Cedar Nokomis Harmful Algae Bloom Project Develop and plan for implementation of in-lake and watershed strategies to improve the water quality of Cedar Lake and Lake Nokomis by addressing the drivers of frequent and persistent blue-green algae blooms with the goal of sustaining high quality water recreation opportunities.

 Project: Milestones
April and May 2022: RFP and Contract Negotiations
June to August 2022: Project Kickoff, Data Compilation and Analysis and Stressor Identification
Feasibility Assessment
October and November 2022: Lakes Sediment and Sampling Analysis
December 2022: Concept Level Design
Spring 2023: Project Report Summaries will be Available

Cedar Lake and Lake Nokomis water quality data from 1992 through to present were compiled and analyzed in spring of 2022 and through the end of 2023. A report of Data Compilation and Analysis with Stressor Identification along with a Feasibility Assessment of proposed strategies was created for the lakes in late summer and early fall 2022 for review and prioritization by MPRB staff. Additional lake sediment sampling was conducted in late October in both lakes to obtain further data that will be used to refine cost estimates and inform implementation.

Cedar Lake and Lake Nokomis
Cedar Lake and Lake Nokomis in Minneapolis, Minnesota, are popular recreation destinations managed by the Minneapolis Park and Recreation Board (MPRB). Both lakes have shown signs of degrading water quality that could affect their recreational value. Lake Nokomis was listed as impaired in 2002 on the US Environmental Protection Agency’s Clean Water Act 303(d) list because of excess nutrients (such as phosphorus). In 2020 swimmers at Lake Nokomis reported eye, ear, and respiratory symptoms that suggested exposure to toxins from blue-green algae, according to the Minnesota Department of Health. Blooms of red-brown algae, which are known to produce toxins, have been observed in the lake during most seasons for many years, and pink-colored water has been observed under the ice. Cedar Lake has not met water-quality standards established by the MPRB during the past five years. Springtime water transparency that had historically been nearly 23 feet deep is now typically a little more than 3 feet. In 2020 a bloom of toxic, scum-forming algae in the lake may have caused the death of a dog.

Blue-Green Algae
Blue-green algae are not algae at all, but a type of bacteria called cyanobacteria. They are photosynthetic microorganisms that occur naturally in lakes, streams, and other waterbodies. When conditions are right, cyanobacteria grow quickly to form blooms. Blooms are often described as looking like pea soup or spilled paint and can be any color, not always green. Blooms aren’t always large and dense; sometimes they can cover only small portions of the lake, with little visible algae present. They can also produce a swampy odor when the cells break down. The conditions for cyanobacteria to reproduce rapidly and produce blooms depend on several factors; some of these include but are not limited to the blue-green algae genera present, nutrient loading and availability, light availability, water temperature, pH changes, turbulence, and alteration of water flow (Paerl & Otten, 2013). Blooms are typically the most severe in July and August when water temperatures are high (≥ 68° Fahrenheit) and water is nutrient rich. Anthropogenic factors such as urban, industrial, and agricultural activities have contributed to nutrient over-enrichment or eutrophication of waterbodies; cyanobacteria are well-adapted to thrive in these waterbodies. Although the process of nutrient loading promotes cyanobacteria growth, warmer temperatures, more intense precipitation events, and longer stratification periods due to climate change will stimulate more intense and frequent future cyanobacteria blooms. The MPRB has seen an increase in frequency and severity of cyanobacteria blooms in Minneapolis lakes in recent years. For more information on blue-green algae: https://www.minneapolisparks.org/park-care-improvements/water_resources/lake_water_resources/blue-green-algae/ .

Creation of the Blue-Green Algae Visual Monitoring Index in 2020
As a result of an unusual early spring blue-green algae bloom on several Minneapolis lakes in 2020, MPRB staff developed a Visual Monitoring Index (VMI) to assess the lakes. The VMI provides a visual guide for lake managers to monitor cyanobacteria concentrations and the potential for blooms that could contain cyanotoxins at a lake and beaches. The VMI was implemented in 2020 as part of the weekly data collection at each of the MPRB beaches. The VMI was based on criteria developed by the Vermont Department of Environmental Conservation and the Lake Champlain Committee (https://www.lakechamplaincommittee.org/get-involved/volunteers/cyanobacteriamonitors/cyanobacteria-bloom-intensity#c4807). The 2020 results served as a base knowledge set from which to begin building a more robust monitoring program. In 2021 and 2022, staff continued using the VMI as part of the MPRB blue-green monitoring program.

Creation of the Lake Water Quality Live Map in 2020
MPRB developed an online GIS-based Lake Water Quality Map in 2020 to better communicate beach advisories, closures, and notifications to lake and beach users. This map was further refined and continued to be a vital communication tool in 2021 to communicate information visually and in real-time. Sampling date, beach status, water temperature, water clarity, and E. coli data were updated weekly with graphics indicating whether beaches were open or closed based on E. coli monitoring results. Results of the VMI were updated on the online MPRB Lake Water Quality Map to indicate the potential for cyanobacteria blooms that could become a health hazard. For 2022, the map included cyanobacteria monitoring results for all lakes. The map includes water quality information for all Minneapolis lakes and can be found on the MPRB website bit.ly/mplsbeaches.

Microcystin 2021 Pilot Sampling Study at Cedar Lake and Lake Nokomis and Expansion in 2022
Water samples were collected for cyanotoxin analysis at the Cedar Lake and Lake Nokomis beaches during the weekly beach monitoring program as part of a 2021 cyanobacteria monitoring pilot project. In 2021, a combination of current standards recommended by California Guidance, Cyanobacteria HABs in Recreational Inland Waters and Minnesota Pollution Control Agency were used for blue-green algae advisories and warnings. This pilot study resulted in the expansion of a cyanobacteria monitoring program at all the MPRB beaches in 2022