Divers in shallow Hawaiian waters will often notice what looks like a new coral species growing on the reef that they had not seen before. What they are looking at is not a hard coral but a soft colonial sea anemone called a Zoanthid.
Divers in shallow Hawaiian waters will often notice what looks like a new coral species growing on the reef that they had not seen before. What they are looking at is not a hard coral but a soft colonial sea anemone called a Zoanthid.
Near shore coral reefs often die due to sewage leaks, farm chemical runoff or a discharge of mud from the rivers or streams. After the corals die the Zoanthids start to grow and can get quite large. They lay flat on the reef or create a mound in the shape of a pillow. They come in several colors from brown to grey, green, yellow or purple. A large outbreak of Zoanthids on the shallow reef is a sign that there is a bad pollution problem in the area.
Recently the corals died and Zoanthids started to grow on the west side of Hanalei Bay which tells us that something bad is coming out of the streams in the area and flowing out onto the reef killing the corals.
Zoanthids are tiny anemones that are all fused together with soft tissue. Each anemone has stinging tentacles used for filter feeding. These anemones have a toxic chemical in their structure called palythoa toxica and for some reason they seem to be able to grow in polluted water and stagnant tide pools. It has been recently discovered that the Zoanthid toxin contains cancer fighting compounds and it is currently being studied in the lab. Somehow these Zoanthids remain healthy in polluted water when the corals die so they must have some kind of protection from the pollution chemicals!
In the past Hawaiian warriors in Hana Maui knew about the toxic properties of the Zoanthids and they collected the anemones and crushed them with rocks releasing mucus of which they dipped their spears in before a battle. Anyone who got stabbed with a spear coated in the toxin usually died! Even research biologists collecting small amounts of the Zoanthid without gloves have had serious reactions and ended up in the hospital for days!
In old times the Zoanthid was thought to be a type of limu (seaweed) and the Hawaiian name limu-make-o-Hana means “the deadly seaweed of Hana”. You can see all of the different types of Zoanthids up on my web at www.underwater2web.com in the species ID section and also see them in my Hawaiian reef creatures movies up on my YouTube Channel at Underwater2web.
•••
Terry Lilley is a marine biologist living in Hanalei Kaua‘i and 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 Hawaii go to www.reefguardianshawaii.org.
