Sponges, corals, and gorgonians living in a reef at the Florida Keys National Marine Sanctuary Click on image for full size (709 Kb) Courtesy of NOAA

There are thousands of types of living things at the bottom of shallow parts of the ocean, where light can penetrate. Some live in places where the ocean floor is sandy or muddy. Others live in places where the ocean floor is rocky. 

Where the shallow ocean floor is sandy or muddy, there are often animals like sand dollars, sea stars, and crabs. There may be snails plowing across the sand and hermit crabs – arthropods wearing snail shells. Some fish and sharks prefer to live near the bottom just above the sand. Sea grass, which looks like a lawn of tall grass, sometimes grows in the sediment.

Other animals, such as clams, worms, and sea urchins that have short spines, spend most of their lives burrowing through the sand or mud. Many animals that live in the sediments are deposit feeders, eating sand or mud and digesting the organic material in it.  Others, like clams, have a tube that reaches to the surface of the sediment where it takes in seawater and filters the plankton and other food from it.

Where the shallow ocean floor is rocky and the water is cold in temperate and polar oceans, habitats called kelp forests can form. These are very unusual places where large brown algae called kelp grow from the ocean floor all the way to the surface of the water – about 20 meters (66 feet) high.  The huge kelp creates an underwater forest where many different animals live. Sea lions swim between the kelp and catch fish. Playful sea otters eat invertebrates like urchins and abalone.

In tropical, warm water, coral reefs grow on rocky areas of the shallow ocean floor. Coral reefs are named after the coral animals whose skeletons make up most of the reef rocks, but reefs are full of hundreds of other types of animals and algae. Many species of colorful fish can be found swimming through reefs. Some of them eat algae from the surface of the reef. Others eat invertebrates or other fish. Invertebrates like sponges, molluscs, sea fans, worms, crabs, and echinoderms are common too.

While different species are found in different areas of the shallow ocean, the general types of animals, algae, and plants that you will find in different places can be similar.  For example, even though the species of kelp is not the same, kelp forests are found in several different ocean basins including the Atlantic Ocean, Pacific Ocean, and the Southern Ocean.

Sponges, corals, and gorgonians living in a reef at the Florida Keys National Marine Sanctuary Click on image for full size (709 Kb) Courtesy of NOAA

At the bottom of the ocean, in areas shallow enough for sunlight to reach them, there are thousands of types of living things. 

Where the shallow ocean floor is sandy or muddy, there may be crabs darting quickly across the sediment and slow-moving sea stars and snails. Crabs wearing snail shells are known as hermit crabs. They can also be found on the sand. Some fish and sharks prefer to live near the bottom swimming just above the sand. Other animals live buried in the sand or mud, such as clams, worms, and sea urchins with short spines. Sea grass, which looks like a lawn of tall grass, can also grow in sand and mud.

Where the shallow ocean floor is rocky and the water is cold, kelp forests can form. These are places where large brown algae called kelp grow from the ocean floor all the way to the surface of the water. The kelp can be as tall as 20 meters (66 feet).  The huge kelp creates an underwater forest where many different animals live. Sea lions swim between the kelp and catch fish. Playful sea otters eat invertebrates like urchins and abalone.

In tropical, warm water, coral reefs grow on rocky areas of the shallow ocean floor. Coral reefs are named after the coral animals whose skeletons make up most of the reef rocks, but reefs are also home to hundreds of other types of animals and algae. Many species of colorful fish can be found swimming through reefs. Invertebrates like sponges, molluscs, sea fans, worms, crabs, and echinoderms are common too.

While different species are found in different areas of the shallow ocean, the general types of animals, algae, and plants that you will find in different places can be similar.  For example, even though the species of kelp is not the same, kelp forests are found in several different ocean basins including the Atlantic Ocean, Pacific Ocean, and the Southern Ocean.

Sponges, corals, and gorgonians living in a reef at the Florida Keys National Marine Sanctuary Click on image for full size (709 Kb) Courtesy of NOAA

Many creatures make their home at the bottom of the ocean where the water is shallow enough for sunlight to reach them.

Where the ocean floor is sandy or muddy, you might find fast-moving crabs and slow-moving sea stars and snails. Some fish and sharks swim about just above the ocean floor. Other animals, like clams, worms, and sea urchins, live buried in the sand or mud. Sea grass, which looks like a lawn of tall grass, can also grow in here.

Where the ocean floor is rocky and water is cold, kelp forests can grow. In these places you will find large algae called kelp growing from the ocean floor all the way to the surface of the water. The kelp makes an underwater forest where many different animals live. You might find sea lions swimming between kelp in search of fish or playful sea otters eating urchins and molluscs called abalone.

In tropical, warm water coral reefs grow on rocky areas of the ocean floor. Coral reefs are named after coral animals. Reefs are full of hundreds of other types of animals and algae too. You can find lots of colorful fish swimming through reefs. On the surface of the reef you can find invertebrates like sponges, snails, sea fans, worms, crabs, and sea stars.