Editing Eutrophication (section)

==Causes==
[[Image:Sodium tripolyphosphate.svg|thumb|[[Sodium triphosphate]], once a component of many detergents, was a major contributor to eutrophication.|230x230px]]
[[File:NRCSTN83003 - Tennessee (6251)(NRCS Photo Gallery).jpg|thumb|212x212px|An example in [[Tennessee]] of how soil from fertilized fields can turn into runoff after a storm, creating a flux of nutrients that flow into local bodies of water such as lakes and creeks]]
Eutrophication is caused by excessive concentrations of nutrients, most commonly [[phosphate|phosphates]] and [[nitrate|nitrates]],<ref name=":6">Schindler, David and Vallentyne, John R. (2004) ''Over fertilization of the World's Freshwaters and Estuaries'', University of Alberta Press, p. 1, {{ISBN|0-88864-484-1}}</ref>  although this varies with location. Prior to their being phasing out in the 1970's, phosphate-containing detergents contributed to eutrophication. Since then, sewage and agriculture have emerged as the dominant phosphate sources.<ref name=":11">Werner, Wilfried (2002) "Fertilizers, 6. Environmental Aspects". ''Ullmann's Encyclopedia of Industrial Biology'', Wiley-VCH, Weinheim. {{doi|10.1002/14356007.n10_n05}}</ref> The main sources of nitrogen pollution are from agricultural runoff containing fertilizers and animal wastes, from sewage, and from atmospheric deposition of nitrogen originating from combustion or animal waste.<ref>{{Cite journal|author1-link=David Fowler (physicist)|last1=Fowler|first1=David|last2=Coyle|first2=Mhairi|last3=Skiba|first3=Ute|last4=Sutton|first4=Mark A.|last5=Cape|first5=J. Neil|last6=Reis|first6=Stefan|last7=Sheppard|first7=Lucy J.|last8=Jenkins|first8=Alan|last9=Grizzetti|first9=Bruna|last10=Galloway|first10=James N.|last11=Vitousek|first11=Peter|date=2013|title=The global nitrogen cycle in the twenty-first century|journal=Philosophical Transactions of the Royal Society B: Biological Sciences|volume=368|issue=1621|pages=20130164|doi=10.1098/rstb.2013.0164|pmc=3682748|pmid=23713126}}</ref>

The limitation of productivity in any aquatic system varies with the rate of supply (from external sources) and removal (flushing out) of nutrients from the body of water.<ref>{{Cite journal |last1=Moore |first1=C. M. |last2=Mills |first2=M. M. |last3=Arrigo |first3=K. R. |last4=Berman-Frank |first4=I. |last5=Bopp |first5=L. |last6=Boyd |first6=P. W. |last7=Galbraith |first7=E. D. |last8=Geider |first8=R. J. |last9=Guieu |first9=C. |last10=Jaccard |first10=S. L. |last11=Jickells |first11=T. D. |last12=La Roche |first12=J. |last13=Lenton |first13=T. M. |last14=Mahowald |first14=N. M. |last15=Marañón |first15=E. |date=September 2013 |title=Processes and patterns of oceanic nutrient limitation |url=https://www.nature.com/articles/ngeo1765 |journal=Nature Geoscience |language=en |volume=6 |issue=9 |pages=701–710 |doi=10.1038/ngeo1765 |bibcode=2013NatGe...6..701M |s2cid=249514 |issn=1752-0908}}</ref> This means that some nutrients are more prevalent in certain areas than others and different ecosystems and environments have different limiting factors. Phosphorus is the limiting factor for plant growth in most freshwater ecosystems,<ref>{{Cite journal |last1=Elser |first1=James J. |last2=Bracken |first2=Matthew E.S. |last3=Cleland |first3=Elsa E. |last4=Gruner |first4=Daniel S. |last5=Harpole |first5=W. Stanley |last6=Hillebrand |first6=Helmut |last7=Ngai |first7=Jacqueline T. |last8=Seabloom |first8=Eric W. |last9=Shurin |first9=Jonathan B. |last10=Smith |first10=Jennifer E. |date=July 2007 |title=Global analysis of nitrogen and phosphorus limitation of primary producers in freshwater, marine and terrestrial ecosystems |url=https://onlinelibrary.wiley.com/doi/10.1111/j.1461-0248.2007.01113.x |journal=Ecology Letters |language=en |volume=10 |issue=12 |pages=1135–1142 |doi=10.1111/j.1461-0248.2007.01113.x |pmid=17922835 |bibcode=2007EcolL..10.1135E |hdl=1903/7447 |s2cid=12083235 |issn=1461-023X|hdl-access=free }}</ref> and because phosphate adheres tightly to soil particles and sinks in areas such as wetlands and lakes,<ref>{{Cite web |title=Phosphorus Basics: Understanding Phosphorus Forms and Their Cycling in the Soil |work=Alabama Cooperative Extension System |url=https://www.aces.edu/blog/topics/crop-production/understanding-phosphorus-forms-and-their-cycling-in-the-soil/ |access-date=February 10, 2024 |language=en-US}}</ref> due to its prevalence nowadays more and more phosphorus is accumulating inside freshwater bodies.<ref>{{Cite web |last=US EPA |first=OW |date=November 27, 2013 |title=Indicators: Phosphorus |url=https://www.epa.gov/national-aquatic-resource-surveys/indicators-phosphorus |access-date=February 10, 2024 |publisher=EPA |language=en}}</ref><ref name=":18">{{Cite journal |last=Schindler |first=David W. |date=2012 |title=The dilemma of controlling cultural eutrophication of lakes |journal=Proceedings of the Royal Society B: Biological Sciences |volume=279 |issue=1746 |pages=4322–4333 |doi=10.1098/rspb.2012.1032 |pmc=3479793 |pmid=22915669}}</ref> In [[marine ecosystem]]s, nitrogen is the primary limiting nutrient; [[nitrous oxide]] (created by the combustion of [[fossil fuel]]s) and its deposition in the water from the atmosphere has led to an increase in nitrogen levels,<ref>{{Cite web |last=Reay |first=Dave |date=November 9, 2002 |title=Nitrous oxide Sources - Oceans |url=https://www.ghgonline.org/nitrousoceans.htm#:~:text=As%20with%20methane%2C%20man's%20impact,in%20estuaries%20and%20coastal%20waters. |access-date=February 11, 2024 |website=ghgonline |archive-date=December 7, 2023 |archive-url=https://web.archive.org/web/20231207225440/http://ghgonline.org/nitrousoceans.htm#:~:text=As%20with%20methane%2C%20man's%20impact,in%20estuaries%20and%20coastal%20waters. |url-status=dead }}</ref> and also the heightened levels of eutrophication in the ocean.<ref>{{Cite journal |last1=Bristow |first1=L. |last2=Mohr |first2=W. |date=2017 |title=Nutrients that limit growth in the ocean |url=https://doi.org/10.1016/j.cub.2017.03.030 |url-status=live |journal=Current Biology |volume=27 |issue=11 |pages=R431–R510 |doi=10.1016/j.cub.2017.03.030 |pmid=28586682 |bibcode=2017CBio...27.R474B |s2cid=21052483 |archive-url=https://web.archive.org/web/20220928180557/https://www.cell.com/current-biology/fulltext/S0960-9822(17)30328-7?_returnURL=https%3A%2F%2Flinkinghub.elsevier.com%2Fretrieve%2Fpii%2FS0960982217303287%3Fshowall%3Dtrue |archive-date=September 28, 2022 |access-date=June 17, 2021 |hdl-access=free |hdl=21.11116/0000-0001-C1AA-5}}</ref>

===Cultural eutrophication===
Cultural or [[Human impact on the environment|anthropogenic]] eutrophication is the process that causes eutrophication because of human activity.<ref name="Smith">{{cite journal |last1=Smith |first1=Val H. |last2=Schindler |first2=David W. |date=2009 |title=Eutrophication science: Where do we go from here? |journal=Trends in Ecology & Evolution |volume=24 |issue=4 |pages=201–207 |doi=10.1016/j.tree.2008.11.009 |pmid=19246117|bibcode=2009TEcoE..24..201S }}</ref><ref name=":7">[https://www.britannica.com/EBchecked/topic/146210/cultural-eutrophication Cultural eutrophication] {{Webarchive|url=https://web.archive.org/web/20150504105403/http://www.britannica.com/EBchecked/topic/146210/cultural-eutrophication |date=May 4, 2015 }} (2010) ''Encyclopedia Britannica''. Retrieved April 26, 2010, from Encyclopedia Britannica Online:</ref> The problem became more apparent following the introduction of chemical fertilizers in agriculture (green revolution of the mid-1900s).<ref>{{Cite journal|last=Smil|first=Vaclav|date=November 2000|title=Phosphorus in the Environment: Natural Flows and Human Interferences|journal=[[Annual Review of Energy and the Environment]]|volume=25|issue=1|pages=53–88|doi=10.1146/annurev.energy.25.1.53|doi-access=free|issn=1056-3466}}</ref> Phosphorus and nitrogen are the two main nutrients that cause cultural eutrophication as they enrich the water, allowing for some aquatic plants, especially algae to grow rapidly and bloom in high densities. Algal blooms can shade out benthic plants thereby altering the overall plant community.<ref name=":2">{{Cite journal|last=Moss|first=Brian|date=1983|title=The Norfolk Broadland: Experiments in the Restoration of a Complex Wetland|url=https://onlinelibrary.wiley.com/doi/abs/10.1111/j.1469-185X.1983.tb00399.x|journal=Biological Reviews|language=en|volume=58|issue=4|pages=521–561|doi=10.1111/j.1469-185X.1983.tb00399.x|s2cid=83803387|issn=1469-185X|access-date=February 8, 2022|archive-date=February 8, 2022|archive-url=https://web.archive.org/web/20220208192439/https://onlinelibrary.wiley.com/doi/abs/10.1111/j.1469-185X.1983.tb00399.x|url-status=live}}</ref> When [[algae]] die off, their degradation by bacteria removes oxygen, potentially, generating [[Anoxic waters|anoxic]] conditions. This anoxic environment kills off aerobic organisms (e.g. fish and invertebrates) in the water body. This also affects terrestrial animals, restricting their access to affected water (e.g. as drinking sources). Selection for algal and aquatic plant species that can thrive in nutrient-rich conditions can cause structural and functional disruption to entire aquatic ecosystems and their food webs, resulting in loss of habitat and species biodiversity.<ref name=":1" />

There are several sources of excessive nutrients from human activity including run-off from fertilized fields, lawns, and golf courses, untreated sewage and wastewater and internal combustion of fuels creating nitrogen pollution.<ref name=":5">Schindler, David W., Vallentyne, John R. (2008). ''The Algal Bowl: Overfertilization of the World's Freshwaters and Estuaries'', University of Alberta Press, {{ISBN|0-88864-484-1}}.</ref>  Cultural eutrophication can occur in fresh water and salt water bodies, shallow waters being the most susceptible. In shore lines and shallow lakes, sediments are frequently resuspended by wind and waves which can result in nutrient release from sediments into the overlying water, enhancing eutrophication.<ref>{{Cite journal|last1=Qin|first1=Boqiang|last2=Yang|first2=Liuyan|last3=Chen|first3=Feizhou|last4=Zhu|first4=Guangwei|last5=Zhang|first5=Lu|last6=Chen|first6=Yiyu|date=October 1, 2006|title=Mechanism and control of lake eutrophication|journal=Chinese Science Bulletin|language=en|volume=51|issue=19|pages=2401–2412|doi=10.1007/s11434-006-2096-y|bibcode=2006ChSBu..51.2401Q|s2cid=198137333|issn=1861-9541}}</ref> The deterioration of water quality caused by cultural eutrophication can therefore negatively impact human uses including potable supply for consumption, industrial uses and recreation.<ref>{{Citation|last1=Khan|first1=M. Nasir|title=Eutrophication: Challenges and Solutions|date=2014|work=Eutrophication: Causes, Consequences and Control: Volume 2|pages=1–15|editor-last=Ansari|editor-first=Abid A.|publisher=Springer Netherlands|language=en|doi=10.1007/978-94-007-7814-6_1|isbn=978-94-007-7814-6|last2=Mohammad|first2=Firoz|editor2-last=Gill|editor2-first=Sarvajeet Singh}}</ref>
[[File:Mono Lake sat zoomed.jpg|thumb|260x260px|The eutrophication of [[Mono Lake]], which is a [[cyanobacteria]]-rich [[soda lake]]]]

=== Natural eutrophication ===
Eutrophication can be a natural process and occurs naturally through the gradual accumulation of sediment and nutrients.  Naturally, eutrophication is usually caused by the natural accumulation of nutrients from dissolved phosphate minerals and dead plant matter in water.<ref name="Sawyer">{{cite journal|title=Basic Concepts of Eutrophication|author=Clair N. Sawyer|journal=Journal (Water Pollution Control Federation)|date=May 1966|volume=38|number=5|pages=737–744|publisher=Wiley|jstor=25035549|url=https://www.jstor.org/stable/25035549|access-date=February 12, 2021|archive-date=June 3, 2021|archive-url=https://web.archive.org/web/20210603164556/https://www.jstor.org/stable/25035549|url-status=live}}</ref><ref>{{Cite web |last=Addy |first=Kelly |date=1996 |title=Phosphorus and Lake Aging |url=https://web.uri.edu/watershedwatch/files/Phosphorus.pdf |url-status=live |archive-url=https://web.archive.org/web/20210728121848/https://web.uri.edu/watershedwatch/files/Phosphorus.pdf |archive-date=July 28, 2021 |access-date=June 16, 2021 |website=Natural Resources Facts - University of Rhode Island}}</ref>

Natural eutrophication has been well-characterized in lakes. [[paleolimnology|Paleolimnologists]] now recognise that climate change, geology, and other external influences are also critical in regulating the natural productivity of lakes. A few artificial lakes also demonstrate the reverse process ([[meiotrophication]]<ref>{{Cite book|last=Wetzel|first=Robert G.|url=https://www.worldcat.org/oclc/46393244|title=Limnology: lake and river ecosystems|date=2001|publisher=Academic Press|isbn=0-12-744760-1|edition=3rd|location=San Diego|oclc=46393244|access-date=February 8, 2022|archive-date=November 2, 2020|archive-url=https://web.archive.org/web/20201102154226/https://www.worldcat.org/oclc/46393244|url-status=live}}</ref>), becoming less nutrient rich with time as nutrient poor inputs slowly elute the nutrient richer water mass of the lake.<ref name=":8">Walker, I. R. (2006) "Chironomid overview", pp. 360–366 in S.A. EIias (ed.) ''Encyclopedia of Quaternary Science'', Vol. 1, Elsevier,</ref><ref name=":9">{{Cite journal|last1=Whiteside|first1=M. C.|year=1983|title=The mythical concept of eutrophication|journal=Hydrobiologia|volume=103|issue=1 |pages=107–150|doi=10.1007/BF00028437|bibcode=1983HyBio.103..107W |s2cid=19039247}}</ref> This process may be seen in artificial lakes and reservoirs which tend to be highly eutrophic on first filling but may become more oligotrophic with time. The main difference between natural and anthropogenic eutrophication is that the natural process is very slow, occurring on geological time scales.<ref name=":10">Callisto, Marcos; Molozzi, Joseline and Barbosa, José Lucena Etham (2014) "Eutrophication of Lakes" in A. A. Ansari, S. S. Gill (eds.), ''Eutrophication: Causes, Consequences and Control'', Springer Science+Business Media Dordrecht. {{doi|10.1007/978-94-007-7814-6_5}}. {{ISBN|978-94-007-7814-6}}.</ref>