Intraspecific variation in multiple trait responses of Alexandrium ostenfeldii towards elevated pCO2

Dissolved oceanic CO2 concentrations are rising as result of increasing atmospheric partial pressure (pCO2), which has large consequences for phytoplankton. To test how higher availability affects different traits the toxic dinoflagellate Alexandrium ostenfeldii, we exposed three strains same population to 400 and 1,000 µatm CO2, measured including growth rate, cell volume, elemental composition, 13C fractionation, toxin content, volatile organic compounds (VOCs). Strains largely increased their rates particulate carbon nitrogen production with pCO2 showed significant changes in VOC profile. One strain a decrease both PSP cyclic imine content thereby cellular toxicity. Fractionation against response elevated pCO2, may point towards enhanced acquisition and/or downscaling concentrating mechanisms. Besides consistent responses some traits, other variation direction strength pCO2. The observed intraspecific phenotypic plasticity important functional within help A. ostenfeldii negate effects immediate environmental fluctuations allow populations adapt more quickly changing environments.