bathypelagic zone

File:Oceanic_basin.svg

The bathypelagic zone is characterized by a nearly constant temperature of approximately {{convert|4|C|F}} and a salinity range of 33-35 g/kg. This region has little to no light because sunlight does not reach this deep in the ocean and bioluminescence is limited.{{Cite book |last=Miller |first=Charles B. |url=https://www.worldcat.org/oclc/768606918 |title=Biological oceanography |date=2012 |publisher=John Wiley & Sons |others=Patricia Wheeler |isbn=978-1-4443-3301-5 |edition=2nd |location=Hoboken, NJ |oclc=768606918}} The hydrostatic pressure in this zone ranges from 100-400 atmospheres (atm) due to the increase of 1 atm for every 10 m depth.{{Cite web |title=Woods Hole Oceanographic Institution |url=https://www.whoi.edu |access-date=2022-12-01 |website=Woods Hole Oceanographic Institution |language=en-US}} It is believed that these conditions have been consistent for the past 8000 years.

This ocean depth spans from the edge of the continental shelf down to the top of the abyssal zone, and along continental slope depths.{{Cite book |url=https://www.worldcat.org/oclc/646756756 |title=Advances in marine biology. Volume 32, The biogeography of the oceans |date=1997 |publisher=Academic Press |others=A. J. Southward, J. H. S. Blaxter |isbn=0-12-026132-4 |location=London |oclc=646756756}} The bathymetry of the bathypelagic zone consists of limited areas where the seafloor is in this depth range along the deepest parts of the continental margins, as well as seamounts and mid-ocean ridges.{{Cite book |last=Marjo. |first=Agostini, Vera N. Vierros |url=http://worldcat.org/oclc/554853878 |title=Global Open Oceans and Deep Seabed (GOODS) biogeographic classification |date=2009 |publisher=UNESCO, Intergovernmental Oceanographic Commission |oclc=554853878}} The continental slopes are mostly made up of accumulated sediment, while seamounts and mid-ocean ridges contain large areas of hard substrate that provide habitats for bathypelagic fishes and benthic invertebrates. Although currents at these depths are very slow, the topography of seamounts interrupts the currents and creates eddies that retain plankton in the seamount region, thus increasing fauna nearby as well{{Cite web |last=US Department of Commerce, National Oceanic and Atmospheric Administration |date=11 November 2022 |title=The Global Conveyor Belt - Currents: NOAA's National Ocean Service Education |url=https://oceanservice.noaa.gov}}

Hydrothermal vents are also a common feature in some areas of the bathypelagic zone and are primarily formed from the spreading of Earth's tectonic plates at mid-ocean ridges.{{Cite journal |last1=Beaulieu |first1=Stace E. |last2=Baker |first2=Edward T. |last3=German |first3=Christopher R. |last4=Maffei |first4=Andrew |date=November 2013 |title=An authoritative global database for active submarine hydrothermal vent fields: GLOBAL VENTS DATABASE |url=http://doi.wiley.com/10.1002/2013GC004998 |journal=Geochemistry, Geophysics, Geosystems |language=en |volume=14 |issue=11 |pages=4892–4905 |doi=10.1002/2013GC004998|s2cid=53604809 |hdl=1912/6496 |hdl-access=free }} As the bathypelagic region lacks light, these vents play an important role in global ocean chemical processes, thus supporting unique ecosystems that have adapted to utilize chemicals as energy, via chemoautotrophy, instead of sunlight, to sustain themselves.{{Cite journal |last=TIVEY |first=MARGARET KINGSTON |date=2007 |title=Generation of Seafloor Hydrothermal Vent Fluids and Associated Mineral Deposits |url=https://www.jstor.org/stable/24859975 |journal=Oceanography |volume=20 |issue=1 |pages=50–65 |doi=10.5670/oceanog.2007.80 |jstor=24859975 |issn=1042-8275|hdl=1912/2775 |hdl-access=free }}{{Cite web |title=Hydrothermal Vents - Woods Hole Oceanographic Institution |url=https://www.whoi.edu/know-your-ocean/ocean-topics/how-the-ocean-works/seafloor-below/hydrothermal-vents/ |access-date=2022-12-01 |website= |language=en-US}} In addition, hydrothermal vents facilitate precipitation of minerals on the seafloor,{{Cite journal |last1=Van Dover |first1=C. L. |last2=Arnaud-Haond |first2=S. |last3=Gianni |first3=M. |last4=Helmreich |first4=S. |last5=Huber |first5=J. A. |last6=Jaeckel |first6=A. L. |last7=Metaxas |first7=A. |last8=Pendleton |first8=L. H. |last9=Petersen |first9=S. |last10=Ramirez-Llodra |first10=E. |last11=Steinberg |first11=P. E. |last12=Tunnicliffe |first12=V. |last13=Yamamoto |first13=H. |date=2018-04-01 |title=Scientific rationale and international obligations for protection of active hydrothermal vent ecosystems from deep-sea mining |url= |journal=Marine Policy |language=en |volume=90 |pages=20–28 |doi=10.1016/j.marpol.2018.01.020 |issn=0308-597X|hdl=1721.1/134956.2 |hdl-access=free }} making them regions of interest for deep-sea mining.{{Cite journal |last1=Miller |first1=Kathryn A. |last2=Thompson |first2=Kirsten F. |last3=Johnston |first3=Paul |last4=Santillo |first4=David |date=2018 |title=An Overview of Seabed Mining Including the Current State of Development, Environmental Impacts, and Knowledge Gaps |journal=Frontiers in Marine Science |volume=4 |doi=10.3389/fmars.2017.00418 |issn=2296-7745|doi-access=free |hdl=10871/130175 |hdl-access=free }}{{Cite web |last=GAO Science, Technology Assessment, and Analytics |date=November 2022 |title=DEEP-SEA MINING |url=https://www.gao.gov/assets/720/718170.pdf}}

File:Champagne_vent_white_smokers.jpg on the Northwest Eifuku seamount.]]

Many of the biogeochemical processes in the bathypelagic region are dependent upon the input of organic matter from the overlying epipelagic and mesopelagic zones. This organic material, sometimes called marine snow, sinks in the water column or is transported within downward convected water masses such as the Thermohaline Circulation. Hydrothermal vents also deliver heat and chemicals such as sulfide and methane.{{Cite journal |last1=Sweetman |first1=Ak |last2=Levin |first2=La |last3=Rapp |first3=Ht |last4=Schander |first4=C |date=2013-01-21 |title=Faunal trophic structure at hydrothermal vents on the southern Mohn's Ridge, Arctic Ocean |url=http://www.int-res.com/abstracts/meps/v473/p115-131/ |journal=Marine Ecology Progress Series |language=en |volume=473 |pages=115–131 |doi=10.3354/meps10050 |bibcode=2013MEPS..473..115S |issn=0171-8630|hdl=1956/19293 |hdl-access=free }} These chemicals can be utilized to sustain metabolism by organisms in the region.{{Cite journal |last1=Arístegui |first1=Javier |last2=Gasol |first2=Josep M. |last3=Duarte |first3=Carlos M. |last4=Herndld |first4=Gerhard J. |date=September 2009 |title=Microbial oceanography of the dark ocean's pelagic realm |url=|journal=Limnology and Oceanography |language=en |volume=54 |issue=5 |pages=1501–1529 |doi=10.4319/lo.2009.54.5.1501 |bibcode=2009LimOc..54.1501A |s2cid=11348058 |issn=0024-3590|hdl=10553/1417 |hdl-access=free }} Our understanding of these biogeochemical processes has historically been limited due to the difficulty and cost of collecting samples from these ocean depths. Other technological challenges, such as measuring microbial activity under the pressure conditions experienced in the bathypelagic zone, have also restricted our knowledge of the region. Although scientific advancements have increased our understanding over the past several decades, many aspects remain a mystery.{{Cite journal |last1=Carlson |first1=Craig A. |last2=Hansell |first2=Dennis A. |last3=Nelson |first3=Norman B. |last4=Siegel |first4=David A. |last5=Smethie |first5=William M. |last6=Khatiwala |first6=Samar |last7=Meyers |first7=Meredith M. |last8=Halewood |first8=Elisa |date=August 2010 |title=Dissolved organic carbon export and subsequent remineralization in the mesopelagic and bathypelagic realms of the North Atlantic basin |url= |journal=Deep Sea Research Part II: Topical Studies in Oceanography |language=en |volume=57 |issue=16 |pages=1433–1445 |doi=10.1016/j.dsr2.2010.02.013|bibcode=2010DSRII..57.1433C }}{{Cite journal |last1=del Giorgio |first1=Paul A. |last2=Duarte |first2=Carlos M. |date=November 2002 |title=Respiration in the open ocean |url=http://www.nature.com/articles/nature01165 |journal=Nature |language=en |volume=420 |issue=6914 |pages=379–384 |doi=10.1038/nature01165 |pmid=12459775 |bibcode=2002Natur.420..379D |s2cid=4392859 |issn=0028-0836|url-access=subscription }} One of the major areas of current research is focused on understanding carbon remineralization rates in the region. Prior studies have struggled to quantify the rates at which prokaryotes in this region remineralize carbon because previously developed techniques may not be adequate for this region, and indicate remineralization rates much higher than expected. Further work is needed to explore this question, and may require revisions to our understanding of the global carbon cycle.

File:Marine_snow.jpg (marine snow) traveling through the water column.]]

Organic material from primary production in the epipelagic zone, and to a far lesser extent, organic inputs from terrestrial sources, make up a majority of the Particulate Organic Matter (POM) in the ocean. POM is delivered to the bathypelagic zone via sinking copepod fecal pellets and dead organisms; these parcels of organic matter fall through the water column and deliver organic carbon, nitrogen, and phosphorus, to organisms that live below the photic zone. These parcels are sometimes referred to as marine snow or ocean dandruff. This is also the dominant delivery mechanism of food to organisms in the bathypelagic zone because there is no sunlight for photosynthesis, with chemoautotrophy playing a more minor role as far as we know.{{Cite journal |last1=Honjo |first1=Susumu |last2=Eglinton |first2=Timothy |last3=Taylor |first3=Craig |last4=Ulmer |first4=Kevin |last5=Sievert |first5=Stefan |last6=Bracher |first6=Astrid |last7=German |first7=Christopher |last8=Edgcomb |first8=Virginia |last9=Francois |first9=Roger |last10=Iglesias-Rodriguez |first10=M. Debora |last11=Van Mooy |first11=Benjamin |last12=Rapeta |first12=Daniel |date=2014-09-01 |title=Understanding the Role of the Biological Pump in the Global Carbon Cycle: An Imperative for Ocean Science |url=https://tos.org/oceanography/article/understanding-the-role-of-the-biological-pump-in-the-globalcarbon-cycle-an- |journal=Oceanography |volume=27 |issue=3 |pages=10–16 |doi=10.5670/oceanog.2014.78|doi-access=free |hdl=1912/6863 |hdl-access=free }}{{Cite journal |last1=Nagata |first1=Toshi |last2=Tamburini |first2=Christian |last3=Arístegui |first3=Javier |last4=Baltar |first4=Federico |last5=Bochdansky |first5=Alexander B. |last6=Fonda-Umani |first6=Serena |last7=Fukuda |first7=Hideki |last8=Gogou |first8=Alexandra |last9=Hansell |first9=Dennis A. |last10=Hansman |first10=Roberta L. |last11=Herndl |first11=Gerhard J. |last12=Panagiotopoulos |first12=Christos |last13=Reinthaler |first13=Thomas |last14=Sohrin |first14=Rumi |last15=Verdugo |first15=Pedro |date=August 2010 |title=Emerging concepts on microbial processes in the bathypelagic ocean – ecology, biogeochemistry, and genomics |url= |journal=Deep Sea Research Part II: Topical Studies in Oceanography |language=en |volume=57 |issue=16 |pages=1519–1536 |doi=10.1016/j.dsr2.2010.02.019|bibcode=2010DSRII..57.1519N }}

As POM sinks through the water column, it is consumed by organisms which deplete it of nutrients. The size and density of these particles affect their likelihood of reaching organisms in the bathypelagic zone. Smaller parcels of POM often become aggregated together as they fall, which quickens their descent and prohibits their consumption by other organisms, increasing their likelihood of reaching lower depths.{{Cite journal |last=Jackson |first=G.A. |date=2002 |title=Collecting The Garbage Of The Sea: The Role Of Aggregation In Ocean Carbon Transport |journal= |pages=20}}{{Citation |last1=Arístegui |first1=Javier |title=Respiration in the mesopelagic and bathypelagic zones of the oceans |date=2005-01-06 |url=http://dx.doi.org/10.1093/acprof:oso/9780198527084.003.0010 |work=Respiration in Aquatic Ecosystems |pages=181–205 |publisher=Oxford University Press |access-date=2022-12-01 |last2=Agustí |first2=Susana |last3=Middelburg |first3=Jack J. |last4=Duarte |first4=Carlos M.|doi=10.1093/acprof:oso/9780198527084.003.0010 |isbn=978-0-19-852708-4 |hdl=10553/51651 |hdl-access=free }} The density of these particles may be increased in some regions where minerals associated with some forms of phytoplankton, such as biogenic silica and calcium carbonate "ballast" resulting in more rapid transport to deeper depth.{{Cite journal |last1=Francois |first1=Roger |last2=Honjo |first2=Susumu |last3=Krishfield |first3=Richard |last4=Manganini |first4=Steve |date=December 2002 |title=Factors controlling the flux of organic carbon to the bathypelagic zone of the ocean: FACTORS CONTROLLING ORGANIC CARBON FLUX |journal=Global Biogeochemical Cycles |language=en |volume=16 |issue=4 |pages=34–1–34-20 |doi=10.1029/2001GB001722|s2cid=128876389 |doi-access=free }}

{{See also|Oceanic carbon cycle}}

A majority of organic carbon is produced in the epipelagic zone, with a small portion transported deeper into the ocean interior. This process, known as the biological pump, plays a large role in the sequestration of carbon from the atmosphere into the ocean. Organic carbon is primarily exported to the bathypelagic zone in the form of particulate organic carbon (POC) and dissolved organic carbon (DOC).{{Cite journal |last1=Burd |first1=Adrian B. |last2=Hansell |first2=Dennis A. |last3=Steinberg |first3=Deborah K. |last4=Anderson |first4=Thomas R. |last5=Arístegui |first5=Javier |last6=Baltar |first6=Federico |last7=Beaupré |first7=Steven R. |last8=Buesseler |first8=Ken O. |last9=DeHairs |first9=Frank |last10=Jackson |first10=George A. |last11=Kadko |first11=David C. |last12=Koppelmann |first12=Rolf |last13=Lampitt |first13=Richard S. |last14=Nagata |first14=Toshi |last15=Reinthaler |first15=Thomas |date=August 2010 |title=Assessing the apparent imbalance between geochemical and biochemical indicators of meso- and bathypelagic biological activity: What the @$♯! is wrong with present calculations of carbon budgets? |url= https://scholarworks.wm.edu/vimsarticles/946|journal=Deep Sea Research Part II: Topical Studies in Oceanography |language=en |volume=57 |issue=16 |pages=1557–1571 |doi=10.1016/j.dsr2.2010.02.022|bibcode=2010DSRII..57.1557B |hdl=10553/51638 |hdl-access=free }}

POC is the largest component of organic carbon delivered to the bathypelagic zone; it primarily takes the form of fecal pellets and dead organisms that sink out of the surface waters and fall toward the ocean floor. Regions with higher primary productivity where particles are able to sink quickly, such as equatorial upwelling zones and the Arabian Sea, have the greatest amount of POC delivery to the bathypelagic zone.{{Cite journal |last1=Antia |first1=Avan N. |last2=Koeve |first2=Wolfgang |last3=Fischer |first3=Gerhard |last4=Blanz |first4=Thomas |last5=Schulz-Bull |first5=Detlef |last6=Schölten |first6=Jan |last7=Neuer |first7=Susanne |last8=Kremling |first8=Klaus |last9=Kuss |first9=Joachim |last10=Peinert |first10=Rolf |last11=Hebbeln |first11=Dirk |last12=Bathmann |first12=Ulrich |last13=Conte |first13=Maureen |last14=Fehner |first14=Uwe |last15=Zeitzschel |first15=B. |date=December 2001 |title=Basin-wide particulate carbon flux in the Atlantic Ocean: Regional export patterns and potential for atmospheric CO 2 sequestration |journal=Global Biogeochemical Cycles |language=en |volume=15 |issue=4 |pages=845–862 |doi=10.1029/2000GB001376|bibcode=2001GBioC..15..845A |s2cid=53462171 |doi-access=free }}

The vertical mixing of DOC-rich surface waters is also a process that delivers carbon to the bathypelagic zone, however, it constitutes a substantially smaller portion of overall transport than POC delivery. DOC transport occurs most readily in regions with high rates of ventilation or ocean turnover, such as the interior of gyres or deep water formation sites along the thermohaline circulation.

The region in the water column at which calcite dissolution begins to occur rapidly, known as the lysocline, is typically located near the base bathypelagic zone at approximately 3,500 m depth, but varies among ocean basins.Chen CTA, Feely RA, Gendron JF. 1988. Lysocline, calcium carbonate compensation depth, and calcareous sediments in the North Pacific Ocean. Pac Sci 42(3-4): 237-252. The lysocline lies below the saturation depth (the transition to undersaturated conditions with respect to calcium carbonate) and above the carbonate compensation depth (below which there is no calcium carbonate preservation). In a supersaturated environment, the tests of calcite-forming organisms are preserved as they sink toward the sea floor, resulting in sediments with relatively high amounts of CaCO₃. However, as depth and pressure increase and temperature decreases, the solubility of calcium carbonate also increases, which results in more dissolution and less net transport to the deeper, underlying seafloor. As a result of this rapid change in dissolution rates, sediments in the bathypelagic region vary widely in CaCO₃ content and burial.{{Citation |last=Broecker |first=W.S. |title=The Oceanic CaCO3 Cycle |date=2003 |url=https://linkinghub.elsevier.com/retrieve/pii/B0080437516061193 |journal=Treatise on Geochemistry |volume=6 |pages=529–549 |publisher=Elsevier |language=en |doi=10.1016/B0-08-043751-6/06119-3 |bibcode=2003TrGeo...6..529B |isbn=978-0-08-043751-4 |access-date=2022-12-01|url-access=subscription }}

The ecology of the bathypelagic ecosystem is constrained by its lack of sunlight and primary producers, with limited production of microbial biomass via autotrophy. The trophic networks in this region rely on particulate organic matter (POM) that sinks from the epipelagic and mesopelagic water, and oxygen inputs from the thermohaline circulation.{{Cite book |url=http://dx.doi.org/10.2305/iucn.ch.2020.13.en |title=IUCN Global Ecosystem Typology 2.0: descriptive profiles for biomes and ecosystem functional groups |date=2020-12-15 |publisher=IUCN, International Union for Conservation of Nature |doi=10.2305/iucn.ch.2020.13.en |isbn=978-2-8317-2077-7 |s2cid=241360441 |editor-last=Keith |editor-first=David A. |editor-last2=Ferrer-Paris |editor-first2=Jose R. |editor-last3=Nicholson |editor-first3=Emily |editor-last4=Kingsford |editor-first4=Richard T.}} Despite these limitations, this open-ocean ecosystem is home to microbial organisms, fish, and nekton.

File:RT8-4.jpg, Crenarchaeaota are linked to dissolved inorganic carbon fixation.]]

A comprehensive understanding of the inputs driving the microbial ecology in the bathypelagic zone is lacking due to limited observational data, but has been improving with advancements in deep-sea technology. A majority of our knowledge of ocean microbial activity comes from studies of the shallower regions of the ocean because it is easier to access, and it was previously assumed that deeper water did not have suitable physical conditions for diverse microbial communities. The bathypelagic zone receives inputs of organic material and POM from the surface ocean on the order of 1-3.6 Pg C/year.{{Cite journal |last1=Jannasch |first1=Holger W. |last2=Wirsen |first2=Carl O. |date=1973-05-11 |title=Deep-Sea Microorganisms: In situ Response to Nutrient Enrichment |url=http://dx.doi.org/10.1126/science.180.4086.641 |journal=Science |volume=180 |issue=4086 |pages=641–643 |doi=10.1126/science.180.4086.641 |pmid=17774289 |bibcode=1973Sci...180..641J |s2cid=7037952 |issn=0036-8075|url-access=subscription }}{{Citation |last=Hansell |first=Dennis A. |title=DOC in the Global Ocean Carbon Cycle |date=2002 |url=http://dx.doi.org/10.1016/b978-012323841-2/50017-8 |work=Biogeochemistry of Marine Dissolved Organic Matter |pages=685–715 |publisher=Elsevier |doi=10.1016/b978-012323841-2/50017-8 |isbn=9780123238412 |access-date=2022-12-01|url-access=subscription }}{{Cite journal |last1=Martin |first1=John H. |last2=Knauer |first2=George A. |last3=Karl |first3=David M. |last4=Broenkow |first4=William W. |date=February 1987 |title=VERTEX: carbon cycling in the northeast Pacific |url=http://dx.doi.org/10.1016/0198-0149(87)90086-0 |journal=Deep Sea Research Part A. Oceanographic Research Papers |volume=34 |issue=2 |pages=267–285 |doi=10.1016/0198-0149(87)90086-0 |bibcode=1987DSRA...34..267M |issn=0198-0149|url-access=subscription }}

Prokaryote biomass in the bathypelagic is dependent and thus correlated with the amount of sinking POM and organic carbon availability. These essential organic carbon inputs for microbes typically decrease with depth as they are utilized while sinking to the bathypelagic.{{Cite journal |last1=Nagata |first1=Toshi |last2=Fukuda |first2=Hideki |last3=Fukuda |first3=Rumi |last4=Koike |first4=Isao |date=March 2000 |title=Bacterioplankton distribution and production in deep Pacific waters: Large-scale geographic variations and possible coupling with sinking particle fluxes |url=http://dx.doi.org/10.4319/lo.2000.45.2.0426 |journal=Limnology and Oceanography |volume=45 |issue=2 |pages=426–435 |doi=10.4319/lo.2000.45.2.0426 |bibcode=2000LimOc..45..426N |s2cid=85409928 |issn=0024-3590|url-access=subscription }}{{Cite journal |last1=Reinthaler |first1=Thomas |last2=van Aken |first2=Hendrik |last3=Veth |first3=Cornelis |last4=Arístegui |first4=Javier |last5=Robinson |first5=Carol |last6=Williams |first6=Peter J. le B. |last7=Lebaron |first7=Philippe |last8=Herndl |first8=Gerhard J. |date=May 2006 |title=Prokaryotic respiration and production in the meso- and bathypelagic realm of the eastern and western North Atlantic basin |url=http://dx.doi.org/10.4319/lo.2006.51.3.1262 |journal=Limnology and Oceanography |volume=51 |issue=3 |pages=1262–1273 |doi=10.4319/lo.2006.51.3.1262 |bibcode=2006LimOc..51.1262R |hdl=10553/1199 |s2cid=17568366 |issn=0024-3590|hdl-access=free }} Microbial production varies over six orders of magnitude based on resource availability in a given area. Prokaryote abundance can range from 0.03-2.3x105 cells ml⁻¹, and have population turnover times that can range from 0.1–30 years. Archaea make up a larger portion of the total prokaryote cell abundance, and different groups have different growth needs, with some archaea groups for example utilizing amino acid groups more readily than others.{{Cite journal |last1=Karner |first1=Markus B. |last2=DeLong |first2=Edward F. |last3=Karl |first3=David M. |date=January 2001 |title=Archaeal dominance in the mesopelagic zone of the Pacific Ocean |url=http://dx.doi.org/10.1038/35054051 |journal=Nature |volume=409 |issue=6819 |pages=507–510 |doi=10.1038/35054051 |pmid=11206545 |bibcode=2001Natur.409..507K |s2cid=6789859 |issn=0028-0836|url-access=subscription }}{{Cite journal |last1=Herndl |first1=Gerhard J. |last2=Reinthaler |first2=Thomas |last3=Teira |first3=Eva |last4=van Aken |first4=Hendrik |last5=Veth |first5=Cornelius |last6=Pernthaler |first6=Annelie |last7=Pernthaler |first7=Jakob |date=May 2005 |title=Contribution of Archaea to Total Prokaryotic Production in the Deep Atlantic Ocean |journal=Applied and Environmental Microbiology |volume=71 |issue=5 |pages=2303–2309 |doi=10.1128/AEM.71.5.2303-2309.2005 |issn=0099-2240 |pmc=1087563 |pmid=15870315|bibcode=2005ApEnM..71.2303H }} Some archaea like Crenarchaeota have Crenarchaeota 16S rRNA and archaeal amoA gene abundances correlated to dissolved inorganic carbon (DIC) fixation.{{Cite journal |last1=Hansman |first1=Roberta L. |last2=Griffin |first2=Sheila |last3=Watson |first3=Jordan T. |last4=Druffel |first4=Ellen R. M. |last5=Ingalls |first5=Anitra E. |last6=Pearson |first6=Ann |last7=Aluwihare |first7=Lihini I. |date=2009-04-21 |title=The radiocarbon signature of microorganisms in the mesopelagic ocean |journal=Proceedings of the National Academy of Sciences of the United States of America |volume=106 |issue=16 |pages=6513–6518 |doi=10.1073/pnas.0810871106 |issn=0027-8424 |pmc=2672484 |pmid=19366673|bibcode=2009PNAS..106.6513H |doi-access=free }}{{Cite journal |last1=Wuchter |first1=Cornelia |last2=Schouten |first2=Stefan |last3=Boschker |first3=Henricus T.S. |last4=Sinninghe Damsté |first4=Jaap S. |date=February 2003 |title=Bicarbonate uptake by marine Crenarchaeota |journal=FEMS Microbiology Letters |volume=219 |issue=2 |pages=203–207 |doi=10.1016/s0378-1097(03)00060-0 |pmid=12620621 |issn=0378-1097|doi-access=free }}{{Cite journal |last1=Pearson |first1=A. |last2=McNichol |first2=A.P. |last3=Benitez-Nelson |first3=B.C. |last4=Hayes |first4=J.M. |last5=Eglinton |first5=T.I. |date=September 2001 |title=Origins of lipid biomarkers in Santa Monica Basin surface sediment: a case study using compound-specific Δ 14 C analysis |url=http://dx.doi.org/10.1016/s0016-7037(01)00657-3 |journal=Geochimica et Cosmochimica Acta |volume=65 |issue=18 |pages=3123–3137 |doi=10.1016/s0016-7037(01)00657-3 |bibcode=2001GeCoA..65.3123P |issn=0016-7037|url-access=subscription }} The utilization of DIC is thought to be fueled by the oxidation of ammonium{{Cite journal |last1=Könneke |first1=Martin |last2=Bernhard |first2=Anne E. |last3=de la Torre |first3=José R. |last4=Walker |first4=Christopher B. |last5=Waterbury |first5=John B. |last6=Stahl |first6=David A. |date=September 2005 |title=Isolation of an autotrophic ammonia-oxidizing marine archaeon |url=http://dx.doi.org/10.1038/nature03911 |journal=Nature |volume=437 |issue=7058 |pages=543–546 |doi=10.1038/nature03911 |pmid=16177789 |bibcode=2005Natur.437..543K |s2cid=4340386 |issn=0028-0836|url-access=subscription }}{{Cite journal |last1=Wuchter |first1=Cornelia |last2=Abbas |first2=Ben |last3=Coolen |first3=Marco J. L. |last4=Herfort |first4=Lydie |last5=van Bleijswijk |first5=Judith |last6=Timmers |first6=Peer |last7=Strous |first7=Marc |last8=Teira |first8=Eva |last9=Herndl |first9=Gerhard J. |last10=Middelburg |first10=Jack J. |last11=Schouten |first11=Stefan |last12=Sinninghe Damsté |first12=Jaap S. |date=2006-08-15 |title=Archaeal nitrification in the ocean |journal=Proceedings of the National Academy of Sciences |volume=103 |issue=33 |pages=12317–12322 |doi=10.1073/pnas.0600756103 |pmid=16894176 |pmc=1533803 |bibcode=2006PNAS..10312317W |issn=0027-8424|doi-access=free }}{{Cite journal |last1=Beman |first1=J. Michael |last2=Popp |first2=Brian N. |last3=Francis |first3=Christopher A. |date=April 2008 |title=Molecular and biogeochemical evidence for ammonia oxidation by marine Crenarchaeota in the Gulf of California |journal=The ISME Journal |language=en |volume=2 |issue=4 |pages=429–441 |doi=10.1038/ismej.2007.118 |pmid=18200070 |s2cid=8607463 |issn=1751-7370|doi-access=free }} and is one form of chemoautotrophy. Based on regional variation and differences in prokaryote abundance, heterotrophic prokaryote production, and particulate organic carbon (POC) inputs to the bathypelagic zone.

Research to quantify bacterial-consuming grazers, like heterotrophic eukaryotes, has been limited by difficulties in sampling. Oftentimes organisms do not survive being brought to the surface due to experiencing drastic pressure changes in a short amount of time.{{Cite journal |last1=Edgcomb |first1=Virginia P. |last2=Beaudoin |first2=David |last3=Gast |first3=Rebecca |last4=Biddle |first4=Jennifer F. |last5=Teske |first5=Andreas |date=2010-08-01 |title=Marine subsurface eukaryotes: the fungal majority |url=http://dx.doi.org/10.1111/j.1462-2920.2010.02318.x |journal=Environmental Microbiology |volume=13 |issue=1 |pages=172–183 |doi=10.1111/j.1462-2920.2010.02318.x |pmid=21199255 |issn=1462-2912|url-access=subscription }} Work is underway to quantify cell abundance and biomass, but due to poor survival, it is difficult to get accurate counts. In more recent years there has been an effort to categorize the diversity of the eukaryotic assemblages in the bathypelagic zone using methods to assess the genetic compositions of microbial communities based on supergroups, which is a way to classify organisms that have common ancestry. Some important groups of bacterial grazers include Rhizaria, Alveolata, Fungi, Stramenopiles, Amoebozoa, and Excavata (listed from most to least abundant), with the remaining composition classified as uncertain or other.{{Cite journal |last1=Pernice |first1=Massimo C |last2=Giner |first2=Caterina R |last3=Logares |first3=Ramiro |last4=Perera-Bel |first4=Júlia |last5=Acinas |first5=Silvia G |last6=Duarte |first6=Carlos M |last7=Gasol |first7=Josep M |last8=Massana |first8=Ramon |date=April 2016 |title=Large variability of bathypelagic microbial eukaryotic communities across the world's oceans |journal=The ISME Journal |language=en |volume=10 |issue=4 |pages=945–958 |doi=10.1038/ismej.2015.170 |pmid=26451501 |pmc=4796934 |issn=1751-7362}}

Viruses influence biogeochemical cycling through the role they play in marine food webs.{{Cite journal |last=Weinbauer |first=Markus G. |date=May 2004 |title=Ecology of prokaryotic viruses |journal=FEMS Microbiology Reviews |volume=28 |issue=2 |pages=127–181 |doi=10.1016/j.femsre.2003.08.001 |pmid=15109783 |s2cid=3495147 |issn=1574-6976|doi-access=free }}{{Cite journal |last1=Motegi |first1=Chiaki |last2=Nagata |first2=Toshi |last3=Miki |first3=Takeshi |last4=Weinbauer |first4=Markus G. |last5=Legendre |first5=Louis |last6=Rassoulzadegand |first6=Fereidoun |date=2009-08-10 |title=Viral control of bacterial growth efficiency in marine pelagic environments |journal=Limnology and Oceanography |volume=54 |issue=6 |pages=1901–1910 |doi=10.4319/lo.2009.54.6.1901 |bibcode=2009LimOc..54.1901M |s2cid=86571536 |issn=0024-3590|doi-access=free }}{{Citation |last1=Breitbart |first1=Mya |title=Marine Viruses: Community Dynamics, Diversity and Impact on Microbial Processes |url=http://dx.doi.org/10.1002/9780470281840.ch12 |work=Microbial Ecology of the Oceans |pages=443–479 |place=Hoboken, NJ, USA |publisher=John Wiley & Sons, Inc. |access-date=2022-12-01 |last2=Middelboe |first2=Mathias |last3=Rohwer |first3=Forest|year=2008 |doi=10.1002/9780470281840.ch12 |isbn=9780470281840 |url-access=subscription }} Their overall abundance can be up to two orders of magnitude lower than the mesopelagic zone, however, there is often high viral abundance found around deep-sea hydrothermal vents.{{Cite journal |last1=Ortmann |first1=Alice C. |last2=Suttle |first2=Curtis A. |date=August 2005 |title=High abundances of viruses in a deep-sea hydrothermal vent system indicates viral mediated microbial mortality |url=http://dx.doi.org/10.1016/j.dsr.2005.04.002 |journal=Deep Sea Research Part I: Oceanographic Research Papers |volume=52 |issue=8 |pages=1515–1527 |doi=10.1016/j.dsr.2005.04.002 |bibcode=2005DSRI...52.1515O |issn=0967-0637|url-access=subscription }} The magnitude of their impacts on biological systems is demonstrated by the varying range of viral-to-prokaryote abundance ratios ranging from 1-223, this indicates that there are the same amount or more viruses than prokaryotes.

{{See also|Bathypelagic fish}}

Despite the lack of light, vision plays a role in life within the bathypelagic with bioluminescence a trait among both nektonic and planktonic organisms.{{Cite journal |last=Widder |first=E. A. |date=2010-05-07 |title=Bioluminescence in the Ocean: Origins of Biological, Chemical, and Ecological Diversity |url=https://www.sciencemag.org/lookup/doi/10.1126/science.1174269 |journal=Science |language=en |volume=328 |issue=5979 |pages=704–708 |doi=10.1126/science.1174269 |pmid=20448176 |bibcode=2010Sci...328..704W |s2cid=2375135 |issn=0036-8075|url-access=subscription }} In contrast to organisms in the water column, benthic organisms in this region tend to have limited to no bioluminescence.{{Cite journal |last1=Frank |first1=Tamara M. |last2=Johnsen |first2=Sönke |last3=Cronin |first3=Thomas W. |date=2012-10-01 |title=Light and vision in the deep-sea benthos: II. Vision in deep-sea crustaceans |journal=Journal of Experimental Biology |volume=215 |issue=19 |pages=3344–3353 |doi=10.1242/jeb.072033 |pmid=22956247 |s2cid=13524696 |issn=1477-9145|doi-access=free |hdl=11603/13394 |hdl-access=free }} The bathypelagic zone contains sharks, squid, octopuses, and many species of fish, including deep-water anglerfish, gulper eel, amphipods, and dragonfish. The fish are characterized by weak muscles, soft skin, and slimy bodies. The adaptations of some of the fish that live there include small eyes and transparent skin. However, this zone is difficult for fish to live in since food is scarce; resulting in species evolving slow metabolic rates in order to conserve energy.{{Cite journal |date=1990-06-19 |title=Responses by benthic organisms to inputs of organic material to the ocean floor: a review |url=https://royalsocietypublishing.org/doi/10.1098/rsta.1990.0060 |journal=Philosophical Transactions of the Royal Society of London. Series A, Mathematical and Physical Sciences |language=en |volume=331 |issue=1616 |pages=119–138 |doi=10.1098/rsta.1990.0060 |bibcode=1990RSPTA.331..119G |issn=0080-4614|last1=Gooday |first1=A. J. |last2=Turley |first2=Carol M. |s2cid=122884530 |url-access=subscription }} Occasionally, large sources of organic matter from decaying organisms, such as whale falls, create a brief burst of activity by attracting organisms from different bathypelagic communities.

Some bathypelagic species undergo vertical migration, which differs from the diel vertical migration of mesopelagic species in that it is not driven by sunlight.{{Cite journal |last=Sutton |first=T. T. |date=December 2013 |title=Vertical ecology of the pelagic ocean: classical patterns and new perspectives |url=http://dx.doi.org/10.1111/jfb.12263 |journal=Journal of Fish Biology |volume=83 |issue=6 |pages=1508–1527 |doi=10.1111/jfb.12263 |pmid=24298949 |issn=0022-1112|url-access=subscription }} Instead, the migration of bathypelagic organisms is driven by other factors, most of which remain unknown. Some research suggests the movement of species within the overlying pelagic region could prompt individual bathypelagic species to migrate, such as Sthenoteuthis sp., a species of squid.{{Cite journal |last1=Kaartvedt |first1=Stein |last2=Røstad |first2=Anders |last3=Christiansen |first3=Svenja |last4=Klevjer |first4=Thor A. |date=June 2020 |title=Diel vertical migration and individual behavior of nekton beyond the ocean's twilight zone |url=http://dx.doi.org/10.1016/j.dsr.2020.103280 |journal=Deep Sea Research Part I: Oceanographic Research Papers |volume=160 |pages=103280 |doi=10.1016/j.dsr.2020.103280 |bibcode=2020DSRI..16003280K |s2cid=216470635 |issn=0967-0637|hdl=10754/662508 |hdl-access=free }} In this particular example, Sthenoteuthis sp. appears to migrate individually over the course of ~4–5 hours towards the surface and then form into groups. While in most regions migration patterns can be driven by predation, in this particular region, the migration patterns are not believed to result solely from predator-prey relations. Instead, these relations are commensalistic, with the species who remain in the bathypelagic benefitting from the POM mixing caused by the upward movement of another species.{{Cite journal |last1=Ochoa |first1=José |last2=Maske |first2=H. |last3=Sheinbaumc |first3=J. |last4=Candela |first4=J. |date=2013-06-14 |title=Diel and lunar cycles of vertical migration extending to below 1000 m in the ocean and the vertical connectivity of depth-tiered populations |journal=Limnology and Oceanography |volume=58 |issue=4 |pages=1207–1214 |doi=10.4319/lo.2013.58.4.1207 |bibcode=2013LimOc..58.1207O |s2cid=83993399 |issn=0024-3590|doi-access=free }} In addition, the vertical migrating species' timing bathypelagic appears linked to the lunar cycle. However, the exact indicators causing this timing are still unknown.

File:ROV_JASON_AT42-22.jpg

This region is understudied due to a lack of data/observations and difficulty of access (i.e. cost, remote locations, extreme pressure).{{Cite journal |last1=Marsh |first1=Leigh |last2=Copley |first2=Jonathan T. |last3=Huvenne |first3=Veerle A. I. |last4=Tyler |first4=Paul A. |last5=the Isis ROV Facility |date=2013-08-01 |title=Getting the bigger picture: Using precision Remotely Operated Vehicle (ROV) videography to acquire high-definition mosaic images of newly discovered hydrothermal vents in the Southern Ocean |url= |journal=Deep Sea Research Part II: Topical Studies in Oceanography |series=Deep-Sea Biodiversity and Life History Processes |language=en |volume=92 |pages=124–135 |doi=10.1016/j.dsr2.2013.02.007 |bibcode=2013DSRII..92..124M |issn=0967-0645}} Historically in oceanography, continental margins were the most sampled and researched due to their relatively easy access. However, more recently locations further offshore and at greater depths, such as ocean ridges and seamounts, are being increasingly studied due to advances in technology and laboratory methods, as well as collaboration with industry.{{Cite journal |last1=Macreadie |first1=Peter I. |last2=McLean |first2=Dianne L. |last3=Thomson |first3=Paul G. |last4=Partridge |first4=Julian C. |last5=Jones |first5=Daniel O. B. |last6=Gates |first6=Andrew R. |last7=Benfield |first7=Mark C. |last8=Collin |first8=Shaun P. |last9=Booth |first9=David J. |last10=Smith |first10=Luke L. |last11=Techera |first11=Erika |last12=Skropeta |first12=Danielle |last13=Horton |first13=Tammy |last14=Pattiaratchi |first14=Charitha |last15=Bond |first15=Todd |date=2018-09-01 |title=Eyes in the sea: Unlocking the mysteries of the ocean using industrial, remotely operated vehicles (ROVs) |url= http://nora.nerc.ac.uk/id/eprint/519953/1/Postprint%20Macreadie%20et%20al%20STOTEN.pdf|journal=Science of the Total Environment |language=en |volume=634 |pages=1077–1091 |doi=10.1016/j.scitotenv.2018.04.049 |pmid=29660864 |bibcode=2018ScTEn.634.1077M |s2cid=4955364 |issn=0048-9697}}{{Cite journal |last1=Bellingham |first1=James G. |last2=Rajan |first2=Kanna |date=2007-11-16 |title=Robotics in Remote and Hostile Environments |url=https://www.science.org/doi/10.1126/science.1146230 |journal=Science |language=en |volume=318 |issue=5853 |pages=1098–1102 |doi=10.1126/science.1146230 |pmid=18006738 |bibcode=2007Sci...318.1098B |s2cid=38842741 |issn=0036-8075|url-access=subscription }}{{Cite journal |last1=McLean |first1=Dianne L. |last2=Parsons |first2=Miles J. G. |last3=Gates |first3=Andrew R. |last4=Benfield |first4=Mark C. |last5=Bond |first5=Todd |last6=Booth |first6=David J. |last7=Bunce |first7=Michael |last8=Fowler |first8=Ashley M. |last9=Harvey |first9=Euan S. |last10=Macreadie |first10=Peter I. |last11=Pattiaratchi |first11=Charitha B. |last12=Rouse |first12=Sally |last13=Partridge |first13=Julian C. |last14=Thomson |first14=Paul G. |last15=Todd |first15=Victoria L. G. |date=2020 |title=Enhancing the Scientific Value of Industry Remotely Operated Vehicles (ROVs) in Our Oceans |journal=Frontiers in Marine Science |volume=7 |doi=10.3389/fmars.2020.00220 |issn=2296-7745|doi-access=free |hdl=10536/DRO/DU:30137212 |hdl-access=free }} The first discovery of communities subsisting off of the chemical energy in hydrothermal vents was aboard an expedition in 1977 led by Jack Corliss, an oceanographer from Oregon State University. More recent advancements include remotely operated vehicles (ROVs), autonomous underwater vehicles (AUVs), and independent gliders and floats.{{Cite web |title=What is an ROV? : Ocean Exploration Facts: NOAA Office of Ocean Exploration and Research |url=https://oceanexplorer.noaa.gov/facts/rov.html |access-date=2022-12-01 |website=oceanexplorer.noaa.gov |language=en-US}}{{Cite journal |last1=Wynn |first1=Russell B. |last2=Huvenne |first2=Veerle A. I. |last3=Le Bas |first3=Timothy P. |last4=Murton |first4=Bramley J. |last5=Connelly |first5=Douglas P. |last6=Bett |first6=Brian J. |last7=Ruhl |first7=Henry A. |last8=Morris |first8=Kirsty J. |last9=Peakall |first9=Jeffrey |last10=Parsons |first10=Daniel R. |last11=Sumner |first11=Esther J. |last12=Darby |first12=Stephen E. |last13=Dorrell |first13=Robert M. |last14=Hunt |first14=James E. |date=2014-06-01 |title=Autonomous Underwater Vehicles (AUVs): Their past, present and future contributions to the advancement of marine geoscience |url= |journal=Marine Geology |series=50th Anniversary Special Issue |language=en |volume=352 |pages=451–468 |doi=10.1016/j.margeo.2014.03.012 |bibcode=2014MGeol.352..451W |issn=0025-3227|doi-access=free }}{{Cite web |title=Measurements in support of the Deepwater Horizon incident's response effort |url=https://spie.org/news/3601-measurements-in-support-of-the-deepwater-horizon-incidents-response-effort |access-date=2022-12-01 |website=spie.org}}

• SERPENT Project {{Cite web |title=SERPENT Project {{!}} SERPENT Project |url=https://serpentproject.com/ |access-date=2022-12-01 |website=serpentproject.com}}
• Ocean Twilight Zone (OTZ) Project{{Cite web |title=The Ocean Twilight Zone : Woods Hole Oceanographic Institution |url=https://twilightzone.whoi.edu/ |access-date=2022-12-01 |website=twilightzone.whoi.edu |language=en-US}}
• DEEP SEARCH Project{{Cite web |last=US Department of Commerce |first=National Oceanic and Atmospheric Administration |title=DEEP SEARCH: DEEP Sea Exploration to Advance Research on Coral/Canyon/Cold seep Habitats: NOAA Office of Ocean Exploration and Research |url=https://oceanexplorer.noaa.gov/explorations/17deepsearch/welcome.html |access-date=2022-12-01 |website=oceanexplorer.noaa.gov |language=EN-US}}
• DEEPEND Project{{Cite web |title=Low res biota images - DEEPEND Consortium |url=https://restore.deependconsortium.org/index.php |access-date=2022-12-01 |website=restore.deependconsortium.org}}
• AUV Sentry{{Cite web |title=AUV Sentry |url=https://ndsf.whoi.edu/sentry/ |access-date=2022-12-01 |website=National Deep Submergence Facility |language=en-US}}
• ROV Jason{{Cite web |title=ROV Jason |url=https://ndsf.whoi.edu/jason/ |access-date=2022-12-01 |website=National Deep Submergence Facility |language=en-US}}
• Hybrid ROV Nereus
• AUV Autosub Long Range{{Cite web |title=Autosub Long Range - AUVAC |url=https://auvac.org/119-2/ |access-date=2022-12-01 |website=AUVAC: Strengthening the AUV Community}}

{{See also|Effects of climate change on oceans}}

The oceans act as a buffer for anthropogenic climate change due to their ability to take up atmospheric CO₂ and absorb heat from the atmosphere. However, the ocean's ability to do so will be negatively affected as atmospheric CO₂ concentrations continue to rise and global temperatures continue to warm. This will lead to changes such as deoxygenation, ocean acidification, temperature increase, and carbon sequestration decrease, among other physical and chemical alterations. These perturbations may have significant impacts on the organisms that dwell in the bathypelagic region and the properties that deliver organic carbon to the deep sea.{{Cite journal |last1=Sweetman |first1=Andrew K. |last2=Thurber |first2=Andrew R. |last3=Smith |first3=Craig R. |last4=Levin |first4=Lisa A. |last5=Mora |first5=Camilo |last6=Wei |first6=Chih-Lin |last7=Gooday |first7=Andrew J. |last8=Jones |first8=Daniel O. B. |last9=Rex |first9=Michael |last10=Yasuhara |first10=Moriaki |last11=Ingels |first11=Jeroen |last12=Ruhl |first12=Henry A. |last13=Frieder |first13=Christina A. |last14=Danovaro |first14=Roberto |last15=Würzberg |first15=Laura |date=2017-01-01 |editor-last=Deming |editor-first=Jody W. |editor2-last=Thomsen |editor2-first=Laurenz |title=Major impacts of climate change on deep-sea benthic ecosystems |journal=Elementa: Science of the Anthropocene |language=en |volume=5 |pages=4 |doi=10.1525/elementa.203 |s2cid=133518883 |issn=2325-1026|doi-access=free |hdl=10722/241753 |hdl-access=free }}

The bathypelagic zone currently acts as a significant reservoir for carbon because of its sheer volume and the century to millennial timescales these waters are isolated from the atmosphere, this ocean zone plays an important role in moderating the effects of anthropogenic climate change. The burial of particulate organic carbon (POC) in the underlying sediments via the biological carbon pump, and the solubility pump of dissolved inorganic carbon (DIC) into the ocean interior via the thermohaline conveyor are key processes for removing excess atmospheric carbon. However, as atmospheric CO₂ concentrations and global temperatures continue to rise, the efficiency at which the bathypelagic will store and bury the influx of carbon will most likely decrease. While some regions may experience an increase in POC input, such as Arctic regions where increased periods of minimal sea ice coverage will increase the downward flux of carbon from the surface oceans, overall, there will likely be less carbon sequestered to the bathypelagic region.

{{Reflist}}

• [https://www.whoi.edu/know-your-ocean/ocean-topics/how-the-ocean-works/ocean-zones/midnight-zone/ Woods Hole Oceanographic Institution - Midnight Zone]
• [https://www.oceanscape-aquarium.org/midnight-zone.html Oregon Coast Aquarium OceanScape - Midnight Zone]

Category:Oceanography