Abstract
Phycological analyses were conducted in the shallow, eutrophic Lake Rosnowskie Duże (western Poland). Water samples were collected in 2002 and 2003 during the growing season from the submerged vegetation zone (Ceratophyllum demersum L.) and comparatively from the emergent vegetation zone (Typha angustifolia L.) and the pelagic zone. Phytoplankton was dominated by Chlorophyta, Bacillariophyceae, and Cyanoprokaryota. In comparison with other zones, the highest values of abundance and biomass of Chlorophyta were recorded in the submerged vegetation zone. Additionally, Ceratophyllum demersum was found to inhibit diatom development, which is probably connected with the secretion of allelopathic substances by this plant. The aim of the current study was to analyze the influence of Ceratophyllum demersum L. on the structure of phytoplankton in a shallow, eutrophic lake.