Synergistic effects of pCO2 and iron availability on nutrient consumption ratio of the Bering Sea phytoplankton community

• Main Authors: Sugie, Koji, Endo, H, Suzuki, Koji, Nishioka, Jun, Kiyosawa, H, Yoshimura, T
• Format: Dataset
• Language: English
• Published: PANGAEA 2013
• Subjects: Alkalinity; total; Ammonium; Aragonite saturation state; Bering_Sea_OA; Bicarbonate ion; Biogenic silica; Biomass/Abundance/Elemental composition; Bottles or small containers/Aquaria (<20 L); Calcite saturation state; Calculated using seacarb after Nisumaa et al. (2010); Carbon; inorganic; dissolved; organic; particulate; Carbonate ion; Carbonate system computation flag; Carbon dioxide; Chlorophyll a; Community composition and diversity; Coulometric titration; Day of experiment; Entire community; EXP; Experiment; Fluorescence intensity; Fugacity of carbon dioxide (water) at sea surface temperature (wet air); Iron; Laboratory experiment; Maximum photochemical quantum yield of photosystem II; standard deviation; Micro-nutrients; Nitrate and Nitrite; Nitrogen; North Pacific; OA-ICC; Ocean Acidification International Coordination Centre; Open ocean; Partial pressure of carbon dioxide (water) at sea surface temperature (wet air); Pelagos; Percentage; pH; Phosphate; Potentiometric titration; Bering Sea; Ocean acidification
• Online Access: https://doi.pangaea.de/10.1594/PANGAEA.846343; https://doi.org/10.1594/PANGAEA.846343

Little is known concerning the effect of CO2 on phytoplankton ecophysiological processes under nutrient and trace element-limited conditions, because most CO2 manipulation experiments have been conducted under elements-replete conditions. To investigate the effects of CO2 and iron availability on phytoplankton ecophysiology, we conducted an experiment in September 2009 using a phytoplankton community in the iron limited, high-nutrient, low-chlorophyll (HNLC) region of the Bering Sea basin . Carbonate chemistry was controlled by the bubbling of the several levels of CO2 concentration (180, 380, 600, and 1000 ppm) controlled air, and two iron conditions were established, one with and one without the addition of inorganic iron. We demonstrated that in the iron-limited control conditions, the specific growth rate and the maximum photochemical quantum efficiency (Fv/Fm) of photosystem (PS) II decreased with increasing CO2 levels, suggesting a further decrease in iron bioavailability under the high-CO2 conditions. In addition, biogenic silica to particulate nitrogen and biogenic silica to particulate organic carbon ratios increased from 2.65 to 3.75 and 0.39 to 0.50, respectively, with an increase in the CO2 level in the iron-limited controls. By contrast, the specific growth rate, Fv/Fm values and elemental compositions in the iron-added treatments did not change in response to the CO2 variations, indicating that the addition of iron canceled out the effect of the modulation of iron bioavailability due to the change in carbonate chemistry. Our results suggest that high-CO2 conditions can alter the biogeochemical cycling of nutrients through decreasing iron bioavailability in the iron-limited HNLC regions in the future.