Results and Discussion
Fish Disease
and Parasites
No evidence of
fish disease or parasites was reported during the inventory period. However,
further examination of game and non-game fish from the preserve would be useful
in ruling out the presence of viral or other diseases in Asylum Lake and Little Asylum
Lake populations.
Lake Eutrophication and Fish Kills
Eutrophication is a process
that occurs naturally over time, but the process can be artificially accelerated
through nutrient inputs from human activities. The growth of algae and aquatic
plants in freshwater ecosystems is usually limited by the availability of
the nutrient phosphorus. Phosphorus and nitrogen, another important nutrient,
enter waterways from
non-point sources, including run-off from septic fields, fertilized lawns
and farm fields, livestock operations, atmospheric deposition and waterfowl
populations. In some cases, phosphorus may also enter water systems from point
sources such as effluents from sewage treatment or manufacturing plants. The
result of these nutrient influxes is increased plant and algae growth (and
eventual decomposition) and the subsequent depletion of lake oxygen levels.
If this trend continues the lake eventually will be overrun by plant growth,
water levels will drop, oxygen in the water will continue to decrease, fish
populations will be extirpated and the lake will “die,” eventually turning
into a wetland area and then possibly dry land.
Lakes with elevated
plant growth and dangerously low oxygen levels are prone to periodic fish
kills especially in the summer and winter months. These lakes often can be
identified by the composition of their fish populations. Species of fish vary
in their tolerance of low oxygen. Trout (undocumented in either lake) are
highly sensitive; bass and bluegill have intermediate sensitivity; and pike,
yellow perch and pumpkinseed are relatively tolerant. Bullheads and certain
minnows are considered very tolerant. In lakes with lower oxygen levels, tolerant
species predominate, sensitive species are rare, and prey greatly out number
predators. The species most prone to summer kills are pike, perch, suckers,
bass and bluegill living in shallow, productive lakes or bays with excessive
amounts of algae or rooted aquatic vegetation.
The presence
of a pike species and the occurrence of the relatively tolerant species yellow
perch (documented as abundant) and pumpkinseed (documented as very common)
suggest that Asylum Lake and Little Asylum Lake have reasonably high oxygen
levels and may have a relatively low risk of fish kills. However, the absence
of
the most sensitive
species may indicate that Asylum Lake and Little Asylum
Lake are at some risk, whether due to lower than optimal oxygen levels, lake
eutrophication or another factor.
Oxygen levels,
vegetative cover, prey abundance and even the levels of some pollutants may
be deduced by monitoring fish species. Future surveys of the property should
include a thorough examination of the fish species present, including onshore
surveys, seining, dip-netting and angling. The species found during these
and future inventories will provide insight to the health and productivity
of the lakes themselves.
As a preventive
measure, the risk of water quality problems can be reduced by identifying
and controlling artificial input of nutrients as much as possible. This would
in turn reduce aquatic plant productivity, lower decomposition rates and prevent
oxygen depletion to critical levels. Further discussions of lake contaminants
and
pollutions can be found
in the wetland and lake discussion sections.
Wetlands
Methods
Much of the documentation,
mapping and characterization of the tributaries, inlets, wetlands and lakes
in and around the Asylum Lake Preserve comes from
Soil and Materials Engineers, Inc.’s 1992 Environmental Site Assessment for
Western Michigan University and the water
quality evaluation of Willow Lake and adjoining
waters by Kieser and Associates in 2000 for the
Parkview Hills Community Association.
According to
a 1991 United States Fish and Wildlife Service Wetland Status and Trends report,
over 50% of Michigan’s original wetlands have been drained or filled, thereby
making the protection of remaining wetlands that much more important. Michigan's
wetland statute, Part 303, Wetlands Protection, of the Natural Resources and
Environmental Protection Act, 1994 PA 451, as amended, defines a wetland as
"land characterized by the presence of water at a frequency and duration
sufficient to support, and that under normal circumstances does support, wetland
vegetation or aquatic life, and is commonly referred to as a bog, swamp, or
marsh." Surface water does not need to be present on a wetland year-round
in order define an area as a wetland.
Wetlands serve
a number of important purposes including flood and storm water control due
to their absorption abilities. They provide wildlife, including amphibians,
reptiles, waterfowl and some rare, threatened, or endangered wildlife species,
with cover and breeding, nesting, and feeding habitat. Wetlands are recharge
areas for groundwater supplies, treat pollution by serving as biological and
chemical oxidation basins, control erosion by serving as sedimentation and
filtering basins and absorb silt and organic matter. They act as sources of
nutrients in aquatic food cycles and serve as nursery grounds and sanctuaries
for fish.
On the Asylum Lake property, there
are large areas of emergent and forested wetlands along the shores of the
lakes. The emergent wetlands on the preserve are dominated by cattails (Typha sp.), sedges (family Cyperaceae) and bulrushes (Scirpus
sp.),
while the forested wetlands are dominated by poplars (Populus sp.), willows (Salix
sp.)
and boxelders (Acer negundo), all often present in wetland conditions.
The wetlands
at Asylum Lake separate the
open water of the lakes from the slopes and upland areas and in many cases
provide the final line of protection and filtration of pollutants in storm
water run-off moving toward Asylum Lake and Little Asylum
Lake.
Future construction
on or near Parkview Avenue and development
of areas adjacent to any part of the preserve could potentially disrupt surface
and sub-surface water flow, affecting the wetlands surrounding the lakes first.
Wetland plant and animal populations should be monitored. Monitoring wells,
both at the developing sites and
within the bounds of
the preserve, could be used for continuing observation of these changes.
Asylum Lake and
Little Asylum Lake
Results and Discussion
For many preserve
users, concerned citizens and land managers, the lakes of the Asylum Lake property are
the focal point of the entire conservation effort. Therefore, citizens and
managers have voiced their opinions and concerns in many venues including
Haven,
A treatise on Asylum
Lake, which presents
a partial summary of the many scientific studies
conducted on the Asylum Lake Preserve, as well as personal reflections and
concerns on the future of the preserve.
The lakes are
indeed a significant, sensitive and visible symbol of the health, solitude
and wildness valued by many at the preserve. Unfortunately appearances can
be deceiving, and the presence of water pollutants or unhealthy floral and
faunal populations are not always evident to park users. Continued research,
detailed inventories and monitoring
will be necessary to ensure the health and prolonged enjoyment of this fragile
lake system.
Lake Morphometry
Asylum Lake has
a maximum depth of 15.8 meters (52 feet), mean depth of 7.2 meters (23.5 feet),
maximum length of 930 meters (3,050 feet), maximum width of 290 meters (950
feet), mean width of 214 meters (702 feet), surface area of 19.9 hectares
(49 acres) and volume of 1.4 million cubic meters (1,157 acre feet) (Engemann, 1977).
Lake Disturbance
The Asylum Lake
Preserve has had a long history of disturbances, both natural and human-caused.
These disturbances include development, agriculture, pesticide use and pollutant
and sewage influxes, some fully documented, some not. Surveys and investigations
completed in the last decade reflect the possibility of past and continued
entry of contaminants into the system.
The 1992 Environmental
Site Assessment conducted by Soils and Materials Engineers, Inc., found “several
areas of potential and confirmed environmental concern.” These concerns included
elevated levels of lead barium, copper and zinc in near-surface samples collected
from the perimeter of the former power plant area in Parcel A. Engemann, in a winter
lake study conducted in 1977, discovered stratified concentrations of calcium
chloride in the lake, indicating a recent influx of salts. This influx caused
an abnormal “uniform temperature gradient within the lake due to the effects
of both temperature and dissolved salts on density.” A comparison of the effects
of salt levels on similar
lakes in the state demonstrates that, at high levels, the natural phenomenon
of lake mixing, also known as fall turnover, can be impeded. At the time of
the survey, Asylum Lake's salt levels had not reached these levels, but significant
changes have occurred within the watershed over the last 25 years.
Also documented
at the time of the Engemann survey was the flushing
time of the lake, estimated at about one year, at three cubic meters per
minute. However, it was also noted that up to 2/3 of the lake would not
be flushed while water was trapped in the identified thermocline
and hypolimnion. This discovery may be important
in predicting the fate of
contaminants entering the lake over time.
Studies on nearby
Willow Lake, prepared by Kieser and Associates,
included analysis of Asylum and Little Asylum lakes and concluded that the
lakes are acting as sinks for TSS (total suspended solids) and TP (total phosphorus).
The study supports the idea that the pollutants entering the headwater lake
system tend to stay within these lakes; i.e., high concentrations are entering
Asylum Lake from the roads,
while lower concentrations are observed leaving Little Asylum Lake and entering
Cherry Creek.
Like many wetlands
and water systems, Asylum Lake receives much
of its water from precipitation falling on the areas immediately adjacent
to it. The lakes and wetlands now surrounded by commercial and residential
development have suffered a long history of documented and undocumented contamination.
Soils naturally remediate rainwater as it infiltrates the ground and reacts
with minerals that neutralize and buffer it before it reaches the lake. Concrete
and paved surfaces increase runoff and introduce contaminants present in rainwater
and other pollutants present on roadways and parking areas into the lake.
In addition,
run-off from residential and commercial areas eventually makes its way toward
the Asylum Lake Preserve directly through storm sewers, surface flows, or
by percolating slowly through the soil. Analysis of natural water ridges,
major and minor drainage flows and stormwater run-off
gives some idea of expected water direction pending further development of
the lands surrounding Asylum Lake and Little Asylum
Lake.
Future developments,
paved areas and buildings will increase the amount of runoff and erosion,
altering the hydrology of the area. Land modifications invariably will affect
the lake; any changes proposed by development will require considerable evaluation
and monitoring. Programs should be agreed upon by Parkview
Hills residents and other concerned citizens and stewards of the Asylum
Lake Preserve.
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