Publication Date:
2024-07-08
Description:
We investigated carbon acquisition by the N2-fixing cyanobacterium Trichodesmium IMS101 in response to CO2 levels of 15.1, 37.5, and 101.3 Pa (equivalent to 150, 370, and 1000 ppm). In these acclimations, growth rates as well as cellular C and N contents were measured. In vivo activities of carbonic anhydrase (CA), photosynthetic O2 evolution, and CO2 and HCO3- fluxes were measured using membrane inlet mass spectrometry and the 14C disequilibrium technique. While no differences in growth rates were observed, elevated CO2 levels caused higher C and N quotas and stimulated photosynthesis and N2 fixation. Minimal extracellular CA (eCA) activity was observed, indicating a minor role in carbon acquisition. Rates of CO2 uptake were small relative to total inorganic carbon (Ci) fixation, whereas HCO{3 contributed more than 90% and varied only slightly over the light period and between CO2 treatments. The low eCA activity and preference for HCO3- were verified by the 14C disequilibrium technique. Regarding apparent affinities, half-saturation concentrations (K1/2) for photosynthetic O2 evolution and HCO3- uptake changed markedly over the day and with CO2 concentration. Leakage (CO2 efflux : Ci uptake) showed pronounced diurnal changes. Our findings do not support a direct CO2 effect on the carboxylation efficiency of ribulose-1,5-bisphosphate carboxylase/oxygenase (RubisCO) but point to a shift in resource allocation among photosynthesis, carbon acquisition, and N2 fixation under elevated CO2 levels. The observed increase in photosynthesis and N2fixation could have potential biogeochemical implications, as it may stimulate productivity in N-limited oligotrophic regions and thus provide a negative feedback in rising atmospheric CO2 levels.
Keywords:
Alkalinity, Gran titration (Gran, 1950); Alkalinity, total; Alkalinity, total, standard deviation; Aragonite saturation state; Bacteria; Based on changes in chla/cells/POC/PON; Bicarbonate ion; Biomass/Abundance/Elemental composition; Bottles or small containers/Aquaria (〈20 L); Calcite saturation state; Calculated; Calculated using CO2SYS; Calculated using seacarb after Nisumaa et al. (2010); Carbon, inorganic, dissolved; Carbon, inorganic, dissolved, standard deviation; Carbon/Nitrogen ratio; Carbon/Nitrogen ratio, standard deviation; Carbonate ion; Carbonate system computation flag; Carbon dioxide; Carbon dioxide, standard deviation; Carbon dioxide, total; Conductivity meter (WTW, Weilheim, Gemany); Cyanobacteria; EPOCA; EUR-OCEANS; European network of excellence for Ocean Ecosystems Analysis; European Project on Ocean Acidification; Experimental treatment; Fugacity of carbon dioxide (water) at sea surface temperature (wet air); Growth/Morphology; Growth rate; Growth rate, standard deviation; Laboratory experiment; Laboratory strains; Mass spectrometer ANCA-SL 20-20 Europa Scientific; Not applicable; OA-ICC; Ocean Acidification International Coordination Centre; Partial pressure of carbon dioxide (water) at sea surface temperature (wet air); Particulate organic carbon, per cell; Particulate organic carbon content per cell, standard deviation; Particulate organic nitrogen per cell; Particulate organic nitrogen per cell, standard deviation; Pelagos; pH; pH, Electrode; pH, standard deviation; Phosphate; Phytoplankton; Radiation, photosynthetically active; Salinity; Single species; Temperature, water; Trichodesmium sp.; Walz 4pi sensor
Type:
Dataset
Format:
text/tab-separated-values, 96 data points
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