Editing Algal bloom

{{short description|Spread of planktonic algae in water}}
{{Use dmy dates|date=November 2024}}
[[File:Toxic Algae Bloom in Lake Erie.jpg|thumb|300px|A very large algae bloom in [[Lake Erie]], North America, which can be seen from space.]]
An '''algal bloom''' or '''algae bloom''' is a rapid increase or accumulation in the population of [[algae]] in [[fresh water]] or [[Ocean|marine]] water systems. It is often recognized by the discoloration in the water from the algae's pigments.<ref>{{cite news|last=Ferris|first=Robert|date=26 July 2016|title=Why are there so many toxic algae blooms this year|url=https://www.cnbc.com/2016/07/26/why-are-there-so-many-toxic-algae-blooms-this-year.html|newspaper=[[CNBC]]|access-date=27 July 2016}}</ref> The term ''algae'' encompasses many types of aquatic [[Photosynthesis|photosynthetic]] organisms, both macroscopic multicellular organisms like [[seaweed]] and microscopic unicellular organisms like [[cyanobacteria]].<ref name=":0">{{Cite book|title=Algae: Anatomy, Biochemistry, And Biotechnology|last1=Barsanti|first1=Laura|last2=Gualtieri|first2=Paolo|publisher=CRC Press|year=2014|isbn=978-1-4398-6733-4|location=Boca Raton, FL|pages=1}}</ref> ''Algal bloom'' commonly refers to the rapid growth of microscopic unicellular algae, not macroscopic algae.<ref name="Smayda1997" >{{cite journal |last=Smayda |first=Theodore J.|author-link=Theodore J. Smayda|date=July 1997 |title=What is a bloom? A commentary |journal=Limnology and Oceanography |volume=42 |issue=5part2 |pages=1132–1136 |doi=10.4319/lo.1997.42.5_part_2.1132 |bibcode=1997LimOc..42.1132S |doi-access=free }}</ref> An example of a macroscopic algal bloom is a [[kelp forest]].<ref name=":0" />

Algal blooms are the result of a nutrient, like [[nitrogen]] or [[phosphorus]] from various sources (for example [[Nutrient pollution|fertilizer runoff]] or other forms of [[nutrient pollution]]), entering the aquatic system and causing excessive growth of algae. An algal bloom affects the whole [[ecosystem]].

Consequences range from benign effects, such as feeding of higher trophic levels, to more harmful effects like blocking sunlight from reaching other organisms, causing a [[Hypoxia (environmental)|depletion of oxygen]] levels in the water, and, depending on the organism, secreting toxins into the water. Yet, algae also play a crucial role by producing about [[Oxygen|70 % of Earth's oxygen]], which supports terrestrial life. Blooms that can injure animals or the ecology, especially those blooms where toxins are secreted by the algae, are usually called "[[harmful algal bloom]]s" (HAB), and can lead to fish die-offs, cities cutting off water to residents, or states having to close fisheries. The process of the oversupply of nutrients leading to algae growth and oxygen depletion is called [[eutrophication]].

Algal and bacterial blooms have persistently contributed to [[mass extinction]]s driven by global warming in the geologic past, such as during the [[end-Permian extinction]] driven by [[Siberian Traps]] volcanism and the biotic recovery following the mass extinction.<ref>{{cite journal |last1=Mays |first1=Chris |last2=McLoughlin |first2=Stephen |last3=Frank |first3=Tracy D. |last4=Fielding |first4=Christopher R. |last5=Slater |first5=Sam M. |last6=Vajda |first6=Vivi |date=17 September 2021 |title=Lethal microbial blooms delayed freshwater ecosystem recovery following the end-Permian extinction |journal=[[Nature Communications]] |volume=12 |issue=1 |page=5511 |doi=10.1038/s41467-021-25711-3 |pmid=34535650 |pmc=8448769 |bibcode=2021NatCo..12.5511M }}</ref>

==Characterization==
The term ''algal bloom'' is defined inconsistently depending on the scientific field and can range from a "minibloom"{{definition|date=October 2021}} of harmless algae to a large, harmful bloom event.<ref name=":02">{{Cite journal|last=Smayda|first=Theodore J.|date=1997|title=What is a bloom? A commentary|journal=Limnology and Oceanography|volume=42|issue=5part2|pages=1132–1136|doi=10.4319/lo.1997.42.5_part_2.1132|issn=1939-5590|bibcode=1997LimOc..42.1132S|doi-access=free}}</ref> Since ''algae'' is a broad term including organisms of widely varying sizes, growth rates, and nutrient requirements, there is no officially recognized threshold level as to what is defined as a bloom. Because there is no scientific consensus, blooms can be characterized and quantified in several ways: measurements of new algal biomass, the concentration of photosynthetic pigment, quantification of the bloom's negative effect, or relative concentration of the algae compared to the rest of the microbial community.<ref name=":02" /> For example, definitions of blooms have included when the concentration of chlorophyll exceeds 100&nbsp;ug/L,<ref>{{Cite journal|last=Tett|first=P|date=1987|title=The Ecophysiology of Exceptional Blooms|journal=Rapp. P.-v. Reun. Cons. Int. Explor. Mer|volume=187|pages=47–60}}</ref> when the concentration of chlorophyll exceeds 5&nbsp;ug/L,<ref>{{Cite journal|last1=Jonsson|first1=Per R.|last2=Pavia|first2=Henrik|last3=Toth|first3=Gunilla|date=7 July 2009|title=Formation of harmful algal blooms cannot be explained by allelopathic interactions|journal=Proceedings of the National Academy of Sciences of the United States of America|volume=106|issue=27|pages=11177–11182|doi=10.1073/pnas.0900964106|issn=0027-8424|pmc=2708709|pmid=19549831|bibcode=2009PNAS..10611177J|doi-access=free}}</ref> when the species considered to be blooming exceeds concentrations of 1000 cells/mL,<ref>{{Cite book|last=Kim|first=H.G.|date=1993|chapter=Population cell volume and carbon content in monospecific dinoflagellate blooms |title=Toxic phytoplankton blooms in the sea|publisher=Elsevier |series=Developments in Marine Biology|volume=3|pages=769–773}}</ref> and when the algae species concentration simply deviates from its normal growth.<ref>{{Cite journal|last=Parker|first=M|date=1987|title=Exceptional Plankton Blooms Conclusion of Discussions: Convener's Report|journal=Rapp. P.-v. Reun. Cons. Int. Explor. Mer|volume=187|pages=108–114}}</ref><ref name=":1">{{Cite journal|last1=Carstensen|first1=Jacob|last2=Henriksen|first2=Peter|last3=Heiskanen|first3=Anna-Stiina|s2cid=15978578|date=January 2007|title=Summer algal blooms in shallow estuaries: Definition, mechanisms, and link to eutrophication|journal=Limnology and Oceanography|volume=52|issue=1|pages=370–384|doi=10.4319/lo.2007.52.1.0370|issn=0024-3590|bibcode=2007LimOc..52..370C|doi-access=|url=https://www.openaccessrepository.it/record/168864 |archive-url=https://web.archive.org/web/20240623110556/https://www.openaccessrepository.it/record/168864 |url-status=dead |archive-date=23 June 2024 |url-access=subscription}}</ref>

Blooms are the result of a nutrient needed by the particular algae being introduced to the local aquatic system. This growth-limiting nutrient is typically nitrogen or phosphorus, but can also be iron, vitamins, or amino acids.<ref name=":0" /> There are several mechanisms for the addition of these nutrients in water. In the open ocean and along coastlines, upwelling from both winds and topographical ocean floor features can draw nutrients to the [[Photic zone|photic]], or sunlit zone of the ocean.<ref>{{cite book|title=Manual on harmful marine microalgae|date=2004|publisher=UNESCO|last1=Hallegraeff|first1=Gustaaf M.|last2=Anderson|first2=Donald Mark|last3=Cembella|first3=Allan D.|last4=Enevoldsen|first4=Henrik O.|isbn=9231039482|edition=Second revised|location=Paris|oclc=493956343}}</ref> Along coastal regions and in freshwater systems, agricultural, city, and sewage runoff can cause algal blooms.<ref>{{Cite journal|last1=Gilbert|first1=Patricia M.|last2=Anderson|first2=Donald M.|last3=Gentien|first3=Patrick|last4=Graneli|first4=Edna|last5=Sellner|first5=Kevin G.|date=2005|title=The Global Complex Phenomena of Harmful Algal Blooms|url=https://www.whoi.edu/fileserver.do?id=35332&pt=2&p=28251|journal=Oceanography|volume=8|issue=2|pages=130–141}}</ref>

Algal blooms, especially large algal bloom events, can reduce the transparency of the water and can discolor the water.<ref name=":0" /> The photosynthetic pigments in the algal cells, like [[chlorophyll]] and photoprotective pigments, determine the color of the algal bloom. Depending on the organism, its pigments, and the depth in the water column, algal blooms can be green, red, brown, golden, and purple.<ref name=":0" /> Bright green blooms in freshwater systems are frequently a result of [[cyanobacteria]] (colloquially known as "blue-green algae") such as ''[[Microcystis aeruginosa|Microcystis]]''.<ref name=":0" /><ref>{{Cite journal|last1=Jacoby|first1=Jean M|last2=Collier|first2=Diane C|last3=Welch|first3=Eugene B|last4=Hardy|first4=F Joan|last5=Crayton|first5=Michele|date=2000|title=Environmental factors associated with a toxic bloom of Microcystis aeruginosa|journal=Canadian Journal of Fisheries and Aquatic Sciences|volume=57|issue=1|pages=231–240|doi=10.1139/f99-234|issn=0706-652X}}</ref> Blooms may also consist of [[macroalgal]] (non-[[phytoplanktonic]]) species. These blooms are recognizable by large blades of algae that may wash up onto the shoreline.<ref>{{Cite journal|last1=Liu|first1=Dongyan|last2=Keesing|first2=John K.|last3=Xing|first3=Qianguo|last4=Shi|first4=Ping|date=1 June 2009|title=World's largest macroalgal bloom caused by expansion of seaweed aquaculture in China|journal=Marine Pollution Bulletin|volume=58|issue=6|pages=888–895|doi=10.1016/j.marpolbul.2009.01.013|pmid=19261301|bibcode=2009MarPB..58..888L |issn=0025-326X}}</ref>

Once the nutrient is present in the water, the algae begin to grow at a much faster rate than usual. In a mini bloom, this fast growth benefits the whole ecosystem by providing food and nutrients for other organisms.<ref name=":1" />

Of particular note are the [[harmful algal bloom]]s (HABs), which are algal bloom events involving toxic or otherwise harmful phytoplankton. Many species can cause harmful algal blooms. For example, ''[[Gymnodinium nagasakiense]]'' can cause harmful [[red tide]]s, [[dinoflagellate]]s ''[[Gonyaulax polygramma]]'' can cause oxygen depletion and result in large fish kills, [[cyanobacteria]] ''[[Microcystis aeruginosa]]'' can make poisonous toxins, and [[diatom]] ''[[Chaetoceros convolutus]]'' can damage fish gills.<ref>{{Cite journal|last=Hallegraef|first=G.M.|date=1993|title=A review of harmful algal blooms and their apparent global increase|url=https://www.researchgate.net/publication/243776284|journal=Phycologia|volume=32|issue=2|pages=79–99|doi=10.2216/i0031-8884-32-2-79.1|bibcode=1993Phyco..32...79H }}</ref>

<gallery mode="packed" heights="170" style="float:center">
File:Ocean phytoplankton bloom feed by the Amazon River.jpg|alt=Rivers, such as the Amazon, deposit nutrients from land into South America's tropical ocean waters, leading to thick blooms along the coastline |Rivers, such as the Amazon, deposit nutrients from land into South America's tropical ocean waters, leading to thick blooms along the coastline.{{hsp}}<ref name=NASA2012 />
File:Algal blooms at the mouth of the Amazon River.jpg|Blooms flourish in a dark plume of nutrient-rich water pouring from the mouth of the Amazon River, as seen by NASA's [[Aqua (satellite)|Aqua satellite]].<ref name=NASA2012 />
File:Coastal phytoplankton bloom change 2003–2020.jpg|Coastal phytoplankton bloom change 2003–2020<ref>[https://earthobservatory.nasa.gov/images/151374/coastal-phytoplankton-on-the-rise Coastal Phytoplankton on the Rise] 30 May 2023, ''[[NASA Earth Observatory]]''. {{PD-notice}}</ref><ref>{{cite journal | last1=Dai | first1=Yanhui | last2=Yang | first2=Shangbo | last3=Zhao | first3=Dan | last4=Hu | first4=Chuanmin | last5=Xu | first5=Wang | last6=Anderson | first6=Donald M. | last7=Li | first7=Yun | last8=Song | first8=Xiao-Peng | last9=Boyce | first9=Daniel G. | last10=Gibson | first10=Luke | last11=Zheng | first11=Chunmiao | last12=Feng | first12=Lian | title=Coastal phytoplankton blooms expand and intensify in the 21st century | journal=Nature | publisher=Springer Science and Business Media LLC | volume=615 | issue=7951 | date=2023-03-01 | issn=0028-0836 | doi=10.1038/s41586-023-05760-y | pages=280–284| pmid=36859547 | pmc=9995273 | bibcode=2023Natur.615..280D | s2cid=257282794 }}</ref>
</gallery>

==Freshwater algal blooms==
{{Further|Eutrophication#Freshwater systems}}
[[File:Lago de coatepeque de color.jpg|thumb|Cyanobacteria activity turns [[Coatepeque Caldera]] lake into a turquoise color.]]
Freshwater algal blooms are the result of an [[Nutrient pollution|excess of nutrients]], particularly some [[phosphate]]s.<ref name="Phytoplankton Blooms: The Basics">{{cite web|last=Diersling|first=Nancy|title=Phytoplankton Blooms: The Basics|url=http://floridakeys.noaa.gov/scisummaries/wqpb.pdf |archive-url=https://web.archive.org/web/20111015162930/http://floridakeys.noaa.gov/scisummaries/wqpb.pdf |archive-date=15 October 2011 |url-status=live|publisher=NOAA | work= Florida Keys National Marine Sanctuary |access-date=26 December 2012}}</ref><ref name="Lake Scientist">{{cite web|last=Hochanadel|first=Dave|title=Limited amount of total phosphorus actually feeds algae, study finds|url=http://www.lakescientist.com/2010/limited-amount-of-total-phosphorus-actually-feeds-algae-study-finds|publisher=Lake Scientist|access-date=10 June 2012|date=10 December 2010|quote=[B]ioavailable phosphorus&nbsp;– phosphorus that can be utilized by plants and bacteria&nbsp;– is only a fraction of the total, according to Michael Brett, a UW engineering professor ...}}</ref> Excess nutrients may originate from fertilizers that are applied to land for agricultural or recreational purposes and may also originate from household cleaning products containing [[phosphorus]].<ref name="pmid249679">{{Citation |last1=Gilbert |first1=P.A. |title=The Use of Phosphate in Detergents and Possible Replacements for Phosphate |date=1 January 1978 |work=Novartis Foundation Symposia |volume=57 |pages=253–268 |editor-last=Porter |editor-first=Ruth |url=https://onlinelibrary.wiley.com/doi/10.1002/9780470720387.ch14 |access-date=18 October 2024 |edition=1 |publisher=Wiley |language=en |doi=10.1002/9780470720387.ch14 |isbn=978-0-470-66347-9 |last2=De Jong |first2=A.L. |issue=57 |pmid=249679 |editor2-last=Fitzsimons |editor2-first=David W.|url-access=subscription }}</ref>

The reduction of phosphorus inputs is required to mitigate blooms that contain cyanobacteria.<ref>{{Cite journal|last1=Higgins|first1=Scott N.|last2=Paterson|first2=Michael J.|last3=Hecky|first3=Robert E.|last4=Schindler|first4=David W.|last5=Venkiteswaran|first5=Jason J.|last6=Findlay|first6=David L.|date=September 2018|title=Biological Nitrogen Fixation Prevents the Response of a Eutrophic Lake to Reduced Loading of Nitrogen: Evidence from a 46-Year Whole-Lake Experiment|journal=Ecosystems|language=en|volume=21|issue=6|pages=1088–1100|doi=10.1007/s10021-017-0204-2|bibcode=2018Ecosy..21.1088H |s2cid=26030685|issn=1432-9840}}</ref> In lakes that are stratified in the summer, autumn turnover can release substantial quantities of bio-available phosphorus potentially triggering algal blooms as soon as sufficient photosynthetic light is available.<ref>{{cite web|url=https://www.fba.org.uk/journals/index.php/IW/article/viewFile/738/439|publisher=Freshwater Biological Association|title=Storm-triggered, increased supply of sediment-derived phosphorus to the epilimnion in a small freshwater lake|access-date=26 October 2019|date=18 November 2014|archive-url=https://web.archive.org/web/20191026222134/https://www.fba.org.uk/journals/index.php/IW/article/viewFile/738/439|archive-date=26 October 2019|url-status=dead}}</ref> Excess nutrients can enter [[Drainage basin|watershed]]s through water runoff.<ref name="phosphorus">{{cite journal|last1=Lathrop|first1=Richard C.|last2=Carpenter|first2=Stephen R.|last3=Panuska|first3=John C.|last4=Soranno|first4=Patricia A.|last5=Stow|first5=Craig A.|date=1 May 1998|title=Phosphorus loading reductions needed to control blue-green algal blooms in Lake Mendota|journal=Canadian Journal of Fisheries and Aquatic Sciences|volume=55|issue=5|pages=1169–1178|url=https://www.proquest.com/openview/6c4b981906ad8b22c3e827c9120b31b7/1?pq-origsite=gscholar |access-date=13 April 2008|doi=10.1139/cjfas-55-5-1169|url-access=subscription}}</ref> Excess [[carbon]] and [[nitrogen]] have also been suspected as causes. Presence of [[Residual Sodium Carbonate Index|residual sodium carbonate]] acts as catalyst for the algae to bloom by providing dissolved carbon dioxide for enhanced photosynthesis in the presence of nutrients.{{citation needed|date=August 2023}}

When phosphates are introduced into water systems, higher concentrations cause increased growth of algae and plants. Algae tend to grow very quickly under high nutrient availability, but each alga is short-lived, and the result is a high concentration of dead organic matter which starts to decompose. Natural decomposers present in the water begin decomposing the dead algae, consuming dissolved oxygen present in the water during the process. This can result in a sharp decrease in available dissolved oxygen for other aquatic life. Without sufficient dissolved oxygen in the water, animals and plants may die off in large numbers. This may also be known as a [[Dead zone (ecology)|dead zone]].{{citation needed|date=August 2023}}

Blooms may be observed in [[freshwater aquarium]]s when fish are overfed and excess nutrients are not absorbed by plants. These are generally harmful for fish, and the situation can be corrected by changing the water in the tank and then reducing the amount of food given.{{citation needed|date=August 2023}}

=== Natural causes of algal blooms ===
Algal blooms in freshwater systems are not always caused by human contamination and have been observed to occur naturally in both eutrophic and oligotrophic lakes. Eutrophic lakes contain an abundance of nutrients such as nitrogen and phosphates which increase the likelihood for blooms. Oligotrophic lakes don't contain much of these nutrients. Oligotrophic lakes are defined by various degrees of scarcity. The trophic state index (TSI) measures nutrients in freshwater systems and a TSI under 30 defines oligotrophic waters.<ref>{{Cite web |title=Lake Monitoring |url=https://www.nfcrwd.org/index.asp?SEC=B69A2E42-4283-4752-9A2E-9B730349E2DA&Type=B_BASIC#:~:text=Definitions:,three%20layers%20during%20the%20summer. |access-date=2024-12-09 |website=www.nfcrwd.org |language=en}}</ref> However, algal blooms in oligotrophic bodies of water have also been observed. This is a result of cyanobacteria which cause blooms in eutrophic lakes and oligotrophic lakes despite the latter containing a lack of natural and man-made nutrients.

==== Nutrient uptake and cyanobacteria ====
A cause for algal blooms in nutrient-lacking environments come in the form of nutrient uptake. Cyanobacteria have evolved to have better nutrient uptake in oligotrophic waters.<ref name=":3">{{Cite journal |last1=Cottingham |first1=Kathryn L. |last2=Ewing |first2=Holly A. |last3=Greer |first3=Meredith L. |last4=Carey |first4=Cayelan C. |last5=Weathers |first5=Kathleen C. |date=2015 |title=Cyanobacteria as biological drivers of lake nitrogen and phosphorus cycling |url=https://esajournals.onlinelibrary.wiley.com/doi/10.1890/ES14-00174.1 |journal=Ecosphere |language=en |volume=6 |issue=1 |pages=art1 |doi=10.1890/ES14-00174.1 |issn=2150-8925|hdl=10919/89390 |hdl-access=free }}</ref> Cyanobacteria utilize nitrogen and phosphates in their biological processes. Because of this, cyanobacteria are known to be important in the nitrogen and phosphate fixing cycle in oligotrophic waters.<ref name=":3" /> Cyanobacteria can fix nitrogen by accessing atmospheric nitrogen ({{chem2|N2}}) that has been dissolved into water and transforming it into nitrogen accessible to other organisms.<ref name=":3" /> This higher amount of nitrogen is then able to sustain large algae blooms in oligotrophic waters.<ref name=":4">{{Cite journal |last1=Reinl |first1=Kaitlin L. |last2=Brookes |first2=Justin D. |last3=Carey |first3=Cayelan C. |last4=Harris |first4=Ted D. |last5=Ibelings |first5=Bas W. |last6=Morales-Williams |first6=Ana M. |last7=De Senerpont Domis |first7=Lisette N. |last8=Atkins |first8=Karen S. |last9=Isles |first9=Peter D. F. |last10=Mesman |first10=Jorrit P. |last11=North |first11=Rebecca L. |last12=Rudstam |first12=Lars G. |last13=Stelzer |first13=Julio A. A. |last14=Venkiteswaran |first14=Jason J. |last15=Yokota |first15=Kiyoko |date=2021 |title=Cyanobacterial blooms in oligotrophic lakes: Shifting the high-nutrient paradigm |url=https://onlinelibrary.wiley.com/doi/full/10.1111/fwb.13791 |journal=Freshwater Biology |language=en |volume=66 |issue=9 |pages=1846–1859 |doi=10.1111/fwb.13791 |issn=1365-2427}}</ref>

Cyanobacteria are able to retain high phosphorus uptake in the absence of nutrients which help their success in oligotrophic environments. Cyanobacteria species such as ''D. lemmermannii'' are able to move between the hypolimnion which is rich in nutrients such as phosphates and the nutrient-poor metalimnion which lacks phosphates.<ref name=":4" /> This causes phosphates to be brought up to the metalimnion and give organisms an abundance of phosphates, exacerbating the likelihood for algal blooms.<ref name=":3" />

==== Upwelling of nutrients ====
Upwelling events happen when nutrients such as phosphates and nitrogen are moved from the nutrient dense hypolimnion to the nutrient poor metalimnion.<ref name=":3" /><ref name=":4" /> This happens as result of geological processes such as seasonal overturn when lake surfaces freeze or melt, prompting mixing due to changing water densities mixing up the composition of limnion layers and mixing nutrients around the system.<ref>{{Cite web |date=2024-08-09 |title=Harmful Algal Blooms |url=https://www.adkwatershed.org/harmful-algal-blooms |access-date=2024-12-09 |website=Adirondack Watershed Institute |language=en-US}}</ref> This overabundance in nutrients leads to blooms.<ref name=":4" />

==Marine algal blooms==
{{Further|Eutrophication#Coastal waters}}
[[File:Competing scientific hypothesis of plankton variability.png|alt=|thumb|Competing hypothesis of plankton variability<ref name="Behrenfeld2018">Behrenfeld, M.J. and Boss, E.S. (2018) "Student's tutorial on bloom hypotheses in the context of phytoplankton annual cycles". ''Global change biology'', '''24'''(1): 55–77. {{doi|10.1111/gcb.13858}}.</ref>|350x350px]]

Turbulent storms churn the ocean in summer, adding nutrients to sunlit waters near the surface. This sparks a feeding frenzy each spring that gives rise to massive blooms of phytoplankton. Tiny molecules found inside these microscopic plants harvest vital energy from sunlight through photosynthesis. The natural pigments, called chlorophyll, allow phytoplankton to thrive in Earth's oceans and enable scientists to monitor blooms from space. Satellites reveal the location and abundance of phytoplankton by detecting the amount of chlorophyll present in coastal and open waters—the higher the concentration, the larger the bloom. Observations show blooms typically last until late spring or early summer, when nutrient stocks are in decline and predatory zooplankton start to graze. The visualization on the left immediately below uses NASA SeaWiFS data to map bloom populations.<ref name=NASA2012>[https://svs.gsfc.nasa.gov/10971 Super Blooms] ''NASA Visualization Explorer'', 8 May 2012. {{PD-notice}}</ref>

The [[NAAMES study]] conducted between 2015 and 2019 investigated aspects of phytoplankton dynamics in ocean ecosystems, and how such dynamics influence [[Atmospheric aerosol particles|atmospheric aerosols]], clouds, and climate.<ref name=Behrenfeld2019>{{Cite journal|last1=Behrenfeld|first1=Michael J.|last2=Moore|first2=Richard H.|last3=Hostetler|first3=Chris A.|last4=Graff|first4=Jason|last5=Gaube|first5=Peter|last6=Russell|first6=Lynn M.|last7=Chen|first7=Gao|last8=Doney|first8=Scott C.|author-link8=Scott Doney|last9=Giovannoni|first9=Stephen|last10=Liu|first10=Hongyu|last11=Proctor|first11=Christopher|date=22 March 2019|title=The North Atlantic Aerosol and Marine Ecosystem Study (NAAMES): Science Motive and Mission Overview|journal=Frontiers in Marine Science|volume=6|pages=122|doi=10.3389/fmars.2019.00122|issn=2296-7745|doi-access=free}}</ref>

In France, citizens are requested to report coloured waters through the project PHENOMER.<ref>{{Cite web|title=Phenomer|url=https://www.phenomer.org/|access-date=22 February 2022|website=www.phenomer.org}}</ref> This helps to understand the occurrence of marine blooms.{{citation needed|date=August 2023}}

[[Wildfire]]s<!--like the [[2019-20 Australian bushfire season|2019–2020 Australian wildfires]]--> can cause phytoplankton blooms via oceanic deposition of wildfire aerosols.<ref>{{cite journal |last1=Tang |first1=Weiyi |last2=Llort |first2=Joan |last3=Weis |first3=Jakob |last4=Perron |first4=Morgane M. G. |last5=Basart |first5=Sara |last6=Li |first6=Zuchuan |last7=Sathyendranath |first7=Shubha |author-link7=Shubha Sathyendranath|last8=Jackson |first8=Thomas |last9=Sanz Rodriguez |first9=Estrella |last10=Proemse |first10=Bernadette C. |last11=Bowie |first11=Andrew R. |last12=Schallenberg |first12=Christina |last13=Strutton |first13=Peter G. |last14=Matear |first14=Richard |last15=Cassar |first15=Nicolas |title=Widespread phytoplankton blooms triggered by 2019–2020 Australian wildfires |journal=Nature |date=September 2021 |volume=597 |issue=7876 |pages=370–375 |doi=10.1038/s41586-021-03805-8 |pmid=34526706 |bibcode=2021Natur.597..370T |hdl=2117/351768 |s2cid=237536378 |language=en |issn=1476-4687 |url=https://www.researchgate.net/publication/354614634|hdl-access=free }}</ref>

==Harmful algal blooms==
{{main|Harmful algal blooms}}
[[File:Van Gogh from Space.jpg|thumb|right|Satellite image of [[phytoplankton]] swirling around the [[Sweden|Swedish]] island of [[Gotland]] in the [[Baltic Sea]], in 2005]]

A [[harmful algal bloom]] (HAB) is an algal bloom that causes negative impacts to other organisms via production of natural toxins, mechanical damage to other organisms, or by other means. The diversity of these HABs make them even harder to manage, and present many issues, especially to threatened coastal areas.<ref>{{cite web |last1=Anderson |first1=Donald |title=Prevention, control and mitigation of harmful algal blooms: multiple approaches to HAB management |website=ResearchGate |date=January 2004 |page=2 |url=https://www.researchgate.net/publication/255649174 |access-date=26 March 2020}}</ref> HABs are often associated with large-scale marine mortality events and have been associated with various types of [[shellfish poisoning]]s.<ref>{{cite web|url=https://www.cdc.gov/hab/redtide/|title=Harmful Algal Blooms: Red Tide: Home|publisher=cdc.gov|access-date=23 August 2009|archive-url=https://web.archive.org/web/20090827120347/http://www.cdc.gov/hab/redtide/|archive-date=27 August 2009|url-status=live}}</ref> Due to their negative economic and health impacts, HABs are often carefully monitored.<ref>{{cite web|author=Florida Fish and Wildlife Research Institute|title=Red Tide Current Status Statewide Information|url=http://research.myfwc.com/features/view_article.asp?id=9670|url-status=dead|archive-url=https://web.archive.org/web/20090822163316/http://research.myfwc.com/features/view_article.asp?id=9670|archive-date=22 August 2009|access-date=23 August 2009|publisher=research.myfwc.com}}</ref><ref>{{cite web|title=Red Tide Index|url=http://www.tpwd.state.tx.us/landwater/water/environconcerns/hab/redtide/|access-date=23 August 2009|publisher=Tpwd.state.tx.us}}
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HAB has been proved to be harmful to humans. Humans may be exposed to toxic algae by direct consuming seafood containing toxins, swimming or other activities in water, and breathing tiny droplets in the air that contain toxins.<ref>{{Cite web|date=30 September 2021|title=Illness and Symptoms: Marine (Saltwater) Algal Blooms {{!}} Harmful Algal Blooms|url=https://www.cdc.gov/habs/illness-symptoms-marine.html|access-date=10 January 2022|website=CDC|language=en-us}}</ref> Because human exposure can take place by consuming seafood products that contain the toxins expelled by HAB algae, food-borne diseases are present and can affect the nervous, digestive, respiratory, hepatic, dermatological, and cardiac systems in the body.<ref>{{Cite journal |last1=Berdalet |first1=Elisa |last2=Fleming |first2=Lora E. |last3=Gowen |first3=Richard |last4=Davidson |first4=Keith |last5=Hess |first5=Philipp |last6=Backer |first6=Lorraine C. |last7=Moore |first7=Stephanie K. |last8=Hoagland |first8=Porter |last9=Enevoldsen |first9=Henrik |date=2015 |title=Marine harmful algal blooms, human health and wellbeing: challenges and opportunities in the 21st century |journal=Journal of the Marine Biological Association of the United Kingdom. Marine Biological Association of the United Kingdom |volume=2015 |pages=61–91 |doi=10.1017/S0025315415001733 |issn=0025-3154 |pmc=4676275 |pmid=26692586}}</ref> Beach users have often experienced upper respiratory diseases, eye and nose irritation, fever, and have often needed medical care in order to be treated. Ciguatera fish poisoning (CFP) is very common from the exposure of algal blooms. Water-borne diseases are also present as our drinking waters can be contaminated by cyanotoxins.

If the HAB event results in a high enough concentration of algae the water may become discoloured or murky, varying in colour from purple to almost pink, normally being red or green. Not all algal blooms are dense enough to cause water discolouration.{{citation needed|date=August 2023}}

=== Bioluminescence ===
''Dinoflagellate''s are microbial eukaryotes that link bioluminesce and toxin production in algal blooms.<ref>{{Cite journal |last1=Cusick |first1=Kathleen D. |last2=Widder |first2=Edith A. |date=1 September 2020 |title=Bioluminescence and toxicity as driving factors in harmful algal blooms: Ecological functions and genetic variability |url=https://www.sciencedirect.com/science/article/pii/S1568988320301293 |journal=Harmful Algae |volume=98 |pages=101850 |doi=10.1016/j.hal.2020.101850 |pmid=33129462 |bibcode=2020HAlga..9801850C |issn=1568-9883|url-access=subscription }}</ref> They use a luciferin-luciferase reaction to create a blue light emission glow.<ref>{{Cite journal |last1=Perin |first1=Luíza S. |last2=Moraes |first2=Gabriela V. |last3=Galeazzo |first3=Gabriela A. |last4=Oliveira |first4=Anderson G. |date=January 2022 |title=Bioluminescent Dinoflagellates as a Bioassay for Toxicity Assessment |journal=International Journal of Molecular Sciences |language=en |volume=23 |issue=21 |pages=13012 |doi=10.3390/ijms232113012 |doi-access=free |pmid=36361798 |issn=1422-0067|pmc=9656108 }}</ref> There are seventeen major types of ''dinoflagellate'' toxins, in which the strains, Saxitoxin and Yessotoxin, are both bioluminescent and toxic. These two strains are found to have similar niches in coastal areas. A surplus of ''Dinoflagellates'' in the night time creates a blue-green glow, however, in the day, it presents as a red brown color which names algal blooms, Red Tides. ''Dinoflagellates'' have been reported to be the cause of seafood poisoning from the neurotoxins.<ref>{{Cite journal |last=Wang |first=Da-Zhi |date=June 2008 |title=Neurotoxins from Marine Dinoflagellates: A Brief Review |url=http://www.mdpi.org/marinedrugs/list08.htm#10.3390_md20080016 |journal=Marine Drugs |volume=6 |issue=2 |pages=349–371 |doi=10.3390/md20080016 |doi-access=free |pmc=2525493 |pmid=18728731}}</ref>

== Management ==
There are three major categories for management of algal blooms consisting of mitigation, prevention, and control.<ref>{{Cite journal |last=Anderson |first=Donald M. |date=July 2009 |title=Approaches to monitoring, control and management of harmful algal blooms (HABs) |journal=Ocean & Coastal Management |language=en |volume=52 |issue=7 |pages=342–347 |doi=10.1016/j.ocecoaman.2009.04.006 |pmc=2818325 |pmid=20161650|bibcode=2009OCM....52..342A }}</ref> 
Within mitigation, routine monitoring programs are implemented for toxins in shellfish for early warnings <ref>Shellfish Killers: An Optimized Early Warning Program to Mitigate HAB Impacts on Shellfish in the Pacific Northwest - NCCOS - National Centers for Coastal Ocean Science. (2021). NCCOS - National Centers for Coastal Ocean Science. https://coastalscience.noaa.gov/project/shellfish-killers-an-optimized-early-warning-program-for-the-mitigation-of-hab-impacts-on-shellfish-in-the-pacific-northwest/</ref> and an overall surveillance of the area to monitor and quantify harmful algal blooms.<ref>Harmful Algal Bloom Monitoring System. (n.d.). NCCOS Coastal Science Website. https://coastalscience.noaa.gov/science-areas/habs/hab-monitoring-system/</ref> The HAB levels of the shellfish will be determined and can manage restrictions to keep contaminated shellfish off the food market. Moving fish pens away from algal blooms is also another form of mitigation. 
Within prevention, we can reduce surface runoff carrying excess nutrients by increasing the amount of permeable surfaces and vegetation. Permeable surfaces help absorb the runoff before it can make its way into the waterway. We can put into place permeable streets and parking lots which help allow for the pollution from vehicles and other runoff nutrients to be soaked up and/or slowed. Vegetation filters, absorbs, and slows the runoff which also helps to reduce the amount of excess nutrients making their way into the waterway. Examples of planted vegetation to help reduce runoff include rain gardens, replacing grass with native plants, planting trees in yards and along waterways, and even rooftop gardens. Farmers can reduce their impact on our waterways by planting cover crops, planting forested buffers, reducing their fertilizer use, and putting up fences to keep livestock out of streams.<ref>Chesapeake Bay Foundation. (2010). Polluted Runoff. Chesapeake Bay Foundation. https://www.cbf.org/issues/polluted-runoff/index.html</ref> Within control, there are mechanical, biological, chemical, genetic and environmental controls. Mechanical control involves dispersing clay into the water to aggregate with the HAB leading to less of these HAB to go through the process of sedimentation. Biological control varies largely and can be used through pheromones or releasing sterile males to reduce reproduction. Chemical control uses toxic chemical release. However, it may cause problems of mortality of other non targeted organisms. Genetic control involves genetically engineering species in their environmental tolerances and reproduction processes. However, there are problems of harming indigenous organisms. For environmental control, it can use water circulation and aeration.

== Environmental impacts ==
[[Harmful algal bloom|Harmful algae blooms]] have many negative environmental impacts and is a worsening issue that is spreading in area. A tiny brown tide organism that was formerly restricted to the northeastern US and South Africa, is now causing massive blooms along the coast of China which is similar to that of other brown tides.<ref>Zhang, Q.-C., Qiu, L.-M., Yu, R.-C., Kong, F.-Z., Wang, Y.-F., Yan, T., Gobler, C. J., & Zhou, M.-J. (2012). Emergence of brown tides caused by Aureococcus anophagefferens Hargraves et Sieburth in China. Harmful Algae, 19, 117–124. https://doi.org/10.1016/j.hal.2012.06.007</ref> HABs can lead to anaerobic (lack of oxygen) environments which can kill any organisms living within the water, fish poisoning, respiratory problems and illness among beach goers.<ref>Anderson, D. (2014). HABs in a changing world: a perspective on harmful algal blooms, their impacts, and research and management in a dynamic era of climactic and environmental change. Harmful Algae 2012 : Proceedings of the 15th International Conference on Harmful Algae : October 29 - November 2, 2012, CECO, Changwon, Gyeongnam, Korea / Editors, Hak Gyoon Kim, Beatriz Reguera, Gustaaf M. Hallegraeff, Chang Kyu Lee, M., 2012, 3. https://pmc.ncbi.nlm.nih.gov/articles/PMC4667985/</ref><ref>National Institute of Environmental Health Sciences. (2023, October 16). Algal Blooms. National Institute of Environmental Health Sciences; National Institute of Environmental Health Sciences. https://www.niehs.nih.gov/health/topics/agents/algal-blooms</ref> HABs have a large effect on the Great Lakes St. Lawrence River Basin. Invasive zebra and quagga mussels are positively correlated with their impact on the environment.<ref>{{Cite journal |last=Creed, Irena |first=Friedman, Kathryn |date=January 1, 2020 |title="Harmful Algal Blooms in the Great Lakes St. Lawrence River Basin: Is It Time fro a Binational Sub-Federal Approach?" |url=https://scholarlycommons.law.case.edu/cgi/viewcontent.cgi?article=2704&context=cuslj |journal=Canada United States Law Journal |volume=45 |issue= |pages=126–143 |via=Case Western Reserve University}}</ref> These mussels increase the cycling of phosphorus which therefore increases harmful algae blooms in areas they are present. Harmful algae blooms continue to infect water supplies at the Binational Great Lakes Basin and due to the world’s recovery from the [[COVID-19 pandemic|Covid-19 Pandemic]], solving the issue has become a low priority. This economical problem has become part of politics in the United States, whereas in allied countries such as Canada there is low concern. 

The impact of harmful algae blooms on the environment have a substantial effect on marine life. For example, in August 2024 the growth of the toxic algae, ''Pseudo-nitzschia'', along California coasts were making sea lions sick and aggressive to beach goers.<ref>{{Cite web |last=Fisheries |first=NOAA |date=2024-04-11 |title=Toxic Algal Bloom Spreads Along California Coast, Poisoning Sea Lions {{!}} NOAA Fisheries |url=https://www.fisheries.noaa.gov/feature-story/toxic-algal-bloom-spreads-along-california-coast-poisoning-sea-lions |access-date=2024-12-09 |website=NOAA |language=en}}</ref> Scientists claim this is a seasonal occurrence. The growth of ''Pseudo-nitzschia'' leads to the production of a dominic acid which accumulates in fishes such as sardines, anchovies, and squids.<ref name=":2">{{Cite web |date=July 4, 2023 |title=A toxic algal bloom off Southern California is blamed for making sea lions sick |url=https://www.npr.org/2023/07/04/1185922760/a-toxic-algal-bloom-off-southern-california-is-blamed-for-making-sea-lions-sick |access-date=December 8, 2024 |website=npr}}</ref> This directly affects the food web and the primary food source of sea lions. Once the toxins are transferred via consumption, they can cause seizures, brain damage, and death to the animal. During this surge, people reported bites and unpredictable, aggressive behavior from the infected sea lions.<ref>{{Cite web |date=2023-06-29 |title=Sea lions aren't acting like themselves — they're more aggressive because of algae bloom in California |url=https://www.nbcnews.com/news/animal-news/sea-lions-aggressive-algae-bloom-california-rcna91912 |access-date=2024-12-09 |website=NBC News |language=en}}</ref> In this sickened state, the sea lions are scared and act out of fear in order to protect themselves. Pregnant sea lions are most vulnerable to toxic algae poisoning and are more likely to die from the effects.<ref name=":2" />

== See also ==<!-- Please respect alphabetical order -->
{{div col}}
* {{annotated link|Amnesic shellfish poisoning}}
* {{annotated link|Anatoxin-a}}
* ''[[Chironomus annularius]]'' – A species of nonbiting midges that act as a natural algae control.
* {{annotated link|Ciguatera fish poisoning}}
* {{annotated link|Dinocyst}}
* {{annotated link|Dinoflagellate}}
* {{annotated link|Domoic acid}}
* {{annotated link|Emiliania huxleyi|''Emiliania huxleyi''}}
* {{annotated link|Milky seas effect}}
* {{annotated link|Neurotoxic shellfish poisoning}}
* {{annotated link|Paralytic shellfish poisoning}}
* {{annotated link|Pfiesteria}}
* {{annotated link|Pseudo-nitzschia|''Pseudi-nitzschia''}}
* {{annotated link|Raphidophyte}}
* {{annotated link|Saxitoxin}}
* {{annotated link|Spring bloom}}
* [[Thin layers (oceanography)]]
{{div col end}}

==References==
{{reflist}}

==External links==
{{Commons category|Algal blooms}}
{{Wikivoyage|Algal bloom|Algal bloom|travel information}}
* [http://oceanservice.noaa.gov/hazards/hab/ FAQ about Harmful Algal Blooms] (NOAA)

{{plankton}}
{{marine pollution}}
{{aquatic ecosystem topics}}
{{fishery science topics}}
{{Underwater diving|scidiv}}
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[[Category:Algal blooms|Algal blooms]]
[[Category:Algae]]
[[Category:Aquatic ecology]]
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[[Category:Biological oceanography]]
[[Category:Environmental issues with water]]