Kristen Kernan
Winter Ecology- Spring 2012

• Productivity- Amount of photosynthesis occurring due to phytoplankton
• Limnetic Zone- Open surface water in a lake, welllit, and can contain many aquatic organisms
• Littoral Zone- near shore area that can maintain aquatic plants
• Chlorophyll- a pigment present in phytoplankton used to absorb light for photosynthesis

• Phytoplankton remain active during the winter and adjust to changing light conditions
(Marchand, 1987)
• Lake productivity is related to nutrient content and affects the number of species found in a lake
• Light is a limiting factor in wintering lakes and snow coverage can make light penetration more difficult

• Evergreen Lake in Evergreen, Colorado
• Within the Bear Creak watershed and created by damming Bear Creek in 1927
• Elevation= 2,200.656 meters
• Size= .1699 km^2

• Heavily used for recreational purposes: ice skating, ice fishing, resides on the outskirts of a golf course
• Completely ice covered
• Snow covered on ~90% of the lake except for the area cleared for ice skating

• Question: Is the limnetic zone or the littoral zone more productive?
– If the limnetic zone is less productive then levels of chlorophyll will be higher in the littoral zone
• Question: How is productivity affected by snow coverage?
– If productivity is affected by snow coverage then sites with less snow will have higher levels of chlorophyll

• Samples were collected using a 2-liter Van Dorn and then stored in a cooler to limit light exposure and temperature change
– Limnetic
• Central Location
• Depth= 4.1 meters
• Ice Thickness=30 cm
• Snow Depth= 35 cm
• Samples were taken at 1meter and 3 meter depths
– Littoral 1
• Near-shore site
• Depth=1.5 meters
• Ice thickness= 15 cm
• Snow Depth= .5cm
• Sample taken at 1 meter depth
– Littoral 2
• Depth=1.5 meters
• Ice thickness= 25 cm
• Snow Depth= 35 cm
• Sample taken at 1 meter depth

• Samples were filtered using a glass fiber and stored in a plastic test tube and kept in a freezer until extraction
• 10 mL of ethanol was placed in each test tube
• Chlorophyll was extracted at 78 degrees
Celsius (the boiling point of ethanol)
• Post extraction samples were filtered once more and then ran on a spectrophotometer at wavelengths of 665nm and 750nm.

6,4
6,3
6,3
6,2
6,2
6,1
6,1
6,0
6,0
5,9
5,9
Chlorophyll in micrograms/liter: Limnetic vs. Littoral
6.3 ug/l
6.0 ug/l
6.2 ug/l
• Chlorophyll was fairly uniform from Limnetic to
Littoral
• Increasing lake depth at limnetic site showed a decrease in chlorophyll by
.3ug/l
Limnetic: 1 meter
Limnetic: 2 meter
Littoral: 1 meter

6,0
5,0
4,0
3,0
2,0
1,0
0,0
9,0
8,0
7,0
Chlorophyll in micrograms/liter Between Sites
8.2 ug/l
6.2 ug/l
Litt 30cm Litt 2mm
• Higher amounts of chlorophyll at littoral site with half centimeter of snow

• Rejection of hypothesis that littoral zone is more productive than limnetic zone in winter lakes
– Chlorophyll at both locations about equal
• Acceptance of hypothesis concerning snow depths affect on productivity
– More snow coverage=less algae=less photosynthesis
• Chlorophyll levels indicate the lake is on the low side of being Mesotrophic (Carlson R.E. and J. Simpson,
1996)
– Some evidence suggesting that this may be a characteristic of a wintering lake (French et al., 2007)

• Bear Creek Reservoir in comparison(Clayshulte
2010):
– Same watershed
– Lower elevation
– Eutrophic lake
– February of 2010 chlorophyll 14 ug/l
– Has experienced algal blooms

• Near shore versus open water doesn’t appear to be much of a factor concerning chlorophyll in wintering lakes
• Snow depth has a larger impact on productivity due to the availability of light
• If given the opportunity to re-do project:
– Couple data with hydrolab depth analysis
– Pick a known eutrophic lake
– Collected more samples

• Carlson R.E. and J. Simpson. “A Coordinator's Guide to Volunteer
Lake Monitoring Methods.” North American Lake Management
Society. (1996):96 pp. Print.
• Clayshulte, Russell. “2010 Annual Report for the Water Quality
Control Commission.” Bear Creek Watershed Association (2010): 1-
38. Print
• French, Todd, and Ellen Petticrew. "Chlorophyll a seasonality in four shallow eutrophic lakes (northern British Columbia, Canada) and the critical roles of internal phosphorus loading and temperature."
Hydrobiologia 575 (2007): 285-299. Print.
• Marchand, Peter J. Life in the cold: an introduction to winter
ecology. Hanover, NH: University Press of New England, 1987. Print.