As the European debt crisis roils the markets, American traders who once awoke at dawn are now rising in the dead of night to gain an edge when business begins in London, Paris and Frankfurt.

Gone are the days when traders showed up to work just before the New York Stock Exchange opened at 9:30 a.m. Now, Wall Street has an unofficial opening bell: the 2:30 a.m. alarm clock.

“We have a new credo: carpe noctem — seize the night,” said Douglas A. Kass, a hedge fund manager who routinely sets his alarm for precisely that time to scan the headlines coming out of Europe. All last week, the musings of the German chancellor, Angela Merkel, and other European leaders put the markets on edge. “You are almost forced to get up and watch the goings-on,” he added.

The nest of night owls is growing more crowded. Senior executives at the Pacific Investment Management Company, the giant bond-trading house, wake up at 1 a.m. in Southern California, to check their BlackBerrys for updates from colleagues in Europe.