Identification Photos: Giant Kelp, Macrocystis pyrifera: Giant Kelp plays an important ecological role providing food and habitat for a wide range of marine species. It is capable of supporting millions of individual organisms and more than 1,000 species of marine plants and animals.

Giant Kelp starts life as a microscopic spore on the ocean floor and can grow to maturity in 12 to 14 months. It reaches lengths of over 200 feet with its upper leaves forming a dense canopy at the surface.

Giant Kelp is normally found attached to hard substrate in waters 15 to 60 feet deep that range in temperature from 5 to 20 degrees centigrade. Giant Kelp forests can be up to one mile wide and several miles long, creating near darkness at the ocean bottom.

The Giant Kelp plant is a perennial that has two parts of about equal length, the holdfast which attaches to the substrate and lives for 4 to 10 years, and the individual fronds which can grow at a rate of up to two feet per day and live from 6 to 12 months. They release trillions of spores each year to assure their longevity.

Giant Kelp growth is adversely affected by elevated water temperatures and inorganic nitrogen depletion that normally occur during the summer. It is plagued by a series of pathogenic parasites, bacteria, and fungi. Young plants provide a valuable food source for a series of crustaceans and marine animals.

Giant Kelp has been harvested for many years and is presently a valuable source of algin, a thickening agent utilized extensively in the baking and dairy industries and in the manufacture of beer, cosmetics, fertilizer, paint, pharmaceuticals, salad dressing, and tooth paste. Giant Kelp is also used as a food supplement for livestock and poultry as it contains high levels of carbohydrates, iodine, potassium, and vitamins. The harvesting of Giant Kelp in California is now restricted and is controlled by the Department of Fish and Game.

Giant Kelp is a member of the Lessoniaceae Family. It is a large brown species of marine algae found along the Pacific coast of North America from central California to northwest Baja California.

Giant Kelp, Macrocystis pyrifera: Giant Kelp, Macrocystis pyrifera (and Egregia laevigata in left hand) captured at Oceanside Beach, Calif., after a ferocious underwater battle with Curtis Martineau. Species identification by Commander Ron McPeak. Description courtesy of John Snow. Photo courtesy of Gene Kira.