Seeing Stars, Sperm and Millions of Spawn After a Valentine’s Day Rendezvous

On Valentine’s Day, Melissa Torres strung up red tinsel hearts around a shallow pool at her workplace, the Birch Aquarium at Scripps Institution of Oceanography in La Jolla, Calif. She and her colleagues were arranging a romantic encounter of sorts, and the stakes were high. The happy couple, a pair of sunflower sea stars, belonged to a species that has nearly vanished because of climate change.

Sunflower sea stars are a far cry from their smaller pink cousins that you might know from Finding Nemo and SpongeBob SquarePants. They have up to 24 arms and can grow to diameters of more than three feet. They’re also voracious hunters that prey upon sea urchins living among the 100-foot-tall stalks of algae that make up the kelp forests of the Pacific Northwest.

“In a perfect, climate-change-free world, they would be keeping the kelp forest ecology at a perfect eco-balance,” Ms. Torres said. But in 2013, a 1,000-mile-wide mass of warm water nicknamed the Blob formed in the North Pacific. As a consequence of the heat, a strange wasting condition began spreading among the sunflower sea star population. Since then, an estimated 90 percent of all sunflower sea stars have perished. They have been declared functionally extinct in California and Oregon.

Without sea stars to keep urchin populations in check, the urchins are eating too much of the kelp forests’ giant algae. It’s a big problem, Ms. Torres said, because the algae “provide not only homes and food for animals, but food and carbon sequestration for humans.”

Since 2019, the Birch Aquarium has been part of a wide network of aquariums and research centers focusing on sunflower sea star conservation, starting with efforts to breed healthy, genetically diverse sea stars in captivity. In this leg of the project, Ms. Torres and her team wanted to see if they could fertilize sea star eggs using both fresh and frozen sperm.