Time series changes in the chlorophyll $alpha$ concentrations before and after the ship Prestige oil spill on 13 November 2002 were analyzed using NCEP wind data and ocean color data. Following the oil spill, southwesterly winds pushed the oil towards the Spanish coast. In addition, the daily chlorophyll $alpha$ concentration decreased dramatically from the middle of November to the end of December 2002, with the minimum value being recorded in December. Additionally, the mean chlorophyll $alpha$ concentration in November and December 2002 was lower than the average value recorded for the same months from 2000 to 2005; however, with the exception of 2000, the concentration was higher in October 2002 before the spill and in January-March 2003 after the spill during the same period from 2000 to 2005.