| Exploration of deep aquatic environments (>30 m) has typically been constrained due to the principles of physics, human physiology, and available technology. Diving to these depths, a person can expect concomitant alterations in the respiratory, circulatory, musculoskeletal, and nervous systems, due to the changing physical parameters with increasing depth. However, several technological advances allow us to partially overcome these physiological obstacles or avoid them altogether by providing ways to explore the oceanic environment from the surface or under constant atmospheric pressure. The most commonly used technologies to explore mesophotic coral ecosystems are discussed below. |
Scientific diving
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Open-circuit SCUBA Used by 34 people in database (e.g. Renato Ferreira, Nicolas Alvarado, Ivonne Bejarano) |  |
| Open-circuit SCUBA provides a gas mixture for a diver to breath with the gas exhaled as bubbles to the environment. It allows for direct observation of communities at mesophotic depths with high dexterity for sampling and recording of data. Advances in gas mixtures, such as Nitrox and Trimix, have allowed for safer operation than air, shortened decompression times, and extension of depth limits. Disadvantages are very limited bottom times, adverse effects of gases on physiology, hypothermia and pressure-related complications. | ||
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Rebreathers (CCR / SCCR) Used by 28 people in database (e.g. ophir lvn, Peter Auster, Greg McFall) |  |
| As opposed to open-circuit SCUBA, exhaust gas consisting of unused oxygen and waste carbon-dioxide is not (constantly) exhaled into the environment, but is rather recycled through a breathing loop conserving oxygen and scrubbing waste gas. There are three main types: semi-closed, closed, and oxygen, which differ in the manner of adding gas to the loop and controlling oxygen concentration. Rebreathers offer the same advantage as open-circuit SCUBA with regards to dexterity, but on top of that offer extended bottom times, ability to reach greater depths, accelerated decompression and reduced bubbles that might frighten certain biota. Disadvantages are increased risk of oxygen toxicity and hypoxia and larger costs. | ||
Other diving techniques: Surface supplied (SSBA or Hooka), Saturation diving
Unmanned underwater vehicles
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Autonomous Underwater Vehicles (AUV) Used by 16 people in database (e.g. John Rooney, Renato Ferreira, Sara Rivero-Calle) |  |
| AUVs operate independent from the surface and are preprogrammed to conduct a variety of tasks like video, water measurements and other surveys. They are able to cover large areas underwater (due to the absence of a tether) and are ideal for benthic survey studies. Disadvantages are that this method is indirect, the program cannot be altered in route, results are not observed in real time and the limited battery life. | ||
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Remotely Operated Vehicles (ROV) Used by 21 people in database (e.g. Richard Appeldoorn, Sam Kahng, Sara Rivero-Calle) |  |
| ROVs are essentially robots tethered to a topside operator who can control video recording, collect samples and other tasks. They provide real time observation, can be small enough to maneuver in tight spaces, greatly extend bottom time, eliminate human risk, can be deployed in rough sea conditions, and are more affordable than other options. Disadvantages are that the observation is still indirect, collection is limited to the ability of the mechanics and movement is controlled by the reach of the tether. | ||
Other unmanned technology: Underwater towed video, Underwater drop camera
Manned underwater vehicles
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Submersibles Used by 15 people in database (e.g. Marcos Rosa, Gregory Boland, Pat Colin) | |
| Submersibles allow for direct human observation and research at depth without the restrictions and safety concerns of wet diving. They can dive to depth deeper and longer than any wet dive. Disadvantages are that collection is limited to the ability of the mechanics, larger size and the large costs involved. | ||
Other manned underwater vehicles: Atmospheric diving suit (ADS)