Recent developments in superhydrophobic surfaces and their relevance to marine fouling: a review

In this review, a brief synopsis of superhydrophobicity (i.e. extreme non-wettability) and its implications on marine fouling are presented. A short overview of wettability and recent experimental developments aimed at fabricating superhydrophobic surfaces by tailoring their chemical nature and physical appearance (i.e. substratum texture) are reviewed. The formation of responsive/"smart" surfaces, which adjust their physico-chemical properties to variations in some outside physical stimulus, including light, temperature, electric field, or solvent, is also described. Finally, implications of tailoring the surface chemistry, texture, and responsiveness of surfaces on the design of effective marine fouling coatings are considered and discussed.     

Interspecific variation in patterns of adhesion of marine fouling to silicone surfaces

Abstract

The adhesion of six fouling organisms: the barnacle Balanus eburneus, the gastropod mollusc Crepidula fornicata, the bivalve molluscs Crassostrea virginica and Ostrea/Dendrostrea spp., and the serpulid tubeworms Hydroides dianthus and H. elegans, to 12 silicone fouling-release surfaces was examined. Removal stress (adhesion strength) varied among the fouling species and among the surfaces. Principal component analysis of the removal stress data revealed that the fouling species fell into two distinct groups, one comprising the bivalve molluscs and tubeworms, and the other the barnacle and the gastropod mollusc. None of the silicone materials generated a minimum in removal stress for all the organisms tested, although several surfaces produced low adhesion strengths for both groups of species. These results suggest that fouling-release materials do not rank (in terms of adhesion strength) identically for all fouling organisms, and thus development of a globally-effective hull coating will continue to require testing against a diversity of encrusting species.     

Sediment challenge to promising ultra-low fouling hydrophilic surfaces in the marine environment

Hydrophilic coatings exhibit ultra-low fouling properties in numerous laboratory experiments. In stark contrast, the antifouling effect of such coatings in vitro failed when performing field tests in the marine environment. The fouling release performance of nonionic and zwitterionic hydrophilic polymers was substantially reduced compared to the controlled laboratory environment. Microscopy and spectroscopy revealed that a large proportion of the accumulated material in field tests contains inorganic compounds and diatomaceous soil. Diatoms adhered to the accumulated material on the coating, but not to the pristine polymer. Simulating field tests in the laboratory using sediment samples collected from the test sites showed that incorporated sand and diatomaceous earth impairs the fouling release characteristics of the coatings. When exposed to marine sediment from multiple locations, particulate matter accumulated on these coatings and served as attachment points for diatom adhesion and enhanced fouling. Future developments of hydrophilic coatings should consider accumulated sediment and its potential impact on the antifouling performance.     

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.     

Interactions between microbial biofilms and marine fouling algae: a mini review

Natural and artificial substrata immersed in the marine environment are typically colonized by microorganisms, which may moderate the settlement/recruitment of algal spores and invertebrate larvae of macrofouling organisms. This mini-review summarizes the major interactions occurring between microbial biofilms and marine fouling algae, including their effects on the settlement, growth and morphology of the adult plants. The roles of chemical compounds that are produced by both bacteria and algae and which drive the interactions are reviewed. The possibility of using such bioactive compounds to control macrofouling will be discussed.     

The impact and control of biofouling in marine aquaculture: a review

Biofouling in marine aquaculture is a specific problem where both the target culture species and/or infrastructure are exposed to a diverse array of fouling organisms, with significant production impacts. In shellfish aquaculture the key impact is the direct fouling of stock causing physical damage, mechanical interference, biological competition and environmental modification, while infrastructure is also impacted. In contrast, the key impact in finfish aquaculture is the fouling of infrastructure which restricts water exchange, increases disease risk and causes deformation of cages and structures. Consequently, the economic costs associated with biofouling control are substantial. Conservative estimates are consistently between 5–10% of production costs (equivalent to US$ 1.5 to 3 billion yr^?1), illustrating the need for effective mitigation methods and technologies. The control of biofouling in aquaculture is achieved through the avoidance of natural recruitment, physical removal and the use of antifoulants. However, the continued rise and expansion of the aquaculture industry and the increasingly stringent legislation for biocides in food production necessitates the development of innovative antifouling strategies. These must meet environmental, societal, and economic benchmarks while effectively preventing the settlement and growth of resilient multi-species consortia of biofouling organisms.     

Biofouling in marine aquaculture: a review of recent research and developments

Biofouling in marine aquaculture is one of the main barriers to efficient and sustainable production. Owing to the growth of aquaculture globally, it is pertinent to update previous reviews to inform management and guide future research. Here, the authors highlight recent research and developments on the impacts, prevention and control of biofouling in shellfish, finfish and seaweed aquaculture, and the significant gaps that still exist in aquaculturalists’ capacity to manage it. Antifouling methods are being explored and developed; these are centred on harnessing naturally occurring antifouling properties, culturing fouling-resistant genotypes, and improving farming strategies by adopting more sensitive and informative monitoring and modelling capabilities together with novel cleaning equipment. While no simple, quick-fix solutions to biofouling management in existing aquaculture industry situations have been developed, the expectation is that effective methods are likely to evolve as aquaculture develops into emerging culture scenarios, which will undoubtedly influence the path for future solutions.     

The role of surface energy and water wettability in aminoalkyl/fluorocarbon/hydrocarbon-modified xerogel surfaces in the control of marine biofouling

Xerogel films with uniform surface topogrophy, as determined by scanning electron microscopy, atomic force microscopy (AFM), and time-of-flight secondary ion mass spectrometry, were prepared from aminopropylsilyl-, fluorocarbonsilyl-, and hydrocarbonsilyl- containing precursors. Young's modulus was determined from AFM indentation measurements. The xerogel coatings gave reduced settlement of zoospores of the marine fouling alga Ulva compared to a poly(dimethylsiloxane) elastomer (PDMSE) standard. Increased settlement correlated with decreased water wettability as measured by the static water contact angle, θ_Ws, or with decreased polar contribution (γ_P) to the surface free energy (γ_S) as measured by comprehensive contact angle analysis. The strength of attachment of 7-day sporelings (young plants) of Ulva on several of the xerogels was similar to that on PDMSE although no overall correlation was observed with either θ_Ws or γ_S. For sporelings attached to the fluorocarbon/hydrocarbon-modified xerogels, the strength of attachment increased with increased water wettability. The aminopropyl-modified xerogels did not follow this trend.     

Recent developments in genomewide association scans: a workshop summary and review

With the imminent availability of ultra-high-volume genotyping platforms (on the order of 100,000-1,000,000 genotypes per sample) at a manageable cost, there is growing interest in the possibility of conducting genomewide association studies for a variety of diseases but, so far, little consensus on methods to design and analyze them. In April 2005, an international group of >100 investigators convened at the University of Southern California over the course of 2 days to compare notes on planned or ongoing studies and to debate alternative technologies, study designs, and statistical methods. This report summarizes these discussions in the context of the relevant literature. A broad consensus emerged that the time was now ripe for launching such studies, and several common themes were identified--most notably the considerable efficiency gains of multistage sampling design, specifically those made by testing only a portion of the subjects with a high-density genomewide technology, followed by testing additional subjects and/or additional SNPs at regions identified by this initial scan.     

Recent developments in selenium metabolism and chemical speciation: a review.

The biological roles of selenium and its mode of action have only recently begun to be revealed. To date, the major functions of selenium can be attributed to its antioxidative properties and its role in the regulation of thyroid hormone metabolism, cell growth and eicosanoid biosynthesis. The unusual feature of selenoprotein synthesis is that selenocysteine insertion is specified by the stop UGA codon. A number of selenocysteine-specific gene products and a stem-loop structure in the 3' untranslated region are required for selenocysteine biosynthesis and the decoding of UGA codons in the open reading frame of the mRNA. The major biological functions of selenium are achieved through its redox activity when present as selenocysteine at the active sites of selenoproteins and these proteins are selenium-dependent since replacement with the sulphur analogue cysteine causes loss of enzyme activity. Both organic and inorganic forms of selenium may be utilised by the body, with the selenoamino acids showing greatest bioavailability. Knowledge of the biochemistry of the element coupled with appropriate techniques for the study of the distribution of selenium species in health and disease could help to identify sensitive markers of selenium status.     

Recent developments on triazole nucleus in anticonvulsant compounds: a review

Epilepsy is one of the common diseases seriously threatening life and health of human. More than 50 million people are suffering from this condition and anticonvulsant agents are the main treatment. However, side effects and intolerance, and a lack of efficacy limit the application of the current anticonvulsant agents. The search for new anticonvulsant agents with higher efficacy and lower toxicity continues to be the focus and task in medicinal chemistry. Numbers of triazole derivatives as clinical drugs or candidates have been frequently employed for the treatment of various types of diseases, which have proved the importance of this heterocyclic nucleus in drug design and discovery. Recently many endeavours were made to involve the triazole into the anticonvulsants design, which have brought lots of active compounds. This work is an attempt to systematically review the research of triazole derivatives in the design and development of anticonvulsant agents during the past two decades.     

Substratum-induced morphological changes in a marine bacterium and their relevance to biofilm structure.

The effects of surfaces on the physiology of bacteria adhering to surfaces or immobilized within biofilms are receiving more interest. A study of the effects of hydrophobic and hydrophilic substrata on the colonization behavior of a marine bacterium, SW5, revealed major differences in the morphology of SW5 on these surfaces. Using epifluorescence, scanning confocal laser, and on-line visualization (time-lapse video) microscopy, the organisms at hydrophobic surfaces were characterized by the formation of tightly packed biofilms, consisting of single and paired cells, whereas those at hydrophilic surfaces exhibited sparse colonization and the formation of chains more than 100 microns long, anchored at the surface by the terminal (colonizing) cell. The results are discussed in terms of the possible factors inducing the observed morphological differences and the significance of these differences in terms of biofilm structure and plasmid transfer when SW5 is the recipient organism.     

Recent developments in monitoring and modelling airborne pollen,a review

Abstract

Public awareness of the rising importance of allergies and other respiratory diseases has led to increased scientific effort to accurately and rapidly monitor and predict pollen, fungal spores and other bioaerosols in our atmosphere. An important driving force for the increased social and scientific concern is the realisation that climate change will increasingly have an impact on worldwide bioaerosol distributions and subsequent human health. In this review we examine new developments in monitoring of atmospheric pollen as well as observation and source-orientated modelling techniques. The results of a Scopus® search for scientific publications conducted with the terms ‘Pollen allergy’ and ‘Pollen forecast’ included in the title, abstract or keywords show that the number of such articles published has increased year on year. The 12 most important allergenic pollen taxa in Europe as defined by COST Action ES0603 were ranked in terms of the most ‘popular’ for model-based forecasting and for forecasting method used. Betula, Poaceae and Ambrosia are the most forecast taxa. Traditional regression and phenological models (including temperature sum and chilling models) are the most used modelling methods, but it is notable that there are a large number of new modelling techniques being explored. In particular, it appears that Machine Learning techniques have become more popular and led to better results than more traditional observation-orientated models such as regression and time-series analyses.     

Membrane fouling in a membrane bioreactor (MBR): sludge cake formation and fouling characteristics

A submerged membrane bioreactor (MBR) with a working volume of 1.4 L and a hollow fiber microfiltration membrane was used to treat a contaminated raw water supply at a short hydraulic retention time (HRT) of approximately 1 h. Filtration flux tests were conducted regularly on the membrane to determine various fouling resistances, and confocal laser scanning microscopy (CLSM) and scanning electron microscopy (SEM) were employed to characterize the biofouling development and sludge cake formation on the membrane. The experimental results demonstrate that the MBR is highly effective in drinking water treatment for the removal of organic pollutants, ammonia, and UV absorbance. During the MBR operation, the fouling materials were not uniformly distributed on the entire surface of all of the membrane fibers. The membrane was covered partially by a static sludge cake that could not be removed by the shear force of aeration, and partially by a thin sludge film that was frequently washed away by aeration turbulence. The filtration resistance coefficients were 308.4 x 10(11) m(-1) on average for the sludge cake, 32.5 x 10(11) m(-1) on average for the dynamic sludge film, and increased from 10.5 x 10(11) to 59.7 x 10(11) m(-1) for the membrane pore fouling after 10 weeks of MBR operation at a filtration flux of 0.5 m3/m2 x d. Polysaccharides and other biopolymers were found to accumulate on the membrane, and hence decreased membrane permeability. More important, the adsorption of biopolymers on the membrane modified its surface property and led to easier biomass attachment and tighter sludge cake deposition, which resulted in a progressive sludge cake growth and serious membrane fouling. The sludge cake coverage on the membrane can be minimized by the separation, with adequate space, of the membrane filters, to which sufficient aeration turbulence can then be applied.     

盐沼草—白骨壤混种减轻污损动物危害的生物防治效果研究

广西北仑河口区新造高程约220 cm 的潮间带裸滩,移植白骨壤与茳芏、沟叶结缕草、芦苇和南水葱四种盐沼草进行混种,研究盐沼草-红树混种减轻污损动物对人工红树林危害的生物防治效果。结果表明：沟叶结缕草和茳芏可快速生长和扩展,缓流、促淤能力高于长势较差的南水葱和芦苇。在盐沼和白骨壤上发现19种污损动物,其中潮间藤壶、白条地藤壶、黑口滨螺和粗糙滨螺为优势种。茳芏和沟叶结缕草受污损程度较南水葱和芦苇轻。四种盐沼草受污损程度均低于白骨壤。白骨壤＋茳芏、白骨壤＋沟叶结缕草混种均可有效减轻污损动物对白骨壤苗木危害,这两类树-草混种处理区苗木的高度、叶数、枝数、枝下高和存活率等指标均较其他处理区好。初步判断“盐沼草-红树林协同生态修复体系”对于营造人工红树林有较高应用价值。     

Fractal analysis provides new insights into the complexity of marine mammal behavior: A review,two methods,their application to diving and surfacing patterns,and their relevance to marine mammal welfare assessment

Fractals have been applied to describe the complexity of behavioral displays in a range of organisms. Recent work suggests that they may represent a promising tool in the quantification of subtle behavioral responses in marine mammals under chronic exposure to disturbance. This paper aims at introducing the still seldom used fractals to the broader community of marine mammal scientists. We first briefly rehearse some of the fundamental principles behind fractal theory and review the previous uses of fractals in marine mammal science. We subsequently introduce two methods that may be used to assess the complexity of marine mammal diving patterns, and we apply them to the temporal dynamics of the diving patterns of killer whales in the presence and absence of sea kayaks, the sequential behavior of harbor and gray seals in environments with distinct levels of anthropogenic influence, and southern right whales with and without calves. We discuss the ecological relevance of identifying fractal properties in marine mammal behavior, and the potential strength of the fractal behavioral parameters in comparison to more standard behavioral metrics. We finally briefly address the relevance fractal methods may have for the design and implementation of management and conservation strategies.     

Recent trends in biological extraction of chitin from marine shell wastes: a review

The natural biopolymer chitin and its deacetylated product chitosan are widely used in innumerable applications ranging from biomedicine, pharmaceuticals, food, agriculture and personal care products to environmental sector. The abundant and renewable marine processing wastes are commercially exploited for the extraction of chitin. However, the traditional chitin extraction processes employ harsh chemicals at elevated temperatures for a prolonged time which can harm its physico-chemical properties and are also held responsible for the deterioration of environmental health. In view of this, green extraction methods are increasingly gaining popularity due to their environmentally friendly nature. The bioextraction of chitin from crustacean shell wastes has been increasingly researched at the laboratory scale. However, the bioextraction of chitin is not currently exploited to its maximum potential on the commercial level. Bioextraction of chitin is emerging as a green, cleaner, eco-friendly and economical process. Specifically in the chitin extraction, microorganisms-mediated fermentation processes are highly desirable due to easy handling, simplicity, rapidity, controllability through optimization of process parameters, ambient temperature and negligible solvent consumption, thus reducing environmental impact and costs. Although, chitin production from crustacean shell waste through biological means is still at its early stage of development, it is undergoing rapid progress in recent years and showing a promising prospect. Driven by reduced energy, wastewater or solvent, advances in biological extraction of chitin along with valuable by-products will have high economic and environmental impact.     

Functional traits explain phytoplankton community structure and seasonal dynamics in a marine ecosystem

A fundamental yet elusive goal of ecology is to predict the structure of communities from the environmental conditions they experience. Trait‐based approaches to terrestrial plant communities have shown that functional traits can help reveal the mechanisms underlying community assembly, but such approaches have not been tested on the microbes that dominate ecosystem processes in the ocean. Here, we test whether functional traits can explain community responses to seasonal environmental fluctuation, using a time series of the phytoplankton of the English Channel. We show that interspecific variation in response to major limiting resources, light and nitrate, can be well‐predicted by lab‐measured traits characterising light utilisation, nitrate utilisation and maximum growth rate. As these relationships were predicted a priori, using independently measured traits, our results show that functional traits provide a strong mechanistic foundation for understanding the structure and dynamics of ecological communities.     

Biomass characteristics and membrane aeration: toward a better understanding of membrane fouling in submerged membrane bioreactors (MBRs)

Fouling in submerged membrane bioreactors (MBRs) was studied under different operating conditions and with varying biomass characteristics. Fouling rates were determined using a flux-step method for seven biomass conditions with mixed liquor solids concentrations ranging from 4.3 to 13.5 g x l(-1), six permeate fluxes (5.5, 11.0, 16.5, 22.0, 27.5, and 33.0 l x m(-2) x h(-1)), and three membrane airflow velocities (0.07, 0.10, and 0.13 m x s(-1)). Statistical analysis was used to specify the degree of influence of each of the biomass characteristics (solids concentration, dewaterability, viscosity, particle size distribution, concentrations of protein and carbohydrate in the soluble microbial products, SMP, and extracellular polymer substances, EPS), the permeate flux and the membrane aeration velocity on the membrane fouling rate. Among all these variables, only the permeate flux, the solids concentration (correlated to the viscosity and the dewaterability), the carbohydrate concentration in the EPS, and the membrane aeration velocity were found to affect the fouling rate. The permeate flux had the greatest effect. A transitional permeate flux was observed between 16.5 and 33 l x m(-2) x h(-1), below which no significant fouling was observed regardless of the biomass characteristics, the permeate flux, and the membrane aeration velocity.