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Activities: 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 9 | 10
Activity Six
What's in This Water?
Objectives
Students
will seek to answer the questions; What are the chemical and biological
characteristics of water in which purple loosestrife occurs? Do these
characteristic differ in wetland water dominated by indigenous wetland
plants ( cattails, rushes, sedges etc.)?
State Science Curriculum Objectives
Constructing
objectives: 13, 14,
15, 18
Reflecting objective: 11
Using objectives: LEC16,
17, 18, EH 10
Methods
Students
will locate 2 wetlands one with and one without a medium to high density
of purple loosestrife. Using water quality measuring kits ( Hach kits
are inexpensive and work well for classroom use), nets and containers,
students will sample and test the water for temperature, pH, nitrate
nitrogen, oxygen, phosphates and macro-invertebrate indicators (all
or part of these test may be used).
Background
A
wide variety of information is valuable in understanding the impact
on and spread of purple loosestrife in the wetlands. Scientist are in
the process of gathering data on this widely spreading plant. In Canada,
scientists mapping the location of purple loosestrife noticed that it
has not taken hold and spread in more acidic waters and soils of the
Canadian Shield but is found widespread in the more basic water and
soils south of the Canadian Shield. Could the type of water and soil
predict the spread of purple loosestrife?
Cattails and other keystone wetland species are
known to cleanse water of pollutants such as nitrates, phosphates, chlorine's
and other more dangerous pollutants originating in waste water, runoff,
industrial discharges and farm runoff. These herbaceous, absorbent plants
help capture and hold, use and change, pollutants and provide a barrier
to sediment runoff as well as a sponge for excess water. Indigenous
plants provide a breeding place for organisms of all sizes and types.
Purple loosestrife forms dense stands of vegetation
crowding out other species. It is not useful for shelter and food as
are indigenous plants. There is no indication that it absorbs and alters
pollutants as do the major keystone wetland species. It definitely alters
the ecosystem. Might this change effect the water and invertebrate organisms
living in it?
It is important for students studying science
to do real science and to do something useful with their findings. Exploring
questions, using the scientific method, and communicating data to others
builds true scientific literacy.
Materials
Hach
kits for water quality tests chosen, thermometers, D nets or even small,
department store fish nets, plastic jars for dipping, containers to
transport biological samples, trays for observing biological samples,
eye droppers and tweezers to place organisms on slides, dissection scopes
or Brock optical magiscopes, biological indicator chart, and data sheets.
Procedure
- Using a USGS map, locate accessible local
wetlands and ask students to assess them independently for stands
of purple loosestrife. Choose one with and one without a medium to
high density of purple loosestrife. The sites should be similar in
as many ways as possible to control for intervening variables such
as impact of nearby human activity or amount of water and depth. Obtain
permission to use the site for sampling.
- Create data sheets to record chosen water
quality tests in several locations at each site. Assign groups of
students to each location at both sites. Groups assign each student
tasks to perform during the sampling. Set parameters for sampling
so that each group uses the same techniques. Do some research on the
meaning of results for each water test.
- Visit site. Record qualitative observations
of the site including kind of vegetation (algae, submerged plants
and emergent plants), human use of site and surrounding area, visible
animal life, overall impressions of the site. Record also an estimate
of the amount of different kinds of vegetation, animals etc. If it
is not possible for the class to visit the site, individual students
could visit the site outside of class and bring observations and samples
in for analysis.
- Collect water samples and biological samples
for testing. Running the tests and observing for invertebrates can
be done on site or back in the classroom.
- Complete water chemistry tests of water samples
as soon as possible. If water is held overnight, hold water in closed
container and refrigerate. Observe and record amount and kind of invertebrates
sampled. Use pollution tolerance index for invertebrates. Complete
data sheets for each site.
- Repeat for the other site.
- Compare the two sites using charts, graphs
(visual representation), written description and group discussion.
Did you notice any differences? Can you account for the differences
based on what you observed on or near the site? Might the purple loosestrife
account for the differences? If there are no differences, what do
you conclude?
- Contribute your data to the Purple Pages (when
available).Publish it in your local press with an explanation
Extensions
Find other schools that could do the same experiment and compare data.
Discuss similarities and differences.
Compare water quality data to open water,
ponds, lakes or streams in your area. Explain your findings.
Evaluation
- A completed scientific investigation including
student created question, hypothesis, experimental design, data collection,
analysis and justification of conclusions based on data.
- Observation of students use of water quality
testing methods.
- Presentation ,with graphics and explanation,
to class of findings.
Activities: 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 9 | 10
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