Abyssal sediments, polymetallic nodules, and water-column samples were collected from the UKSRL1, OMS claim area as well as APEI within the Clarion-Clipperton fracture zone in the Pacific Ocean. The ABYSSLINE 2015 Cruise took place aboard the research vessel Thomas G. Thompson (R/V Thompson) between February 12, 2015 and March 25, 2015, as an expedition jointly funded and supported by Seabed Resources Limited and Ocean Mineral Singapore. The chief objective of the AB02 was to conduct an evaluation of biological and environmental baseline conditions in the UK-1 contract area, and the OMS contract area at depths ranging from 3900 to 4400 meters (m) in the Clarion-Clipperton Zone (CCZ; also known as the Clarion Clipperton Fracture Zone). Specifically, the study targeted two 30 by 30 kilometer (km) areas; one in the UK-1 contract area and one in the OMS contract area, centered approximately at 13 degrees 49 minutes North, 116 degrees 36 minutes West (13 49' N, 116 36' W) and 13 degrees 49 minutes North, 116 degrees 36 minutes West (13 49' N, 116 36' W), respectively. This project consists of samples isolated at the sediment sites described above and inoculated into seawater medium in microcosm experiments to evaluate the influence of bicarbonate on community composition.