This dataset consists of 50 CTD casts and 330 salinity samples from 44 CTD stations collected aboard RRS James Cook cruise JC011, which ran between Southampton and Fairlie from the 13th of July 2007 to the 18 of August 2007. Data were collected using a ship-deployed stainless steel CTD frame mounted with the following equipment: • Sea-Bird 9/11 plus CTD System with dual TC pairs • 24 by 10L Ocean Test Equipment External Spring Water Samplers • Sea-Bird 43 Oxygen Sensor • Chelsea MKIII Aquatracka Fluorometer • Chelsea MKII Alphatracka 25cm path Transmissometer • OED LADCP Pressure Case Battery Pack • RD Instruments Workhorse 300 KHz Lowered ADCP (downward-looking master configuration) • RD Instruments Workhorse 300 KHz Lowered ADCP (upward-looking slave configuration) • Benthos Altimeter • Wetlabs BBRTD backscatter sensor This cruise formed part of the fieldwork component of NERC Discovery Science project ‘Ecosystems of the Mid-Atlantic Ride - ECOMAR’, the UK component of ‘MAR-ECO A field project of the Census of Marine life’. The main objectives of the project are to: • To describe the physical flow regimes, both at the surface and the seafloor, across four sites located to either side of the sub-polar front, with reference to their specific role in mixing mutrients and influencing the down-ward transport of organic carbon. • By remote sensing, produce regional estimates of surface promary production and liekly export flux over the study area. - Measure the export flux of organic matter to the seafloor using sediment trap moorings located at each of the four study sites. • Compare the distribution and abundance of pelagic biomass in relation to the position of the Mid-Atlantic Ridge at either side of the Charlie-Gibbs Fracture Zone and to the accompanying varying regimes of primary production encountered either side of the Sub-Polar Front. • Measure benthic biodiversity and biomass comparing species composition with similar depths at East and West Atlantic margins using traps, suspended camera systems, landers and targeted ROV-based survey and sampling. • Assess the possible boundaries to gene flow at the MAR and Sub-Polar Front and genetic population structure of target species in comparison with the East and West Atlantic margins. Representative vertebrate and invertebrate species with different life histories will be compared to test hypotheses about the relationship between MAR ecology, physical oceanographic factors and genetic dispersal. The Discovery Science project was led by NERC grant reference NE/C512961/1 with principal investigator Professor Imants George Priede of University of Aberdeen, Institute of Biological and Environmental Sciences. Grants held within this were NE/C51300X/1, NE/C512988/1, NE/C512996/1, NE/C513018/1 and NE/C51297X/1 with a collective funding period from 01 October 2006 to 30 September 2012. The CTD and CTD sample data have been received by BODC as raw files from the RRS James Cook, processed and quality controlled using in-house BODC procedures and are available to download from the BODC website.