In situ measurements of Rhodamine WT dye concentration and turbidity made during a tracer experiment on the Big Piney River near St. Robert, MO, on August 25-26, 2021

This data release includes fluorometer measurements of Rhodamine WT dye concentration and turbidity acquired during a tracer experiment performed on the Big Piney River near St. Robert, Missouri on August 25 - 26, 2021. The primary goal of this experiment was to perform a conservative tracer injection to better understand transport and dispersion processes related to environmental DNA (eDNA) transport. The experiment involved introducing a pulse of Rhodamine WT dye into the channel 1.5 kilometers upstream of the study reach then observing the dispersion of the dye along the river using in-situ instruments. In-situ measurements of Rhodamine WT concentration were used to quantify the passage of the dye over the course of the experiment at several locations throughout the study reach. Turner C3 Submersible Fluorometers were placed at three monitoring transects located at distances from 1.5 to 3.7 kilometers downstream from the dye release transect and measured the Rhodamine WT dye concentration in parts per billion (ppb). In addition, the fluorometers measured turbidity in nephelometric turbidity units (NTU). Each fluorometer was secured to a concrete block or attached to a buoy and its position was established using a Trimble R2 real-time kinematic (RTK) integrated global navigation satellite system (GNSS) receiver. At each monitoring transect, a fluorometer was placed approximately five to ten percent of the wetted channel width off both the right and left bank. All fluorometers recorded Rhodamine WT and turbidity data every 30 seconds. At approximately 15:07 CST on August 25, 2021, twelve liters of 20% Rhodamine WT were released into the Big Piney River. The in-situ fluorometers recorded the dye concentration and turbidity at 30 second intervals as the dye transported downstream. All fluorometers were retrieved on August 26, 2025. Data were downloaded to a field laptop and transferred to external hard drives for long-term storage and a custom python script was used to post-process the Rhodamine WT data to removing the background fluorescence and despiking the data.