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‘Supersaturation event’ cause of stingray deaths at ZooTampa

A stingray at ZooTampa. The zoo announced 12 stingrays died have died on May 28, 2021. An investigation is underway to determine the cause. (Image: ZooTampa at Lowry Park) (WKMG 2021)

TAMPA, Fla. – The death of 12 stingrays at ZooTampa in late May was determined to be from “gas bubble disease,” according to experts who investigated.

“We sent water samples to a couple of labs including one in Germany, that’s one of the renowned labs and also sent tissue samples to our pathologist for review,” Dr. Larry Killmar, chief zoological officer at ZooTampa told WFTS-TV.

ZooTampa enlisted independent experts with extensive aquatic experience in the zoo and aquarium field to investigate the incident at Stingray Bay. Analysis and assessment of lab and pathology tests led to their findings that a supersaturation event occurred, likely in the overnight hours, causing gas embolisms (gas bubble disease) in the rays.

“The animals are in their environment, this oxygen bubble, nitrogen bubble is pushed back into the system either due to a malfunction crack in the pipe or pump,” Killmar said.

Gas bubble disease was described as being similar to the “bends” in human scuba divers, caused by bubbles in the bloodstream, the zoo said.

They say the event was not immediately known because the oxygen levels had resolved by the time the water was tested in the morning following a standard water change, the station reported.

Possible causes of the event include a system malfunction or a crack in portions of the pipeline, which was not readily accessible, ZooTampa said.

“We’ll never actually know, we think this occurred overnight and they eventually died in the morning,” Killmar said.

ZooTampa decided not to reopen Stingray Bay. Instead, it will build an updated habitat with a new water management system which will include redundancies, safeguards and updated procedures.