Stock exchanges opened Wednesday morning, following the first close for weather that lasted more than one day since 1888. New York City Michael Bloomberg rang the opening bell on the New York Stock Exchange, which was running on backup power because of blackouts in lower Manhattan. Brokers still had to deal with limited Internet and cell phone service. Trading was brisk, and stocks values began climbing right after the opening bell. However, both the Dow Jones Industrial Average and the S&P 500 were trending downwards by midday.