Meet the underwater red volcano sponge

  • Terry Lilley / Special to The Garden Island

    The red volcano sponge does not have a known Hawaiian name.

Right under some of our Hawaiian piers and docks lives a simple, multi-celled animal that looks like an erupting volcano.

These bright-red, six-inch-tall sea sponges even have an opening at the top that looks like the caldera of a red-hot volcano. They are extremely beautiful but rarely seen by divers unless you have a bright dive light and know where to find them.

Some 100 years ago, people harvested these sponges, dried them out, and used them to clean kitchens. Some sponge species can grow up to eight feet tall and weigh over 300 pounds when wet.

These sponges are living filters that lack a mouth, gills or internal organs. They are covered with pores that draw in water and filter out plankton and organic particles from the sea water. They even filter out toxins from the water like sewage, heavy metals and pesticides without getting sick.

Sea sponges are the oceans’ natural seawater filter, and are very important for the health of our coral reefs. At one time scientists thought these ancient creatures were plants, until they discovered that they can pump water through their bodies.

The sea sponges have colonies of cells that act like small sponges living within a larger sponge. If they are broke apart they can come back together and form the whole sponge again. As scientists, we still do not know exactly how these creatures exist. But we know they are important to the marine ecosystem and should not be removed from the reef.

People used these animals to clean their kitchen because they absorb water extremely well. In the sea they pump and clean more seawater than any known creature, even in polluted water where no other creatures can survive. These sponges grow in shaded areas, and also come in green, blue, yellow, purple and white colors. The best place to see them growing naturally is in calm bays and harbors in the shade under piers and boat docks.

Maybe someday we will grow sponges to help clean up our polluted oceans instead of removing them to clean up our messy kitchens!

Aloha from under the surf.


Terry Lilley is a marine biologist living in Hanalei. He is co-founder of Reef Guardians Hawai‘i, a nonprofit on a mission to provide education and resources to protect the coral reef. To donate to Reef Guardians Hawai‘i go to


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