The composition and density of epiphyton on some macrophyte species in the partly meromictic Lake Verevi

Abstract

The epiphyton on 22 macrophyte species was studied in the hypertrophic stratified Lake Verevi mainly in the midsummer of 2000 and 2001. Some material from 1998 and 1999 was used as well. Chlorophyll a (Chl a) level was high: 330–360 µg g dw⁻¹ on emergent plants, and an average of 117–200 µg on floating-leaved plants and 820–920 µg g dw⁻¹ on submerged plants. Biomass was 15–23, 5–10 and 35–53 mg g dw⁻¹, respectively. The richest in epiphyton were submerged plants with densely growing and fine branchlets such as Ranunculus, Ceratophyllum, Myriophyllum, Utricularia, Potamogeton pectinatus L. and P. friesii Rupr. The share of Chl a in biomass was higher in 2001 (2.3%) than in 2000 (1.7%), which can be associated with lower irradiance in summer 2001. Filiform chlorophytes were dominating on most plants; 60% of biomass on submerged, 69% on emergent and 80% on floating-leaved plants; in some cases, the share of filamentous species was 95%. Diatoms formed 29, 12 and 7%, cyanobacteria 8, 16 and 10% of the same ecotopes, respectively. As a rule, the epiphyton was quite sparse on large Potamogeton leaves. Cyanobacteria were more abundant on large Potamogeton and Nuphar leaves, Elodea, on stems of P. natans L., Nuphar and on some emergent plants with a smooth and soft stem surface, as Butomus and Typha. Diatoms played the most important role on some Potamogeton species and in single samples of Ceratophyllum and Ranunculus. The morphology of plant species appears to be the main factor of epiphyton richness in L. Verevi.