Ecology and Evolutionary Biology

Statistical comparisons of 2008 surface water quality data with a historical data set at weekly and sub-weekly resolution has revealed significant reductions in total phosphorus (TP) and a trend of reduction in dissolved phosphorus following implementation of a municipal ordinance limiting the application of lawn fertilizers containing phosphorus. No reductions were seen at a control river site not affected by the ordinance. Other control analytes, including nitrate and colored dissolved organic matter similarly proved unresponsive compared to P. The data were analyzed in the context of a statistical model that characterized historical temporal variability and predicted the requisite sampling effort to detect changes of expected magnitude. Changes of 25 % in monthly mean value were predicted to require weekly samples during the summer for only 1 or 2 years for TP, and statistically significant reductions measured after 1 year average