Seawater carbonate chemistry and biological processes during experiments with four species of marine diatoms

• Main Authors: Trimborn, Scarlett, Wolf-Gladrow, Dieter A, Richter, Klaus-Uwe, Rost, Björn
• Format: Dataset
• Language: English
• Published: PANGAEA 2009
• Subjects: Alkalinity; Gran titration (Gran; 1950); total; Aragonite saturation state; Bicarbonate ion; Bicarbonate uptake; Bottles or small containers/Aquaria (<20 L); Calcite saturation state; Calculated; Calculated after Freeman & Hayes (1992); Calculated using CO2SYS; Calculated using seacarb after Nisumaa et al. (2010); Carbon; inorganic; dissolved; Carbonate ion; Carbonate system computation flag; Carbon dioxide; Chromista; EPOCA; Eucampia zoodiacus; EUR-OCEANS; European network of excellence for Ocean Ecosystems Analysis; European Project on Ocean Acidification; Experimental treatment; Extracellular carbonic anhydrase activity; Fugacity of carbon dioxide (water) at sea surface temperature (wet air); Intracellular carbonic anhydrase activity per chlorophyll a; Isotopic fractionation; during photosynthis; Laboratory experiment; Laboratory strains; Light:Dark cycle; Measured by loss of 18O (Silverman; 1982); Not applicable; OA-ICC; Ocean Acidification International Coordination Centre; Ochrophyta; Partial pressure of carbon dioxide (water) at sea surface temperature (wet air); Pelagos; pH; pH meter; WTW; pH 3000; Phytoplankton; Primary production/Photosynthesis; Priority Programme 1158 Antarctic Research with Comparable Investigations in Arctic Sea Ice Areas; Antarc*; Antarctic; Ocean acidification; Sea ice
• Online Access: https://doi.pangaea.de/10.1594/PANGAEA.733948; https://doi.org/10.1594/PANGAEA.733948

The effect of pCO2 on carbon acquisition and intracellular assimilation was investigated in the three bloom-forming diatom species, Eucampia zodiacus (Ehrenberg), Skeletonema costatum (Greville) Cleve, Thalassionema nitzschioides (Grunow) Mereschkowsky and the non-bloom-forming Thalassiosira pseudonana (Hust.) Hasle and Heimdal. In vivo activities of carbonic anhydrase (CA), photosynthetic O2 evolution, CO2 and HCO3? uptake rates were measured by membrane-inlet mass spectrometry (MIMS) in cells acclimated to pCO2 levels of 370 and 800 ?atm. To investigate whether the cells operate a C4-like pathway, activities of ribulose-1,5-bisphosphate carboxylase (RubisCO) and phosphoenolpyruvate carboxylase (PEPC) were measured at the mentioned pCO2 levels and a lower pCO2 level of 50 ?atm. In the bloom-forming species, extracellular CA activities strongly increased with decreasing CO2 supply while constantly low activities were obtained for T. pseudonana. Half-saturation concentrations (K1/2) for photosynthetic O2 evolution decreased with decreasing CO2 supply in the two bloom-forming species S. costatum and T. nitzschioides, but not in T. pseudonana and E. zodiacus. With the exception of S. costatum, maximum rates (Vmax) of photosynthesis remained constant in all investigated diatom species. Independent of the pCO2 level, PEPC activities were significantly lower than those for RubisCO, averaging generally less than 3%. All examined diatom species operate highly efficient CCMs under ambient and high pCO2, but differ strongly in the degree of regulation of individual components of the CCM such as Ci uptake kinetics and extracellular CA activities. The present data do not suggest C4 metabolism in the investigated species.