Columbia Management, an asset management subsidiary of Bank of America Merrill Lynch [BAC], will likely see widespread layoffs and departures from its fixed-income division once its acquisition by Ameriprise Financial closes, according to a source familiar with the group.

The deal is expected to close within 30 days and layoffs and departures are expected to intensify once the transition is completed, likely by September. Ameriprise's fixed-income group is at least twice the size of Columbia's existing group, the source said.

Minneapolis-based financial services firm Ameriprise agreed to acquire Columbia Management from Bank of America last September for approximately $1 billion in cash. The firm said at the time that it expected to generate between $130 million and $150 million in annual net synergies, with about half of those savings to be realized in the first year and substantially all in the second year.

The deal will bring Ameriprise’s global assets under management to almost $400 billion. When the acquisition was announced, Boston-based Columbia had approximately $72 billion in fixed-income assets and $93 billion in equity assets under management.

Ameriprise and Columbia representatives were not immediately available for comment.