THE UNKNOWN UNKNOWNS: UNDERSTANDING THE NUTRIENT KINETICS OF DACTYLIOSOLEN FRAGILISSIMUS

Abstract

Dactyliosolen fragilissimus contributes to the largest proportion of the diatom biomass in the oceans. Despite its abundance, D. fragilissimus has not yet been fully studied or characterized. Therefore, the growth rate and the nutrient uptake kinetics of ammonium assimilation were measured for D. fragilissimus growing at 20.0°C under constant light supply of 130 μEin. The nutrient uptake rates were modeled using the Michaelis-Menten equation and analyzed using various regression and linear transformation models. The growth rate of D. fragilissimus is found to have a doubling time of r = 1.86 (±0.2) days. The half-saturation coefficient of ammonium uptake kinetics was found to be KS = 9.7657 μM NH4

(95%CI [3.03, 16.50]), and the maximum uptake rate of ammonium was found to be VMAX = 10.5505 pM NH4 +/hr/cell (95%CI [5.80, 15.30]). Understanding the nutrient kinetics of the most abundant species of diatom could help predict the effects on the marine ecosystems due to pollution and global warming, such as an increase in ammonium in water from fertilization runoff or an increase in the water temperature.