MILC Sessions 19-21 Lake Issues
From Renae Siler
- 0:00- Could Recent Development of Thick Benthic Microalgal Mats in
Oligotrophic Lakes Be Caused by Lower Lake Phosphorus? R. Jan Stevenson,
Michigan State University
- 32:15- Differences in Rural and Urban Lakes and Implications for Management, Jennifer Jermalowicz-Jones, Restorative Lake Sciences LLC.
- 48:30- Lawns and Lakes: Managing Lawns while Preserving Water Quality, Kevin Frank, Michigan State University
Could Recent Development of Thick Benthic Microalgal Mats in Oligotrophic Lakes Be Caused by Lower Lake Phosphorus? R. Jan Stevenson, Michigan State University
Watershed groups for large low phosphorus lakes in the northern region of Michigan’s lower peninsula have observed increases in thick, nuisance-level golden-brown algal mats (GBA) in the last 1-2 decades. Stakeholders and I developed a list of potential hypotheses for causes of GBA, which can include both diatoms and coccoid cyanobacteria. Groundwater contamination by nutrients was deemed the most likely hypothesis, but we also considered many more. Spatial patterns in GBA are poorly related to land use and stream inputs around lakes, as we would expect for groundwater or surface water contamination. In addition, changes in groundwater concentrations have not been observed and related well to GBA proliferations in the last 15 years. The one change in many large lakes in the study region over the last 2 decades, and potentially longer, has been a decrease in surface water phosphorus concentrations. Dreissenid mussels and atmospheric N deposition could cause these phosphorus decreases. Could we have reached a tipping point in decreasing phosphorus to cause development of GBA? Low phosphorus is required for high algal biomass of calcareous algal mats in the Everglades and Didymosphaenia in streams. Could the same microalgal ecological processes be operating in northern Michigan Lakes to generate high benthic algal biomass in low phosphorus? We have not developed conclusions about causes of GBA because of limited data and the novel nature of the problem. We continue to gather more information, test hypotheses for GBA causes, and explore new hypotheses to determine if GBA can be managed.
Differences in Rural and Urban Lakes and Implications for Management, Jennifer Jermalowicz-Jones, Restorative Lake Sciences LLC.
There are over ten thousand lakes in Michigan and most of them are located in either rural or urban areas. The two location types are associated with different challenges relative to successful management outcomes. Trends in rural lake water quality demonstrate increases in nutrient loading from septic systems and agricultural inflows and runoff. Also common are increased concentrations of E. coli bacteria that may pose a human health risk. Reductions in nutrient loads and E. coli are dependent upon the local community resources as well as effective immediate watershed management. Trends in urban water quality demonstrate increases in pollution from storm drains and nutrients from lawn fertilizer applications, runoff, and septic systems. Pollutants such as chlorides and suspended solids are often elevated in these systems. Such issues are a management challenge since urban road runoff and drains are often limited relative to diversions or other changes to reduce pollutant loads to the lakes. This presentation focuses on ten urban and ten rural lakes relative to multiple water quality parameters such as chlorides, nitrogen, phosphorus, E. coli bacteria, total suspended solids, specific conductivity, water clarity, and chlorophyll-a. Graphical trends are offered along with future management recommendations for water quality improvements in both unique rural and urban settings.
Lawns and Lakes: Managing Lawns while Preserving Water Quality, Kevin Frank, Michigan State University.
Michigan is a state with invaluable surface water assets. From the Great Lakes to inland lakes and streams, Michiganders take great pride and enjoyment in our natural waters. Bordering many of the lakes are homes and of course many homes have lawns that are at the waters edge or perhaps separated by a beach or a vegetative buffer. There are many misconceptions about turfgrass management and especially nutrient management and it’s impact on water quality. In this presentation I will discuss the two primary nutrients of interest, nitrogen and phosphorus. I will discuss nutrient sources, application timing, rates, and risk of leaching or runoff. It is possible to maintain a healthy lawn and still preserve surface water quality.
Find more presentations from the 2022 Michigan Inland Lakes Convention here.