Citigroup reported a 51 percent rise in third-quarter profit, while Goldman Sachs profit plunged for the second consecutive quarter, the banks reported Thursday. Citigroup, the third-biggest U.S. bank by assets, said profit rose to $4.29 billion from $2.84 billion in the same period a year ago, as a drop in operating and legal costs more than offset lower revenue, which fell about 5 percent to $18.69 billion. The profit figure beat Wall Street estimates. Meanwhile, Goldman profit fell 38 percent to $1.33 billion in the July-September quarter from $2.14 billion in the same period a year ago. Revenue fell in all of the bank's major businesses except investment banking, which benefited from a surge in mergers. Turbulent trading, much resulting from concerns about China's cooling economy, was aggravated by uncertainty over the timing of a U.S. interest-rate increase. Goldman joins J.P. Morgan Chase, Bank of America, and Citigroup in reporting a drop in revenue from bond trading. Goldman, J.P. Morgan, and Citigroup also saw declines in revenue from fixed-income, currency, and commodity trading (FICC). The Goldman results are the latest example of how the pessimistic trading environment is hurting profits at many Wall Street firms.