Pyrithiones as antifoulants: environmental fate and loss of toxicity

Zinc pyrithione ameliorates colitis in mice by interacting on intestinal epithelial TRPA1 and TRPV4 channels

AIMS

Although zinc pyrithione (ZPT) has been studied as topical antimicrobial and cosmetic consumer products, little is known about its pharmacological actions in gastrointestinal (GI) health and inflammation. Our aims were to investigate the effects of ZPT on transient receptor potential (TRP) channels and Ca2+ signaling in intestinal epithelial cells (IECs) and its therapeutic potential for colitis.

MAIN METHODS

Digital Ca2+ imaging and patch-clamp electrophysiology were performed on human colonic epithelial cells (HCoEpiC) and rat small intestinal epithelial cells (IEC-6). The transcription levels of proinflammatory cytokines such as IL-1β were detected by RTq-PCR. Dextran sulfate sodium (DSS) was used to induce colitis in mice.

KEY FINDINGS

ZPT dose-dependently induced Ca2+ signaling and membrane currents in IECs, which were attenuated by selective blockers of transient receptor potential ankyrin 1 (TRPA1) and transient receptor potential vanilloid 4 (TRPV4) channels, respectively. Interestingly, Ca2+ entry via TRPA1 channels inhibited the activity of TRPV4 channels in HCoEpiC, but not vice versa. ZPT significantly promoted migration of IECs by activating TRPA1 and TRPV4 channels. ZPT reversed lipopolysaccharides (LPS)-induced changes in mRNA expression of TRPA1 and TRPV4. Moreover, ZPT decreased mRNA levels of pro-inflammatory factors promoted by LPS in HCoEpiC, which were restored by selective TRPA1 blocker. In whole animal studies in vivo, ZPT significantly ameliorated DSS-induced body weight loss, colon shortening and increases in stool score, serum calprotectin and lactic acid (LD) in mouse model of colitis.

SIGNIFICANCE

ZPT exerts anti-colitic action likely by anti-inflammation and pro-mucosal healing through TRP channels in IECs. The present study not only expands pharmacology spectrum of ZPT in GI tract, but also repurposes it to a potential drug for colitis therapy.

Environmental occurrence, biological effects, and health implications of zinc pyrithione: A review

Due to the detrimental effects on aquatic organisms and ecosystem, tributyltin as a antifouling agent have been banned worldwide since 1990s. As a replacement for tributyltin, zinc pyrithione (ZnPT) has emerged as a new environmentally friendly antifouling agent. However, the widespread use of ZnPT unavoidably leads to the occurrence and accumulation in aquatic environments, especially in waters with limited sunlight. Despite empirical evidence demonstrating the ecotoxicity and health risks of ZnPT to different organisms, there has been no attempt to compile and interpret this data. The present review revealed that over the past 50 years, numerous studies have documented the toxicity of ZnPT in various organisms, both in vitro and in vivo. However, long-term effects and underlying mechanisms of ZnPT on biota, particularly at environmentally realistic exposure levels, remain largely unexplored. In-depth studies are thus necessary to generate detailed ecotoxicological information of ZnPT for environmental risk assessment and management.

Toxic effects and potential mechanisms of zinc pyrithione (ZPT) exposure on sperm and testicular injury in zebrafish

Zinc pyrithione (ZPT) is widely recognized for its beneficial properties as an antifouling, antibacterial, and antifungal agent. Despite its positive industrial contributions, ZPT has been proven to exhibit toxicity towards various ecosystems, particularly affecting marine life. However, there is still a dearth of comprehensive research on ZPT toxicity and its toxicological mechanism in reproductive systems of aquatic organisms. In our study, we conducted a thorough analysis and unveiled a multitude of abnormalities in zebrafish sperm and testicular tissue caused by ZPT exposure, including a dose-dependent diminishing of testosterone levels, various sperm deformities, decreased sperm concentration and motility, and ROS-induced testicular tissue DNA damage. In addition, our study suggested that ZPT-induced testicular damage is associated with heightened oxidative stress, apoptosis, and possible hyperpolarization of the mitochondrial membrane. Through RNA-seq analysis, a total of 409 DEGs associated with ZPT-induced testicular injury were identified, and the hub gene was determined using a protein-protein interaction network (PPI). The genes and pathways uncovered in this study point to potential mechanisms of ZPT exposure on sperm and testicular injury in zebrafish.

Targeting cuproptosis by zinc pyrithione in triple-negative breast cancer

Triple-negative breast cancer (TNBC) poses a considerable challenge due to its aggressive nature. Notably, metal ion-induced cell death, such as ferroptosis, has garnered significant attention and demonstrated potential implications for cancer. Recently, cuproptosis, a potent cell death pathway reliant on copper, has been identified. However, whether cuproptosis can be targeted for cancer treatment remains uncertain. Here, we screened the US Food and Drug Administration (FDA)-approved drug library and identified zinc pyrithione (ZnPT) as a compound that significantly inhibited TNBC progression. RNA sequencing revealed that ZnPT disrupted copper homeostasis. Furthermore, ZnPT facilitated the oligomerization of dihydrolipoamide S-acetyltransferase, a landmark molecule of cuproptosis. Clinically, high expression levels of cuproptosis-related proteins were significantly correlated with poor prognosis in TNBC patients. Collectively, these findings indicate that ZnPT can induce cell death by targeting and disrupting copper homeostasis, providing a potential experimental foundation for exploring cuproptosis as a target in drug discovery for TNBC patients.

Zinc pyrithione (ZPT) -induced embryonic toxicogenomic responses reveal involvement of oxidative damage, apoptosis, endoplasmic reticulum (ER) stress and autophagy

Zinc pyrithione (ZPT) is a frequently used organometallic biocide, carrying potentially adverse consequences to multiple species in the environment. Previously we have demonstrated its embryonic, organ developmental and liver metabolic toxicity of zebrafish. However, details of ZPT toxicity during embryogenesis are still limited. The present study was designed to evaluate the effects and possible mechanisms of ZPT-induced embryonic toxicogenomic responses by morphological investigations, transcriptome and gene quantitative analysis, as well as biochemical assays. The results revealed that treatment with ZPT caused embryogenesis toxicity, specifically in irregular cell division and rearrangement, delayed differentiations of eyes and notochords, the epiboly and germ ring formation and somite segmentation defects. In addition, ZPT exposure altered gene expression during early embryonic development, especially related with morphological abnormities and metabolic dysfunctions including reduction of oxidoreductase activity. Activities of antioxidants and caspases examinations showed inductions of oxidative stress and apoptosis by ZPT and quantitative analysis of marker genes further indicated that ZPT also triggered endoplasmic reticulum (ER) stress and autophagy. Thus, we deduce here that ZPT-induced embryonic toxicogenomic responses reveal involvement of oxidative damage, apoptosis, endoplasmic reticulum (ER) stress and autophagy.

Comparative toxicity study of waterborne two booster biocides (CuPT and ZnPT) on embryonic flounder (Paralichthys olivaceus)

A new generation of booster biocides that include metal pyrithiones (PTs) such as copper pyrithione (CuPT) and zinc pyrithione (ZnPT) are being used as tributyltin alternatives. In the marine environment, ZnPT can easily transchelate Cu to form CuPT, and the environmental fate and persistence of these two metal pyrithiones are closely related. Although some data on the toxicity of biocides on marine fish are available, little is known about their toxicity and toxic pathway. We thus compared the toxic effects of CuPT and ZnPT on embryonic olive flounder (Paralichthys olivaceus) by investigating their adverse effects based on developmental morphogenesis and transcriptional variation. In our study, the toxic potency of CuPT was greater with respect to developmental malformation and mortality than ZnPT. Consistent with the developmental effects, the expression of genes related to tail fin malformation (including plod2, furin, and wnt3a) was higher in embryonic flounder exposed to CuPT than in those exposed to ZnPT. Genes related to muscle and nervous system development exhibited significant changes on differential gene expression profiles using RNA sequencing (cutoff value P < 0.05). Gene ontology analysis of embryos exposed to CuPT revealed affected cellular respiration and kidney development, whereas genes associated with cell development, nervous system development and heart development showed significant variation in embryonic flounder exposed to ZnPT. Overall, our study clarifies the common and unique developmental toxic effects of CuPT and ZnPT through transcriptomic analyses in embryonic flounder.

Jellyfish Bioprospecting in the Mediterranean Sea: Antioxidant and Lysozyme-Like Activities from Aurelia coerulea (Cnidaria, Scyphozoa) Extracts

Marine invertebrates represent a vast, untapped source of bioactive compounds. Cnidarians are represented by nearly 10,000 species that contain a complex mixture of venoms, collagen, and other bioactive compounds, including enzymes, oligosaccharides, fatty acids, and lipophilic molecules. Due to their high abundance in coastal waters, several jellyfish taxa may be regarded as candidate targets for the discovery of novel lead molecules and biomaterials and as a potential source of food/feed ingredients. The moon jellyfish Aurelia coerulea is one of the most common jellyfish worldwide and is particularly abundant in sheltered coastal lagoons and marinas of the Mediterranean Sea, where it first appeared—as an alien species—in the last century, when Pacific oyster cultivation began. In the present study, the antioxidant and lysozyme antibacterial activities associated with extracts from different medusa compartments—namely the umbrella, oral arms, and secreted mucus—were investigated. Extracts from the oral arms of A. coerulea displayed significant antioxidant activity. Similarly, lysozyme-like activity was the highest in extracts from oral arms. These findings suggest that A. coerulea outbreaks may be used in the search for novel cytolytic and cytotoxic products against marine bacteria. The geographically wide occurrence and the seasonally high abundance of A. coerulea populations in coastal waters envisage and stimulate the search for biotechnological applications of jellyfish biomasses in the pharmaceutical, nutritional, and nutraceutical sectors.

Gender-differentiated metabolic abnormalities of adult zebrafish with zinc pyrithione (ZPT) -induced hepatotoxicity

Zinc pyrithione (ZPT) is an extensively used microbicidal agent and its toxicity to multiple organs has been gradually recognized. However, details of the mechanism of ZPT toxicity are lacking and profile studies at metabolic level are still greatly limited. In this work we investigated the effects of ZPT on metabolic pathways of zebrafish liver after twenty-one days of exposure. Our integrated approach was underpinned by gas chromatography coupled with mass spectroscopy (GC-MS) and liver function analysis. Metabolomic profiles were generated from the livers of ZPT-treated zebrafish and 172 significantly altered metabolite peaks were detected. As a result, ZPT caused altered perturbation of metabolic pathways in male and female zebrafish liver. Moreover, ZPT induced the liver injury with the changes of the metabolites 2,4-diaminobutyric acid (2,4-DABA) with significant distinction between male and female zebrafish. ZPT caused gender-differentiated liver metabolic changes associated with the disruption of glycogenolysis and glycolysis metabolism, purine and pyrimidine metabolism, oxidative phosphorylation, arginine biosynthesis, and amino acid metabolism. Conclusively, exposure of ZPT may result in gender-differentiated metabolic abnormalities of adult zebrafish with induced hepatotoxicity.

Development of complementary CE-MS methods for speciation analysis of pyrithione-based antifouling agents

In the recent decade, metal pyrithione complexes have become important biocides for antifouling purposes in shipping. The analysis of metal pyrithione complexes and their degradation products/species in environmental samples is challenging because they exhibit fast UV degradation, transmetalation, and ligand substitution and are known to be prone to spontaneous species transformation within a chromatographic system. The environmental properties of the pyrithione species, e.g., toxicity to target and non-target organisms, are differing strongly, and it is therefore inevitable to identify as well as quantify all species separately. To cope with the separation of metal pyrithione species with minimum species transformation during analysis, a capillary electrophoresis (CE)-based method was developed. The hyphenation of CE with selective electrospray ionization- and inductively coupled plasma-mass spectrometry (ESI-, ICP-MS) provided complementary molecular and elemental information for the identification and quantification of pyrithione species. To study speciation of pyrithiones, a leaching experiment of several commercial antifouling paints containing zinc pyrithione in ultrapure and river water was conducted. Only the two species pyrithione (HPT) and dipyrithione ((PT)₂) were found in the leaching media, in concentrations between 0.086 and 2.4 μM (HPT) and between 0.062 and 0.59 μM ((PT)₂), depending on the paint and leaching medium. The limits of detection were 20 nM (HPT) and 10 nM ((PT)₂). The results show that complementary CE-MS is a suitable tool for mechanistical studies concerning species transformation (e.g., degradation) and the identification of target species of metal pyrithione complexes in real surface water matrices, laying the ground for future environmental studies. Graphical abstract Hyphenation of CE with ESI- and ICP-MS provided complementary molecular and elemental information. Metal pyrithione species released from commercial antifouling paints could be identified and quantified in ultrapure and river water matrices.

Waterborne zinc pyrithione modulates immunity, biochemical, and antioxidant parameters in the blood of olive flounder

In this study, potential immunological and hematological effects of different concentrations (0, 1, 10, and 50 μg L^-l) of waterborne zinc pyrithione (ZnPT) were studied in the blood of the olive flounder Paralichthys olivaceus over 30 days. Reduced alternative complement activity (ACH50) and lysozyme activity were measured in fish exposed to 10 and/or 50 μg L^-l of ZnPT for 20 days. Decreased levels of total Ig were also observed in response to 10 and/or 50 μg L^-l ZnPT during the exposure period. Levels of cortisol, a marker of stress, were significantly increased by 10 and 50 μg L^-l ZnPT from day 10, and by 1 μg L^-l exposure on day 30. The levels of red blood cells (RBCs) and white blood cells (WBCs) decreased following exposure to 10 and/or 50 μg L^-l ZnPT, while no significant change was observed in hemoglobin level. Concentrations of total protein and albumin were significantly reduced with 50 μg L^-l ZnPT at day 20. Alanine aminotransferase, aspartate aminotransferase, and alkaline phosphatase activities were significantly increased following exposure to 10 and/or 50 μg L^-l ZnPT. Lipid peroxidation was induced by ZnPT, and higher concentrations (10 and 50 μg L^-l) significantly increased intracellular malondialdehyde levels during exposure. Regarding the subsequent antioxidant response, intracellular glutathione levels increased significantly in response to 10 and 50 μg L^-l ZnPT on days 20 and 30. Similarly, catalase and superoxide dismutase activity was significantly increased in response to 10 and 50 μg L^-l ZnPT after day 10. Taken together, changes in the studied parameters suggested the immunotoxicity of ZnPT, with modulations observed in hematological homeostasis and oxidative stress induction in the blood of olive flounder.

Behavioral and biochemical effects of the antifouler and antidandruff zinc pyrithione on the freshwater fish Gambusia holbrooki

The presence of pharmaceutical residues in the aquatic environment is receiving great attention since the levels of these substances have significantly increased in this compartment, potentially leading to adverse ecological effects. Zinc pyrithione (ZnPt) is a widely used organometallic biocide, which is incorporated into antifouling formulas, such as paints, to prevent the establishment of biofilms on surfaces exposed to the aquatic environment. It is also used in cosmetics, such as antidandruff shampoos and soaps. Considering this wide use, and the absence of a significant amount of data on the toxicity of ZnPt especially towards non-target organisms, the objective of this study was to characterize the toxicity of ZnPt, on several ecological relevant endpoints assessed in the fish Gambusia holbrooki. For this purpose, we measured traits related to feeding and aggressive behavior, as well as indicators of oxidative stress (CAT and GSTs), neurotoxicity (AChE), and anaerobic metabolism (LDH), after acute and chronic exposures to ZnPt. In terms of behavioral features, the feeding test showed the occurrence of significant differences between the control animals and those exposed to a concentration of ZnPt of 45 μg/L. In addition, ZnPt caused changes in terms of oxidative stress biomarkers (CAT and GSTs), for both exposure periods. ZnPt was also capable of causing changes in the cholinergic neurotransmission functioning and anaerobic metabolism, but only following the chronic exposure.

Study of the effects of zinc pyrithione in biochemical parameters of the Polychaeta Hediste diversicolor: evidences of neurotoxicity at ecologically relevant concentrations

Nowadays there are various groups of biocidal chemical agents, which can be used in diverse areas, such as personal hygiene, disinfection, antiparasitic action, and also in antifouling mixtures or paints. The versatility and efficacy of some of these agents favors their use and ultimate release into the aquatic environment, where they may still exert toxic activity. Zinc pyrithione is classified as a metal biocide with bactericidal, algicidal, and fungicidal actions. It has been formulated in antifouling paints, which prevent the formation of biofilms in submerged structures, and has also been used for dermocosmetic purposes, in shampoos for the treatment of dandruff and seborrhea. Some of the uses of zinc pyrithione are responsible for its direct release as flakes that reach the bottom sediments, especially in estuarine areas. Considering this fate, the ecotoxicity assessment of its effects towards sediment organisms, namely Polychaetous species, is extremely important. The present study characterized the acute potential toxicity of zinc pyrithione in terms of parameters of oxidative stress (catalase, glutathione S-transferases (GSTs), and thiobarbituric acid reactive substances (TBARS)), and neurotoxicity (acetylcholinesterase) which were evaluated in individuals of the polychaete Hediste diversicolor. Regarding the results obtained, only the activity of GSTs and AChE was significantly altered in relation to non-exposed animals. This set of results indicates that oxidative stress did not occur.

Effects of zinc pyrithione on biochemical parameters of the freshwater Asian clam Corbicula fluminea

Zinc pyrithione (ZnPT) is an organometallic biocide with bactericide, algaecide, and fungicide activity. Considering this biological activity, ZnPT has been used in anti-fouling paints, and also in human therapeutics and cosmetics, in shampoos to treat dandruff and seborrhoea. Despite its potential uses and consequent presence in the aquatic environment, the ecotoxicological effects of ZnPT are poorly understood. This work aims to characterise the effects of ZnPT in biochemical parameters of the Asian clam, one of the most invasive bivalves known for its biofouling action in hydro-dependent industries, using a classical (LC₅₀ determination) and a biomarker-based approach (quantification of the activities of catalase, GSTs, and acetylcholinesterase, and also the muscle glycogen content). The here determined LC₅₀-96 h for zinc pyrithione was 2.17 mg/L. ZnPT caused significant increases in the activity of catalase and of cholinesterases. These findings evidence the pro-oxidative effects caused by the metabolism of ZnPT. Despite the absence of clear effects, it is important to stress that the presence of ZnPT in the wild is usually accompanied by other pyrithiones, whose co-existence can contribute to the exertion of considerable toxic effects.

An integrated approach to assess the impacts of zinc pyrithione at different levels of biological organization in marine mussels

The mechanisms of sublethal toxicity of the antifouling biocide, zinc pyrithione (ZnPT), have not been well-studied. This investigation demonstrates that 14-d sublethal exposure to ZnPT (0.2 or 2 μM, alongside inorganic Zn and sea water controls) is genotoxic to mussel haemocytes but suggests that this is not caused by oxidative DNA damage as no significant induction of oxidised purines was detected by Fpg-modified comet assay. More ecologically relevant endpoints, including decreased clearance rate (CR), cessation of attachment and decreased tolerance of stress on stress (SoS), also showed significant response to ZnPT exposure. Our integrated approach was underpinned by molecular analyses (qRT-PCR of stress-related genes, 2D gel electrophoresis of proteins) that indicated ZnPT causes a decrease in phosphoenolpyruvate carboxykinase (PEPCK) expression in mussel digestive glands, and that metallothionein genes are upregulated; PEPCK downregulation suggests that altered energy metabolism may also be related to the effects of ZnPT. Significant relationships were found between % tail DNA (comet assay) and all higher level responses (CR, attachment, SoS) in addition to PEPCK expression. Principal component analyses suggested that expression of selected genes described more variability within groups whereas % tail DNA reflected different ZnPT concentrations.

Antifouling processes and toxicity effects of antifouling paints on marine environment. A review

The production infrastructure in aquaculture invariably is a complex assortment of submerged components with cages, nets, floats and ropes. Cages are generally made from polyamide or high density polyethylene (PEHD). All of these structures serve as surfaces for biofouling. However, cage nets and supporting infrastructure offer fouling organisms thousands of square meters of multifilament netting. That's why, before immersing them in seawater, they should be coated with an antifouling agent. It helps to prevent net occlusion and to increase its lifespan. Biofouling in marine aquaculture is a specific problem and has three main negative effects. It causes net occlusion and so restricts water and oxygen exchange. Besides, the low dissolved oxygen levels from poor water exchange increases the stress levels of fish, lowers immunity and increases vulnerability to disease. Also, the extra weight imposed by fouling causes cage deformation and structural fatigue. The maintenance and loss of equipment cause the increase of production costs for the industry. Biocides are chemical substances that can prohibit or kill microorganisms responsible for biofouling. The expansion of the aquaculture industry requires the use of more drugs, disinfectants and antifoulant compounds (biocides) to eliminate the microorganisms in the aquaculture facilities. Unfortunately, the use of biocides in the aquatic environment has proved to be harmful as it has toxic effects on the marine environment. The most commonly used biocides in antifouling paints are Tributyltin (TBT), Chlorothalonil, Dichlofluanid, Sea-Nine 211, Diuron, Irgarol 1051 and Zinc Pyrithione. Restrictions were imposed on the use of TBT, that's why organic booster biocides were recently introduced. The replacement products are generally based on copper metal oxides and organic biocides. This paper provides an overview of the effects of antifouling biocides on aquatic organisms. It will focus on the eight booster biocides in common use, despite little data are available for some of them. Toxicity values and effects of these antifoulants will also be mentioned for different species of fish, crustaceans, invertebrates and algae.

Encapsulation of Antifouling Organic Biocides in Poly(lactic acid) Nanoparticles

The scope of the current research was to assess the feasibility of encapsulating three commercial antifouling compounds, Irgarol 1051, Econea and Zinc pyrithione, in biodegradable poly(lactic acid) (PLA) nanoparticles. The emulsification–solvent evaporation technique was herein utilized to manufacture nanoparticles with a biocide:polymer ratio of 40%. The loaded nanoparticles were analyzed for their size and size distribution, zeta potential, encapsulation efficiency and thermal properties, while the relevant physicochemical characteristics were correlated to biocide–polymer system. In addition, the encapsulation process was scaled up and the prepared nanoparticles were dispersed in a water-based antifouling paint in order to examine the viability of incorporating nanoparticles in such coatings. Metallic specimens were coated with the nanoparticles-containing paint and examined regarding surface morphology.

Efficacy and Ecotoxicity of Novel Anti-Fouling Nanomaterials in Target and Non-Target Marine Species

Biofouling is a global problem that affects virtually all the immersed structures. Currently, several novel environmentally friendly approaches are being tested worldwide to decrease the toxicity of biocides in non-fouling species, such as the encapsulation/immobilization of commercially available biocides, in order to achieve control over the leaching rate. The present study addresses the toxicity of two widely used booster biocides, zinc pyrithione (ZnPT) and copper pyrithione (CuPT), in its free and incorporated forms in order to assess their toxicity and anti-fouling efficacy in target and non-target species. To achieve this goal, the following marine organisms were tested; the green microalgae Tetraselmis chuii (non-target species) and both target species, the diatom Phaeodactylum tricornutum and the mussel Mytilus edulis. Organisms were exposed to both biocides, two unloaded nanostructured materials and nanomaterials loaded with biocides, from 10 μg/L to 100 mg/L total weight, following standard protocols. The most eco-friendly and simultaneously efficient anti-fouling solution against the two photosynthetic species (nanoclays loaded with ZnPT) was then tested on mussels to assess its lethal efficacy (LC₅₀ = 123 μg/L) and compared with free biocide (LC₅₀ = 211 μg/L) and unloaded material (LC₅₀ > 1000 μg/L). A second exposure test with sub-lethal concentrations (lower than 100 μg/L), using mussels, was carried out to assess biochemical changes caused by the tested compounds. Oxidative stress, detoxification and neurotransmission markers were not responsive; however, different antioxidant patterns were found with free ZnPT and loaded nanoclay exposures. Thus, the immobilization of the biocide ZnPT into nanoclays proved to be a promising efficient and eco-friendly anti-fouling strategy.

Impact of the biocide Irgarol on meiofauna and prokaryotes from the sediments of the Bizerte lagoon-an experimental study

The biocide Irgarol 1051 has been reported to have negative effects on a large number of living components including non-target organisms, but information on its impact on the marine meiofauna and benthic prokaryotes is completely lacking. Here, we report the results of long-term experimental studies in which we determined the effects of increasing Irgarol concentrations (from 11.5 to 315 ng g(-1) sediment dry weight) on meiofauna and benthic prokaryotes. We found that this biocide had a significant impact on meiofauna abundance, even at the lowest concentrations, causing a drastic decline in the abundance of nematodes (the dominant meiofaunal taxon) and an increase of the relative importance of oligochaetes. Even if no direct effects of Irgarol were found on prokaryotic abundance and biomass, the molecular fingerprinting analyses (automated ribosomal intergenic spacer analysis) showed that the prokaryotic diversity was significantly altered by the biocide. The results of the present study indicate that Irgarol 1051 in marine sediments has a significant impact on the smallest eukaryotic and microbial components also at very low concentrations (ca 12 ng g(-1)).

Ecotoxicological effect of zinc pyrithione in the freshwater fish Gambusia holbrooki

Currently diverse biocidal agents can be used for distinct applications, such as personal hygiene, disinfection, antiparasitic activity, and antifouling effects. Zinc pyrithione is an organometallic biocide, with bactericidal, algicidal and fungicidal activities. It has been recently incorporated in antifouling formulas, such as paints, which prevent the establishment of a biofilm on surfaces exposed to the aquatic environment. It has also been used in cosmetics, such as anti-dandruff shampoos and soaps. Previously reported data has shown the presence of this substance in the aquatic compartment, a factor contributing to the potential exertion of toxic effects, and there is also evidence that photodegradation products of zinc pyrithione were involved in neurotoxic effects, namely by inhibiting cholinesterases in fish species. Additional evidence points to the involvement of zinc pyrithione in alterations of metal homeostasis and oxidative stress, in both aquatic organisms and human cell models. The present work assesses the potential ecotoxicity elicited by zinc pyrithione in the freshwater fish Gambusia holbrooki after an acute (96 h) exposure. The oxidative stress was assessed by the quantification of the activities of specific enzymes from the antioxidant defense system, such as catalase, and glutathione-S-transferases; and the extent of peroxidative damage was quantified by measuring the thiobarbituric acid reactive substances levels. Neurotoxicity was assessed through measurement of acetylcholinesterase activity; and a standardized method for the description and assessment of histological changes in liver and gills of was also used. Zinc pyrithione caused non-specific and reversible tissue alterations, both in liver and gills of exposed organisms. However, histopathological indices were not significantly different from the control group. In terms of oxidative stress biomarkers, none of the tested biomarkers indicated the occurrence of pro-oxidative effects, suggesting that the oxidative pathway is not the major toxicological outcome of exposure to zinc pyrithione.

The Mucus of Actinia equina (Anthozoa, Cnidaria): An Unexplored Resource for Potential Applicative Purposes

The mucus produced by many marine organisms is a complex mixture of proteins and polysaccharides forming a weak watery gel. It is essential for vital processes including locomotion, navigation, structural support, heterotrophic feeding and defence against a multitude of environmental stresses, predators, parasites, and pathogens. In the present study we focused on mucus produced by a benthic cnidarian, the sea anemone Actinia equina (Linnaeus, 1758) for preventing burial by excess sedimentation and for protection. We investigated some of the physico-chemical properties of this matrix such as viscosity, osmolarity, electrical conductivity, protein, carbohydrate, and total lipid contents. Some biological activities such as hemolytic, cytotoxic, and antibacterial lysozyme-like activities were also studied. The A. equina mucus is mainly composed by water (96.2% ± 0.3%), whereas its dry weight is made of 24.2% ± 1.3% proteins and 7.8% ± 0.2% carbohydrates, with the smallest and largest components referable to lipids (0.9%) and inorganic matter (67.1%). The A. equina mucus matrix exhibited hemolytic activity on rabbit erythrocytes, cytotoxic activity against the tumor cell line K562 (human erythromyeloblastoid leukemia) and antibacterial lysozyme-like activity. The findings from this study improve the available information on the mucus composition in invertebrates and have implications for future investigations related to exploitation of A. equina and other sea anemones' mucus as a source of bioactive compounds of high pharmaceutical and biotechnological interest.

Acute and chronic toxicities of zinc pyrithione alone and in combination with copper to the marine copepod Tigriopus japonicus

Zinc pyrithione (ZnPT) is a widely used booster biocide in combination with copper (Cu) in antifouling paints as a substitute for tributyltin. The co-occurrence of ZnPT and Cu in coastal marine environments is therefore very common, and may pose a higher risk to marine organisms if they can result in synergistic toxicity. This study comprehensively investigated the combined toxicity of ZnPT and Cu, on the marine copepod Tigriopus japonicus, for the first time, based on both 96-h acute toxicity tests using adult copepods and chronic full-life cycle tests (21 d) using nauplii <24-h old. As ZnPT has been reported to be easily trans-chelated to copper pyrithione (CuPT) in the presence of Cu, the acute toxicities of CuPT alone and in combination with Cu on adult copepods were also assessed. Our results showed that ZnPT and Cu exhibited a strong synergistic toxic effect on the copepod in both acute and chronic tests. During the acute test, the mortalities of adult copepods increased dramatically even with an addition of Cu at concentrations as low as 1-2 μg/L compared with those exposed to ZnPT alone. Severe chronic toxicities were further observed in the copepods exposed to ZnPT-Cu mixtures, including a significant increase of naupliar mortality, postponing of development from naupliar to copepodid and from copepodid to adult stage, and a significant decrease of intrinsic population growth when compared with those of copepods exposed to ZnPT or Cu alone. Such synergistic effects might be partly attributable to the formation of CuPT by the trans-chelation of ZnPT and Cu, because CuPT was found to be more toxic than ZnPT based on the acute toxicity results. Mixtures of CuPT and Cu also led to synergistic toxic effects to the copepod, in particular at high Cu concentrations. A novel non-parametric response surface model was applied and it proved to be a powerful method for analysing and predicting the acute binary mixture toxicities of the booster biocides (i.e., ZnPT and CuPT) and Cu on the copepod. To better protect precious marine resources, it is necessary to revise and tighten existing water quality criteria for biocides, such as ZnPT and CuPT, to account for their synergistic effects with Cu at environmentally realistic levels.

A novel bioassay for evaluating the efficacy of biocides to inhibit settling and early establishment of marine biofilms

This paper presents a novel assay that allows a quick and robust assessment of the effects of biocides on the initial settling and establishment of marine photoautotrophic biofilms including the multitude of indigenous fouling organisms. Briefly, biofilms are established in the field, sampled, comminuted and re-settled on clean surfaces, after 72h chlorophyll a is measured as an integrating endpoint to reflect both settling and growth. Eight antifoulants were used to evaluate the assay. Efficacy ranking, based on EC98 values from most to least efficacious compound is: copper pyrithione>TPBP>DCOIT>tolylfluanid>zinc pyrithione>medetomidine>copper (Cu(2+)), while ecotoxicological ranking (based on EC10 values) is irgarol, copper pyrithione>zinc pyrithione>TPBP>tolylfluanid>DCOIT>copper (Cu(2+))>medetomidine. The algaecide irgarol did not cause full inhibition. Instead the inhibition leveled out at 95% effect at 30 nmoll(-)(1), a concentration that was clearly lower than for any other of the tested biocides.

A comparison of toxicant-induced succession for five antifouling compounds on marine periphyton in SWIFT microcosms

Five antifouling biocides, chlorothalonile, dichlofluanide, medetomidine, tolylfluanide, and zinc pyrithione, were evaluated regarding their effect on the composition of the periphyton community and the subsequent toxicant-induced succession (TIS). The periphyton communities were exposed in a semi-static setting for 96 h using a SWIFT microcosm. As a measure of community composition, pigment profiles from the exposed communities were used as effect indicators and compared with unexposed parts of the same community using the Bray-Curtis dissimilarity index. Chlorothalonile caused changes in the community starting at 85 μg l(-1) while dichlofluanide had no effect even at the highest concentrations used, 810 μg l(-1). The related substance tolylfluanide only affected the community composition at 2700 μg l(-1). Medetomidine had a different response curve with a small effect on the community composition at 0.8 μg l(-1) which then disappeared only to reappear at 240 μg l(-1). Zinc pyrithione had the largest effect on the periphyton community with changes starting at 10 μg l(-1) and no detectable pigments at 100 μg l(-1). The changes in the community composition for the five substances were also compared using multidimensional scaling. When all substances were analyzed and plotted together, chlorothalonile, dichlofluanide, medetomidine, and tolylfluanide showed surprisingly similar effects compared to zinc pyrithione that gave very different TIS. However, when only chlorothalonile, dichlofluanide, and tolylfluanide were plotted together, clear differences in TIS between the three toxicants were revealed. Dichlofluanide only induced small effects, while concentration-dependent TIS trajectories for chlorothalonile and tolylfluanide took off in opposite directions indicating very different responses of the periphyton communities. This study demonstrates that substances with a similar chemical structure and mechanisms of action can have different effects on the community composition. With the exception of zinc pyrithione, none of the recorded effect levels were at concentrations reported from marine environments so far.

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.

Toxicity and metabolism of copper pyrithione and its degradation product, 2,2'-dipyridyldisulfide in a marine polychaete

We conducted acute toxicity tests and sediment toxicity tests for copper pyrithione (CuPT) and a metal pyrithione degradation product, 2,2'-dipyridyldisulfide [(PS)2], using a marine polychaete Perinereis nuntia. The acute toxicity tests yielded 14-d LC50 concentrations for CuPT and (PS)2 of 0.06 mg L(-1) and 7.9 mg L(-1), respectively. Sediment toxicity tests resulted in 14-d LC50 concentrations for CuPT and (PS)2 of 1.1 mg kg(-1) dry wt. and 14 mg kg(-1) dry wt., respectively. In addition to mortality, sediment avoidance behavior and decreases in animal growth rate were observed; growth rate was the most susceptible endpoint in the sediment toxicity tests of both toxicants. Thus, we propose lowest observed effect concentrations of 0.3 mg kg(-1) dry wt. and 0.2 mg kg(-1) dry wt. for CuPT and (PS)2, respectively, and no observed effect concentrations of 0.1 mg kg(-1) dry wt. for both CuPT and (PS)2. The difference in the toxicity values between CuPT and (PS)2 observed in the acute toxicity test was greater than the difference in these values in the sediment toxicity test, and we attribute this to (PS)2 being more hydrophilic than CuPT. In addition to the toxicity tests, we analyzed conjugation activity of several polychaete enzymes to the toxicants and marked activity of palmitoyl coenzyme-A:biocides acyltransferase and UDP-glucuronosyl transferase was observed.

Novel antifouling agent zinc pyrithione: determination, acute toxicity, and bioaccumulation in marine mussels (Mytilus galloprovincialis)

Antifouling biocide zinc pyrithione (ZnPT) and its biological fate have received little attention because this compound was assumed not to be persistent in marine ecosystems. An analytical procedure was developed that has proved to be efficient and very sensitive in extracting ZnPT and its main secondary products, Zn and ionized pyrithione (PT(-)), from both seawater and biological samples, namely in the gills and digestive gland of the bioindicator species Mytilus galloprovincialis. Short-term experiments were carried out to investigate ZnPT toxicity and bioaccumulation. The effects on survival and tissue bioaccumulation of ZnPT and its secondary products were studied on adult mussels from a natural population, collected in the harbor area of Porto Santo Stefano (Italy) and exposed to sublethal doses of the biocide for up to 7 d. Zinc pyrithione was shown to be persistent in the experimental seawater in the short term. A basal level of ZnPT and ionized PT(-) was detected in the mussels, indicating that ZnPT availability in the sampling site is already high enough to induce a detectable accumulation in individuals of the native population. Zinc pyrithione rapidly accumulated in the tissues of the exposed mussels, proportionately to both exposure concentration and time, identifying the gills and digestive gland as important targets in the biological pathway of the contaminants. Even though the 7-d median lethal concentration (LC50) = 8.27 µM established here appears high with respect to reported ZnPT environmental concentrations, the results indicate that this biocide could represent a threat for marine organisms in coastal environments and that further investigations on its biological effects at sublethal doses are needed.

Acute toxicity and synergism of binary mixtures of antifouling biocides with heavy metals to embryos of sea urchin Glyptocidaris crenularis

Acute toxicity and synergism of four antifouling biocides (Irgarol 1051, dichlofluanid, tolylfluanid and Sea-Nine 211) and five heavy metals (Ni, Pb, Zn, Cd and Cu) are investigated using the sea urchin embryos of Glyptocidaris crenularis (G. crenularis) at six typical developmental stages, that is, 2-cell, 4-cell, 8-cell, blastula, gastrula and 4-arm pluteus. Our results show that the toxicity of the four biocides is in an order of Sea-Nine 211 > tolylfluanid > dichlofluanid > Irgarol 1051 and their -log EC(50) values at all stages are strongly linearly correlated with the 1-octanol/water partition coefficient (log P) values (correlation coefficients R > 0.72) indicating the importance of hydrophobicity for the embryonic toxicity. For the five heavy metals, the EC(50) ranges from 0.36 to 30.78 μM and the toxicity follows an order of Cu > Pb > Zn > Cd >Ni. The significant correlation (R > 0.79) between the -log EC50 and the bioconcentration factor (log BCF) values of metals also indicate that the bioaccumulation property of metals contributes to their aquatic toxicity. In addition, the joint effects of the biocides with the heavy metals in embryonic development are assessed by using a concentration addition model. Synergistic effects are observed in almost all 25 mixtures, showing that Cu yields the strongest while Ni the weakest synergistic toxic effects on the embryos development.

Toxicity of metal pyrithione photodegradation products to marine organisms with indirect evidence for their presence in seawater

We evaluated the acute toxicities of the metal pyrithiones (MePTs)--copper pyrithione (CuPT) and zinc pyrithione (ZnPT)--to four species of marine algae and a marine crustacean (Tigriopus japonicus). We also performed acute toxicity tests using six of the main MePT photodegradation products: pyridine-N-oxide (PO); 2-mercaptopyridine (HPS); pyridine-2-sulfonic-acid (PSA); 2-mercaptopyridine-N-oxide (HPT); 2,2'-dithio-bis-pyridine ([PS](2)); and 2,2'-dithio-bis-pyridine-N-oxide ([PT](2))-and three marine organisms representing three trophic levels: an alga (Skeletonema costatum), a crustacean (T. japonicus), and a fish (Pagrus major). The acute toxicity values (72-h EC(50)) of CuPT, ZnPT, HPT, (PT)(2), (PS)(2), HPS, PO, and PSA for S. costatum, which was the most sensitive of the test organisms to the chemicals tested, were 1.5, 1.6, 1.1, 3.4, 65, 730, >100,000, and >100,000 microg l(-1), respectively. CuPT was detected in the growth media used for S. costatum tests and in seawater containing HPT or (PT)(2); the concentration of CuPT in seawater containing HPT was highly dependent on the Cu(2+) concentration. These results indicate that in the presence of sufficient Cu(2+), the toxicities of HPT and (PT)(2) should be assessed as CuPT because in Japan MePTs are most frequently used as antifouling booster biocides in conjunction with cuprous oxide.

Variation in toxicity of copper pyrithione among populations and families of the barnacle, Balanus amphitrite

Inter- and intra-population variation in the toxicity of the antifouling biocide copper pyrithione (CuPT) was examined for nauplius larvae of the barnacle Balanus amphitrite. Nauplii were collected from brooding adults from four sites within the Newport River estuary (NC), chosen based on an initial estimation of recent and historical human activities that affect local contamination levels. Each site was characterized for the presence of polycyclic aromatic hydrocarbons and for the frequency of gastropod imposex, an indicator of contamination by organotins. Sensitivity of nauplii to CuPT varied significantly across the sites/populations, with LC(50) values ranging from 4.0 microg l(-1) to 6.1 microg l(-1). Larvae from the most contaminated site were the most sensitive to CuPT. Intrapopulation variation in toxicity was investigated by exposing nauplius larvae from 15 maternal families to a fixed concentration of CuPT (6.1 microg l(-1)). Variation in larval mortality among the families was significant, ranging from 15.1% to 98.9%.

Inhibition of acetylcholinesterase by metabolites of copper pyrithione (CuPT) and its possible involvement in vertebral deformity of a CuPT-exposed marine teleostean fish

In a previous study, we demonstrated that exposure to an antifouling biocide, copper pyrithione (CuPT), early during life induced vertebral deformity in the larvae of a marine fish, the mummichog (Fundulus heteroclitus). Skeletal deformities may be caused by inhibition by of acetylcholiensterase (AChE) activity, and to elucidate the mechanism underlying the CuPT-associated vertebral deformity, we first examined whether CuPT, zinc pyrithione (ZnPT), and their degradation products could inhibit AChE activity in the fish. Two of the degradation products, 2,2'-dipyridyldisulfide [(PS)(2)] and 2,2'-dithiobispyridine-N-oxide [(PT)(2)], but neither CuPT nor ZnPT, exhibited prominent AChE-inhibiting activity. Secondly, thin-layer chromatography revealed that mummichog hepatic microsomes metabolized CuPT to produce (PS)(2) in a microsome-dependent manner. The AChE inhibition induced in CuPT-exposed fish is likely due to (PS)(2) that was produced through metabolism of acquired CuPT. (PS)(2) may cause therefore skeletal deformity in CuPT-exposed fish by means of its neuromuscular blocking properties, through a mechanism similar to that proposed for animals exposed to organophosphorous pesticides.

Inorganic-organic hybrid coatings on stainless steel by layer-by-layer deposition and surface-initiated atom-transfer-radical polymerization for combating biocorrosion

To improve the biocorrosion resistance of stainless steel (SS) and to confer the bactericidal function on its surface for inhibiting bacterial adhesion and biofilm formation, well-defined inorganic-organic hybrid coatings, consisting of the inner compact titanium oxide multilayers and outer dense poly(vinyl-N-hexylpyridinium) brushes, were successfully developed. Nanostructured titanium oxide multilayer coatings were first built up on the SS substrates via the layer-by-layer sol-gel deposition process. The trichlorosilane coupling agent, containing the alkyl halide atom-transfer-radical polymerization (ATRP) initiator, was subsequently immobilized on the titanium oxide coatings for surface-initiated ATRP of 4-vinylpyridine (4VP). The pyridium nitrogen moieties of the covalently immobilized 4VP polymer, or P(4VP), brushes were quaternized with hexyl bromide to produce a high concentration of quaternary ammonium salt on the SS surfaces. The excellent antibacterial efficiency of the grafted polycations, poly(vinyl-N-pyridinium bromide), was revealed by viable cell counts and atomic force microscopy images of the surface. The effectiveness of the hybrid coatings in corrosion protection was verified by the Tafel plot and electrochemical impedance spectroscopy measurements.

Prediction and assessment of mixture toxicity of compounds in antifouling paints using the sea-urchin embryo-larval bioassay

The ecotoxicological assessment of alternative "booster" biocides is urgently needed in order to develop environmentally acceptable antifouling paints. However, research has focused mainly on single compounds, and there is still a lack of data on their mixture toxicity. The present study investigated the single and mixture toxicity of three of the most widely used antifouling biocides: zinc pyrithione, chlorothalonil and Sea-Nine, using the sea-urchin (Paracentrotus lividus) embryo-larval bioassay. Also, the predictive ability of the concentration addition (CA) and independent action (IA) concepts for antifouling mixtures was evaluated. Both concepts failed to accurately predict the toxicity of the antifouling mixtures, with the exception of the zinc pyrithione and Sea-Nine mixture, which was accurately predicted by the IA concept, suggesting a dissimilar mode of action of those substances. In general, CA predicted consistently higher toxicity than IA; however, CA overestimated the toxicity of the studied mixtures by a factor of only 1.6, representing a reasonable worst-case approach to be used in the predictive hazard assessment of antifouling mixtures. Finally, the present study demonstrates that the risk of antifouling mixtures for the early developmental stages of sea urchin is higher than the risk of each single substance, and therefore, the inclusion of mixture considerations in the development of water quality criteria for antifouling compounds is strongly recommended.

Synergistic toxic effects of zinc pyrithione and copper to three marine species: Implications on setting appropriate water quality criteria

Zinc pyrithione (ZnPT) is widely applied in conjunction with copper (Cu) in antifouling paints as a substitute for tributyltin. The combined effects of ZnPT and Cu on marine organisms, however, have not been fully investigated. This study examined the toxicities of ZnPT alone and in combination with Cu to the diatom Thalassiosira pseudonana, polychaete larvae Hydroides elegans and amphipod Elasmopus rapax. Importantly, ZnPT and Cu resulted in a strong synergistic effect with isobologram interaction parameter lambda>1 for all test species. The combined toxicity of ZnPT and Cu was successfully modelled using the non-parametric response surface and its contour. Such synergistic effects may be partly due to the formation of copper pyrithione. It is, therefore, inadequate to assess the ecological risk of ZnPT to marine organisms solely based on the toxicity data generated from the biocide alone. To better protect precious marine resources, it is advocated to develop appropriate water quality criteria for ZnPT with the consideration of its compelling synergistic effects with Cu at environmentally realistic concentrations.

Impact of Irgarol 1051 on the larval development and metamorphosis of Balanus amphitrite Darwin, the diatom Amphora coffeaformis and natural biofilm

The effect of Irgarol 1051 on the biofilm-forming diatom, Amphora coffeaformis, and on natural biofilm (NBF) was assessed. A reduction in the number of A. coffeaformis cells within a biofilm was observed after treatment with Irgarol 1051, confirming its role as an inhibitor of photosynthetic activity. The impact of this compound on the development of nauplii of Balanus amphitrite was evaluated through its impact on Chaetoceros calcitrans, which was provided as food for the larvae. A reduction in the number of cells of C. calcitrans was observed when treated with Irgarol 1051. When larvae of B. amphitrite were reared using C. calcitrans in the presence of Irgarol 1051, their mortality increased with an increase in the concentration of Irgarol 1051 (13% at 1 microg l(-1) to 40% at 1000 microg l(-1)) compared with the control (6%). Nauplii reared in the presence of Irgarol 1051 developed more slowly (6-7 days) compared with control larvae (4-5 days). Cyprid bioassay results indicated an increase in percentage metamorphosis (76%) when NBFs were treated with the highest concentration of Irgarol 1051, compared with untreated biofilm (28%). The enhanced rate of metamorphosis appeared to be related to an increase in bacterial numbers in the biofilm, which may have been due to lysis of diatoms caused by Irgarol 1051. A. coffeaformis biofilms grown in the presence of antibiotics showed a significant reduction in cell numbers, which on further treatment with Irgarol 1051 showed an increase in cell numbers. Thus, it can be hypothesised that A. coffeaformis cells that were subjected to stress twice may have expressed resistant genes. Furthermore, if plasmids are present in the biofilms, they may enhance transfer to the surviving cells making them more resistant to hostile conditions.

Combinatorial materials research applied to the development of new surface coatings VI: An automated spinning water jet apparatus for the high-throughput characterization of fouling-release marine coatings

Large numbers of coatings can be generated very quickly using a combinatorial high-throughput approach. Rapid screening assays are typically required to adequately evaluate and down select coating candidates to identify promising compositions. An automated, spinning water jet apparatus was developed to rapidly characterize the adhesion strength of marine organisms to coating surfaces. Coating arrays are cast in multiwell plates and subjected to a jet of water of controlled pressure and duration. Array plates are manipulated by a robotic arm to facilitate accurate and repeatable water jet treatments. Jet pressures of 40-688 kPa can be generated and precisely maintained by computer control. A five axis robotic arm selects plates from three plate stacking hotels yielding a total of 39 plates or 936 individual coating samples for each experimental run. All robotic instructions, process parameters, and data are stored and controlled by the computer. The large plate handling capacity offered by the robotic system enables the analysis of a wide variety of coatings for "fouling-release" properties. A brief example demonstrating the capability of the automated water jet apparatus to evaluate marine bacterial adhesion to coating surfaces is provided.

Aqueous phototransformation of zinc pyrithione

The photochemical behavior of the antifouling agent zinc pyrithione (ZnPT) was studied in aqueous media of different composition under simulated solar irradiation using a xenon light source. The influence of important constituents of natural water (dissolved organic matter and nitrate) was also examined using a multivariate kinetic model. It was found that photodegradation proceeds via a pseudo first-order reaction. Kinetic experiments were monitored by LC-MS and photolytic half-lives ranging between 9.2 and 15.1 min have been observed. The increasing concentration of dissolved organic matter (DOM) accelerates the photolysis reaction, while the effect of nitrate ions was also positive since it increased the degradation rate, but to a lesser extent. Irradiation of the aqueous ZnPT solutions gave rise to several transformation products that were isolated by means of solid-phase extraction using poly(styrene-divinylbenzene) extraction disks. These byproducts were identified using liquid chromatography-atmospheric pressure chemical ionisation mass spectrometry. Besides 2-pyridinesulfonic-acid, other degradation products formed included pyridine-N-oxide, 2-mercaptopyridine, 2,2'-dithiobis(pyridine-N-oxide), 2,2-dipyridyl disulfide and the pyridine/pyrithione mixed disulfide, 2,2'-dithiobispyridine mono-N-oxide (PPMD).

Laboratory screening of coating libraries for algal adhesion

Coatings libraries achieved through a combinatorial chemistry approach, which may generate tens to hundreds of formulations, can be deposited in an array of 12 patches, each approximately 9 cm(2), on 10 x 20 cm primed aluminum panels. However, existing methods to quantify algal biomass on coatings are unsuitable for this type of array format. This paper describes an algorithm modelled on a probability distribution that quantifies the area of surface covered by a green alga from digital images. The method allows coatings with potential fouling-release properties to be down-selected for further evaluation. The use of the algorithm is illustrated by a set of eight siloxane-polyurethane coatings made using organofunctional poly(dimethylsiloxane) (PDMS) and poly(epsilon-caprolactone)-PDMS-poly(epsilon-caprolactone) (PCL-PDMS-PCL) triblock copolymers along with four PDMS standards which were deposited on one panel. Six replicate panels were seeded with Ulva zoospores which grew into sporelings (small plants) that completely covered the surface. The ease of removal of the Ulva sporeling biofilms was determined by automated water jetting at six different impact pressures. The coverage of the biofilm on the twelve individual formulations after jet washing was quantified from the green colour of digital images. The data are discussed in relation to the composition of the coatings.

Combinatorial materials research applied to the development of new surface coatings V. Application of a spinning water-jet for the semi-high throughput assessment of the attachment strength of marine fouling algae

In order to facilitate a semi-high throughput approach to the evaluation of novel fouling-release coatings, a 'spinjet' apparatus has been constructed. The apparatus delivers a jet of water of controlled, variable pressure into the wells of 24-well plates in order to facilitate measurement of the strength of adhesion of algae growing on the base of the wells. Two algae, namely, sporelings (young plants) of the green macroalga Ulva and a diatom (Navicula), were selected as test organisms because of their opposing responses to silicone fouling-release coatings. The percentage removal of algal biofilm was positively correlated with the impact pressure for both organisms growing on all the coating types. Ulva sporelings were removed from silicone elastomers at low impact pressures in contrast to Navicula cells which were strongly attached to this type of coating. The data obtained for the 24-well plates correlated with those obtained for the same coatings applied to microscope slides. The data show that the 24-well plate format is suitable for semi-high throughput screening of the adhesion strength of algae.

Engineered antifouling microtopographies - effect of feature size, geometry, and roughness on settlement of zoospores of the green alga Ulva

The effect of feature size, geometry, and roughness on the settlement of zoospores of the ship fouling alga Ulva was evaluated using engineered microtopographies in polydimethylsiloxane elastomer. The topographies studied were designed at a feature spacing of 2 microm and all significantly reduced spore settlement compared to a smooth surface. An indirect correlation between spore settlement and a newly described engineered roughness index (ERI) was identified. ERI is a dimensionless ratio based on Wenzel's roughness factor, depressed surface fraction, and the degree of freedom of spore movement. Uniform surfaces of either 2 mum diameter circular pillars (ERI=5.0) or 2 microm wide ridges (ERI=6.1) reduced settlement by 36% and 31%, respectively. A novel multi-feature topography consisting of 2 mum diameter circular pillars and 10 microm equilateral triangles (ERI=8.7) reduced spore settlement by 58%. The largest reduction in spore settlement, 77%, was obtained with the Sharklet AF topography (ERI=9.5).

Combinatorial materials research applied to the development of new surface coatings III. Utilisation of a high-throughput multiwell plate screening method to rapidly assess bacterial biofilm retention on antifouling surfaces

The authors recently reported on the development of a novel multiwell plate screening method for the high-throughput assessment of bacterial biofilm retention on surfaces. Two series of biocide containing coatings were prepared to assess the ability of the developed assay to adequately discern differences in antifouling performance: i) a commercially available poly(methyl methacrylate) (PMMA) and silicone elastomer (DC) physically blended with an organic antifouling biocide Sea-Nine 211 (SN211) (4,5-dichloro-2-n-octyl-3(2H)-isothiazolone), and ii) a silanol-terminated polydimethylsiloxane (PDMS-OH) reacted with an alkoxy silane-modified polyethylenimine containing bound ammonium salt groups (PEI-AmCl). Three marine bacteria were utilised to evaluate the SN211 blended coatings (Pseudoalteromonas atlantica ATCC 19262, Cobetia marina ATCC 25374, Halomonas pacifica ATCC 27122) and the marine bacterium Cytophaga lytica was utilised to evaluate the PEI-AmCl/PDMS-OH coatings. The SN211 blended coatings showed a general trend of decreasing biofilm retention as the concentration of SN211 increased in both PMMA and DC. HPLC analysis revealed that reduction in biofilm retention was positively correlated with the amount of SN211 released into the growth medium over the length of the bacterial incubation. When compared to PMMA, DC consistently showed an equal or greater percent reduction in biofilm retention as the level of SN211 loading increased, although at lower loading concentrations. Evaluations of the PEI-AmCl/PDMS-OH coatings with C. lytica showed that all PEI-AmCl loading concentrations significantly reduced biofilm retention (p<0.0001) by a surface contact phenomenon. The high-throughput bacterial biofilm growth and retention assay has been shown to be useful as an effective primary screening tool for the rapid assessment of antifouling materials.

Combinatorial materials research applied to the development of new surface coatings IV. A high-throughput bacterial biofilm retention and retraction assay for screening fouling-release performance of coatings

A high-throughput bacterial biofilm retention screening method has been augmented to facilitate the rapid analysis and down-selection of fouling-release coatings for identification of promising candidates. Coatings were cast in modified 24-well tissue culture plates and inoculated with the marine bacterium Cytophaga lytica for attachment and biofilm growth. Biofilms retained after rinsing with deionised water were dried at ambient laboratory conditions. During the drying process, retained biofilms retracted through a surface de-wetting phenomenon on the hydrophobic silicone surfaces. The retracted biofilms were stained with crystal violet, imaged, and analysed for percentage coverage. Two sets of experimental fouling-release coatings were analysed with the high-throughput biofilm retention and retraction assay (HTBRRA). The first set consisted of a series of model polysiloxane coatings that were systematically varied with respect to ratios of low and high MW silanol-terminated PDMS, level of cross-linker, and amount of silicone oil. The second set consisted of cross-linked PDMS-polyurethane coatings varied with respect to the MW of the PDMS and end group functionality. For the model polysiloxane coatings, HTBRRA results were compared to data obtained from field immersion testing at the Indian River Lagoon at the Florida Institute of Technology. The percentage coverage calculations of retracted biofilms correlated well to barnacle adhesion strength in the field (R(2)=0.82) and accurately identified the best and poorest performing coating compositions. For the cross-linked PDMS-polyurethane coatings, the HTBRRA results were compared to combinatorial pseudobarnacle pull-off adhesion data and good agreement in performance was observed. Details of the developed assay and its implications in the rapid discovery of new fouling-release coatings are discussed.

Improved method for the determination of zinc pyrithione in environmental water samples incorporating on-line extraction and preconcentration coupled with liquid chromatography atmospheric pressure chemical ionisation mass spectrometry

A method has been developed for the determination of zinc pyrithione (ZnPT) in environmental water samples using monolithic reversed-phase silica columns for rapid on-line large volume solid phase extraction in tandem with on-line matrix removal using sacrificial strong anion exchange (SAX) columns. This is coupled with reversed-phase liquid chromatography with atmospheric pressure chemical ionisation mass spectrometric detection. Limits of detection in spiked river water samples, using a 200 mL preconcentration volume, were determined as 18 ng L(-1), with a limit of quantitation of 62 ng L(-1). The percentage recovery from spiked river water was found to be 72+/-9 (n=3 extractions), whilst overall method precision, following 10 repeat complete analyses was found to be 27% RSD at 1 microg L(-1). Linearity was determined over the concentration range of 0.25-10 microg L(-1) and the calculated regression coefficient was R(2)=0.9802. The method was used to investigate the environmental fate of zinc pyrithione in waters and its partition coefficient between sediment and water phases.

Improved estimates of environmental copper release rates from antifouling products

The US Navy Dome method for measuring copper release rates from antifouling paint in-service on ships' hulls can be considered to be the most reliable indicator of environmental release rates. In this paper, the relationship between the apparent copper release rate and the environmental release rate is established for a number of antifouling coating types using data from a variety of available laboratory, field and calculation methods. Apart from a modified Dome method using panels, all laboratory, field and calculation methods significantly overestimate the environmental release rate of copper from antifouling coatings. The difference is greatest for self-polishing copolymer antifoulings (SPCs) and smallest for certain erodible/ablative antifoulings, where the ASTM/ISO standard and the CEPE calculation method are seen to typically overestimate environmental release rates by factors of about 10 and 4, respectively. Where ASTM/ISO or CEPE copper release rate data are used for environmental risk assessment or regulatory purposes, it is proposed that the release rate values should be divided by a correction factor to enable more reliable generic environmental risk assessments to be made. Using a conservative approach based on a realistic worst case and accounting for experimental uncertainty in the data that are currently available, proposed default correction factors for use with all paint types are 5.4 for the ASTM/ISO method and 2.9 for the CEPE calculation method. Further work is required to expand this data-set and refine the correction factors through correlation of laboratory measured and calculated copper release rates with the direct in situ environmental release rate for different antifouling paints under a range of environmental conditions.

Antifouling strategies for marine and riverine sensors

Traditionally, water quality has been monitored by sampling and lab based analysis. However, there are disadvantages associated with this method, for example, deterioration of samples with time, limited sampling points, limited temporal monitoring. This has provided impetus for the development of sensors which can be deployed from remote locations over extended deployment periods. However, a major limitation of these systems is their vulnerability to biofouling. This review outlines the research that has been carried out on strategies for the protection of marine and riverine sensors against fouling.

Biofouling communities on test panels coated with TBT and TBT-free copper based antifouling paints

Formation of biofouling communities on the surfaces of steel panels coated with two different TBT-free copper-based and one TBT-based antifouling paint was examined following submersion for periods of 3, 6, 9 and 12 months in Kastela Bay, Croatia. Test panels coated with Shopprimer and anticorrosive paint were used as control panels. Thirty five taxa of benthic algae and 32 taxa of benthic animals were found. Diatomeae dominated by frequency and abundance on test panels coated with antifouling paints, while the animal species Serpula vermicularis, Mytilus galloprovincialis and Balanus amphitrite amphitrite dominated the fouling communities on control panels. On panels protected by antifouling paints, low values of biomass were found compared to the very high values associated with control panels.

Antifouling potential of cyanobacteria: a mini-review

Cyanobacteria produce a variety of bioactive metabolites that may have allelochemical functions in the natural environment, such as in the prevention of fouling by colonising organisms. Chemical compounds from cyanobacteria are also of biotechnological interest, especially for clinical applications, because of their antibiotic, algicidal, cytotoxic, immunosupressive and enzyme inhibiting activities. Cyanobacterial metabolites have the potential for use in antifouling technology, since they show antibacterial, antialgal, antifungal and antimacrofouling properties which could be expoited in the prevention of biofouling on man-made substrata in the aquatic environment. Molecules with antifouling activity represent a number of types including fatty acids, lipopeptides, amides, alkaloids, terpenoids, lactones, pyrroles and steroids. The isolation of biogenic compounds and the determination of their structure may provide leads for future development of, for example, environmentally friendly antifouling paints. An advantage of exploring the efficacy of cyanobacterial products is that the organisms can be grown in mass culture, which can be manipulated to achieve optimal production of bioactive substances. Phycotoxins and related products from cyanobacteria may serve as materials for antimicro- and antimacrofouling applications. A survey of antibiotic compounds with antifouling potential revealed more than 21 different antifouling substances from 27 strains of cyanobacteria.

A methodology for evaluating biocide release rate, surface roughness and leach layer formation in a TBT-free, self-polishing antifouling coating

Due to the forthcoming IMO ban on the use of tributyltin (TBT) antifouling paints, a new generation of TBT-free coatings has been developed that typically contain cuprous oxide and an organic co-biocide. Accurate and reproducible test methods are needed to evaluate the performance and environmental impact of these new coatings. This study investigated a methodology for evaluating TBT-free, AF coatings containing cuprous oxide. A commercially available AF coating underwent rotary immersion testing at 0, 0.51 and 2.05 m s-1. Scanning electron microscopy (SEM) and energy dispersive x-ray (EDX) analysis were used to assess leach layer formation, percentage cuprous oxide by weight and particle size distribution (PSD). Biocide release rates and surface roughness were also measured. An increase in rotary speed caused a spike in Cu2+ release rate after which the release rate stabilised to previous levels. An increase in leach layer thickness was also observed after the rotary speed increase. A model is suggested to account for the observations.

Sublethal effects of a new antifouling candidate on lumpfish (Cyclopterus lumpus L.) and Atlantic cod (Gadus morhua L.) larvae

Sublethal effects of medetomidine, a new generation antifouling compound, on lumpfish (Cyclopterus lumpus L.) and cod (Gadus morhua L.) larvae were examined. The effects on respiration rate and on colour adaptation of newly hatched larvae were assessed after 24-96 h exposure. Exposure of lumpfish larvae to the experimental concentrations resulted in a significant decrease in respiration rate (Lowest Observed Effect Concentration (LOEC) = 5-10 nM) and in the percentage of dark larvae (LOEC = 4 nM). However, no effects on respiration rate of cod larvae were detected. In addition to lumpfish larvae being affected at low concentrations of medetomidine, a reversibility of the effects was observed when 96 h-exposed larvae were incubated in clean seawater for 24-48 h. Considerations relating to the future commercialisation of medetomidine for antifouling purposes are discussed.