View source for Biology:Marine algae and plants

'''Marine algae and plants''' are a diverse collection of [[Biology:Marine life|marine life]] that, together with [[Biology:Cyanobacteria|cyanobacteria]], form the main [[Earth:Primary producer|primary producer]]s at base of the ocean food chain. Marine primary producers are important because they underpin almost all marine animal life by generating most of the oxygen and food that animals need to exist. Some [[Biology:Algae|algae]] and [[Biology:Plant|plant]]s are also [[Earth:Ecosystem engineer|ecosystem engineer]]s which change the environment and provide [[Earth:Marine habitat|habitats]] for other marine life. 
Marine algae includes the largely invisible and often unicellular [[Biology:Microalgae|microalgae]], which together with [[Biology:Cyanobacteria|cyanobacteria]] form the ocean [[Earth:Phytoplankton|phytoplankton]], as well as the larger, more visible and complex multicellular macroalgae commonly called [[Biology:Seaweed|seaweed]]. Seaweeds are found along coastal areas, living on the floor of continental shelves and washed up in [[Earth:Intertidal zone|intertidal zone]]s. Some seaweeds drift with plankton in the sunlit surface waters (epipelagic zone) of the open ocean.

Back in the [[Earth:Silurian|Silurian]], some phytoplankton evolved into red, [[Biology:Brown algae|brown]] and [[Biology:Green algae|green algae]]. These algae then invaded the land and started evolving into the land plants we know today. Later in the [[Earth:Cretaceous|Cretaceous]] some of these land plants returned to the sea as [[Earth:Mangrove|mangrove]]s and [[Biology:Seagrass|seagrass]]es. These are found along coasts in [[Earth:Intertidal zone|intertidal regions]] and in the brackish water of estuaries. In addition, some seagrasses, like seaweeds, can be found at depths up to 50 metres on both soft and hard bottoms of the continental shelf.

==Primary producers==
[[File:Seawifs global biosphere.jpg|400 px|thumb|right|Composite image showing the global distribution of photosynthesis, including both oceanic phytoplankton and terrestrial vegetation. Dark red and blue-green indicate regions of high photosynthetic activity in the ocean and on land, respectively.]]

[[Earth:Primary producer|Primary producer]]s are the [[Biology:Autotroph|autotroph]] organisms that make their own food instead of eating other organisms. This means primary producers become the starting point in the food chain for [[Biology:Heterotroph|heterotroph]] organisms that do eat other organisms. Some marine primary producers are specialised bacteria and archaea which are [[Biology:Chemotroph|chemotroph]]s, making their own food by gathering around hydrothermal vents and cold seeps and using [[Earth:Chemosynthesis|chemosynthesis]]. However most marine [[Earth:Primary production|primary production]] comes from organisms which use [[Earth:Photosynthesis|photosynthesis]] on the carbon dioxide dissolved in the water. This process uses energy from sunlight to convert water and [[Chemistry:Carbon dioxide|carbon dioxide]]<ref name=Campbell2008>{{cite book| ref = harv |last1=Campbell|first1=Neil A.|last2=Reece|first2=Jane B.|last3=Urry|first3=Lisa Andrea|last4=Cain|first4=Michael L.|last5=Wasserman |first5 =Steven Alexander | last6 = Minorsky | first6 =Peter V. | last7 = Jackson | first7 =Robert Bradley
|title=Biology|edition=8|year=2008|publisher=Pearson – Benjamin Cummings|location=San Francisco|isbn=978-0-321-54325-7}}</ref>{{rp|186–187}} into sugars that can be used both as a source of chemical energy and of organic molecules that are used in the structural components of cells.<ref name=Campbell2008 />{{rp|1242}} Marine primary producers are important because they underpin almost all marine animal life by generating most of the [[Chemistry:Oxygen|oxygen]] and food that provide other organisms with the chemical energy they need to exist. 

The principal marine primary producers are [[Biology:Cyanobacteria|cyanobacteria]], [[Biology:Algae|algae]] and marine plants. The [[Chemistry:Oxygen|oxygen]] released as a by-product of photosynthesis is needed by [[Biology:Anaerobic organism|nearly]] all living things to carry out [[Biology:Cellular respiration|cellular respiration]]. In addition, primary producers are influential in the global [[Earth:Carbon cycle|carbon]] and [[Physics:Water cycle|water]] cycles. They stabilize coastal areas and can provide habitats for marine animals. The term [[Biology:Division|division]] has been traditionally used instead of [[Biology:Phylum|phylum]] when discussing primary producers, although the International Code of Nomenclature for algae, fungi, and plants now accepts the terms as equivalent.<ref name="ICN">{{Cite book |year=2012 |editor-last=McNeill |editor-first=J. |displayeditors=etal|title=International Code of Nomenclature for algae, fungi, and plants (Melbourne Code), Adopted by the Eighteenth International Botanical Congress Melbourne, Australia, July 2011 |edition=electronic |publisher=International Association for Plant Taxonomy |url=http://www.iapt-taxon.org/nomen/main.php?page=art3 |accessdate=2017-05-14 }}</ref>

===Cyanobacteria===
[[File:Cyanobacteria guerrero negro.jpg|thumb|240px|{{center|Cyanobacteria from a [[Biology:Microbial mat|microbial mat]]. Cyanobacteria were the first organisms to release oxygen via photosynthesis}}]]

Cyanobacteria are a phylum (division) of bacteria which range from unicellular to [[Biology:Protein filament|filamentous]] and include [[Biology:Colony#Microbial colonies|colonial species]]. They are found almost everywhere on earth: in damp soil, in both freshwater and marine environments, and even on Antarctic rocks.<ref name="WalshSmith2011">{{cite book|editor-last1=Walsh|editor-first1=Patrick J.|editor-last2=Smith|editor-first2=Sharon|editor-last3=Fleming|editor-first3=Lora|editor-first4=Helena |editor-last4=Solo-Gabriele |editor-first5=William H.|editor-last5= Gerwick| name-list-format = vanc |title=Oceans and Human Health: Risks and Remedies from the Seas|chapter-url={{google books |plainurl=y |id=LMZPqW-PmFYC|page=271}}|date=2 September 2011|chapter=Cyanobacteria and cyanobacterial toxins|pp=271–296|publisher=Academic Press|isbn=978-0-08-087782-2}}</ref> In particular, some species occur as drifting cells floating in the ocean, and as such were amongst the first of the [[Earth:Phytoplankton|phytoplankton]].

The first primary producers that used photosynthesis were oceanic [[Biology:Cyanobacteria|cyanobacteria]] about 2.3&nbsp;billion years ago.<ref>{{Cite web|url= http://www.astrobio.net/news-exclusive/the-rise-of-oxygen/|title= The Rise of Oxygen - Astrobiology Magazine|website= Astrobiology Magazine|language= en-US|access-date= 2016-04-06}}</ref><ref>{{cite journal|last= Flannery|first= D. T.|author2= R.M. Walter|title= Archean tufted microbial mats and the Great Oxidation Event: new insights into an ancient problem|journal= Australian Journal of Earth Sciences|date= 2012|volume= 59|issue= 1|pages= 1–11|doi= 10.1080/08120099.2011.607849 |bibcode = 2012AuJES..59....1F |url= https://semanticscholar.org/paper/8e2fb3f5ab865aed8faceee53c45558724c13c6c}}</ref> The release of molecular [[Chemistry:Oxygen|oxygen]] by [[Biology:Cyanobacteria|cyanobacteria]] as a by-product of photosynthesis induced global changes in the Earth's environment. Because oxygen was toxic to most life on Earth at the time, this led to the near-extinction of [[Biology:Anaerobic organism|oxygen-intolerant organisms]], a dramatic change which redirected the evolution of the major animal and plant species.<ref name=astrobiology>{{cite web |url=http://astrobiology.arc.nasa.gov/roadmap/g5.html |archiveurl=https://www.webcitation.org/664nY11q7?url=http://astrobiology.arc.nasa.gov/roadmap/g5.html |archivedate=11 March 2012 |title=Understand the evolutionary mechanisms and environmental limits of life |accessdate=13 July 2009 |last=Rothschild |first=Lynn |date=September 2003 |publisher=NASA}}</ref>

[[File:Prochlorococcus marinus (cropped).jpg|thumb|120px|left| {{center|''Prochlorococcus marinus''}}]]

The tiny marine cyanobacterium ''[[Biology:Prochlorococcus|Prochlorococcus]]'', discovered in 1986, forms today part of the base of the ocean food chain and accounts for more than half the photosynthesis of the open ocean<ref>{{cite journal | vauthors = Nadis S | title = The cells that rule the seas | journal = Scientific American | volume = 289 | issue = 6 | pages = 52–3 | date = December 2003 | pmid = 14631732 | doi = 10.1038/scientificamerican1203-52 | url = http://guowei.ccps.tp.edu.tw/nc/UploadDocument/255_02%20The%20Cells%20that%20Rules%20the%20Sea.pdf | bibcode = 2003SciAm.289f..52N }}</ref> and an estimated 20% of the oxygen in the Earth's atmosphere.<ref name="npr">{{cite web|url=https://www.npr.org/templates/story/story.php?storyId=91448837|title=The Most Important Microbe You've Never Heard Of|author=|date=|website=npr.org}}</ref> It is possibly the most plentiful genus on Earth: a single millilitre of surface seawater may contain 100,000 cells or more.<ref>{{Cite journal | last1 = Flombaum | first1 = P. | last2 = Gallegos | first2 = J. L. | last3 = Gordillo | first3 = R. A. | last4 = Rincon | first4 = J. | last5 = Zabala | first5 = L. L. | last6 = Jiao | first6 = N. | last7 = Karl | first7 = D. M. | last8 = Li | first8 = W. K. W. | last9 = Lomas | first9 = M. W. | doi = 10.1073/pnas.1307701110 | last10 = Veneziano | first10 = D. | last11 = Vera | first11 = C. S. | last12 = Vrugt | first12 = J. A. | last13 = Martiny | first13 = A. C. | title = Present and future global distributions of the marine Cyanobacteria Prochlorococcus and Synechococcus | journal = Proceedings of the National Academy of Sciences | volume = 110 | issue = 24 | pages = 9824–9829 | year = 2013 | pmid =  23703908| pmc = 3683724}}</ref>

Originally, biologists thought [[Biology:Cyanobacteria|cyanobacteria]] was algae, and referred to it as "blue-green algae". The more recent view is that cyanobacteria is a bacteria, and hence is not even in the same [[Biology:Kingdom|Kingdom]] as algae. Most authorities exclude all prokaryotes, and hence cyanobacteria from the definition of algae.<ref name="IntroBot">{{cite book |last=Nabors |first=Murray W. |title=Introduction to Botany |year=2004 |publisher=Pearson Education, Inc |location=San Francisco, CA |isbn=978-0-8053-4416-5}}</ref><ref name="Allaby 92">{{cite encyclopedia |editor1-last=Allaby |editor1-first=M. |year=1992 |encyclopedia=The Concise Dictionary of Botany |publisher=Oxford University Press |location=Oxford |title=Algae}}</ref>
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==Marine algae==
[[Biology:Algae|Algae]] is an informal term for a widespread and diverse group of photosynthetic eukaryotic organisms which are not necessarily closely related and are thus polyphyletic. Unlike higher plants, algae lack roots, stems, or leaves. Marine algae mainly fall into five groups: [[Biology:Green algae|green algae]], [[Biology:Red algae|red algae]], [[Biology:Brown algae|brown algae]], [[Biology:Diatom|diatom]]s and [[Biology:Dinoflagellate|dinoflagellate]]s. There is also a phylum of unicellular flagellates called euglenophytes. However, these have few marine members.

===Green algae=== 
[[Biology:Green algae|Green algae]] live most of their lives as single cells or are filamentous, while others form [[Biology:Colony|colonies]] made up from long chains of cells, or are highly differentiated macroscopic seaweeds. They form an informal group containing about 8,000 recognized species.<ref>{{cite journal | vauthors = Guiry MD | title = How many species of algae are there? | journal = Journal of Phycology | volume = 48 | issue = 5 | pages = 1057–63 | date = October 2012 | pmid = 27011267 | doi = 10.1111/j.1529-8817.2012.01222.x | url = https://semanticscholar.org/paper/27efb217aa66823b850686a2016c68cb69fdd584 }}</ref>

===Red algae===
Modern [[Biology:Red algae|red algae]] are mostly multicellular with differentiated cells and include many notable [[Biology:Seaweed|seaweed]]s.<ref name=":0" /><ref name="Thomas 02">{{cite book|title=Seaweeds|publisher=Life Series. [[Biology:Natural History Museum, London|Natural History Museum]], London|year=2002|isbn=978-0-565-09175-0|author=D. Thomas}}</ref> As [[Biology:Coralline algae|coralline algae]], they play an important role in the ecology of coral reefs. They form a (disputed) phylum containing about 7,000 recognized species.<ref name=":0">{{Cite web|url=http://www.algaebase.org/browse/taxonomy/?id=97240|title=Algaebase|last=Guiry|first=M.D.|last2=Guiry|first2=G.M.|date=2016|website=www.algaebase.org|publisher=|access-date=November 20, 2016}}</ref>

<gallery mode=packed heights=130px style=float:left;>
File:Cyanidium O5A.jpg| [[Biology:Cyanidiophyceae|Cyanidiophyceae]] colony, a class of unicellular red algae
File:Porphyra umbilicalis Helgoland.JPG| The seaweed ''[[Biology:Porphyra umbilicalis|Porphyra umbilicalis]]''
</gallery>
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===Brown algae=== 
[[Biology:Brown algae|Brown algae]] are mostly multicellular and include many seaweeds, including [[Biology:Kelp|kelp]]. They form a [[Biology:Class|class]] containing about 2,000 recognized species.<ref>{{Cite book|url=https://books.google.com/books?id=s1P855ZWc0kC&pg=166|title=Algae : an introduction to phycology|last1=Hoek|first1=Christiaan|last2=den Hoeck|first2=Hoeck Van|last3=Mann|first3=David|last4=Jahns|first4=H.M.|date=1995|publisher=Cambridge University Press|isbn=9780521316873|oclc=443576944|page=166}}</ref> 

===Diatoms===
<gallery mode=packed heights=130px style=float:left;>
File:Diatoms (248 05) Various diatoms.jpg|[[Biology:Diatom|Diatom]]s are one of the most common types of phytoplankton
File:Diatoms through the microscope.jpg| They are a major algae group generating about 20% of world oxygen production.<ref>[https://www.livescience.com/46250-teasing-apart-the-diatom-genome.html The Air You're Breathing? A Diatom Made That]</ref>
File:Diatom algae Amphora sp.jpg| Diatoms have glass like cell walls called [[Biology:Frustule|frustule]]s which are made of [[Chemistry:Silica|silica]].<ref>{{cite web | title=More on Diatoms | website=University of California Museum of Paleontology | url = http://www.ucmp.berkeley.edu/chromista/diatoms/diatommm.html}}</ref>
</gallery>
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===Dinoflagellate===
<gallery mode=packed heights=130px style=float:left;>
File:CSIRO ScienceImage 7609 SEM dinoflagellate.jpg| Dinoflagellates
File:Euglena mutabilis - 400x - 1 (10388739803) (cropped).jpg|''[[Biology:Euglena|Euglena mutabilis]]'', a photosynthetic [[Biology:Flagellate|flagellate]]
</gallery>
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===Microalgae===
Algae can also be classified by size as ''[[Biology:Microalgae|microalgae]]'' or ''macroalgae''. Microalgae are the microscopic types of algae, not visible to the naked eye. They are mostly unicellular species which exist as individuals or in chains or groups, though some are multicellular. Microalgae are important components of the [[Biology:Marine life#Marine protists|marine protists]], as well as the [[Biology:Marine life#Phytoplankton|marine phytoplankton]]. They are very [[Biology:Biodiversity|diverse]]. It has been estimated there are 200,000-800,000 species of which about 50,000 species have been described.<ref name = Flanders>Starckx, Senne (31 October 2012) [http://www.flanderstoday.eu/current-affairs/place-sun A place in the sun - Algae is the crop of the future, according to researchers in Geel] Flanders Today, Retrieved 8 December 2012</ref> Depending on the species, their sizes range from a few micrometers (µm) to a few hundred micrometers. They are specially adapted to an environment dominated by viscous forces.

<gallery caption="Microalgae" mode=packed heights=130px style=float:left;>
File:Gephyrocapsa oceanica color (lightened).jpg| Single-celled alga, ''Gephyrocapsa oceanica''
File:Emiliania huxleyi coccolithophore (PLoS).png| The [[Biology:Coccolithophore|coccolithophore]] ''Emiliania huxleyi''
File:Cwall99 lg.jpg| [[Biology:Algae bloom|Algae bloom]] of ''Emiliania huxleyi'' off the southern coast of England
File:Zooxanthellae.jpg| [[Biology:Zooxanthellae|Zooxanthellae]] is a photosynthetic algae that lives inside hosts like [[Biology:Coral|coral]]
File:Paramecium bursaria.jpg| A single-celled ciliate with green zoochlorellae living inside endosymbiotically
</gallery>
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===Macroalgae===
[[File:Kelp forest.jpg|thumb| Kelp forests are among the most productive ecosystems on Earth.]]

Macroalgae are the larger, multicellular and more visible types of algae, commonly called [[Biology:Seaweed|seaweed]]s. Seaweeds usually grow in shallow coastal waters where they are anchored to the seafloor by a [[Biology:Holdfast|holdfast]]. Seaweed that becomes adrift can wash up on beaches. [[Biology:Kelp|Kelp]] is a large brown seaweed that forms large underwater [[Biology:Kelp forest|forests]] covering about 25% of the world coastlines.<ref>[https://www.sciencedirect.com/topics/earth-and-planetary-sciences/kelp-forest Kelp Forest - an overview | ScienceDirect Topics]</ref> They are among the most productive and dynamic ecosystems on Earth.<ref name="Mann (1973)">Mann, K.H. 1973. Seaweeds: their productivity and strategy for growth. Science 182: 975-981.</ref> Some ''[[Biology:Sargassum|Sargassum]]'' seaweeds are planktonic (free-floating). Like microalgae, macroalgae (seaweeds) are technically [[Biology:Marine life#Marine protists|marine protists]] since they are not true plants. 

[[File:Algae Pengo.svg|thumb|upright=1.5|left| {{center|A seaweed is a macroscopic form of red or brown or green algae}}]]
[[File:Kelp forest distribution map.png|thumb|upright=1.2| {{center|Global distribution of kelp forests}}]]

<gallery caption="Macroalgae" mode=packed heights=140px style=float:left;>
File:Giant Kelp.jpg| Giant kelp is technically a protist since it is not a true plant, yet it is multicellular and can grow to 50 m 
File:Sargassum on the beach, Cuba.JPG| ''[[Biology:Sargassum|Sargassum]]'' seaweed is a brown alga with air bladders that help it float
<!-- File:Kelp forest at Taranga pinnacles Hen and Chicken Islands PA232359.JPG|[[Biology:Kelp forest|Kelp forest]] -->
File:Histrio histrio by A. H. Baldwin.jpg| [[Biology:Sargassum fish|Sargassum fish]] are camouflaged to live among drifting ''Sargassum'' seaweed
File:Ventricaria ventricosa.JPG| This unicellular [[Biology:Valonia ventricosa|bubble algae]] lives in tidal zones. It can have a 4&nbsp;cm diameter.<ref>{{cite book |last1=Tunnell |first1=John Wesley  |last2=Chávez |first2=Ernesto A. |last3=Withers |first3=Kim |year=2007 |title=Coral reefs of the southern Gulf of Mexico |publisher=Texas A&M University Press |isbn=978-1-58544-617-9 |page=91 |url=https://books.google.com/books?id=tu0sqBp8eAAC&pg=PA91}}</ref> 
</gallery>
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==Marine plants==
[[File:Evolution of seagrasses Pengo 8.png|thumb|360px| {{center|Evolution of mangroves and seagrasses}}]]

Back in the [[Earth:Silurian|Silurian]], some phytoplankton evolved into [[Biology:Red algae|red]], [[Biology:Brown algae|brown]] and [[Biology:Green algae|green algae]]. These algae then invaded the land and started evolving into the land plants we know today. Later, in the [[Earth:Cretaceous|Cretaceous]], some of these land plants returned to the sea as [[Earth:Mangrove|mangrove]]s and [[Biology:Seagrass|seagrass]]es.<ref>Orth, R.J., Carruthers, T.J., Dennison, W.C., Duarte, C.M., Fourqurean, J.W., Heck, K.L., Hughes, A.R., Kendrick, G.A., Kenworthy, W.J., Olyarnik, S. and Short, F.T. (2006) [https://academic.oup.com/bioscience/article/56/12/987/221654 "A global crisis for seagrass ecosystems"]. ''Bioscience'', '''56'''(12): pages 987–996. {{doi|10.1641/0006-3568(2006)56[987:AGCFSE]2.0.CO;2}}</ref>

Marine plants can be found in  [[Earth:Intertidal zone|intertidal zone]]s and shallow waters, such as [[Biology:Seagrass|seagrass]]es like [[Biology:Zostera|eelgrass]] and turtle grass, ''Thalassia''. These plants have adapted to the high salinity of the ocean environment. Plant life can also flourish in the brackish waters of estuaries, where mangroves or cordgrass or beach grass beach grass might grow.

===Mangroves===
Mangroves provide important nursery habitats for marine life, acting as hiding and foraging places for larval and juvenile forms of larger fish and invertebrates. Based on satellite data, the total world area of mangrove forests was estimated in 2010 as {{convert|134,257|km2}}.<ref>Giri C, Ochieng E, Tieszen LL, Zhu Z, Singh A, Loveland T, et al. (2011) "Status and distribution of mangrove forests of the world using earth observation satellite data". ''Global Ecology and Biogeography'', '''20'''(1):154–159. {{doi|10.1111/j.1466-8238.2010.00584.x}}</ref><ref>Thomas, N., Lucas, R., Bunting, P., Hardy, A., Rosenqvist, A. and Simard, M. (2017) "Distribution and drivers of global mangrove forest change, 1996–2010". ''PLOS ONE'', '''12'''(6): e0179302. {{doi|10.1371/journal.pone.0179302}}</ref>

<gallery mode=packed heights=140px style=float:left;>
File:Mangrove-Keti Bundar.jpg|[[Earth:Mangrove|Mangrove]]s
</gallery>
[[File:World map mangrove distribution.jpg|thumb|upright=1.2| {{center|Global mangrove forests in 2000}}]]
[[File:Zostera marina dis.png|thumb|upright=1.2| {{center|The seagrass common eelgrass according to [https://www.iucnredlist.org/species/153538/4516675 IUCN data]}}]] 
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* Spalding, M. (2010) [https://www.taylorfrancis.com/books/9781849776608 ''World atlas of mangroves''], Routledge. {{isbn|9781849776608}}. {{DOI|10.4324/9781849776608}}.

===Seagrasses===
Like mangroves, seagrasses provide important nursery habitats for larval and juvenile forms of larger fish and invertebrates. The total world area of seagrass meadows is more difficult to determine than mangrove forests, but was conservatively estimated in 2003 as {{convert|177000|km2}}.<ref>Short, F.T. and Frederick, T. (2003) [https://www.unep-wcmc.org/resources-and-data/world-atlas-of-seagrasses ''World atlas of seagrasses''], University of California Press, page 24. {{ISBN|9780520240476}}</ref>
<gallery mode=packed heights=140px style=float:left;>
File:Floridian seagrass bed.jpg|[[Biology:Seagrass meadow|Seagrass meadow]]
File:Leafy Sea Dragon SA.jpg| Sea dragons camouflaged to look like floating seaweed live in kelp forests and seagrass meadows<ref>{{FishBase_species |genus=Phycodurus |species=eques |year=2009 |month=July}}</ref>
</gallery>
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==See also==
* [[Biology:Algae|Algae]]
* Marine plants
* [[Biology:Evolutionary history of plants|Evolutionary history of plants]]
* [[Biology:Plant evolution|Plant evolution]]
* [[Biology:Timeline of plant evolution|Timeline of plant evolution]]
* [[Biology:Evolution of photosynthesis|Evolution of photosynthesis]]

==References==
{{reflist}}

{{aquatic ecosystem topics|expanded=marine}}

[[Category:Marine organisms| ]]
[[Category:Marine biology| ]]
[[Category:Biological oceanography| ]]
[[Category:Marine botany]]
[[Category:Algae]]
[[Category:Seagrass]]
[[Category:Seaweeds]]
[[Category:Branches of botany]]

{{Sourceattribution|Marine algae and plants|1}}