Book 30, Question 51
What are diatoms, the tiny algae with glass shells?
Diatoms are single-celled algae that live in lakes and ponds.
Each one builds a tiny shell of glass, called silica, with two halves that fit together like a box and its lid. Thousands of shapes exist, like stars, discs, and boats. Diatoms use sunlight to make food and oxygen, and they are a favorite meal of water fleas. In spring, they often multiply so fast that the lake looks brownish.