This dataset contains coccolithophore abundance data from CTD bottle samples collected during the JC053 cruise in the Atlantic between Southampton, UK and Punta Arenas, Chile in October-November 2010. Niskin samples were collected during the pre-dawn CTD (second cast of the day) from six light depths (1%, 7%, 14%, 33%, 55%, 97%). Samples for microscopic enumeration of coccolithophores and coccoliths were collected on Millipore HA (nitrocellulose) filters and rinsed with potassium tetraborate buffer, then frozen at 20 degC. Samples were then dried, mounted onto slides using Norland Optical Adhesive and enumerated using by birefringent microscopy. These data were collected by scientists from the Bigelow Laboratory for Ocean Sciences and contribute to the Atlantic Meridional Transect (AMT) project.