Abstract：The growth and nutrient contents in alga Nitzschia sp. were studied under different ratios of nitrogen to phosphorus(1:1,5:1,12.5:1,30:1,50:1,and 80:1)to evaluate the uptake ratio of nitrogen to phosphorus. It was found that there was significant differences in growth rate(P<0.05),the maximum at N/P=12.5:1,and the minimum at N/P<5:1 and N/P>50:1.The nutrient contents were obviously in accordance with the growth. There were chlorophyll c(P>0.05)ontent of 1.81 g/ml,29.9% of extracellular polymeric substance(EPS),17.8% of intracellular polymeric substance(IPS),5.3% of protein and 14.2% of lipid in the alga at N/P=12.5:1,higher than those at other ratios of nitrogen to phosphorus.After being cultivated,there was much lower N and P levels in the water media after culture,indicating that there were significant differences in the uptake ratio of total nitrogen(TN),over 55%(the maximum of 78% at N/P=30:1)(P<0.05). However,there were no significant differences in the uptake ratio of total phosphorus(TP),over 90%.
