Intertidal Food Web
The Producers in the Ecosystem
Only two types of living things in the ocean make food using sunlight. These are called producers. One type is phytoplankton. Huge numbers of phytoplankton, most of them only visible under a microscope, drift with the currents and are food for the zooplankton such as copepods and young urchins.
The second type are the seaweeds, which are large algae. The largest seaweeds grow low in the intertidal zone and extend out into the subtidal zone. These are the kelps, large brown seaweeds that are glued to the rocks with their holdfast. Their long blades float at or near the surface of the water where they get sunlight to make food, which allows them to grow very fast. Their holdfast glue is very strong, and it can keep the huge kelp in one place even when strong currents and waves occur during storms.
Snails and sea urchins eat kelp, and fish, crabs, and many other animals find shelter within the dense kelp stands—called a kelp forest. Like a forest on land, the kelp forest provides food, places to hide, and a calm place away from the force of waves and winds. Many kelps die back in the winter and grow again the following spring. Large amounts of dead kelp are recycled by scavengers, including sea urchins, and decomposers.
Consumers: Marine Invertebrates and Fish in the Kelp Forest
Several types of animals depend on the kelp forest as their habitat. They find shelter there because the many tall blades of the kelp break the force of the waves. Inside the kelp forest, the water is calm and small animals can avoid being washed away by the waves. They also cling to the kelp and find hiding places from the other animals that want to eat them.
Sea urchins and snails eat the kelp, either when it is alive or after it has died back each year. Sea urchins feed at the base of the kelp, and large numbers of urchins can actually cut down a tall kelp. Crabs are the resident scavengers. Young salmon and other small fish that live in schools find shelter in kelp forests.
Consumers: Marine Mammals
Seals, sea lions, and killer whales live year-round in the waters near the Aleutian Islands. They eat fish, including salmon and small fish that live in schools. Gray whales and humpback whales migrate through the major passes in the Aleutian Islands to get to their summer feeding areas in the Bering Sea. These baleen whales eat small fish that live in schools and copepods, a type of zooplankton.
Two types of killer whales are found in these waters. Pods of resident killer whales stay together and stay around the same area and feed on fish, including a lot of salmon. Transient killer whales sometimes move through the area, roaming over long distances and preying on seals and sea lions. They may also prey on gray and humpback whales when they are migrating through the passes between the islands on their way to the Bering Sea.
