Fucus costatus, Agarum costatum, A. quinquecostatum, Laminaria costata, Costaria mertensii, C. turneri

Description: Thallus of this light to medium brown kelp has a branched holdfast (haptera), a somewhat flattened, finely grooved stipe, and an elliptical blade up to 2 m (6.5 ft) long and 35 cm (14 in) wide with 5 parallel ribs running its length. Three ribs project on one side of the blade and 2 ribs on the other. Between the ribs the blade is profusely wrinkled or puckered. Habitat: This annual kelp is found on rock in the low intertidal to upper subtidal from semi-protected to semi-exposed habitats.