Editing Biofouling (section)

==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.