Saturating light and not increased carbon dioxide under ocean acidification drives photosynthesis and growth in Ulva rigida (Chlorophyta)

• Main Authors: Rautenberger, Ralf, Fernández, Pamela A, Strittmatter, Martina, Heesch, Svenja, Cornwall, Christopher Edward, Hurd, Catriona L, Roleda, Michael Y
• Format: Dataset
• Language: English
• Published: PANGAEA 2015
• Subjects: Alkalinity; total; standard deviation; Aragonite saturation state; Benthos; Bicarbonate ion; Bottles or small containers/Aquaria (<20 L); Calcite saturation state; Calculated using seacarb after Nisumaa et al. (2010); Calculated using SWCO2 (Hunter; 2007); Carbon; inorganic; dissolved; Carbonate ion; Carbonate system computation flag; Carbon dioxide; Carbonic anhydrase activity; Chlorophyta; Coast and continental shelf; EXP; Experiment; Figure; Fugacity of carbon dioxide (water) at sea surface temperature (wet air); Growth/Morphology; Growth rate; Inhibition of net photosynthesis; Laboratory experiment; Light; Macroalgae; OA-ICC; Ocean Acidification International Coordination Centre; Otago_Harbour; Other metabolic rates; Partial pressure of carbon dioxide; Partial pressure of carbon dioxide (water) at sea surface temperature (wet air); pH; Ocean acidification
• Online Access: https://doi.pangaea.de/10.1594/PANGAEA.846484; https://doi.org/10.1594/PANGAEA.846484

Carbon physiology of a genetically identified Ulva rigida was investigated under different CO2(aq) and light levels. The study was designed to answer whether (1) light or exogenous inorganic carbon (Ci) pool is driving growth; and (2) elevated CO2(aq) concentration under ocean acidification (OA) will downregulate CAext-mediated inline image dehydration and alter the stable carbon isotope (delta13C) signatures toward more CO2 use to support higher growth rate. At pHT 9.0 where CO2(aq) is <1 ?mol/L, inhibition of the known inline image use mechanisms, that is, direct inline image uptake through the AE port and CAext-mediated inline image dehydration decreased net photosynthesis (NPS) by only 56-83%, leaving the carbon uptake mechanism for the remaining 17-44% of the NPS unaccounted. An in silico search for carbon-concentrating mechanism elements in expressed sequence tag libraries of Ulva found putative light-dependent inline image transporters to which the remaining NPS can be attributed. The shift in delta13C signatures from -22 per mil toward -10 per mil under saturating light but not under elevated CO2(aq) suggest preference and substantial inline image use to support photosynthesis and growth. U. rigida is Ci saturated, and growth was primarily controlled by light. Therefore, increased levels of CO2(aq) predicted for the future will not, in isolation, stimulate Ulva blooms.