Publication Date:
2024-03-15
Description:
Dissolution of anthropogenic CO(2) increases the partial pressure of CO(2) (pCO(2)) and decreases the pH of seawater. The rate of Fe uptake by the dominant N(2)-fixing cyanobacterium Trichodesmium declines as pH decreases in metal-buffered medium. The slower Fe-uptake rate at low pH results from changes in Fe chemistry and not from a physiological response of the organism. Contrary to previous observations in nutrient-replete media, increasing pCO(2)/decreasing pH causes a decrease in the rates of N(2) fixation and growth in Trichodesmium under low-Fe conditions. This result was obtained even though the bioavailability of Fe was maintained at a constant level by increasing the total Fe concentration at low pH. Short-term experiments in which pCO(2) and pH were varied independently showed that the decrease in N(2) fixation is caused by decreasing pH rather than by increasing pCO(2) and corresponds to a lower efficiency of the nitrogenase enzyme. To compensate partially for the loss of N(2) fixation efficiency at low pH, Trichodesmium synthesizes additional nitrogenase. This increase comes partly at the cost of down-regulation of Fe-containing photosynthetic proteins. Our results show that although increasing pCO(2) often is beneficial to photosynthetic marine organisms, the concurrent decreasing pH can affect primary producers negatively. Such negative effects can occur both through chemical mechanisms, such as the bioavailability of key nutrients like Fe, and through biological mechanisms, as shown by the decrease in N(2) fixation in Fe-limited Trichodesmium.
Keywords:
Alkalinity, total; Aragonite saturation state; Bacteria; Bicarbonate ion; Bottles or small containers/Aquaria (〈20 L); Calcite saturation state; Calculated; Calculated using seacarb after Nisumaa et al. (2010); Carbon, inorganic, dissolved; Carbon, organic, particulate; Carbon, organic, particulate/Nitrogen, organic, particulate ratio; Carbon, organic, particulate/Nitrogen, organic, particulate ratio, standard deviation; Carbonate ion; Carbonate system computation flag; Carbon dioxide; Chlorophyll a; Chlorophyll a/carbon ratio; Chlorophyll a/carbon ratio, standard deviation; Cyanobacteria; Duration; Fugacity of carbon dioxide (water) at sea surface temperature (wet air); Growth/Morphology; Growth rate; Growth rate, standard deviation; Identification; Incubation duration; Iron; Iron, cellular quota; Iron, cellular quota, standard deviation; Iron, steady state; Iron protein of nitrogenase; Iron protein of nitrogenase, standard deviation; Iron uptake rate; Iron uptake rate, per chlorophyll a; Iron uptake rate, per chlorophyll a, standard deviation; Iron uptake rate, standard deviation; Laboratory experiment; Laboratory strains; Micro-nutrients; Net hydrogen production, per chlorophyll a; Net hydrogen production, per chlorophyll a, standard deviation; Nitrogen fixation rate; Nitrogen fixation rate, standard deviation; Nitrogen fixation rate per chlorophyll a; Not applicable; OA-ICC; Ocean Acidification International Coordination Centre; Other metabolic rates; Partial pressure of carbon dioxide (water) at sea surface temperature (wet air); Pelagos; pH; Photosynthetic carbon fixation rate; Photosynthetic carbon fixation rate, standard deviation; Photosynthetic protein, PsbA, standard deviation; Photosynthetic protein, PsbC; Photosynthetic protein, PsbC, standard deviation; Photosynthetic protein PsbA; Photosynthetic protein Rubisco; Photosynthetic protein Rubisco, standard deviation; Phytoplankton; Potentiometric titration; Primary production/Photosynthesis; Replicate; Salinity; Single species; Species; Spectrophotometric; Temperature, water; Treatment; Trichodesmium erythraeum
Type:
Dataset
Format:
text/tab-separated-values, 6960 data points
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