AME 77:155-166 (2016)  -  DOI: https://doi.org/10.3354/ame01793

ABSTRACT: Environmental factors such as temperature, irradiance, and nitrogen (N) supply affect the growth of Prorocentrum donghaiense, but the interactive effects of these physical factors and the effects of atmospheric CO₂ ( pCO₂) on growth and N uptake have not been examined. We compared growth kinetics of P. donghaiense grown on 4 different N substrates (nitrate [NO₃^-], ammonium [NH₄⁺], urea, and glutamic acid [glu]) with respect to temperature, irradiance, and pCO₂. Temperature (15 to 30°C) had a positive effect on growth (max. growth rates: 0.17 to 0.65 d^-1; optimal temperature: 25 to 30°C); maximum specific growth rates (μ_max) declined when cultures were grown at 30°C. P. donghaiense grew well on all 4 N sources, under irradiances ranging from 10 to 180 µmol quanta m^-2 s^-1. μ_max (2.0 ± 0.1 d^-1) was observed in cultures growing with NH₄⁺ as the sole N source in the highest irradiance treatment (180 µmol quanta m^-2 s^-1). These rates were significantly higher than those measured in cultures grown on NO₃^-, urea, and glu (all ~1.4 d^-1). Half-saturation constants (K_s) ranged from 66.5 ± 4.6 to 99.4 ± 6.7 µmol quanta m^-2 s^-1 for cultures grown with glu or NH₄⁺, respectively, as the sole source of N. Both growth and N uptake rates were higher in cultures grown under elevated pCO₂. Our results suggest that P. donghaiense exhibits flexible adaptation for N utilization under broad environmental conditions (temperature, irradiance, pCO₂), which may play an important role in the formation and duration of P. donghaiense blooms.

KEY WORDS: Prorocentrum donghaiense · Temperature · Irradiance · CO₂ · Nitrogen · Growth rate · Nitrogen uptake