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Concept: Scuba diving


Monitoring temperature of aquatic waters is of great importance, with modelled, satellite and in-situ data providing invaluable insights into long-term environmental change. However, there is often a lack of depth-resolved temperature measurements. Recreational dive computers routinely record temperature and depth, so could provide an alternate and highly novel source of oceanographic information to fill this data gap. In this study, a citizen science approach was used to obtain over 7,000 scuba diver temperature profiles. The accuracy, offset and lag of temperature records was assessed by comparing dive computers with scientific conductivity-temperature-depth instruments and existing surface temperature data. Our results show that, with processing, dive computers can provide a useful and novel tool with which to augment existing monitoring systems all over the globe, but especially in under-sampled or highly changeable coastal environments.

Concepts: Scuba set, Oxygen, Nitrox, Dive computer, Underwater diving, Diving equipment, Oxygen toxicity, Scuba diving


Overfishing has dramatically depleted sharks and other large predatory fishes worldwide except for a few remote and/or well-protected areas. The islands of Darwin and Wolf in the far north of the Galapagos Marine Reserve (GMR) are known for their large shark abundance, making them a global scuba diving and conservation hotspot. Here we report quantitative estimates of fish abundance at Darwin and Wolf over two consecutive years using stereo-video surveys, which reveal the largest reef fish biomass ever reported (17.5 t [Formula: see text] on average), consisting largely of sharks. Despite this, the abundance of reef fishes around the GMR, such as groupers, has been severely reduced because of unsustainable fishing practices. Although Darwin and Wolf are within the GMR, they were not fully protected from fishing until March 2016. Given the ecological value and the economic importance of Darwin and Wolf for the dive tourism industry, the current protection should ensure the long-term conservation of this hotspot of unique global value.

Concepts: Oxygen, Pacific Ocean, Fishing, Coral reef, Scuba diving, Fish, Shark, Ecology


Oxygen uptake by the pulmonary circulation is a chemical reaction. The physicochemical attributes of oxygen are critical when studying pulmonary oxygen toxicity. Extent of lung injury depends on the percentage of oxygen in an oxygen-nitrogen mix in polybaric circumstances (Shanklin, 1969). Further change in extent of lesion follows when other gases are used in the inhalant mix instead of nitrogen (Shanklin and Lester, 1972), with oxygen at 21-100% of the mix. Comparative subatmospheric oxygen levels down to 3% in hydrogen, helium, nitrogen, argon, or sulfur hexafluoride, were run with and without ventilatory distress by the Farber (1937) model, bilateral cervical vagotomy (BCV). This yielded coherent results indicating a need to consider molecular characteristics at the atomic level. Molecular mass and size, gas viscosity, and thermal conductivity yielded no obvious correlates to lung injury. Saturation of the outer electron shells of the diluents fit the empiric data, prospectively an interaction between oxygen and nitrogen from their electronegativity and closely approximate molecular mass, size, and shape. The lesion is essentially eliminated at 7% oxygen in nitrogen. At 3% oxygen, the least lesion is found with N(2), H(2), and SF(6), all gases with incomplete outer electron shells, allowing for transient, possibly polarized, covalent bonding with oxygen as the significant minority component in the mix. Argon and helium do not interfere with oxygen. With 3% oxygen in argon without BCV, the experiments ran so long (>70hours) they were terminated once the point had been made. 3% oxygen in argon after BCV yielded a mean survival more than twice that of BCV in air, indicating a remarkable degree of nitrogen interference with oxygen in the respiratory medium of terrestrial animal life. Argon displayed other advantages for the lung compared to nitrogen. Hydrogen, nitrogen, and oxygen are diatomic molecules, a feature which does relate to the extent of lung injury, but only oxygen is paramagnetic. Magnetic effects on lesion formation were tested: [1] with ventilatory distress induced in newborn rabbits, and [2] in young adult female white mice exposed to 100% oxygen without added mechanical distress. A noninvasive model for ventilatory distress, thoracic restraint (TR), with longer mean survivals of 40-50hours, was employed rather than the Farber model. Parallel runs with TR, one subset receiving 100% oxygen in a plastic chamber resting on six strong ring magnets with measured fields up to +1200 gauss, the other plain 100% oxygen, were performed. Both subsets developed moderate metabolic acidosis with average weight losses circa 25%, but over different time courses, 82.89±4.91hours in magnetized oxygen, 55.4% longer than the 53.34±9.82hours in plain oxygen (p<0.001). The longer survival in magnetized oxygen meant extensive lung injury (99.57±0.42% pleural surface, versus 83.86±14.03%), but the rate of lesion formation was 30.89% faster in plain oxygen (1.5722% per hour) than in magnetized oxygen (1.2012% per hour), a difference significant at p<0.001. The effect of oxygen without mechanical ventilatory distress was examined in female adult white mice exposed to oxygen or magnetized oxygen. Similar survivals and weight losses were achieved. The rate of lung lesion formation was different, 1.2617% per hour in plain oxygen, 46.13% faster than 0.8634% per hour in magnetized oxygen. A variable magnetic field, with animals moving and breathing in chambers flooded with oxygen, has both systemic and pulmonary effects which alter the rate of lesion formation due to oxygen toxicity. Paramagnetic oxygen in a magnetic field influences the effect of oxygen toxicity on the lung but at these strengths of field it does not overcome significant mechanical disturbance.

Concepts: Helium, Oxygen toxicity, Nitrogen, Atom, Scuba diving, Hydrogen, Magnetism, Oxygen


The design of a diving regulator’s mouthpiece increases the risk of a temporomandibular disorder (TMD) in scuba divers. The total weight of a diving regulator is reflected directly on the temporomandibular joint, causing articular and periarticular disorders. In the current study, the prevalence of TMD in scuba divers triggered during diving certification training is investigated. We also aimed to determine the factors that lead to TMD during diving training and clarify the observation that there is an increased incidence of TMD in inexperienced divers. The study was held between 2006 and 2011. Ninety-seven divers were referred with the complaint of pain around temporomandibular area. The divers were classified according to their diving experience. Symptoms and signs of TMD were graded. Fourteen divers were diagnosed with TMD. Temporomandibular disorder was seen more frequently in inexperienced divers than in experienced divers (P = 0.0434). The most prevalent symptom was an increased effort for mouthpiece gripping. Temporomandibular joint tenderness and trigger point activation were the mostly seen physical signs. Thirteen divers had an improvement with therapy. The increased effort for stabilizing the mouthpiece is a recognized factor in TMD development. Attention must be paid to an association of scuba diving with TMDs, especially in inexperienced divers having a scuba certification training.

Concepts: Diving mask, Professional diving, Temporomandibular joint, Scuba set, Disease, Temporomandibular joint disorder, Scuba diving, Underwater diving


Australasian gannets (Morus serrator), like many other seabird species, locate pelagic prey from the air and perform rapid plunge dives for their capture. Prey are captured underwater either in the momentum (M) phase of the dive while descending through the water column, or the wing flapping (WF) phase while moving, using the wings for propulsion. Detection of prey from the air is clearly visually guided, but it remains unknown whether plunge diving birds also use vision in the underwater phase of the dive. Here we address the question of whether gannets are capable of visually accommodating in the transition from aerial to aquatic vision, and analyse underwater video footage for evidence that gannets use vision in the aquatic phases of hunting. Photokeratometry and infrared video photorefraction revealed that, immediately upon submergence of the head, gannet eyes accommodate and overcome the loss of greater than 45 D (dioptres) of corneal refractive power which occurs in the transition between air and water. Analyses of underwater video showed the highest prey capture rates during WF phase when gannets actively pursue individual fish, a behaviour that very likely involves visual guidance, following the transition after the plunge dive’s M phase. This is to our knowledge the first demonstration of the capacity for visual accommodation underwater in a plunge diving bird while capturing submerged prey detected from the air.

Concepts: Lens, Booby, Scuba diving, Sulidae, Gannets, Seabird, Australasian Gannet, Gannet


Recreational diving on coral reefs is an activity that has experienced rapidly growing levels of popularity and participation. Despite providing economic activity for many developing coastal communities, the potential role of dive impacts in contributing to coral reef damage is a concern at heavily dived locations. Management measures to address this issue increasingly include the introduction of programmes designed to encourage environmentally responsible practices within the dive industry. We examined diver behaviour at several important coral reef dive locations within the Philippines and assessed how diver characteristics and dive operator compliance with an environmentally responsible diving programme, known as the Green Fins approach, affected reef contacts. The role of dive supervision was assessed by recording dive guide interventions underwater, and how this was affected by dive group size. Of the 100 recreational divers followed, 88 % made contact with the reef at least once per dive, with a mean (±SE) contact rate of 0.12 ± 0.01 per min. We found evidence that the ability of dive guides to intervene and correct diver behaviour in the event of a reef contact decreases with larger diver group sizes. Divers from operators with high levels of compliance with the Green Fins programme exhibited significantly lower reef contact rates than those from dive operators with low levels of compliance. The successful implementation of environmentally responsible diving programmes, which focus on influencing dive industry operations, can contribute to the management of human impacts on coral reefs.

Concepts: Scleractinia, Coastal and oceanic landforms, Cnidaria, Coral, Underwater, Underwater diving, Scuba diving, Coral reef


Nasal continuous positive airway pressure (nCPAP) stabilizes the residual volume and may decrease the risk of ‘atelectotrauma’, potentially promoting lung development in neonates.

Concepts: Infant, Child development, Fetus, Scuba diving, Childbirth


High-frequency pressure oscillations created by gas bubbling through an underwater seal during bubble CPAP may enhance ventilation and aid in lung recruitment in premature infants. We hypothesized that there are no differences in the magnitude of oscillations in lung volume (ΔV) in a preterm neonatal lung model when different bubble CPAP systems are used.

Concepts: Infant, Fetus, Scuba diving, Fundamental physics concepts, Thermodynamics, Pressure, Lung, Childbirth


It has been widely believed that tissue nitrogen uptake from the lungs during breath-hold diving would be insufficient to cause decompression stress in humans. With competitive free-diving, however, diving depths have been ever increasing over the past decades.

Concepts: Decompression stop, Breathing gas, Underwater diving, Free-diving, Scuba diving


Massive tsunamis induce catastrophic disturbance in marine ecosystems, yet they can provide unique opportunities to observe the process of regeneration. Here, we report the recovery of fauna after the 2011 tsunami in northeast Japan based on underwater visual censuses performed every two months over five years. Both total fish abundance and species richness increased from the first to the second year after the tsunami followed by stabilization in the following years. Short-lived fish, such as the banded goby Pterogobius elapoides, were relatively abundant in the first two years, whereas long-lived species, such as the black rockfish Sebastes cheni, increased in the latter half of the survey period. Tropical fish species were recorded only in the second and third years after the tsunami. The body size of long-lived fish increased during the survey period resulting in a gradual increase of total fish biomass. The recovery of fish assemblages was slow at one site located in the inner bay, where the impact of the tsunami was the strongest. Apart from fish, blooms of the moon jellyfish Aurelia sp. occurred only in the first two years after the tsunami, whereas the abundances of sea cucumber Apostichopus japonicus and abalone Haliotis discus hannai increased after the second year. Although we lack quantitative data prior to the tsunami, we conclude that it takes approximately three years for coastal reef fish assemblages to recover from a heavy disturbance such as a tsunami and that the recovery is dependent on species-specific life span and habitat.

Concepts: Quantitative research, Tsunami, Scuba diving, Abundance of the chemical elements, Aurelia aurita, Abundance, Moon, Abalone