Data from laboratory experiments to assess seasonal carbon, nitrogen, and phosphorus processing in water and sediments from the Illinois River near Starved Rock Lock and Dam, 2022.

Data on carbon and nutrient processing in key locations and over seasonal time scales can provide critical information about the concentrations and potential utilization rates of bioavailable constituents that are known to have a role in cyanobacteria harmful algal blooms (cyanoHABs). Laboratory experiments were performed to measure seasonal nutrient processing rates of carbon, nitrogen and phosphorus in river water and bottom sediments collected just upstream of the Next Generation Water Observing System (NGWOS) location at Starved Rock Lock and Dam USGS gaging station number 05553700 on the Illinois River. This site was chosen based on previous development of cyanoHABs. Sediments and unfiltered river water were collected during the spring (April), summer (August), and fall (November) of 2022 then shipped to Boulder, CO for laboratory experiments. River water alone and river water combined with < 2-millimeter sieved sediments were assessed under ambient nutrient conditions and nitrogen amended conditions to determine rates of production or consumption for the following processes: 1) aerobic carbon dioxide production, oxygen consumption, and aqueous nutrient transformations, and 2) anaerobic denitrification, carbon dioxide production, methanogenesis, and aqueous nutrient transformations. Modifications to certain experiments were made in November 2022 based on results from the April and August 2022 experiments and are noted in the metadata steps. Background sediment total carbon and nitrogen content, deionized water and potassium chloride extractable sediment nutrient concentrations, and river water nutrient concentrations were measured during each collection. Sequential extractions of the sieved sediment were performed using deionized water, sodium bicarbonate, sodium hydroxide, and hydrochloric acid to measure phosphorus content of the sediment during the various steps.

Site information, sediment characterization details, dissolved gases and biogeochemical nutrient experiment data, sediment sequential extraction data, and water-quality data are presented in this data release as nine comma-separated values (.csv) formatted tables. A data dictionary file describes the data found in the .csv files. Method details and references are located in the metadata file Illinois R nutrient processes 2022.xml.