Primary production of aquatic macrophytes and their epiphytes in two shallow lakes (Peipsi and Vrtsjarv) in Estonia

In shallow lakes with large littoral zones, epiphytes and submerged macrophytes can make an important contribution to the total annual primary production. We investigated the primary production (PP) of phytoplankton, submerged macrophytes, and their epiphytes, from June to August 2005, in two large shallow lakes. The production of pelagic and littoral phytoplankton and of the dominant submerged macrophytes in the littoral zone (Potamogeton perfoliatus in Lake Peipsi and P. perfoliatus and Myriopyllum spicatum in Lake Vrtsjarv) and of their epiphytes was measured using a modified (14)C method. The total PP of the submerged macrophyte area was similar in both lakes: 12.4 g C m(-2) day(-1) in Peipsi and 12.0 g C m(-2) day(-1) in Vrtsjarv. In Peipsi, 84.2% of this production was accounted for by macrophytes, while the shares of phytoplankton and epiphytes were low (15.6 and 0.16%, respectively). In Vrtsjarv, macrophytes contributed 58%, phytoplankton 41.9% and epiphytes 0.1% of the PP in the submerged macrophyte area. Epiphyte production in both lakes was very low in comparison with that of phytoplankton and macrophytes: 0.01, 5.04, and 6.97 g C m(-2) day(-1), respectively, in Vrtsjarv, and 0.02, 1.93, and 10.5 g C m(-2) day(-1), respectively, in Peipsi. The PP of the littoral area contributed 10% of the total summer PP of Lake Peipsi sensu stricto and 35.5% of the total summer PP of Lake Vrtsjarv.