Abstract
Effects of nitrogen on biomass accrual of benthic diatom assemblages were examined using indoor artificial streams supplied with spring water (NO3-N,0.306 mg/1; PO4-P,0.075 mg/1; SiO2,35.3 mg/I; pH 7.4; conductivity,148 μS/cm) from the source of the Jigoku River, Nikko City, Japan. We manipulated the NO3-N concentration in the artificial streams at 0.306,0.781,1.586 and 2.349 mg/1 and investigated the temporal pattern of the biomass accrual in each stream to estimate the intrinsic growth rate and maximum biomass using the logistic growth equation. The results showed that there were no significant differences in the intrinsic growth rate and maximum biomass between the streams at the four different NO3-N concentrations. As the concentration of phosphorus in spring water was greater than the concentration saturating benthic algal growth (0.025-0.050 mg/1), the ambient nitrogen concentration of 0.3 mg/1 is already growth-saturating for lotic benthic diatom assemblages.
