Marine Microfouling Research Articles

Modelling and optimization of phlorotannin extraction from Stoechospermum marginatum using response surface methodology and evaluating its activity against marine microfouling bacteria

Modelling and optimization of phlorotannin extraction from Stoechospermum marginatum using response surface methodology and evaluating its activity against marine microfouling bacteria

Marine biofilms on different fouling control coating types reveal differences in microbial community composition and abundance.

Marine biofouling imposes serious environmental and economic impacts on marine applications, especially in the shipping industry. To combat biofouling, protective coatings are applied on vessel hulls which are divided into two major groups: biocidal and non‐toxic fouling release. The current study aimed to explore the effect of coating type on microbial biofilm community profiles to better understand the differences between the communities developed on fouling control biocidal antifouling and biocidal‐free coatings. Biocidal (Intersmooth® 7460HS SPC), fouling release (Intersleek® 900), and inert surfaces were deployed in the marine environment for 4 months, and the biofilms that developed on these surfaces were investigated using Illumina NGS sequencing, targeting the prokaryotic 16S rRNA gene. The results confirmed differences in the community profiles between coating types. The biocidal coating supported communities dominated by Alphaproteobacteria (Loktanella, Sphingorhabdus, Erythrobacter) and Bacteroidetes (Gilvibacter), while other taxa, such as Portibacter and Sva0996 marine group, proliferated on the fouling‐release surface. Knowledge of these marine biofilm components on fouling control coatings will serve as a guide for future investigations of marine microfouling as well as informing the coatings industry of potential microbial targets for robust coating formulations.

Antimicrofouling activities of marine macroalga Dictyota dichotoma from the Red Sea

Introduction. Marine organisms produce a variety of secondary metabolites mainly for achieving the defence against the competitors and predators. These compounds could be used as natural product antifoulants for the management of biofouling growth on marine structures. Objectives. To understand the antifouling defence strategies of marine macroalgae collected from the Red Sea. Methodology. The macroalga Dictyota dichotoma was collected from the Obhur Creek of Red Sea, Saudi Arabia and extracted using methanol. Surface and total extraction methods were performed and tested against a bacterial strain isolated from the microfouling assemblage. Results. The extracts obtained from the macroalgal samples have strong antibacterial and antibiofilm activities against the bacterial strain isolated from the marine microfouling assemblage. The total extracts showed strong bacterial growth inhibitory activities in culture plate method. In microtitre plate assay, surface extract showed strong biofilm inhibitory activity. GC-MS analysis indicated considerable variations in the metabolic profile of the surface and total extracts. Conclusion. This study revealed the importance of surface-associated compounds in antifouling defence mechanism of the marine macroalgae.

Antimicrofouling activities of marine macroalga Dictyota dichotoma from the Red Sea

Introduction. Marine organisms produce a variety of secondary metabolites mainly for achieving the defence against the competitors and predators. These compounds could be used as natural product antifoulants for the management of biofouling growth on marine structures. Objectives. To understand the antifouling defence strategies of marine macroalgae collected from the Red Sea. Methodology. The macroalga Dictyota dichotoma was collected from the Obhur Creek of Red Sea, Saudi Arabia and extracted using methanol. Surface and total extraction methods were performed and tested against a bacterial strain isolated from the microfouling assemblage. Results. The extracts obtained from the macroalgal samples have strong antibacterial and antibiofilm activities against the bacterial strain isolated from the marine microfouling assemblage. The total extracts showed strong bacterial growth inhibitory activities in culture plate method. In microtitre plate assay, surface extract showed strong biofilm inhibitory activity. GC-MS analysis indicated considerable variations in the metabolic profile of the surface and total extracts. Conclusion. This study revealed the importance of surface-associated compounds in antifouling defence mechanism of the marine macroalgae.

Effect of Scanning Speed on the Surface Roughness of Laser Metal Deposited Copper on Titanium Alloy

This paper reports on the effect of scanning speed on the laser deposited Cu on titanium alloy substrate. The experiments were conducted by varying the scanning speed from 0.3 m/min to 1.2 m/min while the laser power, the powder feed rate and the gas flow rate were kept constant. The laser deposited Cu were characterized through the evolving microstructure and surface roughness. Dendrites and acicular were much pronounced in the clad area; found to decrease as the scanning speed increases due to the laser interaction time and the cooling rate. These however, influenced the irregularities in the peaks and valleys of the surface texture. The arithmetic mean deviation, Ra were measured and abridged from 6.70 µm to 1.41 µm as the scanning speed was increased from samples DC1 to DC4. The motivation for this work is to improve the surface performance of Ti6Al4V alloy when exposed and attacked by marine microfouling organisms.

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.

Self-decontaminating photocatalytic zinc oxide nanorod coatings for prevention of marine microfouling: a mesocosm study

The antifouling (AF) properties of zinc oxide (ZnO) nanorod coated glass substrata were investigated in an out-door mesocosm experiment under natural sunlight (14:10 light: dark photoperiod) over a period of five days. The total bacterial density (a six-fold reduction) and viability (a three-fold reduction) was significantly reduced by nanocoatings in the presence of sunlight. In the absence of sunlight, coated and control substrata were colonized equally by bacteria. MiSeq Illumina sequencing of 16S rRNA genes revealed distinct bacterial communities on the nanocoated and control substrata in the presence and absence of light. Diatom communities also varied on nanocoated substrata in the presence and the absence of light. The observed AF activity of the ZnO nanocoatings is attributed to the formation of reactive oxygen species (ROS) through photocatalysis in the presence of sunlight. These nanocoatings are a significant step towards the production of an environmentally friendly AF coating that utilizes a sustainable supply of sunlight.

Progress on Measurement of Adhesion Strength of Marine Microfouling Organisms

The development of novel nontoxic antifouling paint has led to the need for better test methods to evaluate their performance. The adhesion strength of microorganism on material surface is the key parameter to characterize whether they could permanently soiled, therefore it is significant to establish a biological adhesion test method to evaluate the material antifouling ability. In this paper, several types of surface adhesion strength test devices have been introduced, including spinet apparatus, laminar channel flow cell, radial flow chamber, annular flow cell and fully-developed turbulent channel. Their application, advantage and disadvantage have also been discussed.

Determination of microbial fatty acid profiles at femtomolar levels in human urine and the initial marine microfouling community by capillary gas chromatography-chemical ionization mass spectrometry with negative ion detection

Room temperature esterification with the electron capturing pentafluorobenzyl bromide in glass capillaries, with analysis by capillary gas-liquid chromatography coupled with chemical ionization mass spectrometry and negative ion detection in the selected ion mode, allowed detection and identification of fatty acids from microbial biofilms at the femtomolar level. This sensitivity was achieved without loss of specificity of the mass spectrometric analysis. The detection of all the fatty acids commonly associated with bacteria was quantitative and linearly related to their concentration at a sensitivity permitting detection of about 600 bacteria the size of Escherichia coli. With this technique it was possible to detect the characteristic 3-hydroxy fatty acid of the lipopolysaccharide lipid A of E. coli infecting human urine at concentrations representing 10 4 bacteria and define the community structure of the initial marine microfouling community attached to a teflon surface at concentrations below the detectability by gas chromatography with flame ionization detection.

In situ identification of bacterial species in marine microfouling films by using an immunofluorescence technique.

An immunofluorescence technique was developed for the in situ identification of specific bacteria in marine microfouling films. Microorganisms adherent to glass plates after 30 days of immersion in a synthetic seawater system were cultured and classified by biochemical tests, flagellar arrangement, and the API 20E system. All isolates were gram-negative aerobic or facultative motile rods, predominantly Pseudomonas spp. Rabbit antisera to the five dominant organisms including Achromobacter spp., Comamonas terrigena, P. putrefaciens, a yellow-pigmented Pseudomonas sp., and Vibrio alginolyticus were prepared. These antisera were shown to be species specific in indirect immunofluorescence assays against a battery of 26 marine isolates from 14 bacterial species, with the exception of antisera to the Pseudomonas spp, which cross-reacted with each other but not with test bacteria of other genera. These immunofluorescent reagents enabled the in situ identification of all five bacterial species in microfouling films. Low-surface-energy test plates had smaller numbers of adherent bacteria in microfouling films than medium-surface-energy test plates, suggesting that the degree of microfouling may be influenced by the surface energy. In addition, the reagents could identify up to 39% of the attached bacteria in microfouling films spontaneously formed on steel plates in flow cells deployed in different areas of the Atlantic Ocean. The microbial composition of the ocean-formed films varied with the geographical area of their formation. The present results indicate that immunofluorescence techniques may provide a rapid and reliable means to identify, in situ, specific bacteria in marine microfouling films.

Control of an Estuarine Microfouling Sequence on Optical Surfaces Using Low-Intensity Ultraviolet Irradiation

Ultraviolet light has been investigated as an active energy input for the control of slime film formation on optical surfaces submerged in San Francisco Bay for periods up to 6 weeks. Irradiation of quartz underwater windows was carried out from three positions: (i) exterior to the window, (ii) from directly behind the window, and (iii) from the edge of the window with the ultraviolet (UV) energy refracted through the front of the window. Internally administered irradiation reaching levels of 10 to 30 muW per cm measurable at the glass surface was effective in preventing bacterial slime film formation and settlement of metazoan larvae. When administered from the external position, over one order of magnitude more (500 to 600 muW/cm) UV energy was required to accomplish the same result. Irradiation from the edge position was most promising logistically and was effective in fouling control for 6 weeks. The results provide a preliminary quantitation of the energy requirement for control of the marine microfouling sequence which precedes development of macrofouling communities.

Control of an Estuarine Microfouling Sequence on Optical Surfaces Using Low-Intensity Ultraviolet Irradiation

Ultraviolet light has been investigated as an active energy input for the control of slime film formation on optical surfaces submerged in San Francisco Bay for periods up to 6 weeks. Irradiation of quartz underwater windows was carried out from three positions: (i) exterior to the window, (ii) from directly behind the window, and (iii) from the edge of the window with the ultraviolet (UV) energy refracted through the front of the window. Internally administered irradiation reaching levels of 10 to 30 μW per cm 2 measurable at the glass surface was effective in preventing bacterial slime film formation and settlement of metazoan larvae. When administered from the external position, over one order of magnitude more (500 to 600 μW/cm 2 ) UV energy was required to accomplish the same result. Irradiation from the edge position was most promising logistically and was effective in fouling control for 6 weeks. The results provide a preliminary quantitation of the energy requirement for control of the marine microfouling sequence which precedes development of macrofouling communities.