Samenvatting

To increase the yield and quality of aquaculture feed, the effects of N and P concentrations on biomass productivity and cell composition were examined in the marine diatom Skeletonema costatum. Batch-cultured microalgae in Walne’s medium with 3.5 ± 0.5 mmol L-1 N-NO3- and 0.30 ± 0.05 mmol L-1 P-PO43- can achieve highest dry weight (1.6 ± 0.2 g L-1) and growth rate (0.55 ± 0.05 day-1) under the light density of 47 ± 20 μmol.m-2. s-1 and the temperature of 18.9 ± 0.5 ℃. The highest biomass productivity (0.40 ± 0.05 g L-1 day-1) was achieved under 3.25 ± 0.25 mmol L-1 N-NO3- and 0.125 ± 0.025 mmol L-1 P-PO43- . 3D-contour plots were established to predict how much biomass productivity, growth rate and dry weight could be achieved with certain N and P concentration ranging from 0 to 5.0 mmol L-1 and from 0 to 0.45 mmol L-1 respectively. Furthermore, we found nitrate is depleted one day after phosphate. Future research is recommended to focus on the effect of light density on the nutrients utilization because it is unclear if light density would promote S. costatum to consume more N and P in the medium.