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Abstract
Anthropogenic activities greatly accelerate the nutrient input into ecosystems. Rivers and streams not only transport nutrients between terrestrial and oceanic ecosystems but also transform nutrients and control the nutrients export from watersheds. Thus, a robust technique of estimating nutrient uptake rate in streams is necessary. Using pulse release of solutes to estimate nutrient uptake rates is an logistically easy experimental approach but a proper statistical method for analyzing such data is lacking. In this study, we analyzed the theoretical and practical issues of the current methods and propose a new method of estimating nutrient uptake rate from pulse release data based on the solute dynamics described by the advection--dispersion equation. The new method allowed us to estimate the dynamics of nutrient uptake with explicit assumptions. We implemented the estimation routine in R (https://github.com/songchao1986/Nutrient-uptake) for easy application.