Editing Aphotic zone (section)

==The Dark Ocean==
[[File:Pelagiczone.svg|thumb|upright=0.74|left|The layers of the pelagic zone. All but the epipelagic zone make up the aphotic zone.]]
[[File:Light penetration zones in the water column.png|thumb|upright=1.2|right| Zones of the water column as defined by the amount of light penetration. The mesopelagic is sometimes referred to as the dysphotic zone.]]

In the ocean, the aphotic zone is sometimes referred to as the '''dark ocean'''. Depending on how it is defined, the aphotic zone of the ocean begins between depths of about {{convert|200|m|ft|abbr=on}} to {{convert|800|m|ft|abbr=on}} and extends to the [[ocean floor]].<ref>{{Cite book |author1=Earle, Sylvia A. |url=https://archive.org/details/livingoceanunder00thor |title=The living ocean: understanding and protecting marine biodiversity |author2=Thorne-Miller, Boyce |publisher=Island Press |year=1999 |isbn=1-55963-678-5 |location=Washington, D.C. |pages=56–57 |url-access=registration}}</ref><ref>{{Cite book | last=Kunich | first=John C. | title=Killing our oceans: dealing with the mass extinction of marine life | year=2006 | publisher=Praeger Publishers | location=Westport, CT | isbn=978-0-275-98878-4 | pages=[https://archive.org/details/killingouroceans00john/page/8 8–9] | url-access=registration | url=https://archive.org/details/killingouroceans00john/page/8 }}</ref><ref>{{Cite book |last=Williams |first=Linda Meyer |url=https://archive.org/details/earthsciencedemy0000will |title=Earth science demystified |publisher=McGraw-Hill |year=2004 |isbn=0-07-143499-2 |location=London |pages=287 |url-access=registration}}</ref> The majority of the ocean is aphotic, with the average depth of the sea being {{Convert|4267|m|ft|abbr=on}} deep; the deepest part of the sea, the [[Challenger Deep]] in the [[Mariana Trench]], is about {{Convert|11,000|m|ft|abbr=on}} deep. The depth at which the aphotic zone begins in the ocean depends on many factors. In clear, tropical water sunlight can penetrate deeper and so the aphotic zone starts at greater depths. Around the poles, the angle of the sunlight means it does not penetrate as deeply so the aphotic zone is shallower. If the water is turbid, suspended material can block light from penetrating, resulting in a shallower aphotic zone.<ref>{{Cite web |title=Adaptations |url=https://manoa.hawaii.edu/exploringourfluidearth/biological/aquatic-plants-and-algae/adaptations |url-status=live |archive-url=https://web.archive.org/web/20201021194252/https://manoa.hawaii.edu/exploringourfluidearth/biological/aquatic-plants-and-algae/adaptations |archive-date=October 21, 2020 |access-date=2020-09-29 |website=University of Hawaiʻi at Mānoa}}</ref> Temperatures can range from roughly {{convert|0|C|0}} to {{convert|6|C|0}}.{{Citation needed|date=March 2009}}

The aphotic zone is further divided into the [[Mesopelagic zone|mesopelagic]], [[Bathyal zone|bathyal]], [[Abyssal zone|abyssal]], and [[Hadal zone|hadal]] zones. The mesopelagic zone extends from {{convert|200|m|0}} to {{convert|2000|m|0}}. The bathyal zone extends from {{convert|2000|m|0}} to {{convert|4000|m|0}}. The abyssal zone extends from {{convert|4000|m|0}} to {{convert|6000|m|0}} or {{convert|6500|m|0}}, depending on the authority. The hadal zone refers to the greatest depths, deeper than the abyssal zone. Some twilight occurs in the mesopelagic zone, but creatures below the mesopelagic must be able to live in complete darkness.<ref name="invitation">{{Cite book |last=Pinet |first=Paul R. |url=https://books.google.com/books?id=a2QJNVbdjTYC |title=Invitation to Oceanography |publisher=Jones & Bartlett Publishers |year=2009 |isbn=978-0-7637-5993-3 |pages=[https://books.google.com/books?id=a2QJNVbdjTYC&pg=PA294 294] |url-access=}}</ref><ref>{{Cite book |last=Freiwald |first=Andre |url=https://books.google.com/books?id=0DHqVA02GksC&pg=PA980 |title=Cold-Water Corals and Ecosystems (Erlangen Earth Conference Series) (Erlangen Earth Conference Series) |date=20 May 2005 |publisher=Springer |isbn=978-3-540-24136-2 |pages=980}}</ref>