Abstract
Phytoplankton in the littoral zone of the urban Lake Jeziorak Mały (Mazurian Lakeland) were studied between April and October of 2002 and 2003. Five diatom species (Fragilaria delicatissima, Aulacoseira granulata, Fragilaria capucina, Diatoma vulgaris, Fragilaria crotonensis) and one genus (Rhizosolenia sp.), comprising the major proportion of total abundance and biomass of diatoms, were chosen for the study. The relationships between the biomass of these diatoms and water temperature, oxygen content, electrolytic conductivity, orthophosphates, silicon and calcium concentrations were analyzed. The biomass of species F. delicatissima, A. granulata and F. capucina tended to be the highest of the six, which were also associated with the widest temperature range, 10.0°C to 18.7°C. These three species exhibited maximum biomass at the highest orthophosphate concentrations. By contrast, F. crotonensis developed in the narrowest water temperature range, 10.0°C to 13.7°C. The maximum biomass of this species was noted at high silicon and calcium concentrations. The diatoms (except F. capucina and Rhizosolenia sp.) contributed to statistically significant observed reductions in nutrient concentrations during their growth. These results indicate that a range of factors is involved in the productivity and limitation of the studied diatoms, with water temperature being of particular importance.