Phylum: Phaeophyta

Class: Phaeophyceae

Order: Laminariales

Family: Laminaraceae

Costaria costata (Turner) Saunders

Description: This blade-like plant is dark brown in colour; the linear undivided blade has 5-7 longitudinal parallel percurrent ribs and tapers gradually to a conspicuous stipe. The balde is from 10 to 30 cm. wide and from 50 to 250 cm. long; each rib projects on one side of the blade only, and the emergence alternates from side to side from one rib to the next; the blade is coarsely cullate. The stipe is from 3 mm. to 1.5 cm. wide and from 5 to 65 cm. long; it is flattened through most of its length, becoming terete generally only where it merges with the profusely branched root-like holdfast.

This species exhibits dimorphism, where plants growing in exposed areas grow long and thin, while plants that are in more sheltered waters grow broad and short.

Habitat: On rocks and wood in the lower intertidal and upper subtidal zones.

Pacific Coast Distribution: Alaska to California.

Robert Scagel, 1972

Costaria costata backlit at 12m. Joe Downham in background	C. costata in the teaching lab, showing distinctive crinkling	Young C. costata at low tide on the Race Rocks slipway
Two C. costata in the teaching lab, showing habit of plant	Holdfasts of C. costata	C. costata growing with N. luetkeana at low tide
A long specimen of C. costata	A 5-ribbed specimen	Detail of the crinkling pattern
Specimen viewed without artificial lighting	Author with specimen from sheltered waters	C. costaria photo from Japan