Editing Eutrophication (section)

== Effects ==
{{Further|Harmful algal bloom#Harmful effects}}
[[File:Caspian Sea from orbit.jpg|thumb|306x306px|Eutrophication is apparent as increased [[turbidity]] in the northern part of the [[Caspian Sea]], imaged from orbit.]]

=== Ecological effects ===
Eutrophication can have the following ecological effects: increased biomass of [[phytoplankton]], changes in [[macrophyte]] [[species composition]] and [[biomass]], [[Oxygen saturation|dissolved oxygen]] depletion, increased incidences of [[fish kill]]s, loss of desirable fish species.<ref>{{Cite web |title=Nutrients and Eutrophication {{!}} U.S. Geological Survey | date=March 2, 2019 |url=https://www.usgs.gov/mission-areas/water-resources/science/nutrients-and-eutrophication#:~:text=Eutrophication%20is%20a%20natural%20process,and%20clogging%20water-intake%20pipes |access-date=2024-09-29 |publisher=USGS}}</ref>

==== Decreased biodiversity ====
When an ecosystem experiences an increase in nutrients, [[primary producer]]s reap the benefits first. In aquatic ecosystems, species such as [[algae]] experience a population increase (called an [[algal bloom]]). Algal blooms limit the sunlight available to bottom-dwelling organisms and cause wide swings in the amount of dissolved oxygen in the water. Oxygen is required by all aerobically [[Respiration (physiology)|respiring]] plants and animals and it is replenished in daylight by [[photosynthesis|photosynthesizing]] plants and algae. Under eutrophic conditions, dissolved oxygen greatly increases during the day, but is greatly reduced after dark by the respiring algae and by microorganisms that feed on the increasing mass of dead algae. When dissolved oxygen levels decline to [[hypoxia (environmental)|hypoxic]] levels, fish and other [[Marine life|marine animals]] suffocate. As a result, creatures such as fish, shrimp, and especially immobile bottom dwellers die off.<ref name="Horrigan 2002">{{Cite journal|last1=Horrigan|first1=L.|last2=Lawrence|first2=R. S.|last3=Walker|first3=P.|year=2002|title=How sustainable agriculture can address the environmental and human health harms of industrial agriculture|journal=Environmental Health Perspectives|volume=110|issue=5|pages=445–456|doi=10.1289/ehp.02110445|pmc=1240832|pmid=12003747|bibcode=2002EnvHP.110..445H }}</ref> In extreme cases, [[Anaerobic organism|anaerobic]] conditions ensue, promoting growth of bacteria. Zones where this occurs are known as [[Dead zone (ecology)|dead zones]].

==== New species invasion ====
Eutrophication may cause competitive release by making abundant a normally [[Limiting factor|limiting nutrient]]. This process causes shifts in the [[species composition]] of ecosystems. For instance, an increase in nitrogen might allow new, [[invasive species|competitive species]] to invade and out-compete original inhabitant species. This has been shown to occur in [[New England]] [[salt marsh]]es.<ref name="Bertness 2002">{{cite journal|last1=Bertness|first1=M. D.|last2=Ewanchuk|first2=P. J.|last3=Silliman|first3=B. R.|year=2002|title=Anthropogenic modification of New England salt marsh landscapes|journal=Proceedings of the National Academy of Sciences of the United States of America|volume=99|issue=3|pages=1395–1398|bibcode=2002PNAS...99.1395B|doi=10.1073/pnas.022447299|jstor=3057772|pmc=122201|pmid=11818525|doi-access=free}}</ref> In Europe and Asia, the [[common carp]] frequently lives in naturally eutrophic or hypereutrophic areas, and is adapted to living in such conditions. The eutrophication of areas outside its natural range partially explain the fish's success in colonizing these areas after being introduced.

==== Toxicity ====
Some [[harmful algal bloom]]s resulting from eutrophication, are [[toxic]] to plants and animals.<ref name=Smith/><ref name="Anderson 1994">{{cite journal|author=Anderson D. M.|year=1994|title=Red tides|url=http://www.whoi.edu/cms/files/Anderson_1994_SciAm-redtides_31132.pdf|journal=Scientific American|volume=271|issue=2|pages=62–68|bibcode=1994SciAm.271b..62A|doi=10.1038/scientificamerican0894-62|pmid=8066432|access-date=March 31, 2013|archive-date=May 11, 2013|archive-url=https://web.archive.org/web/20130511185552/http://www.whoi.edu/cms/files/Anderson_1994_SciAm-redtides_31132.pdf|url-status=live}}</ref> Freshwater algal blooms can pose a threat to livestock. When the algae die or are eaten, [[neurotoxin|neuro]]- and [[hepatotoxins]] are released which can kill animals and may pose a threat to humans.<ref name="Lawton 1991">{{cite journal|last=Lawton|first=L.A.|author2=G.A. Codd|year=1991|title=Cyanobacterial (blue-green algae) toxins and their significance in UK and European waters|journal=Journal of Soil and Water Conservation|volume=40|issue=4|pages=87–97|doi=10.1111/j.1747-6593.1991.tb00643.x|bibcode=1991WaEnJ...5..460L }}</ref><ref name="Martin 1994">{{cite journal|last=Martin|first=A.|author2=G.D. Cooke|year=1994|title=Health risks in eutrophic water supplies|journal=Lake Line|volume=14|pages=24–26}}</ref> An example of algal toxins working their way into humans is the case of [[shellfish]] poisoning.<ref name="Shumway 1990">{{Cite journal|last1=Shumway|first1=S. E.|year=1990|title=A Review of the Effects of Algal Blooms on Shellfish and Aquaculture|journal=Journal of the World Aquaculture Society|volume=21|issue=2|pages=65–104|doi=10.1111/j.1749-7345.1990.tb00529.x|bibcode=1990JWAS...21...65S }}</ref> Biotoxins created during algal blooms are taken up by shellfish ([[mussel]]s, [[oyster]]s), leading to these human foods acquiring the toxicity and poisoning humans. Examples include [[paralysis|paralytic]], neurotoxic, and [[Diarrhoea|diarrhoetic]] shellfish poisoning. Other marine animals can be [[Vector (epidemiology)|vectors]] for such toxins, as in the case of [[ciguatera]], where it is typically a predator fish that accumulates the toxin and then poisons humans.

There are five types of toxins associated with Harmful Algal Blooms (HABs). They include Domoic Acid, Ciguatoxin, Okadaic Acid, Brevetoxins, and Saxitoxins. All of these toxins, with the exception of Ciguatoxin, involved different types of shellfish poisoning. Domoic Acid<ref>{{Cite journal |last1=Lie |first1=Alle A. Y. |last2=Zimmer-Faust |first2=Amity G. |last3=Diner |first3=Rachel E. |last4=Kunselman |first4=Emily |last5=Daniel |first5=Zachary |last6=Van Artsdalen |first6=Kathryn |last7=Salas Garcia |first7=Mariana C. |last8=Gilbert |first8=Jack A. |last9=Shultz |first9=Dana |last10=Chokry |first10=Jeff |last11=Langlois |first11=Kylie |last12=Smith |first12=Jayme |date=May 2024 |title=Understanding the risks of co-exposures in a changing world: a case study of dual monitoring of the biotoxin domoic acid and Vibrio spp. in Pacific oyster |url=https://link.springer.com/10.1007/s10661-024-12614-1 |journal=Environmental Monitoring and Assessment |language=en |volume=196 |issue=5 |page=447 |doi=10.1007/s10661-024-12614-1 |pmid=38607511 |bibcode=2024EMnAs.196..447L |issn=0167-6369}}</ref> is associated with amnesic shellfish poisoning; Okadaic Acid<ref>{{Cite journal |last1=Zhang |first1=Yuting |last2=Song |first2=Shanshan |last3=Zhang |first3=Bin |last4=Zhang |first4=Yang |last5=Tian |first5=Miao |last6=Wu |first6=Ziyi |last7=Chen |first7=Huorong |last8=Ding |first8=Guangmao |last9=Liu |first9=Renyan |last10=Mu |first10=Jingli |date=February 2023 |title=Comparison of short-term toxicity of 14 common phycotoxins (alone and in combination) to the survival of brine shrimp Artemia salina |url=https://link.springer.com/10.1007/s13131-022-2120-3 |journal=Acta Oceanologica Sinica |language=en |volume=42 |issue=2 |pages=134–141 |doi=10.1007/s13131-022-2120-3 |issn=0253-505X}}</ref> is associated with diarrhetic shellfish poisoning; Brevetoxins<ref>{{Cite journal |last1=Perrault |first1=Justin R. |last2=Stacy |first2=Nicole I. |last3=Lehner |first3=Andreas F. |last4=Mott |first4=Cody R. |last5=Hirsch |first5=Sarah |last6=Gorham |first6=Jonathan C. |last7=Buchweitz |first7=John P. |last8=Bresette |first8=Michael J. |last9=Walsh |first9=Catherine J. |date=December 2017 |title=Potential effects of brevetoxins and toxic elements on various health variables in Kemp's ridley (Lepidochelys kempii) and green (Chelonia mydas) sea turtles after a red tide bloom event |url=https://linkinghub.elsevier.com/retrieve/pii/S004896971731567X |journal=Science of the Total Environment |language=en |volume=605-606 |pages=967–979 |doi=10.1016/j.scitotenv.2017.06.149|pmid=28693110 |bibcode=2017ScTEn.605..967P }}</ref> are associated with neurotoxic shellfish poisoning; and Saxitoxins<ref>{{Cite book |last1=Lalli |first1=Carol M. |title=Biological oceanography: an introduction |last2=Parsons |first2=Timothy Richard |date=1997 |publisher=Butterworth Heinemann |isbn=978-0-7506-3384-0 |edition=2nd |series=Open University oceanography series |location=Oxford [England]}}</ref> are associated with paralytic shellfish poisoning. Different species of algae are associated with the different toxins.<ref>{{Cite book |last1=Lalli |first1=Carol M. |title=Biological oceanography: an introduction |last2=Parsons |first2=Timothy Richard |date=1997 |publisher=Butterworth Heinemann |isbn=978-0-7506-3384-0 |edition=2nd |series=Open University oceanography series |location=Oxford [England]}}</ref> For example, Alexandrium, Pyrodinium, and Gymnodinium generate saxitoxins.<ref>{{Cite book |last1=Lalli |first1=Carol M. |title=Biological oceanography: an introduction |last2=Parsons |first2=Timothy Richard |date=1997 |publisher=Butterworth Heinemann |isbn=978-0-7506-3384-0 |edition=2nd |series=Open University oceanography series |location=Oxford [England]}}</ref> Saxitoxin is known to be 50 times more lethal than strychnine and 10,000 times more lethal than cyanide.<ref>{{Cite book |last1=Lalli |first1=Carol M. |title=Biological oceanography: an introduction |last2=Parsons |first2=Timothy Richard |date=1997 |publisher=Butterworth Heinemann |isbn=978-0-7506-3384-0 |edition=2nd |series=Open University oceanography series |location=Oxford [England]}}</ref>
[[File:Lake Pyramid algal bloom (Copernicus).jpg|thumb|Lake Pyramid Algal Bloom]]

=== Economic effects ===
Eutrophication and harmful algal blooms can have economic impacts due to increasing [[water treatment]] costs, commercial fishing and shellfish losses, recreational fishing losses (reductions in harvestable fish and [[shellfish]]), and reduced tourism income (decreases in perceived aesthetic value of the water body).<ref>{{Cite web |last=US EPA |first=OW |date=2013 |title=The Effects: Economy |url=https://www.epa.gov/nutrientpollution/effects-economy |access-date=February 15, 2022 |publisher=EPA |language=en |archive-date=September 28, 2022 |archive-url=https://web.archive.org/web/20220928180552/https://www.epa.gov/nutrientpollution/effects-economy |url-status=live }}</ref> Water treatment costs can be increased due to decreases in water transparency (increased [[turbidity]]). There can also be issues with color and smell during drinking water treatment. However, controlled eutrophication can potentially be used to increase production in fisheries, which in turn increases community income.<ref>{{Cite journal |title=Eutrophication in a tropical estuary: Is it good or bad? | date=2021 |url=https://validate.perfdrive.com/9730847aceed30627ebd520e46ee70b2/?ssa=39256e8b-8015-4939-8dc3-b2b73e11afeb&ssb=94221292278&ssc=https%3A%2F%2Fiopscience.iop.org%2Farticle%2F10.1088%2F1755-1315%2F744%2F1%2F012010%2Fmeta.&ssi=91b42654-cnvj-4184-83a0-06c0efc5f604&ssk=botmanager_support@radware.com&ssm=98085175173896445106857097371161&ssn=d103143503189e7ed0cb72ac7806a5e5f9f8b8aacfb1-a85c-4798-90d55d&sso=8808843e-db480637d66a9451bacb934cf5b50ea3ca42f547fc6c80bf&ssp=95539659781745220036174523019584955&ssq=30730229263686948521992636917576745583667&ssr=MjA4LjgwLjE1NS4xMTg=&sst=Mozilla/5.0 (Macintosh; Intel Mac OS X 10_15_7) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/110.0.0.0 Safari/537.36 Citoid/WMF (mailto:noc@wikimedia.org)&ssu=&ssv=&ssw=&ssx=eyJfX3V6bWYiOiI3ZjYwMDA0NjAyOGY0Yi00OGVkLTRmOTYtODIwYi02OGQzOTFmMzhlOTAxNzQ1MjkyNjM2NDM3MC00YzAwNDFmYjQyNmY3ODQ0MTAiLCJ1em14IjoiN2Y5MDAwOTAwNDgzNzEtNDE2ZC00NTFkLTgxZDQtNDA5Yjc0Y2NhMzliMS0xNzQ1MjkyNjM2NDM3MC01MmNlNjc2ZjdjNjU0NTQxMTAiLCJyZCI6ImlvcC5vcmcifQ== |doi=10.1088/1755-1315/744/1/012010 | journal=IOP Conference Series: Earth and Environmental Science | volume=744 | issue=1 | page=012010 | bibcode=2021E&ES..744a2010D | vauthors = Damar A, Ervinia A, Kurniawan F, Rudianto BY | doi-access=free }}</ref> Notably, there is a delicate line where eutrophication can become damaging very quickly, and as such is not recommended currently due to high eutrophication rates.

=== Health impacts ===
Human health effects of eutrophication derive from two main issues excess nitrate in drinking water and exposure to toxic algae.<ref>{{Cite web |last=Xiao |date=2017-06-02 |title=Water Eutrophication and its Effect • EnvGuide |url=https://us.envguide.com/eutrop/#:~:text=Drinking,%20accidentally%20swallowing%20or%20swimming,cause%20serious%20health%20problems%20including:&text=Rashes&text=Stomach%20or%20liver%20illness&text=Respiratory%20problems |access-date=2024-10-28 |website=EnvGuide |language=en-US}}</ref> Nitrates in drinking water can cause [[blue baby syndrome]] in infants and can react with chemicals used to treat water to create [[Disinfection by-product|disinfection by-products]] in drinking water.<ref>{{cite web |author=<!--Not stated--> |date=March 1, 2021 |title=The Effects: Human Health |url=https://www.epa.gov/nutrientpollution/effects-human-health |url-status=live |archive-url=https://web.archive.org/web/20200219144746/https://www.epa.gov/nutrientpollution/effects-human-health |archive-date=February 19, 2020 |access-date=February 21, 2022 |website=Nutrient Pollution |publisher=EPA}}</ref> Getting direct contact with toxic algae through swimming or drinking can cause rashes, stomach or liver illness, and respiratory or neurological problems  .<ref>{{Cite web |last=US EPA |first=OW |date=2013 |title=The Effects: Human Health |url=https://www.epa.gov/nutrientpollution/effects-human-health |url-status=live |archive-url=https://web.archive.org/web/20200219144746/https://www.epa.gov/nutrientpollution/effects-human-health |archive-date=February 19, 2020 |access-date=February 15, 2022 |publisher=EPA |language=en}}</ref>