Aquatic Ecology Lesson

In this very hands-on lesson, students will get to get up close and personal with aquatic creatures and experience first-hand ways in which we can test water quality.

Grade

4th-6th

Time

5 hours, with a lunch break, not including set up time.

While this lesson is designed as a 5-hour field study, it could easily be broken into parts, with a section done each day.

Standards Addressed

NGSS:

Organisms and populations of organisms are dependent on their environmental interactions both with other living things and with nonliving factors. (MS-LS2-1)

Ecosystems are dynamic in nature; their characteristics can vary over time. Disruptions
to any physical or biological component of an ecosystem can lead to shifts in all its populations. (MS-LS2-4)

Water continually cycles among land, ocean, and atmosphere via transpiration, evaporation, condensation and crystallization, and precipitation, as well as downhill, flows on land. (MS-ESS2-4)

Global movements of water and its changes in form are propelled by sunlight and gravity. (MS-ESS2-4)

Human activities have significantly altered the biosphere, sometimes damaging or destroying natural habitats and causing the extinction of other species. But changes to Earth’s environments can have different impacts (negative and positive) for different living things. (MS-ESS3-3)

Supplies

Butcher paper, washable markers, spray bottle with water, pH Test strips, thermometers, DO ampoule, Vernier LabQuest, Cones, macroinvertebrate cards, Nets, Ice cube trays, buckets, macroinvertebrate ID keys, Plankton nets, microscopes, Petri dishes, pipettes, Stream table, popsicle sticks

Make up three water bottles full of water. Contaminate one with colored soap or cleaner, so it is obviously blue, maybe bubbly. Add dirt and sticks to another bottle. Dissolve salt or sugar in the third, but not enough to make it cloudy.

Ask the students which one is polluted. Hold up the dirty one. “Would you drink this? Is it polluted? Might a critter live in it?” Hold up the blue one. “Would you drink this? Doesn’t it look like a beautiful swimming pool? Yes, this is chemically polluted, not drinkable.” Lastly, hold up the clear water bottle. Every time I have done this, someone says that they would drink it. I ask them if they would do it in front of the class and it is SO funny to watch their faces. The point is: You can’t tell if water is “polluted” just by looking at it. A crystal clear mountain stream could still have giardia bacteria living in it. This leads well into the question; “How do we know if water is clean and healthy?” “Do all the rivers and lakes have to have water that looks like this to be considered healthy?”

Since watersheds are too large to observe from a hike on the ground, we will create a watershed model using paper.

Show students an unused paper watershed example. Imagine that everyone is viewing a landscape from an airplane. The peaks of the paper are peaks of mountains, and the dips in the paper are valleys. If available, show students a plastic relief map to show a topographic watershed model with context.

Students should work in groups of two or three. Each group gets a sheet of paper, a cardboard base, and a water-soluble marker.

Crumple the paper loosely then un-crumple it and set it on the sheet of cardboard. Tape the edges of the paper onto the cardboard base, leaving at least an inch of cardboard exposed around the perimeter.

Watersheds are defined by ridges. Use the marker to outline them, carefully following them as far as they go – to the edge of the paper if necessary. This may take 5 to 10 minutes.

Give students a minute to discuss in their groups: “When it precipitates on these models, where will the water go?” Check-in with each group to listen to their ideas.

Use the spray bottle to simulate rain by misting the paper watershed while it sits flat. Spray enough so that there are some droplets sliding down the sides to pool, but not enough to drench and sag the paper.

Facilitate discussion based on observations of all watershed models. Ask students to formulate and defend an answer to: “Are watersheds isolated from each other?”

The students should all be exposed to, and understand the process of, the various tests for water quality, but they don’t have to perform each one personally. Below are descriptions of each test and a demonstration of how to explain what it means for water quality. If you have time, see the extension section for ideas on comparing different bodies of water on site.

Divide students into teams. Depending on the resources, the teams can be responsible for performing just one test or all the groups can spread out along the bank and perform all the tests.

Share the data with the group once collected.

pH Test

Test for pH is a logarithmic scale that measures the concentration of hydrogen ions. The scale
ranges from 1 – 14. Low pH is acidic, high pH is basic. Pass out the directions from the test kits to the students, asking them to read and follow the specific steps listed. Students will gather a sample of water, add a few drops of an indicator substance and compare the result to a color chart.

Powers of Ten Cards: Show the 7 pH card. This is the neutral card - for every red dot (H+) there is a blue dot (OH-) Flip to the 6 pH to show that there are now ten times as many (H+) ions as there are (OH-) ions. Flip through them all, going down and back up to watch the exponential power of things that are ten times as large.

Dissolved Oxygen Test

Test for Dissolved Oxygen is a measure of gaseous O2 molecules within the liquid water. DO is
heavily correlated to the water temperature. Cold water holds more DO since the molecules don’t have enough energy to escape the solution. However, the amount of DO is small – it's measured in parts per million (ppm). 1 part per million is about 1 second out of 11 days, 13 hours and 47 minutes. Students will gather a sample of water, place a DO ampoule into it, and then break the tip, allowing the water sample to be drawn into the ampoule. After 1 minute, the ampoule is compared to a color chart. Pass out the directions from the test kits to the students, asking them to read and follow the specific steps listed.

Temperature

Temperature is measured in Celsius, however, be prepared to convert it into Fahrenheit too. The Temperature is taken regularly to watch for non-seasonal fluctuations which can be harmful to populations and indicators of larger issues in the water system. Ask the students to start by taking the outside air temperature. The thermometer should be dry and in sunlight. Students should take the temperature from a couple of places, deep, shallow, shaded, sunny and then report.

Vernier LabQuest

Vernier LabQuest is a technology that quickly takes all of the water quality tests from one handheld device. These devices can be used to create a comparison/support to the chemical tests, or as a tool for inquiry projects when collecting water quality data is about the data, rather than understanding the process.

*This activity is adapted from Project Wet*

This is a sharks and minnows type game that plays out how changes in water quality can affect the entire ecosystem. The pollution source in this game is open to discussion, since interactions between human use and land makes a mix of direct and indirect causes. If you have time, spend a moment on that debate so that students understand that a flow of eroded sediment is just as detrimental to a system as an influx of toxic chemicals.

pH –discharge from a factory, poorly monitored storm drainage, eroded sediments .

DO –change in temperature, or a change in a streams speed

Temp – construction of a human or beaver dam, discharge from electricity plants

Set the safe zones of your “pond” by placing four cones in a rectangle.

Pass out the macroinvertebrate name cards. Tell students which side of the card to use. (Not the side that says Rat-Tailed maggot or Midge Larva)

Inform students that some macroinvertebrates have hindrances to crossing the field (see below). These obstacles symbolize sensitive organisms’ intolerance to pollutants. Have students practice their motions

Caddisfly Must place both feet together like they are in a bag and hop across the field.

Stonefly Must do a push up every 4 steps.

Mayfly Must flap arms and spin in circles when crossing the field

You (or a student) are the environmental stressor and tries to catch the critters as they swim from one side of the lake to the other.

Assemble the macroinvertebrate groups at one end of the playing field and the environmental stressor(s) at mid-field. When a round starts, macroinvertebrates will move toward the opposite end of the field and the stressor will try to tag them. To “survive,” the macroinvertebrates must reach the opposite end of the field without being tagged by the environmental stressor. The environmental stressor can try to tag any of the macroinvertebrates but will find it easier to catch those with hindered movements.

Begin the first round of the game. Tagged macroinvertebrates must go to the sideline and flip their identification labels to display the more tolerant species (i.e., rat-tailed maggot or midge larva). Tagged players who are already in a tolerant species group do not flip their labels.

Record the number of members in each species of macroinvertebrates at the conclusion of each round. Because some players will have flipped their identification labels, there will be a larger number of tolerant species in each successive round.

The game is completed after a few rounds. Discuss the outcome with students. Emphasize the changes in the distribution of organisms among groups. Have students compare the population sizes of groups at the beginning and end of the game and provide reasons for the changes. Review why some organisms are more tolerant of poor environmental conditions than others. Have students compare the stream environment at the beginning of the game to the environment at the end.

The water quality tests are done to answer whether or not the water system is able to support to life. Macroinvertebrates are highly susceptible to changes in the water, and their presence or absence is indicators of the pollution levels. If you have time, see the extension section for how to expand on this activity to discuss adaptations and life and energy cycles.

Demonstrate the proper way to collect specimens. Emphasize that the nets are not for digging, but for scooping. Specimens are the pulled, individually from the net and placed in the water-filled container – not dumped with the lake muck to which they are attached.

As a field study group, the goal is to collect 100 organisms to ensure a large sample size.

In ice cube trays or small buckets filled with water, sort the species to count how many of each were captured. Use the spoons to gently shuffle them between containers.

While the sorting is happening, other students should identify the found species using supplied posters, dichotomy charts or books.

Follow the Biotic Index Sheet to calculate a quantifiable index score for the water system.

Facilitate discussion based on the results of the water quality and the critter catch. Ask students to formulate and defend an answer to: “What is the state of this water system?”

The plankton lab adds another layer to the pond study by observing the micro-ecosystem within the water itself. Seasonal changes directly influence the success of this activity, the blooms of algae pick up mid to late spring as the temperature gets warmer.

To Collect: dip the plankton tow in as far as possible, and bring it up with a constant speed

Use the dropper to place single drops on the slide. Tell each student to melodically search each drop, careful not jostle it to blend them together.

Use the video scope and tv set up to share exciting finds.

Use the posters and ID books to identify the plankton.

Facilitate discussion based on the results of the water quality, the critter catch, and the plankton lab. Ask students to formulate and defend an answer to: “What is the state of this water system?”

Show some pictures of rivers and streams. Tape them up on the whiteboard. Ask the students:

What do all these pictures have in common? Despite differences in rivers and streams due to the landscape around them, they all work the same way. Draw a picture of three types of rivers on the whiteboard. Explain when and where you would find these types.

Straight- can look very different depending on the gradient

Meandering- lots of curves, usually occurring in flat valleys

Braided- many connected channels usually occurring at deltas where the river meets the sea or in other flat areas.

Next talk about the three parts of every river or stream no matter the type- the channel, stream banks, and flood plain. Each of these parts is equally important for the health of a river.

Build a River

Have the students decide what type of river they want to create.

Let them lightly (this is key so the river can still form itself!) dig out the river channel.

Pour in the water until it creates a stream with a lot of interesting features. Discuss what happened as the stream formed. Where did erosion occur? Where was there deposition?

Give the students popsicle sticks with different stream vocabulary and functions written on them (erosion, deposition, ripples, meander, etc.).

Have them place their popsicle sticks next to examples of each of these things in their stream. Talk about why each of these things happens.

In pairs or threes, give them one of the river pictures again. Have them explain to the rest of the group what features they see in their picture and explain why they think their river looks like it does. Where would you find this type of river?

Using the information that the students learned today, ask them to agree or disagree with the statement, “Everybody lives in a watershed.” Their arguments must come from they did or did not learn in the class.