Editing Oxygen minimum zone (section)

== Life in the OMZ ==
{{further|Microbiology of oxygen minimum zones}}
Despite the low oxygen conditions, organisms have evolved to live in and around OMZs.  For those organisms, like the [[vampire squid]], special adaptations are needed to either make do with lesser amounts of oxygen or to extract oxygen from the water more efficiently. For example, the [[Gnathophausia ingens|giant red mysid]] (''Gnathophausia ingens'') continues to live aerobically (using oxygen) in OMZs.  They have highly developed gills with large surface area and thin blood-to-water diffusion distance that enables effective removal of oxygen from the water (up to 90% O<sub>2</sub> removal from inhaled water) and an efficient circulatory system with high capacity and high blood concentration of a protein ([[hemocyanin]]) that readily binds oxygen.<ref>{{Cite journal|last1=Childress|first1=J.J.|last2=Seibel|first2=B.A.|year=1998|title=Life at stable low oxygen levels: adaptations of animals to oceanic oxygen minimum layers.|journal=The Journal of Experimental Biology|volume=201|issue=Pt 8|pages=1223–1232|doi=10.1242/jeb.201.8.1223|pmid=9510533|url=https://digitalcommons.uri.edu/bio_facpubs/15}}</ref><ref>{{Cite journal|last1=Sanders|first1=N.K.|last2=Childress|first2=J.J.|year=1990|title=Adaptations to the Deep-Sea Oxygen Minimum Layer: Oxygen Binding by the Hemocyanin of the Bathypelagic Mysid, Gnathophausia ingens Dohrn|journal=Biological Bulletin|volume=178|issue=3|pages=286–294|doi=10.2307/1541830|pmid=29314949|jstor=1541830|s2cid=33072351 |url=https://www.biodiversitylibrary.org/part/7475}}</ref><ref>{{Cite journal|last1=Torres|first1=J.J.|last2=Grigsby|first2=M.D.|last3=Clarke|first3=M.E.|year=2012|title=Aerobic and anaerobic metabolism in oxygen minimum layer fishes: the role of alcohol dehydrogenase|journal=The Journal of Experimental Biology|volume=215|issue=11|pages=1905–1914|doi=10.1242/jeb.060236|pmid=22573769|doi-access=free}}</ref>

Another strategy used by some classes of bacteria in the oxygen minimum zones is to use nitrate rather than oxygen, thus drawing down the concentrations of this important nutrient. This process is called [[denitrification]]. The oxygen minimum zones thus play an important role in regulating the productivity and ecological community structure of the global ocean.<ref>{{cite journal |doi=10.1038/nature05392 |title=Spatial coupling of nitrogen inputs and losses in the ocean |year=2006 |last1=Deutsch |first1=Curtis |last2=Sarmiento |first2=Jorge L. |last3=Sigman |first3=Daniel M. |last4=Gruber |first4=Nicolas |last5=Dunne |first5=John P. |journal=Nature |volume=445 |issue=7124 |pages=163–7 |pmid=17215838 |bibcode=2007Natur.445..163D|s2cid=10804715 }}</ref> For example, giant bacterial mats floating in the oxygen minimum zone off the west coast of [[South America]] may play a key role in the region's extremely rich fisheries, as bacterial mats the size of [[Uruguay]] have been found there.<ref>{{cite news |first=Stephen |last=Leahy |date=20 April 2010 |agency=Tierramérica |title=Giant Bacteria Colonise the Oceans |url=http://www.ipsnews.net/news.asp?idnews=51117 |publisher=[[Inter Press Service]] |url-status=dead |archive-url=https://web.archive.org/web/20100624092254/http://ipsnews.net/news.asp?idnews=51117 |archive-date=24 June 2010 }}</ref>

=== Zooplankton ===
Decreased oxygen availability results in decreases in many zooplankton species’ egg production, food intake, respiration,<ref name="Elliott2013">{{cite journal |last1=Elliott |first1=DT |last2=Pierson |first2=JJ |last3=Roman |first3=MR |date=2013 |title=Elliott, D.T., Pierson, J.J. and Roman, M.R., 2013. Predicting the effects of coastal hypoxia on vital rates of the planktonic copepod Acartia tonsa Dana |journal=PLOS ONE |volume=8 |issue=5 |page=e63987 |doi=10.1371/journal.pone.0063987 |pmc=3656935 |pmid=23691134 |doi-access=free}}</ref> and metabolic rates.<ref name="ES2015">{{cite journal |last1=Elder |first1=LE |last2=Seibel |first2=BA |date=2015 |title=Ecophysiological implications of vertical migration into oxygen minimum zones for the hyperiid amphipod Phronima sedentaria |journal=Journal of Plankton Research |volume=37 |issue=5 |pages=897–911 |doi=10.1093/plankt/fbv066 |doi-access=free}}</ref><ref name="Seibel2011">{{cite journal |last1=Seibel |first1=BA |date=2011 |title=Critical oxygen levels and metabolic suppression in oceanic oxygen minimum zones |journal=Journal of Experimental Biology |volume=214 |issue=2 |pages=326–336 |doi=10.1242/jeb.049171 |pmid=21177952 |s2cid=16469678 |doi-access=free}}</ref><ref name="Kiko2016">{{cite journal |last1=Kiko |first1=R |last2=Hauss |first2=H |last3=Bucholz |first3=F |last4=Melzner |first4=F |date=2016 |title=Ammonium excretion and oxygen respiration of tropical copepods and euphausiids exposed to oxygen minimum zone conditions |journal=Biogeosciences |volume=13 |issue=8 |pages=2241–2255 |bibcode=2016BGeo...13.2241K |doi=10.5194/bg-13-2241-2016 |doi-access=free}}</ref> Temperature and salinity in areas of decreased oxygen concentrations also affect oxygen availability. Higher temperatures and salinity lower oxygen solubility decrease the partial pressure of oxygen. This decreased partial pressure increases organisms’ respiration rates, causing the oxygen demand of the organism to increase.<ref name="Elliott2013" /><ref name="Kiko2016" />

In addition to affecting their vital functions, zooplankton alter their distribution in response to hypoxic or anoxic zones. Many species actively avoid low oxygen zones,<ref name="Elliott2012">{{cite journal |last1=Elliott |first1=DT |last2=Pierson |first2=JJ |last3=Roman |first3=MR |date=2012 |title=Relationship between environmental conditions and zooplankton community structure during summer hypoxia in the northern Gulf of Mexico. |journal=Journal of Plankton Research |volume=34 |issue=7 |pages=602–613 |doi=10.1093/plankt/fbs029 |doi-access=free}}</ref><ref name="Vanderploeg2009a">{{cite journal |last1=Vanderploeg |first1=HA |last2=Ludsin |first2=SA |last3=Cavaletto |first3=JF |last4=Höök |first4=TO |last5=Pothoven |first5=SA |last6=Brandt |first6=SB |last7=Liebig |first7=JR |last8=Lang |first8=GA |date=2009 |title=Hypoxic zones as habitat for zooplankton in Lake Erie: refuges from predation or exclusion zones? |journal=Journal of Experimental Marine Biology and Ecology |volume=381 |pages=S108–S120 |doi=10.1016/j.jembe.2009.07.015|bibcode=2009JEMBE.381S.108V }}</ref><ref name="Vanderploeg2009b">{{cite journal |last1=Vanderploeg |first1=HA |last2=Ludsin |first2=SA |last3=Ruberg |first3=SA |last4=Höök |first4=TO |last5=Pothoven |first5=SA |last6=Brandt |first6=SB |last7=Lang |first7=GA |last8=Liebig |first8=JR |last9=Cavaletto |first9=JF |date=2009 |title=Hypoxia affects spatial distributions and overlap of pelagic fish, zooplankton, and phytoplankton in Lake Erie |journal=Journal of Experimental Marine Biology and Ecology |volume=381 |pages=S92–S107 |doi=10.1016/j.jembe.2009.07.027|bibcode=2009JEMBE.381S..92V }}</ref> while others take advantage of their predators’ low tolerance for hypoxia and use these areas as a refuge.<ref name="Elliott2012" /><ref name="Vanderploeg2009a" /><ref name="Vanderploeg2009b" /> Zooplankton that exhibit daily vertical migrations to avoid predation and low oxygen conditions also excrete ammonium near the oxycline and contribute to increased anaerobic ammonium oxidation (anammox,<ref name="Bianchi2014">{{cite journal |last1=Bianchi |first1=D |last2=Babbin |first2=AR |last3=Galbraith |first3=ED |date=2014 |title=Enhancement of anammox by the excretion of diel vertical migrators |journal=Proceedings of the National Academy of Sciences |volume=111 |issue=44 |pages=15653–15658 |bibcode=2014PNAS..11115653B |doi=10.1073/pnas.1410790111 |pmc=4226083 |pmid=25288743 |doi-access=free}}</ref><ref name="Kiko2016" /> which produces N<sub>2</sub> gas. As hypoxic regions expand vertically and horizontally,<ref name="Stramma2012">{{cite journal |last1=Stramma |first1=L |last2=Prince |first2=ED |last3=Schmidtko |first3=S |last4=Luo |first4=J |last5=Hoolihan |first5=JP |last6=Visbeck |first6=M |last7=Wallace |first7=DWR |last8=Brandt |first8=P |last9=Körtzinger |first9=A |date=2012 |title=Expansion of oxygen minimum zones may reduce available habitat for tropical pelagic fishes |url=http://oceanrep.geomar.de/13127/2/Stramma.pdf |journal=Nature Climate Change |volume=2 |issue=1 |pages=33–37 |bibcode=2012NatCC...2...33S |doi=10.1038/nclimate1304 |hdl-access=free |hdl=10961/1538}}</ref><ref name="PG2006">{{cite journal |last1=Prince |first1=ED |last2=Goodyear |first2=CP |date=2006 |title=Hypoxia-based habitat compression of tropical pelagic fishes |journal=Fisheries Oceanography |volume=15 |issue=6 |pages=451–464 |doi=10.1111/j.1365-2419.2005.00393.x|bibcode=2006FisOc..15..451P }}</ref> the habitable ranges for phytoplankton, zooplankton, and [[nekton]] increasingly overlap, increasing their susceptibility to predation and human exploitation.<ref name="deMutsert2016">{{cite journal |last1=de Mutsert |first1=K |last2=Steenbeek |first2=J |last3=Lewis |first3=K |last4=Buszowski |first4=J |last5=Cowan Jr. |first5=JH |last6=Christensen |first6=V |date=2016 |title=Exploring effects of hypoxia on fish and fisheries in the northern Gulf of Mexico using a dynamic spatially explicit ecosystem model |journal=Ecological Modelling |volume=331 |pages=142–150 |bibcode=2016AGUOSAH43A..07D |doi=10.1016/j.ecolmodel.2015.10.013 |doi-access=free}}</ref><ref name="ES2015" /><ref name="Kraus2015">{{cite journal |last1=Kraus |first1=RT |last2=Secor |first2=DH |last3=Wingate |first3=RL |date=2015 |title=Testing the thermal-niche oxygen-squeeze hypothesis for estuarine striped bass |journal=Environmental Biology of Fishes |volume=98 |issue=10 |pages=2083–2092 |doi=10.1007/s10641-015-0431-3 |bibcode=2015EnvBF..98.2083K |s2cid=16052635}}</ref><ref name="Roman2012">{{cite journal |last1=Roman |first1=MR |last2=Pierson |first2=JJ |last3=Kimmel |first3=DG |last4=Boicourt |first4=WC |last5=Zhang |first5=X |date=2012 |title=Impacts of hypoxia on zooplankton spatial distributions in the northern Gulf of Mexico |journal=Estuaries and Coasts |volume=35 |issue=5 |pages=1261–1269 |doi=10.1007/s12237-012-9531-x |bibcode=2012EstCo..35.1261R |s2cid=84592608}}</ref><ref name="Vanderploeg2009a" />