Deep-water Macroalgal and Seagrass Assemblages

Submersibles

The Hawai'i Underwater Research Laboratory (HURL) has access to two deep-diving submersibles, Pisces V and Pisces IV.  These battery-powered vehicles can hold up to three people (usually a submersible pilot and two scientists) and can operate up to a maximum depth of 2000 meters (6,280 feet).  Submersibles, such as the Pisces V and Pisces IV, enable scientists to observe and describe the deep sea using a variety of methods: through multiple view ports, video records, sample collecting, and environmental monitoring (temperature, salinity, etc.).

A Pisces submersible weighs 13 tons and has a payload of 600 pounds.  Their personnel spheres are 7 feet each in diameter and are made of HY 100 steel, which allows the spheres to maintain 1 atmosphere of pressure at depths of at least 6,200 feet.  Two side-mounted reversible thrusters allow the pilot to maneuver at speeds up to 2 knots.  Both submersibles are also equipped with three digital cameras, one of which is a special low-light black and white camera that allows deep environments (up to 1000 feet)  to be evaluated under natural light conditions, as well as two manipulator arms each.

A typical dive may last from 6 to 10 hours but the submersibles have emergency life support for its three-person crew for 5 days.  The Pisces V and Pisces IV are launched from and recovered by their support vessel, the R/V Ka'imikai-o-Kanaloa, during only daylight hours.  At night, they are serviced in the submersible hangar.  Normally, one submersible is on board the support vessel to conduct science dives while the other remains in 'ready' status in case of an emergency.

Remotely Operated Vehicles (ROVs)

Remotely operated vehicles (ROVs) are underwater robots that are unoccupied and highly maneuverable.   They are connected to a surface vessel by a group of cables that carry electrical signals back and forth between a human operator and the vehicle.  The operator uses a joystick, a camera control, and a video monitor to move the vehicle and its camera to desired locations.

ROVs may be as small as a bread box to as large as a small truck.  These vehicles often have four thrusters that allow for horizontal, lateral, or vertical movement.  Two horizontally mounted thrusters allow the vehicle to move forward and backward, and to turn left and right.  Two thrusters mounted at an angle, slanted in opposite directions, provide vertical thrust and lateral thrust.  While most ROVs have at least a video camera and lights, they may also be equipped with a manipulator or cutting arm, water samplers, and instruments that measure water clarity, light penetration, and temperature.

The vehicles may be deployed either by simply dropping the ROV over the side of a small boat or by lowering the ROV in a "garage" to the bottom.  In the case of the "garage," the ROV leaves it to explore and then returns when its mission is completed.  To recover a deployed ROV on the R/V Ka'imikai-o-Kanaloa, large winches for lifting and A-frames to swing the ROV back on deck are used.

Submersible and ROV Images

Pisces V	Pisces V  being launched	Pisces V
Pisces IV ready to launch	ROV, RCV-150	ROV launch