Marlene Schoeneck initiated this lesson.
lakes are sealed off from terrestrial influences in the winter by
a lid of ice. The ice limits gas exchange at the lake / air interface,
and reduces light levels as snow cover accumulates. Life processes
go on, but decreased photosynthesis, accumulated waste products,
and continued respiration make survival in the self-contained environment
more difficult. Prolonged exposure to such conditions may create
problems in managed systems where maintenance of fish populations
is an important factor to consider.
Part I -
Winter Lake Laboratory Simulation
Discuss in your
lab group, or as a class, problems that have developed in area
lakes from winter conditions. What physical and biological factors determine
the severity of ice effects? What types of management practices
may improve or limit the negative impacts of ice cover?
You will need
the following equipment:
1. 2, 250 ml clear bottles or jars with essentially airtight lids
2. Pond, lake, or aged tap water
3. Organic/mucky sediment
4. Several sprigs of Anacharis (Elodea) or other aquatic plant
5. A refrigerator or other method of keeping one of the microcosms
chilled. (The colder the better, without freezing the jar solid!)
Your goal is
to develop an experiment that will model what might happen in a
lake in the summer compared to the same lake in the winter. Set
up 2 jars as simulated "lakes" using the materials listed
above. Determine amounts of materials to use in each jar. Remember
you want to generate data that will allow you to make a fair comparison
of the results in each "lake." Cap each jar. Place one
jar under a plant light in room temperature. Put the second jar
in the refrigerator or other means you have selected to keep it
cold. Take care not to allow the jar to freeze solid! You may need
to do some experimenting with temperature settings previous to the
start of your experiment. Record the procedures you have developed
so other scientists could replicate your experiment.
1. Decide what
factors you would like to measure that you feel would be relevant
to an ice-covered lake. Sensors, rather than test kits, are preferable
for data collection. (If using a test kit, slowly replenish the
water taken from each bottle with water from the original source,
so as not to significantly change the sample. Write a brief rationale
explaining why you chose to measure these factors.
2. Take readings
once or twice a day over a 5-day period. Formulate a chart to enter
your values for each reading.
1. Graph your
data by hand or use an Excel spreadsheet. Follow instructions for
template on the WOW site. Be sure all parts of the graph are properly
1. What changes occurred in your "lakes" over the course
of the study?
2. How do you
account for changes in your lake?
3. How are these
changes related to conditions in an actual lake in winter? What
ramifications do they have for lake life?
4. What aspects of this simulation are not realistic? Suggest some
revisions to more accurately simulate winter lake conditions?
1. Keep results
to turn in with part 2.
Part II. - Changes in a Winter Lake
results of your winter lake simulation. What lake chemistry changes
might you expect to see in an actual lake? Recall your discussion
of the physical and biological components of lakes as you consider
their influence on a specific lake and its winter dynamics.
local Sportsmen's Club has been asked to purchase aerators for
one of the lakes monitored by WOW in order to reduce winter fish
They first would like to be sure that winter conditions in the
lake justify the installation of these units. Since your science
has been monitoring the lakes for several years, the club has come
to your school in search of the needed evidence.
Use RUSS data
on the WOW site to determine a study lake with relevant data (many
lakes have gaps in winter data sets). Consider how you will determine
ice formation and ice out on your lake. What factors will you need
to monitor in order determine the need for aerators on the lake?
Over how long of a period of time will you need to look at data?
Be prepared to explain the reasoning behind your experimental design.
RUSS data for your lake to make a recommendation to the Sportsmen's
Club for or against the purchase of aerators. You must make the
determination of how much data is "enough" to provide
clear direction, as well as what type of data is needed. Write
brief rationale for your decision (imagine justifying your plan
to the club).
Use the data
visualization tools or an Excel spreadsheet on WOW to organize
and interpret the data you have collected.
following questions as you prepare for your presentation for the
class on your winter lake:
1. What changes
did you observe in the factors you measured over the winter at your
2. What physical
characteristics of your lake might have had an influence on the
results that you observed in your data? How?
3. What knowledge do you have of the biological characteristics
and trophic state of your lake? How might these have affected the
life sustaining ability of your lake? What else would you like to
know to increase your confidence in your recommendations?
4. Based on
the above research, what recommendations would you have for the
Sportsmen's Club in regards to installing aerators on the lake?
5. What other
management practices might help prevent fish kills in the lake besides
Develop a presentation
using graphs and other visual aids for your class, pretending they
represent the "Sportsmen's Club". Explain your recommendations
for installing (or not installing) aerators on your local lake.
Be sure to back up your reasoning with data and explanations based
on general lake processes and the characteristics of your particular
lake. Compare your results to other members of the class. Turn
your presentation materials and question responses from parts 1
and 2 to your teacher.