Human shoreline development and the nutrient stoichiometry of aquatic plant communities in Canadian Shield lakes

Abstract

Human activities associated with residential development potentially alter ecological processes in lake littoral zones. We determined how the nutrient stoichiometry of aquatic plant communities relates to residential density around lakes of south-central Ontario. We calculated the elemental composition of entire plant communities from multiple sites in 12 lakes using measurements of individual plant C:N:P ratios and their areal biomass. We found considerable variability in the C:N:P ratios of whole aquatic plant communities among sites and lakes, which was not accounted for by intraspecific variability in the elemental composition of aquatic plants. Instead, differences in community-level C:N:P ratios primarily resulted from high interspecific variability in the elemental composition among dominant plant taxa and variable taxonomic composition of sampled plant communities. Plant community composition differed among lakes with and without shoreline residences, and we found lower C:N and C:P ratios in communities from littoral zones in human-developed lakes. Our results thus demonstrate a link between the elemental and taxonomic composition of aquatic plant communities, which may mediate biogeochemical responses of littoral zones to development of lake shorelines.