Sea urchins are echinoderms found in warm and cold saltwater all over the world. More than 700 species of sea urchins exist; they're prevalent in all oceans. Sea urchins often live in clusters or in solitary settings among other types of ocean life. The habitats of these spiny creatures vary, from rocks close to shorelines to deep on the ocean floor.
Home in the World's Oceans
Sea urchins are saltwater dwellers, never found in bodies of freshwater. Various species of urchins live in all oceans throughout the world, though they are more abundant in warmer climates. The Atlantic Ocean in the Caribbean, the Pacific Ocean surrounding the Islands of Hawaii and both the Indian and Pacific Oceans around Australia's coastline are the world's waters most heavily inhabited by sea urchins.
Among Rocks in Shallow Waters
Rocky shorelines are common habitats for sea urchins. In these areas of shallow water, echinoderms feed off organic material, plant life and animals such as shellfish and barnacles. Urchins in shallow waters attempt to make their homes in rock crevices, often becoming prey to sea otters, gulls and humans who eat them as delicacies. In rocky shorelines, thousands of urchins live in clusters called urchin beds that stretch for miles. Many types of urchins found in shallow intertidal regions, often exposed to more sunlight, are darker in color. Some scientists suspect this is an adaptation of ultraviolet-light protection that aids against sun exposure during low tide periods.
In Coral Reefs
In the warm waters of the Caribbean and around the Hawaiian Islands, sea urchins commonly live among the thriving ecosystem of coral reefs. Here urchins not only benefit from the protection of the structure of the coral but also find plentiful amounts of food, from algae to small shellfish to ample ocean plants. In a coral reef, urchins may live by themselves on in small groups, with fish swimming about them and plants growing around their spiny bodies.
Deep in the Sea
Urchins that reside at the bottom of the sea are often situated on the rocky ocean floor or a substrate of gravely sand. They have been witnessed as deep as 4 miles beneath the surface. In this habitat, sea urchins feed off algae, plant and dead fish that accumulate in the ocean depths. Urchins also live in lush kelp forests deep in the sea. With fewer predators at these deep sea levels, urchins often grow larger and live longer than their intertidal counterparts. The Pacific-dwelling red sea urchin is an example of these fascinating echinoderms that make the ocean bottom their home and are thought to live more than 200 years.
- sea urchin image by Savio Araujo from Fotolia.com