Moody's Investors Service lowered the credit ratings of 15 major banks Thursday, including Bank of America, JPMorgan Chase and Goldman Sachs, saying their long-term prospects for profitability and growth are shrinking. The ratings agency said it was especially concerned about banks with significant financial markets businesses because those markets have become so volatile. Some of the largest European banks were also downgraded, including Barclays, Deutsche Bank and HSBC.