THE AQUATIC PLANT COMMUNITY
OF HILL LAKE, ADAMS COUNTY, WI
NOVEMBER 2014
Presented by Reesa Evans,
Certified Lake Manager, Lake Specialist,
Adams County Land & Water Conservation Department
P.O Box 287, Friendship, WI 53934
1
THE AQUATIC PLANT COMMUNITY OF HILL LAKE
ADAMS COUNTY
2014
I. INTRODUCTION
A field study of the aquatic macrophytes (plants) in Hill Lake was conducted
during August 2014 by staff from the Adams County Land and Water
Conservation Department and Golden Sands RC & D. This appears to be
the first aquatic plant survey of any kind done in Hill Lake.
Information about the diversity, density and distribution of aquatic plants is
an essential component in understanding a lake’s ecosystem due to the
integral ecological role of aquatic vegetation in the lake and the ability of
vegetation to impact water quality (Dennison et al, 1993). This study will
provide some baseline information that may help in effective management of
Hill Lake, including fish habitat improvement, protection of sensitive areas,
aquatic plant management, and water resource regulation. This baseline data
will provide information that can be used for comparison to future
information and offer insight into changes in the lake.
Ecological Role: Lake plant life is the beginning of the lake’s food chain,
the foundation for all other lake life. Aquatic plants and algae provide food
and oxygen for fish and wildlife, as well as cover and food for the
invertebrates that many aquatic organisms depend on. Plants provide habitat
and protective cover for aquatic animals. They also improve water quality,
protect shorelines and lake bottoms, add to the aesthetic quality of the lake,
and impact recreation.
2
Characterization of Water Quality: Aquatic plants can serve as indicators
of water quality because of their sensitivity to water quality parameters such
as clarity and nutrient levels (Dennison et al, 1993).
Background and History: Hill Lake, in Adams County, WI, is a 12surface acre impoundment located in the Town of Jackson.
It has a
maximum depth of about 10 feet, with an average depth of less than 5 feet.
There is no defined public access. This private lake is managed by the Hill
Estates Property Owner’s Association.
Soils in the watershed are mostly sand, although the lake itself has
significant peat and muck substrate. Most of the residences around the lake
do have buffers of 35 feet landward or more. Predominant land use in the
surface watershed includes mostly non-irrigated agriculture and residential
development.
II. METHODS
Field MethodsThe 2014 aquatic plant survey was conducted using the Point Intercept
(PI) method required by the Wisconsin Department of Natural Resources, with some near
shore points added. This method involves calculating the surface area of a lake and
dividing it (using a formula developed by the WDNR) into a grid of several points,
always placed at the same interval from the next one(s). These points are related to a
particular latitude and longitude reading. At each geographic point, the depth is noted
and one rake is taken, with a score given between 1 and 3 to each species on the rake.
A rating of 1 = a small amount present on the rake;
A rating of 2 = moderate amount present on the rake;
A rating of 3 = abundant amount present on the rake.
3
Several near-shore sites were added to the PI grid in order to capture the
significant emergent community in the shallows.
A visual inspection was done between points to record the presence of any
species that didn’t occur at the raking sites. Gleason and Cronquist (1991)
nomenclature was used in recording plants found.
Data Analysis:
The percent frequency (number of sampling sites at which it occurred/total
number of sampling sites) of each species was calculated.
Relative
frequency (number of species occurrences/total all species occurrences) was
also determined. The mean density (sum of species’ density rating/number
of sampling sites) was calculated for each species. Relative density (sum of
species’ density/total plant density) was also determined. Mean density
where present (sum of species’ density rating/number of sampling sites at
which species occurred) was calculated. Relative frequency and relative
density results were summed to obtain a dominance value. Species diversity
was measured by Simpson’s Diversity Index.
The Average Coefficient of Conservation and Floristic Quality Index were
calculated as outlined by Nichols (1998) to measure plant community
disturbance. A coefficient of conservation is an assigned value between 0
and 10 that measures the probability that the species will occur in an
undisturbed habitat. The Average Coefficient of Conservationism is the
mean of the coefficients for the species found in the lake. The coefficient of
4
conservatism is used to calculate the Floristic Quality Index, a measure of a
plant community’s closeness to an undisturbed condition.
An Aquatic Macrophyte Index was determined using the method developed
by Nichols et al (2000). This measurement looks at the following seven
parameters and assigns each of them a number on a scale of 1-10: maximum
depth of rooted plant growth; percentage of littoral zone vegetated;
Simpson’s Diversity Index; relative frequency of submersed species; relative
frequency of sensitive species; taxa number; and relative frequency of exotic
species. The average total for the North Central Hardwoods lakes and
impoundments is between 48 and 57.
III. RESULTS
Physical Data
The aquatic plant community can be impacted by several physical
parameters. Water quality, including nutrients, algae and clarity, influence
the plant community; the plant community in turn can modify these
boundaries. Lake morphology, sediment composition and shoreline use also
affect the plant community.
The trophic state of a lake is a classification of water quality. Phosphorus
concentration, chlorophyll a concentration and water clarity data are
collected and combined to determine a trophic state. Eutrophic lakes are
very productive, with high nutrient levels and large biomass presence.
Oligotrophic lakes are those low in nutrients with limited plant growth and
small fisheries. Mesotrophic lakes are those in between, i.e., those which
5
have increased production over oligotrophic lakes, but less than eutrophic
lakes; those with more biomass than oligotrophic lakes, but less than
eutrophic lakes; those with a good and more varied fishery than either the
eutrophic or oligotrophic lakes.
Hill Lake does not have a history of water quality monitoring for total
phosphorus or chlorophyll-a. However, volunteers have been taking several
water clarity readings each year since 2001. Water clarity is a critical factor
for plants. If plants don’t get more than 2% of the surface illumination, they
won’t survive.
Water clarity can be reduced by turbidity (suspended
materials such as algae and silt) and dissolved organic chemicals that color
or cloud the water, among other things. Water clarity is measured with a
Secchi disk. Average summer Secchi disk clarity in Hill Lake in 2001-2014
was 7.4 feet. This is good water clarity.
Figure 1: Average Summer Water Clarity
6
It is normal for this value to fluctuate during a growing season. They can be
affected by human use of the lake, by summer temperature variations, by
algae growth & turbidity, and by rain or wind events. Phosphorus tends to
rise in early summer, than decline as late summer and fall progress.
Chlorophyll a tends to rise in level as the water warms, then decline as
autumn cools the water. Water clarity also tends to decrease as summer
progresses, sometimes due to algae growth and resuspension of sediments
from boat traffic or weather, then decline as fall approaches.
Figure 2: Trophic State
Trophic State
Oligotrophic
Mesotrophic
Eutrophic
Hill Lake
Quality Index Phosphorus
(ug/l)
Chlorophyll a
(ugm/l)
Sechhi Disk
(ft)
Excellent
Very Good
Good
<1
1 to 10
10 to 30
<1
1 to 5
5 to 10
>19
8 to 19
6 to 8
Fair
Poor
30 to 50
50 to 150
No data
10 to 15
15 to 30
No data
5 to 6
3 to 4
7.4
According to the water clarity results, Hill Lake scores as “mesotrophic” in
all three categories, with “fair” to “good” water quality and good water
clarity.
This state would favor moderate plant growth and more than
occasional algal blooms.
Lake morphology is an important factor in distribution of lake plants.
Duarte & Kalff (1986) determined that the slope of a littoral zone could
explain 72% of the observed variability in the growth of submerged plants.
Gentle slopes support higher plant growth than steep slopes (Engel 1985).
7
Figure 3: Hill Lake Aerial View
Hill Lake is an irregularly-shaped shallow basin that with gradual slopes
within most of the lake. There are small areas of steeper slopes around the
shore, with houses often located at the top of a slope.
When these factors
are added to the overall very shallow aspect of the lake and the good water
clarity, plant growth is favored in Hill Lake based on the morphology.
Shoreline land use often strongly impacts the aquatic plant community and
thus the entire aquatic community.
Impacts can be caused by increased
erosion and sedimentation and higher run-off of nutrients, fertilizers and
toxins applied to the land. Such impacts occur in both rural and residential
settings.
8
Most shore sites around Hill Lake have significant buffers of native plants.
However, in some instances, mostly at the west end of the lake, there is a lot
of cultivated lawn that is unlikely to sufficiently filter runoff into the lake.
Macrophyte Data
SPECIES PRESENT
Of the 53 species found in Hill Lake, 41 were emergent, 2 were floating-leaf
rooted species, and the 10 were submergent types. Two plant-like algae
species in the Charophyte family--Chara contraria and Lychnothamnus
barbatus--are included in the submergent count. The only invasive species
found were Reed Canarygrass (Phalaris arundinacea) and Spiny Naiad
(Najas marina). No endangered or threatened species were found.
Figure 4: Aquatic Species Found in Hill Lake 2014
Scientific Name
Asclepias incarnata
Betula pumila
Bidens connata
Carex stricta
Cephalanthus occidentalis
Chara contraria
Cicuta bulbifera
Comarum palustre
Cornus amomum
Cornus rugosa
Cornus stolonifera
Eleocharis erythropoda
Eupatorium maculatum
Eupatorium perfoliatum
Iris versicolor
Juncus canadensis
Lathyrus palustris
Lobelia kalmii
Lychnothamnus barbatus
Lycopus uniflorus
Lysimachia terrestris
Lysimachia thyrsiflora
Myriophyllum sibircum
Common Name
Swamp Milkweed
Bog Birch
Purple-Stem Beggsrd-Tick
Conmon Tussock Sedge
Buttonbush
Opposite Stonewort
Bulb-Bearing Water Hemlock
Marsh Cinquefoil
Silky Dogwood
Round-Leaved Dogwood
Red Osier Dogwoof
Bald Spikerush
Spotted Joe Pye Weed
Boneset
Blue-Flag Iris
Canadian Rush
Marsh Pea
Bog Lobelia
Bearded Stonewort
Northern Bugleweed
Swamp Candle
Swamp Loosestrife
Northern Milfoil
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Type
Emergent
Emergent
Emergent
Emergent
Emergent
Submergent
Emergent
Emergent
Emergent
Emergent
Emergent
Emergent
Emergent
Emergent
Emergent
Emergent
Emergent
Emergent
Submergent
Emergent
Emergent
Emergent
Submergent
Najas flexlis
Najas marina
Onoclea sensibilis
Pedicularis lanceolata
Phalaris arundinacea
Polygonum amphibium
Potamogeton amphifolius
Potamogeton foliosus
Potamogeton gramineus
Potamogeton illinoensis
Potamogeton natans
Potamogeton pusillus
Pycantheum virginiatum
Sagittaria latifolia
Salix exigua
Salix nigra
Sambucus canadensis
Schoenoplectus acutus
Sschoenoplectus tabernaemontani
Scirpus atrovirens
Scirpus cyperinus
Solanum dulcamara
Solidago altimissma
Solidago gigantea
Spirea alba
Spirea tomentosa
Stuckenia pectinata
Triadenum fraseri
Typha spp
Verbena hastata
Bushy Pondweed
Spiny Naiad
Sensitive Fern
Swamp Betony
Reed Canarygrass
Water Smartweed
Larrge-Leaf Pondweed
Leafy Pondweed
Various-Leaved Pondweed
Illinois Pondweed
Floating-Leaf Pondweed
Small Pondweed
Common Mountain Mint
Common Arrowhead
Sandbar Willow
Black Willow
Elderberry
Hard-Stemmed Bulrush
Soft-Stemmed Bulrush
Black Bulrush
Woolgrass
Bittersweet Nightshade
Common Goldenrod
Giant Goldenrod
White Meadowsweet
Meadowsweet
Sago Pondweed
Bog St John's Wort
Cattail
Blue Vervain
Submergent
Submergent
Emergent
Emergent
Emergent
Floating-Leaf
Submergent
Submergent
Submergent
Submergent
Floating-Leaf
Submergent
Emergent
Emergent
Emergent
Emergent
Emergent
Emergent
Emergent
Emergent
Emergent
Emergent
Emergent
Emergent
Emergent
Emergent
Submergent
Emergent
Emergent
Emergent
FREQUENCY OF OCCURRENCE
Opposite Stonewort (Chara contraria) was the most-frequently occurring
species found in the 2014 survey.
The next most-frequently aquatic
occurring species was Bearded Stonewort (Lychnothamnus barbatus), a rate
endangered species. These two species together made up over 42% of the
aquatic plant community in Hill Lake in 2014. These species play multiple
roles in an aquatic ecosystem as part of the food web, in providing habitat,
and in increasing water quality.
10
Almost all groups in an aquatic food web benefit from the presence of
Charophytes.
Many ducks, amphibians and reptiles use them directly as
food. In addition, Charophytes serve as an important grazing location for
insects that in turn provide food for fish and other wildlife. Charophytes
also serve as protection and cover for young fish. They are important in the
predator-prey ratio. Their presence has even been known to inhibit the
survival of mosquito larvae.
Figure 5: Most Frequently-Occurring Species 2014
Perhaps the most important role in an aquatic ecosystem that Charophytes
serve is in water quality.
They naturally filter the water and play an
important part in nutrient cycling. Charophytes hold massive amounts of
nutrients such as phosphorus and nutrients and metals.
This results in
reducing and/or and blocking the availability of phosphorus for other less
desirable algae and aquatic vegetation.
11
One thing that happens when oxygen becomes low in a lake is the re-release
of nutrients into the water column from the sediments, often resulting in
algal blooms or an increase in nuisance plant growth. Charophytes stabilize
bottom sediments, thus reducing the occurrence of this process. Studies
have shown that Charophytes restrict the resuspension of sediments up to
100 times more than other aquatic vegetation. Studies in China suggest that
the alleopathic (inhibitory) aspects of Charophytes may discourage blooms
of potentially-toxic blue-green algae like Microcystis.
Lychnothamnus barbatus, the second most-frequently occurring species in
Hill Lake in 2014, was discovered in Adams County in 2011. It is the rarest
Charophyte in the world, listed as critically endangered world-wide. Until
the recent discovery, it had never been found in the Western Hemisphere
before. It has now been found in eight lakes in Adams County and three in
Waushara County—including now in Hill Lake.
Although there were more species of emergent plants found in Hill Lake in
2014, submergent plants actually were more frequently-occurring.
Emergent plants were the second-most frequently occurring species type,
with rooted floating-leaf plants the least frequently occurring.
12
Figure 6: Occurrence Frequency by Plant Type
DENSITY OF OCCURRENCE
In general, aquatic plants were not especially dense in Hill Lake in 2014.
Instead, plants occurred throughout most of the lake and were found at 152
of the 156 sites sampled. There was some localized high density, usually
involving Chara contraria or Lychnothamnus barbartus. These two species
had the highest relative density. Cattails also tended to occur in fairly dense
patches.
DOMINANCE
Relative frequency and relative density are combined into a dominance
value that demonstrates how dominant a species is within its aquatic plant
community. Based on dominance value, Opposite Stonewort was by far the
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dominant aquatic species in both the 2014 survey.
Sub-dominant was
Bearded Stonewort. All other species came far behind.
Figure 7: Dominance in 2014
DISTRIBUTION
Submergent plants were found at all the vegetated sites. However, the
rooted floating-leaf and emergent plants were slightly scarcer.
There were
only two invasives found in Hill Lake in 2014: the emergent species, Reed
Canarygrass, and the submergent species, Spiny Naiad. Submergent species
were found at all PI points.
14
Figure 8: Distribution of Emergent Plants 2014 (in green)
15
Figure 9: Distribution of Floating-Leaf Plants (in blue)
16
Figure 10: Distribution of Rare Species, Lychnothamnus barbatus
DENSITY
1
2
3
Spiny Naiad (Najas marina) has been in Hill Lake for many years. It is
proposed to be added to the Wisconsin Department of Natural Resources
Invasive Species list, since it is not native to Wisconsin. It does not appear
to have increased to the point where it is in danger of negatively impacting
the aquatic plant community in Hill Lake. During the 2014 survey, it was
generally found mixed with native submergents like Bushy Pondweed
(Najas flexilis), Opposite Stonewort, Northern Milfoil (Myriophyllum
sibiricum), and Variable-Leaf Pondweed (Potamogeton gramineus).
17
Figure 11: Distribution of Najas marina in 2014
THE COMMUNITY
The Simpson’s Diversity Index for Hill Lake was .87, suggesting fair species
diversity. A rating of 1.0 would mean that each plant in the lake was a
different species (the most diversity achievable).
This figure is in the
average range for the North Central Hardwood Forest region (which
contains Adams County) of .8 to .9 and in the average range for all
Wisconsin Lakes of .82 to .9.
18
The only invasives present in Hill Lake in 2014 were Spiny Naiad and Reed
Canarygrass. Currently, their density and relative occurrence frequency
don’t establish them as dominant among the aquatic plant community;
instead, they appear to just be a small part of the overall community, with
native species still dominating. So far, the most common aquatic invasive in
Adams County Lakes, Eurasian Watermilfoil (Myriophyllum spicatum) is
not present in Hill Lake. However, with several lakes with five miles that do
contain that invasive, users of Hill Lake need to be extra careful about
cleaning their aquatic equipment (including boats) if they use them on other
lakes before coming back into Hill Lake.
A Coefficient of Conservatism and a Floristic Index calculation were
performed on the field results.
Technically, the average Coefficient of
Conservatism measures the community’s sensitivity to disturbance, while
the Floristic Index measures the community’s closeness to an undisturbed
condition. Indirectly, they measure past and/or current disturbance to the
particular community.
The Average Coefficient of Conservation and Floristic Quality Index were
calculated as outlined by Nichols (1998) to measure plant community
disturbance.
Previously, a value was assigned to all plants known in
Wisconsin to categorize their probability of occurring in an undisturbed
habitat, using a scale of 0 to 10.
This value is called the plant’s Coefficient
of Conservatism. A score of 0 indicates a native or alien opportunistic
invasive plant. Plants with a value of 1 to 3 are widespread native plants.
Values of 4 to 6 describe native plants found most commonly in early
successional ecosystem. Plants scoring 6 to 8 are native plants found in
19
stable climax conditions. Finally, plants with a value of 9 or 10 are native
plants found in areas of high quality and are often endangered or threatened.
In other words, the lower the numerical value a plant has, the more likely it
is to be found in disturbed areas.
The Average Coefficient of
Conservationism is the mean of the coefficients for the species found in the
lake.
The coefficient of conservatism is used to calculate the Floristic Quality
Index (FQI), a measure of a plant community’s closeness to an undisturbed
condition. The Floristic Quality Index is also a tool that can be used to
identify areas of high conservation value, monitor sites over time, assess the
anthropogenic (human-caused) impacts affecting an area and measure the
ecological condition of an area (M. Bourdaghs, 2006).
The Average Coefficient of Conservation for Hill Lake was 5.9. This puts it
in the lowest quartile for Wisconsin Lakes and for lakes in the North Central
Hardwood Region. Using this scale, the aquatic plant community in Hill
Lake is in the category of those most tolerant of disturbance, probably due to
selection by a series of past disturbances.
“Disturbance” is a term that covers many disruptions to a natural
community. It includes physical disturbances to plant beds such as boat
traffic, plant harvesting, docks and other structure placements, shoreline
development and fluctuating water levels.
Indirect disturbances like
sedimentation, erosion, increased algal growth, and other water quality
impacts will also negatively affect an aquatic plant community. Biological
disturbances such as the introduction of non-native and/or invasive species,
20
destruction of plant beds, or changes in aquatic wildlife can also decrease an
aquatic plant community. In Hill Lake, the most likely disturbances are boat
traffic, resuspension of the substrate, and some water level fluctuations.
Figure 12: Floristic Quality and Coefficient of Conservatism of Hill
Lake, Compared to Wisconsin Lakes and Northern Wisconsin Lakes.
Wisconsin Lakes
NCHR
Hill Lake 2014
Average
Coefficient of
Conservatism †
5.5, 6.0, 6.9 *
5.2, 5.6, 5.8 *
5.09
Floristic Quality ‡
16.9, 22.2, 27.5
17.0, 20.9, 24.4
37.09
* - Values indicate the highest value of the lowest quartile, the mean and the lowest value of the
upper quartile.
† - Average Coefficient of Conservatism for all Wisconsin lakes ranged from a low of 2.0 (the
most disturbance tolerant) to a high of 9.5 (least disturbance tolerant).
‡ - lowest Floristic Quality was 3.0 (farthest from an undisturbed condition) and the high was 44.6
(closest to an undisturbed condition).
The Floristic Quality Index of the aquatic plant community in Hill Lake of
37.09 is far above average for Wisconsin Lakes and the North Central
Hardwood Region. This indicates that the plant community in Hill Lake is
closer to an undisturbed condition than the average lake in Wisconsin overall
and in the North Central Hardwood Region.
Although at first these two scores may be contradictory, they have to be
evaluated within the context of Hill Lake itself. Hill Lake is a very small
shallow impoundment with mucky or sandy substrate. Use of boats on the
lake, in such shallow conditions, is likely to disturb the substrate all the way
to the bed of the lake, which can inhibit establishment of aquatic plants. The
Average Coefficient of Conservatism mainly looks at the likelihood of a
21
certain plant’s growth by using the numbers assigned from 0 to 10. Due to
the type of substrate present in Hill Lake and its shallow depth, there are a
number of aquatic plants that are unlikely to grow in those conditions. The
Floristic Quality Index, however, uses the mean Coefficient of Conservatism
as one of its factors (quality of the plants in the community), while taking
into account others such as occurrence.
Figure 13: AMCI for Hill Lake 2014
Criteria
Data
Score
Maximum rooting depth
6.5
8
% littoral zone vegetated
98.1
10
% submerged species relative frequency
52
4
% sensitive species relative frequency
10
6
% exotic species relative frequency
9
5
0.87
7
53
10
SI
Taxa number
Total score
50
The Aquatic Macrophyte Community Index was developed as an assessment
tool to determine the biological quality of lake aquatic plant communities. It
considers several components: maximum depth of plant growth; percentage
of littoral zone vegetated; Simpson’s Diversity Index; relative frequency of
submersed, sensitive and exotic species; and species number. The Aquatic
Macrophyte Community Index (AMCI) for Hill Lake is 50. This is in the
average range for Central Wisconsin Hardwood Lakes and Impoundments
(48 to 57 and for all Wisconsin Lakes (45 to 57).
22
IV. DISCUSSION AND CONCLUSION
Based on water clarity, Hill Lake is a mesotrophic impoundment with good
water clarity and fair aquatic species diversity.
This trophic state should
support moderate plant growth and occasional localized algal blooms.
Sufficient nutrients (trophic state), shallow depth and gradually-sloped
littoral zone in Hill Lake favor plant growth.
Aquatic vegetation occurred at over 97% of the sample sites, with about
30% if the sites having rooted aquatic plants. The lake does have a mixture
of emergent, floating-leaf, and submergent rooted plants, as well as two
species of the macrophytic Charophyte algae family. Of the 53 aquatic
species record in Hill Lake in summer 2014, 40 were emergent, 2 were
floating-leaf rooted plants, and 11 were submergent (includes both rooted
and unrooted species. The dominant species was the macrophytic algae,
Opposite Stonewort, with the sub-dominant aquatic species being another
macrophytic algae (although much more rate), Bearded Stonewort. The
most dominant aquatic plant was the Floating-Leaf Pondweed, followed
closely by Variable-Leaved Pondweed and Spiny Naiad.
The only invasive aquatic plants found in Hill Lake in 2014 were Spiny
Naiad and Reed Canarygrass. They appear to just be a small part of the
overall community, with native species still dominating. So far, the most
common aquatic invasive in Adams County Lakes, Eurasian Watermilfoil
(Myriophyllum spicatum) is not present in Hill Lake. However, with several
lakes within five miles that do contain that invasive, users of Hill Lake need
23
to be extra careful about cleaning their aquatic equipment (including boats)
if they use them on other lakes before coming back into Hill Lake.
Most of Hill Lake has shore buffer areas that meet or exceed the county
requirement of 35 feet landward, with almost all of it consisting of native
trees, shrubs, grasses and forbs. There are a few areas where traditional
cultivated lawn has high coverage, with only a strip of native vegetation.
These areas have been identified and reported to the Hill Lake Property
Owners’ Association.
These conditions offer fairly good protection for
water quality from increased runoff (including lawn fertilizers, pet waste,
pesticides) and shore erosion.
A healthy and diverse aquatic plant community plays a vital role within the
lake ecosystem. Plants help improve water quality by trapping nutrients,
debris and pollutants in the water body; by absorbing and/or breaking down
some pollutants; by reducing shore erosion by decreasing wave action and
stabilizing shorelines and lake bottoms; and by tying-up nutrients that would
otherwise be available for algae blooms. Aquatic plants provide valuable
habitat resources for fish and wildlife, often being the base level for the
multi-level food chain in the lake ecosystem, and also produce oxygen
needed by animals.
Further, a healthy and diverse aquatic plant community can better resist the
invasion of species (native and non-native) that might otherwise “take over”
and create a lower quality aquatic plant community. A well-established and
diverse plant community of natives can help check the growth of more
24
tolerant (and less desirable) plants that would otherwise crowd out some of
the more sensitive species, thus reducing diversity.
Figure 14: Aquatic Food Web
Vegetated lake bottoms support larger and more diverse invertebrate
populations that in turn support larger and more diverse fish and wildlife
populations (Engel, 1985). Also, a mixed stand of aquatic macrophytes
(plants) supports 3 to 8 times more invertebrates and fish than do
monocultural stands (Engel, 1990). A diverse plant community creates more
microhabitats for the preferences of more species.
25
MANAGEMENT RECOMMENDATIONS
(1) There are a few areas where larger natural shoreline restoration is
needed. The buffer area of native plants should be increased in those
around the lake, especially on those sites that now have traditional
lawns mowed to near the water’s edge.
(2) No lawn chemicals, especially lawn chemicals with phosphorus,
should be used on properties around the lake. If they must be used,
they should be used no closer than 50 feet to the shore.
(3) An aquatic plant management plan should be developed with a
regular schedule. This plan should include how the lake will handle
aquatic invasives if the current ones should drastically increase or
new ones enter the lake.
(4) Development of a full lake management plan might also be useful.
This would provide guidance for future board members and
landowners in managing the lake.
(5) Some of the property owners should be trained to identify the aquatic
plants present and how to identify the most common aquatic
invasives. This training, along with regular visual monitoring, should
make quick discovery of new invasions more likely and more
manageable. Free training from the Adams County Land & Water
Conservation Department is available.
(6) Volunteers have taken water clarity readings for more than 10 years
on Hill Lake. Since it is a private lake, no public funding is available
to pay for laboratory testing for total phosphorus and chlorophyll-a.
However, the Hill Lake Property Owners Association might consider
paying for at least three samplings each summer to start accumulating
26
more data for water quality assessment. At current rate, this would
cost less than $200 per year. Free training from the Adams County
Land & Water Conservation Department is available.
(5) Depth mapping for the lake might also be considered. Since Hill
Lake is small, the cost might be minimal.
This would provide
baseline information for future evaluation, which might be important
because the lake is so shallow in several areas and thus susceptible to
filling in and becoming even shallower.
(6) Education to the landowners and users of Hill Lake about water
quality and invasive species issues should occur.
No invasive
animals, such as mystery snails, rusty crayfish, or zebra mussels were
found during the 2014 survey. However, Hill Lake is close to several
lakes that contain one or more invasive animals and aquatic plants,
making it vulnerable to colonization. With regular monitoring and
education, perhaps invasions can be stopped or at least reduced.
27
LITERATURE CITED
Dennison, W., R. Orth, K. Moore, J. Stevenson, V. Carter, S. Kollar, P. Bergstrom and R. Batuik.
1993. Assessing water quality with submersed vegetation. BioScience 43(2):86-94.
Duarte, Carlos M. and Jacob Kalff. 1986. Littoral slope as a predictor of the maximum biomass
of submerged macrophyte communities. Limnol.Oceanogr. 31(5):1072-1080.
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