Identification Photos: Boa Kelp, Egregia menziesii: Boa Kelp is a member of the Alariaceae Family. It has an olive green to brown coloration and is a very conspicuous species of marine algae. Its range is the west coast of North America from Alaska to northwest Baja California. It is found in mid and subtidal habitats on lower intertidal rocks in protected to moderately wave-exposed areas. Originally two species of Egregia were thought to be present along the west coast of the United States, E. menziesii and E. laevigata, but these have now been consolidated into E. menziesii.

Boa Kelp is a fast-growing algae that is characterized by a cylindrical stem at the base that branches irregularly into thick, flattened strap-like leaves. The leaves have numerous small, lateral, broad blades that attain 1 to 2 cm in width and 5 cm in length with elliptical floats along the margin. Boa Kelp is often found in dense patches in shallow water and can reach 60 feet in length. The holdfast, attached to rocks, is fleshy and cone-like in larger plants.

Boa Kelp is often found together with Giant Kelp, Macrocystis pyrifera, at the inner edges of kelp beds.

Boa Kelp plays an important ecological role, providing food and habitat for many species of algae and invertebrates. Its growth is adversely affected by elevated water temperatures, inorganic nitrogen depletion, and sewage outfall that normally occur during the summer. It is preyed upon by the Seaweed Limpet, Notoacmea insessa, and a number of abalone from the Haloiotis Genus, causing mortality for the host. With corrective conditions Egregia populations can return to normal status in five months to two years.

Boa Kelp has been harvested for many years and used by coastal farmers for fertilizer due to its high content of nitrogen and phosphate. It is also a valuable source of alginic acid utilized extensively in the baking and dairy industries and in the manufacture of beer, cosmetics, fertilizer, paint, pharmaceuticals, salad dressing, and tooth paste. The harvesting of Boa Kelp in California is now restricted and is controlled by the Department of Fish and Game.

Boa Kelp, Egregia menziesii: In left hand. With Giant Kelp, Macrocystis pyrifera around neck, Oceanside Beach, Calif., displayed by Curtis Martineau. Species identifications by Commander Ron McPeak. Description courtesy of John Snow. Photo courtesy of Gene Kira.