Sea Technology

DEC 2012

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Ultradeep-Sea Exploration In the Puerto Rico Trench Robotic Vehicle System Captures Video of Benthic Life at 8,000 Meters By Fredrik Søreide T he Puerto Rico Trench is the fourth-deepest ocean The Puerto Rico Trench robot vehicle system, 11K. trench in the world and the deepest point in the Atlantic (Photo Credit: Promare) Ocean but has remained virtually unexplored. It is located approximately 100 miles north of Puerto Rico and forms the boundary of the Caribbean Sea where the North American tectonic plate is being subducted under the Caribbean plate. The trench can be divided into two parts along 65 to 66 degrees west longitude. The western part includes the deepest sector of the trench and is 10 to 15 kilometers wide and approximately 8,300 meters deep. The bottom is remarkably fat and covered by nonrefective pelagic sediments. The eastern part is slightly shallower (by about 700 meters) and more rugged. In light of past fnds, it is likely that the Puerto Rico Trench has a unique biological life compared to the Pacifc Ocean trenches. It holds, for instance, the record for the deepest fsh, Abyssobrotula galatheae, which was dredged from the bottom at a depth of more than 8,000 meters in 1970. However, it was dead by the time it reached the surface, and its presence on the bottom has never been concamera and lithium-ion battery pack from OceanServer frmed by video data. Technology Inc. (Fall River, Massachusetts). In addition, the The trench was mapped extensively in 2002 and 2003 system includes a high-resolution, full-ocean-depth preswith a multibeam echosounder by the U.S. Geological Sursure sensor custom-made by Presens AS (Oslo, Norway), vey during three cruises. In early August 2012, video data and full-ocean-depth LED lights and a drop-weight system and biological samples were retrieved by a team from the developed by Promare. nonproft research group Promare, which dove a prototype In ROV mode, the system incorporates full-ocean-depth robotic underwater vehicle system to the bottom of the thrusters customized by Tecnadyne (San Diego, Califortrench. nia) and a fber-optic connector custom-made by Teledyne Impulse-PDM Ltd. (Alton, England) that connects to a thin Robotic Vehicle Development single-mode fber-optic cable to the surface. In order to explore the deepest parts of the world's oceans The glass sphere is a 1-atmosphere electronics pressure on a small budget, Promare began development of a lowvessel that also provides buoyancy for the vehicle. An extercost, full-ocean-depth robotic vehicle system more than nal frame made from thermoplastics holds the glass sphere two years ago. The prototype vehicle, 11K, is depth-rated to and other external components, such as the thrusters, pres11,000 meters and can be operated in AUV or ROV mode. sure sensor, lights and drop-weight system. The system measures weighs 60 kilograms. The drop-weight system was designed with the capacity The basic vehicle consists of a glass sphere from Nautito drop weights in three stages: one descent weight, which lus Marine Service GmbH (Bremen, Germany) that contains is dropped just above or on the seafoor; several small proprietary software and hardware, as well as an assortment weights, which can be dropped to obtain neutral buoyancy of off-the-shelf components, such as a high-defnition video on the seafoor; and an ascent weight at the end of the dive. 54 st / DECEMBER 2012 www.sea-technology.com

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