Abstract: The influence of iron and silicon nutrients on the growth rates of three benthic diatoms, namely Cocconeis scutellum var. Parva, Amphora coffeaeformis and Navicula mollis was studied by using an in situ OD measurement. The results showed that Fe EDTA was better than ferric citrate in the acceleration of the growth rates for all the three diatoms. The optimum concentration of Fe EDTA was 0.5 mg/L and the optimum silicate concentration was 2 mg/L in the artificial seawater medium for C. scutellum var. Parva , and 2.5 in the natural seawater medium for all the three diatoms. The orthogonal test of the four factors of nitrogen, phosphorous, iron and silicon showed that the optimal concentration ratios (mg/L) of the four nutrients were as follows: 5.0∶0.25∶0.5∶2.0 for C. scutellum var. Parva ; 2.5∶1.0∶1.0∶2.0 for A. coffeaeformis ; 5.0∶0.15∶0.5∶2.0 for N. mollis. And among the four factors, silicon had very remarkable promotion to the growth rate of the three diatoms.
1998, Vol. 13 
