The settlement and succession of marine fouling organisms were monitored on three structural materials—stainless steel (SS), titanium (Ti), and fibre-reinforced plastic (FRP)—over a 300-day static immersion in coastal waters of Kalpakkam along the eastern coast of India. Barnacles were found to be initial settlers, with 15 fouling species identified during the study period. The final climax community was dominated by green mussels, hydroids, and barnacles on all three substrates. Biofouling load was the highest on FRP (23.6 kg/m²), followed by SS (20.11 kg/m²) and Ti (16.19 kg/m²) after 300 days of exposure. Interestingly, green mussels colonized after 150 days of exposure signifying their preference for cues from the substratum. Correlation analysis revealed strong relationships between environmental parameters and fouling loads. Temperature and salinity were positively correlated (r = 0.874), while temperature and dissolved oxygen showed a negative correlation (r = -0.646). FRP surfaces supported the highest diversity and biomass accumulation compared to Ti and SS surfaces. Results of the study indicate material-specific differences in biofouling loads and findings have implication in the choice of material selection for cooling water system as well as for offshore aquaculture structures.

Biofilm is a conglomeration of microbial cells, encased in extracellular polymeric matrix. Biofilm formation at solid-liquid interfaces is imminent to microfouling and poses serious operational problems in various industrial, clinical and environmental settings. Surface modification strategies are essential to mitigate biofilm formation. In this study, self-assembled monolayers (SAMs) of a spectrum of trimethoxy, triethoxy, and chlorosilanes were prepared on glass surfaces and evaluated for their antibiofilm potential against Staphylococcus lentus, a strong biofilm producer of marine origin. ATR-FTIR spectroscopy confirmed successful silanization by identifying characteristic vibrational modes. Wettability analysis further validated the modifications, with variations in water contact angle (WCA) correlating with silane type and functional group chemistry. Fluorescence microscopic and Flow cytometry analyses demonstrated significant inhibition of microbial colonization, with certain hydrophobic silanes reducing biofilm formation substantially. The live/dead ratio analysis further confirmed the impact of silane coatings on microbial viability. This study highlights the antibiofilm propensity of hydrophobic silanes which can be explored in developing environmentally benign antifouling solutions.

The increasing use of natural products from marine organisms and their synthetic analogs as antifouling agents is replacing chemical biocides due to their ecological compatibility. This study evaluated the antifouling potential of pyrrolo compound (PC) from the sponge-associated bacterium Halobacillus kuroshimensis against the barnacle Amphibalanus reticulatus larval survival, metamorphosis and settlement in the laboratory. The successful concentrations were also subjected to field based static immersion tests to study the efficacy of the PC extract on macrofouling settlement. Results showed decreased naupliar survival and affected larval metamorphosis in a dose-dependent manner, with varying sensitivity among developmental stages. Higher PC concentrations significantly reduced cyprid yield and settlement, with over 50% of cyprid larvae failing to settle at concentrations of 1300 mu g/ml and above. Field experiments confirmed a steady decline in barnacle settlement on PCtreated coupons, with less than 50% settlement observed at concentrations of 500-2000 mu g/ml over 50 days. The LC50/EC50 ratio for nauplius N-II was 1.11, with higher ratios observed in later stages and for the cypris (1.66), suggesting moderate toxicity and a narrow margin of safety. These ratios suggest barnacle settlement inhibition occurring through a toxic mechanism. The results demonstrate the compound's ability to disrupt barnacle settlement, but also raise concerns about its environmental impact (long-term usage), particularly the potential risks to non-target species before using the compound in real-world antifouling applications. Despite higher concentrations used compared to previous reports, PC shows potential as an effective natural antifouling compound.

Efficacy of Actibromide® (formulation of bromide with sodium hypochlorite) as a supplementary biocide for process seawater heat exchangers was evaluated on Perna viridis at Madras Atomic Power Station. Continuous chlorination (0.2 mg/L) required prolonged exposure for 100% mortality. Actibromide® at 0.2, 0.5 and 1.0 mg/L achieved complete mussel mortality within 12, 7 and 4 days, respectively. Reactive oxygen species generation increased antioxidant enzyme activity like superoxide dismutase, catalase which was found to be higher in the digestive gland. Inhibition of cellular functions was evident in haemolymph, inducing DNA damage (34%) and acetylcholinesterase inhibition (80-91%). The study clearly demonstrated that Actibromide® penetrates at the cellular level, causing severe damage to the gills and digestive glands, reducing feed consumption and inducing both neurotoxic and genotoxic effects resulting in mortality. Supplemental targeted dosing at 0.2 mg/L seems to be a promising strategy for effective green mussel control in cooling water systems.

We report the complete genome sequence of Mammaliicoccus lentus strain BARC, a copper-tolerant, biofilm-forming bacterium isolated from marine biofilms formed on titanium coupons exposed to the Bay of Bengal. The genome consisted of a single circular contig of 2.9 Mb with 31.89% GC content, 2,988 genes, including 2,623 coding sequences.

Biofilms constitute 80 % of all nosocomial infections associated with invasive medical devices. Polydimethylsiloxane, a highly elastic, inert, non-reactive, biocompatible silicone polymer is widely used as implant biomaterial due to its non-toxic and low-immunogenic nature. Owing to its hydrophobicity, PDMS suffers from microbial adhesion. Inhibition of biofilm formation on PDMS surfaces is imperative to prevent morbidity, mortality and replacement of implants. The present study investigates the efficacy of capsaicin (0.5 % w/v) loaded PDMS as a broad spectrum antimicrobial surface against Staphylococcus aureus, Escherichia coli and Candida albicans. Capsaicin exhibited minimum inhibitory concentration of 1024 mu g mL(-1) for S. aureus, E. coli and 256 mu g mL(-1) for C. albicans. Capsaicin inhibited biofilms of S. aureus, E. coli and C. albicans at much lower concentrations of 2, 64 and 8 mu g mL(-1) respectively. The minimum capsaicin concentrations required for total biofilm eradication was found to be 256, 512, 128 mu g mL(-1) for S. aureus, E. coli and C. albicans respectively. Probing sub-lethal concentrations of capsaicin revealed 38, 32, 30 % reduction in metabolic activity of S. aureus, E. coli & C. albicans planktonic cells respectively. Similarly, there was an increase in permeability of cells to propidium iodide compared to control. By reducing the metabolic activity and perturbing membrane integrity, capsaicin could prevent biofilm formation and this was also observed with capsaicin-PDMS surfaces that exhibited 1 log (similar to 90 %) reduction of viable bacterial counts.

Heavy infestation by Perna viridis has been observed in the sub-seabed seawater intake tunnel and CWS of a tropical coastal power station in-spite of continuous low dose chlorination regime (0.2 ± 0.1 mg L-1) (CLDC), indicating periodical settlement and growth. Continuous arrival of mussels (colonized in the sub seabed tunnel intake section) at the pump house indicated that the mussels were able to tolerate and survive in a chlorinated environment, for varying time periods and were dislodged when they become weak and subsequent death, leading to flushing out of the system. In the present study, effect of continuous chlorination [0.2 mg L-1 (in-plant use); 0.5 mg L-1 (shock dose) & 1.0 mg L-1 (high levels)] was evaluated on mussels to assess; (a) time taken for mortality, (b) action of chlorine on physiological, genetic, metabolic and neuronal processes. 100% mortality of mussels was observed after 15 (0.2 mg L-1); 9 (0.5 mg L-1) and 6 days (1.0 mg L-1) respectively. Extended valve closure due to chlorination resulted in stress, impairing the respiratory and feeding behavior leading to deterioration in mussel health. Pseudofaeces excretion reduced to 68% (0.2 mg L-1); 10% (0.5 mg L-1) and 89% (1.0 mg L-1) compared to controls. Genotoxicity was observed with increase in % tail DNA fraction in all treatments such as 86% (0.2 mg L-1); 76% (0.5 mg L-1) and 85% (1.0 mg L-1). ROS stress biomarkers increased drastically/ peaked within the first 3 days of continuous chlorination with subsequent quenching by antioxidant enzymes. Gill produced highest generation of ROS; 38% (0.2 mg L-1); 97% (0.5 mg L-1); 98% (1.0 mg L-1). Additionally, it was shown that 84% (0.2 mg L-1), 72% (0.5 mg L-1), and 80.4% (1.0 mg L-1) of the neurotransmitter acetylcholinesterase activity was inhibited by chlorine at the nerve synapse. The cumulative impact of ROS generation, neuronal toxicity, and disrupted functions weakens the overall health of green mussels resulting in mortality.

Candida albicans is a common commensal fungus and fourth most frequent causative agent of nosocomial infections including life-threatening invasive candidiasis in humans. The effectiveness of present antifungal therapies using azoles, polyenes, flucytosine and echinocandins has plateaued in managing fungal infections. The limitations of these antifungal drugs are related to polymorphic morphology, biofilm formation, emergence of drug-resistant strains and production of several virulence factors. Development of new antifungal agents, which can particularly afflict multiple cellular targets and limiting evolving resistant strains are needed. Recently, metal nanoparticles have emerged as a source of new antifungal agents for antifungal formulations. Furthermore, green nanotechnology deals with the use of biosynthetic routes that offer new avenue for synthesizing antifungal nanoparticles coupled with less toxic chemical inventory and environmental sustainability. This article reviews the recent developments on C. albicans pathogenesis, biofilm formation, drug resistance, mode of action of antifungal drugs and antifungal activities of metal nanoparticles. The antifungal efficacy and mode of action of metal nanoparticles are described in the context of prospective therapeutic applications.

Thermal-discharges from power plants highly disturb the biological communities of the receiving water body and understanding their influence is critical, given the relevance to global warming. We employed 16 S rRNA gene sequencing to examine the response of two dominant marine bacterial lifestyles (planktonic and biofilm) against elevated seawater temperature (+5 ℃). Obtained results demonstrated that warming prompted high heterogeneity in diversity and composition of planktonic and biofilm microbiota, albeit both communities responded contrastingly. Alpha diversity revealed that temperature exhibited positive effect on biofilm microbiota and negative effect on planktonic microbiota. The community composition of planktonic microbiota shifted significantly in warming area, with decreased abundances of Bacteroidetes, Cyanobacteria, and Actinobacteria. Contrastingly, these bacterial groups exhibited opposite trend in biofilm microbiota. Co-occurrence networks of biofilm microbiota displayed higher node diversity and co-presence in warming area. The study concludes that with increasing ocean warming, marine biofilms and biofouling management strategies will be more challenging.

A systematic assessment of biogrowth development on titanium coupons exposed to ambient seawater (intake) and chlorinated seawater (pump house) environments of a coastal nuclear power plant was carried out. Titanium coupons were exposed for a period of 2 years and periodically removed at monthly intervals for biogrowth assessment. Biofouling biomass at the seawater intake station ranged from 0.8-12.5 kg m-2 during the 2 years of study. Continuous chlorination of 0.2 ± 0.1 mg L-1 and shock dose chlorination for 1 h/day at residuals of 0.4 ± 0.1 mg L-1 was very effective in reducing the biofouling load in the cooling water system. A reduction in fouling biomass of 95% was observed on titanium coupons between the intake and the pump house stations. Biofoulants recruitment was found to occur throughout the year at varying intensities. Diversity of organisms on the coupon was influenced by seasonality and distinct successional patterns were observed at the seawater intake. Barnacles were the dominant fouling organisms followed by mat forming ascidians, bryozoans, oysters, hydroids and seaweeds at the intake station. Sluggish biofouling development was observed on coupons at the intake due to the sub-tidal intake system (-5 m), which had a lesser load of meroplanktonic organisms. The study also showed that low dose continuous chlorination was an effective strategy for biofouling control in the cooling water system of the tropical power station which uses titanium heat exchangers for steam condensation.

The non-stick & foul release property of silicones was first reported in the early 1970s, with surface free energy of 22 – 24 dynes/cm offering a minimally adhesive surface to biological organisms. The superior antifouling performance of tri-butyl tin- self-polishing coatings TBT-SPC systems outshone all other antifouling formulations from 1970 to 1980s until environmental regulations warranted a total ban on the use of the TBT-SPC system. Foul release coatings (FRC’s) use hydrodynamic stress during navigation to minimize adhesion between fouling organisms and coating surfaces so that fouling can be removed. Addition of hydrophobic silicone oils along with other properties like low surface energy, elasticity and low glass transition temperature, low micro-roughness, attributed to the foul release property of siloxane polymers. Inhibition of fouling on FRC is dependent on several factors like chemical bonding of marine bio adhesives, electrostatic interactions, physical adsorptions between coatings and secreted bio adhesives, diffusion, penetration and interlocking of bio adhesives within the coating matrix. Foul release coatings are prone to biofouling and their fouling load decreases with an increase in hydrodynamic stress due to water flow. Fouling release occurs due to weak interfacial bond created by the organism’s cement and the coating surfaces as a result of low surface free energy (SFE) and cohesive failure of bio adhesives occurs due to shear forces created by flowing water across the coatings. Even though FRC has been shown to be eco-friendly & reduce drag they have many drawbacks viz: weak adhesion strength between coating and substrate, weak mechanical properties, poor AF performance under static conditions, inefficient against diatom and bacterial slimes. Bacterial and diatom biofilms on FRC’s increase frictional resistance reduce drag reduction and fuel savings. To improve the biofouling resistance of FRC, several approaches like amphiphiles, zwitterions, quaternary ammonium salts (QAs), and metal oxide nanoparticles have been investigated. PEG-based amphiphiles is one such example where findings have translated into a commercial paint Intersleek 1100SR and HempasilX3 formulations which have been reported to offer better fouling release of barnacles and diatoms. Surface chemistry, mechanical property, binding to substrates, and durability are vital factors in designing modern-day antifouling coatings and fouling resistance is a ubiquitous parameter in consideration. This review reports the advancements and modifications to the siloxane backbone by each of these parameters which have enabled in development of superior and environmentally benign foul release coatings.

Increased adhesion and biofilm formation by marine microalgae as well as inhibition of settlement of invertebrate larval forms on polydimethylsiloxane (PDMS) foul release coatings is a challenge to overcome. Copper oxide nanoparticles (CuO-NP) were synthesized by a wet chemical precipitation route and incorporated into PDMS foul release surfaces to improve its anti-microfouling nature. In situ antifouling performance of PDMS-CuO nanocomposite (NC) was evaluated in coastal waters and compared with plain PDMS surface. Adhesion and settlement of microalgae and macrofoulers and their succession were monitored for 7 and 90 days respectively. Plain PDMS surfaces were abundantly colonized by microalgae (1.3 x 103 cm-2), wherein significant (p < 0.05) reduction (1.76 x 102) was observed with PDMS-CuO NC. In addition, CuO reinforcement significantly (p < 0.05) reduced the biofouling load and surface area coverage upto 1.6 +/- 0.22 Kg m- 2 90 day-1 and 27.5 +/- 4.5% respectively, whereas plain PDMS surfaces experienced 10.6 +/- 1.5 Kg m- 2 90 day- 1 and 89.6 +/- 7.96% respectively. Incorporation of CuO nanoparticles as nanofillers into PDMS matrix offers a promising antifouling alternative to inhibit algal fouling as well as larval settlement by imparting toxicity at the surface through release of metal ions.

Marine biogrowth infestation of a seawater intake system was investigated. A digital camera fixed onto a skid was used to record the biogrowth at intervals of 5 m up to a depth of 55 m. Divers inspected the intake shaft and collected the biogrowth samples for biomass estimation. A biomass density of 7.5 kg m(-2) and 28.2 kg m(-2) was recorded at 5 and 30 m depths respectively. Inspection by the divers revealed that hard-shelled organisms such as oysters and brown and green mussels were observed in plenty up to a thickness of 15 cm and bryozoans grew as epibionts. At lower depths ( m), hydroids grew on the shells of green mussels along with silt accumulation. The biofouling community was composed of 46 organisms, exhibiting variation in distribution and abundance. The study explains the extent and type of marine biogrowth phenomena with depth and describes biofouling preventive methods. Supplemental data for this article is available online at https://doi.org/10.1080/08927014.2021.1933457 .