Baseline isotope data for Spirodela sp.: Nutrient differentiation in aquatic systems

► Spirodela clearly differentiated between KNO3 and cow manure nutrient sources. ► Spirodela tended towards isotopic equilibration by day four for both δ15N and δ13C. ► Plant δ15N was depleted for KNO3 and enriched for manure with increasing concentrations. ► Spirodela was found to have a commensal cyanobacterial relationship. ► Using plants to describe N-loading requires δ15N, δ13C and descriptors of N uptake.