Merrill Lynch contributed more than $3 billion to Bank of America’s first-quarter $4.2 billion net income.

Citing first quarter league tables, the Charlotte-based bank said that Merrill Lynch was No. 2 in global and U.S. investment banking fees based on volume; No. 1 in U.S. equity capital markets; No. 1 in U.S. high yield debt, leveraged and syndicated loans; and a top-five advisor in mergers and acquisitions.

Bank of America said that the integration of Merrill, which was acquired on Jan. 1, is “on track and expected to meet targeted cost savings.” It cited early success with a sales program for certificates of deposits, which booked more than $135 million in CDs in Florida. That program soon will be rolled out nationally, the bank said.

Overall, the bank’s net income increased 250% over the same time period last year, when it posted $1.2 billion. Chairman and CEO Kenneth Lewis said that the bank continues to face “extremely difficult challenges” due to declining credit quality as a result of a weak economy and rising unemployment.

Investors apparently took those challenges to heart, as shares in the bank fell 17% in morning trading to $8.83 at press time.

This could signal a new wave of credit worries, according to press reports. A bellwether gauge of financial stocks, the Financial Select Sector SPDR exchange traded fund, rallied in recent weeks but gave back some of those gains today. It closed at $11.11 on Friday, after dipping as low as $5.88 in intraday trading on March 6. Today, it slipped 6.6% to $10.35 as of press time.