Publication Date:
2024-05-22
Description:
Stable carbon isotope fractionation (%) of 7 marine phytoplankton species grown in different irradiance cycles was measured under nutrient-replete conditions at a high light intensity in batch cultures. Compared to experiments under continuous light, all species exhibited a significantly higher instantaneous growth rate (pi), defined as the rate of carbon fixation during the photo period, when cultivated at 12:12 h. 16:8 h, or 186 h light:dark (L/D) cycles. Isotopic fractionation by the diatoms Skeletonema costatum, Asterionella glacialis, Thalassiosira punctigera, and Coscinodiscus wailesii (Group I) was 4 to 6% lower in a 16:8 h L/D cycle than under continuous light, which we attribute to differences in pi. In contrast, E, in Phaeodactylum tn'cornutum, Thalassiosira weissflogii, and in the dinoflagellate Scrippsiella trochoidea (Group 11) was largely insensitive to day length-related differences in instantaneous growth rate. Since other studies have reported growth-rate dependent fractionation under N-limited conditions in P. tricornutum, pi-related effects on fractionation apparently depend on the factor controlling growth rate. We suggest that a general relationship between E, and pi/[C02,,,] may not exist. For 1 species of each group we tested the effect of variable CO2 concentration, [COz,,,], on isotopic fractionation. A decrease in [CO2,,,] from ca 26 to 3 pm01 kg-' caused a decrease in E, by less than 3%0 This indicates that variation in h in response to changes in day length has a similar or even greater effect on isotopic fractionation than [COz,,,] m some of the species tested. In both groups E, tended to be higher in smaller species at comparable growth rates. In 24 and 48 h time series the algal cells became progressively enriched in 13C during the day and the first hours of the dark period, followed by l3C depletion in the 2 h before beginning of the following Light period. The daily amplitude of the algal isotopic composition (613C), however, was 〈1.5%0, which demonstrates that diurnal variation in Fl3C is relatively small.
Keywords:
Alkalinity, Gran titration (Gran, 1950); Alkalinity, total; Aragonite saturation state; Asterionella glacialis; Bicarbonate ion; Biomass/Abundance/Elemental composition; Bottles or small containers/Aquaria (〈20 L); Burkhardt_etal_99; Calcite saturation state; Calculated; Calculated after Freeman & Hayes (1992); Calculated using seacarb after Nisumaa et al. (2010); Carbon, inorganic, dissolved; Carbonate ion; Carbonate system computation flag; Carbon dioxide; Chromista; Coulometric titration; EPOCA; EUR-OCEANS; European network of excellence for Ocean Ecosystems Analysis; European Project on Ocean Acidification; EXP; Experiment; Experimental treatment; Fugacity of carbon dioxide (water) at sea surface temperature (wet air); Growth/Morphology; Growth rate; Isotopic fractionation, during photosynthis; Laboratory experiment; Laboratory strains; Light; Light:Dark cycle; Mass spectrometer ANCA-SL 20-20 Europa Scientific; Mass spectrometer Finnigan Delta-S; Measured; Myzozoa; Nitrate; Not applicable; OA-ICC; Ocean Acidification International Coordination Centre; Ochrophyta; Partial pressure of carbon dioxide (water) at sea surface temperature (wet air); Pelagos; pH; Phaedactylum tricornutum; Phosphate; Phytoplankton; Radiation, photosynthetically active; Salinity; Scrippsiella trochoidea; Silicate; Single species; Skeletonema costatum; Species; Temperature, water; Thalassiosira punctigera; Thalassiosira weissflogii; δ13C, carbon dioxide, aquatic; δ13C, particulate organic carbon
Type:
Dataset
Format:
text/tab-separated-values, 480 data points
Permalink
