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Effects of Cu2+, Ni2+, Pb2+, Zn2+ and pentachlorophenol on photosynthesis and motility in Chlamydomonas reinhardtii in short-term exposure experiments.

Danilov RA, Ekelund NG - BMC Ecol. (2001)

Bottom Line: Copper and pentachlorophenol turned out to be especially toxic for photosynthetic efficiency (PE) in C. reinhardtii.Copper and pentachlorophenol turned out to be especially toxic for PE in C. reinhardtii.Zinc has been concluded to be moderately toxic while nickel and lead had stimulatory effects on the PE.

View Article: PubMed Central - HTML - PubMed

Affiliation: Department of Natural and Environmental Sciences, Mid Sweden University, 871 88 Härnösand, Sweden. roman.danilov@tnv.mh.se

ABSTRACT

Background: Heavy metals, especially copper, nickel, lead and zinc, have adverse effects on terrestrial and in aquatic environments. However, their impact can vary depending on the nature of organisms. Taking into account the ability of heavy metals to accumulate in sediments, extended knowledge of their effects on aquatic biota is needed. In this context the use of model organisms (often unicellular), which allows for rapid assessment of pollutants in freshwater, can be of advantage. Pentachlorophenol has been extensively used for decades as a bleaching agent by pulp- and paper industry. Pentachlorophenol tends to accumulate in the nature. We aim to determine if photosynthesis and motility can be used as sensitive physiological parameters in toxicological studies of Chlamydomonas reinhardtii, a motile green unicellular alga. It is discussed if photosynthesis and motility can be used as sensitive physiological parameters in toxicological studies.

Results: The concentrations studied ranged from 0.1 to 2.0 mg l-1 for copper, nickel, lead and zinc, and from 0.1 to 10.0 mg l-1 for pentachlorophenol. Exposure time was set to 24 h. Copper and pentachlorophenol turned out to be especially toxic for photosynthetic efficiency (PE) in C. reinhardtii.

Conclusion: Copper and pentachlorophenol turned out to be especially toxic for PE in C. reinhardtii. Zinc has been concluded to be moderately toxic while nickel and lead had stimulatory effects on the PE. Because of high variance, motility was not considered a reliable physiological parameter when assessing toxicity of the substances using C. reinhardtii.

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The dependence of photosynthetic response curves in C. reinhardtii to different concentrations of pentachlorophenol (mg l-1) after 24 h exposure: a) 0.1, b) 0.5, c) 1.0, d) 5.0, e) 10.0. Thick solid line - oxygen evolution, thin dashed line - light evolution.
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Figure 5: The dependence of photosynthetic response curves in C. reinhardtii to different concentrations of pentachlorophenol (mg l-1) after 24 h exposure: a) 0.1, b) 0.5, c) 1.0, d) 5.0, e) 10.0. Thick solid line - oxygen evolution, thin dashed line - light evolution.

Mentions: The photosynthetic response curve (PRC) of the control was characterised by an increase in oxygen evolution according to the increase in PFD up to 612 μmol m-2 s-1 (the highest PFD-value used in the experiments) and a decrease in oxygen evolution due to the inhibition of photosynthesis when PFD became constant (612 μmol m-2 s-1, Fig. 1a). A peak of higher respiration immediately after the cessation of illumination can be explained by the light-enhanced dark respiration (LEDR, the rate of change of oxygen consumption - an acceleration), which contributed to the basal dark respiration. The behaviour of PRC is important evidence of how favourable the conditions are for photosynthesis [14]. The type of PRC described above was found in similar investigations to be typical in the green flagellate Euglena gracilis [15]. Similarly, this type of PRC can be considered as common in C. reinhardtii, too. At all treatments this basic type of PRC was observed. The stepwise drop in oxygen evolution at the maximum irradiance value in fig. 3a,b and fig. 5a,b should be considered as an artefact specific to the Light Pipette model used (when the value of oxygen saturation in the cuvette exceeds 200 %, unpublished results of a methodical study). Increasing concentrations of copper led to decrease in maximum values of oxygen evolution compared to the control, demonstrating especially severe impacts at the concentrations of 0.5 mg l-1 and higher (Fig. 1b,c,d,e,f). The treatments with nickel, lead or zinc did not caused such strong inhibitory effects as in the case of copper. Moreover, in the case of nickel (Fig. 2) maximum values of oxygen evolution were higher than those in the control and no inhibition of photosynthesis was observed when the PFD became constant (612 μmol m-2 s-1). Increasing concentrations of nickel seemed to be stimulative based on the shape of PRCs. Only slight inhibition of photosynthesis at the constant maximal PFD values was detected in the cases of lead or zinc treatments (Figs. 3, 4, respectively) and maximum values of oxygen evolution were equal to or higher than in the control. The treatment with pentachlorophenol led to prolongated compensation points at lower concentrations (0.1 and 0.5 mg l-1) and to severe impacts on photosynthesis at concentrations of 1.0 mg l-1 and higher (Fig. 5) comparable to those caused by copper treatments.


Effects of Cu2+, Ni2+, Pb2+, Zn2+ and pentachlorophenol on photosynthesis and motility in Chlamydomonas reinhardtii in short-term exposure experiments.

Danilov RA, Ekelund NG - BMC Ecol. (2001)

The dependence of photosynthetic response curves in C. reinhardtii to different concentrations of pentachlorophenol (mg l-1) after 24 h exposure: a) 0.1, b) 0.5, c) 1.0, d) 5.0, e) 10.0. Thick solid line - oxygen evolution, thin dashed line - light evolution.
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Related In: Results  -  Collection

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getmorefigures.php?uid=PMC32206&req=5

Figure 5: The dependence of photosynthetic response curves in C. reinhardtii to different concentrations of pentachlorophenol (mg l-1) after 24 h exposure: a) 0.1, b) 0.5, c) 1.0, d) 5.0, e) 10.0. Thick solid line - oxygen evolution, thin dashed line - light evolution.
Mentions: The photosynthetic response curve (PRC) of the control was characterised by an increase in oxygen evolution according to the increase in PFD up to 612 μmol m-2 s-1 (the highest PFD-value used in the experiments) and a decrease in oxygen evolution due to the inhibition of photosynthesis when PFD became constant (612 μmol m-2 s-1, Fig. 1a). A peak of higher respiration immediately after the cessation of illumination can be explained by the light-enhanced dark respiration (LEDR, the rate of change of oxygen consumption - an acceleration), which contributed to the basal dark respiration. The behaviour of PRC is important evidence of how favourable the conditions are for photosynthesis [14]. The type of PRC described above was found in similar investigations to be typical in the green flagellate Euglena gracilis [15]. Similarly, this type of PRC can be considered as common in C. reinhardtii, too. At all treatments this basic type of PRC was observed. The stepwise drop in oxygen evolution at the maximum irradiance value in fig. 3a,b and fig. 5a,b should be considered as an artefact specific to the Light Pipette model used (when the value of oxygen saturation in the cuvette exceeds 200 %, unpublished results of a methodical study). Increasing concentrations of copper led to decrease in maximum values of oxygen evolution compared to the control, demonstrating especially severe impacts at the concentrations of 0.5 mg l-1 and higher (Fig. 1b,c,d,e,f). The treatments with nickel, lead or zinc did not caused such strong inhibitory effects as in the case of copper. Moreover, in the case of nickel (Fig. 2) maximum values of oxygen evolution were higher than those in the control and no inhibition of photosynthesis was observed when the PFD became constant (612 μmol m-2 s-1). Increasing concentrations of nickel seemed to be stimulative based on the shape of PRCs. Only slight inhibition of photosynthesis at the constant maximal PFD values was detected in the cases of lead or zinc treatments (Figs. 3, 4, respectively) and maximum values of oxygen evolution were equal to or higher than in the control. The treatment with pentachlorophenol led to prolongated compensation points at lower concentrations (0.1 and 0.5 mg l-1) and to severe impacts on photosynthesis at concentrations of 1.0 mg l-1 and higher (Fig. 5) comparable to those caused by copper treatments.

Bottom Line: Copper and pentachlorophenol turned out to be especially toxic for photosynthetic efficiency (PE) in C. reinhardtii.Copper and pentachlorophenol turned out to be especially toxic for PE in C. reinhardtii.Zinc has been concluded to be moderately toxic while nickel and lead had stimulatory effects on the PE.

View Article: PubMed Central - HTML - PubMed

Affiliation: Department of Natural and Environmental Sciences, Mid Sweden University, 871 88 Härnösand, Sweden. roman.danilov@tnv.mh.se

ABSTRACT

Background: Heavy metals, especially copper, nickel, lead and zinc, have adverse effects on terrestrial and in aquatic environments. However, their impact can vary depending on the nature of organisms. Taking into account the ability of heavy metals to accumulate in sediments, extended knowledge of their effects on aquatic biota is needed. In this context the use of model organisms (often unicellular), which allows for rapid assessment of pollutants in freshwater, can be of advantage. Pentachlorophenol has been extensively used for decades as a bleaching agent by pulp- and paper industry. Pentachlorophenol tends to accumulate in the nature. We aim to determine if photosynthesis and motility can be used as sensitive physiological parameters in toxicological studies of Chlamydomonas reinhardtii, a motile green unicellular alga. It is discussed if photosynthesis and motility can be used as sensitive physiological parameters in toxicological studies.

Results: The concentrations studied ranged from 0.1 to 2.0 mg l-1 for copper, nickel, lead and zinc, and from 0.1 to 10.0 mg l-1 for pentachlorophenol. Exposure time was set to 24 h. Copper and pentachlorophenol turned out to be especially toxic for photosynthetic efficiency (PE) in C. reinhardtii.

Conclusion: Copper and pentachlorophenol turned out to be especially toxic for PE in C. reinhardtii. Zinc has been concluded to be moderately toxic while nickel and lead had stimulatory effects on the PE. Because of high variance, motility was not considered a reliable physiological parameter when assessing toxicity of the substances using C. reinhardtii.

Show MeSH
Related in: MedlinePlus