HOME

TheInfoList



OR:

Biofouling or biological fouling is the accumulation of
microorganism A microorganism, or microbe,, ''mikros'', "small") and ''organism'' from the el, ὀργανισμός, ''organismós'', "organism"). It is usually written as a single word but is sometimes hyphenated (''micro-organism''), especially in olde ...
s,
plant Plants are predominantly photosynthetic eukaryotes of the kingdom Plantae. Historically, the plant kingdom encompassed all living things that were not animals, and included algae and fungi; however, all current definitions of Plantae exclud ...
s,
alga Algae (; singular alga ) is an informal term for a large and diverse group of photosynthetic eukaryotic organisms. It is a polyphyletic grouping that includes species from multiple distinct clades. Included organisms range from unicellular micr ...
e, or small
animal Animals are multicellular, eukaryotic organisms in the biological kingdom Animalia. With few exceptions, animals consume organic material, breathe oxygen, are able to move, can reproduce sexually, and go through an ontogenetic stage in ...
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 An epibiont (from the Ancient Greek meaning "living on top of") is an organism that lives on the surface of another living organism, called the basibiont ("living underneath"). The interaction between the two organisms is called epibiosis. An ep ...
'' 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 Food processing is the transformation of agricultural products into food, or of one form of food into other forms. Food processing includes many forms of processing foods, from grinding grain to make raw flour to home cooking to complex indust ...
, underwater construction, and desalination plants.
Anti-fouling Biofouling or biological fouling is the accumulation of microorganisms, plants, algae, or small animals where it is not wanted on surfaces such as ship and submarine hulls, devices such as water inlets, pipework, grates, ponds, and rivers that ...
is the ability of specifically designed materials (such as toxic biocide paints, or non-toxic paints) to remove or prevent biofouling. The buildup of biofouling on marine vessels poses a significant problem. In some instances, the hull structure and propulsion systems can be damaged. The accumulation of biofoulers on hulls can increase both the hydrodynamic volume of a vessel and the hydrodynamic friction, leading to increased drag of up to 60%. 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. 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.


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. Biofouling is divided into microfouling—
biofilm A biofilm comprises any syntrophic consortium of microorganisms in which cells stick to each other and often also to a surface. These adherent cells become embedded within a slimy extracellular matrix that is composed of extracellular p ...
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 Calcareous () is an adjective meaning "mostly or partly composed of calcium carbonate", in other words, containing lime or being chalky. The term is used in a wide variety of scientific disciplines. In zoology ''Calcareous'' is used as an adje ...
(hard) fouling organisms include
barnacles A barnacle is a type of arthropod constituting the subclass Cirripedia in the subphylum Crustacea, and is hence related to crabs and lobsters. Barnacles are exclusively marine, and tend to live in shallow and tidal waters, typically in erosiv ...
, encrusting
bryozoa Bryozoa (also known as the Polyzoa, Ectoprocta or commonly as moss animals) are a phylum of simple, aquatic invertebrate animals, nearly all living in sedentary colonies. Typically about long, they have a special feeding structure called a l ...
ns,
mollusks Mollusca is the second-largest phylum of invertebrate animals after the Arthropoda, the members of which are known as molluscs or mollusks (). Around 85,000 extant species of molluscs are recognized. The number of fossil species is estim ...
,
polychaete Polychaeta () is a paraphyletic class of generally marine annelid worms, commonly called bristle worms or polychaetes (). Each body segment has a pair of fleshy protrusions called parapodia that bear many bristles, called chaetae, which are ma ...
and other tube worms, and
zebra mussels The zebra mussel (''Dreissena polymorpha'') is a small freshwater mussel. The species originates from the lakes of southern Russia and Ukraine, but has been accidentally introduced to numerous other areas and has become an invasive species in ma ...
. Examples of non-calcareous (soft) fouling organisms are
seaweed Seaweed, or macroalgae, refers to thousands of species of macroscopic, multicellular, marine algae. The term includes some types of ''Rhodophyta'' (red), '' Phaeophyta'' (brown) and ''Chlorophyta'' (green) macroalgae. Seaweed species such a ...
,
hydroids Hydroids are a life stage for most animals of the class Hydrozoa, small predators related to jellyfish. Some hydroids such as the freshwater '' Hydra'' are solitary, with the polyp attached directly to the substrate. When these produce buds ...
, algae and biofilm "slime". Together, these organisms form a
fouling community Fouling communities are communities of organisms found on artificial surfaces like the sides of docks, marinas, harbors, and boats. Settlement panels made from a variety of substances have been used to monitor settlement patterns and to examine s ...
.


Ecosystem formation

Marine fouling is typically described as following four stages of ecosystem development. Within the first minute the 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 process of bacterial adhesion to occur, with both diatoms and bacteria (e.g. ''
Vibrio alginolyticus ''Vibrio alginolyticus'' is a Gram-negative marine bacterium. It is medically important since it causes otitis and wound infection. It is also present in the bodies of animals such as pufferfish, where it is responsible for the production of t ...
'', ''
Pseudomonas putrefaciens ''Shewanella putrefaciens'' is a Gram-negative pleomorphic bacterium. It has been isolated from marine environments, as well as from anaerobic sandstone in the Morrison Formation in New Mexico. ''S. putrefaciens'' is also a facultative anaerobe ...
'') attaching, initiating the formation of a
biofilm A biofilm comprises any syntrophic consortium of microorganisms in which cells stick to each other and often also to a surface. These adherent cells become embedded within a slimy extracellular matrix that is composed of extracellular p ...
. 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 ''Ulva intestinalis'' is a green alga in the family Ulvaceae, known by the common names sea lettuce, green bait weed, gutweed and grass kelp. Until they were reclassified by genetic work completed in the early 2000s, the tubular members of the ...
'', ''
Ulothrix ''Ulothrix'' is a genus of green algae in the family Ulotrichaceae. ''Ulothrix'' is a genus of non-branching filamentous green algae, generally found in fresh and marine water. Its cells are normally as broad as they are long, and they thrive ...
'') and protozoans (e.g. ''
Vorticella ''Vorticella'' is a genus of bell-shaped ciliates that have stalks to attach themselves to substrates. The stalks have contractile myonemes, allowing them to pull the cell body against substrates. The formation of the stalk happens after the fre ...
'', ''Zoothamnium'' sp.) to attach themselves. Within two to three weeks, the tertiary colonizers—the macrofoulers—have attached. These include
tunicates A tunicate is a marine invertebrate animal, a member of the subphylum Tunicata (). It is part of the Chordata, a phylum which includes all animals with dorsal nerve cords and notochords (including vertebrates). The subphylum was at one time cal ...
, mollusks and
sessile Sessility, or sessile, may refer to: * Sessility (motility), organisms which are not able to move about * Sessility (botany), flowers or leaves that grow directly from the stem or peduncle of a plant * Sessility (medicine), tumors and polyps that ...
cnidarians Cnidaria () is a phylum under kingdom Animalia containing over 11,000 species of aquatic animals found both in freshwater and marine environments, predominantly the latter. Their distinguishing feature is cnidocytes, specialized cells that th ...
.


Impact

Governments and industry spend more than US$5.7 billion annually to prevent and control marine biofouling. Biofouling occurs everywhere but is most significant economically to the shipping industries, since fouling on a ship's hull significantly increases drag, reducing the overall
hydrodynamic In physics and engineering, fluid dynamics is a subdiscipline of fluid mechanics that describes the flow of fluids—liquids and gases. It has several subdisciplines, including ''aerodynamics'' (the study of air and other gases in motion) and ...
performance of the vessel, and increases the fuel consumption. 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 Mariculture or marine farming is a specialized branch of aquaculture (which includes freshwater aquaculture) involving the cultivation of marine organisms for food and other animal products, in enclosed sections of the open ocean ( offshore mar ...
, membrane systems (''e.g.'',
membrane bioreactors Membrane bioreactor (MBR) is a combination of membrane processes like microfiltration or ultrafiltration with a biological wastewater treatment process, the activated sludge process. It is now widely used for municipal and industrial wastewater t ...
and
reverse osmosis Reverse osmosis (RO) is a water purification process that uses a partially permeable membrane to separate ions, unwanted molecules and larger particles from drinking water. In reverse osmosis, an applied pressure is used to overcome osmotic pr ...
spiral wound membranes) and cooling water cycles of large industrial equipment and
power station A power station, also referred to as a power plant and sometimes generating station or generating plant, is an industrial facility for the generation of electric power. Power stations are generally connected to an electrical grid. Many pow ...
s. Biofouling can occur in oil pipelines carrying oils with entrained water, especially those carrying used oils,
cutting oil Cutting fluid is a type of coolant and lubricant designed specifically for metalworking processes, such as machining and stamping. There are various kinds of cutting fluids, which include oils, oil-water emulsions, pastes, gels, aerosols (mists), ...
s, oils rendered
water-soluble In chemistry, solubility is the ability of a substance, the solute, to form a solution with another substance, the solvent. Insolubility is the opposite property, the inability of the solute to form such a solution. The extent of the solubil ...
through
emulsification An emulsion is a mixture of two or more liquids that are normally immiscible (unmixable or unblendable) owing to liquid-liquid phase separation. Emulsions are part of a more general class of two-phase systems of matter called colloids. Although ...
, and
hydraulic oil A hydraulic fluid or hydraulic liquid is the medium by which power is transferred in hydraulic machinery. Common hydraulic fluids are based on mineral oil or water. Examples of equipment that might use hydraulic fluids are excavators and backhoes, ...
s. Other mechanisms impacted by biofouling include microelectrochemical drug delivery devices, papermaking and pulp industry machines, underwater instruments, fire protection system piping, and sprinkler system nozzles. 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. Medical devices often include fan-cooled heat sinks, to cool their electronic components. While these systems sometimes include
HEPA HEPA (, high-efficiency particulate air) filter, also known as high-efficiency particulate absorbing filter and high-efficiency particulate arrestance filter, is an efficiency standard of air filters. Filters meeting the HEPA standard must s ...
filters to collect microbes, some pathogens do pass through these filters, collect inside the device and are eventually blown out and infect other patients. 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. 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. Over time, the accumulation of biofoulers on hulls increases both the hydrodynamic volume of a vessel and the frictional effects leading to increased drag of up to 60% The additional drag can decrease speeds up to 10%, which can require up to a 40% increase in fuel to compensate. With fuel typically comprising up to half of marine transport costs, biofouling is estimated to cost the US Navy alone around $1 billion per year in increased fuel usage, maintenance and biofouling control measures. 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. Biofouling also impacts aquaculture, increasing production and management costs, while decreasing product value. Fouling communities may compete with shellfish directly for food resources, impede the procurement of food and oxygen by reducing water flow around shellfish, or interfere with the operational opening of their valves. Consequently, stock affected by biofouling can experience reduced growth, condition and survival, with subsequent negative impacts on farm productivity. Although many methods of removal exist, they often impact the cultured species, sometimes more so than the fouling organisms themselves.


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.
LED A light-emitting diode (LED) is a semiconductor device that emits light when current flows through it. Electrons in the semiconductor recombine with electron holes, releasing energy in the form of photons. The color of the light (cor ...
manufacturers have developed a range of UVC (250–280 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 nm when irradiated at 280 nm.


Methods


Antifouling

Antifouling is the process of preventing accumulations from forming. In
industrial process Industrial processes are procedures involving chemical, physical, electrical or mechanical steps to aid in the manufacturing of an item or items, usually carried out on a very large scale. Industrial processes are the key components of heavy ind ...
es, biodispersants 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 In chemistry, a zwitterion ( ; ), also called an inner salt or dipolar ion, is a molecule that contains an equal number of positively- and negatively-charged functional groups. : With amino acids, for example, in solution a chemical equilibrium w ...
s, or creating
nanoscale The nanoscopic scale (or nanoscale) usually refers to structures with a length scale applicable to nanotechnology, usually cited as 1–100 nanometers (nm). A nanometer is a billionth of a meter. The nanoscopic scale is (roughly speaking) a lo ...
surface topologies similar to the skin of sharks and dolphins, which only offer poor anchor points.


Coatings


= Non-toxic coatings

= Non-toxic anti-sticking coatings prevent attachment of microorganisms thus negating the use of biocides. These coatings are usually based on organic polymers. There are two classes of non-toxic anti-fouling coatings. The most common class relies on low
friction Friction is the force resisting the relative motion of solid surfaces, fluid layers, and material elements sliding against each other. There are several types of friction: *Dry friction is a force that opposes the relative lateral motion of t ...
and low surface energies. Low surface energies result in
hydrophobic In chemistry, hydrophobicity is the physical property of a molecule that is seemingly repelled from a mass of water (known as a hydrophobe). In contrast, hydrophiles are attracted to water. Hydrophobic molecules tend to be nonpolar and, t ...
surfaces. These coatings create a smooth surface, which can prevent attachment of larger microorganisms. For example,
fluoropolymers A fluoropolymer is a fluorocarbon-based polymer with multiple carbon–fluorine bonds. It is characterized by a high resistance to solvents, acids, and bases. The best known fluoropolymer is polytetrafluoroethylene under the brand name "Teflon," ...
and silicone coatings are commonly used. These coatings are ecologically inert but have problems with mechanical strength and long-term stability. Specifically, after days
biofilms A biofilm comprises any syntrophic consortium of microorganisms in which cells stick to each other and often also to a surface. These adherent cells become embedded within a slimy extracellular matrix that is composed of extracellular po ...
(slime) can coat the surfaces, which buries the chemical activity and allows microorganisms to attach. The current standard for these coatings is
polydimethylsiloxane Polydimethylsiloxane (PDMS), also known as dimethylpolysiloxane or dimethicone, belongs to a group of polymeric organosilicon compounds that are commonly referred to as silicones. PDMS is the most widely used silicon-based organic polymer, as its ...
, or PDMS, which consists of a non-polar backbone made of repeating units of silicon and oxygen atoms. 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. 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 In chemistry, a zwitterion ( ; ), also called an inner salt or dipolar ion, is a molecule that contains an equal number of positively- and negatively-charged functional groups. : With amino acids, for example, in solution a chemical equilibrium w ...
s, such as
glycine betaine Trimethylglycine is an amino acid derivative that occurs in plants. Trimethylglycine was the first betaine discovered; originally it was simply called betaine because, in the 19th century, it was discovered in sugar beets. It has a sweet and umami ...
and 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. These coatings are not yet commercially available and are being designed as part of a larger effort by the
Office of Naval Research The Office of Naval Research (ONR) is an organization within the United States Department of the Navy responsible for the science and technology programs of the U.S. Navy and Marine Corps. Established by Congress in 1946, its mission is to plan ...
to develop environmentally safe
biomimetic Biomimetics or biomimicry is the emulation of the models, systems, and elements of nature for the purpose of solving complex human problems. The terms "biomimetics" and "biomimicry" are derived from grc, βίος (''bios''), life, and μίμησ ...
ship coatings.


= Biocides

= 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 A biofilm comprises any syntrophic consortium of microorganisms in which cells stick to each other and often also to a surface. These adherent cells become embedded within a slimy extracellular matrix that is composed of extracellular p ...
s. Other biocides are toxic to larger organisms in biofouling, such as the
fungi A fungus ( : fungi or funguses) is any member of the group of eukaryotic organisms that includes microorganisms such as yeasts and molds, as well as the more familiar mushrooms. These organisms are classified as a kingdom, separately from t ...
and
algae Algae (; singular alga ) is an informal term for a large and diverse group of photosynthesis, photosynthetic eukaryotic organisms. It is a polyphyletic grouping that includes species from multiple distinct clades. Included organisms range from u ...
. Formerly, the so-called
tributyltin Tributyltin (TBT) is an umbrella term for a class of organotin compounds which contain the (C4H9)3 Sn group, with a prominent example being tributyltin oxide. For 40 years TBT was used as a biocide in anti-fouling paint, commonly known as b ...
(TBT) compounds were used as biocides (and thus anti-fouling agents). TBTs are toxic to both microorganisms and larger aquatic organisms. The international maritime community has phased out the use of organotin-based coatings. Replacing organotin compounds is
dichlorooctylisothiazolinone Dichlorooctylisothiazolinone, DCOIT or DCOI, is the organic compound with the formula SC(Cl)=C(Cl)C(O)NC7H15. It is a white solid that melts near room temperature. It is an isothiazolinone, a class of heterocyclic compounds used as biocides. DCO ...
. This compound, however, also suffers from broad toxicity to marine organisms.


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.


Energy methods

Pulsed laser irradiation is commonly used against
diatoms A diatom ( Neo-Latin ''diatoma''), "a cutting through, a severance", from el, διάτομος, diátomos, "cut in half, divided equally" from el, διατέμνω, diatémno, "to cut in twain". is any member of a large group comprising se ...
. 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. Similarly, another method shown to be effective against algae buildups bounced brief high-energy acoustic pulses down pipes.


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 °F (40 °C) for 30 minutes. The medical industry utilizes a variety of energy methods to address
bioburden Bioburden is normally defined as the number of bacteria living on a surface that has not been sterilized. The term is most often used in the context of bioburden testing, also known as microbial limit testing, which is performed on pharmaceutical ...
issues associated with biofouling.
Autoclaving An autoclave is a machine used to carry out industrial and scientific processes requiring elevated temperature and pressure in relation to ambient pressure and/or temperature. Autoclaves are used before surgical procedures to perform sterilizat ...
typically involves heating a medical device to 121 °C (249 °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. 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.


History

Biofouling, especially of ships, has been a problem for as long as humans have been sailing the oceans. The earliest written mention of fouling was by Plutarch who recorded this explanation of its impact on ship speed: "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." The use of pitch and copper plating as anti-fouling techniques were attributed to ancient seafaring nations, such as the Phoenicians and Carthaginians (1500- 300BC). Wax, tar and
asphaltum Asphaltite (also known as uintahite, asphaltum, gilsonite or oil sands) is a naturally occurring soluble solid hydrocarbon, a form of asphalt (or bitumen) with a relatively high melting temperature. Its large-scale production occurs in the Uintah ...
have been used since early times. An Aramaic record dating from 412 B.C. tells of a ship's bottom being coated with a mixture of arsenic, oil and sulphur. In ''
Deipnosophistae The ''Deipnosophistae'' is an early 3rd-century AD Greek work ( grc, Δειπνοσοφισταί, ''Deipnosophistaí'', lit. "The Dinner Sophists/Philosophers/Experts") by the Greek author Athenaeus of Naucratis. It is a long work of liter ...
'',
Athenaeus Athenaeus of Naucratis (; grc, Ἀθήναιος ὁ Nαυκρατίτης or Nαυκράτιος, ''Athēnaios Naukratitēs'' or ''Naukratios''; la, Athenaeus Naucratita) was a Greek rhetorician and grammarian, flourishing about the end of th ...
described the anti-fouling efforts taken in the construction of the great ship of
Hieron of Syracuse Hieron I ( el, Ἱέρων Α΄; usually Latinized Hiero) was the son of Deinomenes, the brother of Gelon and tyrant of Syracuse in Sicily from 478 to 467 BC. In succeeding Gelon, he conspired against a third brother, Polyzelos. Life During hi ...
(died 467 BC). Before the 18th century, various anti-fouling techniques were used, with three main substances employed: "White stuff", a mixture of
train oil Whale oil is oil obtained from the blubber of whales. Whale oil from the bowhead whale was sometimes known as train oil, which comes from the Dutch word ''traan'' (" tear" or "drop"). Sperm oil, a special kind of oil obtained from the hea ...
(Whale oil),
rosin Rosin (), also called colophony or Greek pitch ( la, links=no, pix graeca), is a solid form of resin obtained from pines and some other plants, mostly conifers, produced by heating fresh liquid resin to vaporize the volatile liquid terpene comp ...
and
sulfur Sulfur (or sulphur in British English) is a chemical element with the symbol S and atomic number 16. It is abundant, multivalent and nonmetallic. Under normal conditions, sulfur atoms form cyclic octatomic molecules with a chemical formula ...
; "Black stuff", a mixture of
tar Tar is a dark brown or black viscous liquid of hydrocarbons and free carbon, obtained from a wide variety of organic materials through destructive distillation. Tar can be produced from coal, wood, petroleum, or peat. "a dark brown or black b ...
and pitch; and "Brown stuff", which was simply sulfur added to Black stuff. 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 The shipworms are marine bivalve molluscs in the family Teredinidae: a group of saltwater clams with long, soft, naked bodies. They are notorious for boring into (and commonly eventually destroying) wood that is immersed in sea water, including ...
s. In 1708, Charles Perry suggested
copper sheathing Copper sheathing is the practice of protecting the under-water hull of a ship or boat from the corrosive effects of salt water and biofouling through the use of copper plates affixed to the outside of the hull. It was pioneered and developed by ...
explicitly as an anti-fouling device but the first experiments were not made until 1761 with the sheathing of HMS Alarm, after which the bottoms and sides of several ships' keels and false keels were sheathed with copper plates. 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 In chemistry, molecular oxohalides (oxyhalides) are a group of chemical compounds in which both oxygen and halogen atoms are attached to another chemical element A in a single molecule. They have the general formula , where X = fluorine (F), chlor ...
, 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. From about 1770, the
Royal Navy The Royal Navy (RN) is the United Kingdom's naval warfare force. Although warships were used by English and Scottish kings from the early medieval period, the first major maritime engagements were fought in the Hundred Years' War against ...
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 corrosive interaction with iron.
Anti-fouling paint Anti-fouling paint is a specialized category of coatings applied as the outer (outboard) layer to the hull of a ship or boat, to slow the growth of and facilitate detachment of subaquatic organisms that attach to the hull and can affect a ves ...
s were tried, and in 1860, the first practical paint to gain widespread use was introduced in
Liverpool Liverpool is a city and metropolitan borough in Merseyside, England. With a population of in 2019, it is the 10th largest English district by population and its metropolitan area is the fifth largest in the United Kingdom, with a populat ...
and was referred to as "McIness" hot plastic paint. These treatments had a short service life, were expensive, and relatively ineffective by modern standards. 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. 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. The 1960s brought a breakthrough, with self-polishing paints that slowly
hydrolyze Hydrolysis (; ) is any chemical reaction in which a molecule of water breaks one or more chemical bonds. The term is used broadly for substitution, elimination, and solvation reactions in which water is the nucleophile. Biological hydrolysi ...
, slowly releasing toxins. These paints employed
organotin chemistry Organotin compounds or stannanes are chemical compounds based on tin with hydrocarbon substituents. Organotin chemistry is part of the wider field of organometallic chemistry. The first organotin compound was diethyltin diiodide (), discovered by ...
("tin-based") biotoxins such as
tributyltin oxide Tributyltin oxide (TBTO) is an organotin compound chiefly used as a biocide (fungicide and molluscicide), especially a wood preservative. Its chemical formula is C4H9)3Snsub>2O. It is a colorless viscous liquid. It is poorly soluble in water (2 ...
(TBT) and were effective for up to four years. These biotoxins were subsequently banned by the
International Maritime Organization The International Maritime Organization (IMO, French: ''Organisation maritime internationale'') is a specialised agency of the United Nations responsible for regulating shipping. The IMO was established following agreement at a UN conference ...
when they were found to be very toxic to diverse organisms. TBT in particular has been described as the most toxic pollutant ever deliberately released in the ocean. 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. Study of biofouling began in the early 19th century with Davy's experiments linking the effectiveness of copper to its solute rate. In the 1930s microbiologist Claude ZoBell showed that the attachment of organisms is preceded by the
adsorption Adsorption is the adhesion of atoms, ions or molecules from a gas, liquid or dissolved solid to a surface. This process creates a film of the ''adsorbate'' on the surface of the ''adsorbent''. This process differs from absorption, in which a ...
of organic compounds now referred to as
extracellular polymeric substances Extracellular polymeric substances (EPSs) are natural polymers of high molecular weight secreted by microorganisms into their environment. EPSs establish the functional and structural integrity of biofilms, and are considered the fundamental comp ...
. 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. Materials research into superior antifouling surfaces for
fluidized bed reactor A fluidized bed reactor (FBR) is a type of reactor device that can be used to carry out a variety of multiphase chemical reactions. In this type of reactor, a fluid (gas or liquid) is passed through a solid granular material (usually a catalyst ...
s suggest that low
wettability Wetting is the ability of a liquid to maintain contact with a solid surface, resulting from intermolecular interactions when the two are brought together. This happens in presence of a gaseous phase or another liquid phase not miscible with t ...
plastics such as polyvinyl chloride (PVC),
high-density polyethylene High-density polyethylene (HDPE) or polyethylene high-density (PEHD) is a thermoplastic polymer produced from the monomer ethylene. It is sometimes called "alkathene" or "polythene" when used for HDPE pipes. With a high strength-to-density ratio, ...
and
polymethylmethacrylate Poly(methyl methacrylate) (PMMA) belongs to a group of materials called engineering plastics. It is a transparent thermoplastic. PMMA is also known as acrylic, acrylic glass, as well as by the trade names and brands Crylux, Plexiglas, Acrylite ...
("plexiglas") demonstrate a high correlation between their resistance to bacterial adhesion and their
hydrophobicity In chemistry, hydrophobicity is the physical property of a molecule that is seemingly repelled from a mass of water (known as a hydrophobe). In contrast, hydrophiles are attracted to water. Hydrophobic molecules tend to be nonpolar and, t ...
. 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 Bufotoxins are a family of toxic steroid lactones or substituted tryptamines of which some may or may not be toxic. They occur in the parotoid glands, skin, and poison of many toads (genus ''Bufo'') and other amphibians, and in some plants and mus ...
, was found to be over 100 times as potent as TBT, and over 6,000 times more effective in anti-settlement activity against barnacles. One approach to antifouling entails coating surfaces with
polyethylene glycol Polyethylene glycol (PEG; ) is a polyether compound derived from petroleum with many applications, from industrial manufacturing to medicine. PEG is also known as polyethylene oxide (PEO) or polyoxyethylene (POE), depending on its molecular we ...
(PEG). Growing chains of PEG on surfaces is challenging. The resolution to this problem may come from understanding the mechanisms by which
mussel Mussel () is the common name used for members of several families of bivalve molluscs, from saltwater and freshwater habitats. These groups have in common a shell whose outline is elongated and asymmetrical compared with other edible clams, which ...
s adhere to solid surfaces in marine environments. Mussels utilize adhesive proteins, or MAPs. The service life of PEG coatings is also doubtful.


See also

*
Fouling Fouling is the accumulation of unwanted material on solid surfaces. The fouling materials can consist of either living organisms (biofouling) or a non-living substance (inorganic or organic). Fouling is usually distinguished from other surf ...
* Biomimetic antifouling coatings *
Tributyltin Tributyltin (TBT) is an umbrella term for a class of organotin compounds which contain the (C4H9)3 Sn group, with a prominent example being tributyltin oxide. For 40 years TBT was used as a biocide in anti-fouling paint, commonly known as b ...
*
Bottom paint Bottom may refer to: Anatomy and sex * Bottom (BDSM), the partner in a BDSM who takes the passive, receiving, or obedient role, to that of the top or dominant * Bottom (sex), a term used by gay couples and BDSM * Buttocks or bottom, part of t ...
*
Corrosion engineering Corrosion engineering is an engineering specialty that applies scientific, technical, engineering skills, and knowledge of natural laws and physical resources to design and implement materials, structures, devices, systems, and procedures to mana ...


References


Further reading

* {{Citation , doi=10.1146/annurev-matsci-070511-155012, title=Bio-Inspired Antifouling Strategies, journal=
Annual Review of Materials Research The ''Annual Review of Materials Research'' is a peer-reviewed journal that publishes review articles about materials science. It has been published by the nonprofit Annual Reviews since 1971, when it was first released under the title the ''Ann ...
, volume=42, pages=211–229, year=2012, last1=Kirschner, first1=Chelsea M, last2=Brennan, first2=Anthony B, bibcode=2012AnRMS..42..211K Fouling Pollution Ecology