Editing Pelagic zone (section)

==Depth and layers==
The pelagic zone is subdivided into five vertical regions. From the top down, these are:

===Epipelagic (sunlight)===
{{See also|Photic zone|Epipelagic fish}}
{{Hatnote|From the surface ([[sea level|MSL]]) down to around {{cvt|200|m|ft}}}}

The illuminated zone at the surface of the sea with sufficient light for photosynthesis. Nearly all [[primary production]] in the ocean occurs here, and marine life is concentrated in this zone, including [[plankton]], [[Sargassum|floating seaweed]], [[jellyfish]], [[tuna]], many [[shark]]s and [[dolphin]]s.{{Citation needed|date=January 2021}}

===Mesopelagic (twilight)===
{{See also|Mesopelagic zone|Pelagic fish#Mesopelagic fish}}
{{Hatnote|From {{cvt|200|m|ft}} down to around {{cvt|1000|m|ft}}}}

The most abundant organisms thriving into the mesopelagic zone are [[heterotrophic]] bacteria.<ref>{{cite journal |last1=Mazuecos |first1=E. |last2=Arístegui |first2=J. |last3=Vázquez-Domínguez |first3=E. |last4=Ortega-Retuerta |first4=E. |last5=Gasol |first5=J.M. |last6=Reche |first6=I. |year=2012 |title=Temperature control of microbial respiration and growth efficiency in the mesopelagic zone of the South Atlantic and Indian Oceans. |journal=Deep Sea Research Part I: Oceanographic Research Papers |doi=10.3354/ame01583 |volume=95 |pages=131–138|doi-access=free |hdl=10261/95626 |hdl-access=free }}</ref> Creatures living in this zone include [[swordfish]], [[squid]], [[Anarhichadidae|wolffish]] and some species of [[cuttlefish]]. Many organisms living here are [[bioluminescence|bioluminescent]].<ref name="marinebio.com">[https://web.archive.org/web/20100410222157/http://www.marinebio.com/Oceans/open-ocean.asp The Open Ocean - MarineBio.org]</ref> Some mesopelagic creatures rise to the epipelagic zone at night to feed.<ref name="marinebio.com"/>

===Bathypelagic (midnight)===
{{See also|Bathyal zone|Pelagic fish#Bathypelagic fish}}
{{Hatnote|From {{cvt|1000|m|ft}} down to around {{cvt|4000|m|ft}}}}

The name stems {{ety|grc|[[wikt:βαθύς|βαθύς]]|deep}}. The ocean is pitch black at this depth apart from occasional [[bioluminescence|bioluminescent]] organisms, such as [[anglerfish]]. No plants live here. Most creatures survive on [[detritus]] known as "[[marine snow]]" falling from the zones above or, like the [[marine hatchetfish]], by preying on other inhabitants of this zone. Other examples of this zone's inhabitants are [[giant squid]], smaller [[squid]], [[viperfish]], [[Saccopharynx|gulper eel]], and [[dumbo octopus]].

===Abyssopelagic (abyssal zone)===
{{Main|Abyssal zone}}
{{Hatnote|From around {{cvt|4000|m|ft}} down to above the [[ocean floor]]}}

The name is derived {{ety|grc|[[wikt:ἄβυσσος|ἄβυσσος]]|bottomless}} – a holdover from times when the deep ocean was believed to be bottomless. Among the very few creatures living in the cold temperatures, high pressures and complete darkness here are several species of squid; [[echinoderm]]s including the [[basket star]], swimming cucumber, and the [[Scotoplanes|sea pig]]; and marine arthropods including the [[sea spider]]. Many species at these depths are transparent and eyeless.<ref name="marinebio.com"/>

===Hadopelagic (hadal zone)===
{{Main|Hadal zone}}

The name is derived from the realm of [[Hades]], the [[Greek underworld]]. This is the deepest part of the ocean at more than {{cvt|6000|m|ft}} or {{cvt|6500|m|ft}}, depending on authority. Such depths are generally located in [[ocean trench|trenches]].{{Citation needed|date=January 2021}}