『Abstract
　We estimated net anthropogenic phosphorus inputs (NAPI) to 18 Lake Michigan (LM) and 6 Lake Erie (LE) watersheds for 1974, 1978, 1982, 1987, and 1992. NAPI quantifies all anthropogenic inputs of P (fertilizer use, atmospheric deposition, and detergents) as well as trade of P in food and feed, which can be a net input or output. Fertilizer was the dominant input overall, varying by three orders of magnitude among the 24 watersheds, but detergent was the largest input in the most urbanized watershed. NAPI increased in relation to area of disturbed land (R² = 0.90) and decreased with forested and wetland area (R² = 0.90). Export of P by rivers varied with NAPI, especially for the 18 watersheds of LM (R² = 0.93), whereas the relationship was more variable among the six LE watersheds (R² = 0.59). On average, rivers of the LE watersheds exported about 10％ of NAPI, whereas LM watersheds exported 5％ of estimated NAPI. A comparison of our results with others as well as nitrogen (N) budgets suggests that fractional export of P may vary regionally, as has been reported for N, and the proportion of P inputs exported by rivers appears lower than comparable findings with N.

Keywords: Phosphorus; NAPI; P export; River; Watershed; Nutrient budget; Nutrient loading; Lake Michigan; Lake Erie 』

Abbreviations
Introduction
Methods
　Study area
　Phosphorus budgets
　Riverine TP concentration and fluxes
Results
　Phosphorus budgets
　Riverine TP exports
　Relating NAPI to river export
　　Spatial relationship between NAPI and river export across watersheds
　　Temporal relationship between NAPI and river export within a watershed
Discussion
　NAPI as a predictor of river P loads
　Comparison of NAPI with NANI
Acknowledgements
References