Editing Eutrophication (section)

== Reversal and remediation ==
Reducing nutrient inputs is a crucial precondition for restoration. Still, there are two caveats: Firstly, it can take a long time, mainly because of the storage of nutrients in [[sediment]]s. Secondly, restoration may need more than a simple reversal of inputs since there are sometimes several stable but very different ecological states.<ref>{{Cite journal|last1=May|first1=L|last2=Olszewska|first2=J|last3=Gunn|first3=I D M|last4=Meis|first4=S|last5=Spears|first5=B M|date=2020|title=Eutrophication and restoration in temperate lakes|journal=IOP Conference Series: Earth and Environmental Science|volume=535|issue=1|pages=012001|doi=10.1088/1755-1315/535/1/012001|bibcode=2020E&ES..535a2001M|s2cid=225481650|issn=1755-1307|doi-access=free}}</ref> Recovery of eutrophicated lakes is slow, often requiring several decades.<ref name=":18" />

In [[environmental remediation]], nutrient removal technologies include [[biofiltration]], which uses living material to capture and biologically degrade pollutants. Examples include green belts, [[riparian]] areas, natural and constructed wetlands, and treatment ponds.

===Algae bloom forecasting===
The National Oceanic Atmospheric Admiration in the United States has created a forecasting tool for regions such as the Great Lakes, the Gulf of Maine, and The Gulf of Mexico.<ref>{{cite web |title=Lake Erie Harmful Algal Bloom Forecast |url=https://coastalscience.noaa.gov/science-areas/habs/hab-forecasts/lake-erie/ |website=NCCOS |publisher=NOAA |access-date=12 February 2024}}</ref> Shorter term predictions can help to show the intensity, location, and trajectory of blooms in order to warn more directly affected communities. Longer term tests in specific regions and bodies help to predict larger scale factors like scale of future blooms and factors that could lead to more adverse effects.<ref>{{Cite web |title=HAB Forecasts |url=https://coastalscience.noaa.gov/science-areas/habs/hab-forecasts/ |access-date=2024-11-04 |website=NCCOS Coastal Science Website |language=en-US}}</ref>

===Nutrient bioextraction===
Nutrient bioextraction is bioremediation involving cultured plants and animals. Nutrient bioextraction or bioharvesting is the practice of farming and harvesting [[shellfish]] and [[seaweed]] to remove nitrogen and other nutrients from natural water bodies.<ref>{{cite web|title=Nutrient Bioextraction Overview|url=http://longislandsoundstudy.net/issues-actions/water-quality/nutrient-bioextraction-overview/|access-date=March 22, 2018|publisher=Long Island Sound Study partnership|location=Stamford, Conn.|archive-date=October 6, 2017|archive-url=https://web.archive.org/web/20171006062352/http://longislandsoundstudy.net/issues-actions/water-quality/nutrient-bioextraction-overview/|url-status=live}}</ref>

==== Shellfish in estuaries ====
[[File:Mussels at Strawberry Rocks PC013145.JPG|thumb|Mussels are an example of organisms that act as nutrient bioextractors. They consume the nitrogen in water, depleting algae of their nutrients.|231x231px]]
{{See also|Nutrient pollution}}It has been suggested that nitrogen removal by oyster reefs could generate net benefits for sources facing nitrogen emission restrictions, similar to other nutrient trading scenarios. Specifically, if oysters maintain nitrogen levels in estuaries below thresholds, then oysters effectively stave off an enforcement response, and compliance costs parties responsible for nitrogen emission would otherwise incur.<ref>{{cite web|last=Kroeger|first=Timm|year=2012|title=Dollars and Sense: Economic Benefits and Impacts from two Oyster Reef Restoration Projects in the Northern Gulf of Mexico|url=http://www.nature.org/ourinitiatives/regions/northamerica/oyster-restoration-study-kroeger.pdf|url-status=dead|archive-url=https://web.archive.org/web/20160304002313/http://www.nature.org/ourinitiatives/regions/northamerica/oyster-restoration-study-kroeger.pdf|archive-date=March 4, 2016|access-date=May 29, 2013|publisher=The Nature Conservancy}}</ref> Several studies have shown that oysters and mussels can dramatically impact nitrogen levels in estuaries.<ref>{{cite book| vauthors = Newell RI, Fisher TR, Holyoke RR, Cornwell JC |title=The Comparative Roles of Suspension Feeders in Ecosystems | volume = 47 |publisher=Springer|year=2005| veditors = Dame R, Olenin S |edition=NATO Science Series IV: Earth and Environmental Sciences|location=Netherlands|pages=93–120|contribution=Influence of eastern oysters on nitrogen and phosphorus regeneration in Chesapeake Bay, USA}}</ref><ref>{{cite book| vauthors = Grabowski JH, Petersen CM |title=Restoring oyster reefs to recover ecosystem services|publisher=Elsevier-Academic Press|year=2007| veditors = Cuddington K, Byers JE, Wilson WG, Hastings A |edition=Ecosystem Engineers: Concepts, Theory and Applications|location=Amsterdam|pages=281–298}}</ref><ref>{{cite web|year=2010|title=International Workshop on Bioextractive Technologies for Nutrient Remediation Summary Report|url=http://www.nefsc.noaa.gov/nefsc/publications/|publisher=US Dept Commerce, Northeast Fish Sci Cent Ref Doc. 10-19; 12 p. Available from: National Marine Fisheries Service, 166 Water Street, Woods Hole, MA 02543-1026|vauthors=Rose JM, Tedesco M, Wikfors GH, Yarish C|access-date=February 15, 2022|archive-date=October 29, 2019|archive-url=https://web.archive.org/web/20191029030853/https://www.nefsc.noaa.gov/nefsc/publications/|url-status=live}}</ref> Filter feeding activity is considered beneficial to water quality<ref>Burkholder, JoAnn M. and Sandra E. Shumway. (2011) "Bivalve shellfish aquaculture and eutrophication", in ''Shellfish Aquaculture and the Environment''. Ed. Sandra E. Shumway. John Wiley & Sons, {{ISBN|0-8138-1413-8}}.</ref> by controlling phytoplankton density and sequestering nutrients, which can be removed from the system through shellfish harvest, buried in the sediments, or lost through [[denitrification]].<ref>{{Cite journal|last1=Kaspar|first1=H. F.|last2=Gillespie|first2=P. A.|last3=Boyer|first3=I. C.|last4=MacKenzie|first4=A. L.|year=1985|title=Effects of mussel aquaculture on the nitrogen cycle and benthic communities in Kenepuru Sound, Marlborough Sounds, New Zealand|journal=Marine Biology|volume=85|issue=2|pages=127–136|doi=10.1007/BF00397431|bibcode=1985MarBi..85..127K |s2cid=83551118}}</ref><ref>{{Cite journal|last1=Newell|first1=R. I. E.|last2=Cornwell|first2=J. C.|last3=Owens|first3=M. S.|year=2002|title=Influence of simulated bivalve biodeposition and microphytobenthos on sediment nitrogen dynamics: A laboratory study|journal=Limnology and Oceanography|volume=47|issue=5|pages=1367–1379|bibcode=2002LimOc..47.1367N|doi=10.4319/lo.2002.47.5.1367|doi-access=free}}</ref> Foundational work toward the idea of improving marine water quality through shellfish cultivation was conducted by Odd Lindahl et al., using [[mussels]] in Sweden.<ref>{{Cite journal|last1=Lindahl|first1=O.|last2=Hart|first2=R.|last3=Hernroth|first3=B.|last4=Kollberg|first4=S.|last5=Loo|first5=L. O.|last6=Olrog|first6=L.|last7=Rehnstam-Holm|first7=A. S.|last8=Svensson|first8=J.|last9=Svensson|first9=S.|last10=Syversen|first10=U.|year=2005|title=Improving marine water quality by mussel farming: A profitable solution for Swedish society|url=http://www.aquacircle.org/images/pdfdokumenter/efterret07/ambi3402_131-138.pdf|journal=Ambio|volume=34|issue=2|pages=131–138|citeseerx=10.1.1.589.3995|doi=10.1579/0044-7447-34.2.131|pmid=15865310|bibcode=2005Ambio..34..131L |s2cid=25371433|access-date=November 1, 2017|archive-date=September 22, 2017|archive-url=https://web.archive.org/web/20170922011833/http://www.aquacircle.org/images/pdfdokumenter/efterret07/ambi3402_131-138.pdf|url-status=live}}</ref> In the United States, shellfish restoration projects have been conducted on the East, West and Gulf coasts.<ref>Brumbaugh, R.D. et al. (2006). [http://www.conservationgateway.org/Files/Pages/practitioner%E2%80%99s-guide-desi.aspx A Practitioners Guide to the Design and Monitoring of Shellfish Restoration Projects: An Ecosystem Services Approach] {{Webarchive|url=https://web.archive.org/web/20130701024305/http://www.conservationgateway.org/Files/Pages/practitioner%E2%80%99s-guide-desi.aspx |date=July 1, 2013 }}. The Nature Conservancy, Arlington, Va.</ref>

====Seaweed farming====
Studies have demonstrated seaweed's potential to improve nitrogen levels.<ref>{{Cite journal |last1=Kim |first1=Jang K. |last2=Kraemer |first2=George P. |last3=Yarish |first3=Charles |date=2014 |title=Field scale evaluation of seaweed aquaculture as a nutrient bioextraction strategy in Long Island Sound and the Bronx River Estuary |journal=Aquaculture |volume=433 |pages=148–156 |bibcode=2014Aquac.433..148K |doi=10.1016/j.aquaculture.2014.05.034}}</ref><ref>{{cite web |last1=Kroeger |first1=Timm |date=May 2012 |title=Dollars and Sense: Economic Benefits and Impacts from two Oyster Reef Restoration Projects in the Northern Gulf of Mexico |url=https://www.conservationgateway.org/Files/Pages/dollars-and-sense-economi.aspx |url-status=live |archive-url=https://web.archive.org/web/20200803151420/http://www.conservationgateway.org/Files/Pages/dollars-and-sense-economi.aspx |archive-date=August 3, 2020 |access-date=July 29, 2020 |publisher=The Nature Conservancy}}</ref>  [[Seaweed farming|Seaweed aquaculture]] offers an opportunity to mitigate, and adapt to climate change.<ref>{{cite journal|last1=Duarte|first1=Carlos M.|last2=Wu|first2=Jiaping|last3=Xiao|first3=Xi|last4=Bruhn|first4=Annette|last5=Krause-Jensen|first5=Dorte|date=April 12, 2017|title=Can Seaweed Farming Play a Role in Climate Change Mitigation and Adaptation?|journal=Frontiers in Marine Science|volume=4|page=100 |doi=10.3389/fmars.2017.00100|doi-access=free|bibcode=2017FrMaS...4..100D |hdl=10754/623247|hdl-access=free}}</ref> Seaweed, such as kelp, also absorbs phosphorus and nitrogen<ref>{{Cite web|url=https://e360.yale.edu/features/new_breed_of_ocean_farmer_aims_to_revive_global_seas|title=Can We Save the Oceans By Farming Them?|website=Yale E360|access-date=March 8, 2019|archive-date=October 19, 2019|archive-url=https://web.archive.org/web/20191019150923/https://e360.yale.edu/features/new_breed_of_ocean_farmer_aims_to_revive_global_seas|url-status=live}}</ref> and is thus helpful to remove excessive nutrients from polluted parts of the sea.<ref>{{Cite journal|last1=Xiao|first1=X.|last2=Agusti|first2=S.|last3=Lin|first3=F.|last4=Li|first4=K.|last5=Pan|first5=Y.|last6=Yu|first6=Y.|last7=Zheng|first7=Y.|last8=Wu|first8=J.|last9=Duarte|first9=C. M.|year=2017|title=Nutrient removal from Chinese coastal waters by large-scale seaweed aquaculture|journal=Scientific Reports|volume=7|pages=46613|bibcode=2017NatSR...746613X|doi=10.1038/srep46613|pmc=5399451|pmid=28429792}}</ref> Some cultivated seaweeds have very high productivity and could absorb large quantities of N, P, {{CO2}}, producing large amounts of {{chem2|O2}} having an excellent effect on decreasing eutrophication.<ref>{{Citation|last=Duarte|first=Carlos M.|title=Coastal eutrophication research: A new awareness |date=2009|work=Eutrophication in Coastal Ecosystems|pages=263–269|publisher=Springer Netherlands|doi=10.1007/978-90-481-3385-7_22|isbn=978-90-481-3384-0}}</ref> It is believed that seaweed cultivation in large scale should be a good solution to the eutrophication problem in [[coastal waters]].

===Geo-engineering===
[[File:Application of a phosphorus sorbent to a lake - The Netherlands.jpg|thumb|Application of a phosphorus sorbent to a lake - The Netherlands]]
Another technique for combatting [[Hypoxia (environmental)|hypoxia]]/eutrophication in localized situations is direct injection of compressed air, a technique used in the restoration of the [[Salford Docks]] area of the [[Manchester Ship Canal]] in England.<ref>{{cite web|url= http://www.mangeogsoc.org.uk/egm/5_1.pdf|access-date=December 11, 2007|date=August 21, 2003|title= Exploring Greater Manchester&nbsp;– a fieldwork guide: The fluvioglacial gravel ridges of Salford and flooding on the River Irwell|author= Hindle, P.|publisher=Manchester Geographical Society}} p. 13</ref> For smaller-scale waters such as aquaculture ponds, pump aeration is standard.<ref>{{cite web | url=https://thefishsite.com/articles/pond-aeration | title=Pond Aeration | date=April 10, 2006 }}</ref>

===Chemical removal of phosphorus===
{{Further|Chemical phosphorus removal}}
Removing [[phosphorus cycle|phosphorus]] can remediate eutrophication.<ref>{{Cite journal|doi=10.1021/es5036267|pmid=25137490|title=Geo-Engineering in Lakes: A Crisis of Confidence?|journal=Environmental Science & Technology|volume=48|issue=17|pages=9977–9979|year=2014|last1=Spears|first1=Bryan M.|last2=Maberly|first2=Stephen C.|last3=Pan|first3=Gang|last4=MacKay|first4=Ellie|last5=Bruere|first5=Andy|last6=Corker|first6=Nicholas|last7=Douglas|first7=Grant|last8=Egemose|first8=Sara|last9=Hamilton|first9=David|last10=Hatton-Ellis|first10=Tristan|last11=Huser|first11=Brian|last12=Li|first12=Wei|last13=Meis|first13=Sebastian|last14=Moss|first14=Brian|last15=Lürling|first15=Miquel|last16=Phillips|first16=Geoff|last17=Yasseri|first17=Said|last18=Reitzel|first18=Kasper|bibcode=2014EnST...48.9977S|url=http://ir.rcees.ac.cn/handle/311016/9551|access-date=September 8, 2020|archive-date=October 21, 2021|archive-url=https://web.archive.org/web/20211021121418/http://ir.rcees.ac.cn/handle/311016/9551|url-status=live}}</ref><ref>{{Cite journal |doi=10.5268/IW-4.4.769|title=Geoengineering in lakes: Welcome attraction or fatal distraction?|journal=Inland Waters|volume=4|issue=4|pages=349–356|year=2014|last1=MacKay|first1=Eleanor|last2=Maberly|first2=Stephen|last3=Pan|first3=Gang|last4=Reitzel|first4=Kasper|last5=Bruere|first5=Andy|last6=Corker|first6=Nicholas|last7=Douglas|first7=Grant|last8=Egemose|first8=Sara|last9=Hamilton|first9=David|last10=Hatton-Ellis|first10=Tristan|last11=Huser|first11=Brian|last12=Li|first12=Wei|last13=Meis|first13=Sebastian|last14=Moss|first14=Brian|last15=Lürling|first15=Miquel|last16=Phillips|first16=Geoff|last17=Yasseri|first17=Said|last18=Spears|first18=Bryan|bibcode=2014InWat...4..349M |hdl=10072/337267|s2cid=55610343|hdl-access=free}}</ref> Of the several phosphate sorbents, [[alum]] ([[aluminium sulfate]]) is of practical interest.<ref>{{cite web|url=http://www.dnr.state.wi.us/org/water/fhp/papers/alum_brochure.pdf |title=Wisconsin Department of Natural Resources |access-date=August 3, 2010 |url-status=dead |archive-url=https://web.archive.org/web/20091128030217/http://www.dnr.state.wi.us/org/water/fhp/papers/alum_brochure.pdf |archive-date=November 28, 2009 }}</ref>)   Many materials have been investigated.<ref>{{Cite journal|doi=10.1007/s10452-016-9575-2|title=Guiding principles for the development and application of solid-phase phosphorus adsorbents for freshwater ecosystems|journal=Aquatic Ecology|volume=50|issue=3|pages=385–405|year=2016|last1=Douglas|first1=G. B.|last2=Hamilton|first2=D. P.|last3=Robb|first3=M. S.|last4=Pan|first4=G.|last5=Spears|first5=B. M.|last6=Lurling|first6=M.|bibcode=2016AqEco..50..385D |hdl=10072/406333 |s2cid=18154662|url=http://irep.ntu.ac.uk/id/eprint/27767/1/PubSub5337_Pan.pdf|access-date=December 15, 2019|archive-date=September 19, 2020|archive-url=https://web.archive.org/web/20200919184710/http://irep.ntu.ac.uk/id/eprint/27767/1/PubSub5337_Pan.pdf|url-status=live}}</ref><ref>{{Cite journal|doi=10.1016/J.WATRES.2016.03.035|pmid=27039034|title=Editorial – A critical perspective on geo-engineering for eutrophication management in lakes|journal=Water Research|volume=97|pages=1–10|year=2016|last1=Lürling|first1=Miquel|last2=MacKay|first2=Eleanor|last3=Reitzel|first3=Kasper|last4=Spears|first4=Bryan M.|bibcode=2016WatRe..97....1L |url=http://nora.nerc.ac.uk/id/eprint/513724/1/N513724PP.pdf|access-date=December 15, 2019|archive-date=July 31, 2020|archive-url=https://web.archive.org/web/20200731023813/http://nora.nerc.ac.uk/id/eprint/513724/1/N513724PP.pdf|url-status=live}}</ref>  The phosphate sorbent is commonly applied in the surface of the water body and it sinks to the bottom of the lake reducing phosphate, such sorbents have been applied worldwide to manage eutrophication and algal bloom (for example under the commercial name [[Phoslock]]).<ref>{{Cite journal |doi=10.1016/j.watres.2015.06.051|pmid=26250754|title=Longevity and effectiveness of aluminum addition to reduce sediment phosphorus release and restore lake water quality|journal=Water Research|volume=97|pages=122–132|year=2016|last1=Huser|first1=Brian J.|last2=Egemose|first2=Sara|last3=Harper|first3=Harvey|last4=Hupfer|first4=Michael|last5=Jensen|first5=Henning|last6=Pilgrim|first6=Keith M.|last7=Reitzel|first7=Kasper|last8=Rydin|first8=Emil|last9=Futter|first9=Martyn|bibcode=2016WatRe..97..122H |doi-access=free}}</ref><ref>{{Cite journal |doi=10.1016/j.watres.2013.08.019|pmid=24041525|title=Controlling eutrophication by combined bloom precipitation and sediment phosphorus inactivation|journal=Water Research|volume=47|issue=17|pages=6527–6537|year=2013|last1=Lürling|first1=Miquel|last2=Oosterhout|first2=Frank van|bibcode=2013WatRe..47.6527L }}</ref><ref>{{Cite journal |doi=10.1080/10402381.2016.1265618|title=Attempted management of cyanobacteria by Phoslock (Lanthanum-modified clay) in Canadian lakes: Water quality results and predictions|journal=Lake and Reservoir Management|volume=33|issue=2|pages=163–170|year=2017|last1=Nürnberg|first1=Gertrud K.|bibcode=2017LRMan..33..163N |s2cid=89762486}}</ref><ref>{{Cite journal |doi=10.1080/10402381.2016.1263693|title=Nine years of phosphorus management with lanthanum modified bentonite (Phoslock) in a eutrophic, shallow swimming lake in Germany|journal=Lake and Reservoir Management|volume=33|issue=2|pages=119–129|year=2017|last1=Epe|first1=Tim Sebastian|last2=Finsterle|first2=Karin|last3=Yasseri|first3=Said|bibcode=2017LRMan..33..119E |s2cid=90314146}}</ref><ref name=":110">{{Cite journal |last1=Kennedy |first1=Robert H. |last2=Cook |first2=G. Dennis |title=Control of Lake Phosphorus with Aluminum Sulfate: Dose Determination and Application Techniques |date=June 1982 |url=https://doi.org/10.1111/j.1752-1688.1982.tb00005.x |journal=Journal of the American Water Resources Association |volume=18 |issue=3 |pages=389–395 |doi=10.1111/j.1752-1688.1982.tb00005.x |bibcode=1982JAWRA..18..389K |issn=1093-474X}}</ref> In a large-scale study, 114 lakes were monitored for the effectiveness of alum at phosphorus reduction. Across all lakes, alum effectively reduced the phosphorus for 11 years. While there was variety in longevity (21 years in deep lakes and 5.7 years in shallow lakes), the results express the effectiveness of alum at controlling phosphorus within lakes.<ref>{{Cite book |last1=Huser |first1=Brian J. |last2=Egemose |first2=Sara |last3=Harper |first3=Harvey |last4=Hupfer |first4=Michael |last5=Jensen |first5=Henning |last6=Pilgrim |first6=Keith M. |last7=Reitzel |first7=Kasper |last8=Rydin |first8=Emil |last9=Futter |first9=Martyn |date=2016 |title=Longevity and effectiveness of aluminum addition to reduce sediment phosphorus release and restore lake water quality |location=[[Fjärdingen]] |publisher=Uppsala universitet, Limnologi Uppsala universitet |oclc=1233676585 }}</ref> Alum treatment is less effective in deep lakes, as well as lakes with substantial external phosphorus loading.<ref name=":22">Cooke, G. D., Welch, E. B., Martin, A. B., Fulmer, D. G., Hyde, J. B., & Schrieve, G. D. (1993). Effectiveness of Al, Ca, and Fe salts for control of internal phosphorus loading in shallow and deep lakes. ''Hydrobiologia'', ''253''(1), 323-335.</ref>

Finnish phosphorus removal measures started in the mid-1970s and have targeted rivers and lakes polluted by industrial and municipal discharges. These efforts have had a 90% removal efficiency.<ref name="Raike 2003">{{Cite journal|last1=Räike|first1=A.|last2=Pietiläinen|first2=O. -P.|last3=Rekolainen|first3=S.|last4=Kauppila|first4=P.|last5=Pitkänen|first5=H.|last6=Niemi|first6=J.|last7=Raateland|first7=A.|last8=Vuorenmaa|first8=J.|year=2003|title=Trends of phosphorus, nitrogen and chlorophyll a concentrations in Finnish rivers and lakes in 1975–2000|journal=Science of the Total Environment|volume=310|issue=1–3|pages=47–59|bibcode=2003ScTEn.310...47R|doi=10.1016/S0048-9697(02)00622-8|pmid=12812730}}</ref> Still, some targeted point sources did not show a decrease in runoff despite reduction efforts.