W HILE the tide is high, water covers much of Holiday Shore. Bright-colored fish swim among the rocks. Snails crawl about eating plants. Pink and blue starfishes hunt for clams, while seaweeds nod their red and green fronds. Plantlike animals attached to stones spread their legs and tentacles (flexible organs of touch) to catch food.
When the tide is low, all this is changed. Seaweeds hang limp and motionless from Holiday Cliff. Little fish hide in wet cracks and big fish swim away in the bay. Many snails hide under stones, and so do the starfishes and crabs. The shore seems to lie asleep, waiting for the tide to return.
But the animals that burrow in the fine sand are not asleep. Those holes over there were dug by clams and if you stamp your foot near them the clams will squirt water and you will know that they are awake. Those wrinkled lumps of mud were brought up by long green worms that live in burrows under the sand.
If you dig farther out, you will find sand dollars. They are circular flat creatures with very thick shells covered with silky brown spines. In deeper water they live on the bottom. Codfish and haddock visit Holiday Bay just to get meals of sand dollars.
There are pools on the shore where creatures swim, crawl, and eat, no matter how low the tide may be. These are hollows or basins worn in the rock near the foot of Holiday Cliff. When the tide goes out, water still remains in these hollows. That is why we call them "tide pools."
Let us visit one of these pools while the rest of the shore is free from water.
The rocks around the pool are covered with thick bunches of brownish-green seaweed. In the water float some bright purple sheets. They are the fronds of seaweed called "dulse," which many people like to eat. If you go to grocery stores in seashore towns, you may find baskets of dried dulse for sale. It has a musty, salty taste and it will make you very thirsty if you eat any of it.
On the rocks at the bottom of the pool are hard, rough patches of pink. They are made by a strange seaweed that covers itself with colored lime. Some seaweeds spread out on flat stones. Others, like those in that corner, form lacy fronds of lime.
Those plants that look like huge brown leaves have drifted in from Holiday Bay. The biggest seaweeds in this Eastern bay have fronds that are two or three feet long. But if you visit the coast of Washington, you may find seaweeds called kelp that sometimes are hundreds of feet in length. One of them has a cluster of fronds fastened to a big, hollow ball. This ball is on the end of a stem so long that it reaches to the bottom of the bay. There it anchors the kelp to a stone. Sailors sometimes have thought that these long, twisting stems were brown sea serpents.
Seaweeds, of course, are not really weeds. They have no
roots or true leaves. They never have flowers or seeds.
Seaweeds belong to a very ancient group of plants
Those sharp, rough shells fastened to rocks in our tide pool belong to animals called barnacles. Barnacles often live on rocks so high that they are left dry by the low tide. Then they close their shells and wait for the water to cover them before they can have anything to eat.
There in the pool, too, are tubes built by little worms with red gills. They cannot come out and crawl away, like the worms you found burrowing in the beach.
What are those pretty, checkered mats? They are the homes of creatures so plantlike in appearance that they have been given a name meaning "moss animals." Some of their relatives live on the seaweeds that float in Holiday Bay.
Sponges also are animals, even though they look like plants in the pool. Some are green, while others are yellow or pink. Each sponge has a great many tiny mouths, through which it sucks in water and food. When it has eaten as much as it can, it sends the water out through another larger hole.
In a shady corner of the pool are some large sea
Some sea anemones in a corner of the tide pool.
Though it is pretty and flowerlike and is named for a flower, the sea anemone is an animal. It is a relative of the corals that build banks and reefs in the sea near Florida. Other relatives are the pale pink jellyfish that swim in the shallows of Holiday Bay.
Some sea anemones cover their bodies with pieces of broken shell. When they close their mouths you can hardly tell them from rubbish that has been caught in a crack.
Some sea anemones cover themselves with pieces of shell.
How do sea anemones eat? Watch this big one when a little fish swims near. His tentacles wave and stretch. Three of them catch the fish and sting it so it cannot swim. Then other tentacles get to work. They pull and push the little fish into the anemone's mouth. He will eat all of it but the fat before he is ready for another meal.
At one end of the tide pool the bottom is covered with sand. There lies a long purple creature with branched tentacles at one end. Five double rows of suckers run the whole length of his body. As he stays there undisturbed his body grows longer and longer, till it looks like a huge purple worm. If you pick him up, however, his body becomes short and stiff. He does not bite or sting.
This queer creature is a sea cucumber. It is a distant cousin of the starfish, even though it looks more like a worm.
The sea cucumber is a relative of the starfish even though he looks like a worm.
There are other sea cucumbers in Holiday Bay, but most of them live in the mud or sand. They swallow a lot of it every day, to get the bits of food it contains. That means a great deal of work for a little meal—but they are sure of getting something to eat.
The strangest animal in the tide pool is the little white tunicate, or sea squirt. When a baby, he swims freely about in the bay. He has a head, eyes, and a long tail. Down his back runs a piece of gristle like that which in higher animals comes before the backbone is developed. It means that the baby sea squirt is related to fish and frogs.
But this gristle never becomes a backbone. After swimming about for a while, the sea squirt settles down on a stone. He fastens himself by his head, and loses his eyes and tail. Soon he looks like a little vase with two spouts.
Sea squirts look like little vases with two spouts.
Into one spout he sucks water containing food. From the other he sends the water out after he has taken all he can eat. The animal that once seemed to have the promise of a backbone now lives and eats like a sponge!
One sea squirt in the pool near Holiday Shore even buds much as a plant does and forms colonies somewhat like those of the "bread-crumb" sponge.
But why call him sea squirt? Pick up a pebble to which one of these little animals is attached. Squeeze him suddenly. Watch him squirt water two or three feet across the pool. Could you give him a better name than the one he has?
If you go to a tide pool on the Pacific coast, what will you expect to see?
You will find barnacles, seaweeds, and snails. The barnacles will not be quite like those on Holiday Shore. The seaweeds will be bigger. Some of them even may be kelp that waves have washed in from the bay.
You will see many moss animals and creatures that resemble them, though they are really relatives of the corals. You will find purple clams on the shore above the pool, and yellow or red sponges in it. You may think that many of the animals are much like those in the pool on Holiday Shore.
You will find purple clams on the rocks above the pool.
Yet you will find many things that are different. Most of the sea anemones are green; more of the sponges are red. The crabs are purple with green spots. Their shells are longer than those of the crabs in the pool near Holiday Cliff.
Western sea cucumbers are very large, but their tentacles are short. The commonest one often lives in pools. He is long and red, with purple and orange lumps on his skin. If you pick him up, he becomes so slimy and limp that he may slip out of your hands.
Many of the starfish are purple, too. Instead of living in the pools, they like to crawl between cobbles, where they are covered by clumps of damp seaweed. Sometimes you may find five or six, all crowded into one corner.
The most common sea squirt in Western pools is bright red, with a tough, wrinkled skin. Often it is so dirty that you may think its color is brown. A big one will squirt five or six feet if you squeeze him quickly and firmly.
We may spend a long time watching the animals and plants of either a Western or an Eastern tide pool. Even then we shall miss many of them unless we hunt with a microscope. Every sea plant and animal we have met in this chapter begins its life as a very tiny creature that spends its days floating or swimming. Some plants, called diatoms, never do grow big enough to be seen without a microscope.
These young and tiny animals and plants are eaten by their big neighbors. When sea squirts suck and barnacles wave their legs, they are carrying animals too small to be seen into their hungry mouths. Moss animals feed in the same way, and so do worms and clams.
What do the tiny animals eat? Some eat their still tinier neighbors. But those neighbors must also have food. Where do they get their meals?
The affair really starts with plants—both the little ones that float all their lives, and larger ones like scums and seaweeds.
Plants cannot think, neither can they feel as animals do. But they do one thing that no animal can do—they make their own food.
A seaweed or a diatom eats water (which is made of oxygen and hydrogen) and a gas called carbon dioxide that is contained in the water. You know this gas, which gives soda water its "bitey" taste.
Next, the plant uses sunlight. With the sunlight that comes into a tide pool, green cells in a seaweed turn the water and gas into one of the many kinds of sugar. Then they change that sugar into still other foods, such as starch.
In this work, part of the carbon dioxide is not used. So the seaweed or diatom throws it away in the water. That part is the gas called oxygen. Snails, crabs, sea anemones and other sea animals breathe this gas. Some people believe that no animals could live in the sea until plants had time to throw away a lot of oxygen for them to breathe.
Here, then, Holiday Shore's food chain begins. Plants are nourished by the food they make from gas and water during the day while the sun shines. Sunlight, like dissolved gas, is more plentiful in shallow water near shore than in the deep waters of the ocean. Also, the shore offers protection for animals like barnacles, snails, and crabs.
Now you see why Holiday Shore is such a good place to find plants and certain animals of the sea. It gives them more food, more light, and more shelter than they would find on the bottom of the deep ocean, or even in Holiday Bay. It is because they find the sort of home they need there that animals and plants of so many kinds live on the rocks, in the pools, and even in the sand that make up Holiday Shore.