[Seasonal succession of lotic epiphyton: effects of macrophyte cover and grazing by chironomid larvae].
The epiphyton is a community of periphyton on the aquatic plants. The seasonal dynamics of biomass, production and community structure of epiphytic algae on Potamogeton perfoliatus was studied at the Moscow River reach with low flow velocity from May to October 2000. The relative importance of physical-chemical environmental variables and herbivorous pressure in structuring the epiphyton community was accessed using multivariate redundancy analysis. Algal composition was mainly determined by the macrophyte cover, suggestion the overriding importance of the underwater light availability in seasonal development of epiphyton. There was a significant positive relationship between biomass of attached diatom Cocconeis placentula and abundance of chironomid larvae (r = 0.57; p < 0.01). This indicates that increase in herbivorous pressure caused the shift in epiphyton community structure. However, the intensity of herbivorous impact on epiphyton was ultimately determined by light availability in macrophyte stands. At low irradiance level and consequent slow growth of algae the upper layer of epiphyton was seriously destroyed by chironomids that resulted in dominance of C. placentula. As irradiance level and epiphyton productivity increased chironomids were unable to prevent biomass accumulation of the upper layer thus inhibiting the growth of C. placentula. The high concentrations of nutrients and relatively stable discharge determined the crucial role of light regime in the regulation of trophic interactions between epiphyton and chironomid larvae.
Rusanov
A G
AG
Khromov
V M
VM
D000818:Animals; D018533:Biomass; D002683:Chironomidae / Q000502:physiology*; D017753:Ecosystem; D056890:Eukaryota / Q000254:growth & development*; D005618:Fresh Water; D007814:Larva / Q000502:physiology; D008027:Light; D010944:Plants / Q000382:microbiology*; D012426:Russia; D012621:Seasons