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Interactive Effects of Temperature and UV Radiation on Photosynthesis of Chlorella Strains from Polar, Temperate and Tropical Environments: Differential Impacts on Damage and Repair.

Wong CY, Teoh ML, Phang SM, Lim PE, Beardall J - PLoS ONE (2015)

Bottom Line: The three isolates of Chlorella from different regions showed different trends in their photosynthesis responses under the combined effects of UVR (PAR + UV-A + UV-B) and temperature.In accordance with the noted strain-specific characteristics, we can conclude that the repair (r) mechanisms at higher temperatures were not sufficient to overcome damage caused by UVR in the Antarctic Chlorella strain, suggesting negative effects of global climate change on microalgae inhabiting (circum-) polar regions.For temperate and tropical strains of Chlorella, damage from UVR was independent of temperature but the repair constant increased with increasing temperature, implying an improved ability of these strains to recover from UVR stress under global warming.

View Article: PubMed Central - PubMed

Affiliation: Department of Human Biology, International Medical University, No. 126, Jalan Jalil Perkasa 19, Bukit Jalil, 57000, Kuala Lumpur, Malaysia; Institute of Ocean & Earth Sciences, University of Malaya, 50603, Kuala Lumpur, Malaysia; National Antarctic Research Centre, Institute of Graduate Studies, University of Malaya, 50603, Kuala Lumpur, Malaysia.

ABSTRACT
Global warming and ozone depletion, and the resulting increase of ultraviolet radiation (UVR), have far-reaching impacts on biota, especially affecting the algae that form the basis of the food webs in aquatic ecosystems. The aim of the present study was to investigate the interactive effects of temperature and UVR by comparing the photosynthetic responses of similar taxa of Chlorella from Antarctic (Chlorella UMACC 237), temperate (Chlorella vulgaris UMACC 248) and tropical (Chlorella vulgaris UMACC 001) environments. The cultures were exposed to three different treatments: photosynthetically active radiation (PAR; 400-700 nm), PAR plus ultraviolet-A (320-400 nm) radiation (PAR + UV-A) and PAR plus UV-A and ultraviolet-B (280-320 nm) radiation (PAR + UV-A + UV-B) for one hour in incubators set at different temperatures. The Antarctic Chlorella was exposed to 4, 14 and 20°C. The temperate Chlorella was exposed to 11, 18 and 25°C while the tropical Chlorella was exposed to 24, 28 and 30°C. A pulse-amplitude modulated (PAM) fluorometer was used to assess the photosynthetic response of microalgae. Parameters such as the photoadaptive index (Ek) and light harvesting efficiency (α) were determined from rapid light curves. The damage (k) and repair (r) rates were calculated from the decrease in ΦPSIIeff over time during exposure response curves where cells were exposed to the various combinations of PAR and UVR, and fitting the data to the Kok model. The results showed that UV-A caused much lower inhibition than UV-B in photosynthesis in all Chlorella isolates. The three isolates of Chlorella from different regions showed different trends in their photosynthesis responses under the combined effects of UVR (PAR + UV-A + UV-B) and temperature. In accordance with the noted strain-specific characteristics, we can conclude that the repair (r) mechanisms at higher temperatures were not sufficient to overcome damage caused by UVR in the Antarctic Chlorella strain, suggesting negative effects of global climate change on microalgae inhabiting (circum-) polar regions. For temperate and tropical strains of Chlorella, damage from UVR was independent of temperature but the repair constant increased with increasing temperature, implying an improved ability of these strains to recover from UVR stress under global warming.

No MeSH data available.


Related in: MedlinePlus

Effect of temperature and UVR on the maximum quantum yield of fluorescence (ΦPSIImax) of (a) polar, (b) temperate and (c) tropical isolates of Chlorella.Vertical bars denote standard deviations from triplicate samples. Different letters indicate significant differences at p<0.05. PAR (filled), PAR + UV-A (open), PAR + UV-A + UV-B (hatched).
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pone.0139469.g001: Effect of temperature and UVR on the maximum quantum yield of fluorescence (ΦPSIImax) of (a) polar, (b) temperate and (c) tropical isolates of Chlorella.Vertical bars denote standard deviations from triplicate samples. Different letters indicate significant differences at p<0.05. PAR (filled), PAR + UV-A (open), PAR + UV-A + UV-B (hatched).

Mentions: A general trend was observed in the effect of UVR on maximum quantum yield (ΦPSIImax) of the three isolates of Chlorella. A significant reduction in ΦPSIImax was observed when the cultures were exposed to both PAR + UV-A and PAR + UV-A + UV-B compared to PAR alone (P<0.05) (Fig 1), with exposure to PAR+UVA+UVB causing maximum inhibition. However, isolates showed different trends in ΦPSIImax in their responses to increasing temperature. The effect of UVR on ΦPSIImax of both Antarctic and tropical Chlorella was temperature-dependent. The Antarctic Chlorella showed decreasing ΦPSIImax with increasing temperature under UVR exposure while the reverse trend was observed in the tropical Chlorella (Fig 1a). The ΦPSIImax values of the Antarctic Chlorella were 0.339, 0.163 and 0.156 when exposed to PAR + UV-A + UV-B at 4, 14 and 20°C, respectively. In contrast, the corresponding values of the tropical Chlorella were 0.181, 0.262, 0.314 when exposed PAR + UV-A + UV-B at 24, 28 and 30°C, respectively (Fig 1c). However, the reduction of ΦPSIImax in the temperate Chlorella under exposure to UVR was temperature-independent, whereby ΦPSIImax values at 11 and 25°C were significantly lower than that at 18°C (P<0.05) (ΦPSIImax = 0.116, 0.158 and 0.109 for 11, 18 and 25°C, respectively, under PAR + UV-A + UV-B) (Fig 1b).


Interactive Effects of Temperature and UV Radiation on Photosynthesis of Chlorella Strains from Polar, Temperate and Tropical Environments: Differential Impacts on Damage and Repair.

Wong CY, Teoh ML, Phang SM, Lim PE, Beardall J - PLoS ONE (2015)

Effect of temperature and UVR on the maximum quantum yield of fluorescence (ΦPSIImax) of (a) polar, (b) temperate and (c) tropical isolates of Chlorella.Vertical bars denote standard deviations from triplicate samples. Different letters indicate significant differences at p<0.05. PAR (filled), PAR + UV-A (open), PAR + UV-A + UV-B (hatched).
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4591349&req=5

pone.0139469.g001: Effect of temperature and UVR on the maximum quantum yield of fluorescence (ΦPSIImax) of (a) polar, (b) temperate and (c) tropical isolates of Chlorella.Vertical bars denote standard deviations from triplicate samples. Different letters indicate significant differences at p<0.05. PAR (filled), PAR + UV-A (open), PAR + UV-A + UV-B (hatched).
Mentions: A general trend was observed in the effect of UVR on maximum quantum yield (ΦPSIImax) of the three isolates of Chlorella. A significant reduction in ΦPSIImax was observed when the cultures were exposed to both PAR + UV-A and PAR + UV-A + UV-B compared to PAR alone (P<0.05) (Fig 1), with exposure to PAR+UVA+UVB causing maximum inhibition. However, isolates showed different trends in ΦPSIImax in their responses to increasing temperature. The effect of UVR on ΦPSIImax of both Antarctic and tropical Chlorella was temperature-dependent. The Antarctic Chlorella showed decreasing ΦPSIImax with increasing temperature under UVR exposure while the reverse trend was observed in the tropical Chlorella (Fig 1a). The ΦPSIImax values of the Antarctic Chlorella were 0.339, 0.163 and 0.156 when exposed to PAR + UV-A + UV-B at 4, 14 and 20°C, respectively. In contrast, the corresponding values of the tropical Chlorella were 0.181, 0.262, 0.314 when exposed PAR + UV-A + UV-B at 24, 28 and 30°C, respectively (Fig 1c). However, the reduction of ΦPSIImax in the temperate Chlorella under exposure to UVR was temperature-independent, whereby ΦPSIImax values at 11 and 25°C were significantly lower than that at 18°C (P<0.05) (ΦPSIImax = 0.116, 0.158 and 0.109 for 11, 18 and 25°C, respectively, under PAR + UV-A + UV-B) (Fig 1b).

Bottom Line: The three isolates of Chlorella from different regions showed different trends in their photosynthesis responses under the combined effects of UVR (PAR + UV-A + UV-B) and temperature.In accordance with the noted strain-specific characteristics, we can conclude that the repair (r) mechanisms at higher temperatures were not sufficient to overcome damage caused by UVR in the Antarctic Chlorella strain, suggesting negative effects of global climate change on microalgae inhabiting (circum-) polar regions.For temperate and tropical strains of Chlorella, damage from UVR was independent of temperature but the repair constant increased with increasing temperature, implying an improved ability of these strains to recover from UVR stress under global warming.

View Article: PubMed Central - PubMed

Affiliation: Department of Human Biology, International Medical University, No. 126, Jalan Jalil Perkasa 19, Bukit Jalil, 57000, Kuala Lumpur, Malaysia; Institute of Ocean & Earth Sciences, University of Malaya, 50603, Kuala Lumpur, Malaysia; National Antarctic Research Centre, Institute of Graduate Studies, University of Malaya, 50603, Kuala Lumpur, Malaysia.

ABSTRACT
Global warming and ozone depletion, and the resulting increase of ultraviolet radiation (UVR), have far-reaching impacts on biota, especially affecting the algae that form the basis of the food webs in aquatic ecosystems. The aim of the present study was to investigate the interactive effects of temperature and UVR by comparing the photosynthetic responses of similar taxa of Chlorella from Antarctic (Chlorella UMACC 237), temperate (Chlorella vulgaris UMACC 248) and tropical (Chlorella vulgaris UMACC 001) environments. The cultures were exposed to three different treatments: photosynthetically active radiation (PAR; 400-700 nm), PAR plus ultraviolet-A (320-400 nm) radiation (PAR + UV-A) and PAR plus UV-A and ultraviolet-B (280-320 nm) radiation (PAR + UV-A + UV-B) for one hour in incubators set at different temperatures. The Antarctic Chlorella was exposed to 4, 14 and 20°C. The temperate Chlorella was exposed to 11, 18 and 25°C while the tropical Chlorella was exposed to 24, 28 and 30°C. A pulse-amplitude modulated (PAM) fluorometer was used to assess the photosynthetic response of microalgae. Parameters such as the photoadaptive index (Ek) and light harvesting efficiency (α) were determined from rapid light curves. The damage (k) and repair (r) rates were calculated from the decrease in ΦPSIIeff over time during exposure response curves where cells were exposed to the various combinations of PAR and UVR, and fitting the data to the Kok model. The results showed that UV-A caused much lower inhibition than UV-B in photosynthesis in all Chlorella isolates. The three isolates of Chlorella from different regions showed different trends in their photosynthesis responses under the combined effects of UVR (PAR + UV-A + UV-B) and temperature. In accordance with the noted strain-specific characteristics, we can conclude that the repair (r) mechanisms at higher temperatures were not sufficient to overcome damage caused by UVR in the Antarctic Chlorella strain, suggesting negative effects of global climate change on microalgae inhabiting (circum-) polar regions. For temperate and tropical strains of Chlorella, damage from UVR was independent of temperature but the repair constant increased with increasing temperature, implying an improved ability of these strains to recover from UVR stress under global warming.

No MeSH data available.


Related in: MedlinePlus