforests of the Sea

Kelp is a type of brown seaweed (or marine algae) that comprises 40+ species worldwide. The largest of these seaweeds is Macrocystis pyrifera, commonly known as giant kelp.  Giant kelp can grow to more than 100 feet at a rate of 2 ft per day, which makes it one of the fastest-growing organisms on Earth.

Giant kelp fronds grow close together to the surface where they form a canopy. These kelp dense areas are known as kelp forests.  A giant kelp forest can extend for miles.

Kelp Forests are found in cold (below 70F), nutrient-rich waters along the Pacific eastern Pacific Ocean, from Baja California north to southeast Alaska, and in the southern oceans near South America, South Africa, Australia, and New Zealand. Because of their dependence on sunlight, they generally occur in shallower waters and are rarely deeper than 150 feet.

Beneath the surface, kelp takes on a magical appearance. The gently swaying fronds create an undersea jungle of incredible beauty. Exploring a kelp forest is like being on a safari, offering the promise of surprising animal encounters. Kelp forests provide food and shelter for large diversity of fish, invertebrates, and marine mammal species.

Kelp needs rocky substrate to secure itself. The rocks are covered in life. No space is wasted. Kelp forests harbor a higher density of life than almost any other ocean ecosystem.

My first underwater experience with giant kelp was a  voyage of discovery. Even the most common species left a lasting impression under the incredible backdrop of this unique ecosystem….


The Garibaldi damselfish (Hypsypops rubicundus) is endemic to the Eastern Pacific from northern Baja to northern California. Garibaldis are very common among rocky bottoms in the kelp forest ecosystem in southern California coastal waters. Their bright orange color and pugnacious behavior stand out from their surroundings to warn other fishes to stay clear. California designated Garibaldi as the official state marine fish in 1995, largely as a response to the fishing pressure of the aquarium trade. State law now protects the fish and prohibits taking Garibaldi for either sport or commercial purposes. It faces no threats.

Like many damselfish, male Garibaldis aggressively defend the nest site after the female lays eggs. The eggs hatch after about three weeks. Young garibaldi are found in the shallows in late summer and fall. Garibaldis are one of the few fish to use the same nesting site every year.

California Sheephead

California Sheephead (Semicossyphus pulcher) generally associate with rocky-reefs and kelp-beds. Like many wrasse species, Sheephead are protogynous hermaphrodites (capable of changing sex to male).  Male and female Sheephead look very different, so this transition is quite dramatic. California Sheephead feed on urchins (which feast on kelp) and are consequently an important (keystone) species to help foster kelp growth in southern California’s coastal waters.  This species is heavily fished off Southern California and listed as vulnerable.

Kelp Bass

As the name suggest, Kelp Bass (Paralabrax clathratus) typically associate with kelp beds. This species occurs in the Eastern Pacific from Baja California to Washington. Kelp Bass are delicious and consequently a popular food fish in Southern California. Though abundant, large individuals are relatively rare due to fishing pressure. Commercial fishing for this species has been illegal since the 1950s.

Kelp Bass form spawning groups in deeper water in California during the warmer months (May to September). The larval duration is about one month. The juveniles settle among kelp fronds.


The cryptically colored Giant Kelpfish, Heterostichus rostratus, inhabits rocks with large seaweeds, most often inshore kelp. It’s range spans from British Columbia to southern Baja California. Kelpfish occur in three color morphs (red, green and brown) to match the color of the surrounding plant habitat. Brown individuals are most common in kelp beds. Kelpfish also possess special pigments that allow them to rapidly change their color pattern to achieve camouflage.

Giant Kelpfish spawn year-round, but are most fecund during spring. The female attaches her eggs to algae. The male then guards the nest for about two weeks when the eggs hatch. The Kelpfish larval duration is about two weeks. The young fish school in the kelp canopy and remain relatively transparent until they become solitary at about 3 inches.

Giant Sea Bass

The Giant Sea Bass (Stereolepis gigas) is native to the Eastern Pacific Ocean from Humboldt Bay, California, to the Gulf of California, Mexico. This sea bass can grow to a whopping 7 feet in length and weigh up to 500 lb. Aside from its tremendous size, the Giant Sea Bass is also known for its lengthy lifespan, which can exceed 75 years.

The Giant Sea Bass has a history of being overfished in California. By the late 1970s, biologists recognized that the local population was facing local extinction and took action, resulting in protection from all fishing. The population has since partially rebounded.

Bluebanded Goby

The Bluebanded Goby (Lythrypnus dalli) is native to the eastern Pacific northern Peru to Monterey Bay, California. It is very common in the shallows, mostly inhabiting rocks with crevices. Although this species is collected for the aquarium trade, there is no current indication of population decline.  A particularly interesting characteristic of the Bluebanded Goby is its ability to change sex in either direction. The fish can take on the opposite sex of its partner within just a few days to form a pair.

Other common Kelp Forest Residents

Senorita, Halfmoon, Black Surfperch, Treefish, Island Kelpfish, Spotted Scorpionfish, Spiny Lobster, Flabellina Nudibranch.

Major issues of concern facing kelp forests include kelp harvesting and fisheries; invasive species; storm damage; El Niño events; sedimentation; pollution and grazing by fishes, sea urchins, and crustaceans.

  • Overfishing/hunting disrupts the natural balance of kelp forest communities by removing predators (eg. sheephead, sea otters) consequently allowing herbivore populations (e.g. sea urchins, moonfish) to explode, leading to over-grazing of kelp.
  • Invasive species; such as the brown algae, Sargassum horneri, displace giant kelp.
  • Commercial kelp harvesting for products, such as algin and aquaculture feed, threatens kelp forests.
  • Storms or swells can uproot entire plants and break away fronds.
  • El Niño/warm water events disrupt the nutrient rich upwelling that fuels kelp growth.

Marine protected areas (MPAs) regulate the harvest of kelp and the taking of kelp forest species by fisheries thereby helping protect these important ecosystems.

Interested in experiencing a kelp forest underwater? Numerous California dive operators will get you there. I really enjoyed my experience with Truth Aquatics based in Santa Barbara. You can also visit the Monterey Aquarium – home of one the largest kelp forest exhibit in the world.