UC specimens and range limits for Macrocystis pyrifera

• Blue markers: specimen records
• Yellow marker: type locality, if present
• Red markers: endpoints of range from literature

View map from the Consortium of Pacific Northwest Herbaria

Notes: Kodiak Island, Alaska (57.616667, -152.16666) through upwelling sites in Baja California, Mexico, and southern hemisphere.

Status: This species is easy to identify.

Habitat: Low intertidal to deep subtidal (30m).

Life History: Alternation of heteromorphic phases (large diploid sporophyte and microscopic haploid dioecious gametophytes). Sporophyte perennial. Sporophylls borne at base of plant, just above the holdfast. Juveniles can be identified when they make their first dichotomous branching point.

Search Sequences in GenBank

Illustration from DeCew's Guide to the Seaweeds of British Columbia, Washington, Oregon, and Northern California

Macrocystis C. Agardh 1820

Sporangial thalli with basal portion perennial; holdfast conical and consisting of long-branched haptera, or prostrate, branched, subligulate, andcreeping, with short, forked haptera along lateral margins. Stipe erect, cylindrical, dichotomously branched 2-4 times near base. Blades at regular intervals along stipe, unilaterally arranged immediately behind growing tips, soon becoming spirally arranged. Mature lateral blades undivided, more or less bullate, the margins denticulate, the stipe short, the basal pneumatocyst subglobose to fusiform. Sporangia (in Calif.) restricted to sporophylls borne on stipe near holdfast, with or without pneumatocysts. Sporophylls at first entire, later splitting from base to apex into 2 equal parts, eventually dividing 4 or 5 times, the divisions narrowly linear, with sporangia covering most of surface. In Australia and S. Africa, sori usually on undifferentiated blades.

Macrocystis pyrifera (L.) C. Ag.

Fucus pyriferus Linnaeus 1771: 311. Macrocystis pyrifera (L.) C. Agardh 1820: 47; Setchell & Gardner 1925: 627; Smith 1944: 144.

Sporangial thalli to 45.7 m long; holdfast of old plants conical, to 1 m tall, new holdfast produced in irregular whorls at junction of lower stipes and holdfast, growing throughout life of plant; stipe usually 4 or 5 times dichotomously divided near base; terminal blade of each branch broadly falcate when growing rapidly, becoming narrower with age, length 3-5 times breadth of 7-15(20) cm; mature lateral blades lanceolate, strongly bullate in most individuals, the blade to 80 cm long, 40 cm broad; sporophylls borne near base of branches, usually with pneumatocyst, the ultimate segments to 30 cm long, 4 cm broad. Frequent in extensive stands (kelp "forests") on rocky substrata or occasionally anchoring in coarse sand, subtidal (6-20(80) m), forming most of the kelp forests in N. American part of its range; distribution nearly continuous (if undisturbed), except in Baja Calif., where confined to localities of cool, upwelling water; Alaska to Bahia Magdalena, Baja Calif., and S. America. Also S. Africa and S. Australia. Type locality: S. Atlantic.

As Macrocystis integrifolia Bory: Sporangial thalli to 6 m long; holdfast flattened, subligulate, irregularly subdichotomous, creeping, with numerous branched haptera along lateral margins; stipe dichotomously branched 1-4 times, the terminal region of each branch narrowly falcate, becoming more narrow as growth slows; mature lateral blades lanceolate, bullate; pneumatocysts narrowly to broadly pyriform; lateral blades to 40 cm long, 8 cm broad; sporophylls usually without pneumatocyst, ultimately dividing dichotomously 4 or 5 times, the ultimate divisions to 30 cm long, 4 cm broad. Infrequent in tidal channels and on gently sloping rocky ledges, lower intertidal to shallow subtidal, Br. Columbia to C. Calif. Type locality: western coast of S. America. The growing tips change their general outline from falcate (with numerous young blades in the process of differentiation) to narrowly falcate (with few young blades), as illustrated in Smith (1944: pl. 26, fig. 2). A form of Macrocystis from Calif. resembling M. angustifolia from Australia has been described by Neushul (1971) from S. Calif. The presence of a rhizome-like holdfast, usually flattened in cross section, distinguishes M. angustifolia from M. pyrifera. Upwards of 140,000 tons wet weight of M. pyrifera are harvested each year from the state-owned kelp beds off the S. Calif. coast for the extraction of alginates, colloids widely used in industry and in the preparation of certain foods. Since current demand exceeds supply, many new management methods have been developed relative to the ecology of the species. Important new basic as well as practical information has been gathered by North (l971) and others, contributing to an understanding of the Macrocystis community, which contains numerous species of sport fish as well as commercial quantities of sea urchins.

Excerpt from Abbott, I. A., & Hollenberg, G. J. (1976). Marine algae of California. Stanford University Press, Stanford, California. xii [xiii] + 827 pp., 701 figs.

Notes: Macrocystis pyrifera and M. integrifolia were merged on the basis of molecular and morphological studies (Coyer et al. 2001, Westermeier et al. 2007, Demes et al. 2009).