Lila Holcombe, age 13, of Canton, North Carolina, for her question:
Is kelp a plant or animal?
Sponges look for all the world like underwater plants. But the experts assure us that they are bushy shaped animals, anchored to the sea floor. They also tell us that sea lilies, sea cucumbers and sea anemones are really animals. The underwater kelps look for all the world like members of the plant world and it's natural to suspect that they too may be animals in disguise. Not at all. Kelps which look like plants, really are plants.
The kelps are at home in the littoral zone of the seas, in the shallow waters between the shores and the deep ocean basins. This sun speckled watery world teems with .fishes and populations of other marine animals.
In that watery world, the kelps play the role of forests. Unlike the sturdy trees of land forests, they have no true roots or branches. Nevertheless they are true members of the plant world. They have boxy, plant type cells and use the energy of sunlight to manufacture their basic plant food from water, carbon dioxide and other dissolved chemicals. No member of the animal kingdom can process its food by this miraculous photosynthesis.
The various kelps are algae, members of the oldest and most successful plant groups. Their ancestors were among the first miniature living things on the earth. Among these pioneers, the single celled algae provided the oxygen and basic food that made life possible for the single celled animals. This plant and animal partnership is still in business, after more than a billion years.
Though other plants advanced with the times, the algae never gave up the simplified life systems of their earliest ancestors. For example, no matter how large an alga seaweed may grow, none of its numerous cells are adapted for special duties. Each cell can carry on all the necessary life processes of metabolism and reproduction.
Some of the modern kelps are ragged ribbons as long as 200 feet. One end of each trailing streamer is attached to the floor of the sea by a group of average cells acting as a holdfast. There are no cells to carry on the specialized duties of roots and no stem c6lls to support the brownish green banners of kelp foliage.
The kelp algae like salty sea waters that are cool but not too cool. They thrive off Scotland and Ireland, where the northern seas are warmed by the Gulf Stream. Dense kelp forests also grow in the Pacific, especially off the shores of Japan and California.
Some of the most spectacular kelp forests are around Catalina and other islands off California. Visitors can take guided tours in special boats with underwater windows. Through the thick glass, they see the long kelp streamers, gently waving in the water. And all sorts of fishes dash and dart, glide and rest in the tangled forest of kelp foliage.