‘Terrifying’ sea stars could help revive dying Kelp forests, say researchers

Sea Stars May Help Revive Kelp Forests (Image: Canva)

In the cold waters of Alaska, students found hope. As part of a diving course, they studied how fear shapes life underwater. Their work now suggests sea stars might help kelp forests grow again.

How sea stars change sea urchin behaviour
The research took place near Sitka, Alaska, where kelp has vanished. Sea urchins have cleared large areas, leaving ocean floors bare. The team from the University of California, Santa Cruz, wanted to find out if sunflower sea stars could stop this.

They placed cages with and without sea stars underwater. Kelp blades were tied nearby to check urchin movement. Within a day, red sea urchins stayed six feet away from the sea stars. But green sea urchins showed no fear and ate the kelp.

The result pointed to a simple truth. Red sea urchins respond to sea stars, even without thinking. With no brain or heart, they still sense threat and avoid it.

Why kelp forests matter to marine life and people
Kelp forests are vital for ocean health and biodiversity. They shelter fish, feed marine life, and support economies. Kelp products are found in food, makeup, and medicine. Global kelp-related industries are worth about $500 billion each year.

But around 2013, things began to change. A disease wiped out sunflower sea stars along the west coast. Without them, kelp forests in California and Oregon also started vanishing. Sea urchins grew unchecked and ate through the kelp.

This study, done by students and ecologists, hopes to change that. By testing natural fear responses, they explored a new way to control urchins. If sea stars return, kelp might have a chance to grow again.

What this means for future kelp recovery
The students worked across three sites in urchin-heavy areas. Each cage was placed 60 to 100 feet apart. They watched how urchins behaved when sea stars were near. Results showed that even hungry urchins avoided the scent of danger.

Lead author Rae Mancuso said the experience was life-changing. From diving to research writing, she called it both exciting and meaningful. She hopes the findings will help protect kelp forests in the future.

This method may also reduce the need for manual culling. Divers often spend hours removing urchins by hand. But if fear alone can work, it might save time and money.

Scientists are now asking bigger questions. Could sunflower sea stars also scare purple sea urchins, the main threat in California? The answer is not yet clear. Researcher Kristy Kroeker believes they might, but more tests are needed.

The full study was published in the journal Proceedings of the Royal Society B: Biological Sciences.