Santee, CA, United States


Santee, CA, United States
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Au W.W.L.,Hawaii Institute of Marine Biology | Houser D.S.,Biomimetica | Finneran J.J.,U.S. Navy | Lee W.-J.,Woods Hole Oceanographic Institution | And 2 more authors.
Journal of the Acoustical Society of America | Year: 2010

Arrays of up to six broadband suction cup hydrophones were placed on the forehead of two bottlenose dolphins to determine the location where the beam axis emerges and to examine how signals in the acoustic near-field relate to signals in the far-field. Four different array geometries were used; a linear one with hydrophones arranged along the midline of the forehead, and two around the front of the melon at 1.4 and 4.2 cm above the rostrum insertion, and one across the melon in certain locations not measured by other configurations. The beam axis was found to be close to the midline of the melon, approximately 5.4 cm above the rostrum insert for both animals. The signal path coincided with the low-density, low-velocity core of the melon; however, the data suggest that the signals are focused mainly by the air sacs. Slight asymmetry in the signals were found with higher amplitudes on the right side of the forehead. Although the signal waveform measured on the melon appeared distorted, when they are mathematically summed in the far-field, taking into account the relative time of arrival of the signals, the resultant waveform matched that measured by the hydrophone located at 1 m. © 2010 Acoustical Society of America.

Hooker S.K.,University of St. Andrews | Fahlman A.,Texas A&M University-Corpus Christi | Moore M.J.,Woods Hole Oceanographic Institution | Aguilar de Soto N.,University of La Laguna | And 25 more authors.
Proceedings of the Royal Society B: Biological Sciences | Year: 2012

Decompression sickness (DCS; 'the bends') is a disease associated with gas uptake at pressure. The basic pathology and cause are relatively well known to human divers. Breath-hold diving marine mammals were thought to be relatively immune to DCS owing to multiple anatomical, physiological and behavioural adaptations that reduce nitrogen gas (N 2) loading during dives. However, recent observations have shown that gas bubbles may form and tissue injury may occur in marine mammals under certain circumstances. Gas kinetic models based on measured time-depth profiles further suggest the potential occurrence of high blood and tissue N 2 tensions. We review evidence for gas-bubble incidence in marine mammal tissues and discuss the theory behind gas loading and bubble formation. We suggest that diving mammals vary their physiological responses according to multiple stressors, and that the perspective on marine mammal diving physiology should change from simply minimizing N 2 loading to management of the N 2 load. This suggests several avenues for further study, ranging from the effects of gas bubbles at molecular, cellular and organ function levels, to comparative studies relating the presence/absence of gas bubbles to diving behaviour. Technological advances in imaging and remote instrumentation are likely to advance this field in coming years. © 2011 The Royal Society.

Habran S.,University of Liège | Debier C.,Catholic University of Louvain | Crocker D.E.,Sonoma State University | Houser D.S.,BIOMIMETICA | And 3 more authors.
Marine Mammal Science | Year: 2010

Abstract: Effects of physiological processes such as gestation, lactation and nutritional stress on stable isotope ratios remain poorly understood. To determine their impact, we investigated these processes in simultaneously fasting and lactating northern elephant seals (Mirounga angustirostris). Stable carbon and nitrogen isotope values were measured in blood and milk of 10 mother-pup pairs on days 5 and 22 of lactation. As long- and short-term integrators of diet, blood cells and serum may reflect foraging data or energy reserves from late gestation and lactation, respectively. Limited changes in isotopic signatures of maternal blood over the lactating period were highlighted. Nitrogen isotope fractionation associated with mother-to-offspring transfer of nutrients was generated between mother and offspring during gestation and lactation. This fractionation was tissue and time-specific, it varied between early and late lactation from +0.6‰ to +1.3‰ in blood cells and from +1.1‰ to nonsignificant value in serum. Therefore, if pups appear to be good proxies to investigate the female trophic ecology especially for C sources, much more caution is required in using δ 15N values. Further studies are also needed to better define the relative impact of fasting and lactation on the enrichment or depletion of isotopes in different tissues. © 2010 by the Society for Marine Mammalogy.

Habran S.,University of Liège | Debier C.,Catholic University of Louvain | Crocker D.E.,Sonoma State University | Houser D.S.,BIOMIMETICA | Das K.,University of Liège
Environmental Pollution | Year: 2011

The effects of reproduction and maternal investment (i.e., milk transfer) on trace element levels remain poorly understood in marine mammals. We examined the blood dynamics of mercury (Hg) and selenium (Se) during lactation in the northern elephant seal (Mirounga angustirostris), a top predator from the North Pacific Ocean. Total Hg and Se levels were measured in whole blood and milk of 10 mother-pup pairs on days 5 and 22 of lactation. Both Hg and Se were transferred to offspring through the milk. Results suggested that the maternal transfer of Se was prominent during lactation, whereas the Hg transfer was larger during gestation. The lactation period affected Hg and Se levels in the blood of elephant seal mothers and pups. Physiological processes and their relationship to body condition should be considered carefully when interpreting trace element levels in the framework of biomonitoring. © 2010 Published by Elsevier Ltd.

Houser D.S.,Biomimetica | Dankiewicz-Talmadge L.A.,SAIC | Dankiewicz-Talmadge L.A.,University of California at San Diego | Stockard T.K.,University of California at San Diego | Ponganis P.J.,University of California at San Diego
Journal of Experimental Biology | Year: 2010

The production of venous gas emboli (VGE) resulting from altered dive behavior is postulated as contributing to the stranding of beaked whales exposed to mid-frequency active sonar. To test whether nitrogen gas uptake during repetitive breath-hold diving is sufficient for asymptomatic VGE formation in odontocetes, a bottlenose dolphin (Tursiops truncatus Montagu) was trained to perform 10-12 serial dives with 60s surface intervals to depths of 30, 50, 70 or 100m. The dolphin remained at the bottom depth for 90s on each dive. Doppler and/or two-dimensional imaging ultrasound did not detect VGE in the portal and brachiocephalic veins following a dive series. Van Slyke analyses of serial, post-dive blood samples drawn from the fluke yielded blood nitrogen partial pressure (PN2) values that were negligibly different from control samples. Mean heart rate (HR; ±1 s.d.) recorded during diving was 50±3 beats min-1 and was not significantly different between the 50, 70 and 100 m dive sessions. The absence of VGE and elevated blood P N2 during post-dive periods do not support the hypothesis that N 2 supersaturation during repetitive dives contributes to VGE formation in the dolphin. The diving HR pattern and the presumed rapid N 2 washout during the surface-interval tachycardia probably minimized N2 accumulation in the blood during dive sessions.

Schecklman S.,Portland State University | Houser D.,Biomimetica | Cross M.,Biomimetica | Hernandez D.,HLS Research 3366 North Torrey Pines Court | Siderius M.,Portland State University
Marine Environmental Research | Year: 2011

Concern about the impact of sound on marine mammals has increased over the last decade, causing governments to take a more rigorous look at the potential impact of activities that introduce sound into the ocean. Environmental Impact Statements (EIS's) can be prepared using differing analysis methods to estimate the impact on marine mammals. To assess consistency in assessment methods, differences in the base assumptions were investigated; in particular, differences that arise between assumptions of dynamic marine mammals (animat method) and static distributions of marine mammals (static distribution method). Using several ocean environment scenarios and species, it is demonstrated that differences consistently arise between the two methods. The static distribution method underestimates the number of behavioral harassments compared with the animat method. Repeating many simulations with the animat method provides a robust risk assessment, provides a measure of variability, and allows the probability of " spurious events" to be estimated. © 2011 Elsevier Ltd.

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