Editing Coral bleaching (section)

== Trends due to climate change ==
{{See also|Effects of climate change on oceans}}
Extreme bleaching events are directly linked with climate-induced phenomena that increase [[ocean temperature]], such as [[El Niño–Southern Oscillation|El Niño-Southern Oscillation]] (ENSO).<ref>{{Cite journal |last1=Baker |first1=Andrew C. |last2=Glynn |first2=Peter W. |last3=Riegl |first3=Bernhard |date=December 2008 |title=Climate change and coral reef bleaching: An ecological assessment of long-term impacts, recovery trends and future outlook |url=https://doi.org/10.1016/j.ecss.2008.09.003 |journal=Estuarine, Coastal and Shelf Science |volume=80 |issue=4 |pages=435–471 |doi=10.1016/j.ecss.2008.09.003 |bibcode=2008ECSS...80..435B |issn=0272-7714|url-access=subscription }}</ref> The [[Sea surface temperature|warming ocean surface waters]] can lead to bleaching of corals which can cause serious damage and coral death. The [[IPCC Sixth Assessment Report]] in 2022 found that: "Since the early 1980s, the frequency and severity of mass coral bleaching events have increased sharply worldwide".<ref name=":43">Cooley, S., D. Schoeman, L. Bopp, P. Boyd, S. Donner, D.Y. Ghebrehiwet, S.-I. Ito, W. Kiessling, P. Martinetto, E. Ojea, M.-F. Racault, B. Rost, and M. Skern-Mauritzen, 2022: [https://www.ipcc.ch/report/ar6/wg2/downloads/report/IPCC_AR6_WGII_Chapter03.pdf Chapter 3: Oceans and Coastal Ecosystems and Their Services]. In: [https://www.ipcc.ch/report/ar6/wg2/ Climate Change 2022: Impacts, Adaptation and Vulnerability. Contribution of Working Group II to the Sixth Assessment Report of the Intergovernmental Panel on Climate Change] [H.-O. Pörtner, D.C. Roberts, M. Tignor, E.S. Poloczanska, K. Mintenbeck, A. Alegría, M. Craig, S. Langsdorf, S. Löschke, V. Möller, A. Okem, B. Rama (eds.)]. Cambridge University Press, Cambridge, UK and New York, NY, USA, pp. 379–550, doi:10.1017/9781009325844.005.</ref>{{rp|416}} Coral reefs, as well as other shelf-sea ecosystems, such as [[rocky shore]]s, [[kelp forest]]s, [[seagrass]]es, and [[mangrove]]s, have recently undergone mass mortalities from [[marine heatwave]]s.<ref name=":43" />{{rp|381}} It is expected that many coral reefs will "undergo irreversible phase shifts due to marine heatwaves with global warming levels >1.5°C".<ref name=":43" />{{rp|382}}

This problem was already identified in 2007 by the [[Intergovernmental Panel on Climate Change]] (IPCC) as the greatest threat to the world's reef systems.<ref name="IPCC2007">{{Cite book |author=IPCC |chapter=Summary for policymakers |chapter-url=http://www.ipcc.ch/pdf/assessment-report/ar4/wg2/ar4-wg2-spm.pdf |veditors=Parry ML, Canziani OF, Palutikof JP, van der Linden PJ, Hanson CE |title=Climate Change 2007: impacts, adaptation and vulnerability: contribution of Working Group II to the fourth assessment report of the Intergovernmental Panel on Climate Change |publisher=Cambridge University Press |location=Cambridge, UK |year=2007 |pages=7–22 |isbn=978-0-521-70597-4 |access-date=8 July 2009 |archive-date=13 January 2018 |archive-url=https://web.archive.org/web/20180113141313/http://www.ipcc.ch/pdf/assessment-report/ar4/wg2/ar4-wg2-spm.pdf |url-status=live }}</ref><ref>{{Cite book |vauthors=Fischlin A, Midgley GF, Price JT, Leemans R, Gopal B, Turley C, Rounsevell MD, Dube OP, Tarazona J, Velichko AA |chapter=Ch 4. Ecosystems, their properties, goods and services |chapter-url=http://www.ipcc.ch/pdf/assessment-report/ar4/wg2/ar4-wg2-chapter4.pdf |veditors=Parry ML, Canziani OF, Palutikof JP, van der Linden PJ, Hanson CE |title=Climate Change 2007: impacts, adaptation and vulnerability: contribution of Working Group II to the fourth assessment report of the Intergovernmental Panel on Climate Change |publisher=Cambridge University Press |location=Cambridge, UK |year=2007 |pages=211–72 |isbn=978-0-521-70597-4 |access-date=8 July 2009 |archive-date=11 October 2017 |archive-url=https://web.archive.org/web/20171011185727/http://www.ipcc.ch/pdf/assessment-report/ar4/wg2/ar4-wg2-chapter4.pdf |url-status=live }}</ref>

The [[Great Barrier Reef]] experienced its first major bleaching event in 1998. Since then, bleaching events have increased in frequency, with three events occurring in the years 2016–2020.<ref>{{Cite news |last1=Davidson |first1=Jordan |date=25 March 2020 |title=Great Barrier Reef Has Third Major Bleaching Event in Five Years |agency=Ecowatch |url=https://www.ecowatch.com/coral-bleaching-great-barrier-reef-2645576557.html |access-date=27 March 2020}}</ref> Bleaching is predicted to occur three times a decade on the Great Barrier Reef if warming is kept to 1.5&nbsp;°C, increasing every other year to 2&nbsp;°C.<ref>{{cite journal |last1=McWhorter |first1=Jennifer K. |last2=Halloran |first2=Paul R. |last3=Roff |first3=George |last4=Skirving |first4=William J. |last5=Perry |first5=Chris T. |last6=Mumby |first6=Peter J. |title=The importance of 1.5°C warming for the Great Barrier Reef |journal=Global Change Biology |date=February 2022 |volume=28 |issue=4 |pages=1332–1341 |doi=10.1111/gcb.15994 |pmid=34783126 |bibcode=2022GCBio..28.1332M |hdl=10871/127948 |s2cid=244131267 |hdl-access=free }}</ref>

With the increase of coral bleaching events worldwide, ''[[National Geographic]]'' noted in 2017, "In the past three years, 25 reefs—which comprise three-fourths of the world's reef systems—experienced severe bleaching events in what scientists concluded was the worst-ever sequence of bleachings to date."<ref>{{Cite web |url=https://news.nationalgeographic.com/2017/06/coral-reef-bleaching-global-warming-unesco-sites/|title=Coral Reefs Could Be Gone in 30 Years |date=2017-06-23 |website=National Geographic News |access-date=2019-05-07 |archive-date=7 May 2019 |archive-url=https://web.archive.org/web/20190507044023/https://news.nationalgeographic.com/2017/06/coral-reef-bleaching-global-warming-unesco-sites/ |url-status=dead}}</ref>

In a study conducted on the Hawaiian mushroom coral ''[[Lobactis scutaria]]'', researchers discovered that higher temperatures and elevated levels of [[photosynthetically active radiation]] (PAR) had a detrimental impact on its reproductive physiology. The purpose of this study was to investigate the survival of reef-building corals in their natural habitat, as coral reproduction is being hindered by the effects of climate change.<ref>{{Cite journal |last1=Bouwmeester |first1=Jessica |last2=Daly |first2=Jonathan |last3=Zuchowicz |first3=Nikolas |last4=Lager |first4=Claire |last5=Henley |first5=E. Michael |last6=Quinn |first6=Mariko |last7=Hagedorn |first7=Mary |date=2023-01-05 |title=Solar radiation, temperature and the reproductive biology of the coral Lobactis scutaria in a changing climate |url=http://dx.doi.org/10.1038/s41598-022-27207-6 |journal=Scientific Reports |volume=13 |issue=1 |page=246 |doi=10.1038/s41598-022-27207-6 |pmid=36604569 |issn=2045-2322|pmc=9816315 |bibcode=2023NatSR..13..246B }}</ref>