Editing Coral (section)

===Sexual===
[[File:Coral Life Cycles ZP.svg|thumb|upright=1.75|Life cycles of broadcasters and brooders]]
Corals predominantly reproduce [[sexual reproduction|sexually]]. About 25% of [[hermatypic coral]]s (reef-building stony corals) form single-sex ([[gonochoristic]]) colonies, while the rest are [[hermaphroditic]].{{Citation needed|date=September 2021}} It is estimated more than 67% of coral are [[Simultaneous hermaphroditism|simultaneous hermaphrodites]].<ref>{{Cite book|last=Avise|first=John C.|url=https://books.google.com/books?id=jqiR8C0lEckC&q=most+coral+are+hermaphrodites&pg=PA83|title=Hermaphroditism: A Primer on the Biology, Ecology, and Evolution of Dual Sexuality|date=2011-03-18|publisher=Columbia University Press|isbn=978-0-231-52715-6|pages=83|language=en}}</ref>

====Broadcasters====
{{external media | width = 210px | float = right | headerimage= [[File:Brain coral spawning.jpg |210px]] | video1 = [https://www.youtube.com/watch?v=PR4bpVKVeQ4 " Out of Tune – Breakdown of Coral Spawning Synchrony"], Tom Shlesinger, Sep 5, 2019.}}

About 75% of all hermatypic corals "broadcast spawn"{{citation needed|date=March 2023}} by releasing [[gamete]]s—[[egg (biology)|eggs]] and [[sperm]]—into the water where they meet and fertilize to spread offspring. Corals often synchronize their time of spawning. This [[reproductive synchrony]] is essential so that male and female gametes can meet. Spawning frequently takes place in the evening or at night, and can occur as infrequently as once a year, and within a window of 10–30 minutes.<ref name="Markandeya"/><ref name="Häfker"/>
Synchronous spawning is very typical on the coral reef, and often, all corals spawn on the same night even when multiple [[species]] are present.<ref name="Veron"/> Synchronous spawning may form hybrids and is perhaps involved in coral [[speciation]].<ref name=Hatta>{{cite journal |author1=Hatta, M. |author2=Fukami, H. |author3=Wang, W. |author4=Omori, M. |author5=Shimoike, K. |author6=Hayashibara, T. |author7=Ina, Y. |author8=Sugiyama, T. | title=Reproductive and genetic evidence for a reticulate evolutionary theory of mass spawning corals | journal=Molecular Biology and Evolution | year=1999 | pages=1607–13 | volume=16 | issue=11 | pmid=10555292 | doi=10.1093/oxfordjournals.molbev.a026073| doi-access=free }}</ref>

[[File:Stony coral spawning 2.jpg|thumb|A male [[great star coral]], ''Montastraea cavernosa'', releasing sperm into the water.]]
Environmental cues that influence the release of gametes into the water vary from species to species. The cues involve temperature change, [[Lunar phase|lunar cycle]], [[day length]], and possibly chemical signalling.<ref name="Veron">{{cite book|author=Veron, J.E.N.|title=Corals of the World. Vol 3|publisher=Australian Institute of Marine Sciences and CRR Qld|year=2000|isbn=978-0-642-32236-4|edition=3rd|location=Australia}}</ref> 
Other factors that affect the rhythmicity of organisms in marine habitats include salinity, mechanical forces, and pressure or magnetic field changes.<ref name="Häfker"/>

Mass coral spawning often occurs at night on days following a full moon.<ref name="Markandeya"/><ref name="Lin"/> A full moon is equivalent to four to six hours of continuous dim light exposure, which can cause [[light-dependent reactions]] in protein.<ref name="Markandeya"/><ref name="Häfker"/> Corals contain light-sensitive [[cryptochromes]], proteins whose light-absorbing flavin structures are sensitive to different types of light. This allows corals such as ''[[Dipsastraea speciosa]]'' to detect and respond to changes in sunlight and moonlight.<ref name="Markandeya"/><ref name="Häfker">{{cite journal |last1=Häfker |first1=N. Sören |last2=Andreatta |first2=Gabriele |last3=Manzotti |first3=Alessandro |last4=Falciatore |first4=Angela |last5=Raible |first5=Florian |last6=Tessmar-Raible |first6=Kristin |title=Rhythms and Clocks in Marine Organisms |journal=Annual Review of Marine Science |date=16 January 2023 |volume=15 |issue=1 |pages=509–538 |doi=10.1146/annurev-marine-030422-113038 |pmid=36028229 |bibcode=2023ARMS...15..509H |s2cid=251865474 |language=en |issn=1941-1405|doi-access=free }}</ref><ref name="Jabr">{{cite news |last1=Jabr |first1=Ferris |title=The Lunar Sea |url=https://hakaimagazine.com/features/lunar-sea/ |access-date=6 March 2023 |work=Hakai Magazine |date=June 13, 2017 |language=en}}</ref>

Moonlight itself may actually suppress coral spawning. The most immediate cue to cause spawning appears to be the dark portion of the night between sunset and moonrise. 
Over the lunar cycle, moonrise shifts progressively later, occurring after sunset on the day of the full moon. The resulting dark period between day-light and night-light removes the suppressive effect of moonlight and enables coral to spawn.<ref name="Markandeya"/><ref name="Lin">{{cite journal |last1=Lin |first1=Che-Hung |last2=Takahashi |first2=Shunichi |last3=Mulla |first3=Aziz J. |last4=Nozawa |first4=Yoko |title=Moonrise timing is key for synchronized spawning in coral Dipsastraea speciosa |journal=Proceedings of the National Academy of Sciences |date=24 August 2021 |volume=118 |issue=34 |pages=e2101985118 |doi=10.1073/pnas.2101985118 |pmid=34373318 |pmc=8403928 |bibcode=2021PNAS..11801985L |language=en |issn=0027-8424 |doi-access=free }}</ref>

The spawning event can be visually dramatic, clouding the usually clear water with gametes. Once released, gametes fertilize at the water's surface and form a microscopic [[larva]] called a [[planula]], typically pink and elliptical in shape. A typical coral colony needs to release several thousand larvae per year to overcome the odds against formation of a new colony.<ref name=Barnes99>{{cite book | last1= Barnes |first1=R. and |first2=R. |last2=Hughes | year = 1999 | title = An Introduction to Marine Ecology | edition = 3rd | pages = 117–41 | publisher = Blackwell | location = Malden, MA | isbn = 978-0-86542-834-8}}</ref><ref name="Cameron">{{cite journal |last1=Cameron |first1=Kerry A. |last2=Harrison |first2=Peter L. |title=Density of coral larvae can influence settlement, post-settlement colony abundance and coral cover in larval restoration |journal=Scientific Reports |date=26 March 2020 |volume=10 |issue=1 |pages=5488 |doi=10.1038/s41598-020-62366-4 |pmid=32218470 |pmc=7099096 |bibcode=2020NatSR..10.5488C |language=en |issn=2045-2322}}</ref>

Studies suggest that light pollution desynchronizes spawning in some coral species.
In areas such as the [[Red Sea]], as many as 10 out of 50 species may be showing spawning asynchrony, compared to 30 years ago. The establishment of new corals in the area has decreased and in some cases ceased. The area was previously considered a refuge for corals because mass bleaching events due to climate change had not been observed there.<ref name="Markandeya">{{cite journal |last1=Markandeya |first1=Virat |title=How lunar cycles guide the spawning of corals, worms and more |journal=Knowable Magazine |publisher= Annual Reviews |date=22 February 2023 |doi=10.1146/knowable-022223-2 |s2cid=257126558 |doi-access=free |url=https://knowablemagazine.org/article/living-world/2023/lunar-cycles-guide-spawning |access-date=6 March 2023 |language=en}}</ref><ref name="Ayalon">{{cite journal |last1=Ayalon |first1=Inbal |last2=Rosenberg |first2=Yaeli |last3=Benichou |first3=Jennifer I. C. |last4=Campos |first4=Celine Luisa D. |last5=Sayco |first5=Sherry Lyn G. |last6=Nada |first6=Michael Angelou L. |last7=Baquiran |first7=Jake Ivan P. |last8=Ligson |first8=Charlon A. |last9=Avisar |first9=Dror |last10=Conaco |first10=Cecilia |last11=Kuechly |first11=Helga U. |last12=Kyba |first12=Christopher C. M. |last13=Cabaitan |first13=Patrick C. |last14=Levy |first14=Oren |title=Coral Gametogenesis Collapse under Artificial Light Pollution |journal=Current Biology |date=25 January 2021 |volume=31 |issue=2 |pages=413–419.e3 |doi=10.1016/j.cub.2020.10.039 |pmid=33157030 |s2cid=226257589 |language=English |issn=0960-9822|doi-access=free |bibcode=2021CBio...31E.413A }}</ref> Coral restoration techniques for coral reef management are being developed to increase fertilization rates, larval development, and settlement of new corals.<ref name="Suzuki">{{cite journal |last1=Suzuki |first1=Go |last2=Okada |first2=Wataru |last3=Yasutake |first3=Yoko |last4=Yamamoto |first4=Hidekazu |last5=Tanita |first5=Iwao |last6=Yamashita |first6=Hiroshi |last7=Hayashibara |first7=Takeshi |last8=Komatsu |first8=Toshiaki |last9=Kanyama |first9=Toru |last10=Inoue |first10=Masahito |last11=Yamazaki |first11=Masashi |title=Enhancing coral larval supply and seedling production using a special bundle collection system "coral larval cradle" for large-scale coral restoration |journal=Restoration Ecology |date=September 2020 |volume=28 |issue=5 |pages=1172–1182 |doi=10.1111/rec.13178 |s2cid=218796945 |language=en |issn=1061-2971|doi-access=free |bibcode=2020ResEc..28.1172S }}</ref>

====Brooders====
Brooding species are most often ahermatypic (not reef-building) in areas of high current or wave action. Brooders release only sperm, which is negatively buoyant, sinking onto the waiting egg carriers that harbor unfertilized eggs for weeks. Synchronous spawning events sometimes occur even with these species.<ref name=Veron /> After fertilization, the corals release planula that are ready to settle.<ref name=MilneBay />

[[File:Life Cycle of Corals.svg|thumb|left|upright=1.2|Generalized life cycle of corals via sexual reproduction: Colonies release gametes in clusters (1) which float to the surface (2) then disperse and fertilize eggs (3). Embryos become planulae (4) and can settle onto a surface (5). They then metamorphose into a juvenile polyp (6) which then matures and reproduces asexually to form a colony (7, 8).]]

====Planulae====
The time from spawning to larval settlement is usually two to three days but can occur immediately or up to two months.<ref name=Jones>{{cite book |author1=Jones, O.A. |author2=Endean, R. | year = 1973 | title = Biology and Geology of Coral Reefs | pages = 205–45 | publisher = Harcourt Brace Jovanovich | location = New York, US | isbn = 978-0-12-389602-5}}</ref> Broadcast-spawned [[planula]] larvae develop at the water's surface before descending to seek a hard surface on the benthos to which they can attach and begin a new colony.<ref>{{Cite journal|last1=HARRISON|first1=P. L|last2=WALLACE|first2=C. C.|date=1990|title=Reproduction, dispersal and recruitment of scleractinian corals|url=https://pascal-francis.inist.fr/vibad/index.php?action=getRecordDetail&idt=19736342|journal=Reproduction, Dispersal and Recruitment of Scleractinian Corals|volume=25|pages=133–207|issn=0167-4579}}</ref> The larvae often need a biological cue to induce settlement such as specific crustose [[coralline algae]] species or microbial biofilms.<ref>{{Cite journal|last1=Morse|first1=Daniel E.|last2=Hooker|first2=Neal|last3=Morse|first3=Aileen N. C.|last4=Jensen|first4=Rebecca A.|date=1988-05-24|title=Control of larval metamorphosis and recruitment in sympatric agariciid corals|url=https://dx.doi.org/10.1016%2F0022-0981%2888%2990027-5|journal=Journal of Experimental Marine Biology and Ecology|language=en|volume=116|issue=3|pages=193–217|doi=10.1016/0022-0981(88)90027-5|bibcode=1988JEMBE.116..193M |issn=0022-0981}}</ref><ref>{{Cite journal|last1=Webster|first1=Nicole S.|last2=Smith|first2=Luke D.|last3=Heyward|first3=Andrew J.|last4=Watts|first4=Joy E. M.|last5=Webb|first5=Richard I.|last6=Blackall|first6=Linda L.|author6-link= Linda Blackall |last7=Negri|first7=Andrew P.|date=2004-02-01|title=Metamorphosis of a Scleractinian Coral in Response to Microbial Biofilms|journal=Applied and Environmental Microbiology|language=en|volume=70|issue=2|pages=1213–1221|doi=10.1128/AEM.70.2.1213-1221.2004|issn=0099-2240|pmid=14766608|pmc=348907|bibcode=2004ApEnM..70.1213W}}</ref> High failure rates afflict many stages of this process, and even though thousands of eggs are released by each colony, few new colonies form.<!--thousands of gametes or millions?--> During settlement, larvae are inhibited by physical barriers such as sediment,<ref>{{Cite journal|date=2017-12-31|title=Settlement patterns of the coral Acropora millepora on sediment-laden surfaces|journal=Science of the Total Environment|language=en|volume=609|pages=277–288|doi=10.1016/j.scitotenv.2017.07.153|issn=0048-9697|last1=Ricardo|first1=Gerard F.|last2=Jones|first2=Ross J.|last3=Nordborg|first3=Mikaela|last4=Negri|first4=Andrew P.|pmid=28750231|bibcode=2017ScTEn.609..277R|doi-access=free}}</ref> as well as chemical (allelopathic) barriers.<ref>{{Cite journal|last1=Birrell|first1=CL|last2=McCook|first2=LJ|last3=Willis|first3=BL|last4=Harrington|first4=L|date=2008-06-30|title=Chemical effects of macroalgae on larval settlement of the broadcast spawning coral Acropora millepora|url=https://www.int-res.com/abstracts/meps/v362/p129-137/|journal=Marine Ecology Progress Series|language=en|volume=362|pages=129–137|doi=10.3354/meps07524|bibcode=2008MEPS..362..129B|issn=0171-8630|doi-access=free}}</ref> The larvae metamorphose into a single polyp and eventually develops into a juvenile and then adult by asexual budding and growth.