Episodes of low dissolved oxygen are common during the summer in the bottom water of the central basin of Lake Erie. Dissolved oxygen and temperature observations at a high temporal frequency and a broad spatial extent provide the supporting data for the development of experimental hypoxia hindcast and forecast models and aid our understanding of the development and extent of hypoxia. Underwater sensor moorings were deployed across the central basin of Lake Erie to monitor oxygen conditions by the National Oceanic and Atmospheric Administration (NOAA) Great Lakes Environmental Research Laboratory and the Cooperative Institute for Great Lakes Research (CIGLR), University of Michigan. Moorings were deployed during the summer season beginning in 2017 to collect in situ data for the following parameters, water temperature, dissolved oxygen, water current speed and direction, specific conductivity, pH, turbidity, oxidation-reduction potential (ORP), chlorophyll, phycocyanin, dissolved organic matter, and phosphorus at hourly or sub-hourly time intervals.

Two moorings were deployed near the M110 station by the NOAA Great Lakes Environmental Research Laboratory (GLERL) from May 2021 to May 2022 and September 2021 to May 2022. These observations support the GLERL Long-Term Ecological Research program. The M110 station is part of the Muskegon Transect in Lake Michigan near the NOAA Lake Michigan Field Station, Muskegon, MI. The first mooring, “M110”, is an oceanographic mooring containing a temperature string and an acoustic doppler current profiler approximately 200 meters from the temperature string. The second mooring, “M110X”, is a physical and biological mooring that collects temperature and fluorometer measurements over the winter. The approximate depth of this mooring location was 110 m. The M110 deployment’s temperature string collects vertical water temperatures at hourly time intervals at 16 depths by SeaBird and Tidbits thermistors. Current speed and direction were collected at sub-hourly time intervals at 49 depths by a Teledyne RDI WorkHorse acoustic doppler current profiler. The data files for this mooring contain the station name “noaa-glerl-michigan-lter-m110-” in the file name. The physical and biological mooring collects surface and bottom temperature and fluorometer measurements hourly. The temperature sensors were Sea-Bird 39. The Wet Labs fluorometers measured voltage, which were converted to chlorophyll concentrations. Please see the “Supplemental Information” for more information about the chlorophyll concentrations. The data files for this mooring contain the station name “noaa-glerl-michigan-lter-m110x-” in the file name. All measurements were collected continuously during this time period. Included in this data package are two data formats, netCDF and CSV. Metadata is included in the netCDF file, the CSV files also contain a data dictionary explaining the column headings.

Two moorings were deployed near the M110 station by the NOAA Great Lakes Environmental Research Laboratory (GLERL) from 2014 through 2020. These observations support the GLERL Long-Term Ecological Research program. The M110 station is part of the Muskegon Transect in Lake Michigan near the NOAA Lake Michigan Field Station, Muskegon, MI. The first mooring, “M110”, is an oceanographic mooring containing a temperature string and an acoustic doppler current profiler approximately 200 meters from the temperature string. The second mooring, “M110X”, is a physical and biological mooring that collects temperature and fluorometer measurements over the winter. The approximate depth of this mooring location was 110 m. The M110 deployment’s temperature string collects vertical water temperatures at hourly time intervals at multiple depths by SeaBird, HOBO Onset, and HOBO Tidbits thermistors. Current speed and direction were collected at sub-hourly time intervals at multiple depths by a Teledyne RDI WorkHorse acoustic doppler current profiler. The data files for this mooring contain the station name “noaa-glerl-michigan-lter-m110-” in the file name. The physical and biological mooring collects surface and bottom temperature and fluorometer measurements hourly. The temperature sensors were HOBO Tidbit and Sea-Bird 39 thermistors. The Wet Labs fluorometers measured voltage, which were converted to chlorophyll concentrations. Please see the “Supplemental Information” for more information about the chlorophyll concentrations. The data files for this mooring contain the station name “noaa-glerl-michigan-lter-m110x-” in the file name. All measurements were collected continuously during the deployments. Note the deployments are not continuous throughout this time period. Several sensors shown on the mooring diagrams failed during deployments, those data are not included in this accession. Included in this data package are two data formats, netCDF and CSV. Metadata is included in the netCDF file, the CSV files also contain a data dictionary explaining the column headings.

One mooring was deployed near the M45 station by the NOAA Great Lakes Environmental Research Laboratory (GLERL) from October 2020 to June 2021. These observations support the GLERL Long-Term Ecological Research program. The M45 station is part of the Muskegon Transect in Lake Michigan near the NOAA Lake Michigan Field Station, Muskegon, MI. The “M45X” mooring is a physical and biological mooring that collects temperature and fluorometer measurements near the surface and bottom over the winter. The approximate depth of this mooring location was 45 m. The M45X mooring collects surface and bottom temperature and fluorometer measurements hourly. The temperature sensors were Sea-Bird 39. The Wet Labs fluorometers measured voltage, which were converted to chlorophyll concentrations. Please see the “Supplemental Information” for more information about the chlorophyll concentrations. The data files for this mooring contain the station name “noaa-glerl-michigan-lter-m45x-” in the file name. Note, during the 2020-2021 deployment a fluorometer was deployed at the bottom of the M45X mooring, but only collected data for the first several days. These data are not included in the accession. All measurements were collected continuously during this time period. Included in this data package are two data formats, netCDF and CSV. Metadata is included in the netCDF file, the CSV files also contain a data dictionary explaining the column headings.

Two moorings were deployed near the M110 station by the NOAA Great Lakes Environmental Research Laboratory (GLERL) from August 2020 to May 2021 and October 2020 to May 2021. These observations support the GLERL Long-Term Ecological Research program. The M110 station is part of the Muskegon Transect in Lake Michigan near the NOAA Lake Michigan Field Station, Muskegon, MI. The first mooring, “M110”, is an oceanographic mooring containing a temperature string and an acoustic doppler current profiler approximately 200 meters from the temperature string. The second mooring, “M110X”, is a physical and biological mooring that collects temperature and fluorometer measurements near the surface and bottom over the winter. The approximate depth of this mooring location was 110 m. The M110 deployment’s temperature string collects vertical water temperatures at hourly and sub-hourly time intervals at 16 depths by Hobo Onset and Tidbits thermistors. Current speed and direction were collected at sub-hourly time intervals at 49 depths by a Teledyne RDI WorkHorse acoustic doppler current profiler. The data files for this mooring contain the station name “noaa-glerl-michigan-lter-m110-” in the file name. The physical and biological mooring collects surface and bottom temperature and fluorometer measurements hourly. The temperature sensors were Sea-Bird 39. The Wet Labs fluorometers measured voltage, which were converted to chlorophyll concentrations. Please see the “Supplemental Information” for more information about the chlorophyll concentrations. The data files for this mooring contain the station name “noaa-glerl-michigan-lter-m110x-” in the file name. All measurements were collected continuously during this time period. Included in this data package are two data formats, netCDF and CSV. Metadata is included in the netCDF file, the CSV files also contain a data dictionary explaining the column headings.

One mooring was deployed near the M45 station by the NOAA Great Lakes Environmental Research Laboratory (GLERL) from September 2021 to May 2022. These observations support the GLERL Long-Term Ecological Research program. The M45 station is part of the Muskegon Transect in Lake Michigan near the NOAA Lake Michigan Field Station, Muskegon, MI. The “M45X” mooring is a physical and biological mooring that collects temperature and fluorometer measurements over the winter. The approximate depth of this mooring location was 45 m. The M45X mooring collects surface and bottom temperature and fluorometer measurements hourly. The temperature sensors were Sea-Bird 39. The Wet Labs fluorometers measured voltage, which were converted to chlorophyll concentrations. Please see the “Supplemental Information” for more information about the chlorophyll concentrations. The data files for this mooring contain the station name “noaa-glerl-michigan-lter-m45x-” in the file name. All measurements were collected continuously during this time period. Included in this data package are two data formats, netCDF and CSV. Metadata is included in the netCDF file, the CSV files also contain a data dictionary explaining the column headings.

Vertical water temperature data were collected at multiple depths on a single mooring in the central basin of Lake Huron from May 2021 through May 2023. This mooring was located approximately 36 miles east of South Ninemile Point, Alpena, Michigan. Vertical temperatures were collected sub-hourly at 21 depths; maximum depth of this mooring location was 220 m. Seabird 39 and 56 models were used for the observations with a temperature accuracy of ±0.002 °C.

Vertical water temperature data were collected at multiple depths on a single mooring in the central basin of Lake Huron from June 2019 through May 2021. This mooring was located approximately 36 miles east of South Ninemile Point, Alpena, Michigan. Vertical temperatures were collected hourly at 21 depths; maximum depth of this mooring location was 215 m. Seabird 39 and 56 models were used for the observations with a temperature accuracy of ±0.002 °C.

Vertical water temperature data were collected at multiple depths on a single mooring in the western basin of Lake Erie from May 2017 through September 2017. Vertical temperatures were collected hourly at 13 depths over the period of record; maximum depth of this mooring location was 13 m. Two brands of thermistors were used including R. Brancker and Seabird 39, both have a temperature accuracy of ±0.002 °C.

Water-quality constituents were measured along planned survey lines, which were generally perpendicular to the shoreline and spaced 100 meters apart, over an approximately 2.3-mile section of nearshore Lake Erie on June 10-12, 2019 (survey 1), and August 19-21, 2019 (survey 2), with a YSI EcoMapper autonomous underwater vehicle (AUV) using an undulating dive pattern (a 15-degree dive angle between the surface and 6 feet above the bottom). Water-quality data collected in this area included three-dimensional measurements of water temperature, specific conductance, pH, dissolved oxygen, chlorophyll, and phycocyanin (blue-green algae). The water-quality data were measured at 1-second intervals and were geo-referenced with the AUV onboard Global Positioning System (GPS WAAS) system. There was a total of 40 survey lines which typically started about 50 meters offshore and ended 500 meters offshore, and the survey lines covered the area around the mouth of Euclid Creek, Villa Angela Beach, Wildwood Marina, and the Easterly Wastewater Treatment Plant. Data were post-processed with a custom MATLAB script. Each water-quality measurement has an associated latitude and longitude (WGS84) and sample depth (in meters) below the surface. All water-quality sensors were calibrated per USGS standard methods prior to the start of the survey. These water-quality measurements were collected over the course of six total days, three in early summer (survey 1) and three in late summer (survey 2), to characterize circulation, mixing, and transport patterns in nearshore Lake Erie in the vicinity of Euclid Creek and Villa Angela Beach.