1. Order the algal culture in advance from a biology supplier.
2. Make copies of the Algae Growth Chart.
3. Purchase fertilizer. It is best if all students use varying amounts of the same fertilizer; however, an extension of this lesson is to compare different types of fertilizers, such as liquid vs. dry, organic vs. synthetic, and fertilizers with different concentrations of nitrogen and phosphorus.
4. Prepare culture water by drawing 1 gallon of hot water from the tap and letting it stand for 1 day.

1. Discuss algal blooms with the students, including common causes. (Answer: industrial wastes and fertilizer runoff) Review why engineers would be interested in preventing algal blooms. (Answers: To determine the health of a body of water, to protect other living organisms, to prevent the strain on water treatment processes for drinking water and other water resources.)
2. Explain that each group will have four identical jars of water and algae, and their job as environmental engineers will be to experiment to find the effect of fertilizer on algae. Tell students that 1 of the 4 jars should be left as a "control sample," that is, it should be a reference against which the other jars can be compared. The control jar should have a concentration of zero, meaning students should not add any fertilizer to the jar.
3. Break students into groups of four. Each student should have his/her own jar. Number each group or let students pick a team name.
4. Introduce the fertilizer to be used, and determine how it should be measured (for example, eyedroppers full for liquids, teaspoons for dry fertilizer, or numbers of pellets). Groups should plan their own experiments by selecting four different fertilizer concentrations (remember: one concentration they choose must be zero). Within the class, there should be a broad range of concentrations.
5. Label the jars with masking tape or wax pencils. Include the group number or name, student's name, and amount of fertilizer added. Have the students add fertilizer first, and then fill with aged tap water to within a centimeter of the top.
6. Add one eyedropper full of live algae to each sample jar. Leave jars uncovered.
7. Have students wash their hands after handling fertilizer or algae.
8. Place all jars in areas with similar light intensities. An artificial light source may be used if needed. Make sure the source of light is held constant for all jars. Dark at night is fine.
9. Have students observe their jars daily for any visual evidence of algal growth. Keep records on the algae growth charts or in engineering log books. After about three days, algae growth should become obvious as indicated by an increased 'greenness' in the jars and possibly odor. Have students (7th and 8th grade) determine a way to quantify their algae growth (for example, percent of greenness in jars or percent of light blocked when jar is held up to light).
10. At the end of one week, have students fill out the "Growth After 1 Week" section of the Algae Growth Chart. The members of each group should work together to decide how the algal growth in their control jar compares with their other jars. They may also record any other observations on their growth chart.
11. Discuss different ways the data could be presented. One way would be to use water color paints or crayons to color in a square for each fertilizer concentration, showing that each concentration resulted in a different shade of green. There are many other options. Have students make a graph of their results. Their graphs should be a line graph or a bar graph and should have time along the x-axis. Concentration of algal growth should be recorded on the y-axis either as a quantified percent of greens or light or a relative amount; i.e., high, medium and low algal growth.
12. Have groups present their results. Did different groups have similar findings?
13. Ask if any students observed any dead algae on the bottom of their jars. If yes, what will eventually happen to the algae? (Answer: Bacteria will decompose the dead algae.) Would this be good or bad for animals living in the water? (Answer: It would be bad, since it would use up the existing oxygen.) How would this affect a wastewater treatment plant? (Answer: More decomposition would change the chemistry of the water entering the treatment plant.)
14. Conclude by discussing with students why an excess of algae can be harmful to lakes. Are there any practices students have seen that could contribute to this problem? (Possible ideas: fertilizing lawns, fertilizing just before rainstorms, and throwing or sweeping organic matter like leaves or grass clippings in a lake.) Are there actions students could take that would improve the situation? (Possible ideas: reducing or eliminating lawn fertilizer, using a different — low phosphorus — fertilizer, or composting organic matter.) How might engineers solve this problem? (Possible ideas: providing legislature with evidence of poor farming and industrial habits so that laws and regulations can be created, plan alternative water treatment operations for times of high algal stress.)
15. Clean up: The algal cultures should be poured on the ground, especially in areas that could use fertilizer. Avoid adding the cultures to surface water. If you pour them down the drain, they may burden your sewage treatment system.

Brainstorming: In small groups, have the students engage in open discussion. Remind students that in brainstorming, no idea or suggestion is "silly." All ideas should be respectfully heard. Encourage wild ideas and discourage criticism of ideas. Ask the students what things could cause pollution of a stream. Record their answers on the board. (Possible ideas include: chemicals, gasoline, garbage, human waste.)

Discussion Question: Solicit, integrate and summarize student responses.

• Ask students if they think too much food can ever be a bad thing? (Answer: It can if there are too many nutrients or oxygen in a stream. Too much algae can then result, which then takes nutrients and oxygen from other organisms living there.)

Algae Growth Chart: Have the students record observations and follow along with the activity on their Algae Growth Chart. After students have completed their charts, have them compare answers with their peers.

Graphing: Have students make a graph of their results. Their graphs can be a line graph or a bar graph and should have time along the x-axis. Concentration of algal growth should be recorded on the y-axis either as a quantified percent of greens or light or a relative amount (i.e., high medium and low algal growth).

Presentations: Each group should present their results to the rest of the class as if they were a small environmental engineering group monitoring the water quality and health of a specific body of water near some agricultural land that uses the same brand of fertilizer that they used in their experiment. Their presentations should include the following:

• Experimental set up - Listing of what concentrations of fertilizer they used in each jar and which jar was the control jar.
• Results - How much algae grew in each jar (for older students as a quantified number such as percent of green/light block or for younger students have them report how much algae grew in a relative sense; for example, jar one grew more algae then jar number two. They should show any graphs created.
• Conclusions - What do the results say? Did fertilizer affect the growth of algae? What could the agricultural farmers do to help prevent harmful algae growth? What could their engineering group do to prevent harmful algae growth? What else did the students learn from the experiment?
• (If time permits, see activity scaling for 8th grade to add additional components to this presentation.)