MILC Sessions 19-21 Lake Issues
From Renae Siler
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Lake Issues
- 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.
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