Sea-nine antifoulant: an environmentally acceptable alternative to organotin antifoulants

Biomarkers responses in the amphipod Tiburonella viscana exposed to the biocide DCOIT and CO2-induced ocean acidification

Anthropogenic carbon dioxide emissions (CO2) have led to climate change and marine acidification, with an estimated decrease in ocean surface pH of 0.3-0.4 units by the end of the current century. Chemical pollution also contributes to biodiversity loss in marine environments. This issue is particularly critical in areas under pressure from shipping activities, where the introduction of new antifouling system formulations poses a major threat to non-target species. The biocide DCOIT is the most widely used alternative to organotin compounds due to its rapid degradation in seawater. The toxicity of waterborne DCOIT to marine organisms has been documented, but sediment-bound effects are limited to apical responses and pH scenarios corresponding to current levels. In this study, we determine in a combined way, the toxicity of DCOIT under marine acidification scenarios assessing biomarker responses in the burrowing amphipod Tiburonella viscana as a parameter of sublethal effects in solid phase exposures. Environmental relevant concentrations of DCOIT caused inhibition of the enzyme glutathione S-transferases (GST), changed acetylcholinesterase-like activity (AChE), and increased DNA damage at pHs of 7.7 and 7.4. For lipid peroxidation (LPO), increased levels caused by DCOIT were found for both control (8.1) and intermediate (7.7) conditions of pH. Our data provides evidence of oxidative and genotoxic effects induced by DCOIT, with activation of detoxification and defense mechanisms in T. viscana. These results are important for ecological risk assessment and managing of antifouling paint biocides in multiple stressors scenarios.

Algicidal activity and mechanism of novel Bacillamide a derivative against red tide algae Skeletonema costatum and Prorocentrum minimum

Frequent red tide outbreaks pose a serious threat to biodiversity and the safety of aquatic ecosystems. Bacillamides showed algicidal activity against algae. However, the low natural concentrations and their structural complexity hinder development of these molecules. Inspired by the natrual algicide Bacillamide A, a series of thiourea derivatives were synthesized. Bacillamide A derivative (3B) showed excellent algicidal activity against S. costatum (EC50 = 0.52 μg/mL) and P. minimum (EC50 = 2.99 μg/mL), respectively. In addition, it has low toxicity to mammals and is less toxic than copper sulfate. 3B treatment resulted in loss of algal cell integrity. It also decreased the Chlorophyll a content and Fv/fm of algal cells, while increasing the levels of malondialdehyde content, superoxide dismutase, and reactive oxygen. 3B also induced expression of the photosynthetic genes, including psaB, psbB, as well as the antioxidant genes SOD2 and CAT. This study demonstrates that Bacillamide A derivatives could provide a safer alternative for red tide algal management.

Thyroid Endocrine Disruption and Mechanism of the Marine Antifouling Pollutant 4,5-Dichloro-2-n-octyl-4-isothiazolin-3-one

The antifoulant 4,5-dichloro-2-n-octyl-4-isothiazolin-3-one (DCOIT) is an emerging pollutant in the marine environment, which may disrupt the thyroid endocrine system. However, DCOIT toxicity in relation to thyroid endocrine disruption and the underlying mechanisms remains largely unclear. In this study, in vivo, in silico, in vitro, and ex vivo assays were performed to clarify DCOIT's thyroid toxicity. First, marine medaka (Oryzias melastigma) were exposed to environmentally realistic concentrations of DCOIT for an entire life cycle. The results demonstrated that DCOIT exposure potently stimulated the hypothalamic-pituitary-thyroid axis, characterized by hyperthyroidism symptom induction and prevalent key gene and protein upregulation in the brain. Moreover, the in silico and in vitro results evidenced that DCOIT could bind to thyroid hormone receptor β (TRβ) and interact synergistically with triiodothyronine, thus promoting GH3 cell proliferation. The CUT&Tag experiment found that DCOIT interfered with the affinity fingerprint of TRβ to target genes implicated in thyroid hormone signaling cascade regulation. Furthermore, ex vivo, Chem-seq revealed that DCOIT directly bound to the genomic sequences of thyrotropin-releasing hormone receptor b and thyroid-stimulating hormone receptor in marine medaka brain tissues. In conclusion, the current multifaceted evidence confirmed that DCOIT has a strong potency for thyroid endocrine system disruption and provided comprehensive insights into its toxicity mechanisms.

A Chemical Toolbox to Unveil Synthetic Nature-Inspired Antifouling (NIAF) Compounds

The current scenario of antifouling (AF) strategies to prevent the natural process of marine biofouling is based in the use of antifouling paints containing different active ingredients, believed to be harmful to the marine environment. Compounds called booster biocides are being used with copper as an alternative to the traditionally used tributyltin (TBT); however, some of them were recently found to accumulate in coastal waters at levels that are deleterious for marine organisms. More ecological alternatives were pursued, some of them based on the marine organism mechanisms' production of specialized metabolites with AF activity. However, despite the investment in research on AF natural products and their synthetic analogues, many studies showed that natural AF alternatives do not perform as well as the traditional metal-based ones. In the search for AF agents with better performance and to understand which molecular motifs were responsible for the AF activity of natural compounds, synthetic analogues were produced and investigated for structure-AF activity relationship studies. This review is a comprehensive compilation of AF compounds synthesized in the last two decades with highlights on the data concerning their structure-activity relationship, providing a chemical toolbox for researchers to develop efficient nature-inspired AF agents.

Unraveling the binding behavior of the antifouling biocide 4,5-dichloro-2-n-octyl-4-isothiazolin-3-one with human serum albumin: Multi-spectroscopic, atomic force microscope, computational simulation, and esterase activity

As a marine antifouling biocide, 4,5-dichloro-2-n-octyl-4-isothiazolin-3-one (DCOIT) exhibited high toxicity to marine organisms. This study investigated the interaction between DCOIT and human serum albumin (HSA) using several spectroscopic techniques combined with computer prediction methods. The UV-vis absorption spectra, Stern-Volmer constant (KSV) and fluorescence resonance energy transfer (FRET) results indicated that DCOIT caused static quenching of HSA fluorescence. The ΔG°, ΔH° and ΔS° values were -31.03 ± 0.17 kJ·mol-1, -133.54 ± 0.88 kJ·mol-1 and -348.46 ± 2.86 J.mol-1·K-1, respectively, suggesting that van der Waals forces and hydrogen bonds governed the spontaneous formation of the complex. Synchronous fluorescence and circular dichroism (CD) spectroscopy observed the burial of Trp residues within HSA and the unfolding of HSA secondary structure induced by DCOIT. Three-dimensional (3D) fluorescence and Atomic Force Microscopy (AFM) further detected DCOIT-induced loosening of HSA peptide chain structure. Site displacement experiments indicated that DCOIT binding at site I of HSA. Computational predictions indicated that hydrophobic interactions were also essential in the complex. The increased RMSD, Rg, SASA, and RMSF confirmed that DCOIT weakened the stability and compactness of HSA, rendering residues more flexible. Lastly, esterase activity assays demonstrated that DCOIT inhibited esterase activity and interfered with the human detoxification process.

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.

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.

Developmental cardiotoxicity of 4,5-dichloro-2-n-octyl-4-isothiazolin-3-one (DCOIT) in marine medaka (Oryzias melastigma)

The application of 4,5-dichloro-2-n-octyl-4-isothiazolin-3-one (DCOIT) as an antifouling biocide causes high toxicity to non-target marine organisms. To examine the developmental cardiotoxicity and mechanisms of DCOIT, we concurrently performed sub-chronic exposure and life-cycle exposure experiments using marine medaka embryos. After sub-chronic exposure to DCOIT at 1, 3, 10, and 33 μg/L, cardiac defects were caused by upregulation of cardiac gene transcriptions, decreasing heart size, and accelerating heartbeat. Hyperthyroidism in medaka larvae was identified as the cause of developmental cardiotoxicity of DCOIT sub-chronic exposure. In addition, parental life-cycle exposure to 1, 3, and 10 μg/L DCOIT led to transgenerational impairment of cardiogenesis in offspring medaka. A crossbreeding strategy discriminated a concentration-dependent mechanism of transgenerational cardiotoxicity. At 1 μg/L, the DCOIT-exposed female parent transferred a significantly higher amount of triiodothyronine (T3) hormone to offspring, corresponding to an accelerated heart rate. However, DCOIT at higher exposure concentrations modified the methylome imprinting in larval offspring, which was associated with cardiac dysfunction. Overall, the findings provide novel insights into the developmental cardiotoxicity of DCOIT. The high risks of DCOIT-even at environmentally realistic concentrations-raise concerns about its applicability as an antifoulant in a marine environment.

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.

Scientific Investigation of Antifouling Activity from Biological Agents and Distribution of Marine Foulers-Coastal Areas of Tamil Nadu

Biofouling is the result of a biological process that is the accumulation of micro- and macro-organisms on the surfaces of the ship which causes serious environmental problems. The consequence of biofouling includes modifying the hydrodynamic response, affecting heat exchange, can make structures heavier, accelerate or generating corrosion, biodegradation, increasing the fatigue of certain materials, and blocking mechanical functions. It causes severe problems for the objects in the water such as ships and buoys. Also, its impact on shellfish and other aquaculture was sometimes devastating. The main scope of this study is to review the currently available biocides from biological agents for marine submerged foulants and marine foulers that are present around the coastal areas of Tamil Nadu. Biological anti-fouling methods are preferred than that of the chemical and physical anti-fouling methods as it have some toxic effects on the non targeted marine biodiversity. This study focuses on the marine foulers that are present around the coastal areas of Tamil Nadu which will be helpful for the researchers to discover the suitable anti-foulers from a biological source, which will be very useful to protect the marine ecosystem and marine economy. A total of 182 antifouling compounds from marine biological sources were discovered. The marine microbes, Penicillium sp. and Pseudoalteromonas issachenkonii, were reported to possess EC50. The survey results obtained from this study show that Chennai coastal region has a lot of barnacles, and 8 different species were present in Pondicherry region.

Adults of Sun Coral Tubastraea coccinea (Lesson 1829) Are Resistant to New Antifouling Biocides

Biocides used in antifouling (AF) paints, such as 4,5-dichlorine-2-n-octyl-4-isothiazole-3-one (DCOIT), can gradually leach into the environment. Some AF compounds can persist in the marine environment and cause harmful effects to non-target organisms. Nanoengineered materials, such as mesoporous silica nanocapsules (SiNCs) containing AF compounds, have been developed to control their release rate and reduce their toxicity to aquatic organisms. This study aimed to evaluate the acute toxicity of new nanoengineered materials, SiNC-DCOIT and a silver-coated form (SiNC-DCOIT-Ag), as well as the free form of DCOIT and empty nanocapsules (SiNCs), on the sun coral Tubastraea coccinea. T. coccinea is an invasive species and can be an alternative test organism for evaluating the risks to native species, as most native corals are currently threatened. The colonies were collected from the Alcatrazes Archipelago, SP, Brazil, and acclimatized to laboratory conditions. They were exposed for 96 h to different concentrations of the tested substances: 3.33, 10, 33, and 100 µg L-1 of free DCOIT; 500, 1000, 2000, and 4000 µg L-1 of SiNC; and 74.1, 222.2, 666.7, and 2000 µg L-1 of SiNC-DCOIT and SiNC-DCOIT-Ag. The test chambers consisted of 500 mL flasks containing the test solutions, and the tests were maintained under constant aeration, a constant temperature of 23 ± 2 °C, and photoperiod of 12 h:12 h (light/dark). At the end of the experiments, no lethal effect was observed; however, some sublethal effects were noticeable, such as the exposure of the skeleton in most of the concentrations and replicates, except for the controls, and embrittlement at higher concentrations. Adults of T. coccinea were considered slightly sensitive to the tested substances. This resistance may indicate a greater capacity for proliferation in the species, which is favored in substrates containing antifouling paints, to the detriment of the native species.

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.

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.

Water and sediment toxicity and hazard assessment of DCOIT towards neotropical marine organisms

DCOIT is an effective antifouling biocide, which presence in the environment and toxicity towards non-target species has been generating great concern. This study evaluated the waterborne toxicity of DCOIT on marine invertebrates (i.e., survival of brine shrimp Artemia sp., larval development of the sea urchin Echinometra lucunter and the mussel Perna perna), as well as DCOIT-spiked-sediment toxicity on the fecundity rate of the copepod Nitrocra sp. And the mortality of the amphipod Tiburonella viscana. The data outcomes were used to calculate environmental hazards and risks, which were compared to their corresponding values obtained from temperate regions. Waterborne toxicity can be summarized as follows: Artemia sp. (LC_50-48h = 163 (135-169) μg/L), E. lucunter (EC_50-36h = 33.9 (17-65) μg/L), and P. perna (EC_50-48h = 8.3 (7-9) μg/L). For whole-sediment toxicity, metrics were calculated for T. viscana (LC_50-10d = 0.5 (0.1-2.6) μg/g) and Nitrocra sp, (EC_50-10d = 200 (10-480) μg/kg). The DCOIT hazard was assessed for both tropical and non-tropical pelagic organisms. The predicted no-effect concentration (PNEC) for tropical species (0.19 μg/L) was 1.7-fold lower than that for non-tropical organisms (0.34 μg/L). In whole-sediment exposures, DCOIT presented a PNEC of 0.97 μg/kg, and the risk quotients (RQs) were >1 for areas with constant input of DCOIT such as ports ship/boatyards, marinas, and maritime traffic zones of Korea, Japan, Spain, Malaysia, Indonesia, Vietnam, and Brazil. The presented data are important for supporting the establishment of policies and regulations for booster biocides worldwide.

Hydrogel-Anchored Fe-Based Amorphous Coatings with Integrated Antifouling and Anticorrosion Functionality

Biofouling and corrosion of underwater equipment induced by marine organisms have become major issues in the marine industry. The superior corrosion resistance of Fe-based amorphous coatings makes them suitable for marine applications; however, they have a poor antifouling ability. In this work, a hydrogel-anchored amorphous (HAM) coating with satisfactory antifouling and anticorrosion performance is designed, utilizing an interfacial engineering strategy involving micropatterning, surface hydroxylation, and a dopamine intermediate layer to increase the adhesion strength between the hydrogel layer and the amorphous coating. The as-obtained HAM coating exhibits exceptional antifouling properties, achieving 99.8% resistance to algae, 100% resistance to mussels, and excellent biocorrosion resistance against Pseudomonas aeruginosa. Antifouling and anticorrosion performance of the HAM coating was also explored by conducting a marine field test in the East China Sea, and no signs of corrosion and fouling are observed after 1 month of immersion. It is revealed that the outstanding antifouling properties stem from the killing-resisting-camouflaging trinity that resists organism attachment across different length scales, and the excellent anticorrosion performance originates from the remarkable barrier of the amorphous coating against Cl^- ion diffusion and microbe-induced biocorrosion. This work presents a novel methodology for designing marine protective coating with excellent antifouling and anticorrosion properties.

Toxicological signature for thyroid endocrine disruption of dichlorooctylisothiazolinone in zebrafish larvae

Dichlorooctylisothiazolinone (DCOIT), which is one of the isothiazolinone preservatives, is applied to water-based adhesives in food packaging. This study investigated the effects of DCOIT on the embryonic growth and thyroid endocrine system using zebrafish. Organism-level (hatchability, survival, and growth), hormone-level (triiodothyronine (T3) and thyroxine (T4)), gene-level (genes associated with the hypothalamus-pituitary-thyroid axis), and microRNA-level (microRNAs related to thyroid endocrine disruption) endpoints were measured. Significant rise in embryonic coagulation and delayed hatching (≥0.3 μg/L), and decreased larval length (30 μg/L) were observed in fish exposed to DCOIT. Lower contents of T3 and T4 were observed after exposure to DCOIT, which was accompanied by the upregulation of genes associated with the thyrotropin releasing hormone and thyroid stimulating hormone and the downregulation of genes associated with the thyroid hormone receptors and deiodination. Strong influence of DCOIT on dre-miR-193b and -499 may be a critical mechanism to inhibit transcription of trαa and trβ, which in turn may affect thyroid hormones and development of the organism. Our findings suggest that hypothyroidism induced by the exposure to DCOIT is potentially associated with genetic and microRNA-level changes, which eventually affects development.

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.

Antifouling coatings can reduce algal growth while preserving coral settlement

In the early stages after larval settlement, coral spat can be rapidly overgrown and outcompeted by algae, reducing overall survival for coral reef replenishment and supply for restoration programs. Here we investigated three antifouling (AF) coatings for their ability to inhibit algal fouling on coral settlement plugs, a commonly-used restoration substrate. Plugs were either fully or partially coated with the AF coatings and incubated in mesocosm systems with partial recirculation for 37 days to track fouling succession. In addition, settlement of Acropora tenuis larvae was measured to determine whether AF coatings were a settlement deterrent. Uncoated control plugs became heavily fouled, yielding only 4–8% bare substrate on upper surfaces after 37 days. During this period, an encapsulated dichlorooctylisothiazolinone (DCOIT)-coating was most effective in reducing fouling, yielding 61–63% bare substrate. Antiadhesive and cerium dioxide (CeO_2−x) nanoparticle (NP) coatings were less effective, yielding 11–17% and 2% bare substrate, respectively. Average settlement of A. tenuis larvae on the three types of AF-coated plugs did not statistically differ from settlement on uncoated controls. However, settlement on the NP-coating was generally the highest and was significantly higher than settlement found on the antiadhesive- and DCOIT-coating. Furthermore, on plugs only partially-covered with AF coatings, larval settlement on coated NP- areas was significantly higher than settlement on coated antiadhesive- and DCOIT-areas. These results demonstrate that AF coatings can reduce fouling intensity on biologically-relevant timescales while preserving robust levels of coral settlement. This represents an important step towards reducing fine-scale competition with benthic fouling organisms in coral breeding and propagation.

Toxicity of innovative antifouling additives on an early life stage of the oyster Crassostrea gigas: short- and long-term exposure effects

Recent advances in nanotechnology have allowed the encapsulation of hazardous antifouling (AF) biocides in silica mesoporous nanocapsules (SiNC) reducing their short-term toxicity. However, the chronic effects of such novel nanoadditives remain understudied. The present study aimed to assess short- and long-term sub-lethal effects of soluble forms (DCOIT and Ag) and nanostructured forms (SiNC-DCOIT and SiNC-DCOIT-Ag) of two AF biocides and the "empty" nanocapsule (SiNC) on juveniles of Crassostrea gigas after 96 h and 14 days of exposure. Juvenile oysters exposed for a short period to free DCOIT and AgNO₃ presented worse physiological status comparing with those exposed to the nanostructured forms. The long-term exposure to DCOIT and Ag⁺ caused an extensive biochemical impairment comparing with the tested nanomaterials, which included oxidative damage, activation of the antioxidant defense system, and neurotransmission impairment. Despite the negative effects mostly observed on the health condition index and AChE, the encapsulation of the abovementioned AF biocides into SiNC seems to be a technological advantage towards the development of AF nanoadditives with lower long-term toxicity comparing with the soluble forms of such biocides.

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.

A preliminary study on multi-level biomarkers response of the tropical oyster Crassostrea brasiliana to exposure to the antifouling biocide DCOIT

This study investigated the sublethal effects of environmentally relevant concentrations of DCOIT on the neotropical oyster Crassostrea brasiliana. Gills and digestive glands of animals exposed to increasing concentrations of DCOIT were analyzed for biochemical, cellular, and histopathological responses. Exposure to DCOIT (0.2 to 151 μg L^-1) for 120 h triggered oxidative stress in both tissues (through the modulation of GPX, GST, GSH and GR), which led to damage of membrane lipids (increase of LPO and reduction of the NRRT). DCOIT increased histopathological pathologies in gills, such as necrosis, lymphocyte infiltration and epithelial desquamation. This study showed that short term exposure to environmental concentrations of DCOIT causes negative effects on C. brasiliana at biochemical, physiological, and histological levels. Therefore, the use of DCOIT as a booster biocide in antifouling paints should be further assessed, as it may cause environmental hazards to marine organisms.

Effects of nanostructure antifouling biocides towards a coral species in the context of global changes

Biofouling prevention is one of the biggest challenges faced by the maritime industry, but antifouling agents commonly impact marine ecosystems. Advances in antifouling technology include the use of nanomaterials. Herein we test an antifouling nano-additive based on the encapsulation of the biocide 4,5-dichloro-2-octyl-4-isothiazolin-3-one (DCOIT) in engineered silica nanocontainers (SiNC). The work aims to assess the biochemical and physiological effects on the symbiotic coral Sarcophyton cf. glaucum caused by (1) thermal stress and (2) DCOIT exposure (free or nanoencapsulated forms), in a climate change scenario. Accordingly, the following hypotheses were addressed: (H1) ocean warming can cause toxicity on S. cf. glaucum; (H2) the nanoencapsulation process decreases DCOIT toxicity towards this species; (H3) the biocide toxicity, free or encapsulated forms, can be affected by ocean warming. Coral fragments were exposed for seven days to DCOIT in both free and encapsulated forms, SiNC and negative controls, under two water temperature regimes (26 °C and 30.5 °C). Coral polyp behavior and photosynthetic efficiency were determined in the holobiont, while biochemical markers were assessed individually in the endosymbiont and coral host. Results showed transient coral polyp retraction and diminished photosynthetic efficiency in the presence of heat stress or free DCOIT, with effects being magnified in the presence of both stressors. The activity of catalase and glutathione-S-transferase were modulated by temperature in each partner of the symbiosis. The shifts in enzymatic activity were more pronounced in the presence of free DCOIT, but to a lower extent for encapsulated DCOIT. Increased levels of oxidative damage were detected under heat conditions. The findings highlight the physiological constrains elicited by the increase of seawater temperature to symbiotic corals and demonstrate that DCOIT toxicity can be minimized through encapsulation in SiNC. The presence of both stressors magnifies toxicity and confirm that ocean warming enhances the vulnerability of tropical photosynthetic corals to local stressors.

DCOIT unbalances the antioxidant defense system in juvenile and adults of the marine bivalve Amarilladesma mactroides (Mollusca: Bivalvia)

DCOIT is a co-biocide that is part of the formulation of the commercial antifouling Sea-Nine 211® and although it is "safe to use", negative effects have been reported on the antioxidant defense system of non-target organisms. Therefore, the objective of this research was to verify and compare the response of antioxidant enzymes of juveniles and adults of Amarilladesma mactroides exposed to DCOIT. The animals were exposed to solvent control (DMSO 0.01%) and DCOIT (measured concentration 0.01 mg/L and 0.13 mg/L) for 96 h, then gills, digestive gland and mantle were collected for analysis of the enzymatic activity of glutathione S-transferase (GST), superoxide dismutase (SOD) and catalase (CAT). The results revealed that adults, in relation to juveniles, have low basal activity of GST and SOD enzymes in the gills and digestive gland and high basal activity of SOD and CAT in the mantle. DCOIT did not alter GST activity in the gills of any life stage, while both concentrations decreased SOD and CAT in adults. In the digestive gland, it was observed that DCOIT (0.13 mg/L) decreased the GST activity in adults and CAT in juveniles, and both concentrations of the co-biocide decreased the SOD and CAT in adults. In the mantle, DCOIT (0.13 mg/L) increased CAT in juveniles. We conclude that juveniles have greater basal activity of antioxidant enzymes than adults and, in addition, DCOIT negatively affected the adults of A. mactroides, mainly decreasing the activity of GST, SOD and CAT in the gills and digestive gland of these organisms.

Ecological risk assessment of booster biocides in sediments of the Brazilian coastal areas

Although booster biocides (Irgarol, diuron, chlorothalonil, dichlofluanid, and DCOIT) have been detected in sediments along the Brazilian coastal areas, the risk associated to their occurrence and levels is still unknown. Thus, the ecological risk of booster biocides to sediment-dwelling organisms from the Brazilian coast was assessed using a risk characterization approach through the Risk Quotient (Measured environmental concentration (MEC)/Predicted no effect concentrations (PNECs)). Sedimentary PNECs for Irgarol, diuron, chlorothalonil and DCOIT were derived based on published ecotoxicological data from both freshwater and marine studies, while a NORMAN methodology was used to derived it for dichlofluanid. Results showed that DCOIT, diuron, Irgarol, chlorothalonil, and dichlofluanid can pose high risk on 47%, 35%, 15%, 1% and 1%, respectively, of the 113 Brazilian sites appraised. Considering the trend of expansion of navigation/maritime activities, DCOIT may worsen its impact over the coastal areas of Brazil, especially ports, but also ship/boatyards, marinas, and maritime traffic zones. The present study is an important contribution to support advance on policy formulation concerning booster biocides worldwide, particularly considering the lack of regulation on the use of antifouling biocides in Brazil.

The Effect of a Zinc-Containing Additive on the Properties of PVC Compounds

Polymeric materials that undergo degradation under the influence of biological media have attracted widespread attention in recent decades. This is due to the ability to eliminate the negative impact on the environment, gradually reducing the scale of plastic waste pollution. At the same time, it remains relevant to ensure the necessary performance characteristics of products for a certain period of use. An important direction in the field of biodegradable composite compositions is the development of nontoxic additives in order to ensure their safe interaction with biological media. In this regard, a method has been developed for the joint production of a new nontoxic plasticizer decyl phenoxyethyl adipate and a biocidal additive of zinc decyl adipate. The effect of the obtained additives on the biodegradation of PVC film samples under natural conditions was studied. The period of biocidal action of zinc compound formed in situ in an amount of 0.3% in the composition of PVC films using the developed plasticizer was determined.

Selectfluor-Promoted Intramolecular N-S Bond Formation of α-Carbamoyl Ketene Dithioacetals in the Presence of Water: Synthesis of Multifunctionalized Isothiazolones

A practical and efficient protocol toward fully substituted isothiazolones through Selectfluor-mediated intramolecular oxidative annulation of α-carbamoyl ketene dithioacetals has been developed in the presence of H₂O and metal-free conditions. Notably, the experimental results reveal that H₂O was crucial to the formation of new N-S bonds and the elimination of alkyl group from the sulfur atom. This protocol provides readily prepared substrates and possesses good functional group tolerance, mild reaction conditions, and operational simplicity, which provides potential access to applications in the pharmaceutical chemistry.

Biodegradation of third-generation organic antifouling biocides and their hydrolysis products in marine model systems

The environmental fate for some selected antifouling biocides, dichlofluanid, tolylfluanid, tralopyril, and medetomidine, is relatively poorly understood with nearly all data derived from the assessment reports. Water/sediment systems and biofilms were used to determine biodegradation of the antifouling biocides. Dichlofluanid and tolylfluanid are known to hydrolyze to form DMSA (N,N-dimethyl-N'-phenylsulfamide) and DMST (N,N-Dimethyl-N'-(4-methylphenyl)sulfamide), respectively. DMSA did not show biodegradation, but it was shown to transform abiotically into N,N-dimethylsulfamide (N,N-DMS). In contrast, the structurally similar DMST did show biodegradation with a half-life of 5.78 days. The resulting transformation product of the biodegradation of DMST is also N,N-DMS. N,N-DMS accounted for the majority of the mass balance after 27 days in the water/sediment systems. Moreover, the biofilm systems also degraded both DMSA and DMST to N,N-DMS. The hydrolysis product of tralopyril, called BCCPCA (3-bromo-5-(4-chlorophenyl)-4-cyano-1 H-pyrrole-3-carboxylic acid), was not metabolized in the experiments and remained persistent. For this compound, a new log K_ow of 2.47 was determined since the previously reported K_ow value seemed to overestimate sediment partitioning. Medetomidine was removed from the water/sediment system, though, not significantly more than the control. However, a transformation product (medetomidine-acid) was detected in the incubation but not in the control, pointing to limited biodegradation. These results show that tolylfluanid can be rapidly removed by biodegradation in the marine environment, while dichlofluanid, tralopyril, and medetomidine remained in the system for a longer period of time. The prolonged stability of these biocides could mean that there is potential for accumulation in the environment. This potential is also there for the DMSA (dichlofluanid) and DMST (tolylfluanid) derived transformation product N,N-DMS, which was recalcitrant.

Rapid and cost-effective multiresidue analysis of pharmaceuticals, personal care products, and antifouling booster biocides in marine sediments using matrix solid phase dispersion

Currently, there are many contaminants of concern that need to be accurately determined to help assess their potential environmental hazard. Despite their increasing interest, yet few environmental occurrence data exist, likely because they are present at low levels and in very complex matrices. Therefore, multiresidue analytical methods for their determination need to be highly sensitive, selective, and robust. Particularly, due to the trace levels of these chemicals in the environment, an extensive extraction procedure is required before determination. This work details the development of a fast and cheap vortex-assisted matrix solid-phase dispersion-high performance liquid chromatography tandem-mass spectrometry (VA-MSPD-HPLC-MS/MS) method for multiresidue determination of 59 contaminants of emerging concern (CECs) including pharmaceuticals, personal care products, and booster biocides, in sediment. The validated method provided high sensitivity (0.42-36.8 ngg^-1 dw quantification limits), wide and good linearity (r² > 0.999), satisfactory accuracy (60-140%), and precision below 20% for most target analytes. In comparison with previous methods, relying on traditional techniques, the proposed method demonstrated to be more environmentally friendly, cheaper, simpler, and faster. The method was applied to monitor the occurrence of these compounds in sediments collected in Brazil, using only 2 g dw sediment samples, free-solid support, and 5 mL methanol as extraction solvent. The UV filter avobenzone, the UV stabilizer and antifreeze methylbenzotriazole, the preservative methylparaben, the fluoroquinolone antibiotic ciprofloxacin, and the biocides irgarol and 4,5-dichloro-2-octyl-4-isothiazolin-3-one were determined at concentrations in the range 1.44-69.7 ngg^-1 dw.

Molecular and biochemical effects of the antifouling DCOIT in the mussel Perna perna

Biological fouling is an unwanted phenomenon that results in economic losses to the shipping industry. To prevent fouling, antifouling paints are used. DCOIT (4,5- dichloro-2-n-octyl-4-isothiazolin-3-one) is a biocide present in many antifouling paint formulations, and is toxic to a wide range of organisms. The aim of the present study was to evaluate the effects of DCOIT on oxidative stress indicators of the brown mussel, Perna perna. Molecular (SOD-like, GSTO-like and MGST-like mRNA levels) and biochemical (activities of superoxide dismutase (SOD), catalase (CAT) and glutathione S-transferase (GST), and levels of glutathione (GSH), reactive oxygen species (ROS) and protein carbonyls (PCO)) components were evaluated. Further, levels of biomarkers were assessed in the gills and digestive glands of mussels. Bivalves were exposed to DCOIT (control, 0.1 μg/L and 10 μg/L) for up to 96 h. DCOIT exposure decreased GSH content in gills. Moreover, exposure to DCOIT also decreased CAT activity in the gills and digestive glands of mussels. GST activity increased in digestive gland after exposure for 24 h to both concentrations of DCOIT tested. SOD activity, ROS levels and PCO content were not affected by exposure to the contaminant. Regarding the molecular biomarkers evaluated, DCOIT exposure altered mRNA levels of SOD-like in both tissues after 24 and 96 h of exposure, and decreased MGST-like mRNA levels in the digestive gland after 96 h of exposure to the chemical. These findings suggested that exposure to DCOIT may alter the biochemical and molecular functioning of P. perna, which may harm the species.

Analysis of NMR Spectra of Submicro-Containers with Biocide DCOIT

Nowadays, the search for and development of new forms of materials with biocides is an actual problem of the modern science of nanosized materials due to the problem of microbiological contamination, which can be solved by using nanocontainers carrying biocides. Depending on the morphology of the nanocontainers and the filled active agents, it is possible to create coatings with specially designed self-healing functionality or multifunctional properties. The purpose of this work was to produce submicro-containers (SMCs) with a shell of SiO2 nanoparticles and a core of polymerized 3-(trimethoxysilyl) propyl methacrylate filled with 5-dichloro-2-n-octyl-4-isothiazolin-3-one (DCOIT) in an oil in water (O/W) emulsion. The chemical nature of the individual components of the system and nano-capsules were investigated using NMR spectroscopy. The size and zeta potential of the SMCs were measured by a dynamic light scattering method (d = 170–180 nm, polydispersity index PDI = 0.125 and zeta-potential = 55 mV), the morphology of their outer surface was determined using SEM. The results of NMR analysis showed that during the addition of the biocide into the SMCs, its chemical structure is retained, as is its activity. Minor changes in the chemical shifts of the 1H NMR spectra of the SMCs with DCOIT, as well as of the biocide itself, confirm the inclusion of DCOIT inside the SMCs.

Are antifouling residues a matter of concern in the largest South American port?

In the present study, levels of booster biocides (diuron, Irgarol, chlorothalonil, dichlofluanid and DCOIT), butyltin compounds (TBT, DBT and MBT) and antifouling paint particles (APPs) were assessed in sediments of areas under the influence of the largest Latin American port, marinas, boat traffic and ship/boat maintenance facilities located within Santos-São Vicente Estuarine System (SSES). Contamination profile was directly related to local maritime activities, where sediments from the main navigation channel (MNC) presented low levels of antifouling residues while adjacent areas (AA), characterized by the presence of boats and boatyards, showed higher contamination considering all analyzed residues. Moreover, areas under the influence of fishing boats/yards presented relevant levels of butyltins (ΣBTs > 300 ng g^-1) and APPs (>100 μg g^-1), while marinas dominated by recreational boats showed higher booster biocides occurrence. Sites located nearby shipyards in the MNC and boatyards in the AA presented expressive amounts of APPs (>200 μg g^-1). These APPs represent an important long-term source of biocides to the SSES. Thus, the profile of maritime activities in association to local oceanographic conditions drive the spatial distribution of antifouling residues within SESS, which in some case presented levels above sediment guidelines for TBT, DCOIT and diuron.

Is hull cleaning wastewater a potential source of developmental toxicity on coastal non-target organisms?

Chemical contaminants can be discharged by vessel hull cleaning processes, such as scraping, jet spraying, and painting, all of which produce readily transportable contaminants into the marine environment, where they are referred to as 'hotspots' of contamination in coastal areas. However, many countries have not yet established effective evaluation methods for disposal of waste mixtures or management guidelines for areas of hull cleaning. To define the toxic effects of wastewater from vessel hull cleaning in dry docks on resident non-target organisms, we investigated the chemical concentrations and developmental toxicity on embryonic flounder, which is an organism sensitive to chemical contamination. In this study, the dominant inorganic metal discharged was zinc when cleaning Ship A (300 tons) and copper for Ship B (5,000 tons). The wastewater from high-pressure water blasting (WHPB) of Ship A (300 tons) and Ship B (5,000 tons) produced a largely overlapping suite of developmental malformations including pericardial edema, spinal curvature, and tail fin defects. Forty-eight hours after exposure, the frequency percentage of malformation began to increase in embryos exposed to a 500-fold dilution of WHPB from Ships A and B. We performed transcriptome sequencing to characterize the toxicological developmental effects of WHPB exposure at the molecular level. The results of the analysis revealed significantly altered expression of genes associated with muscle cell differentiation, actin-mediated cell contraction, and nervous system development (cutoff P < 0.01) in embryonic flounder exposed to high-pressure cleaning effluent from Ship A. Genes associated with chromatin remodeling, cell cycling, and insulin receptor signaling pathways were significantly altered in embryonic flounder exposed to WHPB of Ship B (cutoff P < 0.01). These findings provide a greater understanding of the developmental toxicity and potential effects of WHPB effluent on coastal embryonic fish. Furthermore, our results could inform WHPB effluent management practices to reduce impacts on non-target coastal organisms.

The occurrence of modern organic antifouling biocides in Danish marinas

Antifouling biocides are known to leach out of paints and into the aquatic environment. There is currently a data gap on the occurrence of the current antifouling biocides, as legislative changes caused a change in the antifouling market. Therefore, a comprehensive monitoring study was performed across 13 Danish marinas, both waters and sediments were analyzed, including a transect and a study with seasonal resolution. Three biocides, i.e., Medetomidine, Tralopyril, and DCOIT were not detected in any of the samples. More commonly found, in 11 of the 13 marinas, were the hydrolysis products of Dichlofluanid (DMSA) and Tolylfluanid (DMST). These biocides rapidly dropped in concentration and reached background levels around 200 m from the source. The antifouling biocide Irgarol 1051 was found in all sediment samples and half of all water samples. The concentrations of Irgarol were lower than previously monitored. The decrease can likely be attributed to legislative changes and its disapproval for use since 2016.

Rapid toxicity assessment of six antifouling booster biocides using a microplate-based chlorophyll fluorescence in Undaria pinnatifida gametophytes

Biocides of antifouling agents can cause problems in marine ecosystems by damaging to non-target algal species. Aquatic bioassays are important means of assessing the quality of water containing mixtures of contaminants and of providing a safety standard for water management in an ecological context. In this study, a rapid, sensitive and inexpensive test method was developed using free-living male and female gametophytes of the brown macroalga Undaria pinnatifida. A conventional fluorometer was employed to evaluate the acute (48 h) toxic effects of six antifouling biocides: 4,5-Dichloro-2-octyl-isothiazolone (DCOIT), diuron, irgarol, medetomidine, tolylfluanid, zinc pyrithione (ZnPT). The decreasing toxicity in male and female gametophytes as estimated by EC50 (effective concentration at which 50% inhibition occurs) values was: diuron (0.037 and 0.128 mg l-1, respectively) > irgarol (0.096 and 0.172 mg l-1, respectively) > tolylfluanid (0.238 and 1.028 mg l-1, respectively) > DCOIT (1.015 and 0.890 mg l-1, respectively) > medetomidine (12.032 and 12.763 mg l-1, respectively). For ZnPT, 50% fluorescence inhibition of U. pinnatifida gametophytes occurred at concentrations above 0.4 mg l-1. The Undaria method is rapid, simple, practical, and cost-effective for the detection of photosynthesis-inhibiting biocides, thus making a useful tool for testing the toxicity of antifouling agents in marine environments.

Effects of DCOIT (4,5-dichloro-2-octyl-4-isothiazolin-3-one) to the haemocytes of mussels Perna perna

Bivalve molluscs rely only on an innate immune system to execute cellular and humoral processes. Haemocytes, the haemolymph circulating cells, play a major role in this type of immunity, principally regarding cellular defences. Considering that environmental pollutants can affect the immune system of invertebrates, this work evaluated the effects of the antifouling biocide 4,5-dicloro-2-n-octil-4-isotiazolin-3-ona (DCOIT) on the haemocytes of mussels Perna perna. Individuals were exposed to 0 (control), 0.1 μg L^-1 and 10 μg L^-1 of DCOIT for up to 96 h. The analysed parameters included: total (THC) and differential (DHC) haemocyte count, cellular viability, adhesion capacity, phagocytic activity, levels of reactive oxygen species and DNA damage. Moreover, the stress on stress (SOS) response of mussels was analysed as a general stress index. The results show that DCOIT increased the haemocyte adhesion capacity and caused a decrease in THC and in the haemocyte viability after 24 h of exposure. After 96 h of exposure, DCOIT only affected the haemocyte adhesion capacity, which was decreased by biocide exposure. Moreover, exposure to DCOIT for 96 h did not affect the capacity for air survival of mussels. These results indicate that DCOIT interferes in important parameters associated with the innate immunity of P. perna, mainly after 24 h of exposure. It is suggested that the animals were able to develop some compensatory response strategy, making them more resistant to the biocide.

Isothiazolinone Biocides: Chemistry, Biological, and Toxicity Profiles

The importance of isothiazole and of compounds containing the isothiazole nucleus has been growing over the last few years. Isothiazolinones are used in cosmetic and as chemical additives for occupational and industrial usage due to their bacteriostatic and fungiostatic activity. Despite their effectiveness as biocides, isothiazolinones are strong sensitizers, producing skin irritations and allergies and may pose ecotoxicological hazards. Therefore, their use is restricted by EU legislation. Considering the relevance and importance of isothiazolinone biocides, the present review describes the state-of-the-art knowledge regarding their synthesis, antibacterial components, toxicity (including structure–activity–toxicity relationships) outlines, and (photo)chemical stability. Due to the increasing prevalence and impact of isothiazolinones in consumer’s health, analytical methods for the identification and determination of this type of biocides were also discussed.

Overlapping and unique toxic effects of three alternative antifouling biocides (Diuron, Irgarol 1051®, Sea-Nine 211®) on non-target marine fish

The use of alternative biocides has increased due to their economic and ecological relevance. Although data regarding the toxicity of commercial alternative biocides in marine organisms are accumulating, little is known about their toxic pathways or mechanisms. To compare the toxic effects of commercial alternative biocides on non-target pelagic fish (flounder) embryos, we investigated the adverse effects of developmental malformation and transcriptional changes. Three biocides including Diuron, Irgarol 1051^® and Sea-Nine 211^® produced a largely overlapping suite of developmental malformations, including tail-fin fold defects and dorsal body axis curvature. In our test, the potencies of these biocides were ranked in the following order with respect to malformation and mortalities: Sea-Nine 211^® > Irgarol 1051^® > Diuron. Consistent with the toxicity rankings, the expression of genes related to heart formation was greater in embryonic flounder exposed to Sea-Nine 211^® than in those exposed to Irgarol 1051^® or Diuron, while expression of genes related to fin malformation was greater in the Irgarol 1051^® exposure group. In analyses of differential gene expression (DEG) profiles (fold change of genes with a cutoff P < 0.05) by high-throughput sequencing (RNA-seq), genes associated with nervous system development, transmembrane transport activity, and muscle cell development were significantly changed commonly. Embryos exposed to Diuron showed changes related to cellular protein localization, whereas genes associated with immune system processes were up-regulated significantly in embryos exposed to Irgarol 1051^®. Genes related to actin filament organization and embryonic morphogenesis were up-regulated in embryos exposed to Sea-Nine 211^®. Overall, our study provides a better understanding of the overlapping and unique developmental toxic effects of three commercial booster biocides through transcriptomic analyses in a non-target species, embryonic flounder.

Effects of sublethal concentrations of the antifouling biocide Sea-Nine on biochemical parameters of the marine polychaete Perinereis aibuhitensis

Sea-Nine™ 211 is an emerging biocide that has an adverse impact on aquatic environments. In this study, the marine polychaete Perinereis aibuhitensis was exposed to Sea-Nine (0.1, 1, and 10 μg L^-1), and acute toxicity and biochemical responses such as changes in the intracellular contents of malondialdehyde (MDA) and glutathione (GSH) and enzymatic activities of catalase (CAT), superoxide dismutase (SOD), glutathione peroxidase (GPx), glutathione reductase (GR), glutathione S-transferase (GST), and acetylcholinesterase (AChE) were evaluated over a period of 14 d. Determined median lethal doses, LC50 were 268 μg L^-1, 142 μg L^-1, and 55 μg L^-1 at 24 h, 96 h, and 14 d, respectively. The MDA content increased significantly in a dose- and time-dependent manner, indicative of lipid peroxidation-related oxidative damage. Significantly higher intracellular GSH levels and antioxidant defense-related enzyme (CAT, SOD, GPx, GR, and GST) activities were observed after exposure to 10 μg L^-1 Sea-Nine. In contrast, Sea-Nine treatment significantly reduced AChE activity at the highest concentration of Sea-Nine used (10 μg L^-1). Taken together, these results indicate that sublethal concentrations of Sea-Nine are toxic to marine polychaetes through potential lipid peroxidation, induction of oxidative stress, and modulation of the cholinergic system. Our results can contribute to biomonitoring of aquatic environments and ecotoxicological research through the measurements of polychaete cellular defenses against waterborne biocides.

Toxicity of 4,5-dichloro-2-n-octyl-4-isothiazolin-3-one (DCOIT) in the marine decapod Litopenaeus vannamei

DCOIT (4,5-dichloro-2-n-octyl-4-isothiazolin-3-one) is the main component of SeaNine-211, a new antifouling agent that replaces tributyltin to prevent the growth of undesirable organisms on ships. There have been some studies on the toxicity of DCOIT, but the mechanism of DCOIT's toxicity to crustaceans still requires elucidation. This study examined the chronic toxicity (4 weeks) of 0, 3, 15, and 30 μg/L DCOIT to the Pacific white shrimp (Litopenaeus vannamei) from the aspects of growth and physiological and histological changes in the hepatopancreas and gills. A transcriptomic analysis was performed on the hepatopancreas to reveal the underlying mechanism of DCOIT in shrimp. The exposure to 30 μg/L DCOIT significantly reduced the survival and weight gain of L. vannamei. High Na⁺/K⁺-ATPase activity and melanin deposition were found in the gills after 4 weeks of 15 μg/L or 30 μg/L DCOIT exposure. The highest concentration of DCOIT (30 μg/L) induced changes in hepatopancreatic morphology and metabolism, including high anaerobic respiration and the accumulation of triglycerides. Compared with the exposure to 3 μg/L DCOIT, shrimp exposed to 15 μg/L DCOIT showed more differentially expressed genes (DEGs) than those in the control, and these DEGs were involved in biological processes such as starch and sucrose metabolism and choline metabolism in cancer. The findings of this study indicate that L. vannamei is sensitive to the antifouling agent DCOIT and that DCOIT can induce altered gene expression at a concentration of 15 μg/L and can interfere with shrimp metabolism, growth and survival at 30 μg/L.

Biodegradable Poly(ester- co-acrylate) with Antifoulant Pendant Groups for Marine Anti-Biofouling

Polymer resins are critical for marine anti-biofouling coatings. In this study, degradable poly(ester- co-acrylate) with antifoulant pendant groups has been prepared by the radical ring-opening polymerization of 2-methylene-1,3-dioxepane, methyl methacrylate, and N-methacryloyloxy methyl benzoisothiazolinone. Such a polymer containing main-chain esters can hydrolytically and enzymatically degrade. Both degradation rates increase with main-chain ester content. Moreover, since the antifoulant groups are chemically grafted to the degradable main chain, their release can be controlled by the degradation besides the hydrolysis of side groups. Our study shows that the copolymer coating is efficient in inhibiting the accumulation of marine bacterial biofilm of Pseudomonas sp. and diatom Navicular incerta. Marine field test reveals that the copolymer has excellent efficiency in preventing biofouling for more than 6 months.

From Ecology to Biotechnology, Study of the Defense Strategies of Algae and Halophytes (from Trapani Saltworks, NW Sicily) with a Focus on Antioxidants and Antimicrobial Properties

This study aimed at the characterization of the antioxidant power of polyphenol extracts (PE) obtained from the algae Cystoseira foeniculacea (CYS) (Phaeophyta) and from the halophyte Halocnemum strobilaceum (HAL), growing in the solar saltworks of western Sicily (Italy), and at the evaluation of their anti-microfouling properties, in order to correlate these activities to defense strategies in extreme environmental conditions. The antioxidant properties were assessed in the PE based on the total antioxidant activity test and the reducing power test; the anti-microfouling properties of the two PE were evaluated by measuring the growth inhibition of marine fish and shellfish pathogen bacteria as well as marine surface fouling bacteria and microalgae exposed to the fractions. Similar polyphenol content (CYS 5.88 ± 0.75 and HAL 6.03 ± 0.25 mg gallic acid equivalents (GAE) g-1 dried weight, DW) and similar reducing power percentage (93.91 ± 4.34 and 90.03 ± 6.19) were recorded for both species, even if they exhibited a different total antioxidant power (measured by the percentage of inhibition of the radical 2,2 diphenyl-1-picrylhydrazyl DPPH), with CYS (79.30) more active than HAL (59.90). Both PE showed anti-microfouling properties, being inhibitors of adhesion and growth of marine fish and shellfish pathogen bacteria (V. aestuarianus, V. carchariae, V. harveyi, P. elyakovii, H. aquamarina) and fouling bacteria (V. natriegens, V. proteolyticus, P. iirgensii, R. litoralis) with minimum inhibitory concentrations comparable to the commercial antifouling products used as a positive control (SEA-NINE™ 211N). Only CYS was a significant inhibitor of the microalgae strains tested, being able to reduce E. gayraliae and C. closterium growth (MIC 10 µg·mL-1) and the adhesion of all three strains tested (E. gayraliae, C. closterium and P. purpureum), suggesting its promise for use as an antifouling (AF) product.

Design of surfaces for controlling hard and soft fouling

In this review, we present a framework to guide the design of surfaces which are resistant to solid fouling, based on the modulus and length scale of the fouling material. Solid fouling is defined as the undesired attachment of solid contaminants including ice, clathrates, waxes, inorganic scale, polymers, proteins, dust and biological materials. We first provide an overview of the surface design approaches typically applied across the scope of solid fouling and explain how these disparate research efforts can be united to an extent under a single framework. We discuss how the elastic modulus and the operating length scale of a foulant determine its ability or inability to elastically deform surfaces. When surface deformation occurs, minimization of the substrate elastic modulus is critical for the facile de-bonding of a solid contaminant. Foulants with low modulus or small deposition sizes cannot deform an elastic bulk material and instead de-bond more readily from surfaces with chemistries that minimize their interfacial free energy or induce a particular repellant interaction with the foulant. Overall, we review reported surface design strategies for the reduction in solid fouling, and provide perspective regarding how our framework, together with the modulus and length scale of a foulant, can guide future antifouling surface designs. This article is part of the theme issue 'Bioinspired materials and surfaces for green science and technology'.

Synthesis of Submicrocontainers with “Green” Biocide and Study of Their Antimicrobial Activity

The synthesis and properties of submicrocontainers with a shell of nanoparticles of silicon dioxide and a core of polymerized 3-(Trimethoxysilyl) propyl methacrylate loaded with 5-Dichloro-2-n-octyl-4-isothiazolin-3-one (DCOIT) are considered. The resulting containers were characterized by scanning electron microscopy SEM, laser correlation spectroscopy and thermogravimetric analysis. The obtained submicrocontainers show low polydispersity with a small increase in size in comparison with the initial droplet size of the Pickering emulsion. The Zeta potential of the final containers was sufficiently negative at pH7 to be stable. The maximum release of encapsulated biocide was observed over approximately 24–27 h with a lease of about 78% of the encapsulated biocide during 3.5 h. The effectiveness of the encapsulated biocide by the Pickering emulsion technique was studied by tests on the growth rate of a microfungi colony (Aspergillus niger, Aspergillus awamori) and the growth rate of the bacteria Bacillus cereus. The test shows that the submicrocontainers of DCOIT facilitate a growth inhibition of 70% against 52% for the free biocide after 5 days; this is due to the fact that free biocide loses its activity promptly, while the encapsulated biocide is released gradually, and thus retains its effectivity for a longer time.

Constant exposure to environmental concentrations of the antifouling biocide Sea-Nine retards growth and reduces acetylcholinesterase activity in a marine mysid

Sea-Nine (4,5-dichloro-2-n-octyl-4-isothiazoline3-one; DCOIT) antifoulant has been widely used owing to its broad spectrum of biocide activity against major fouling organisms. In this study, several physiological parameters of a marine mysid were analyzed upon exposure to sublethal environmental concentrations (1 and 100 ng L^-1) of Sea-Nine in two exposure conditions, intermittent (weekly; once per week) and constant (daily; once per 24 h) exposure, for 4 weeks. In both experimental conditions, growth retardation, acetylcholinesterase (AChE) activity, glutathione S-transferase (GST) activity, and number of newborn juveniles as second generation, together with their survival were measured. Morphometric parameters of total body, antennal scale, exopod, endopod, and telson were significantly retarded by 22%, 14%, 13%, and 24%, respectively, by daily exposure to 100 ng L^-1 Sea-Nine for 4 weeks. Significant inhibition of AChE activity was observed at week 4 in the 100 ng L^-1 daily Sea-Nine-exposed groups, whereas no significant GST activity was measured at the same experimental conditions. Inhibition of AChE activity would be associated with impairment of cholinergic system and may adversely modulate growth parameters of the mysid. The number of newly hatched juveniles from females that were exposed daily to 100 ng L^-1 Sea-Nine was significantly lower than that of the control. Although no significant differences were observed between survival percentages of newborn juveniles for 30 days, mortality (NOEC and LC50) increased in the surviving offspring from the 100 ng L^-1-exposed 1st generation of mysids. These findings suggested that constant exposure to Sea-Nine has detrimental effects on the growth parameters of marine mysids with inhibition of AChE activity.

Endoplasmic reticulum stress mediates 4,5-dichloro-2-n-octyl-4-isothiazolin-3-one (DCOIT)-induced toxicity and liver lipid metabolism changes in Nile tilapia (Oreochromis niloticus)

DCOIT (4,5-dichloro-2-n-octyl-4-isothiazolin-3-one) is the main active ingredient in an emerging water environment antifoulant, the toxicity and environmental impacts of which need to be further investigated. Thus, this study examined the toxicity of DCOIT on Nile tilapia (Oreochromis niloticus), including its effects on behavior, respiration and energy metabolism as well as the role of endoplasmic reticulum stress (ER stress) in mediating its toxicity and metabolic changes. The changes in fish behavior, respiration, neuronal signal transmission, energy metabolism, ER stress, and liver histology were examined via acute (4 days) and chronic (28 days) exposures to 0, 3, 15, 30 μg/L DCOIT in vivo. Additionally, ER stress levels were measured in 24-h periods of hepatocyte exposure to 0, 3, 15, 30 and 300 μg/L DCOIT in vitro. The hyper-locomotor activities decreased, but the respiration rate increased after a 4-day acute exposure period, indicating that DCOIT exposure altered fish energy metabolism. After acute exposure at a low DCOIT concentration, the activation of ER stress induced triglyceride accumulation in the liver. After chronic exposure for 28 days, the prolonged ER stress induced a series of pathological cellular changes. At the cellular level, exposure to a high DCOIT concentration induced ER stress in the hepatocytes. In addition, as a neurotoxin, DCOIT has the potential to disrupt the neurotransmission of the cholinergic system, resulting in motor behavior disruption. This study demonstrates that DCOIT plays a role in time- and concentration-dependent toxicity and that changes in lipid metabolism are directly related to endoplasmic reticulum function after exposure to an antifouling agent. This work advances the understanding of the toxic mechanism of DCOIT, which is necessary for its evaluation.

Review: ecotoxicity of organic and organo-metallic antifouling co-biocides and implications for environmental hazard and risk assessments in aquatic ecosystems

Hazard assessments of Irgarol 1051, diuron, 2-(thiocyanomethylthio)benzothiazole (TCMTB), dichloro-octylisothiazolin (DCOIT), chlorothalonil, dichlofluanid, thiram, zinc pyrithione, copper pyrithione, triphenylborane pyridine (TPBP), capsaicin, nonivamide, tralopyril and medetomidine were performed to establish robust environmental quality standards (EQS), based on predicted no effect concentrations (PNECs). Microalgae, zooplankton, fish and amphibians were the most sensitive ecological groups to all the antifoulants evaluated, especially in the early life stages. No differences were identified between freshwater and seawater species. The use of toxicity tests with non-standard species is encouraged because they increase the datasets, allowing EQS to be derived from probabilistic-based PNECs whilst reducing uncertainties. The global ban of tributyltin (TBT) has been heralded as a major environmental success; however, substitute antifoulants may also pose risks to aquatic ecosystems. Environmental risk assessments (ERAs) have driven decision-makings for regulating antifouling products, but in many countries there is still a lack of regulation of antifouling biocides which should be addressed.

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.