Kamlarz said Spring, a member of the council since 1993, passed away Sunday afternoon.
City spokeswoman Mary Kay Clunies-Ross said Spring had been in the hospital for more than a week and died of natural causes related to a long illness.
Spring represented Berkeley's downtown area and was known for being a strong advocate of tenants' rights and rights for the disabled.
Kamlarz said in a memo to council members, "With her passing, we lose a true public servant devoted to her district and to Berkeley. She was a passionate advocate on behalf of her constituents, her city and people of all walks of life who she cared so deeply about."
"My sympathies and those of the rest of the city are with her friends and family and with you, her colleagues, during this time," Kamlarz wrote.
Kamlarz said funeral services are pending.
Spring suffered from rheumatoid arthritis and used a wheelchair. She didn't attend many City Council meetings in person, often participating remotely via a hookup from her home.
According to Kamlarz, Spring, who was born in Plentywood, Mont., graduated from the University of California, Berkeley with honors in anthropology and psychology.
Spring came under scrutiny last year when she reached a stipulation with the Berkeley Fair Campaign Practices Commission that called for her to pay a small fine and admit violating the city's election laws.
Spring admitted that she didn't report all the contributions she received and that there were discrepancies between her bank balance and campaign statements dating back to 1998.
But Spring said the omissions were only mistakes, weren't deliberate and didn't affect the outcome of the 2006 election or previous elections.
Spring was re-elected in 2006 with 72 percent of the vote. Her term expires at the end of 2010.
Clunies-Ross said city officials are discussing today how to determine who will serve out the rest of Spring's term.