John Kish, age 12, of Youngstown, Ohio, for his question:
What do corals eat?
Needless to say, those beautiful bits of artistic stonework that we call corals are not really corals at all. They are underwater apartment houses patiently built by generations of tiny coral animals. And naturally, these living marine animals need a diet of suitable food.
Nature ordains a special diet for each species of plant and animal. Each species thrives where conditions provide the opportunity to get the free groceries that happen to be right for it. When local conditions change, they exert themselves to leave and seek their proper supplies elsewhere. Most animals simply move away. Rooted plants can extend their ranges by scattering their seeds to establish new generations in new locations.
Plants, of course, do not have to hunt for their food. They manufacture their own basic diet from air and from the sunbeams and raindrops that fall upon every corner of the earth. The essential minerals they need wait to be taken from the earthy soil. Most animals have to shop around for their food. But a few do not. The corals and several other animals merely wait like plants for nature to serve their food to them.
Most of these settled animals are marine dwellers. We know that sea water is rich with a wide assortment of dissolved minerals. Many of these are essential body¬building chemicals necessary to animal life. But the sea also teems with a vast assort¬ment of organic chemicals created by plants and animals living or dead. It also swarms with uncountable plants and animals too small for human eyes to behold.
A baby coral may enjoy a free swimming life of her own for a little while. But very soon she returns to the stay at home life of her ancestors. She extracts dis¬solved minerals from the water and adds a stony room to the family apartment house. Her
room is just big enough to hold her soft body and its open window is just big enough for her small round mouth with its circular moustache of sensitive tentacles. Here she stays for the rest of her life, just letting the restless sea wash food within her reach.
Now and then, her waving tentacles grab a tiny fishlet as he swims by. Often she samples a salad snack of drifting alga. She also grabs the floating eggs and larvae of assorted sea dwellers, including the infants of her own relatives. Her diet also includes falling scraps from victims devoured by larger hunters of the sea. All these groceries are snagged by her tentacles and stuffed whole into her open mouth.
The warm and tropical oceans are populated with a wide variety of corals. All of them live their adult lives like stay at home plants. And none of them are fussy eaters. Any meat or vegetable morsel small enough to be stuffed into the mouth is a digestible snack. Many items on the coral menu are dead and decaying fragments that we would call garbage. But nature approves of such groceries. After all, a good housekeeper must have plans to remove garbage. Her hungry little corals help with the necessary garbage disposal chores of the teeming oceans.