SCUBA diving is an exciting and first-hand way for scientists to study the underwater environment, and the most effective way to perform underwater experiments that require fine-scale measurements and a light touch. SCUBA literally stands for Self-Contained Underwater Breathing Apparatus meaning that the diver carries all the needed breathing equipment and gases with them, and is subject to the water temperature, pressure, currents, and other environmental factors present at their diving depth. In an average year, the NURP Program through its Centers supports approximately 10,000 SCUBA dives for scientific research.

NURP provides scientists the equipment and technical assistance to conduct diving missions using open circuit breathing apparatuses and, more recently, closed circuit breathing apparatuses. The primary difference between open circuit and closed circuit breathing apparatuses is what happens to the exhaled gas. In open circuit diving, the diver's breathing gas is exhaled directly into the water; where as, in closed circuit diving, the diver's breathing apparatus recycles the diver's exhaled breath by removing the carbon dioxide and adding oxygen to replace the consumed oxygen. By recycling the diver's breathing gas, closed circuit breathing apparatuses allow the diver to be more streamlined and reduce the amount of gas tanks required.

The primary breathing gases provided by NURP include compressed air, NITROX (gas mixtures of nitrogen and oxygen), and TRIMIX (gas mixtures of Oxygen, Nitrogen, and Helium). NITROX is of special interest to NOAA. In the late 1970's, NOAA pioneered the use of nitrogen-oxygen breathing mixtures or NITROX, which allows the diver to spend considerably more time at depth, then when breathing compressed air. Each breathing gas has different properties and allows the diver to dive to certain maximum depths. The NOAA Dive Manual (4th edition, available at http://www.ntis.gov/), produced through a collaboration between NURP and the NOAA Marine and Aviation Operations, which operates the NOAA Dive Program, offers a comprehensive review of diving equipment, breathing gas mixtures, safety, first aid, marine life, and a brief history of diving.

Click here for more info on Advanced Diving through the NOAA's Undersea Research Program.

Scientific divers that use SCUBA diving to conduct their research do have limitations that can inhibit their productivity underwater. Limiting factors such as, diving depth, gas mixtures and supply, weather, and decompression obligations can have a significant impact on the amount of time a scientist will actually have to conduct their research underwater. Saturation diving, a technique developed by the U.S. Navy in the 1950s, has proven to be useful to several scientists to extend their work time. Saturation diving works on the premise that if a diver's tissues are in equilibrium with the surrounding water, then the decompression time will not change for the length of time spent underwater. This "saturation" process takes approximately 24 hours and means that the diver needs to remain at the same depth.

The revolutionary development of undersea habitats (also known as undersea laboratories) has made "saturation" diving a reality for scientific divers. An undersea habitat is a pressurized facility that provides a living space for small teams of divers on the ocean floor that extends the depth ranges and time at depth for the divers. Divers can either undergo compression and decompression at depth in the undersea habitat or in a surface chamber.

NURP provides the ability to live and work beneath the waves in the Aquarius undersea laboratory (right), the only undersea habitat in the world devoted to science. The habitat, owned by NOAA and operated by the Southeastern & Gulf of Mexico center, is located three miles off Key Largo in 20 m (64 ft) at the base of a coral reef within the Florida Keys National Marine Sanctuary, an ideal site for studying the health of sensitive coastal ecosystems. The habitat accommodates four scientists and two technicians for missions averaging ten days. Aquarius successfully supported 80 missions between 1993 and 2003.

Through the use of occupied submersibles, scientists can be physically transported to great depths of the oceans, far beyond the physiological restrictions of wet diving on the human body. NURP makes a variety of research submersibles available. The Pisces IV and Pisces V (left) are operated by the Hawaii & West Pacific regional center. Both subs carry a pilot and two scientists. They are capable of diving to 2000 meters. The submersible is custom equipped to accommodate a variety of mission requirements. Standard gear includes external video and still cameras, two hydraulic manipulator arms, a CTD profiler and color sonar. Pisces V's mother ship is the 220 ft. RV Ka'imikai-o-Kanaloa (RV KOK).

JSL is owned and operated by the Harbor Branch Oceanographic Institution (HBOI) and leased to NURP scientists. With its fish bowl acrylic sphere, two scientists can make observations and conduct experiments at 920 m (3,000 ft) while inside the Johnson-Sea-Link (JSL) submersible.
The Delta submersible has nineteen viewing ports and can reach a depth of 335 m (1,100 ft). Owned and operated by Delta Oceanographics, the submersible is small enough to be flown by plane to research sites around the world and versatile enough to be operated from ships of opportunity.
The Alvin is a three-person deep submersible vehicle (DSV) with a depth capability of 4,500 m(14,450 ft). It is owned by the U.S. Navy, operated by the Woods Hole Oceanographic Institute (WHOI) and funded by the National Science Foundation (NSF), National Oceanographic and Atmospheric Administration (NOAA), and the Navy. Alvin has taken more than 8,300 people to the deep sea on about 4,000 dives and about 20,000 hours underwater.

Human Occupied Submersibles (left to right): Johnson Sea Link, Delta, Alvin

Rutgers University and Woods Hole Oceanographic Institution (WHOI) have developed a Long-term Ecosystem Observatory (LEO-15) that sits 15 meters deep on the inner continental shelf, six miles off the New Jersey coastline. The observatory includes numerous sensors that continuously monitor the local environment. An electro-fiber optic cable runs along the bottom of the ocean to two submerged nodes. These nodes have profiling instruments that measure temperature, salinity, and depth and are readily controlled by scientists onshore, via the Internet. LEO's website provides access to real-time data from in-situ sensors, transmitted via satellite. Since it's inception, many projects have been supported with funding from NURP, the National Science Foundation, and National Ocean Partnership Program. LEO-15 supports a broad spectrum of research sponsored by NURP's Mid-Atlantic Bight (MAB) research center.

Click here for more info on Ocean Observing Systems through NOAA's Undersea Research Program.