World Ocean Census - Extract 7 - Reaching the research site

2 February 2010

Seventh amazing extract from The World Ocean Census: A global survey of marine life: Expanding the use of technology - Reaching the research site.

To reach the depths of some ocean realms, scientists often use manned submersibles carried on the RVs. These underwater vessels are compact and self-contained but are dependent on their surface support vessels. Unlike the more well-known military submarines, research submersibles usually have a limited power supply and life-support capacity; they are designed for short-duration dives for the express purpose of collecting scientific data and samples. However, in some cases military submarines have been converted for oceanographic research. Some famous and well-used manned submersibles include the Alvin and Johnson Sealink from the United States and Russia’s Mir. The Census also relies heavily on France’s Nautile.

Working in a manned submersible requires patience and an ability to remain in very tight quarters for long periods of time. There is no room to stand in these vessels, so the many hours it takes to dive to a research site and then return to the surface make for a very long work day! Considering the vastness of the deep sea and the extremely small field of view from a submersible, some of the known discoveries are nothing short of a miracle. Despite these disadvantages, groundbreaking accomplishments such as the discovery of hydrothermal vents in the late 1970s were achieved by ocean scientists tightly packed into submersibles, peering out of small round windows into the dimly lit abyss.

Manned submersibles, although important to ocean science research, are usually not capable of reaching the deepest ocean regions. They are also costly to operate and lack the versatility and endurance of unmanned remotely operated vehicles (ROVs), which give scientists an opportunity to study and collect organisms from greater depths without the risk to human life and with less expense, time and effort. ROVs are becoming one of the primary tools for studying the biodiversity of the deepest oceanic ecosystems, and are a key technology in Census research. They are linked to a surface support RV via an umbilical cord through which scientists control the ROV’s underwater activity. This umbilical cord also supplies virtually limitless power and conveys data signals and video feed from the ROV’s sensor array to the control station aboard ship.

Text and images reprinted with permission from World Ocean Census: A Global Survey of Marine Life by Darlene Trew Crist, Gail Scowcroft and James M. Harding Jr., Firefly Books, 2009.

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