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Learning Exercise

Material: Water on the Web
Submitted by: Marty Zahn on Jul 20, 2004
Date Last Modified: Jul 20, 2004
Title: Lake Ecology
Description: This assignment was designed for a lab but could be done in a regular classroom. It is intended to take at least three weeks. This assignment focuses on lake ecology and the use of data sets to define the ecology of a selected lake. Students will select a lake from a list at the Water on the Web internet site and use the data provided there to describe various features and conditions of that lake. That description will be provided to the instructor in a written report and an oral presentation in class.
Time Required Minimum of three weeks.
Course: General Biology
Prerequisites Skills: Use of computer, including browser, excel and word processor software.
Learning Objectives: 1. Understand the basics of lake ecology to include physical and geologic characteristics, chemistry, productivity, annual turnover of nutrients and oxygen, food webs, and trophic status.
2. Estimate land use surrounding the lake selected and its impact on the lakes functioning.
3. Acquire and present data in graphic form to support conclusions.
Text of Learning Exercise: This exercise starts with the concept of a problem space (BioQUEST Notes, Spring
2004). A problem space is the intersection of three separate sets of
information and tools that will allow you to explore, ask, and answer questions
about that space.

Area of Research

The area of research in this investigation is lake ecology. Lakes are complex,
freshwater ecosystems that exemplify the interaction of biotic and abiotic
factors to form a dynamic, interdependent system. As in any ecosystem, energy
flow through the system will result in a definite trophic structure (food webs),
biotic diversity (range of different types of organisms), and material cycles
(cycling of elements through the system). These interactions result in a
continually changing set of conditions that are also impacted by the use of the
surrounding land. While more detail will be in the procedures portion of this
exercise, you will work in groups of one to three individuals to characterize a
specific lake and present that characterization with supporting data to the lab
section in written and oral formats.

To assist you in this exercise, you will be provided with three sets whose
intersection will define the problem space. These sets will all the found at the
Water On the Web internet site ( The first set is
background information on the biological principles underlying lake ecology and
is found under the heading Understanding. You may use other sources to
supplement this site as desired. The second set will be data sets collected on a
variety of parameters on indicated lakes in Minnesota, New York, and
Washington. These lakes have (or have had) automated sensors that collected a
set of information up to three times per day. The data sets are also located at
the Water On the Web site under the heading Data. The third set consists of
several analysis tools for accessing and displaying the data for your use. The
intersection of these biological principles, data sets, and analysis tools
defines your problem space.

Questions to answer before starting exercise:

1. Describe the concept of a problem area and the sources of data you will be
using to complete this lab exercise.
2. Briefly explain what the elements of an ecosystem are and how they interact.
3. List the abiotic factors that determine where and what type of life will be
found in a lake ecosystem.


Week One:

1. Using the information given below, your group will research a particular lake
and answer the questions presented in the procedures below. The results of this
lab will be presented in a report done on a word processor that should be no
less than three (3) double spaced pages with one (1?) inch margins and using the
Times New Roman font in a size not larger than twelve (12). Graphs and data
tables are expected as part of the report. They will be placed in appendices to
the paper and are not included as part of the page count for the paper. In
addition each group will do an oral presentation giving the results of their
research. This presentation will be no less than ten minutes per group. All
group members will participate in the presentation. You may present your tables
and graphs either on a poster or in an electronic display. Part of your grade
will be a peer grading sheet where the other group members will evaluate your
contributions to the group. Obviously this sheet will not be required if you
work alone.
2. Determine group members. Provide instructor with a list of the members of
your group.
3. View video on pond/lake ecology. This video will serve as an introduction to
lake ecology and the problems that humans cause. Suggest a worksheet to be
completed individually and turned in for grading. Possible videos are "A New
England Pond" (available from Hawkhill Associates) or National Geographic: A
rocky Mountain Beaver Pond.
4. The rest of the class time is available for the group to organize their
research plans and do a preliminary review of the data available at the web
site. Make sure you understand how to find and what data is found in the three
sets of information/data/tools at the Water On the Web site.
a. Background information: Go to the web site and click on the heading
?Understanding?. This will take you to a Lake Ecology Primer. Make sure you
read all parts of the primer?this is your basic background information. Without
this information you will not be able to understand and interpret the data in
this exercise. Topics include the following:
i. Overview
ii. Lake Variability
iii. Physical Structure and Geological Characteristics
iv. Light
v. Density Stratification
vi. The Watershed
vii. Chemical
viii. Dissolved Oxygen
ix. Nutrients
x. Biological?Lake Zones
xi. The Food web
xii. Primary Producers
xiii. Chlorophyll?A Measure of Algae
xiv. Algal Succession
xv. Consumers
xvi. Trophic Status
xvii. Eutrophication
xviii. Biological Differences
xix. Water Quality: Non-Point Pollution and, Exotic Species
b. Data Sets: Go to the web site and click on the heading ?Data?. This will take
you to the data sets and the analysis tools. You will not actually view tables
of raw data. The analysis tools will analyze the data for you.
c. Analysis Tools: Go to the web site and click on the heading ?Data?. Select
the first sub-heading that will display a map showing the sites available. From
that page you will see a link to a WOW Tutorial that will explain use of the
data analysis tools available. In addition, when you select a lake, in the left
margin you will see heading ?Data Visualization Tools?. Click on that and then
click on ?Overview? in the drop down menu. This page will also give you an
overview of the tools. Explore what each set of tools will show you before you
do your final selection of a lake.

5. Required Topics To Be Covered in Paper/Report:
a. When you select a lake, look at the Depth vs. Time (DxT) Plotter for the lake
and select a lake that has at least one complete year of mostly unbroken data.
In some cases, you will find only one complete ice-free season?that will
suffice. However, you may NOT copy the DxT plot directly into the paper as your
only graph or data source. You will need to use the Profile Plotter and/or Color
Mapper to extract specific sets of data to use to support the conclusions in
your paper. This data should then be presented in both tabular and graphic form.
b. The following topics should be described/explained as appropriate in your
characterization of the lake you selected:
i. The location and physical structure (size, depth, etc) of the lake. Include
whatever geological data is provided about the lake and how it was formed.
ii. Describe the abiotic conditions of the lake. This section would include
chemistry (use at least pH) of the lake, light, density stratification and
annual changes in this stratification, anoxic zones and seasonal changes in
these zones, temperature. This portion would include turnover times for the
lake; explain why turnover occurs. Use appropriate quantitative data (tabular
and graphs of the data in the tables) to support your discussion.
iii. Describe the biotic conditions of the lake. This section would include
typical lake zones and food web for the lake you chose. In addition, discuss the
trophic status of the lake. Is it oligotrophic or eutrophic? Support your
position with data from the site. This section should also include changes by
iv. Define what is meant by pollution. What kinds of things constitute
pollutants and are they always ?man-made? chemicals? Describe any evidence that
there are pollutants in the lake and their sources. Based on development around
the lake and past trends, predict what you think the condition of the lake will
be in 2015.

Week Two:

1. Review progress on your report with the instructor. Provide the instructor
with an outline of your paper and presentation with the name ofall students
working in your group. The outline needs to have some data to support it at this
2. Recommend the video ?Clear Water, Cloudy Future.? This video is about the
cleanup of Lake Erie and the new problems created by the attempt to restore the
ecosystem. Suggest a worksheet to be completed individually and turned in for

Week Three:

1. Class presentations.
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