Nereocystis (Greek, 'mermaid's bladder') is a monotypic taxon genus of subtidal kelp containing the species Nereocystis luetkeana.
Due to the English name, bull kelp can be confused with
Durvillaea, which are found in the Southern Hemisphere.
forms thick beds on subtidal rocks, and is an important part of
.
Etymology
The species
Nereocystis luetkeana was named (as
Fucus luetkeanus) after the German-Russian explorer
Fyodor Litke (also spelled Lütke) by Mertens. The species was renamed in a description by Postels and Ruprecht.
Description
Nereocystis is a
Brown algae that derives chemical energy from
photosynthesis.
Nereocystis in particular, similar to
Pelagophycus, can be identified by a single large pneumatocyst between the end of its hollow stipe and the blades.
[FOREMAN, R. E. (1970). Physiology, Ecology, And Development Of The Brown Alga, Nereocystis Luetkeana (mertens) P. & R (Order No. 7109813). Available from ProQuest Dissertations & Theses Global. (302503381).] Individuals can grow to a maximum of .
has a holdfast of about , and a single stipe, topped with a
pneumatocyst containing
carbon monoxide, from which sprout the numerous (about 30-64) blades. The blades may be up to long, and up to wide. It is usually annual, sometimes persisting up to 18 months.
Nereocystis is the only kelp which will drop spore patches, so that the right concentration of spores lands near the parent's holdfast.
The thallus of this common canopy-forming kelp has a richly branched holdfast (haptera) and a cylindrical stipe 10–36 m (33–118 ft) long. The stipe terminates in a single, gas-filled pneumatocyst from which many blades grow. Each blade can grow up to 10 m (33 ft) long, and blade growth can reach 15 cm (5.9 in) per day.
Nereocystis grows in areas where Pterygophora californica also inhabits. Bull kelp will often grow on the stipe of Pterygophora, with up anywhere from 10 to 20 individuals of Nereocystis attaching to a single Pterygophora stipe.[
]
Reproduction
Reproduction in
Nereocystis is characterized by an alternation of generations.
[ The Ploidy generation is the recognizable macroscopic sporophyte. During sexual reproduction, reproductive patches (sori) develop on the blades of the sporophyte and drop to the seafloor at maturity.]
Distribution
The species is common along the Pacific Coast of North America, from Southern California to the Aleutian Islands, Alaska.[Bushing WW (1994) Biogeographical and ecological implications of kelp rafting as a dispersal vector for marine invertebrates. In: Halvorson W, Maender G (eds) Proceedings of the Fourth California Islands Symposium: Update on the Status of Resources, March 22–25, 1994. Santa Barbara Museum of Natural History, Santa Barbara, CA] Offshore beds can persist for one or many years, usually in deeper water than Eualaria or Macrocystis, where they co-occur.
This annual kelp grows on rock from the low Intertidal zone to subtidal zones; it prefers semi-exposed habitats or high-current areas. It also does not grow in areas with breaking waves or swells.[ Its distribution is limited by the requirement of light for photosynthesis, and preference for areas of high water movement where the microscopic gametophyte stage will not be covered by sediment.]
Other factors such as salinity, turbidity and water temperature can affect Nereocystis distribution. Nereocystis tends to thrive in temperatures ranging from 5 to 20 degrees Celsius.[ Nereocystis fails to thrive in areas of reduced salinity, such as brackish Estuary waters, because it has difficulty adjusting to changes in salinity. The increased turbidity of such waters also decreases light available for photosynthesis, limiting its growth. Additionally, disease, competition, and herbivory can affect distribution.
]
Ecology
Nereocystis, like other large, canopy forming kelps, play a crucial role in maintaining the biologically diverse kelp forests in the temperate marine environments where they flourish.[Wheeler, W. N., and Druehl, L. D. (1986). Seasonal growth and productivity of Macrocystis integrifolia in British Columbia, Canada. Mar. Biol. 90, 181–186. doi: 10.1007/BF00569125] Its fast growth and size provide an important habitat not only for the fish and invertebrates that reside in kelp forests, but also for species that use kelp forests as foraging grounds.[Calvert EL, Siddon CE, Stekoll MS (in prep). Direct and Indirect Effects of Kelp Beds in Structuring Fish and Invertebrate Assemblages in Southeastern Alaska.] In bull kelp forests, are important grazers that control the ecosystem by feeding on large canopy kelps such as Nereocystis.[Dobkowski, Katie. “The Role of Kelp Crabs as Consumers in Bull Kelp Forests—Evidence from Laboratory Feeding Trials and Field Enclosures.” PeerJ, PeerJ Inc., 1 May 2017]
Microbial communities
Nereocystis fosters microbacteria species, affecting the ecology on a microscopic level. These microbial bacteria species foster the growth of seaweed, producing growth-promoting substances.[Ravindra Pal Singh, C.R.K. Reddy, Seaweed–microbial interactions: key functions of seaweed-associated bacteria, FEMS Microbiology Ecology, Volume 88, Issue 2, April 2014] According to studies by Weigel, the microbial communities that grow on Nereocystis are composed mostly of Proteobacteria, Bacteroidota, Verrucomicrobia, and Planctomycetota. Nereocystis is unique in that it contains a large percentage of Verrucomicrobia, with it composing approximately 10% of microbacteria populations on Nereocystis.[Weigel, Brooke L., et al. “Successional Dynamics and Seascape-Level Patterns of Microbial Communities on the Canopy-Forming Kelps Nereocystis luetkeana and Macrocystis pyrifera.” Frontiers in Microbiology, vol. 10, 2019.]
Human effects
Abalone mariculture (the commercial farming and harvest of abalone) and an increasing demand in human consumption have led to a notable and marked increase in Nereocystis extraction. This extraction is done by hand and removes the top two meters of the forest. These first two meters contain bull kelp's pneumatocysts and its reproductive organs, so this method of extraction destroys kelp forests that depend on Nereocystis.[Hansen GI, Mumford TF (1995) 1994/1995 Regulations for Seaweed Harvesting on the West Coast of North America.] Since bull kelp tend to only reproduce once a year, removal of these organs renders Nereocystis unable to reproduce.[Springer, Yuri; Hays, Cynthia; Carr, Mark; Mackey, Megan; Bloeser, Jennifer (March 2007). "Ecology and Management of the Bull Kelp, Nereocystis Luetkeana" (PDF).] The tissues of bull kelp are processed and turned into liquid fertilizer as well as food for abalones.
Human uses
Nereocystis was not commercially harvested off the coast of California until around the 1980s. The beginning of this harvest is attributed to the Abalone International company, which was seeking mariculture expansion and efficiency. Kelp harvesters are legally mandated to record every aspect of their harvest, including but not limited to the amount of kelp, the species, and the location where it was taken from. Kelp is currently harvested from the Californian coast, Oregon, Washington, British Columbia, and Alaska.[
]
Human uses of Nereocystis include consumption and agriculture. It is pickled and eaten as a delicacy as well as used for creative purposes. In South Korea, Nereocystis used to make miyeok-guk (Korean kelp soup) weekly by new mothers as it's revered as a blood-cleanser. It is also customary to eat it on one's birthday.[
]
Further reading
External links
