The environmental fate and effects of antifouling paint biocides

Preliminary hazard assessment of a new nature-inspired antifouling (NIAF) agent

A recently synthesized aminated 3,4-dioxygenated xanthone (Xantifoul2) was found to have promising antifouling (AF) effects against the settlement of the macrofouler Mytilus galloprovincialis larvae. Preliminary assessment indicated that Xantifoul2 has reduced ecotoxicological impacts: e.g., being non-toxic to the marine crustacea Artemia salina (<10 % mortality at 50 μM) and showing low bioconcentration factor in marine organisms. In order to meet the EU Biocidal Product Regulation, a preliminary hazard assessment of this new nature-inspired antifouling (NIAF) agent was conducted in this work. Xantifoul2 did not affect the swimming ability of the planktonic crustacean Daphnia magna, the growth of the diatom Phaeodactylum tricornutum, and the cellular respiration of luminescent Gram-negative bacteria Vibrio fischeri, supporting the low toxicity towards several non-target marine species. Regarding human cytotoxicity, Xantifoul2 did not affect the cell viability of retinal human cells (hTERT-RPE-1) and lipidomic studies revealed depletion of lipids involved in cell death, membrane modeling, lipid storage, and oxidative stress only at a high concentration (10 μM). Accelerated degradation studies in water were conducted under simulated sunlight to allow the understanding of putative transformation products (TPs) that could be generated in the aquatic ecosystems. Both Xantifoul2 and photolytic-treated Xantifoul2 in the aqueous matrix were therefore evaluated on several nuclear receptors (NRs). The results of this preliminary hazard assessment of Xantifoul2, combined with the high degradation rates in water, provide strong evidence of the safety of this AF agent under the evaluated conditions, and provide the support for future validation studies before this compound can be introduced in the market.

Exposure to hull cleaning wastewater induces mortality through oxidative stress and cholinergic disturbance in the marine polychaete Perinereis aibuhitensis

While wastewater and paint particles discharged from the in-water cleaning process of ship hulls are consistently released into benthic ecosystems, their hazardous effects on non-target animals remain largely unclear. In this study, we provide evidence on acute harmful effects of hull cleaning wastewater in marine polychaete Perinereis aibuhitensis by analyzing physiological and biochemical parameters such as survival, burrowing activity, and oxidative status. Raw wastewater samples were collected during ship hull cleaning processes in the field. Two wastewater samples for the exposure experiment were prepared in the laboratory: 1) mechanically filtered in the in-water cleaning system (MF) and 2) additionally filtered with a 0.45 μm filter in the laboratory (LF). These wastewater samples contained high concentrations of metals (zinc and copper) and metal-based booster biocides (copper pyrithione and zinc pyrithione) compared to those analyzed in seawater. Polycheates were exposed to different concentrations of the two wastewater samples for 96 h. Higher mortality was observed in response to MF compared to LF-exposed polychaetes. Both wastewater samples dose-dependently decreased burrowing activity and AChE activity. Drastic oxidative stress was observed in response to the two wastewater samples. MDA levels were significantly increased by MF and LF samples. Significant GSH depletion was observed with MF exposure, while increased and decreased GSH contents were observed in LF-exposed polychaetes. Enzymatic activities of antioxidant components, catalase, superoxide dismutase, and glutathione S-transferase were significantly modulated by both wastewater samples. These results indicate that even filtered hull cleaning wastewater can have deleterious effects on the health status of polychaetes.

Bioinspired Zwitterionic Nanowires with Simultaneous Biofouling Reduction and Release

Marine biofouling is a complex and dynamic process that significantly increases the carbon emissions from the maritime industry by increasing drag losses. However, there are no existing non-toxic marine paints that can achieve both effective fouling reduction and efficient fouling release. Inspired by antifouling strategies in nature, herein, a superoleophobic zwitterionic nanowire coating with a nanostructured hydration layer is introduced, which exhibits simultaneous fouling reduction and release performance. The zwitterionic nanowires demonstrate >25% improvement in fouling reduction compared to state-of-the-art antifouling nanostructures, and four times higher fouling-release compared to conventional zwitterionic coatings. Fouling release is successfully achieved under a wall shear force that is four orders of magnitude lower than regular water jet cleaning. The mechanism of this simultaneous fouling reduction and release behavior is explored, and it is found that a combination of 1) a mechanical biocidal effect from the nanowire geometry, and 2) low interfacial adhesion resulting from the nanostructured hydration layer, are the major contributing factors. These findings provide insights into the design of nanostructured coatings with simultaneous fouling reduction and release. The newly established synthesis procedure for the zwitterionic nanowires opens new pathways for implementation as antifouling coatings in the maritime industry and biomedical devices.

Zwitterionic Hydrogel Coating with Antisediment Properties for Marine Antifouling Applications

Biofouling is a serious issue affecting the marine industry because the attached micro- and macrocontaminants can increase fuel consumption and damage ship hulls. A hydrophilic hydrogel-based coating is considered a promising antifouling material because it is environmentally friendly and the dense hydration layer can protect the substrate from microbial attachment. However, sediment adsorption can be an issue for hydrogel-based coatings. Their natural soft and porous structures can trap sediment from the marine environment and weaken the antifouling capability. There is still little research on the antisediment properties of hydrogels, and none of them deal with this problem. Here, we report on optimizing zwitterionic hydrogel-based coatings to improve their antisediment properties and achieve comparable performance to commercial biocidal coatings, which are the gold standard in the antifouling coating area. After 1 week of sediment contamination and 2 weeks of diatom coculturing, this optimized zwitterionic hydrogel coating maintained its antifouling properties with a few diatoms on the surface. Its large-scale samples also achieved antifouling performance similar to that of biocidal coatings in the Atlantic Ocean for 1.5 months. More importantly, our research provides a universal strategy to improve the antisediment properties of soft hydrogel-based coatings. For the first time, we report that the introduction of interfacial electrostatic interactions enhanced the antisediment properties of hydrogels.

Hull-cleaning wastewater poses serious acute and chronic toxicity to a marine mysid-A multigenerational study

We conducted a comprehensive assessment involving acute effects on 96-hour survival and biochemical parameters, as well as chronic effects on growth and reproduction spanning three generations of the marine mysid Neomysis awatschensis exposed to filtered wastewater to evaluate the potential impact of ship hull-cleaning wastewater on crustaceans. The analyzed wastewater exhibited elevated concentrations of metals, specifically zinc (Zn) and copper (Cu) and metal-based antifoulants, i.e., Cu pyrithoine (CuPT) and Zn pyrithoine (ZnPT). The results revealed dose-dependent reductions in survival rates, accompanied by a notable increase in oxidative stress, in response to the sublethal values of two wastewater samples: 1) mechanically filtered using the cleaning system (MF) and 2) additionally filtered in the laboratory (LF) for 96 h. Mysids exposed to MF displayed higher mortality than those exposed to LF. Furthermore, mysids subjected to continuous exposure of 0.001% LF across three generations exhibited significant inhibition of the feeding rate, more pronounced growth retardation along with an extended intermolt duration, and a diminished rate of reproduction compared to the control. A noteworthy inhibition of the feeding rate and growth was observed in the first generation exposed only to the LF sample. However, although the reproduction rate was not significantly affected. Collectively, these findings underscore the potential harm posed by sublethal concentrations of wastewater to the health of mysid populations under consistent exposure.

Detrimental effects of hull cleaning wastewater on oxidative status, life cycle parameters, and population growth of the monogonont rotifer Brachionus manjavacas

While wastewater discharged from in-water cleaning process of ship hulls on rotifer consistently released into aquatic ecosystem, its detrimental effects on non-target animals are largely unclear. In this study, we provide evidence on detrimental effects of hull cleaning wastewater in the monogonont rotifer Brachionus manjavacas by analyzing biochemical and physiological parameters in its oxidative status, survival, lifespan, growth, fecundity, and population. The wastewater contained high concentrations of metals (Zn and Cu) and metal-based antifoulants (CuPT and ZnPT). Significant oxidative stress was observed in response to two wastewater samples [1) raw wastewater (RW) and 2) mechanical filtrated in the cleaning system (MF)]. Higher detrimental effects in survival, lifespan, fecundity, and population growth for 10 days were measured in the RW-exposed rotifers than those results analyzed in the MF-exposed rotifers. Two growth parameters, lorica length and width were also significantly modulated by both wastewater samples. These results indicate that even filtered hull cleaning wastewater would have deleterious effects on the maintenance of the rotifer population when they exposed constantly.

Chlorothalonil as a potential endocrine disruptor in male zebrafish (Danio rerio): Impact on the hypothalamus-pituitary-gonad axis and sperm quality

Chlorothalonil is a broad-spectrum organochlorine fungicide widely employed in agriculture to control fungal foliar diseases. This fungicide enters aquatic environments through the leaching process, leading to toxicity in non-target organisms. Organic contaminants can impact organism reproduction as they have the potential to interact with the neuroendocrine system. Although there are reports of toxic effects of chlorothalonil, information regarding its impact on reproduction is limited. The aim of the present study was to evaluate the influence of chlorothalonil on male reproductive physiology using the zebrafish (Danio rerio) as ecotoxicological model. Zebrafish were exposed for 7 days to two concentrations of chlorothalonil (0.1 and 10 μg/L) along with a control group (with DMSO - 0.001%). Gene expression of hypothalamus-pituitary-gonad axis components (gnrh2, gnrh3, lhr, fshr, star, hsd17b1, hsd17b3, and cyp19a1), as well as hepatic vitellogenin concentration were assessed. In sperm cells, reactive oxygen species (ROS) content, lipid peroxidation (LPO), mitochondrial functionality, and membrane integrity and fluidity were evaluated. Results indicate that exposure to the higher concentration of chlorothalonil led to a reduction in brain gnr2 expression. In gonads, mRNA levels of lhr, star, and hsd17b1 were decreased at both chlorothalonil concentrations tested. Similarly, hepatic vitellogenin concentration was reduced. Regarding sperm cells, a decreased ROS level was observed, without significant difference in LPO level. Additionally, a higher mitochondrial potential and lower membrane fluidity were observed in zebrafish exposed to chlorothalonil. These findings demonstrate that chlorothalonil acts as an endocrine disruptor, influencing reproductive control mechanisms, as evidenced by changes in expression of genes HPG axis, as well as hepatic vitellogenin concentration. Furthermore, our findings reveal that exposure to this contaminant may compromise the reproductive success of the species, as it affected sperm quality parameters.

Self-healing and durable antifouling zwitterionic hydrogels based on functionalized liquid metal microgels

Hydrogels are a promising new class of antifouling materials. But their utility is constrained by low mechanical strength and unsatisfactory antifouling performance over the long term. Herein, we successfully prepared zwitterionic polymer PEIS cross-linked gallium-based liquid metal microgels-based (PEIS-Gel@PMPC-GLM) hydrogels via UV-curing and amidation reaction. The as-prepared hydrogels showed preferable mechanical properties and superior hydrophilicity to the original hydrogels. The PEIS-Gel@PMPC-GLM hydrogels could prevent the adhesion of more than 90 % of microalgae and nearly 100 % of bacteria in a short-term antifouling test. PEIS-Gel@PMPC-GLM hydrogels also performed exceptionally well in the high concentration antibacterial test and the long-term antifouling test (remove more than 90 % bacteria and 80 % microalgae). In addition to releasing a high concentration of gallium ions, as shown by the ICP-OES test, PEIS-Gel@PMPC-GLM hydrogels also exhibitedexcellent lubrication performance, as demonstrated by the friction test (coefficient of friction as low as 0.023). Therefore, the antifouling effect of gallium ions combined with the strong hydration ability of the surfaces endowed the hydrogels remarkable antibacterial and antifouling properties. As a result of the exposed gallium atoms inducing further crosslinking of residual vinyl monomer in hydrogels, PEIS-Gel@PMPC-GLM hydrogels revealed certain self-healing performance.

Emerging marine environmental pollution and ecosystem disturbance in ship hull cleaning for biofouling removal

Numerous marine sessile organisms adhere to ship hulls and increase the sailing resistance. Antibiofouling paints are employed to maintain the ship performance. However, the chemicals employed for antifouling purposes are becoming increasingly diverse, lacking clear toxicological information. Particularly, the imperfect antibiofouling efficacies of these chemicals necessitate periodic hull cleaning to dislodge attached marine organisms. This hull cleaning process inadvertently releases a plethora of hazardous substances, including antibiofouling chemicals, heavy metals, and cleaning agents, alongside exotic microorganisms. This results in profound marine pollution and ecosystem disruption. Specifically, these exotic microorganisms pose a novel ecological threat in coastal waters. However, despite the gravity of ship hull cleaning-related issues, comprehensive investigations have been lacking, and international regulatory measures are gaining attention recently. Aiming to provide solutions to the emerging challenges associated with hull cleaning, this review endeavors to comprehensively address the biofouling organisms and their mechanisms, potential antifouling paint hazards, and effective hull cleaning methodologies.

Protecting the invisible: Establishing guideline values for copper toxicity to marine microbiomes

Understanding the rapid responses of marine microbiomes to environmental disturbances is paramount for supporting early assessments of harm to high-value ecosystems, such as coral reefs. Yet, management guidelines aimed at protecting aquatic life from environmental pollution remain exclusively defined for organisms at higher trophic levels. In this study, 16S rRNA gene amplicon sequencing was applied in conjunction with propidium monoazide for cell-viability assessment as a sensitive tool to determine taxon- and community-level changes in a seawater microbial community under copper (Cu) exposure. Bayesian model averaging was used to establish concentration-response relationships to evaluate the effects of copper on microbial composition, diversity, and richness for the purpose of estimating microbiome Hazard Concentration (mHCx) values. Predicted mHC5 values at which a 5 % change in microbial composition, diversity, and richness occurred were 1.05, 0.72, and 0.38 μg Cu L-1, respectively. Threshold indicator taxa analysis was applied across the copper concentrations to identify taxon-specific change points for decreasing taxa. These change points were then used to generate a Prokaryotic Sensitivity Distribution (PSD), from which mHCxdec values were derived for copper, suitable for the protection of 99, 95, 90, and 80 % of the marine microbiome. The mHC5dec guideline value of 0.61 μg Cu L-1, protective of 95 % of the marine microbial community, was lower than the equivalent Australian water quality guideline value based on eukaryotic organisms at higher trophic levels. This suggests that marine microbial communities might be more vulnerable, highlighting potential insufficiencies in their protection against copper pollution. The mHCx values proposed here provide approaches to quantitatively assess the effects of contaminants on microbial communities towards the inclusion of prokaryotes in future water quality guidelines.

Assessing the risk of booster biocides for the marine environment: A case study at the Belgian part of the North Sea

The biofouling of submerged surfaces such as ship hulls is often prevented by using anti-fouling components in combination with booster biocides. These booster biocides enter the water column and may affect non-target organisms. Although different negative effects have been associated with the use of booster biocides, their effects on non-target organisms are often unknown. So far, the environmental risks for booster biocides have barely been quantified in the North Sea. In this work, the concentration of five commonly used booster biocides as well as tributyltin has been monitored at five dredged spoil disposal sites in the Belgian part of the North Sea and the harbour and ports of Nieuwpoort, Oostende, and Zeebrugge. Hotspots were discovered where the concentration of one or more booster biocides exceeded the predicted no-effect concentration. Tributyltin has been banned since 2008, but concentrations of 237- to 546-fold of the predicted no-effect concentration were detected in the harbours and ports. Moreover, TBT has been detected in the same order of magnitude in other sea basins, emphasizing the need to monitor the trends and impact of booster biocides and TBT in environmental monitoring programs.

Isothiazolinone dysregulates the pattern of miRNA secretion: Endocrine implications for neurogenesis

Isothiazolinones are extensively used as preservatives and disinfectants in personal care products and household items. The unintended exposure of humans and animals to isothiazolinones has led to increasing concerns about their health hazards. The compound 4,5-Dichloro-2-n-octyl-4-isothiazolin-3-one (DCOIT), a representative isothiazolinone, can simultaneously induce endocrine disruption and neurotoxicity. However, the underlying mechanisms and linkages remain unclear. Our purpose was to elucidate the role of miRNAs as the signaling communicator during the crosstalk between endocrine and nervous systems in response to DCOIT stress. H295R cells were exposed to DCOIT, after which the alterations in intracellular miRNA composition, exosome secretory machinery, and extracellular miRNA composition were examined. Then, a PC12 cell line of neuronal differentiation potential was cultured with the extract of extracellular miRNAs from DCOIT-exposed H295R cell media to explore the functional implications in neurogenesis. The results showed that DCOIT exposure resulted in 349 differentially expressed miRNAs (DEMs) in H295R cells, which were closely related to the regulation of multiple endocrine pathways. In the media of H295R cells exposed to DCOIT, 66 DEMs were identified, showing distinct compositions compared to intracellular DEMs with only 2 common DEMs (e.g., novel-m0541-5p of inverse changes in the cell and medium). Functional annotation showed that extracellular DEMs were not only associated with sex endocrine synchronization, but were also implicated in nervous system development, morphogenesis, and tumor. Incubating PC12 cells with the extracellular exosomes (containing miRNAs) from DCOIT-exposed H295R cells significantly increased the neurite growth, promoted neuronal differentiation, and shaped the transcriptomic fingerprint, implying that miRNAs may communicate transduction of toxic information of DCOIT in endocrine system to neurons. Overall, the present findings provide novel insight into the endocrine disrupting and neural toxicity of DCOIT. The miRNAs have the potential to serve as the epigenetic mechanism of systems toxicology.

Effect of wastewater from the in-water cleaning of ship hulls on attached and unattached microalgae

Environmental spills of in-water hull cleaning wastewater (HCW) containing heavy metals and biocides is inevitable, and the effects of HCW on microalgae are unknown. To investigate this, we conducted microcosm experiments by adding HCW to natural seawater. HCW samples were obtained from two different cleaning methods (soft: sponge, hard: brush), and 5 % or 10 % were added to natural seawater as treatments. Dissolved Cu concentrations were 5 to 10 times higher in the treatments than those in the control. There were significant differences in growth of unattached microalgae depending on HCW dose (chlorophyll a: 34.1 ± 0.8 μg L-1 in control vs. 12.6 ± 4.3 μg L-1 in treatments). Conversely, the biomass of attached microalgae increased with HCW dose, which was associated with most of the nutrient reduction later in the experiment, rather than unattached microalgae. Our findings suggest that HCW can significantly impact microalgal community, especially depending on spill volume.

Immunotoxic effects of exposure to the antifouling copper(I) biocide on target and nontarget bivalve species: a comparative in vitro study between Mytilus galloprovincialis and Ruditapes philippinarum

Edible bivalves constitute an important bioresource from an economic point of view, and studies on their immune responses to environmental pollutants are crucial for both the preservation of biodiversity and economic reasons. The worldwide diffusion of copper(I)-based antifouling paints has increased copper leaching into coastal environments and its potential impact on both target and nontarget organisms. In this study, immunotoxicity assays were carried out with short-term (60 min) cultures of hemocytes from the bivalves Mytilus galloprovincialis-a mussel dominant in the macrofouling community-and Ruditapes philippinarum-a clam dominant in the soft-sediment community-exposed to CuCl to compare the toxic effects on their immune responses. The LC50 values were similar, 40 μM (3.94 mg L-1) for the mussel and 44 μM (4.33 mg L-1) for the clam. In both species, apoptosis occurred after exposure to 1 µM (98.9 μg L-1) CuCl, the concentration able to significantly increase the intracellular Ca2+ content. Biomarkers of cell morphology and motility revealed microfilament disruption, a significant decrease in yeast phagocytosis and lysosome hydrolase (β-glucuronidase) inhibition beginning from 0.5 µM (49.5 μg L-1) CuCl in both the mussel and clam. The same concentration of CuCl affected biomarkers of oxidative stress, as a significant decrease in reduced glutathione content in the cytoplasm and inhibition of mitochondrial cytochrome-c oxidase (COX) were detected in both species. Comparison of the biomarkers showed that clam is more sensitive than the mussel regarding alterations to the lysosomal membrane and reactive oxygen species (ROS) production, which supports the potential harmful effects of antifouling biocides on the survival of nontarget pivotal species in the coastal community.

Multilevel assessment of chlorothalonil sediment toxicity to Latin American estuarine biota: Effects on biomarkers, reproduction and survival in different benthic organisms

Chlorothalonil is an organochlorine compound that has long been used in agriculture. In recent years, this compound has been used as an antifouling booster biocide and its presence has been reported in marine coastal environments, especially in navigational areas. Although sediment can be a sink for chlorothalonil due to high affinity to fine particulate matter, toxicity studies with non-target marine and/or estuarine organisms is focused on waterborne exposure only. This study aimed to determine sediment-borne ecotoxicological effects of chlorothalonil on different benthic organisms of the Latin American biota using a integrative multilevel approach. Marine/estuarine organisms were exposed to sediments spiked with chlorothalonil (from 0 to 10.0 μg g^-1) and effects at sub-individual (biochemical biomarkers in Anomalocardia flexuosa), individual (lethal effects to Tiburonella viscana and Artemia salina) and subpopulation levels (Nitokra sp. reproduction) were assessed. Increasing chlorothalonil concentrations in sediment caused increasing ecotoxicological effects in different levels of biological organisation, from biochemical to subpopulation levels. The highest exposure concentrations showed increased biomarkers of effects (lipid peroxidation and DNA damage in gills and/or digestive gland of A. flexuosa), lower fecundity and lower survival of the test organisms. GPx activity associated with LPO levels in the digestive gland suggested a response to the oxidant challenge provided by the biocide. At the lowest concentration (0.001 μg g^-1), chlorothalonil detoxification mechanisms and defense against its oxidising action, involving GSH and glutathione-dependent enzymes (GST and GPx) were induced. At intermediate concentrations, there was a tendency of decreasing GSH levels, probably due to conjugation with chlorothalonil, which also affected the activities of the glutathione-dependent enzymes. At the highest tested concentration (10.0 μg g^-1), chlorothalonil may have restimulated GSH synthesis in the gills of A. flexuosa, although the prooxidant activity has induced effects. This study contributes to assessing the environmental risk of chlorothalonil in sediment for non-target marine and estuarine organisms.

Toxicity of antifouling biocides on planktonic and benthic neotropical species

Organotin-based (OTs: TBT and TPT) antifouling paints have been banned worldwide, but recent inputs have been detected in tropical coastal areas. However, there is a lack of studies evaluating the toxicity of both legacy and their substitute antifouling booster biocides (e.g., Irgarol and diuron) on neotropical species. Therefore, the acute toxicity of four antifouling biocides (TBT, TPT, Irgarol, and diuron) was investigated using the marine planktonic organisms Acartia tonsa and Mysidopsis juniae, the estuarine tanaid Monokalliapseudes schubarti (water exposure), and the burrowing amphipod Tiburonella viscana (spiked sediment exposure). Results confirmed the high toxicity of the OTs, especially to planktonic species, being about two orders of magnitude higher than Irgarol and diuron. Toxic effects of antifouling compounds were observed at levels currently found in tropical coastal zones, representing a threat to planktonic and benthic invertebrates. Furthermore, deterministic PNEC_{marine sediment} values suggest that environmental hazards in tropical regions may be higher due to the higher sensitivity of tropical organisms. Since regulations on antifouling biocides are still restricted to a few countries, more ecotoxicological studies are needed to derivate environmental quality standards based on realistic scenarios. The present study brings essential contributions regarding the ecological risks of these substances in tropical and subtropical zones.

Development of Antifouling Coatings Based on Quaternary Ammonium Compounds through a Multilayer Approach

The development of polymeric materials as antifouling coatings for aquaculture nets is elaborated in the present work. In this context, cross-linked polymeric systems based on quaternary ammonium compounds (immobilized or releasable) prepared under mild aqueous conditions were introduced as a more environmentally friendly methodology for coating nets on a large scale. To optimize the duration of action of the coatings, a multilayer coating method was applied by combining the antimicrobial organo-soluble copolymer poly(cetyltrimethylammonium 4-styrenesulfonate-co-glycidyl methacrylate) [P(SSAmC16-co-GMA20)] as the first layer with either the water-soluble copolymer poly(vinylbenzyl trimethylammonium chloride-co-acrylic acid) [P(VBCTMAM-co-AA20)] or the water-soluble polymers poly(acrylic acid) (PAA) and poly(hexamethylene guanidine), PHMG, as the second layer. The above-mentioned approach, followed by thermal cross-linking of the polymeric coatings, resulted in stable materials with controlled release of the biocidal species. The coated nets were studied in terms of their antifouling efficiency under accelerated biofouling conditions as well as under real conditions in an aquaculture field. Resistance to biofouling after three water-nutrient replenishments was observed under laboratory accelerated biofouling conditions. In addition, at the end of the field test (day 23) the uncoated nets were completely covered by marine contaminants, while the coated nets remained intact over most of their extent.

Antifouling booster biocides in Latin America and the Caribbean: A 20-year review

This review summarized booster biocides studies from Latin America and the Caribbean during the last two decades. Studies were focused on six countries, with most of them in Brazil. In water and sediment, diuron and Irgarol were the most abundant and frequent biocides, probably due to their former intense use. Antifouling paint particles were also reported and had mainly DCOIT, which is currently the most used booster biocide. Toxicity of individual booster biocides was tested in laboratory, and most effects were related to chlorothalonil, DCOIT, dichlofluanid, and Irgarol, including, but not limited to DNA damage, fertility decrease, and mortality at different trophic levels. This review highlighted the need for further studies on environmental occurrence of booster biocides in Latin America and Caribbean associated to ecotoxicological studies. Such information is essential to determine the potential ecological risks and to create directives regarding safe limits of booster biocides in aquatic systems.

The Lethal and Sub-Lethal Effects of Fluorinated and Copper-Based Pesticides-A Review

In recent decades, pollution levels have increased, mainly as a result of the intensive anthropogenic activities such industrial development, intensive agricultural practices, among others. The impact of metals and organic contaminants is, nowadays, a great concern to the scientific and political communities. Copper compounds are the main sold pesticides in Europe, as well as herbicides, including glyphosate. Diphenyl ethers are the second ones most sold. Glyphosate and copper compounds are intensively studied, but the opposite is seen in the case of diphenyl ethers, including fluorinated pesticides (e.g., oxyfluorfen). Some research has been performed to increase the knowledge about these contaminants, daily inputted on the aquatic systems and with dangerous effects at physical and biochemical levels on the organisms. A wide range of biomarkers (e.g., growth, survival, reproductive success, enzymatic activity, lipid metabolism) has been applied to determine the potential effects in many species. This review intends to: (a) perform a compilation of the knowledge in previous research about the action mode of organic (fluorinated-based herbicide) and inorganic (copper-based pesticides) contaminants; (b) carry out an information survey about the lethal and sub-lethal effects of the fluorinated-based pesticides, namely the oxyfluorfen and the copper-based pesticides, on aquatic species from different trophic levels, according to in vitro and in vivo studies; (c) understand the impact of oxyfluorfen and copper-based pesticides, considering their effects reported in in vitro studies and, simultaneously, the authorized concentrations by legal organizations and the effective concentrations of each pollutant found in the environment. The literature analyzed revealed noxious effects of Cu and oxyfluorfen to aquatic organisms, including freshwater and marine species, even when exposed to the reference as well as to environmental concentrations, thus highlighting the importance of more monitoring and ecotoxicological studies, to chemical pollutants and different species from different ecological niches, to sustain and improve the legislation.

Distribution in marine fish and EDI estimation of contaminants of emerging concern by vortex-assisted matrix solid-phase dispersion and HPLC-MS/MS

Due to their persistence or continuous discharge, toxic substances are present in the aquatic environment, and can bioaccumulate and biomagnify in the food web, generating a significant ecological risk and a threat to human health. The present study assess the occurrence and tissue (muscle, liver, stomach and gills) distribution of 59 anthropogenic contaminants of emerging concern (CECs) in marine fish from Brazil. A simpler and faster analytical methodology based on vortex-assisted matrix solid-phase dispersion (VA-MSPD) and liquid chromatography coupled to tandem mass spectrometry (LC-MS/MS) was developed and validated. Limits of quantification ranged from 3.31 to 114 ng g^-1 dw with recovery rates between 60 and 140 % and relative standard deviation below 20 %. The ultraviolet filters 4-hydroxybenzophenone (4HB) (benzophenone-3 metabolite) and benzocaine (Et-PABA), and the antibacterial salicylic acid were frequently accumulated in muscle and liver at concentrations between 39.5 and 21.0 ngg^-1 dw. The determined concentrations resulted to be lower than the tolerable daily intake recommended by the European Food Safety Authority (EFSA).

Anti-Barnacle Activities of Isothiocyanates Derived from β-Citronellol and Their Structure-Activity Relationships

Antifouling agents with low toxicity are in high demand for sustaining marine industries and the environment. This study aimed to synthesize 15 isothiocyanates derived from β-citronellol and evaluate their antifouling activities and toxicities against cypris larvae of the barnacle Amphibalanus amphitrite. The synthesized isothiocyanates exhibited effective antifouling activities (EC₅₀ =0.10-3.33 μg mL^-1 ) with high therapeutic ratios (LC₅₀ /EC₅₀ >30). Four isothiocyanates with an amide or isocyano group showed great potential as effective antifouling agents (EC₅₀ =0.10-0.32 μg mL^-1 , LC₅₀ /EC₅₀ =104-833). The enantiomers of the isothiocyanates only slightly differed in their antifouling activities. These results may serve as a basis for further research and development of β-citronellol-derived isothiocyanates as effective low-toxic antifouling agents. To the best of our knowledge, this study is the first to report the antifouling activities of isothiocyanates derived from accessible natural products.

Water quality criteria derivation and tiered ecological risk evaluation of antifouling biocides in marine environment

This study provides a comprehensive compilation of published toxicological and environmental data further used to assess the ecological risks of six antifouling biocides, including tributyltin (TBT), Irgarol 1051, Diuron, Chlorothalonil, 4,5-Dichloro-N-octyl-3(2H)-isothiazolone (DCOIT), and Dichlofluanid. The standard maximum concentration and standard continuous concentration of antifouling biocides were derived by the species susceptibility distribution method. Following that, the ecological risk assessment of antifouling biocides in the aquatic environment was conducted using the hazard quotient, margin of safety, joint probability curve, and Monte Carlo random sampling method. The following is a concise list of the antifouling biocide dangers associated with acute and chronic risks: Irgarol 1051 > TBT > Diuron > DCOIT > Chlorothalonil > Dichlofluanid. It is strongly advised that systematic and ongoing monitoring of these biocides in coastal areas take place, as well as the creation of acceptable and efficient environmental protection measures, to safeguard the coastal environment's services and functions.

Green Synthesis of TiO2 Nanoparticles Using Natural Marine Extracts for Antifouling Activity

Titanium dioxide (TiO₂) nanoparticles were synthesized via a novel eco-friendly green chemistry approach using marine natural extracts of two red algae (Bostrychia tenella and Laurencia obtusa), a green alga (Halimeda tuna), and a brown alga (Sargassum filipendula) along with a marine sponge sample identified as Carteriospongia foliascens. X-ray diffraction (XRD), scanning electron microscope (SEM), UV-Vis, X-ray spectroscopy (EDS), X-ray photoelectron spectroscopy (XPS), and Fourier-transform infrared spectroscopy (FTIR) were employed to characterize the crystal structure, surface morphology, and optical properties of the synthesized nanoparticles. Each of the as-synthesized marine extract based TiO₂ nanoparticles was individually incorporated as an antifouling agent to form a newly fabricated marine paint formulation. The newly prepared formulations were applied on unprimed steel panels. A comparative study with a commercial antifouling paint (Sipes Transocean Coatings Optima) was carried out. After 108 days of the coated steel panels' immersion in the Eastern Harbour seawater of Alexandria-Egypt, the prepared paints using B. tenella and C. foliascens extracts demonstrated an excellent antifouling performance toward fouling organisms by inhibiting their settlement and controlling their adhesion onto the immersed panels. In contrast, heavy fouling with barnacles was observed on the surface of the coated panel with the commercial paint. The physicochemical parameters of the seawater surrounding the immersed coated panels were estimated to investigate the influence of the fabricated paint formulations. Interestingly, no effects of the immersed coated panels on the physicochemical characteristics of the surrounding seawater were observed. Based on the obtained results and a comparison with commercially available antifouling products, the marine extract based TiO₂ nanoparticle preparations of B. tenella and C. foliascens are promising candidates for eco-friendly antifouling agents. Based on the obtained results and a comparison with commercially available antifouling products, the marine extract based TiO₂ nanoparticle preparations of B. tenella and C. foliascens are promising candidates for eco-friendly antifouling agents, which could be attributed to the small crystallite sizes of 22.86 and 8.3 nm, respectively, in addition to the incorporation of carbon in the crystal structure of the nanoparticles.

Chemical synthesis and antifouling activity of monoterpene-furan hybrid molecules

Geraniol, a monoterpene, and furan are structural motifs that exhibit antifouling activity. In this study, monoterpene-furan hybrid molecules with potentially enhanced antifouling activity were designed and synthesized. The nine synthetic hybrids showed antifouling activity against the cypris larvae of the barnacle Balanus (Amphibalanus) amphitrite with EC₅₀ values of 1.65-4.70 μg mL^-1. This activity is higher than that of geraniol and the reference furan compound. This hybridization approach to increase antifouling activity is useful and can also be extended to other active structural units.

Environmental and Economic Impact of an Innovative Biocide-Free Antifouling Coating for Naval Applications

The work provides an economic sustainability and environmental impact analysis for the validation of a biocide-free antifouling coating for marine applications able to reduce fuel consumption during navigation, CO₂ emissions, and the overall environmental impacts associated with shipping, thanks to the reduction of incrustation and the avoidance of biocides release into the water. The results, related to the life cycle of the coating of a motor yacht, with an average sailing life of 25 years, show around 8.8% reduction in overall costs compared to a conventional paint, thanks to a more efficient antifouling action, which reduces the annual fuel consumption by ~13,700 kg/y, or ~9.6%. This leads to a reduction in CO₂ emissions, associated with fuel consumption, of ~43.3 ton/y, as well as a lowering of the overall environmental impacts associated with the life cycle of the paint, by almost 10% for the most impactful damage classes, ensuring a greater environmental sustainability of the innovative coating, for the overall service life of the yacht on which it is applied.

Acute Toxicity of a Novel anti-fouling Material Additive DCOIT to Marine Chlorella sp

DCOIT (4,5-dichloro-2-n-octyl-4-isothiazolin-3-one) is the main ingredient in SeaNine-211, a new antifouling agent that replaces organotin compounds to prevent the growth of fouling organisms on board. Biocides from antifoulants can cause problems for marine ecosystems by destroying non-target algal species. This study evaluated the potential adverse effects DCOIT using the Marine Chlorella sp. The concentration of DCOIT were set according to the semi-inhibitory concentrations for acute exposure experiments, and relevant oxidative stress indicators were measured to assess the acute toxic effects. The results showed that the inhibition concentrations (IC50) of DCOIT against Marine Chlorella sp was 2.522 mg/L. The genes related to photosynthesis and antioxidant capacity showed the effect of promoting low concentration and inhibiting high concentration. In addition, based on the ultrastructural observation and the expression analysis of photosynthesis related genes, it was found that DCOIT had a significant effect on plant photosynthesis.

Adding functions to marine infrastructure: Pollutant accumulation, physiological and microbiome changes in sponges attached to floating pontoons inside marinas

The rate of introduction of man-made habitats in coastal environments is growing at an unprecedented pace, as a consequence of the expansion of urban areas. Floating installations, due to their unique hydrodynamic features, are able to provide great opportunities for enhancing water detoxification through the use of sessile, filtering organisms. We assessed whether the application of sponges to floating pontoons could function as a tool for biomonitoring organic and inorganic pollutants and for improving water quality inside a moderately contaminated marina in the NW Mediterranean. Fragments of two common Mediterranean sponges (Petrosia (Petrosia) ficiformis and Ircinia oros) were fixed to either suspended natural fibre nets beneath a floating pontoon or to metal frames deployed on the sea bottom. We assessed the accumulation of organic and inorganic contaminants in sponge fragments and, in order to provide an insight into their health status, we examined changes in their metabolic and oxidative stress responses and associated microbiomes. Fragments of both sponge species filtered out pollutants from seawater on both support types, but generally showed a better physiological and metabolic status when fixed to nets underneath the pontoon than to bottom frames. P. (P) ficiformis maintained a more efficient metabolism and exhibited a lower physiological stress levels and higher stability of the associated microbiome in comparison with I. oros. Our study suggests that the application of sponges to floating pontoon represents a promising nature-based solution to improve the ecological value of urban environments.

Are silicone foul-release coatings a viable and environmentally sustainable alternative to biocidal antifouling coatings in the Baltic Sea region?

To combat unwanted fouling on immersed hulls, biocidal antifouling coatings are commonly applied to vessels trafficking the Baltic Sea. Here, the efficacy, environmental sustainability and market barriers of silicone foul-release coatings (FRCs) was assessed for this region to evaluate their viability as replacements for biocidal coatings. Coated panels were exposed statically over a 1 year period at three locations in the Baltic Sea region to assess the long-term performance of a biocide-free FRC and two copper coatings. The FRC was found to perform equally well or significantly better than the copper coatings. Even though most silicone FRCs on the market are biocide-free, a review of the literature regarding toxic effects and the identity and environmental fate of leachables shows that they may not be completely environmentally benign, simply for the lack of biocides. Nonetheless, FRCs are substantially less toxic compared to biocidal antifouling coatings and their use should be promoted.

Preparation and Properties of Fluorosilicone Fouling-Release Coatings

To improve the antifouling performance of silicone fouling-release coatings, some fluorosilicone and silicone fouling-release coatings were prepared and cured at room temperature with hydroxyl-terminated fluoropolysiloxane (FPS) or hydroxy-terminated polydimethylsiloxane (PDMS) as a film-forming resin, tetraethyl orthosilicate (TEOS) as a crosslinking agent, and dibutyltin dilaurate (DBTDL) as a catalyst. The chemical structure, surface morphology and roughness, tensile properties, and antifouling properties of the coating were studied by infrared spectroscopy, a laser confocal scanning microscope, contact angle measurement, tensile tests, and marine bacteria and benthic diatom attachment tests. The results showed that the FPS coatings were not only hydrophobic but also oleophobic, and the contact angles of the FPS coatings were larger than those of the PDMS coatings. The surface free energies of the FPS coatings were much lower than those of the PDMS coatings. Generally, the fluorine groups can improve the antifouling performance of the coating. Introducing nonreactive silicone oil into PDMS or FPS coatings can improve the antifouling performance of the coating to a certain extent. The prepared fluorosilicone fouling-release coatings showed good application prospects.

Impact of Tralopyril and Triazolyl Glycosylated Chalcone in Human Retinal Cells’ Lipidome

Antifouling (AF) coatings containing booster biocides are used worldwide as one of the most cost-effective ways to prevent the attachment of marine organisms to submerged structures. Nevertheless, many of the commercial biocides, such as Econea® (tralopyril), are toxic in marine environments. For that reason, it is of extreme importance that new efficient AF compounds that do not cause any harm to non-target organisms and humans are designed. In this study, we measured the half-maximal inhibitory concentration (IC50) of a promising nature-inspired AF compound, a triazolyl glycosylated chalcone (compound 1), in an immortalized human retinal pigment epithelial cell line (hTERT-RPE-1) and compared the results with the commercial biocide Econea®. We also investigated the effects of these biocides on the cellular lipidome following an acute (24 h) exposure using liquid chromatography quadrupole time-of-flight mass spectrometry (LC-Q-TOF/MS). Our results showed that compound 1 did not affect viability in hTERT-RPE-1 cells at low concentrations (1 μM), in contrast to Econea®, which caused a 40% reduction in cell viability. In total, 71 lipids were found to be regulated upon exposure to 10 µM of both compounds. Interestingly, both compounds induced changes in lipids involved in cell death, membrane modeling, lipid storage, and oxidative stress, but often in opposing directions. In general, Econea® exposure was associated with an increase in lipid concentrations, while compound 1 exposure resulted in lipid depletion. Our study showed that exposure to human cells at sublethal Econea® concentrations results in the modulation of several lipids that are linked to cell death and survival.

Long-term exposure to antifouling biocide chlorothalonil modulates immunity and biochemical and antioxidant parameters in the blood of olive flounder

In this study, the potential effects of 30-day exposure to environmentally relevant concentrations of chlorothalonil (0, 5, 10, and 20 μg L^-l) were tested in the blood of the economically important olive flounder, Paralichthys olivaceus, using biochemical endpoints. Significant decreases in the enzymatic activities of immunity markers, alternative complements, and lysozymes were detected in the fish exposed to 10 or 20 μg L^-l of chlorothalonil at day 20 or 30. The total immunoglobulin content was lowered in response to 20 μg L^-l chlorothalonil at day 10 and 20, even when later exposed to 5 μg L^-l at day 30. Among the essential blood components, the cortisol level was increased in response to chlorothalonil throughout the study with a decrease in white blood cells, while no changes were observed in hemoglobin, red blood cells, total protein concentration, and glucose in all exposures. The enzymatic activities of the three hepatic toxicity markers, alanine transferases, aspartate transaminase, and alkaline phosphatase, increased by 10 and/or 20 μg L^-l of chlorothalonil. Significant oxidative stress was induced by chlorothalonil in the fish exposed to 10 or 20 μg L^-l of chlorothalonil, as revealed by increased malondialdehyde and fluctuating glutathione levels with increase in the enzymatic activities of antioxidant defense system, including catalase and superoxide dismutase, during exposure. Taken together, these results suggest that long-term exposure to environmentally relevant concentrations of chlorothalonil can affect susceptibility to pathogens through immunosuppression, hepatic toxicity, and oxidative stress in olive flounder. These results can contribute to the monitoring of aquatic environments and ecotoxicological research through the measurement of blood components against waterborne chlorothalonil.

Antifouling Effects of Superhydrophobic Coating on Sessile Marine Invertebrates

Biofouling is a significant problem in the aquaculture and marine shipping industries; thus, various antifouling methods have been developed to prevent the resultant economic losses. In the present study, the superhydrophobic surface of a lotus leaf was bio-mimicked to achieve antifouling. Specifically, fabric substrates with and without superhydrophobic coatings on the surface were installed on the Tongyeong yacht in December 2020 (group A) and April 2021 (group B), and the coverage of the attached invertebrates was recorded every month until August 2021. The coverage of solitary ascidians (Ascidiella aspersa and Ciona robusta) and branching bryozoans (Bugula neritina) was lower on the coated substrates than on the non-coated ones, and coating or non-coating was significantly correlated with the extent of coverage. Superhydrophobic substrates with a low surface energy and micro-nano dual structure may be unsuitable for the attachment of larvae. Therefore, superhydrophobic coating is a more effective and simpler method of antifouling for certain taxa than other antifouling strategies. However, the antifouling effect of the superhydrophobic substrate in group A reduced after 5 months from the first installation; thus, the durability of the antifouling coating should be further improved, and solving this problem remains a major task, necessitating further research.

Biocide vs. Eco-Friendly Antifoulants: Role of the Antioxidative Defence and Settlement in Mytilus galloprovincialis

Antifoulant paints were developed to prevent and reduce biofouling on surfaces immersed in seawater. The widespread use of these substances over the years has led to a significant increase of their presence in the marine environment. These compounds were identified as environmental and human threats. As a result of an international ban, research in the last decade has focused on developing a new generation of benign antifoulant paints. This review outlines the detrimental effects associated with biocide versus eco-friendly antifoulants, highlighting what are effective antifoulants and why there is a need to monitor them. We examine the effects of biocide and eco-friendly antifoulants on the antioxidative defence mechanism and settlement in a higher sessile organism, specifically the Mediterranean mussel, Mytilus galloprovincialis. These antifoulants can indirectly assess the potential of these two parameters in order to outline implementation of sustainable antifoulants.

Preparation and Properties of Environmentally Friendly Marine Antifouling Coatings Based on a Collaborative Strategy

Long-term and green marine antifouling coatings are an important means to prolong the service life of ships and other marine instruments and equipment. To accomplish this, we prepared three new green and high-efficiency antifouling coatings containing phthalimide derivatives inspired by capsaicin (PDIC-AC) by using a collaborative strategy that incorporates self-polishing, fouling repelling, and antifouling properties. Static simulation tests confirmed that the zinc acrylate resin of the PDIC-AC has excellent self-polishing properties due to changes in the roughness, surface free energy, and mass loss. Antifouling tests demonstrated that both PDIC and PDIC-AC possess efficient antibacterial and anti-algal effects. Moreover, marine field tests showed that the PDIC-AC are highly antifouling for at least 9 months, and their antifouling effect is similar to that of an antifouling coating with chlorothalonil (CT-AC). The collaborative strategy in this study can be used to research and develop long-term environmentally friendly antifouling coatings.

The degradation and environmental risk of camptothecin, a promising marine antifoulant

Given the adverse environmental impacts of the antifoulants currently used in marine antifouling paints, such as copper and booster biocides, it is urgent to identify potential substitutes that are environmentally benign. Here, we examined the degradation of camptothecin (a natural product previously identified as an efficient antifoulant in the laboratory and in the field) under various conditions and evaluated the environmental risks associated with its use as a marine antifoulant. We found that camptothecin was rapidly photolyzed in seawater: the half-life of camptothecin was less than 1 d under a light intensity of 1000-20,000 lx and was approximately 0.17 d under sunlight irradiation. At pH 4 and pH 7, camptothecin had half-lives of 30.13 and 16.90 d, respectively; at 4 °C, 25 °C, and 35 °C, the half-lives of camptothecin were 23.90, 21.66, and 26.65 d, respectively. Camptothecin biodegradation in seawater was negligible. The predicted no-effect concentration (PNEC) of camptothecin was 2.19 × 10^-1 μg L^-1, while the average predicted environmental concentrations (PECs) in open seas, shipping lanes, commercial harbors, and marinas were 6.14 × 10^-7, 9.39 × 10^-7, 6.80 × 10^-3, and 5.03 × 10^-2 μg L^-1, respectively. The PEC/PNEC ratio of camptothecin was much lower than 1 (i.e., 2.80 × 10^-6, 4.29 × 10^-6, 3.11 × 10^-2, and 2.30 × 10^-1 for open seas, shipping lanes, commercial harbors, and marinas, respectively), indicating that the use of camptothecin as a marine antifoulant posed little environmental risk.

Mexican paradise under threat: The impact of antifouling biocides along the Yucatán Peninsula

Levels of booster biocides (Irgarol, diuron, chlorothalonil, dichlofluanid and DCOIT), organotins (TBT, DBT, MBT, TPhT, DPhT and MPhT) and antifouling paint particles (APPs) were assessed in sediments of sites under the influence of maritime activities along the coastal zone of the Yucatán Peninsula, Mexico. Imposex incidence and organotin levels were also evaluated in seven caenogastropod species. The incidence of imposex was detected in five species from sites nearby fishing harbors and marinas, including the first reports to Gemophos tinctus and Melongena bispinosa. Butyltins levels were higher than phenyltins in gastropod tissues, sediments, and APPs. Regarding booster biocides, chlorothalonil was the most frequently detected compound and DCOIT was the most abundant biocide in sediments. DCOIT levels were registered in APPs from fishing harbors and marina areas. In addition, the highest levels of TBT, Irgarol, diuron and DCOIT exceeded the threshold limits set by international sediment quality guidelines, indicating that toxic effects could be expected in some of the studied areas, thus being a potential threat to marine life. Based on such outputs, Mexico urgently needs to adopt restrictive actions aiming at conserving the rich biological heritage of the Yucatán Peninsula.

Anti-barnacle biofouling coatings for the protection of marine vessels: synthesis and progress

Marine biofouling has gnawed both mobile and non-mobile marine structures since time immemorial, leading to the deterioration of designed operational capabilities as well as a loss of valuable economic revenues. Mitigation of biofouling has been the primary focus of researchers and scientists from across the globe to save billions of dollars wasted due to the biological fouling of marine structures. The availability of an appropriate environment along with favorable substrata initiates biofilm formation within a few minutes. The crucial element in establishing a gelatinous biofilm is the excreted metabolites of destructive nature and exopolymeric substances (EPSs). These help in securing as well as signaling numerous foulants to establish themselves on this substrate. The larvae of various benthic invertebrates adhere to these suitable surfaces and transform from juveniles to adult barnacles depending upon the environment. Despite biofouling being characteristically witnessed for a month or lengthier timeframe, the preliminary phases of the fouling process typically transpire on a much lesser timescale. A few natural and synthetic additives had demonstrated excellent non-toxic anti barnacle establishment capability; however, further development into commercial products is still far-fetched. This review collates the specific anti-barnacle coatings, emphasizing natural additives, their sources of extraction, general life cycle analysis, and concluding future perspectives of this niche product.

Biocides in antifouling paint formulations currently registered for use

Antifouling paints incorporate biocides in their composition seeking to avoid or minimize the settlement and growing of undesirable fouling organisms. Therefore, biocides are released into the aquatic environments also affecting several nontarget organisms and, thus, compromising ecosystems. Despite global efforts to investigate the environmental occurrence and toxicity of biocides currently used in antifouling paints, the specific active ingredients that have been used in commercial products are poorly known. Thus, the present study assessed the frequencies of occurrence and relative concentrations of biocides in antifouling paint formulations registered for marketing worldwide. The main data were obtained from databases of governmental agencies, business associations, and safety data sheets from paint manufacturers around the world. The results pointed out for 25 active ingredients currently used as biocides, where up to six biocides have been simultaneously used in the examined formulations. Cuprous oxide, copper pyrithione, zinc pyrithione, zineb, DCOIT, and cuprous thiocyanate were the most frequent ones, with mean relative concentrations of 35.9 ± 12.8%, 2.9 ± 1.6%, 4.0 ± 5.3%, 5.4 ± 2.0%, 1.9 ± 1.9%, and 18.1 ± 8.0% (w/w) of respective biocide present in the antifouling paint formulations. Surprisingly, antifouling paints containing TBT as an active ingredient are still being registered for commercialization nowadays. These results can be applied as a proxy of biocides that are possibly being used by antifouling systems and, consequently, released into the aquatic environment, which can help to prioritize the active ingredients that should be addressed in future studies.

Effects of short-term exposure to tralopyril on physiological indexes and endocrine function in turbot (Scophthalmus maximus)

Tralopyril is an emerging marine antifouling agent with potential toxic effects on non-target aquatic organisms. To evaluate the toxicity of tralopyril, to turbot (Scophthalmus maximus), we assessed biomarkers, including oxidative stress, neurotoxicity, and osmotic homeostasis regulation enzymes, after a 7-day exposure to tralopyril (5 μg/L, 15 μg/L, 30 μg/L). Superoxide dismutase activity was significantly decreased at 30 μg/L, and Ca²⁺-Mg²⁺-ATPase activity in the gills was significantly increased at 15 μg/L and 30 μg/L. No statistically significant differences in the responses of acetylcholinesterase and nitric oxide were detected. In addition, 15 μg/L and 30 μg/L tralopyril induced hyperthyroidism, reflected by significantly increased of T3 levels. The expression levels of hypothalamus-pituitary-thyroid axis-related genes were also upregulated. The molecular docking results showed that the thyroid system disruption was not caused by competitive binding to the receptor. In addition, the integrated biomarker response index showed that 15 μg/L tralopyril had the greatest effect on turbot. In general, tralopyril caused oxidative damage, affected energy metabolism, and interfered with the endocrine system. These findings could provide reference data for assessing the ecological risk of tralopyril in marine environments.

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.

Effective Synthesis and Antifouling Activity of Dolastatin 16 Derivatives

Some derivatives of dolastatin 16, a depsipeptide natural product first obtained from the sea hare Dolabella auricularia, were synthesized through second-generation synthesis of two unusual amino acids, dolaphenvaline and dolamethylleuine. The second-generation synthesis enabled derivatizations such as functionalization of the aromatic ring in dolaphenvaline. The derivatives of fragments and whole structures were evaluated for antifouling activity against the cypris larvae of Amphibalanus amphitrite. Small fragments inhibited the settlement of the cypris larvae at potent to moderate concentrations (EC50 = 0.60-4.62 μg/mL), although dolastatin 16 with a substituent on the aromatic ring (24) was much less potent than dolastatin 16.

Effects of tralopyril on histological, biochemical and molecular impacts in Pacific oyster, Crassostrea gigas

Recently, the toxic effects of tralopyril, as a new antifouling biocide, on aquatic organisms have aroused widespread attention about the potential toxicity. However, the mechanism of tralopyril on marine mollusks has not been elaborated clearly. In this study, the histological, biochemical and molecular impacts of tralopyril on adult Crassostrea gigas were investigated. The results indicated that the 96 h LC50 of tralopyril to adult Crassostrea gigas was 911 μg/L. After exposure to tralopyril (0, 40, 80 and 160 μg/L) for 6 days, the mantle mucus secretion coverage ratio of Crassostrea gigas was increased with a dose-dependent pattern. Catalase (CAT) activity was significantly increased, amylase (AMS) activity, acid phosphatase (ACP) activity and calcium ion (Ca²⁺) concentration significantly decreased. Meanwhile, integrated biomarker responses (IBR) index suggested that higher concentrations of tralopyril caused severer damage to Crassostrea gigas. In addition, the mRNA expression levels of biomineralization related genes in the mantle were significantly upregulated. Collectively, this study firstly revealed the histological, biochemical and molecular impacts of tralopyril exposure on adult Crassostrea gigas, which provided new insights for understanding the toxicity of tralopyril in marine mollusks.

One-pot method for preparation of capsaicin-containing double-network hydrogels for marine antifouling

Marine biofouling which interferes with normal marine operation and also causes huge economic loss has become a worldwide problem. With the development of society, there is an urgent need to develop non-toxic and efficient anti-fouling strategies. Capsaicin is an environmentally friendly antifouling agent, but controlling the stable release of capsaicin from the coating is still a challenge to be solved. To achieve long-lasting antifouling property, in this work, we incorporate a derivative of capsaicin N-(4-hydroxy-3-methoxybenzyl)acrylamide (HMBA) to prepare double network (DN) hydrogels and make HMBA a part of the polymer network. Polyvinyl alcohol (PVA) has good hydrophilicity, and as a soft and ductile network, acrylamide (AM) and HMBA can polymerize to generate a rigid and brittle network. By adjusting the content of HMBA in the DN hydrogels, we can obtain a PVA–PAHX hydrogel with high mechanical strength, low swelling rate, and excellent antifouling effect, which provides a feasible way for the practical application of a hydrogel coating in long-term marine antifouling.

Double-network hydrogel coatings containing capsaicin analogs were prepared by a one-pot method based on a green strategy, by incorporating a derivative of capsaicin N-(4-hydroxy-3-methoxybenzyl) acrylamide into the polymer network. An antifouling effect can be achieved.

A multi-bioassay integrated approach to assess antifouling potential of extracts from the Mediterranean sponge Ircinia oros

The phylum Porifera and their symbionts produce a wide variety of bioactive compounds, playing a central role in their ecology and evolution. In this study, four different extracts (obtained by non-polar and semi-polar extraction methodologies) of the Mediterranean sponge Ircinia oros were tested through a multi-bioassay integrated approach to assess their antifouling potential. Tests were performed using three common species, associated with three different endpoints: the marine bacterium Aliivibrio fischeri (inhibition of bioluminescence), the marine diatom Phaeodactylum tricornutum (inhibition of growth), and different development stages of the brackish water serpulid Ficopomatus enigmaticus (gametes: sperm motion, vitality inhibition and cellular damage; larvae: development; adults: AChE (acetylcholinesterase)-inhibitory activity). The effects of extracts were species specific and did not vary among different extraction methodologies. In particular, no significant reduction of bioluminescence of A. fischeri was observed for all tested samples. By contrast, extracts inhibited P. tricornutum growth and had toxic effects on different F. enigmaticus' developmental stages. Our results suggest that the proposed test battery can be considered a suitable tool as bioactivity screening of marine natural products.

Mechanistic revealing of reproductive behavior impairment in male guppy (Poecilia reticulata) induced by environmentally realistic 2,2'-dithiobis-pyridine exposure

Although (PS)₂, the primary degradation product of emerging antifouling biocides metal pyrithiones (MePTs), can disrupt the reproductive behavior of fish at an environmentally relevant ng/L level, the underlying mechanism is still largely unknown. This study exposed sexually mature male guppy (Poecilia reticulata) to 20, 200, and 2000 ng/L (PS)₂ to explore the compromised effect of (PS)₂ on reproductive behavior through a realistic competing scenario. The results showed that (PS)₂ suppressed male guppies' sexual interest to stimulus females, reduced their competitive behavior frequencies toward rival males, and decreased their mating time and frequency. (PS)₂ exposure did not affect male guppies' secondary sexual characteristics or induce estrogenic activity. Whole-brain transcriptome sequencing identified 1070 differentially expressed genes (DEGs) with 872 up-regulated genes, which were functionally enriched into Gene Ontology terms pertaining to extracellular matrix (ECM) and extracellular region. KEGG enrichment for the DEGs uncovered that the activations of ECM-receptor interaction and focal adhesion pathways could be the underlying molecular mechanism implicated in the (PS)₂ induced reproductive behavior impairment. This work would deliver a substantial contribution to the understanding of the ecological safety of MePTs biocides.

Synthesis and Antifouling Activity Evaluation of Analogs of Bromosphaerol, a Brominated Diterpene Isolated from the Red Alga Sphaerococcus coronopifolius

Marine biofouling is an epibiotic biological process that affects almost any kind of submerged surface, causing globally significant economic problems mainly for the shipping industry and aquaculture companies, and its prevention so far has been associated with adverse environmental effects for non-target organisms. Previously, we have identified bromosphaerol (1), a brominated diterpene isolated from the red alga Sphaerococcus coronopifolius, as a promising agent with significant antifouling activity, exerting strong anti-settlement activity against larvae of Amphibalanus (Balanus) amphitrite and very low toxicity. The significant antifouling activity and low toxicity of bromosphaerol (1) motivated us to explore its chemistry, aiming to optimize its antifouling potential through the preparation of a number of analogs. Following different synthetic routes, we successfully synthesized 15 structural analogs (2–16) of bromosphaerol (1), decorated with different functional groups. The anti-settlement activity (EC₅₀) and the degree of toxicity (LC₅₀) of the bromosphaerol derivatives were evaluated using cyprids and nauplii of the cirriped crustacean A. amphitrite as a model organism. Derivatives 2, 4, and 6–16 showed diverse levels of antifouling activity. Among them, compounds 9 and 13 can be considered as well-performing antifoulants, exerting their activity through a non-toxic mechanism.

Microplastics in the Weddell Sea (Antarctica): A Forensic Approach for Discrimination between Environmental and Vessel-Induced Microplastics

Microplastic (MP) pollution has been found in the Southern Ocean surrounding Antarctica, but many local regions within this vast area remain uninvestigated. The remote Weddell Sea contributes to the global thermohaline circulation, and one of the two Antarctic gyres is located in that region. In the present study, we evaluate MP (>300 μm) concentration and composition in surface (n = 34) and subsurface water samples (n = 79, ∼11.2 m depth) of the Weddell Sea. All putative MP were analyzed by attenuated total reflection Fourier transform infrared (ATR-FTIR) spectroscopy. MP was found in 65% of surface and 11.4% of subsurface samples, with mean (±standard deviation (SD)) concentrations of 0.01 (±0.01 SD) MP m^-3 and 0.04 (±0.1 SD) MP m^-3, respectively, being within the range of previously reported values for regions south of the Polar Front. Additionally, we aimed to determine whether identified paint fragments (n = 394) derive from the research vessel. Environmentally sampled fragments (n = 101) with similar ATR-FTIR spectra to reference paints from the research vessel and fresh paint references generated in the laboratory were further subjected to micro-X-ray fluorescence spectroscopy (μXRF) to compare their elemental composition. This revealed that 45.5% of all recovered MP derived from vessel-induced contamination. However, 11% of the measured fragments could be distinguished from the reference paints via their elemental composition. This study demonstrates that differentiation based purely on visual characteristics and FTIR spectroscopy might not be sufficient for accurately determining sample contamination sources.