We found that the Florida Lake Vegetation Index (LVI) did not identify Florida lakes that were impaired due to excess loading of phosphorus or nitrogen from anthropogenic sources. The index is based on 4 plant metrics: the Coefficient of Conservatism of the dominant or co-dominant taxa, the percent of sensitive taxa, the percent of native taxa, and the percent of invasive exotic taxa. Our analysis of the data used by the Florida Department of Environmental Protection to establish and calibrate this biotic index found no link between nutrient concentrations and the LVI. The LVI was primarily associated with the pH and specific conductance of the lake waters, with the best scores found in acidic lakes and the poorest scores in more alkaline lakes. These variables are the result of natural gradients, not pollution, and are not included in the calculation of the LVI. Our study illustrates the importance of considering natural factors that determine the value of any index of biological integrity before it is used to indicate anthropogenic pollution
