The U.S. Geological Survey (USGS) collected continuous select fluorescence, transmission, and water temperature data at Illinois River at Starved Rock, Illinois, near Utica, Illinois (USGS 05553700) from June 2023 through December 2024. The purpose of data collection was to quantify select algal fluorescence and water-quality parameters to further understand harmful algal blooms. This data release presents six comma-separated values (csv) files containing 15-minute time-series data of cryptophyta fluorescence, cyanobacteria fluorescence, diatom fluorescence, green algae fluorescence, transmission, and water temperature results collected from Illinois River at Starved Rock, Illinois.