Ocean acidification may alleviate the toxicity of zinc to the macroalga, Ulva lactuca.

We investigated the toxic effects of different zinc (Zn) concentrations (natural seawater, 25 µg/L, and 100 µg/L) under two CO2 concentrations (410 ppmv, and 1000 ppmv) on Ulva lactuca. A significant decrease in the relative growth rate of U. lactuca was observed with an increase in Zn concentration under the low CO2 treatment condition, and we observed a notable decrease at 100 µg/L Zn under the high CO2 treatment condition. Moreover, the net photosynthetic rate increased when thalli were cultured under 25 and 100 µg/L Zn under the high CO2 treatment condition. The concentrations of chlorophyll a and b were significantly increased under 100 µg/L Zn and the high CO2 treatment conditions. Malondialdehyde content decreased under high CO2 treatment conditions, compared with the low CO2 treatment conditions, regardless of the Zn concentration. These findings suggest that ocean acidification may alleviate the toxic effects of Zn pollution on U. lactuca.

Differential effects of petroleum hydrocarbons on the growing development and physiological characteristics of Ulva species.

To compare the different effects of petroleum hydrocarbons on intertidal Ulva macroalgae, three dominant Ulva species (U. prolifera, U. linza, and U. lactuca) were exposed to two water-accommodated fractions (WAFs) of 0# diesel oil and crude oil at three concentration levels. The results indicated that two WAFs had significant concentration effects on the physiological characteristics of Ulva, the toxicity of 0# diesel oil was greater than crude oil, and crude oil had hormesis effect. Exposure of high WAFs concentrations, the growth, pigment, carbohydrate, and protein contents of Ulva were inhibited, while the antioxidant system was activated. In addition, the integrated biomarker response (IBR) indicated that U. prolifera had higher resistance to WAFs than U. linza and U. lactuca. Considering that U. prolifera is the main species of green tide in the Yellow Sea (YS) of China, the comparative effects of WAFs on different development stages of U. prolifera were also explored. The results showed that spore was the most sensitive to WAFs, while adult thalli was the most tolerant. The increased resistance of U. prolifera thalli and the hormesis effect triggered by crude oil may influence the outbreak scale of green tides. This study provides a new perspective for understanding the formation of green tides in the YS.

Mechanism of up-regulated H2O2 BPA-derived production and production of (poly)phenols by two seaweeds of the genus Ulva.

The present study provides information on the effects of BPA on ROS production-related phenomena in the chlorophytes Ulva rigida and U. intestinalis, and on the mechanism they establish against BPA toxicity, at environmentally relevant concentrations (0.1-3 µg L-1). Up-regulated H2O2 generation seems to be a key factor causing oxidative damage. Interspecific differences, in terms of the mechanism and the temporal response to BPA toxicity were observed. BPA effects on U. rigida were more intense and appeared earlier (on 1D at 0.1 µg L-1) compared to U. intestinalis and mostly after 7D (LOEC: 0.3 µg L-1, Terminal time, Tt: 7D). In U. rigida, on 1-5D, the 'mosaic' type effect patterns ('models' 3A/3B) with 'unaffected' and 'affected' areas (dark content, positive H2DCF-DA staining signal/H2O2 production and chlorophyll autofluorescence signal loss) indicated a time-dependent manner. After 7D, only U. rigida cells with dark content formed aggregates, showing positive H2O2 production ('model' 4) or in some cells oxidative damages triggering retrograde signaling in the neighboring 'unaffected' areas ('model' 5). H2O2 overproduction (CTCF ratio) in U. rigida, on 1D at the lowest concentration and after 7D at 0.3-1/3 µg L-1, respectively, seems to stimulate (poly)phenolic production, in a dose- and time-dependent manner. U. intestinalis did not display severe BPA impact (i.e., 'models' 4, 5) at any exposures, although at a later time indicated a lower LOEC (0.1 µg L-1, Tt: 9D) than that in U. rigida. In U. intestinalis, H2O2 production does not appear to stimulate high (poly)phenolic amounts.

Copper Is Accumulated as Copper Sulfide Particles, and Not Bound to Glutathione, Phytochelatins or Metallothioneins, in the Marine Alga Ulva compressa (Chlorophyta).

To analyze the mechanism of copper accumulation in the marine alga Ulva compressa, it was cultivated with 10 µM of copper, with 10 µM of copper and increasing concentrations of a sulfide donor (NaHS) for 0 to 7 days, and with 10 µM of copper and a concentration of the sulfide acceptor (hypotaurine) for 5 days. The level of intracellular copper was determined as well as the level of glutathione (GSH) and phytochelatins (PCs) and the expression of metallothioneins (UcMTs). The level of intracellular copper in the algae treated with copper increased at day 1, slightly increased until day 5 and remained unchanged until day 7. The level of copper in the algae cultivated with copper and 100 or 200 µM of NaHS continuously increased until day 7 and the copper level was higher in the algae cultivated with 200 µM of NaHS compared to 100 µM of NaHS. In contrast, the level of intracellular copper decreased in the algae treated with copper and hypotaurine. The level of intracellular copper did not correlate with the level of GSH or with the expression of UcMTs, and PCs were not detected in response to copper, or copper and NaHS. Algae treated with copper and with copper and 200 µM of NaHS for 5 days were visualized by TEM and the elemental composition of electrondense particles was analyzed by EDXS. The algae treated with copper showed electrondense particles containing copper and sulfur, but not nitrogen, and they were mainly located in the chloroplast, but also in the cytoplasm. The algae treated with copper and NaHS showed a higher level of electrondense particles containing copper and sulfur, but not nitrogen, and they were located in the chloroplast, and in the cytoplasm. Thus, copper is accumulated as copper sulfide insoluble particles, and not bound to GSH, PCs or UcMTs, in the marine alga U. compressa.

Layer-by-Layer Deposited Hybrid Polymer Coatings Based on Polysaccharides and Zwitterionic Silanes with Marine Antifouling Properties.

Polyelectrolyte multilayer (PEM) assembly is a versatile tool to construct low-fouling coatings. For application in the marine environment, their structure needs to be stabilized by covalent linkage. Here, we introduce an approach for spin coating of silane-based sol-gel chemistries using layer-by-layer assembly of polysaccharide-based hybrid polymer coatings (LBLHPs). The silane sol-gel chemistry allows the films to be cross-linked under water-based and mild reaction conditions. Two different silanes were used for this purpose, a conventional triethoxymethyl silane and a de novo synthesized zwitterionic silane. The polysaccharide-silane hybrid polymer coatings were thoroughly characterized with spectroscopic ellipsometry, water contact angle (WCA) goniometry, attenuated total reflection-Fourier transform infrared spectroscopy, and atomic force microscopy. The coatings showed good stability in seawater, smooth surfaces, a high degree of hydration, and WCAs below or close to the Berg limit. LBLHPs showed low-fouling properties in biological assays against nonspecific protein adsorption, attachment of the diatom Navicula perminuta, and settlement of zoospores of the macroalga Ulva linza.

Photoprotection and antioxidative metabolism in Ulva lactuca exposed to coastal oceanic acidification scenarios in the presence of Irgarol.

Anthropogenic changes such as ocean acidification, eutrophication, and the release of hazardous chemicals affect coastal environments and aquatic organisms. We investigated the effects of seawater pH (7.4 and 8.2) isolated and in combination with Irgarol on Ulva lactuca. Stress indicators such as membrane damage, lipid peroxidation, and hydrogen peroxide content were assessed. In addition, chlorophyll fluorescence and antioxidant enzyme activities were measured. The photosynthetic yield was affected by low pH in assays with and without Irgarol. However, the combination of low pH and Irgarol promoted photoinhibition, besides the induction of non-photochemical quenching (NPQ) and changes in photosynthetic pigment contents. The induction of NPQ was directly influenced by low pH. The membrane damage was increased in low pH with and without Irgarol exposure. Total soluble protein and carbohydrate contents decreased in low pH, and in presence of Irgarol. The H2O2 content and lipid peroxidation were not affected by low pH. In contrast, Irgarol exposure strongly increased lipid peroxidation in both pHs, suggesting a possible synergistic effect. To avoid the harmful effects of high H2O2, U. lactuca increased antioxidant enzyme activities in treatments under low pH and in presence of Irgarol. Our results indicate that U. lactuca is tolerant to low pH by inducing NPQ, changing pigment contents, and increasing antioxidant defenses. In contrast, these protective mechanisms could not avoid the harmful effects of the combination with Irgarol.

Benzopyrene induces oxidative stress and increases expression and activities of antioxidant enzymes, and CYP450 and GST metabolizing enzymes in Ulva lactuca (Chlorophyta).

MAIN CONCLUSION: Benzopyrene is rapidly incorporated and metabolized, and induces oxidative stress and activation of antioxidant enzymes, and CYP450 and GST metabolizing enzymes in Ulva lactuca. To analyze absorption and metabolism of benzo[a]pyrene (BaP) in Ulva lactuca, the alga was cultivated with 5 µM of BaP for 72 h. In the culture medium, BaP level rapidly decreased reaching a minimal level at 12 h and, in the alga, BaP level increased until 6 h, remained stable until 24 h, and decreased until 72 h indicating that BaP is being metabolized in U. lactuca. In addition, BaP induced an initial increase in hydrogen peroxide decreasing until 24 h, superoxide anions level that remained high until 72 h, and lipoperoxides that initially increased and decreased until 72 h, showing that BaP induced oxidative stress. Activities of antioxidant enzymes superoxide dismutase (SOD), catalase (CAT), ascorbate peroxidase (AP), glutathione reductase (GR) and glutathione peroxidase (GP) were increased, whereas dehydroascorbate reductase (DHAR) activity was unchanged. The level of transcripts encoding these antioxidant enzymes was increased, but transcripts encoding DHAR remained unchanged. Interestingly, the activity of glutathione-S-transferase (GST) was also increased, and inhibitors of cytochrome P450 (CYP450) and GST activities enhanced the level of BaP in algal tissue, suggesting that these enzymes participate in BaP metabolism.

Variation in microbial populations and antibiotic resistance genes in mariculture sediments in the present of the seaweed Ulva fasciata and under selective pressure of oxytetracycline.

The widely distributed seaweed Ulva fasciata has nutrient absorption abilities and can be used in the bioremediation of polluted maricultural environments. This study explored microbial community and antibiotic resistance gene (ARG) variation in mariculture sediments in response to different trace levels (10, 100, and 500 µg L-1) of oxytetracycline (OTC) and the presence of Ulva fasciata. The increase in OTC level promoted nutrient (NO3_-N and PO43--P) removal mainly due to Ulva fasciata adsorption. The abundances of the Euryarchaeota and Planctomycetes phyla in sediments were positively related to the increase in OTC stress, while a negative correlation occurred for the Proteobacteria phylum via metagenomic analysis. Compared with the control system, the increase rates of total ARGs were 3.90%, 7.36% and 13.42% at the OTC levels of 10, 100 and 500 µg L-1, respectively. OTC stress mainly favoured the collateral enrichment of non-corresponding polypeptide and MLS ARGs, mainly due to the enrichment of the phyla Planctomycetes and Euryarchaeota by the synergistic effect of OTC and nutrients. The results of quantitative PCR with tetracycline resistance genes (TRGs) (tetO, tetT, tetPB, tetW and otrA) and a horizontal transfer gene (intl1) demonstrated that all of genes had much higher gene numbers in sediments after 3 months of OTC stress than in those without OTC stress, which was strongly related to the variation in the phyla Bacteroidetes, Gemmatimonadetes and Acidobacteria. The significant correlation between intl1 and the target TRGs is indicative of the important role of the horizontal transfer of integron-resistant genes in the spread of TRGs.

Effect of allelochemicals on photosynthetic and antioxidant defense system of Ulva prolifera.

Ulva prolifera is a macroalgae that forms massive blooms, negatively impacting natural communities, aquaculture operations and recreation. The effects of the natural products, eugenol, ß-myrcene, citral and nonanoic acid on the growth rate, antioxidative defense system and photosynthesis of Ulva prolifera were investigated as a possible control strategy for this harmful taxon. Negative effects on growth were observed with all four chemicals, due to the excessive production of reactive oxygen species and oxidative damage to the thalli. However, the response of U. prolifera under the four chemicals stress was different at the cellular level. ß-myrcene, the most effective compound in terms of growth inhibition, induced oxidative stress as shown by the damage of total antioxidant capacity (T-AOC) and the downregulation of the glutathione-ascorbate (GSH-ASA) cycle which inhibited the antioxidative system. This chemical also inhibited photosynthesis and photoprotection mechanisms in U. prolifera, resulting in growth limitation. In contrast, U. prolifera was less affected by the second tested chemical, eugenol, and showed no significant change on photosynthetic efficiency in the presence of the chemical. The inhibition effects of the third and fourth tested chemicals, nonanoic acid and citralon, on growth and on the antioxidant defense system in U. prolifera were inferior. These results provide a potential avenue for controlling green tides in the future.

Application of a programmed semi-automated Ulva pertusa bioassay for testing single toxicants and stream water quality.

A toxicity test based on inhibition of reproduction in the green macroalga Ulva pertusa involves quantifying the change in thallus color as reproduction progresses. However, interpretation of this color change is reliant on the skill level of the examiner. This study aimed to validate a new toxicity test based on inhibition of reproduction in the green macroalga U. pertusa using a vital stain and programmed semi-automated analysis (using Image J) of the change in thallus color. The toxicity rank by inverse EC50 values was: irgarol (0.048 mg L-1) > Ag (0.132 mg L-1) > As (0.172 mg L-1) > simazine (0.378 mg L-1) > formaldehyde (0.442 mg L-1) > DCOIT (0.783 mg L-1) > ZnPT (3.556 mg L-1) > medetomidine (11.600 mg L-1) > phenol (29.316 mg L-1) > methanol (2,736 mg L-1) > ethanol (3,306 mg L-1). The sensitivity of the U. pertusa test to stream waters was similar to or lower than those of the commonly-used Lemna minor and Daphnia magna bioassays. The U. pertusa bioassay is sensitive to, and suitable for, testing various toxicants including metals, volatile organic compounds, herbicide, antifouling agents and phenol and can also be applied to testing freshwater quality after salinity adjustment.

Copper-induced concomitant increases in photosynthesis, respiration, and C, N and S assimilation revealed by transcriptomic analyses in Ulva compressa (Chlorophyta).

BACKGROUND: The marine alga Ulva compressa is the dominant species in copper-polluted coastal areas in northern Chile. It has been shown that the alga tolerates micromolar concentrations of copper and accumulates copper at the intracellular level. Transcriptomic analyses were performed using total RNA of the alga cultivated with 10 µ M copper for 0, 1, 3 and 5 days using RNA-seq in order to identify processes involved in copper tolerance. RESULTS: The levels of transcripts encoding proteins belonging to Light Harvesting Complex II (LHCII), photosystem II (PSII), cytochrome b6f, PSI, LHCI, ATP synthase and proteins involved in repair of PSII and protection of PSI were increased in the alga cultivated with copper. In addition, the level of transcripts encoding proteins of mitochondrial electron transport chain, ATP synthase, and enzymes involved in C, N and S assimilation were also enhanced. The higher percentages of increase in the level of transcripts were mainly observed at days 3 and 5. In contrast, transcripts involved protein synthesis and degradation, signal transduction, and replication and DNA repair, were decreased. In addition, net photosynthesis and respiration increased in the alga cultivated with copper, mainly at days 1 to 3. Furthermore, the activities of enzymes involved in C, N and S assimilation, rubisco, glutamine synthase and cysteine synthase, respectively, were also increased, mainly at days 1 and 3. CONCLUSIONS: The marine alga U. compressa tolerates copper excess through a concomitant increase in expression of proteins involved in photosynthesis, respiration, and C, N and S assimilation, which represents an exceptional mechanism of copper tolerance.

Efficient enzymatic saccharification of macroalgal biomass using a specific thermostable GH 12 endoglucanase from Aspergillus terreus JL1.

Stranded green macroalgae represents an important and renewable biomass that remains under valorized despite the numerous environmental problems generated by their accumulation in coastal regions. This work describes the isolation of a filamentous thermophile fungus identified as Aspergillus terreus JL1 that produces an efficient cellulolytic activity for green macroalgae saccharification. The characterization of the endoglucanase activity obtained after submerged fermentation showed a differential induction depending on the carbon source used with a unique isoform released when Ulva lactuca was used as inducer. The crude extract obtained hydrolyzed efficiently the untreated algal biomass (70.5%) compared to other cellulolytic extracts. The unique endoglucanase released was then purified to homogeneity (Yield: 49.6%; Specific activity: 30.1 U/mg; Purification fold: 4.36) and characterized biochemically. Its peptidic sequence was then determined and showed its belonging to the GH12. The described enzyme represents a promising biotechnological tool for algal biomass conversion.

Antifouling Properties of Dendritic Polyglycerols against Marine Macrofouling Organisms.

Dendritic polyglycerols (PGs) were synthesized and postmodified by grafting of poly(ethylene glycol) (PEG) and polypropylene glycol (PPG) diglycidyl ether groups, and their antifouling and fouling-release properties were tested. Coating characterization by spectroscopic ellipsometry, contact angle goniometry, attenuated total internal reflection-Fourier transform infrared spectroscopy (ATR-FTIR), and atomic force microscopy showed brushlike morphologies with a high degree of microscale roughness and the ability to absorb large amounts of water within seconds. PGs with three different thicknesses were tested in laboratory assays against settlement of larvae of the barnacle Balanus improvisus and against the settlement and removal of zoospores of the alga Ulva linza. Very low coating thicknesses, e.g., 11 nm, reduced the settlement of barnacles, under static conditions, to 2% compared with 55% for an octadecyltrichlorosilane reference surface. In contrast, zoospores of U. linza settled readily but the vast majority were removed by exposure to a shear force of 52 Pa. Both PEG and PPG modification increased the antifouling properties of the PG films, providing a direct comparison of the ultralow fouling properties of all three polymers. Both, the modified and the nonmodified PGs are promising components for incorporation into amphiphilic fouling-resistant coatings.

Hazardous effects of silver nanoparticles for primary producers in transitional water systems: The case of the seaweed Ulva rigida C. Agardh.

The acute toxicity of citrate capped silver nanoparticles (AgNP) and silver nitrate was evaluated on the marine macroalga Ulva rigida C. Agardh (1823). Silver bioaccumulation, ultrastructural chloroplast damages verified by TEM microscopy, inhibition of primary production, neutral lipid production and oxidative stress were observed after 24 h of exposure to AgNP. The toxic effects of silver nitrate in artificial seawater started from a concentration of 0.05 ppm and was more toxic than AgNP that produced effects from a concentration of 0.1 ppm. However only AgNP induced lipid peroxidation in U. rigida. The addition of natural organic and inorganic ligands, represented by transparent exopolymer particles (TEP) and clay, drastically reduced AgNP acute toxicity in a ratio AgNP:ligand of 1:100 and 1:200, respectively. The findings suggest a marked toxicity of Ag on marine macroalgae which however should be mitigated by the high natural ligand concentrations of the transitional environments.

A Hybrid Phase I-Phase II Toxicity Identification Evaluation (TIE) for the Simultaneous Characterization and Identification of Toxicants of Concern in Coastal and Estuarine Environments.

A sequential TIE procedure combining in a single framework Phase I manipulations and Phase II methods, including chemical analyses and complementary Phase I treatments, was proposed for characterization and identification of toxicants of concern in estuarine environments. Interstitial water was chosen as test matrix and embryo-larval development with the bivalve Crassostrea gigas as toxicity endpoint. TIE treatments included addition of Ulva rigida and elution through zeolite column for addressing effects due to ammonia, addition of EDTA and elution through a Cation-Exchange Solid-Phase Extraction column for characterize metals, and elution through two different type of polymers (XAD and DPA) with different affinity for polar and nonpolar organic pollutants. Chemical analyses concerned determination of ammonia and trace elements in the untreated sample and after manipulation intended to remove or modify bioavailability of ammonia and metals. The "hybrid" Phase I-Phase II TIE sequence proved to be a reliable and effective tool for the identification of main toxicant of concern in a highly toxic and contaminated interstitial water sample, also in presence of high concentration of potential confounding factors (ammonia). The addition of U. rigida was the more reliable treatment for the removal of ammonia, due to the concurrent release of particles and potentially toxic elements, such as Ba, Rb, and Tl by zeolite column, which may increase toxicity in the post-column sample. The combined use of polymers with different affinity for the various classes of organic pollutants was essential to identify the contribution of polar organic compounds to the observed toxicity.

Phytoremediation potential of Ulva ohnoi (Chlorophyta): Influence of temperature and salinity on the uptake efficiency and toxicity of cadmium.

Ulva ohnoi is a green macroalga with fast growth and high rates of nitrogen and phosphorus absorption. Recently, this species has been recorded in several places with record green tide formation in some of them. Using molecular tools, we herein report the first occurrence of this species in Brazil and demonstrate its potential for phytoremediation in typical environmental concentrations of Cd (0.625-15 µg L-1). Similarly, the effects of physicochemical parameters (salinity and temperature) on the toxicity and uptake efficiency of this species were evaluated. Molecular analysis of two sequences (1141 bp) obtained corroborates another 34 sequences for U. ohnoi obtained from GenBank. The addition of Cd in the medium affected photosynthetic parameters and reduced growth rate. U. ohnoi showed resistance to Cd when cultivated at 18 °C, S15 and 18-25 °C, S35, at concentrations between 0.625 and 2.5 µg. L-1 of Cd; yet, positive growth rate was maintained. Dose-dependent accumulation was observed in all combinations of factors used with a maximum value of 4.20 µg Cd per gram of dry seaweed at 15 µg. L-1 of Cd at 18 °C and S35. Maximum value of the concentration factor was 81.3 ±â€¯1.1% of Cd added at the concentration of 0.625 µg. L-1 to S15 and 18 °C. Our results demonstrate the potential of using U. ohnoi in the phytoremediation of Cd in saltwater or brackish water.

The effect of salinity and alkalinity on growth and the accumulation of copper and zinc in the Chlorophyta Ulva fasciata.

Copper and zinc accumulation in macroalgae is a complex issue. While these metals exist as micronutrients and can serve to add nutritional value to the macroalgae when consumed by both plants and animals, elevated levels of the metals can reduce growth or even kill the algae. Many water parameters can influence the toxicity of the metals, though past studies have rarely isolated individual water parameters. This study aimed to independently determine the effects that salinity and alkalinity have on the growth and accumulation of these two metals on the macroalgae Ulva fasciata, distinguishing the effects of salinity and alkalinity as whole parameters from the collective effects of the water different constituents. The effect of salinity was determined using sodium chloride additions rather than seawater dilution, as performed in past studies, while alkalinity was tested using sodium bicarbonate additions to artificial seawater. The results of the study reinforce previous findings that copper is very toxic to macroalgae, even at low concentrations (50 µg L-1) though the effects of zinc remain inconclusive at 50 µg L-1, since the experiment was conducted over only a two-week trial period. The research suggests that salinity and alkalinity have no significant effect on the toxicity of copper to the growth of the macroalgae, but alkalinity significantly reduced copper and increased zinc accumulation in U. fasciata. The results of this study warrant further research in the field to investigate which other components of seawater and macroalgae reduce metal toxicity in the macroalgae. Additionally, these findings suggest the need for further refinement of toxicity models when adapted to macroalgae.

Copper excess detoxification is mediated by a coordinated and complementary induction of glutathione, phytochelatins and metallothioneins in the green seaweed Ulva compressa.

In order to analyze the involvement of intracellular thiol-chelators in the accumulation and detoxification of copper, the marine alga Ulva compressa was cultivated with increasing concentrations of copper such as 2.5, 5, 7.5 and 10 µM for up to 12 d, and the amount of intracellular copper, glutathione (GSH), phytochelatins (PCs) and transcripts encoding three metallothioneins (MTs) were determined. Over this exposure period and concentration range there was a linear correlation between intracellular copper and the copper concentration in the culture medium. Increases in GSH concentrations occurred mainly between days 1 and 3 and at lower concentrations of copper (2.5 and 5 µM). The level of PCs, and particularly PC2, increased from day 1 of exposure mainly at higher concentrations of copper (7.5 and 10 µM). The levels of transcripts encoding MT7 increased at day 3, whereas those of MT3 and MT6 increased between days 9-12, mainly at higher concentrations of copper. Thus in U. compressa, the initial responses to increasing intracellular copper concentrations are increases in GSH and PCs that are followed by higher levels of MTs expression, suggesting that thiol-containing peptides and proteins may participate in copper accumulation and detoxification responding in a coordinated and complementary manner. In addition, the alga was cultivated with 10 µM copper for 5 d and transferred to synthetic seawater with no copper and cultivated for 3 d. The release of copper from cells to culture medium was observed and accompanied by a similar nanomolar amount of GSH; no PCs or small proteins were detected. These results could suggest that a component of the detoxification mechanism also involves the release of copper and GSH to the extracellular medium.

Effect of oil spill stress on fatty acid stable carbon isotope composition of Ulva pertusa.

Petroleum is one of the most important pollutants in the marine ecosystem, and oil spills have a long-term effect on the marine environment. After an oil spill, petroleum continues to diffuse, flowing to the intertidal zone where it accumulates. Ulva pertusa is the main macroalgae species in the intertidal zone of the ocean, and petroleum is toxic to marine macroalgae. Fatty acids, which are involved in various physiological activities, including metabolism, are indispensable substances in organisms. Thus, an organism's fatty acid composition reflects its physiological state. Because fatty acids are carbon-rich compounds, their stable carbon isotope composition can be measured to assess the state of the organism. In this study, the effects of the water accommodated fraction (WAF) of different concentrations of 180# fuel oil and 0# diesel oil on the chlorophyll a and fatty acid carbon stable isotope composition (δ13CFAs) of U. pertusa were assessed. The fatty acid carbon stable isotope value varied among the different petroleum treatments, and high WAF concentrations significantly inhibited the synthesis of unsaturated fatty acids. Thus, exposure to petroleum products affected the synthesis of fatty acids in U. pertusa and also caused carbon stable isotope fractionation during the fatty acid synthesis process. The results indicate that the saturated fatty acid δ13C16:0 and the unsaturated fatty acid δ13C18:1 can be used as biomarkers to evaluate the degree of petroleum-induced stress in U. pertusa and that carbon stable isotope analysis of U. pertusa can be used as an environmental risk assessment tool in the intertidal zone.

Antimicrobial Fatty Acids from Green Alga Ulva rigida (Chlorophyta).

This study deals with the antimicrobial potential assessment of Ulva rigida, in regard to collection period and sampling site. Besides, we assess the chemical composition of bioactive compounds. For this purpose, Ulva rigida was seasonally collected from two northern sites in Tunisia, Cap Zebib rocky shore (CZ) and Ghar El Melh lagoon (GEM). Crude organic extracts were prepared using dichloromethane and dichloromethane/methanol and tested against 19 indicator microorganisms using the disk diffusion method and microdilution technique to determine the minimum inhibitory concentration (MIC). Silica gel column and thin layer chromatography were used for purification of active compounds. Nuclear magnetic resonance (NMR) and gas chromatography were used for compounds identification. Samples of Ulva rigida collected from the two sites have uniform antimicrobial activity throughout the year. Algae collected from the lagoon showed the largest spectrum of activity and were used for subsequent analysis. Bioguided purification of extracts from Ulva rigida, collected at GEM, leads to 16 active fractions with antibacterial effect mainly against Staphylococcus aureus ATCC 25923 and Enterococcus faecalis ATCC 29212. These fractions were identified as fatty acids, mainly oleic (C18: 1 w9), linoleic (C18: 2 w6), palmitic (C16: 0), and stearic (C14: 0). MICs values ranged from 10 to 250 µg/ml.