KELP FORESTS
Gustavo Hernández Carmona
1 and Rafael RiosmenaRodríguez
2
1
Instituto Politécnico Nacional- Centro Interdisciplinario
de Ciencias Marinas, Av IPN s/n, Col., La Paz,
Baja California Sur, Mexico
2
Programa de Investigación en Botãnica Marina,
Departamento Académico de Biología Marina,
Universidad Autónoma de Baja California Sur, La Paz,
Baja California Sur, Mexico
Synonyms
Giant kelps; Giant seaweed; Kelpos; Sargazo Gigante
Definition
Kelp is the common name given to the large algae belonging to the class Phaeophyceae (brown algae) in the order
Laminariales or the morphologically similar fucoids. Both
canopy types include fronds suspended in the water column by some form of flotation (Macrocystis pyrifera,
Egregia menziesii, Cystoseira osmundacea, Sargassum
spp), fronds supported above the substratum by semirigid
stipes (Pterygophora californica, Eisenia arborea), and
fronds lying on or immediately above the substratum
(Laminaria farlowii, Agarum fimbriatum) (McPeak et al.,
1988; Lobban and Harrison, 1994; Graham et al., 2008).
Structures
The giant kelp (M. pyrifera) consists of one thallus
(or body) formed by the holdfast that holds it fast to the
substrate. The holdfast also provides a home for many
marine creatures. It presets many stipes which are elongated stemlike structures. The blades are formed along
the stipe. Pneumatocysts occur at the connection of the
stipe and the blade; these are gas-filled bladders that provide buoyancy to lift the fronds toward the surface. Other
kelps, such as Nereocystis luetkeana, have only one big
blade, and still others, such as Eisenia arborea, lack
a bladder. The part of the organism that lies on the surface
of the sea is called the canopy.
Reproduction
The life cycle of the large kelps involves an alternation of
generations between the adult sporophyte (diploid) that
produces spores and the microscopic gametophyte
(haploid) that produces sperm or eggs. Sexual reproduction results in the beginning of the diploid sporophyte
stage, which develops into a mature individual. In Fucales,
meiosis takes place in the conceptacles and gamete fertilization on the conceptacle surface. The propagules that
disperse are diploids.
Environmental factors
Kelps are affected by many biotic (grazers and competition) and abiotic (nutrients, substrate, light, and temperature) factors. Large kelps require nutrient-rich water with
temperatures between 6
C and 14
C. They are known
for their high growth rate. The genera Macrocystis and
Nereocystis can grow as fast as 50 cm per day, ultimately
reaching 30–80 m in size.
Conclusions
Kelp forests exhibit very complex ecological relationships
among their associated species in which complex trophic
networks develop based on species abundance. Kelp forests are vital areas where many fish species recruit, using
them as nursery and reproductive habitat. Giant kelps
can be easily harvested because of their surface canopy.
Initially they were harvested to produce soda ash but
now are used to produce alginate, a carbohydrate that
thickens products or forms gels (ice cream, jelly, salad
dressing, or pet food). Alginate is also used for dental
impressions and beer production as well as many other
products. In other uses, kelps are good sources of
biodiesel, but the lack of extensive culture techniques prevents their wide use for this commercial purpose.
Bibliography
Graham, M. H., Halpern, B. S., and Carr, M. H., 2008. Diversity and
dynamics of Californian subtidal kelp forests. In McClanahan,
T. R., and Branch, G. R. (eds.), Food Webs and the
Dynamics of Marine Benthic Ecosystems. Oxford: Oxford
University Press, pp. 103–134.
Lobban, C. S., and Harrison, P. J., 1994. Seaweed Ecology and
Physiology. Cambridge: Cambridge University Press.
McPeak, R. H., Glantz, D. A., and Shaw, C. R., 1988. The Amber
Forest. San Diego: Watersport Publishing.
Cross-references
Macroalgae
KELP FORESTS
381
Gustavo Hernández Carmona
1 and Rafael RiosmenaRodríguez
2
1
Instituto Politécnico Nacional- Centro Interdisciplinario
de Ciencias Marinas, Av IPN s/n, Col., La Paz,
Baja California Sur, Mexico
2
Programa de Investigación en Botãnica Marina,
Departamento Académico de Biología Marina,
Universidad Autónoma de Baja California Sur, La Paz,
Baja California Sur, Mexico
Synonyms
Giant kelps; Giant seaweed; Kelpos; Sargazo Gigante
Definition
Kelp is the common name given to the large algae belonging to the class Phaeophyceae (brown algae) in the order
Laminariales or the morphologically similar fucoids. Both
canopy types include fronds suspended in the water column by some form of flotation (Macrocystis pyrifera,
Egregia menziesii, Cystoseira osmundacea, Sargassum
spp), fronds supported above the substratum by semirigid
stipes (Pterygophora californica, Eisenia arborea), and
fronds lying on or immediately above the substratum
(Laminaria farlowii, Agarum fimbriatum) (McPeak et al.,
1988; Lobban and Harrison, 1994; Graham et al., 2008).
Structures
The giant kelp (M. pyrifera) consists of one thallus
(or body) formed by the holdfast that holds it fast to the
substrate. The holdfast also provides a home for many
marine creatures. It presets many stipes which are elongated stemlike structures. The blades are formed along
the stipe. Pneumatocysts occur at the connection of the
stipe and the blade; these are gas-filled bladders that provide buoyancy to lift the fronds toward the surface. Other
kelps, such as Nereocystis luetkeana, have only one big
blade, and still others, such as Eisenia arborea, lack
a bladder. The part of the organism that lies on the surface
of the sea is called the canopy.
Reproduction
The life cycle of the large kelps involves an alternation of
generations between the adult sporophyte (diploid) that
produces spores and the microscopic gametophyte
(haploid) that produces sperm or eggs. Sexual reproduction results in the beginning of the diploid sporophyte
stage, which develops into a mature individual. In Fucales,
meiosis takes place in the conceptacles and gamete fertilization on the conceptacle surface. The propagules that
disperse are diploids.
Environmental factors
Kelps are affected by many biotic (grazers and competition) and abiotic (nutrients, substrate, light, and temperature) factors. Large kelps require nutrient-rich water with
temperatures between 6
C and 14
C. They are known
for their high growth rate. The genera Macrocystis and
Nereocystis can grow as fast as 50 cm per day, ultimately
reaching 30–80 m in size.
Conclusions
Kelp forests exhibit very complex ecological relationships
among their associated species in which complex trophic
networks develop based on species abundance. Kelp forests are vital areas where many fish species recruit, using
them as nursery and reproductive habitat. Giant kelps
can be easily harvested because of their surface canopy.
Initially they were harvested to produce soda ash but
now are used to produce alginate, a carbohydrate that
thickens products or forms gels (ice cream, jelly, salad
dressing, or pet food). Alginate is also used for dental
impressions and beer production as well as many other
products. In other uses, kelps are good sources of
biodiesel, but the lack of extensive culture techniques prevents their wide use for this commercial purpose.
Bibliography
Graham, M. H., Halpern, B. S., and Carr, M. H., 2008. Diversity and
dynamics of Californian subtidal kelp forests. In McClanahan,
T. R., and Branch, G. R. (eds.), Food Webs and the
Dynamics of Marine Benthic Ecosystems. Oxford: Oxford
University Press, pp. 103–134.
Lobban, C. S., and Harrison, P. J., 1994. Seaweed Ecology and
Physiology. Cambridge: Cambridge University Press.
McPeak, R. H., Glantz, D. A., and Shaw, C. R., 1988. The Amber
Forest. San Diego: Watersport Publishing.
Cross-references
Macroalgae
KELP FORESTS
381