The Resazurin-Resorufin System: Insights From a Decade of “Smart” Tracer Development for Hydrologic Applications

Abstract

The resazurin-resorufin tracer system has been used to quantify surface water-sediment interactions and microbial metabolic activity in stream ecosystems for one decade. This review describes the evolution of the tracer technique and summarizes how it has been used by the hydrologic and stream ecology communities. We highlight major hydrologic applications and milestones in the advancement of the reactive tracer system on scales ranging from cells to river reaches and catchments. We discuss the advantages and limitations of the resazurin-resorufin system for hydrologic applications and suggest new directions of research, including how to address existing knowledge gaps. Beyond the goal of summarizing information that is specific to the development of the resazurin-resorufin system, this review seeks to inform on the development of new “smart” tracer techniques as they, very likely, will face the same or similar challenges and opportunities encountered in the development of the resazurin-resorufin system. The supporting information furthermore contains a detailed manual for the application of the resazurin-resorufin system as hydrologic tracer and MATLAB codes for the analysis of their reactive transport.