Kinney Dull, age 10, of High Point, North Carolina, for her question:

Where does Plankton get its food?

First let's say that Kinney Dull does not ask dull questions. A person who wonders about this one must be very thoughtful indeed. Of course, we all know that plankton is the basis of the world's largest food chain. Directly or indirectly it provides the groceries for all the creatures that dwell in the seas. And the seas cover almost three quarters of our watery world. But not many of us wonder where the plankton gets its food to start the fabulous food chain.

The basic seafood menu starts with simple chemicals and the ingredients are processed with energy from the sun. These non living raw materials provide all the food for all the living plants and animals in the worldwide ocean. Animals, of course, cannot convert them into the useable food elements they need. But plants can use the energy of sunlight to create the basic recipe, just as plants start the various food chains that support life on the land.

In the seas, most of these plants are microscopic algae, too small for human eyes to see. They make up most of the rich plankton meadows that float just below the surface to a depth of 100 feet or more. Most of them are single celled algae and each small miracle can carry on all the life processes needed to create its food, grow and multiply. More than 1,500 species of plant plankton are known, and the microscope reveals that all of them are wondrously beautiful.

Each miraculous plant cell is tinted with chlorophyll    usually with its own blended shade of greens or yellows, blues, or browns or reds. The chlorophyll, of course, is the magic material that uses sunlight to build nonliving chemicals into biochemical plant food. The raw materials are water; carbon dioxide and various other chemicals dissolved in the ocean. All types absorb and use quantities of dissolved nitrates and phosphates. Some types need extra helpings of sulphur and iron, manganese and copper, zinc or even arsenic.

During the hours of sunlight, astronomical numbers of plankton plants carry on photosynthesis. Their chlorophyll uses sunlight to synthesize absorbed chemicals into the basic sugary food that supports all plants on land and in the sea. It feeds the tiny floating alga cells and they provide food for numerous small creatures that share the vast plankton meadows. These include many species of single celled and slightly larger animals, eggs and larvae of larger sea creatures, small shrimp type creatures and often swarms of krill two inches long.

Herring sized fishes swim in to feed on the shrimp sized plankton dwellers, tuna sized fishes arrive to feed on the herrings. Dolphins, sharks and hungry killer whales come to devour the medium and larger fishes. The great balleen whales sift and swallow tons of fine plankton food every day. It is estimated that ocean plankton provides 40 billion tons of sea food salad a year. Directly or indirectly this fantastic food chain feeds all life in the oceans    and it starts with photosynthesis, the magic sunshine recipe.