A disoriented sea lion that wandered into Knightsen last weekend has been euthanized.

The adult sea lion, known as Na’au, was put down at the Marine Mammal Center in Sausalito on Tuesday after officials discovered Na’au had suffered irreparable brain damage from eating fish contaminated by toxic algae blooms in the waters. The disease is known to cause navigational problems and fatal seizures in animals.

The California sea lion was a startling sight to Knightsen residents when it came walking up the center of Delta Road on Dec. 4, disoriented and more than a mile from the nearest waterway. But Na’au was a familiar face to Bay Area wildlife agencies, which had twice rescued Na’au off the waters of Santa Cruz County and treated her for the same toxic algae poisoning she apparently suffered from this last time.

Contra Costa County Sheriff’s deputies, California Highway Patrol officers, the Oakley Police, Contra Costa Canal Patrol, Sheriff’s Marine Patrol and Contra Costa Animal Control all arrived on the scene to keep Na’au safe. The coalition of public officials managed to corral her safely into the fenced-in Knightsen schoolyard until workers from the Marine Mammal Center arrived to help.

After medical testing, it was determined that Na’au could not go back into the wild due to the extensive damage to her brain and nervous system. Officials say Na’au suffered from epileptic seizures possibly caused by the toxic algae, and researchers were planning to perform a necropsy in the hopes of gaining a better understanding of sea lion brains and the disorders that affect them.

According to Jim Oswald, spokesperson for the Marine Mammal Center, the center has experienced an especially busy season, rescuing more than 970 mammals this year. The average is 600.

John Gonzales contributed to this story.