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INTRODUCTION In humans, and other terrestrial animals, acoustic and non-acoustic detrimental effects of noise have been described long ago. In recent years there is an increased interest in the damaging consequences of acoustic pollution to marine life. The general increase in underwater noise and the use of sonar are associated with pathological changes in diving mammalians exposed to those environments. The use of high-intensity sonar is associated with stranding and acute death of whales. So, sonar activity per se may induce bubble formation similar to decompression sickness (DCS) or direct tissue disruption in diving mammals e.g. in proximity of high intensity sonars. Signs of DCS observed in stranded cetaceans exposed to the mid-range sonar activity may result from accelerated ascent from deep water after being affected by the sonar. We postulate that sonar, and intense noise, may disrupt sensorineural mechanisms affecting the behavior of diving cetaceans. We also propose that the effects of noise at frequency may be enhanced during deep diving due to a synergistic combination of the adaptive response of the central nervous system (CNS) at high pressure. The echolocation system of cetaceans (mostly demonstrated in odontocetes), in contrast with that of bats, lacks of automatic gain-control on the receiver (ear). So, to compensate for propagation loss, or to protect the ear, cetaceans have to automatically adjust the emission (their output vocal click signal) as they approach the target. Because of this feature intense noise may damage the ears resulting in functional impairment disabling their echolocation system. Failure of echolocation during deep-dive may lead to disorientation, speed up ascent from the depth, and DCS. If brain function is affected the autonomic nervous system may be dysfunctional, impairing preventive maneuvers that impede gas diffusion during the dive response (redistribution of pulmonary blood flow producing bubbles formation. Non-auditory effects of noise in humans involve annoyance disruption of short-term memory acquisition and maintenance of ordered information, disturbed auditory verbal processing, and diminished attention span. Moreover, high intensity noise may elicit startle response or even severe fear or a panic disrupting the diving response of cetacean. The effects of noise may be enhanced at high pressure because of CNS adaptive mechanisms. Humans and experimental animals exposed to deep-diving high pressure experience the high pressure nervous syndrome (HPNS) characterized by hyperexcitability of the CNS, cognitive disturbance, and eventually epilepsy-like seizures. Auditory stimuli as noise or rhythmic activity may eventually induce epileptic seizures. HPNS is associated with unusual discomfort and abnormal psychological symptoms when subjects are exposed to the clicks of an auditory evoked potential (AEP) test. The repetitive high-intensity noise produced by the sonar pinging may activate more brain areas under HPNS conditions producing deleterious cognitive and autonomic responses impairing orientation, or maintenance of the regular diving response of the cetacean. It is possible that strong noise or sonar signals are more prone to disrupt brain activity when animals are concomitantly exposed to high pressure at the depth. These phenomena may interfere with their orientation cues, alter behavioral traits and eventually cause the stranding of whales. Further studies are necessary to assess neural effects of sound waves on diving mammals under various pressures conditions.
Copyright © 2005 Undersea and Hyperbaric Medical Society, Inc.
UHM 2005, Vol. 32, No. 2 – Noise may disrupt neural activity in deep-diving cetaceans.
Sonar versus Whales: Noise may disrupt neural
activity in deep-diving cetaceans.
Department of Physiology, Faculty of Health Sciences, Zlotowski Center forNeuroscience, Ben-Gurion University of the Negev,
Beer-Sheva 84105, Israel
In humans, and other terrestrial
animals, acoustic and non-acoustic detrimental
effects of noise have been described long
ago (1,2). In the recent years there is an
increase in public and expert interest in the
potential damaging consequences of acoustic
pollution to marine life. The general increase
in underwater noise and the use of sonar
(1,2) have been associated with behavioral
(3, 4) and pathological changes (5) in diving
mammalians exposed to such an environment.
Among these last, the connection established
between the use of high-intensity sonar and
the stranding and acute death of whales (6,)
is particularly striking. It has been suggested
that sonar activity per se may induce either
bubble formation similar to decompression
sickness (DCS (7)), or direct tissue disruption
in diving mammalians (8,9). This may be
true at the proximity of high intensity sonars
(10,11). But the general signs of DCS observed
in stranded cetaceans that were presumably
exposed to the mid-range sonar activity at
distance (5) suggest a behavioral cause: an
accelerated ascent from deep water after being
affected by the sonar. We postulate here novel
auditory and sensorineural mechanisms by
which sonar, and intense noise, may disrupt
the behavior of diving cetaceans. Together
with this, we also propose that the effects of
noise at frequency may be enhanced during
deep diving due to a synergistic combination
with the adaptive response of the central
nervous system (CNS) at high pressure.
Auditory Effects of High Intensity
Dolphins and whales are able to
perceive sound beyond the human hearing
range. Many species use sounds for behavioral
functions like mating (2), echolocation of
prey (
12,13,14) and orientation during diving
(15,16). The echolocation system of cetaceans
(mostly demonstrated in odontocetes), in
contrast with that of bats, lacks of automatic
gain-control on the receiver (ear). So, to
compensate for propagation loss, or to protect
the ear, cetaceans have to automatically adjust
the emission (their output vocal click signal)
as they approach the target (17). Because of
this feature, the damage inflicted by intense
noise to the ears may result in a severe
auditory threshold shift (18) and may lead to
permanent or transient hearing-impairment.
Thus, disabling the echolocation system of
the cetacean. If this happens during a deep
dive, failure of echolocation may lead to
disorientation, speeding up ascent from the
depth, and ultimately DCS. Such sensitivity
of the ear turns the cetaceans prone to the
acoustic assault. This may explain why
whales and dolphins can be more susceptible
to sonar stimuli (13) than young elephant
seals (19). A sensitive auditory system may
be the direct target of intense noise (13), but
UHM 2005, Vol. 32, No. 2 – Noise may disrupt neural activity in deep-diving cetaceans.
it may also be the trigger of secondary effects
Non-auditory Effects of High
Intensity Sound
Whales and other deep-diving
mammals perform breath-hold diving with
pre-dive expiration, which is followed by
lung collapse and redistribution of blood flow.
This procedure impedes any gas exchange in
the lungs (20). Piantadosi and Thalmann (8)
argued that this diving response is enough
to avoid DCS under normal conditions.
However, if brain function is affected (see
Startle response below), the autonomic
nervous system may as well be dysfunctional,
impairing the preventive maneuvers that
impede gas diffusion during the dive response
(redistribution of pulmonary blood flow). Thus,
a static diffusion of nitrogen in supersaturated
tissues, usually affected by repetitive dives,
is a possible mechanism for vascular bubbles
formation. The crucial question is why whales
should react so abnormally, changing their
diving or decompression profile in presence
of the sonar signal? Even at low pressures
high intensity underwater noise was shown to
disturb human behavior (21). Non-auditory
effects of noise in humans involve annoyance
(22), disruption of short-term memory
acquisition and maintenance of ordered
information (23,24), disturbed auditory
verbal processing, and diminished attentional
control (25). Startle is a motor and also an
autonomic reaction to a totally unanticipated
and potentially frightening stimulus. A sudden
noise may develop a normal startle response,
but a high intensity noise may elicit severe
fear or a panic response (26). This kind of
response, involving an autonomic component,
may disrupt the regular diving response of
the cetacean. Furthermore, certain auditory
stimuli, such as noise (27) or music (28,29),
may eventually provoke epileptic seizures in
susceptible subjects.
Effects of high intensity noise may
be enhanced at high pressure because of
CNS adaptive mechanisms
Humans and experimental animals
exposed to high pressure suffer the high
pressure nervous syndrome (HPNS), which
is characterized by hyperexcitability of the
CNS. HPNS often begins with tremor and
cognitive disturbance, but also involves
autonomic reactions like nausea, vertigo,
vomiting and dizziness, and may, in extreme
cases, induce epilepsy-like seizures (30).
The normal inhibition the respiratory drive
by trigeminal and vagal nerves stimulation
was reduced, or even reversed to stimulation,
under hyperbaric conditions (31).
Development of HPNS has also been
associated with unusual discomfort and
abnormal psychological symptoms when
subjects were exposed to the clicks of an
auditory evoked potential (AEP) test (32).
Generation of late AEP waves is associated
with activation of high-level areas in the
cerebrum. Corticohippocampal areas have
been shown to participate in these phases
of the AEP (33). Some of these high-level
areas, are which when abnormally activated
by noise at atmospheric conditions, produce
the non-auditory deleterious effects of
noise. Reduction of synaptic transmission,
diminished action potentials conduction
velocity and paradoxical hyperexcitability
(34,35) are well-known phenomena in the
CNS under hyperbaric conditions. Humans,
and deep-diving animals may cope with these
effects due to certain adaptability of the CNS
at high pressure. This adaptation is which
presumably allows them to perform and carry
out relatively normal tasks at great depths. Our
recent experiments in isolated rat brain-slices
revealed at a cellular level that this adaptation
to high-pressure involves counterbalance of
high-pressure-induced synaptic depression
by increased dendritic excitability and
UHM 2005, Vol. 32, No. 2 – Noise may disrupt neural activity in deep-diving cetaceans.
conduction (36). But this adjustment is not
devoid of secondary effects: stimulation of
large number of cortical inputs at certain
frequencies may boost the activity patterns
in neural circuits, and even promote seizure
development (38). By this mechanism the
repetitive high-intensity noise produced by the
sonar pinging may activate more fibers under
high-pressure conditions than on surface.
Massive activation of corticohippocampal
areas will induce corresponding cognitive
and autonomic secondary responses that
may impair orientation, or maintenance of
the regular diving response of the cetacean.
Moreover, deep-diving whales seem to be the
most affected by sonars (7): the phenomenon
of massive stranding is almost exclusive
of odontocetes that use echolocation for
foraging at great depths. Within this group,
the Cuviers beaked whales are the most
likely to be found massively stranded.
These whales are also the deepest divers of
the group, using to submerge for more than
20 min at depths of approximately 2000 m
(37). Other beaked whales found stranded
after sonar use, such as Blainville’s and
Gervais, are also deep divers. Sperm whales,
which have the deep-diving world record,
occasionally strand, and display signs of DCS
in their bones (38). Presence of a huge mass
of undigested squid in the stomach of beaked
Cuvier whales stranded in the Canary Islands
(5) suggest that these animals were severely
disturbed by the sonar short after ingesting
their meal at great depth (39). Therefore, it
is in our opinion, reasonable to assume that
in this case whales dead by DCS due to rapid
ascent from the depth and/or dysfunction of
their physiologic diving response.
Intense noise affects animals at
various levels. Direct effects of noise on
matter and animal tissue are expected only in
the proximity of high intensity active sonars
(mostly low frequency sonars). The auditory
effects of intense noise may be particularly
harmful for deep-diving cetaceans because
of lack of gain-control in their ears. This
feature may lead to permanent or transient ear
damage together with secondary loss of the
echolocation function. Lack of echolocation
may be crucial for orientation, in particular
when the animal is diving at great depths.
Non-acoustic effects of noise may give rise
to an enhanced startle response leading to
disturbance in the normal behavior. A severe
startle response, possibly involving fear or
panic, may cause stranding as a flight response.
The cumulative effects of high-intensity
noise with CNS adaptation to high-pressure
seem to play a relevant role in the association
sonar use with stranding/DCS in whales.
Thus, it is possible that strong noise or sonar
signals are more prone to abnormally activate
brain areas when animals are concomitantly
exposed to high pressure at the depth of the
ocean. We propose that these phenomena may
interfere with their orientation cues, and alter
behavioral traits. In extreme cases, this could
cause the stranding of whales. Therefore, it
is necessary to encourage the study of neural
effects of sound waves on diving mammals
under various ambient pressures conditions.
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... Dans ce cas, les courants primaires et secondaires ayant même pulsation, la fréquence de résonance doit être identique pour les deux enroulements ce qui impose les conditions d'accord suivantes : 38) où < 2 est la pulsation de résonance et ! le condensateur de charge série de la boucle réceptrice. ...
... [35][36][37][38][39][40], il est toutefois possible de déterminer certains seuils de dangerosité pour la faune et la flore. Ces informations nous permettent de construire un indicateur composite qui sera noté ( 2&9: ...
... 38 Exemple de composants utilisés dans le circuit récepteur : OPA1S2384, INA116, … ( ...
La surveillance de l’environnement sous-marin nécessite le déploiement de capteurs et d’infrastructures dédiées dont le coût et l’impact sur la faune et la flore doivent être réduits. L’application cible vise des zones géographiques inférieures à 1km2 dans lesquelles les transmissions de flux vidéo et de mesures, prélevés par des capteurs immergés, doivent être réalisées sans-fil sur des distances supérieures à 10m avec un débit minimum de 80kbps pour des puissances d’émission d’une dizaine de Watts. Une étude comparative des méthodes de communication acoustiques, optiques et électromagnétiques en eau de mer est présentée. Cette analyse est introduite en définissant un ensemble de critères de performances destinés à évaluer et sélectionner la technique la mieux adaptée aux besoins applicatifs. Les méthodes électromagnétiques, dont les coûts de déploiements et l’impact environnemental sont minimaux, présentent toutefois des limitations de portée pour le débit de données souhaité. La suite de cette thèse présente les travaux de recherche qui ont été menés pour lever ces verrous technologiques. Un premier modèle simplifié de propagation des champs électromagnétiques en milieu subaquatique a été développé pour différencier les modes de propagation favorisant les pertes par conduction de celles engendrées par les propriétés diélectriques de l’eau de mer. Des prototypes d’antennes ont été développés pour tenter d’exciter le milieu en favorisant l’un ou l’autre mode. Finalement, l’étude détaillée d’un modèle de couplage magnéto-inductif a permis de réaliser et d’évaluer les performances d’une telle liaison en utilisant des techniques originales d’élargissement de bande passante qui ont été implémentées avec succès dans un prototype de MODEM sous-marin.
... Los animales que bucean de forma natural, como los cetáceos odontocetos y los elefantes marinos, llegan a profundidades mucho mayores que los humanos (hasta 2.000 m durante 40 min), y ascienden desde ellas a respirar a la superficie frecuentemente [9]. Se desconocen datos acerca del SNAP en estos animales, pero investigaciones recientes indican que durante el buceo su SNC es más sensible a otras alteraciones medioambientales, como el exceso de ruido [10]. ...
... Un estímulo un 50% menos intenso produce en alta presión una respuesta similar a la de control, mientras que la magnitud de la respuesta producida por un estímulo constante aumenta un 250% [42]. Este fenómeno ha llevado a conjeturar que los sonares navales producirían una exagerada respuesta de sobresalto en las ballenas durante el buceo [10]. Eso las haría ascender rápidamente, causándoles enfermedad de descompresión, varado y muerte [43]. ...
... Puede ser el caso de las altas concentraciones de gases (helio), que se presuponen inertes (pero cuyos efectos directos no se conocen bien), con cambios en las propiedades de la materia (como aumento de densidad) o con variación de pro-piedades (como aumento en la velocidad de conducción del calor, sonido y otros), que podrían producir efectos secundarios; éstos generarían síntomas neurológicos, sin ser propiamente SNAP. Por ejemplo, el aumento de la velocidad de conducción del sonido en helio podría causar desorientación, ya que no permitiría la percepción normal de su dirección por diferencia de fase interauricular [10]. Por otra parte, se ha diferenciado el SNAP (efectos neurológicos dependientes de presión estable) de efectos resultantes del proceso de compresión (incremento progresivo de la presión), el cual es particularmente notorio en compresiones rápidas [59]. ...
... As a result, questions about the role anthropogenic activities could play in facilitating such conditions have increased. One concern is that human activities could serve as stressors, eliciting a physiological stress response that could alter normal physiology and compromise protective adaptations (Wright et al., 2007;Talpalar and Grossman, 2005). One mechanism through which anthropogenic stressors could impact health is through modulation of the immune system (Romano et al., 2004;Wright et al., 2011). ...
... In addition, higher baseline glucocorticoids associated with ocean noise have been reported in fecal samples from North Atlantic right whales (Eubalaena glacialis). A startle response occurring during a dive may be abnormal due to physiological adjustments which occur during this behavior (Talpalar and Grossman, 2005) and this in turn can result in augmentation of the stress response during a dive. It is unknown how any of these behavioral or physiological changes affect immune function. ...
... Thus, immune cells which are less reactive to changes in these hormones, perhaps due to low binding affinity of receptors, may be protective and allow for normal immune responses to occur in the face of challenges such as repetitive diving. However, in the presence of an additional physiological challenge, changes in neuroendocrine hormones may be of abnormal magnitude (Talpalar and Grossman, 2005) in belugas following in vitro pressure exposure during baseline and stressor conditions. Beluga blood samples (n=4) were obtained from animals at the Mystic Aquarium during baseline and stressor conditions, and from free ranging animals in Alaska. ...
Marine mammals possess adaptations for repetitive and extended diving to great depths without suffering the ill effects seen in humans [e.g. decompression sickness (DCS)] which involve altered immune activity. In recent decades, DCS-like symptoms in marine mammals have increased concerns about marine mammal health and whether anthropogenic activities can interfere with adaptive dive responses, increasing susceptibility to dive related pathologies. The purpose of this work was to address these concerns by: 1) evaluating the in vitro response of marine mammal immune cells to increased pressure, 2) comparing the response of cells between baseline and stressor conditions, and 3) developing a non –invasive means of monitoring cortisol in belugas (Delphinapterus leucas). Blood samples were obtained from belugas during baseline and stressor (e.g. out of water examination, wild chase and capture) conditions, as well as from stranded harbor seals (Phoca vitulina), harp seals (Phoca groenlandica) and grey seals (Halichoerus grypus) at the time of admit to rehabilitation and again pre-release. Catecholamines and cortisol were measured to demonstrate a physiological stress response. Phagocytosis, lymphocyte proliferation and cell activation were compared between pressure exposed and non-exposed cells for each condition, between different pressure profiles and between conditions using mixed generalized linear models (α=0.05). The response of cells to pressure varied 1) between species, with baseline beluga samples and admit phocid samples showing opposite patterns of change than humans, 2) with stressor condition as responses differing from baseline but resembling human responses were detected for all stressor conditions in belugas, and 3) with exposure characteristics, with deeper exposures resulting in larger changes in phagocytosis but smaller changes in IL2R expression than shallower exposures. Blow (exhaled breath condensate) was also collected from belugas and validated as a matrix for monitoring cortisol using a commercial enzyme immunoassay. Changes in cortisol were observable in blow following known stressor conditions, supporting use of blow sampling for future endocrinology, dive physiology, health and conservation studies. This work validates non-invasive methodology for monitoring stress responses in cetaceans and provides the first evidence suggesting that anthropogenic stressors may impact marine mammal health by altering the relationship between dive behavior and immune function.
... Physiologically, the use of prolonged sonar has been shown to induce temporary hearing loss in species such as the Bottlenose Dolphin (Tursiops truncatus) in addition to mild behavioural alterations and disorientation (Mooney et al., 2009). The loss of hearing and subsequent loss of echolocational abilities in cetaceans likely impairs the orientational abilities and maintenance of ordinary dive behaviour in cetaceans (Talpalar and Grossman, 2005). ...
... This particular syndrome is induced by behavioural alterations associated with exposure to MFS and particularly affects deep-diving Beaked Whales, such as Cuvier's Beaked Whales (Ziphius cavirostris) and Blainville's Beaked Whales (Mesoplodon densirostris). The reason behind the heightened sensitivity of deep diving species to sonar is believed to be due to the fact that under high pressures at depth, sonar activity may stimulate more sensory fibres than at the surface water pressures, due to increased dendritic conduction and excitability as part of the adaptation of the CNS to high pressures (Talpalar and Grossman, 2005). This is supported by the stranding and death of fourteen Beaked Whales in the Canary's in September 2002, close to the site of an international naval exercise. ...
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The ban on commercial whaling by most countries in the 1970's paved the way for the coexistence of humans and cetaceans i.e. modern whales and dolphins. Despite this advance cetaceans still find themselves unintentionally in conflict with humans through the presence of anthropogenic acoustic noise in the oceans, particularly through the use of naval sonar. The use of naval sonar has been associated with both behavioural changes, such as modified dive behaviour, and physiological changes, such as Gas and Fat Embolic Syndrome, across many cetacean species. As a result of such changes, the lethal mass strandings of several cetacean species has occurred globally. High levels of public support and scientific data have prompted recent changes to naval sonar usage including complete moratoriums and limited activity in areas frequented by cetaceans. This contemporary issue and our response, demonstrates a greater understanding of the impacts human activities have on other species. Introduction:
... 1 3 (Fernandez et al. 2017), or a startle response (Talpalar and Grossman 2005). Each of these involves what may be described as an unusual or abnormal behavioral or physiological response. ...
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Immune responses to nitrogen gas bubbles, particularly activation of inflammation via the complement cascade, have been linked to the development of symptoms and damage associated with decompression sickness (DCS) in humans. Marine mammals were long thought not to be susceptible to such dive-related injury, yet evidence of DCS-like injury and new models of tissue nitrogen super-saturation suggest that bubbles may routinely form. As such, it is possible that marine mammals have protective adaptations that allow them to deal with a certain level of bubble formation during normal dives, without acute adverse effects. This work evaluated the complement response, indicative of inflammation, to in vitro nitrogen bubble exposures in several marine mammal species to assess whether a less-responsive immune system serves a protective role against DCS-like injury in these animals. Serum samples from beluga (Delphinapterus leucas), and harbor seals (Phoca vitulina) (relatively shallow divers) and deep diving narwhal (Monodon monoceros), and Weddell seals (Leptonychotes weddellii) were exposed to nitrogen bubbles in vitro. Complement activity was evaluated by measuring changes in the terminal protein C5a in serum, and results suggest marine mammal complement is less sensitive to gas bubbles than human complement, but the response varies between species. Species-specific differences may be related to dive ability, and suggest moderate or shallow divers may be more susceptible to DCS-like injury. This information is an important consideration in assessing the impact of changing dive behaviors in response to anthropogenic stressors, startle responses, or changing environmental conditions that affect prey depth distributions.
... Thus, an animal fighting infection or sustaining a wound may have elevated hormone levels prior to diving, which may subsequently result in an abnormal dive response. Conversely, an animal with elevated levels of catecholamines or cortisol due to natural diving adjustments may display an unusual or extreme response to an additional stressor (Talpalar and Grossman 2005). Hochachka et al. (1995) reported increased plasma catecholamines in Weddell seals following diving, noting higher values (for both resting periods, as well as dives) in a single animal with obvious injury (Hochachka et al. 1995) suggesting that the presence of an injury, in conjunction with adjustments made for diving resulted in a magnified response of the sympathetic nervous system. ...
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The ability of marine mammals to cope with environmental challenges is a key determining factor in strandings and successful release of rehabilitated animals. Dive behavior is related to foraging and thus survival. While dive adaptations have been well studied, it is unknown how the immune system responds to diving and whether health status impacts immune function during diving. This study investigated the functional response of ex situ immune cells from stranded phocids to in vitro increased pressure, over the course of rehabilitation. Blood samples were drawn from stranded harbor seals (Phoca vitulina), gray seals (Halichoerus grypus) and harp seals (Phoca groenlandica) at the time of admit to the Mystic Aquarium, Mystic, CT and again after rehabilitation (pre-release). Phagocytosis, lymphocyte proliferation and immune cell activation were measured in vitro, with and without exposure to 2000 psi (simulated dive depth of 1360 m). Plasma epinephrine and norepinephrine, and serum cortisol were measured in vivo. All hormone values decreased between admit and release conditions. Under admit or release conditions, pressure exposures resulted in significant changes in granulocyte and monocyte phagocytosis, granulocyte expression of CD11b and lymphocyte expression of the IL2 receptor (IL2R). Overall, pressure exposures resulted in decreased phagocytosis for admit conditions, but increased phagocytosis in release samples. Expression of leukocyte activation markers, CD11b and IL2R, increased and the response did not differ between admit and release samples. Specific hematological and serum chemistry values also changed significantly between admit and release and were significantly correlated with pressure-induced changes in immune function. Results suggest (1) dive duration affects the response of immune cells, (2) different white blood cell types respond differently to pressure and (3) response varies with animal health. This is the first study describing the relationship between diving, immune function and health status in phocids.
... In the Gulf of Alaska (GOA), a designated Temporary Maritime Activities Area ( Fig. 1) extends from the shelf region into deep offshore waters and is where the US Navy conducts training exercises. Naval activities, including the use of tactical mid-frequency active sonar and explosives, may pose a risk for cetaceans, particularly deep-diving species like sperm whales (Talpalar and Grossman, 2005). ...
Sperm whales Physeter macrocephalus produce loud, stereotypical click sequences and are an ideal species to be studied with passive acoustic techniques. To increase our limited knowledge of sperm whale occurrence patterns in remote and inaccessible locations of the North Pacific, we analyzed a five-year-long (June 2007–April 2012)acoustic data set recorded at Ocean Station PAPA (OSP; 50°N, 145°W)in the Gulf of Alaska (GOA). Firstly, we assessed the sperm whale detection performance of the Passive Aquatic Listener (PAL), and secondly, we investigated temporal patterns of sperm whale presence at OSP. The PAL proved highly efficient, with above 50% probability of detecting more than two sperm whales, a condition met for over 50% of the recordings. Results indicated that sperm whale clicks were recorded year-round, with a clear seasonal pattern. The number of detections during the summer months was approximately 70% higher compared to the winter. An ambient noise analysis showed that differences in detection rates were likely not driven by seasonal changes in ambient noise levels. The average propagation range of sperm whale clicks ranged between 7 and 8 km between summer and winter, with slightly decreased detection distances observed in winter. Seasonal shifts in the intensity of the Alaska Current and the latitudinal oscillations of the North Pacific Transition Zone results in changes in water mixing, transport of nutrients and the concentration of prey such as squid, which likely drives sperm whale distribution.
A wide variety of air-breathing animals temporarily suspend their normal breathing, and go under water, experiencing the hydrostatic pressure arising from depths of a few centimetres to several kilometres. Generally, zoologists apply the term diver to vertebrate specialists such as seals and penguins, so, for the sake of completeness, it is necessary to mention those to which the term, as a convention, does not apply.
Technical Report
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Action Plan for Marine Mammals in Israel, 2017-2022 — SUMMARY — The Mediterranean waters of Israel cover a sea surface of approximately 26,000 km2. Israel also has a small 14 km window open to the Red Sea, at the northwestern tip of the Gulf of Aqaba/Eilat. These waters host a considerable variety of marine mammals: most of the cetacean species known to be present in the Mediterranean also occur in the waters of Israel. On the southern coast, the deep Gulf of Aqaba/Eilat hosts several of the cetacean species occurring in the entire Red Sea. Israel’s marine mammal fauna also includes one member of the Family Phocidae (the rare Mediterranean monk seal); one sirenian—the dugong—may still occur in the Gulf of Aqaba/Eilat. Israel has formally committed to the preservation of biodiversity by ratifying a number of international conservation treaties and issuing strict nature and animal conservation laws. However, action taken so far has not been capable of mitigating the diversity and vehemence of human pressures on the marine environment. While all marine mammal species in Israel are formally protected, little action has been taken to prevent unintentional damage. Timely conservation action is needed to prevent marine mammal decline. The Action Plan for Marine Mammals in Israel, prepared by Giovanni Bearzi (Dolphin Biology and Conservation) in consultation with Israel Marine Mammal Research & Assistance Center (IMMRAC), contributes background information, a rationale and a set of actions to protect marine mammals in Israel. The Plan outlines a set of legislative, management, research, education and awareness initiatives which aim to: 1) improve the management of human activities known or likely to have negative impacts on marine mammals, and produce scientific information that can support and guide such process, 2) prominently feature marine mammals in national legislation and management decision, 3) make the general public and the institutions fully aware of the need of protecting marine mammals, as well as of the long-term benefits of preserving healthy marine ecosystems, 4) ensure the protection of areas containing important marine mammal habitat and prey resources, and 5) support the development of expertise and establish the social and economic framework necessary to accomplish the marine mammal conservation objectives listed above. In recent years, field research by Israeli and other scientists has produced important information on marine mammal occurrence, ecology and behaviour. Such knowledge, together with a growing popular appreciation of the importance of protecting marine biodiversity, represents a solid background to start a formal process of nation-wide recognition of marine mammals—leading to more intensive research efforts, increased public and institutional awareness, and concrete conservation action. Besides representing a resource for nature tourism, a healthy marine mammal fauna can raise Israel’s international reputation as a nation aware of the importance of protecting its natural heritage. Science-based actions inspired by the precautionary principle can set high standards of conservation management, representing a model for marine mammal protection in the region and propelling broad marine conservation efforts.
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Hyperbaric environments induce the high pressure neurological syndrome (HPNS) characterized by hyperexcitability of the central nervous system (CNS) and memory impairment. Human divers and other animals experience the HPNS at pressures beyond 1.1 MPa. High pressure depresses synaptic transmission and alters its dynamics in various animal models. Medial perforant path (MPP) synapses connecting the medial entorhinal cortex with the hippocampal formation are suppressed by 50% at 10.1MPa. Reduction of synaptic inputs is paradoxically associated with enhanced ability of dentate gyrus (DG)' granule cells (GCs) to generate spikes at high pressure. This mechanism allows MPP inputs to elicit standard GC outputs at 0.1–25 Hz frequencies under hyperbaric conditions. An increased postsynaptic gain of MPP inputs probably allows diving animals to perform in hyperbaric environments, but makes them vulnerable to high intensity/frequency stimuli producing hyperexcitability. Increasing extracellular Ca 2+ ([Ca 2+ ] o) partially reverted pressure-mediated depression of MPP inputs and increased MPP's low-pass filter properties. We postulated that raising [Ca 2+ ] o in addition to increase synaptic inputs may reduce network excitability in the DG potentially improving its function and reducing sensitivity to high intensity and pathologic stimuli. For this matter, we activated the MPP with single and 50 Hz frequency stimuli that simulated physiologic and deleterious conditions, while assessing the GC's output under various conditions of pressure and [Ca 2+ ] o. Our results reveal that the pressure and [Ca 2+ ] o produce an inverse modulation on synaptic input strength and network excitability. These coincident phenomena suggest a potential general mechanism of networks that adjusts gain as an inverse function of synaptic inputs' strength. Such mechanism may serve for adaptation to variable pressure and other physiological and pathological conditions and may explain the increased sensitivity to strong sensory stimulation suffered by human deep-divers and cetaceans under hyperbaric conditions.
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Environmental policy with regard to noise abatement has traditionally only considered whether the noise levels in a given setting are high enough to be deemed a source of annoyance, disturbance, or threat to well being. However, laboratory studies using both simple and more complex work-related tasks have shown that task-irrelevant sound, regardless of its intensity, intrudes upon cognitive processing and disrupts performance substantially; furthermore, its damaging effect does not diminish with repeated exposure to the sound over time. For tasks that require short-term memory processing (particularly the short-term maintenance of order information) sound assumes disruptive power if it is acoustically varying over its time course. However, other properties of sound (e.g., the semanticity of speech) can incur an additional cost if the primary task necessitates or tends to evoke the extraction of meaning. It will be argued that interference in each case is explained by reference to a conflict between two concurrent mental processes; that being demanded by the task and that being involuntarily applied to properties of the sound. Such harmful effects, as well as having direct consequences for the general well-being of those working in noisy environments, may have far reaching consequences for health insofar as extraneous sound is a feature of many safety-critical work settings. Implications for noise abatement policy are highlighted.
Toothed whales (Odontoceti, Cetacea) navigate and locate prey by means of active echolocation. Studies on captive animals have accumulated a large body of knowledge concerning the production, reception and processing of sound in odontocete biosonars, but there is little information about the properties and use of biosonar clicks of free-ranging animals in offshore habitats. This study presents the first source parameter estimates of biosonar clicks from two free-ranging oceanic delphinids, the opportunistically foraging Pseudorca crassidens and the cephalopod eating Grampus griseus. Pseudorca produces short duration (30 μs), broadband (Q=2–3) signals with peak frequencies around 40 kHz, centroid frequencies of 30–70 kHz, and source levels between 201–225 dB re. 1 μPa (peak to peak, pp). Grampus also produces short (40 μs), broadband (Q=2–3) signals with peak frequencies around 50 kHz, centroid frequencies of 60–90 kHz, and source levels between 202 and 222 dB re. 1 μPa (pp). On-axis clicks from both species had centroid frequencies in the frequency range of most sensitive hearing, and lower peak frequencies and higher source levels than reported from captive animals. It is demonstrated that sound production in these two free-ranging echolocators is dynamic, and that free-ranging animals may not always employ biosonar signals comparable to the extreme signal properties reported from captive animals in long-range detection tasks. Similarities in source parameters suggest that evolutionary factors other than prey type determine the properties of biosonar signals of the two species. Modelling shows that interspecific detection ranges of prey types differ from 80 to 300 m for Grampus and Pseudorca, respectively.
During foraging dives, sperm whales (Physeter macrocephalus) produce long series of regular clicks at 0.5-2 s intervals interspersed with rapid-click buzzes called "creaks". Sound, depth and orientation recording Dtags were attached to 23 whales in the Ligurian Sea and Gulf of Mexico to test whether the behaviour of diving sperm whales supports the hypothesis that creaks are produced during prey capture. Sperm whales spent most of their bottom time within one or two depth bands, apparently feeding in vertically stratified prey layers. Creak rates were highest during the bottom phase: 99.8% of creaks were produced in the deepest 50% of dives, 57% in the deepest 15% of dives. Whales swam actively during the bottom phase, producing a mean of 12.5 depth inflections per dive. A mean of 32% of creaks produced during the bottom phase occurred within 10 s of an inflection (13x more than chance). Sperm whales actively altered their body orientation throughout the bottom phase with significantly increased rates of change during creaks, reflecting increased manoeuvring. Sperm whales increased their bottom foraging time when creak rates were higher. These results all strongly support the hypothesis that creaks are an echolocation signal adapted for foraging, analogous to terminal buzzes in taxonomically diverse echolocating species.
Though the adverse psychological effects of noise as an environmental pollutant are well recognised, much of the relevant work has been focused on the ambiguous concept of "annoyance". The relation between noise and mental ill-health calls for more direct investigation. In particular, the pronounced individual variation in reactions to noise requires elucidation.
The effect of localized application of acetylcholine (ACh) on well characterized components of sensory evoked and electrically induced potentials in the dentate gyrus was investigated in rats while performing a tone discrimination task. Local pressure application of ACh to the granule cell layer of the dentate gyrus through the recording pipette increased the amplitude of perforant path evoked population spikes without changing the amplitude of the field EPSP. When the pipette was relocated to the outer molecular layer of the dentate gyrus (OM), ACh application decreased the amplitude of the perforant path field EPSP. Two major components of the averaged auditory evoked potential (AEP) recorded during criterion performance of the discrimination task were significantly changed by dendritic application of ACh. The N1 component of the OM AEP which has been shown to reflect perforant path synaptic activity decreased in amplitude while the N2 component which represents activity from septal connections, was significantly increased. These effects were not due to the pressure ejection procedure nor drug related changes in behavioral performance of the task. The results suggest that ACh may act to differentially modulate the synaptic excitability of dentate granule cells, allowing them to acquire responses to sensory stimulation during the establishment and maintenance of discrimination learning.