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Biofouling and underwater measurements

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... barnacles, mussels and tubeworms) and soft communities, where no solid structure is notable (e.g. macroalgae, anemones, soft corals, hydroids, tunicates and sponges) (J. A. Callow and Callow, 2011;Gölzhäuser and Wöll, 2010;Lehaitre and Compère, 2008;Railkin, 2004). Additional epifaunal organisms may also settle on the present ones, producing a multi-layered structure that provides shelter against hydrodynamics for vagile animals like crustaceans, worms, gastropods, and echinoderms (Krone et al., 2013;Railkin, 2004). ...
... The influence of salinity is mostly seen in coastal regions, where its values have a more pronounced variation due to freshwater inputs coming from rivers, contrasting with oceanic waters, where salinity is very stable (Nauw et al., 2015). Most biofouling organisms are either filter feeders or photosynthetic, relying on the presence of suspended particulate matter (living micro-organisms and detritus) and on the light penetration levels in the water column (Lehaitre and Compère, 2008). High concentrations of particulate matter (turbid waters) correspond to low light penetration levels and vice versa (Miller and Macleod, 2016). ...
... High concentrations of particulate matter (turbid waters) correspond to low light penetration levels and vice versa (Miller and Macleod, 2016). Hydrodynamics affect biofouling through currents and waves: strong currents may influence biofouling organisms negatively or positively depending on the species' adaptations (Miller and Macleod, 2016), while strong waves usually have a negative impact causing physical damage and detachment from the substrate (Lehaitre and Compère, 2008). Biofouling communities are more abundant in coastal areas than in oceanic waters (Yebra et al., 2004). ...
Article
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Offshore energy production has been a rising industry in the North Sea since the past century and will likely gain more importance in the future with the increasing development of renewable alternatives. The platforms that are responsible for harvesting and producing energy provide a hard substrate in areas where most substrate is soft, establishing a habitat for fouling communities to settle and to grow on. With time, these communities start to compose a problem for energy production companies, as their natural increase in biomass may pose risks to the platform foundations, leading to the necessity of performing regular inspection so the installations can keep working properly. To address this issue and to better understand how cleaning efforts can be directed, a model was created to relate the growth of these fouling communities with different environmental variables. The variables tested were related to sea surface salinity and temperature, seafloor topography, distance to shore, depth, current and wind velocity, fish abundance, concentration of suspended particulate matter and chlorophyll and presence or absence of artificial structures. Our results indicated that depth and chlorophyll concentration in the water column where the main factors affecting biomass variations in fouling communities.
... Correction of beam attenuation coefficient Fouling is a well know problem of autonomously operated optical sensors deployed on platforms such as moorings, gliders and drifters (e.g., Kerr et al., 1998a Kerr et al., , 1998b Manov et al., 2004). It often limits the accuracy of transmissometer measurements and therefore needs to be addressed carefully (Lehaitre et al., 2008). The recommendation of the International Ocean-Colour Coordinating Group (IOCCG) to mount transmissometers vertically on floats with the source window looking downwards was followed to avoid sedimentation of particles on the collector (IOCCG, 2011). ...
... Such a baseline shift of transmittance during long-term measurements has been verified by different authors. Already a few hours can be sufficient for the biofouling to decrease the transmission by more than 10% but also up to 90% after 16 days (in Lehaitre et al., 2008 after Kerr et al., 1998b). After 170 (float 6900631) and 70 (float 6900632) days, respectively, the steady growth had stopped and the transmittance minimum had fallen to a plateau indicating equilibrium between biofilm growth and loss. ...
... 10 Biofouling of sensor surfaces is a major concern in all physico-chemical sensors, including pH and redox sensors, optical sensors, and electrochemical sensors, and could result in unreliable measurements. 11,12 Biolms start to grow as soon as a sensor is immersed in water, and it has been reported that the quality of measurements decreases in less than a week. 10 Although many potential solutions have been proposed to combat biofouling in underwater measurements and monitoring, there is no single universally accepted method applicable to underwater environmental sensors. ...
... Various methods and technologies have been used to prevent biofouling or remove biolms from biofouled surfaces, such as mechanical treatment (wipers, water jetting, ultrasonic or electrical surface excitation), 11,13 chemical detergents and biocides, 14 UV light exposure (which may kill bacteria but will not completely remove the biolm), 15,16 chlorination, 8 chemical modications of surfaces (e.g., using zwitterions, carboxylation, and charged hydrogels), and coating surfaces with antimicrobials 17 or repellent coatings. [18][19][20] For sensing surfaces, however, cleaning methods should be chosen with care. ...
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Bacterial biofilms are aggregates of bacterial cells embedded in a self-produced extracellular polymeric matrix. Biofilm formation has always been considered a major challenge for sensors used in underwater measurements, and is a primary source of measurement error, especially when it comes to long-termin situmonitoring. We demonstrate the utility of lytic bacteriophages (bacterial viruses) as a non-invasive strategy for removing bacterial biofilms formed on the gas permeable membrane of electrochemical dissolved oxygen sensors. Our results show that a 4 dayPseudomonas aeruginosabiofilm with a fully developed matrix significantly affected the sensor signal and response time, decreasing the signal by 32% and increasing the response time by 94%. In addition, measurements with the biofouled membrane had a very low signal to nose ratio compared to a clean sensor membrane. A single dose of overnight phage treatment effectively removed the biofilm (as indicated by scanning electron micrographs and fluorescence images of the membrane), without the need for repeated treatments. Furthermore, the sensor signal that had plummeted by 32% for a fully biofouled membrane, was returned to the original value (7.96 ± 0.27 mg L⁻¹) after phage treatment and the signal to noise ratio (calculated as the ratio of mean to standard deviation) increased 8 folds for a phage-treated membrane compared to a biofouled membrane. Our data indicate near complete regeneration and signal recovery for the dissolved oxygen sensor, making the biofouled sensor reusable without the use of harsh chemicals that could destroy the fragile sensor membrane.
... Because of fouling on aquaculture installations for fi sh, shellfi sh and other organisms their cultivation is faced with environmental problems such as anoxia, eutrophication, increased turbidity, and all of these can lead to plague organisms and major economic losses (LEWIS et al. 1997). Settling allows for the colonization of multicellular organisms such as larvae, invertebrates, multicellular fi lamentous algae and other macro-invertebrates (LEHAITRE and COMPÈRE 2007). Periphyton includes all plant and animal organisms attached to various types of substrates that are submerged in water, and that do not penetrate the surface and is divided into 'euperiphyon' (basic part of the periphyton, formed by attached organisms adapted to a sessile lifestyle) and 'pseudoperiphyton' (part that is associated with the periphyton formed by communities of organisms that move freely among attached species, depending on them as a source of food and protection from predators and planktonic organisms caught and retained in a dense network of organic matter). ...
... During the fi rst hours of contact with seawater we could observe the deposition of a thin fi lm on the substrate. Subsequently, we confi rmed that the bacteria are the fi rst colonizers in the process of immobilization (reversible binding), where they fi rst examine the substrate and check for the availability of nutrients, which is followed by the process of consolidation (irreversible binding) when they begin to exude EPS (LEHAITRE and COMPÈRE 2007). On this sticky mixture of proteins, proteoglycans and carbohydrate diatoms start to attach, and they tend to form permanently adhesive complex structures such as pads, stalks, capsules and tubes. ...
Article
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Every surface that is immersed in seawater becomes rapidly covered with an unavoidable biofi lm. Such biofi lm formation, also known as fouling, is a complex multi-stage process and not yet thoroughly investigated. In this study, the succession of diatoms and bacteria was investigated during a one month exposure on an artifi cial substrate of plexiglass (polymer of methyl methacrylate) mounted above the seafl oor at a depth of 5 m. For biofi lm analyses, the fouling was investigated using selective agar plates, epifl uores-cence, light and electronic microscopy, as well as high performance liquid chromatography (HPLC) pigment analysis. During biofi lm development, the abundance of all biofi lm components increased and reached maximum values after a one month exposure. In the bacterial community, heterotrophic marine bacteria were dominant and reached 1.96 ± 0.79 × 10 4 colony forming units (CFU) cm –2. Despite the fact that faecal coliforms and intestinal enterococci were detected in the water column, faecal coliforms were not detected in the biofi lm and intestinal enterococci appeared after one month of exposure but in the negligible number of 60 ± 10 CFU cm –2. The phototrophic component of the biofi lm was dominated by diatoms and reached a concentration of 6.10 × 10 5 cells cm –2 , which was supported by pigment analysis with fucoxanthin as dominant pigment in a concentration up to 110 ng cm –2. The diatom community was dominated by Cylindrotheca closterium and other pennate benthic diatoms. A detailed taxonomic analysis by electronic microscopy revealed 30 different taxa of diatoms. The study confi rmed that a plexiglass surface in a marine environment is susceptible to biofouling within 30 days of contact. Furthermore, the co loni-zation process sequence fi rstly involved bacteria and cyanobacteria, and secondly diatoms, which together formed a primary biofi lm in the sea.
... f housing can cause measurement interference, even if the sensing surface is clean. Because the biofouling of housing can disturb the biological and chemical properties of the seawater around the sensing surface, it can also modify the local underwater environment surrounding the sensors and introduce errors into the data (Whelan. and Regan., 2006;Lehaitre. and Compère., 2008;Delauney et al., 2010;Li et al., 2021). When the sensors are taken out from the seawater for maintenance after deployment, they have to be cleaned if fouling organisms are present on the sensor housing. Cleaning of the housing can change the status of the sensing surface, making a sensor response comparison before and after deployment di ...
... that the CPT-based paint was effective in preventing biofouling on the six different materials used for manufacturing marine sensors. Furthermore, the practical application of this coating on in situ sensors showed good antifouling performance in a real marine environment. As it becomes increasingly important to obtain long-term ocean observations (Lehaitre. and Compère., 2008), and a major limitation of in situ sensors for long-term monitoring is their vulnerability to biofouling (macrofouling has been found even on long-term deep-sea instrumentation) (Blanco et al., 2013), treatment with CPT-based paint provides a potential solution for managing the challenges of biofouling. ...
Article
Biofouling is a common challenge for underwater sensors, especially for long-term in situ monitoring in marine environments. In this study, we assessed the antifouling efficacy of a paint containing a natural product camptothecin (CPT) on six materials (316 L stainless steel, TC4 titanium alloy, 7075 aluminum alloy, poly-oxymethylene, polyvinyl chloride, and Teflon), which are frequently used in the construction of underwater sensor housings. Additionally, a buoy-based sea-trial was performed to test the antifouling performance of the CPT-based paint on housings of three in situ sensors used for practical seawater monitoring applications, namely a spectrophotometer for chemical oxygen demand (COD) measurements and two fluorimeters for biochemical oxygen demand (BOD) and chlorophyll a (Chl a) concentration measurements. The results showed significantly lower macrofouling coverage on the areas painted with the CPT-based paint compared to the unpainted areas for each tested material over 9 months of seawater immersion. The CPT-based paint exhibited different antifouling performance for the different materials; in particular, it exhibited better antifouling performance on the plastic materials compared to the metal materials. Furthermore, when applied on submersible sensor housings in the sea-trial test, the CPT-based paint kept the housings of the COD sensor and the Chl a sensor clean for over 4 months. In addition, the paint prevented fouling of the BOD sensor housing even after 6 months of seawater immersion. Thus, our results suggest that the CPT-based paint could be used as a potential solution to control the biofouling of sensor housings for long-term in situ applications in marine environments.
... Cell electrodes contaminated with oil, biological growths, or other foreign material will eventually cause low conductivity readings. To control growth of bio-organisms in the conductivity cell rinsing and cleaning is recommended for short term observations, whereas in the long-term observations there should be rugged mechanism to protect the cells against biological growth 17 . ...
Conference Paper
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This paper details about the corrosion in the deep sea moored data buoy and its allied components and fouling growth in sensors. Equipment and structures built for service in seawater and other marine environments must employ components that are resistant to corrosion by the aggressive service conditions to which they are exposed. Data buoy comprises of many components in various metals and sensors in different depth to measure the surface and subsurface in-situ data. Due to the corrosion in the buoy components and fouling growth in sensors are being observed at various depths, the performance and data quality of the sensors depreciating from its original characteristic which also results in reduction of servicing lead time and cost wastage. This detail study about the corrosion in different components and fouling growth experienced in moored buoy sensors at various depth and action taken to protect against the corrosion and fouling to increase the servicing endurance of the buoy system to obtain the continuous quality real time data.
... Remote sensing applications from satellites and airborne surveillance sensors cover large surface areas, whereas stationary and mobile bio-optical in situ sensors systems may now be integrated into networks within three dimensional submarine areas (Cullen et al., 1997a, Cembella et al., 2005. Nevertheless, since differentiation of algal blooms into HAB vs. non-HAB types necessitates the discrimination of the target organism at the species level and/or via an independent monitoring of toxigenic properties, it appears that these issues can only be resolved through in situ sensors deployed within the water column (Table 2.1), provided that for long-term deployment, size, weight, and power (SWaP) factors, and antifouling measures (see e.g., Lehaitre et al., 2008), are adjusted. ...
Thesis
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The surveillance of Harmful Algal Blooms (HABs) in aquaculture zones is a crucial component in monitoring and mitigation of adverse effects caused by accumulation of high biomass of algal cells and/or associated toxins. Integrated findings of this thesis strongly stress the significance of synoptic bio-optical and conventional measures for efficient surveillance of HABs and their environmental triggers over required spatio-temporal scales, here shown for a case study in the Ebro Delta, NW Mediterranean. In particular, the installation of an environmental observatory in the Ebro Delta aquaculture area, and the capability of a radiometric sensor system as key component are highly motivated by study results. Yet it was clearly shown that for the interpretation of bio-optical data, detailed knowledge on bloom characteristics is crucial. By such effective coverage of bloom dynamics, combined with insights on environmental scenarios that promote the proliferation of certain taxa, public and private responses can be optimised. In a future scenario, this knowledge can be transferred to predictive models of HABs. In this sense, these future steps may advance towards preventive measures rather than mitigation actions to deal with this environmental hazard.
... Adding fouling control experiments to the protocols for environmental assessments could provide crucial information for protection from biofouling. In addition, fouling communities pose potential threats to autonomous equipment operating on the seafloor, particularly instruments equipped with optical lenses or highly sensitive sensors (Lehaitre et al., 2008). Potential bias caused by effects of fouling organisms can be reduced by developing a better understanding of their recruitment, diversity, community development, and variation with depth. ...
Article
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Biofouling of artificial substrates is a well-known phenomenon that can negatively impact offshore industry operations as well as data collection in the ocean. Fouling communities worldwide have mostly been studied within the top 50 m of the ocean surface, while biofouling below this depth remains largely underreported. Existing methods used to study biofouling are labor intensive and expensive when applied to the deep sea. Here, we propose a simple and cost-effective modification of traditional methods for studying biofouling by mounting test plates on autonomous seafloor equipment and preserving them in ethanol upon retrieval for transport to the laboratory. This method can greatly advance our understanding of biofouling processes in the deeper ocean, including fouling community biodiversity, recruitment, and seasonality. We present two case studies from the Laptev Sea and the Sea of Okhotsk in support of this method. In the first study, we looked at fouling communities on the surfaces of ocean-bottom seismometers deployed for one year in the 36–350 m depth range. In the second study, we tested metal and plexiglass (poly(methyl methacrylate) plates mounted on autonomous bottom stations and found evidence of both micro- and macrofouling after three months of deployment. Our results demonstrate that various autonomous seafloor equipment can be used as supporting platforms for biofouling studies.
... The bacteria then excrete a slime-like EPS which aids the adherence of other microorganisms such as fungi, yeast, algae, and other bacteria species[Salta et al., 2013]. It has been shown that these films can have disruptive effects on sensors within a week[Lehaitre et al., 2008]. When microorganisms come into contact with a surface, they attach themselves in a matter of seconds to minutes. ...
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This paper describes a novel low power method to reduce biofilm formation in microfluidic channels. When an ultrasonic (≈2 MHz) standing wave is set up across a microfluidic channel (≈ 250 μm) the resulting pressure amplitude can move small particles to the pressure node or anti-node, depending on the properties of the particle. This effect has been applied to Vibrio natriegens within poly(methyl methacrylate) (PMMA) microfluidic channels and a reduction in biofilm formation has been seen over a period of a week. This is a novel low power biofilm reduction strategy.
... • attachment of microorganisms, • colonisation of microorganisms, • growth of organisms. This process was visually presented in numerous publications, [2,6] among other sources, while the mechanism of this process was described in [1]. The process of underwater ship hull part biofouling is exposed to a combined action of various factors of physical, chemical, and biological nature (Fig. 2). ...
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One of most important issues concerning technical objects is the increase of their operating performance. For a ship this performance mainly depends on the efficiency of its main pro-pulsion system and the resistance generated during its motion on water. The overall ship re-sistance, in turn, mainly depends on the hull friction resistance, closely related with the pres-ence of different types of roughness on the hull surface, including underwater part biofouling. The article analyses the effect of hull biofouling on selected parameters characterising the efficiency of the ship propulsion system with adjustable propeller. For this purpose a two-year research experiment was performed on a sailing vessel during its motor navigation phases. Based on the obtained results, three groups of characteristics were worked out for different combinations of engine rotational speed and adjustable propeller pitch settings. The obtained results have revealed that the phenomenon of underwater hull biofouling affects remarkably the parameters characterising propulsion system efficiency. In particular, the development of the biofouling layer leads to significant reduction of the speed of navigation.
... For example, cyprid stage barnacles exhibit settlement behavior in response to physical cues such as water flow, pressure, light, surface texture, and chemical cues such as those associated with larval and adult conspecifics and biofilms (Pechenik et al. 1993;Dobretsov et al. 2013). The movement of vessels is also thought to promote the growth of some hull fouling organisms through improved opportunities for feeding (Lehaitre & Compere 2007). Various methods of reducing biofouling on ships have been used, mostly involving the use of toxic coatings on vessel hulls to kill or deter the settlement of biofouling organisms (Schultz et al. 2011). ...
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Fouling of submerged vessel hulls due to the rapid settlement of algae and invertebrates is a longstanding and costly problem. It is widely thought that the presence of extensive vacant surfaces on vessel hulls is responsible for the rapid attachment and growth of biofouling. We investigated whether noise from vessels in port could also be involved in promoting the settlement and growth of common biofouling organisms on vessel hulls. Three important biofouling species exhibited significantly faster development and settlement and better survival when exposed to vessel noise compared with control species. The extent of these responses appeared to vary in relation to the intensity of the vessel noise and may help to explain differences in biofouling observed on vessel hulls.
... They also often have planktonic larvae which enhance dispersal capabilities and enable them to colonize areas that would otherwise be unavailable to adult life stages. The researcher reported that biofouling influenced by factors like water temperature, conductivity, pH, dissolved oxygen, organic content, nature of substrate, roughness of substrate surface, surface charge, hydrophobicity, hydrodynamic conditions, location and depth of water bodies, seasons etc [12] . The water quality is directly proportional to growth of mosquito larvae, salt and other dissolved organic substances acts as inhibitory factors on mosquito growth, dissolved organic matter such as effluent from sugar factories is inhibitory effect on breeding of Anopheles sp. ...
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The present study was designed to determine development of periphyton and biofouling by aquatic insect larvae on substrates like I) N1-Cotton stem II) N2-Sugarcane Baggasse III) N3-Ipomea stem IV) A1-Stones V) A2-Bisleri Bottle Strips VI) A3-Rubber Strips of Vehicle Tyre were assessed. Results showed that periphyton growth in case of Sedgewick Rafter counting and biomass on N1 substrate was 41666.67±577.3503 no.lit-1 and 33.79 gm.lit-1 respectively compare to remaining substrates, among periphytic community class chlorophyceae was diverse. N1 substrate was high in the form of aquatic insect larvae percentage due to nature and nutrient diffusing ability of substrates, all larval forms of insects Culex sp. was dominant 69.76%. The study revealed that N1 is most specific substrate for periphytic growth and ALI. Hence, N1 is used for improving primary productivity of fresh water ecosystem for aquaculture yields.
... Nevertheless, since differentiation of algal blooms into HAB vs non-HAB types necessitates the discrimination of the target organism at the species level and/ or via an independent monitoring of toxigenic properties, it appears that these issues can only be resolved through in situ sensors deployed within the water column (Table 8.1), provided that for long-term deployment, size, weight, and power (SWaP) factors, and antifouling measures (see e.g. Lehaitre et al. , 2008), are adjusted. Bulk optical measurements and interpretations are in a development stage, such that they provide useful adjuncts to address both types of HAB monitoring, but there are only a few examples of validated case studies for which the required high taxonomic resolution has been achieved. ...
Chapter
The surveillance of harmful algal blooms (HABs) in aquatic environments is a crucial component in monitoring and mitigation of adverse effects caused by accumulation of high biomass of algal cells and/or associated toxins. The high diversity among HABs necessitates observational approaches that cover a broad spectrum of temporal and spatial scales. Current approaches range from remote sensing to in situ discrete and profiling observations. The challenge is to develop new systems and approaches driven by the need for sensitive and discrete detection of HAB species and associated bio-optical properties. Herein we review state-of-the art technology and address the diversity of HABs with an appropriate set of approaches for operational long-term monitoring.
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These days, many marine autonomous environment monitoring networks are set up in the world. These systems take advantage of existing superstructures such as offshore platforms, lightships, piers, breakwaters or are placed on specially designed buoys or underwater oceanographic structures. These systems commonly use various sensors to measure parameters such as dissolved oxygen, turbidity, conductivity, pH or fluorescence. Emphasis has to be put on the long term quality of measurements, yet sensors may face very short-term biofouling effects. Biofouling can disrupt the quality of the measurements, sometimes in less than a week. Many techniques to prevent biofouling on instrumentation are listed and studied by researchers and manufacturers. Very few of them are implemented on instruments and of those very few have been tested in situ on oceanographic sensors for deployment of at least one or two months. This paper presents a review of techniques used to protect against biofouling of in situ sensors and will give a short list and description of promising techniques.
Chapter
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Oceans environmental monitoring and seafloor exploitation need in situ sensors and optical devices (cameras, lights) in various locations and on various carriers in order to initiate and to calibrate environmental models or to operate underwater industrial process supervision. For more than 10 years Ifremer deploys in situ monitoring systems for various seawater parameters and in situ observation systems based on lights and HD Cameras. To be economically operational, these systems must be equipped with a biofouling protection dedicated to the sensors and optical devices used in situ. Indeed, biofouling, in less than 15 days [1] will modify the transducing interfaces of the sensors and causes unacceptable bias on the measurements provided by the in situ monitoring system. In the same way biofouling will decrease the optical properties of windows and thus altering the lighting and the quality fot he images recorded by the camera.
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As the health of the ocean continues to decline, more and more marine populations are at risk of extinction. A significant challenge facing conservation biologists is the ability to effectively monitor at-risk populations due to the challenges of the underwater environment. Obtaining visual data on a marine species typically requires significant time spent by humans observing in the field, which is both costly and time-consuming, and often yields a small amount of data. We present a low-cost, acoustically-triggered camera system to enable remote monitoring and identification of marine populations.
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Multibeam echosounders (MBES) have become a widely used acoustic remote sensing tool to map and study the seafloor, providing co-located bathymetry and seafloor backscatter. Although the uncertainty associated with MBES-derived bathymetric data has been studied extensively, the question of backscatter uncertainty has been addressed only minimally and hinders the quantitative use of MBES seafloor backscatter. This paper explores approaches to identifying uncertainty sources associated with MBES-derived backscatter measurements. The major sources of uncertainty are catalogued and the magnitudes of their relative contributions to the backscatter uncertainty budget are evaluated. These major uncertainty sources include seafloor insonified area (1–3 dB), absorption coefficient (up to > 6 dB), random fluctuations in echo level (5.5 dB for a Rayleigh distribution), and sonar calibration (device dependent). The magnitudes of these uncertainty sources vary based on how these effects are compensated for during data acquisition and processing. Various cases (no compensation, partial compensation and full compensation) for seafloor insonified area, transmission losses and random fluctuations were modeled to estimate their uncertainties in different scenarios. Uncertainty related to the seafloor insonified area can be reduced significantly by accounting for seafloor slope during backscatter processing while transmission losses can be constrained by collecting full water column absorption coefficient profiles (temperature and salinity profiles). To reduce random fluctuations to below 1 dB, at least 20 samples are recommended to be used while computing mean values. The estimation of uncertainty in backscatter measurements is constrained by the fact that not all instrumental components are characterized and documented sufficiently for commercially available MBES. Further involvement from manufacturers in providing this essential information is critically required.
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Biofouling is a major problem shared among all maritime sectors employing submerged structures where it leads to substantially increased costs and lowered operational lifespans if poorly addressed. Insight into the ongoing processes at the relevant marine locations is key to effective management of biofouling. Of specific concern for the marine renewable energy (MRE) sector is the fact that information on biofouling composition and magnitude across geographies is dispersed throughout published papers and consulting reports. To enable rapid access to relevant key biofouling events the present work describes a European biofouling database to support the MRE sector and other maritime industries. The database compiles in one document qualitative and quantitative data for challenging biofouling groups, including non-native species associated with MRE and related marine equipment, in different European Ecoregions. It provides information on the occurrence of fouling species and data on key biofouling parameters, such as biofouling thickness and weight. The database aims to aid the MRE sector and offshore industries in understanding which biofouling communities their devices are more susceptible to at a given site, to facilitate informed decisions. In addition, the biofouling mapping is useful for the development of biosecurity risk management plans as well as academic research.
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Biofilms are surface-attached multicellular communities that play critical roles in inducing biofouling and biocorrosion in the marine environment. Given the serious economic losses and problems caused by biofouling and biocorrosion, effective biofilm control strategies are highly sought after. In a screening program of antibiofilm compounds against marine biofilms, we discovered the potent biofilm inhibitory activity of elasnin. Elasnin effectively inhibited the biofilm formation of seven strains of bacteria isolated from marine biofilms. With high productivity, elasnin-based coatings were prepared in an easy and cost-effective way, which exhibited great performance in inhibiting the formation of multi-species biofilms and the attachment of large biofouling organisms in the marine environment. The 16S amplicon analysis and anti-larvae assay revealed that elasnin could prevent biofouling by the indirect impact of changed microbial composition of biofilms and direct inhibitory effect on larval settlement with low toxic effects. These findings indicated the potential application of elasnin in biofilm and biofouling control in the marine environment.
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The synthesis of environmentally friendly antimicrobial polymeric coatings, especially in the case of aquaculture, that inhibit the growth of bio-deposits is a very important issue that will contribute to the cost reduction of nets’ cleaning process as well as the protection of the submarine wealth from the biostatic substances used so far. In the present work, the antimicrobial polymers P(SSAmC16-co-VBCHAMx) and the terpolymer P(SSAmC16w-co-VBCHAMx-co-GMAy) were synthesized, bearing quaternary ammonium compounds, electrostatically bound and covalently attached at the same polymer chain. The combination of the two types is of particular importance, as it can provide effective antimicrobial polymeric materials with self-polishing capabilities as a result of the released nature of the antimicrobial, in combination with the permanent local action of the immobilized species. The cross-linking reaction of the terpolymer P(SSAmC16w-co-VBCHAMx-co-GMAy) with the homopolymer polyacrylic acid (PAA) was tested at 120 °C in terms of the equivalent ratio between epoxy and carboxyl groups. The synthesized polymers were further used for the coating of aquaculture nets and tested in terms of antifouling efficiency in lab and scale-up conditions. Uncoated nets were also used in all applications for comparison reasons. The coated nets performed efficiently for 35 days in lab-scale and 66 days in scale-up conditions, showing a high antifouling activity in both fields compared to the uncoated nets.
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Marina El-Alamein Resort is a popular summer destination located on the western shores of the Egyptian Mediterranean Sea. In February, April, July, September, and November 2017, fouling specimens were obtained by scraping the submerged artificial substrata of the resort using (40 × 25 cm rectangular frames) with a metal knife. A total of 61 fouling taxa were identified in the samples. Polychaeta was the most diverse group, comprising 25% of the total number of recorded taxa. Three species of Polychaeta were firstly recorded in the Egyptian Mediterranean Sea, comprising one sedentarian species (Protoaricia oerstedii) and two errantian species (Myrianida brachycephala and Syllis jorgei). Temporal variations in fouling communities showed significantly higher species number in February and April. November showed the highest total abundance of individuals, followed by July, and both events were significantly higher than that in other months. The encrusting bryozoan Schizoporella errata, a habitat-forming species, was the most abundant taxon found in April, September, and November meanwhile, the bivalve Brachidontes pharaonis was the most dominant in February and July. Six of the identified species were non-indigenous for the Mediterranean Sea forming and comprised approximately 10% of the total biodiversity.
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Requirements for understanding the relationships between ocean color and suspended and dissolved materials within the water column, and a rapidly emerging photonics and materials technology base for performing optical based analytical techniques have generated a diverse offering of commercial sensors and research prototypes that perform optical measurements in water. Through inversion, these tools are now being used to determine a diverse set of related biogeochemical and physical parameters. Techniques engaged include measurement of the solar radiance distribution, absorption, scattering, stimulated fluorescence, flow cytometry, and various spectroscopy methods. Selective membranes and other techniques for material isolation further enhance specificity, leading to sensors for measurement of dissolved oxygen, methane, carbon dioxide, common nutrients and a variety of other parameters. Scientists are using these measurements to infer information related to an increasing set of parameters and wide range of applications over relevant scales in space and time.
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1. ABSTRACT Harmful algal blooms are becoming more frequent phenomena in the coastal environment. As this escalating trend continues, an early warning system based upon non-invasive rapid detection of harmful algal blooms is desired. A discoloration of water is often associated with these blooms, suggesting the feasibility of detection via ocean color measurements. Previous research has focused on absorption characteristics and pigment compositions of the algae as being responsible for the unique optical signatures observed. Harmful algal species do not contain unique pigments, and thus absorption alone can not explain the distinct changes in water color. However, taxon-specific optical properties, in particular scattering and backscattering, in combination with high concentrations of a monodispersed population may be responsible for the significant changes in ocean color during bloom events. We measured the inherent optical properties (IOPs) of several harmful algal species to determine the source for the frequently observed changes in ocean color during blooms. Four common harmful algal species (Prorocentrum minimum, Gymnodinium splendens, Heterosigma akashiwo, and Aureococcus anophagefferens) were investigated under controlled growth conditions to determine IOPs and particle size distributions (PSD) for exponential and stationary phase cells in order to understand how ocean color might change over the course of a bloom. Only slight distinctions in the shape of the absorption spectra were observed between species or growth phase, indicating that pigments are not responsible for the distinct ocean colors associated with blooms. The exception was G. splendens which was in a heterotrophic mode, and therefore contained few pigments, resulting in low absorption. The data demonstrate that absorption is not the source of distinct ocean color during harmful algal blooms, but rather the algal scattering and backscattering properties. The scattering and backscattering spectra are affected by cell size and growth phase, providing a major contribution to the changes in water color associated with blooms as the PSD changes from a polydispersed to a monodispersed population and as the phytoplankton physiology changes. Therefore our ability to detect these blooms optically will depend upon our ability to determine and interpret accurately scattering and backscattering spectra. 2. INTRODUCTION There are approximately 60-80 phytoplankton species that comprise the category harmful algae. Their modes of destruction include the production of potent biotoxins, physical damage imparted to other organisms (i.e. grazers), the creation of eutrophic and anoxic conditions in their surrounding environment, as well as numerous other problems (Smayda, 1997; Taylor, 1990). The occurrence of these toxic outbreaks is increasing
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The quantitative filter technique (QFT), whereby particles are concentrated onto glass-fiber filters and analyzed in a spectrophotometer, is used extensively to estimate the absorption coefficients of aquatic particles. A number of empirically derived correction factors (ß) have been developed to account for the amplified optical path length associated with the highly scattering glass-fiber filters. Published results are inconsistent, and ß remains the largest source of uncertainty in estimated absorption coefficients. In this study, path-length amplification was estimated from the average cosine of diffusely traveling photons in the filter pad using a theoretical approach. This amplification factor, combined with variability in blank filter pad optical density, explains many of the confounding observations in the literature. Absorption coefficients for phytoplankton cultures and field samples were estimated from a modified QFT using the new model for path-length amplification and tested against absorption coefficients measured with a nine-wavelength absorption and attenuation meter (ac9, WETLabs). A linear regression between the modeled and measured particulate absorption coefficients was highly significant (r2 > 0.99, n = 99), with estimated slope and intercept not significantly different from 1 and 0, respectively (P < 0.001). The model outperforms published, empirically derived correction factors over a broad range of absorption coefficients and particulate compositions. Results indicate that the modified QFT combined with the new model for path-length amplification yields accurate estimates of spectral particulate absorption coefficients regardless of the concentration or composition of the particulate material.
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Biofouling is one of the primary limiting factors in terms of measurement accuracy and deployment longevity for oceanographic studies involving autonomous sampling. Copper can significantly reduce marine fouling for long-term optical sensor deployments in coastal and open-ocean environments. Copper can effectively replace previously used highly toxic chemical antifoulant methods. Copper-based antifouling systems can be employed with three types of optical sensors: 1) open, 2) enclosed or semienclosed, and 3) shuttered. Copper plates on open-faced backscattering sensors can enable deployment periods of longer than 60 days in coastal waters without biofouling. In addition, copper tubing on nine-wavelength absorption-attenuation meters (ac-9s) has extended measurement capabilities from about 10 days to greater than 60 days with no signs of biofouling in coastal waters. Implementation of copper shutters on optical sensors in open-ocean waters off Japan has resulted in extended deployment periods (410 days and possibly longer) for optical measurements whereas previous optical measurements in the open ocean were typically degraded within several weeks to at most a few months due to biofouling.
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The Underwater Video Profiler is a vertically deployed survey system designed for the quantification of particles >280 μm and of large zooplankton in the 0–1000 m water column. Light reflected by undisturbed target objects forms a dark-field image, which is recorded at 25 Hz frequency. The recorded images are automatically digitized and analysed. The results are expressed as abundance or size distributions and they can be converted to volume or mass units. The system can be configured as a multi-instrument array and can simultaneously acquire biological and physical data. From May 1994 to April 1995 a monthly survey was performed across a frontal structure associated to the North Ligurian geostrophic current. In winter and spring 1995 the front, as well as the offshore dispersion limit of particles, were located near to the coast. In contrast, during autumn 1994, its position was open sea and the terrestrial matter was dispersed far from the coast. The continuous presence of intermediate nepheloid layers along the continental slope indicates that different processes may supply and transport the particulate matter to deeper layers, from where it can be diffused into the basin.
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Adhesion of microorganisms to surfaces in marine environments leads to biofouling. The deleterious effects of biofilm growth in the marine environment are numerous and include energy losses due to increased fluid frictional resistance or to increased heat transfer resistance, the risk of corrosion induced by microorganisms, loss of optical properties, and quality control and safety problems. Antifouling agents are generally used to protect surfaces from such a biofilm. These agents are toxic and can be persistent, causing harmful environmental and ecological effects. Moreover, the use of biocides and regular cleaning considerably increase the maintenance costs of marine industries. An improved knowledge of biofilm adhesion mechanisms is needed for the development of an alternative approach to the currently used antifouling agents. The aim of this study is to characterise the chemical composition of the molecules first interacting with stainless steel during the period immediately following immersion in natural seawater and to elucidate the kinetics of the adsorbtion process. Proteins are shown to adhere very rapidly, closely followed by carbohydrates. The distribution on the surface of organic molecules is also examined. The adsorbate on the surface is not a continuous film but a heterogeneous deposit, whose average thickness varies widely. The cleaning procedures used affect the adsorption kinetics. In particular, cleaning with hexane results in slower adsorption of nitrogen-containing species than does cleaning in acetone.
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This paper reports the effect of a galvanically produced negative surface potential on the accumulation of marine biofouling. The potential was created by connecting pieces of copper or stainless steel to a layer of Indium/Tin Oxide semiconductor deposited on glass. It was shown that the negative potential significantly reduced the accumulation of biofouling. As the conductive layer is transparent, the technique was used to protect the windows of commercial optical instruments. This technology could provide an inexpensive way of extending deployment times for marine instruments.
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This paper records the results of an investigation into the effects of biofouling on optical marine sensors and the organisms responsible for the deterioration in sensor accuracy. Two kinds of commercial sub-surface optical marine sensor, commonly used to measure water quality, were operated in a natural marine environment and allowed to foul while measurements of the actual conditions were made daily using clean instruments. A number of glass and acrylic coupons were placed in the same environment and were removed at intervals throughout the trial. These coupons were examined and the biological population quantified. Deterioration in the optical properties of the coupons was measured using image analysis and UV-visible spectroscopy. The results from the coupons were compared with the results from the commercial instruments. It was observed that the major deterioration in instrumental accuracy occurred when a bacterial population exceeding 105/mm2 was found on the coupons. The algal population had little effect on the instruments over this time period. The acrylic coupons supported a lower fouling population, apparently due to the increased solubility of acrylic in seawater. The two optical techniques returned similar patterns of results for the surface area fouled, although the numerical values returned by each technique were different. Neither of these two techniques returned values directly comparable with the deterioration in accuracy of the commercial instruments. The trial took place on the Isle of Cumbrae in the Firth of Clyde on the west coast of Scotland, U.K.
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Direct observations have clearly shown that biofilm bacteria predominate, numerically and metabolically, in virtually all nutrient-sufficient ecosystems. Therefore, these sessile organisms predominate in most of the environmental, industrial, and medical problems and processes of interest to microbiologists. If biofilm bacteria were simply planktonic cells that had adhered to a surface, this revelation would be unimportant, but they are demonstrably and profoundly different. We first noted that biofilm cells are at least 500 times more resistant to antibacterial agents. Now we have discovered that adhesion triggers the expression of a sigma factor that derepresses a large number of genes so that biofilm cells are clearly phenotypically distinct from their planktonic counterparts. Each biofilm bacterium lives in a customized microniche in a complex microbial community that has primitive homeostasis, a primitive circulatory system, and metabolic cooperativity, and each of these sessile cells reacts to its special environment so that it differs fundamentally from a planktonic cell of the same species.
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High-temporal-resolution spectral absorption data were acquired by use of one bottom-mounted (approximately 68-m) and three moored spectral absorption and attenuation meters (ac-9 meters at 14, 37, and 52 m) on the Middle Atlantic Bight continental shelf during the fall 1996 period of the Coastal Mixing and Optics experiment. We employed a previously published spectral absorption model with the data to partition total absorption into absorption by water, phytoplankton, detritus, and gelbstoff (dissolved matter). We validated the model by comparing its results against coincident in vivo absorption coefficients derived from discrete bottle samples. Correlations between modeled and in vivo spectra range from 0.873 to 0.998. We optimized these correlations to determine the model parameters. These parameters could not be determined solely from the moored ac-9 results. Therefore a separate set of absorption measurements (from discrete bottle samples) was necessary to permit values for the model parameters to be determined. Model results allow us to separate particulate and dissolved components of absorption and to examine the temporal variability and the vertical distributions and concentrations of each component, given the total absorption in the water column.
Chapter
The intensity and spectrum of the light in the ocean have a major influence on the biological processes. These processes in turn determine the concentrations of much of the suspended and dissolved matter in the ocean, which affect the way in which the light is scattered and absorbed. These relationships can perhaps be most easily illustrated schematically as in Fig. 3-1. At the upper boundary we have the sun and sky radiances and the surface transmission conditions that combine to provide the energy entering through the surface. The ocean itself contains the vertical structure of those optical properties that do not depend on the structure of the light field, but depend only on the properties of the suspended and dissolved materials: the absorption coefficient a(λ,z), the beam attenuation coefficient c(λ,z), and the volume scattering function β(θ,λ,z). These are known as inherent optical properties, because they do not depend on the source radiance field (Preisendorfer, 1976). They are a function only of the suspended and dissolved materials in the water, and of the water itself. How does the vertical structure of the inherent optical properties affect the vertical structure of the radiance field in the ocean itself? This is the problem of radiative transfer in which we try to predict the intensity, direction, and spectrum of the light (spectral radiance) in the ocean, based on a set of given inherent optical properties. Those properties of the light field in the ocean that depend on the radiance are known as the apparent optical properties. Radiance field integrals, such as the vector irradiance, E(λ,z), the scalar irradiance E0(λ,z), and their attenuation coefficients are also apparent optical properties.
Chapter
The inherent optical properties of a water body (mesoscale), namely, the absorption coefficient, the scattering coefficient, and the volume scattering function combine with the radiant distribution above the sea to yield the apparent optical properties (Preisendorfer, 1961). The radiative transfer equation is the link between these two classes of optical properties. Locally, the inherent properties of seawater are governed by, and strictly result from, the sum of the contributions of the various components, namely, the water itself, the various particles in suspension able to scatter and absorb the radiant energy, and finally the dissolved absorbing compounds. Analyzing these contributions is an important goal of optical oceanography. Among these particles, the phytoplanktonic cells, with their photosynthetic pigments, are of prime importance, in particular in oceanic waters far from terrestrial influence. They also are at the origin of other kinds of particles, such as their own debris, as well as other living “particles” grazing on them (bacteria, flagellates and other heterotrophs). Studying optics at the level of single cells and particles is therefore a requirement for a better understanding of bulk optical properties of oceanic waters. Independently of this goal, the study of the individual cell optics per se is fundamental when analyzing the pathways of radiant energy, in particular the light harvesting capabilities and the photosynthetic performances of various algae or their fluorescence responses. The following presentation is a guidline for readers who will find detailed studies in the classic books Light Scattering by Small Particles by van de Hulst (1957) and Light and Photosynthesis in Aquatic Ecosystems by Kirk (1983), as well as in a paper dealing specifically with the optics of phytoplankton by Morel and Bricaud (1986). This chapter is organized according to the title, with first a summary of the relevant theories to be applied when studying the interaction of an electromagnetic field with a particle, and then, as a transition between this scale and that of in vitro experiments, some results concerning the optical behavior of pure algal suspensions; finally the more complicated situations encountered in natural environments are briefly described to introduce the “nonlinear biological” effect (Smith and Baker, 1978a) upon the optical coefficients for oceanic waters, and to examine some of the empirical relationships, as presently available, between the pigment concentration and the optical properties of the upper ocean at mesoscale and global scale.
Article
Biofilm formation on structural materials in deep-sea environment after long duration of exposure is reported here for the first time. Some structural material specimens such as steel, steel with zinc and aluminum anodes and carbon fibre-reinforced composite were exposed at depths of 500, 1200, 3500 and 5100 in for 174 days. The bacterial colony formation on these specimens was studied after their retrieval from the ocean. Macrofouling was not found in any of these materials. Carbon fibre-reinforced composite did not support bacterial colony formation at all the tested depths. Steel supported bacterial colonies at all depths. Aluminium and zinc anodes did not support bacterial colonies at 3500 and 5100 m depths. This could be related to lower temperatures prevailing at these depths. Also, all the identified bacterial colonies were aerobic as dissolved oxygen was present even at 5100 m depth. Hence, anaerobic conditions did not exist during exposure under these structural conditions. Dissolved oxygen data at the experimental site is also presented and discussed.
Chapter
The role of exocellular polymers in the adhesion of bacteria to surfaces has been considered by comparing it with the adsorption of free polymers on surfaces. In this, the roles of the various interactions between the polymer segment, solvent, surface, and solution components have been discussed. The importance of the multisegment nature of a polymer has been emphasized, together with the special properties and behavior of polyelectrolytes. Factors influencing the time dependence of the adhesion of (inert) particles to surfaces and their applicability to bacterial adhesion are discussed.
Article
Most benthic invertebrates produce planktonic larvae, which swim or float for a while and embark on search for location to settle and metamorphose. Many factors influence this process, among which chemical cues derived from conspecific adults or prey organisms are believed to be important; larvae start to settle in response to chemical cues. Although various compounds have been reported to induce larval settlement and metamorphosis for many species, those which real chemical cues have been known are quite few. On the other hands, settlement of larvae of other species endangers the survivorship of benthic organisms which in turn possess chemical defense against larval settlement. An array of marine natural products have been obtained as inhibitors of settlement of the barnacle Balanus amphtirite which is one of most popular fouling organisms. Since the Fusetani Biofouling Project started in October 1991, we have been trying to discover from marine organisms compounds which induce larval settlement and metamorphosis of the ascidian Halocynthia roretzi, which resulted in the isolation of more than 40 active metabolites including simple benzenoids, alkaloids, amino acid derivatives, and polyacetylenes. These compounds were found to mimic a real cue, lumichrome. We have also attempted to isolate antibarnacle metabolites from sessile marine organisms, mainly sponges and nudibranchs. More than 60 active substances including terpenoids, steroids, amino acid derivatives, alkaloids, and polyacetylenes have been obtained. Sesqui- and diterpenoids containing isocyano and related functionalities showed potent activity, but their toxicity was low, thus suggesting their promising properties for nontoxic antifoulants.
Article
The impact of initial surface chemistry on settlement of barnacle, bryozoan, and hydroid larvae was assessed. Temporal (on a scale of weeks to months) and fine scale spatial (centimeter to meter) variation in settlement were quantified. Four arrays of silanized glass surfaces, deployed at almost-equal-to 2-wk intervals, were monitored after 1 and 3 days of immersion. Settlement of all larval types exhibited strong temporal variation. There was a 25, 22- and 18-fold difference between the highest and lowest Day 1 settlement for barnacles, bryozoans and hydroids, respectively. Bryozoan and hydroid settlement was spatially variable, barnacle settlement was not. Barnacle and bryozoan settlement was influenced by initial surface chemistry, hydroid settlement was not. For barnacles, there was a 2-fold difference between total settlement over the four arrays on untreated glass and diphenyl-silanized surfaces; for bryozoans, there was a 5 1 -fold difference, and in the opposite direction. There was a negative correlation between barnacle and bryozoan settlement with respect to surface. This result was independent of the presence of the other species. Bryozoan settlement was also spatially and temporally quantified in a separate, single surface 56-h array, and total bryozoan settlement.h-1 was found to be correlated with light intensity. Patterns of initial colonization were strongly influenced by surface chemistry and spatial and temporal variation in larval supply. These effects on initial colonization may influence subsequent community development.
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Article
This chapter discusses the coastal environment of the seine bay area monitored by a new French system of automated measurement stations. The general architecture of the monitoring system, called MAREL, includes an innovative measuring system, a telecommunication link using Internet protocols and a land-based management station for the collection, processing, and dissemination of quality controlled data. The measuring system is adapted to coastal conditions and able to work autonomously. It also offers the flexibility, modularity, and immediate availability of the measurements. Water samples are pumped from different levels in the sea water column and are analyzed by sensors located in a measuring cell on the floating structure. This technical solution allows a continuous cleaning of sensors to guarantee measurement quality and the injection of chlorinated ions in the hydraulic circuit to avoid biofouling. The Coastal Environment Monitoring program of the Seine Bay attempts to detect and then to understand the mechanisms of natural or artificial phenomena in the coastal environment of this area. The automated monitoring approach allows high frequency measurements and so gives the opportunity to detect fast variations and to have a rather continuous observation of the water.
Conference Paper
Profiles of spectral attenuation and absorption were measured in situ with a WET Labs AC-9; scattering coefficients were calculated by difference. Closure of the absorption and scattering coefficients was obtained on this limited data set for in situ and discrete sample measurements. Centimeter-scale fine structures were observed in the vertical profiles. Total absorption coefficients were dominated by the phytoplankton component. Total attenuation coefficients were dominated by scattering although the effects of strong absorption were apparent in both the attenuation and scattering spectra. The vertical structure of absorption and scattering were not spatially coherent, nor were the vertical structures of phytoplankton and non- phytoplankton absorption. The strongest spatial coherence was observed between the non- phytoplanktonic component absorption and particle scattering coefficients. The spectral absorption coefficients of the in situ phytoplankton component exhibited decreasing blue to red absorption ratios as a function of depth and spectral flattening of the blue absorption peak indicative of photoadaptation.© (1994) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.
Article
This paper presents and discusses the results of laboratory and field experiments on the interrelation of cathodic protection (CP) and marine macrofouling. Tests in the sea revealed that fouling settlements were greatly enhanced by CP. Calcareous shell‐dwelling organisms such as barnacles and oysters, and a calcareous alga, Jania rubens, were particularly prolific on cathodically protected substrata. Laboratory studies with the oyster, Crassostrea madrasensis (L.), indicated that interfacial alkalinity generated by CP might enhance shell growth in the organism. The oyster reached a larger size on cathodically protected substrata than on the controls. Tests done in the presence and absence of fouling under natural conditions showed that fouling can bring about rapid decay of potential during interruption of the protective current, causing early corrosion. The implications of the findings to the performance of fixed marine and offshore structures are discussed.
Article
The surface of a metal immersed in solutions containing organic and inorganic molecules is modified by an adsorbed layer that influences the subsequent biofilm formation. Little is known about the first steps of surface modifications in the complex medium of seawater. The ‘BASIS’ group has characterized the conditioning film formed on a stainless-steel surface immersed in natural seawater. The chemical composition, morphology and growth mode of this film have been determined using complementary surface analytical techniques: x-ray photoelectron spectroscopy (XPS), infrared reflection absorption spectroscopy (IRAS), atomic force microscopy (AFM), surface free energy measurements and time-of-flight secondary ion mass spectrometry (ToF-SIMS).The XPS and ToF-SIMS data show that the primary film is mainly composed of proteins in the early stages of immersion. The SIMS, XPS, surface free energy and AFM data indicate that the adsorbed protein layer is discontinuous, leaving bare oxide areas. Our results and interpretations are supported by similar experiments in artificial seawater containing controlled amounts of proteins. Copyright © 2000 John Wiley & Sons, Ltd.
Article
1. The area investigated embraces Suez harbour, El Shalloufa, Geneva, Kebret (at the Bitter Lakes), Devresoir and Tossoum pilotage stations. It extends about 75 km along the Suez Canal. 2. The Suez-Geneva section is poorly fouled, mainly due to the high silt content of the water. At Suez the standing crop of fouling reached its lowest value in the Canal (0.02 g/cm2/month). 3. Settlement was much greater on the long-term panels than on the panels exposed for one month, but reached a constant weight after about two months of exposure, apparently due to the accumulation of silt which prevented the attachment of many organisms. 4. Fouling was equally poor at all depths down to 5.5.m below the water surface, but a small increase was noticed at the uppermost 1.5 m of the water column. 5. The standing crop of fouling steadily increased northward and was found 0.14 g/cm2/month in Tossoum. 6. Kebret, representing the Bitter Lakes, was found densely fouled with calcarious animals, particularly bryozoans. 7. Ascidians and the amphipods are very common in Tossoum and Devresoir. 8. The presence of a local, southward current in the Canal, even after damming of the River Nile, is discussed.
Article
Six bulk polymers potentially suitable for use as optical ports of underwater instruments were exposed to a solution of marine bacteria after soaking in distilled water or surfactant solutions. The effect of the surfactant solutions was to reduce fouling build-up on four of the six polymers. The presence of the surfactant altered the surface energy of the polymers. The surfactant reduced the importance of physical characteristics, such as surface roughness, on fouling build-up. It was found that untreated polyethylene terephthalate out-performed polymethyl methacrylate, over short time periods. This result was repeated when these polymers were tested on optical underwater instruments exposed to a marine environment.
Article
A system was designed for the continuous surface monitoring of hydrological, bio-optical, and biogeochemical properties in the vicinity of the Almeria-Oran jet-front system (Northwestern Mediterranean Sea). This system included a thermosalinograph, a fluorometer, an optical particle counter, and an absorbance-attenuance meter (AC9), allowing the estimation of the absorption [a(λ), (m-1)] and scattering [b(λ), (m-1)] coefficients at nine wavelengths. More than 500 multivariate records were acquired over a transect crossing the jet-front system three times and encompassing the diversity of water types encountered in this area. A method is proposed to retrieve relevant biogeochemical or bio-optical quantities, among which are the chlorophyll a concentration [from a(676)], the particulate carbon concentration [from b(555)], the colored dissolved organic matter [CDOM, from a(412)], and the chlorophyll-specific scattering coefficient at 555 nm, b*(555) (m2 mg Chl a-1). The analyses of these various quantities with respect to the surface hydrodynamic fields reveal two main features. First, the particle pool displays highly dynamic quantitative variations across the frontal structure. Qualitatively, flagellate-dominated populations are associated with moderate density waters and maximal jet velocity, while diatoms are recorded at the narrow limit between the jet-front and the Mediterranean waters, where jet velocity is minimal. Second, the CDOM pool presents remarkable covariations with the surface-density field. In particular, the lowest a(CDOM)(412) values are reproducibly associated with the highest density values, which track upwelled flow associated with the frontal circulation; accumulation of CDOM is always observed inside the frontal waters, at a density value of 27.2 kg m-3. These CDOM variations suggest that the frontal system is the place of enhanced biological activity.
Article
The effect of season on "biofilming";, as a cue for the settlement of marine invertebrate larvae, was investigated in a long-term field study during the years 1992-1994. The series of settlement experiments was conducted in a tidal rapid on the west coast of Scotland, and involved manipulations of artificial panels. Biofilming of substrata, whilst excluding larval settlement, was achieved by the enclosure of panels within tight-fitting (but removable) mesh screens so that the number of settlers on filmed and unfilmed substrata were counted in the initial absence of other incumbent post-larvae. Depending on larval species, the effects of biofilming were found to be either facilitatory or inhibitory. Significant within- and between-species seasonal differences in the settlement responses were detected, and a reversal of the effect of biofilming on larval settlement response, from inhibitory to facilitatory and vice versa, was noted with season in the case of some taxonomic groups and species (e.g. Tubulipora sp., Plagioecia sp., Electra pilosa (L.)). The present study emphasizes the need for extended field studies of larval responses to environmental cues, when the focus of interest is in drawing general inferences about naturally occurring behavioural patterns at settlement.
Article
A. KERR, T. HODGKIESS, M.J. COWLING, C.M. BEVERIDGE, M.J. SMITH AND A.C.S. PARR. 1998. The effect of modest imposed surface potentials on the adhesion of marine bacteria to an electrically conducting layer deposited on silica glass is recorded. A positive shift increased bacterial settlement. However, a negative shift in potential was extremely beneficial in reducing numbers of adhered bacteria. An applied surface potential of - 66 mV SCE resulted in the bacterial population decreasing to approximately 12% of that on the uncharged reference sample. There was no further significant decrease in the adhered bacterial population when the magnitude of the negative potential was increased. The potential was maintained with very little current flow (less than 0·25 nA mm(-2) ). The results were not due to any effect of the material used and therefore the technique could be useful for reducing bacterial fouling in many situations, including medical applications.
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Article
A design for a new underwater video-system to detect and observe suspended particles is presented. Particles are collected and isolated in a rectangular box where they are highly illuminated by a white light plane. The total field of view is determined. The camera, equipped with a remote controlled zoom, can resolve particles sizes ranging from 25 mum to several millimetres. Real-time image analyses are therefore performed. Particle counts and size spectra are calculated and displayed. Total light intensity scattered by the illuminated particles is closely related to the back-scattering values determined by an optical back-scatter sensor. A particle size analyser using diffraction analysis is associated to this video-system on a custom profiler. Hydrological parameters are measured by a standard CTD probe associated to a chlorophyll sensor. Results are acquired and graphically presented in real time. This custom profiler presents numerous advantages in oceanographic research. Two examples of its use in different coastal areas are presented. In an estuary, temporal evolution of particle characteristics was described in relation to the tide cycle. While the video-system allows direct visualization and characterization of the largest particles, the particle-size analyser performs precise quantification of the finest ones. it was shown that the two methods were in accordance for quantification of large aggregates, which were observed around slack tide when salinity decreased. Video analyses cannot be performed above 25 mg l(-1) dry weight equivalent. The system reliability, resolution and limits were also demonstrated during a cruise in the Gulf of Finland. A typical profile is presented here showing different layers, one characterized by the association of heterotrophic flagellates and detritals, and another dominated by zooplankton, the surface layer being characterized by cyanobacterial colonies. Video associated to diffraction analyses allows the study of flocculation processes in estuaries and a detailed description of thin layers.
Article
The effect of substratum topography on bacterial surface colonization was studied using a chemically homogeneous silicon coupon. "Grooves" 10 µm deep and 10, 20, 30, and 40 µm wide were etched on the coupon perpendicular to the direction of flow. Flow (Re = 5.5) of a bacterial suspension (10(8) cells/ml) was directed through a parallel plate flow chamber inverted on a confocal microscope. Images were collected in real time to obtain rate and endpoint colonization data for each of three strains of bacteria: Pseudomonas aeruginosa and motile and nonmotile Pseudomonas fluorescens. A higher velocity experiment (Re = 16.6) and an abiotic control using hydrophilic, negatively charged microspheres were also performed. Using a colloidal deposition expression, the initial rates of attachment were compared. P. aeruginosa attached at a higher rate than P. fluorescens mot+ which attached at a higher rate than P. fluorescens mot-. For all bacteria the rate was independent of groove size and was greatest on the downstream edges of the grooves. Only the motile organisms were found in the bottoms of the grooves. A higher fluid velocity resulted in an increase in the initial rate of attachment. In contrast, there was no adhesion of the beads. Attachment of the bacteria appears to be predominated by transport from the bulk phase to the substratum. Copyright 1998 Academic Press.
Article
In this review, initial microbial adhesive interactions are divided into adhesion to substratum surfaces, coaggregation between microbial pairs and co-adhesion between sessile and planktonic microorganisms of different strains or species. The physico-chemical mechanisms underlying the adhesive interactions are described and a critical review is given of currently employed methods to study microbial adhesive interactions, with an emphasis on the use of the parallel plate flow chamber. Subsequently, for each of the three microbial adhesive interactions distinguished, the role of Lifshitz-van der Waals, acid-base and electrostatic interactions is described based on existing literature.
Article
Effects of hydrocarbon-contaminated substrata on recruitment of three species of fouling organisms were studied along the Louisiana gulf coast. Clay tiles (232 cm2) were exposed to crude oil, 10% water soluble fraction of crude oil, or 25 g/kg artificial seawater, and placed out at two locations, in two seasons, and at two tidal levels in an estuary near Port Fourchon, Louisiana. Bryozoan (Membranipora savartii) recruitment was significantly reduced in all experiments on crude oil-exposed tiles. However, oysters (Crassostrea virginica) and barnacles (Balanus eburneus) exhibited recruitment facilitation, and oysters grew to larger size, on crude oil-exposed tiles in 1-4 of the five experiments. When oyster larvae were exposed to the same treatments in the laboratory, settlement was, however, significantly depressed on crude oil-exposed tiles as compared with controls, although oyster size was larger on crude-oil exposed tiles. Recruitment on tiles exposed to the water soluble fraction of crude oil was similar to control tiles in nearly all experiments for all taxa. We suggest naturally occurring biofilms (which hydrocarbons facilitate) may promote or inhibit recruitment, depending on the taxon, because hydrocarbons facilitated recruitment only in field experiments, not in lab experiments without biofilms. However, stronger currents in the field experiments may have more rapidly diluted hydrocarbons, and hydrocarbon effects were not large in comparison with natural seasonal and tidal variation in recruitment.
Article
We investigated vertical distribution and depth-related patterns (from 670 to 2,570 metres) of bacterial diversity in sediment samples collected along a transect in the warm deep Mediterranean sea. Analyses of bacterial diversity were compared with the abundance of benthic bacteria, their metabolically active fraction and the substrates potentially available for their growth. The number of active bacteria was dependent upon the availability of organic substrate in the sediment deriving from phytopigment inputs from the photic layer. The T-RFLP analysis revealed that the surface layers of all sediments analysed were dominated by the same ribotypes, but clear shifts in bacterial community structure were observed in deeper sediment layers. High values of bacterial diversity (expressed as D, H') and evenness (as J) were observed at all stations (a total of 61 ribotypes was identified), and as a result of the large fraction of rare ribotypes (c. 35%), the overall bacterial diversity in the deep sea region investigated was among the highest reported so far in literature. Biodiversity parameters did not display any relationship with water depth, but ribotype richness was related with the number and percentage of active bacteria, suggesting a coupling between organic inputs stimulating bacterial growth and deep-sea bacterial diversity.
Conference Paper
The MAREL programme attempts to develop automated monitoring stations for classical sea water analysis, able to work autonomously in coastal areas. A land-based station automatically receives and stores data, keeps them available for the users via the Internet and may also receive alarm messages from monitoring stations. Water samples are pumped from different levels in the sea water column and are analysed by sensors located in a measuring cell on the floating structure. This allows a continuous cleaning of the sensors to secure measurement quality and the injection of chlorinated ions in the hydraulic circuit to avoid biofouling. The system status can be known at any time and, if necessary, in some cases, can be repaired by remote operating maintenance, saving data and saving an onerous on-site intervention. The measuring system can be adapted to different conditions of the coastal environment, for example estuary environment with turbid waters and very fast variations of the parameters. It will be able to evolve by replacing or adding new modules for new parameter analysis. The data transmission system is also standardized, using the telephone and GSM network, VHF or satellites if necessary. Sensors used for the Seine Bay MAREL programme analyse water temperature, salinity, turbidity, pH, amount of dissolved oxygen, nitrates and chlorophyll in the sea water, and added parameters such as hydrological (current, wave) and meteorological (air temperature and pressure, wind) ones
Conference Paper
The effectiveness of optical lenses deployed in water less than 100 m deep is significantly reduced by biofouling caused by the settlement of macrofauna, such as barnacles, hydroids, and tunicates. However, machineable porous plastic rings can be used to dispense antifoulant into the water in front of the lens to retard macrofaunal growth without obstructing the light path. Unlike coatings which can degrade the optical performance, antifouling rings do not interfere with the instrument optics. The authors have designed plastic, reusable cup-like antifouling rings to slip over the optical lenses of a transmissometer. These rings have been used for several deployments on shallow moorings in Massachusetts Bay, MA and have increased the time before fouling degrades optical characteristics
Article
Theoretical and experimental results are presented to analyze the mechanical vibrations of elastic structures activated by piezopolymer transducers. Elastic thin plates and cylindrical shell structures are activated by polyvinylidene fluoride piezoelectric films. Vibrational behavior of activated structures are observed in gaseous and liquid surrounding media. These structures have been considered in view of applications for protection of oceanographic sensors against marine fouling by mechanical surface vibrations
The BASIS group. A study of the initial stages of biofilm formation on stainless steel immersed in sea water
  • M G Walls
  • B Rondot
  • D Costa
  • C M Pradier
  • P Marcus
  • M N Bellon-Fontaine
  • C Compère
  • J Guezennec
Walls, M. G., Rondot, B., Costa, D., Pradier, C. M., Marcus, P., Bellon-Fontaine, M. N., Compère, C. and Guezennec, J. 1998. The BASIS group. A study of the initial stages of biofilm formation on stainless steel immersed in sea water. In: L. Faria (ed.), Proc. Euromat 98 (Materials in Oceanic Environment). Lisbon, Sociedade Portuguesa de Materiais, 1, pp. 421-30
  • P Stoodley
  • D Debeer
  • Z Lewandowski
Stoodley, P., deBeer, D. and Lewandowski, Z. 1994. Z. Appl. Environ. Microbiol., 60, pp. 2711-16.