CHICAGO (AP) — The Chicago Tribune carried out its plan to trim 14 percent of newsroom staff on Friday as the Tribune Co.'s flagship paper moves to save $8.8 million in annual costs.

The biggest Chicago daily, with average circulation of 541,663, laid off 80 newsroom personnel, editor Gerould Kern said in a letter to staff, a copy of which was obtained by The Associated Press.

"While painful, these staff reductions are necessary to establish the foundation for a sustainable future," Kern said in the memo.

Newspaper revenue and circulation have shrunk as readers — with advertisers in tow — increasingly move online. Advertisers spend online a small fraction of what they used to pay newspapers for prime ad space.

The Chicago Tribune now has 480 newsroom staff, which Kern said makes it the largest news organization in the city. The memo made no mention of specific people or jobs that were cut.