Assessing the Impact of Residential Expansion on a Freshwater Ecosystem: A Comparative
Study of Donut Pond from 2007 Revisited
By: Shawn Frye, Advisor—Dr. Rebecca Doyle-Morin
Summary
Donut Pond, a small lentic ecosystem has served as a focus of several research
studies at a local high school, one of which I completed in 2007. Recently there
has been an expansion in the residential area adjacent to the pond along with a
change in property management. With the use of previous and current student’s
work, including my 2007 and replicated 2012 study, I hypothesized that these
recent changes would reduce the biodiversity within and around the pond. There
was a significant decrease (p-value = 0.0443) in the biodiversity also supported by
a significant decrease in Shannon-Weiner Diversity Index values. Organisms that
showed increases included Ocillatoria, Scenedesmus, and exotic Purple
Loosestrife while many grazers decreased or were not found, including Daphnia,
Rotifers, and Cyclops. The pond had been dredged recently and much of the
terrestrial and aquatic vegetation was reduced. Drastic changes in weather
patterns, including a severe drought, surely impacted the pond as well. Although
my hypothesis was supported, further studies should be carried out in order to
ensure findings were human-derived.
Introduction
Donut Pond is a small lentic, or still, freshwater ecosystem located in northeastern
Illinois. The property is currently owned and managed by the Richmond Hunt Club. For over a
decade, this small water body has been the focus of an ongoing research endeavor at the local
high school, Richmond-Burton Community High. During the early fall season, students
interested in ecological studies venture out to Donut Pond in order to collect a variety of biotic
and abiotic features, including macro-invertebrate sampling, vegetation distribution within and
along the pond, depth measurements and water quality tests.
In 2007, I took part in this study. In the last few years, however, a change of hands in
management of the property took place. Coinciding with the residential expansion
encroachment, new management procedures have reduced the vegetation in the area and
proceeded with dredging the pond. Dredging can reduce the abundance of phytoplankton and
rooted vegetation by increasing turbidity or by directly removing the plants (OSPAR, 2008).
Other common anthropogenic disturbances commonly linked to residential expansion include
increased erosion, both inorganic and organic intrusions (i.e. oil, detergent, phosphorus, nitrogen,
body waste) and eutrophication (Antonucci, 2006).
Since my original study preceded the changes in land management, I was curious to see
how the alterations may have impacted the pond. Seemingly, removing the vegetation and
sediment may drive down invertebrate and microorganism population due to the loss of food
sources and habitat (Antonucci, 2006). Therefore, I hypothesized the increase of human
influence will cause a noticeable decrease in the biodiversity within Donut Pond.
Methods
In order to have more samples to compare my 2007 and 2012 studies to, I contacted the
current High School teacher, Ms. Katie Coon to obtain previous student’s work, and my brother,
Jeff Frye, who took part in the study in 2005. Ms. Coon was only able to obtain biotic data from
2011. However, now I had access to two studies before the residential expansion took place and
two following the institution of new management practices.
The study began by returning to Donut Pond for three-day period. First, the water body
was divided into three sections of equal length (roughly 50 meters). From each section, two dip
net samples were taken along the shore in order to collect macroinvertebrates within the area.
The samples were placed into a plastic white tray for increased contrast from the murky substrate
expelled. Visible organisms were removed from the tray, placed into containers identified for the
region of collection. Algae was also preserved if found within the net. Each sample collected was
preserved in 95% ethanol for later identification.
Microorganism samples within the pond were extracted using plankton net tow, one from
each section, which is dragged through the water column. These samples were not preserved in
order to maintain color and structure of the organisms. Evidence of large animal presence within
the area (i.e. fecal matter, prints, and sightings) was also recorded. Rooted and free floating
distribution of vegetation within and along the pond was documented with the use of labeled
drawings and photographs. All organisms collected were classified down to their class to
compare with previous studies.
Shannon-Wiener Diversity Index, which compares species richness and evenness
(Molles, 1999) was used to compare how organisms fluctuated overtime. Two-sample t-tests (α=
0.05) were used to compare pre-disturbance (2005-07) to post-disturbance (2011-12).
Depth measurements were taken throughout the pond by dropping a weighted object on a
known length of rope. ArcMap 2010 Software was used to produce maps comparing water depth
change. Two water samples from the benthic and pelagic zones were tested for chemical
concentrations using HACH Permachem® Reagent Pillows and Test Strips. Temperatures were
also collected from each of the two samples. Weather information was collected from the past
decade only for the months of May through August based out of Lake County’s weather station
records (“Weather History,” 2013). These months were chosen because the precipitation or
temperatures likely drove the changes seen within September, the month in which the study took
place.
Results
The Shannon-Wiener Index illustrated that there was a decrease in the index values after
residential expansion took place (Table 1). Although some 2012 taxa showed increased in
abundance compared tom my 2007 study, most organisms diminished greatly or were not found
all together. The two sample t-test showed that there was a significant change in the predisturbance and post disturbance data (p-value = 0.0443) (Figure 1).
A noticeable decline in three different grazing taxa, Cyclops, Rotifers, and Daphnia was
observed during this study. On the contrary, two types of algae increased drastically within the
system in 2012: colonial green Scenedesmus and filamentous blue-green Oscillatoria (Figure 2).
Reduction of native rooted aquatic and terrestrial plants was prevalent as well (Figures 3-4).
However, numerous invasive weeds actually increased such as Purple Loosestrife, Burdock, and
Multiflora Rose.
Water testing drew few comparable results due to different sampling practices between
study years; the student’s work only acknowledged changes in the water’s content by indicating
an “increase or decrease” from previous studies. Therefore, I was only able to directly compare
my 2007 and 2012 data. A noticeable change in water temperature was noted. Temperatures
within the Pelagic zone increased by 8° and the Benthic by 5° Celsius from 2007 to 2012. A slight
drop in phosphorous levels was apparent with a 2 ppm (parts per million) decrease from pelagic
zone.
The results from depth sampling indicated that there was a drastic loss of water over the
past five years accounting for over a meter drop in most areas. However, the western portion of
the pond actually increased in depth over the time between studies (Figure 5-6). Among the
weather data collected, there noticeably less precipitation in 2005 and 2012 compared to the
other study periods (Figure 7). Also, 2012 had the warmest temperatures documented throughout
the entire decade (Figure 8).
Discussion
Through this study, I found that Donut Pond has lost some of its biodiversity through
vegetation removal and shifts in the evenness of organisms within the ecosystem. The ShannonWiener Index significant loss of organisms within the pond. It is not uncommon for algal groups
to increase in response to different human derived perturbations, including dredging or increased
use of fertilizers (Antonucci, 2006). A decrease in the grazers within the pond was a symptom of
a diminishing habitat quality. Not only are these organisms essential for maintaining algal
levels, they are also important sources of food within an ecosystem. Daphnia is also considered a
bio-indicator due to their notorious sensitivity to water quality changes (Meinertz et al., 2011).
Ocillatoria is frequently problematic because it is resistant to extreme conditions, such as
the presence of heavy metals, high salinity and typically is not preyed upon (Gribovskaya et al.,
2009). Scenedesmus however, is often a favorable food among grazers. This colonial algae was
not apparent it previous studies, possibly due to over-predation. Aquatic rooted plants may have
been outcompeted by the overabundance of algae in the system (Farrow, 2009). However, it is
apparent that the pond was dredged by the land owners, possibly in attempt to thwart algal
blooms and produce better habitat for fish; the plants were likely removed in the process or
smothered by suspended sediment in the process (OSPAR, 2008). It was apparent that vegetation
around the pond was reduced for recreational uses including the addition of two beaches. The
increase of exotic weeds in the area is troubling since non-native plants can often out-compete
native plants (Great Lakes, 1999).
The lack of rain and abnormally warm weather left northeastern Illinois drought-stricken.
Droughts can decrease water levels leading to a decrease in the habitat for aquatic dwelling
organisms (Lake, 2003). Although some changes observed were obviously human derived,
including the management work involved, more studies would be required in order to confirm
evidence of harm inflicted by development. Supplemental study samples with consistent
methodologies could assist in compiling information difficult to conclude in this study, such as
the annual changes in water depth rather than over a five year span, and overall dissolved
chemical concentrations within the system. However, these findings were still intriguing; there
was certainly a decrease in diversity, loss of habitat, and dramatic alterations to Donut Pond.
Acknowledgment
I would like to thank the Pioneer Undergraduate Research Fellowship including the
Association of Retirees for Excellence, UWP Foundation, and UW-Platteville for funding my
study proposal. Mrs. Judy Boisen and Miss Katie Coon, biology teachers at RBCHS, with their
current and previous classes, and Brother Jeff Frye for providing more data for this study. My
advisor Dr. Rebecca Doyle-Morin and the UWP Biology department who have assisted me in the
completion of this study. I appreciate the Richmond Hunt Club for allowing me to conduct
research on their property. Last, I would like to thank my family and friends who always offer
their support and encouragement in my endeavors.
Reference
Antonucci, D.C. (2006). Environmental Problems Facing Lake Tahoe. Science and Research at
Lake Tahoe. Page (1-5).
Farrow, J. (2009). What the heck is Algae anyway? AlgaeControl.us. Retrieved April 29, 2013,
from http://www.algaecontrol.us/research.html.
Great Lakes Indian Fish & Wildlife Commission. (1999). Plants Out of Place. WI DNR Bureau
of Endangered Resources.
Gribovskaya, I.V., Kalacheva, & Bayanova, (2009). Physiology-biochemical properties of the
cyanobacterium Oscillatoria deflexa. Applied Biochemestry And Microbiology, 45(3)
285-290.
Lake, P. S. (2003). Ecological effects of perturbation by drought in flowing waters. Freshwater
Biology. 48, 1161-1172.
(N.D.) Weather History. Weather.org. Retrieved April 11, 2013, from
http://weather.org/weatherorg_records_and_averages.htm.
Meinertz, J., Schreier, T., & Bernardy, J. (2011). Chronic Toxicity of Erythromycin Thiocyanate
to Daphnia magna in a Flow-Through, Continuous Exposure Test System. Bulletin Of
Environmental Contamination & Toxicology, 87(6) 621-625.
Molles, M. C. Jr. (1999). Ecology: Concepts and applications. USA, WCB McGraw-Hill Co.
(2008). Assessment of the environmental impact of dredging for navigational purposes. OSPAR
COMMISSION. Retrieved April 28, 2013 from
http://qsr2010.ospar.org/media/assessments/p00366_supplements/p00366_suppl_1_dredg
ing_what_are_the_problem.pdf
Table 1: Shannon-Wiener Diversity Index Values for four study
years. Indices include the compilation of all biotic data collected.
Year of Study:
2005
2007
2011
2012
Index Value:
3.52
3.30
2.69
2.77
Average numb of organisms foun
(per taxa)
70
60
50
40
30
20
10
0
Pre-Disturbance (2005-07)
Post-Disturbance (2011-12)
Figure 1: Comparing the average number of organisms per taxa
before and after new management procedures and residential
expansion took place (p-value = 0.0443)
800
700
Relative Numbers
600
500
2005
400
2007
2011
300
2012
200
100
0
Rotifer
Cyclops
Daphnia
Scenedesmus
Oscillatoria
Figure 2: Illustrating the decrease in 3 types of grazing
organisms Rotifers, Cyclops, and Daphnia with an increase in
algae taxa, Scenedesmus and Oscillatoria.
Figure 3: ArcMap 2010 illustration produced
displaying the Vegetation Distribution during
the 2007 Study (Pre-Disturbance)
Figure 4: ArcMap 2010 illustration of Vegetation
Distribution for 2010 Study (Post-Disurbance).
Note: addition of beaches (northeast).
Figure 5: ArcMap 2010 illustration of
2007 water depths
Figure 6: ArcMap 2010 illustration of
2012 water depths
50
Amount of Precipitaton (cm)
45
40
35
30
25
20
15
10
5
0
1998
2000
2002
2004
2006
2008
2010
2012
2014
Years
Figure 7: Weather data documented for
averaged monthly precipitation for May
through August. Arrows Indicate the years in
which the studies compared took place
30
Temperature (Celsius)
25
20
15
10
5
0
1998
2000
2002
2004
2006
2008
Figure 8: Average annual temperatures
May through August
2010
2012
2014