Effect of macrophyte-driven transient storage on phosphorus uptake in spring coulee creek

Abstract

Investigations of phosphorus cycling and transport in streams lend insight into potential mechanisms of nutrient sequestration and can help mitigate human impact. In this study, we show a relationship between transient storage and phosphorus uptake in a cold-water stream in western Wisconsin. Hydrologic characteristics, nutrient spiraling metrics, macrophyte biomass, and geomorphological properties were quantified in seven reaches of Spring Coulee Creek. In each reach a solute transport model was used to estimate the median travel-time spent in transient storage, and uptake velocity was measured using pulsed additions of PO43- to the surface water. Stepwise linear regression was used to build models for transient storage and uptake velocity. Macrophyte biomass, stream bed slope, and riffle to pool ratio accounted for 99.6% of the variation in transient storage (P < 0.001). Transient storage, canopy cover, and slope accounted for 98.0% of the variation in uptake velocity (P = 0.002). This study shows that transient storage, primarily resulting from macrophyte beds, is positively correlated with phosphorus uptake but acknowledges the importance of other factors as well.