Thermal acclimation in the marine diatom Chaetoceros calcitrans (Bacillariophyceae)

Abstract

Thermal acclimation following changes from 6 mC to 15 mC and from 15 mC to 25 mC was investigated in the diatom Chaetoceros calcitrans. Cell division rate increased with temperature. Cellular carbon showed a slight decrease with an increase in temperature from 6 mC to 15 mC but showed no further change with an increase to 25 mC. Cells grown at 6 mC had low levels of light-harvesting components and a high carotenoid to chlorophyll a (Chla) ratio due to an increase in abundance of photoprotective pigments. The abundance of light-harvesting pigments increased with temperature and this was mirrored by a decrease in carotenoid : Chla ratio. All pigments showed an immediate change in abundance following each temperature shift. However, changes in photoprotective pigments reached a plateau after 12 h, in contrast to the lightharvesting pigments that took 4 days to become acclimated. Light-saturated rates of photosynthesis were at a minimum at 6 mC and increased twofold with temperature between 6 mC and 25 mC. Light-limited photosynthesis showed little change with temperature. It is suggested that, at low temperatures, the rate of carbon fixation is impaired due to a decrease in the activity of photosynthetic enzymes. This imparts an increase in excitation pressure due to an imbalance between light absorption and utilization. Cells respond to this by decreasing their light-harvesting capacity and increasing their ability to dissipate the excess energy. This fairly rapid regulation may be ecologically advantageous in areas where there are transient temperature changes.

Effects of temperature on photosynthetic parameters and TEP production in eight species of marine microalgae

“…5), the other species were not able to acclimate their light-harvesting capacity at extreme temperatures after at least 1 wk of acclimation. Anning et al (2001) described an increase of the ratio E/E k in the marine diatom Chaetoceros calcitrans at low temperature, as we observed particularly for S. marinoi and L. chlorophorum and more generally for all tested species. This confirms the apparent similarity of acclimation at low temperature and high irradiance.…”

“…A decrease in chlorophyll content is a typical algal response to high irradiance, along with increased content of photoprotective carotenoids whose function is to dissipate excess energy. Several previous studies have shown that acclimation to low temperature mimics adaptation to high irradiance (Anning et al 2001, El-Sabaawi & Harrison 2006.…”

“…For Lepidodinium chlorophorum and Skeletonema marinoi, the E/E k ratio increased with a decrease in temperature, while the ratio was quite stable for I. galbana and Thalassiosira pseudonana. A high E/E k ratio indicates light saturation and an imbalance between light-harvesting and downstream photosynthetic reactions (Anning et al 2001), while a ratio around 1 indicates optimization of light harvesting with photosynthetic metabolism as a function of the incident light. In the present study, it appears that, except for I. galbana and T. pseudonana, which exhibited a relatively stable value of E/E k (Fig.…”

Temperature is a key factor in Micromonas–virus interactions

“…The decrease in auto-fluorescence intensity of coldadapted Micromonas (Supplementary Figure S3) suggests a reduction in chlorophyll content with decreasing temperatures as previously reported (Claquin et al, 2008). Several studies pointed out the similarity of photoacclimation trends at low temperatures to those at high irradiance (Anning et al, 2001;El-Sabaawi and Harrison, 2006;Claquin et al, 2008). Reports on the effect of light intensity evidenced the importance of this factor in regulating algal host-virus interactions (Waters and Chan, 1982;Bratbak et al, 1998;Brown et al, 2007;Baudoux and Brussaard, 2008).…”

How Well Does Chlorophyll Explain the Seasonal Variation in Phytoplankton Activity?

“…4). The data shows that the average monthly P max values covary with temperature and peak in August concurrent with the temperature peak, which indicates that temperature directly affects P max (Anning et al 2001) due to enzyme-driven processes. Temperature also has an indirect effect on PP in that higher temperatures increase remineralization rates and thereby increase nutrient availability for phytoplankton production (Kemp and Boynton 1984).…”