Nereocystis luetkeana (K. Mertens) Postels & Ruprecht

Nereocystis luetkeana (K. Mertens) Postels & Ruprecht

Common names: bull kelp, bull-whip kelp, [as a confection] seatron

“Overall, this species reminds me of a very large gothic brown onion of extraterrestrial origin”

-Druel (2009), p. 91

Etymology: Named for Fjodor Petrowitsch Lütke, Russian naval officer and commander of the corvette Seniavin during the Russian expedition of 1826-1829 to North America. Nereocystis roughly translates into Greek as “mermaid’s bladder”

Type locality: Norfolksund, Sitka, Alaska


Ochrophyta: Phaeophyceae: Laminariales: Laminariaceae


The thallus of Nereocystis leutkeana consists of a cylindrical, hollow, and elongate stipe, a gas filled pneumatocyst, and two clusters of blades (Fig. 1), all of which are anchored to the sea floor by a holdfast. Thalli can reach lengths of up to 40m and are held erect in the water column by the buoyant pneumatocyst (M.D. Guiry, 2013). Blades are smooth and flat with straight margins.  Reproductive matter (sori) appears as a dark brown patch in the blades, which detaches and sinks to the sea floor to release spores (Fig 2). These microscopic spores are part of a heteromorphic alternation of generations. Although Nereocystis leutkeana grows in the sublittoral zone, it can often be found washed up in the intertidal.


Figure 1. The streamer like blades of Nereocystis leukeana flutter in the currents off the docks of Friday Harbor Laboratories, Friday Harbor, WA.


Nereocystis luetkeana is found along the Pacific coast from central California to the Aleutian Islands and is a common component of the Salish Sea marine flora. It forms subtidal forests with dense canopies of blades from 10-17m of depth (M.D. Guiry, 2013). The Friday Harbor Laboratories herbarium records for this species date as far back as 1910 and include the following collection locations:


Figure 2. The sori of Nereocystis leukeana appear as dark brown patches on the blade. There is a patch present on the left of this blade, and an empty space where a patch was before it detached.


Salmon Beach

Minnesota Reef

FHL Docks

San Juan Point

Turn Island

Mar Vista

Cattle Point

Hein Bank

Fort Renfrew

Mt. Dallas Beach

Whibey Island

Jura Island Ballard, Seattle

Canoe Island

Cannery Village


One voucher specimen was prepared for this page. A portion of the pneumatocyst was preserved in silica beads and the remaining thallus was pressed and entered into the FHL herbarium (Fig 3). The recorded collection location and date were FHL Docks and 25 June 2013.

Figure 3. Voucher of Nereocystis leutkeana, collected on 25 June 2013 from the docks of Friday Harbor Laboratories, Friday Harbor, WA.

Research Notes:

Life history and sexual reproduction

Nereocystis leutkeana is a member of the Phaeophyceans, or Brown Algae group, and as such exhibits a life cycle known as alternation of generations, cycling between a macroscopic diploid sporophyte phase and a microscopic haploid gametophyte phase (Graham et al., 2009). When the organisms reaches maturity as a sporophyte, it produces patches of reproductive structure called sori in its blades. These sori drop from the blades and sink to the ocean floor surrounding the holdfast, ensuring the organism’s reoccupation of optimal real estate once the annual sporophyte is gone (Druehl, 2000). The sori then release motile haploid zoospores, which are produced via meiosis in single compartment chambers known as unilocular sporangia. Haploid zoospores germinate and become male and female gametophytes, which reproduce oogamously (Fig 4a,b). The resulting diploid zygote germinates and grows into a sporophyte, completing the cycle (Mondragon et al., 2003).

Pneumatocyst gas composition

Also of note is the gas composition of the pneumatocyst. Between 15 and 25 percent is oxygen, 1 to 12 percent carbon monoxide, and the remainder nitrogen. The average carbon monoxide content is 4%. Free carbon monoxide has not yet been observed within any living plant, and it is thought that the carbon monoxide in the pneumatocyst of Nereocystis leutkeana is either a product of the photosynthetic process, in particular in association with the reduction of carbon dioxide, or a product of respiration. Experiments conducted in which the gas in the living pneumatocyst was replaced with air showed carbon monoxide to form within a couple of days, ruling out decay and autolysis as sources (Press 2013).


Figure 4a. Nereocystis leukeana gametophyte at 20X

Figure 4b. Nereocystis leukeana gametophyte forming a oogonium at 20X








Literature cited:

Druehl, L., 2000. Pacific Seaweeds. Madeira Park: Harbour Publishing.


Graham, L. E., Wilcox, L.W. & Graham, J., 2009. Algae. 2nd ed. San Francisco: Pearson Education,


Press, C., 2013. Carbon Monoxide a Respiration Product of Nereocystis Luetkeana Author ( s ): Seth C . Langdon and W . R . Gailey Published by : The University of Chicago Press

M.D. Guiry in Guiry, M.D. & Guiry, G.M. 2013. AlgaeBase. World-wide electronic publication,                National University of Ireland, Galway.; searched on 28   June 2013.

Mondragon, J., Mondragon J., 2003. Seaweeds of the Pacific Coast. Monteray: Sea Challengers

Links to additional sources:

Illustration of the life cycle:

Page authors and assocations:

Una Miller

University of Washington, Department of Biology, Seattle, Washington