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The marine algae Ulva spp. are commonly used as model biofouling organisms. As biofouling studies are primarily conducted using field-collected specimens, factors including species identity, seasonal availability, and physiological status can hinder the replicability of the results. To address these limitations, a protocol was developed for the on-demand laboratory culture and release of Ulva zoospores. The biofouling potential of laboratory-cultured and field-collected Ulva blades was compared using a waterjet. No significant differences were found between field and laboratory-cultured samples in either spore adhesion (before waterjet) or the proportion of spores retained after waterjet exposure. However, there was significant variability within each session type in pre- and post-waterjet exposures, indicating that spore adhesion and retention levels vary significantly among trial runs. In addition, all our laboratory cultures were Ulva Clade C (LPP complex). In contrast, our field samples contained a mix of Ulva Clade C, U. compressa clade I, and U. flexuosa Clade D. This protocol for on-demand production of Ulva spores can improve biofouling research approaches, enables comparison of results across laboratories and regions, and accelerate the development of anti-biofouling strategies. [ABSTRACT FROM AUTHOR]

Microbial fouling involves the physicochemical interactions between microorganisms and solid surfaces. An electromagnetic field (EMF) may change the diffusion rates of microbial cells and the electrical double layer around the cells and contacting surfaces. In the current study, polycardanol exhibiting antibiofouling activity was modified with ferromagnetic iron oxide (IO) to investigate the EMF effects on bacterial adhesion. When there was a flow of electrolyte that contained bacterial cells, flow-induced EMF was generated according to Faraday's principle. It was observed that the IO-ionic solution (IS)-modified surfaces, with an induced current of 44, 53, 66 nA, showed decreases in the adhesion of bacteria cells more than the unmodified (polycardanol) and IO-nanoparticles-modified ones. In addition to the EMF effects, the nano-scale uniform roughness of the modified surfaces appeared to play an important role in the reduction of cell adhesion. The results demonstrated that the IOIS-modified surface (3.2 × 10−6 mM IO) had the highest antibiofouling activity. [ABSTRACT FROM AUTHOR]

Biofouling on marine surfaces causes immense material and financial harm for maritime vessels and related marine industries. Previous reports have shown the effectiveness of amphiphilic coating systems based on poly(dimethylsiloxane) (PDMS) against such marine foulers. Recent studies on biofouling mechanisms have also demonstrated acidic microenvironments in biofilms and stronger adhesion at low-pH conditions. This report presents the design and utilization of amphiphilic polymer coatings with buffer functionalities as an active disruptor against four different marine foulers. Specifically, this study explores both neutral and zwitterionic buffer systems for marine coatings, offering insights into coating design. Overall, these buffer systems were found to improve foulant removal, and unexpectedly were the most effective against the diatom Navicula incerta. [ABSTRACT FROM AUTHOR]

Pathogenic bacteria in drinking-water pose a health risk to consumers, as they compromise the quality of portable water. Chemical disinfection of water containing dissolved organic matter (DOM) causes harmful disinfection by-products. In this work, 4-hydroxybenzoic acid (4-HBA) blended polyethersulfone membranes were fabricated and characterised using microscopic and spectroscopic techniques. The membranes were evaluated for the removal of bacteria and DOM from synthetic and environmental water. Permeate flux increased from 287.30 to 374.60 l m−2 h−1 at 3 bars when 4-HBA increased from 0 to 1.5 wt.%, suggesting that 4-HBA influenced the membrane's affinity for water. Furthermore, 4-HBA demonstrated antimicrobial properties by inhibiting bacterial growth. The membrane with 1 wt.% 4-HBA recorded 99.4 and 100% bacteria removal in synthetic and environmental water, respectively. Additionally, DOM removal of 55–73% was achieved. A flux recovery ratio (FRR) of 94.6% was obtained when a mixture of bacteria and humic acid was filtered, implying better fouling layer reversibility during cleaning. Furthermore, 100% FRR was achieved when a multimedia granular filtration step was installed prior to membrane filtration. The results illustrated that the membranes had a high permeate flux with low irreversible fouling. This indicated the potential of the membranes in treating complex feed streams using simple cleaning protocols. [ABSTRACT FROM AUTHOR]

Despite the Baltic Sea being one of the most intensive shipping regions in the world the potential magnitude of the biofouled hulls in this region is unknown. This study estimated the biofouling load to Baltic Sea Region (BSR) based on the wetted surface area (WSA) method with regard to country, ship type and donor bioregion. WSA flux reached 656 km2, of which 86% was associated with ships operating inside and 14% was WSA flux brought by ships from outside of the Baltic Sea. Most of the WSA was transported to Swedish, Finnish and Danish ports as well. The highest WSA flux was assigned to roll-on/roll-off, passenger and general cargo ships. The high biofouling potential in BSR indicates a potential high risk to the environment and, therefore there is an urgent need for appropriate guidelines to be introduced into daily use by the commercial shipping community. [ABSTRACT FROM AUTHOR]

Thermal bubble-driven micro-pumps are an upcoming micro-actuator technology that can be directly integrated into micro/mesofluidic channels, have no moving parts, and leverage existing mass production fabrication approaches. These micro-pumps consist of a high-power micro-resistor that boils fluid in microseconds to create a high-pressure vapor bubble which performs mechanical work. As such, these micro-pumps hold great promise for micro/mesofluidic systems such as lab-on-a-chip technologies. However, to date, no current work has studied the interaction of these micro-pumps with biofluids such as blood and protein-rich fluids. In this study, the effects of organic fouling due to egg albumin and bovine whole blood are characterized using stroboscopic high-speed imaging and a custom deep learning neural network based on transfer learning of RESNET-18. It was found that the growth of a fouling film inhibited vapor bubble formation. A new metric to quantify the extent of fouling was proposed using the decrease in vapor bubble area as a function of the number of micro-pump firing events. Fouling due to egg albumin and bovine whole blood was found to significantly degrade pump performance as well as the lifetime of thermal bubble-driven micro-pumps to less than 104 firings, which may necessitate the use of protective thin film coatings to prevent the buildup of a fouling layer. [ABSTRACT FROM AUTHOR]

Updated understanding on the effect of biofouling on corrosion rate is needed to protect marine structures as climate change is altering seawater physiochemistry and biofouling organism distribution. Multi-disciplinary techniques can improve understanding of biofouling development and associated corrosion rates on metals immersed in natural seawater (NSW). In this study, the development of biofouling and corrosion on welded Nickel Aluminium Bronze (NAB) was investigated through long-term immersion tests in NSW, simulated seawater (SSW) and air. Biofouling was affected by geographic location within the marina and influenced corrosion extent. The corrosion rate of NAB was accelerated in the initial months of exposure in NSW (1.27 mm.yr−1) and then settled to 0.11 mm.yr−1 (annual average). This was significantly higher than the 0.06 mm.yr−1 corrosion rate measured in SSW, which matched published rates. The results suggest that corrosion rates for cast NAB should be revised to take account of biofouling and updated seawater physiochemistry. [ABSTRACT FROM AUTHOR]

Quorum quenching (QQ) by cell entrapping beads (CEBs) is known to inhibit biofouling by its biological and physical cleaning effect. Although there are better QQ media reported, due to the ease of fabrication of QQ-CEBs, this study focused on improving the quality of CEBs by comparing two distinct bead-making methods – polyvinyl alcohol-alginate (PVA-alginate) and phase inversion – and on finding the optimum concentration of QQ bacteria in the CEBs. The evaluation of PVA-alginate bead showed better uniformity, and higher mechanical and chemical strength in comparison with the phase inversion bead. Through the operations of two control membrane bioreactors (MBRs) (no bead, vacant bead) and four QQ-MBRs with different Rhodococcus sp. BH4 concentrations (2.5–15 mg cell ml−1) in PVA-alginate CEBs, the maximum QQ effect was observed by 5 mg ml−1 BH4 concentration beads. This implies that an optimum cell concentration of QQ-CEBs is crucial to economically improve MBR performance using QQ. [ABSTRACT FROM AUTHOR]

The identification and management of biofouling remain pressing challenges in marine and freshwater ecosystems, with significant implications for environmental sustainability and industrial operations. This comprehensive review synthesizes the current state-of-the-art in biofouling identification technologies, examining eight prominent methodologies: Microscopy Examination, Molecular Biology, Remote Sensing, Community Involvement, Ecological Methods, Artificial Intelligence, Chemical Analysis, and Macro Photography. Each method is evaluated for its respective advantages and disadvantages, considering factors such as precision, scalability, cost, and data quality. Furthermore, the review identifies current obstacles that inhibit the optimal utilization of these technologies, ranging from technical limitations and high operational costs to issues of data inconsistency and subjectivity. Finally, the review posits a future outlook, advocating for the development of integrated, standardized systems that amalgamate the strengths of individual approaches. Such advancement will pave the way for more effective and sustainable strategies for biofouling identification and management. [ABSTRACT FROM AUTHOR]

Coral reefs are highly biodiverse ecosystems, enriched by a range of biofouling species. Temporal variations in biofouling can affect ecosystem stability, but these diverse coral-associated communities remain underexplored in some regions. In the present study, biofouling assemblages of coral reefs in the Chabahar Bay were investigated during a summer monsoon at three deployment periods. In total, 26 taxa were identified with barnacles and polychaetes being the dominant taxa during the whole study. The coverage percentage was driven mostly by the encrusting taxa such as bryozoans and algae while biomass was determined by the dominance of shell-forming taxa. The results of PERMANOVA showed that the effects of the submersion period were significant on the assemblage structure. Biofouling assessment plays a pivotal role in safeguarding the intricate balance and long-term health of coral reef ecosystems. For a comprehensive understanding of biofouling dynamics and interactions with coral-associated species, conducting long-term studies is vital. [ABSTRACT FROM AUTHOR]

Nuclear facility discharge pipelines accumulate inorganic and microbial fouling and radioactive contamination, however, research investigating the mechanisms that lead to their accumulation is limited. Using the Sellafield discharge pipeline as a model system, this study utilised modified Robbins devices to investigate the potential interplay between inorganic and biological processes in supporting fouling formation and radionuclide uptake. Initial experiments showed polyelectrolytes (present in pipeline effluents), had minimal effects on fouling formation. Biofilms were, however, found to be the key component promoting fouling, leading to increased uptake of inorganic particulates and metal contaminants (Cs, Sr, Co, Eu and Ru) compared to a non-biofilm control system. Biologically-mediated uptake mechanisms were implicated in Co and Ru accumulation, with a potential bioreduced Ru species identified on the biofilm system. This research emphasised the key role of biofilms in promoting fouling in discharge pipelines, advocating for the use of biocide treatments methods. [ABSTRACT FROM AUTHOR]

Bryozoans are commonly associated with various artificial structures in marine environments and have been responsible for several bioinvasion events worldwide. Understanding the interactions between bryozoans and artificial structures is therefore essential to prevent the establishment and spread of potential bioinvaders. This study investigated bryozoan recruitment on four different substrates (PET, nautical ropes, metal, and PVC) placed in three orientations (vertical, horizontal facing down and facing up) in an area of the Western Atlantic. In total, 15 species of bryozoans were found. The results revealed significant variations in assemblages' richness, with bryozoans showing a preference for settling on PVC (14 species found) and on the underside of horizontal substrates (15 species found), resulting in the higher representativity observed in this study. Cryptogenic (nine species) and exotic (five species) bryozoans dominated the assemblages in all treatments, indicating that the type of substrate (especially artificial) and its orientation can favor the settlement of bryozoans, particularly non-native species. Therefore, the availability of multiple types of artificial substrates in marine environments should be treated as a cause for concern. [ABSTRACT FROM AUTHOR]

Ecological monitoring has been recognized as a key tool for guiding biofouling management practices. A two-year study was designed to collect comprehensive data on the biofouling community progression at Port Canaveral, Florida, using clear recruitment panels and a scanner to directly observe organisms attached to the surface. This method allowed for minimal disruption to the natural community development and aided the collection of a suite of metrics to explore environmental relationships. Seasonal changes in community composition and biofouling pressure, especially at earlier stages, were related to abiotic conditions. Interannual variation within seasonal communities was also observed. The type of dominant organism present impacted the rate at which surfaces were covered (e.g. fastest cover with tunicates) and the overall biomass accumulation (e.g. highest rate with tubeworms). Results highlight that understanding the influence of the time of year and the dominant organism identity is ecologically vital for improving biofouling management. [ABSTRACT FROM AUTHOR]

Marine biofouling is a global problem affecting various industries, particularly the shipping industry due to long-distance voyages across various ecosystems. Therein fouled hulls cause increased fuel consumption, greenhouse gas emissions, and the spread of invasive aquatic species. To counteract these issues, biofouling management plans are employed using manual cleaning protocols and protective coatings. This review provides a comprehensive overview of adhesion strategies of marine organisms, and currently available mitigation methods. Further, recent developments and open challenges of antifouling (AF) and fouling release (FR) coatings are discussed with regards to the future regulatory environment. Finally, an overview of the environmental and economic impact of fouling is provided to point out why and when the use of biocidal solutions is beneficial in the overall perspective. [ABSTRACT FROM AUTHOR]

This study investigated the biofouling potential of surface-enhanced Raman scattering (SERS)-based sensor materials in the context of marine environments. Uncoated and monolithic commercial gold (Au) silicon nanopillar array SERS substrates, Au-coated carbon black nanoparticle (AuCB NP) substrates, uncoated and Au sputter-coated in-house SERS, and uncoated and Au sputter-coated glass controls were tested for biofouling potential using Ulva spp. as model biofouling organisms. The mean percentages of Ulva spp. zoospores that adhered per mm2 (×103) on the uncoated and coated Au silicon nanopillar array, AuCB NP, uncoated and Au sputter-coated in-house, and uncoated and Au sputter-coated glass substrates were 10.28%, 5.45%, 10.49%, 3.25%, 24.84%, 12.86% and 7.78%, respectively. Results indicated that surface properties such as hydrophobicity, roughness, Au sputter-coating and the presence of micro-refuges on nano- and microstructured substrates were critical to the biofouling formation. [ABSTRACT FROM AUTHOR]

In order to build an efficient closed-photobioreactor (PBR) in which biofouling formation is avoided, a non-toxic coating with high transparency is required, which can be applied to the interior surface of the PBR walls. Nowadays, amphiphilic copolymers are being used to inhibit microorganism adhesion, so poly(dimethylsiloxane)-based coatings mixed with poly(ethylene glycol)-based copolymers could be a good option. The 7 poly(dimethylsiloxane)-based coatings tested in this work contained 4% w/w of poly(ethylene glycol)-based copolymers. All were a good alternative to glass because they presented lower cell adhesion. However, the DBE-311 copolymer proved the best option due to its very low cell adhesion and high transmittance. Furthermore, XDLVO theory indicates that these coatings should have no cell adhesion at time 0 since they create a very high-energy barrier that microalgae cells cannot overcome. Nevertheless, this theory also shows that their surface properties change over time, making cell adhesion possible on all coatings after 8 months of immersion. The theory is useful in explaining the interaction forces between the surface and microalgae cells at any moment in time, but it should be complemented with models to predict the conditioning film formation and the contribution of the PBR's fluid dynamics over time. [ABSTRACT FROM AUTHOR]

Microbial biofilm development on the membrane surface of bioreactors results in membrane flux decline (biofouling). Biofouling is one of the most severe problems limiting the use of these bioreactors. For detailed understanding of the biofouling, microbial community and dissolved organic matter analyses have been performed in recent decades. Although most previous studies have focused on mature biofilms at the end point of biofouling, understanding of the early stages is crucial to mitigate biofilm formation. Thus, recent studies have focused on the impact of early-stage biofilm development and indicated a clear difference in microbial communities between early-stage and mature biofilms. In addition, certain bacteria play a significant role in early-stage biofilms. The present mini-review systematically summarizes the foulants present during early-stage fouling, provides novel perspectives on fouling mechanisms, and discusses the neglected effect of planktonic bacteria. [ABSTRACT FROM AUTHOR]

This work assesses the biofouling formation of a microalgal consortium, cultivated in wastewater, on dialysis tubular membranes with no supporting layer, in both batch and continuous FO dewatering modes. The biological adhesion strength was compared with the predictions from the Baier and Vogler biocompatibility theories, employing critical surface tension ( γ c ) and water adhesion tension (τ0), respectively, as measurable parameters of surface wettability. The results indicate that most of the tested membranes presented amphiphilic surface characteristics (τ0=22 to 45 mJ.m−2, θW ≈ 65˚) with a minimal biological adhesion tendency, which is compatible with the Vogler criteria. However, the membrane exposed the longest time to the microalgal culture presented more hydrophobic characteristics and poor wettability. The existing thermodynamic models succeeded in predicting cell-cell and cell-surface interactions as a competitive phenomenon. Nevertheless, the XDLVO model was used to determine changes in the cell-to-surface attraction dynamics. This assessment of microalgal foulant-membrane interfacial interactions helps to enhance understanding of the fouling mechanisms present on a novel FO membrane surface. [ABSTRACT FROM AUTHOR]

In biofouling communities, ascidians are among the most damaging species, presenting severe threats, such as depressed growth rates and decreased chances of lower survival, to shellfish aquaculture. However, little is known concerning the fouled shellfish physiology. In an effort to obtain information for the magnitude of stress caused by ascidians to farmed Mytilus galloprovincialis, five seasonal samplings took place in a mussel aquaculture farm suffering from ascidian biofoulants, in Vistonicos Bay, Greece. The dominant ascidian species were recorded and several stress biomarkers, including Hsp gene expression at both mRNA and protein levels, as well as MAPKs levels, and enzymatic activities of intermediate metabolism were examined. Almost all investigated biomarkers revealed elevated stress levels in fouled mussels compared to non-fouled. This enhanced physiological stress seems to be season-independent and can be attributed to the oxidative stress and/or feed deprivation caused by ascidian biofouling, thus illuminating the biological impact of this phenomenon. [ABSTRACT FROM AUTHOR]

Biofouling is a major challenge for sustainable shipping, filter membranes, heat exchangers, and medical devices. The development of fouling-resistant coatings requires the evaluation of their effectiveness. Such an evaluation is usually based on the assessment of fouling progression after different exposure times to the target medium (e.g. salt water). The manual assessment of macrofouling requires expert knowledge about local fouling communities due to high variances in phenotypical appearance, has single-image sampling inaccuracies for certain species, and lacks spatial information. Here an approach for automatic image-based macrofouling analysis was presented. A dataset with dense labels prepared from field panel images was made and a convolutional network (adapted U-Net) for the semantic segmentation of different macrofouling classes was proposed. The establishment of macrofouling localization allows for the generation of a successional model which enables the determination of direct surface attachment and in-depth epibiotic studies. [ABSTRACT FROM AUTHOR]

This study explored the applicability of chemical cleaning and air-backwash to alleviate biofouling on seawater membrane distillation (SWMD). Membrane performance and wettability properties maintained at optimum duration and frequency of the treatments, as indicated by low permeate conductivity throughout the tests. The cleaning of the membrane using 2% NaOH by immersing the membrane for 30 min after 240 min operation removed the biofouling layer, indicated by low permeate conductivity of 370 µScm−1 after cleaning. However, more frequent membrane cleaning led to membrane damage, more severe wetting, and membrane hydrophobicity reduction. Ten-second air-backwash after 240 min of operation was also effective in controlling the biofouling, particularly when conducted at air pressure of 1 bar. More frequent air-backwash resulted in more aggravated inorganic fouling and accelerated biofouling formation due to the recurring introduction of air, leading to rapid membrane wetting. [ABSTRACT FROM AUTHOR]

The decline in the performance of spiral-wound reverse osmosis (SWRO) membranes is frequently due to biofouling. This study focus on qualitative and quantitative diagnosis of SWRO membrane biofouling. Bacterial counts on the different surfaces of the fouled membranes were carried out. Surface enhanced Raman spectroscopy (SERS) was performed to highlight clogging materials as well as their natures and identity. The topography of the fouled membranes and the structures of biofilms were visualized by fluorescence microscopy (FM) and scanning electron microscopy (SEM). The results indicated the presence of bacteria in the different SWRO membrane areas. Those strongly adhered were significantly higher than those weakly. It varied between 26 × 105 and 262 × 105 CFU m−2. However, SERS mapping showed different fouling levels and the thickness of the fouling layer was 5 µm. Microscopic imaging revealed biotic and abiotic deposits. These data can together allow better management of the seawater desalination process. [ABSTRACT FROM AUTHOR]

Vessel hull-fouling is responsible for most bioinvasion events in the marine environment, yet it lacks regulation in most countries. Although experts advocate a preventative approach, research efforts on pre-arrival processes are limited. The performance of mobile epifauna during vessel transport was evaluated via laboratory simulations, using the well-known invasive Japanese skeleton shrimp (Caprella mutica), and its native congener C. laeviuscula as case study. The invader did not possess any advantage in terms of inherent resistance to drag. Instead, its performance was conditioned by the complexity of secondary substrate. Dislodgement risk was significantly reduced when sessile fouling basibionts were added, which provided refugia and boosted the probability of C. mutica remaining attached from 7 to 65% in flow exposure trials. Interestingly, the invader exhibited significantly higher exploratory tendency and motility than its native congener at zero-flow conditions. Implications in terms of en-route survivorship, invasion success and macrofouling management are discussed. [ABSTRACT FROM AUTHOR]

The impact of barnacle epibionts on the condition of the shore crab Carcinus maenas was studied for the western Wadden Sea population. Approximately 39% of the crabs were fouled with the barnacle Balanus crenatus. Although the morphological Fulton's K condition decreased by 5.8% in fouled crabs, Linear Mixed-Effects Models (LMM) showed that only the energetic condition of the crabs was significantly affected by fouling. The energy density of fouled crabs was consistently poorer (4.1% in AFDW; 8.7% in dry weight) than that of non-fouled crabs, especially in females and green forms in dry weight (12.8% and 11.4% reduction, respectively). Cumulative infection with Sacculina carcini, detected in 4.5% of the fouled crabs, additionally reduced by 14.3% the energy density in dry weight and almost to half of the total energy of the fouled crabs. Impacts of energy density reduction on crabs' growth and reproduction are discussed. [ABSTRACT FROM AUTHOR]

Biofouling is a problem affecting the operation of nanofiltration systems due to the complexity of the carbon matrix affecting bacteria and biofilm growth. This study used membrane fouling simulators to investigate the effects of five different carbon sources on the biofouling of nanofiltration membranes. For all the carbon sources analyzed, the increase in pressure drop was most accelerated for acetate. The use of acetate as the single carbon source produced less adenosine triphosphate but more extracellular polymers than glucose. The microbial community was analyzed using 16 s rRNA. The use of more than a single carbon source produced an increase in bacteria diversity even at similar concentrations. The relative abundance of proteobacteria was the highest at the phylum level (95%) when a single carbon source was added. Additionally, it was found that the use of different carbon sources produced a shift in the microbial community, affecting the biofouling and pressure drop on membranes. [ABSTRACT FROM AUTHOR]

Biofouling on marine renewable energy devices presents engineering challenges for this developing sector, and has implications for the spread of marine non-native species (NNS) in coastal waters. This is particularly true at sites with abundant energy resource, little existing infrastructure, and few established NNS. Device coatings, such as antifouling paints, could reduce the risk of NNS spread. Settlement on coatings of various types and colours, representing those likely to be used on renewable energy devices, was assessed in the Orkney Islands, northern Scotland. Assemblage composition, but not overall biofouling cover, varied initially among different coloured surfaces, although differences decreased over time. Different coating types (an anticorrosive paint, a biocidal paint and a fouling-release coating) differed in biofouling abundance and composition for the full duration of the experiment. NNS were mostly, but not completely, absent from antifouling surfaces. These results can help informing antifouling strategies for the marine renewable energy industry. [ABSTRACT FROM AUTHOR]

The deep sea survivability and biofouling characteristics of corrosion-resistant bulk carbon nanotubes (CNTs) have been studied after deployment in the Atlantic Ocean over the course of 12 months. Quantification of barnacle count, biofouling density, and non-combustible residue shows cyanoacrylate coatings increase durability and reduce the colonization of biofouling compared to as-received CNTs. Scanning electron microscopy was performed on the biofouled CNTs, and the majority of species were identified as diatoms, consisting of an ordered silica cell wall. Both the as-received and cyanoacrylate-treated CNTs were successfully acid purified to remove biogrowth, leading to complete recovery of tensile strength and electrical transport properties. Thermogravimetric analysis, scanning electron microscopy, contact angle, dynamic mechanical analysis, and current carrying capacity measurements validated the refunctionalization results. Thus, the multifunctional property recovery and enhanced durability confirms that CNTs are electrochemically stable in saltwater environments and are resilient to biofouling conditions in real-world environments after extended exposure. [ABSTRACT FROM AUTHOR]

Past studies of Ultraviolet-C (UV-C) radiation as a marine antifoulant have focused on repeated doses. However, single or very low frequency exposures of UV-C could create more plausible applications for certain marine structures. The objective of the study reported here was to apply a single treatment of UV-C radiation to an early stage marine biofouling community to observe subsequent effects on biofouling development. Biofouling formed over a 2-week field immersion received UV-C treatments of 0 (control), 4, 20, or 120 min, and subsequent progression was then monitored weekly for 16 weeks. Analysis of acute effects and later macrofouling development suggested direct toxicity of UV-C illumination to invertebrate recruits caused reduction of subsequent biofouling (compared to controls) that persisted for up to 16 weeks following the longest UV-C treatment. Thus, UV-C treatments spaced by days or even weeks could be an option for some applications of UV-C radiation as an antifoulant. [ABSTRACT FROM AUTHOR]

This work analyses the adhesion of flagellated microalgae to seven surfaces that have different water adhesion tension characteristics. Chlamydomonas reinhardtii and Isochrysis galbana, were cultivated in batch and fed-batch mode at four nitrogen/phosphorus (N/P) ratios (from 1.29 to 70) and subjected to four irradiance levels (50, 100, 200 and 400 µE·s−1·m−2) at 23 °C. Cell adhesion was greater in C. reinhardtii and a higher biomass concentration was obtained for this strain, reaching 2 g·L−1 compared to 1 g·L−1 for I. galbana. The adhesion of cells and exopolymeric substances was measured upon the batch and the first fed-batch reaching the stationary growth phase, observing a direct correlation between them and inversely to biomass generation in the cultures. The protein adhesion data for the different materials are comparable to those for cell adhesion coinciding with minimums of Baier's theory and Vogler. It is observed displacements in the curves as a function of the irradiance level. [ABSTRACT FROM AUTHOR]

Membrane costs and biofouling limit applications of membrane bioreactors (MBRs) for wastewater treatment. Here, powdered activated carbon (PAC) utilization in the formation and performance of a self-forming dynamic membrane consisting of activated sludge and PAC during hybrid wastewater treatment process was studied. Short-term agitation helped (non)biological particles to quickly uniformly settle on mesh filter, forming more uniform PAC-containing dynamic membranes (PAC-DMs). PAC adsorbed adhesive materials, resulting in an increase in average floc size and DM permeability while decreasing biofouling. The most efficient PAC concentration was 4 g L−1 considering techno-economics, i.e. the highest effluent quality (turbidity of 19.89 NTU) and the lowest biofouling (transmembrane pressure rise of 2.89 mbar). Short-term performance of hybrid PAC-DM bioreactor (PAC-DMBR) showed stability in effluent quality improvement including 92%, 95%, 83%, 84% and 98% reductions in turbidity, chemical oxygen demand, total dissolved solids, total nitrogen, and total phosphorous, respectively. Accordingly, adopting hybrid PAC-DMBR has potential to alleviate biofouling and capital cost. [ABSTRACT FROM AUTHOR]

Grooming may be an effective technique to control marine biofouling without damaging the coating or discharging active ingredients into the environment. This study assessed the grooming performance of three experimental biocide-free siloxane polyurethane (SiPU) fouling-release coatings. Coatings were statically immersed in Port Canaveral, Florida, and groomed every two weeks for five months using three different brush types. The ungroomed panels became heavily fouled with biofilm, tubeworms, barnacles, and bryozoans. Two of the brushes were able to control the fouling with a coverage of <5%. The commercial silicone elastomer coating was damaged from grooming procedures, while the SiPU coatings were not. Laboratory biological assays were carried out and mirrored the grooming results. Through surface characterization techniques, it was concluded that the coatings were unaffected by the grooming procedures. This study shows that marine fouling on durable SiPU fouling-release coatings can be controlled via grooming without damage or changing the surface properties. [ABSTRACT FROM AUTHOR]

Ostreid herpesvirus 1 (OsHV-1) has caused mass mortalities in Pacific oysters (Crassostrea gigas) in Europe, Australia, and New Zealand. While aquaculture-associated movements of infected Pacific oysters are a well-known cause of OsHV-1 spread once established in a region, translocation via biofouling of aquaculture equipment or vessels needs further investigation to explain the more distant spread of OsHV-1. Laboratory experiments were designed to test for transmission of OsHV-1 between infected and naïve Pacific oysters via a simulated biofouling translocation scenario. Three common biofouling species [Sydney rock oysters (Saccostrea glomerata), Mediterranean mussels (Mytilus galloprovincialis) and Pacific oysters] were tested as intermediaries using a cohabitation challenge with Pacific oysters infected by injection. Transmission occurred, albeit for one of eight replicates when Pacific oysters were the intermediary species. This demonstrated a possible pathway for pathogen spread via biofouling containing Pacific oysters while highlighting the complexity of OsHV-1 transmission. Such complexities require further investigation to inform future risk assessments and management of fouled aquaculture equipment and vessels. [ABSTRACT FROM AUTHOR]

The study included the sampling of 12 marinas across six areas of the Baltic Sea with settlement plates and scraping of submerged structures to assess the role of marinas in the spread of non-indigenous species (NIS) via biofouling. 15 NIS were detected in the marinas and secondary spread of previously introduced NIS was detected in five out of six sea areas. Salinity and sea area significantly affected the composition of the fouling assemblages. Settlement plates appeared as the more efficient sampling method over scraping, while the seasonal analyses revealed that the monitoring effort should span over the summer and early autumn in the south-eastern, central, and northern Baltic Sea. The present findings indicate that marinas contribute to the spread of non-indigenous fouling organisms, and there is an increasing demand for the monitoring of marinas and stricter regulations regarding the biofouling management of leisure boats in the Baltic Sea. [ABSTRACT FROM AUTHOR]

The development of biofouling is a major problem for marine industries. The conception of antifouling and fouling release coatings, with controlled physical-chemical properties is a promising strategy. Among them, amphiphilic systems, such as those composed of a hydrophobic polydimethylsiloxane matrix and a hydrophilic polyethyleneglycol additive are the most efficient and up to date. Despite their effectiveness, these systems are questioned due to the petrochemical origin of PDMS. The aim of this project was to substitute the PDMS matrix with a biopolymer, poly(3-hydroxybuyrate-co-3-hydroxyvalerate) and to improve its anti-adhesion properties through the elaboration of an amphiphilic system, via the addition of PEG or PHBHHx-b-PEG copolymer. The results, including the physico-chemical properties of PHBHV based coatings and static adhesion tests on a marine bacterium, Bacillus 4J6 and a diatom, Phaeodactylum tricornutum are compared with those of PDMS and PEG-modified PDMS coatings. Real antiadhesion activity was obtained for the PHBHV/PHBHHx-b-PEG system for a promising eco-friendly strategy. [ABSTRACT FROM AUTHOR]

Biofouling, or the build-up of microorganisms in a biofilm at the solid-water or water-air interface, is an interdisciplinary problem. Biofouling causes various issues including clogging systems, contaminating devices, and creating infections that are extremely difficult to treat, to name but a few. Therefore, engineers, pharmacologists, microbiologists, wastewater treatment operators, chemists, food preservative formulators, home and personal care product formulators, and toxicologists all play a role in studying and have an interest in solving biofouling. High-throughput studies on biofilm prevention and removal can take the form of biofilm antimicrobial microdilution susceptibility (BAMS) tests. Due to vested interests of many disciplines, the results from these tests should be applicable and useful to each discipline. This critical review analyses the focuses, biological implications, and metrics required by each discipline. The possible detection methods that could satisfy each desired metric are then summarized. The detection methods were analysed in order to recommend two methods of biofilm detection, Crystal Violet stain and the LIVE/DEAD BacLight stain, which correspond with three metrics including total biomass, log reduction, and the MIC, BPC, MBIC, MBC, BBC, and/or MBEC values. Determining these three metrics for each BAMS test will allow this type of research to be widely applicable and useful across many disciplines. [ABSTRACT FROM AUTHOR]

A rapid benchtop method to measure the torque associated with minidiscs rotating in water using a sensitive analytical rheometer has been used to monitor the drag caused by marine fouling on coated discs. The method was calibrated using sandpaper surfaces of known roughness. Minidiscs coated with commercial fouling control coatings, plus an inactive control, were exposed in an estuarine harbour. After 176 days the drag on the fouling control-coated discs, expressed as a moment coefficient, was between 73% and 90% less than the drag on the control coating. The method has potential use as a screen for novel antifouling and drag reducing coatings and surfaces. Roughness functions derived using Granville's indirect similarity law are similar to patterns found in the general hydrodynamics literature, and so rotational minidisc results can be considered with reference to other fouling drag datasets. Supplemental data for this article is available online at https://doi.org/10.1080/08927014.2021.1929937. [ABSTRACT FROM AUTHOR]

A novel system was developed to deploy settlement panels to monitor biofouling growth in situ and evaluate antifouling coatings at depths representative of operational conditions of full-scale marine renewable energy devices. Biofouling loading, species diversity, and succession were assessed at depths ranging from 25-40 m at four tests sites in Orkney (UK) featuring extreme wave and tidal current exposure to more sheltered conditions. Evaluations were carried out over a period of 8 months with intermediate retrieval of samples after 3 months. Early pioneer fouling communities, comprised of colonial hydroids, were succeeded by tube-forming amphipods across sites while solitary tunicates dominated in greater shelter. The highest biofouling loading was observed on high-density polyethylene (HDPE) panels (6.17 kg m−2) compared with coated steel (3.34 kg m−2) panels after 8 months. Distinct assemblages were present at exposed vs sheltered sites. Better understanding of fouling and antifouling strategies may provide guidance to more effectively manage biofouling impacts in this sector. [ABSTRACT FROM AUTHOR]

It is well-established that hydrodynamics affect the settlement of biofouling organisms. Laboratory studies have demonstrated a connection between larval attachment rates and the prevalence of time windows that satisfy certain instantaneous flow conditions. However, it is unclear whether a link exists between short-term hydrodynamics and long-term macrofouling survival and growth, or if it is applicable at an ecosystem-wide level. This study used single bubble stream aeration in field and laboratory experiments to find critical flow characteristics that correlate to long-term, multi-species fouling prevention. The research was accomplished by combining PIV-derived flow statistics with fouling severity measured over seven weeks in the field. Flows with a decreasing proportion of time windows defined by a flow speed < 15.1 mm s−1 for longer than 0.03 s correlated to decreased biofouling growth and survival. These results provide a potential framework for studying and comparing flow fields that successfully inhibit biofouling growth. [ABSTRACT FROM AUTHOR]

Biofouling is a widespread phenomenon in oceans worldwide. With increasing human development and activities in open and coastal waters, and due to the environmental impact of AF organotins and copper-based paint, the demand for nontoxic antifouling (AF) paints is increasing. Various bioassays for antimicrobial activity, anti-biofilm formation and anti-barnacle settlement were established to evaluate the possibility of using marine natural products as AF agents. A series of natural products, isolated from the marine-derived fungi Trichoderma atroviride and T. reesei, were evaluated for their AF activity. One pyrone-type compound (1) demonstrated significant inhibitory activities toward barnacle cyprid settlement. Furthermore, a series of pyrone analogues (S1–S6) were synthesized, and their bioactivities were evaluated in the established systems. The results showed that compounds S5 and S6 exhibited a broad spectrum of bioactivities, such as anti-barnacle settlement, anti-biofilm formation and antimicrobial activities. [ABSTRACT FROM AUTHOR]

3-D printing allows for rapid prototyping and manufacture of components in a cost effective and timely manner, becoming a popular technology for oceanographic and maritime engineering applications. However, 3-D printed components are at risk of accumulating marine biofouling. This study examined the antifouling (AF) performance of three Cu-containing 3-D printing polymer filaments for potential marine use. The amount of Cu present in each filament was the primary determinant of AF performance. The lowest Cu-content (30%) filament recording 29% biofouling cover after 1 month and near 100% cover after 3 months. These AF results were comparable to polylactide acid (PLA) and acrylonitrile butadiene styrene (ABS) polymer filament controls. The medium (50%) Cu-content filament remained largely free of biofouling until 3 months (where 48% coverage was observed), after which fouling cover increased to 100% by ∼12 months. The highest Cu-content (80%) filament remained free of all macrofouling for the entire 24 months of the experiment. [ABSTRACT FROM AUTHOR]

This study first examines the minimum power requirements of a tanker according to the IMO 2013 Interim Guideline (IMO 2013). For the estimation of the added resistance in waves a recently introduced semi-empirical method is used. Secondly, the influence of the increase in surface roughness of the hull and propeller due to fouling is investigated, reflecting the actual condition of a ship in service. The results show that even if ships are fulfilling the IMO 2013 Guideline, they may become unsafe in operation. Lastly, the uncertainties involved in the assessment procedure are discussed. The investigation conducted is particularly of interest for the assessment of the safety of ships now being idle or used as floating storage due to the impact of the pandemic COVID-19 on the world economy, while they are expected to go again into service once the demand for transport recovers. [ABSTRACT FROM AUTHOR]

Biofouling communities are spatiotemporally diverse, underscoring the need to assess fouling-release (FR) coating performance against common biofouling taxa at multiple field sites. Adhesion strength assessments of FR coatings incorporate few taxa into standardized protocols. This study tested the feasibility of incorporating existing ASTM barnacle protocols on tubeworms and encrusting bryozoans (EB). Additionally, trends in adhesion strength among these taxa were compared at two field sites. EB adhesion at both field sites showed consistent results and adhesion strength followed the same trend: tubeworms > barnacles >EB. Testing EB adhesion was feasible and enhanced assessments of FR coatings by increasing the diversity of assessed taxa. [ABSTRACT FROM AUTHOR]

To develop a better understanding of 'in-service' performance of modern marine coatings, this study explored the combined effects of different roughness ranges of foul-release coating (FRC) and light biofouling (slime) on the surface, boundary layer and drag characteristics under a range of 'in-service' conditions. Natural and laboratory biofilms were grown dynamically on FRC panels by exposing panels in facilities dedicated to realistic fouling culture. The boundary layer experiments were conducted in a circulating water tunnel. Boundary layer similarity-law scaling was used to predict the combined effects of coating roughness and biofilms on the added frictional resistance (% Δ C F) and added required effective power (% Δ P E ) for a benchmark KRISO container ship (KCS) and a bulk carrier. The increase in % Δ P E due to the presence of biofilms on commercial FRC is estimated to be between 7% and 16% depending on the biofilm type, biofilm thickness and percentage coverage. Significant increases in effective power are estimated for non-fouling control primers with heavy fouling. Moreover, the paper suggests updated roughness allowances ( Δ C F ) for two vessel types assuming FRCs on their hulls with more representative hull roughness ranges and fluffy biofilms. [ABSTRACT FROM AUTHOR]

The biofouling removal ability of a shear-based device was tested on two submerged surface types, Garolite G-10 and Intersleek 1100SR. Each surface was groomed at four frequencies along with a control group. The seven-week grooming study was conducted in Narragansett Bay, Rhode Island. The Bernoulli pad device uses confined radial outflow to generate both surface-normal forces to grip the submerged surface and shear stress to groom the surface without contact. An image-processing algorithm was developed and used to assess the effectiveness of the various grooming protocols, along with direct measurements of chlorophyll a per surface area. The image-processing data showed that the grooming resulted in ∼50% cleanliness on the Garolite at the end of the study whereas the Intersleek was continuously restored to nearly its initial clean state. Chlorophyll a data supported these overall conclusions. These results indicate that surface cleanliness can be maintained effectively on Intersleek using frequent shear-based grooming. [ABSTRACT FROM AUTHOR]

Phosphate limitation has been suggested as a preventive method against biofilms. P-limited feed water was studied as a preventive strategy against biofouling in cooling towers (CTs). Three pilot-scale open recirculating CTs were operated in parallel for five weeks. RO permeate was fed to the CTs (1) without supplementation (reference), (2) with supplementation by biodegradable carbon (P-limited) and (3) with supplementation of all nutrients (non-P-limited). The P-limited water contained ≤10 µg PO4 l−1. Investigating the CT-basins and coupons showed that P-limited water (1) did not prevent biofilm formation and (2) resulted in a higher volume of organic matter per unit of active biomass compared with the other CTs. Exposure to external conditions and cycle of concentration were likely factors that allowed a P concentration sufficient to cause extensive biofouling despite being the limiting compound. In conclusion, phosphate limitation in cooling water is not a suitable strategy for CT biofouling control. [ABSTRACT FROM AUTHOR]

Cyanobacteria promote marine biofouling with significant impacts. A qualitative proteomic analysis, by LC-MS/MS, of planktonic and biofilm cells from two cyanobacteria was performed. Biofilms were formed on glass and perspex at two relevant hydrodynamic conditions for marine environments (average shear rates of 4 s−1 and 40 s−1). For both strains and surfaces, biofilm development was higher at 4 s−1. Biofilm development of Nodosilinea sp. LEGE 06145 was substantially higher than Nodosilinea sp. LEGE 06119, but no significant differences were found between surfaces. Overall, 377 and 301 different proteins were identified for Nodosilinea sp. LEGE 06145 and Nodosilinea sp. LEGE 06119. Differences in protein composition were more noticeable in biofilms formed under different hydrodynamic conditions than in those formed on different surfaces. Ribosomal and photosynthetic proteins were identified in most conditions. The characterization performed gives new insights into how shear rate and surface affect the planktonic to biofilm transition, from a structural and proteomics perspective. [ABSTRACT FROM AUTHOR]

Biofouling control in reverse osmosis membranes (ROMs) is challenging due to the high cost of treatments, and reduction in the life of ROMs. This study characterizes the biofouling in the ROMs from a desalination plant and reports its effective removal using the supernatant obtained from Alteromonas sp. strain Ni1-LEM. The characterization of the bacterial community revealed that the most abundant taxa in ROMs were the genera Fulvivirga and Pseudoalteromonas, and unclassified species of the families Flavobacteriaceae and Sphingomonadaceae. This bacterial community significantly decreased upon treatment with the supernatant from Alteromonas sp. Ni1-LEM, resulting in the prevalence of the genus Pseudoalteromonas. Furthermore, this bacterial supernatant significantly inhibited cell adhesion of seven benthic microalgae isolated from ROMs as well as promoting cell detachment of the existing microbial biofilms. The study showed that the extracellular supernatant modified the conformation of extracellular polymeric substances (EPS) in the biofouling of ROMs without any biocidal effects. [ABSTRACT FROM AUTHOR]

Biofouling accumulation on ships' submerged surfaces typically occurs during stationary periods that render surfaces more susceptible to colonization than when underway. As a result, stationary periods longer than typical port residence times (hours to days), often referred to as lay-ups, can have deleterious effects on hull maintenance strategies, which aim to minimize biofouling impacts on ship operations and the likelihood of invasive species transfers. This experimental study tested the effects of different lay-up durations on the magnitude of biofouling, before and after exposure to flow, using fouling panels with three coating treatments (antifouling, foul-release, and controls), at two sites, and a portable field flume to simulate voyage sheer forces. Control panels subjected to extended stationary durations (28-, 45- and 60-days) had significantly higher biofouling cover and there was a 13- to 25-fold difference in biofouling accumulation between 10-days and 28-days of static immersion. Prior to flume exposure, the antifouling coating prevented biofouling accumulation almost entirely at one site and kept it below 20% at the other. Foul-release coatings also proved effective, especially after flume exposure, which reduced biofouling at one site from >52% to <6% cover (on average). The experimental approach was beneficial for co-locating panel deployments and flume processing using a consistent (standardized) flow regime on large panels across sites of differing conditions and biofouling assemblages. While lay-ups of commercial vessels are relatively common, inevitable, and unavoidable, it is important to develop a better understanding of the magnitude of their effects on biofouling of ships' submerged surfaces and to develop workable post-lay-up approaches to manage and respond to elevated biofouling accumulation that may result. [ABSTRACT FROM AUTHOR]

Various quorum quenching (QQ) media have been developed to mitigate membrane biofouling in a membrane bioreactor (MBR). However, most are expensive, unstable and easily trapped in hollow fibre membranes. Here, a sol-gel method was used to develop a mesoporous silica medium entrapping a QQ bacterial strain (Rhodococcus sp. BH4). The new silica QQ medium was able to remove quorum sensing signalling molecules via both adsorption (owing to their mesoporous hydrophobic structure) and decomposition with an enzyme (lactonase), preventing MBR biofouling without affecting the water quality. It also demonstrated a relatively long life span due to its non-biodegradability and its relatively small particle size (<1.0 mm), which makes it less likely to clog in a hollow fibre membrane module. [ABSTRACT FROM AUTHOR]

The attachment efficiency of biofouling organisms on solid surfaces depends on a variety of factors, including fouler species, nutrition abundance, flow rate, surface morphology and the stiffness of the solid to which attachment is to be made. So far, extensive research has been carried out to investigate the effects of these factors on the attachment of various fouling species. However, the results obtained are species-dependent and scattered. There is no universal rule that can be applied to predict the attachment efficiency of different species. To solve this problem, the authors carried out meta-analysis of the effects of ten selected factors on attachment efficiency, resulting in a universal correlation between the attachment density and the selected factors, which was validated by attachment tests of tubeworms on PDMS surfaces. The results provide a practical approach to predicting the attachment efficiency of fouling organisms and should be of great value in the design of anti-biofouling materials. [ABSTRACT FROM AUTHOR]