Christine Sherrer, age 13, of Wilmington, Del., for her question:
ARE ALL SEASHORES ABOUT THE SAME?
A seashore is a place where the sea and the land meet. All seashores are not alike. Scientists classify them into three main types, depending on their surfaces: rocky shores, including coral reefs; muddy shores; and sandy shores.
A seashore is an area of continual change. As the sea rolls in at high tide, much of the shore becomes part of the ocean. At low tide, the sea retreats and the same area again becomes part of the land.
Inspite of an ever changing enivornment, the seashore supports a great variety of animals and plants. Many of these organisms live nowhere except along the oceans edge.
Life on rocky shores is much more plentiful than on any other type of seashore. Great numbers of animals and plants crowd the hard, rough surfaces of coral reefs and steep cliffs. These organisms must withstand powerful waves that could wash them away or smash them on the rocks.
Most organisms of rocky seashores have special features that hold them securely to the rocks and coral. Many adult animals, including barnacles, muscles, oysters, sea squids and sponges, permanently anchor themselves to the shore. Others, such as limpets, sea anemones, sea urchins and starfish, also attach themselves firmly to the shore, but they are capable of moving short distances.
Some animals, including plantlike bryozoans and hydroids, have flexible bodies that bend with the motion of the waves. Large seaweeds, such as kelps and rockweeds, cling to the shore with structures called holdfasts.
Most muddy shorelines lie in bays, protected from strong waves. Rivers empty into much such bays, decreasing the saltiness of the sea. Land plants thrive along muddy shores.
Sandy beaches have fewer forms of life than do rocky or muddy shores.
Most of the animals of sandy shores, including clams, crabs and sand dollars, burrow under the sand. Few plants live on sandy shores between the levels of high and low tide.
Various tiny animals and plants, called plankton, play an important role in the life of ail seashores. These organisms swim or flat in the ocean tide. Many of them remain part of the plankton for their entire life, but others grow into larger animals and plants of the seashore.
Plankton serves as more than a nursery for seashore life. As the waves of the ocean sweep across the shore, they carry with them a feast of plankton. Many seashore animals feed on these tiny organisms. Such creatures or barnacles, oysters and sponges eat the plankton when it comes to them. Even various shorebirds that feed on the plankton eatinc creatures rely indirectly on the plankton.
Most animals that on rocky shores eat plankton.
The plants of rocky shores are simple organisms called algae. Algae, like most kinds of plants, create their own food. But unlike most animals that grow on land, algae have no leaves, roots or stems.