WATER QUALITY DATA TO HELP DEFINE CAUSES AND POSSIBLE SOLUTIONS TO CYANOBACTERIAL BLOOMS IN TUG LAKE

Tug Lake is a small, stained, lowland drainage lake in north central Wisconsin. Although the water quality has met state water quality standards for phosphorus and chlorophyll, cyanobacterial blooms of varying intensity take place in some years. Shoreline property owners formed a Lake District in 2021 and worked with Wisconsin DNR and partners to collect water quality data and create a nutrient budget for the lake in 2022. A stage discharge relationship was developed for the inlet stream. Bimonthly nutrient samples were collected at the inlet, outlet, and in the lake to quantify nutrient loading. Temperature and dissolved oxygen profiles were collected to understand lake stratification dynamics. Sediment cores were collected from the anoxic hypolimnion and phosphorus release rates were quantified. Phytoplankton samples were identified to genus and counted. Nutrients were highest during spring and fall overturn and declined in the epilimnion over the summer months. Early summer algal blooms did not appear to be related to lake mixing and the phytoplankton species differed from previous blooms in the lake that were associated with turnover events. Most of the external nutrient load to the lake came in the spring and there appeared to be a moderate amount of internal loading in the summer months. The results will be used by the Tug Lake District and DNR to design management strategies to reduce nutrient loading to the lake and the likelihood of blue-green algae blooms.

Primary Presenter: Scott Van Egeren, Wisconsin Department of Natural Resources (scott.vanegeren@wi.gov)

Authors:

Pat Oldenburg, Wisconsin Department of Natural Resources  (Patrick.Oldenburg@wi.gov)

Reid Badeau, Tug Lake District  (rbad0@frontier.com)

Cutler Nowak, University of Wisconsin - Stevens Point  (NowakCutler@gmail.com)

Al Wirt, Wisconsin Department of Natural Resources  (Alan.Wirt@wi.gov)