Universal response pattern of phytoplankton growth rates to increasing CO2.

Phytoplankton growth rate is a key variable controlling species succession and ecosystem structure throughout the surface ocean. Carbonate chemistry conditions are known to influence phytoplankton growth rates but there is no conceptual framework allowing us to compare growth rate responses across taxa. Here we analyse the literature to show that phytoplankton growth rates follow an optimum curve response pattern whenever the tested species is exposed to a sufficiently large gradient in proton (H+ ) concentrations. Based on previous findings with coccolithophores and diatoms, we argue that this 'universal reaction norm' is shaped by the stimulating influence of increasing inorganic carbon substrate (left side of the optimum) and the inhibiting influence of increase H+ (right side of the optimum). We envisage that exploration of carbonate chemistry-dependent optimum curves as a default experimental approach will boost our mechanistic understanding of phytoplankton responses to ocean acidification, like temperature curves have already boosted our mechanistic understanding to global warming.

Absolute intensities of NH-stretching transitions in dimethylamine and pyrrole.

Vibrational spectra of vapor-phase dimethylamine (DMA) and pyrrole have been recorded in the 1000 to 13000 cm(-1) region using long path conventional spectroscopy techniques. We have focused on the absolute intensities of the NH-stretching fundamental and overtone transitions; Δν(NH) = 1-4 regions for DMA and the Δν(NH) = 1-3 regions for pyrrole. In the Δν(NH) = 1-3 regions for DMA, evidence of tunneling splitting associated with the NH-wagging mode is observed. For DMA, the fundamental NH-stretching transition intensity is weaker than the first NH-stretching overtone. Also, the fundamental NH-stretching transition in DMA is much weaker than the fundamental transition in pyrrole. We have used an anharmonic oscillator local mode model with ab initio calculated local mode parameters and dipole moment functions at the CCSD(T)/aug-cc-pVTZ level to calculate the NH-stretching intensities and explain this intensity anomaly in DMA.