Connie Irby., Age 12, Of East Rutherford., N.J.., for her question:

Is seaweed good for anything?

We harvest many kinds of seaweed and put them to a multitude of uses. As a rule, we do not recognize them as seaweeds when they get to market. They do most of the jobs behind the scenes. Yes, we have uses for seaweeds, but the greatest good they do by far is in the sea.

The drifting and floating seaweeds absorb all kinds of minerals from the watery ocean. We extract iodine and algin from wavy ribbons of kelp seaweed. Algin is a chemical gifted with a quality which enables it to hold several liquids together. We use quantities of it as an ingredient in ice cream. The milky ingredients in ice cream contain water. The algin prevents this water from freezing into needle crystals of ice.

The algin extracted from kelp adds smoothness to ice cream, chocolate milk, certain salad. Dressings and yummy pudding mixes. Forests of the giant kelps are anchored to the floors of warm, shallow seas. They are harvested and used as fertilizers to enrich the soil and also used in the manufacture of explosives.

Ceylon moss is a red alga of tropical seas. It is harvested along with other red algae to make a jelly called agar. This pale jelly is used in laboratories as a culture medium, a sort of food bath, in which the scientists grow bacteria for their experiments. Other seaweeds are used as foods.

We have many uses for seaweeds, but if we took all of them out of the sea, life, as we know it, would come to an end. In the ocean where they belong, the seaweeds perform a vital role. There they correspond to the greenery that growss on the land. The land plants provide the oxygen and the food for all the land animals. The seaweeds provide much of the oxygen and the basic food for all fish and other marine animals.

Seaweeds float near the sunlit surface of the sea. They use the energy of sunlight to manufacture their food from water and carbon dioxide. In this process of photosynthesis, they return free oxygen to the water for the marine animals to use as we use the oxygen in the air. Clouds of microscopic seaweeds form meadows of plankton to feed the small shrimps, the fish larvae and the great whales. Bigger fish feed upon the small plankton eaters and are eaten by bigger fish, which are eaten by still bigger fish. Seaweeds are the basic item in the food chain which nourishes all the big and little dwellers of the ocean.

If we lost all the seaweeds, we would have no more fish, shellfish and other delicacies from the sea. Luckily for us, the oceans teem with seaweeds ranging from microscopic diatoms to giant kelps. In the orient, many varieties of seaweed have been used in cooking since ancient times. We are just learning to add. Some of them to our diets. In the future, if our land crops fail to keep pace with our needs, we may be using more of the seaweeds for food.