Colorful, beautiful, (mostly) colonial coral

An individual coral organism is called a polyp. Most corals are colonial, which means they live in colonies. So what looks like a single coral may actually be composed of hundreds of individual polyps!

Bright purple, pink and yellow corals

Warm-and cold-water dwellers

Most people associate corals with tropical waters—but you may be surprised to find that a stunning variety of corals live off the coast in the decidedly chilly waters of the Pacific Northwest. They make their homes in deep water on rocky reefs along the Olympic Coast, all the way up through Alaska and the Aleutian Islands. Unlike their warm-water counterparts, these corals take food right out of the water instead of relying on sunlight and symbiotic algae for sustenance. You can see both warm- and cold-water corals at the Seattle Aquarium. See an infographic about warm vs. cold water corals here.


A habitat made of skeletons

Coral reefs are, primarily, made by stony corals. Each individual stony coral polyp secretes a skeleton of calcium carbonate. Over time (a long, long time!), these skeletons can build up and form massive coral reefs, with colonies consisting of millions of coral polyps living atop the remains of former colonies. Most established coral reefs are between 5,000 and 10,000 years old. It’s estimated that some existing reefs began growing over 50 million years ago!


Home to (almost) countless living things

Coral reefs are one of the most complex ecosystems on Earth and provide habitat for a tremendous diversity of life forms. In fact, they support approximately 25 percent of all known marine species—including more than 4,000 species of fish, 700 species of coral, and thousands of other plants and animals.

Critically important—and in critical condition

It’s hard to overestimate the importance of coral reefs to the marine environment. But the world’s coral reefs are in danger. Two of the biggest threats to coral reefs are ocean acidification and bottom trawling (dragging a net across the sea floor to catch fish and other animals). Ocean acidification changes the chemistry of seawater, making it harder for corals to build their skeletons, and making the skeletal structures they do build weaker and more prone to breakage. And a single sweep of a bottom trawl can reduce a deep sea coral reef to rubble in matter of minutes—not only destroying the coral, but also the habitat for just about every other species that lives there.


Taking steps to protect coral reefs

Establishing and maintaining marine protected areas may be the best way to protect deep sea coral reefs from further destruction. Many such areas have already been established, but more are needed to ensure the health of the world’s coral reefs, as well as the countless number of living things that rely on the reefs for survival. On an individual level, there are many actions you can take that will help coral reefs, including saving water; reducing pollution by walking, biking or riding the bus; choosing environmentally friendly home and garden products; disposing of waste properly; and reducing your carbon footprint.

Other Invertebrates

Sea Anemone

These creatures can survive at depths of more than 32,000 feet.

Hermit Crabs

There are over 500 species of hermit crabs around the world.

Moon Jelly

Jellies have been around for hundreds of millions of years!

Sea Star

Sea stars don’t have brains but are still able to detect light!


These sedentary creatures lock onto (or into) objects and animals and include more than 1,000 species.