George Spak, age 13, of Vanier, Ottawa, Ontario, Canada, for his question:
Where do we find diatoms?
Most likely your nearest diatoms are in your kitchen. Diatomaceous earth is the gritty ingredient in the cleansing powder used to scour the kitchen sink. However; this material is shells of diatoms that died ages ago. The nearest living diatoms are in the outdoor ponds, streams or moist marshes. The largest numbers of diatoms teem in all the salty seas and worldwide oceans.
There is no shortage of diatoms in the world, though without a microscope they are invisible to most human eyes. At least 10,000 species have been classified and no doubt as many more will be added to the list. All of them live in water and at least a few. species are to be found in every freshwater pond and stream, in every sea and ocean. All of them are members of the plant world. This seems strange because every diatom encases itself in a pair of shells.
Under the microscope, a drop of pond water reveals a fabulous zoo of miniature organisms. Some are midget members of the animal kingdom. Some are single celled algae and other members of the plant world. Chances are, at least one specimen will be a diatom. But if there are several, it is not likely that any two of them look alike. In the world of diatoms, the word is variety.
A living diatom is a single celled plant, equipped with chlorophyll for using solar energy to manufacture its own food. Its raw materials are water, dissolved chemicals and carbon dioxide provided by various fishes that swim near the sunny surface. As a rule, the green chlorophyll is masked by diatomin, a yellowish pigment that tints the living cell with golden amber.
The living cell is remarkable, but the shells it builds are even more so. Its building material is dissolved silica, extracted molecule by molecule from the water. The shells are built like a pair of trays, seamed together to form a miniature box. This is the basic design. But each species outdoes itself in decorating its surface.
The boxy shells may be square or oblong, globular or triangular, oval or shaped like a dew drop, a stick, a new moon or cushion. The outside is decorated with an elaborate design of grooves and ridges, tiny buttons and pockets. And all this beauty is splurged on a tiny plant that measures about one thousandth part of an inch.
Nature supplies these miniature marvels in astronomical numbers. They start the food chain that supports all life in fresh and salt water. These tiniest of plants teem in the plankton that feeds the earth's largest animal, the great blue baleen whale.
Diatoms have thronged the seas through millions of years and almost everywhere the seabed is carpeted with their discarded shells. They mix with oozy mud and form diatomaceous earth. This fossilized material has many industrial uses and its fragments of hard silica add the scouring zest to our household cleansing powders