More CO2 but Less Nitrogen: A Double Whammy for Diatoms?
Li, W., Gao, K. and Beardall, J. 2012. Interactive effects of ocean acidification and nitrogen-limitation on the diatom Phaeodactylum tricornutum. PLOS ONE 7: e51590.
In exploring this thesis, Li et al. "investigated the diatom Phaeodactylum tricornutum as a model organism," culturing its cells in both low CO2 (390 ppm) and high CO2 (1000 ppm), as well as at low nitrogen (10 µmol/L) and high nitrogen (110 µmol/L) concentrations.
Results of the experimental analysis revealed that: (1) "no direct effects on growth rate were found between the CO2 treatments," (2) "no direct effects on pigmentation were found between the CO2 treatments," (3) "no significant change in the [quantum] yield was found between the low and high CO2 levels," (4) "increased dissolved CO2 concentration did not affect the mean cell size and cell volume of Phaeodactylum tricornutum," (5) "under the nitrogen replete treatment the CO2 concentration did not affect the C:N ratio, even though the cells at the high CO2 level significantly increased their nitrogen content by 13%," but that (6) "nitrogen limitation decreased all these parameters in the diatom."
When looking for predicted negative effects of increased CO2 (due to the burning of fossil fuels) and decreased nitrogen (due to intensified water stratification in the surface mixed layer of the world's presumed-to-be-warming oceans), it is encouraging to see that the consequences of the more-sure-to-occur of these phenomena (increased CO2) had hardly any negative consequences for P. tricornutum, while the truly unsure-to-occur phenomenon (warming-induced stratification of surface ocean water) - which did have negative consequences - may well not occur.