MAR-ECO (2003 - 2010)was an international exploratory study of the animals inhabiting the northern mid-Atlantic. Scientists from 16 nations around the northern Atlantic Ocean participated in research of the waters around the mid-Atlantic Ridge from Iceland to the Azores. This data set is subset of the data collected, and comprises presence/absence records for zooplankton and nekton, collected in 2003 on R/V Arni Fridriksson. Contact person Thorsteinn Sigurdsson, Marine Research Institute, Iceland, e-mail: steini@hafro.is