Trophic State Classification of Lakes with Aquatic Macrophytes

We developed an approach for assessing the trophic status of lakes having growths of aquatic macrophytes because conventional criteria for classifying trophic state emphasize conditions in the open water and ignore the nutrients, plant biomass, and production associated with macrophytes. We propose that a potential water column nutrient concentration be determined through adding the nutrients contained in macrophytes to those in the water. Potential nutrient concentrations can be used in existing indices to classify lake trophic status. This approach permits a first approximation of the potential impact of macrophytes on lake trophic state.