Brown algae
Brown algae | |
---|---|
![]() | |
Giant kelp ( Macrocystis pyrifera )
| |
Scientific classification ![]() | |
Domain: | Eukaryota |
Clade: | Diaphoretickes |
Clade: | SAR |
Clade: | Stramenopiles |
Phylum: | Gyrista |
Subphylum: | Ochrophytina |
Infraphylum: | Chrysista
|
Superclass: | Fucistia |
Class: | Phaeophyceae Kjellman, 1891[3] |
Orders | |
See classification | |
Synonyms | |
|
Brown algae (sg.: alga) are a large group of
Between 1,500 and 2,000
Brown algae belong to the
Morphology
Brown algae exist in a wide range of sizes and forms. The smallest members of the group grow as tiny, feathery tufts of threadlike
Regardless of size or form, two visible features set the Phaeophyceae apart from all other algae. First, members of the group possess a characteristic color that ranges from an
Visible structures
![](http://upload.wikimedia.org/wikipedia/commons/thumb/0/03/Laminaria_hyperborea.jpg/240px-Laminaria_hyperborea.jpg)
Whatever their form, the body of all brown algae is termed a thallus, indicating that it lacks the complex xylem and phloem of vascular plants. This does not mean that brown algae completely lack specialized structures. But, because some botanists define "true" stems, leaves, and roots by the presence of these tissues, their absence in the brown algae means that the stem-like and leaf-like structures found in some groups of brown algae must be described using different terminology.[12] Although not all brown algae are structurally complex, those that are typically possess one or more characteristic parts.
A holdfast is a rootlike structure present at the base of the alga. Like a root system in plants, a holdfast serves to anchor the alga in place on the substrate where it grows, and thus prevents the alga from being carried away by the current. Unlike a root system, the holdfast generally does not serve as the primary organ for water uptake, nor does it take in nutrients from the substrate. The overall physical appearance of the holdfast differs among various brown algae and among various substrates. It may be heavily branched, or it may be cup-like in appearance. A single alga typically has just one holdfast, although some species have more than one stipe growing from their holdfast.
A
Many algae have a flattened portion that may resemble a leaf, and this is termed a blade, lamina, or frond. The name blade is most often applied to a single undivided structure, while frond may be applied to all or most of an algal body that is flattened, but this distinction is not universally applied. The name lamina refers to that portion of a structurally differentiated alga that is flattened. It may be a single or a divided structure, and may be spread over a substantial portion of the alga. In rockweeds, for example, the lamina is a broad wing of tissue that runs continuously along both sides of a branched midrib. The midrib and lamina together constitute almost all of a rockweed, so that the lamina is spread throughout the alga rather than existing as a localized portion of it.
![](http://upload.wikimedia.org/wikipedia/commons/thumb/8/80/Bladder_Wrack_%28Fucus_vesiculosus%29_-_geograph.org.uk_-_224125.jpg/240px-Bladder_Wrack_%28Fucus_vesiculosus%29_-_geograph.org.uk_-_224125.jpg)
In some brown algae, there is a single lamina or blade, while in others there may be many separate blades. Even in those species that initially produce a single blade, the structure may tear with rough currents or as part of maturation to form additional blades. These blades may be attached directly to the stipe, to a holdfast with no stipe present, or there may be an air bladder between the stipe and blade. The surface of the lamina or blade may be smooth or wrinkled; its tissues may be thin and flexible or thick and leathery. In species like
Gas-filled floats called pneumatocysts provide buoyancy in many kelps and members of the Fucales. These bladder-like structures occur in or near the lamina, so that it is held nearer the water surface and thus receives more light for photosynthesis. Pneumatocysts are most often spherical or ellipsoidal, but can vary in shape among different species. Species such as Nereocystis luetkeana and Pelagophycus porra bear a single large pneumatocyst between the top of the stipe and the base of the blades. In contrast, the giant kelp Macrocystis pyrifera bears many blades along its stipe, with a pneumatocyst at the base of each blade where it attaches to the main stipe. Species of Sargassum also bear many blades and pneumatocysts, but both kinds of structures are attached separately to the stipe by short stalks. In species of Fucus, the pneumatocysts develop within the lamina itself, either as discrete spherical bladders or as elongated gas-filled regions that take the outline of the lamina in which they develop.
Growth
![](http://upload.wikimedia.org/wikipedia/commons/thumb/0/0b/Capo_Gallo_Dicotoma.jpg/240px-Capo_Gallo_Dicotoma.jpg)
The brown algae include the largest and fastest growing of seaweeds.[6] Fronds of Macrocystis may grow as much as 50 cm (20 in) per day, and the stipes can grow 6 cm (2.4 in) in a single day.[13]
Growth in most brown algae occurs at the tips of structures as a result of divisions in a single apical cell or in a row of such cells. They are single cellular organisms.[7] As this apical cell divides, the new cells that it produces develop into all the tissues of the alga. Branchings and other lateral structures appear when the apical cell divides to produce two new apical cells. However, a few groups (such as Ectocarpus) grow by a diffuse, unlocalized production of new cells that can occur anywhere on the thallus.[11]
Tissue organization
The simplest browns are filamentous—that is, their cells are elongate and have septa cutting across their width. They branch by getting wider at their tip, and then dividing the widening.[14]
These filaments may be haplostichous or polystichous, multiaxial or monoaxial forming or not a
The
Evolutionary history
Genetic and ultrastructural evidence place the Phaeophyceae among the
The closest relatives of the brown algae include unicellular and filamentous species, but no unicellular species of brown algae are known. However, most scientists assume that the Phaeophyceae evolved from unicellular ancestors.
Fossils
The occurrence of Phaeophyceae as fossils is rare due to their generally soft-bodied nature,[31] and scientists continue to debate the identification of some finds.[32] Part of the problem with identification lies in the convergent evolution of morphologies between many brown and red algae.[33] Most fossils of soft-tissue algae preserve only a flattened outline, without the microscopic features that permit the major groups of multicellular algae to be reliably distinguished. Among the brown algae, only species of the genus Padina deposit significant quantities of minerals in or around their cell walls.[34] Other algal groups, such as the red algae and green algae, have a number of calcareous members. Because of this, they are more likely to leave evidence in the fossil record than the soft bodies of most brown algae and more often can be precisely classified.[35]
Fossils comparable in morphology to brown algae are known from strata as old as the Upper
A number of
The earliest known fossils that can be assigned reliably to the Phaeophyceae come from
Classification
Phylogeny
Based on the work of Silberfeld, Rousseau & de Reviers 2014.[46]
| |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
Taxonomy
This is a list of the orders in the class Phaeophyceae:[46][47]
- Class Phaeophyceae Hansgirg 1886 [Fucophyceae; Melanophycidae Rabenhorst 1863 stat. nov. Cavalier-Smith 2006]
- Subclass DiscosporangiophycidaeSilberfeld, Rousseau & Reviers 2014
- Order Discosporangiales Schmidt 1937 emend. Kawai et al. 2007
- Family Choristocarpaceae Kjellman 1891
- Family Discosporangiaceae Schmidt 1937
- Order Discosporangiales Schmidt 1937 emend. Kawai et al. 2007
- Subclass IshigeophycidaeSilberfeld, Rousseau & Reviers 2014
- Order Ishigeales Cho & Boo 2004
- Family IshigeaceaeOkamura 1935
- Family Petrodermataceae Silberfeld, Rousseau & Reviers 2014
- Family
- Order Ishigeales Cho & Boo 2004
- Subclass Dictyotophycidae Silberfeld, Rousseau & Reviers 2014
- Order Dictyotales Bory de Saint-Vincent 1828 ex Phillips et al.
- Family DictyotaceaeLamouroux ex Dumortier 1822 [Scoresbyellaceae Womersley 1987; Dictyopsidaceae]
- Family
- Order OnslowialesDraisma & Prud’homme van Reine 2008
- Family Onslowiaceae Draisma & Prud’homme van Reine 2001
- Order Sphacelariales Migula 1909
- Family Cladostephaceae Oltmanns 1922
- Family Lithodermataceae Hauck 1883
- Family Phaeostrophiaceae Kawai et al. 2005
- Family Sphacelariaceae Decaisne 1842
- Family Sphacelodermaceae Draisma, Prud’homme & Kawai 2010
- Family Stypocaulaceae Oltmanns 1922
- Order SyringodermatalesHenry 1984
- Family Syringodermataceae Henry 1984
- Order Dictyotales Bory de Saint-Vincent 1828 ex Phillips et al.
- Subclass Fucophycidae Cavalier-Smith 1986
- Order Ascoseirales Petrov1964 emend. Moe & Henry 1982
- Family AscoseiraceaeSkottsberg 1907
- Family
- Order Asterocladales T.Silberfeld et al. 2011
- Family Asterocladaceae Silberfeld et al. 2011
- Order Desmarestiales Setchell & Gardner 1925
- Family Arthrocladiaceae Chauvin 1842
- Family Desmarestiaceae (Thuret) Kjellman 1880
- Order Ectocarpales Bessey 1907 emend. Rousseau & Reviers 1999a [Chordariales Setchell & Gardner 1925; Dictyosiphonales Setchell & Gardner 1925; Scytosiphonales Feldmann 1949]
- Family Acinetosporaceae Hamel ex Feldmann 1937 [Pylaiellaceae; Pilayellaceae]
- Family Adenocystaceae Rousseau et al. 2000 emend. Silberfeld et al. 2011 [Chordariopsidaceae]
- Family Chordariaceae Greville 1830 emend. Peters & Ramírez 2001 [Myrionemataceae]
- Family Ectocarpaceae Agardh 1828 emend. Silberfeld et al. 2011
- Family Petrospongiaceae Racault et al. 2009
- Family Scytosiphonaceae Ardissone & Straforello 1877 [Chnoosporaceae Setchell & Gardner 1925]
- Order Fucales Bory de Saint-Vincent 1827 [Notheiales Womersley 1987; Durvillaeales Petrov 1965]
- Family Bifurcariopsidaceae Cho et al. 2006
- Family Durvillaeaceae(Oltmanns) De Toni 1891
- Family Fucaceae Adanson 1763
- Family Himanthaliaceae(Kjellman) De Toni 1891
- Family HormosiraceaeFritsch 1945
- Family Notheiaceae Schmidt 1938
- Family Sargassaceae Kützing 1843 [Cystoseiraceae De Toni 1891]
- Family Seirococcaceae Nizamuddin 1987
- Family Xiphophoraceae Cho et al. 2006
- Order Laminariales Migula1909 [Phaeosiphoniellales Silberfeld, Rousseau & Reviers 2014 ord. nov. prop.]
- Family Agaraceae Postels & Ruprecht 1840 [Costariaceae]
- Family Akkesiphycaceae Kawai & Sasaki 2000
- Family Alariaceae Setchell & Gardner 1925
- Family Aureophycaceae Kawai & Ridgway 2013
- Family ChordaceaeDumortier 1822
- Family Laminariaceae Bory de Saint-Vincent 1827 [Arthrothamnaceae Petrov 1974]
- Family Lessoniaceae Setchell & Gardner 1925
- Family PseudochordaceaeKawai & Kurogi 1985
- Order NemodermatalesParente et al. 2008
- Family NemodermataceaeKuckuck ex Feldmann 1937
- Family
- Order Phaeosiphoniellales Silberfeld, Rousseau & Reviers 2014
- Family Phaeosiphoniellaceae Phillips et al. 2008
- Order Ralfsiales Nakamura ex Lim & Kawai 2007
- Family Mesosporaceae Tanaka & Chihara 1982
- Family Neoralfsiaceae Lim & Kawai 2007
- Family Ralfsiaceae Farlow 1881 [Heterochordariaceae Setchell & Gardner 1925]
- Order Scytothamnales Peters & Clayton 1998 emend. Silberfeld et al. 2011
- Family AsteronemataceaeSilberfeld et al. 2011
- Family Bachelotiaceae Silberfeld et al. 2011
- Family Splachnidiaceae Mitchell & Whitting 1892 [Scytothamnaceae Womersley 1987]
- Family
- Order Sporochnales Sauvageau1926
- Family Sporochnaceae Greville 1830
- Order Tilopteridales Bessey 1907 emend. Phillips et al. 2008 [Cutleriales Bessey 1907]
- Family Cutleriaceae Griffith & Henfrey 1856
- Family Halosiphonaceae Kawai & Sasaki 2000
- Family Phyllariaceae Tilden 1935
- Family Stschapoviaceae Kawai 2004
- Family Tilopteridaceae Kjellman 1890
- Order
- Subclass
![](http://upload.wikimedia.org/wikipedia/commons/thumb/6/63/Laminaria_Life_Cycle.png/220px-Laminaria_Life_Cycle.png)
![](http://upload.wikimedia.org/wikipedia/commons/thumb/1/16/Fucus_conceptacle_XS3.jpg/220px-Fucus_conceptacle_XS3.jpg)
Life cycle
Most brown algae, with the exception of the
Certain species of brown algae can also perform asexual reproduction through the production of motile diploid zoospores. These zoospores form in plurilocular sporangium, and can mature into the sporophyte phase immediately.
In a representative species
In the order
![](http://upload.wikimedia.org/wikipedia/commons/thumb/c/cd/Saccharina_latissima_NOAA.jpg/220px-Saccharina_latissima_NOAA.jpg)
Ecology
Brown algae have adapted to a wide variety of marine ecological niches including the tidal splash zone, rock pools, the whole intertidal zone and relatively deep near shore waters. They are an important constituent of some brackish water ecosystems, and have colonized freshwater on a minimum of six known occasions.[50] A large number of Phaeophyceae are intertidal or upper littoral,[26] and they are predominantly cool and cold water organisms that benefit from nutrients in up welling cold water currents and inflows from land; Sargassum being a prominent exception to this generalisation.
Brown algae growing in brackish waters are almost solely asexual.[26]
Chemistry
Algal group | δ13C range[51] |
---|---|
HCO3-using red algae | −22.5‰ to −9.6‰ |
CO2-using red algae | −34.5‰ to −29.9‰ |
Brown algae | −20.8‰ to −10.5‰ |
Green algae | −20.3‰ to −8.8‰ |
Brown algae have a δ13C value in the range of −30.0‰ to −10.5‰, in contrast with red algae and greens. This reflects their different metabolic pathways.[52]
They have cellulose walls with alginic acid and also contain the polysaccharide fucoidan in the amorphous sections of their cell walls. A few species (of Padina) calcify with aragonite needles.[26]
In addition to alginates, fucoidan and cellulose, the carbohydrate composition of brown algae consists of mannitol, laminarin and glucan.[53]
The photosynthetic system of brown algae is made of a P700 complex containing chlorophyll a. Their plastids also contain chlorophyll c and carotenoids (the most widespread of those being fucoxanthin).[54]
Brown algae produce a specific type of tannin called phlorotannins in higher amounts than red algae do.
Importance and uses
Brown algae include a number of
Alginic acid can also be used in aquaculture. For example, alginic acid enhances the immune system of rainbow trout. Younger fish are more likely to survive when given a diet with alginic acid.[57]
Brown algae including kelp beds also fix a significant portion of the earth's carbon dioxide yearly through photosynthesis.[58] Additionally, they can store a great amount of carbon dioxide which can help us in the fight against climate change.[59] Sargachromanol G, an extract of Sargassum siliquastrum, has been shown to have anti-inflammatory effects.[60]
Edible brown algae
Kelp (Laminariales)
|
Fucales
|
Ectocarpales
|
See also
References
- ^ ISBN 978-3-211-83035-2. Archived(PDF) from the original on 5 October 2013. Retrieved 27 August 2012.
- ^ from the original on 10 January 2015. Retrieved 27 August 2012.
- ^ Kjellman, F. R. (1891). "Phaeophyceae (Fucoideae)". In Engler, A.; Prantl, K. (eds.). Die natürlichen Pflanzenfamilien. Vol. 1. Leipzig: Wilhelm Engelmann. pp. 176–192.
- ^ PMID 21820616.
- from the original on 16 October 2023. Retrieved 26 April 2018.
- ^ a b c
Connor, J.; Baxter, C. (1989). Kelp Forests. ISBN 978-1-878244-01-7.
- ^ a b
Dittmer, H. J. (1964). Phylogeny and Form in the Plant Kingdom. Princeton, NJ: ISBN 978-0-88275-167-2.
- ^
Abbott, I. A.; Hollenberg, G. J. (1976). Marine Algae of California. California: ISBN 978-0-8047-0867-8.
- ^ Cribb, A. B. (1953). "Macrocystis pyrifera (L.) Ag. in Tasmanian waters". .
- ^ Jones, W. E. (1962). "A key to the genera of the British seaweeds" (PDF). Field Studies. 1 (4): 1–32.[permanent dead link]
- ^ a b c d
Bold, H. C.; Alexopoulos, C. J.; Delevoryas, T. (1987). Morphology of Plants and Fungi (5th ed.). New York: ISBN 978-0-06-040839-8.
- ^
Raven, P. H.; Evert, R. F.; Eichhorn, S. E. (2005). Biology of Plants (7th ed.). New York: ISBN 978-0-7167-1007-3.
- ^
Round, F. E. (1981). The Ecology of Algae. Cambridge: ISBN 978-0-521-26906-3.
- ISBN 978-0-520-04585-9. Archivedfrom the original on 16 October 2023. Retrieved 11 May 2020.
- ^ a b
Sharma, O. P (1986). Textbook of Algae. ISBN 978-0-07-451928-8.
- ISBN 9780321603128.)
{{cite book}}
: CS1 maint: multiple names: authors list (link - ^ Fritsch, F. E. 1945. The Structure And Reproduction Of The Algae. Cambridge University Press, Cambridge.
- from the original on 16 October 2023. Retrieved 13 November 2020.
- (PDF) from the original on 8 January 2022. Retrieved 17 September 2022.
- PMID 20618907.
- PMID 24875633.
- (PDF) from the original on 29 May 2013. Retrieved 27 August 2012.
- (PDF) from the original on 20 June 2013. Retrieved 27 August 2012.
- ^ ISBN 978-0-521-31687-3.
- ^
Niklas, K. J. (1997). The Evolutionary Biology of Plants. Chicago: ISBN 978-0-226-58082-1.
- ^ a b c d e
Lee, R. E. (2008). Phycology (4th ed.). ISBN 978-0-521-63883-8.
- ^
Ariztia, E. V.; Andersen, R. A.; Sogin, M. L. (1991). "A new phylogeny of chromophyte algae using 16S-like rRNA sequences from Mallomonas papillosa (Synurophyceae) and Tribonema aequale (Xanthophyceae)". S2CID 84693030.
- ^
Taylor, T. N.; Taylor, E. L. (1993). The Biology and Evolution of Fossil Plants. Englewood Cliffs, NJ: ISBN 978-0-13-651589-0.
- ^
Dittmer, H. J. (1964). Phylogeny and Form in the Plant Kingdom. Princeton, NJ: D. Van Nostrand Company. pp. 115–137. ISBN 978-0-88275-167-2.
- ^
Hori, H.; Osawa, S. (1987). "Origin and evolution of organisms as deduced from 5S ribosomal RNS sequences". PMID 2452957.
- ^ a b
Arnold, C. A. (1947). An Introduction to Paleobotany. New York; London: ISBN 978-1-4067-1861-4.
- from the original on 16 October 2023. Retrieved 27 August 2012.
- ^ a b c
Fry, W. L.; Banks, H. P. (1955). "Three new genera of algae from the Upper Devonian of New York". JSTOR 1300127.
- ^
Prescott, G. W. (1968). The Algae: A Review. Boston: ISBN 978-3-87429-244-3.
- ^ Simpson, G. G. (1953). Life of the Past: An Introduction to Paleontology. New Haven: Yale University Press. pp. 158–159.
- ^ Fry, W. L. (1983). "An algal flora from the Upper Ordovician of the Lake Winnipeg region, Manitoba, Canada". .
- ^ Speer, B. R.; Waggoner, B. M. (2000). "Phaeophyta: Fossil Record". Archived from the original on 9 June 2007. Retrieved 24 April 2007.
- ^
Loeblich, A. R. (1974). "Protistan Phylogeny as Indicated by the Fossil Record". JSTOR 1218707.
- ^
Hofmann, H. J. (1985). "Precambrian Carbonaceous Megafossils". In D. F. Toomey; M. H. Nitecki (eds.). Paleoalgology: Contemporary Research and Applications. Berlin: Springer-Verlag. pp. 20–33.
- ^ Hofmann, H. J. (1994). "Proterozoic carbonaceous compressions ("metaphytes" and "worms")". In Bengtson, S. (ed.). Life on Earth. Nobel Symposium. Vol. 84. New York: Columbia University Press. pp. 342–357.
- ^ Hueber, F. M. (2001). "Rotted wood-alga-fungus: the history and life of Prototaxites Dawson 1859". .
- ^
Taylor, W. A.; Taylor, T. N. (1987). "Spore wall ultrastructure of Protosalvinia" (PDF). JSTOR 2443819. Archived from the original(PDF) on 17 June 2010.
- ^
Leary, R. L. (1986). "Three new genera of fossil noncalcareous algae from Valmeyeran (Mississippian) strata of Illinois". JSTOR 2444080.
- ^
Bold, H. C.; Wynne, M. J. (1978). Introduction to the Algae (2nd ed.). ISBN 978-0-13-477786-3.
- ^
Parker, B. C.; Dawson, E. Y. (1965). "Non-calcareous marine algae from California Miocene deposits". Nova Hedwigia. 10: 273–295, plates 76–96.
- ^ S2CID 86227768.
- ^ Guiry, M. D.; Guiry, G. M. (2009). "AlgaeBase". National University of Ireland. Archived from the original on 12 October 2009. Retrieved 31 December 2012.
- ISBN 9780134777467. Archivedfrom the original on 16 October 2023. Retrieved 11 May 2020.
- )
- (PDF) from the original on 26 February 2020. Retrieved 11 May 2020.
- ^
Maberly, S. C.; Raven, J. A.; Johnston, A. M. (1992). "Discrimination between 12C and 13C by marine plants". JSTOR 4220100.
- ^
Fletcher, B. J.; S2CID 85079041.
- PMID 34822491.
- S2CID 7160955.
- ^ "Alginic acid". www.fao.org. Archived from the original on 20 April 2017. Retrieved 20 April 2017.
- S2CID 6523029.
- S2CID 86175912.
- S2CID 14492051.
- doi:10.1038/ngeo2790.
- S2CID 39748571.
External links
![](http://upload.wikimedia.org/wikipedia/en/thumb/4/4a/Commons-logo.svg/30px-Commons-logo.svg.png)
![](http://upload.wikimedia.org/wikipedia/commons/thumb/d/df/Wikispecies-logo.svg/34px-Wikispecies-logo.svg.png)
- Monterey Bay Flora
- The Monterey Formation of California, University of California Museum of Paleontology
- Phaeophyceae, National University of Ireland, Galway