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[[Image:Laurencia.jpg|thumb|A seaweed (''Laurencia'') up close: the "branches" are multicellular and only about 1 mm thick. Much smaller algae are seen growing attached to the structure extending upwards in the lower right quarter]]
[[Image:River algae Sichuan.jpg|right|thumb|[[Algal blooms]] can present problems for ecosystems and human society]]
'''Algae''' (singular ''alga'') encompass several groups of relatively simple, eukaryotic, living aquatic organisms that capture [[light]] energy through [[photosynthesis]], using it to convert [[inorganic compound|inorganic substances]] into [[organic matter]].
Algae are photosynthetic organisms that occur in most [[habitat]]s. Algae varies from small, single-[[Cell (biology)|celled]] forms to complex [[multicellular]] forms, such as the giant [[kelp]]s that grow to 65 meters in length. The US Algal Collection is represented by almost 300,000 accessioned and inventoried herbarium specimens.[http://www.nmnh.si.edu/botany/projects/algae/herbarium.htm]
Although algae have conventionally been regarded as simple [[plant]]s, they actually span more than one [[Three-domain system|domain]], including both [[Eukaryota]] and [[Bacteria]] (''see [[Blue-green algae]]''), as well as more than one [[kingdom (biology)|kingdom]], including [[Plantae|plants]] and [[protist]]s, the latter being traditionally considered more animal-like (''see [[Protozoa]]''). Thus algae do not represent a single evolutionary direction or line but a level of organization that may have developed several times in the early [[Timeline of evolution|history of life on Earth]].
Algae range from [[unicellular|single-cell]] organisms to [[multicellular]] organisms, some with fairly complex differentiated form and (if marine) called [[seaweed]]s. All lack [[leaf|leaves]], [[root]]s, [[flower]]s, [[seed]]s and other [[Organ (anatomy)|organ]] structures that characterize higher plants ([[vascular plants]]). They are distinguished from other [[protozoa]] in that they are [[autotrophic|photoautotrophic]] although this is not a hard and fast distinction as some groups contain members that are [[mixotrophic]], deriving energy both from photosynthesis and uptake of organic carbon either by [[osmotrophy]], [[myzocytosis|myzotrophy]], or [[phagocytosis|phagotrophy]]. Some unicellular [[species]] rely entirely on external energy sources and have reduced or lost their photosynthetic apparatus.
All algae have photosynthetic machinery ultimately derived from the [[cyanobacteria]], and so produce [[oxygen]] as a byproduct of photosynthesis, unlike non-cyanobacterial photosynthetic [[bacteria]]. It is estimated that algae produce about 73 to 87 percent of the net global production of oxygen<ref>http://www.ecology.com/dr-jacks-natural-world/most-important-organism/index.html</ref> - which is available to humans and other terrestrial animals for [[Cellular respiration|respiration]].
Algae are usually found in damp places or bodies of water and thus are common in terrestrial as well as aquatic environments. However, terrestrial algae are usually rather inconspicuous and far more common in moist, [[tropical]] regions than dry ones, because algae lack [[vascular tissue]]s and other adaptations to live on land. Algae can endure dryness and other conditions in [[symbiosis]] with a [[fungus]] as [[lichen]].
The various sorts of algae play significant roles in aquatic ecology. Microscopic forms that live suspended in the water column — called '''[[phytoplankton]]''' — provide the food base for most marine [[food chain]]s. In very high densities (so-called [[algal bloom]]s) these algae may discolor the water and outcompete or poison other life forms. Seaweeds grow mostly in shallow marine waters. Some are used as human food or harvested for useful substances such as [[agar]] or fertilizer.
The study of marine and freshwater algae is called [[phycology]] or algology.
==Classification==
[[Image:AlgaeTree.png|thumb|180px|left|The lineage of algae according to Thomas Cavallier-Smith. The three supergroups [[Archaeplastida]], [[Chromalveolata]] and [[Cabozoa]] of eukaryotic algae are denoted to reflect the table below. Endosymbiotic events are noted by dotted lines.]]
=== Prokaryotic algae ===
Traditionally the [[Cyanobacteria]] have been included among the algae, referred to as the ''cyanophytes'' or ''Blue-green algae'', (the term "algae" refers to any aquatic organisms capable of photosynthesis)<ref>http://www.ucmp.berkeley.edu/bacteria/cyanolh.html</ref> though some recent treatises on algae specifically exclude them. Cyanobacteria are some of the oldest organisms to appear in the [[fossil record]] dating back to the [[Precambrian]], possibly as far as about 3.5 billion years.<ref>Schopf, JW, and Packer, BM, Science, 1987, 237, 70</ref> Ancient cyanobacteria likely produced much of the [[oxygen]] in the Earth's atmosphere.
[[Cyanobacteria]] can be unicellular, colonial, or filamentous. They have a [[prokaryote|prokaryotic]] cell structure typical of bacteria and conduct photosynthesis on specialized cytoplasmic membranes called [[thylakoid membranes]], rather than in organelles. Some filamentous [[blue-green algae]] have specialized cells, termed heterocysts, in which [[nitrogen fixation]] occurs.<ref>http://www.biologie.uni-hamburg.de/b-online/e42/42a.htm</ref>
=== Eukaryotic algae ===
All other algae are [[eukaryotes]] and conduct photosynthesis within membrane-bound structures (organelles) called [[chloroplasts]]. Chloroplasts contain [[DNA]] and are similar in structure to cyanobacteria, presumably representing reduced cyanobacterial [[endosymbiotic theory|endosymbionts]]. The exact nature of the chloroplasts is different among the different lines of algae, reflecting different endosymbiotic events. The table below lists the three major groups of eukaryotic algae and their lineage relationship is shown in the figure on the left. Note many of these groups contain some members that are no longer photosynthetic. Some retain plastids, but not chloroplasts, while others have lost them entirely.
{| class="wikitable"
|-
! Supergroup affiliation !! Members !! [[Endosymbiont]] !! Summary
|-
|[[Primoplantae]]/<br>[[Archaeplastida]]
|
* [[Green algae]]
* [[Red algae]]
* [[Glaucophytes]]
|Cyanobacterium
|These algae have ''primary'' chloroplasts, i.e. the chloroplasts are surrounded by ''two membranes'' and probably developed through a single endosymbiosis. The chloroplasts of red algae have a more or less typical cyanobacterial pigmentation, while those of the green alga have chloroplasts with chlorophyll ''a'' and ''b'', the latter found in some cyanobacteria and not most. Higher plants are pigmented similarly to green algae and probably developed from them.
|-
| [[Cabozoa]]<br>or<br>[[Excavata]] and [[Rhizaria]]
|
* [[Chlorarachniophytes]]
* [[Euglenids]]
|Green alga
|
<p>These groups have green chloroplasts containing chlorophyll ''b''. Their chloroplasts are surrounded by ''three and four membranes'', respectively, and were probably retained from an ingested green alga.</p>
<p>'''Chlorarachniophytes''', which belong to the phylum [[Cercozoa]], contain a small [[nucleomorph]], which is a [[relict]] of the alga's [[cell nucleus|nucleus]].</p>
<p>'''Euglenids''', which belong to the phylum [[Euglenozoa]], have chloroplasts with only three membranes. It has been suggested that the endosymbiotic green algae were acquired through [[myzocytosis]] rather than [[phagocytosis]].</p>
|-
|[[Chromalveolata]]<br>or<br>[[Chromista]] and [[Alveolata]]
|
* [[Chromista]]
** [[Heterokonts]]
** [[Haptophyta]]
** [[Cryptomonad]]s
* [[Dinoflagellates]]
|Red alga
|
<p>These groups have chloroplasts containing chlorophylls ''a'' and ''c''. The latter chlorophyll type is not known from any prokaryotes or primary chloroplasts, but genetic similarities with the red algae suggest a relationship there.</p>
<p>In the first three of these groups ('''Chromista'''), the chloroplast has four membranes, retaining a nucleomorph in cryptomonads, and they likely share a common pigmented ancestor.</p>
<p>The typical '''dinoflagellate''' chloroplast has three membranes, but there is considerable diversity in chloroplasts among the group, as some members have acquired theirs from different sources. The [[Apicomplexa]], a group of closely related parasites, also have [[plastid]]s called [[apicoplast]]s. Apicoplasts are not photosynthetic but appear to have a common origin with dinoflagellates chloroplasts.</p>
|}
It was W.H.Harvey (1811 — 1866) who first divided the algae into four divisions based on their pigmentation. This is the first use of a biochemical criterion in plant systematics. Harvey's four divisions were: red algae (Rhodophyta), brown algae (Heteromontophyta), green algae (Chlorophyta) and Diatomaceae (Dixon, 1973 p.232).<ref name="Dixon 73" p.232>'''Dixon, P.S.''' 1973 ''Biology of the Rhodophyta.'' Oliver & Boyd, Edinburgh. ISBN 0 05 002485 X</ref>
== Forms of algae ==
Most of the simpler algae are unicellular [[flagellate]]s or [[amoeboid]]s, but colonial and non-motile forms have developed independently among several of the groups. Some of the more common organizational levels, more than one of which may occur in the [[Biological life cycle|life cycle]] of a species, are:
* ''Colonial'' - small, regular groups of motile cells
* ''Capsoid'' - individual non-motile cells embedded in [[mucilage]]
* ''Coccoid'' - individual non-motile cells with cell walls
* ''Palmelloid'' - non-motile cells embedded in mucilage
* ''Filamentous'' - a string of non-motile cells connected together, sometimes branching
* ''Parenchymatous'' - cells forming a [[thallus (tissue)|thallus]] with partial differentiation of tissues
In three — lines even higher levels of organization have been reached, leading to organisms with full tissue differentiation. These are the [[brown alga]]e [http://www.ucmp.berkeley.edu/chromista/phaeophyta.html] — some of which may reach 50 m in length ([[kelp]]s)<ref name="Thomas 02">'''Thomas, D.N.''' 2002 ''Seaweeds.'' The Natural History Museum, London. ISBN 0 565 09175 1</ref> — the [[red alga]]e [http://www.ucmp.berkeley.edu/protista/rhodophyta.html], and the [[green alga]]e [http://www.ucmp.berkeley.edu/greenalgae/greenalgae.html]. The most complex forms are found among the green algae (see [[Charales]] and [[Charophyta]]), in a lineage that eventually led to the higher [[land plants]]. The point where these non-algal plants begin and algae stop is usually taken to be the presence of reproductive organs with protective cell layers, a characteristic not found in the other alga groups.
The first plants on earth were algae and these still thrive in a range of aquatic habitats today. The land plants evolved from the algae, more specifically green algae. Some 400 million years ago freshwater, green, filamentous algae invaded the land. These probably had an isomorphic alternation of generations and were probably heterotrichous. Fossils of isolated land plant spores suggest land plants may have been around as long as 475 million years ago.
== Algae and symbioses==
Some species of algae form [[symbiosis|symbiotic relationships]] with other organisms. In these [[symbioses]], the algae supply photosynthates (organic substances) to the host organism providing protection to the algal cells. The host organism derives some or all of its energy requirements from the algae. Examples include:
* ''[[lichen]]s'' - a fungus is the host, usually with a green alga or a cyanobacterium as its symbiont. Both fungal and algal species found in lichens are capable of living independently, although habitat requirements may be greatly different from those of the lichen pair.
* ''[[coral]]s'' - algae known as [[zooxanthella]]e are symbionts with [[coral]]s. Notable amongst these is the dinoflagellate ''Symbiodinium'', found in many hard corals. The loss of ''Symbiodinium'', or other zooxanthellae, from the host is known as [[coral bleaching]].
* ''[[sea sponge|sponge]]s'' - green algae live close to the surface of some sponges, for example, breadcrumb sponge (''Halichondria panicea''). The alga is thus protected f
rom predators; the sponge is provided with oxygen and sugars which can account for 50 to 80% of sponge growth in some species.<ref>http://www.uwsp.edu/cnr/UWEXlakes/laketides/vol26-4/vol26-4.pdf</ref>
==Life-cycle==
[[Rhodophyta]], [[Chlorophyta]] and [[Heterokontophyta]], the three main algal [[Phyla]], have life-cycles which show tremendous variation with considerable complexity. In general there is an asexual phase where the seaweed's cells are [[diploid]], a sexual phase where the cells are [[haploid]] followed by fusion of the male and female [[gametes]]. Asexual reproduction is advantageous in that it permits efficient population increases, but less variation is possible. Sexual reproduction allows more variation but is more costly because of the waste of gametes that fail to mate, among other things. Often there is no strict alternation between the sporophyte and gametophyte phases and also because there is often an asexual phase, which could include the fragmentation of the thallus.<ref name="Thomas 02">'''Thomas, D.N.''' 2002 ''Seaweeds.'' The Natural History Museum, London. ISBN 0 565 09175 1</ref><ref name="Lobban and Harrison 94">'''Lobban, C.S. and Harrison, P.J.''' 1997. ''Seaweed Ecology and Physiology.'' Cambridge Uiversity Press. ISBN 0-521-40897-00</ref>
==Numbers and distribution==
In the British Isles the UK Biodiversity Steering Group Report estimated there to be 20,000 algal species in the UK, freshwater and marine, about 650 of these are seaweeds. Another checklist of freshwater algae reported only about 5000 species. It seems therefore that the 20,000 is an overestimate or an error (John, 2002 p.1).<ref name="John 02">'''John, D.M., Whitton, B.A. and Brook, A.J.''' 2002. ''The Freshwater Algae Flora of the British Isles.'' Cambridge University Press, Cambridge. ISBN 0 521 77051 3</ref>
World-wide it is thought that there are over 5,000 species of red algae, 1,500 — 2,000 of brown algae and 8,000 of green algae. In Australia it is estimated that there are over 1,300 species of red algae, 350 species of brown algae and approximately 2,000 species of green algae totalling 3,650 species of algae in Australia.<ref name="Huisman 00">'''Huisman, J.M.''' 2000. ''Marine Plants of Australia.'' University of Western Australian Press, Australian Biological Resources Study. ISBN 1 876268 33 6</ref>
Around 400 species appear to be an average figure for the coastline of South [[Africa]]n west coast.<ref name"Stegenga 97">'''Stegenga, H., Bolton, J.J. and Anderson, R.J.''' 1997. ''In'' Hall, A.V. (Ed.) '' Seaweeds of the South African West coast.'' Bolus Herbarim No. 18. ISBN 0-7992-1793-X</ref>
669 marine species have been described from California (U.S.A.).<ref name="Abbott and Hollenberg 76">'''Abbott, I.A. and Hollenberg, G.J.''' 1976. ''Marine Algae of [[California]].'' Stanford University Press, California. ISBN 0-8047-0867-3</ref>
642 entities are listed in the check-list of Britain and Ireland (Hardy and Guiry, 2006).<ref name="Hardy nad Guiry 06">'''Hardy, F.G. and Guiry, M.D. ''' 2006. ''A Check-list and Atlas of the Seaweeds of Britain and Ireland.'' Britiah Phycological Society, London. ISBN 3-906166-35-X</ref>
==Distribution==
===Britain and Ireland===
'''Hardy, F.G. and Guiry, M.D.''' 2006. ''A Check-list and Atlas of the Seaweeds of Britain and Ireland.'' British Phycological Society, London. ISBN 3 906166 35 X
===Northumberland and Durham (England)===
'''Hardy, F.G. and Aspinall, R.J.''' 1988. ''An Atlas of the Seaweeds of Northumberland and Durham.'' Northumberland Biological Records Centre. The Hancock Museum. The University Newcastle upon Tyne. Special publication: 3. ISBN 0 9509680 5 6
===Northern Ireland===
'''Morton, O.''' 1994. ''Marine Algae of Northern Ireland.'' Ulster Museum, Belfast. ISBN 0 900761 28 8
===Ireland: County Donegal===
'''Morton, O.''' The marine macroalgae of County Donegal, Ireland. ''Bull. Ir. biogeog. Soc.'' '''27''':3 - 164.
== Uses of algae ==
[[Image:Seaweed.jpg|right|thumb|[[Seaweed]] is used as a fertiliser]]
===Fertilizer===
For centuries seaweed has
been used as manure; Orwell writing in the 16th Century referring to drift weed in South Wales: "This kind of ore they often gather and lay in heaps where it heteth and rotteth, and will have a strong and loathsome smell; when being so rotten they cast it on the land, as they do their muck, and thereof springeth good corn, especially barley" and "After spring tides or great rigs of the sea, they fetch it in sacks on horse brackets, and carry the same three, four, or five miles, and cast it on the lande, which doth very much better the ground for corn and grass" (Chapman p.35).<ref name="Chapman 50">'''Chapman, V.J.''' 1950. ''Seaweeds and their Uses.'' Methuen & Co. Ltd., London</ref>
There are also commercial uses of algae as agar.<ref name="Lewis ''et al'' 88">'''Lewis, J.G., Stanley, N.F and Guist, G.G.''' 1988. 9 Commercial production of algal hydrocolloides. ''in'' Lembi, C.A. and Waaland, J.R. (Eds.) ''Algae and Human Affairs.'' Cambridge University Press, Cambridge ISBN 0 521 32115 8</ref>
[[Maerl]] is still harvested at Falmouth (also extensively in Brittany and western Ireland) and is a popular fertiliser in these days of organic gardening (Blunden ''et al.'', 1981).<ref name="Blunden 81"> '''Blunden, G., Farnham, W.F. Jephson, N., Barwell, C.J., Fenn, R.H. and Plunkett, B.A.''' 1981 The composition of maerl beds of economic interest in northern Brittany, Cornwall, and Ireland. ''Proceedings of the International Seaweed Symposium.'' '''10''': 651 - 656</ref> investigated Falmouth maerl and found that ''L. corallioides'' predominated down to 6 m and ''P. calcareum'' from 6-10 m.
Chemical analysis of maerl showed that it contained 32.1% CaCO<sub>3</sub> and 3.1% MgCO<sub>3</sub> (dry weight).
===Energy source===
* Algae can be used to make [[biodiesel]] (see [[algaculture#Biodiesel production|algaculture]]), and by some estimates can produce vastly superior amounts of oil, compared to terrestrial crops grown for the same purpose.
* Algae can be grown to produce [[hydrogen]]. In 1939 a German researcher named [[Hans Gaffron]], while working at the University of Chicago, observed that the algae he was studying, ''[[Chlamydomonas reinhardtii]]'' (a green-alga), would sometimes switch from the production of oxygen to the production of hydrogen.[http://www.wired.com/news/technology/0,1282,54456,00.html] Gaffron never discovered the cause for this change and for many years other scientists failed to repeat his findings. In the late 1990s professor Anastasios Melis a researcher at the University of California at Berkeley discovered that if the algae culture medium is deprived of sulfur it will switch from the production of oxygen (normal photosynthesis), to the production of hydrogen. He found that the [[enzyme]] responsible for this reaction is [[hydrogenase]], but that the hydrogenase lost this function in the presence of oxygen. Melis found that depleting the amount of sulfur available to the algae interrupted its internal oxygen flow, allowing the hydrogenase an environment in which it can react, causing the algae to produce hydrogen. [http://www.wired.com/wired/archive/10.04/mustread.html?pg=5] ''Chlamydomonas moeweesi'' is also a good strain for the production of hydrogen.
* Algae can be grown to produce [[biomass]], which can be burned to produce heat and electricity. [http://pmb.berkeley.edu/newPMB/faculty/melis/melis.shtml]
===Pollution control===
* Algae are used in wastewater treatment facilities, reducing the need for more dangerous chemicals.
* Algae can be used to capture [[fertilizers]] in runoff from farms. If this algae is then harvested, it itself can be used as fertilizer.
* Algae bioreactors are used by some powerplants to reduce CO<sub>2</sub> [[emissions]]. [http://www.usatoday.com/tech/science/2006-01-10-algae-powerplants_x.htm] The CO<sub>2</sub> can be pumped into a pond, or some kind of tank, on which the algae feed. Alternatively, the bioreactor can be installed directly on top of a smokestack. This technology has been pioneered by Massachusetts-based GreenFuelTechnologies.[http://www.green
fuelonline.com/]
===Nutrition===
Algae are used by humans in many ways. They are used as fertilizers, soil conditioners and are a source of livestock feed.<ref name="Thomas 02">'''Thomas, D.N.''' 2002 ''Seaweeds.'' The Natural History Museum, London. ISBN 0 565 09175 1</ref> Because many species are aquatic and microscopic, they are cultured in clear tanks or ponds and either harvested or used to treat effluents pumped through the ponds. [[Algaculture]] on a large scale is an important type of [[aquaculture]] in some places.
Human food.
Seaweeds are an important source of food, especially in Asia; They are excellent sources of many vitamins including: A, [[Thiamine|B1]], [[Riboflavin|B2]], [[Vitamin B6|B6]], [[niacin]] and [[Vitamin C|C]]. They are rich in [[iodine]], [[potassium]], [[iron]], [[magnesium]] and [[calcium]].<ref name="Mondragon 03"> '''Mondragon, J. and Mondragon, J.''' 2003. ''Seaweeds of the Pacific Coast.'' Sea Challengers Publications, Monterey, California. ISBN 0-930118-29-4</ref>
Algae is commercially cultivated as a nutritional supplement. One of the most popular [[microalgal]] species is [[Spirulina (dietary supplement)|Spirulina]] ''(Arthrospira platensis),'' which is a [[Cyanobacteria]] (known as blue-green algae), and has been hailed by some as a superfood.[http://www.siu.edu/~ebl/leaflets/algae.htm] Other algal species cultivated for their nutritional value include; [[Chlorella]] (a green algae), and [[Dunaliella]] (''Dunaliella salina''), which is high in [[beta-carotene]] and is used in vitamin C supplements.
In China at least 70 species of algae are eaten as is the Chinese "vegetable" known as ''[[fat choy (vegetable)|fat choy]]'' (which is actually a [[cyanobacterium]]). Roughly 20 species of algae are used in everyday cooking in Japan.<ref name="Mondragon 03"> '''Mondragon, J. and Mondragon, J.''' 2003. ''Seaweeds of the Pacific Coast.'' Sea Challengers Publications, Monterey. ISBN 0-930118-29-4</ref>
Certain species are edible; the best known, especially in Ireland is ''[[Palmaria palmata]]'' (Linnaeus) O. Kuntze (''Rhodymenia palmata'' (Linnaeus) Kuntze, common name: [[dulse]]). [http://www.seaveg.co.uk/dulse.html] This is a red alga which is dried and may be bought in the shops in [[Ireland]]. It is eaten raw, fresh or dried, or cooked like spinach. Similarly, ''Durvillaea antarctica'' [http://www.algaebase.org/speciesdetail.lasso?species_id=11752&sk=0&from=results&-session=abv3:51909EC30802716127sVj3EDC9C7] is eaten in Chile, common name: cochayuyo.
[http://www.seaveg.co.uk/dulse.html]
''[[Porphyra]]'' (common name: purple laver), is also collected and used in a variety of ways (e.g. "laver bread" in the British Isles). In Ireland it is collected and made into a jelly by stewing or boiling. Preparation also involves frying with fat or converting to a pinkish jelly by heating the fronds in a saucepan with a little water and beating with a fork. It is also collected and used by people parts of Asia, specifically China and Japan as [[nori]] and along most of the coast from [[California]] to [[British Columbia]]. The Hawaiians and the Maoris of [[New Zealand]] also use it. ''[[Chondrus crispus]]'', (probably confused with ''[[Mastocarpus stellatus]]'', common name: Irish moss), is also used as "[[carrageen]]" for the stiffening of milk and dairy products, such as ice-cream. One particular use is in "instant" puddings, sauces and creams. ''Ulva lactuca'' (common name: sea lettuce), is used locally in Scotland where it is added to soups or used in salads. ''[[Alaria esculenta]]'' (common name: dabberlocks), is used either fresh or cooked, in [[Greenland]], [[Iceland]], [[Scotland]] and Ireland.
* The oil from some algae have high levels of unsaturated fatty acids. [[Arachidonic acid]] (a polyunsaturated fatty acid), is very high in ''[[Parietochloris incisa]]'', (a green alga) where it reaches up to 47% of the triglyceride pool (Bigogno C et al. Phytochemistry 2002, 60, 497). [http://www.spirulinasource.com/earthfoodch8a.html] [http://www.cfsan.fda.gov/~rdb/opa-g137.html]
===Other use
s===
The natural [[pigment]]s produced by algae can be used as an alternative to chemical [[dyes]] and coloring agents.[http://www.bgu.ac.il/bgn/Microalgae.html] Many of the paper products used today are not recyclable because of the chemical inks that they use, paper recyclers have found that inks made from algae are much easier to break down. There is also much interest in the food industry into replacing the coloring agents that are currently used with coloring derived from algal pigments.
===Alginate===
Between 100,000 and 170,000 wet tons of ''[[Macrocystis]]'' are harvested annually in [[California]] for alginate extraction and abalone feed.[http://www.algaebase.org/generadetail.lasso?genus_id=35715&-session=abv3:51909EC307dcf25DFApmi3530315]
===Further references to the uses===
* '''Guiry, M.D. and Blunden, G.''' (Eds) 1991. ''Seaweed Resources in Europe: Uses and Potential''. John Wiley & Sons. ISBN 0-471-92947-6
* '''Mumford, T.F. and Miura, A.''' 1988. 4. ''Porphyra'' as food: cultivation and economics. p.87 — 117. In Lembi, C.A. and Waaland, J.R. (Ed.) ''Algae and Human Affairs''. 1988. Cambridge University Press. ISBN 0 521 32115 8
==History of Phycology ==
{{main|History of phycology}}
==Collecting and preserving specimens==
Seaweed specimens are collected, preserved for research. Such preserved specimens will keep for two or three hundred years. Those of [[Carl von Linné]] (1707 — 1778) are still available for reference, and are used. Specimens may be collected from the shore; those below low tide must be collected by diving or dredging. The whole algal specimen should be collected, that is the [[holdfast]], stipe and lamina. Specimens of algae reproducing will be the more useful for identification and research. When collected the details of the location and site should be noted.
==Biological Exposure Scale==
A useful biological exposure scale is given in Lewis, J.R.1964 (Chapter:17 p.284 — 285).<ref name="Lewis 64">'''Lewis, J.R.''' 1964. ''The Ecology of Rocky Shores.'' The English Universities Press, London</ref>
===Ecology===
The ecology of the shores of the British Isles including a discussion of the different shores from sheltered to exposed along with a an exposure scale is given by Lewis 1964. The exposure scale of five stages is given: Very Exposed Shores; Expose Shores; Semi-exposed Shores; Sheltered Shores and Very Sheltered Shores. Factors indicating the differences between these exposure scales are detailed.<ref name="Lewis 64"/>
==Examples==
''[[Atractophora]] hypnoides'' P.L.Crouan and H.M.Crouan ([[red algae]])
''[[Ascophyllum nodosum]]''
''[[Charales]]'' ([[green algae]])
''[[Chondrus crispus]]''
''[[Codium]]''
''[[Fucus]]''
''[[Ulva lactuca]]''
''[[Laminaria]]''
''[[Lemanea]]''
''[[Macrocystis]]''
''[[Mastocarpus stellatus]]''
''[[Pelvetia canaliculata]]''
''[[Palmaria palmata]]''
''[[Porphyra]]''
==See also==
* [[Algaculture]]
* [[Biological hydrogen production (Algae)]]
* [[Brown Algae]]
* [[Chlorophyta]]
* [[Coccolithophore]]
* [[Coralline algae]]
* [[Cyanobacteria]]
* [[Diatom]]
* [[Golden Algae]]
* [[Green Algae]]
* [[Hydrology transport model]]
* [[List of publications in biology#Phycology|Important publications in phycology]]
* [[Kelp]]
* [[Laminaria|''Laminaria'']]
* [[Nori]]
* [[Red Algae]]
* [[Yellow-Green Algae]]
== External links ==
{{commonscat}}
* [http://www.algaebase.org/ AlgaeBase] - a comprehensive database of over 35,000 Algae (132,000 names), including seaweeds, with over 5000 images and some 40,000 references.
* [http://en.phyco.org/index.php/Main_Page www.phyco.org]; a wiki-based site that is focused on energy production from algae.
* [http://forums.biodieselnow.com/forum.asp?FORUM_ID=71 biodieselnow.com] biodiesel production-biodiesel from algae
* [http://www.rbgsyd.nsw.gov.au/information_about_plants/botanical_info/australian_freshwater_algae2 Australian freshwater algae] - Sydney Botanic Gardens
* [http://www.algae.info/ Learn about Algae & Algal Blooms] - Rural Chemical Industries (Aust.) Pty Ltd.
* [http://www.whoi.edu/redtide/ Harmful Algal Blooms - "Red tide"] - National Office for Marine Biotoxins and Harmful Algal Blooms, USA.
* [http://www.professorpatents.com/algae.htm Patent Listing]Algae Related United States Patents
* [http://www.nmnh.si.edu/botany/projects/algae/ Algae Section, National Museum of Natural History] - Smithsonian Institution
* [http://www.plantphysiol.org/ www.plantphysiol.org]
* [http://www-cyanosite.bio.purdue.edu/ Cyanosite]
* [http://www.naturalenviro.com/pondproblems.htm Algae Growth]
* [http://www.swelluk.com/advice/blanketweed.html Blanket Weed]
* [http://www.brphycsoc.org British Phycological Society]
* [http://www.seaweed.ie Seaweed site by Michael Guiry]
* http://www.botanicgardens.ie/educ/vis12.htm
* http://www.ucmp.berkeley.edu/protista/rhodophyta.html - Introduction to Rhodophyta]
* http://www.botany.uwc.ac.za/algae/
* http://www.marlin.ac.uk - Marlin
* http://www.mbari.org/staff/conn/botany/flora/reds.htm - Monterey Bay Flora
* http://www.mbari.org/staff/conn/botany/flora/browns.htm - Monterey Bay Flora
* http://www.mbari.org/staff/conn/botany/flora/green.htm - Monterey Bay Flora
==References==
===Cited references===
<div class="references-small">
<references/>
===Identification===
* Abbott, I.A. and Hollenberg, G.J. 1976. ''Marine Algae of California.'' Stanford University Press, California. ISBN 0-8047-0867-3
* Brodie, J.A. and Irvine, L.M. 2003. ''Seaweeds of the British Isles. Volume 1 Part 3B.'' The Natural History Museum, London. ISBN 1 898298 87 4
* Burrows, E.M. 1991. ''Seaweeds of the British Isles. Volume 2.'' British Museum (Natural History), London. ISBN 0-565-00981-8
* Christensen, T. 1987. ''Seaweeds of the British Isles. Tribophyceae. Volume 4.'' British Museum (Natural History), London. ISBN 0-565-00980-X
* Dixon, P.S. and Irvine, L.M. 1977. ''Seaweeds of the British Isles. Volume 1. Part 1. Introduction, Nemaliales, Gigartinales.'' British Museum (Natural History), London. ISBN 0 565 00781 5
* Irvine, L.M. 1983. ''Seaweeds of the British Isles. Volume 1, Part 2A.'' British Museum (Natural History), London. ISBN 0-565-00871-4
* Irvine, L.M. and Chamberlain, Y.M. 1994. ''Seaweeds of the British Isles. Volume 1 Part 2B.'' The Natural History Museum, London. ISBN 0 11 310016 7
* Fletcher, R.L. 1987. ''Seaweeds of the British Isles. Volume 3 Part 1.'' British Museum (Natural History), London. ISBN 0-565-00992-3
* John, D.M., Whitton, B.A. and Brook, J.A. (Eds.) 2002. ''The Freshwater Algal Flora of the British Isles.'' Cambridge University Press, UK. ISBN 0 521 77051 3
* Stegenga, H., Bolton, J.J. and Anderson, R.J.1997. ''Seaweeds of the South African west coast.'' Boltus Herbarium, University of Cape Town. ISBN 0-7992-1793-x
* Taylor, W.R. 1957. ''Marine algae of the north-eastern coasts of North America.'' Revised edition. University of Michigan Press. Ann Arbor.
===General===
* Chapman, V.J. 1950.p.36. '' Seaweeds and their Uses.'' Methuen & Co. Ltd., London.
* Guiry, M.D. and Blunden, G. (Eds) 1991. ''Seaweed Resources in Europe: Uses and Potential''. John Wiley & Sons. ISBN 0-471-92947-6
* Lembi, C.A. and Waaland, J.R. (Eds.) 1988. ''Algae and Human Affairs''. Cambridge University Press, Cambridge. ISBN 0-521-32115-8
</div>
[[Category:Algae|Algae]]
[[Category:Botany]]
[[Category:Biofuels]]
[[Image:River algae Sichuan.jpg|right|thumb|[[Algal blooms]] can present problems for ecosystems and human society]]
'''Algae''' (singular ''alga'') encompass several groups of relatively simple, eukaryotic, living aquatic organisms that capture [[light]] energy through [[photosynthesis]], using it to convert [[inorganic compound|inorganic substances]] into [[organic matter]].
Algae are photosynthetic organisms that occur in most [[habitat]]s. Algae varies from small, single-[[Cell (biology)|celled]] forms to complex [[multicellular]] forms, such as the giant [[kelp]]s that grow to 65 meters in length. The US Algal Collection is represented by almost 300,000 accessioned and inventoried herbarium specimens.[http://www.nmnh.si.edu/botany/projects/algae/herbarium.htm]
Although algae have conventionally been regarded as simple [[plant]]s, they actually span more than one [[Three-domain system|domain]], including both [[Eukaryota]] and [[Bacteria]] (''see [[Blue-green algae]]''), as well as more than one [[kingdom (biology)|kingdom]], including [[Plantae|plants]] and [[protist]]s, the latter being traditionally considered more animal-like (''see [[Protozoa]]''). Thus algae do not represent a single evolutionary direction or line but a level of organization that may have developed several times in the early [[Timeline of evolution|history of life on Earth]].
Algae range from [[unicellular|single-cell]] organisms to [[multicellular]] organisms, some with fairly complex differentiated form and (if marine) called [[seaweed]]s. All lack [[leaf|leaves]], [[root]]s, [[flower]]s, [[seed]]s and other [[Organ (anatomy)|organ]] structures that characterize higher plants ([[vascular plants]]). They are distinguished from other [[protozoa]] in that they are [[autotrophic|photoautotrophic]] although this is not a hard and fast distinction as some groups contain members that are [[mixotrophic]], deriving energy both from photosynthesis and uptake of organic carbon either by [[osmotrophy]], [[myzocytosis|myzotrophy]], or [[phagocytosis|phagotrophy]]. Some unicellular [[species]] rely entirely on external energy sources and have reduced or lost their photosynthetic apparatus.
All algae have photosynthetic machinery ultimately derived from the [[cyanobacteria]], and so produce [[oxygen]] as a byproduct of photosynthesis, unlike non-cyanobacterial photosynthetic [[bacteria]]. It is estimated that algae produce about 73 to 87 percent of the net global production of oxygen<ref>http://www.ecology.com/dr-jacks-natural-world/most-important-organism/index.html</ref> - which is available to humans and other terrestrial animals for [[Cellular respiration|respiration]].
Algae are usually found in damp places or bodies of water and thus are common in terrestrial as well as aquatic environments. However, terrestrial algae are usually rather inconspicuous and far more common in moist, [[tropical]] regions than dry ones, because algae lack [[vascular tissue]]s and other adaptations to live on land. Algae can endure dryness and other conditions in [[symbiosis]] with a [[fungus]] as [[lichen]].
The various sorts of algae play significant roles in aquatic ecology. Microscopic forms that live suspended in the water column — called '''[[phytoplankton]]''' — provide the food base for most marine [[food chain]]s. In very high densities (so-called [[algal bloom]]s) these algae may discolor the water and outcompete or poison other life forms. Seaweeds grow mostly in shallow marine waters. Some are used as human food or harvested for useful substances such as [[agar]] or fertilizer.
The study of marine and freshwater algae is called [[phycology]] or algology.
==Classification==
[[Image:AlgaeTree.png|thumb|180px|left|The lineage of algae according to Thomas Cavallier-Smith. The three supergroups [[Archaeplastida]], [[Chromalveolata]] and [[Cabozoa]] of eukaryotic algae are denoted to reflect the table below. Endosymbiotic events are noted by dotted lines.]]
=== Prokaryotic algae ===
Traditionally the [[Cyanobacteria]] have been included among the algae, referred to as the ''cyanophytes'' or ''Blue-green algae'', (the term "algae" refers to any aquatic organisms capable of photosynthesis)<ref>http://www.ucmp.berkeley.edu/bacteria/cyanolh.html</ref> though some recent treatises on algae specifically exclude them. Cyanobacteria are some of the oldest organisms to appear in the [[fossil record]] dating back to the [[Precambrian]], possibly as far as about 3.5 billion years.<ref>Schopf, JW, and Packer, BM, Science, 1987, 237, 70</ref> Ancient cyanobacteria likely produced much of the [[oxygen]] in the Earth's atmosphere.
[[Cyanobacteria]] can be unicellular, colonial, or filamentous. They have a [[prokaryote|prokaryotic]] cell structure typical of bacteria and conduct photosynthesis on specialized cytoplasmic membranes called [[thylakoid membranes]], rather than in organelles. Some filamentous [[blue-green algae]] have specialized cells, termed heterocysts, in which [[nitrogen fixation]] occurs.<ref>http://www.biologie.uni-hamburg.de/b-online/e42/42a.htm</ref>
=== Eukaryotic algae ===
All other algae are [[eukaryotes]] and conduct photosynthesis within membrane-bound structures (organelles) called [[chloroplasts]]. Chloroplasts contain [[DNA]] and are similar in structure to cyanobacteria, presumably representing reduced cyanobacterial [[endosymbiotic theory|endosymbionts]]. The exact nature of the chloroplasts is different among the different lines of algae, reflecting different endosymbiotic events. The table below lists the three major groups of eukaryotic algae and their lineage relationship is shown in the figure on the left. Note many of these groups contain some members that are no longer photosynthetic. Some retain plastids, but not chloroplasts, while others have lost them entirely.
{| class="wikitable"
|-
! Supergroup affiliation !! Members !! [[Endosymbiont]] !! Summary
|-
|[[Primoplantae]]/<br>[[Archaeplastida]]
|
* [[Green algae]]
* [[Red algae]]
* [[Glaucophytes]]
|Cyanobacterium
|These algae have ''primary'' chloroplasts, i.e. the chloroplasts are surrounded by ''two membranes'' and probably developed through a single endosymbiosis. The chloroplasts of red algae have a more or less typical cyanobacterial pigmentation, while those of the green alga have chloroplasts with chlorophyll ''a'' and ''b'', the latter found in some cyanobacteria and not most. Higher plants are pigmented similarly to green algae and probably developed from them.
|-
| [[Cabozoa]]<br>or<br>[[Excavata]] and [[Rhizaria]]
|
* [[Chlorarachniophytes]]
* [[Euglenids]]
|Green alga
|
<p>These groups have green chloroplasts containing chlorophyll ''b''. Their chloroplasts are surrounded by ''three and four membranes'', respectively, and were probably retained from an ingested green alga.</p>
<p>'''Chlorarachniophytes''', which belong to the phylum [[Cercozoa]], contain a small [[nucleomorph]], which is a [[relict]] of the alga's [[cell nucleus|nucleus]].</p>
<p>'''Euglenids''', which belong to the phylum [[Euglenozoa]], have chloroplasts with only three membranes. It has been suggested that the endosymbiotic green algae were acquired through [[myzocytosis]] rather than [[phagocytosis]].</p>
|-
|[[Chromalveolata]]<br>or<br>[[Chromista]] and [[Alveolata]]
|
* [[Chromista]]
** [[Heterokonts]]
** [[Haptophyta]]
** [[Cryptomonad]]s
* [[Dinoflagellates]]
|Red alga
|
<p>These groups have chloroplasts containing chlorophylls ''a'' and ''c''. The latter chlorophyll type is not known from any prokaryotes or primary chloroplasts, but genetic similarities with the red algae suggest a relationship there.</p>
<p>In the first three of these groups ('''Chromista'''), the chloroplast has four membranes, retaining a nucleomorph in cryptomonads, and they likely share a common pigmented ancestor.</p>
<p>The typical '''dinoflagellate''' chloroplast has three membranes, but there is considerable diversity in chloroplasts among the group, as some members have acquired theirs from different sources. The [[Apicomplexa]], a group of closely related parasites, also have [[plastid]]s called [[apicoplast]]s. Apicoplasts are not photosynthetic but appear to have a common origin with dinoflagellates chloroplasts.</p>
|}
It was W.H.Harvey (1811 — 1866) who first divided the algae into four divisions based on their pigmentation. This is the first use of a biochemical criterion in plant systematics. Harvey's four divisions were: red algae (Rhodophyta), brown algae (Heteromontophyta), green algae (Chlorophyta) and Diatomaceae (Dixon, 1973 p.232).<ref name="Dixon 73" p.232>'''Dixon, P.S.''' 1973 ''Biology of the Rhodophyta.'' Oliver & Boyd, Edinburgh. ISBN 0 05 002485 X</ref>
== Forms of algae ==
Most of the simpler algae are unicellular [[flagellate]]s or [[amoeboid]]s, but colonial and non-motile forms have developed independently among several of the groups. Some of the more common organizational levels, more than one of which may occur in the [[Biological life cycle|life cycle]] of a species, are:
* ''Colonial'' - small, regular groups of motile cells
* ''Capsoid'' - individual non-motile cells embedded in [[mucilage]]
* ''Coccoid'' - individual non-motile cells with cell walls
* ''Palmelloid'' - non-motile cells embedded in mucilage
* ''Filamentous'' - a string of non-motile cells connected together, sometimes branching
* ''Parenchymatous'' - cells forming a [[thallus (tissue)|thallus]] with partial differentiation of tissues
In three — lines even higher levels of organization have been reached, leading to organisms with full tissue differentiation. These are the [[brown alga]]e [http://www.ucmp.berkeley.edu/chromista/phaeophyta.html] — some of which may reach 50 m in length ([[kelp]]s)<ref name="Thomas 02">'''Thomas, D.N.''' 2002 ''Seaweeds.'' The Natural History Museum, London. ISBN 0 565 09175 1</ref> — the [[red alga]]e [http://www.ucmp.berkeley.edu/protista/rhodophyta.html], and the [[green alga]]e [http://www.ucmp.berkeley.edu/greenalgae/greenalgae.html]. The most complex forms are found among the green algae (see [[Charales]] and [[Charophyta]]), in a lineage that eventually led to the higher [[land plants]]. The point where these non-algal plants begin and algae stop is usually taken to be the presence of reproductive organs with protective cell layers, a characteristic not found in the other alga groups.
The first plants on earth were algae and these still thrive in a range of aquatic habitats today. The land plants evolved from the algae, more specifically green algae. Some 400 million years ago freshwater, green, filamentous algae invaded the land. These probably had an isomorphic alternation of generations and were probably heterotrichous. Fossils of isolated land plant spores suggest land plants may have been around as long as 475 million years ago.
== Algae and symbioses==
Some species of algae form [[symbiosis|symbiotic relationships]] with other organisms. In these [[symbioses]], the algae supply photosynthates (organic substances) to the host organism providing protection to the algal cells. The host organism derives some or all of its energy requirements from the algae. Examples include:
* ''[[lichen]]s'' - a fungus is the host, usually with a green alga or a cyanobacterium as its symbiont. Both fungal and algal species found in lichens are capable of living independently, although habitat requirements may be greatly different from those of the lichen pair.
* ''[[coral]]s'' - algae known as [[zooxanthella]]e are symbionts with [[coral]]s. Notable amongst these is the dinoflagellate ''Symbiodinium'', found in many hard corals. The loss of ''Symbiodinium'', or other zooxanthellae, from the host is known as [[coral bleaching]].
* ''[[sea sponge|sponge]]s'' - green algae live close to the surface of some sponges, for example, breadcrumb sponge (''Halichondria panicea''). The alga is thus protected f
rom predators; the sponge is provided with oxygen and sugars which can account for 50 to 80% of sponge growth in some species.<ref>http://www.uwsp.edu/cnr/UWEXlakes/laketides/vol26-4/vol26-4.pdf</ref>
==Life-cycle==
[[Rhodophyta]], [[Chlorophyta]] and [[Heterokontophyta]], the three main algal [[Phyla]], have life-cycles which show tremendous variation with considerable complexity. In general there is an asexual phase where the seaweed's cells are [[diploid]], a sexual phase where the cells are [[haploid]] followed by fusion of the male and female [[gametes]]. Asexual reproduction is advantageous in that it permits efficient population increases, but less variation is possible. Sexual reproduction allows more variation but is more costly because of the waste of gametes that fail to mate, among other things. Often there is no strict alternation between the sporophyte and gametophyte phases and also because there is often an asexual phase, which could include the fragmentation of the thallus.<ref name="Thomas 02">'''Thomas, D.N.''' 2002 ''Seaweeds.'' The Natural History Museum, London. ISBN 0 565 09175 1</ref><ref name="Lobban and Harrison 94">'''Lobban, C.S. and Harrison, P.J.''' 1997. ''Seaweed Ecology and Physiology.'' Cambridge Uiversity Press. ISBN 0-521-40897-00</ref>
==Numbers and distribution==
In the British Isles the UK Biodiversity Steering Group Report estimated there to be 20,000 algal species in the UK, freshwater and marine, about 650 of these are seaweeds. Another checklist of freshwater algae reported only about 5000 species. It seems therefore that the 20,000 is an overestimate or an error (John, 2002 p.1).<ref name="John 02">'''John, D.M., Whitton, B.A. and Brook, A.J.''' 2002. ''The Freshwater Algae Flora of the British Isles.'' Cambridge University Press, Cambridge. ISBN 0 521 77051 3</ref>
World-wide it is thought that there are over 5,000 species of red algae, 1,500 — 2,000 of brown algae and 8,000 of green algae. In Australia it is estimated that there are over 1,300 species of red algae, 350 species of brown algae and approximately 2,000 species of green algae totalling 3,650 species of algae in Australia.<ref name="Huisman 00">'''Huisman, J.M.''' 2000. ''Marine Plants of Australia.'' University of Western Australian Press, Australian Biological Resources Study. ISBN 1 876268 33 6</ref>
Around 400 species appear to be an average figure for the coastline of South [[Africa]]n west coast.<ref name"Stegenga 97">'''Stegenga, H., Bolton, J.J. and Anderson, R.J.''' 1997. ''In'' Hall, A.V. (Ed.) '' Seaweeds of the South African West coast.'' Bolus Herbarim No. 18. ISBN 0-7992-1793-X</ref>
669 marine species have been described from California (U.S.A.).<ref name="Abbott and Hollenberg 76">'''Abbott, I.A. and Hollenberg, G.J.''' 1976. ''Marine Algae of [[California]].'' Stanford University Press, California. ISBN 0-8047-0867-3</ref>
642 entities are listed in the check-list of Britain and Ireland (Hardy and Guiry, 2006).<ref name="Hardy nad Guiry 06">'''Hardy, F.G. and Guiry, M.D. ''' 2006. ''A Check-list and Atlas of the Seaweeds of Britain and Ireland.'' Britiah Phycological Society, London. ISBN 3-906166-35-X</ref>
==Distribution==
===Britain and Ireland===
'''Hardy, F.G. and Guiry, M.D.''' 2006. ''A Check-list and Atlas of the Seaweeds of Britain and Ireland.'' British Phycological Society, London. ISBN 3 906166 35 X
===Northumberland and Durham (England)===
'''Hardy, F.G. and Aspinall, R.J.''' 1988. ''An Atlas of the Seaweeds of Northumberland and Durham.'' Northumberland Biological Records Centre. The Hancock Museum. The University Newcastle upon Tyne. Special publication: 3. ISBN 0 9509680 5 6
===Northern Ireland===
'''Morton, O.''' 1994. ''Marine Algae of Northern Ireland.'' Ulster Museum, Belfast. ISBN 0 900761 28 8
===Ireland: County Donegal===
'''Morton, O.''' The marine macroalgae of County Donegal, Ireland. ''Bull. Ir. biogeog. Soc.'' '''27''':3 - 164.
== Uses of algae ==
[[Image:Seaweed.jpg|right|thumb|[[Seaweed]] is used as a fertiliser]]
===Fertilizer===
For centuries seaweed has
been used as manure; Orwell writing in the 16th Century referring to drift weed in South Wales: "This kind of ore they often gather and lay in heaps where it heteth and rotteth, and will have a strong and loathsome smell; when being so rotten they cast it on the land, as they do their muck, and thereof springeth good corn, especially barley" and "After spring tides or great rigs of the sea, they fetch it in sacks on horse brackets, and carry the same three, four, or five miles, and cast it on the lande, which doth very much better the ground for corn and grass" (Chapman p.35).<ref name="Chapman 50">'''Chapman, V.J.''' 1950. ''Seaweeds and their Uses.'' Methuen & Co. Ltd., London</ref>
There are also commercial uses of algae as agar.<ref name="Lewis ''et al'' 88">'''Lewis, J.G., Stanley, N.F and Guist, G.G.''' 1988. 9 Commercial production of algal hydrocolloides. ''in'' Lembi, C.A. and Waaland, J.R. (Eds.) ''Algae and Human Affairs.'' Cambridge University Press, Cambridge ISBN 0 521 32115 8</ref>
[[Maerl]] is still harvested at Falmouth (also extensively in Brittany and western Ireland) and is a popular fertiliser in these days of organic gardening (Blunden ''et al.'', 1981).<ref name="Blunden 81"> '''Blunden, G., Farnham, W.F. Jephson, N., Barwell, C.J., Fenn, R.H. and Plunkett, B.A.''' 1981 The composition of maerl beds of economic interest in northern Brittany, Cornwall, and Ireland. ''Proceedings of the International Seaweed Symposium.'' '''10''': 651 - 656</ref> investigated Falmouth maerl and found that ''L. corallioides'' predominated down to 6 m and ''P. calcareum'' from 6-10 m.
Chemical analysis of maerl showed that it contained 32.1% CaCO<sub>3</sub> and 3.1% MgCO<sub>3</sub> (dry weight).
===Energy source===
* Algae can be used to make [[biodiesel]] (see [[algaculture#Biodiesel production|algaculture]]), and by some estimates can produce vastly superior amounts of oil, compared to terrestrial crops grown for the same purpose.
* Algae can be grown to produce [[hydrogen]]. In 1939 a German researcher named [[Hans Gaffron]], while working at the University of Chicago, observed that the algae he was studying, ''[[Chlamydomonas reinhardtii]]'' (a green-alga), would sometimes switch from the production of oxygen to the production of hydrogen.[http://www.wired.com/news/technology/0,1282,54456,00.html] Gaffron never discovered the cause for this change and for many years other scientists failed to repeat his findings. In the late 1990s professor Anastasios Melis a researcher at the University of California at Berkeley discovered that if the algae culture medium is deprived of sulfur it will switch from the production of oxygen (normal photosynthesis), to the production of hydrogen. He found that the [[enzyme]] responsible for this reaction is [[hydrogenase]], but that the hydrogenase lost this function in the presence of oxygen. Melis found that depleting the amount of sulfur available to the algae interrupted its internal oxygen flow, allowing the hydrogenase an environment in which it can react, causing the algae to produce hydrogen. [http://www.wired.com/wired/archive/10.04/mustread.html?pg=5] ''Chlamydomonas moeweesi'' is also a good strain for the production of hydrogen.
* Algae can be grown to produce [[biomass]], which can be burned to produce heat and electricity. [http://pmb.berkeley.edu/newPMB/faculty/melis/melis.shtml]
===Pollution control===
* Algae are used in wastewater treatment facilities, reducing the need for more dangerous chemicals.
* Algae can be used to capture [[fertilizers]] in runoff from farms. If this algae is then harvested, it itself can be used as fertilizer.
* Algae bioreactors are used by some powerplants to reduce CO<sub>2</sub> [[emissions]]. [http://www.usatoday.com/tech/science/2006-01-10-algae-powerplants_x.htm] The CO<sub>2</sub> can be pumped into a pond, or some kind of tank, on which the algae feed. Alternatively, the bioreactor can be installed directly on top of a smokestack. This technology has been pioneered by Massachusetts-based GreenFuelTechnologies.[http://www.green
fuelonline.com/]
===Nutrition===
Algae are used by humans in many ways. They are used as fertilizers, soil conditioners and are a source of livestock feed.<ref name="Thomas 02">'''Thomas, D.N.''' 2002 ''Seaweeds.'' The Natural History Museum, London. ISBN 0 565 09175 1</ref> Because many species are aquatic and microscopic, they are cultured in clear tanks or ponds and either harvested or used to treat effluents pumped through the ponds. [[Algaculture]] on a large scale is an important type of [[aquaculture]] in some places.
Human food.
Seaweeds are an important source of food, especially in Asia; They are excellent sources of many vitamins including: A, [[Thiamine|B1]], [[Riboflavin|B2]], [[Vitamin B6|B6]], [[niacin]] and [[Vitamin C|C]]. They are rich in [[iodine]], [[potassium]], [[iron]], [[magnesium]] and [[calcium]].<ref name="Mondragon 03"> '''Mondragon, J. and Mondragon, J.''' 2003. ''Seaweeds of the Pacific Coast.'' Sea Challengers Publications, Monterey, California. ISBN 0-930118-29-4</ref>
Algae is commercially cultivated as a nutritional supplement. One of the most popular [[microalgal]] species is [[Spirulina (dietary supplement)|Spirulina]] ''(Arthrospira platensis),'' which is a [[Cyanobacteria]] (known as blue-green algae), and has been hailed by some as a superfood.[http://www.siu.edu/~ebl/leaflets/algae.htm] Other algal species cultivated for their nutritional value include; [[Chlorella]] (a green algae), and [[Dunaliella]] (''Dunaliella salina''), which is high in [[beta-carotene]] and is used in vitamin C supplements.
In China at least 70 species of algae are eaten as is the Chinese "vegetable" known as ''[[fat choy (vegetable)|fat choy]]'' (which is actually a [[cyanobacterium]]). Roughly 20 species of algae are used in everyday cooking in Japan.<ref name="Mondragon 03"> '''Mondragon, J. and Mondragon, J.''' 2003. ''Seaweeds of the Pacific Coast.'' Sea Challengers Publications, Monterey. ISBN 0-930118-29-4</ref>
Certain species are edible; the best known, especially in Ireland is ''[[Palmaria palmata]]'' (Linnaeus) O. Kuntze (''Rhodymenia palmata'' (Linnaeus) Kuntze, common name: [[dulse]]). [http://www.seaveg.co.uk/dulse.html] This is a red alga which is dried and may be bought in the shops in [[Ireland]]. It is eaten raw, fresh or dried, or cooked like spinach. Similarly, ''Durvillaea antarctica'' [http://www.algaebase.org/speciesdetail.lasso?species_id=11752&sk=0&from=results&-session=abv3:51909EC30802716127sVj3EDC9C7] is eaten in Chile, common name: cochayuyo.
[http://www.seaveg.co.uk/dulse.html]
''[[Porphyra]]'' (common name: purple laver), is also collected and used in a variety of ways (e.g. "laver bread" in the British Isles). In Ireland it is collected and made into a jelly by stewing or boiling. Preparation also involves frying with fat or converting to a pinkish jelly by heating the fronds in a saucepan with a little water and beating with a fork. It is also collected and used by people parts of Asia, specifically China and Japan as [[nori]] and along most of the coast from [[California]] to [[British Columbia]]. The Hawaiians and the Maoris of [[New Zealand]] also use it. ''[[Chondrus crispus]]'', (probably confused with ''[[Mastocarpus stellatus]]'', common name: Irish moss), is also used as "[[carrageen]]" for the stiffening of milk and dairy products, such as ice-cream. One particular use is in "instant" puddings, sauces and creams. ''Ulva lactuca'' (common name: sea lettuce), is used locally in Scotland where it is added to soups or used in salads. ''[[Alaria esculenta]]'' (common name: dabberlocks), is used either fresh or cooked, in [[Greenland]], [[Iceland]], [[Scotland]] and Ireland.
* The oil from some algae have high levels of unsaturated fatty acids. [[Arachidonic acid]] (a polyunsaturated fatty acid), is very high in ''[[Parietochloris incisa]]'', (a green alga) where it reaches up to 47% of the triglyceride pool (Bigogno C et al. Phytochemistry 2002, 60, 497). [http://www.spirulinasource.com/earthfoodch8a.html] [http://www.cfsan.fda.gov/~rdb/opa-g137.html]
===Other use
s===
The natural [[pigment]]s produced by algae can be used as an alternative to chemical [[dyes]] and coloring agents.[http://www.bgu.ac.il/bgn/Microalgae.html] Many of the paper products used today are not recyclable because of the chemical inks that they use, paper recyclers have found that inks made from algae are much easier to break down. There is also much interest in the food industry into replacing the coloring agents that are currently used with coloring derived from algal pigments.
===Alginate===
Between 100,000 and 170,000 wet tons of ''[[Macrocystis]]'' are harvested annually in [[California]] for alginate extraction and abalone feed.[http://www.algaebase.org/generadetail.lasso?genus_id=35715&-session=abv3:51909EC307dcf25DFApmi3530315]
===Further references to the uses===
* '''Guiry, M.D. and Blunden, G.''' (Eds) 1991. ''Seaweed Resources in Europe: Uses and Potential''. John Wiley & Sons. ISBN 0-471-92947-6
* '''Mumford, T.F. and Miura, A.''' 1988. 4. ''Porphyra'' as food: cultivation and economics. p.87 — 117. In Lembi, C.A. and Waaland, J.R. (Ed.) ''Algae and Human Affairs''. 1988. Cambridge University Press. ISBN 0 521 32115 8
==History of Phycology ==
{{main|History of phycology}}
==Collecting and preserving specimens==
Seaweed specimens are collected, preserved for research. Such preserved specimens will keep for two or three hundred years. Those of [[Carl von Linné]] (1707 — 1778) are still available for reference, and are used. Specimens may be collected from the shore; those below low tide must be collected by diving or dredging. The whole algal specimen should be collected, that is the [[holdfast]], stipe and lamina. Specimens of algae reproducing will be the more useful for identification and research. When collected the details of the location and site should be noted.
==Biological Exposure Scale==
A useful biological exposure scale is given in Lewis, J.R.1964 (Chapter:17 p.284 — 285).<ref name="Lewis 64">'''Lewis, J.R.''' 1964. ''The Ecology of Rocky Shores.'' The English Universities Press, London</ref>
===Ecology===
The ecology of the shores of the British Isles including a discussion of the different shores from sheltered to exposed along with a an exposure scale is given by Lewis 1964. The exposure scale of five stages is given: Very Exposed Shores; Expose Shores; Semi-exposed Shores; Sheltered Shores and Very Sheltered Shores. Factors indicating the differences between these exposure scales are detailed.<ref name="Lewis 64"/>
==Examples==
''[[Atractophora]] hypnoides'' P.L.Crouan and H.M.Crouan ([[red algae]])
''[[Ascophyllum nodosum]]''
''[[Charales]]'' ([[green algae]])
''[[Chondrus crispus]]''
''[[Codium]]''
''[[Fucus]]''
''[[Ulva lactuca]]''
''[[Laminaria]]''
''[[Lemanea]]''
''[[Macrocystis]]''
''[[Mastocarpus stellatus]]''
''[[Pelvetia canaliculata]]''
''[[Palmaria palmata]]''
''[[Porphyra]]''
==See also==
* [[Algaculture]]
* [[Biological hydrogen production (Algae)]]
* [[Brown Algae]]
* [[Chlorophyta]]
* [[Coccolithophore]]
* [[Coralline algae]]
* [[Cyanobacteria]]
* [[Diatom]]
* [[Golden Algae]]
* [[Green Algae]]
* [[Hydrology transport model]]
* [[List of publications in biology#Phycology|Important publications in phycology]]
* [[Kelp]]
* [[Laminaria|''Laminaria'']]
* [[Nori]]
* [[Red Algae]]
* [[Yellow-Green Algae]]
== External links ==
{{commonscat}}
* [http://www.algaebase.org/ AlgaeBase] - a comprehensive database of over 35,000 Algae (132,000 names), including seaweeds, with over 5000 images and some 40,000 references.
* [http://en.phyco.org/index.php/Main_Page www.phyco.org]; a wiki-based site that is focused on energy production from algae.
* [http://forums.biodieselnow.com/forum.asp?FORUM_ID=71 biodieselnow.com] biodiesel production-biodiesel from algae
* [http://www.rbgsyd.nsw.gov.au/information_about_plants/botanical_info/australian_freshwater_algae2 Australian freshwater algae] - Sydney Botanic Gardens
* [http://www.algae.info/ Learn about Algae & Algal Blooms] - Rural Chemical Industries (Aust.) Pty Ltd.
* [http://www.whoi.edu/redtide/ Harmful Algal Blooms - "Red tide"] - National Office for Marine Biotoxins and Harmful Algal Blooms, USA.
* [http://www.professorpatents.com/algae.htm Patent Listing]Algae Related United States Patents
* [http://www.nmnh.si.edu/botany/projects/algae/ Algae Section, National Museum of Natural History] - Smithsonian Institution
* [http://www.plantphysiol.org/ www.plantphysiol.org]
* [http://www-cyanosite.bio.purdue.edu/ Cyanosite]
* [http://www.naturalenviro.com/pondproblems.htm Algae Growth]
* [http://www.swelluk.com/advice/blanketweed.html Blanket Weed]
* [http://www.brphycsoc.org British Phycological Society]
* [http://www.seaweed.ie Seaweed site by Michael Guiry]
* http://www.botanicgardens.ie/educ/vis12.htm
* http://www.ucmp.berkeley.edu/protista/rhodophyta.html - Introduction to Rhodophyta]
* http://www.botany.uwc.ac.za/algae/
* http://www.marlin.ac.uk - Marlin
* http://www.mbari.org/staff/conn/botany/flora/reds.htm - Monterey Bay Flora
* http://www.mbari.org/staff/conn/botany/flora/browns.htm - Monterey Bay Flora
* http://www.mbari.org/staff/conn/botany/flora/green.htm - Monterey Bay Flora
==References==
===Cited references===
<div class="references-small">
<references/>
===Identification===
* Abbott, I.A. and Hollenberg, G.J. 1976. ''Marine Algae of California.'' Stanford University Press, California. ISBN 0-8047-0867-3
* Brodie, J.A. and Irvine, L.M. 2003. ''Seaweeds of the British Isles. Volume 1 Part 3B.'' The Natural History Museum, London. ISBN 1 898298 87 4
* Burrows, E.M. 1991. ''Seaweeds of the British Isles. Volume 2.'' British Museum (Natural History), London. ISBN 0-565-00981-8
* Christensen, T. 1987. ''Seaweeds of the British Isles. Tribophyceae. Volume 4.'' British Museum (Natural History), London. ISBN 0-565-00980-X
* Dixon, P.S. and Irvine, L.M. 1977. ''Seaweeds of the British Isles. Volume 1. Part 1. Introduction, Nemaliales, Gigartinales.'' British Museum (Natural History), London. ISBN 0 565 00781 5
* Irvine, L.M. 1983. ''Seaweeds of the British Isles. Volume 1, Part 2A.'' British Museum (Natural History), London. ISBN 0-565-00871-4
* Irvine, L.M. and Chamberlain, Y.M. 1994. ''Seaweeds of the British Isles. Volume 1 Part 2B.'' The Natural History Museum, London. ISBN 0 11 310016 7
* Fletcher, R.L. 1987. ''Seaweeds of the British Isles. Volume 3 Part 1.'' British Museum (Natural History), London. ISBN 0-565-00992-3
* John, D.M., Whitton, B.A. and Brook, J.A. (Eds.) 2002. ''The Freshwater Algal Flora of the British Isles.'' Cambridge University Press, UK. ISBN 0 521 77051 3
* Stegenga, H., Bolton, J.J. and Anderson, R.J.1997. ''Seaweeds of the South African west coast.'' Boltus Herbarium, University of Cape Town. ISBN 0-7992-1793-x
* Taylor, W.R. 1957. ''Marine algae of the north-eastern coasts of North America.'' Revised edition. University of Michigan Press. Ann Arbor.
===General===
* Chapman, V.J. 1950.p.36. '' Seaweeds and their Uses.'' Methuen & Co. Ltd., London.
* Guiry, M.D. and Blunden, G. (Eds) 1991. ''Seaweed Resources in Europe: Uses and Potential''. John Wiley & Sons. ISBN 0-471-92947-6
* Lembi, C.A. and Waaland, J.R. (Eds.) 1988. ''Algae and Human Affairs''. Cambridge University Press, Cambridge. ISBN 0-521-32115-8
</div>
[[Category:Algae|Algae]]
[[Category:Botany]]
[[Category:Biofuels]]
