Floating algal mats in the Rideau River and their relationship to nutrient concentrations and sources

Abstract

Metaphyton is a poorly studied algal community that can develop into large floating mats in rivers, wetlands and lakes. In this thesis, I examined the role of nutrients in determining differences in metaphyton biomass both seasonally and spatially within a lowland temperate river, the Rideau River, Ontario. The source of nutrients was also examined by analyzing the stable isotope signature of the mats in relation to adjacent land-use. Metaphyton in the river was restricted to slow-flowing areas of the littoral zone and was mainly comprised of filamentous green algae (Spirogyra and Cladophora). From the results of this study, conditions for the presence of large metaphyton communities in rivers include: (1) shallow littoral zones with minimal current, (2) the presence of macrophytes (as a substratum), and (3) moderate to high nutrient concentrations (particularly dissolved inorganic nitrogen). To control metaphyton in the Rideau River, the nitrogen loading to the system must be considered as well as phosphorus. (Abstract shortened by UMI.)