View source for Biology:Human impact on marine life

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[[File:Global cumulative human impact on the ocean.png|thumb|upright=1.8|Global cumulative human impact on the ocean<ref name=Halpern2019>Halpern, B. S., Frazier, M., Afflerbach, J. et&nbsp;al. (2019) "Recent pace of change in human impact on the world’s ocean." ''Scientific Reports'', '''9''': 11609. {{doi|10.1038/s41598-019-47201-9}}.</ref><ref>Halpern, B. S., Walbridge, S., Selkoe, K. A., Kappel, C. V., Micheli, F., D'agrosa, C., Bruno, J. F., Casey, K. S., Ebert, C., Fox, H. E. and Fujita, R. (2008) "A global map of human impact on marine ecosystems". ''Science'', '''319'''(5865): 948–952. {{doi|10.1126/science.1149345}}.</ref>]]
{{marine life sidebar}}

Human activities affect [[Biology:Marine life|marine life]] and [[Earth:Marine habitat|marine habitat]]s through overfishing, habitat loss, the introduction of [[Earth:Invasive species|invasive species]], [[Earth:Marine pollution|ocean pollution]], [[Biology:Ocean acidification|ocean acidification]] and ocean warming. These impact [[Earth:Marine ecosystem|marine ecosystem]]s and [[Biology:Marine food web|food webs]] and may result in consequences as yet unrecognised for the [[Biology:Biodiversity|biodiversity]] and continuation of marine life forms.<ref>[https://www.geomar.de/en/research/human-impacts-on-marine-ecosystems/ Human impacts on marine ecosystems] {{Webarchive|url=https://web.archive.org/web/20191022064526/https://www.geomar.de/en/research/human-impacts-on-marine-ecosystems/ |date=22 October 2019 }}. GEOMAR Helmholtz Centre for Ocean Research. Retrieved 22 October 2019.</ref>

The ocean can be described as the world's largest ecosystem and it is home for many species of marine life. Different activities carried out and caused by human beings such as global warming, ocean acidification, and pollution affect marine life and its habitats. For the past 50 years, more than 90 percent of [[Earth:Climate change|global warming]] resulting from human activity has been absorbed into the ocean. This results in the rise of ocean temperatures and ocean acidification which is harmful to many fish species and causes damage to habitats such as [[Earth:Coral reef|coral]].<ref>{{Cite web |title=5 ways that climate change affects the ocean |url=https://www.conservation.org/blog/5-ways-that-climate-change-affects-the-ocean?gclid=CjwKCAiAs8acBhA1EiwAgRFdwzv2_n9LKPsvS_WGgBosQvNoIh9wBLPcedFJNynJGZMmJcO43-_4nBoCioAQAvD_BwE |access-date=2022-12-09 |website=www.conservation.org}}</ref> With coral producing materials such as carbonate rock and calcareous sediment, this creates a very unique and valuable ecosystem not only providing food/homes for marine creatures but also having many benefits for humans too. Ocean acidification caused by rising levels of [[Chemistry:Carbon dioxide|carbon dioxide]] leads to coral bleaching where the rates of calcification is lowered affecting coral growth.<ref>{{Cite journal |last1=Kawahata |first1=Hodaka |last2=Fujita |first2=Kazuhiko |last3=Iguchi |first3=Akira |last4=Inoue |first4=Mayuri |last5=Iwasaki |first5=Shinya |last6=Kuroyanagi |first6=Azumi |last7=Maeda |first7=Ayumi |last8=Manaka |first8=Takuya |last9=Moriya |first9=Kazuyoshi |last10=Takagi |first10=Haruka |last11=Toyofuku |first11=Takashi |last12=Yoshimura |first12=Toshihiro |last13=Suzuki |first13=Atsushi |date=2019-01-17 |title=Perspective on the response of marine calcifiers to global warming and ocean acidification—Behavior of corals and foraminifera in a high CO2 world "hot house" |journal=Progress in Earth and Planetary Science |volume=6 |issue=1 |pages=5 |doi=10.1186/s40645-018-0239-9 |issn=2197-4284|doi-access=free }}</ref> Additionally, another issue caused by humans which impacts marine life is [[Earth:Marine plastic pollution|marine plastic pollution]], which poses a threat to marine life.<ref>{{Cite journal |last1=Villarrubia-Gómez |first1=Patricia |last2=Cornell |first2=Sarah E. |last3=Fabres |first3=Joan |date=2018-10-01 |title=Marine plastic pollution as a planetary boundary threat – The drifting piece in the sustainability puzzle |journal=Marine Policy |language=en |volume=96 |pages=213–220 |doi=10.1016/j.marpol.2017.11.035 |issn=0308-597X|doi-access=free }}</ref> According to the IPCC (2019), since 1950 "many marine species across various groups have undergone shifts in geographical range and seasonal activities in response to ocean warming, sea ice change and biogeochemical changes, such as oxygen loss, to their habitats."<ref>{{Cite report| title = Special Report on the Ocean and Cryosphere in a Changing Climate (SROCC) |work=IPCC| access-date = 25 March 2020 |date = 25 September 2019| url = https://www.ipcc.ch/report/srocc |pages=2 }}</ref>

It has been estimated only 13% of the ocean area remains as wilderness, mostly in open ocean areas rather than along the coast.<ref>Jones, K. R., Klein, C. J., Halpern, B. S., Venter, O., Grantham, H., Kuempel, C. D., Shumway, N., Friedlander, A. M., Possingham, H. P. and Watson, J. E. (2018) "The location and protection status of Earth’s diminishing marine wilderness". ''Current Biology'', '''28'''(15): 2506–2512. {{doi|10.1016/j.cub.2018.06.010}}.</ref>

==Overfishing==
[[File:Fishing down the food web.jpg|thumb|upright=1.5|Fishing down the foodweb. Overfishing of high trophic fish like tuna can result in them being replaced by low trophic organisms, like jellyfish]]

Overfishing is occurring in one third of world fish stocks, according to a 2018 report by the Food and Agriculture Organization of the United Nations.<ref>{{Cite news|url=http://www.fao.org/state-of-fisheries-aquaculture/en/|title=SOFIA 2018 - State of Fisheries and Aquaculture in the world 2018|last=fao.org|work=www.fao.org|access-date=2018-11-09}}</ref> In addition, industry observers believe illegal, unreported and unregulated fishing occurs in most fisheries, and accounts for up to 30% of total catches in some important fisheries.<ref>World Wildlife Fund. "[http://www.panda.org/about_wwf/what_we_do/marine/problems/problems_fishing/illegal_fishing/index.cfm Fishing problems: Illegal fishing]" {{webarchive|url=https://web.archive.org/web/20080411060604/http://www.panda.org/about_wwf/what_we_do/marine/problems/problems_fishing/illegal_fishing/index.cfm |date=2008-04-11 }}</ref> In a phenomenon called fishing down the foodweb, the mean trophic level of world fisheries has declined because of overfishing high [[Earth:Trophic level|trophic level]] fish.<ref>Pauly, Daniel and Watson, Reg (2009) [http://www.seaaroundus.org/researcher//dpauly/PDF/2009/Books%26Chapters/SpatialDynamicsOfFisheries.pdf "Spatial Dynamics of Marine Fisheries"] {{Webarchive|url=https://web.archive.org/web/20120611044204/http://www.seaaroundus.org/researcher/dpauly/PDF/2009/Books%26Chapters/SpatialDynamicsOfFisheries.pdf |date=2012-06-11 }} ''In:'' Simon A. Levin (ed.) ''The Princeton Guide to Ecology''. Pages 501–509.</ref>

{{Quote box
 |align = left
 |width = 388px
 |title = 
 |quote = "It is almost as though we use our military to fight the animals in the ocean. We are gradually winning this war to exterminate them."
 |author = – Daniel Pauly, pioneer on human impacts on global fisheries
 |source = <ref>{{cite video |url=https://www.youtube.com/watch?v=Tf1EgeHDxpA|title=Fisheries on the brink
}}

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==Habitat loss==
[[File:Cumulative human impacts on marine ecosystems.png|thumb|upright=1.5| Relationship between annual trend and current cumulative impacts for different marine ecosystems<ref name=Halpern2019 />]]

Coastal ecosystems are being particularly damaged by humans.<ref name=Waycott2009>Waycott, M., Duarte, C. M., Carruthers, T. J., Orth, R. J., Dennison, W. C., Olyarnik, S., Calladine, A., Fourqurean, J. W., Heck, K. L., Hughes, A. R. and Kendrick, G. A. (2009) [https://www.pnas.org/content/106/30/12377.full "Accelerating loss of seagrasses across the globe threatens coastal ecosystems"]. ''Proceedings of the national academy of sciences'', '''106'''(30): 12377–12381. {{doi|10.1073/pnas.0905620106}}.</ref> Significant habitat loss is occurring particularly in seagrass meadows, mangrove forests and coral reefs, all of which are in global decline due to human disturbances.

[[Earth:Coral reef|Coral reef]]s are among the more productive and diverse ecosystems on the planet, but one-fifth of them have been lost in recent years due to anthropogenic disturbances.<ref name=Wilkinson>Wilkinson, Clive (2008) [http://www.icriforum.org/sites/default/files/Status%20Coral%20%20Reefs%20of%20World%202008%20%20Executive%20Summary_0.pdf Status of Coral Reefs of the World: Executive Summary] {{Webarchive|url=https://web.archive.org/web/20131219004526/http://www.icriforum.org/sites/default/files/Status%20Coral%20%20Reefs%20of%20World%202008%20%20Executive%20Summary_0.pdf |date=19 December 2013 }}. Global Coral Reef Monitoring Network.</ref><ref>{{Cite journal |last1=Zainal Abidin |first1=Siti Zulaiha |last2=Mohamed |first2=Badaruddin |date=2014 |editor-last=Othuman Mydin |editor-first=M. A. |editor2-last=Marzuki |editor2-first=A. |title=A Review of SCUBA Diving Impacts and Implication for Coral Reefs Conservation and Tourism Management |journal=SHS Web of Conferences |volume=12 |pages=01093 |doi=10.1051/shsconf/20141201093 |issn=2261-2424|doi-access=free }}</ref>  Coral reefs are microbially driven ecosystems that rely on [[Biology:Marine microorganism|marine microorganism]]s to retain and recycle nutrients in order to thrive in oligotrophic waters. However, these same microorganisms can also trigger feedback loops that intensify declines in coral reefs, with cascading effects across [[Biology:Marine biogeochemical cycles|biogeochemical cycles]] and [[Biology:Marine food web|marine food web]]s. A better understanding is needed of the complex microbial interactions within coral reefs if reef conservation has a chance of success in the future.<ref>Vanwonterghem, I. and Webster, N. S. (2020) "Coral reef microorganisms in a changing climate". ''Iscience'', '''23'''(4). {{doi|10.1016/j.isci.2020.100972}}.</ref>

[[Biology:Seagrass meadow|Seagrass meadow]]s have lost {{convert|30000|km2|sqmi|abbr=on}} during recent decades. Seagrass [[Biology:Ecosystem service|ecosystem service]]s, currently worth about $US1.9 trillion per year, include nutrient cycling, the provision of food and habitats for many marine animals, including the endangered [[Biology:Dugong|dugong]]s, [[Biology:Manatee|manatee]] and green turtles, and major facilitations for [[Earth:Coral reef fish|coral reef fish]].<ref name=Waycott2009 />

One-fifth of the world's [[Biology:Mangrove forest|mangrove forest]]s have also been lost since 1980.<ref name="nature.org">{{cite web|archive-url= https://web.archive.org/web/20100717013054/http://www.nature.org/pressroom/press/press4573.html|archive-date= 2010-07-17|url=http://www.nature.org/pressroom/press/press4573.html |title= 2010a. ""World Atlas of Mangroves" Highlights the Importance of and Threats to Mangroves: Mangroves among World's Most Valuable Ecosystems." Press release. Arlington, Virginia |publisher=The Nature Conservancy|access-date=2014-01-25|url-status= dead}}</ref> The most pressing threat to [[Biology:Kelp forest|kelp forest]]s may be the overfishing of coastal ecosystems, which by removing higher trophic levels facilitates their shift to depauperate [[Biology:Urchin barren|urchin barren]]s.<ref name="Sala1998">Sala, E., C. F. Bourdouresque and M. Harmelin-Vivien. 1998. Fishing, trophic cascades, and the structure of algal assemblages: evaluation of an old but untested paradigm. Oikos 82: 425–439.</ref>

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==Invasive species==
[[File:Ship pumping ballast water.jpg|thumb|A cargo ship pumps ballast water over the side.]]

An [[Earth:Invasive species|invasive species]] is a species not native to a particular location which can spread to a degree that causes damage to the environment, human economy or human health.<ref>{{Citation|title=Ecosystem Consequences of Biological Invasions |author=Joan G. Ehrenfeld |journal=Annual Review of Ecology, Evolution, and Systematics |year=2010 |volume=41 |pages=59–80 |doi=10.1146/annurev-ecolsys-102209-144650 }}</ref> In 2008, Molnar et&nbsp;al. documented the pathways of hundreds of marine invasive species and found shipping was the dominant mechanism for the transfer of invasive species in the ocean. The two main maritime mechanisms of transporting marine organisms to other ocean environments are via hull fouling and the transfer of ballast water.<ref>{{Cite journal|last1=Molnar|first1=Jennifer L.|last2=Gamboa|first2=Rebecca L.|last3=Revenga|first3=Carmen|last4=Spalding|first4=Mark D|date=2008|title=Assessing the global threat of invasive species to marine biodiversity|journal=Frontiers in Ecology and the Environment|volume=6|issue=9|pages=485–492|doi=10.1890/070064|issn=1540-9295}}</ref>

[[File:Comb jelly.tif|thumb|left|''Mnemiopsis leidyi'']]

Ballast water taken up at sea and released in port is a major source of unwanted exotic marine life. The [[Earth:Invasive species|invasive]] freshwater zebra mussels, native to the Black, Caspian, and Azov seas, were probably transported to the Great Lakes via ballast water from a transoceanic vessel.<ref>[http://www.wsg.washington.edu/mas/pdfs/leastwanted.pdf Aquatic invasive species. A Guide to Least-Wanted Aquatic Organisms of the Pacific Northwest]. {{webarchive|url=https://web.archive.org/web/20080725040002/http://www.wsg.washington.edu/mas/pdfs/leastwanted.pdf |date=25 July 2008}}. 2001. University of Washington.</ref> Meinesz believes that one of the worst cases of a single invasive species causing harm to an ecosystem can be attributed to a seemingly harmless [[Biology:Jellyfish|jellyfish]]. ''Mnemiopsis leidyi'', a species of comb jellyfish that spread so it now inhabits estuaries in many parts of the world, was first introduced in 1982, and thought to have been transported to the Black Sea in a ship's ballast water. The population of the jellyfish grew exponentially and, by 1988, it was wreaking havoc upon the local fishing industry. "The [[Biology:Anchovy|anchovy]] catch fell from 204,000 tons in 1984 to 200 tons in 1993; [[Biology:Sprat|sprat]] from 24,600 tons in 1984 to 12,000 tons in 1993; horse [[Biology:Mackerel|mackerel]] from 4,000 tons in 1984 to zero in 1993."<ref name="Meinesz">Meinesz, A. (2003) [https://www.pbs.org/wgbh/nova/algae/impact.html Deep Sea Invasion: The Impact of Invasive Species]. PBS: NOVA. Retrieved 26 November 2009.</ref> Now that the jellyfish have exhausted the [[Earth:Zooplankton|zooplankton]], including fish larvae, their numbers have fallen dramatically, yet they continue to maintain a stranglehold on the [[Earth:Ecosystem|ecosystem]].

[[Earth:Invasive species|Invasive species]] can take over once occupied areas, facilitate the spread of new diseases, introduce new [[Biology:Genetics|genetic]] material, alter underwater seascapes, and jeopardize the ability of [[Earth:Native species|native species]] to obtain food. Invasive species are responsible for about $138&nbsp;billion annually in lost revenue and management costs in the US alone.<ref name=pimental>{{cite journal |doi= 10.1016/j.ecolecon.2004.10.002 |title= Update on the environmental and economic costs associated with alien-invasive species in the United States |journal= Ecological Economics |volume= 52 |issue= 3 |pages= 273–288 |year= 2005 |last1= Pimentel |first1= D. |last2= Zuniga |first2= R. |last3= Morrison |first3= D.}}</ref>

==Marine pollution==
{{excerpt|marine pollution|paragraphs=1-3|file=no}}

===Nutrient pollution===
[[Earth:Nutrient pollution|Nutrient pollution]] is a primary cause of [[Earth:Eutrophication|eutrophication]] of surface waters, in which excess nutrients, usually [[Chemistry:Nitrate|nitrate]]s or [[Chemistry:Phosphate|phosphate]]s, stimulate algae growth. This algae then dies, sinks, and is decomposed by bacteria in the water. This decomposition process consumes oxygen, depleting the supply for other marine life and creating what is referred to as a "dead zone." Dead zones are hypoxic, meaning the water has very low levels of dissolved oxygen. This kills off marine life or forces it to leave the area, removing life from the area and giving it the name dead zone. Hypoxic zones or dead zones can occur naturally, but nutrient pollution from human activity has turned this natural process into an environmental problem.<ref>{{Cite web|last=US Department of Commerce|first=National Oceanic and Atmospheric Administration|title=What is a dead zone?|url=https://oceanservice.noaa.gov/facts/deadzone.html|access-date=2021-04-30|website=oceanservice.noaa.gov|language=EN-US}}</ref>

There are five main sources of nutrient pollution. The most common source of nutrient runoff is municipal sewage. This sewage can reach waterways through storm water, leaks, or direct dumping of human sewage into bodies of water. The next biggest sources come from agricultural practices. Chemical fertilizers used in farming can seep into ground water or be washed away in rainwater, entering water ways and introducing excess nitrogen and phosphorus to these environments. Livestock waste can also enter waterways and introduce excess nutrients. Nutrient pollution from animal manure is most intense from industrial animal agriculture operations, in which hundreds or thousands of animals are raised in one concentrated area. Stormwater drainage is another source of nutrient pollution. Nutrients and fertilizers from residential properties and impervious surfaces can be picked up in stormwater, which then runs into nearby rivers and streams that eventually lead to the ocean. The fifth main source of nutrient runoff is aquaculture, in which aquatic organisms are cultivated under controlled conditions. The excrement, excess food, and other organic wastes created by these operations introduces excess nutrients into the surrounding water.<ref>{{Cite web|title=Nutrient Pollution|url=http://www.oceanhealthindex.org/methodology/components/nutrient-pollution|access-date=2021-04-30|website=Ocean Health Index|language=en}}</ref>

===Toxic chemicals===

Toxic chemicals can adhere to tiny particles which are then taken up by [[Earth:Plankton|plankton]] and [[Earth:Benthos|benthic animals]], most of which are either deposit feeders or [[Biology:Filter feeder|filter feeder]]s. In this way, toxins are concentrated upward within ocean food chains. Many particles combine chemically in a manner which depletes oxygen, causing [[Earth:Estuary|estuaries]] to become [[Earth:Hypoxia (environmental)|anoxic]]. [[Biology:Pesticide|Pesticide]]s and toxic metals are similarly incorporated into marine food webs, harming the biological health of marine life. Many animal feeds have a high [[Chemistry:Fish meal|fish meal]] or [[Chemistry:Fish hydrolysate|fish hydrolysate]] content. In this way, marine toxins are transferred back to farmed land animals, and then to humans.

[[Earth:Phytoplankton|Phytoplankton]] concentrations have increased over the last century in coastal waters, and more recently have declined in the open ocean. Increases in nutrient runoff from land may explain the rise in coastal phytoplankton, while warming surface temperatures in the open ocean may have strengthened stratification in the water column, reducing the flow of nutrients from the deep that open ocean phytoplankton find useful.<ref>Boyce, D. G. and Worm, B. (2015) "Patterns and ecological implications of historical marine phytoplankton change". ''Marine Ecology Progress Series'', '''534''':251–272. {{doi|10.3354/meps11411}}.</ref>

===Plastic pollution===
{{Further|Earth:Marine plastic pollution}}
<!--In 2015, between 93 and 236 thousand metric tons of plastic were estimated to be in the world’s oceans.<ref>{{cite journal |doi=10.1088/1748-9326/10/12/124006 |title=A global inventory of small floating plastic debris |journal=Environmental Research Letters |volume=10 |issue=12 |pages=124006 |year=2015 |last1=Van Sebille |first1=Erik |last2=Wilcox |first2=Chris |last3=Lebreton |first3=Laurent |last4=Maximenko |first4=Nikolai |last5=Hardesty |first5=Britta Denise |last6=Van Franeker |first6=Jan A. |last7=Eriksen |first7=Marcus |last8=Siegel |first8=David |last9=Galgani |first9=Francois |last10=Law |first10=Kara Lavender }}</ref> --> 
Over 300 million tons of plastic are produced every year, half of which are used in single-use products like cups, bags, and packaging. At least 14 million<ref>{{Cite web|date=2018-05-25|title=Marine plastic pollution|url=https://www.iucn.org/resources/issues-briefs/marine-plastic-pollution|access-date=2022-01-31|website=IUCN|language=en}}</ref> tons of plastic enter the oceans every year. It is impossible to know for sure, but it is estimated that about 150 million metric tons of plastic exists in our oceans. Plastic pollution makes up 80% of all marine debris from surface waters to deep-sea sediments. Because plastics are light, much of this pollution is seen in and around the ocean surface, but plastic trash and particles are now found in most marine and terrestrial habitats, including the [[Earth:Deep sea|deep sea]], Great Lakes, coral reefs, beaches, rivers, and estuaries. The most eye-catching evidence of the ocean plastic problem are the [[Earth:Garbage patch|garbage patch]]es that accumulate in [[Physics:Ocean gyre|gyre regions]]. A gyre is a circular ocean current formed by the Earth's wind patterns and the forces created by the rotation of the planet.<ref name=":1">{{Cite web|last=US EPA|first=OW|date=2020-11-06|title=Plastic Pollution|url=https://www.epa.gov/trash-free-waters/plastic-pollution|access-date=2021-04-30|website=US EPA|language=en}}</ref> There are five main ocean gyres: the [[Earth:North Pacific Gyre|North]] and South Pacific Subtropical Gyres, the [[Earth:North Atlantic Gyre|North]] and [[Earth:South Atlantic Gyre|South Atlantic Subtropical Gyres]], and the [[Earth:Indian Ocean Gyre|Indian Ocean Subtropical Gyre]]. There are significant garbage patches in each of these.<ref>{{Cite web|title=Discover the plastic islands that pollute our oceans|url=https://www.iberdrola.com/environment/5-garbage-patches-in-the-ocean|access-date=2021-04-30|website=Iberdrola|language=en}}</ref>

Larger plastic waste can be ingested by marine species, filling their stomachs and leading them to believe they are full when in fact they have taken in nothing of nutritional value. This can bring seabirds, [[Biology:Whale|whale]]s, [[Biology:Fish|fish]], and [[Biology:Turtle|turtle]]s to die of starvation with plastic-filled stomachs. Marine species can also be suffocated or entangled in plastic garbage.<ref>{{Cite web|date=2018-05-25|title=Marine plastics|url=https://www.iucn.org/resources/issues-briefs/marine-plastics|access-date=2021-04-30|website=IUCN|language=en}}</ref>

The biggest threat of ocean plastic pollution comes from [[Earth:Microplastics|microplastics]]. These are small fragments of plastic debris, some of which were produced to be this small such as microbeads. Other microplastics come from the weathering of larger plastic waste. Once larger pieces of plastic waste enter the ocean, or any waterway, the sunlight exposure, temperature, humidity, waves, and wind begin to break the plastic down into pieces smaller than five millimeters long. Plastics can also be broken down by smaller organisms who will eat plastic debris, breaking it down into small pieces, and either excrete these microplastics or spit them out. In lab tests, it was found that amphipods of the species ''Orchestia gammarellus'' could quickly devour pieces of plastic bags, shredding a single bag into 1.75 million microscopic fragments.<ref>{{Cite web|date=2018-05-16|title=We Depend on Plastic. Now We're Drowning in It.|url=https://www.nationalgeographic.com/magazine/article/plastic-planet-waste-pollution-trash-crisis|archive-url=https://web.archive.org/web/20210227082642/http://www.nationalgeographic.com/magazine/article/plastic-planet-waste-pollution-trash-crisis|url-status=dead|archive-date=27 February 2021|access-date=2021-04-30|website=Magazine|language=en}}</ref> Although the plastic is broken down, it is still an artificial material that does not biodegrade. It is estimated that approximately 90% of the plastics in the pelagic marine environment are microplastics.<ref name=":1" /> These microplastics are frequently consumed by marine organisms at the base of the food chain, like plankton and fish larvae, which leads to a concentration of ingested plastic up the food chain. Plastics are produced with toxic chemicals which then enter the marine food chain, including the fish that some humans eat.<ref>{{Cite web|title=Marine Microplastics |website=Woods Hole Oceanographic Institution|url=https://www.whoi.edu/know-your-ocean/ocean-topics/pollution/marine-microplastics/|access-date=2021-04-30|language=en-US}}</ref>

<gallery mode="packed" heights="150px" style="float:left;">
File:Microplastics in sediment from the Rhine.jpg| Microplastics among sand and glass spheres in sediment from the [[Place:Rhine|Rhine]]. The white bar represents 1&nbsp;mm.
File:Pacific-garbage-patch-map 2010 noaamdp.jpg| Vast [[Earth:Great Pacific garbage patch|plastic garbage patches]] have accumulated at the centre of [[Physics:Ocean gyre|ocean gyre]]s.<ref>{{Cite web |url=https://marinedebris.noaa.gov/movement/great-pacific-garbage-patch |title=Great Pacific Garbage Patch |website=Marine Debris Division – Office of Response and Restoration |publisher=NOAA |url-status=dead |archive-url=https://web.archive.org/web/20140417124654/https://marinedebris.noaa.gov/movement/great-pacific-garbage-patch |archive-date=17 April 2014 |df=dmy-all |date=2013-07-11 |access-date=7 December 2019 }}</ref>
File:Ocean plasic count density.gif| Model results for the count density of small planktonic plastic particles.<ref>Eriksen, M., Lebreton, L. C., Carson, H. S., Thiel, M., Moore, C. J., Borerro, J. C., Galgani, F., Ryan, P. G. and Reisser, J. (2014) [http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0111913 "Plastic pollution in the world's oceans: more than 5 trillion plastic pieces weighing over 250,000 tons afloat at sea"]. ''PLOS ONE'', '''9''' (12): e111913. {{doi|10.1371/journal.pone.0111913.g002}}</ref><br /> {{align|left|Red: more dense}} {{align|right|Green: less dense}}
File:Interactions between marine microorganisms and microplastics.webp|Interactions between [[Biology:Marine microorganism|marine microorganism]]s and microplastics<ref>Urbanek, A. K., Rymowicz, W. and Mirończuk, A. M. (2018) "Degradation of plastics and plastic-degrading bacteria in cold marine habitats". ''Applied microbiology and biotechnology'', '''102'''(18): 7669–7678. {{doi|10.1007/s00253-018-9195-y}}.</ref>
</gallery>
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=== Noise pollution ===

There is a natural soundscape to the ocean that organisms have evolved around for tens of thousands of years. However, human activity has disrupted this soundscape, largely drowning out sounds organisms depend on for mating, warding off predators, and travel. Ship and boat propellers and engines, industrial fishing, coastal construction, oil drilling, seismic surveys, warfare, sea-bed mining and sonar-based navigation have all introduced [[Physics:Noise pollution|noise pollution]] to ocean environments. Shipping alone has contributed an estimated 32-fold increase of low-frequency noise along major shipping routes in the past 50 years, driving marine animals away from vital breeding and feeding grounds.<ref>{{Cite magazine|title=Underwater Noise Pollution Is Disrupting Ocean Life—But We Can Fix It|url=https://time.com/5936110/underwater-noise-pollution-report/|access-date=2021-04-30|magazine=Time}}</ref> Sound is the sensory cue that travels the farthest through the ocean, and anthropogenic noise pollution disrupts organisms' ability to utilize sound. This creates stress for the organisms that can affect their overall health, disrupting their behavior, physiology, and reproduction, and even causing mortality.<ref>{{Cite web|title=The Ocean is Too Loud for Marine Life|url=https://www.discovery.com/nature/the-ocean-is-too-loud-for-marine-life|access-date=2021-04-30|website=Discovery|language=en}}</ref> Sound blasts from seismic surveys can damage the ears of marine animals and cause serious injury. Noise pollution is especially damaging for marine mammals that rely on echolocation, such as whales and dolphins. These animals use echolocation to communicate, navigate, feed, and find mates, but excess sound interferes with their ability to use echolocation and, therefore, perform these vital tasks.<ref>{{Cite web|date=2019-07-16|title=Noise Pollution|url=https://education.nationalgeographic.org/resource/noise-pollution/|access-date=2021-04-30|website=National Geographic Society|language=en}}</ref>

=== Mining ===
The prospect of [[Earth:Deep sea mining|deep sea mining]] has led to concerns from scientists and environmental groups over the impacts on fragile [[Earth:Deep sea community|deep sea ecosystems]] and wider impacts on the ocean's [[Biology:Biological pump|biological pump]].<ref>{{Cite web|date=2020-03-12|title=David Attenborough calls for ban on 'devastating' deep sea mining|url=http://www.theguardian.com/environment/2020/mar/12/david-attenborough-calls-for-ban-on-devastating-deep-sea-mining|access-date=2021-09-11|website=The Guardian|language=en}}</ref><ref>{{Cite journal|last1=Halfar|first1=Jochen|last2=Fujita|first2=Rodney M.|date=2007-05-18|title=Danger of Deep-Sea Mining|url=https://www.science.org/doi/abs/10.1126/science.1138289|journal=Science|volume=316|issue=5827|pages=987|language=EN|doi=10.1126/science.1138289|pmid=17510349|s2cid=128645876}}</ref>

===Human induced disease===
Rapid change to ocean environments allows disease to flourish. Disease-causing microbes can change and adapt to new ocean conditions much more quickly than other marine life, giving them an advantage in ocean ecosystems. This group of organisms includes viruses, bacteria, fungi, and protozoans. While these pathogenic organisms can quickly adapt, other marine life is weakened by rapid changes to their environment. In addition, microbes are becoming more abundant due to aquaculture, the farming of aquatic life, and human waste polluting the ocean. These practices introduce new pathogens and excess nutrients into the ocean, further encouraging the survival of microbes.<ref name=":0">{{Cite book |title=World seas : an Environmental Evaluation |volume=III, Ecological Issues and Environmental Impacts|date=2019|editor=Charles Sheppard|isbn=978-0-12-805204-4|edition=Second |location=London, United Kingdom|oclc=1052566532}}</ref>

Some of these microbes have wide host ranges and are referred to as multi-host pathogens. This means that the pathogen can infect, multiply, and be transmitted from different, unrelated species. Multi-host pathogens are especially dangerous because they can infect many organisms, but may not be deadly to all them. This means the microbes can exist in species that are more resistant and use these organisms as vessels for continuously infecting a susceptible species. In this case, the pathogen can completely wipe out the susceptible species while maintaining a supply of host organisms.<ref name=":0" />

==Climate change==
{{Further|Earth:Effects of climate change on oceans}}
In marine environments, microbial [[Earth:Primary production|primary production]] contributes substantially to [[Earth:Carbon sequestration|{{CO2}} sequestration]]. [[Biology:Marine microorganism|Marine microorganism]]s also recycle nutrients for use in the [[Biology:Marine food web|marine food web]] and in the process release {{CO2}} to the atmosphere. Microbial biomass and other organic matter (remnants of plants and animals) are converted to fossil fuels over millions of years. By contrast, burning of fossil fuels liberates greenhouse gases in a small fraction of that time. As a result, the [[Earth:Carbon cycle|carbon cycle]] is out of balance, and atmospheric {{CO2}} levels will continue to rise as long as fossil fuels continue to be burnt.<ref name=Cavicchioli2019>Cavicchioli, R., Ripple, W. J., Timmis, K. N., Azam, F., Bakken, L. R., Baylis, M., Behrenfeld, M. J., Boetius, A., Boyd, P. W., Classen, A. T. and Crowther, T. W. (2019) "Scientists’ warning to humanity: microorganisms and climate change". ''Nature Reviews Microbiology'', '''17''': 569–586. {{doi|10.1038/s41579-019-0222-5}}.</ref>

[[File:Microorganisms and climate change.png|thumb|upright=2|left|Microorganisms and climate change in marine and terrestrial biomes<ref name=Cavicchioli2019 />]]
[[File:Overview of climatic changes and their effects on the ocean.png|thumb|upright=2|Overview of climatic changes and their effects on the ocean<ref name="Käse2018">{{cite book |doi = 10.1007/978-3-319-93284-2_5|chapter = Phytoplankton Responses to Marine Climate Change – an Introduction|title = YOUMARES 8 – Oceans Across Boundaries: Learning from each other|year = 2018|last1 = Käse|first1 = Laura|last2 = Geuer|first2 = Jana K.|pages = 55–71|isbn = 978-3-319-93283-5| s2cid=134263396 }} 50px Modified text was copied from this source, which is available under a [https://creativecommons.org/licenses/by/4.0/ Creative Commons Attribution 4.0 International License].</ref>]]

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===Ocean warming===
[[File:Global Temperature Anomaly 1880-2010 (Fig.A).gif|thumb|upright=1.5|Global mean land-ocean temperature change from 1880 to 2011, relative to the 1951–1980 mean. Source: [http://data.giss.nasa.gov/gistemp/ NASA GISS].]]

Most heat energy from global warming goes into the ocean, and not into the atmosphere or warming up the land.<ref name=IPCC2007 /><ref name=ss /> Scientists realized over 30 years ago the ocean was a key fingerprint of human impact on [[Earth:Climate change|climate change]] and "the best opportunity for major improvement in our understanding of climate sensitivity is probably monitoring of internal ocean temperature".<ref>Hansen, J., Fung, I., Lacis, A., Rind, D., Lebedeff, S., Ruedy, R., Russell, G. and Stone, P. (1988) "Global climate changes as forecast by Goddard Institute for Space Studies three‐dimensional model". ''Journal of geophysical research: Atmospheres'', '''93'''(D8): 9341–9364. {{doi|10.1029/JD093iD08p09341}}.</ref>

Marine organisms are moving to cooler parts of the ocean as global warming proceeds. For example, a group of 105 marine fish and invertebrate species were monitored along the US Northeast coast and in the eastern Bering Sea. During the period from 1982 to 2015, the average center of biomass for the group shifted northward about 10 miles as well moving about 20 feet deeper.<ref>Data source: NOAA and Rutgers University (2016) [https://oceanadapt.rutgers.edu/ ''OceanAdapt'']</ref><ref name=Pinsky2013>Pinsky, M. L., Worm, B., Fogarty, M. J., Sarmiento, J. L. and Levin, S. A. (2013) "Marine taxa track local climate velocities". ''Science'', '''341'''(6151): 1239–1242. {{doi|10.1126/science.1239352}}.</ref>

[[File:WhereIsTheHeatOfGlobalWarming.svg|left|thumb|Most heat energy from global warming goes into the ocean<ref name=IPCC2007>IPCC (2007) [https://archive.ipcc.ch/publications_and_data/ar4/wg1/en/ch5s5-2-2.html Ocean Heat Content]. Fourth Assessment Report.</ref>]]
[[File:GlobalWarmingOceanHeatContent.jpg|thumb|upright=1.5| Global heat accumulation data, from Nuccitelli et al. (2012)<ref>Nuccitelli, D., Way, R., Painting, R., Church, J. and Cook, J. (2012) [https://skepticalscience.com/docs/Comment_on_DK12.pdf "Comment on 'Ocean heat content and Earthʼs radiation imbalance. II. Relation to climate shifts'"]. ''Physics Letters A'', '''376'''(45): 3466–3468. {{doi|10.1016/j.physleta.2012.10.010}}.</ref><ref name=ss>[https://skepticalscience.com/graphics.php?g=65 Nuccitelli et al 2012 Total Heat Content]. ''Skeptical Science''. Accessed 30 December 2019.</ref>]]

There is evidence increasing ocean temperatures are taking a toll on marine ecosystem. For example, a study on [[Earth:Phytoplankton|phytoplankton]] changes in the [[Earth:Indian Ocean|Indian Ocean]] indicates a decline of up to 20% in marine phytoplankton during the past six decades.<ref name="onlinelibrary.wiley.com">{{cite journal |last1=Roxy |first1=M. K. |title=A reduction in marine primary productivity driven by rapid warming over the tropical Indian Ocean | year = 2016 | journal = Geophysical Research Letters | volume = 43 | issue = 2 |pages=826–833 | doi=10.1002/2015GL066979|bibcode=2016GeoRL..43..826R |url=https://hal.archives-ouvertes.fr/hal-01259414/file/Roxy_2016_A_reduction_in.pdf |doi-access=free }}</ref> During summer, the western Indian Ocean is home to one of the largest concentrations of marine phytoplankton blooms in the world. Increased warming in the Indian Ocean enhances ocean stratification, which prevents nutrient mixing in the euphotic zone where ample light is available for photosynthesis. Thus, primary production is constrained and the region's entire food web is disrupted. If rapid warming continues, the Indian Ocean could transform into an ecological desert and cease being productive.<ref name="onlinelibrary.wiley.com"/>

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<gallery mode="packed" heights="130px" style="float:right;">
File:Antarctic krill (Euphausia superba).jpg| Ocean warming is changing the distribution of the keystone species Antarctic krill<ref name=pewtrusts2019 /><ref name=Rogers2019 />
File:Trematomus bernacchii.jpg| In the Antarctic, limited-range shallow-water species, like this [[Biology:Emerald rockcod|emerald rockcod]], are under threat.<ref name=pewtrusts2019>[https://www.pewtrusts.org/en/research-and-analysis/articles/2019/10/25/climate-change-could-threaten-many-antarctic-marine-species Climate Change Could Threaten Many Antarctic Marine Species]. ''Pew'', 25 October 2019.</ref><ref name=Rogers2019>Rogers, A. D., Frinault, B. A. V., Barnes, D. K. A., Bindoff, N. L., Downie, R., Ducklow, H. W., Friedlaender, A. S., Hart, T., Hill, S. L., Hofmann, E. E. and Linse, K. (2019) "Antarctic futures: an assessment of climate-driven changes in ecosystem structure, function, and service provisioning in the Southern Ocean". ''Annual review of marine science'', '''12''': 87–120. {{doi|10.1146/annurev-marine-010419-011028}}.</ref>
</gallery>

The [[Earth:Antarctic oscillation|Antarctic oscillation]] (also called the ''Southern Annular Mode'') is a belt of [[Earth:Westerlies|westerly winds]] or low pressure surrounding [[Earth:Antarctica|Antarctica]] which moves north or south according to which phase it is in.<ref>[http://www.bom.gov.au/climate/enso/history/ln-2010-12/SAM-what.shtml The Southern Annular Mode]. Australian Bureau of Meteorology. Accessed 25 Oct 2013.</ref> In its positive phase, the westerly wind belt that drives the [[Earth:Antarctic Circumpolar Current|Antarctic Circumpolar Current]] intensifies and contracts towards [[Earth:Antarctica|Antarctica]],<ref>{{Cite journal|last1=Thompson|first1=David W. J.|last2=Solomon|first2=Susan|last3=Kushner|first3=Paul J.|last4=England|first4=Matthew H.|last5=Grise|first5=Kevin M.|last6=Karoly|first6=David J.|date=2011-10-23|title=Signatures of the Antarctic ozone hole in Southern Hemisphere surface climate change|journal=Nature Geoscience|language=En|volume=4|issue=11|pages=741–749|doi=10.1038/ngeo1296|bibcode=2011NatGe...4..741T|issn=1752-0894}}</ref> while its negative phase the belt moves towards the Equator. Winds associated with the Antarctic oscillation cause oceanic [[Earth:Upwelling|upwelling]] of warm circumpolar deep water along the Antarctic continental shelf.<ref>{{Cite journal |last1=Hayakawa |first1=Hideaki |last2=Shibuya |first2=Kazuo |last3=Aoyama |first3=Yuichi |last4=Nogi |first4=Yoshifumi |last5=Doi |first5=Koichiro |date=2012 |title=Ocean bottom pressure variability in the Antarctic Divergence Zone off Lützow-Holm Bay, East Antarctica |journal=Deep Sea Research Part I: Oceanographic Research Papers |volume=60 |pages=22–31 |doi=10.1016/j.dsr.2011.09.005 |bibcode=2012DSRI...60...22H |issn=0967-0637}}</ref><ref>{{Cite journal|last1=Spence|first1=Paul|last2=Griffies|first2=Stephen M.|last3=England|first3=Matthew H.|last4=Hogg|first4=Andrew McC.|last5=Saenko|first5=Oleg A.|last6=Jourdain|first6=Nicolas C.|date=2014-07-12|title=Rapid subsurface warming and circulation changes of Antarctic coastal waters by poleward shifting winds|journal=Geophysical Research Letters|language=en|volume=41|issue=13|pages=4601–4610|doi=10.1002/2014gl060613|bibcode=2014GeoRL..41.4601S|issn=0094-8276|url=https://openresearch-repository.anu.edu.au/bitstream/1885/56321/2/01_Spence_Rapid_subsurface_warming_and_2014.pdf|hdl=1885/56321|doi-access=free}}</ref> This has been linked to [[Earth:Ice shelf|ice shelf]] basal melt,<ref>{{Cite journal |last1=Greene |first1=Chad A. |last2=Blankenship |first2=Donald D. |last3=Gwyther| first3=David E. |last4=Silvano |first4=Alessandro |last5=Wijk |first5=Esmee van |date=2017-11-01 |title=Wind causes Totten Ice Shelf melt and acceleration |journal=Science Advances |language=en |volume=3 |issue=11 |pages=e1701681 |doi=10.1126/sciadv.1701681 |pmid=29109976 |issn=2375-2548 |pmc=5665591 |bibcode=2017SciA....3E1681G}}</ref> representing a possible wind-driven mechanism that could destabilize large portions of the Antarctic Ice Sheet.<ref>{{Cite journal |last1=Anderson |first1=R. F. |last2=Ali |first2=S. |last3=Bradtmiller |first3=L. I. |last4=Nielsen |first4=S. H. H. |last5=Fleisher |first5=M. Q. |last6=Anderson |first6=B. E. |last7=Burckle |first7=L. H. |date=2009-03-13 |title=Wind-Driven Upwelling in the Southern Ocean and the Deglacial Rise in Atmospheric CO<sub>2</sub> |journal=Science |language=en |volume=323 |issue=5920 |pages=1443–1448 |doi=10.1126/science.1167441 |issn=0036-8075 |pmid=19286547 |bibcode=2009Sci...323.1443A |s2cid=206517043}}</ref> The Antarctic oscillation is currently in the most extreme positive phase that has occurred for over a thousand years. Recently this positive phase has been further intensifying, and this has been attributed to increasing [[Chemistry:Greenhouse gas|greenhouse gas]] levels and later stratospheric ozone depletion.<ref>{{Cite web|url = https://www.ncdc.noaa.gov/paleo-search/study/16197|access-date = 5 January 2020|title = 1000-year Southern Annular Mode Reconstruction|publisher = NOAA: [[Earth:National Climatic Data Center|National Climatic Data Center]]}}</ref><ref>{{cite news |last=Abram |first=Nerilie|url=http://www.nature.com/nclimate/journal/v4/n7/full/nclimate2235.html |title=Evolution of the Southern Annular Mode during the past millennium |work=Nature |date=2014-05-11 |access-date=2014-09-13 }}</ref> These large-scale alterations in the physical environment are "driving change through all levels of Antarctic marine food webs".<ref name=pewtrusts2019 /><ref name=Rogers2019 /> Ocean warming is also changing the distribution of Antarctic krill.<ref name=pewtrusts2019 /><ref name=Rogers2019 /> Antarctic krill is the [[Biology:Keystone species|keystone species]] of the Antarctic ecosystem beyond the coastal shelf, and is an important food source for [[Biology:Marine mammal|marine mammal]]s and birds.<ref>{{cite book |editor1=Guido di Prisco |editor2=Cinzia Verde |volume=1 |publisher=Springer Science & Business Media |year=2012 |isbn=9783642273513 |author=Mario Vacchi |author2=Philippe Koubbi |author3=Laura Ghigliotti |author4=Eva Pisano |title=Adaptation and Evolution in Marine Environments, Volume 1 |chapter=Sea-Ice Interactions with Polar Fish: Focus on the Antarctic Silverfish Life History |pages=51–73<!-- at p. 63 --> |doi=10.1007/978-3-642-27352-0_4}}</ref>

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The IPCC (2019) says marine organisms are being affected globally by ocean warming with direct impacts on human communities, fisheries, and food production.<ref>{{Cite report | series = Special Report on the Ocean and Cryosphere in a Changing Climate (SROCC) | title = Chapter 5: Changing Ocean, Marine Ecosystems, and Dependent Communities | work = IPCC | access-date = 25 March 2020 | date = 25 September 2019 | url = https://report.ipcc.ch/srocc/pdf/SROCC_FinalDraft_Chapter5.pdf | pages = 5–6 | archive-date = 19 December 2019 | archive-url = https://web.archive.org/web/20191219012652/https://report.ipcc.ch/srocc/pdf/SROCC_FinalDraft_Chapter5.pdf | url-status = dead }}</ref> It is likely there will be a 15% decrease in the number of marine animals and a decrease of 21% to 24% in fisheries catches by the end of the 21st century because of climate change.<ref>{{Cite web| title = 'We're All in Big Trouble': Climate Panel Sees a Dire Future |newspaper= {{wipe|The New York Times}} via the Associated Press | access-date = 25 March 2020 |date = 25 September 2019| url = https://www.nytimes.com/aponline/2019/09/25/science/ap-us-sci-climate-report.html?partner=IFTTT}}</ref>

A 2020 study reports that by 2050 global warming could be spreading in the deep ocean seven times faster than it is now, even if emissions of greenhouse gases are cut. Warming in mesopelagic and deeper layers could have major consequences for the deep ocean food web, since ocean species will need to move to stay at survival temperatures.<ref>[https://www.theguardian.com/environment/2020/may/26/climate-change-in-deep-oceans-could-be-seven-times-faster-by-middle-of-century-report-says Climate change in deep oceans could be seven times faster by middle of century, report says] ''The Guardian'', 25 May 2020.</ref><ref>Brito-Morales, I., Schoeman, D. S., Molinos, J. G., Burrows, M. T., Klein, C. J., Arafeh-Dalmau, N., Kaschner, K., Garilao, C., Kesner-Reyes, K. and Richardson, A. J. (2020) "Climate velocity reveals increasing exposure of deep-ocean biodiversity to future warming". ''Nature Climate Change'', pp. 1–6. {{doi|10.5281/zenodo.3596584}}.</ref>

===Rising sea levels===
[[File:Sea level change 1993 to 2018.jpg|thumb|upright=1.5| Between 1993 and 2018, the mean sea level has risen across most of the world ocean (blue colors).<ref>Lindsey, Rebecca (2019) [https://www.climate.gov/news-features/understanding-climate/climate-change-global-sea-level Climate Change: Global Sea Level]. ''NOAA Climate'', 19 November 2019.</ref>]]

Coastal ecosystems are facing further changes because of rising sea levels. Some ecosystems can move inland with the high-water mark, but others are prevented from migrating due to natural or artificial barriers. This coastal narrowing, called coastal squeeze if human-made barriers are involved, can result in the loss of habitats such as [[Earth:Mudflat|mudflat]]s and [[Earth:Marsh|marsh]]es.<ref name=":7">{{Cite web|url=http://datazone.birdlife.org/sea-level-rise-poses-a-major-threat-to-coastal-ecosystems-and-the-biota-they-support|title=Sea level rise poses a major threat to coastal ecosystems and the biota they support|date=2015|website=birdlife.org|publisher=Birdlife International}}</ref><ref>{{cite journal |last1=Pontee |first1=Nigel |title=Defining coastal squeeze: A discussion |journal=Ocean & Coastal Management |date=November 2013 |volume=84 |pages=204–207 |doi=10.1016/j.ocecoaman.2013.07.010 |bibcode=2013OCM....84..204P }}</ref> Mangroves and [[Earth:Tidal marsh|tidal marsh]]es adjust to rising sea levels by building vertically using accumulated [[Earth:Sediment|sediment]] and [[Chemistry:Organic matter|organic matter]]. If [[Earth:Sea level rise|sea level rise]] is too rapid, they will not be able to keep up and will instead be submerged.<ref>{{cite journal|last1=Krauss|first1=Ken W.|last2=McKee|first2=Karen L.|last3=Lovelock|first3=Catherine E.|last4=Cahoon|first4=Donald R.|last5=Saintilan|first5=Neil|last6=Reef|first6=Ruth|last7=Chen|first7=Luzhen|date=April 2014|title=How mangrove forests adjust to rising sea level|url=https://digitalcommons.unl.edu/usgsstaffpub/986|journal=New Phytologist|volume=202|issue=1|pages=19–34|doi=10.1111/nph.12605|pmid=24251960}}</ref>

<gallery mode="packed" style="float:left">
File:Sea Level Change 1880 to 2015.png|Sea-level change, 1880 to 2015<ref>[http://www.cmar.csiro.au/sealevel/sl_data_cmar.html CSIRO 2015 update] to data originally published in: Church, J. A., and N. J. White (2011) "Sea-level rise from the late 19th to the early 21st century". ''Surv. Geophys.'', '''32''': 585–602.</ref><ref>NOAA Laboratory for Satellite Altimetry (2016) [https://www.star.nesdis.noaa.gov/sod/lsa/SeaLevelRise/LSA_SLR_timeseries_global.php Global sea level time series]. Accessed: June 2016.</ref>
File:Spring storm on the West Wales coast.jpg| As the sea level rises it moves further inland
</gallery>

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Coral, important for bird and fish life, also needs to grow vertically to remain close to the sea surface in order to get enough energy from sunlight. So far it has been able to keep up, but might not be able to do so in the future.<ref>{{Cite book|title=Climate Change 2014: Impacts, Adaptation, and Vulnerability.|last1=Wong|first1=Poh Poh|last2=Losado|first2=I. J.|last3=Gattuso|first3=J.-P.|last4=Hinkel|first4=Jochen|publisher=Cambridge University Press|year=2014|location=New York|chapter=Coastal Systems and Low-Lying Areas|chapter-url=http://www.ipcc.ch/pdf/assessment-report/ar5/wg2/WGIIAR5-Chap5_FINAL.pdf|access-date=28 December 2019|archive-date=23 November 2018|archive-url=https://web.archive.org/web/20181123125554/http://www.ipcc.ch/pdf/assessment-report/ar5/wg2/WGIIAR5-Chap5_FINAL.pdf|url-status=dead}}</ref> These ecosystems protect against storm surges, waves and tsunamis. Losing them makes the effects of sea level rise worse.<ref>{{cite journal |last1=Crosby |first1=Sarah C. |last2=Sax |first2=Dov F. |last3=Palmer |first3=Megan E. |last4=Booth |first4=Harriet S. |last5=Deegan |first5=Linda A. |last6=Bertness |first6=Mark D. |last7=Leslie |first7=Heather M. |title=Salt marsh persistence is threatened by predicted sea-level rise |journal=Estuarine, Coastal and Shelf Science |date=November 2016 |volume=181 |pages=93–99 |doi=10.1016/j.ecss.2016.08.018 |bibcode=2016ECSS..181...93C |doi-access=free }}</ref><ref>{{cite web|url=https://www.nature.org/media/oceansandcoasts/mangroves-for-coastal-defence.pdf|title=Mangroves for coastal defence. Guidelines for coastal managers & policy makers|author1=Spalding M.|author2=McIvor A.|date=2014|publisher=[[Organization:Wetlands International|Wetlands International]] and The Nature Conservancy|author3=Tonneijck F.H.|author4=Tol S.|author5=van Eijk P.}}</ref> Human activities, such as dam building, can prevent natural adaptation processes by restricting sediment supplies to wetlands, resulting in the loss of [[Earth:Tidal marsh|tidal marsh]]es.<ref>{{cite journal |last1=Weston |first1=Nathaniel B. |title=Declining Sediments and Rising Seas: an Unfortunate Convergence for Tidal Wetlands |journal=Estuaries and Coasts |date=16 July 2013 |volume=37 |issue=1 |pages=1–23 |doi=10.1007/s12237-013-9654-8 |s2cid=128615335 }}</ref>  When seawater moves inland, the [[Earth:Coastal flooding|coastal flooding]] can cause problems with existing terrestrial ecosystems, such as contaminating their soils.<ref name=":18">{{Cite web|url=https://www.nationalgeographic.com/environment/global-warming/sea-level-rise/|archive-url=https://web.archive.org/web/20170117004107/http://www.nationalgeographic.com/environment/global-warming/sea-level-rise/|url-status=dead|archive-date=17 January 2017|title=Sea Level Rise|date=January 13, 2017|website=National Geographic}}</ref> The [[Biology:Bramble Cay melomys|Bramble Cay melomys]] is the first known land mammal to go extinct as a result of sea level rise.<ref>{{cite web|url=http://www.australiangeographic.com.au/news/2016/06/extinct-bramble-cay-melomys|title=Extinct: Bramble Cay melomys|last=Smith|first=Lauren|date=2016-06-15|website=Australian Geographic|access-date=2016-06-17}}</ref><ref>{{Cite web|url=https://www.smh.com.au/environment/climate-change/our-little-brown-rat-first-climate-change-caused-mammal-extinction-20190219-p50yry.html|title='Our little brown rat': first climate change-caused mammal extinction|last=Hannam|first=Peter|date=2019-02-19|website=The Sydney Morning Herald|language=en|access-date=2019-06-25}}</ref>

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===Ocean circulation and salinity===

Ocean salinity is a measure of how much dissolved [[Earth:Sea salt|salt]] is in the ocean. The salts come from erosion and transport of dissolved salts from the land. The surface salinity of the ocean is a key variable in the climate system when studying the global [[Physics:Water cycle|water cycle]], ocean–atmosphere exchanges and ocean circulation, all vital components transporting heat, momentum, carbon and nutrients around the world.<ref name=ESA>[https://phys.org/news/2019-12-salinity-reveal-impact-climate-variability.html New maps of salinity reveal the impact of climate variability on oceans]. European Space Agency, 2 December 2019, ''PHYS.ORG''.</ref> Cold water is more dense than warm water and salty water is more dense than freshwater. This means the density of ocean water changes as its temperature and salinity changes. These changes in density are the main source of the power that drives the ocean circulation.<ref name=ESA />

Surface ocean salinity measurements taken since the 1950s indicate an intensification of the global water cycle with high saline areas becoming more saline and low saline areas becoming more less saline.<ref>{{cite news |url=https://www.nytimes.com/2012/04/27/world/study-hints-at-greater-threat-of-extreme-weather.html |title=Study Indicates a Greater Threat of Extreme Weather |first=Justin |last=Gillis |date=April 26, 2012 |newspaper=The New York Times |access-date=2012-04-27 |url-status=live |archive-url=https://web.archive.org/web/20120426225622/http://www.nytimes.com/2012/04/27/world/study-hints-at-greater-threat-of-extreme-weather.html |archive-date=2012-04-26 }}</ref><ref>{{Cite news |url=https://www.nasa.gov/mission_pages/aquarius/news/data-first-year.html |title=NASA's Aquarius Sees Salty Shifts |last=Vinas |first=Maria-Jose |date=June 6, 2013 |publisher=NASA |access-date=2018-01-15 |url-status=live |archive-url=https://web.archive.org/web/20170516200108/https://www.nasa.gov/mission_pages/aquarius/news/data-first-year.html |archive-date=2017-05-16}}</ref>

[[File:Overturning circulation of the global ocean.jpg|thumb|360px|left|[[Earth:Thermohaline circulation|Thermohaline circulation]], the ocean conveyor belt]]
[[File:Aquarius flat 2048x1024.ogv|thumb|360px|Surface salinity changes measured by the [[Engineering:Aquarius (SAC-D instrument)|NASA Aquarius]] satellite instrument from December 2011 to December 2012. Blue: low salinity, red: high salinity.]]

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=== Ocean acidification ===
[[File:Potential impacts of ocean acidification.png|thumb|right|upright=2|Potential impacts of ocean acidification. An overview of the potential upcoming ecological and biogeochemical consequences, linking different environmental drivers, processes, and cycles related to acidification in the future ocean.<ref>Mostofa, K. M., Liu, C.Q., Zhai, W., Minella, M., Vione, D. V., Gao, K., Minakata, D., Arakaki, T., Yoshioka, T., Hayakawa, K. and Konohira, E. (2016) "Reviews and Syntheses: Ocean acidification and its potential impacts on marine ecosystems". ''Biogeosciences'', '''13''': 1767–1786. {{doi|10.5194/bg-13-1767-2016}}. 50x50px Modified text was copied from this source, which is available under a Creative Commons Attribution 3.0 International License.</ref> ]]

[[Biology:Ocean acidification|Ocean acidification]] is the increasing acidification of the oceans, caused mainly by the uptake of [[Chemistry:Carbon dioxide|carbon dioxide]] from the atmosphere.<ref name="cald03">{{Cite journal|last=Caldeira|first=K.|author2=Wickett, M. E.|year=2003|title=Anthropogenic carbon and ocean pH|url=https://zenodo.org/record/1233227|journal=Nature|volume=425|issue=6956|pages=365|bibcode=2001AGUFMOS11C0385C|doi=10.1038/425365a|pmid=14508477|s2cid=4417880|doi-access=free}}</ref> The rise in atmospheric carbon dioxide due to the burning of fossil fuels leads to more  carbon dioxide dissolving in the ocean. When carbon dioxide dissolves in water it forms hydrogen and carbonate ions. This in turn increases the [[Biology:Ocean acidification|acidity of the ocean]] and makes survival increasingly harder for microorganisms, shellfish and other marine organisms that depend on [[Chemistry:Calcium carbonate|calcium carbonate]] to form their shells.<ref>Trujillo A. P. and Thurman H. V. (2009) ''Essentials of Oceanography'', 9th edition, page 151, Pearson Education International: {{ISBN|9780138150709}}.</ref>

Increasing acidity also has potential for other harm to marine organisms, such as depressing metabolic rates and immune responses in some organisms, and causing [[Earth:Coral bleaching|coral bleaching]].<ref name="bleaching">{{cite journal|last=Anthony|first=KRN|display-authors=et al|year=2008|title=Ocean acidification causes bleaching and productivity loss in coral reef builders|journal=Proceedings of the National Academy of Sciences|volume=105|issue=45|pages=17442–17446|bibcode=2008PNAS..10517442A|doi=10.1073/pnas.0804478105|pmc=2580748|pmid=18988740|doi-access=free}}</ref> Ocean acidification has increased 26% since the beginning of the industrial era.<ref>IPCC (2019) Summary for Policymakers. In: [https://report.ipcc.ch/srocc/pdf/SROCC_FinalDraft_FullReport.pdf ''IPCC Special Report on the Ocean and Cryosphere in a Changing Climate''] {{Webarchive|url=https://web.archive.org/web/20200905194730/https://report.ipcc.ch/srocc/pdf/SROCC_FinalDraft_FullReport.pdf |date=5 September 2020 }}, Chapter 1, page 14. [H. O. Pörtner, D. C. Roberts, V. Masson-Delmotte, P. Zhai, M. Tignor, E. Poloczanska, K. Mintenbeck, M. Nicolai, A. Okem, J. Petzold, B. Rama, N. Weyer (eds.)]. Final draft: 24 September 2019.</ref> It has been compared to anthropogenic climate change and called the "evil twin of [[Earth:Global warming|global warming]]"<ref name="HPost">{{cite web|date=9 July 2012|title=Ocean Acidification Is Climate Change's 'Equally Evil Twin,' NOAA Chief Says|url=https://www.huffingtonpost.com/2012/07/09/ocean-acidification-reefs-climate-change_n_1658081.html|url-status=dead|archive-url=https://web.archive.org/web/20120712003629/http://www.huffingtonpost.com/2012/07/09/ocean-acidification-reefs-climate-change_n_1658081.html|archive-date=12 July 2012|access-date=2012-07-09|work=Huffington Post|df=dmy-all}}</ref> and "the other {{CO2}} problem".<ref>{{cite journal|last1=Doney|first1=S. C.|last2=Fabry|first2=V. J.|last3=Feely|first3=R. A.|last4=Kleypas|first4=J. A.|year=2009|title=Ocean Acidification: The Other CO2 Problem|url=http://pdfs.semanticscholar.org/3df7/eebe38b6c8cbc6e4bca5035a339d832a570c.pdf|journal=Annual Review of Marine Science|volume=1|pages=169–192|bibcode=2009ARMS....1..169D|doi=10.1146/annurev.marine.010908.163834|pmid=21141034|archive-url=https://web.archive.org/web/20190222230042/http://pdfs.semanticscholar.org/3df7/eebe38b6c8cbc6e4bca5035a339d832a570c.pdf|archive-date=22 February 2019|s2cid=402398}}</ref>

[[File:WOA05 GLODAP del pH AYool.png|thumb|left|upright=1.5| Estimated change in sea water [[Chemistry:PH|pH]] caused by human created {{chem|CO|2}} from the start of the industrial revolution to the end of the twentieth century]]

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=== Ocean deoxygenation ===
<!-- Deleted image removed: [[File:Nitrogen cycle OMZ.jpg|thumb|upright=1.5|[[Biology:Nitrogen cycle|Nitrogen cycle]] and the oxygen minimum zone]] -->

[[Earth:Ocean deoxygenation|Ocean deoxygenation]] is an additional stressor on marine life. Ocean deoxygenation is the expansion of [[Earth:Oxygen minimum zone|oxygen minimum zone]]s in the oceans as a consequence of burning fossil fuels. The change has been fairly rapid and poses a threat to fish and other types of marine life, as well as to people who depend on marine life for nutrition or livelihood.<ref>[https://www.theguardian.com/environment/2018/jan/04/oceans-suffocating-dead-zones-oxygen-starved Oceans suffocating as huge dead zones quadruple since 1950, scientists warn]. The Guardian, 2018</ref><ref>[https://www.scientificamerican.com/article/ocean-s-oxygen-starts-running-low/ Ocean's Oxygen Starts Running Low].</ref><ref>[https://agupubs.onlinelibrary.wiley.com/doi/full/10.1002/2015GB005310 Finding forced trends in oceanic oxygen].</ref><ref>[https://www.carbonbrief.org/guest-post-how-global-warming-is-causing-ocean-oxygen-levels-to-fall How global warming is causing ocean oxygen levels to fall].</ref> Ocean deoxygenation poses implications for [[Earth:Primary production|ocean productivity]], nutrient cycling, carbon cycling, and [[Biology:Marine habitats|marine habitats]].<ref>{{Cite news|url=https://www.theguardian.com/environment/2019/dec/07/oceans-losing-oxygen-at-unprecedented-rate-experts-warn|title=Oceans losing oxygen at unprecedented rate, experts warn|last=Harvey|first=Fiona|date=2019-12-07|work=The Guardian|access-date=2019-12-07|language=en-GB|issn=0261-3077}}</ref><ref>Laffoley, D. and Baxter, J. M. (eds.) (2019) [https://www.iucn.org/content/ocean-deoxygenation-everyones-problem Ocean deoxygenation : everyone’s problem] {{Webarchive|url=https://web.archive.org/web/20220308184645/https://www.iucn.org/content/ocean-deoxygenation-everyones-problem |date=8 March 2022 }}, IUCN Report.</ref>

Ocean warming exacerbates ocean deoxygenation and further stresses marine organisms, limiting nutrient availability by increasing [[Earth:Ocean stratification|ocean stratification]] through density and solubility effects while at the same time increasing metabolic demand.<ref>Bednaršek, N., Harvey, C. J., Kaplan, I. C., Feely, R. A. and Možina, J. (2016) "Pteropods on the edge: Cumulative effects of ocean acidification, warming, and deoxygenation". ''Progress in Oceanography'', '''145''': 1–24. {{doi|10.1016/j.pocean.2016.04.002}}.</ref><ref>Keeling, Ralph F., and Hernan E. Garcia (2002) "The change in oceanic O2 inventory associated with recent global warming". ''Proceedings of the National Academy of Sciences'', '''99'''(12): 7848–7853. {{doi|10.1073/pnas.122154899}}.</ref> According to the IPCC 2019 Special Report on the Ocean and Cryosphere in a Changing Climate, the viability of species is being disrupted throughout the ocean food web due to changes in [[Chemistry:Ocean chemistry|ocean chemistry]]. As the ocean warms, [[Earth:Mixed layer|mixing between water layers]] decreases, resulting in less oxygen and nutrients being available for [[Biology:Marine life|marine life]].<ref>{{Cite press release |series=Special Report on the Ocean and Cryosphere in a Changing Climate (SROCC) |title=Press Release |work=IPCC| access-date = 25 March 2020 |date = 25 September 2019| url = https://www.ipcc.ch/site/assets/uploads/sites/3/2019/09/SROCC_PressRelease_EN.pdf |pages=3}}</ref>

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===Polar ice sheets===
[[File:Climate change causes sea ice to melt.jpg|thumb|upright=1.5|right| Climate change causes sea ice to melt, transforming the Arctic from an icy desert into an open ocean. Polar bears and seals may lose their habitats, phytoplankton growth may increase and fuel the Arctic food web, which may lead to higher carbon burial rates and possibly decrease the amount of {{CO2}} in the atmosphere.<ref>{{cite journal |doi = 10.3389/frym.2019.00136|title = The Carbon Story of a Melting Arctic|year = 2019|last1 = Faust|first1 = Johan C.|last2 = März|first2 = Christian|last3 = Henley|first3 = Sian F.|journal = Frontiers for Young Minds|volume = 7|s2cid = 208531858|doi-access = free}}50px Modified text was copied from this source, which is available under a [https://creativecommons.org/licenses/by/4.0/ Creative Commons Attribution 4.0 International License].</ref>]]


Until recently, [[Earth:Ice sheet|ice sheet]]s<ref>{{Cite web|title=Quick Facts on Ice Sheets {{!}} National Snow and Ice Data Center|url=https://nsidc.org/cryosphere/quickfacts/icesheets.html|access-date=2021-09-14|website=nsidc.org}}</ref> were viewed as inert components of the carbon cycle and largely disregarded in global models. Research in the past decade has transformed this view, demonstrating the existence of uniquely adapted microbial communities, high rates of biogeochemical/physical weathering in ice sheets and storage and cycling of organic carbon in excess of 100 billion tonnes, as well as nutrients.<ref name=Wadham2019 />

[[File:Carbon stores and fluxes in present day ice sheets.webp|thumb|upright=1.5|left| Carbon stores and fluxes in present-day ice sheets (2019), and the predicted impact on carbon dioxide (where data exists). Estimated carbon fluxes are measured in Tg/a (megatonnes of carbon per year) and estimated sizes of carbon stores are measured in Pg C (thousands of megatonnes of carbon). DOC = [[Chemistry:Dissolved organic carbon|dissolved organic carbon]], POC = particulate organic carbon.<ref name=Wadham2019>Wadham, J. L., Hawkings, J. R., Tarasov, L., Gregoire, L. J., Spencer, R. G. M., Gutjahr, M., Ridgwell, A. and Kohfeld, K. E. (2019) "Ice sheets matter for the global carbon cycle". ''Nature communications'', '''10'''(1): 1–17. {{doi|10.1038/s41467-019-11394-4}}. 50px Modified text was copied from this source, which is available under a [https://creativecommons.org/licenses/by/4.0/ Creative Commons Attribution 4.0 International License].</ref>]]

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==Biogeochemical==
[[File:Anthropogenic effects on the marine nitrogen cycle.jpg|thumb|upright=1.8|Anthropogenic effects on the marine nitrogen cycle<ref name=Pajares2018>{{cite journal |title = Processes and Microorganisms Involved in the Marine Nitrogen Cycle: Knowledge and Gaps |journal=Frontiers in Marine Science |date=29 November 2019 |author=Silvia Pajares |author2=Ramiro Ramos |volume=6 |doi = 10.3389/fmars.2019.00739|doi-access = free}} 50px Modified text was copied from this source, which is available under a [https://creativecommons.org/licenses/by/4.0/ Creative Commons Attribution 4.0 International License].</ref>]]

The diagram on the right shows some human impacts on the marine nitrogen cycle. Bioavailable nitrogen (Nb) is introduced into marine ecosystems by runoff or atmospheric deposition, causing [[Earth:Eutrophication|eutrophication]], the formation of [[Earth:Dead zone (ecology)|dead zones]] and the expansion of the [[Earth:Oxygen minimum zone|oxygen minimum zone]]s (OMZs). The release of nitrogen oxides (N<sub>2</sub>O, NO) from anthropogenic activities and oxygen-depleted zones causes stratospheric [[Earth:Ozone depletion|ozone depletion]] leading to higher UVB exposition, which produces the damage of marine life, [[Earth:Acid rain|acid rain]] and ocean warming. Ocean warming causes water stratification, deoxygenation, and the formation of dead zones. Dead zones and OMZs are hotspots for [[Biology:Anammox|anammox]] and [[Biology:Denitrification|denitrification]], causing nitrogen loss (N<sub>2</sub> and N<sub>2</sub>O). Elevated atmospheric carbon dioxide acidifies seawater, decreasing pH-dependent N-cycling processes such as nitrification, and enhancing N<sub>2</sub> [[Biology:Nitrogen fixation|fixation]].<ref name=Pajares2018 />

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===Calcium carbonates===
{{multiple image
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 | caption2  = [[Biology:Sea urchin|Sea urchin]]
 | footer    = Increases in acidity makes it difficult for microorganisms like coccolithophores, and shellfish like sea urchins, to build their carbonate shells
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[[Chemistry:Aragonite|Aragonite]] is a form of [[Chemistry:Calcium carbonate|calcium carbonate]] many marine animals use to build carbonate skeletons and shells. The lower the aragonite [[Biology:Ocean acidification#Decrease in saturation state|saturation level]], the more difficult it is for the organisms to build and maintain their skeletons and shells. The map below shows changes in the aragonite saturation level of ocean surface waters between 1880 and 2012.<ref>{{cite web| title=Changes in Aragonite Saturation of the World's Oceans, 1880–2015| url=https://www.epa.gov/climate-indicators/climate-change-indicators-ocean-acidity|author=Woods Hole Oceanographic Institution| date=August 2016}}<br />{{cite journal|last1=Feely|first1=R. A.|first2=S. C.|last2=Doney|first3=S. R.|last3=Cooley|year=2009|title=Ocean acidification: Present conditions and future changes in a high-CO<sub>2</sub> world|url=https://darchive.mblwhoilibrary.org/bitstream/handle/1912/3180/22-4_feely.pdf?sequence=1|journal=Oceanography|volume=22|issue=4|pages=36–47|doi=10.5670/oceanog.2009.95|hdl=1912/3180|via=Woods Hole Open Access Server|doi-access=free}}<br />{{cite web| title=Climate Change Indicators in the United States, 2012, 2nd ed.: Ocean Acidity: Figure 2. Changes in Aragonite Saturation of the World's Oceans, 1880–2012 | publisher=US Environmental Protection Agency (EPA) | url=http://www.epa.gov/climatechange/science/indicators/oceans/acidity.html#fragment-2 }}</ref>

To pick one example, pteropods are a group of widely distributed swimming [[Biology:Sea snail|sea snail]]s. For pteropods to create shells they require [[Chemistry:Aragonite|aragonite]] which is produced through carbonate ions and dissolved calcium. Pteropods are severely affected because increasing acidification levels have steadily decreased the amount of water supersaturated with carbonate which is needed for the aragonite creation.<ref name="biogeosciences">{{cite web | url=http://www.biogeosciences.net/8/919/2011/bg-8-919-2011.pdf | title=Impact of ocean acidification and elevated temperatures on early juveniles of the polar shelled pteropod Limacina helicina : mortality, shell degradation, and shell growth | publisher=Biogeosciences | work=Report |date=15 April 2011 | access-date=14 November 2013 |author1=Lischka, S. |author2=Büdenbender J. |author3=Boxhammer T. |author4=Riebesell U. | pages=919–932}}</ref>

When the shell of a pteropod was immersed in water with a pH level the ocean is projected to reach by the year 2100, the shell almost completely dissolved within six weeks.<ref>{{Cite journal|title = Limacina helicina shell dissolution as an indicator of declining habitat suitability owing to ocean acidification in the California Current Ecosystem|journal = Proc. R. Soc. B|date = 2014|issn = 0962-8452|pmc = 4024287|pmid = 24789895|pages = 20140123|volume = 281|issue = 1785|doi = 10.1098/rspb.2014.0123|first1 = N.|last1 = Bednaršek|first2 = R. A.|last2 = Feely|first3 = J. C. P.|last3 = Reum|first4 = B.|last4 = Peterson|first5 = J.|last5 = Menkel|first6 = S. R.|last6 = Alin|first7 = B.|last7 = Hales}}</ref> Likewise [[Biology:Coral|coral]]s,<ref>{{Cite journal|last1=D'Olivo|first1=Juan P.|last2=Ellwood|first2=George|last3=DeCarlo|first3=Thomas M.|last4=McCulloch|first4=Malcolm T.|date=2019-11-15|title=Deconvolving the long-term impacts of ocean acidification and warming on coral biomineralisation|journal=Earth and Planetary Science Letters|volume=526|pages=115785|doi=10.1016/j.epsl.2019.115785|bibcode=2019E&PSL.52615785D|issn=0012-821X|doi-access=free}}</ref> [[Biology:Coralline algae|coralline algae]],<ref name="kuffner">{{Cite journal | last=Kuffner | first=I. B. |author2=Andersson, A. J.|author3=Jokiel, P. L.|author4=Rodgers, K. S. |author5=Mackenzie, F. T. | year=2007 | title=Decreased abundance of crustose coralline algae due to ocean acidification | journal=[[Earth:Nature Geoscience|Nature Geoscience]] | volume=1 |issue=2 |pages=114–117 |doi=10.1038/ngeo100 |bibcode=2008NatGe...1..114K | s2cid=3456369 }}</ref> coccolithophores,<ref name="delille05">{{Cite journal | last=Delille | first=B. | author2=Harlay, J. | author3=Zondervan, I. | author4=Jacquet, S. | author5=Chou, L. | author6=Wollast, R. | author7=Bellerby, R.G.J. | author8=Frankignoulle, M. | author9=Borges, A.V. | author10=Riebesell, U. | author11=Gattuso, J.-P. | year=2005 | title=Response of primary production and calcification to changes of pCO2 during experimental blooms of the coccolithophorid ''Emiliania huxleyi'' | journal=Global Biogeochemical Cycles | volume=19 | doi=10.1029/2004GB002318 | pages=GB2023 | bibcode=2005GBioC..19.2023D | issue=2 | doi-access=free }}</ref> [[Biology:Foraminifera|foraminifera]],<ref>{{Cite news |last=Phillips |first=Graham |author2=Chris Branagan |title=Ocean Acidification – The BIG global warming story |date=2007 |publisher=Australian Broadcasting Corporation |url=http://www.abc.net.au/catalyst/stories/s2029333.htm |work =ABC TV Science: Catalyst |access-date=2007-09-18  }}</ref> as well as shellfish generally,<ref name="gaz07">{{Cite journal |last=Gazeau |first=F. |author2=Quiblier, C. |author3=Jansen, J. M. |author4=Gattuso, J.-P. |author5=Middelburg, J. J. |author6=Heip, C. H. R. |year=2007 |title=Impact of elevated {{chem|CO|2}} on shellfish calcification |url=http://www.obs-vlfr.fr/~gattuso/jpg_papers_list.php |journal=[[Earth:Geophysical Research Letters|Geophysical Research Letters]] |volume=34 |issue=7 |pages=L07603 |doi=10.1029/2006GL028554 |bibcode= |hdl=20.500.11755/a8941c6a-6d0b-43d5-ba0d-157a7aa05668 |s2cid=130190489 |hdl-access=free |access-date=1 January 2020 |archive-date=20 July 2019 |archive-url=https://web.archive.org/web/20190720181400/http://www.obs-vlfr.fr/~gattuso/jpg_papers_list.php |url-status=dead }}</ref> all experience reduced calcification or enhanced dissolution as an effect of ocean acidification.

<gallery mode="packed" heights="170px" style="float:left;">
File:Changes in aragonite saturation of the world's oceans, 1880-2012 (US EPA).png|Decreases in aragonite saturation make it more difficult for marine organisms like pteropods to build [[Biology:Seashell|calcium shells]]
File:Effect of Ocean Acidification on Calcification.svg|Shells of pteropods dissolve in increasingly acidic conditions caused by increased amounts of atmospheric {{CO2}}
</gallery>

[[File:Impacts of ocean acidification (NOAA EVL).webm|thumb|355px| Video summarizing impacts of ocean acidification – Source: NOAA]]

{{multiple image
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 | caption1  = Unhealthy pteropod showing effects of ocean acidification
 | image2    = FMIB 52630 Ophiopholis aculeata.jpeg
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 | caption2  = Ocean acidification causes brittle stars to lose muscle mass
 | footer    = Pteropods and [[Biology:Brittle star|brittle star]]s form the base of Arctic food webs
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[[Biology:Pteropoda|Pteropods]] and [[Biology:Brittle star|brittle star]]s together form the base of the Arctic [[Biology:Food web|food web]]s and both are seriously damaged by acidification. Pteropods shells dissolve with increasing acidification and brittle stars lose muscle mass when re-growing appendages.<ref>{{cite web|title=Effects of Ocean Acidification on Marine Species & Ecosystems|url=http://oceana.org/en/our-work/climate-energy/ocean-acidification/learn-act/effects-of-ocean-acidification-on-marine-species-ecosystems|work=Report|publisher=OCEANA|access-date=13 October 2013|archive-date=25 December 2014|archive-url=https://web.archive.org/web/20141225091214/http://oceana.org/en/our-work/climate-energy/ocean-acidification/learn-act/effects-of-ocean-acidification-on-marine-species-ecosystems|url-status=dead}}</ref> Additionally the brittle star's eggs die within a few days when exposed to expected conditions resulting from Arctic acidification.<ref>{{cite web |url=http://www.cicero.uio.no/webnews/index_e.aspx?id=11909 | title=Comprehensive study of Arctic Ocean acidification | publisher=CICERO | work=Study | access-date=14 November 2013}}</ref> Acidification threatens to destroy Arctic food webs from the base up. Arctic waters are changing rapidly and are advanced in the process of becoming undersaturated with aragonite.<ref name="biogeosciences" /> Arctic food webs are considered simple, meaning there are few steps in the food chain from small organisms to larger predators. For example, pteropods are "a key prey item of a number of higher predators – larger plankton, fish, seabirds, whales".<ref>{{cite web|title=Antarctic marine wildlife is under threat, study finds|url=https://www.bbc.co.uk/nature/20461646|publisher=BBC Nature|access-date=13 October 2013}}</ref>

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===Silicates===
The rise in agriculture of the past 400 years has increased the exposure rocks and soils, which has resulted in increased rates of silicate weathering. In turn, the leaching of [[Physics:Amorphous solid|amorphous]] silica stocks from soils has also increased, delivering higher concentrations of dissolved silica in rivers.<ref name=":4">{{cite journal|last1=Gaillardet |first1=J.|last2=Dupré|first2=B. |last3=Louvat |first3=P.|last4=Allègre |first4=C. J. |date=July 1999 |title=Global silicate weathering and CO2 consumption rates deduced from the chemistry of large rivers|journal=Chemical Geology|volume=159|issue=1–4|pages=3–30|doi=10.1016/s0009-2541(99)00031-5|issn=0009-2541|bibcode=1999ChGeo.159....3G}}</ref> Conversely, increased damming has led to a reduction in silica supply to the ocean due to uptake by freshwater diatoms behind dams. The dominance of non-siliceous [[Earth:Phytoplankton|phytoplankton]] due to anthropogenic nitrogen and phosphorus loading and enhanced silica dissolution in warmer waters has the potential to limit silicon ocean sediment export in the future.<ref name=":4" />

In 2019 a group of scientists suggested acidification is reducing [[Biology:Diatom|diatom]] silica production in the [[Earth:Southern Ocean|Southern Ocean]].<ref>[https://phys.org/news/2019-08-threat-ocean-acidification-emerges-southern.html New threat from ocean acidification emerges in the Southern Ocean], ''Phys.org'', 26 August 2019.</ref><ref>Petrou, K., Baker, K. G., Nielsen, D. A. et&nbsp;al.  (2019) "Acidification diminishes diatom silica production in the Southern Ocean". ''Nature: Climate Change'', '''9''': 781–786. {{doi|10.1038/s41558-019-0557-y}}.</ref>

{{multiple image
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 | footer    = Changes in [[Chemistry:Orthosilicic acid#Oceanic silicic acid|ocean silicic acid]] can make it difficult for the [[Biology:Marine microorganism|marine microorganism]]s that construct silica shells
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 | image1    = Stephanopyxis grunowii.jpg
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 | caption1  = [[Biology:Diatom|Diatom]]
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 | caption2  = Radiolarian
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<gallery mode="packed" heights="190px" style="float:right;">
File:WOA09 sea-surf H4SIO4 AYool.png| Concentration of [[Chemistry:Silicic acid|silicic acid]] in the upper [[Earth:Pelagic zone|pelagic zone]],<ref>{{cite web|url=http://www.nodc.noaa.gov/OC5/WOA09/pr_woa09.html|title=World Ocean Atlas 2009|first=US Department of Commerce, NOAA National Centers for Environmental|last=Information|website=www.nodc.noaa.gov|access-date=17 April 2018}}</ref> showing high levels in the Southern Ocean
File:Marine Silica Cycle.png| Generalized [[Biology:Silica cycle#Marine silica cycling|marine silica cycle]], adapted from Treguer et&nbsp;al., 1995<ref>{{Cite journal |last1=Tréguer |first1=Paul |last2=Nelson |first2=David M. |last3=Bennekom |first3=Aleido J. Van |last4=DeMaster |first4=David J. |last5=Leynaert |first5=Aude |last6=Quéguiner |first6=Bernard |date=1995-04-21 |title=The Silica Balance in the World Ocean: A Reestimate |journal=Science |language=en |volume=268 |issue=5209 |pages=375–379 |doi=10.1126/science.268.5209.375 |issn=0036-8075|pmid=17746543 |bibcode=1995Sci...268..375T |s2cid=5672525}}</ref>
</gallery>
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===Carbon===
[[File:Anthropogenic changes in the global carbon cycle.png|thumb|upright=2.5|right|Anthropogenic changes in the global carbon cycle 2009–2018. Schematic representation of the overall perturbation of the global carbon cycle caused by anthropogenic activities, averaged globally for the decade 2009–2018. See legends for the corresponding arrows and units. The uncertainty in the atmospheric CO2 growth rate is very small (±0.02 GtC yr−1) and is neglected for the figure. The anthropogenic perturbation occurs on top of an active carbon cycle, with fluxes and stocks represented in the background<ref>Ciais, P., Sabine, C., Govindasamy, B., Bopp, L., Brovkin, V., Canadell, J., Chhabra, A., DeFries, R., Galloway, J., Heimann, M., Jones, C., Le Quéré, C., Myneni, R., Piao, S., and Thornton, P.: Chapter 6: Carbon and Other Biogeochemical Cycles, in: Climate Change 2013 The Physical Science Basis, edited by: Stocker, T., Qin, D., and Platner, G.-K., Cambridge University Press, Cambridge, 2013.</ref> for all numbers, with the ocean gross fluxes updated to 90 GtC yr−1 to account for the increase in atmospheric CO2 since publication. The carbon stocks in coasts are from a literature review of coastal marine sediments.<ref>Price, J. T. and Warren, R (2016) [http://avoid-net-uk.cc.ic.ac.uk/wpcontent/uploads/delightful-downloads/2016/03/Literature-review-of-the-potential-of-bluecarbon-activities-to-reduce-emissions-AVOID2-WPE2.pdf Review of the Potential of “Blue Carbon” Activities to Reduce Emissions].</ref><ref>Friedlingstein, P., Jones, M., O'Sullivan, M., Andrew, R., Hauck, J., Peters, G., Peters, W., Pongratz, J., Sitch, S., Le Quéré, C. and 66 others (2019) "Global carbon budget 2019". ''Earth System Science Data'', '''11'''(4): 1783–1838. {{doi|10.5194/essd-11-1783-2019}}. 50px Modified text was copied from this source, which is available under a [https://creativecommons.org/licenses/by/4.0/ Creative Commons Attribution 4.0 International License].</ref>]]

[[File:Nitrogen–carbon–climate interactions.jpg|thumb|upright=1.7|left| Nitrogen–carbon–climate interactions. Shown are the main interacting drivers during the Anthropocene. Signs indicate an increase (+) or a decrease (−) in the factor shown; (?) indicate an unknown impact. Colors of the arrow indicate direct anthropogenic impacts (red) or natural interactions (blue, many of which also modified by human influence). Strength of the interaction is expressed by the arrow thickness.<ref>Cardini, U., Bednarz, V. N., Foster, R. A. and Wild, C. (2014) "Benthic N2 fixation in coral reefs and the potential effects of human‐induced environmental change". ''Ecology and evolution'', '''4'''(9): 1706–1727. {{doi|10.1002/ece3.1050}} 50px Modified text was copied from this source, which is available under a [https://creativecommons.org/licenses/by/4.0/ Creative Commons Attribution 4.0 International License].</ref><ref>Adapted from: Gruber, N., and J. N. Galloway (2008) "An Earth‐system perspective of the global nitrogen cycle". ''Nature'', 451:293–296. {{doi|10.1038/nature06592}}.</ref>]]

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[[File:Proposed marine carbon dioxide removal options.jpg|thumb|upright=1.7|right|Proposed marine carbon dioxide removal options<ref name=Boettcher2021>{{cite journal |doi = 10.3389/fclim.2021.664456|doi-access = free|title = Navigating Potential Hype and Opportunity in Governing Marine Carbon Removal|year = 2021|last1 = Boettcher|first1 = Miranda|last2 = Brent|first2 = Kerryn|last3 = Buck|first3 = Holly Jean|last4 = Low|first4 = Sean|last5 = McLaren|first5 = Duncan|last6 = Mengis|first6 = Nadine|journal = Frontiers in Climate|volume = 3}} 50px Modified text was copied from this source, which is available under a [https://creativecommons.org/licenses/by/4.0/ Creative Commons Attribution 4.0 International License].</ref>]]

As the technical and political challenges of land-based carbon dioxide removal approaches become more apparent, the oceans may be the new "blue" frontier for carbon drawdown strategies in climate governance.<ref name=Boettcher2021 /> Marine environments are the blue frontier of a strategy for novel carbon sinks in post-Paris climate governance, from nature-based ecosystem management to industrial-scale technological interventions in the Earth system. Marine carbon dioxide removal approaches are diverse{{hsp}}<ref>Royal Society/Royal Academy of Engineering (2018). [https://royalsociety.org/-/media/policy/projects/greenhouse-gas-removal/royal-society-greenhouse-gas-removal-report-2018.pdf ''Greenhouse Gas Removal'']. {{ISBN|978-1-78252-349-9}}</ref><ref>GESAMP (2019). "High level review of a wide range of proposed marine geoengineering techniques", in ''Rep. Stud. GESAMP''. '''98''', (IMO/FAO/UNESCO-IOC/UNIDO/WMO/IAEA/UN/UN Environment/ UNDP/ISA Joint Group of Experts on the Scientific Aspects of Marine Environmental Protection). Eds: P. W. Boyd and C. M. G. Vivian, ''International Maritime Organization'', London.</ref> — although several resemble key terrestrial carbon dioxide removal proposals.<ref name=Boettcher2021 /> Ocean alkalinisation (adding silicate mineral such as [[Chemistry:Olivine|olivine]] to coastal seawater, to increase {{CO2}} uptake through chemical reactions) is enhanced weathering, [[Earth:Blue carbon|blue carbon]] (enhancing natural biological {{CO2}} drawdown from coastal vegetation) is marine reforestation, and cultivation of marine biomass (i.e., seaweed) for coupling with consequent carbon capture and storage is the marine variant of bioenergy and carbon capture and storage. [[Earth:Wetland|Wetland]]s, [[Earth:Coast|coast]]s, and the open ocean are being conceived of and developed as managed carbon removal-and-storage sites, with practices expanded from the use of soils and forests.<ref name=Boettcher2021 />

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==Effect of multiple stressors==
[[File:Drivers of hypoxia and acidification in upwelling shelf systems.svg|thumb|upright=1.7|Ecosystem impacts amplified by ocean warming and deoxygenation. Drivers of [[Earth:Hypoxia (environmental)|hypoxia]] and ocean acidification intensification in upwelling shelf systems. Equatorward winds drive the upwelling of low dissolved oxygen (DO), high nutrient, and high dissolved inorganic carbon (DIC) water from above the oxygen minimum zone. Cross-shelf gradients in productivity and bottom water residence times drive the strength of DO (DIC) decrease (increase) as water transits across a productive continental shelf.<ref name=Chan2019>Chan, F., Barth, J. A., Kroeker, K. J., Lubchenco, J. and Menge, B. A. (2019) "The dynamics and impact of ocean acidification and hypoxia". ''Oceanography'', '''32'''(3): 62–71. {{doi|10.5670/oceanog.2019.312}}. 50px Modified text was copied from this source, which is available under a [https://creativecommons.org/licenses/by/4.0/ Creative Commons Attribution 4.0 International License].</ref><ref>Gewin, V. (2010) "Oceanography: Dead in the water". ''Nature'', '''466'''(7308): 812. {{doi|10.1038/466812a}}.</ref>]]

If more than one stressor is present the effects can be amplified.<ref>Breitburg, D.L. and Riedel, G.F. (2005) [https://books.google.com/books?id=J-2JcCC_Yn0C&dq=%22Multiple+stressors+in+marine+systems%22&pg=PA167 "Multiple stressors in marine systems"]. In: M. E. Soulé, ''Marine conservation biology: the science of maintaining the sea's biodiversity'', Island Press, pages 167–182. {{ISBN|9781597267717}}</ref><ref>Bopp, L., Resplandy, L., Orr, J. C., Doney, S. C., Dunne, J. P., Gehlen, M., Halloran, P., Heinze, C., Ilyina, T., Seferian, R. and Tjiputra, J. (2013) "Multiple stressors of ocean ecosystems in the 21st century: projections with CMIP5 models". ''Biogeosciences'', '''10''': 6225–6245. {{doi|10.5194/bg-10-6225-2013}}.</ref> For example, the combination of ocean acidification and an elevation of ocean temperature can have a compounded effect on marine life far exceeding the individual harmful impact of either.<ref name="Kroeker, 2013">Kroeker, et al. (June  2013) "Impacts of ocean acidification on marine organisms: quantifying sensitivities and interaction with warming". Glob Chang Biol. 19(6): 1884–1896</ref><ref name=Harvey2013>Harvey B. P., Gwynn‐Jones D. and Moore P. J. (2013) "Meta‐analysis reveals complex marine biological responses to the interactive effects of ocean acidification and warming". ''Ecology and evolution'', '''3'''(4): 1016–1030. {{doi|10.1002/ece3.516}}</ref><ref name="ReferenceA">Nagelkerken Global alteration of ocean ecosystem functioning due to increasing human CO2 emissions, PNAS vol. 112 no. 43, 2015.</ref>

While the full implications of elevated {{CO2}} on marine ecosystems are still being documented, there is a substantial body of research showing that a combination of ocean acidification and elevated ocean temperature, driven mainly by {{CO2}} and other [[Earth:Greenhouse gas emissions|greenhouse gas emissions]], have a compounded effect on marine life and the ocean environment. This effect far exceeds the individual harmful impact of either.<ref name="Kroeker, 2013"/><ref>Harvey, et al. (April 2013) "Meta-analysis reveals complex marine biological responses to the interactive effects of ocean acidification and warming". Ecol Evol. 3(4): 1016–1030</ref><ref name="ReferenceA"/>  In addition, ocean warming exacerbates [[Earth:Ocean deoxygenation|ocean deoxygenation]], which is an additional stressor on marine organisms, by increasing ocean stratification, through density and solubility effects, thus limiting nutrients,<ref>{{cite journal | last1 = Bednaršek | first1 = N. | last2 = Harvey | first2 = C. J. | last3 = Kaplan | first3 = I. C. | last4 = Feely | first4 = R. A. | last5 = Možina | first5 = J. | year = 2016 | title = Pteropods on the edge: Cumulative effects of ocean acidification, warming, and deoxygenation | journal = Progress in Oceanography | volume = 145 | pages = 1–24 | doi = 10.1016/j.pocean.2016.04.002 | bibcode = 2016PrOce.145....1B | doi-access = free }}</ref><ref>{{cite journal | last1 = Keeling | first1 = Ralph F. | last2 = Garcia | first2 = Hernan E. | year = 2002 | title = The change in oceanic O2 inventory associated with recent global warming | journal = Proceedings of the National Academy of Sciences | volume = 99 | issue = 12| pages = 7848–7853 | doi = 10.1073/pnas.122154899 | bibcode = 2002PNAS...99.7848K | doi-access = free | pmid = 12048249 | pmc = 122983 }}</ref> while at the same time increasing metabolic demand.

[[File:Ecological Processes Coral Reefs.jpg|thumb|360px|left|Multiple stressors acting on [[Earth:Environmental issues with coral reefs|coral reefs]]<ref>Pendleton, L. H., Hoegh-Guldberg, O., Langdon, C. and Comte, A. (2016) "Multiple stressors and ecological complexity require a new approach to coral reef research". ''Frontiers in Marine Science'', '''3''': 36. {{doi|10.3389/fmars.2016.00036}}.</ref>]]

The direction and magnitude of the effects of ocean acidification, warming and deoxygenation on the ocean has been quantified by meta-analyses,<ref name=Harvey2013 /><ref>Gruber, Nicolas. "Warming up, turning sour, losing breath: ocean biogeochemistry under global change". Philosophical Transactions of the Royal Society of London A: Mathematical, Physical and Engineering Sciences 369.1943 (2011): 1980–1996.</ref><ref>Anthony, et al. (May 2011) "Ocean acidification and warming will lower coral reef resilience". Global Change biology, Volume 17, Issue 5, Pages 1798–1808</ref> and has been further tested by [[Physics:Mesocosm|mesocosm]] studies. The mesocosm studies simulated the interaction of these stressors and found a catastrophic effect on the marine food web, namely, that the increases in consumption from thermal stress more than negates any primary producer to herbivore increase from more available carbon dioxide.<ref>Goldenberg, Silvan U, et al. (2017) "Boosted food web productivity through ocean acidification collapses under warming". Global Change Biology.</ref><ref>Pistevos, Jennifer C. A., et al. (2015) "Ocean acidification and global warming impair shark hunting behaviour and growth". Scientific reports 5: 16293.</ref>

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==Drivers of change==
[[File:Drivers of change in marine ecosystems.png|thumb|360px|Drivers of change in marine ecosystems<ref name=Österblom2017>Österblom, H., Crona, B. I., Folke, C., Nyström, M. and Troell, M. (2017) "Marine ecosystem science on an intertwined planet". ''Ecosystems'', '''20'''(1): 54–61. {{doi|10.1007/s10021-016-9998-6}}.</ref>]]

Changes in marine ecosystem dynamics are influenced by socioeconomic activities (for example, fishing, pollution) and human-induced biophysical change (for example, temperature, ocean acidification) and can interact and severely impact marine ecosystem dynamics and the [[Biology:Ecosystem services|ecosystem services]] they generate to society. Understanding these direct—or proximate—interactions is an important step towards sustainable use of marine ecosystems. However, proximate interactions are embedded in a much broader socioeconomic context where, for example, economy through trade and finance, human migration and technological advances, operate and interact at a global scale, influencing proximate relationships.<ref name=Österblom2017 />

In 2024 a study<ref>{{cite journal |title=Satellite mapping reveals extensive industrial activity at sea |journal=Nature |date=3 January 2024 |volume=625 |doi=10.1038/s41586-023-06825-8 |url=https://www.nature.com/articles/s41586-023-06825-8 |access-date=10 January 2024|pmc=10764273 }}</ref> was released, dedicated to the impact of fishing and non fishing ships on the coastal waters of the ocean when 75% of the industrial activity occur. According to the study: "A third of fish stocks are operated beyond biologically sustainable levels and an estimated 30–50% of critical [[Earth:Marine habitat|marine habitats]] have been lost owing to human industrialization". It mentions that except traditional impacts like fishing, maritime trade and oil extraction there are new emerging like [[Earth:Deep sea mining|mining]], aquaculture and offshore wind turbines. It used satellite data to monitor the vessels. It found that 72% - 76% of [[Engineering:Fishing vessel|fishing ships]] and 21%-30% of energy and transport ships are "missing from [[Tracking system|public tracking systems]]". When the data was added to previously existing information about ships that were publicly tracked, this led to several discoveries including:

{| class="wikitable"
|+ Comparison between findings before and after the study.
|-
! Characteristic !! Assumptions before the study !! After the study when satellite data was added
|-
| Dispersion of fishing between continents || [[Earth:Europe|Europe]] and [[Earth:Asia|Asia]] have roughly equal fishing activity || Asia accounts for 70% of global fishing.
|-
| Dispersion of fishing activity in the [[Place:Mediterranean Sea|Mediterranean sea]] || European countries has 10 times more fishing hours than African countries || Europe and Africa has approximately equal fishing activity.
|-
| Illegal fishing near the Korean peninsula || Most activity occurs to the east of the Korean peninsula || Most activity occurs to the west of the Korean peninsula
|-
| Fishing ships in [[Earth:Marine protected area|marine protected areas]] ||  || Significant presence of fishing vessels in marine protected areas, for example, 5 per week in the Galápagos Marine Reserve and 20 per week in the Great Barrier Reef Marine Park
|}

The study discovered a significant increase in offshore wind turbins which had overpassed [[Engineering:Oil platform|oil platforms]] by number already in 2021. Fishing increased only a little in the latest years and may begin to decline because fisheries are exhausted. It concluded that "transport and energy vessel traffic may continue to expand, following trends in global trade and the rapid development of renewable energy infrastructure. In this scenario, changes to marine ecosystems brought by infrastructure and vessel traffic may rival fishing in impact".
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==Shifting baselines==
{{Quote box
 |title = 
 |quote = "Application of the physical and biological sciences has made today arguably the best of times: we live longer and healthier lives, food production has doubled in the past 35 years and [[Finance:Energy subsidies|energy subsidies]] have substituted for human labour, washing away hierarchies of servitude. But the unintended consequences of these well-intentioned actions — climate change, biodiversity loss, inadequate water supplies, and much else — could well make tomorrow the worst of times." 
 |source =  – [[Biography:Robert May, Baron May of Oxford|''Robert May'']] 2006 <ref>[https://www.newscientist.com/article/mg19225780-093-robert-may-forecasts-the-future Robert May forecasts the future]. ''New Scientist'', 15 November 2006.</ref> 
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}}

Shifting baselines arise in research on marine ecosystems because changes must be measured against some previous reference point (baseline), which in turn may represent significant changes from an even earlier state of the ecosystem.<ref name=Pauly1995>Pauly, Daniel (1995) [http://legacy.seaaroundus.s3.amazonaws.com/doc/Researcher+Publications/dpauly/PDF/1995/Journal+Articles/Anecdotes%26ShiftingBaselineSyndromeFisheries.pdf "Anecdotes and the shifting baseline syndrome of fisheries"]. ''Trends in ecology & evolution'', '''10'''(10): 430.</ref> For example, radically depleted fisheries have been evaluated by researchers who used the state of the fishery at the start of their careers as the baseline, rather than the fishery in its unexploited or untouched state. Areas that swarmed with a particular species hundreds of years ago may have experienced long-term decline, but it is the level a few decades previously that is used as the reference point for current populations. In this way large declines in ecosystems or species over long periods of time were, and are, masked. There is a loss of perception of change that occurs when each generation redefines what is natural or untouched.<ref name=Pauly1995 />

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==See also==
{{div col|colwidth=26em}}
* [[Earth:Effects of climate change on ecosystems|Effects of climate change on ecosystems]]
* [[Deep-sea exploration]]
* [[Earth:Garbage patch|Garbage patch]]
* [[Earth:Marine heatwave|Marine heatwave]]
* [[Earth:Oceanic carbon cycle|Oceanic carbon cycle]]
* [[Engineering:Offshore construction|Offshore construction]]
* Ocean exploration
* Special Report on the Ocean and Cryosphere in a Changing Climate
* [[Earth:Sustainable Development Goal 14|Sustainable Development Goal 14]]
* [[Earth:World Oceans Day|World Oceans Day]]
{{div col end}}

==References==
{{reflist}}


[[Category:Marine biology]]

{{Sourceattribution|Human impact on marine life}}