Antifouling activity of macroalgal extracts on Fragilaria pinnata (Bacillariophyceae): a comparison with Diuron

An Analysis of the Nutritional and Health Values of Caulerpa racemosa (Forsskål) and Ulva fasciata (Delile)-Two Chlorophyta Collected from the Philippines

Polysaccharides, lipids and amino acid profiles were investigated to understand the nutritional value of Caulerpa racemosa and Ulva fasciata from the Philippines. The results revealed that both species contain high amounts of proteins (8.8-19.9% for C. racemosa and 8.0-11.1% for U. fasciata). The portions of the total amino acids that were essential amino acids (EAAs) (45.28 ± 0.12% for C. racemosa and 42.17 ± 0.12% for U. fasciata) out were comparable to FAO/WHO requirements. Leucine, valine, isoleucine, and lysine are the dominant EAAs in C. racemosa, while leucine, valine, lysine, and phenylalanine are those in U. fasciata. The fatty acid profiles are dominated by monounsaturated fatty acids and polyunsaturated fatty acids in C. racemosa (56.2%), while saturated fatty acids (72.1%) are dominant in U. fasciata. High C18/C20 polyunsaturated fatty acid ratios were recorded in both species. Mineral contents for both seaweeds were within levels considered safe for functional foods. Total pigment content of C. racemosa (140.84 mg/g dw) was almost 20 times higher than that of U. fasciata (7.54 mg/g dw). Hot water extract (HWE) from C. racemosa showed in vitro antiherpetic activity without cytotoxicity. Nutritional characteristics confirmed that C. racemosa could be potentially used as a nutritious and functional food items for human consumption.

Adsorption of phenylurea herbicides by tropical soils

The distribution of pesticides in soils with consequences for their mobility, bioavailability and water contamination is mainly ruled by sorption processes. Such processes are seldom investigated in tropical soils. Thus, specific interactions between tropical soils and most pesticides are widely unknown. Furthermore, the question arises whether the same factors govern adsorption in tropical and temperate soils. Thus, the sorption behaviour of five phenylurea herbicides (PUHs) was studied in eighteen differently composed soils originating from southwestern Nigeria. Sorption data were obtained by equilibrating the soil samples with 0.01 M CaCl2 solutions spiked with increasing concentrations of the target PUHs. The equilibrium data fitted well to the Freundlich isotherm equation (R2 ≥ 0.96), delivering the corresponding parameters (Kf and n). Linear distribution coefficients (Kd) were also calculated. The Pearson correlation was used to identify the specific soil and herbicide properties that have statistically significant correlations with sorption parameters. High correlations were established for various soil properties (pH, cation exchange capacity, organic carbon content, content of amorphous Fe and Mn oxides, clay/silt mass proportions) as well as molecular descriptors (octanol-water partition coefficient (log Kow) and molecular mass (Mw)) of the moderately hydrophobic herbicides. Monuron, chlorotoluron and isoproturon showed higher affinities for soil than previously reported. The gathered knowledge might assist in the assessment and in the precautionary avoidance of potential risks generated by these compounds in tropical soils.

Impact of diuron and S-metolachlor on the freshwater diatom Gomphonema gracile: Complementarity between fatty acid profiles and different kinds of ecotoxicological impact-endpoints

Fatty acids (FA) are crucial for the maintenance of membrane fluidity and play a central role in metabolic energy storage. Polyunsaturated fatty acids play an essential ecological role since they are key parameters in the nutritional value of algae. Pesticide impacts on fatty acid profiles have been documented in marine microalgae, but remain understudied in freshwater diatoms. The aims of this study were to: 1) investigate the impact of diuron and S-metolachlor on "classical descriptors" (photosynthesis, growth rate, pigment contents, and on the expression levels of target genes in freshwater diatoms), 2) examine the impact of these pesticides on diatom fatty acid profiles and finally, 3) compare fatty acid profiles and "classical descriptor" responses in order to evaluate their complementarity and ecological role. To address this issue, the model freshwater diatom Gomphonema gracile was exposed during seven days to diuron and S-metolachlor at 10 μg.L^-1. G. gracile was mostly composed of the following fatty acids: 20:5n3; 16:1; 16:0; 16:3n4; 14:0 and 20:4n6 and highly unsaturated fatty acids were overall the best represented fatty acid class. S-metolachlor decreased the growth rate and chlorophyll a content of G. gracile and induced the expression of cox1, nad5, d1 and cat genes, while no significant impacts were observed on photosynthesis and carotenoid content. In a more global way, S-metolachlor did not impact the fatty acid profiles of G. gracile. Diuron inhibited photosynthesis, growth rate, chlorophyll a content and induced cat and d1 gene expressions but no significant effect was observed on carotenoid content. Diuron decreased the percentage of highly unsaturated fatty acids but increased the percentage of monounsaturated fatty acids. These results demonstrated that fatty acids responded to diuron conversely to pigment content, suggesting that fatty acids can inform on energy content variation in diatoms subjected to herbicide stress.

From Ecology to Biotechnology, Study of the Defense Strategies of Algae and Halophytes (from Trapani Saltworks, NW Sicily) with a Focus on Antioxidants and Antimicrobial Properties

This study aimed at the characterization of the antioxidant power of polyphenol extracts (PE) obtained from the algae Cystoseira foeniculacea (CYS) (Phaeophyta) and from the halophyte Halocnemum strobilaceum (HAL), growing in the solar saltworks of western Sicily (Italy), and at the evaluation of their anti-microfouling properties, in order to correlate these activities to defense strategies in extreme environmental conditions. The antioxidant properties were assessed in the PE based on the total antioxidant activity test and the reducing power test; the anti-microfouling properties of the two PE were evaluated by measuring the growth inhibition of marine fish and shellfish pathogen bacteria as well as marine surface fouling bacteria and microalgae exposed to the fractions. Similar polyphenol content (CYS 5.88 ± 0.75 and HAL 6.03 ± 0.25 mg gallic acid equivalents (GAE) g-1 dried weight, DW) and similar reducing power percentage (93.91 ± 4.34 and 90.03 ± 6.19) were recorded for both species, even if they exhibited a different total antioxidant power (measured by the percentage of inhibition of the radical 2,2 diphenyl-1-picrylhydrazyl DPPH), with CYS (79.30) more active than HAL (59.90). Both PE showed anti-microfouling properties, being inhibitors of adhesion and growth of marine fish and shellfish pathogen bacteria (V. aestuarianus, V. carchariae, V. harveyi, P. elyakovii, H. aquamarina) and fouling bacteria (V. natriegens, V. proteolyticus, P. iirgensii, R. litoralis) with minimum inhibitory concentrations comparable to the commercial antifouling products used as a positive control (SEA-NINE™ 211N). Only CYS was a significant inhibitor of the microalgae strains tested, being able to reduce E. gayraliae and C. closterium growth (MIC 10 µg·mL-1) and the adhesion of all three strains tested (E. gayraliae, C. closterium and P. purpureum), suggesting its promise for use as an antifouling (AF) product.

The role of chemical antifouling defence in the invasion success of Sargassum muticum: A comparison of native and invasive brown algae

Competition and fouling defence are important traits that may facilitate invasions by non-indigenous species. The 'novel weapons hypothesis' (NWH) predicts that the invasive success of exotic species is closely linked to the possession of chemical defence compounds that the recipient community in the new range is not adapted to. In order to assess whether chemical defence traits contribute to invasion success, anti-bacterial, anti-quorum sensing, anti-diatom, anti-larval and anti-algal properties were investigated for the following algae: a) the invasive brown alga Sargassum muticum from both, its native (Japan) and invasive (Germany) range, b) the two non- or weak invasive species Sargassum fusiforme and Sargassum horneri from Japan, and c) Fucus vesiculosus, a native brown alga from Germany. Crude and surface extracts and lipid fractions of active extracts were tested against common fouling organisms and zygotes of a dominant competing brown alga. Extracts of the native brown alga F. vesiculosus inhibited more bacterial strains (75%) than any of the Sargassum spp. (17 to 29%). However, Sargassum spp. from Japan exhibited the strongest settlement inhibition against the diatom Cylindrotheca closterium, larvae of the bryozoan Bugula neritina and zygotes of the brown alga F. vesiculosus. Overall, extracts of S. muticum from the invasive range were less active compared to those of the native range suggesting an adaptation to lower fouling pressure and competition in the new range resulting in a shift of resource allocation from costly chemical defence to reproduction and growth. Non-invasive Sargassum spp. from Japan was equally defended against fouling and competitors like S. muticum from Japan indicating a necessity to include these species in European monitoring programs. The variable antifouling activity of surface and crude extracts highlights the importance to use both for an initial screening for antifouling activity.

Antifouling Activity of Lipidic Metabolites Derived from Padina tetrastromatica

An attempt has been made to identify the potential seaweed for antifouling property due to the growing need for environmentally safe antifouling systems. The antibacterial, antimicroalgal, and antimussel foot adherence potentials of methanol, dichloromethane, and hexane extracts of the chosen seaweeds such as Padina tetrastromatica, Caulerpa taxifolia, and Amphiroa fragilissima have been compared against copper sulfate. Among the extracts, the maximum antibacterial activities were exhibited by the methanol extract of P. tetrastromatica. The minimum inhibitory concentration (MIC) of the methanolic extract of P. tetrastromatica was found to be 10 and 1 μg/ml against test biofilm bacteria and diatoms, respectively. The antimussel foot adherence assay indicated that the extract had inhibited the foot adherence of the green mussels Perna viridis with the effective concentration (EC50) of 25.51 ± 0.03 μg/ml, and lethal concentration for 50 % mortality (LC50) was recorded at 280.22 ± 0.12 μg/ml. Based on the prolific results, the crude methanolic extract of P. tetrastromatica was subjected to purification using silica gel column and thin-layer chromatography (TLC). Then, the active compounds of the bioassay-guided fraction (F13) were identified using gas chromatography coupled with mass spectroscopy (GC-MS), and it was observed that fatty acids were the major components, which may be responsible for the antifouling properties.

Distribution of butyltins and alternative antifouling biocides in sediments from shipping and shipbuilding areas in South Korea

The occurrence and distribution of tributyltin (TBT) and alternative biocides were investigated in sediment from semi-enclosed bays, fishing ports, and large commercial harbors in Korea. Extremely high concentration of TBT (55,264ngSn/g) was detected near a large shipyard, even after a total ban on its use in Korea. Diuron was the biocide with the highest detection frequency and concentration levels, followed by Irgarol 1051. Sea-Nine 211 was detected at 3 of 32 stations surveyed. Dichlofluanid, zinc and copper pyrithiones levels were below the detection limits at all the stations surveyed. The relatively high levels of Diuron (9-62.3ng/g) and Irgarol 1051 (1.5-11.5ng/g) were detected in harbor and shipyard areas. Diuron and Irgarol 1051 levels including TBT in sediments from hot spots in Korea exceeded global sediment quality guidelines.

Current and emerging environmentally-friendly systems for fouling control in the marine environment

Following the ban in 2003 on the use of tributyl-tin compounds in antifouling coatings, the search for an environmentally-friendly alternative has accelerated. Biocidal TBT alternatives, such as diuron and Irgarol 1051®, have proved to be environmentally damaging to marine organisms. The issue regarding the use of biocides is that concerning the half-life of the compounds which allow a perpetuation of the toxic effects into the marine food chain, and initiate changes in the early stages of the organisms' life-cycle. In addition, the break-down of biocides can result in metabolites with greater toxicity and longevity than the parent compound. Functionalized coatings have been designed to repel the settlement and permanent attachment of fouling organisms via modification of either or both surface topography and surface chemistry, or by interfering with the natural mechanisms via which fouling organisms settle upon and adhere to surfaces. A large number of technologies are being developed towards producing new coatings that will be able to resist biofouling over a period of years and thus truly replace biocides as antifouling systems. In addition urgent research is directed towards the exploitation of mechanisms used by living organisms designed to repel the settlement of fouling organisms. These biomimetic strategies include the production of antifouling enzymes and novel surface topography that are incompatible with permanent attachment, for example, by mimicking the microstructure of shark skin. Other research seeks to exploit chemical signals and antimicrobial agents produced by diverse living organisms in the environment to prevent settlement and growth of fouling organisms on vulnerable surfaces. Novel polymer-based technologies may prevent fouling by means of unfavourable surface chemical and physical properties or by concentrating antifouling compounds around surfaces.

Comparative efficiency of macroalgal extracts and booster biocides as antifouling agents to control growth of three diatom species

The application of 'booster biocides' Diuron, Tolylfluanid and Copper thiocyanate inbantifouling paints, used to prevent development of biofouling, needs to be monitored before assessing their impacts on the environment. An alternative approach aims to propose eco-friendly and effective antifoulants isolated from marine organisms such as seaweeds. In this study, the effects of 'booster biocides' and the ethanol and dichloromethane extracts from a brown (Sargassum muticum) and a red alga (Ceramium botryocarpum) have been compared by algal growth inhibition tests of marine diatoms. The most efficient extracts were ethanol fraction of S. muticum and C. botryocarpum extracts with growth EC(50)=4.74 and 5.3μg mL(-1) respectively, with reversible diatom growth effect. The booster biocides are more efficient EC(50)=0.52μg mL(-1), but are highly toxic. Results validate the use of macroalgal extracts as non toxic antifouling compounds, and they represent valuable environmentally friendly alternatives in comparison with currently used biocides.

Booster biocides and microfouling

Antifouling (AF) paints are used to prevent the attachment of living organisms to the submerged surfaces of ships, boats and aquatic structures, usually by the release of biocides. Apart from copper, organic booster biocides are the main active components in AF paints, but their use can have a negative impact on the marine environment. The direct effects of biocides on marine bacteria are poorly known. This work investigates the impact of two biocides, viz. diuron and tolylfluanid, on the growth and the viability of marine microorganisms and on their ability to form biofilms. The biocides in solution were found to inhibit growth of two strains of marine bacteria, viz. Pseudoalteromonas and Vibrio vulnificus, at a high concentration (1000 microg ml(-1)), but only a small effect on viability was observed. Confocal laser scanning microscopy (CLSM) showed that the booster biocides decreased biofilm formation by both bacteria. At a concentration of 10 microg ml(-1), the biocides inhibited cell attachment and reduced biofilm thickness on glass surfaces. The percentage of live cells in the biofilms was also reduced. The effect of the biocides on two diatoms, Fragilaria pinnata and Cylindrotheca closterium, was also evaluated in terms of growth rate, biomass, chlorophyll a content and attachment to glass. The results demonstrate that diuron and tolylfluanid are more active against diatoms than bacteria.

Color measurements as a reliable method for estimating chlorophyll degradation to phaeopigments

The application of biocides is a traditional method of controlling biodecay of outdoor cultural heritage. Chlorophyll degradation to phaeopigments is used to test the biocidal efficacy of the antimicrobial agents. In the present study, the usefulness of color measurements in estimating chlorophyll degradation was investigated. An aeroterrestrial stone biofilm-forming cyanobacterium of the genus Nostoc was chosen as test organism, comparing its different behaviour in both planktonic and biofilm mode of growth against the isothiazoline biocide Biotin T®. Changes in A(435 nm)/A(415 nm) and A(665 nm)/A(665a nm) and in the chlorophyll a and adenosine triphosphate (ATP) cell content were compared with the variations in the CIELAB color parameters (L*, a*, b*, C*(ab) and h(ab)). Our findings showed that both the phaeophytination indexes are useful in describing degradation of chlorophyl a to phaeopigments. Moreover, the CIELAB color parameters represented an effective tool in describing chlorophyll degradation. L* CIELAB parameter appeared to be the most informative parameter in describing the biocidal activity of Biotin T® against Nostoc sp. in both planktonic and biofilm mode of growth.