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Application of a Primary Production Model to Epiphytic Algae in a Shallow, Eutrophic Lake

Jones, R. Christian
Ecology 1984 v.65 no.6 pp. 1895-1903
Myriophyllum spicatum, absorption, algae, biomass, carbon, diurnal variation, epiphytes, equations, eutrophication, growing season, lakes, light intensity, littoral zone, macrophytes, models, photosynthesis, phytoplankton, primary productivity, Wisconsin
A modification of Fee's phytoplankton model was used to calculate the production of algae epiphytic on the submersed macrophyte Myriophyllum spicatum in shallow, eutrophic Lake Wingra, Wisconsin. The model involved integration of four basic relationships using time— and depth—stepped difference equations: (1) depth distribution of algal biomass; (2) photosynthesis per unit biomass as a function of light intensity, (3) irradiance—depth relationship, and (4) diurnal variation in surface irradiance. Epiphyte production in the littoral zone of Lake Wingra, measured (as carbon) for two growing seasons, was 29—38 g°m— ²°yr— ¹, placing the lake at the lower range of reported values. Since epiphyte production was 48—79% of macrophyte production, well within the reported range, the lower production values resulted from less dense weedbeds (lower substrate availability) rather than lower density of epiphytes. Algal biomass defined the upper bound for production, while irradiance levels on each day determined actual production by decreasing this potential by varying degrees. Other parameters of the production model, such as light extinction coefficient and photosynthetic parameters, explained little of the variation in production. These results emphasize the importance of accurately determining the quantity and vertical distribution of attached algal biomass when making production estimates.