Publication Date:
2024-03-15
Description:
The response of marine phytoplankton to the ongoing increase in atmospheric pCO2 reflects the consequences of both increased CO2 concentration and decreased pH in surface seawater. In the model diatom Thalassiosira weissflogii, we explored the effects of varying pCO2 and pH, independently and in concert, on photosynthesis and respiration by incubating samples in water enriched in H218O. In long-term experiments (6-h) at saturating light intensity, we observed no effects of pH or pCO2 on growth rate, photosynthesis or respiration. This absence of a measurable response reflects the very small change in energy used by the carbon concentrating mechanism (CCM) compared to the energy used in carbon fixation. In short-term experiments (3 min), we also observed no effects of pCO2 or pH, even under limiting light intensity. We surmise that in T. weissflogii, it is the photosynthetic production of NADPH and ATP, rather than the CO2-saturation of Rubisco that controls the rate of photosynthesis at low irradiance. In short-term experiments, we observed a slightly higher respiration rate at low pH at the onset of the dark period, possibly reflecting the energy used for exporting H+ and maintaining pH homeostasis. Based on what is known of the biochemistry of marine phytoplankton, our results are likely generalizable to other diatoms and a number of other eukaryotic species. The direct effects of ocean acidification on growth, photosynthesis and respiration in these organisms should be small over the range of atmospheric pCO2 predicted for the twenty-first century.
Keywords:
Alkalinity, total; Aragonite saturation state; Bicarbonate ion; Bottles or small containers/Aquaria (〈20 L); Calcite saturation state; Calculated using seacarb after Nisumaa et al. (2010); Carbon, inorganic, dissolved; Carbonate ion; Carbonate system computation flag; Carbon dioxide; Cell density; Chromista; Error; Experiment; Experiment duration; Fugacity of carbon dioxide (water) at sea surface temperature (wet air); Gross photosynthesis rate, oxygen, per cell; Gross photosynthesis rate, oxygen, per chlorophyll a; Gross photosynthesis rate, standard deviation; Irradiance; Laboratory experiment; Laboratory strains; Light; Net photosynthesis rate, oxygen, per cell; Net photosynthesis rate, oxygen, per chlorophyll a; Net photosynthesis rate, standard deviation; Not applicable; OA-ICC; Ocean Acidification International Coordination Centre; Ochrophyta; Partial pressure of carbon dioxide (water) at sea surface temperature (wet air); Pelagos; pH; Phytoplankton; Primary production/Photosynthesis; Registration number of species; Replicate; Respiration; Respiration rate, oxygen, per chlorophyll a; Salinity; Single species; Species; Temperature, water; Thalassiosira weissflogii; Time in days; Type; Uniform resource locator/link to reference
Type:
Dataset
Format:
text/tab-separated-values, 3916 data points
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