Fernández's research work in marine biology began in 1972 when she began working with the Instituto de Investigaciones Pesqueras (IIP) in Uruguay.[3] She received her doctoral degree in biology in 1992 from the University of Santiago.[3] From 2006 to 2011, Ríos was the director of the Spanish National Research Council,[4] and she also led an International Geosphere-Biosphere Programme committee focused on studying climate change from 2005 to 2011.[5] She was initiated into the Royal Galician Academy of Sciences on 6 June 2015, where she gave an inaugural speech on the increasing acidity of the Atlantic Ocean due to carbon dioxide titled, "Acidificación do Mar: Unha consecuencia das emisións de CO2."[6]