Comparative primary productivity of algal epiphytes on three species of macrophyte in the littoral zone of Lake Ohrid, Yugoslavia

Primary productivity of algal epiphytes on the surfaces of Phragmites, Potamogeton , and Nuphar was measured seasonally from June 1978, through June 1979, in the littoral zone of Lake Ohrid, using 14 C methodology. Surface areas of individual macrophytes were determined throughout the study period through the use of a non‐miscible surfactant and a calibration curve of surfactant weight versus known, calculated surface areas. Mean total surface area available for epiphytic colonization during the study period was 1.032 m 2 macrophyte surface per m 2 of littoral zone for Phragmites , 0.810 m 2 for Potamogeton , and 0.167 m 2 for Nuphar . Seasonal rates of mean primary productivity of algal epiphytes on Phragmites from the surface to the light‐compensation depth ranged from 84–1406 mg C m −2 littoral zone d −1 ; ranges for epiphytes on Potamogeton and Nuphar were 77–586 and 69–268 mg C m −2 littoral zone d −1 , respectively. Maximum rates were observed typically during June; minimum rates were observed typically during August to December. Mean daily productivity rates over the 12 month period were for epiphytes on Potamogeton 167.0, on Nuphar 100.4 and on Phragmites 671.2 mg C m −2 littoral zone d −1 . Calculated annual production for epiphytes on Nuphar was 36.65, on Potamogeton 60.95 and on Phragmites 245.0 g C m −2 littoral zone yr −1 . Epiphytic production data were typically considerably higher than production data obtained for littoral and pelagial planktonic algae and compare favorably with published data for epiphytic and periphytic production in Lawrence Lake, Marion Lake, and Borax Lake.