Ken Turgeon, age lI, of Coventry, Rhode Island, for his question:
What is the littoral zone?
The littoral zone is the coastline where the salty seas meet the solid land. It is a special world of its own, where tide tossed waters exchange strips of territory with the continents twice every calendar day. Plants and animals of the land cannot withstand these daily salt water dunkings. So the littoral zone is populated with its own, highly specialized, forms of marine life.
Every zone of life has its own ecology of balanced give and take. It has assorted populations of plants and animals, all adapted to make themselves at home in the special surroundings it has to offer. The littoral zone of tidal waters that surrounds every island and continent is a turbulent realm of storm tossed, tide tossed shallow salt sea water. And all its inhabitants must be adjusted to cope with this restless, surging environment.
You might suppose that such wild water would discourage plant and animal populations, especially the small creatures. Not at all. The surging tidal waters happen to be extra rich in both oxygen and nutrients. Splashing water captures and dissolves oxygen and other gases from the air. Rivers empty in organic minerals and other food chemicals. Beached seaweeds and animals are bashed by the pounding waves into small fragments that become morsels of food for the survivors.
Most of the successful survivors are small animals, perhaps because it is easier for them to clutch onto solid rocks or bury themselves in the sand. The starfish. have dozens of tube feet that cling like hydraulic suckers. They can withstand the strength of most surging tides and also travel at speeds of six inches a minute in search of food. The sea urchin also clings and creeps on tiny tube feet. Assorted limpets and barnacles cling with one sturdy foot that acts as a suction cup.
The flowery sea anemone also anchors himself with one foot. In troublesome times he withdraws his waving tentacles and becomes a rubbery bump or glides very slowly to a safer place. Sponges anchor themselves and let the turbulent water filter through their pores. Clams can bury themselves in the silty sand. Many larger shellfish can scuttle around. The crabs hunt for food and find shelter in rocky crevices. As everywhere in the sea, the creatures of the littoral zone prey upon each other. And the basis for their food chain is plankton that floating mixture of microscopic
plant and animal life that provides oxygen and nourishment for all marine dwellers.
Some seaweeds float in the surging ride water, others have holdfasts to anchor them to the rocks. The microscopic plankton populations are small enough to ride with the tossing water, unharmed. However, the clams, oysters and many other littoral creatures are lurking to devour them. They let in constant streams of water which serves them the oxygen they need, plus a never ending supply of scraps, minerals and morsels of seafood plankton.