Risks of using antifouling biocides in aquaculture

Biocides are chemical substances that can deter or kill the microorganisms responsible for biofouling. The rapid expansion of the aquaculture industry is having a significant impact on the marine ecosystems. As the industry expands, it requires the use of more drugs, disinfectants and antifoulant compounds (biocides) to eliminate the microorganisms in the aquaculture facilities. The use of biocides in the aquatic environment, however, has proved to be harmful as it has toxic effects on the marine environment. Organic booster biocides were recently introduced as alternatives to the organotin compounds found in antifouling products after restrictions were imposed on the use of tributyltin (TBT). The replacement products are generally based on copper metal oxides and organic biocides. The biocides that are most commonly used in antifouling paints include chlorothalonil, dichlofluanid, DCOIT (4,5-dichloro-2-n-octyl-4-isothiazolin-3-one, Sea-nine 211^®), Diuron, Irgarol 1051, TCMS pyridine (2,3,3,6-tetrachloro-4-methylsulfonyl pyridine), zinc pyrithione and Zineb. There are two types of risks associated with the use of biocides in aquaculture: (i) predators and humans may ingest the fish and shellfish that have accumulated in these contaminants and (ii) the development of antibiotic resistance in bacteria. This paper provides an overview of the effects of antifouling (AF) biocides on aquatic organisms. It also provides some insights into the effects and risks of these compounds on non-target organisms.     

Biofouling Growth in Cold Estuarine Waters and Evaluation of Some Chitosan and Copper Anti-Fouling Paints

Ecological concerns about antifouling paints containing non-green tin and copper compounds have highlighted the need for environmentally friendly alternatives. We report here a field test conducted in estuarine waters over two months designed to evaluate the efficiency of a number of active natural and man-made chemical ingredients added into a silicon-polyurethane marine paint. Early steps of biofouling in cold seawater of the St. Lawrence Estuary (Canada) were observed. Analyses, including dry biomass, flow cytometry and spectrofluorimetry, demonstrated a short-term antibacterial action of chitosan-based paints although no significant anti-algal action was observed. Cuprous oxide paints were efficient against bacteria and algae invasion in the first two weeks, especially those with added organic biocides such as isothiazolone and copper pyrithione. However, the overall dry biomass and chlorophyll a content were similar for all chitosan-and copper-based paints after 63 days. Microscopic observations revealed variation in the highly diverse benthic diatom population including species Navicula, Melosira, Cocconeis, Nitshzcia, Fragilaria and Amphora. Results suggest no real long-term efficiency for tested antifouling paints and highlight a particular need for green antifouling ingredients that are active under northern estuarine conditions.     

RP-HPLC optimization of econea by using artificial neural networks and its antifouling performance on the Turkish coastline

Coverage of artificial surfaces within seawater by fouling organisms is defined as biofouling. Although biofouling is a natural process, it has some disadvantages for shipping industry such as increased fuel consumption, and CO₂ emission. Therefore, the ships' hull must be covered by antifouling (AF) or fouling release type coatings to overcome biofouling. In general, the so-called self-polishing AF paints contain biocides for preventing fouling organisms. Their concentrations and release rates from AF coatings are of great importance and they definitely affect both quality and cost of the coating. In the present study, we aimed at applying a new robust method. In this method, we used a model biocide, i.e., econea, to obtain its RP-HPLC optimization through artificial neural networks (ANN) and to see its antifouling performance. Column temperature, mobile phase ratio, flow rate, concentration and wavelength as input parameters and retention time as an output parameter were used in the ANN modeling. In conclusion, the R&D groups in AF paint industry may use RP-HPLC method supported with ANN modeling in further studies.     

Bioactive materials for antifouling coatings

Marine fouling is the result of the settling and subsequent growth of marine organisms on surfaces immersed in seawater. The most successful principle in use today for the protection of ship's hulls against this unwanted growth is the release of bioactive materials from antifouling coatings.

Antifouling coatings containing a mixture of cuprous oxide and triorganotin compounds in combination with sophisticated release mechanisms are considered to be today's most efficient systems. However, ever since the first biologically active materials were introduced into antifouling coatings, a search for alternatives has been continuing. Until the mid-1970s this research mainly involved the development of biocides which could simply prolong existing drydocking intervals, i.e. prolong the period in which the ship was fouling free. During the last decade, however, environmental aspects have become a top priority in the development of new biocides for antifouling coatings.     

Polymer brush coatings for combating marine biofouling

A variety of functional polymer brushes and coatings have been developed for combating marine biofouling and biocorrosion with much less environmental impact than traditional biocides. This review summarizes recent developments in marine antifouling polymer brushes and coatings that are tethered to material surfaces and do not actively release biocides. Polymer brush coatings have been designed to inhibit molecular fouling, microfouling and macrofouling through incorporation or inclusion of multiple functionalities. Hydrophilic polymers, such as poly(ethylene glycol), hydrogels, zwitterionic polymers and polysaccharides, resist attachment of marine organisms effectively due to extensive hydration. Fouling release polymer coatings, based on fluoropolymers and poly(dimethylsiloxane) elastomers, minimize adhesion between marine organisms and material surfaces, leading to easy removal of biofoulants. Polycationic coatings are effective in reducing marine biofouling partly because of their good bactericidal properties. Recent advances in controlled radical polymerization and click chemistry have also allowed better molecular design and engineering of multifunctional brush coatings for improved antifouling efficacies.     

环境友好型纳米银海洋防污损涂料研究

开发低毒、无毒的环境友好型抗海洋生物污损涂料的途径主要有两个方面：一是寻找防污高分子材料;二是寻找无毒的防污剂,在不破坏环境的前提下防止生物附着。综述了环境友好型抗海洋生物污损涂料的研究现状,结合纳米银在防污涂料中的应用,探讨了抗海洋生物污损涂料的发展趋势。     

Antifouling effect of hydrogen peroxide release from enzymatic marine coatings: Exposure testing under equatorial and Mediterranean conditions

Hydrogen peroxide (H₂O₂) may be considered an environmentally friendly antifouling alternative to common biocides such as Cu₂O and various organic compounds. In this work, the efficiency of antifouling coatings releasing hydrogen peroxide via enzyme-mediated conversion of starch, under Mediterranean and equatorial climatic conditions, is investigated. During seawater exposure of the coatings, starch is first converted to glucose by glucoamylase (rate-controlling step) and subsequently glucose is rapidly oxidised by hexose oxidase in a reaction producing hydrogen peroxide.     

Seawater-soluble pigments and their potential use in self-polishing antifouling paints: simulation-based screening tool

This work concerns the on-going development of efficient and environmentally friendly antifouling paints for biofouling control on large ocean-going ships. It is illustrated how a detailed mathematical model for a self-polishing antifouling paint exposed to seawater can be used as a product engineering tool to obtain a quick estimate of the paint behaviour that a given seawater-soluble pigment will provide. In the present context, “pigment” refers to relevant particulate solids of organic-, inorganic-, or biological nature. Simulations performed at 15 and 30 °C suggest that pigment solubility and seawater diffusivity of dissolved pigment species have a significant influence on the polishing and leaching behaviour of a typical self-polishing paint system. The pigment size distribution, on the other hand, only has a minor influence on the paint–seawater interaction. Simulations also indicate that only compounds which are effective against biofouling at very low seawater concentrations are useful as active antifouling paint ingredients. The need for model verification and exploration of practical issues, subsequent a given pigment has been found of interest, is discussed. The model approach is of relevance in the search for novel antifouling paints and for the development of accelerated test methods.     

Adsorption of antifouling booster biocides on metal oxide nanoparticles: Effect of different metal oxides and solvents

Controlling the release rate of biocides (antifouling agents) from a paint coating is a key issue for the development of multi-season antifouling marine coatings. One promising approach is the use of nanoparticles onto which biocides are adsorbed to prevent premature depletion of the biocide. Adsorption of one novel (Medetomidine) and six commercially available and widely used antifouling biocides (Chlorothalonile, Dichlofluanid, Diuron, Irgarol, Seanine, Tolylfluanid) onto oxide nanoparticles (Al₂O₃, CuO, MgO, SiO₂, TiO₂, ZnO) was investigated by HPLC and NMR in different organic solvents. Large differences in adsorption strength depending on the type of nanoparticle and solvent employed were observed. It was shown that nanoparticles coordinate preferentially with the imidazole moiety of Medetomidine. Independent of the type of particle this interaction was considerably stronger in comparison to the other biocides. However, the interaction strength was strongly dependant on the type of solvent, where the largest strongest interaction was achieved in o-xylene. In addition field tests were performed where a considerable decrease in release rate was displayed from coatings containing Medetomidine adsorbed to nanoparticles compared to coatings containing Medetomidine as single additive.     

Cupric tannate: A low copper content antifouling pigment

Fouling organisms attached to man-made surfaces submerged in seawater constitute a major worldwide technical and economical problem. Protection against biofouling is essential for efficient service of boats and ships. Due to recent and imminent restrictions of the use of traditional toxic antifouling paints, there is a growing need for new alternative compounds that ensure a good performance without polluting the marine ecosystem.

The aim of this work is to develop a new antifouling formulation using compounds of natural origin, i.e. tannates, in combination with a minimum concentration of a known bioactive pigment, i.e. copper.

Laboratory assays have shown that cupric tannate has a narcotic effect on biofouling larvae. In the field, after 12 months of immersion in Mar del Plata harbor (Argentine), none of the tested painted panels showed macrofouling organisms. This result was obtained with a large decrease in copper content in the order of 40 times relative to conventional cuprous oxide based paints.

Because copper tannate is not lethal at low concentrations, this pigment has an excellent potential as an antifouling agent.     

Marine macrofouling: a review of control technology in the context of an on-line experiment in the turbine condenser water box of Al-Jubail Phase-1 power/MSF plants

The problem of macrofouling has serious implications in the performance of desalination and power plants. Intake structures, screens, seawater piping systems and heat-exchanger tubes are the sites worst affected in the plants, causing an overall decline in plant efficiency at great economic cost. The last half century has witnessed significant advancements in the development ofmacrofouling control technologies. Materials of inherent antifouling properties are widely used in the construction sector. Control technologies available include antifouling paints and coatings, injection of biocides, marine bio-active compounds, materials of inherent antifouling properties, heat treatment, pulse-power devices, UV and nuclear radiation, scrubbing devices, biological control, etc. A literature search carried out during the last few years has yielded about 450 references. This paper presents, in a very concise manner, state-of-the- art macrofouling control technologies pertinent to desalination and power plants in the Kingdom. The paper also discusses the issues of biofouling control in the Al-Jubail plants based on the results of an on-line macrofouling experiment conducted in one of the turbine condensers of Al-Jubail phase-I MSF/power plants.     

Inorganic precursor peroxides for antifouling coatings

Modern antifouling coatings are generally based on cuprous oxide (Cu₂O) and organic biocides as active ingredients. Cu₂O is prone to bioaccumulation, and should therefore be replaced by more environmentally benign compounds when technically possible. However, cuprous oxide does not only provide antifouling properties, it is also a vital ingredient for the antifouling coating to obtain its polishing and leaching mechanism. In this paper, peroxides of strontium, calcium, magnesium, and zinc are tested as pigments in antifouling coatings. The peroxides react with seawater to create hydrogen peroxide and highly seawater-soluble ions of the metal. The goals have been to establish the antifouling potency of an antifouling coating that releases hydrogen peroxide as biocide, and to investigate the potential use of peroxides as water-soluble polishing and leaching pigments. The investigations have shown that it is possible to identify particulates that, when applied as pigments in antifouling coatings, will provide polishing and leaching rates comparable to those of Cu₂O-based coatings. Furthermore, the combination of polishing and hydrogen peroxide leaching by a coating based on zinc peroxide in a suitable binder matrix provides antifouling properties exceeding those of a similar coating based entirely on zinc oxide.     

High-Throughput Screening of Fouling-Release Properties: An Overview

Marine biofouling of ship hulls has significant cost, performance and environmental implications. Due to environmental concerns associated with traditional antifouling paints that mitigate fouling with the use of biocides, increasing research and development efforts have been made on fouling-release (FR) coatings. FR coatings do not actively deter settlement of marine organisms, but, instead, mitigate biofouling by minimizing the strength of adhesion. Ideally, an FR coating will allow the fouling community to be removed by simply running the vessel at relatively high speed. Traditional methods for characterizing FR properties involve immersion of relatively large samples in the ocean and waiting months for enough fouling to occur to enable reliable measurements to be made. To greatly enhance research and development relative to FR coatings, a combinatorial/high-throughput workflow was developed that includes a suite of FR laboratory assays involving marine bacteria, microalgae, and live, adult barnacles. The novel high-throughput FR measurement systems have been shown to allow for rapid screening of FR characteristics of miniaturized coating samples arranged in an array format.     

The Microbial Mechanisms of a Novel Photosensitive Material (Treated Rape Pollen) in Anti-Biofilm Process under Marine Environment

Marine biofouling is a worldwide problem in coastal areas and affects the maritime industry primarily by attachment of fouling organisms to solid immersed surfaces. Biofilm formation by microbes is the main cause of biofouling. Currently, application of antibacterial materials is an important strategy for preventing bacterial colonization and biofilm formation. A natural three-dimensional carbon skeleton material, TRP (treated rape pollen), attracted our attention owing to its visible-light-driven photocatalytic disinfection property. Based on this, we hypothesized that TRP, which is eco-friendly, would show antifouling performance and could be used for marine antifouling. We then assessed its physiochemical characteristics, oxidant potential, and antifouling ability. The results showed that TRP had excellent photosensitivity and oxidant ability, as well as strong anti-bacterial colonization capability under light-driven conditions. Confocal laser scanning microscopy showed that TRP could disperse pre-established biofilms on stainless steel surfaces in natural seawater. The biodiversity and taxonomic composition of biofilms were significantly altered by TRP (p < 0.05). Moreover, metagenomics analysis showed that functional classes involved in the antioxidant system, environmental stress, glucose–lipid metabolism, and membrane-associated functions were changed after TRP exposure. Co-occurrence model analysis further revealed that TRP markedly increased the complexity of the biofilm microbial network under light irradiation. Taken together, these results demonstrate that TRP with light irradiation can inhibit bacterial colonization and prevent initial biofilm formation. Thus, TRP is a potential nature-based green material for marine antifouling.     

有机硅和氟树脂在海洋防污涂料中的应用研究进展

海洋生物污损是一个世界性难题,随着人们环境保护意识的增强,发展有效的环保型海洋防污体系成为该领域最重要的研究方向。有机硅/氟基海洋防污涂料具有环保无毒的特点,是目前的研究热点之一。文章概述了有机硅和氟低表面能防污涂料的研究进展,重点介绍了基于仿生原理的有机硅/氟污损释放型防污涂料,论述了材料表面特性包括物理特性、化学特性、结构特征等对生物附着的影响,介绍了两亲性添加剂改性的有机硅防污涂料的开发,展望了污损释放型防污涂料未来的发展方向。     

新型海洋防污涂料用防污剂及树脂的研究进展

防污剂和树脂是决定海洋防污涂料性能的关键成分。本文综述了近年来用于新型海洋防污涂料的天然产物防污剂和人工合成防污剂的研究进展;进一步从防污机理出发,总结了用于新型海洋防污涂料的基体树脂的种类,介绍了无锡自抛光树脂、生物可降解树脂、含杀菌官能团树脂、低表面能树脂和具有微相分离结构的树脂。此外,还展望了新型海洋防污涂料的未来发展方向,即环境友好的同时注重方式友好。     

Electrochemical treatments using tin oxide anode to prevent biofouling

Organic matter and living micro-organisms are responsible for surface modifications of any materials immersed in seawater. This phenomenon, called biofouling, has many detrimental effects and has to be prevented. Electrochemistry could be a very efficient tool for biofouling prevention in two ways, either by local biocide production through seawater electrolysis or by immobilizing electrogenerated biocides. In this paper, both strategies will be developed and illustrated in the particular case of tin dioxide as anode material. Chloride and bromide ions present in seawater are efficiently oxidized at antimony doped tin dioxide to form biocidal hypohalogenous acids, namely HOCl and HOBr. Underwater optical instruments having glass window coated with a transparent tin dioxide layer can be effectively protected against biofouling without environmental damages because hypohalogenous acids are produced at a low level and on the window itself. Another possibility explored in this paper is to perform a pre-treatment of the surface to be protected. It consists in seawater electrolysis in the presence of organic macromolecules, as for instance bovine serum albumin. In these conditions, chlorinated and brominated organic deposit is formed on the tin oxide surface as proved by EDX and XPS analyses. By testing adhesion and growth of Escherichia coli bacteria, it was shown that this deposit possesses biocidal property. Actually, this property is due to the presence of chloramine and bromamine groups.     

Development of polyorganosilazane–silicone marine coatings

The objective of the present work is the development and characterization of marine coatings based on polyorganosilazanes (PSZ). Two types of coatings containing silicone oils and biocidal compounds were investigated as anticorrosive and antifouling coatings. The flexibility, hydrophobicity and adhesion properties of the PSZ-based coatings on aluminum substrates were studied. Static immersions in natural seawater were investigated to evaluate the antifouling performances of these coatings. The corrosion properties were studied by salt spray tests. Results demonstrated that coatings based on silicone oils appeared to be the most efficient coatings in terms of antifouling and anticorrosive properties. Ten-month antifouling efficiency was revealed for biocide-free polydimethylsiloxane-based PSZ coatings in natural seawater static immersion. The adjunction of dicopper oxide as biocidal pigments was shown to decrease the stability in cans of the corresponding paints and therefore decreasing the flexibility of coatings. In addition, this pigment affected badly the anticorrosive properties of the coatings together with a short antifouling efficiency time. Thus, the silicone oil-based PSZ displayed remarkable advantages in addition to their dual antifouling and anticorrosive properties which are the absence of biocidal compounds released in marine environment and the absence of volatile solvent.     

海洋船舶无毒、低毒防污涂料的研究进展

介绍了现代海洋船舶防污涂料的研究和应用情况,分别阐述了电化学防污涂料、化学活性物质释放型防污涂料和非化学活性物质释放型防污涂料的原理及其应用进展,并着重介绍了无毒低毒防污剂及防污涂料,指出长效、无毒的防污涂料将是未来涂料的发展方向。     

Enzymes for Antifouling Strategies

During the past decades, much effort has been made to find efficient alternative solutions to prevent and/or disrupt the adhesion of fouling organisms to surfaces. The use of enzymes emerges among the investigated approaches as one of the favorite candidate antifouling technologies due to enzymes' biodegradability and affordable prices. An overview of the different enzymatic antifouling strategies is presented, highlighting the most promising groups of enzymes, and their utilization upon surface-confinement to control biofouling. While the main strategies to control marine biofouling include the degradation of secreted adhesives and the production of antifouling compounds, the main concepts to control pathogenic biofilms are based on cell lysis and on the degradation of extracellular matrix polymers. Although immobilization can improve enzyme stability, activity and antifouling performance, up to date relatively few scientific articles concerning the use of immobilized enzymes to control biofouling have been published. The successful incorporation of enzymes into coatings yielding surfaces with broad antifouling spectrum and long-term efficacy remains a challenge.