Species of Sea Urchins that Live in the Kelp Forest

Kelp forests are found along the Pacific coast of the United States from Alaska to Baja California at depths of between 6 and 90 feet. Sea urchins are herbivorous echinoderms related to sea stars. Sea urchins live in kelp forests and feed directly on kelp. They can multiply to the point where they destroy kelp forests, especially if predators such as the sea otter have been eliminated from the ecosystem.

  1. Purple Sea Urchin

    • The purple sea urchin (Strongylocentrotus purpuratus) lives along the coastline of North America from Alaska to Mexico. It thrives in areas with strong waves and is common in kelp forests. Purple sea urchins can eat through the main stems of kelp blades and destroy whole kelp beds if their numbers are not controlled. Purple sea urchins are eaten by sea otters and also harvested and exported to Japan for human consumption.

    Red Sea Urchin

    • The red sea urchin (Strongylocentrotus franciscanus) has a similar range to the purple sea urchin but lives to depths of 270 feet. The red sea urchins can grow to 5 inches in diameter, with shorter spines than the purple sea urchin. They feed on red and brown algae, kelp and even small mollusks, such as mussels and periwinkles.

    White Sea Urchin

    • The white sea urchin (Lytechinus anamesus) is only 1.5 inches long with white or cream signs. They are found off the Californian coast and can form large groups or herds in areas. White sea urchins feed on algae such as diatoms and turtle grass.

    Crowned Sea Urchin

    • The crowned or coronado sea urchin (Centrostephanus coronatus) has long, dark-purple spines and is found from California south to the Galapagos Islands. They can be 6 inches in diameter and live on rocks below the low tide mark, feeding on algae and corals.