Honolulu Star-Bulletin owner David Black has become part owner of the San Diego Union-Tribune, the dominant daily in the nation's eighth-largest city.

The purchase, by Beverly Hills private-equity firm Platinum Equity, was announced yesterday. The price was undisclosed and Black was described as part of the team.

La Jolla-based Copley Press Inc. had put the paper on the market in July and Platinum was the winning bidder.

“;This is a vital business with a long tradition of public service and a pre-eminent position in one of America's finest media markets,”; said Copley Executive Vice President Harold Fuson Jr. in a statement quoted by the Union-Tribune.

The seller, the Copley family, had owned the paper for some 80 years. It was purchased by Col. Ira Copley in 1928 from the estate of John D. Spreckels, a key player in San Diego's early development, according to the Union-Tribune.

Spreckels is also a prominent name in Hawaii's history, as San Francisco sugar refiner Claus Spreckels served as an adviser to King David Kalakaua. Claus Spreckels was the father of John D. Spreckels, according to a story in the Union-Tribune archives provided by reporter Jim Hebert. Spreckelsville, Maui, is named after the family.

In addition to the Star-Bulletin, Black also owns dozens of community newspapers, mostly in western Canada, but also owns the Akron Beacon Journal in Ohio, as well as MidWeek and HI Luxury magazine in Hawaii.

“;The Union-Tribune is a premier media property in an outstanding market,”; Black said in a statement. “;We are extremely excited about partnering with the management team and dedicated employees of the Union-Tribune and building this franchise for the future.”;

Black's expertise will be drawn upon, but Platinum principal Mark Barnhill declined to specify what role he might play at the paper.

“;He kind of teamed up with us early in the process,”; Barnhill said. “;David will continue to be part of this process going forward.”;

Platinum specializes in acquiring challenged businesses and has purchased more than 100 companies in various industries since 1995, the Union-Tribune reported. This is its first newspaper purchase.

The newspaper industry has long struggled with declining circulation, as readers have migrated to the Internet, and with deepening loss of advertising revenue in the downturned economy.

Union-Tribune Chief Executive Gene Bell told employees in January that the Union-Tribune's advertising revenue fell 40 percent since 2006.

The Associated Press contributed to this report.