Editing Biofouling

{{Short description|Growth of marine organisms on surfaces}}
{{use dmy dates|date=August 2016}}
[[File:Zebra mussel GLERL 4.jpg|thumb|Current measurement instrument encrusted with [[zebra mussel]]s]]
[[File:Gaine cable électrique Moyenne-Deûle à Lille 03.jpg|thumb|Plant organisms, bacteria and animals ([[freshwater sponge]]s) have covered (fouled) the sheath of an [[Submarine power cable|electric cable]] in a canal (Mid-[[Deûle]] in [[Lille]], north of France).]]

'''Biofouling''' or '''biological fouling''' is the accumulation of [[microorganism]]s, [[plant]]s, [[alga]]e, or small [[animal]]s where it is not wanted on surfaces such as ship and submarine hulls, devices such as water inlets, pipework, grates, ponds, and rivers that cause degradation to the primary purpose of that item. Such accumulation is referred to as ''[[epibiosis]]'' when the host surface is another organism and the relationship is not parasitic. Since biofouling can occur almost anywhere water is present, biofouling poses risks to a wide variety of objects such as boat hulls and equipment, medical devices and membranes, as well as to entire industries, such as paper manufacturing, [[food processing]], underwater construction, and desalination plants.

Anti-fouling is the ability of specifically designed materials (such as [[Anti-fouling paint|toxic biocide paints, or non-toxic paints]])<ref name="antifouling_review"/> to remove or prevent biofouling.<ref name=Vladkova/>

The buildup of biofouling on marine vessels poses a significant problem. In some instances, the hull structure and propulsion systems can be damaged.<ref name="Chambers">{{cite journal|author=L.D. Chambers|display-authors=et al|year=2006|title=Modern approaches to marine antifouling coatings|journal=Surface and Coatings Technology|volume=6|issue=4|pages=3642–3652|doi=10.1016/j.surfcoat.2006.08.129|url=https://eprints.soton.ac.uk/43767/1/our_anti-fouling.pdf}}</ref> The accumulation of biofoulers on hulls can increase both the hydrodynamic volume of a vessel and the hydrodynamic friction, leading to increased [[drag (physics)|drag]] of up to 60%.<ref name=V1>{{citation|url=http://www.eurekalert.org/pub_releases/2009-06/oonr-nhc060409.php|title=New hull coatings for Navy ships cut fuel use, protect environment|first=Peter|last=Vietti|publisher=Office of Naval Research|date=4 June 2009|access-date=21 May 2012}}</ref> The drag increase has been seen to decrease speeds by up to 10%, which can require up to a 40% increase in fuel to compensate.<ref name=V2>{{cite journal|last=Vietti|first=P.|title=New Hull Coatings Cut Fuel Use, Protect Environment|journal=Currents|date=Fall 2009|pages=36–38|url=http://www.enviro-navair.navy.mil/currents/fall2009/Fall09_New_Hull_Coatings.pdf|access-date=6 June 2011|url-status=dead|archive-url=https://web.archive.org/web/20111005011946/http://www.enviro-navair.navy.mil/currents/fall2009/Fall09_New_Hull_Coatings.pdf|archive-date=5 October 2011|df=dmy-all}}</ref> With fuel typically comprising up to half of marine transport costs, antifouling methods save the shipping industry a considerable amount of money. Further, increased fuel use due to biofouling contributes to adverse environmental effects and is predicted to increase emissions of carbon dioxide and [[sulfur dioxide]] between 38% and 72% by 2020, respectively.<ref name="Salta">{{cite journal|last=Salta|display-authors=et al|first=M.|year=2008|title=Designing biomimetic antifouling surfaces|journal=Philosophical Transactions of the Royal Society|volume=368|issue=1929|pages=4729–4754|doi=10.1098/rsta.2010.0195|pmid=20855318|bibcode=2010RSPTA.368.4729S|doi-access=free}}</ref>

==Biology==
Biofouling organisms are highly diverse, and extend far beyond the attachment of barnacles and seaweeds. According to some estimates, over 1,700 species comprising over 4,000 organisms are responsible for biofouling.<ref>{{Citation|last1=Almeida|first1=E|title=Marine paints: The particular case of antifouling paints|journal=Progress in Organic Coatings|year=2007|volume=59|issue=1|pages=2–20|doi=10.1016/j.porgcoat.2007.01.017|last2=Diamantino|first2=Teresa C.|last3=De Sousa|first3=Orlando}}</ref> Biofouling is divided into '''microfouling'''—[[biofilm]] formation and bacterial adhesion—and '''macrofouling'''—attachment of larger organisms. Due to the distinct chemistry and biology that determine what prevents them from settling, organisms are also classified as hard- or soft-fouling types. [[Calcareous]] (hard) fouling organisms include [[barnacle]]s, encrusting [[bryozoa]]ns, [[Mollusca|mollusks]] such as [[zebra mussel]]s, and [[polychaete]] and other [[Tube worm (body plan)|tube worms]]. Examples of non-calcareous (soft) fouling organisms are [[seaweed]], [[Hydroid (zoology)|hydroids]], algae, and biofilm "slime".<ref name=stanczak>{{citation |title=Biofouling: It's Not Just Barnacles Anymore |date=March 2004 |first=Marianne |last=Stanczak |url=http://www.csa.com/discoveryguides/biofoul/overview.php |access-date=21 May 2012}}</ref> Together, these organisms form a [[fouling community]].

===Ecosystem formation===
[[File:Biofilm Formation.jpg|thumb|Biofouling initial process: (left) Coating of submerged "substratum" with polymers. (moving right) Bacterial attachment and [[extracellular polymeric substance]] (EPS) matrix formation.]]

Marine fouling is typically described as following four stages of ecosystem development. Within the first minute the [[Van der Waals force|van der Waals interaction]] causes the submerged surface to be covered with a conditioning film of organic polymers. In the next 24 hours, this layer allows the [[Bacterial adhesion in aquatic system|process of bacterial adhesion]] to occur, with both diatoms and bacteria (e.g. ''[[Vibrio alginolyticus]]'', ''[[Pseudomonas putrefaciens]]'') attaching, initiating the formation of a [[biofilm]]. By the end of the first week, the rich nutrients and ease of attachment into the biofilm allow secondary colonizers of spores of macroalgae (e.g. ''[[Enteromorpha intestinalis]]'', ''[[Ulothrix]]'') and protozoans (e.g. ''[[Vorticella]]'', ''Zoothamnium'' sp.) to attach themselves. Within two to three weeks, the tertiary colonizers—the macrofoulers—have attached. These include [[tunicates]], mollusks, and [[Sessility (zoology)|sessile]] [[cnidarians]].<ref name="antifouling_review">{{cite journal |last1=Yebra |first1=Diego Meseguer |last2=Kiil |first2=Søren |last3=Dam-Johansen |first3=Kim |title=Antifouling technology—past, present and future steps towards efficient and environmentally friendly antifouling coatings |journal=Progress in Organic Coatings |date=July 2004 |volume=50 |issue=2 |pages=75–104 |doi=10.1016/j.porgcoat.2003.06.001 }}</ref>

==Impact==
[[File:Antifouling 8212.jpg|thumb|right|220px|Dead biofouling, under a wood boat (detail)]]
Governments and industry spend more than US$5.7&nbsp;billion annually to prevent and control marine biofouling.<ref>{{cite journal |last1=Rouhi |first1=A. Maureen |title=The Squeeze On Tributyltins: Former EPA adviser voices doubts over regulations restricting antifouling paints |journal=Chemical & Engineering News Archive |date=27 April 1998 |volume=76 |issue=17 |pages=41–42 |doi=10.1021/cen-v076n017.p041 }}</ref>
Biofouling occurs everywhere but is most significant economically to the [[shipping industry|shipping industries]], since fouling on a ship's hull significantly increases [[Drag (physics)|drag]], reducing the overall [[Hydrodynamics|hydrodynamic]] performance of the vessel, and increases the fuel consumption.<ref>{{citation|title=Marine Fouling and its Prevention|year=1952|contribution=The Effects of Fouling|author=Woods Hole Oceanographic Institute|publisher=United States department of the Navy, Bureau of Ships|url=https://darchive.mblwhoilibrary.org/bitstream/handle/1912/191/chapter%201.pdf?sequence=8}}</ref>

Biofouling is also found in almost all circumstances where water-based liquids are in contact with other materials. Industrially important impacts are on the maintenance of [[mariculture]], membrane systems (''e.g.'', [[membrane bioreactors]] and [[reverse osmosis]] spiral wound membranes) and [[cooling water]] cycles of large industrial equipment and [[power station]]s. Biofouling can occur in oil pipelines carrying oils with entrained water, especially those carrying used oils, [[cutting oil]]s, oils rendered [[water-soluble]] through [[emulsification]], and [[hydraulic oil]]s.{{citation needed|date=January 2021}}<ref name=":0">{{Cite web |title=Sample records for oil-water emulsified fuel |url=https://worldwidescience.org/topicpages/o/oil-water+emulsified+fuel.html |website=World Wide Science}}</ref>

Other mechanisms impacted by biofouling include [[Microelectromechanical systems|microelectrochemical]] drug delivery devices, papermaking and pulp industry machines, underwater instruments, fire protection system piping, and sprinkler system nozzles.<ref name=Vladkova>{{Citation|last=Vladkova|first=T.|year=2009|title=Surface Modification Approach to Control Biofouling|journal=Marine and Industrial Biofouling|volume=4|issue=1|pages=135–163|doi=10.1007/978-3-540-69796-1_7|series=Springer Series on Biofilms|isbn=978-3-540-69794-7}}</ref><ref name=stanczak/> In groundwater wells, biofouling buildup can limit recovery flow rates, as is the case in the exterior and interior of ocean-laying pipes where fouling is often removed with a [[tube cleaning process]]. Besides interfering with mechanisms, biofouling also occurs on the surfaces of living marine organisms, when it is known as epibiosis.<ref name=":0" />{{citation needed|date=January 2021}}

Medical devices often include fan-cooled heat sinks, to cool their electronic components. While these systems sometimes include [[HEPA]] filters to collect microbes, some pathogens do pass through these filters, collect inside the device and are eventually blown out and infect other patients.<ref>{{Cite journal |last1=Capelletti |first1=Raquel Vannucci |last2=Moraes |first2=Ângela Maria |date=2015-08-07 |title=Waterborne microorganisms and biofilms related to hospital infections: strategies for prevention and control in healthcare facilities |url=https://doi.org/10.2166/wh.2015.037 |journal=Journal of Water and Health |volume=14 |issue=1 |pages=52–67 |doi=10.2166/wh.2015.037 |pmid=26837830 |issn=1477-8920}}</ref> Devices used in operating rooms rarely include fans, so as to minimize the chance of transmission. Also, medical equipment, HVAC units, high-end computers, swimming pools, drinking-water systems and other products that utilize liquid lines run the risk of biofouling as biological growth occurs inside them.<ref>{{cite journal |last1=Babič |first1=Monika |last2=Gunde-Cimerman |first2=Nina |last3=Vargha |first3=Márta |last4=Tischner |first4=Zsófia |last5=Magyar |first5=Donát |last6=Veríssimo |first6=Cristina |last7=Sabino |first7=Raquel |last8=Viegas |first8=Carla |last9=Meyer |first9=Wieland |last10=Brandão |first10=João |title=Fungal Contaminants in Drinking Water Regulation? A Tale of Ecology, Exposure, Purification and Clinical Relevance |journal=International Journal of Environmental Research and Public Health |date=13 June 2017 |volume=14 |issue=6 |pages=636 |doi=10.3390/ijerph14060636 |pmc=5486322 |doi-access=free }}</ref>

Historically, the focus of attention has been the severe impact due to biofouling on the speed of marine vessels. In some instances the hull structure and propulsion systems can become damaged.<ref name="Chambers" /> Over time, the accumulation of biofoulers on hulls increases both the hydrodynamic volume of a vessel and the frictional effects leading to increased [[drag (physics)|drag]] of up to 60%<ref name="V2" /> The additional drag can decrease speeds up to 10%, which can require up to a 40% increase in fuel to compensate.<ref name="V2" /> With fuel typically comprising up to half of marine transport costs, biofouling is estimated to cost the US Navy alone around $1&nbsp;billion per year in increased fuel usage, maintenance and biofouling control measures.<ref name="V2" /> Increased fuel use due to biofouling contributes to adverse environmental effects and is predicted to increase emissions of carbon dioxide and sulfur dioxide between 38 and 72 percent by 2020.<ref name="Salta" />

Biofouling also impacts aquaculture, increasing production and management costs, while decreasing product value.<ref>{{cite journal |last1=Fitridge |first1=Isla |last2=Dempster |first2=Tim |last3=Guenther |first3=Jana |last4=de Nys |first4=Rocky |title=The impact and control of biofouling in marine aquaculture: a review |journal=Biofouling |date=9 July 2012 |volume=28 |issue=7 |pages=649–669 |doi=10.1080/08927014.2012.700478|pmid=22775076 |doi-access=free |bibcode=2012Biofo..28..649F }}</ref> Fouling communities may compete with shellfish directly for food resources,<ref>{{cite journal |last1=Sievers |first1=Michael |last2=Dempster |first2=Tim |last3=Fitridge |first3=Isla |last4=Keough |first4=Michael J. |title=Monitoring biofouling communities could reduce impacts to mussel aquaculture by allowing synchronisation of husbandry techniques with peaks in settlement |journal=Biofouling |date=8 January 2014 |volume=30 |issue=2 |pages=203–212 |doi=10.1080/08927014.2013.856888|pmid=24401014 |bibcode=2014Biofo..30..203S |s2cid=13421038 }}</ref> impede the procurement of food and oxygen by reducing water flow around shellfish, or interfere with the operational opening of their valves.<ref>{{cite journal |last1=Pit |first1=Josiah H. |last2=Southgate |first2=Paul C. |title=Fouling and predation; how do they affect growth and survival of the blacklip pearl oyster, Pinctada margaritifera, during nursery culture? |journal=Aquaculture International |date=2003 |volume=11 |issue=6 |pages=545–555 |doi=10.1023/b:aqui.0000013310.17400.97|bibcode=2003AqInt..11..545P |s2cid=23263016 }}</ref> Consequently, stock affected by biofouling can experience reduced growth, condition and survival, with subsequent negative impacts on farm productivity.<ref>{{cite journal |last1=Sievers |first1=Michael |last2=Fitridge |first2=Isla |last3=Dempster |first3=Tim |last4=Keough |first4=Michael J. |title=Biofouling leads to reduced shell growth and flesh weight in the cultured mussel |journal=Biofouling |date=20 December 2012 |volume=29 |issue=1 |pages=97–107 |doi=10.1080/08927014.2012.749869|pmid=23256892 |s2cid=6743798 |url=https://figshare.com/articles/journal_contribution/825501 }}</ref> Although many methods of removal exist, they often impact the cultured species, sometimes more so than the fouling organisms themselves.<ref>{{cite journal |last1=Sievers |first1=Michael |last2=Fitridge |first2=Isla |last3=Bui |first3=Samantha |last4=Dempster |first4=Tim |title=To treat or not to treat: a quantitative review of the effect of biofouling and control methods in shellfish aquaculture to evaluate the necessity of removal |journal=Biofouling |date=6 September 2017 |volume=33 |issue=9 |pages=755–767 |doi=10.1080/08927014.2017.1361937|pmid=28876130 |bibcode=2017Biofo..33..755S |s2cid=3490706 |url=https://figshare.com/articles/journal_contribution/5379502 }}</ref>

==Detection==
Shipping companies have historically relied on scheduled biofouler removal to keep such accretions to a manageable level. However, the rate of accretion can vary widely between vessels and operating conditions, so predicting acceptable intervals between cleanings is difficult.

[[Light-emitting diode|LED]] manufacturers have developed a range of [[Ultraviolet#Subtypes|UVC]] (250–280&nbsp;nm) equipment that can detect biofouling buildup, and can even prevent it.

Fouling detection relies on the biomass' property of fluorescence. All microorganisms contain natural intracellular fluorophores, which radiate in the UV range when excited. At UV-range wavelengths, such fluorescence arises from three aromatic amino acids—tyrosine, phenylalanine, and tryptophan. The easiest to detect is tryptophan, which radiates at 350&nbsp;nm when irradiated at 280&nbsp;nm.<ref>{{cite journal |first= Hari |last= Venugopalan |title= Photonic Frontiers: LEDs - UVC LEDs reduce marine biofouling |journal= Laser Focus World |date= July 2016 |pages= 28–31 |volume= 52 |issue= 7 |url= http://www.laserfocusworld.com/articles/print/volume-52/issue-07/features/photonic-frontiers-leds-uvc-leds-reduce-marine-biofouling.html }}</ref>

==Prevention==

=== Antifouling ===
'''Antifouling''' is the process of preventing accumulations from forming. In [[industrial process]]es, [[dispersant|biodispersant]]s can be used to control biofouling. In less controlled environments, organisms are killed or repelled with coatings using biocides, thermal treatments, or pulses of energy. Nontoxic mechanical strategies that prevent organisms from attaching include choosing a material or coating with a slippery surface, creating an [[ultra-low fouling]] surface with the use of [[zwitterion]]s, or creating [[Nanoscopic scale|nanoscale]] surface topologies similar to the skin of sharks and dolphins, which only offer poor anchor points.<ref name="antifouling_review" />

====Coatings====
===== Non-toxic coatings =====
[[File:ProteinAdsorptionPrevention.png|thumb|upright=1.3|A general idea of non-toxic coatings. (Coating represented here as light pea green layer.) They prevent [[proteins]] and microorganisms from attaching, which prevents large organisms such as [[barnacles]] from attaching. Larger organisms require a [[biofilm]] to attach, which is composed of [[proteins]], [[polysaccharides]], and [[microorganisms]].]]
Non-toxic anti-sticking coatings prevent attachment of microorganisms thus negating the use of biocides. These coatings are usually based on organic polymers.<ref>{{citation|title=Integrated Antimicrobial and Nonfouling Hydrogels to Inhibit the Growth of Planktonic Bacterial Cells and Keep the Surface Clean|author=Gang Cheng|display-authors=et al|journal=[[Langmuir (journal)|Langmuir]]|date=2 June 2010|volume=26|pages=10425–10428|doi=10.1021/la101542m|pmid=20518560|issue=13}}</ref>

There are two classes of non-toxic anti-fouling coatings. The most common class relies on low [[friction]] and low [[Surface energy|surface energies]]. Low surface energies result in [[hydrophobic]] surfaces. These coatings create a smooth surface, which can prevent attachment of larger microorganisms. For example, [[fluoropolymers]] and silicone coatings are commonly used.<ref>{{citation|title=Clean Hulls Without Poisons: Devising and Testing Nontoxic Marine Coatings|first=R.F.|last=Brady|journal=Journal of Coatings Technology|volume=72|number=900|pages=44–56|date=1 January 2000|doi=10.1007/BF02698394|s2cid=137350868|url=http://www.highbeam.com/doc/1G1-59245245.html|archive-url=https://web.archive.org/web/20140611030850/http://www.highbeam.com/doc/1G1-59245245.html|url-status=dead|archive-date=11 June 2014|access-date=22 May 2012}}</ref> These coatings are ecologically inert but have problems with mechanical strength and long-term stability. Specifically, after days [[biofilms]] (slime) can coat the surfaces, which buries the chemical activity and allows microorganisms to attach.<ref name=antifouling_review/> The current standard for these coatings is [[polydimethylsiloxane]], or PDMS, which consists of a non-polar backbone made of repeating units of silicon and oxygen atoms.<ref>{{Citation|last1=Krishnan|first1=S|title=Advances in polymers for anti-biofouling surfaces|journal=Journal of Materials Chemistry|year=2008|volume=12|issue=29|pages=3405–3413|doi=10.1039/B801491D|last2=Weinman|first2=Craig J.|last3=Ober|first3=Christopher K.}}</ref> The non-polarity of PDMS allows for biomolecules to readily adsorb to its surface in order to lower interfacial energy. However, PDMS also has a low modulus of elasticity that allows for the release of fouling organisms at speeds of greater than 20 knots. The dependence of effectiveness on vessel speed prevents use of PDMS on slow-moving ships or those that spend significant amounts of time in port.<ref name="Vladkova"/>

The second class of non-toxic antifouling coatings are hydrophilic coatings. They rely on high amounts of hydration in order to increase the energetic penalty of removing water for proteins and microorganisms to attach. The most common examples of these coatings are based on highly hydrated [[zwitterion]]s, such as [[glycine betaine]] and [[Polysulfobetaine|sulfobetaine]]. These coatings are also low-friction, but are considered by some to be superior to hydrophobic surfaces because they prevent bacteria attachment, preventing biofilm formation.<ref>{{citation|first1=S.|last1=Jiang|first2=Z.|last2=Cao|title=Ultralow-Fouling, Functionalizable, and Hydrolyzable Zwitterionic Materials and Their Derivatives for Biological Applications|journal=Advanced Materials|year=2010|volume=22|pages=920–932|doi=10.1002/adma.200901407|issue=9|pmid=20217815|bibcode=2010AdM....22..920J |s2cid=205233845 }}</ref> These coatings are not yet commercially available and are being designed as part of a larger effort by the [[Office of Naval Research]] to develop environmentally safe [[biomimetic]] ship coatings.<ref name=V1/>

===== Biocides =====
{{main|Biocide|Biomimetic antifouling coating}}
Biocides are chemical substances that kill or deter microorganisms responsible for biofouling. The biocide is typically applied as a paint, i.e. through [[physical adsorption]]. The biocides prevent the formation of [[biofilm]]s.<ref name="antifouling_review" /> Other biocides are toxic to larger organisms in biofouling, such as [[algae]]. Formerly, the so-called [[tributyltin]] (TBT) compounds were used as biocides (and thus anti-fouling agents).  TBTs are toxic to both microorganisms and larger aquatic organisms.<ref name="TBT_review">{{cite journal |last1=Evans |first1=S.M. |last2=Leksono |first2=T. |last3=McKinnell |first3=P.D. |title=Tributyltin pollution: A diminishing problem following legislation limiting the use of TBT-based anti-fouling paints |journal=Marine Pollution Bulletin |date=January 1995 |volume=30 |issue=1 |pages=14–21 |doi=10.1016/0025-326X(94)00181-8 |bibcode=1995MarPB..30...14E }}</ref> The international maritime community has phased out the use of organotin-based coatings.<ref>{{Cite web|url=http://www.imo.org/en/OurWork/Environment/Anti-foulingSystems/Pages/Default.aspx|title=Anti-fouling Systems|access-date=10 June 2017|archive-date=11 June 2017|archive-url=https://web.archive.org/web/20170611064311/http://www.imo.org/en/OurWork/Environment/Anti-foulingSystems/Pages/Default.aspx|url-status=dead}}</ref> Replacing organotin compounds is [[dichlorooctylisothiazolinone]]. This compound, however, also suffers from broad toxicity to marine organisms.

==== Ultrasonic antifouling ====
{{main|Ultrasonic antifouling}}
Ultrasonic transducers may be mounted in or around the hull of small to medium-sized boats. Research has shown these systems can help reduce fouling, by initiating bursts of ultrasonic waves through the hull medium to the surrounding water, killing or denaturing the algae and other microorganisms that form the beginning of the fouling sequence. The systems cannot work on wooden-hulled boats, or boats with a soft-cored composite material, such as wood or foam. The systems have been loosely based on technology proven to control algae blooms.<ref>{{cite journal|last1=Lee|first1=TJ|last2=Nakano|first2=K|last3=Matsumara|first3=M|year=2001|title=Ultrasonic irradiation for blue-green algae bloom control|journal=Environ Technol|volume=22|issue=4|pages=383–90|doi=10.1080/09593332208618270|pmid=11329801|bibcode=2001EnvTe..22..383L |s2cid=22704787}}</ref>

====Energy methods====
Pulsed laser irradiation is commonly used against [[diatoms]]. Plasma pulse technology is effective against zebra mussels and works by stunning or killing the organisms with microsecond-duration energizing of the water with high-voltage electricity.<ref name=stanczak/>

Similarly, another method shown to be effective against algae buildups bounces brief high-energy acoustic pulses down pipes.<ref>{{citation|last1=Walch|first1=M.|last2=Mazzola|first2=M.|last3=Grothaus|first3=M.|year=2000|title=Feasibility Demonstration of a Pulsed Acoustic Device for Inhibition of Biofouling in Seawater Piping|publisher=Naval Surface Warfare Center Carderock Div.|location=Bethesda, MD|id=NSWCCD-TR-2000/04|url=http://www.dtic.mil/cgi-bin/GetTRDoc?Location=U2&doc=GetTRDoc.pdf&AD=ADA376166|archive-url=https://web.archive.org/web/20130408130814/http://www.dtic.mil/cgi-bin/GetTRDoc?Location=U2&doc=GetTRDoc.pdf&AD=ADA376166|url-status=dead|archive-date=8 April 2013|format=pdf|access-date=21 May 2012}}</ref>

====Other methods====
Regimens to periodically use heat to treat exchanger equipment and pipes have been successfully used to remove mussels from power plant cooling systems using water at 105&nbsp;°F (40&nbsp;°C) for 30 minutes.<ref>{{citation|title=Oceans 86 Proceedings|contribution=Development of a Site Specific Biofouling Control Program for the Diablo Canyon Power Plant|first=David C.|last=Sommerville|pages=227–231|doi=10.1109/OCEANS.1986.1160543|date=September 1986|publisher=IEEE Conference Publications|s2cid=110171493}}</ref>

The medical industry utilizes a variety of energy methods to address [[bioburden]] issues associated with biofouling. [[Autoclave|Autoclaving]] typically involves heating a medical device to 121&nbsp;°C (249&nbsp;°F) for 15–20 minutes. Ultrasonic cleaning, UV light, and chemical wipe-down or immersion can also be used for different types of devices.

Medical devices used in operating rooms, ICUs, isolation rooms, biological analysis labs, and other high-contamination-risk areas have negative pressure (constant exhaust) in the rooms, maintain strict cleaning protocols, require equipment with no fans, and often drape equipment in protective plastic.<ref>{{cite book |doi=10.1007/978-3-319-99921-0_35 |chapter=Operation Department: Infection Control |title=Prevention and Control of Infections in Hospitals |year=2019 |last1=Andersen |first1=Bjørg Marit |pages=453–489 |isbn=978-3-319-99920-3 |s2cid=86654083 }}</ref>

[[Ultraviolet#Subtypes|UVC]] irradiation is a noncontact, nonchemical solution that can be used across a range of instruments. Radiation in the UVC range prevents biofilm formation by deactivating the [[DNA]] in bacteria, viruses, and other microbes. Preventing biofilm formation prevents larger organisms from attaching themselves to the instrument and eventually rendering it inoperable.<ref>Hari Venugopalan, ''Photonic Frontiers: LEDs - UVC LEDs reduce marine biofouling'', Laser Focus World (July 2016) pp.&nbsp;28–31 [http://www.laserfocusworld.com/articles/print/volume-52/issue-07/features/photonic-frontiers-leds-uvc-leds-reduce-marine-biofouling.html StackPath]</ref>

==History ==
Biofouling, especially of ships, has been a problem for as long as humans have been sailing the oceans.<ref name=whoi/> 

The earliest attestations of attempts to counter fouling, and thus also the earliest attestation of knowledge of it, is the use of pitch and copper plating as anti-fouling solutions that were attributed to ancient seafaring nations, such as the [[Phoenicians]] and [[Carthaginians]] (1500–300&nbsp;BC). Wax, tar and [[Gilsonite|asphaltum]] have been used since early times.<ref name=whoi>{{citation|title=Marine Fouling and its Prevention|year=1952|contribution=The History and Prevention of Foulng|author=Woods Hole Oceanographic Institute|publisher=United States department of the Navy, Bureau of Ships|url=https://darchive.mblwhoilibrary.org/bitstream/handle/1912/191/chapter%2011.pdf?sequence=20 }}</ref> An Aramaic record dating from 412&nbsp;BC tells of a ship's bottom being coated with a mixture of arsenic, oil and sulphur.<ref>{{citation|last1=Culver|first1=Henry E.|first2=Gordon|last2=Grant|title=The Book of Old Ships|isbn=978-0486273327|publisher=Dover Publications|year=1992}}</ref> In ''[[Deipnosophistae]]'', [[Athenaeus]] described the anti-fouling efforts taken in the construction of the great ship of [[Hieron of Syracuse]] (died 467&nbsp;BC).<ref>Athenaeus of Naucratis, ''The deipnosophists, or, Banquet of the learned of Athenæus'', [http://digicoll.library.wisc.edu/cgi-bin/Literature/Literature-idx?type=turn&id=Literature.AthV1&entity=Literature.AthV1.p0334&q1=Hiero&pview=hide Volume I, Book V, Chapter 40] ff.</ref>

A recorded explanation by [[Plutarch]] of the impact fouling had on ship speed goes as follows: "when weeds, ooze, and filth stick upon its sides, the stroke of the ship is more obtuse and weak; and the water, coming upon this clammy matter, doth not so easily part from it; and this is the reason why they usually calk their ships."<ref>{{citation|last=Plutarch|title=The Complete Works of Plutarch, Volume 3|contribution=Essays and Miscellanies|url=http://www.gutenberg.org/files/3052/3052-h/3052-h.htm|date=February 2002}}</ref>

Before the 18th century, various anti-fouling techniques were used, with three main substances employed: "White stuff", a mixture of [[train oil]] (whale oil), [[rosin]] and [[sulfur]]; "Black stuff", a mixture of [[tar]] and [[resin|pitch]]; and "Brown stuff", which was simply sulfur added to Black stuff.<ref>{{citation|last=Lavery|first=Brian|year=2000|title=The Arming and Fitting of English Ships of War 1600-1815|publisher=Conway Maritime Press|isbn=978-0-85177-451-0}}</ref> In many of these cases, the purpose of these treatments is ambiguous. There is dispute whether many of these treatments were actual anti-fouling techniques, or whether, when they were used in conjunction with lead and wood sheathing, they were simply intended to combat wood-boring [[shipworm]]s.

[[File:Lebreton engraving-07.jpg|thumb|left|300px|Ships brought ashore on the [[Torres Strait]] and [[careening|careened]] in preparation for cleaning the hull]]
In 1708, [[Charles Perry (traveller)|Charles Perry]] suggested [[copper sheathing]] explicitly as an anti-fouling device but the first experiments were not made until 1761 with the sheathing of [[HMS Alarm (1758)|HMS Alarm]], after which the bottoms and sides of several ships' keels and false keels were sheathed with copper plates.<ref name=whoi/>

The copper performed well in protecting the hull from invasion by worm, and in preventing the growth of weed, for when in contact with water, the copper produced a poisonous film, composed mainly of [[oxychloride]], that deterred these marine creatures. Furthermore, as this film was slightly soluble, it gradually washed away, leaving no way for marine life to attach itself to the ship.{{Citation needed|date=January 2010}}
From about 1770, the [[Royal Navy]] set about coppering the bottoms of the entire fleet and continued to the end of the use of wooden ships. The process was so successful that the term ''copper-bottomed'' came to mean something that was highly dependable or risk free.

With the rise of iron hulls in the 19th century, copper sheathing could no longer be used due to its [[galvanic corrosion|galvanic corrosive]] interaction with iron. [[Anti-fouling paint]]s were tried, and in 1860, the first practical paint to gain widespread use was introduced in [[Liverpool]] and was referred to as "McIness" hot plastic paint.<ref name=whoi/> These treatments had a short service life, were expensive, and relatively ineffective by modern standards.<ref name=antifouling_review/>

By the mid-twentieth century, copper oxide-based paints could keep a ship out of drydock for as much as 18 months, or as little as 12 in tropical waters.<ref name=whoi/> The shorter service life was due to rapid leaching of the toxicant, and chemical conversion into less toxic salts, which accumulated as a crust that would inhibit further leaching of active cuprous oxide from the layer under the crust.<ref>{{cite book |id={{DTIC|ADA134019}} |last1=Dowd |first1=Theodore |title=An Assessment of Ablative Organotin Antifouling (AF) Coatings |date=1983 }}</ref>

The 1960s brought a breakthrough, with self-polishing paints that slowly [[hydrolysis|hydrolyze]], slowly releasing toxins. These paints employed [[organotin chemistry]] ("tin-based") biotoxins such as [[tributyltin oxide]] (TBT) and were effective for up to four years. These biotoxins were subsequently banned by the [[International Maritime Organization]] when they were found to be very toxic to diverse organisms.<ref>{{citation|url=http://www.imo.org/blast/blastDataHelper.asp?data_id=7986&filename=FOULING2003.pdf|year=2002|title=Focus on IMO - Anti-fouling systems|publisher=[[International Maritime Organization]]|access-date=22 May 2012|archive-date=20 February 2014|archive-url=https://web.archive.org/web/20140220091905/http://www.imo.org/blast/blastDataHelper.asp?data_id=7986&filename=FOULING2003.pdf|url-status=dead}}</ref><ref>{{Citation|last1=Gajda|first1=M.|author2=Jancso, A.|year=2010|title=Organotins, formation, use, speciation and toxicology|journal=Metal Ions in Life Sciences|publisher=RSC publishing|location=Cambridge|volume=7, Organometallics in environment and toxicology|pages=111–51|isbn=9781847551771|doi=10.1039/9781849730822-00111|pmid=20877806}}</ref> TBT in particular has been described as the most toxic pollutant ever deliberately released in the ocean.<ref name=TBT_review/>

As an alternative to organotin toxins, there has been renewed interest in copper as the active agent in ablative or self polishing paints, with reported service lives up to 5 years; yet also other methods that do not involve coatings. Modern adhesives permit application of copper alloys to steel hulls without creating galvanic corrosion. However, copper alone is not impervious to diatom and algae fouling. Some studies indicate that copper may also present an unacceptable environmental impact.<ref>{{cite journal |last1=Swain |first1=Geoffrey |title=Redefining Antifouling Coatings |journal=Journal of Protective Coatings & Linings |date=1999 |volume=16 |issue=9 |pages=26–35 |oclc=210981215 |url=http://www.paintsquare.com/library/articles/redefining_antifouling_coatings.pdf }}</ref>

Study of biofouling began in the early 19th century with [[Humphry Davy|Davy's]] experiments linking the effectiveness of copper to its solute rate.<ref name=whoi/> In the 1930s microbiologist [[Claude ZoBell]] showed that the attachment of organisms is preceded by the [[adsorption]] of organic compounds now referred to as [[extracellular polymeric substances]].<ref>{{citation|page=225|title=Scripps Institution of Oceanography: Probing the Oceans 1936 to 1976|location=San Diego, Calif|publisher=Tofua Press|year=1978|url=http://publishing.cdlib.org/ucpressebooks/view?docId=kt109nc2cj|first=Elizabeth Noble |last=Shor|access-date=21 May 2012}}</ref><ref>{{citation|contribution=Claude E. Zobell – his life and contributions to biofilm microbiology|first=Hilary M.|last=Lappin-Scott|title=Microbial Biosystems: New Frontiers, Proceedings of the 8th International Symposium on Microbial Ecology|isbn=9780968676332|publisher=Society for Microbial Ecology|location=Halifax, Canada|url=http://plato.acadiau.ca/isme/Symposium03/lappin-scott.PDF|access-date=23 May 2012|year=2000}}</ref>

One trend of research is the study of the relationship between wettability and anti-fouling effectiveness. Another trend is the study of living organisms as the inspiration for new functional materials. For example, the mechanisms used by marine animals to inhibit biofouling on their skin.<ref>{{cite journal |last1=Carman |first1=Michelle L. |last2=Estes |first2=Thomas G. |last3=Feinberg |first3=Adam W. |last4=Schumacher |first4=James F. |last5=Wilkerson |first5=Wade |last6=Wilson |first6=Leslie H. |last7=Callow |first7=Maureen E. |last8=Callow |first8=James A. |last9=Brennan |first9=Anthony B. |title=Engineered antifouling microtopographies – correlating wettability with cell attachment |journal=Biofouling |date=January 2006 |volume=22 |issue=1 |pages=11–21 |doi=10.1080/08927010500484854 |pmid=16551557 |bibcode=2006Biofo..22...11C |s2cid=5810987 }}</ref>

Materials research into superior antifouling surfaces for [[fluidized bed reactor]]s suggest that low [[wetting|wettability]] plastics such as [[polyvinyl chloride]] (PVC), [[high-density polyethylene]] and [[polymethylmethacrylate]] ("plexiglas") demonstrate a high correlation between their resistance to bacterial adhesion and their [[Hydrophobe|hydrophobicity]].<ref>{{citation|contribution=Hydrophobicity in Bacterial Adhesion|publisher=BioLine|title=Biofilm community interactions: chance or necessity?|author=R. Oliveira|display-authors=et al|isbn=978-0952043294|url=http://repositorium.sdum.uminho.pt/bitstream/1822/6706/1/BIOCLUB2%255B1%255D.pdf|year=2001}}</ref>

A study of the biotoxins used by organisms has revealed several effective compounds, some of which are more powerful than synthetic compounds. [[Bufalin]], a [[bufotoxin]], was found to be over 100 times as potent as TBT, and over 6,000 times more effective in anti-settlement activity against barnacles.<ref>{{citation|last=Omae|first=Iwao|title=General Aspects of Tin-Free Antifouling Paints|journal=[[Chemical Reviews]]|year=2003|volume=103|issue=9|pages=3431–3448|doi=10.1021/cr030669z|pmid=12964877|url=http://web.centre.edu/workmanj/che%20454%20stuff/antifouling.pdf|access-date=23 May 2012|archive-date=24 June 2010|archive-url=https://web.archive.org/web/20100624001700/http://web.centre.edu/workmanj/CHE%20454%20STUFF/antifouling.pdf|url-status=dead}}</ref>

One approach to antifouling entails coating surfaces with [[polyethylene glycol]] (PEG).<ref name="Dalsin">{{cite journal|last1=Dalsin|first1=J.|last2=Messersmith|first2=P.|year=2005|title=Bioinspired antifouling polymers|journal=Materials Today|volume=8|issue=9|pages=38–46|doi=10.1016/S1369-7021(05)71079-8|doi-access=free}}</ref> Growing chains of PEG on surfaces is challenging. The resolution to this problem may come from understanding the mechanisms by which [[mussel]]s adhere to solid surfaces in marine environments. Mussels utilize [[Bioadhesive|adhesive proteins]], or MAPs.<ref>{{cite journal|last=Taylor|first=S.|display-authors=et al|year=1994|title=trans-2,3-cis-3,4-Dihydroxyproline, a New Naturally Occurring Amino Acid, Is the Sixth Residue in the Tandemly Repeated Consensus Decapeptides of an Adhesive Protein from Mytilus edulis|journal=J. Am. Chem. Soc.|volume=116|issue=23|pages=10803–10804|doi=10.1021/ja00102a063}}</ref> The service life of PEG coatings is also doubtful.

==See also==
*[[Fouling]]
*[[Biomimetic antifouling coating]]s
*[[Tributyltin]]
*[[Bottom paint]]
*[[Corrosion engineering]]

==References==
<references/>

==Further reading==
* {{Citation |doi=10.1146/annurev-matsci-070511-155012|title=Bio-Inspired Antifouling Strategies|journal=[[Annual Review of Materials Research]]|volume=42|pages=211–229|year=2012|last1=Kirschner|first1=Chelsea M|last2=Brennan|first2=Anthony B|bibcode=2012AnRMS..42..211K}}

[[Category:Fouling]]
[[Category:Pollution]]
[[Category:Ecology]]