Editing Algal bloom (section)

{{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>