TAXONOMY AND ECOLOGY OF PHYTOPLANKTON IN A HYPERTROPHIC, GRAVEL-PIT LAKE .3. DIATOMOPHYCEAE

This work shows the taxonomy and ecology of 5 taxa of Diatomophyceae p resent in El Porcal from 1984 to 1985 with the data obtained weekly. I n order of biomass abundance were Cyclotella meneghiniana, Nitzschia g racilis, Nitzschia acicularis, Stephanodiscus hantschii and Nitzschia palea var. debilis. The most opportunist populations were N. aciculari s and S. ephanodiscus hantzschii. C meneghiniana was present in greate r abundance in the mixing period, N. gracilis had growth periods, in b oth mixing and stratification process. In the mixing-stratification pe riod were N. acicularis and S. hantzschii. N. palea var. debilis only appeared for a few weeks in mixing-stratification period in 1984. The study of morphology of C meneghiniana shows a positive relation betwee n diameter and diameter: pervalvar axis ratio and a surface:volume rat io constant throughout study period. In El Porcal lake diatom biomass dynamics are related with physical and nutritional disturbance periods and not only physical disturbances such as have been demonstrated.