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The Giant Kelp Forests

The Giant Kelp Forests
                         Video              Audio

Below the surface of the water in the Channel Islands region is a vast forest of giant kelp that rivals the giant redwood stands of Northern California for breathtaking scenery.

All five of the islands in the sanctuary are surrounded by beds of giant kelp (Macrocystis Pyrifera), a type of brown alga that grows faster than any other plant on earth. With favorable conditions - ample nutrients, a rocky substrate, and 20 to 80 feet of cool ( 50 - 65 * Fahrenheit) seawater - kelp can grow at a record-breaking rate of two feet per day.

With a maximum size of 200 feet in length, Macrocystis is the world's largest marine plant. It reaches its phenomenal size without a root system. instead, giant kelp is anchored to rocks by a holdfast, a mass of tangled, brightly hued strands called haptera. Sturdy yet flexible fronds rise like vines to the top of the water. The fronds are held up by gas filled floats that grow at the base of the plant's leafy, wrinkled blades. At the surface, the fronds entwine to form a thick canopy, creating a shadowy forest below.

Every part of the kelp plant has the capacity to photosynthesize, although the canopy does most of the work. Unlike the root systems of terrestrial vegetation, the holdfast does not take in nutrients; all of the other surfaces of the plant absorb such essentials as nitrates and phosphates from the water.

The kelp forest provides a multilevel home, full and part time, for nearly 1,000 plant and animal species, ranging in size from tiny "moss" animals, the bryozoan that populate the kelp blades, to huge gray whales that pause in the kelp beds during their migration. The forest is made up of three communities: the canopy or upper region, the mid-water area and the holdfast section. Animals that are mobile travel from one neighborhood to another; sessile animals homestead for life in one of the three areas.

The canopy creates shelter and camouflage for fish such as the kelp pipe fish, the kelp cling fish and the kelp gunnel. It also provides a floating perch and feeding ground for seabirds, and, when sea otters flourished here, the canopy cradled sleeping pups while their mothers dove for food.


Midway down the forest live schooling fish such as the opal eye and the blacksmith. Here the kelp fronds are encrusted with filter feeders such as bryozoan and hydroids that use special tentacles to sift through the seawater for plankton. These filter feeders are the preferred food of another mid-level resident, the nudibranch, also called a sea slug. Some nudibranch, such as the purple and orange Spanish shawl pictured above, have vibrant colors that make them stand out against the muted brown or green kelp. This coloration serves to warn other animals that eating the soft-bodied nudibranch could be dangerous.


Members of the teeming holdfast community include shrimp hiding from the kelp rockfish, brittle stars, which grab the haptera with two of their five arms, and swell sharks, which use the haptera to anchor their egg cases. Lobsters, abalone and sea urchins also live here.

Over 125 types of fish live in the kelp forest. The forest serves as a nursery for many commercially important fish such as the kelp bass, who hide there untile they are ready for life in the open sea.

The kelp forest provides a multilevel home, full and part time, for nearly 1,000 plant and animal species, ranging in size from tiny "moss" animals, the bryozoan that populate the kelp blades, to huge gray whales that pause in the kelp beds during their migration. The forest is made up of three communities: the canopy or upper region, the mid water area and the holdfast section. Animals that are mobile travel from one neighborhood to another; sessile animals homestead for life in one of the three areas.

The canopy creates shelter and camouflage for fish such as the kelp pipe fish, the kelp cling fish and the kelp gunnel. It also provides a floating perch and feeding ground for seabirds, and, when sea otters flourished here, the canopy cradled sleeping pups while their mothers dove for food.

Midway down the forest live schooling fish such as the opal eye and the blacksmith. Here the kelp fronds are encrusted with filter feeders such as bryozoan and hydroids that use special tentacles to sift through the seawater for plankton. These filter feeders are the preferred food of another mid-level resident, the nudibranch, also called a sea slug. Some nudibranch, such as the purple and orange Spanish shawl pictured above, have vibrant colors that make them stand out against the muted brown or green kelp. This coloration serves to warn other animals that eating the soft-bodied nudibranch could be dangerous.

Members of the teeming holdfast community include shrimp hiding from the kelp rockfish, brittle stars, which grab the haptera with two of their five arms, and swell sharks, which use the haptera to anchor their egg cases. Lobsters, abalone and sea urchins also live here.

Over 125 types of fish live in the kelp forest. The forest serves as a nursery for many commercially important fish such as the kelp bass, who hide there until they are ready for life in the open sea. One of the most interesting fishes that lives here is the boldly striped California sheephead. juvenile sheephead develop first as females; later, most cilatige into males growing a characteristic hump on top of their heads that grows larger with age. Sheepheads can live as long as fifty years. The bright orange Garibaldi fish, is a Protected fish in State of California territorial waters, which extend from mean high tiae to three tudes offshore along the California coastline and around islands within the state. The gregarious Garibaldi, with their neon color and fearless attitude toward humans, have endeared themselves so much to divers and underwater photographers that the state forbids taking or possessing them. Garibaldi reach just over a foot in length.

The kelp forest is much less stable than a forest of redwood or pine. Mature fronds are continually dying and breaking away, replaced by new ones. The normal life span for a single frond of giant kelp is six months, Thus the forest may completely regenerate twice a year as part of its natural cycle.

Oceanic and atmospheric conditions can have dramatic effects on the size of the forest. Storms and strong waves may detach plants and send them to shore, wiping out whole sections. Plants that have been ripped from their anchors ensnare additional plants, uprooting them and dragging them along to the beach. Changes in water temperature, such as the warming trend associated with the weather phenomenon called El Niņo can also be devastating. During the 1982 -1984 El Niņo, normally cool Southern California waters reached a sultry 77.5 Fahrenheit, thinning the formerly lush kelp beds to just a few fronds.

Pollution and the removal of predators can also conspire to reduce the size of the kelp forest by altering the natural balance of the organisms that reside there. Sea urchins, for example, feed on giant kelp. Their most effective predators, the sea otters, were once numerous enough to keep sea urchin populations in check. With the sea otter nearly vanished from the channel, the voracious sea urchins have begun to multiply rapidly. Some scientists contend that they have been fortified by nutrients they find in sewage in areas where ocean dumping is heavy.

The forests of giant kelp in the Santa Barbara Channel have attracted humans for centuries. The Chumash established communities nearby to take advantage of the abundant food, and early navigators in the area used kelp to identify dangerous rocky areas. Today the forest provides a lucrative crop, so versatile that Americans use it, in one form or another, an estimated 15 times every day.