Relationships between resource ratios and phytoplankton species composition during spring in five north German lakes

Phytoplankton species composition and the availability of potentially limiting resources were investigated in five northern German lakes (Suhrer See, Kellersee, Behler See, Plußsee, and Krummsee) during spring 1988. Species composition was related to resource ratios to test Tilman’s resource‐ratio hypothesis. The clearest results were obtained for Aulacoseira spp. Both the time‐courses within the lakes and the comparison among the lakes suggest a strong tendency of this genus to become dominant at high Si : light ratios. Fragilariaceae occupied the next position on the Si: light gradient. Such conditions permitted them to become important even when Si : P ratios were quite low. With the onset of stratification diatoms were replaced by flagellates.