Beverly Michael, age 12, of Des Moise Iowa, for her question:

What exactly is plankton?

This way come as a surprise. But none of us could survive without a watery world of miniature plants and animals, too small to be seen. These teeming specks of life cover almost half tile surface of the .globe, sometimes to a depth of 1,000 feet. Together they make up the plankton that thrives in all fresh and salty sunlit waters. Together they supply most of the breathable oxygen in the air, plus the basic food that supports all the creatures that live in the world wide ocean.

A glass of clear water from a quiet pond is not what it seems to be. If you hold it in front of a page of white paper, you may see swarms of tiny shadows, smaller than pinpoints. idany of these mini specks of life are members of the plankton populations that thrive in all streams, lakes and seas.

The most numerous plankton populations are single celled alga plants. Others are single celled animals. Some of the larger plankton personalities are as big as wheat grains and pumpkin seeds. Among the giants are shrimpish crustaceans that measure all of two inches. Jellified eggs and baby larvae of all the larger fishes in the sea also float around in the great mass of teeming plankton.

i3ore than half of the mixture is made up of tiny diatoms. These one¬celled alga plants live inside silica shells designed like ornate little jewel boxes. Other single celled plankton plants include species of colored and phosphorescent algae. They are too small to be visible. But when con¬ditions are right, their population explosions add tinges of green or blue, brown or red to the water.

Life in the sea depends on symbiosis, a never ending give and take be¬tween plants and animals. Plankton plants absorb dissolved minerals and use the energy of sunlight to manufacture their own food. In the process they use carbon dioxide, provided by plankton animals. They also add uncountable tons of breathable oxygen to the water and the atmosphere.

In the hungry ocean, the rule is eat or be eaten. The bountiful plankton meadows are feeding grounds for small, large and still larger creatures of the sea. The base of this food chain includes teeming plankton populations of miniature plants and animals. For example, copepods are pinhead sized crustaceans. They are devoured by frisky splinter sized arrow worms    which are devoured by whiskery comb jellies, which are the size of blackberries.

All life in the sea depends directly or indirectly on basic plankton food. A typical lunch for a humpbacked whale may be about one ton of silvery herrings. Each herring may have lunched on perhaps 6,000 copepods. Each copepod consumed perhaps 130,000 pretty little diatoms. Of course, all sorts of other large and small sea dwellers dine on herrings and copepods  ¬and all of them try to eat each other.