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Silver nanoparticle dissolution in the presence of ligands and of hydrogen peroxide
2015
Sigg, Laura | Lindauer, Ursula
Dissolution of silver nanoparticles (AgNP with carbonate or citrate coating, total Ag 1–5 μM) was examined in the presence of the ligands cysteine, chloride and fulvic acids and of the oxidant hydrogen peroxide (H2O2) at low concentrations at pH 7.5. Dissolved Ag was separated from AgNP by ultrafiltration. Cysteine in the concentration range 0.2–5 μM resulted in an initial increase of dissolved Ag within few hours. Chloride (up to 0.1 mM) and fulvic acids (up to 15 mg L−1) had little effect on the dissolution of AgNP within hours to days. In contrast, very rapid dissolution within 1–2 h of both carbonate and citrate coated AgNP was observed in the presence of H2O2 in the concentration range 0.1–10 μM, under dark or light conditions. The high efficiency of H2O2 in dissolving AgNP is likely to be of importance in toxic effects of AgNP to algae, as H2O2 is produced and released into solution by algae.
Afficher plus [+] Moins [-]Tracking polycyclic aromatic hydrocarbons in lichens: It's all about the algae
2015
Augusto, Sofia | Sierra, Jordi | Nadal, Martí | Schuhmacher, Marta
Lichens, symbioses of fungi and algae and/or cyanobacteria, have the remarkable ability to uptake and accumulate semivolatile organic compounds (SVOC) from air, including polycyclic aromatic hydrocarbons (PAHs), but the mechanism of accumulation is still unknown. Understanding these mechanisms is critical to standardize the use of lichens as environmental bioindicators and to further integrate them in air monitoring networks. Through a series of experiments we show that gas phase PAHs easily cross lichen's surface and accumulate in the photosynthetic algal layer of lichens. Once accumulated, they remain in the algal layer and not within the fungus hyphae, or adhered to lichen's surface, as it was previously supposed to happen. Additionally, when lichens are washed, gas phase PAHs still remain in the algal layer. Our results reveal that lichens may be utilized as bioindicators of gas phase PAHs, overcoming current limitations of air monitoring.
Afficher plus [+] Moins [-]Interactions of multiwalled carbon nanotubes with algal cells: Quantification of association, visualization of uptake, and measurement of alterations in the composition of cells
2015
Rhiem, Stefan | Riding, Matthew J. | Baumgartner, Werner | Martin, Francis L. | Semple, K. T. (Kirk T.) | Jones, K. C. (Kevin C.) | Schäffer, Andreas | Maes, Hanna M.
Carbon nanotubes (CNTs) are considered promising materials in nanotechnology. We quantified CNT accumulation by the alga Desmodesmus subspicatus. Cells were exposed to radiolabeled CNTs (14C-CNTs; 1 mg/L) to determine uptake and association, as well as elimination and dissociation in clear media. Attenuated total reflection Fourier-transform infrared spectroscopy (ATR-FTIR) was used to detect effects of CNTs on algae. CNT-cell interactions were visualized by electron microscopy and related to alterations in their cell composition. A concentration factor of 5000 L/kg dry weight was calculated. Most of the material agglomerated around the cells, but single tubes were detected in the cytoplasm. Computational analyses of the ATR-FTIR data showed that CNT treated algae differed from controls at all sampling times. CNT exposure changed the biochemical composition of cells. The fact that CNTs are bioavailable for algae and that they influence the cell composition is important with regard to environmental risk assessment of this nanomaterial.
Afficher plus [+] Moins [-]What does impacted look like? High diversity and abundance of epibiota in modified estuaries
2015
Clark, Graeme F. | Kelaher, Brendan P. | Dafforn, Katherine A. | Coleman, Melinda A. | Knott, Nathan A. | Marzinelli, Ezequiel M. | Johnston, Emma L.
Ecosystems modified by human activities are generally predicted to be biologically impoverished. However, much pollution impact theory stems from laboratory or small-scale field studies, and few studies replicate at the level of estuary. Furthermore, assessments are often based on sediment contamination and infauna, and impacts to epibiota (sessile invertebrates and algae) are seldom considered. We surveyed epibiota in six estuaries in south-east Australia. Half the estuaries were relatively pristine, and half were subject to internationally high levels of contamination, urbanisation, and industrialisation. Contrary to predictions, epibiota in modified estuaries had greater coverage and were similarly diverse as those in unmodified estuaries. Change in epibiota community structure was linearly correlated with sediment-bound copper, and the tubeworm Hydroides elegans showed a strong positive correlation with sediment metals. Stressors such as metal contamination can reduce biodiversity and productivity, but others such as nutrient enrichment and resource provision may obscure signals of impact.
Afficher plus [+] Moins [-]Effects of atrazine on egg masses of the yellow-spotted salamander (Ambystoma maculatum) and its endosymbiotic alga (Oophila amblystomatis)
2015
Baxter, Leilan | Brain, Richard A. | Hosmer, Alan J. | Nema, Mohini | Müller, Kirsten M. | Solomon, Keith R. | Hanson, Mark L.
Embryonic growth of the yellow-spotted salamander (Ambystoma maculatum) is enhanced by the presence of the green alga Oophila amblystomatis, in the egg capsule. To further assess potential impacts of herbicides on this relationship, A. maculatum egg masses were exposed to atrazine (0–338 μg/L) until hatching (up to 66 days). Exposure to atrazine reduced PSII yield of the symbiotic algae in a concentration-dependent manner, but did not significantly affect visible algal growth or any metrics associated with salamander development. Algal cells were also cultured in the laboratory for toxicity testing. In the 96-h growth inhibition test (0–680 μg/L), ECx values were generally greater than those reported for standard algal test species. Complete recovery of growth rates occurred within 96-h of transferring cells to untreated media. Overall, development of A. maculatum embryos was not affected by exposure to atrazine at concentrations and durations exceeding those found in the environment.
Afficher plus [+] Moins [-]Spatio-temporal variations in biomass and mercury concentrations of epiphytic biofilms and their host in a large river wetland (Lake St. Pierre, Qc, Canada)
2015
Hamelin, Stéphanie | Planas, Dolors | Amyot, Marc
Within wetlands, epiphytes and macrophytes play an important role in storage and transfer of metals, through the food web. However, there is a lack of information about spatial and temporal changes in their metal levels, including those of mercury (Hg), a key priority contaminant of aquatic systems. We assessed total mercury (THg) and methylmercury (MeHg) concentrations of epiphyte/macrophyte complexes in Lake St. Pierre, a large fluvial lake of the St. Lawrence River (Québec, Canada). THg and MeHg concentrations were ten fold higher in epiphytes than in macrophytes. THg concentrations in epiphytes linearly decreased as a function of the autotrophic index, suggesting a role of algae in epiphyte Hg accumulation, and % of MeHg in epiphytes reached values as high as 74%. Spatio-temporal variability in THg and MeHg concentrations in epiphytes and macrophytes were influenced by water temperature, available light, host species, water level, dissolved organic carbon and dissolved oxygen.
Afficher plus [+] Moins [-]Biosorption of nonylphenol by pure algae, field-collected planktons and their fractions
2015
Zhang, Dainan | Ran, Yong | Cao, Xiaoyan | Mao, Jingdong | Cui, Jinfang | Schmidt-Rohr, Klaus
Algal samples were fractionated into lipid (LP), lipid free (LF), alkaline nonhydrolyzable carbon (ANHC), and acid nonhydrolyzable carbon (NHC) fractions, and were characterized by the quantitative 13C multiCP NMR technique. The biosorption isotherms for nonylphenol (NP) were established and compared with previously published data for phenanthrene (Phen). The log KOC values are significantly higher for the field-collected plankton samples than for the commercial algae and cultured algae samples, correlating with their lipid contents and aliphatic carbon structure. As the NHC fraction contains more poly(methylene) carbon, it exhibits a higher biosorption capacity. The sorption capacities are negatively related to the polarity index, COO/N–C=O, polar C and O-alkyl C concentrations, but are positively related to the H/O atomic ratios and poly(methylene) carbon. The higher sorption capacities observed for NP than for Phen on the investigated samples are explained by specific interactions such as hydrogen bonding and π–π interaction.
Afficher plus [+] Moins [-]Responses of primary production, leaf litter decomposition and associated communities to stream eutrophication
2015
Dunck, Bárbara | Lima-Fernandes, Eva | Cássio, Fernanda | Cunha, Ana | Rodrigues, Liliana | Pascoal, Cláudia
We assessed the eutrophication effects on leaf litter decomposition and primary production, and on periphytic algae, fungi and invertebrates. According to the subsidy-stress model, we expected that when algae and decomposers were nutrient limited, their activity and diversity would increase at moderate levels of nutrient enrichment, but decrease at high levels of nutrients, because eutrophication would lead to the presence of other stressors and overwhelm the subsidy effect. Chestnut leaves (Castanea sativa Mill) were enclosed in mesh bags and immersed in five streams of the Ave River basin (northwest Portugal) to assess leaf decomposition and colonization by invertebrates and fungi. In parallel, polyethylene slides were attached to the mesh bags to allow colonization by algae and to assess primary production. Communities of periphytic algae and decomposers discriminated the streams according to the trophic state. Primary production decomposition and biodiversity were lower in streams at both ends of the trophic gradient.
Afficher plus [+] Moins [-]Relative bioavailability and toxicity of fuel oils leaking from World War II shipwrecks
2015
Faksness, Liv-Guri | Daling, Per | Altin, Dag | Dolva, Hilde | Fosbæk, Bjørn | Bergstrøm, Rune
The Norwegian Authorities have classified 30 WWII shipwrecks to have a considerable potential for pollution to the environment, based on the location and condition of the wreck and the types and amount of fuel. Oil thus far has been removed from eight of these shipwrecks. The water accommodated fractions of oils from two British wrecks and two German wrecks have been studied with special emphasis on chemistry and biological effects (algae growth (Skeletonema costatum) and copepod mortality (Calanus finmarchicus)). Chemical analyses were also performed on three additional German wreck oils. The results from these studies show that the coal based oils from German WWII shipwrecks have higher toxicity to marine organisms than the mineral oils from the British shipwrecks. The potential for higher impact on the marine environment of coal based oils has resulted in an altering of the priority list for oil recovery from WWII wrecks by the authorities.
Afficher plus [+] Moins [-]Radioactivity levels in the marine environment along the Exclusive Economic Zone (EEZ) of Qatar
2015
Al-Qaradawi, Ilham | Abdel-Moati, Mohamed | Al-Yafei, Mohsin Al-Ansi | Al-Ansari, Ebrahim | Al-Maslamani, Ibrahim | Holm, E. (Elis) | Al-Shaikh, Ismail | Mauring, Alexander | Pinto, Primal V. | Abdulmalik, Dana | Amir, Amina | Miller, Mark | Yigiterhan, Oguz | Persson, Bertil
A study on 137Cs, 40K, 226Ra, 228Ra, and 238U was carried out along the EEZ of Qatar. Results serve as the first ever baseline data. The level of 137Cs (mean value 1.6±0.4Bqm−3) in water filters was found to be in the same order of magnitude as reported by others in worldwide marine radioactivity studies. Results are also in agreement with values reported from other Gulf regions. The computed values of sediment–water distribution coefficients Kd, are lower than the values given by IAEA. Measurements were carried out for bottom sediments, biota samples like fish, oyster, sponge, seashell, mangrove, crab, shrimp, starfish, dugong and algae. The ‘concentration factors’ reported for biota samples are below the levels published by IAEA and cause no significant impact on human health for seafood consumers in Qatar.
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