Tierney Thys: As Jellyfish Take Hold of Emptying Oceans, Molas to the Rescue

Text by Molly Webster

Marine biologist Tierney Thys can often be found off the California coastline aboard a panga (skiff), squinting up at a spotter plane circling overhead. If she's lucky, the 41-year-old gets a radio call to cut the engine if the pilot has spied a mola, another possible clue to solving one of the ocean's most perplexing mysteries.

The Mola mola (aka ocean sunfish) is a gigantic sea creature, part Dr. Seuss bit player, part VW Beetle. It feeds on jellyfish, giving molas a front-row seat to an unfolding ecological disaster. "Jellyfish are like weeds," Thys explains, and have begun to thrive in species-devoid niches caused by overfishing and climate change.

In the last year, swarming masses of the stinging invertebrates have suffocated salmon at an Irish farm, disrupted a New York triathlon, and closed Barcelonaуs beaches. Highly visible examples aside, jelly dataяhow populations are growing, and whereяis hard to come by. (Tracking tags won't stick to the cnidarianуs gooey bell.) So researchers are left with few options, one of which is to follow the jellyfishуs biggest predator: the mola. "Molas offer insight into the jellyfish web," Thys says. "But research is spotty at best. As jelly numbers rise, the animals that prey upon them, molas in particular, become really important."

Thys's work as a conservationist and researcher has taken her on numerous Antarctic expeditions and a six-month solo journey through the Australian bush. Earlier this year, she was in the Galapagos, searching for more molas. And now she's back in California, crunching data from sunfish tagged on recent trips to Indonesia and Africa. Are mola populations growing along with jellies? It appears that way. Will molas be able to keep jellyfish in check? "It's all part of the big puzzle of how the ocean works," Thys says before returning to her panga, squinting at the sky, piecing together a mystery of the ocean deep.  

Photograph by Martin Sundberg