Algae Covers Shallow Water

In the picture

1. 1Bright green bottom plants on the left bed.
2. 2Sunbeams passing through clear water on the left.
3. 3Thick green algal mat floating at the right surface.
4. 4Murky brown water beneath the algal mat.
5. 5Limp brown bottom plant on the right bed.

Examples

• A garden pond after too much fertiliser runs in from the soil.
• A slow river near farm fields after heavy rain.

Quiz: Algae Covers Shallow Water (Age 13)

1. 1

   What can extra nutrients cause in a shallow lake?

   • Algae grow into a thick mat at the surface
   • The water becomes clearer so more sunlight reaches the bottom
   • The rooted plants take in the extra nutrients and grow faster
2. 2

   How does a thick algal mat harm rooted water plants below?

   • It covers the plants' leaves so they cannot take in oxygen
   • It blocks sunlight, so the plants cannot photosynthesise
   • It uses up all the nutrients the plants need
3. 3

   What happens to rooted water plants when they cannot make food for a long time?

   • They grow longer roots to find food in the mud
   • They produce more leaves to catch more light
   • They become weak and brown

The answers, each with its explanation, are in the app. This lesson has left the free week, so its quiz is part of the subscription.