HABs and Lake Mendota

Lake Information

Lake Mendota is located in south central Wisconsin in the Upper Rock Watershed. It has been called the most studied lake in the world and has been studied since the 1880’s. Cyanobacterial blooms have been reported on Lake Mendota as early as 1976 with a very severe bloom in the spring of 1990. Many efforts have been made to reduce the frequency of harmful algal blooms on Lake Mendota.

For more information on Lake Mendota, please visit the Mendota Research Group website.

The cyanobacteria found in Lake Mendota from 1995-2008 with a biomass concentration greater than 1.000 were Aphanizomenon flos-aquae, Microcystis aeruginosa, Oscillatoria agardhii, Anabaena angstumalis, and Aphanothece nidulans.



Photo Credit: UW SSEC and WisconsinView

Photo Credit: UW SSEC and WisconsinView

Mendota Research Group (MeRG) – MeRG is a collaboration between the UW Center for Limnology, Space Science and Engineering Center, and Civil and Environmental Engineering Department along with GLEON and NTL-LTER. An in-situ buoy is placed on Lake Mendota each summer and data about water temperature, dissolved oxygen saturation, chlorophyll-a, phycocianin, wind speed and direction, air temperature, and relative humidity are taken every two minutes from its sensors. Some of the research and projects being done using the buoy data have been on cyanobacterial population structure in the Yahara Lakes (CEE), data integration from the buoy, MODIS, and manual sampling (CFL), and relating satellite data to pigment concentration on Mendota’s surface (SSEC). An archive of data from the buoy can be found under “Data” on the North Temperate Lakes Long Term Ecological Research (NTL-LTER) website.

EPA Assessment of Water Quality – Under the Federal Clean Water Act, a list of impaired waters list must be submitted to the EPA biyearly by every state. Waters that don’t meet the standards of chapters NR 102-105 of the Wisconsin Administrative Code are put on the list. Criteria for Phosphorous levels are not currently included, but they are being developed. There is also work being done to help monitoring programs assess the impact of algae. Lake Mendota was first placed on the list in 1998 and has been in the low priority category in 2002, 2004, and 2006 (a list was not submitted in 2000) which means that a TMDL will most likely be completed in 5-13 years.

Public Health-Madison and Dane County – PHMDC monitors Dane County beaches during the swimming season.  Governor Nelson State Park, James Madison, Lake Mendota County Park, Maple Bluff, Marshall, the Memorial Union, Spring Harbor, Tenney, and Warner beaches are all monitored. Each month, the water is tested for harmful chemicals, fecal coliform, E. coli, and now they are also screening for algal toxins like microcystin and cylindrospermopsin. Occasionally, beaches are closed due to unsafe levels of harmful substances. Lifeguards note the visible water quality and observations or citizens’ calls can prompt sampling. The samples are tested for presence and abundance of cyanobacterial species and they are screened for toxins. During visible blooms, monitoring is done frequently.

USGS Wisconsin Water Science Center – Dane County Water Quality Program-The aim of this program is to find a long-term base of water quality. It began in March 1992 and continues today. Four continuous-record stream flow gauging stations are set up at Pheasant Branch, Spring Harbor Storm Sewer, the Yahara River and SH113 (major tributaries to Lake Mendota). They collect samples for analysis during low flow and when surface runoff is entering the streams and the samples are analyzed for suspended sediment and phosphorous concentrations. Another gage on Black Earth Creak records stream flow continuously and base-flow and water quality sampling is done six times per year during the open-water season on certain streams in Dane County. All data was published in the report “Water Resources Data-Wiscinsin, Water Year 2003”.



2007 graph

2008 graph final