Chicago Zoo Accidentally Kills 54 Stingrays Animals in shallow pool died from low oxygen levels By Newser Editors and Wire Services Posted Jul 13, 2015 7:40 AM CDT 42 comments Comments In this photo taken on Tuesday, March 25, 2014, a youngster touches the glass as a stingray glides past in the shark tank at the Loveland Living Planet Aquarium in Draper, Utah. (AP Photo/The Salt Lake Tribune, Al Hartmann) (Newser) – Officials say all 54 stingrays in a popular exhibit at a suburban Chicago zoo died because the oxygen levels in their tank dropped too low. The Chicago Zoological Society says the four southern stingrays and 50 cow-nose rays in the Brookfield Zoo exhibit were in a shallow pool that allows visitors to touch and feed the creatures. Most died Friday afternoon. A senior VP says zoo staffers worked hard to try to save the rays and are devastated by their deaths. The staff is working to get the tank's oxygen levels back to normal; the seasonal exhibit will remain closed for the rest of the summer.