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Name derivation:

'Mermaid's bladder' -- commonly called 'Bull kelp' because of the resemblance of detached and beached organisms to bull whips.


Macrocystis C.Agardh, 1820: There are three species of which only one (N. luetkeana ) has been taxonomically accepted (Guiry and Guiry 2013).

Order Laminariales; Family Laminariaceae


A large seaweed with a 'holdfast', long hollow stipe ('stem') kept afloat with a pneumatocyst (air bladder or ‘bulb’) at the upper end of the stipe, and 30 - 60 blades emanating from the distal (upper) end of the stipe. Develops a 'holdfast' up to 40 cm long. Each blade can be up to 4 m long. The stipe elongates until it reaches the surface, apparently mediated by the phytochrome switch sensitive to red/infrared light.

Haplodiplontic Life Cycle:

Dominant alga is the diploid sporophyte. ‘Sori’ up to 30 cm long located near the distal end of blades produce an abundance of haploid spores by meiosis. Once spores are mature the sori abscise from the sporophyte blad and with four hours their spores are released into the water. Germinating spores divide mitotically to produce a sessile haploid gametophyte that is microscopic and multicellular, thus the life cycle has alternation of multicellular thalli (Springer et al. 2007). a.k.a. ‘haplodiplontic life cycle).

Spatial density of male and female gametophyes (dioecious) is critical for effective fertilization even though the eggs (attached to oogonium on female gametophyte) produce a pheromone (lamoxirene) that causes an explosive release of sperm from spermatia attached to the male gametophyte, and attract them to the eggs (Langstroth and Langstroth 2000).

To enhance reproductivity the sporophytes produce extraordinary numbers of spores. Because spores themselves are photosynthetic, they are generally released at dawn to maximize their PS production of metabolites for germination. They are viable for several days prior to germination (Ibid.).

Annual or biennial (in shallow water or protected areas, when produced late in the year), may persist for 18 months, and cannot grow from its base, in contrast with the perennial Macrocystis spp.. Grows rapidly, up to 25 m per day.

Similar genera:

Macrocystis, Laminaria, Saccharina

Recent genetic data group Nereocystis with Macrocystis, Pelagophycus and Postelsia, the latter being its closest relative (Ibid.).


It grows within the shallow to mid sublittoral zones on the northeast Pacific Coast of North America from Monterey, California to the Aleutian Islands, where it forms extensive 'forests' usually mixed with Macrosystis spp. Nereocystis is dominant north of Santa Cruz, California (Ibid.).


Because of their fast growth rate (up to 6 cm per day) and large stature, these algae are thought to contribute markedly to both the productivity of shallow coastal marine ecosystems and as habitat for a diversity of fishes and invertebrates (Ibid.).

Bull kelp, N. luetkeana, has commercial and recreational value as a harvestable resource, intrinsic value as habitat and food for hundreds of species in the nearshore ecosystem, and aesthetic value for non-consumptive users such as scuba divers. Because of the multiple uses of bull kelp, management concerns are much more complex than for most species. The Fish and Game Commission of California has restricted harvest from April through July to help preserve beds within the boundary of the Monterey Bay National Marine Sanctuary.

Nereocystis is edible and is made into pickles, and can be stuffed and baked, candied, dried and ground to powder, stir fried, etc. It is also used in pharmaceuticals, and as food for commercial mariculture of abalone.



Abbott, I. A. and G. J. Hollenberg. 1976, Marine Algae of California. Stanford University Press, Stanford, xii + 827 pp.

Agardh, C.A. 1820 '1821'. Species algarum rite cognitae, cum synonymis, differentiis specificis et descriptionibus succinctis. Volumen primum. Pars prima. pp. [i-iv], [1]-168. Lundae [Lund]: ex officina Berlingiana.

Guiry, M.D., and G.M. Guiry 2013. AlgaeBase. World-wide electronic publication, National University of Ireland, Galway. http://www.algaebase.org; searched on 16 January 2013.

Langstroth, L. and L. Langstroth 2000. A living bay: The underwater world of Monterey Bay. University of California Press. [online]

Springer, Y., C. Hays, M. Carr, and M. Mackay 2007. Ecology and management of the bull kelp, Nereocystis luetkeana. Report supported by the Lenfest Ocean Program. [online]




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