The dataset comprises physical, biogeochemical and biological measurements from the Southern Ocean. The data were collected in the Bransfield and Gerlache Straits and Bellingshausen Sea between 1995 and 1996. Hydrographic casts provided profiles of temperature, salinity, dissolved oxygen, transmittance, chlorophyll and photosynthetically active radiation, while water samples were analysed for bacteria, zooplankton and a biogeochemical parameters such as nutrient concentrations. Sediment cores were also analysed for nutrients, while drifting traps provided sedimentation flux measurements and shipboard experiments yielded production data. The majority of measurements were collected during two consecutive cruises of the BIO Hesperides between early December 1995 and early February 1996. The hydrographic profiles were collected using a CTD and the data were stored as approximately 300 individual ASCII files per cruise, with data stored at 1dbar resolution. Several hundred discrete measurements (water samples and sediment cores) were collected in total. An array of moorings deployed for one year in the Western Bransfield Strait Basin provided sediment trap samples for biological and biogeochemical analysis. The FRUELA project was part of the Spanish contribution to the study of biogeochemical carbon fluxes in the Southern Ocean. Three major zones, with contrasting physico-chemical and biological characteristics were considered: Bellingshausen, including the Northwest Bellingshausen Sea and comprising the southern boundary of the Antarctic Circumpolar Current (SbyACC); Bransfield, including the Western Bransfield Strait and the northeastern part of the Gerlache Strait; and Gerlache, including the rest of the Gerlache Strait. The research involved a number of Spanish institutions and was coordinated by the University of Oviedo and the Institute of Marine Sciences (CSIC). The data are held by the British Oceanographic Data Centre.