Editing Marine biology (section)

=== Reefs ===
[[File:Maldivesfish2.jpg|thumb|left|[[Coral reef]]s form complex marine ecosystems with tremendous [[biodiversity]].]]
{{Main|Coral reef}}

[[Reef]]s comprise some of the densest and most diverse habitats in the world. The best-known types of reefs are [[tropical]] [[coral reef]]s which exist in most tropical waters; however, reefs can also exist in cold water. Reefs are built up by [[coral]]s and other [[calcium]]-depositing animals, usually on top of a rocky outcrop on the ocean floor. Reefs can also grow on other surfaces, which has made it possible to create [[artificial reef]]s. Coral reefs also support a huge community of life, including the corals themselves, their symbiotic [[zooxanthellae]], tropical fish and many other organisms.

Much attention in marine biology is focused on coral reefs and the [[El Niño]] weather phenomenon. In 1998, coral reefs experienced the most severe mass bleaching events on record, when vast expanses of reefs across the world died because [[sea surface temperature]]s rose well above normal.<ref>NOAA (1998) Record-breaking coral bleaching occurred in tropics this year. [[National Oceanic and Atmospheric Administration]], Press release (October 23, 1998).</ref><ref>ICRS (1998) Statement on Global Coral Bleaching in 1997-1998. International Coral Reef Society, October 15, 1998.</ref> Some reefs are recovering, but scientists say that between 50% and 70% of the world's coral reefs are now endangered and predict that [[global warming]] could exacerbate this trend.<ref>Bryant, D., Burke, L., McManus, J., et al. (1998) "Reefs at risk: a map-based indicator of threats to the world's coral reefs". World Resources Institute, Washington, D.C.</ref><ref>{{cite journal | last1=Goreau | first1=T. J. | year=1992 | title=Bleaching and Reef Community Change in Jamaica: 1951 - 1991 | journal=Am. Zool. | volume=32 | issue=6| pages=683–695 | doi=10.1093/icb/32.6.683| doi-access=free }}</ref><ref>{{cite journal | last1=Sebens | first1=K. P. | year=1994 | title=Biodiversity of Coral Reefs: What are We Losing and Why? | journal=Am. Zool. | volume=34 | pages=115–133 | doi=10.1093/icb/34.1.115| doi-access=free }}</ref><ref>Wilkinson, C. R., and Buddemeier, R. W. (1994) "Global Climate Change and Coral Reefs:Implications for People and Reefs". Report of the UNEP-IOC-ASPEI-IUCN Global Task Team on the Implications of Climate Change on Coral Reefs. IUCN, Gland, Switzerland.</ref>{{clear left}}

[[File:Representative ocean animal life.jpg|thumb|upright=1.7| Some representative ocean animal life (not drawn to scale) within their approximate depth-defined ecological habitats. [[Marine microorganisms]] exist on the surfaces and within the tissues and organs of the diverse life inhabiting the ocean, across all ocean habitats.<ref name="Apprill2017">Apprill, A. (2017)"Marine animal microbiomes: toward understanding host–microbiome interactions in a changing ocean". ''Frontiers in Marine Science'', '''4''': 222. {{doi|10.3389/fmars.2017.00222}}. [[File:CC-BY icon.svg|50px]] Material was copied from this source, which is available under a [https://creativecommons.org/licenses/by/4.0/ Creative Commons Attribution 4.0 International License].</ref>]]