Editing Algae (section)

==Symbiotic algae==
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 are:

===Lichens===
{{Main|Lichen}}
[[File:Lichens near Clogher Head (stevefe).jpg|thumb|Rock lichens in Ireland]]
[[Lichen]]s are defined by the [[International Association for Lichenology]] to be "an association of a fungus and a photosynthetic [[symbiont]] resulting in a stable vegetative body having a specific structure".<ref>{{cite book |last1=Brodo |first1=Irwin M. |last2=Sharnoff |first2=Sylvia Duran |last3=Sharnoff |first3=Stephen |last4=Laurie-Bourque |first4=Susan |title=Lichens of North America |date=2001 |publisher=Yale University Press |location=New Haven |isbn=978-0-300-08249-4 |page=8}}</ref> The fungi, or mycobionts, are mainly from the [[Ascomycota]] with a few from the [[Basidiomycota]]. In nature, they do not occur separate from lichens. It is unknown when they began to associate.<ref>{{cite book |last=Pearson |first=Lorentz C. |title=The Diversity and Evolution of Plants |date=1995 |publisher=CRC Press |isbn=978-0-8493-2483-3 |page=221}}</ref> One or more<ref>{{Cite journal |last1=Tuovinen |first1=Veera |last2=Ekman |first2=Stefan |last3=Thor |first3=Göran |last4=Vanderpool |first4=Dan |last5=Spribille |first5=Toby |last6=Johannesson |first6=Hanna |date=2019-01-17 |title=Two Basidiomycete Fungi in the Cortex of Wolf Lichens |url=https://linkinghub.elsevier.com/retrieve/pii/S0960982218316543 |journal=Current Biology |volume=29 |issue=3 |pages=476–483.e5 |doi=10.1016/j.cub.2018.12.022 |pmid=30661799 |bibcode=2019CBio...29E.476T |issn=0960-9822}}</ref> mycobiont associates with the same phycobiont species, from the green algae, except that alternatively, the mycobiont may associate with a species of cyanobacteria (hence "photobiont" is the more accurate term). A photobiont may be associated with many different mycobionts or may live independently; accordingly, lichens are named and classified as fungal species.<ref>Brodo et al. (2001), p. 6: "A species of lichen collected anywhere in its range has the same lichen-forming fungus and, generally, the same photobiont. (A particular photobiont, though, may associate with scores of different lichen fungi)."</ref> The association is termed a morphogenesis because the lichen has a form and capabilities not possessed by the symbiont species alone (they can be experimentally isolated). The photobiont possibly triggers otherwise latent genes in the mycobiont.<ref>Brodo et al. (2001), p. 8.</ref>

[[Trentepohlia (alga)|Trentepohlia]] is an example of a common green alga genus worldwide that can grow on its own or be lichenised. Lichen thus share some of the habitat and often similar appearance with specialized species of algae (''[[aerophyte]]s'') growing on exposed surfaces such as tree trunks and rocks and sometimes discoloring them.

===Coral reefs===
{{Main|Coral|Coral reef|Symbiodinium}}
[[File:Coral Reef.jpg|thumb|Floridian coral reef]] [[Coral reef]]s are accumulated from the [[calcareous]] exoskeletons of [[marine invertebrate]]s of the order [[Scleractinia]] (stony [[coral]]s). These animals [[Metabolism|metabolize]] sugar and oxygen to obtain energy for their cell-building processes, including [[secretion]] of the exoskeleton, with water and [[carbon dioxide]] as byproducts. Dinoflagellates (algal protists) are often [[endosymbiont]]s in the cells of the coral-forming marine invertebrates, where they accelerate host-cell metabolism by generating sugar and oxygen immediately available through photosynthesis using incident light and the carbon dioxide produced by the host. Reef-building stony corals ([[hermatypic coral]]s) require endosymbiotic algae from the genus ''[[Symbiodinium]]'' to be in a healthy condition.<ref>{{cite book |last=Taylor |first=Dennis L. |editor-last=Goff |editor-first=Lynda J. |title=Algal Symbiosis: A Continuum of Interaction Strategies |date=1983 |publisher=CUP Archive |isbn=978-0-521-25541-7 |pages=[https://archive.org/details/algalsymbiosisco0000unse/page/19 19]–20 |contribution=The coral-algal symbiosis |url-access=registration |url= https://archive.org/details/algalsymbiosisco0000unse}}</ref> The loss of ''Symbiodinium'' from the host is known as [[coral bleaching]], a condition which leads to the deterioration of a reef.

===Sea sponges===
{{Main|Sea sponge}}
[[Endosymbiont]]ic green algae live close to the surface of some sponges, for example, breadcrumb sponges (''[[Halichondria panicea]]''). The alga is thus protected from predators; the sponge is provided with oxygen and sugars which can account for 50 to 80% of sponge growth in some species.<ref>{{cite journal |url= http://uwsp.edu/cnr/UWEXlakes/laketides/vol26-4/vol26-4.pdf |title=Are There Sponges in Your Lake? |first=Susan |last=Knight |journal=Lake Tides |via=UWSP.edu |volume=26 |issue=4 |pages=4–5 |publisher=Wisconsin Lakes Partnership |date=Fall 2001 |access-date=4 August 2007 |url-status=dead |archive-url= https://web.archive.org/web/20070702204058/http://www.uwsp.edu/cnr/UWEXlakes/laketides/vol26-4/vol26-4.pdf |archive-date=2 July 2007}}</ref>