ABSTRACTThree diatom species,Stephanodiscus hantzschii(Ehr.) Grun.,Asterionella formosaHass. andFragilaria crotonensisKitt. Hass. were isolated from Lake Maarsseveen where they are dominant and show a successional sequence. The physiological responses of each species to temperature and limitation by silicon and phosphorus were determined over the temperature range of 5° to 20° C using short‐term batch culture methods.Stephanodiscus hantzschiihad higher maximum growth rates than the other two species at all temperatures, and the maximum growth rates of all species increased with increasing temperature. Temperature affected not only maximum growth rates but also half‐saturation constants (Ks) and the minimum cell quotas.S. hantzschiihad low silicon requirements for growth under Si‐limiting conditions, andA. formosaandF. crotonensishad higher and nearly identical silicon requirements. The Ksvalues for silicon forS. hantzschiiwere essentially constant from5° to 20° C but variedgreatly for the other two species.A. formosahad the lowest requirements for growth under phosphorus limitation,F. crotonensiswas intermediate andS. hantzschiihad the highest growth requirements for phosphorus. The K1values for phosphorus were constant over the temperature range for bothA. formosaandF. crotonensisand were much higher and variable forS. hantzschii.Nutrient competition experiments were performed in continuous cultures at four temperatures and various Si:P ratios. The results generally, but not always, confirmed the predictions based on the Monod relationships for each species. Results not in agreement with predictions were usually because of similar physiological properties ofA. formosaandF. crotonensisor because of decreased loss rates forF. crotonensisdue to wall growth. In cultures with all three species phosphorus‐limited (Si:P>75),A. formosaoften dominated as predicted, althoughF. crotonensiswas sometimes the most abundant species. As predicted,S. hantzschiinever dominated at high Si:P ratios. At intermediate Si:P ratios whenA. formosaandF. crotonensiswere both Si‐limited andS. hantzschiiP‐limited, all three species coexisted becauseA. formosaandF. crotonensishave almost identical silicon requirements, although sometimesF. crotonensiswas more abundant than predicted. At 10°C the results agreed best with the predictions;A. formosadominated at high Si:P ratios andS. hantzschiidominated as predicted at low Si:P ratios when all three species