Editing Benthos (section)

===Microbenthos===
{{see also|Seabed#Sediments|Marine sediment#Microbenthos|bioturbation|bioirrigation}}

Microbenthos, prefix from the Greek ''mikrós'' 'small', comprises microscopic benthic organisms that are less than about 0.1&nbsp;mm in size. Some examples are [[bacteria]], [[diatoms]], [[ciliate]]s, [[amoeba]], [[flagellate]]s.

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File:Diatoms through the microscope.jpg| [[Diatoms]]
File:Paramecium bursaria.jpg| [[Ciliate]]
File:CSIRO ScienceImage 7609 SEM dinoflagellate.jpg| [[Dinoflagellate]]s
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Marine microbenthos are microorganisms that live in the [[benthic zone]] of the ocean – that live near or on the seafloor, or within or on surface seafloor sediments.  Microbenthos are found everywhere on or about the seafloor of continental shelves, as well as in deeper waters, with greater diversity in or on seafloor sediments. In [[photic zone]]s benthic diatoms dominate as photosynthetic organisms. In [[intertidal zone]]s changing [[tide]]s strongly control opportunities for microbenthos.

<gallery mode="packed" heights="180px" style="float:left;">
File:Elphidium-incertum hg.jpg|''[[Elphidium]]'' a widespread abundant genus of benthic forams
File:FMIB 50025 Textilaria.jpeg|''[[Heterohelix]]'', an extinct genus of benthic forams
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<gallery mode="packed" heights="150px" style="float:right;" caption="Marine microanimals">
File:Gastrotrich.jpg|[[Dark field microscopy|Darkfield photo]] of a [[gastrotrich]], 0.06-3.0&nbsp;mm long, a worm-like animal living between sediment particles
File:Pliciloricus enigmatus.jpg|Armoured ''[[Pliciloricus enigmaticus]]'', about 0.2&nbsp;mm long, live in spaces between marine gravel
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Both foraminifera and diatoms have [[planktonic]] and [[benthic]] forms, that is, they can drift in the [[water column]] or live on sediment at the bottom of the ocean. Regardless of form, their shells sink to the seafloor after they die. These shells are widely used as [[climate proxy|climate proxies]]. The chemical composition of the shells are a consequence of the chemical composition of the ocean at the time the shells were formed. Past water temperatures can be also be inferred from the ratios of stable [[oxygen isotope]]s in the shells, since lighter isotopes evaporate more readily in warmer water leaving the heavier isotopes in the shells. Information about past climates can be inferred further from the abundance of forams and diatoms, since they tend to be more abundant in warm water.<ref>Bruckner, Monica (2020) [https://serc.carleton.edu/microbelife/topics/proxies/index.html"Paleoclimatology: How Can We Infer Past Climates?"] ''[[Science Education Resource Center|SERC]]'', Carleton College. Modified 23 July 2020. Retrieved 10 September 2020.</ref>[[File:Benthic Diatom.jpg|thumb|{{center|Benthic diatom}}]]The sudden [[Cretaceous–Paleogene extinction event|extinction event]] which killed the dinosaurs 66 million years ago also rendered extinct three-quarters of all other animal and plant species. However, deep-sea benthic forams flourished in the aftermath. In 2020 it was reported that researchers have examined the chemical composition of thousands of samples of these benthic forams and used their findings to build the most detailed climate record of Earth ever.<ref>[https://www.livescience.com/oldest-climate-record-ever-cenozoic-era.html Earth barreling toward 'Hothouse' state not seen in 50 million years, epic new climate record shows] ''LiveScience'', 10 September 2020.</ref><ref name="Westerhold2020">{{cite journal | url=https://www.science.org/doi/10.1126/science.aba6853 | doi=10.1126/science.aba6853 | title=An astronomically dated record of Earth's climate and its predictability over the last 66 million years | year=2020 | last1=Westerhold | first1=Thomas | last2=Marwan | first2=Norbert | last3=Drury | first3=Anna Joy | last4=Liebrand | first4=Diederik | last5=Agnini | first5=Claudia | last6=Anagnostou | first6=Eleni | last7=Barnet | first7=James S. K. | last8=Bohaty | first8=Steven M. | last9=De Vleeschouwer | first9=David | last10=Florindo | first10=Fabio | last11=Frederichs | first11=Thomas | last12=Hodell | first12=David A. | last13=Holbourn | first13=Ann E. | last14=Kroon | first14=Dick | last15=Lauretano | first15=Vittoria | last16=Littler | first16=Kate | last17=Lourens | first17=Lucas J. | last18=Lyle | first18=Mitchell | last19=Pälike | first19=Heiko | last20=Röhl | first20=Ursula | last21=Tian | first21=Jun | last22=Wilkens | first22=Roy H. | last23=Wilson | first23=Paul A. | last24=Zachos | first24=James C. | journal=Science | volume=369 | issue=6509 | pages=1383–1387 | pmid=32913105 | bibcode=2020Sci...369.1383W | hdl=11577/3351324 | s2cid=221593388 | hdl-access=free }}</ref>

Some [[endolith]]s have extremely long lives. In 2013 researchers reported evidence of endoliths in the ocean floor, perhaps millions of years old, with a generation time of 10,000 years.<ref>Bob Yirka [http://phys.org/news/2013-08-soil-beneath-ocean-harbor-bacteria.html 29 Aug 2013]</ref> These are slowly metabolizing and not in a dormant state. Some [[Actinomycetota]] found in [[Siberia]] are estimated to be half a million years old.<ref>[http://www.guardian.co.uk/theobserver/2010/may/02/rachel-sussman-oldest-plants Sussman: Oldest Plants], [[The Guardian]], 2 May 2010</ref><ref>{{Cite web |url=https://www.itsokaytobesmart.com/post/91481365622/siberian-actinobacteria-oldest-living-thing |title=It's Okay to be Smart • the oldest living thing in the world: These |access-date=2018-07-13 |archive-url=https://web.archive.org/web/20180713074804/https://www.itsokaytobesmart.com/post/91481365622/siberian-actinobacteria-oldest-living-thing |archive-date=2018-07-13 |url-status=dead }}</ref><ref>{{Cite journal|title=Ancient bacteria show evidence of DNA repair|first1=Eske |last1=Willerslev|first2=Duane |last2=Froese|first3=David |last3=Gilichinsky|first4=Regin |last4=Rønn|first5=Michael|last5=Bunce|first6=Maria T.|last6=Zuber |first7=M. Thomas P.|last7=Gilbert |first8=Tina |last8=Brand |first9=Kasper |last9=Munch |first10=Rasmus|last10=Nielsen |first11=Mikhail|last11=Mastepanov|first12=Torben R. |last12=Christensen |first13=Martin B.|last13=Hebsgaard |first14=Sarah Stewart|last14=Johnson |date=4 September 2007|journal=Proceedings of the National Academy of Sciences|volume=104|issue=36|pages=14401–14405|doi=10.1073/pnas.0706787104 |pmid=17728401|pmc=1958816 |bibcode=2007PNAS..10414401J|doi-access=free }}</ref>

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