Blood Bank of the Redwoods in Santa Rosa has shut its doors as it prepares to merge Friday with the Bay Area's largest blood bank, Blood Centers of the Pacific.

On Thursday, the San Francisco-based blood bank was moving supplies and equipment into Blood Bank of the Redwoods' headquarters in Santa Rosa.

The blood bank stopped taking donations Tuesday and held a farewell staff party on Wednesday.

Of the Santa Rosa location's 100 employees, 48 will stay on with the new blood bank.

"Some positions at Blood Bank of the Redwoods were eliminated, however many staff will remain at that center so blood donors will likely see the same faces they've come to know," Blood Centers of the Pacific said in a statement Thursday.

The Santa Rosa location will be back in business Friday for staff training and systems integration, but it is not scheduled to resume taking blood donations until Aug. 1.

In the meantime, Pacific will supply the blood bank's hospital customers with blood from its other locations, said Lisa Bloch, spokeswoman for the San Francisco nonprofit.

In March, the two nonprofit blood banks announced plans to merge. Blood Bank of the Redwoods, founded in 1948, said it had lost money for two consecutive years. The blood bank lost its contract to supply Santa Rosa Memorial Hospital in 2008, and also faced a drop in blood donations.

It served nine hospitals in Sonoma, Lake and Mendocino counties.

Blood Centers of the Pacific serves more than 50 hospitals from San Jose to the Oregon border, with 11 blood bank locations.

Terms of the merger were not announced.

Cathy Bryan, Redwoods' CEO, will stay in the short term to help with the transition, the two sides said.

The merger will bring new technology and cost savings, said Dr. Nora Hirschler, Pacific's CEO.

"We are pleased to combine forces to ensure safe blood is always there for patients who depend on it," she said.

While Santa Rosa blood donors won't notice many changes, they'll be able to earn points with every blood donation toward thank-you gifts and receive free cholesterol testing with each blood donation, Pacific said.