Publication Date:
2024-07-08
Description:
Recent studies on the diazotrophic cyanobacterium Trichodesmium erythraeum(IMS101) showed that increasing CO2 partial pressure (pCO2) enhances N2 fixation and growth. Significant uncertainties remain as to the degree of the sensitivity to pCO2, its modification by other environmental factors, and underlying processes causing these responses. To address these questions, we examined the responses ofTrichodesmium IMS101 grown under a matrix of low and high levels of pCO2 (150 and 900 µatm) and irradiance (50 and 200 µmol photons m-2 s-1). Growth rates as well as cellular carbon and nitrogen contents increased with increasing pCO2 and light levels in the cultures. The pCO2-dependent stimulation in organic carbon and nitrogen production was highest under low light. High pCO2 stimulated rates of N2fixation and prolonged the duration, while high light affected maximum rates only. Gross photosynthesis increased with light but did not change with pCO2. HCO3- was identified as the predominant carbon source taken up in all treatments. Inorganic carbon uptake increased with light, but only gross CO2 uptake was enhanced under high pCO2. A comparison between carbon fluxes in vivo and those derived from 13C fractionation indicates high internal carbon cycling, especially in the low-pCO2treatment under high light. Light-dependent oxygen uptake was only detected underlow pCO2 combined with high light or when low-light-acclimated cells were exposed to high light, indicating that the Mehler reaction functions also as a photoprotective mechanism in Trichodesmium. Our data confirm the pronounced pCO2 effect on N2fixation and growth in Trichodesmium and further show a strong modulation of these effects by light intensity. We attribute these responses to changes in the allocation of photosynthetic energy between carbon acquisition and the assimilation of carbon and nitrogen under elevated pCO2. These findings are supported by a complementarystudy looking at photosynthetic fluorescence parameters of photosystem II, photosynthetic unit stoichiometry (photosystem I:photosystem II), and pool sizes of key proteins in carbon and nitrogen acquisition.
Keywords:
Alkalinity, Gran titration (Gran, 1950); Alkalinity, total; Alkalinity, total, standard deviation; Aragonite saturation state; Bacteria; Bicarbonate ion; Bicarbonate uptake in chlorophyll, standard deviation; Bicarbonate uptake rate, per chlorophyll a; Biomass/Abundance/Elemental composition; Bottles or small containers/Aquaria (〈20 L); Calcite saturation state; Calculated; Calculated, see reference(s); Calculated using CO2SYS; Calculated using seacarb after Nisumaa et al. (2010); Carbon, inorganic, dissolved; Carbon, inorganic, dissolved, standard deviation; Carbon, organic, particulate, per cell; Carbon, organic, particulate, production per cell; Carbon/Nitrogen ratio; Carbon/Nitrogen ratio, standard deviation; Carbonate ion; Carbonate system computation flag; Carbon dioxide; Carbon dioxide, standard deviation; Carbon dioxide uptake, per chlorophyll, standard deviation; Carbon dioxide uptake rate, per chlorophyll a; Chlorophyll a, standard deviation; Chlorophyll a per cell; Comment; Cyanobacteria; Determined by acetylene reduction assay using a gas chromatograph; EPOCA; EUR-OCEANS; European network of excellence for Ocean Ecosystems Analysis; European Project on Ocean Acidification; Experimental treatment; Fixation of carbon in chlorophyll; Fixation of carbon in chlorophyll, standard deviation; Fugacity of carbon dioxide (water) at sea surface temperature (wet air); Gross oxygen evolution, per chlorophyll a; Gross oxygen evolution, standard deviation; Growth/Morphology; Growth rate; Growth rate, standard deviation; Laboratory experiment; Laboratory strains; Light; Mass spectrometer ANCA-SL 20-20 Europa Scientific; Nitrogen fixation rate, standard deviation; Nitrogen fixation rate per chlorophyll a; Not applicable; OA-ICC; Ocean Acidification International Coordination Centre; Other metabolic rates; Oxygen consumption, standard deviation; Oxygen consumption per chlorophyll a; Partial pressure of carbon dioxide (water) at sea surface temperature (wet air); Particulate organic carbon, production, standard deviation; Particulate organic carbon content per cell, standard deviation; Particulate organic nitrogen per cell; Particulate organic nitrogen per cell, standard deviation; Particulate organic nitrogen production, standard deviation; Particulate organic phosphorus per cell; Particulate organic phosphorus per cell, standard deviation; Pelagos; pH; pH, standard deviation; pH meter (Metrohm electrodes); Phytoplankton; Primary production/Photosynthesis; Production of particulate organic nitrogen; Radiation, photosynthetically active; Respiration; Salinity; see reference(s); Single species; Temperature, water; Time in hours; Trichodesmium sp.
Type:
Dataset
Format:
text/tab-separated-values, 1788 data points
Permalink
