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ZooTampa today revealed the cause of death of 12 stingrays that died in the Stingray Bay touch tank May 27.
According to ZooTampa's announcement about the incident, the stingrays died due to a "supersaturation event" that caused oxygen levels to drop and gas bubbles to form. The gas bubbles cause a fatal condition similar to that seen in human scuba divers called the "bends."
The cause of the stingrays' death was not immediately known because the oxygen levels had corrected themselves by the next morning, ZooTampa said.
Although ZooTampa said they do not know the exact cause of the supersaturation event, they believe it was because of a system malfunction or a crack in the tank's pipeline.
Former ZooTampa employee Jeff Kremer said this is not an isolated incident of concern for the Stingray Bay exhibit, which brings in extra revenue for the zoo by charging patrons to feed the stingrays.
Kremer described an incident during his time at ZooTampa when a chiller system for the touch tank began leaking and drained 75% of the water out of the tank. He and other keepers had to shut the system down and quickly replenish the system with thousands of gallons of new saltwater.
In another incident, Kremer said a keeper accidentally turned off the aeration system for a large koi exhibit which killed almost every large koi in the exhibit at ZooTampa.
"There are numerous other such issues that I and other employees raised regarding animal welfare and public/employee safety," he said.
ZooTampa said they will not be reopening Stingray Bay. Instead, they announced plans to build an updated habitat, with a new water management system with safeguards to prevent another incident from harming their animals.
Full statement:
ZOOTAMPA RECEIVES FINAL RESULTS OF STINGRAY INCIDENT INVESTIGATION
ZooTampa has been committed to conducting a thorough and transparent investigation to the May 27th incident at Stingray Bay, enlisting the assistance of independent experts who have extensive aquatic experience in the zoo and aquarium field. 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. Gas bubble disease is a fatal condition that is similar to the “bends” in human scuba divers which is caused by bubbles in the blood stream. 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 pipe line which was not readily accessible. The Life Support System was checked daily and maintained by trained aquarists and maintenance staff on a schedule which followed the manufacturer’s recommendations and industry standards. 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.