North Temperate Lakes LTER: High Frequency Data: Meteorological, Dissolved Oxygen, Chlorophyll, Phycocyanin - Lake Mendota Buoy 2006 - current

The instrumented buoy on Lake Mendota is equipped with limnological and meteorological sensors that provide fundamental information on lake thermal structure, weather conditions, and lake metabolism. Data are collected every minute. Hourly and daily averages are derived from the high resolution (1 minute) data. Hourly and daily values may not be current with high resolution data as they are calculated at the end of the season.
Meteorological sensors measure wind speed, wind direction, relative humidity, air temperature, and photosynthetically active radiation (PAR). Not all sensors are deployed each season. A list of sensors used since the first deployment in 2006 is provided as a downloadable CSV file. The buoy is removed during the winter when the lake is ice-covered (typically Dec-Apr). Lake temperature data collected at the same buoy site can be found in an ancillary dataset.
Number of sites: 1. Location lat/long: 43.0995, -89.4045
Notable events:
2017 - A boating mishap caused the loss of air temperature, relative humidity, and wind sensors between May 28 and July 11. The dissolved oxygen sensor had significant biofouling from algae and zebra mussels.
2019 - A YSI EXO2 sonde was added to the buoy and includes DO, chlorophyll, phycocyanin, specific conductance, pH, fDOM, and turbidity sensors. The chlorophyll and phycocyanin sensors replace Turner Cyclops 7 fluorometers that had been in use in prior years. Both sets of sensors output RFU, but have significant magnitude differences. The YSI pH, DO, and specific conductance sensors were cleaned and recalibrated every two weeks.
2020 - Cleaning and calibration of the YSI sensors occurred nearly every week. The dissolved CO2 sensor was not operating between July 2 and September 17.
2021 - Due to power and communications issues, the buoy was not operating August 22-31, and data is intermittent between November 8 and December 3. An effective method to keep the underwater PAR sensor mostly free of biofouling algae has been employed.
2022 - Buoy was not operating June 6-9 and July 2-5 due to power issues. Underwater PAR sensor unusable after October 1.
2023 - Conductivity sensor was not operational Apr 27 - May 24. The sensor was replaced. The wiper for the YSI sonde had failed Nov 4 - 14, which significantly affected four sensors: chlorophyll, phycocyanin, conductivity, and turbidity.