scholarly journals Ocean acidification mediates photosynthetic response to UV radiation and temperature increase in the diatom <i>Phaeodactylum tricornutum</i>

2012 ◽  
Vol 9 (10) ◽  
pp. 3931-3942 ◽  
Author(s):  
Y. Li ◽  
K. Gao ◽  
V. E. Villafañe ◽  
E. W. Helbling
Keyword(s):  
Ocean Acidification ◽  
Elevated Co2 ◽  
Uv Radiation ◽  
Phaeodactylum Tricornutum ◽  
Carbon Fixation ◽  
Co2 Concentration ◽  
Photochemical Quenching ◽  
Fixation Rate ◽  
Ps Ii ◽  
Temperature Levels

Abstract. Increasing atmospheric CO2 concentration is responsible for progressive ocean acidification, ocean warming as well as decreased thickness of upper mixing layer (UML), thus exposing phytoplankton cells not only to lower pH and higher temperatures but also to higher levels of solar UV radiation. In order to evaluate the combined effects of ocean acidification, UV radiation and temperature, we used the diatom Phaeodactylum tricornutum as a model organism and examined its physiological performance after grown under two CO2 concentrations (390 and 1000 μatm) for more than 20 generations. Compared to the ambient CO2 level (390 μatm), growth at the elevated CO2 concentration increased non-photochemical quenching (NPQ) of cells and partially counteracted the harm to PS II (photosystem II) caused by UV-A and UV-B. Such an effect was less pronounced under increased temperature levels. The ratio of repair to UV-B induced damage decreased with increased NPQ, reflecting induction of NPQ when repair dropped behind the damage, and it was higher under the ocean acidification condition, showing that the increased pCO2 and lowered pH counteracted UV-B induced harm. As for photosynthetic carbon fixation rate which increased with increasing temperature from 15 to 25 °C, the elevated CO2 and temperature levels synergistically interacted to reduce the inhibition caused by UV-B and thus increase the carbon fixation.

scholarly journals Ocean acidification mediates photosynthetic response to UV radiation and temperature increase in the diatom <i>Phaeodactylum tricornutum</i>

2012 ◽  
Vol 9 (6) ◽  
pp. 7197-7226 ◽  
Author(s):  
Y. Li ◽  
K. Gao ◽  
V. E. Villafañe ◽  
E. W. Helbling
Keyword(s):  
Ocean Acidification ◽  
Uv Radiation ◽  
Phaeodactylum Tricornutum ◽  
Carbon Fixation ◽  
Mixing Layer ◽  
Model Organism ◽  
Co2 Concentration ◽  
Photochemical Quenching ◽  
Temperature Levels ◽  
Increasing Temperature

Abstract. Increasing atmospheric CO2 concentration is responsible for progressive ocean acidification, ocean warming as well as decreased thickness of upper mixing layer (UML), thus exposing phytoplankton cells not only to lower pH and higher temperatures but also to higher levels of solar UV radiation. In order to evaluate the combined effects of ocean acidification, UV radiation and temperature, we used the diatom Phaeodactylum tricornutum as a model organism and examined its physiological performance after grown under two CO2 concentrations (390 and 1000 µatm) for more than 20 generations. Compared to the ambient CO2 level (390 µatm), growth at the elevated CO2 concentration increased non-photochemical quenching (NPQ) of cells and partially counteracted the harm to PSII caused by UV-A and UV-B. Such an effect was less pronounced under increased temperature levels. As for photosynthetic carbon fixation, the rate increased with increasing temperature from 15 to 25 °C, regardless of their growth CO2 levels. In addition, UV-induced inhibition of photosynthesis was inversely correlated to temperature. The ratio of repair to UV-induced damage showed inverse relationship with increased NPQ, showing higher values under the ocean acidification condition against UV-B, reflecting that the increased pCO2 and lowered pH counteracted UV-B induced harm.

scholarly journals Nitrate limitation and ocean acidification interact with UV-B to reduce photosynthetic performance in the diatom <i>Phaeodactylum tricornutum</i>

2015 ◽  
Vol 12 (8) ◽  
pp. 2383-2393 ◽  
Author(s):  
W. Li ◽  
K. Gao ◽  
J. Beardall
Keyword(s):  
Ocean Acidification ◽  
Uv Radiation ◽  
Phaeodactylum Tricornutum ◽  
Nitrogen Limitation ◽  
Multiple Stressors ◽  
Photosynthetic Performance ◽  
Photochemical Quenching ◽  
Low Co2 ◽  
Uv Irradiance ◽  
Non Photochemical Quenching

Abstract. It has been proposed that ocean acidification (OA) will interact with other environmental factors to influence the overall impact of global change on biological systems. Accordingly we investigated the influence of nitrogen limitation and OA on the physiology of diatoms by growing the diatom Phaeodactylum tricornutum Bohlin under elevated (1000 μatm; high CO2 – HC) or ambient (390 μatm; low CO2 – LC) levels of CO2 with replete (110 μmol L−1; high nitrate – HN) or reduced (10 μmol L−1; low nitrate – LN) levels of NO3- and subjecting the cells to solar radiation with or without UV irradiance to determine their susceptibility to UV radiation (UVR, 280–400 nm). Our results indicate that OA and UVB induced significantly higher inhibition of both the photosynthetic rate and quantum yield under LN than under HN conditions. UVA or/and UVB increased the cells' non-photochemical quenching (NPQ) regardless of the CO2 levels. Under LN and OA conditions, activity of superoxide dismutase and catalase activities were enhanced, along with the highest sensitivity to UVB and the lowest ratio of repair to damage of PSII. HC-grown cells showed a faster recovery rate of yield under HN but not under LN conditions. We conclude therefore that nutrient limitation makes cells more prone to the deleterious effects of UV radiation and that HC conditions (ocean acidification) exacerbate this effect. The finding that nitrate limitation and ocean acidification interact with UV-B to reduce photosynthetic performance of the diatom P. tricornutum implies that ocean primary production and the marine biological C pump will be affected by OA under multiple stressors.

scholarly journals Physiological and biochemical responses of <i>Emiliania huxleyi</i> to ocean acidification and warming are modulated by UV radiation

2017 ◽  
Author(s):  
Shanying Tong ◽  
David A. Hutchins ◽  
Kunshan Gao
Keyword(s):  
Ocean Acidification ◽  
Uv Radiation ◽  
Carbon Fixation ◽  
Co2 Concentration ◽  
Emiliania Huxleyi ◽  
Marine Phytoplankton ◽  
Negative Effects ◽  
Photosynthetic Carbon Fixation ◽  
Photosynthetic Carbon ◽  
Increasing Temperature

Abstract. Marine phytoplankton such as bloom-forming, calcite-producing coccolithophores, are naturally exposed to solar UV radiation (UVR, 280–400 nm) in the ocean's upper mixed layers. Nevertheless, effects of increasing CO2-induced ocean acidification and warming have rarely been investigated in the presence of UVR. We examined calcification and photosynthetic carbon fixation performance in the most cosmopolitan coccolithophorid, Emiliania huxleyi, grown under high (1000 μatm, HC; pHT: 7.70) and low (400 μatm, LC; pHT: 8.02) CO2 levels, at 15 °C (LT), 20 °C (MT) and 24 °C (HT) with or without UVR. The HC treatment didn't affect photosynthetic carbon fixation at 15 °C, but significantly enhanced it with increasing temperature. Exposure to UVR inhibited photosynthesis, with higher inhibition by UVA (320–395 nm) than UVB (295–320 nm), except in the HC and 24 °C-grown cells, in which UVB caused more inhibition than UVA. Reduced thickness of the coccolith layer in the HC-grown cells appeared to be responsible for the UV-induced inhibition, and an increased repair rate of UVA-derived damage in the HCHT-grown cells could be responsible for lowered UVA-induced inhibition. While calcification was reduced with the elevated CO2 concentration, exposure to UVB or UVA affected it differentially, with the former inhibiting and the latter enhancing it. UVA-induced stimulation of calcification was higher in the HC-grown cells at 15 and 20 °C, whereas at 24 °C, observed enhancement was not significant. The calcification to photosynthesis ratio (Cal / Pho ratio) was lower in the HC treatment, and increasing temperature also lowered the value. However, at 20 and 24 °C, exposures to UVR significantly increased the Cal / Pho ratio, especially in HC-grown cells, by up to 100 %. This implies that UVR can counteract the negative effects of the greenhouse treatment on the Cal / Pho ratio, and so may be a key stressor when considering the impacts of future greenhouse conditions on E. huxleyi.

scholarly journals CO<sub>2</sub>-induced seawater acidification affects physiological performance of the marine diatom <i>Phaeodactylum tricornutum</i>

2010 ◽  
Vol 7 (9) ◽  
pp. 2915-2923 ◽  
Author(s):  
Y. Wu ◽  
K. Gao ◽  
U. Riebesell
Keyword(s):  
Phaeodactylum Tricornutum ◽  
Carbon Fixation ◽  
Dissolved Inorganic Carbon ◽  
Dark Respiration ◽  
Marine Diatom ◽  
Photochemical Quenching ◽  
Negative Effects ◽  
High Co2 ◽  
Seawater Acidification ◽  
Key Factor

Abstract. CO2/pH perturbation experiments were carried out under two different pCO2 levels (39.3 and 101.3 Pa) to evaluate effects of CO2-induced ocean acidification on the marine diatom Phaeodactylum tricornutum. After acclimation (>20 generations) to ambient and elevated CO2 conditions (with corresponding pH values of 8.15 and 7.80, respectively), growth and photosynthetic carbon fixation rates of high CO2 grown cells were enhanced by 5% and 12%, respectively, and dark respiration stimulated by 34% compared to cells grown at ambient CO2. The half saturation constant (Km) for carbon fixation (dissolved inorganic carbon, DIC) increased by 20% under the low pH and high CO2 condition, reflecting a decreased affinity for HCO3– or/and CO2 and down-regulated carbon concentrating mechanism (CCM). In the high CO2 grown cells, the electron transport rate from photosystem II (PSII) was photoinhibited to a greater extent at high levels of photosynthetically active radiation, while non-photochemical quenching was reduced compared to low CO2 grown cells. This was probably due to the down-regulation of CCM, which serves as a sink for excessive energy. The balance between these positive and negative effects on diatom productivity will be a key factor in determining the net effect of rising atmospheric CO2 on ocean primary production.

scholarly journals CO<sub>2</sub>-induced seawater acidification affects physiological performance of the marine diatom <I>Phaeodactylum tricornutum</I>

2010 ◽  
Vol 7 (3) ◽  
pp. 3855-3878 ◽  
Author(s):  
Y. Wu ◽  
K. Gao ◽  
U. Riebesell
Keyword(s):  
Phaeodactylum Tricornutum ◽  
Carbon Fixation ◽  
Dissolved Inorganic Carbon ◽  
Dark Respiration ◽  
Atmospheric Co2 ◽  
Marine Diatom ◽  
Photochemical Quenching ◽  
Negative Effects ◽  
High Co2 ◽  
Seawater Acidification

Abstract. CO2/pH perturbation experiments were carried out under two different pCO2 levels (39.3 and 101.3 Pa) to evaluate effects of CO2-induced ocean acidification on the marine diatom Phaeodactylum tricornutum. After acclimation (>20 generations) to ambient and elevated CO2 conditions (with corresponding pH values of 8.15 and 7.80, respectively), growth and photosynthetic carbon fixation rates of high CO2 grown cells were enhanced by 5% and 12%, respectively, and dark respiration stimulated by 34% compared to cells grown at ambient CO2. The K1/2 (dissolved inorganic carbon, DIC) for carbon fixation increased by 20% under the low pH and high CO2 condition, reflecting a decreased photosynthetic affinity for HCO3− or/and CO2 and down-regulated carbon concentrating mechanism (CCM). In the high CO2 grown cells, the electron transport rate from photosystem II (PSII) was photoinhibited to a greater extent at high levels of photosynthetically active radiation, while non-photochemical quenching was reduced compared to low CO2 grown cells. This was probably due to the down-regulation of CCM, which serves as a sink for excessive energy. Increasing seawater pCO2 and decreasing pH associated with atmospheric CO2 rise may enhance diatom growth, down-regulate their CCM, and enhanced their photo-inhibition and dark respiration. The balance between these positive and negative effects on diatom productivity will be a key factor in determining the net effect of rising atmospheric CO2 on ocean primary production.

scholarly journals Nitrate limitation and ocean acidification interact with UV-B to reduce photosynthetic performance in the diatom <i>Phaeodactylum tricornutum</i>

2014 ◽  
Vol 11 (12) ◽  
pp. 17675-17706 ◽  
Author(s):  
W. Li ◽  
K. Gao ◽  
J. Beardall
Keyword(s):  
Superoxide Dismutase ◽  
Ocean Acidification ◽  
Phaeodactylum Tricornutum ◽  
Nitrogen Limitation ◽  
Multiple Stressors ◽  
Photosynthetic Performance ◽  
Photochemical Quenching ◽  
Uv Irradiance ◽  
Co2 Levels ◽  
Non Photochemical Quenching

Abstract. It has been proposed that ocean acidification (OA) will interact with other environmental factors to influence the overall impact of global change on biological systems. Accordingly we investigated the influence of nitrogen limitation and OA on the physiology of diatoms by growing the diatom Phaeodactylum tricornutum Bohlin under elevated (1000 μatm, HC) or ambient (390 μatm, LC) levels of CO2 with replete (110 μmol L-1, HN) or reduced (10 μmol L-1, LN) levels of NO3- and subjecting the cells to solar radiation with or without UV irradiance to determine their susceptibility to UV radiation (280–400 nm). Our results indicate that OA and UVB induced significantly higher inhibition of both the photosynthetic rate and quantum yield under LN than under HN conditions. UVA or/and UVB increased the cells' non-photochemical quenching (NPQ) regardless of the CO2 levels. Under LN and OA conditions, activity of superoxide dismutase and catalase activities were enhanced, along with the highest sensitivity to UVB and the lowest ratio of repair to damage of PSII. HC-grown cells showed a faster recovery rate of yield under HN but not under LN conditions. The finding that nitrate limitation and ocean acidification interact with UV-B to reduce photosynthetic performance of the diatom P. tricornutum implies that ocean primary production and the marine biological C pump will be affected by the OA under multiple stressors.

scholarly journals Carboxylation Capacity Can Limit C3 Photosynthesis at Elevated CO2 throughout Diurnal Cycles

Plants ◽  
2021 ◽  
Vol 10 (12) ◽  
pp. 2603
Author(s):  
James Bunce
Keyword(s):  
Elevated Co2 ◽  
Carbon Fixation ◽  
Leaf Gas Exchange ◽  
Co2 Concentration ◽  
Ambient Air ◽  
Early Morning ◽  
C3 Plants ◽  
Lablab Purpureus ◽  
Diurnal Cycles ◽  
Air Temperatures

The response of carbon fixation in C3 plants to elevated CO2 is relatively larger when photosynthesis is limited by carboxylation capacity (VC) than when limited by electron transport (J). Recent experiments under controlled, steady-state conditions have shown that photosynthesis at elevated CO2 may be limited by VC even at limiting PPFD. These experiments were designed to test whether this also occurs in dynamic field environments. Leaf gas exchange was recorded every 5 min using two identical instruments both attached to the same leaf. The CO2 concentration in one instrument was controlled at 400 μmol mol−1 and one at 600 μmol mol−1. Leaves were exposed to ambient sunlight outdoors, and cuvette air temperatures tracked ambient outside air temperature. The water content of air in the leaf cuvettes was kept close to that of the ambient air. These measurements were conducted on multiple, mostly clear days for each of three species, Glycine max, Lablab purpureus, and Hemerocallis fulva. The results indicated that in all species, photosynthesis was limited by VC rather than J at both ambient and elevated CO2 both at high midday PPFDs and also at limiting PPFDs in the early morning and late afternoon. During brief reductions in PPFD due to midday clouds, photosynthesis became limited by J. The net result of the apparent deactivation of Rubisco at low PPFD was that the relative stimulation of diurnal carbon fixation at elevated CO2 was larger than would be predicted when assuming limitation of photosynthesis by J at low PPFD.

scholarly journals Elevated CO2 Concentration Alters Photosynthetic Performances under Fluctuating Light in Arabidopsis thaliana

Cells ◽  
2021 ◽  
Vol 10 (9) ◽  
pp. 2329
Author(s):  
Shun-Ling Tan ◽  
Xing Huang ◽  
Wei-Qi Li ◽  
Shi-Bao Zhang ◽  
Wei Huang
Keyword(s):  
Arabidopsis Thaliana ◽  
Elevated Co2 ◽  
Co2 Concentration ◽  
Atmospheric Co2 ◽  
Photochemical Quenching ◽  
Elevated Atmospheric Co2 ◽  
Actinic Light ◽  
Fluctuating Light ◽  
Photosynthetic Performances ◽  
Atmospheric Co2 Concentrations

In view of the current and expected future rise in atmospheric CO2 concentrations, we examined the effect of elevated CO2 on photoinhibition of photosystem I (PSI) under fluctuating light in Arabidopsis thaliana. At 400 ppm CO2, PSI showed a transient over-reduction within the first 30 s after transition from dark to actinic light. Under the same CO2 conditions, PSI was highly reduced after a transition from low to high light for 20 s. However, such PSI over-reduction greatly decreased when measured in 800 ppm CO2, indicating that elevated atmospheric CO2 facilitates the rapid oxidation of PSI under fluctuating light. Furthermore, after fluctuating light treatment, residual PSI activity was significantly higher in 800 ppm CO2 than in 400 ppm CO2, suggesting that elevated atmospheric CO2 mitigates PSI photoinhibition under fluctuating light. We further demonstrate that elevated CO2 does not affect PSI activity under fluctuating light via changes in non-photochemical quenching or cyclic electron transport, but rather from a rapid electron sink driven by CO2 fixation. Therefore, elevated CO2 mitigates PSI photoinhibition under fluctuating light at the acceptor rather than the donor side. Taken together, these observations indicate that elevated atmospheric CO2 can have large effects on thylakoid reactions under fluctuating light.

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