Seaweed is one of only two producers in the ocean. Seaweed is a type of very large algae. Seaweeds such as kelps let their long blades float at the surface of the water, where they absorb sunlight and serve as a food source.

Phytoplankton is the other producer in the ocean and is considered a type of seaweed, according to the National Ocean Service. Seaweed is packed with minerals, fiber and vitamins, making it an important food source for many different marine animals. Many species of seaweed also have medicinal benefits thanks to antimicrobial and anti-inflammatory agents. Some species have cancer-fighting properties.

Seaweed provides important habitats for marine animals. Some seaweed species form vast edible forests. Kelp forests are one of the most productive ecosystems on the planet. Many animals such as sea urchins feed on the holdfasts, which keep kelp anchored to rocks and other objects on the seabed. This can lead to the gradual destruction of kelp forests when sea urchin populations get out of control, but Monterey Bay Aquarium states that sea urchins' natural predators, such as otters, keep their populations in check.