Crew with the research submersible Shinkai 6500 on board the Yokosuka vessel. Nuku‘alofa, Tonga. 22 October, 2013

The first exploration of the Tonga Trench by a deep sea submersible vehicle was completed by Japanese researchers from October 7-20.

Scientists hope to understand and document the environmental conditions and living species that exist in the second deepest point in the world's oceans.

The Tonga Trench Survey was led by Chief Scientist Dr Hiroshi Kitazato from the Japan Agency for Marine-Earth Science and Technology (JAMSTEC) on board the Yokosuka vessel, and using a manned research submersible Shinkai 6500 and two lander systems to study the depth distribution of organisms underwater.

Dr Kitazato said the main area they surveyed was the 10,850 meter deep Horizon Deep in the Tonga Trench.

“The aim of the survey was to describe the environmental characteristics of the ‘hadal zone’ deepest trenches including depths greater than 10,000m and sample the living organisms in the environment and to find out exactly how the trench environment was created."

He said they found exciting results that included drawing a detailed bathymetric (underwater) chart of the sea area around the Horizon Deep.

“We were able to measure oxygen profile, video recorded the seafloor with a high definition camera and sampled organisms living in or near the seabed. A marine geological survey was carried out on the western side of the Tonga Trench where rocks and core samples were collected to provide clues to its geological features,” he said.

“JAMSTEC plans to analyse and compare the data and samples obtained from the Tonga Trench with those from the Mariana Trench the deepest trench to determine if there is any difference in environmental conditions and living species between the first and second deepest trenches in the world.”

The researchers had earlier conducted a survey at the Challenger Deep in the Mariana Trench.

Global voyage

The Tonga Trench survey was carried out under QUELLE 2013 a global scale voyage of scientific surveys and research on ecosystems in unique and extreme environments in the Indian, Atlantic and Pacific Oceans by JAMSTEC.

The crew included 14 researchers with a Tongan official from the Ministry of Lands, Environment, Climate Change and Natural Resources who observed their work.

Princess Pilolevu Tuita and Lord Tuita toured the vessel this morning accompanied by the Japanese Ambassador to Tonga HE Dr Kazuchika Hamuro and his wife.

The vessel will depart Nuku’alofa on October 24 to survey the Kermadec Arc in New Zealand before turning to Japan in early December.