Jessica A. Maurer | Geology Reports

USGS2022

Understanding sources and distribution of Escherichia coli at Lake St. Clair Metropark Beach, Macomb County, Michigan

Lake St. Clair Metropark Beach (LSCMB) in Michigan is a public beach near the mouth of the Clinton River that has a history of beach closures for public health concerns. The Clinton River is designated as a Great Lakes Area of Concern, and the park has a Beneficial Use Impairment for beach closings because of elevated Escherichia coli ( E. coli ) concentrations. The U.S. Geological Survey, in cooperation with the U.S. Environmental Protection Agency and in collaboration with the Michigan Department of the Environment, Great Lakes, and Energy, Macomb County Health Department, and Huron-Clinton Metroparks, completed a 2-year study to determine sources of E. coli in LSCMB. Samples were collected during dry and wet weather periods to observe the sampling sites under different conditions. Nearshore surface water samples were collected biweekly July through October in 2018 and May through September in 2019. There were 20 sampling sites along the shoreline of the park and in the channel north of the park. In addition to collecting nearshore surface-water samples, samples were collected from shallow groundwater, lake-bottom material, standing water on the beach and surrounding the recreational beach area, solids (beach sands and detritus), and offshore surface-water sites. In 2019, additional samples for microbial source tracking (MST) were collected on three dates in midsummer and were analyzed for human (HF183) and bird/waterfowl (GFD) MST markers. The concentrations of E. coli at LSCMB (in order of highest to lowest E. coli concentrations) were as follows: shallow groundwater nearest to the water’s edge, surface sands and organic matter (detritus), standing water on the beach, nearshore surface water in and surrounding the recreational beach area, lake-bottom material, and offshore surface water. The combination of low E. coli concentrations offshore and higher concentrations nearshore indicate nearshore sources, possibly from beach sands or groundwater, rather than sources coming from offshore Lake St. Clair waters. The subset of samples for MST analysis did not have enough positive results to illustrate MST trends, but this study demonstrated that both human and waterfowl sources can affect the water quality at LCSMB.

Michigan↗

USGS2017

Groundwater flux and nutrient loading in the northeast section of Bear Lake, Muskegon County, Michigan, 2015

Bear Lake in North Muskegon, Michigan, is listed as part of the Muskegon Lake area of concern as designated by the U.S. Environmental Protection Agency. This area of concern was designated as a result of eutrophication and beneficial use impairments. On the northeast end of Bear Lake, two man-made retention ponds (Willbrandt Pond East and Willbrandt Pond West), formerly used for celery farming, may contribute nutrients to Bear Lake. Willbrandt Ponds (East and West) were previously muck fields that were actively used for celery farming from the early 1900s until 2002. The restoration and reconnection of the Willbrandt Ponds into Bear Lake prompted concerns of groundwater nutrient loading into Bear Lake. Studies done by the State of Michigan and Grand Valley State University revised initial internal phosphorus load estimates and indicated an imbalance in the phosphorus budget in Bear Lake. From June through November 2015, the U.S. Geological Survey (USGS) did an investigative study to quantify the load of nutrients from shallow groundwater around the Willbrandt Ponds in an effort to update the phosphorus budget to Bear Lake. Seven sampling locations were established, including five shallow groundwater wells and two surface-water sites, in the Willbrandt pond study area and Bear Lake. A total of 12 nutrient samples and discrete water-level measurements were collected from each site from June through November 2015. Continuous water-level data were recorded for both surface-water monitoring locations for the entire sampling period. Water-level data indicated that Willbrandt Pond West had the highest average water-level elevation of all sites monitored, which indicated the general direction of flux is from Willbrandt Pond West to Bear Lake. Nutrient and chloride loading from Willbrandt Pond West to Bear Lake was calculated using two distinct methods: Dupuit and direct seepage methods. Shallow groundwater loading calculations were determined by using groundwater levels to first determine a flux of shallow groundwater, then nutrient concentrations to determine a load. It was determined that Willbrandt Pond East and Willbrandt Pond West contributed between 2 to 4 percent of the total annual phosphorus load to Bear Lake by way of shallow groundwater flow. Annual loads calculated for other constituents include orthophosphate (40–100 pounds per year [lb P/yr]), total nitrogen (200–830 lb/yr), chloride (12,700–32,100 lb/yr), and ammonia (130–670 lb N/yr). Study results indicated that mean groundwater and surface-water nutrient concentrations calculated in this study were higher than reported Michigan statewide values. The data collected in this study allow understanding of groundwater nutrient loading into Bear Lake in an effort to help inform future restoration and management decisions.

Michigan↗