We performed 16S rDNA amplicon V6 region sequencing of Bacteria and Archaea on bottom water samples collected from four locations, and three filter pore size fractions (3. 0.2 and 1 microns). The locations in question are the west pond and the middle pond of the Challenger Deep (~ 10.9 km water column depth) within the Mariana Trench, the Sirena Deep (~10.7 km water column depth) within the Mariana Trench, and a control location outside the Mariana Trench at a water column depth of about 750 m.
The Mariana Trench lies at the boundary between the eastern edge of the Philippine Sea plate and the subducting Pacific plate. The Challenger Deep represents the deepest ocean depth on Earth. Its main depression is about 40 km long, with depths greater than 10,400 m occurring throughout this zone. The Sirena Deep is the second deepest site in the Mariana Trench, with a maximum depth of 10,732. It is located south of the shallow Santa Rosa Bank, about 90 miles south of the island of Guam.
Douglas Bartlett was the Chief Scientist during the James Cameron Deepsea Challenge Expedition, February – April, 2012. During this expedition an autonomous lander was used to collect bottom seawater from the Mariana Trench and south of the Mariana Trench near the Ulithi Atoll. This lander was equipped with lights, 3D videography, a high definition camera, Niskin water samplers and baited traps.