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DRAFT

Life in Extreme Environments - Lakes Under Ice

Overview
Students will collect chemical, physical, and biological data from a local lake throughout the year. These data will be contrasted with parallel data from an ice-covered lake in the Dry Valleys. They will explore the differences between their local environment and a perennially ice covered fresh water lake in the Dry Valleys, Antarctica.


Rationale
The Dry Valleys are one of the harshest environments on Earth, and yet, life, mostly microscopic, thrives! Even the perennially ice-covered lakes offer niches exploited by phytoplankton, protozoa, rotifers, and bacteria within the lake communities. How do these lakes compare to lakes not covered by ice throughout the year? How do the communities of organisms compare? Researchers are interested in these communities to help them understand where and how life may exist elsewhere in our Universe. They are also interested in how small changes in climate impact the living conditions for the communities of organisms.


Grade Level/ Discipline
Grade 9 - 12
Ecology, Environmental Science, Biology, Earth Science



Objectives

  • discuss the design of an experimental structure for water collection at several specific depths
  • collect and analyze chemical, physical, and biological lake water data from a local watershed for several months
  • analyze parallel chemical, physical, and biological lake water data from the Dry Valleys
  • present the lake data in appropriate graphical and tabular formats
  • assess the physical factors that affect solubility of gases in the lakes
  • compare and contrast the two lake environments
  • describe the impact of perennial ice cover on lake chemistry and biology
  • propose links between the lake ecosystem and the environment

  • National Standards
    Content standards C; Life Science, Interdependence of Organisms; Matter, Energy and Organization in living systems
    Content standard D; Energy in the Earth System
    Biology Advanced Placement Lab #12 (primary productivity)


    Teacher Preparation for Activity

    Materials
    For the class:

    several sheets of poster-sized paper
    markers
    For each group of 4 students:
    sample vials
    lake water collected in an appropriate manner described above
    colored pencils
    Option A:
    1 thermometer
    several strips of pH paper (range: inclusive of 4 - 9 )
    dissolved oxygen titration test kits (acquired from: Hach )
    procedure sheets for analyzing selected water quality parameters (RM#1, 2, 3, 4)
    several sheets of graph paper
    Option B:
    calculator based data collection units (CBL)
    appropriate probes:
  • pH
  • temperature
  • dissolved oxygen
  • ions
  • procedure sheets for analyzing selected water quality parameters with CBL's (RM#5, 6, 7, 8)
    Pre-activity set-up
    Visit the LTER web site to discover the myriad of research projects being done this field season. Later, you may want your students to view the site. Together you can share the applications of their procedures and contrast any differences in the environments.

    Become familiar with the LTER data sets (http://huey.colorado.edu/LTER/data.html). There is a wealth of meteorological, limnological, geographical, etc. data available. Locate the data sets that will be used for comparison with your students.

    Locate an appropriate, safe field location for your students to visit and sample water. This may be a creek, lake, drainage ditch, or stream. Alternatively, sample a sufficient quantity of water for your students and bring the water to class in an insulated container to conserve temperature. You may want to test distilled water to use as a control. (distilled water may have a low pH due to carbonic acid)

    The students also can acquire a water sample from their local neighborhood and bring it to class. As a class, discuss what parameters are appropriate. The students should not sample tap water. They should sample in a safe location. Have them appropriately label the sample.

    Time Frame
    Engagement, Exploration, Explanation: 2 class periods, excluding optional field trip(s).
    Elaboration: 1 class period each week, two weeks, or month, depending on the experimental design.
    Exchange: 3 class periods.


    Teaching Sequence

    Engagement and Exploration (Teaching Sequence)
    Have several poster-sized pieces of paper ready to write the student hypotheses about lake conditions in Antarctica and their local neighborhood. Perhaps one or two students can assume the role of class recorders. Subsequent results will be compared to these records. Students can also document the discussion in their lab notebooks.

    Ask the students to share their thoughts on what the water quality is in their local environment. Record their thoughts on a wall chart.

    What lives in the local lakes and streams? What do the organisms need to live? What might the temperature be? Is it constant through the day? The year? What about the salinity? The oxygen level? The pH?

    Have the students read the journals entries of Barb Schulz and Paul Jones.

    These journal pages provide the flavor of the lake system in the Dry Valleys. What might the conditions be in the fresh water lakes in Antarctica (pH, oxygen, temperature, etc.)? Record their thoughts on a wall chart.

    What are the environmental conditions in Antarctica? What may live in these lakes?

    In the Dry Valleys of Antarctica, some of the lakes are perennial ice covered. How might ice cover influence the lake conditions? Record their thoughts on a wall chart.

    Some of the students may not know what "perennial" means. Perhaps prompt them by asking when "annual" flowers bloom? What about "perennial" flowers?

    In your area, perhaps there are lakes that freeze each winter. What are the conditions in the lake under the ice?

    On the dry valley lakes, the ice cover averages 3 to 4 meters thick. Very little light penetrates the ice. At 12 meters below the ice surface, the depth at which phytoplankton are found, only 1% of the available light penetrates the ice! This ice cover prevents the atmosphere from mixing with the water. There are no waves or water currents at the water surface. There is no atmospheric gas (air) exchange or mixing with the waters. There is no easy way for gas (such as oxygen or carbon dioxide) to escape from the water into the atmosphere*. There is no rain water falling into the lake. No animals can drink from the lakes (...in the Dry Valleys there are no vertebrates except for human researchers and mummified seals).

    * as the ice sublimates (changes from the frozen state to the gaseous state - the process where ice cubes in a frost-free-freezer get smaller) gases are released to the atmosphere. This process of gas release from the lake, is very slow. Some microbial mat from the lake bottom is also trapped in lake ice and moves toward the surface to be released into the wind and dispursed throughout the valleys.

    How might the lakes in Antarctica be different from or similar to the local lakes?

    What about temperature? Organisms? Recreational use? Ask the students to think about human impacts and their impressions of the complexity of the two ecosystems. What organisms do they think make up the different ecosystems?

    Explanation (Discussing)
    Ask the students to examine their predictions about lake conditions that are recorded on the wall charts.

    How might they determine if their predictions are correct?

    Explain that they will be collecting data from a local system (or analyzing water, if they will not collect it themselves).

    They will analyze Dry Valley lake data (Lake Hoare) that are posted on the web (specific sites listed below).

    Have the student groups visit to the Long Term Ecological Research website and examine the Dry Valleys data sets (http://huey.colorado.edu/LTER/data.html data sets). What data may be comparable to information they can collect in their local system?

    For their own lake system, ask the students how they will design their experiment.

    What are the types of questions that they wish to ask? How much data do they want to collect. For how long? Do they need replicate samples? Why or why not? How will they record the data? How will they display them? What types of comparisons will they undertake between the two ecosystems?

    Set out test kits so that the student groups can access the needed materials. Provide the students with the procedure sheets appropriate to the data the students will collect.

    Ask the students to read the procedures. Demonstrate the use of the equipment and allow the students to work with the equipment until they are comfortable. You can learn how to doeach test using tap water or distilled water.

    I will e-mail our lab sheet to you Steph

    Notes to teachers on how the analyses are conducted - needed.

    Elaboration (Polar Applications)
    Depending on the experiment design, the students will collect and analyze the local lake data each week, once every two weeks, once a month, or once each season. During that day of analysis, the students should locate and record the parallel data for Lake Hoare for that same month and day (or the closest equivalent day for the year; i.e., 1 March 1996 data can be compared to 10 March 1999).

    Students should agree on a common data table with all parameters available. A possible template is available if you wish to use it.

    *** If a field trip is taken, it is important to document the depth at which water is sampled. For the Lake Hoare study, water is sampled every two meters up to a depth of 40 meters. You may wish to take samples from at least two different depths. With portable equipment like the CBL units, or field test kits like those from Hach, test the water immediately after collecting it. If there is no easily available water and you absolutely can not get your students to a testing site, collect some water yourself from several depths at the lake of your choice on the day of the lab and bring it to school. It is important to keep the water at a constant temperature to maintain the dissolved oxygen and water temperature accuracy. An ice chest or cooler works well. This is sometimes problematic, but may be better than no lab at all. Go to the Lake Hoare (http://huey.colorado.edu/LTER/lakedata.html data sets) and download the appropriate data sets for comparison to the parameters your students are measuring in the local lake system)

    http://huey.colorado.edu/lter/data.html
    Map
    Temp
    DO
    Ph (http:// ...)
    Ice thickness
    Phytoplankton Density (summer and winter
    Primary Productivity
    Nutrients
    Chlorophyll
    Ions

    Extensions
    Have students create their own data table and document what they do in lab as they do it. Acknowledge that water taken at different depths will yield quite different results for some of the water quality tests. Discuss possible causes for the results. If you have time, ask students to ask their own question and design an experiment to extend their knowledge of this ecosystem. One option is to look at the data and find another way to analyze it.

    Evaluate / Class Discussion
    In small groups, students should discuss their results and the impact of the ice cover on the chemistry of the lake. Have students account for any differences they find. Each group should present their ideas to the class and discussions of reasons for research in the dry valley ecosystem should be held. Students should have read the material about the ecosystem from the LTER web site on the McMurdo Dry Valleys research study and make comments on the impact of small climatic changes on the dry valley ecosystem. Lab reports should be written. This can be individual or in small groups depending on teacher preference.


    Author
    Barbara Schulz
    Biology Teacher, lakeside School, Seattle WA
    TEA teacher, 1996/97 field season in the McMurdo Dry Valleys

    Background
    The lakes in the dry valleys are unique in that they have a perennial ice cover that fluctuates in depth but maintains approximently 3 - 4 meters in depth. This ice cover is thought to have been in place for at LEAST 10,000 years. As such, the lake waters have had no mixing with the atmospheric gases, no wind driven water currents and no direct escape of gases from the lake to the atmosphere. The lake contains a simple ecosystem of bacteria, cyanobacteria, protozoa and perhaps viruses. The largest organism in the lake appears to be a rotifer, a macro-invertebrate of less than one mm in length. There is a unique water column in the lake. This means that various things are vertically stratified within the lake water. For example, oxygen is supersaturated at the lake-ice interface. As one moves down the water column to the bottom of the lake at about 40 meters, the water becomes anoxic. This column remains stable thus causing a column of organisms to live at the preferred oxygen content level. Anaerobic organisms can live at the bottom, very few organisms live at the ice - water interface and most organisms can be found at about 12 meters depth, an area that receives about 1% of the light through the ice during the austral summer. There are also ion columns of stratification which serve to select for various members of the biotic community. Ice ablates (sublimates) from the lake surface rapidly during the long dark winters; water enters the lakes during the short austral summers when glacial meltwater causes ephemeral streams to flow into the lakes at the lake edges where a small moat of melting occurs. It is thought that the rate of ice sublimating from the surface of the lake will cause the ice cover to be completely cycled in 12 years. Thus any material trapped in the ice as it freezes at the lake water - ice interface will take 12 years to reach the surface and blow away. Mats of algal matter that have trapped oxygen bubbles float to the top of the water, become trapped in the ice and eventually make it to the surface, blow to another area and may "grow" during the next season. Two large research questions are being considered by the LTER. They deal with materials transport. Included in this study is how salts and ions get carried into the lake by streams, how wind moves sand and rock parcticles on to the lake surfaces and how materials trapped in the ice cover work their way to the surface as the ice ablates, eventually becoming free and airborne. The other large question deals with energy balance. The energy balance question looks at how the glacial meltwaters are tied directly to solar radiation. Albedo or energy reflected back into the atmosphere is measured as is the amount of energy absorbed by dark material, both from sand and gravel on the ice cover of the lakes and the ice free land. Any changes in the energy available will significantly impact the lakes in these dry valleys.

    Directly from the LTER web site...
    The McMurdo Dry Valleys are located on the western coast of McMurdo Sound (7700'S 16252'E) and form the largest relatively ice-free area (approximately 4800 square kilometers) on the Antarctic continent. These ice-free areas of Antarctica display a sharp contrast to most other ecosystems in the world, which exist under far more moderate environmental conditions. The perennially ice-covered lakes, ephemeral streams and extensive areas of exposed soil within the McMurdo Dry Valleys are subject to low temperatures, limited precipitation and salt accumulation. Thus, the dry valleys represent a region where life approaches its environmental limits, and is an "end-member" in the spectrum of environments included in the LTER Network. The dry valleys, unlike most other ecosystems, are dominated by microorganisms, mosses, lichens, and relatively few groups of invertebrates; higher forms of life are virtually non-existent. The overall objectives of the McMurdo LTER are to understand the influence of physical and biological constraints on the structure and function of dry valley ecosystems and to understand the modifying effects of material transport on these ecosystems. The McMurdo Dry Valley ecosystems are driven by the same basic processes, such as microbial utilization and re-mineralization of nutrients found in all ecosystems, but they lack many confounding variables, such as higher plants and animals, found in other ecosystems. McMurdo LTER research contributes to general ecological understanding through studies of processes that are readily resolved in these ecosystems. To successfully accomplish these studies, scientists must be present in the field--the McMurdo Dry Valleys. Samples and measurements cannot be obtained remotely and experiments must be conducted in situ if they are to have any relevance to the environment.

    Why is it necessary to conduct long-term ecological research on the McMurdo Dry Valleys of Antarctica? To summarize from the McMurdo LTER Site Review Committee's January 1997 report, "the McMurdo LTER project is working on an incredible system for ecological study. It is not just a unique area, but more importantly, it exists at one end of the arid and cold spectra of terrestrial ecosystmes." All ecosystems are dependent upon liquid water and shaped to varying degrees by climate and material transport, but nowhere is this more apparent than in the McMurdo Dry Valleys. In very few places on this planet are there environments where minor changes in climate so dramatically affect the capabilities of organisms to grow and reproduce. Indeed, the data being collected by the LTER indicate that the dry valleys are very sensitive to small variations in solar radiation and temperature and that this site may well be an important natural regional-scale laboratory for studying responses to human alterations of climate. While the Antarctic ice sheets respond to climate change on the order of thousands of years, the glaciers, streams and ice-covered lakes in the McMurdo Dry Valleys respond to change almost immediately. Thus, it is in the McMurdo Dry Valleys that the first effects of climate change in Antarctica should be observed.

    Research ACTIVITIES
    The McMurdo Dry Valleys LTER project has successfully completed five field seasons (October-February) since 1993. During the1993-94 season 18 scientists were deployed toMcMurdo Station and Taylor Valley to conduct research associated with the LTER project. These scientists initiated core measurement programs to obtain baseline ecologically-relevant data from thermosphere, glaciers, streams, soils, and lakes. Twenty-six scientists in the field during the 1994-95 field season, 27 scientists in 1995-96, and 26 in 1996-1997 continued the program of systematic environmental data collection and long-term experiments.

    During the 1996-97 field season, the field team based operations at the Lake Hoare field camp while collecting samples and conducting experiments on the glaciers, streams, soils and lakes in the Taylor Valley. Types of investigations conducted included: 1)glacial hydrology studies on the Commonwealth, Canada, Taylor, Howard, Hughes and Suess glaciers, 2) stream gauging, collection of water samples and biological studies of streams in the Lake Fryxell, Hoare, Vanda and Bonney basins, 3) studies of planktonic, sediment and ice-associated communities in Lakes Fryxell, Hoare, Vida, Bonney and Joyce, 4) limnological studies of benthic microbial-mat communities and sediments in Lakes Fryxell, Hoare, and Joyce using SCUBA, 5) soil ecosystem studies near Lakes Hoare and Bonney and 6) maintenance and upgrades of meteorological stations and submerged sensor arrays within Taylor, Wright and Victoria Valleys.

    taken from http://huey.colorado.edu/LTER/project.html

    Engagement discussions may take one 55 minute class period.

    Water quality tests will take one 55 minute class period. If you need to take a field trip to get to a local body of water, you need to judge the amount of time required. You may have each student group make all of the tests on the lake, or you may want to have different lab groups responsible for specific tests and share their data. Students should also document environmental conditions, flora and fauna, evidence of human impact and weather .

    Testing primary productivity will take two lab days and must use lake water and not tap water.

    This activity can be done with or without the primary productivity.

    Sharing data and making data tables may take half of a class period.

    Comparing student data with that from Lake Hoare in small groups may take one 55 minute class period but could take longer depending on the interest of the students in pursuing other questions about the ecosystem found in the dry valley. Students should access the web to find the data on Lake Hoare in Taylor Valley, Southern Victorialand, Antarctica. If you do not have web access for your students, you can download and provide copies for students. However, the web site also provides photos of the lake. My web page has photos of the lake as well as photos of doing some of the data collection.

    Resources
    See links to the McMurdo Dry Valleys web site. http://huey.colorado.edu/LTER/project.html

    See links to the LTER web site http://lternet.edu/

    Project Green water quality testing

    Access Excellence web site with activities to go http://www.gene.com/ae/

    Life on Mars? Video. Discovery Channel School - PO Box 970, Oxon Hill, MD, 20750-0970, 1-888-892-3484, $29.95.

    Student Reproducible Masters

    Reproducible Master 1
    Student Procedure Sheet - Acquiring pH Data

    Reproducible Master 1
    Student Procedure Sheet - Acquiring Temperature Data

    Reproducible Master 1
    Student Procedure Sheet - Acquiring Dissolved Oxygen Data

    Reproducible Master 1
    Student Procedure Sheet - Acquiring Ion Data

    Please review this activity.



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