Marine Biofouling Research Articles

Application of Natural Antibacterial Plants in the Extraction of Uranium from Seawater.

Marine biofouling directly affects the performance and efficiency of uranium (U(VI)) extraction from seawater. Compared to traditional chemical methods, natural plant extracts are generally biodegradable and nontoxic, making them an environmentally friendly alternative to synthetic chemicals in solving the marine biofouling problem. The effectiveness of natural antibacterial plants (i.e., pine needle, peppermint, Acorus gramineus Soland, Cacumen platycladi, and wormwood) in solving the marine biofouling problem was evaluated in this work. Experimental results showed that natural antibacterial plants could kill Vibrio alginolyticus in solution and effectively solve the marine biofouling problem of U(VI) extraction. To improve the adsorption capacity of natural plants for U(VI) in seawater, poly(vinylphosphonic acid) (PVPA) was modified on natural antibacterial plant surfaces by irradiation grafting technology. PVPA and natural antibacterial plants work as active sites and base materials for the U(VI) extraction material, respectively. The recovery performance of PVPA/pine needle for U(VI) was preliminarily studied. Results show that the adsorption of U(VI) on PVPA/pine needle follows pseudo-second-order and Langmuir models, and the maximum adsorption capacity is 111 mg/g at 298 K and pH 8.2.

Photocatalytic mediated marine biofouling inhibition using nano CuO: TiO2-carbon dot embedded on organo silane surface modified polyethylene aquaculture cage nets

Biofouling in aquaculture cages is a potential problem and its management become major concern to the planners and farmers. The study aimed to modify the surface of polyethylene aquaculture cage nets using organo silane and to evaluate the effectiveness of a nano CuO:TiO2-carbon dot biocide treatment in inhibiting marine biofouling through photocatalytic action. Polyethylene aquaculture cage net surface modified using organo silane and the surface embedded with biocide of nano CuO:TiO2 and carbon dot (CD) derived from fish eye. The biocide-treated surface was characterized using UV–Visible and Fourier Transform Infrared spectrometry. The organo silane interacts with polyethylene via hydrogen bonding, CuO:TiO2 interacts with the silane's Si, and the carbon dots' conjugated CC bonds interact with the transition metal and silane through van der Waals electrostatic forces and hydrogen bonding. Varied concentrations of CuO:TiO2 and CD was coated sequentially over silane surface modified polyethylene, exposed in the marine environment to evaluate biofouling inhibition efficiency and found 0.05% each of CuO:TiO2 and CD was optimum. The CuO:TiO2–CD coated polyethylene cage net tested for its biofouling inhibition for 8 months in marine environment and exhibited excellent biofouling inhibition. The inhibition of biofouling was attributed to the enhanced photocatalytic action, resulting from increased electron-hole recombination, thus generating ROS, O2٠, and OH٠ radicals. This led to the highest electronic activity around the cage net and also the formation of an acidic environment deterred microorganisms. The study highlighted the use of organo silane for surface modification of polyalkenes to load the biocide and also CuO:TiO2–CD is a potential biocide for biofouling inhibition in aquaculture cages.

Fighting against biofilm: The antifouling and antimicrobial material.

Biofilms are groups of microorganisms protected by self-secreted extracellular substances. Biofilm formation on the surface of biomaterial or engineering materials becomes a severe challenge. It has caused significant health, environmental, and societal concerns. It is believed that biofilms lead to life-threatening infection, medical implant failure, foodborne disease, and marine biofouling. To address these issues, tremendous effort has been made to inhibit biofilm formation on materials. Biofilms are extremely difficult to treat once formed, so designing material and coating bearing functional groups that are capable of resisting biofilm formation has attracted increasing attention for the last two decades. Many types of antibiofilm strategies have been designed to target different stages of biofilm formation. Development of the antibiofilm material can be classified into antifouling material, antimicrobial material, fouling release material, and integrated antifouling/antimicrobial material. This review summarizes relevant research utilizing these four approaches and comments on their antibiofilm properties. The feature of each method was compared to reveal the research trend. Antibiofilm strategies in fundamental research and industrial applications were summarized.

Proof of Concept of Natural and Synthetic Antifouling Agents in Coatings.

Marine biofouling, caused by the deposition and accumulation of marine organisms on submerged surfaces, represents a huge concern for the maritime industries and also contributes to environmental pollution and health concerns. The most effective way to prevent this phenomenon is the use of biocide-based coatings which have proven to cause serious damage to marine ecosystems. Several research groups have focused on the search for new environmentally friendly antifoulants, including marine and terrestrial natural products and synthetic analogues. Some of these compounds have been incorporated into marine coatings and display interesting antifouling activities caused by the interference with the biofilm-forming species as well as by the inhibition of the settlement of macroorganisms. This review highlights the proof-of-concept studies of emerging natural or synthetic antifouling compounds in coatings, from lab-made to commercial ones, performed between 2019 and 2023 and their results in the field or in in vivo laboratorial tests.

Photoacoustic imaging-based in situ biofouling monitoring in underwater optical windows—A novel approach

The accuracy of optical instruments is inevitably affected by marine biofouling as their optical windows become obscured in seawater. The continuous removal of biofouling imposes a substantial energy burden on the offshore instruments. Therefore, monitoring biofouling and selecting an appropriate time for biofouling removal is essential. However, an efficient in situ monitoring strategy for biofouling in underwater optical windows is currently lacking. To address these challenges, we conducted exploratory research on a new technology based on photoacoustic imaging for the in situ monitoring of marine biofouling in optical windows. First, poly methyl methacrylate coupons were hung and immersed in the coastal waters of Qingdao for varying durations during the sea trials. Evident photoacoustic signals from the biofouling attached to the surfaces of the coupons were collected by means of photoacoustic experimental platform. Two-dimensional photoacoustic images were reconstructed using photoacoustic microscopy. On comparing the optical and photoacoustic images of biofouling, photoacoustic images can more effectively reflect the degree of biological fouling. Finally, the optical and photoacoustic images of coupons subjected to ultrasonic treatment were compared and analyzed to further review the feasibility of fouling monitoring based on photoacoustic technology. These findings provide new insights into in situ detection of marine biofouling.

Experimental insights on biofouling growth in marine renewable structures.

Marine biofouling is a threat to industries working in the marine environment, representing significant costs associated with equipment impairment and loss of performance. In the Marine Renewable Energy (MRE) and other maritime sectors which operate at sea for long periods, an important aspect of biofouling is related to the type and frequency of inspections and biofouling removal procedures. This study investigated important parameters of macrofouling ( e.g. composition, including the presence of non-indigenous species, thickness, and weight) from communities growing on samples that emulate tubular components of marine renewable devices. The trials were performed during short periods of submersion (one to eight weeks) in the seasons when the colonisation process should be most intensive (spring, summer, and autumn). Furthermore, the frictional resistance forces generated during the scraping of biofouling from those components were investigated. Overall, results provide insights on the growth rates and removal requirements of biofouling in marine components. The results show that, while biofouling growth in early colonization stages might not present great detrimental effects to wave energy components, the consequent marine corrosion (fostered by biofouling) and the settlement of non-indigenous species (NIS) should be factors of concern. Performing biofouling-related maintenance activities after the peak of maximum growth and reproduction (during the warmer seasons in temperate to cold environments) is suggested to reduce the number and frequency of activities. NIS can be detected at very early stages in the colonization process, highlighting the importance of biofouling monitoring and the implementation of biosecurity risk assessment plans early in the operational stage of MRE projects.

Improved numerical model for simulating biofouling-induced ship resistance

Marine biofouling has long been a problem in the worldwide shipping sector, and there are no ideal solutions to prevent it. Previous studies primarily focus on height of marine biofoulers sticked to ship wetted surfaces, with other factors, such as hardness, shape, density, etc., remaining less consideration. Our recent studies show that any single element is not likely to completely describe the compositions of ship total resistance. Here we develop a smart numerical method which can precisely capture the characteristics of each single component of marine biofoulers in generating additional resistance. In the early paper, the standard model was modified by only taking into account the rotating and swirling of fluids over wetted surfaces of ships as a result of marine biofouling. Nevertheless, the modified model is found possible to further develop by considering potential jetting and surging of fluids induced by the specific features of macro-biofoulers. The results obtained from the twice-modified model are allowed to compare with those yielded from the standard model, with an apparent improvement of the total resistance, more consistent with measured, demonstrating that the twice-modified model behaves in a more reasonable manner in modeling the biofouling-induced ship total resistance. Another important finding in this paper is that the ship block coefficient is found to be modified due to inhomogeneous distributions of biofouling, with less in the fore parts and more in the aft parts of ships, leading to a growth of the ship block coefficient, in turn, a modification of ships’ shape. The objective of this paper is to reveal the relationship between ship resistance and the characteristics of the marine biofoulers using the modified numerical model.

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.

Multi-strategy combined bionic coating for long-term robust protection against marine biofouling

Polyurethane-fluorinated polysiloxane (PU-FPDMS) with high-strength, high-bonding and low surface energy is synthesized as the matrix, and the PU-FPDMS/MCs/Ag marine anti-fouling coating on the surface of imitation crab shells is constructed by assembling butenolide@1,1-stilbene-modified hydrolyzed polyglycidyl methacrylate/graphene oxide microcapsules (Bu@PGMAm/GO MCs) with compact multi-shell structure and Ag nanoparticles (AgNPs) step by step on the PU-FPDMS matrix. The PU-FPDMS/MCs/Ag bionic anti-fouling coatings achieve long-term and stable anti-fouling effect under the combination of robust low-surface-energy PU-FPDMS matrix, steady-state sustained release of butenolide encapsulated by the compact multi-shell, bionic surface formed by the microcapsules and AgNPs, and the release of Ag+. The shear strength, tensile strength, and elongation at break of the PU-FPDMS/MCs/Ag are 3.53 MPa, 6.7 MPa, and 192.83 %, respectively. Its static contact angle and sliding angle are 161.8° and 3.6°, respectively. The antibacterial rate of PU-FPDMS/MCs/Ag against Escherichia coli, Staphylococcus aureus, and Candida albicans can reach 100 %. Compared with glass blank, PU, PU-FPDMS, PU-FPDMS/Ag, and PU-FPDMS/MCs, both the adhesion number and coverage percentage of chlorella adhere to PU-FPDMS/MCs/Ag are the minimum values, which are 600 cell mm–2 and 1.53 %, respectively. After 6 months of marine field test, the primer blank, PU, PU-FPDMS all show different degrees of attachment by shellfish, spirorbis, algae and other biofouling, while the PU-FPDMS/MCs/Ag coating is still not covered with biofouling, while the PU-FPDMS/MCs/Ag coatings still exhibit little attachment of marine fouling. The PU-FPDMS/MCs/Ag bionic anti-fouling coatings are expected to be widely used in the fields of anti-fouling, anti-icing, anti-fogging, drag reduction, self-cleaning, and antibacterial.

Surface Reconstruction of Silicone-Based Amphiphilic Polymers for Mitigating Marine Biofouling.

Poly(dimethylsiloxane) (PDMS) coatings are considered to be environmentally friendly antifouling coatings. However, the presence of hydrophobic surfaces can enhance the adhesion rate of proteins, bacteria and microalgae, posing a challenge for biofouling removal. In this study, hydrophilic polymer chains were synthesised from methyl methacrylate (MMA), Poly(ethylene glycol) methyl ether methacrylate (PEG-MA) and 3-(trimethoxysilyl) propyl methacrylate (TPMA). The crosslinking reaction between TPMA and PDMS results in the formation of a silicone-based amphiphilic co-network with surface reconstruction properties. The hydrophilic and hydrophobic domains are covalently bonded by condensation reactions, while the hydrophilic polymers migrate under water to induce surface reconstruction and form hydrogen bonds with water molecules to form a dense hydrated layer. This design effectively mitigates the adhesion of proteins, bacteria, algae and other marine organisms to the coating. The antifouling performance of the coatings was evaluated by assessing their adhesion rates to proteins (BSA-FITC), bacteria (B. subtilis and P. ruthenica) and algae (P. tricornutum). The results show that the amphiphilic co-network coating (e.g., P-AM-15) exhibits excellent antifouling properties against protein, bacterial and microalgal fouling. Furthermore, an overall assessment of its antifouling performance and stability was conducted in the East China Sea from 16 May to 12 September 2023, which showed that this silicon-based amphiphilic co-network coating remained intact with almost no marine organisms adhering to it. This study provides a novel approach for the development of high-performance silicone-based antifouling coatings.

Macrophage-Inspired marine antifouling coating with dynamic surfaces based on regulation of dynamic covalent bonds

Macrophages can kill bacteria and viruses by releasing free radicals, which provides a possible approach to construct antifouling coatings with dynamic surfaces that release free radicals if the breaking of dynamic covalent bonds is precisely regulated. Herein, inspired by the defensive behavior of macrophages of releasing free radicals to kill bacteria and viruses, a marine antifouling coating composed of polyurethane incorporating dimethylglyoxime (PUx-DMG) is prepared by precise regulation of dynamic oxime-urethane covalent bonds. The obtained alkyl radical (R·) derived from the cleavage of the oxime-urethane bonds manages to effectively suppress the attachment of marine biofouling. Moreover, the intrinsic dynamic surface makes it difficult for biofouling to adhere and ultimately achieves sustainable antifouling property. Notably, the PU50-DMG coating not only presents efficient antibacterial and antialgae properties, but also prevents macroorganisms from settling in the sea for up to 4 months. This provides a pioneer broad-spectrum strategy to explore the marine antifouling coatings.

A highly stable electrochemical sensor with antifouling and antibacterial capabilities for mercury ion detection in seawater

The monitoring of heavy metal ions in ocean is crucial for environment protection and assessment of seawater quality. However, the detection of heavy metal ions in seawater with electrochemical sensors, especially for long-term monitoring, always faces challenges due to marine biofouling caused by the nonspecific adsorption of microbial and biomolecules. Herein, an electrochemical aptasensor, integrating both antifouling and antibacterial properties, was developed for the detection of Hg2+ in the ocean. In this electrochemical aptasensor, eco-friendly peptides with superior hydrophilicity served as anti-biofouling materials, preventing nonspecific adsorption on the sensing interface, while silver nanoparticles were employed to eliminate bacteria. Subsequently, a ferrocene-modified aptamer was employed for the specific recognition of Hg2+, leveraging the aptamer's ability to fold into a thymine-Hg2+-thymine (T-Hg2+-T) structure upon interaction, and bringing ferrocene nearer to the sensor surface, significantly amplifying the electrochemical response. The prepared electrochemical aptasensor significantly reduced the nonspecific adsorption in seawater while maintaining sensitive electrochemical response. Furthermore, the biosensor exhibited a linear response range of 0.01–100 nM with a detection limit of 2.30 pM, and realized the accurate monitoring of mercury ions in real marine environment. The research results offer new insights into the preparation of marine antifouling sensing devices, and it is expected that sensors with antifouling and antimicrobial capabilities will find broad applications in the monitoring of marine pollutants.

Unsupervised learning-based image recovery and diagnosis method for blade attachment of marine current turbine

Marine current energy is a clean and renewable resource that is an available energy source with future power generation potential. However, complex subsea conditions can cause blade failures in marine current turbines (MCTs); therefore, the fault diagnosis of MCTs is essential to ensure their good operation. Image-based diagnosis is a nondestructive approach. To improve the efficiency of using human capital, this study uses the unsupervised learning network GANomaly trained only with normal samples to diagnose the leaf attachment of MCTs. Marine biofouling is a lengthy process, and according to the literature, the blades were contaminated by a 1.1-mm-thick layer of lithium lubricating grease, therefore, this study uses ropes to simulate this attachment. First, we address the problem of blurred underwater images collected using a multiscale retinex enhancement algorithm with color recovery to form a new dataset. GANomaly is modified to diagnose MCT blades with different attachment degrees. The experimental results show that the accuracy of the enhanced dataset is improved by 1.75 %, and the accuracy of the improved GANomaly model reaches 91.23 %, thereby enhancing the efficiency of the fault diagnosis of MCTs.

Smart antibiofouling composite coatings based on photothermally-active polyaniline and thermo-responsive poly(N-isopropylacrylamide)

Marine biofouling profoundly affects the economic viability of the marine sector. With a view towards addressing this issue, this work reported the successful development of smart photo-responsive and thermo-responsive antibiofouling coatings by combining photothermally-active polyaniline (PANI) with temperature-sensitive poly(N-isopropylacrylamide) (PNIPAM). Under light irradiation, the PNIPAM/PANI coating could be photothermally heated to temperatures as high as 89.3 ± 1.6 °C, delivering a maximum antibacterial rate of 99.99 %. Impressively, light-induced temperature changes in the PNIPAM/PANI coating caused dynamic changes in film morphology and wettability. Upon lowering the temperature to below the lower critical solution temperature (LCST) of PNIPAM, the water contact angle of the PNIPAM/PANI coating decreased from 81° to 35° and the coating surface roughened appreciably, resulting in a 99.99 % release rate for both E.coli and S. aureus, thus achieving a dynamic self-cleaning effect. Furthermore, the developed PNIPAM/PANI coating demonstrated excellent resistance against protein and algae adhesion. These findings showcase the broad application potential of PNIPAM/PANI antifouling coatings in the marine sector.

Fabrication of a scalable slippery surface via novel sprayable breath figure technique for sustainable drag reduction and anti-biofouling in marine environments

The maritime industry has been seeking efficient solutions to combat hydrodynamic friction and biofouling, which increase operational costs and environmental issues. To address these concerns, we developed a novel sprayable breath figure (sBF) method to create a scalable and cost-effective lubricant-infused surface (LIS) for reducing frictional drag forces on marine vehicles. The proposed sBF method facilitated the rapid production of multilayered porous polymer films with micron-scale spherical cavities. It can be applied to large and curved surfaces, thus overcoming the limitations of traditional breath figure methods. Further surface treatment of oxygen plasma etching followed by polydimethylsiloxane (PDMS) brush grafting was employed to optimize the interfacial slip and lubricant retention of the slippery surface coating. The PDMS brush-grafted slippery surfaces demonstrated significant drag reduction under turbulent flow conditions. This was confirmed by direct velocity field measurements, showing nonzero slip velocity unlike conventional no-slip surfaces. The same surfaces also exhibited remarkable anti-biofouling performance, severely resisting marine biofouling in real-sea field tests over 50 days. The proposed sBF method was successfully applied to large-area and curved submerged bodies, and achieved a noticeable drag reduction under high-speed turbulent flows. This study is a critical step toward the practical implementation of this technology in the marine industry.

Enhanced marine biofouling and corrosion resistance through springtails-inspired papillate-like micropillar arrays surface modified by antimicrobial peptide

Marine biological fouling has a serious impact on artificial facilities, and traditional antifouling coatings are not beneficial to green development, which lead to the urgent to develop green strategies that can effectively prevent fouling. In this study, an innovative confluence of physical and biological approaches was employed to mitigate the harm caused by biofouling on a material substrate. Firstly, a hierarchical microstructured morphology was prepared on an aluminum surface by reactive ion etching and characterised. The antibacterial peptide, A-2S, was surface modified with dopamine as a coupling agent to produce a physico-biological synergistic antifouling surface. X-ray photoelectron spectroscopy, fourier transform infrared spectroscopy, and electrochemical experiments were then used to analyse the binding effect and corrosion resistance performance. A-2S was successfully modified on the sample surface and exhibited good corrosion resistance with a corrosion inhibition efficiency of 86.57 %. Compared to a bare aluminum plate, the microstructure surface has a certain inhibitory effect on fouling organisms, and the antifouling performance decreases over time. In contrast, the antimicrobial peptide synergistic surfaces demonstrated superior durable antifouling performance. Compared with the 50 % of the antifouling performance on the microstructure surface, the synergistic surface has a unique contact point effect of the microstructure and excellent antibacterial and bactericidal properties of antimicrobial peptides, resulting in a surface antifouling performance of over 80 %. The synergistic modification method enhanced the corrosion resistance of the material and reduced the adhesion of fouling organisms, mitigating the harm caused by biofouling on the marine equipment substrate.

In Situ Reduction of Silver Nanoparticles/Urushiol-Based Polybenzoxazine Composite Coatings with Enhanced Antimicrobial and Antifouling Performances.

Marine anti-fouling coatings represent an efficient approach to prevent and control the marine biofouling. However, a significant amount of antifouling agent is added to improve the static antifouling performance of the coatings, which leads to an issue whereby static antifouling performance conflicts with eco-friendly traits. Herein, this work reports an in situ reduction synthesis of silver nanoparticles (AgNPs) within polymers to produce composite coatings, aiming to solve the aforementioned issue. Firstly, urushiol-based benzoxazine monomers were synthesized by the Mannich reaction, using an eco-friendly natural product urushiol and n-octylamine and paraformaldehyde as the reactants. Additionally, AgNPs were obtained through the employment of free radicals formed by phenolic hydroxyl groups in the urushiol-based benzoxazine monomers, achieved by the in situ reduction of silver nitrate in benzoxazine. Then, the urushiol-based benzoxazine/AgNPs composite coatings were prepared by the thermosetting method. AgNPs exhibit broad-spectrum and highly efficient antimicrobial properties, with a low risk to human health and a minimal environmental impact. The composite coating containing a small amount of AgNPs (≤1 wt%) exhibits effective inhibition against various types of bacteria and marine microalgae in static immersion, thereby displaying outstanding antifouling properties. This organic polymer and inorganic nanoparticle composite marine antifouling coating, with its simple preparation method and eco-friendliness, presents an effective solution to the conflict between static antifouling effectiveness and environmental sustainability in marine antifouling coatings.

Experimental and molecular dynamics simulation study on antifouling performance of antimicrobial peptide‐modified aluminum alloy surfaces

Marine biofouling poses a major challenge to ship navigation and hinders the development of the shipping industry. Urgent action is required to tackle this problem through the implementation of innovative strategies. Antimicrobial peptides have garnered considerable attention due to their outstanding effectiveness, wide range of activity, and eco‐friendly characteristics. This study involved grafting the antibacterial peptide andricin 01 (AIGHCLGATL) onto the surface of an aluminum alloy, thereby creating a modified surface with antibacterial properties. In summary, amino groups were introduced onto the surface of aluminum alloys through the silanization process using (3‐aminopropyl) triethoxysilane (APTES), and then the peptides were covalently immobilized on the treated surface using glutaraldehyde as a cross‐linking agent. The successful modification of the peptide was confirmed by Fourier transform‐infrared spectroscopy (FT‐IR) and X‐ray photoelectron spectroscopy (XPS) analysis. The antimicrobial peptide‐modified aluminum alloy surfaces exhibited significant bactericidal activity, killing 75.3% of Bacillus sp. and 85.5% of Escherichia coli, while achieving antifouling efficiencies of 88.6% and 90.7% against Bacillus sp. and E. coli, respectively. Furthermore, molecular dynamics simulations showed that the inserted of the peptides into the phospholipid membrane caused a change in the local membrane curvature, which eventually led to membrane rupture. These results provide valuable information for the application of antimicrobial peptides in the field of antifouling and the elucidation of antifouling mechanisms.

Fouling-Resistant Behavior of Hydrophobic Surfaces Based on Poly(dimethylsiloxane) Modified by Green rGO@ZnO Nanocomposites.

In line with global goals to solve marine biofouling challenges, this study proposes an approach to developing a green synthesis inspired by natural resources for fouling-resistant behavior. A hybrid antifouling/foul release (HAF) coating based on poly(dimethylsiloxane) containing a green synthesized nanocomposite was developed as an environmentally friendly strategy. The nanocomposites based on graphene oxide (GO) and using marine sources, leaves, and stems of mangroves (Avicennia marina), brown algae (Polycladia myrica), and zinc oxide were compared. The effectiveness of this strategy was checked first in the laboratory and then in natural seawater. The performance stability of the coatings after immersion in natural seawater was also evaluated. With the lowest antifouling (17.95 ± 0.7%) and the highest defouling (51.2 ± 0.9%), the best fouling-resistant performance was for the coatings containing graphene oxide reduced with A. marina stem/zinc oxide (PrGZS) and graphene oxide reduced with A. marina leaves/zinc oxide with 50% multiwall carbon nanotubes (PrGZHC50), respectively. Therefore, the HAF coatings can be considered as developed and eco-friendly HAF coatings for the maritime industry.

Inhibition of mussel settlement by calcined mussel shell powder through altering biofilms and bacterial community

Sustainability-driven innovations with non-toxic coating developing is essential. Here, we utilized the waste mussel shells as an alternative antifouling coating to test the potential impacts on biofilm formation and then Mytilus coruscus settlement. Compared with Natural Mussel Shell Powder (NMSP), the bacterial density of biofilm on 10 mg/mL Calcined Mussel Shell Powder (CMSP) coating was 63.09%, lowered significantly (p < 0.05). Further analysis of X-ray diffraction test showed the phase transformation appeared in the CMSP in comparison to NMSP. The biofilm bioassays showed that in 28-day-old natural biofilm, compared with Glass and PDMS, the bacterial density in 10 mg/mL CMSP decreased by 46.58 % and 34.60 %, respectively, and the diatom density decreased by 71.07 % and 42.99 %, respectively. Compared to Glass and PDMS, the relative abundance of Psychrobacter and Loktanella in the 28-day-old biofilms on CMSP coating was reduced, but that of Erythrobacter increased. Simultaneously, settlement on 10 mg/mL CMSP was reduced by 65.31 % and 72.13 %, respectively, compared to PDMS and Glass in the case of 28-day-old biofilms. These results demonstrate the viability of CMSP as a coating and provide a sustainable solution to against marine biofouling.