Ocean acidification slows nitrogen fixation and growth in the dominant diazotroph Trichodesmium under low-iron conditions, supplement to: Shi, Dalin; Kranz, Sven A; Kim, Ja-Myung; Morel, Francois M M (2012): Ocean acidification slows nitrogen fixation and growth in the dominant diazotroph Trichodesmium under low-iron conditions. Proceedings of the National Academy of Sciences, 109(45), E3094-E3100

• Main Authors: Shi, Dalin, Kranz, Sven A, Kim, Ja-Myung, Morel, Francois M M
• Format: Dataset
• Language: English
• Published: PANGAEA - Data Publisher for Earth & Environmental Science 2012
• Subjects: Bacteria; Bottles or small containers/Aquaria <20 L; Cyanobacteria; Growth/Morphology; Laboratory experiment; Laboratory strains; Micro-nutrients; Not applicable; Other metabolic rates; Pelagos; Phytoplankton; Primary production/Photosynthesis; Single species; Trichodesmium erythraeum; Species; Identification; Treatment; Replicate; Iron; Iron uptake rate; Iron uptake rate, standard deviation; Iron, steady state; Iron uptake rate, per chlorophyll a; Iron uptake rate, per chlorophyll a, standard deviation; Iron, cellular quota; Iron, cellular quota, standard deviation; Growth rate; Growth rate, standard deviation; Nitrogen fixation rate per chlorophyll a; Nitrogen fixation rate, standard deviation; Net hydrogen production, per chlorophyll a; Net hydrogen production, per chlorophyll a, standard deviation; Duration; Iron protein of nitrogenase; Iron protein of nitrogenase, standard deviation; Photosynthetic protein PsbC; Photosynthetic protein PsbC standard deviation; Photosynthetic protein PsbA; Photosynthetic protein PsbA standard deviation; Photosynthetic protein Rubisco; Photosynthetic protein Rubisco, standard deviation; Incubation duration; Carbon, organic, particulate; Chlorophyll a; Photosynthetic carbon fixation rate; Photosynthetic carbon fixation rate, standard deviation; Nitrogen fixation rate; Carbon, organic, particulate/Nitrogen, organic, particulate ratio; Carbon, organic, particulate/Nitrogen, organic, particulate ratio, standard deviation; Chlorophyll a/carbon ratio; Chlorophyll a/carbon ratio, standard deviation; Salinity; Temperature, water; pH; Carbon, inorganic, dissolved; Alkalinity, total; Partial pressure of carbon dioxide water at sea surface temperature wet air; Carbonate system computation flag; Carbon dioxide; Fugacity of carbon dioxide water at sea surface temperature wet air; Bicarbonate ion; Carbonate ion; Aragonite saturation state; Calcite saturation state; Spectrophotometric; Calculated; Potentiometric titration; Calculated using seacarb after Nisumaa et al. 2010; Ocean Acidification International Coordination Centre OA-ICC; Sven; Ocean acidification
• Online Access: https://dx.doi.org/10.1594/pangaea.830475; https://doi.pangaea.de/10.1594/PANGAEA.830475

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. : In order to allow full comparability with other ocean acidification data sets, the R package seacarb (Lavigne and Gattuso, 2011) was used to compute a complete and consistent set of carbonate system variables, as described by Nisumaa et al. (2010). In this dataset the original values were archived in addition with the recalculated parameters (see related PI). The date of carbonate chemistry calculation by seacarb is 2014-03-03.