Editing Estuary (section)

== Implications of eutrophication on estuaries ==
{{Further|Eutrophication#Coastal waters}}

=== Effects of eutrophication on biogeochemical cycles ===
[[File:Table_of_the_Processes_in_the_Nitrogen_Cycle.jpg|thumb|Processes that nitrogen undergo in estuarine systems]]
Nitrogen is often the lead cause of [[eutrophication]] in estuaries in temperate zones.<ref>{{Cite journal |last1=Howarth |first1=Robert W. |last2=Marino |first2=Roxanne |date=2006 |title=Nitrogen as the limiting nutrient for eutrophication in coastal marine ecosystems: Evolving views over three decades |journal=Limnology and Oceanography |language=en |volume=51 |issue=1part2 |pages=364–376 |doi=10.4319/lo.2006.51.1_part_2.0364 |bibcode=2006LimOc..51..364H |s2cid=18144068 |issn=0024-3590|doi-access=free }}</ref> During a eutrophication event, biogeochemical feedback decreases the amount of available [[Silica cycle|silica]].<ref>{{Cite journal |last1=Howarth |first1=Robert |last2=Chan |first2=Francis |last3=Conley |first3=Daniel J |last4=Garnier |first4=Josette |last5=Doney |first5=Scott C |last6=Marino |first6=Roxanne |last7=Billen |first7=Gilles |date=2011 |title=Coupled biogeochemical cycles: eutrophication and hypoxia in temperate estuaries and coastal marine ecosystems |journal=Frontiers in Ecology and the Environment |language=en |volume=9 |issue=1 |pages=18–26 |doi=10.1890/100008 |hdl=1813/60819 |issn=1540-9295|doi-access=free |bibcode=2011FrEE....9...18H |hdl-access=free }}</ref> These feedbacks also increase the supply of [[Nitrogen cycle|nitrogen]] and phosphorus, creating conditions where harmful algal blooms can persist. Given the now off-balance [[nitrogen cycle]], estuaries can be driven to [[Phosphorus cycle|phosphorus]] limitation instead of nitrogen limitation. Estuaries can be severely impacted by an unbalanced phosphorus cycle, as phosphorus interacts with nitrogen and silica availability.

With an abundance of nutrients in the ecosystem, plants and algae overgrow and eventually decompose, which produce a significant amount of carbon dioxide.<ref>{{Cite journal |last1=Morales-Williams |first1=Ana M. |last2=Wanamaker |first2=Alan D. |last3=Williams |first3=Clayton J. |last4=Downing |first4=John A. |date=2021 |title=Eutrophication Drives Extreme Seasonal {{CO2}} Flux in Lake Ecosystems |url=https://link.springer.com/10.1007/s10021-020-00527-2 |journal=Ecosystems |language=en |volume=24 |issue=2 |pages=434–450 |doi=10.1007/s10021-020-00527-2 |bibcode=2021Ecosy..24..434M |s2cid=220856626 |issn=1432-9840}}</ref> While releasing {{CO2}} into the water and atmosphere, these organisms are also intaking all or nearly all of the available oxygen creating a [[Dead zone (ecology)|hypoxic]] environment and unbalanced [[oxygen cycle]].<ref>{{Cite book |last1=Selman |first1=Mindy |url=https://www.wri.org/research/eutrophication-and-hypoxia-coastal-areas |title=Eutrophication and Hypoxia in Coastal Areas |last2=Sugg |first2=Zachary |last3=Greenhalgh |first3=Suzie |date=2008 |publisher=World Resources Institute |isbn=978-1-56973-681-4 |language=en}}</ref> The excess carbon in the form of {{CO2}} can lead to low pH levels and [[ocean acidification]], which is more harmful for vulnerable coastal regions like estuaries.

=== Effects of eutrophication on estuarine plants ===
[[File:Wood_storks_wading_in_a_marsh.jpg|thumb|A salt marsh with wood storks wading]]
[[Eutrophication]] has been seen to negatively impact many plant communities in estuarine [[ecosystem]]s.<ref name=":5">{{Cite journal |last1=Deegan |first1=Linda A. |last2=Johnson |first2=David Samuel |last3=Warren |first3=R. Scott |last4=Peterson |first4=Bruce J. |last5=Fleeger |first5=John W. |last6=Fagherazzi |first6=Sergio |last7=Wollheim |first7=Wilfred M. |date=2012 |title=Coastal eutrophication as a driver of salt marsh loss |url=http://dx.doi.org/10.1038/nature11533 |journal=Nature |volume=490 |issue=7420 |pages=388–392 |doi=10.1038/nature11533 |pmid=23075989 |bibcode=2012Natur.490..388D |s2cid=4414196 |issn=0028-0836}}</ref> [[Salt marsh]]es are a type of ecosystem in some estuaries that have been negatively impacted by eutrophication.<ref name=":5" /> [[Spartina|Cordgrass]] vegetation dominates the salt marsh landscape.<ref>{{Cite journal |last1=Donnelly |first1=Jeffrey P. |last2=Bertness |first2=Mark D. |date=2001 |title=Rapid shoreward encroachment of salt marsh cordgrass in response to accelerated sea-level rise |journal=Proceedings of the National Academy of Sciences |volume=98 |issue=25 |pages=14218–14223 |doi=10.1073/pnas.251209298 |pmid=11724926 |pmc=64662 |bibcode=2001PNAS...9814218D |issn=0027-8424|doi-access=free }}</ref> Excess nutrients allow the plants to grow at greater rates in above ground biomass, however less energy is allocated to the roots since nutrients is abundant.<ref name=":5" /><ref name=":0">{{Cite journal |last1=Lovelock |first1=Catherine E. |last2=Ball |first2=Marilyn C. |last3=Martin |first3=Katherine C. |last4=C. Feller |first4=Ilka |date=2009 |title=Nutrient Enrichment Increases Mortality of Mangroves |journal=PLOS ONE |volume=4 |issue=5 |pages=e5600 |doi=10.1371/journal.pone.0005600 |pmid=19440554 |pmc=2679148 |bibcode=2009PLoSO...4.5600L |issn=1932-6203|doi-access=free }}</ref> This leads to a lower [[Biomass (ecology)|biomass]] in the vegetation below ground which destabilizes the banks of the marsh causing increased rates of [[erosion]].<ref name=":5" /> A similar phenomenon occurs in [[Mangrove forest|mangrove swamps]], which are another potential ecosystem in estuaries.<ref name=":0" /><ref>{{Cite journal |last1=Guest |first1=Michaela A. |last2=Connolly |first2=Rod M. |date=2005 |title=Fine-scale movement and assimilation of carbon in saltmarsh and mangrove habitat by resident animals |url=http://dx.doi.org/10.1007/s10452-005-0442-9 |journal=Aquatic Ecology |volume=38 |issue=4 |pages=599–609 |doi=10.1007/s10452-005-0442-9 |bibcode=2005AqEco..38..599G |s2cid=20771999 |issn=1386-2588}}</ref> An increase in nitrogen causes an increase in shoot growth and a decrease in root growth.<ref name=":0" /> Weaker root systems cause a mangrove tree to be less resilient in seasons of drought, which can lead to the death of the mangrove.<ref name=":0" /> This shift in above ground and below ground biomass caused by eutrophication could hindered plant success in these ecosystems.<ref name=":5" /><ref name=":0" />

=== Effects of eutrophication on estuarine animals ===
[[File:Whitefish, from the Fish from American Waters series (N8) for Allen & Ginter Cigarettes Brands MET DP830737.jpg|thumb|Example of a whitefish]]
Across all biomes, [[eutrophication]] often results in plant death but the impacts do not end there. Plant death alters the entire food web structure which can result in the death of animals within the afflicted [[biome]]. Estuaries are hotspots for [[biodiversity]], containing a majority of commercial fish catch, making the impacts of eutrophication that much greater within estuaries.<ref>{{Cite journal |last1=Waltham |first1=Nathan J. |last2=McCann |first2=Jack |last3=Power |first3=Trent |last4=Moore |first4=Matt |last5=Buelow |first5=Christina |date=2020 |title=Patterns of fish use in urban estuaries: Engineering maintenance schedules to protect broader seascape habitat |journal=[[Estuarine, Coastal and Shelf Science]] |volume=238 |pages=106729 |doi=10.1016/j.ecss.2020.106729 |bibcode=2020ECSS..23806729W |s2cid=216460098 |issn=0272-7714|doi-access=free }}</ref> Some specific estuarine animals feel the effects of eutrophication more strongly than others. One example is the whitefish species from the [[Alps|European Alps]].<ref name=":1">[https://ec.europa.eu/environment/integration/research/newsalert/pdf/290na1_en.pdf Vonlanthen, P., Bittner, D., Hudson A.G., et al. (2012). Eutrophication causes speciation reversal in whitefish adaptive radiations. Nature. 482, 337–362. DOI: 10.1038/nature0824.]</ref> Eutrophication reduced the oxygen levels in their habitats so greatly that whitefish eggs could not survive, causing local extinctions.<ref name=":1" /> However, some animals, such as carnivorous fish, tend to do well in nutrient-enriched environments and can benefit from eutrophication.<ref name=":2">{{Citation |last1=Jeppesen |first1=Erik |date=1997 |url=http://dx.doi.org/10.1007/978-94-011-5648-6_17 |work=Shallow Lakes '95 |pages=151–164 |place=Dordrecht |publisher=Springer Netherlands |isbn=978-94-010-6382-1 |access-date=2022-04-20 |last2=Peder Jensen |first2=Jens |last3=Søndergaard |first3=Martin |last4=Lauridsen |first4=Torben |last5=Junge Pedersen |first5=Leif |last6=Jensen |first6=Lars|title=Top-down control in freshwater lakes: The role of nutrient state, submerged macrophytes and water depth |doi=10.1007/978-94-011-5648-6_17 }}</ref> This can be seen in populations of bass or pikes.<ref name=":2" />

=== Effects of eutrophication on human activities ===
[[File:Fishing_boat_at_Wrangell_Harbor.jpg|thumb|Commercial fishing boat]]
Eutrophication can affect many marine habitats which can lead to economic consequences. The commercial fishing industry relies upon estuaries for approximately 68 percent of their catch by value because of the great biodiversity of this ecosystem.<ref name=":4">{{Cite journal |last=Lellis-Dibble |first=K.A. |date=2008 |title=Estuarine Fish and Shellfish Species in US commercial and Recreational Fisheries: Economic Value as an Incentive to Protect and Restore Estuarine Habitat |journal=National Oceanic and Atmospheric Administration}}</ref> During an [[algal bloom]], fishermen have noticed a significant increase in the quantity of fish.<ref name=":3">{{Cite journal |last1=Gao |first1=Yang |last2=Lee |first2=Jeong-Yeol |date=2012-12-30 |title=Compensatory Responses of Nile Tilapia Oreochromis niloticus under Different Feed-Deprivation Regimes |journal=Fisheries and Aquatic Sciences |volume=15 |issue=4 |pages=305–311 |doi=10.5657/fas.2012.0305 |issn=2234-1749|doi-access=free }}</ref> A sudden increase in primary productivity causes spikes in fish populations which leads to more oxygen being utilized.<ref name=":3" /> It is the continued deoxygenation of the water that then causes a decline in fish populations. These effects can begin in estuaries and have a wide effect on the surrounding water bodies.  In turn, this can decrease fishing industry sales in one area and across the country.<ref>{{Cite journal |last1=Fay |first1=Gavin |last2=DePiper |first2=Geret |last3=Steinback |first3=Scott |last4=Gamble |first4=Robert J. |last5=Link |first5=Jason S. |date=2019 |title=Economic and Ecosystem Effects of Fishing on the Northeast US Shelf |journal=Frontiers in Marine Science |volume=6 |page=133 |doi=10.3389/fmars.2019.00133 |issn=2296-7745|doi-access=free |bibcode=2019FrMaS...6..133F }}</ref> Production in 2016 from recreational and commercial fishing contributes billions of dollars to the United States' gross domestic product (GDP).<ref name=":4" /> A decrease in production within this industry can affect any of the 1.7 million people the fishing industry employs yearly across the United States.