Stocks opened higher on Monday, but moved lower during the session as concerns about the economic crisis in Turkey continued to weigh on the market. The Dow Jones Industrial Average (DJINDICES: ^DJI) and the S&P 500 (SNPINDEX: ^GSPC) both lost ground.Data source: Yahoo! Finance.Energy was the weakest sector, with the SPDR S&P Oil & Gas Exploration & Production ETF (NYSEMKT: XOP) falling 2.5%.