Why does the bottom of a lake sometimes run out of oxygen?

What Crafty Clover says in this video

Intro

Hi there, curious minds! I'm Crafty Clover! Let's discover something amazing. Why does the bottom of a lake sometimes run out of oxygen?

The Big Idea

Deep parts of a lake can run out of oxygen! They're called dead zones. How does it happen?

Layers

Step one: Layers. A dead zone is a deep part of a lake with so little oxygen that most fish and animals can't live there. It can happen in summer when a warm top layer keeps the bottom layer from mixing.

Rotting Algae

Step two: Rotting Algae. Algae sink to the bottom and rot. The bacteria breaking them down use up the oxygen in that bottom layer.

Lake Erie

Step three: Lake Erie. In Lake Erie, part of the central basin forms a dead zone each summer. Cutting nutrients like fertilizer runoff means less algae, which helps reduce it.

A Closer Look

Let's take a closer look! Floats above. Trapped. Sink and rot. Used up.

Quick Facts

Quick facts! Fish move away from low-oxygen water. Forms in summer. Rotting algae use oxygen. Fewer nutrients help.

Think Like a Scientist

Now, think like a scientist! Draw a lake from the side. Color a warm top layer. Color a cold bottom layer. Shade where oxygen runs low. Draw fish where they'd go.

Outro

A dead zone is a deep lake area with so little oxygen that most animals can't live there. In summer, a warm top layer stops mixing, and rotting algae use up oxygen below, as in Lake Erie's central basin, so cutting nutrients helps. Science is amazing! Keep wondering and keep exploring! Share what you learned with someone at home, and see what they think! Crafty Clover can be found on Amazon Books, Google Bookstore, and Apple Books. Available for purchase or download! Bye for now!