Bottom Time Research Articles

Linking marine predator diving behavior to local prey fields in contrasting habitats in a subarctic glacial fjord

lower percent bottom time, and generally traveled further to forage. The increased diving effort for seals from the glacial ice site corresponded to lower prey densities and prey at deeper depths at the glacial ice site. In contrast, seals captured at terrestrial sites dived shallower, had shorter dive durations, higher percent bottom time, and traveled shorter distances to access foraging areas with much higher prey densities at shallower depths. The increased diving effort for seals from glacial ice sites suggests that the lower relative availability of prey may be offset by other factors, such as the stability of the glacial ice as a resting platform and as a refuge from predation. We provide evidence of differences in prey accessibility for seals associated with glacial ice and terrestrial habitats and suggest that seals may balance trade-offs between the costs and benefits of using these habitats.

Estimates of the bottom reflection coefficient involving vector sensor

Estimates of the bottom reflection coefficient made in the frequency range of 4–8 kHz, as part of the Targets Reverberation Experiment (TREX) are presented. The TREX experiment took place in the Gulf of Mexico, near Panama City, FL, in waters 20 m deep. At the measurement site the sediments are loosely classified as fine sand. The reflection coefficient R is estimated over the nominal grazing angular range 1 to 20 deg., using measurements made at ranges 50 to 800 m and received on a vertical line array (length 1.6 m). The arrival time and magnitude of the bottom reflection is determined by the matched filtered output of a frequency modulated signal, 4–8 kHz. In addition, the match filter processing technique is applied to the vector sensor data (measured simultaneously and co-located with the line array.) This allows for an extraction of the active intensity contribution associated with the bottom reflection, and provides a vector intensity-based estimate of the bottom reflection coefficient. The estimates of the bottom reflection arrival time are also used to time-gate simultaneously transmitted cw tones (1–4 kHz) to analyze the Lloyd’s mirror pattern associated with seabed reflection. [Research supported by ONR, with partial support from ONRG.]

Investigating the relationship between foraging odontocetes and ocean acoustic biomass off the Kona coast of the Island of Hawaii

To understand the distribution of deep diving odontocetes, it is important to investigate the relationship between foraging whales and their prey. Tagged sperm whales have been documented to dive as deep as 1202 m. Short-finned pilot whales in Hawaii dive deeper during the day down to 600–800 m and shallower dives at night, driven possibly by the migration of organisms at night. Foraging sperm and pilot whales off the Island of Hawaii were located using a hydrophone array detecting echolocation clicks. A 500 m by 500 m active acoustics survey box was set up over two foraging sites: one during the night above foraging sperm whales and one during the day over foraging pilot whales. A four-frequency (38, 70, 120, and 200 kHz) split-beam echosounder collected acoustic data over foraging populations and non-foraging control sites of a similar bottom depth and time. The Nautical Acoustic Scattering Coefficient (NASC) or acoustic biomass (m2nmi−2) profile over the complete water column was statically compared over foraging and non-foraging populations to analyze the relationship between foraging and ocean biomass.

Observations of the Alaskan Stream near Samalga Pass and its connection to the Bering Sea: 2001–2004

Year-long moorings were deployed across the Alaskan Stream near Samalga Pass (169°W) on two occasions, first in 2001–2002 (5 moorings) and again in 2003–2004 (3 moorings). Currents were measured throughout the water column, and temperature and salinity were measured at selected depths. Satellite altimetry and satellite-tracked drifters revealed a well defined Alaskan Stream, with the largest near-surface average speeds (>60cms−1) and highest eddy kinetic energy just upstream from the mooring sites. Excluding periods when large eddies disrupted the flow, transport in the Alaskan Stream ranged from 10 to 30×106m3s−1. The estimated mean transport in 2001–2002 was 19×106m3s−1, and in 2003–2004 was 21×106m3s−1. Large (diameter>200km), anti-cyclonic eddies were not uncommon in the vicinity of Samalga Pass (14 times in 20 year period, 1992–2012). Although there were no such eddies observed during the period 2000–2003, one of the largest ever recorded eddies occurred in spring 2004. In addition, smaller eddies occurred on several occasions. Eddies disrupted the flow, shifting the Alaskan Stream farther off shore and were clearly evident in both the satellite imagery and the mooring data. Other energetic events, which were less evident in the satellite records, but clearly evident in the mooring measurements, also disrupted the flow. In addition to the moorings in the Alaskan Stream, pressure gauges were placed in Samalga Pass and a single mooring measuring currents was placed in the Aleutian North Slope Current (ANSC) in the Bering Sea. The alongshore, near-surface flow measured at the moorings deployed on the 1000-m isobaths in the Alaskan Stream and the ANSC were significantly correlated with the bottom pressure time series. In addition, at periods longer than 14 days, the bottom pressure measured at the mooring sites in Samalga Pass was significantly correlated with the sea surface height measured by the satellites. The eddy kinetic energies measured from the satellites and from moorings were also significantly correlated.

Interannual variation in the at‐sea behavior of California sea lions (Zalophus californianus)

AbstractTo be successful, marine predators must alter their foraging behavior in response to changes in their environment. To understand the impact and severity of environmental change on a population it is necessary to first describe typical foraging patterns and identify the underlying variability that exists in foraging behavior. Therefore, we characterized the at‐sea behavior of adult female California sea lions (n = 32) over three years (2003, 2004, and 2005) using satellite transmitters and time‐depth recorders and examined how foraging behavior varied among years. In all years, sea lions traveled on average 84.7 ± 11.1 km from the rookery during foraging trips that were 3.2 ± 0.3 d. Sea lions spent 42.7% ± 1.9% of their time at sea diving and displayed short (2.2 ± 0.2 min), shallow dives (58.5 ± 8.5 m). Among individuals, there was significant variation in both dive behavior and movement patterns, which was found in all years. Among years, differences were found in trip durations, distances traveled, and some dive variables (e.g., dive duration and bottom time) as sea lions faced moderate variability in their foraging habitat (increased sea‐surface temperatures, decreased upwelling, and potential decreased prey abundance). The flexibility we found in the foraging behavior of California sea lions may be a mechanism to cope with environmental variability among years and could be linked to the continuing growth of sea lion populations.

Effect of Bottom Blowing Time and Bottom Blowing Rate on the Nitrogen Content of High Nitrogen Steel

The Cr18 - Mn18 steel was prepared by the high temperature and high pressure reaction kettle. With bottom blowing time and bottom blowing flow as object to do single factor experiment, the relationship between the nitrogen content in steel smelting process and the bottom blowing time, the bottom blowing flow were studied.The research results show that when the other conditions must be, the nitrogen content in steel increases with the bottom blowing time increasing gradually, when the bottom blowing time reach more than 35 min, the variation of nitrogen content in steel decreases. With the increase of bottom blowing flow rate, the nitrogen content in steel increases gradually, when the bottom blowing flow rate reaches more than 0.24 m3/h, the nitrogen content in steel close to the maximum value and does not change with bottom blowing flow rate.

Supervised accelerometry analysis can identify prey capture by penguins at sea.

Determining where, when and how much animals eat is fundamental to understanding their ecology. We developed a technique to identify a prey capture signature for little penguins from accelerometry, in order to quantify food intake remotely. We categorised behaviour of captive penguins from HD video and matched this to time-series data from back-mounted accelerometers. We then trained a support vector machine (SVM) to classify the penguins' behaviour at 0.3 s intervals as either 'prey handling' or 'swimming'. We applied this model to accelerometer data collected from foraging wild penguins to identify prey capture events. We compared prey capture and non-prey capture dives to test the model predictions against foraging theory. The SVM had an accuracy of 84.95±0.26% (mean ± s.e.) and a false positive rate of 9.82±0.24% when tested on unseen captive data. For wild data, we defined three independent, consecutive prey handling observations as representing true prey capture, with a false positive rate of 0.09%. Dives with prey captures had longer duration and bottom times, were deeper, had faster ascent rates, and had more 'wiggles' and 'dashes' (proxies for prey encounter used in other studies). The mean (±s.e.) number of prey captures per foraging trip was 446.6±66.28. By recording the behaviour of captive animals on HD video and using a supervised machine learning approach, we show that accelerometry signatures can classify the behaviour of wild animals at unprecedentedly fine scales.

Environmental influences on the at-sea behaviour of a major consumer,Mirounga leonina, in a rapidly changing environment

Understanding the distribution and foraging ecology of major consumers within pelagic systems, specifically in relation to physical parameters, can be important for the management of bentho-pelagic systems undergoing rapid change associated with global climate change and other anthropogenic disturbances such as fishing (i.e., the Antarctic Peninsula and Scotia Sea). We tracked 11 adult male southern elephant seals (Mirounga leonina), during their five-month post-moult foraging migrations from King George Island (Isla 25 de Mayo), northern Antarctic Peninsula, using tags capable of recording and transmitting behavioural data and in situ temperature and salinity data. Seals foraged mostly within the Weddell–Scotia Confluence, while a few foraged along the western Antarctic Peninsula shelf of the Bellingshausen Sea. Mixed model outputs suggest that the at-sea behaviour of seals was associated with a number of environmental parameters, especially seafloor depth, sea-ice concentrations and the temperature structure of the water column. Seals increased dive bottom times and travelled at slower speeds in shallower areas and areas with increased sea-ice concentrations. Changes in dive depth and durations, as well as relative amount of time spent during the bottom phases of dives, were observed in relation to differences in overall temperature gradient, likely as a response to vertical changes in prey distribution associated with temperature stratification in the water column. Our results illustrate the likely complex influences of bathymetry, hydrography and sea ice on the behaviour of male southern elephant seals in a changing environment and highlight the need for region-specific approaches to studying environmental influences on behaviour.Keywords: Southern elephant seals; foraging ecology; satellite-relay data loggers; King George Island; Isla 25 de Mayo; at-sea behaviourTo access the supplementary material for this article, please see the supplementary files in the column to the right (under Article Tools).(Published: 26 November 2014)Citation: Polar Research 2014, 33, 23808, http://dx.doi.org/10.3402/polar.v33.23808

Changes in diversity and assemblages of foraminifera through the Holocene in an atoll from the Maldives, Indian Ocean

Abstract This study presents the first high-resolution Holocene records of diversity and assemblages of benthic foraminifera from tropical reef environments in the Indian Ocean. Two 3.2 m and 4.4 m long cores from the lagoon of Rasdhoo Atoll (4°N/73°W) in the central Maldives, were sampled at ~ 250 yr intervals. Core #16 covers most of the Holocene (10.32–0 kyr BP) and was taken in the deep lagoon of the atoll (35 m water depth). Core #19 covers the time span 7.375–0 kyr BP and is from a sublagoon (14 m water depth) on the northern margin of the atoll. In Core #16, an early colonization phase during Holocene sea-level rise is characterized by an Ammonia sp. 1 dominated assemblage until ~ 7 kyr BP. The slowdown of sea-level rise in the Mid Holocene (~ 4 kyr BP) marks the onset of a phase of stable environmental conditions in the deep lagoon with high diversity. A shift toward lower diversity and the dominance of Textularia foliacea has occurred from ~ 4–1 kyr BP, which may be explained with the Intermediate Disturbance Hypothesis. An environmental change at ~ 1.4 kyr has caused a distinct faunal change, the decrease of T. foliacea and an increased recovery in diversity. In Core #19, a significant faunal change at ~ 4.0 kyr BP from an Ammonia sp. 2 dominated fauna to a fauna with Ammonia sp. 1, miliolid taxa and a higher diversity might be related to the formation of a sand spit that separates the sublagoon from the main lagoonal basin. The westward extension of the sand spit during the Late Holocene could have changed the restricted bottom water circulation in the main lagoon and caused longer residence times of water and the build-up of lower oxygen and higher nutrient concentrations. This study underlines the importance of the factor time on diversity and the significance of lagoon circulation and bottom water residence times on assemblages and diversity of benthic foraminifera.

Size and experience matter: diving behaviour of juvenile New Zealand sea lions (Phocarctos hookeri)

The diving ability of juvenile animals is constrained by their physiology, morphology and lack of experience, compared to adults. We studied the influences of age and mass on the diving behaviour of juvenile (2–3-year-old females, n = 12; 3–5-year-old males, n = 7) New Zealand (NZ) sea lions (Phocarctos hookeri) using time–depth recorders (TDRs) from 2008 to 2010 in the NZ subantarctic Auckland Islands. Diving ability (e.g. dive depth, duration and bottom time per dive) improved with age and mass. However, the percentage of each dive spent at the bottom, along with percentage time at sea spent diving, was comparable between younger and lighter juveniles and older and heavier juveniles. These suggest that younger and older juveniles expend similar foraging effort in terms of the amount of time spent underwater. Only, 5-year-old male juveniles dove to adult female depths and durations and had the highest foraging efficiency at depths >250 m. It appears that juvenile NZ sea lions attain adult female diving ability at around 5 years of age (at least in males), but prior to this, their performance is limited. Overall, the restricted diving capabilities of juvenile NZ sea lions may limit their available foraging habitat and ability to acquire food at deeper depths. The lower diving ability of juvenile NZ sea lions compared to adults, along with juvenile-specific constraints, should be taken into consideration for the effective management of this declining, nationally critical species.

Effect of a single, open-sea, air scuba dive on human micro- and macrovascular function

Previous studies have shown that bubble formation induced endothelial damage on conduit arteries. We aim to evaluate the effect of diving on microvascular and macrovascular function. Nine divers took part in a SCUBA dive at 30msw (400kPa), for 30min of bottom time. Pre- and post-dive, they underwent an assessment of endothelial-dependent (acetylcholine) and endothelial-independent (sodium nitroprusside) microvascular function (laser Doppler flowmetry), as well as endothelial-dependent (flow-mediated dilation) and endothelial-independent (nitroglycerin-mediated dilation) function. Bubble grades were monitored with Doppler according to the Spencer grade. The mean KISS bubble score ranged from 21.10±4.7 at rest to 55.03±8.8 after knee flexion. The increase in cutaneous vascular conductance elicited by either acetylcholine (25.34±6.71 to 7.63±1.25%, p=0.021) or sodium nitroprusside (35.24±8.75 to 7.61±1.86%, p=0.017) was significantly reduced after diving. Similarly, both flow-mediated dilation (10.8±0.9 to 5.4±1.5%, p=0.002) and nitroglycerin-mediated dilation (15±1.1 to 6.5±1.6%, p=0.002) were also significantly decreased. There were no correlations between vascular parameters and bubble formation. There appears to be a reduction in endothelium-dependent and endothelium-independent, macro- and microvascular function associated with diving. Our results suggest that in the process of vascular dysfunction during diving, functional changes in the vessel wall may not be limited to the endothelium and may be mediated by alterations in vascular smooth muscle.

Influence of Repeated Daily Diving on Decompression Stress

Acclimatization (an adaptive change in response to repeated environmental exposure) to diving could reduce decompression stress. A decrease in post-dive circulating venous gas emboli (VGE or bubbles) would represent positive acclimatization. The purpose of this study was to determine whether four days of daily diving alter post-dive bubble grades. 16 male divers performed identical no-decompression air dives on 4 consecutive days to 18 meters of sea water for 47 min bottom times. VGE monitoring was performed with transthoracic echocardiography every 20 min for 120 min post-dive. Completion of identical daily dives resulted in progressively decreasing odds (or logit risk) of having relatively higher grade bubbles on consecutive days. The odds on Day 4 were half that of Day 1 (OR 0.50, 95% CI: 0.34, 0.73). The odds ratio for a >III bubble grade on Day 4 was 0.37 (95% CI: 0.20, 0.70) when compared to Day 1. The current study indicates that repetitive daily diving may reduce bubble formation, representing a positive (protective) acclimatization to diving. Further work is required to evaluate the impact of additional days of diving and multiple dive days and to determine if the effect is sufficient to alter the absolute risk of decompression sickness.

Dissociating the effects of habituation, black walls, buspirone and ethanol on anxiety-like behavioral responses in shoaling zebrafish. A 3D approach to social behavior

Understanding the different patterns of anxiety-like behavioral responses is of great interest for pharmacological and genetic research. Here we report the effects of 3.5-hr habituation, buspirone and ethanol on those responses in shoaling zebrafish (Danio rerio). Since in these experiments we used a container with white walls, the effects of black-vs.-white walls were tested in a separate experiment. An important objective was to determine whether factors unrelated to anxiety played a role in modulating the responses. The anxiety-like behavioral responses studied here are social cohesion, distance from bottom and bottom-dwell time, radial distribution (to study thigmotaxis), transparent-wall preference (to study escape responses), locomotion and freezing. The experimental conditions yielded distinctly different response patterns. Thigmotaxis was the most obvious response to white walls and it was significantly reduced after 3.5-hr habituation. It was not affected by any of the drugs. The reduction of social cohesion after 3.5-hr habituation and in the 0.5% ethanol group was probably the most interesting effect seen in this study. A role of anxiety herein was suggested but could not be established with certainty. Other hypotheses were also discussed. The large increase of distance-from-bottom resulting in swimming close to the water surface, which occurred in both buspirone groups and in the 0.5%-ethanol group, is most likely not an anxiolytic response, because of the discrepancy with the in the literature well-established time-course and the absence of any effect of 3.5-hr habituation or black walls on vertical measures. Finally, locomotion and duration freezing could not be specifically taken as indicators for the state of anxiety and the results concerning transparent-wall preference were not sufficient clear. We conclude that the neuronal and ethological mechanisms underlying the effects of habituation, white-aversion, buspirone and ethanol on anxiety-like behavioral responses are complex and need further exploration.

Integrative modelling of animal movement: incorporatingin situhabitat and behavioural information for a migratory marine predator

A fundamental goal in animal ecology is to quantify how environmental (and other) factors influence individual movement, as this is key to understanding responsiveness of populations to future change. However, quantitative interpretation of individual-based telemetry data is hampered by the complexity of, and error within, these multi-dimensional data. Here, we present an integrative hierarchical Bayesian state-space modelling approach where, for the first time, the mechanistic process model for the movement state of animals directly incorporates both environmental and other behavioural information, and observation and process model parameters are estimated within a single model. When applied to a migratory marine predator, the southern elephant seal (Mirounga leonina), we find the switch from directed to resident movement state was associated with colder water temperatures, relatively short dive bottom time and rapid descent rates. The approach presented here can have widespread utility for quantifying movement-behaviour (diving or other)-environment relationships across species and systems.

The emulsified perfluorocarbon Oxycyte improves spinal cord injury in a swine model of decompression sickness

A prospective, animal model for pharmacological intervention of decompression sickness (DCS), including spinal cord (SC) injury. Signs and symptoms of DCS can include joint pain, skin discoloration, cardiopulmonary congestion and SC injury; severity ranges from trivial to fatal. Non-recompressive therapy for DCS may improve time-to-treatment and therefore impact mortality and morbidity. Oxycyte at 5 cc kg(-1) provides both SC protection and statistically significant survival benefit in a swine model of DCS. The purpose of this study was to test whether a reduced dose of Oxycyte (3 cc kg(-1)) would provide similar benefit. Silver Spring, MD, USA METHODS: Male Yorkshire swine (N=50) underwent a non-linear compression profile to 200 fsw (feet of sea water), which was identical to previous work using the 5 cc kg(-1) dose of Oxycyte. After 31 min of bottom time, decompression was initiated at 30 fsw per minute until surface pressure was reached. Following decompression and the onset of DCS, intravenous Oxycyte or saline was administered with concurrent 100% O(2) for 1 h. The primary end point was DCS-induced mortality, with Tarlov score and SC histopathology as secondary end points. Oxycyte administration of 3 cc kg(-1) following surfacing produced no significant detectable survival benefit. Animals that received Oxycyte, however, had reduced SC lesion area. Further studies to determine the lowest fully efficacious dose of Oxycyte for the adjunct treatment of DCS are warranted.

Caffeine neuroprotects against dexamethasone-induced anxiety-like behaviour in the Zebrafish (Danio rerio)

The early-life stress has critical impact on brain development which can lead to long-term effects on brain functions during adulthood. It has been reported that caffeine possesses a protective effect in neurodegenerative diseases. Thus, this study investigates the potential of caffeine to protect brain functions from adverse effects due to stress exposure during early-life development in the male zebrafish. In the first part of this study, synthetic glucocorticoid, dexamethasone (DEX) (2–200mg/L for 24h) was used to induce stress effects in the zebrafish larvae from 4 to 5days post-fertilisation (dpf) and the effect of DEX administration on zebrafish larvae on anxiety-like behaviour during adulthood in novel tank test was investigated. Next, the possible protective effect of caffeine pre-treatment (5–50mg/L for 24h from 3 to 4dpf) before DEX administration was studied. DEX-treated adult male zebrafish showed higher anxiety levels in behavioural tests, as seen in longer latency to enter the top part of the tank, lower transition numbers between the top and bottom parts with more time spent at the bottom and lesser time spent at the top and lower distance travelled at top part. The effect of DEX on anxiety-like behaviour was dose-dependent. Importantly, adult male zebrafish pre-treated with caffeine before DEX treatment did not show any anxiety-like behaviour. These results show that exposure to stress during early-life leads to anxiety-like behaviour in the adult male zebrafish but pre-treatment with caffeine protects from stress-induced anxiety.

Depletion of deep marine food patches forces divers to give up early

Many optimal foraging models for diving animals examine strategies that maximize time spent in the foraging zone, assuming that prey acquisition increases linearly with search time. Other models have considered the effect of patch quality and predict a net energetic benefit if dives where no prey is encountered early in the dive are abandoned. For deep divers, however, the energetic benefit of giving up is reduced owing to the elevated energy costs associated with descending to physiologically hostile depths, so patch residence time should be invariant. Others consider an asymptotic gain function where the decision to leave a patch is driven by patch-depletion effects - the marginal value theorem. As predator behaviour is increasingly being used as an index of marine resource density and distribution, it is important to understand the nature of this gain function. We investigated the dive behaviour of the world's deepest-diving seal, the southern elephant seal Mirounga leonina, in response to patch quality. Testing these models has largely been limited to controlled experiments on captive animals. By integrating in situ measurements of the seal's relative lipid content obtained from drift rate data (a measure of foraging success) with area-restricted search behaviour identified from first-passage time analysis, we identified regions of high- and low-quality patches. Dive durations and bottom times were not invariant and did not increase in regions of high quality; rather, both were longer when patches were of relatively low quality. This is consistent with the predictions of the marginal value theorem and provides support for a nonlinear relationship between search time and prey acquisition. We also found higher descent and ascent rates in high-quality patches suggesting that seals minimized travel time to the foraging patch when quality was high; however, this was not achieved by increasing speed or dive angle. Relative body lipid content was an important predictor of dive behaviour. Seals did not schedule their diving to maximize time spent in the foraging zone in higher-quality patches, challenging the widely held view that maximizing time in the foraging zone translates to greater foraging success.

Differences in Diving Behaviour Optimality May Cause Differences in Reproductive Success in Chinstrap Penguins: A Cases Study

Bio-logging is a useful technique for obtaining information on foraging behaviour, physiology, and environ- mental conditions from animals in marine ecosystems. By integrating this information, researchers can investigate the ecology of general prey-predator system in terms of their behaviour with the help of theoretical models. In the present study, I analyse the diving behaviour of two chinstrap penguins using an index of diving behaviour optimality as a case study. Because of small sample size in the study, I demonstrate possibility to prove the association between calcu- lated optimality index and breeding success in birds and how it basically would be possible if more individuals would be included in analyses. This index is the proportion of observed dive time to standard dive time. Standard dive time is de- fined as an optimal dive time that maximises the proportion of bottom time to the duration of a dive cycle for a given travel time. Using this index, I found a difference in the optimality of diving behaviour and prey conditions experienced between birds, which may cause differences in chick growth rate. Because many dives have already been recorded using bio-logging techniques, using this index to analyse diving behaviour could give new insights into the foraging ecology of top predators in marine ecosystems.

Pseudomonas aeruginosa produce autoantibodies against HSP60 in rats

Skin and ear infections, primarily caused by Pseudomonas aeruginosa (P. aeruginosa) are recurrent problems for saturation divers, while infections caused by P. aeruginosa are seldom observed in healthy people outside saturation chambers. Cystic fibrosis (CF) patients suffer from pulmonary infections by P. aeruginosa and it has been demonstrated that CF patients have high levels of anti‐HSP60 compared to controls, probably induced by P. aeruginosa. The present study investigated whether rats immunized with P. aeruginosa produced autoantibodies against their own HSP60 and whether diving influenced the level of circulating anti‐ HSP60 antibodies.MethodsRats were randomly assigned to one of three groups. Group 1 and 3 were immunized with P. aeruginosa, every other week. Groups 2 and 3 were exposed to simulated air dives to 400 kPa (4 ata) with 45 min bottom time, every week for seven weeks. The amount of anti‐HSP60 rat antibodies in the serum was analyzed by ELISA.ResultsThe immunized rats showed a significant increase in the level of autoantibodies against HSP60, while no autoantibodies were detected in the dived rats. The rats both immunized and dived show no significant increase in circulating autoantibodies against HSP60. A possible explanation may be that HSP60 is expressed during diving and that cross reacting antibodies are bound.

Concentration of circulating autoantibodies against HSP 60 is lowered through diving when compared to non-diving rats

ObjectiveSkin and ear infections, primarily caused by Pseudomonas aeruginosa (P. aeruginosa), are recurrent problems for saturation divers, whereas infections caused by P. aeruginosa are seldom observed in healthy people outside saturation chambers. Cystic fibrosis (CF) patients suffer from pulmonary infections by P. aeruginosa, and it has been demonstrated that CF patients have high levels of autoantibodies against Heat shock protein 60 (HSP60) compared to controls, probably due to cross-reacting antibodies induced by P. aeruginosa. The present study investigated whether rats immunised with P. aeruginosa produced autoantibodies against their own HSP60 and whether diving influenced the level of circulating anti-HSP60 antibodies.MethodsA total of 24 rats were randomly assigned to one of three groups (‘immunised’, ‘dived’ and ‘immunised and dived’). The rats in group 1 and 3 were immunised with the bacteria P. aeruginosa, every other week. Groups 2 and 3 were exposed to simulated air dives to 400 kPa (4 ata) with 45 min bottom time, every week for 7 weeks. Immediately after surfacing, the rats were anaesthetised and blood was collected from the saphenous vein. The amount of anti-HSP60 rat antibodies in the serum was analysed by enzyme linked immunosorbent assay.ResultsThe immunised rats (group 1) showed a significant increase in the level of autoantibodies against HSP60, whereas no autoantibodies were detected in the dived rats (group 2). The rats both immunised and dived (group 3) show no significant increase in circulating autoantibodies against HSP60. A possible explanation may be that HSP60 is expressed during diving and that cross-reacting antibodies are bound.