California’s kelp forests are in deep trouble, but an unexpected hero has surfaced on the ocean floor: a 24-armed predatory creature often called the “marine snowman.”
However, don’t let the common name of the sunflower sea star (Pycnopodia helianthoides) fool you—these echinoderms are voracious eaters. Luckily for us, that’s a good thing. Sunflower sea stars help keep one of the ocean’s most abundant sea urchin species in check.
In the early 2010s, purple sea urchin populations exploded by over 10,000 percent. What triggered this? A sudden collapse of sunflower sea stars, driven by a mix of environmental shifts and disease.
In 2013, the northeastern Pacific endured a devastating marine heatwave, which coincided with a mass die-off of sea stars from a wasting disease. This double blow is believed to have wiped out around 99 percent of California’s sunflower sea stars.
Great news for purple sea urchins, but terrible for nearly everything else. By 2017, the region’s already struggling kelp forests were decimated, with over 90 percent of the forests along the West Coast vanishing. While some of this decline was due to warmer waters, any chance of kelp recovery is crushed by the insatiable purple sea urchins.
The issue is that there’s no simple way to eliminate purple sea urchins to give kelp a fighting chance.
Divers and beachcombers have tried manually removing urchins, but it’s a labor-intensive process. On the bright side, purple sea urchins are edible, yet no one eats them as quickly as sunflower sea stars would. Sadly, sea star numbers dropped so drastically that scientists, unable to find any traces of them, dubbed them “marine snowmen.” That is, until recently.
“The moment I first spotted a sunflower sea star underwater, I was so thrilled I literally screamed through my regulator,” said Racheal Carm, a researcher at the Laboratory of Coastal Ecology and Conservation at Sonoma State University. “For most of my career, I thought seeing a sunflower sea star was something unattainable—something you hear about but never witness yourself because the odds are so slim.”
Later, Carm and her team uncovered the largest southern population of these sea stars recorded since the double blow of heatwave and disease. Just 18 individuals—hardly an army, but enough for reproductive potential. Their DNA samples could reveal what allowed them to survive while so many others perished.
It’s likely there are more sunflower sea stars hiding out of sight. This is excellent news not only for the stars themselves but also for one of California’s most critical habitats.
The importance of kelp forests cannot be overstated. They’re essential for marine biodiversity, providing food and breeding grounds for countless species. They also regulate the climate by absorbing carbon, taking in 20 times more CO₂ than an equivalent area of land forest. Additionally, kelp forests reduce erosion by absorbing wave energy, making them a vital habitat for protecting coastal communities.
Today, they rank among the most vulnerable marine ecosystems on Earth. The Nature Conservancy found that from San Francisco to Oregon, we’ve lost about 96 percent of our kelp forests over the last decade, pushing this stretch toward collapse.
But even if we lost the kelp forests entirely and tried to start over, that still wouldn’t address their main threat. Because when purple sea urchins run out of food, they can enter a “zombie mode,” clustering on the seafloor in a dormant state. They can survive like this until nutrients become available again and they spring back to life.
So, while we can’t starve out the urchins, discovering a hidden lair of their worst nightmare offers hope that we might restore balance to California’s precious kelp forests. We’ve seen in places like Papahānaumokuākea, one of the world’s largest marine conservation areas, how effectively and quickly oceans can recover when given the chance.
It’s strange to think that this unexpected savior looks like a 24-armed marine snowman, but that’s the beauty of conservation.
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