The aim of this work was to present a quantitative and qualitative analysis of a phytoplankton assemblage under the influence of Ceratophyllum demersum L. during a two-year field study. Literature data obtained under laboratory conditions indicate that C. demersum may cause a decrease in the blue-green algae biomass, which is considered to be evidence of the significance of allelopathy. The observations reported in the current paper indicated that there was no clear effect on cyanoprokaryota whereas decreases in the quantity of Cryptophyta, Dinophyta, Chlorophyta, and Chrysophyceae are noted.
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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.
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Studies on the role of Ceratophyllum demersum L. as a substratum for epiphytic midges in relation to lake status were conducted within two shallow polymictic lakes of Polesie Lubelskie. Lake Skomielno is classified as macrophyte dominated (MD), clear water state and Lake Syczyńskie represents phytoplankton dominated (PD), turbid water state. The results demonstrated that lake status is a determinant of community composition of epiphytic chironomids. Both species richness and abundance showed significantly higher values in the macrophyte dominated lake. The studied ecosystems differ in the composition of dominant chironomid taxa. In the clear state lake, the group of dominants included four taxa: Psectrocladius sp. (gr. sordidellus), Glyptotendipes sp., Ablabesmyia phatta and Paratanytarsus austriacus, the contribution of which changed during the studied months. In the turbid state lake two midge taxa dominated: Cricotopus sp. (gr. sylvestris) and Endochironomus albipennis. The CCA ordination showed the important differences between the studied lake types. In the MD lake, four environmental factors (temperature, chlorophyll-a, total P, P-PO4) influenced mostly the distribution and composition of epiphytic chironomids. In the MD lake, five variables (periphyton biomass, total suspension, N-NH4, total P, pH) affected the structure of midges.
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