The Seasonal Succession of Epiphytic Communities within an Equisetum fluviatile L. Stand in Lake Pääjärvi, Southern Finland

Abstract The seasonal succession of epiphytic communities on Equisetum fluviatile was controlled both directly and indirectly by the macrophyte. Decaying macrophytic material supported rich algal growth and biomass accumulation in spring and early summer. Emergence of the macrophytes severely reduced underwater light availability, and the epiphytic algal biomass declined rapidly as a result of both lower photosynthetic activity of the epiphytic algae, and more intensive grazing by invertebrate herbivores. Epiphytic N: P ratios were lower than those in the water around suggesting that either the water was not the only source of phosphorus for the epiphytic algae or the algae took phosphorus up selectively from the water. Low epiphytic C: N ratios suggested a high potential nutritional value for herbivores.