Seasonal Variability of Biofouling Community Structure in the Gulf of Mannar,Southeast Coast of India:A Multivariate Approach

In this research,an Underwater Biofouling Panel(UWBFP)system was erected for the qualitative and quantitative estimation of macro fouling organisms in the Gulf of Mannar.Forty-four biofoulers were identified from four types of selected test panels.Among these biofoulers,Amphibalanus amphitrite(Darwin,1854)was the dominant one.The concrete panel encouraged the highest barnacle density compared to the other panels.Three series of test panels were used to assess the seasonal density of biofouling communities.The overall variation in barnacle count in the seaward and shoreward sides of all these three series were tested.They were found to be significantly different from each other.The greater variations in the barnacle density observed in this study in A-series of test panels could be due to the lack of or absence of other foulers to compete within the fortnight.The Shannon-Wiener species diversity index showed the highest diversity in wood substratum among the three series with greater accumulation of different types of fouling organisms.Multivariate analyses were also performed to understand the seasonal variation as well as the settlement pattern on the different directions of test panels based on validated data.PCA showed a strong variability(PC1 between 70.8%and 98.6%variance)between the directions of the panels in connection with barnacle density.The shade plot and CAP analysis segregated the short-term A-series test panels from the long-term(B-and C-series)test panels.Hence,the output was helpful in understanding the recruitment status of various faunal resources involved in the biofouling processes.

A Study on the Composition of Wastewater Produced during Ship Biofouling Management

The IMO(International Maritime Organization)recognized the problem of invasive species invasion and adopted the“International Convention for the Control and Management of Ships’Ballast Water and Sediments”in 2004,which came into force on September 8,2017.In 2011,the IMO approved the“Guidelines for the Control and Management of Ships’Biofouling to Minimize the Transfer of Invasive Aquatic Species”to minimize the movement of invasive species by hull-attached organisms and required ships to manage the organisms attached to their hulls.Invasive species enter new environments through ships’ballast water and hull attachment.However,several obstacles to implementing these guidelines have been identified,including a lack of underwater cleaning equipment,regulations on underwater cleaning activities in ports,and difficulty in accessing crevices in underwater areas.The shipping industry,which is the party responsible for understanding these guidelines,wants to implement them for fuel cost savings resulting from the removal of organisms attached to the hull,but they anticipate significant difficulties in implementing the guidelines due to the obstacles mentioned above.Robots or people remove the organisms attached to the hull underwater,and the resulting wastewater includes various species of organisms and particles of paint and other pollutants.Currently,there is no technology available to sterilize the organisms in the wastewater or stabilize the heavy metals in the paint particles.In this study,we aim to analyse the characteristics of the wastewater generated from the removal of hull-attached organisms and select the optimal treatment technology.The organisms in the wastewater generated from the removal of the attached organisms meet the biological treatment standard(D-2)using the sterilization technology applied in the ships’ballast water treatment system.The heavy metals and other pollutants in the paint particles generated during removal are treated using stabilization technologies such as thermal decomposition.The wastewater generated is treated using a two-step process:(1)development of sterilization technology through pretreatment filtration equipment and electrolytic sterilization treatment and(2)development of technology for removing particle pollutants such as heavy metals and dissolved inorganic substances.Through this study,we will develop a biological removal technology and an environmentally friendly processing system for the waste generated after removal that meets the requirements of the government and the shipping industry and lay the groundwork for future treatment standards.

MARINE BIOFOULING IN OFFSHORE AREAS SOUTH OF HAINAN ISLAND, NORTHERN SOUTH CHINA SEA

This study on the characteristics of fouling communities in offshore areas south of Hainan Island, northern South China Sea, was conducted at four sites there. At each station, test panels on iron frames were hung on the mooring system at different depths. Data on biofouling were mainly obtained by examination of the fouled test panels. Organisms attached to buoys and anchors were scraped off and examined also. The results showed that the thickness and biomass of marine growth that increased the fluid loading on offshore installations depended to a large extent on hard foulers, i.e. mollusks and acorn barnacles. Algae, hydroids, stalked barnacles and bryozoans were important fouling species. The occurrence frequency and biomass of acorn barnacles decreased with increasing distance from the shore.

Experimental Study of Invasion and Biofouling of Freshwater Mussel <i>Limnoperna fortunei</i>

Golden mussel Limnoperna fortunei(Dunker 1857) is a filter-collector species of fresh water mussel originating from southern China. In the water transfer tunnels from the East River to Shenzhen and Hong Kong, golden mussels attach to the walls of pipelines and gates, causing serious biofouling, increased flow resistance, and resulted in corrosion of the tunnel wall. Golden mussel has very high environmental adaptability and may colonize habitats with low dissolved oxygen and a wide range of trophic levels. The colonization process of the species on solid surface was studied in the Xizhijiang River, a tributary of the East River and the main water resource of Shenzhen from March 2010 to April 2011. The results showed that the golden mussel completed three generations and reproduced six cohorts per year in the tropic zone. Water temperature was the controlling factor for the growth rate and maturity of each cohort. Based on the results, an ecological method for controlling the invasion of golden mussels in water transfer tunnels was proposed.

Notes Marine biofouling in Hong Kong: a review

From 1980 to 1998, biofouling communities in Hong Kong waters, the Zhujiang River Estuary and the Mirs Bay were studied and a total of 610 samples. The samples were collected from vessels, buoys, piers and cages. Totally, 340 species (see Appendix I) have been recorded and identified, six of which are new. At the same time, research on the biology of the cirripede, bryozoan, polychaete and mollusc communities were also conducted. Twenty-three related papers have been published. This review summarizes works in Hong Kong over past twenty years, and some unpublished data are also reported.

Impact assessment of biofouling resistant nano copper oxide-polyaniline coating on aquaculture cage nets

Biofouling is a major issue in aquaculture cages and nano materials based antifouling strategies became more prominent in recent years.Polyethylene aquaculture cage net surface which is modified with polyaniline and nano-copper oxide(CuO),reported to have biofouling resistance.Leaching of nano CuO from the net to the aquatic environment and its bioaccumulation in fish is the major concern against the technology adoption.The present study aimed to understand the accumulation of copper in fishes grown in a nano CuO treated aquaculture cage net.Studied the leaching pattern of nano CuO,biofouling inhibition and changes in strength of the cage net due to the nano CuO treatments.Fishes grown in the treated cages exhibited normal growth characteristics with no signs of abnormalities and also copper in their organs were within the prescribed standard limit.The CuO treated cage net exhibited excellent biofouling resistance and the percentage of occlusion of mesh by foulers were 56.77%more efficient than untreated cage net.Rate of nano CuO leached to the aquatic system was less than 8μg/g⋅d.The fouling organism assemblage on untreated and treated net was 18 and 11 species,respectively.Major calcareous shelled foulers were absent on treated nets.The study highlighted the potential application of nano CuO treatment to control biofouling in aquaculture cages.

Cathodic biofouling control by microbial separators in air-breathing microbial fuel cells

Microbial fuel cells(MFCs)incorporating air-breathing cathodes have emerged as a promising ecofriendly wastewater treatment technology capable of operating on an energy-free basis.However,the inevitable biofouling of these devices rapidly decreases cathodic catalytic activity and also reduces the stability of MFCs during long-term operation.The present work developed a novel microbial separator for use in air-breathing MFCs that protects cathodic catalytic activity.In these modified devices,microbes preferentially grow on the microbial separator rather than the cathodic surface such that biofouling is prevented.Trials showed that this concept provided low charge transfer and mass diffusion resistance values during the cathodic oxygen reduction reaction of 4.6±1.3 and 17.3±6.8 U,respectively,after prolonged operation.The maximum power density was found to be stable at 1.06±0.07 W m
2 throughout a long-term test and the chemical oxygen demand removal efficiency was increased to 92%compared with a value of 83%for MFCs exhibiting serious biofouling.In addition,a cathode combined with a microbial separator demonstrated less cross-cathode diffusion of oxygen to the anolyte.This effect indirectly induced the growth of electroactive bacteria and produced higher currents in air-breathing MFCs.Most importantly,the present microbial separator concept enhances both the lifespan and economics of air-breathing MFCs by removing the need to replace or regenerate the cathode during longterm operation.These results indicate that the installation of a microbial separator is an effective means of stabilizing power generation and ensuring the cost-effective performance of air-breathing MFCs intended for future industrial applications.

A state-of-the-art review on passivation and biofouling of Ti and its alloys in marine environments

High strength-to-weight ratio, commendable biocompatibility and excellent corrosion resistance make Ti alloys widely applicable in aerospace, medical and marine industries. However, these alloys suffer from serious biofouling, and may become vulnerable to corrosion attack under some extreme marine conditions. The passivating and biofouling performance of Ti alloys can be attributed to their compact, stable and protective films. This paper comprehensively reviews the passivating and biofouling behavior, as well as their mechanisms, for typical Ti alloys in various marine environments. This review aims to help extend applications of Ti alloys in extremely harsh marine conditions.

Biocorrosion induced by red-tide alga-bacterium symbiosis and the biofouling induced by dissolved iron for carbon steel in marine environment

The assemblages of unicellular microalgae and bacteria in phytoplankton communities can generally result in biodeterioration of metals in marine environment.In this study,the self-promoted biofouling mechanism underneath red-tide alga Phaeodactylum tricornutum and its symbiotic bacterium Bacillus altitudinis was systematically revealed.The mutualistic interaction of the bacteria and algae quadrupled the corrosion rate in comparison to the individual effect of the bacterium or algal strain alone.Reversely,the corroded metal appeared to be an accelerator that can stimulate the activity of the P.tricornutum and aggravate the biological pollution based on the result of 62.3%up-regulation of the key photosynthesis genes.The corrosion-biofouling-accelerated corrosion-deteriorated biofouling formed a vicious cycle.

Transparent exopolymer particles(TEPs)-associated protobiofilm:A neglected contributor to biofouling during membrane filtration

Transparent exopolymer particles(TEPs)are a class of transparent gel-like polysaccharides,which have been widely detected in almost every kind of feed water to membrane systems,including freshwater,seawater and wastewater.Although TEP have been thought to be related to the membrane fouling,little information is currently available for their influential mechanisms and the pertinence to biofouling development.The present study,thus,aims to explore the impact of TEPs on biofouling development during ultrafiltration.TEP samples were inoculated with bacteria for several hours before filtration and the formation of“protobiofilm”(pre-colonized TEP by bacteria)was examined and its influence on biofouling was determined.It was observed that the bacteria can easily and quickly attach onto TEPs and form protobiofilms.Ultrafiltration experiments further revealed that TEP-protobiofilms served as carriers which facilitated and accelerated transport of bacteria to membrane surface,leading to rapid development of biofouling on the ultrafiltration membrane surfaces.Moreover,compared to the feed water containing independent bacteria and TEPs,more flux decline was observed with TEP-protobiofilms.Consequently,it appeared from this study that TEP-protobiofilms play a vital role in the development of membrane biofouling,but unfortunately,this phenomenon has been often overlooked in the literature.Obviously,these findings in turn may also challenge the current understanding of organic fouling and biofouling as membrane fouling caused by TEP-protobiofilm is a combination of both.It is expected that this study might promote further research in general membrane fouling mechanisms and the development of an effective mitigation strategy.

Eco-friendly biodegradable polyurethane based coating for antibacterial and antifouling performance

Biofouling, which comprises the absorption of proteins and the adhesion of bacteria to the surface of living entities, is a severe concern for the maritime sector since it ultimately leads to hydrodynamic drag,resulting in a higher increase in fuel consumption. As a result, polymer resins are crucial in the marine sector for anti-biofouling coatings. In this work, the poly(caprolactone-ethylene glycol-caprolactone)-p olyurethane(PECL-PU) are prepared through ε-caprolactone(CL), poly(ethylene glycol)(PEG), 4,4'-methylene bis(cyclohexyl isocyanate) and 1,4 butanediol. Our study demonstrate that the PECL-PU copolymer degraded in artificial seawater(5.21%), enzymatic solution(12.63%), and seawater(13.75%)due to the presence of PEG segments in the laboratory-based test under static condition. Because the addition of PEG segments are increased the polymer's amorphous area and decreased the crystallization of the polycaprolactone(PCL) in the copolymer, as demonstrated by differential scanning calorimetry, X-ray diffraction, and water contact angle studies. Therefore, the hydrolysis rates of PECL-PU were higher than the caprolactone-co-polyurethane(CL-PU). The antifouling test showed that PECL-PU3 copolymer had about 90.29% protein resistance, 85.2% Escherichia coli(E. coli) reduction and 94.61% marine diatom Navicula incerta reduction comparison to the control. We have developed an eco-friendly and inexpensive promising degradable polyurethane for reduction of bacterial biofilm, which can preserve the formation of biofouling on marine coating under practical sea conditions.

Fouling in offshore areas southeast of the Zhujiang(Pearl)River Delta,the northern South China Sea

In order to understand the type and extent of marine fouling in offshore areas southeast ofthe Zhujiang (Pearl) River delta, within the period form May 1986 to June 1987, two biological buoys were deployed at water depths of 95 m and 113 m located in 114 km and 160 km off the coast of Hong Kong, respectively. Moreover, the fouling community of a Marex hydrological buoy located in 115 m depth water 172 km off Hong Kong was also surveyed. The results show that a total of 78 species were collected and identified. The panels exposed for 3 months were mainly dominated by stalked barnacles Conchoderma hunteri and Lepas anatifera and hydroids Orthopyxis sp. As for the buoys, including the subsurface buoy, and their mooring systems exposed for 6 and 12 months, respectively, some hard foulers such as common oysters, pearl oysters, acorn barnacles and bryozoans were also found. The compositions of fouling communities also varied greatly with depth.

水下船舶清洗技术综述

This paper presents a comprehensive review and analysis of ship hull cleaning technologies.Various cleaning methods and devices applied to dry-dock cleaning and underwater cleaning are introduced in detail,including rotary brushes,high-pressure and cavitation water jet technology,ultrasonic technology,and laser cleaning technology.The application of underwater robot technology in ship cleaning not only frees divers from engaging in heavy work but also creates safe and efficient industrial products.Damage to the underlying coating of the ship caused by the underwater cleaning operation can be minimized by optimizing the working process of the underwater cleaning robot.With regard to the adhesion technology mainly used in underwater robots,an overview of recent developments in permanent magnet and electromagnetic adhesion,negative pressure force adhesion,thrust force adhesion,and biologically inspired adhesion is provided.Through the analysis and comparison of current underwater robot products,this paper predicts that major changes in the application of artificial intelligence and multirobot cooperation,as well as optimization and combination of various technologies in underwater cleaning robots,could be expected to further lead to breakthroughs in developing next-generation robots for underwater cleaning.

Offshore fouling: investigation methods

On the hasis of the reason that the offshore oil development areas in the northern South China Sea are at greater depth,more hazardous conditions and distance from shore, the methods and technologies used in coastal waters are notfeasible because of the higher risk of losing investigation equipment or facilities. A series of methods and technologiesfor offshore fouling investigation that have been successfully applied is given in detail and it is hoped that theexperience can be helpful for further studies.

Fouling community characteristics in subtropical coastal waters of the southwestern East China Sea

A fouling study was conducted in coastal waters southwest of the East China Sea between December 2013 and November 2014. A total of 84 species of fouling organisms belonging to 69 genera, 49 families, and 10 phyla were recorded over the entire year. The community composition was dominated by coastal warm-water species belonging to typical subtropical inner bay communities. The prosperous stage of settlement lasted from April to September, and the adhesion strength of the fouling organisms was the highest in summer. Sessile suspension feeders constituted the main core of settlement for the fouling community. Amphibalanus reticulatus was the most dominant and representative species of fouling organism, and other dominant species included Caprella equilibra, Ectopleura crocea, Anthopleura nigrescens, Stylochus ijimai, Spirobranchus kraussii, Crassostrea angulata, Perna viridis, Jassa falcata, Stenothoe valida, Sphaerozius nitidus, and Biflustra grandicella. The individuals in the fouling community showed a mutual dependence or constraint relationship due to competition for settlement space and food, and they exhibited a particular spatiotemporal distribution in accordance with adaptation to environmental factors. Temperature was the most important environmental factor determining the geographic distribution of fouling organisms. The temperature characteristics of species essentially reflect the differences in the fouling community composition in various climate zones. The species number, settlement stage, and settlement rate of fouling organisms are closely related to water temperature. Local natural environmental conditions（salinity, water currents, light, etc.） as well as human activity（such as aquaculture production） are all important factors affecting the settlement of fouling organisms.

Extraction of Protease Produced by Sea Mud Bacteria and Evaluation of Antifouling Performance

Enzyme-based antifouling coatings are potential alternative to traditional tributyltin-based coatings in the marine biofouling control depended on its environmental friendliness.Proteases are usually the key antifouling active components in enzyme based antifouling coatings.In this work,based on biological antagonism effect,a marine proteolytic bacterial strain of Bacillus velezensis was isolated from the sea mud,and denoted as SM-1.The scanning electron microscope(SEM)revealed that the bacteria are rod-shaped with length 1-1.3μm.The protease-producing conditions of SM-1 were investigated,and it was found that the culture solution displays higher proteolytic activity under the culture conditions of 35℃,10‰-20‰salinity,pH 6-9 and more than 7 d culture time.Moreover,the 25 kDa protein was confirmed to be the main active component in the crude protease,which was revealed via the experiment of SDS-PAGE.The antifouling assay indicated that the protease SM-1 has remarkable effect on the decomposition of barnacle cement and diatom secretion,and also can effectively inhibit the attachment of barnacle cyprids,diatom and mussel byssus.Therefore,this protease potentially can be used as environmental-friendly antifoulant of enzyme-based marine antifouling coatings,and this work also provides a new approach to obtain antifouling protease via isolating proteolytic bacteria from the sea mud surrounding representative fouling organisms.

Inhibition of spore germination of Ulva pertusa by the marine bacterium Pseudoalteromonas haloplanktis CI4

The effect of the bacterial strain C14 on the germination of spores from the green alga Ulva pertusa was assayed and it was found that the bacterial biofilm and cell-free supernatant strongly inhibited spore germination. In attempts to define the chemical nature of she antifouling substance in the supernatant of C14, the culture supernatants were tested for activity after heat treatment, enzymatic treatments, size fractionation, and separation into aqueous and organic fractions. Results suggest that this bacterium produces an extracellular component with specific activity toward algal spores that was heat-sensitive and between 3 and 10 kDa in molecular size. The exposure of the organic phase fraction to spores showed inhibitive effect on spore germination. Pronase and carboxypeptidase y did not significantly affect the activity of inhibitory component, suggesting that the component was not a protein or a peptide. The bacterium C14 was identified as Pseudoalteromonas haloplanktis based on the phenotypic characters and 16S rRNA gene analvsis.

污垢组合对印度玛纳尔湾水域低碳钢腐蚀行为的影响研究(英文)

Corrosion behaviour and biofouling characteristics of mild steel in three different coastal locations in the Gulf of Mannar,India have been studied over a period of 24 months.Oyster fouling was predominant at Open sea-Tuticorin,while barnacle fouling was dominant at both Mandapam and Harbour-Tuticorin.The rate of corrosion for 24 months exposure period was highest at Mandapam,where fouling was minimal.The surface of the mild steel was characterized by etchings&crevices beneath the hard foulers attached on it,at all the test locations.The depth of crevice caused by hard foulers was higher at Open sea-Tuticorin followed by Harbour-Tuticorin and Mandapam.The loss in ultimate tensile strength was more in Open sea-Tuticorin than the other two locations.Corrosion behaviour of mild steel is discussed based on the variation in the biofouling assemblage at the three test locations.

Characterization and antifouling activity analysis of extracellular polymeric substances produced by an epibiotic bacterial strain Kocuria flava associated with the green macroalga Ulva lactuca

Extracellular polymeric substances(EPS)are present externally to the microorganisms and play an important role in attachment and biofilm formation.These polymers possess antibacterial and antifouling activities.In this study,the antifouling activity of EPS produced by an epibiotic bacterium associated with macroalga Ulva lactuca was assessed against fouling bacteria and barnacle larvae.Results indicate that the EPS isolated from the epibiotic bacterium inhibits the biofilm formation of the bacteria without much antibacterial activity.Also,the EPS reduced the settlement of barnacle larvae on the hard substrate under laboratory conditions.The epibiotic bacterium was identified as Kocuria flava based on 16 S rRNA gene sequencing.The EPS was further analysed using Fourier transform infrared(FT-IR),nuclear magnetic resonance(NMR)and X-ray diffraction(XRD)to understand the biochemical composition.NMR analysis revealed the presence of polysaccharides,proteins,acetyl amine and succinyl groups.Scanning electron microscope analysis indicated that the EPS consisted of aggregated and irregular sphere-shaped particles.

Bifunctional nanozyme activities of layered double hydroxide derived Co-A1-Ce mixed metal oxides for antibacterial application

Marine biofouling is an expensive problem that needs evolved chemical or physical antifouling strategies.However,most of the current antifouling materials that would damage the environment through metal leaching and bacteria resistance are being halted.Nanozyme is one kind of environmental antifouling materials through generating reactive oxygen species(ROS).We prepared various contents of CeO2 that could uniform disperse compounding with Co3 O4 and CoAl2 O4 to form a stable Co-Al-Ce mixed metal oxide(MMO) by a layered double hydroxide derived method.We find that coupling with CeO2 can improve the peroxidase(POx) activity.When the molar ratio of Ce is 2.5% and the calcination temperature is 200℃,the POx activity of Co-Al-Ce MMO is the best caused by the good dispersion of catalytically active components and the high specific area(150.10±4.95 m2/g).This novel Co-Al-Ce MMO also exhibits an antibacterial mode of action Gram-negative bacteria in near-neutral pH solution through generating ROS(mainly ·O2-)in the presence of H2 O2.Ce containing MMO can be utilized as potential green marine antifouling material.