High spatial resolution sensor-based surface water quality data along the Lake Winnebago-Fox River-Green Bay continuum in 2023-2025

In support of multiple Great Lakes Restoration Initiative (GLRI) projects focusing on Green Bay and upland sources, surface water quality metrics related to primary producers, nutrients, and conductivity were measured using a boat-mounted, continuous sampling platform. These data are used to document changes in water quality as water flows from Lake Winnebago through the lower Fox River and ultimately into Green Bay. Surface water quality was measured using a boat-mounted, continuous sampling platform known as the Fast Limnological Automated Measurements (FLAMe; https://doi.org/10.1021/es504773x). Water was continually pumped onboard a moving boat to a series of water quality sensors configured to capture data continuously. Measurements were georeferenced and spatially corrected using established routines and can be used to produce maps of water quality where the boat traveled. Overall, 455,102 point measurements were collected across the inland water continuum (available in file: FLAMe_data.csv). Additionally, sensor-based measurements are associated with 239 discrete field measurements and/or water samples analyzed for additional chemical and biological attributes (available in file: FLAMe_samples.csv).
Up to nine onboard multiparameter instruments recording data from one or more sensors were used to collect up to 82 variables during eight sampling campaigns between August 2023 and July 2025. Onboard water quality sensors varied among campaigns, and included a YSI EXO2 (temperature, specific conductivity, turbidity, pH, dissolved oxygen, dissolved organic matter fluorescence, and total algal fluorescence), a Seabird SUNA V2 optical nitrate sensor (nitrate, absorbance), a bbe fluoroprobe (green algae, blue green algae, diatoms, and cryptophytes), and a Los Gatos Research Ultraportable Greenhouse Gas Analyzer (dissolved carbon dioxide and methane). Additional instruments included two Garmin Global Positioning System (GPS) receivers (latitude, longitude, time), a Garmin depth sounder (water temperature and depth), and a Vaisala CS106 barometer (barometric pressure). All data were recorded continuously on a Campbell Scientific CR6 datalogger. System attributes (e.g., internal temperature, boat speed, wiper position, battery voltage) were also recorded to aid data quality control. Details on data attributes including descriptions, units, and sources are included in the file: FLAMe_data_dictionary.csv.
This data release contains spatial data from three overlapping GLRI-funded research projects focused in Lake Winnebago, the lower Fox River, and Green Bay using common equipment. Six 3- to 4-day campaigns (August 2023, June 2024, July 2024, August 2024, May 2025, and July 2025) targeted phytoplankton distribution in the Lake Winnebago-Fox River-Green Bay continuum. Spatial transects were established crossing the north-half of Lake Winnebago, along the Fox River, and out into Green Bay. Two additional 2- to 3-day campaigns (April 2025, June 2025) focused on salinity patterns in Green Bay with 14 littoral/pelagic transects circumnavigating Green Bay from Marinette, WI to Brussels, WI. The crew attempted to sample the same features on each campaign; however, the exact sample path varied based on weather and hydrologic conditions. Actual sampling locations loosely followed pre-determined routes, but they were adjusted based on weather, field observations, and communication with local guides. See file: FLAMe_map.png for transect paths organized by campaign.