As data on sea otters gets a technological boost, a looming threat rears its head.

Over the last two years, The Marine Mammal Center has been retrofitting its Sausalito headquarters so that it can rehabilitate sea otters, and on Sept. 22, the effort bore its first fruit: Otto, an 8-year-old otter that was rescued on a beach last spring, was released back into Morro Bay after recovering from domoic acid poisoning.

Shawn Johnson, MMC’s director of veterinary science, says when Otto was stranded on the beach, he was depressed and underweight. Johnson didn’t know why until he ran Otto’s blood work, which showed high levels of domoic acid, the first time that’s ever been observed in a stranded otter.

Since then, MMC has rescued another otter with domoic acid poisoning, a trend Johnson is concerned might continue. “I think part of it is the frequency and size of toxic [algal] blooms is ever-increasing,” he says. “It only makes sense this toxin is getting into the food chain that otters eat as well.”

But Otto represents an opportunity for scientists to learn more about how otters live and die in the sea. MMC vets implanted a life-transmitter tag in Otto’s abdomen – otters’ pelts are crucial to their survival, so external tags aren’t possible – that will track things like temperature and motion, and the information will be uploaded to a satellite after Otto dies. The tag’s upload is triggered by a temperature change, and it’s the first time the technology has ever been employed on a released otter.

MMC plans to release another rescued otter in Half Moon Bay in mid-October that will also be implanted with a transmitter. Johnson hopes the tags will help scientists better understand what has been stifling the recovery of the species, which has been struggling for years to expand its range.

“If animals are dying quickly, we know it’s sharks. If it’s a slow death, there’s something else wrong.”