Marine antifouling laboratory bioassays: an overview of their diversity

Biofouling dynamics and antifouling innovations: Transitioning from traditional biocides to nanotechnological interventions

Biofouling is a common phenomenon caused by waterborne organisms such as bacteria, diatoms, mussels, barnacles, algae, etc., accumulating on the surfaces of engineering structures submerged under water. This leads to corrosion of such surfaces and decreases their moving efficiency. Conventional antifouling agents are synthetic chemicals which are hazardous to non-target species. Further, these agents are mixed with paints, releasing toxins in the water bodies that affect other organisms. Thus, the development of natural alternatives for anti-fouling chemicals is urgently needed. This review examines the development of environmentally friendly antifouling technologies, focusing on the switch from biocidal coatings that leach toxic elements like mercury and copper to sustainable substitutes such as hybrid, biomimetic, and nanotechnology-based antifouling solutions. Research also focuses on increasing antifouling properties and reducing environmental impact by incorporating natural antifouling agents and constructing hybrid coatings that include multiple technologies. The financial effects of implementing these new technologies compared to more conventional approaches highlight the significance of sustainable practices in the maritime industry. This thorough review sheds light on the state of antifouling technology. It recommends future research to maximize ecological compatibility and apply these advancements to broader applications.

A comprehensive review of environment-friendly biomimetic bionic superhydrophobic surfaces

Marine fouling is a global problem that harms the ocean's ecosystem and the marine industrial sector. Traditional antifouling methods use harmful agents that damage the environment. As a result, recent research has focused on developing environmentally friendly, long-lasting, and sustainable antifouling solutions. Scientists have turned to nature for inspiration, particularly the water-repellent properties found in the microstructures of plants, insects and animals like the lotus leaf, butterfly, and shark. This review summarizes the current trends in developing superhydrophobic materials and fabrication techniques for bionic antifouling strategies. These strategies mimic the surface microstructures of various biological species, including the lotus leaf, coral tentacles, and the skins of sharks, whales, and dolphins. The review also discusses the technological applications of these biomimetic materials and the challenges associated with implementing them in the marine sector. Overall, the goal is to harness the superhydrophobicity of natural surfaces to create effective antifouling solutions.

Novel metabolite madeirone and neomarinone extracted from Streptomyces aculeoletus as marine antibiofilm and antifouling agents

Introduction: Biofouling poses a significant economic threat to various marine industries, leading to financial losses that can reach billions of euros annually. This study highlights the urgent need for effective alternatives to traditional antifouling agents, particularly following the global ban on organotin compounds. Material and methods: Streptomyces aculeolatus PTM-346 was isolated from sediment samples on the shores of the Madeira Archipelago, Portugal. The crude extract was fractionated using silica flash chromatography and preparative HPLC, resulting in two isolated marinone compounds: madeirone (1), a novel marinone derivative discovered in this study, and neomarinone (2). The antifouling activities of these compounds were tested against five marine bacterial species and the larvae of the mussel Mytilus galloprovincialis. Additionally, in silico and in vivo environmental toxicity evaluations of madeirone (1) and neomarinone (2) were conducted. Results: Madeirone (1) demonstrated significant antibiofilm efficacy, inhibiting Phaeobacter inhibens by up to 66%, Marinobacter hydrocarbonoclasticus by up to 60%, and Cobetia marina by up to 40%. Neomarinone (2) also exhibited substantial antibiofilm activity, with inhibition rates of up to 41% against P. inhibens, 40% against Pseudo-oceanicola batsensis, 56% against M. hydrocarbonoclasticus, 46% against C. marina, and 40% against Micrococcus luteus. The growth inhibition activity at the same concentrations of these compounds remained below 20% for the respective bacteria, highlighting their effectiveness as potent antibiofilm agents without significantly affecting bacterial viability. Additionally, both compounds showed potent effects against the settlement of Mytilus galloprovincialis larvae, with EC50 values of 1.76 µg/mL and 0.12 µg/mL for compounds (1) and (2), respectively, without impairing the viability of the targeted macrofouling species. In silico toxicity predictions and in vivo toxicity assays both support their potential for further development as antifouling agents. Conclusion: The newly discovered metabolite madeirone (1) and neomarinone (2) effectively inhibit both micro- and macrofouling. This distinct capability sets them apart from existing commercial antifouling agents and positions them as promising candidates for biofouling prevention. Consequently, these compounds represent a viable and environmentally friendly alternative for incorporation into paints, primers, varnishes, and sealants, offering significant advantages over traditional copper-based compounds.

Exploring fishery waste potential as antifouling component

Marine biofouling is a global issue with economic and ecological implications. Existing solutions, such as biocide-based antifouling paints, are toxic for the environment. The search for better antifouling agents remains crucial. Recent research focuses on eco-friendly antifouling paints containing natural compounds like enzymes. This study evaluates enzymatic extracts from fishery residues for antifouling potential. Extracts from Pleoticus muelleri shrimp, Illex argentinus squid, and Lithodes santolla king crab were analyzed. Proteolytic activity and thermal stability were assessed, followed by bioassays on mussel byssus thread formation and barnacle cypris adhesive footprints. All three extracts demonstrated proteolytic activity and 24-h stability at temperate oceanic temperatures, except I. argentinus. P. muelleri extracts hindered cyprid footprint formation and mussel byssus thread generation. Further purification is required for L. santolla extract to assess its antifouling potential activity. This study introduces the use of fishery waste-derived enzyme extracts as a novel antifouling agent, providing a sustainable tool to fight against biofouling formation.

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.

Genetic Diversity, Population Structure, and Environmental Adaptation Signatures of Chinese Coastal Hard-Shell Mussel Mytilus coruscus Revealed by Whole-Genome Sequencing

The hard-shell mussel (Mytilus coruscus) is widespread in the temperate coastal areas of the northwest Pacific and holds a significant position in the shellfish aquaculture market in China. However, the natural resources of this species have been declining, and population genetic studies of M. coruscus are also lacking. In this study, we conducted whole-genome resequencing (WGR) of M. coruscus from eight different latitudes along the Chinese coast and identified a total of 25,859,986 single nucleotide polymorphism (SNP) markers. Our findings indicated that the genetic diversity of M. coruscus from the Zhoushan region was lower compared with populations from other regions. Furthermore, we observed that the evolutionary tree clustered into two primary branches, and the Zhangzhou (ZZ) population was in a separate branch. The ZZ population was partly isolated from populations in other regions, but the distribution of branches was not geographically homogeneous, and a nested pattern emerged, consistent with the population differentiation index (FST) results. To investigate the selection characteristics, we utilized the northern M. coruscus populations (Dalian and Qingdao) and the central populations (Zhoushan and Xiangshan) as reference populations and the southern ZZ population as the target population. Our selection scan analysis identified several genes associated with thermal responses, including Hsp70 and CYP450. These genes may play important roles in the adaptation of M. coruscus to different living environments. Overall, our study provides a comprehensive understanding of the genomic diversity of coastal M. coruscus in China and is a valuable resource for future studies on genetic breeding and the evolutionary adaptation of this species.

The movement and settlement behaviour of cyprids of Balanus reticulatus on the surfaces of the titanium alloys

The motion paths of Balanus reticulatus cyprids were similar on all the titanium alloys surfaces. On the parallel grinding surfaces, the temporary attachment duration and the settlement ratio of the cyprids were influenced by the roughness and the composition of the surfaces and correlated positively. The surface roughness could also change the contact area and the numbers of the attachment points of the cyprids in the similar pattern. Consequently, the roughness and the composition of the surfaces regulated the cyprid settlement by the temporary attachment duration. The cross grinding increased the temporary attachment duration but drastically decreased the settlement ratio to 0 compared to the parallel grinding, possibly due to the voids and the drastic decrease of the contact area and the numbers of the attachment points of the cyprids on the cross grinding surface, respectively. The cross grinding therefore significantly reduced the cyprid settlement compared to the parallel grinding.

Interplay of physico-chemical and mechanical bacteria-surface interactions with transport processes controls early biofilm growth: A review

Biofilms initiate when bacteria encounter and are retained on surfaces. The surface orchestrates biofilm growth through direct physico-chemical and mechanical interactions with different structures on bacterial cells and, in turn, through its influence on cell-cell interactions. Individual cells respond directly to a surface through mechanical or chemical means, initiating "surface sensing" pathways that regulate gene expression, for instance producing extra cellular matrix or altering phenotypes. The surface can also physically direct the evolving colony morphology as cells divide and grow. In either case, the physico-chemistry of the surface influences cells and cell communities through mechanisms that involve additional factors. For instance the numbers of cells arriving on a surface from solution relative to the generation of new cells by division depends on adhesion and transport kinetics, affecting early colony density and composition. Separately, the forces experienced by adhering cells depend on hydrodynamics, gravity, and the relative stiffnesses and viscoelasticity of the cells and substrate materials, affecting mechanosensing pathways. Physical chemistry and surface functionality, along with interfacial mechanics also influence cell-surface friction and control colony morphology, in particular 2D and 3D shape. This review focuses on the current understanding of the mechanisms in which physico-chemical interactions, deriving from surface functionality, impact individual cells and cell community behavior through their coupling with other interfacial processes.

High-throughput method development for in-situ quantification of aquatic phototrophic biofilms

In the maritime field where biofouling has both economic and environmental impacts, in situ quantification methods of biofilm development are of outstanding importance. Indeed, it is challenging to temporally monitor biofilm formation due to the complexity of the marine ecosystem, common inaccessibility of sampling location and lack of standardized techniques. Here, an artificial polymeric surface was tested in situ and in vitro against natural phototrophic biofilms and monoculture biofilms using plate reader fluorescence. The suitability of the developed method was verified using fluorescence microscopy coupled with image analysis - a common quantification technique - demonstrating a strong correlation between the tested methods. The results indicated the efficiency of inherent chlorophyll fluorescence in quantifying undisturbed phototrophic biofilms in field and laboratory conditions using microplate reader. This work demonstrated that the suggested approach is promising for biofilm high-throughput testing, and therefore has the potential to be used in several research and industrial sectors for monitoring phototrophic biofilm development.

Resilience of a microphytobenthos community from the Severn Estuary, UK, to chlorination: A mesocosm approach

The Severn Estuary is a large macrotidal estuary which includes an extensive mudflat with microphytobenthos (MPB) playing a key role in the ecosystem. This study evaluated the impact of chlorination at two different dosing levels (0.05 and 0.5 mg/l as total residual oxidants, TRO, representative of potential concentrations in the mixing zone and within the cooling water systems of a power station) on a MPB community representative of the Severn Estuary. Biomass and diversity were not negatively impacted while physiology was partially affected at the beginning of the experiment, and it recovered towards the end of the experiment. Further investigations for diversity are needed to consolidate our findings. In conclusion our results show that MPB is resilient to chlorination up to a concentration of 0.5 mg/l which is much higher (>10 times) than what might be expected near the chlorinated discharges for most coastal power stations.

Macroorganisms fouled in marine anthropogenic litter (rafting) arround a tropical bay in the Southwest Atlantic

The presence of floating marine anthropogenic litter in marine environments increase the possibility of transportation of fouling organisms using these substrates as a vector, mainly for those species with close affinities to artificial substrates. The objectives were to qualitatively and quantitatively report anthropogenic litter and its associated fouling groups arround Ilha Grande Bay (IGB). Litter was collected, classified and examined for the presence of fouling organisms on beaches located at two different levels of wave exposure during rainy and dry seasons. The types of litter do not differ among beaches, and the highest density and cover of fouling were reported on exposed beaches due the currents, winds, and storm waves. Bryozoans, barnacles, polychaetes, and mollusks were the most frequent fouling groups observed in litter and represents a potential vector for the dispersion of species in the IGB and adjacent coastal areas.

Anti-fouling activity and toxicity of the Mediterranean alien sponge Paraleucilla magna Klautau, Monteiro & Borojevic, 2004 (Porifera, Calcarea)

Poriferans, as sessile organisms without rigid external covering, use secondary metabolites for protection from predators and fouling organisms. The present study tested the antifouling activity of ethanolic extract of the Mediterranean alien calcareous sponge Paraleucilla magna towards juvenile mussels Mytilus galloprovincialis. Furthermore, toxicity tests on nauplii of brine shrimp Artemia salina and two microalgae strains, Nannochloropsis sp. and Tetraselmis suecica, were also conducted. A total attachment inhibition of M. galloprovincialis was achieved at a concentration of 400 µg/mL of sponge extract. The 50% mortality of A. salina nauplii was recorded at a concentration of 500 µg/mL of ethanolic extract. The growth inhibitory effect on both marine microalgae strains has been registered at a concentration of 300 µg/mL. Our results suggest promising natural antifouling activity and low toxicity of the ethanolic extract of P. magna that could be used as antifouling compound.

Chromosome-level genome assembly of the hard-shelled mussel Mytilus coruscus, a widely distributed species from the temperate areas of East Asia

BACKGROUND

The hard-shelled mussel (Mytilus coruscus) is widely distributed in the temperate seas of East Asia and is an important commercial bivalve in China. Chromosome-level genome information of this species will contribute not only to the development of hard-shelled mussel genetic breeding but also to studies on larval ecology, climate change biology, marine biology, aquaculture, biofouling, and antifouling.

FINDINGS

We applied a combination of Illumina sequencing, Oxford Nanopore Technologies sequencing, and high-throughput chromosome conformation capture technologies to construct a chromosome-level genome of the hard-shelled mussel, with a total length of 1.57 Gb and a median contig length of 1.49 Mb. Approximately 90.9% of the assemblies were anchored to 14 linkage groups. We assayed the genome completeness using BUSCO. In the metazoan dataset, the present assemblies have 89.4% complete, 1.9% incomplete, and 8.7% missing BUSCOs. Gene modeling enabled the annotation of 37,478 protein-coding genes and 26,917 non-coding RNA loci. Phylogenetic analysis showed that M. coruscus is the sister taxon to the clade including Modiolus philippinarum and Bathymodiolus platifrons. Conserved chromosome synteny was observed between hard-shelled mussel and king scallop, suggesting that this is shared ancestrally. Transcriptomic profiling indicated that the pathways of catecholamine biosynthesis and adrenergic signaling in cardiomyocytes might be involved in metamorphosis.

CONCLUSIONS

The chromosome-level assembly of the hard-shelled mussel genome will provide novel insights into mussel genome evolution and serve as a fundamental platform for studies regarding the planktonic-sessile transition, genetic diversity, and genomic breeding of this bivalve.

The association between initial adhesion and cyanobacterial biofilm development

Although laboratory assays provide valuable information about the antifouling effectiveness of marine surfaces and the dynamics of biofilm formation, they may be laborious and time-consuming. This study aimed to determine the potential of short-time adhesion assays to estimate how biofilm development may proceed. The initial adhesion and cyanobacterial biofilm formation were evaluated using glass and polymer epoxy resin surfaces under different hydrodynamic conditions and were compared using linear regression models. For initial adhesion, the polymer epoxy resin surface was significantly associated with a lower number of adhered cells compared with glass (-1.27 × 105 cells.cm-2). Likewise, the number of adhered cells was significantly lower (-1.16 × 105 cells.cm-2) at 185 than at 40 rpm. This tendency was maintained during biofilm development and was supported by the biofilm wet weight, thickness, chlorophyll a content and structure. Results indicated a significant correlation between the number of adhered and biofilm cells (r = 0.800, p < 0.001). Moreover, the number of biofilm cells on day 42 was dependent on the number of adhered cells at the end of the initial adhesion and hydrodynamic conditions (R2 = 0.795, p < 0.001). These findings demonstrate the high potential of initial adhesion assays to estimate marine biofilm development.

A rapid benchtop method to assess biofilm on marine fouling control coatings

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 .

Developing New Marine Antifouling Surfaces: Learning from Single-Strain Laboratory Tests

The development of antifouling (AF) technology for marine environments is an area of intense research given the severe economic and ecological effects of marine biofouling. Preliminary data from in vitro assays is frequently used to screen the performance of AF coatings. It is intuitive that microbial composition plays a major role in surface colonization. The rationale behind this study is to investigate whether using a mixed population for the in vitro tests yields substantially different results than using single strains during initial screening. A polymeric coating was tested against single- and dual-species cultures of two common microfouler organisms for 49 days. A bacterium (Pseudoaltermonas tunicata) and a cyanobacterium (Cyanobium sp. LEGE 10375) were used in this study. Linear regression analysis revealed that Cyanobium sp. biofilms were significantly associated with a higher number of cells, wet weight, thickness, and biovolume compared to dual-species biofilms. P. tunicata alone had a biofilm growth kinetics similar to dual-species biofilms, although the P. tunicata–Cyanobium sp. mixture developed less dense and thinner biofilms compared to both single-species biofilms. Cyanobium sp. LEGE 10375 biofilms provided the worst-case scenario, i.e., the conditions that caused higher biofilm amounts on the surface material under test. Therefore, it is likely that assessing the AF performance of new coatings using the most stringent conditions may yield more robust results than using a mixed population, as competition between microfouler organisms may reduce the biofilm formation capacity of the consortium.

Antifouling Technology Trends in Marine Environmental Protection

Marine fouling is a worldwide problem, which is harmful to the global marine ecological environment and economic benefits. The traditional antifouling strategy usually uses toxic antifouling agents, which gradually exposes a serious environmental problem. Therefore, green, long-term, broad-spectrum and eco-friendly antifouling technologies have been the main target of engineers and researchers. In recent years, many eco-friendly antifouling technologies with broad application prospects have been developed based on the low toxicity and non-toxicity antifouling agents and materials. In this review, contemporary eco-friendly antifouling technologies and materials are summarized into bionic antifouling and non-bionic antifouling strategies (2000-2020). Non-bionic antifouling technologies mainly include protein resistant polymers, antifoulant releasing coatings, foul release coatings, conductive antifouling coatings and photodynamic antifouling technology. Bionic antifouling technologies mainly include the simulated shark skin, whale skin, dolphin skin, coral tentacles, lotus leaves and other biology structures. Brief future research directions and challenges are also discussed in the end, and we expect that this review would boost the development of marine antifouling technologies.

Flavonoid Glycosides with a Triazole Moiety for Marine Antifouling Applications: Synthesis and Biological Activity Evaluation

Over the last decades, antifouling coatings containing biocidal compounds as active ingredients were used to prevent biofouling, and eco-friendly alternatives are needed. Previous research from our group showed that polymethoxylated chalcones and glycosylated flavones obtained by synthesis displayed antifouling activity with low toxicity. In this work, ten new polymethoxylated flavones and chalcones were synthesized for the first time, including eight with a triazole moiety. Eight known flavones and chalcones were also synthesized and tested in order to construct a quantitative structure-activity relationship (QSAR) model for these compounds. Three different antifouling profiles were found: three compounds (1b, 11a and 11b) exhibited anti-settlement activity against a macrofouling species (Mytilus galloprovincialis), two compounds (6a and 6b) exhibited inhibitory activity against the biofilm-forming marine bacteria Roseobacter litoralis and one compound (7b) exhibited activity against both mussel larvae and microalgae Navicula sp. Hydrogen bonding acceptor ability of the molecule was the most significant descriptor contributing positively to the mussel larvae anti-settlement activity and, in fact, the triazolyl glycosylated chalcone 7b was the most potent compound against this species. The most promising compounds were not toxic to Artemia salina, highlighting the importance of pursuing the development of new synthetic antifouling agents as an ecofriendly and sustainable alternative for the marine industry.

New amphiphilic copolymers for PDMS-based nanocomposite films with long-term marine antifouling performance

Amphiphilic methacrylate copolymers (Si-co-EF) containing polysiloxane (Si) and mixed poly(oxyethylene)-perfluorohexyl (EF) side chains were synthesized with different compositions and used together with polysiloxane-functionalized nanoparticles as additives of condensation cured nanocomposite poly(siloxane) films. The mechanical properties of the nanocomposite films were consistent with the elastomeric behavior of the poly(siloxane) matrix without significant detriment from either the copolymer or the nanoparticles. Films were found to be markedly hydrophobic and liphophobic, with both properties being maximized at an intermediate content of EF units. The high enrichment in fluorine at the film surface was proven by angle-resolved X-ray photoelectron spectroscopy (AR-XPS). Long-term marine antifouling performance was evaluated in field immersion trials of test panels for up to 10 months of immersion. Both nanoparticles and amphiphilic copolymer were found to be highly effective in reducing the colonization of foulants, especially hard macrofoulants, when compared with control panels. Lowest percentage of surface coverage was 20% after 10 months of immersion (films with 4 wt% copolymer and 0.5 wt% nanoparticles), which was further decreased to less than 10% after exposure to a water jet for 10 s. The enhanced antifouling properties of coatings containing both nanoparticles and copolymer were confirmed by laboratory assays against the polychaete Ficopomatus enigmaticus and the diatom Navicula salinicola.

Using encrusting bryozoan adhesion to evaluate the efficacy of fouling-release marine coatings

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.

One Step Forward towards the Development of Eco-Friendly Antifouling Coatings: Immobilization of a Sulfated Marine-Inspired Compound

Marine biofouling represents a global economic and ecological challenge and few eco-friendly antifouling agents are available. The aim of this work was to establish the proof of concept that a recently synthesized nature-inspired compound (gallic acid persulfate, GAP) can act as an eco-friendly and effective antifoulant when immobilized in coatings through a non-release strategy, promoting a long-lasting antifouling effect. The synthesis of GAP was optimized to provide quantitative yields. GAP water solubility was assessed, showing values higher than 1000 mg/mL. GAP was found to be stable in sterilized natural seawater with a half-life (DT₅₀) of 7 months. GAP was immobilized into several commercial coatings, exhibiting high compatibility with different polymeric matrices. Leaching assays of polydimethylsiloxane and polyurethane-based marine coatings containing GAP confirmed that the chemical immobilization of GAP was successful, since releases up to fivefold lower than the conventional releasing systems of polyurethane-based marine coatings were observed. Furthermore, coatings containing immobilized GAP exhibited the most auspicious anti-settlement effect against Mytilus galloprovincialis larvae for the maximum exposure period (40 h) in laboratory trials. Overall, GAP promises to be an agent capable of improving the antifouling activity of several commercial marine coatings with desirable environmental properties.

Medusa polyps adherence inhibition: A novel experimental model for antifouling assays

Although in the last decades significant advances have been made to improve antifouling formulations, the main current options continue to be highly toxic to marine environment, leading to an urgent need for new safer alternatives. For anti-adherence studies, barnacles and mussels are commonly the first choice for experimental purposes. However, the use of these organisms involves a series of laborious and time-consuming stages. In the present work, a new approach for testing antifouling formulations was developed under known formulations and novel proposed options. Due to their high resilience, ability of surviving in hostile environments and high abundance in different ecosystems, medusa polyps present themselves as prospect candidates for antifouling protocols. Thus, a complete protocol to test antifouling formulations using polyps is presented, while the antifouling properties of two invasive seaweeds, Asparagopsis armata and Sargassum muticum, were evaluated within this new test model framework. The use of medusa polyps as model to test antifouling substances revealed to be a reliable alternative to the conventional organisms, presenting several advantages since the protocol is less laborious, less time-consuming and reproductive. The results also show that the seaweeds A. armata and S. muticum produce compounds with anti-adherence properties being therefore potential candidates for the development of new greener antifouling formulations.

Anti-Fouling Effects of Saponin-Containing Crude Extracts from Tropical Indo-Pacific Sea Cucumbers

Sea cucumbers are bottom dwelling invertebrates, which are mostly found on subtropical and tropical sea grass beds, sandy reef flats, or reef slopes. Although constantly exposed to fouling communities in these habitats, many species are surprisingly free of invertebrate epibionts and microfouling algae such as diatoms. In our study, we investigated the anti-fouling (AF) activities of different crude extracts of tropical Indo-Pacific sea cucumber species against the fouling diatom Cylindrotheca closterium. Nine sea cucumber species from three genera (i.e., Holothuria, Bohadschia, Actinopyga) were selected and extracted to assess their AF activities. To verify whether the sea cucumber characteristic triterpene glycosides were responsible for the observed potent AF activities, we tested purified fractions enriched in saponins isolated from Bohadschia argus, representing one of the most active anti-fouling extracts. Saponins were quantified by vanillin-sulfuric acid colorimetric assays and identified by LC-MS and LC-MS/MS analyses. We were able to demonstrate that AF activities in sea cucumber extracts were species-specific, and growth inhibition as well as attachment of the diatom to surfaces is dependent on the saponin concentration (i.e., Actinopyga contained the highest quantities), as well as on the molecular composition and structure of the present saponins (i.e., Bivittoside D derivative was the most bioactive compound). In conclusion, the here performed AF assay represents a promising and fast method for selecting the most promising bioactive organism as well as for identifying novel compounds with potent AF activities for the discovery of potentially novel pharmacologically active natural products.

Antifouling Napyradiomycins from Marine-Derived Actinomycetes Streptomyces aculeolatus

The undesired attachment of micro and macroorganisms on water-immersed surfaces, known as marine biofouling, results in severe prevention and maintenance costs (billions €/year) for aquaculture, shipping and other industries that rely on coastal and off-shore infrastructures. To date, there are no sustainable, cost-effective and environmentally safe solutions to address this challenging phenomenon. Therefore, we investigated the antifouling activity of napyradiomycin derivatives that were isolated from actinomycetes from ocean sediments collected off the Madeira Archipelago. Our results revealed that napyradiomycins inhibited ≥80% of the marine biofilm-forming bacteria assayed, as well as the settlement of Mytilus galloprovincialis larvae (EC₅₀ < 5 µg/ml and LC₅₀/EC₅₀ >15), without viability impairment. In silico prediction of toxicity end points are of the same order of magnitude of standard approved drugs and biocides. Altogether, napyradiomycins disclosed bioactivity against marine micro and macrofouling organisms, and non-toxic effects towards the studied species, displaying potential to be used in the development of antifouling products.

Evaluation of Antifouling Potential and Ecotoxicity of Secondary Metabolites Derived from Red Algae of the Genus Laurencia

Red algae of the genus Laurencia are known to biosynthesize and secrete an immense variety of secondary metabolites possessing a spectrum of biological activities against bacteria, invertebrates and mammalian cell lines. Following a rigorous cross-species screening process, herein we report the antifouling potential of 25 secondary metabolites derived from species of the genus Laurencia, as well as the thorough evaluation of the ecotoxicity of selected metabolites against non-target marine arthropods and vertebrate cell lines. A number of these secondary metabolites exhibited potent antifouling activity and performed well in all screening tests. Our results show that perforenol (9) possesses similar antifouling activity with that already described for bromosphaerol, which is used herein as a benchmark.

Control of mussel Mytilus galloprovincialis Lamarck fouling in water-cooling systems using plasma discharge

To prevent marine macrofouling, the anti-fouling effect of liquid discharge on mussels Mytilus galloprovincialis Lamarck was investigated in a simulated water-cooling system. The effects of input energy, mussel distance from discharge center, continuous discharge time, and discharge energy distribution mode on mussel response (death or detachment) were systematically studied. The results showed that excellent anti-fouling effects could be achieved by increasing input energy, but the detachment rate and mortality of mussels decreased sharply when the mussels were farther away from the discharge center. Low frequency discharge for a long, continuous time and multiple stimuli at long intervals improved the anti-fouling effect. Shock waves are the most likely cause of mussel eradication, and the threshold values of peak pressure to prevent mussel settlement and to cause death were 0.02 MPa and 0.05 MPa, respectively.

Effects of surface texture and interrelated properties on marine biofouling: a systematic review

This systematic review examines effects of surface texture on marine biofouling and characterizes key research methodologies. Seventy-five published articles met selection criteria for qualitative analysis; experimental data from 36 underwent quantitative meta-analysis. Most studies investigated fouling mechanisms and antifouling performance only in laboratory assays with one to several test species. Textures were almost exclusively a single layer of regularly arranged geometric features rather than complex hierarchical or irregular designs. Textures in general had no effect or an inconclusive effect on fouling in 46% of cases. However, effective textures more often decreased (35%) rather than increased (19%) fouling. Complex designs were more effective against fouling (51%) than were regular geometric features (32%). Ratios of feature height, width, or pitch to organism body length were significant influences. The authors recommend further research on promising complex and hierarchical texture designs with more test species, as well as field studies to ground-truth laboratory results.

Polymer-Based Marine Antifouling and Fouling Release Surfaces: Strategies for Synthesis and Modification

In marine industries, the accumulation of organic matter and marine organisms on ship hulls and instruments limits performance, requiring frequent maintenance and increasing fuel costs. Current coatings technology to combat this biofouling relies heavily on the use of toxic, biocide-containing paints. These pose a serious threat to marine ecosystems, affecting both target and nontarget organisms. Innovation in the design of polymers offers an excellent platform for the development of alternatives, but the creation of a broad-spectrum, nontoxic material still poses quite a hurdle for researchers. Surface chemistry, physical properties, durability, and attachment scheme have been shown to play a vital role in the construction of a successful coating. This review explores why these characteristics are important and how recent research accounts for them in the design and synthesis of new environmentally benign antifouling and fouling release materials.

Designing a Laboratory Bioassay for Evaluating the Efficacy of Antifouling Paints on Amphibalanus amphitrite Using a Flow-Through System

With the aim of establishing a protocol for evaluating the efficacy of antifouling paints on different organisms, a flow-through laboratory test using triangular boxes was developed for cyprids of the barnacle Amphibalanus (=Balanus) amphitrite. Six different formulations of antifouling paints were prepared in increasing content (0 to 40 wt.%) of Cu2O, which is the most commonly used antifouling substance, and each formulation of paint was coated on one surface of each test plate. The test plates were aged for 45 days by rotating them at a speed of 10 knots inside a cylinder drum with continuously flowing seawater. The settlement behavior of 3-day-old cyprids released inside triangular boxes made from the test plates was observed. A decreasing number of juveniles settled on surfaces of test plates that were coated with paint containing more than 30 wt.% of Cu2O. Results of the laboratory bioassays were consistent with those from the field experiments.

The Plant Alkaloid Camptothecin as a Novel Antifouling Compound for Marine Paints: Laboratory Bioassays and Field Trials

The extensive use of copper and booster biocides in antifouling (AF) paints has raised environmental concerns and the need to develop new AF agents. In the present study, 18 alkaloids derived from terrestrial plants were initially evaluated for AF activity using laboratory bioassays with the bryozoan Bugula neritina and the barnacle Balanus albicostatus. The results showed that 4 of the 18 alkaloids were effective in inhibiting larval settlement of B. neritina, with an EC₅₀ range of 6.18 to 43.11 μM, and 15 of the 18 alkaloids inhibited larval settlement of B. albicostatus, with EC₅₀ values ranging from 1.18 to 67.58 μM. Field trials that incorporated five alkaloids respectively into paints with 20% w/w indicated an in situ AF efficiency of evodiamine, strychnine, camptothecin (CPT), and cepharanthine, with the most potent compound being CPT, which also exhibited stronger AF efficiency than the commercial antifoulants cuprous oxide and zinc pyrithione in the field over a period of 12 months. Further field trials with different CPT concentrations (0.1 to 20% w/w) in the paints suggested a concentration-dependent AF performance in the natural environment, and the effective concentrations to significantly inhibit settlement of biofoulers in the field were ≥ 0.5% w/w (the efficiency of 0.5% w/w lasted for 2 months). Moreover, CPT toxicity against the crustacean Artemia salina, the planktonic microalgae Phaeodactylum tricornutum and Isochrysis galbana, was examined. The results showed that 24 h LC₅₀ of CPT against A. salina was 20.75 μM, and 96 h EC₅₀ (growth inhibition) values of CPT to P. tricornutum and I. galbana were 55.81 and 6.29 μM, respectively, indicating that CPT was comparatively less toxic than several commercial antifoulants previously reported. Our results suggest the novel potential application of CPT as an antifoulant.

Sphaerocyclamide, a prenylated cyanobactin from the cyanobacterium Sphaerospermopsis sp. LEGE 00249

Cyanobactins are a family of linear and cyclic peptides produced through the post-translational modification of short precursor peptides. A mass spectrometry-based screening of potential cyanobactin producers led to the discovery of a new prenylated member of this family of compounds, sphaerocyclamide (1), from Sphaerospermopsis sp. LEGE 00249. The sphaerocyclamide biosynthetic gene cluster (sph) encoding the novel macrocyclic prenylated cyanobactin, was sequenced. Heterologous expression of the sph gene cluster in Escherichia coli confirmed the connection between genomic and mass spectrometric data. Unambiguous establishment of the orientation and site of prenylation required the full structural elucidation of 1 using Nuclear Magnetic Resonance (NMR), which demonstrated that a forward prenylation occurred on the tyrosine residue. Compound 1 was tested in pharmacologically or ecologically relevant biological assays and revealed moderate antimicrobial activity towards the fouling bacterium Halomonas aquamarina CECT 5000.

A Facile Method to Prepare a Hydrophilic/Hydrophobic Metal Surface by Peptide

A facile method to prepare a hydrophilic/hydrophobic metal surface by metal-binding peptide was proposed in this article. Metal-binding peptide sequenced NLNPNTASAMHV was taken as the target peptide to interact with stainless steel. The surface morphology, roughness and Fourier-Transform Infrared spectroscopy (FTIR) showed that some changes occurred on the modified stainless steel surface. Not only were the surfaces coarser but also some organic groups appeared on the modified sample surfaces. By comparing the CAs of all the samples, the most suitable concentration of peptide and treating time were determined. A new and facile way to endow some metals surfaces with hydrophobicity or hydrophilicity has been developed, which is useful especially for antibiofouling.

Biofilm Inhibition by Novel Natural Product- and Biocide-Containing Coatings Using High-Throughput Screening

The use of natural products (NPs) as possible alternative biocidal compounds for use in antifouling coatings has been the focus of research over the past decades. Despite the importance of this field, the efficacy of a given NP against biofilm (mainly bacteria and diatoms) formation is tested with the NP being in solution, while almost no studies test the effect of an NP once incorporated into a coating system. The development of a novel bioassay to assess the activity of NP-containing and biocide-containing coatings against marine biofilm formation has been achieved using a high-throughput microplate reader and highly sensitive confocal laser scanning microscopy (CLSM), as well as nucleic acid staining. Juglone, an isolated NP that has previously shown efficacy against bacterial attachment, was incorporated into a simple coating matrix. Biofilm formation over 48 h was assessed and compared against coatings containing the NP and the commonly used booster biocide, cuprous oxide. Leaching of the NP from the coating was quantified at two time points, 24 h and 48 h, showing evidence of both juglone and cuprous oxide being released. Results from the microplate reader showed that the NP coatings exhibited antifouling efficacy, significantly inhibiting biofilm formation when compared to the control coatings, while NP coatings and the cuprous oxide coatings performed equally well. CLSM results and COMSTAT analysis on biofilm 3D morphology showed comparable results when the NP coatings were tested against the controls, with higher biofilm biovolume and maximum thickness being found on the controls. This new method proved to be repeatable and insightful and we believe it is applicable in antifouling and other numerous applications where interactions between biofilm formation and surfaces is of interest.

Design and Biological Evaluation of Antifouling Dihydrostilbene Oxime Hybrids

By combining the recently reported repelling natural dihydrostilbene scaffold with an oxime moiety found in many marine antifoulants, a library of nine antifouling hybrid compounds was developed and biologically evaluated. The prepared compounds were shown to display a low antifouling effect against marine bacteria but a high potency against the attachment and growth of microalgae down to MIC values of 0.01 μg/mL for the most potent hybrid. The mode of action can be characterized as repelling via a reversible non-toxic biostatic mechanism. Barnacle cyprid larval settlement was also inhibited at low μg/mL concentrations with low levels or no toxicity observed. Several of the prepared compounds performed better than many reported antifouling marine natural products. While several of the prepared compounds are highly active as antifoulants, no apparent synergy is observed by incorporating the oxime functionality into the dihydrostilbene scaffold. This observation is discussed in light of recently reported literature data on related marine natural antifoulants and antifouling hybrids as a potentially general strategy for generation of improved antifoulants.

A multi-step approach for testing non-toxic amphiphilic antifouling coatings against marine microfouling at different levels of biological complexity

Marine biofouling on artificial surfaces such as ship hulls or fish farming nets causes enormous economic damage. The time for the developmental process of antifouling coatings can be shortened by reliable laboratory assays. For designing such test systems, it is important that toxic effects can be excluded, that multiple parameters can be addressed simultaneously and that mechanistic aspects can be included. In this study, a multi-step approach for testing antifouling coatings was established employing photoautotrophic biofilm formation of marine microorganisms in micro- and mesoscoms. Degree and pattern of biofilm formation was determined by quantification of chlorophyll fluorescence. For the microcosms, co-cultures of diatoms and a heterotrophic bacterium were exposed to fouling-release coatings. For the mesocosms, a novel device was developed that permits parallel quantification of a multitude of coatings under defined conditions with varying degrees of shear stress. Additionally, the antifouling coatings were tested for leaching of potential compounds and finally tested in sea trials. This multistep-approach revealed that the individual steps led to consistent results regarding antifouling activity of the coatings. Furthermore, the novel mesocosm system can be employed for advanced antifouling analysis including metagenomic approaches for determination of microbial diversity attaching to different coatings under changing shear forces.

Surface thiolation of silicon for antifouling application

Thiol groups grafted silicon surface was prepared as previously described. 1H,1H,2H,2H-perfluorodecanethiol (PFDT) molecules were then immobilized on such a surface through disulfide bonds formation. To investigate the contribution of PFDT coating to antifouling, the adhesion behaviors of Botryococcus braunii (B. braunii) and Escherichia coli (E. coli) were studied through biofouling assays in the laboratory. The representative microscope images suggest reduced B. braunii and E. coli accumulation densities on PFDT integrated silicon substrate. However, the antifouling performance of PFDT integrated silicon substrate decreased over time. By incubating the aged substrate in 10 mM TCEP·HCl solution for 1 h, the fouled PFDT coating could be removed as the disulfide bonds were cleaved, resulting in reduced absorption of algal cells and exposure of non-fouled silicon substrate surface. Our results indicate that the thiol-terminated substrate can be potentially useful for restoring the fouled surface, as well as maximizing the effective usage of the substrate.

Co, Zn and Ag-MOFs evaluation as biocidal materials towards photosynthetic organisms

In the present study, the biocidal activity of three different metal organic frameworks (MOFs) based on Co (Co-SIM1), Zn (Zn-SIM1) and Ag (Ag-TAZ) has been evaluated towards one green alga and two cyanobacteria. These organisms are present in fresh- and seawater and take part in the early stages of the biofouling process. The biocidal activity of these materials was evaluated by measuring chlorophyll a concentration and by inhibition zone testing. After 24h of exposure the three different MOFs caused >50% of chlorophyll a concentration inhibition towards both cyanobacteria, however, although the green alga presented a great sensitivity for Ag-TAZ (reaching 90% of chlorophyll a concentration inhibition), it was much more resistant to the rest of MOFs. Bioavailability of these metals was studied using ICP-MS, the chemical speciation program Visual MINTEQ, and a heavy metal bioreporter bioanalytical tool. We have elucidated that the biocidal activity presented by these MOFs was due to the dissolved metals released from them and more exactly, it depended on the bioavailability presented by these metal ions, which was closely related with the free ion concentration. This article highlights the potential use of different MOFs as biocidal material towards photosynthetic organisms and reveals important differences in the sensitivity between these organisms that should be taken into account in order to increase the biocidal spectrum of these materials.

A new flow-through bioassay for testing low-emission antifouling coatings

Current antifouling (AF) technologies are based on the continuous release of biocides into the water, and consequently discharge into the environment. Major efforts to develop more environmentally friendly coatings require efficient testing in laboratory assays, followed by field studies. Barnacles are important fouling organisms worldwide, increasing hydrodynamic drag on ships and damaging coatings on underwater surfaces, and thus are extensively used as models in AF research, mostly in static, laboratory-based systems. Reliable flow-through test assays for the screening of biocide-containing AF paints, however, are rare. Herein, a flow-through bioassay was developed to screen for diverse low-release biocide paints, and to evaluate their effects on pre- and post-settlement traits in barnacles. The assay distinguishes between the effects from direct surface contact and bulk-water effects, which are crucial when developing low-emission AF coatings. This flow-through bioassay adds a new tool for rapid laboratory-based first-stage screening of candidate compounds and novel AF formulations.

A Method for Evaluating the Efficacy of Antifouling Paints Using Mytilus galloprovincialis in the Laboratory in a Flow-Through System

A laboratory test with a flow-through system was designed and its applicability for testing antifouling paints of varying efficacies was investigated. Six different formulations of antifouling paints were prepared to have increasing contents (0 to 40 wt.%) of Cu₂O, which is the most commonly used antifouling substance, and each formulation of paint was coated on just one surface of every test plate. The test plates were aged for 45 days by rotating them at a speed of 10 knots inside a cylinder drum. A behavioral test was then conducted using five mussels (Mytilus galloprovincialis) that were pasted onto the coated surface of each aged test plate. The number of the byssus threads produced by each mussel generally decreased with increasing Cu₂O content of the paint. The newly designed method was considered valid owing to the high consistency of its results with observations from the field experiment.

Hybrid Sol-Gel-Derived Films That Spontaneously Form Complex Surface Topographies

Surface patterns over multiple length scales are known to influence various biological processes. Here we report the synthesis and characterization of new, two-component xerogel thin films derived from carboxyethylsilanetriol (COE) and tetraethoxysilane (TEOS). Atomic force microscopy (AFM) reveals films surface with branched and hyper branched architectures that are ∼2 to 30 μm in diameter, that extend ∼3 to 1300 nm above the film base plane with surface densities that range from 2 to 77% surface area coverage. Colocalized AFM and Raman spectroscopy show that these branched structures are COE-rich domains, which are slightly stiffer (as shown from phase AFM imaging) and exhibit lower capacitive force in comparison with film base plane. Raman mapping reveals there are also discrete domains (≤300 nm in diameter) that are rich in COE dimers and densified TEOS, which do not appear to correspond with any surface structure seen by AFM.

Comparison of laboratory and field testing performance evaluations of siloxane-polyurethane fouling-release marine coatings

A series of eight novel siloxane-polyurethane fouling-release (FR) coatings were assessed for their FR performance in both the laboratory and in the field. Laboratory analysis included adhesion assessments of bacteria, microalgae, macroalgal spores, adult barnacles and pseudobarnacles using high-throughput screening techniques, while field evaluations were conducted in accordance with standardized testing methods at three different ocean testing sites over the course of six-months exposure. The data collected were subjected to statistical analysis in order to identify potential correlations. In general, there was good agreement between the laboratory screening assays and the field assessments, with both regimes clearly distinguishing the siloxane-polyurethane compositions comprising monofunctional poly(dimethyl siloxane) (PDMS) (m-PDMS) as possessing superior, broad-spectrum FR properties compared to those prepared with difunctional PDMS (d-PDMS). Of the seven laboratory screening techniques, the Cellulophaga lytica biofilm retraction and reattached barnacle (Amphibalanus amphitrite) adhesion assays were shown to be the most predictive of broad-spectrum field performance.

Antifouling Activity of Lipidic Metabolites Derived from Padina tetrastromatica

An attempt has been made to identify the potential seaweed for antifouling property due to the growing need for environmentally safe antifouling systems. The antibacterial, antimicroalgal, and antimussel foot adherence potentials of methanol, dichloromethane, and hexane extracts of the chosen seaweeds such as Padina tetrastromatica, Caulerpa taxifolia, and Amphiroa fragilissima have been compared against copper sulfate. Among the extracts, the maximum antibacterial activities were exhibited by the methanol extract of P. tetrastromatica. The minimum inhibitory concentration (MIC) of the methanolic extract of P. tetrastromatica was found to be 10 and 1 μg/ml against test biofilm bacteria and diatoms, respectively. The antimussel foot adherence assay indicated that the extract had inhibited the foot adherence of the green mussels Perna viridis with the effective concentration (EC50) of 25.51 ± 0.03 μg/ml, and lethal concentration for 50 % mortality (LC50) was recorded at 280.22 ± 0.12 μg/ml. Based on the prolific results, the crude methanolic extract of P. tetrastromatica was subjected to purification using silica gel column and thin-layer chromatography (TLC). Then, the active compounds of the bioassay-guided fraction (F13) were identified using gas chromatography coupled with mass spectroscopy (GC-MS), and it was observed that fatty acids were the major components, which may be responsible for the antifouling properties.

Microcosm-based interaction studies between members of two ecophysiological groups of bioemulsifier producer and a hydrocarbon degrader from the Indian intertidal zone

Isolates were obtained from intertidal zone site samples from all five western and one eastern coastal states of India and were screened. These ecophysiological groups of aerobic, mesophilic, heterotrophic, sporulating, and bioemulsifier-producing bacteria were from Planococcaceae and Bacillaceae. This is the first report of bioemulsifier production by Sporosarcina spp., Lysinibacillus spp., B. thuringiensis, and B. flexus. In this group, Solibacillus silvestris AM1 was found to produce the highest emulsification activity (62.5 %EI) and the sample that yielded it was used to isolate the ecophysiological group of non-bioemulsifier-producing, hydrocarbon-degrading bacteria (belonging to Chromatiales and Bacillales). These yielded hitherto unreported degrader, Rheinheimera sp. CO6 which was selected for the interaction studies (in a microcosm) with bioemulsifier-producing S. silvestris AM1. The gas chromatographic study of these microcosm experiments revealed increased degradation of benzene, toluene, and xylene (BTX) and the growth of Rheinheimera sp. CO6 in the presence of bioemulsifier produced by S. silvestris AM1. Enhancement of the growth of S. silvestris AM1 in the presence of Rheinheimera sp. CO6 was observed possibly due to reduced toxicity of BTX suggesting mutualistic association between the two. This study elucidates the presence and interaction between enhancers and degraders in a hydrocarbon-contaminated intertidal zone and contributes to the knowledge during application of the two in remediation processes.

Antifouling activity of green-synthesized 7-hydroxy-4-methylcoumarin

In the search for new environmental-friendly antifoulants for replace metallic biocides, 7-hydroxy-4-methylcoumarin was synthesized according to green chemistry procedures. This compound was characterized by current organic analysis and its antifouling properties were firstly evaluated on the bivalve Mytilus edulis platensis in the laboratory. In the second stage, a soluble matrix antifouling coating formulated with this compound was assayed in marine environment. Laboratory experiments showed that 7-hydroxy-4-methylcoumarin was effective in inhibiting both the settlement as well as the byssogenesis of mussels. In addition, after exposure time in the sea, painted panels containing this compound showed strong antifouling effect on conspicuous species of the fouling community of Mar el Plata harbor. In conclusion, green-synthesized coumarin could be a suitable antifoulant candidate for marine protective coatings.

Oxasqualenoids from Laurencia viridis: Combined Spectroscopic-Computational Analysis and Antifouling Potential

The chemical study of the red alga Laurencia viridis has led to the isolation of four new polyether triterpenoids: 28-hydroxysaiyacenol B (2), saiyacenol C (3), 15,16-epoxythyrsiferol A (4), and 15,16-epoxythyrsiferol B (5). The structures of 2 and 3 were established mainly by NMR data analysis and comparison with the well-known metabolite dehydrothyrsiferol (1). However, due to the existence of a nonprotonated carbon within the epoxide functionality, stereochemical assignments in 4 and 5 required an in-depth structural study that included NOESY data, J-based configuration analysis, comparison with synthetic models, and DFT calculations. The biological activities of the new metabolites and other related oxasqualenoids were evaluated for the first time against a panel of relevant biofouling marine organisms, and structure-activity conclusions were obtained.

Photopolymerized Network Polysiloxane Films with Dangling Hydrophilic/Hydrophobic Chains for the Biofouling Release of Invasive Marine Serpulid Ficopomatus enigmaticus

Novel photopolymerized network films based on a polysiloxane matrix containing varied amounts of polyoxyethylene (P3) or perfluorohexylethyl (F) dangling side chains were investigated. For films containing less than 10 wt % P3 and F, the wettability and elastic modulus were similar to those of the photopolymerized network matrix. However, angle-resolved X-ray photoelectron spectroscopy measurements proved that the surface of films with F dangling chains was highly enriched in fluorine depending on both the amount of P3 and F and their relative ratio in the films. The biological performance of the films was evaluated against a new widespread and invasive marine biofoulant, the serpulid Ficopomatus enigmaticus. The diatom Navicula salinicola was also assayed as a conventional model organism for comparison. Films richer in P3 better resisted the settlement and promoted the release of calcified tubeworms of F. enigmaticus.

Structure and Function of Macroalgal Natural Products

Since the initial discovery of marine phyco-derived secondary metabolites in the 1950s there has been a rapid increase in the description of new algal natural products. These metabolites have multiple ecological roles as well as commercial value as potential drugs or lead compounds. With the emergence of resistance to our current arsenal of drugs as well as the development of new chemotherapies for currently untreatable diseases, new compounds must be sourced. As outlined in this chapter algae produce a diverse range of chemicals many of which have potential for the treatment of human afflictions.In this chapter we outline the classes of metabolites produced by this chemically rich group of organisms as well as their respective ecological roles in the environment. Algae are found in nearly every environment on earth, with many of these organisms possessing the ability to shape the ecosystem they inhabit. With current challenges to climate stability, understanding how these important organisms interact with their environment as well as one another might afford better insight into how they respond to a changing climate.

Dynamic surface deformation of silicone elastomers for management of marine biofouling: laboratory and field studies using pneumatic actuation

Many strategies have been developed to improve the fouling release (FR) performance of silicone coatings. However, biofilms inevitably build on these surfaces over time. Previous studies have shown that intentional deformation of silicone elastomers can be employed to detach biofouling species. In this study, inspired by the methods used in soft-robotic systems, controlled deformation of silicone elastomers via pneumatic actuation was employed to detach adherent biofilms. Using programmed surface deformation, it was possible to release > 90% of biofilm from surfaces in both laboratory and field environments. A higher substratum strain was required to remove biofilms accumulated in the field environment as compared with laboratory-grown biofilms. Further, the study indicated that substratum modulus influences the strain needed to de-bond biofilms. Surface deformation-based approaches have potential for use in the management of biofouling in a number of technological areas, including in niche applications where pneumatic actuation of surface deformation is feasible.