Tricia Zdonzyk, age 11, of Costa Mesa, California, for her question:

Is it possible to grow food in the sea?

Our small planet's farmlands are limited, and as human populations explode, everybody gets a smaller share. Smart experts who think ahead are concerned deeply about food supplies for the teeming billions of the future. About a decade ago, they had high hopes for farming shallow areas of the sea. At present, the oceans provide only about 2 per cent of the world's food. It is estimated that specialized farming techniques could make the seas even more productive than the land.

This sea farming would be hard and expensive work. It could produce more fish than we now take, but its main harvest would be floating plankton. However, though this mixture of microscopic plant and animals marine life is highly nutritious, nobody has found a way to make it tasty enough for people to eat. Meantime, it has been discovered that most shore waters where sea farming might be possible were being contaminated by sewage and industrial pollution.

So, at present, our hopes for growing more food in the sea are rather dim.