Eutrophication: More Nutrients, Less Life

Lab Brief #2

🎯 Your mission

Set it up. Test it. Be amazed.

⚡ The twist

Living things break the rules of non-living things — find the rule they break.

What you'll learn

Fertiliser that misses the crop runs off into rivers, where the extra nitrogen and phosphorus trigger algal blooms. The algae grow, die, and decomposing bacteria multiply on the remains; their respiration strips dissolved oxygen from the water and fish suffocate. The system ends with more nutrients and less life — the standard example of a change that benefits one organism enormously and collapses the community around it.

Key words

eutrophication
The sequence in which nutrient enrichment causes algal blooms, decomposition and oxygen loss in water.
dissolved oxygen
Oxygen present in water, consumed by decomposing bacteria and needed by fish.

Make a hypothesis first

Predict: what will happen to the plant if you change the water?

Say your guess out loud — then find out if you were right.

Get ready

🧰 What you need

pond water
jars
liquid fertiliser
dissolved oxygen test kit
graph paper

Get ready

⚠️ Safety first

Wash your hands thoroughly after handling pond water and keep it away from your face.
Wear eye protection when handling liquid fertiliser and keep it off skin.

Step 1 of 4 · Read

Think about what you just learned: say what "eutrophication" and "dissolved oxygen" mean in your own words before you start.

Step 2 of 4 · Do

Set up three jars of pond water with none, a little and a lot of liquid fertiliser, and record colour and dissolved oxygen every two days for a fortnight. Plot oxygen against time for all three and identify at what point each declined.

Step 3 of 4 · Observe

Record what actually happened, including anything that did not match what you expected.

Step 4 of 4 · Record

Write a conclusion that answers the question this lesson opened with, and state your uncertainty.

Question 1 of 3

Fish die during eutrophication because decomposers remove:

How sure are you?😐 maybe

Question 2 of 3

Eutrophication begins with an excess of:

How sure are you?😐 maybe

Question 3 of 3

The sequence in eutrophication is:

How sure are you?😐 maybe

Mind = blown

🦠 You have more bacterial cells in your body than human cells.

Nice work!

You got 0 of 3 right.

Next: Ocean Acidification Is a pH Calculation All lessons

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✨ More to explore

🌍 Where you see this in real life: Your own body is doing this thousands of times every second.

🏆 Stretch challenge (try it this week): Find one thing about your body that's different from a friend's. Wonder why.

👨‍👩‍👧 For the dinner table: “Tell me something you noticed about your own body today.”

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