| 1. |
- Bonet, Berta, et al.
(författare)
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Antioxidant enzyme activities as biomarkers of Zn pollution in fluvial biofilms
- 2012
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Ingår i: Ecotoxicology and Environmental Safety. - : Elsevier BV. - 0147-6513 .- 1090-2414. ; 80, s. 172-178
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Tidskriftsartikel (refereegranskat)abstract
- The potential of the antioxidant enzyme catalase (CAT) and ascorbate peroxidase (APX) as molecular biomarkers of Zn toxicity in freshwater biofilms has been explored in this study jointly with other classical functional and structural endpoints (photosynthetic parameters, algal group composition and bioaccumulation). Biofilms were colonized in an indoor microcosm system for 5 weeks and then exposed to Zn for 5 weeks. To evaluate Zn effects, biofilms were sampled 5 and 3 days before exposure, just before exposure (time 0), and after 6h, 1, 3, 7, 21 and 35 days of metal exposure. Most endpoints measured were affected by Zn exposure (320μgZnL -1) during both periods of exposure. APX was the only functional parameter responding after a few hours of Zn exposure, highlighting its use as an early toxicity biomarker. Structural changes began after 3 days of exposure, starting with a decrease in algal biomass and an increase in the OD 430:665 ratio. Structural changes in biofilm communities were observed after 1 week, leading to a shift from diatoms to cyanobacteria and green algae-dominated communities. CAT activity was thereafter enhanced (after three weeks of exposure) and attributed not only to a direct effect of Zn bioaccumulation but also to an indirect effect of the community composition changes driven by chronic metal exposure. It can be concluded that biofilm antioxidant enzyme activities may provide evidence of early stress caused by metal exposure and also provide information about the mechanism of community adaptation. This information can be of great interest to improve current tools used for risk assessment. © 2012 Elsevier Inc.
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| 2. |
- Corcoll, Natàlia, 1981, et al.
(författare)
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Chl-a fluorescence parameters as biomarkers of metal toxicity in fluvial biofilms: An experimental study
- 2011
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Ingår i: Hydrobiologia. - : Springer Science and Business Media LLC. - 0018-8158 .- 1573-5117. ; 673, s. 119-136
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Tidskriftsartikel (refereegranskat)abstract
- A study was carried out to evaluate the sensitivity of different chlorophyll-a (chl-a) fluorescence parameters measured in freshwater biofilms as metal pollution biomarkers of short- and long-term metal exposures at environmentally realistic concentrations. A microcosm experiment was performed using indoor channels. Mature biofilms were exposed from hours to weeks to three different treatments: No-Metal, Zn (400 μg l-1); and Zn plus Cd (400 μg l-1 and 20 μg l-1, respectively). Metal concentration was based on a real case study: the Riou-Mort River (France). Biofilms exposed to Zn bioaccumulated similar Zn contents per dry weight to those exposed to the mixture (Zn plus Cd) causing a similar inhibition of the effective quantum yield, during the first hours of exposure. A reduction of the algal biomass, a shift in the community composition (a high reduction of diatoms), a reduction of the maximal quantum yield (ΦM) and a strong reduction of non-photochemical quenching (NPQ) were observed from day 14 until the end of the experiment (35 days). The results indicate that the effects of the metal mixture present in the Riou-Mort on biofilms could be attributed to Zn toxicity. The use of a set of chl-a fluorescence measurements, including photochemical and NPQ parameters, are recommended as a reliable biomarker tool box to evaluate both short- and long-term effects of metals on biofilms containing oxygenic photoautotrophs, suggesting its use in field applications. © 2011 Springer Science+Business Media B.V.
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| 3. |
- Corcoll, Natàlia, 1981, et al.
(författare)
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Light History Influences the Response of Fluvial Biofilms to Zn Exposure
- 2012
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Ingår i: Journal of Phycology. - : Wiley. - 0022-3646 .- 1529-8817. ; 48, s. 1411-1423
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Tidskriftsartikel (refereegranskat)abstract
- Fluvial biofilms are subject to multistress situations in natural ecosystems, such as the co-occurrence of light intensity changes and metal toxicity. However, studies simultaneously addressing both factors are rare. This study evaluated in microcosm conditions the relationship between short-term light intensity changes and Zn toxicity on fluvial biofilms with long-term photoacclimation to different light conditions. Biofilms that had long-term photoacclimation to 25 μmol photons · m-2 · s-1 (low light [LL] biofilms), 100 μmol photons · m-2 · s-1 (medium light [ML] biofilms), and 500 μmol photons · m-2 · s-1 (high light [HL] biofilms) were characterized by different structural (Chlorophyll-a [Chl-a], total biomass-AFDW, EPS, algal groups, and diatom taxonomy) and physiological attributes (ETR-I curves and photosynthetic pigments). HL biofilms showed higher light saturation intensity and a higher production of xanthophylls than LL biofilms. In contrast, LL biofilms had many structural differences; a higher proportion of diatoms and lower AFDW and EPS contents than ML and HL biofilms. A clear effect of light intensity changes on Zn toxicity was also demonstrated. Zn toxicity was enhanced when a sudden increase in light intensity also occurred, mainly with LL biofilms, causing higher inhibition of both the Φ′PSII and the ΦPSII. A decoupling of NPQ from de-epoxidation reaction (DR) processes was also observed, indicating substantial damage to photoprotective mechanisms functioning in biofilms (i.e., xanthophyll cycle of diatoms) due to Zn toxicity. This study highlights the need to take into account environmental stress (e.g., light intensity changes) to better assess the environmental risks of chemicals (e.g., metals). © Phycological Society of America.
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| 4. |
- Corcoll, Natàlia, 1981, et al.
(författare)
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The effect of metals on photosynthesis processes and diatom metrics of biofilm from a metal-contaminated river: A translocation experiment
- 2012
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Ingår i: Ecological Indicators. - : Elsevier BV. - 1470-160X. ; 18, s. 620-631
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Tidskriftsartikel (refereegranskat)abstract
- With the aim of evaluating cause-effect relationships between metal pollution and biofilm structure and function, a translocation study was performed in a metal-polluted stream (the Osor stream "la riera d'Osor", NE Spain). Biofilm responses were measured as temporal changes in chl-a fluorescence parameters, pigment composition and diatom species composition. Biofilms from a non-polluted site were translocated to four downstream sites presenting a gradient of metal pollution, corresponding to scenarios of low and moderate metal pollution. Metal effects (Zn bioaccumulation, Fe bioaccumulation and Zn in water) were distinguished from other stressors (phosphate concentration in water). Based on the results obtained, a fast bioaccumulation of Zn (after few hours of exposure) was linked to a decrease in photosynthetic efficiency and an enhancement of mechanisms of protection through the xanthophyll cycle. After longer exposure, differences in Zn and Fe bioaccumulation and Zn water concentration between sites were linked to diatom community changes; decrease in diatom cell biovolume, along with a decrease in the IPS index of diatoms. Based on our results, we recommend including Zn in the list of priority pollutant substances of the European Water Framework Directive (2000/60/EC), due to its occurrence and toxicity. In addition, our study supports the use of chl-a fluorescence parameters together with the analysis of photosynthetic pigments of biofilms as suitable functional endpoints of early toxicity. Furthermore, diatom community studies are recommended for their clear response after chronic exposure. However, new diatom indices beyond the use of the IPS are required to increase their sensitivity to metal pollution, e.g. to identify the damage caused by moderate to low metal pollution. © 2012 Elsevier Ltd. All rights reserved.
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| 5. |
- Tlili, Ahmed, et al.
(författare)
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In situ spatio-temporal changes in pollution-induced community tolerance to zinc in autotrophic and heterotrophic biofilm communities
- 2011
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Ingår i: Ecotoxicology. - : Springer Science and Business Media LLC. - 0963-9292 .- 1573-3017. ; 20, s. 1823-1839
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Tidskriftsartikel (refereegranskat)abstract
- Pollution-induced community tolerance (PICT) uses increased tolerance in populations at contaminated sites as an indicator of contaminant effects. However, given the broad structural and functional complexity that characterizes biological communities, the acquisition of PICT could vary with (i) target community, (ii) intensity of toxicant exposure, (iii) the species succession stage, and (iv) the physicochemical characteristics of the studied site. To assess the spatio-temporal changes of zinc-induced tolerance in fluvial biofilm communities, we conducted an in situ study in Osor River (North-East Catalonia, Spain), which has zinc contamination. Biofilms were developed for 5 weeks in a non-metal-polluted site, and were then transferred to different sites in Osor River with different levels of zinc contamination. The spatio-temporal changes of biofilm PICT to zinc was determined using photosynthetic activity bioassays and respiration-induced aerobic bioassays at T 0, and at 1, 3 and 5 weeks of exposure. We also performed physicochemical characterization of the sites, taxonomic analysis of diatoms, bacterial and fungal diversity and profiled pigments of phototrophic communities. We used multivariate ordination to analyze results. In addition to natural species succession, the intensity of metal pollution exerted structural pressure by selecting the most metal-tolerant species, but differently depending on the type of biofilm. Zn-tolerance values indicated that exposure to high levels of zinc had effects that were similar to a longer exposure to lower levels of zinc. © 2011 Springer Science+Business Media, LLC.
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