Mary Gerstenberger, age 12, of Phoenix, Arizona, for her question;
What are diatoms?
A few weeks ago, Andy wrote about the diatomaceous earth we use for cleansing powders. There was not room to tell much about the tiny diatoms who made it. So a lot of readers became curious about them. That, of course, was wonderful ‑ but it gave Andy a problem. Mary's question was chosen from fifteen just as good. All of them were clearly written, all included full names, addresses and ages.
Since thirteen readers are going to feel sad about this, thought Andy, maybe I had better choose a less popular question. But that, he decided, is not fair. His readers are sensible' understanding people. They know he can choose only one at a time. They also know that there is no limit to how many more questions they can ask, Besides, many readers want to know more about diatoms and after all, Andys most important job is to help satisfy, this wonderful curiosity.
There is no limit to the number of questions nor, it seems, is there any limit to the number of diatoms in the world. Some 10,000 different varieties have been classified. They thrive in both fresh and salt water. They teGrj: in the oceans and every river, pond and stagnant pool has its quota. Diatom, come in a variety of sizes and countless shapes. The giants arc just big enough for our eyes to see as tiny dots. The smaller ones measure about one thousand to an inch. To see the variety of shapes, you need a microscope. Then you might want to classify them among the fairy population ‑ they are so dainty. Actually, the diatoms are members of the plant world, microscopic cousins of the brown algae seaweeds. Diatoms have been orb earth for millions and millions of years and they play an important role in the world of nature.
Dozens of different varieties may show up in a single drop of pond water. Some are triangles, some globes, others shaped like sausages, boats or sticks. Each looks like a miracle of the glass blowers art done by a midget pixie. This is not surprising, for the tiny plants live in shells made of ~ice made of silica, the same element we use to make glass. Andy says they arem just right for the pixies to use as Christmas tree: ornaments.
No matter what its basic shape, each diatom shell is in two equal halves joined together with a slender seari. Tiny spikes, hollows, grooves, globes and buttons are used to ornament the outside of the shells in neat designs. Each little diatom lives inside one of these fancy glass houses. Being a planti the diatom contains green chlorophyll and ogre would expect a greenish tinge to show through the glass work, However, most diatoms also contain a yellowish pigment called diatomin. This masks the green and gives a yellowish or brownish cast.
The little diatom jewels live on sunshine, carbon dioxide and chemicals from the water. They are food for fish and other water dwelling animals. The plankton on which the big whales feed is mostly diatoms. Hence the biggest animal in the world is fed by some of the smallest of the plants. And the diatoms pour oxygen into the water for the fish to breather just as the land plants pour oxygen in the air for us to breathe.