UC specimens and range limits for Sargassum agardhianum

• 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: Although there are many archival specimens (pre-1950) from southern California mainland sites, this species is now more common at Santa Catalina and San Clemente islands than on the mainland. There was an unusual isolated population (UC1837202) from Montana de Oro State Park, San Luis Obispo Co., but most occur south of Point Conception.

Status: A distinct species in southern California. A specimen from Santa Catalina Island was included in Phillips et al. (2005), an overview of the genus Sargassum using rbcLS spacer region sequences of the rbcLS operon.

Habitat: Lower intertidal bedrock in moderately exposed habitats

Life History: Diplontic, with gametic meiosis; monoecious. This species is highly seasonal, eroding back during the winter and growing in the late spring-summer.

Search Sequences in GenBank

Sargassum C. Agardh 1820

Thalli annual or perennial, attached by irregular, solid holdfast or by rhizoidal outgrowths from main axis. Main axis sometimes slightly differentiated into basal portion with flattened, elongate "leaves" and upper portion bearing shorter appendages, these sometimes radially arranged. "Leaves" with midrib and cryptostomata. Pneumatocysts common. Receptacles on special branches and developing in axils of "leaves." Oogonia and antheridia as in family. Both monoecious and dioecious species in Calif. flora.

Sargassum agardhianum J. Ag.

J. Agardh 1889: 93; Setchell & Gardner 1925: 716.

Thalli to 40(100) cm tall, attached by irregular, lumpy holdfast, the basal portions perennial, much reduced in winter; young plants simple, branching later from basal area; branches few to many, 1 mm diam., terete, the main stipe shorter than laterals; branches with clusters of branchlets, pneumatocysts and/or receptacles in axils; leaves alternate to radial, linear-lanceolate with toothed margins; cryptostomata conspicuous. Pneumatocysts spherical or slightly ellipsoid, smooth or toothed, apiculate, 1.5-2.5 mm diam., on pedicels 1-1.5 mm long. Receptacles irregularly forked, with numerous conspicuous conceptacles; antheridia and oogonia usually in separate conceptacles, sometimes mixed in 1 receptacle.

Locally frequent, saxicolous, often forming dense stands, lower intertidal to upper subtidal, Pt. Dume (Los Angeles Co.) and Santa Catalina I., Calif., to Pta. Eugenia, Baja Calif. Type locality: San Diego, Calif.

Some forms have been reported to be almost entirely devoid of pneumatocysts.

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: Also common at San Clemente Island