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Stingrays at ZooTampa died of gas bubble disease caused by 'supersaturation event,' tests reveal

Posted at 2:15 PM, Jun 15, 2021
and last updated 2021-06-15 23:24:00-04

The investigation into the death of 12 stingrays at the end of May concluded the animals died of gas bubble disease.

"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, said Dr. Larry Killmar, Chief Zoological Officer at ZooTampa.

ZooTampa enlisted the help of independent experts who have extensive aquatic experience in the zoo and aquarium field following the incident at Stingray Bay. Following their analysis and assessment of lab and pathology tests, it’s been concluded that a supersaturation event took place, 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," said Dr. Killmar.

Gas bubble disease is a fatal condition that is similar to the “bends” in human scuba divers which is caused by bubbles in the bloodstream, the zoo says.

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 exact cause of the supersaturation is unknown, however, possible causes include a system malfunction or a crack in portions of the pipeline which was not readily accessible, ZooTampa said. The Life Support System was checked daily and maintained by trained aquarists and maintenance staff on a schedule that followed the manufacturer’s recommendations and industry standards.

"We'll never actually know, we think this occurred overnight and they eventually died in the morning," said
Dr. Killmar.

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