Seasonal effects of irradiance and pCO2 enrichment on brown alga Fucus vesiculosus in the Baltic Sea

Carbon content, nitrogen content, carbon:nitrogen ratio, chlorophyll a and chlorophyll fluorescence parameters (ETRmax, Ek, alpha, Fv/Fm) of Fucus vesiculosus were measured in two experiments (winter-summer) in the Tvärminne Zoological Station, SW Finland, Northern Baltic Sea. The algae were exposed to two irradiance treatments: 165 µmol photons/m²/s and 81 µmol photons/m²/s (winter) and 198 µmol photons/m²/s and 131 µmol photons/m²/s (summer) for high and low light treatments, respectively, with 8:16 h (winter) and 16:8 h (summer) light/dark rhythm. Irradiance was provided by Philips TL-D Super 80 58W 830 fluorescent light bulbs. Three pCO2 treatments were used: 'ambient' (236 µatm or 512 µatm, summer/winter), 'high' (1582 µatm or 2263 µatm, summer/winter) and 'extreme' (4673 µatm or 7074 µatm, summer/winter). The duration of the experiment was 18 days in winter and 22 days in summer. Algal specimens were kept in 1 liter glass jars receiving constant flow-through (80 ml/min) of pCO2-adjusted water. In the winter experiment, a single algal thallus tip was grown in each jar, in the summer experiment, three individuals were grown in the same jar. In the data files, "ID" is unique identifier for the jars, and "Sample ID" is unique identifier for each algal specimen. Note that because Fv/Fm measurements were conducted in darkness, there is no "Sample ID" for these measurements.