Aquarium President Jeff Swanagan said Marina, who had been suffering from ulcers, died before daylight despite the presence of numerous employees attempting to save its life, The Atlanta Journal-Constitution reported.
Swanagan said the whale had been having problems swimming in recent weeks due to its ailment, but had appeared to be recovering Friday.
He said the loss of Marina, who had earlier been removed from the aquarium's Arctic Quest exhibit, was a blow to all those involved in the fight for the whale's life.
"We gave each other some well-deserved hugs and encouragement," Swanagan said of employees' reaction to Marina's passing.
The Journal-Constitution reported a necropsy would be performed on the whale's body.