Mike van der Schaar

Identifying Cetacean Hearing Impairment at Stranding Sites

While noise is now considered a marine hazard that can directly affect cetaceans and induce a stranding, no clinical approach has yet introduced the detection of a possible hearing loss at a stranding site as a necessary practice. This can be explained by the lack of time when facing vital decisions for the animal’s welfare as well as the unavailability of reliable, lightweight, autonomous, and portable audiometry equipment. Herein, we correlate measured electrophysiological evidence of a permanent threshold shift (PTS) in a rehabilitated striped dolphin (Stenella coeruleoalba) that prevented its release, with the postmortem analysis of an abnormal dilatation of the central nervous system ventricles that prevented the correct acoustic reception of the animal. We further propose to follow a five-minute auditory evoked potential (AEP) standard protocol of hearing measurements in-air on cetaceans at a stranding site that includes the stimulation of auditory brainstem responses (ABRs) with a single 4-μs broadband (> 150 kHz) pulse at three decreasing levels (129, 117, and 105 dBpp re 1 μPa at 15 cm), which covers most of the cetaceans’ known maximum acoustic sensitivity and allows the immediate sensing of an individual’s hearing capability before any final clinical decision is taken.

Evidence of Cnidarians sensitivity to sound after exposure to low frequency underwater sources

Jellyfishes represent a group of species that play an important role in oceans, particularly as a food source for different taxa and as a predator of fish larvae and planktonic prey. The massive introduction of artificial sound sources in the oceans has become a concern to science and society. While we are only beginning to understand that non-hearing specialists like cephalopods can be affected by anthropogenic noises and regulation is underway to measure European water noise levels, we still don’t know yet if the impact of sound may be extended to other lower level taxa of the food web. Here we exposed two species of Mediterranean Scyphozoan medusa, Cotylorhiza tuberculata and Rhizostoma pulmo to a sweep of low frequency sounds. Scanning electron microscopy (SEM) revealed injuries in the statocyst sensory epithelium of both species after exposure to sound, that are consistent with the manifestation of a massive acoustic trauma observed in other species. The presence of acoustic trauma in marine species that are not hearing specialists, like medusa, shows the magnitude of the problem of noise pollution and the complexity of the task to determine threshold values that would help building up regulation to prevent permanent damage of the ecosystems.

Contribution to the Understanding of Particle Motion Perception in Marine Invertebrates.

Marine invertebrates potentially represent a group of species whose ecology may be influenced by artificial noise. Exposure to anthropogenic sound sources could have a direct consequence on the functionality and sensitivity of their sensory organs, the statocysts, which are responsible for their equilibrium and movements in the water column. The availability of novel laser Doppler vibrometer techniques has recently opened the possibility of measuring whole body (distance, velocity, and acceleration) vibration as a direct stimulus eliciting statocyst response, offering the scientific community a new level of understanding of the marine invertebrate hearing mechanism.

Classification of Sperm Whale Clicks (Physeter Macrocephalus) with Gaussian- Kernel-Based Networks

Abstract: With the aim of classifying sperm whales, this report compares two methods thatcan use Gaussian functions, a radial basis function network, and support vector machineswhich were trained with two different approaches known as C -SVM and ” -SVM. The meth-ods were tested on data recordings from seven different male sperm whales, six containingsingle click trains and the seventh containing a complete dive. Both types of classifiers coulddistinguish between the clicks of the seven different whales, but the SVM seemed to havebetter generalisation towards unknown data, at the cost of needing more information andslower performance.Keywords: classification; sperm whale; radial basis function; support vector machine1. IntroductionSperm whales (Physeter macrocephalus) , when living in a social community, often forage in smallgroups. During their feeding dive, which may be to depths up to 2 kilometres [1], they start producingsonar signals fairly soon after the start of a dive and generally continue until the ascent back to thesurface. Usually one click per second is produced on average, but at times this frequency is increased(presumably when they have found prey) and up to fifty signals per second may be produced [2]. This

Offshore exposure experiments on cuttlefish indicate received sound pressure and particle motion levels associated with acoustic trauma

Recent findings on cephalopods in laboratory conditions showed that exposure to artificial noise had a direct consequence on the statocyst, sensory organs, which are responsible for their equilibrium and movements in the water column. The question remained about the contribution of the consequent near-field particle motion influence from the tank walls, to the triggering of the trauma. Offshore noise controlled exposure experiments (CEE) on common cuttlefish (Sepia officinalis), were conducted at three different depths and distances from the source and particle motion and sound pressure measurements were performed at each location. Scanning electron microscopy (SEM) revealed injuries in statocysts, which severity was quantified and found to be proportional to the distance to the transducer. These findings are the first evidence of cephalopods sensitivity to anthropogenic noise sources in their natural habitat. From the measured received power spectrum of the sweep, it was possible to determine that the animals were exposed at levels ranging from 139 to 142 dB re 1 μPa2 and from 139 to 141 dB re 1 μPa2, at 1/3 octave bands centred at 315 Hz and 400 Hz, respectively. These results could therefore be considered a coherent threshold estimation of noise levels that can trigger acoustic trauma in cephalopods.

Localising Cetacean Sounds for the Real-Time Mitigation and Long-Term Acoustic Monitoring of Noise

Noise can have a detrimental effect on cetaceans, as well as on other marine animal species. It can cause stress and increase risk of mortality by interfering with their use of sounds in communication (social behaviour and reproduction) and in navigation (echolocation or biosonar to orientate and look for food). Acoustic overexposure, e.g. in areas of heavy shipping, seismic surveys, military exercises, offshore windmills or gas/oil exploration, can lead to hearing loss. While temporary threshold shift (TTS) represents a reversible hearing loss over time, a permanent threshold shift (PTS) results in non-reversible lesions in mammal ears, i.e. a permanent hearing loss caused by long term and/or intense exposure. Although the impact of low to mid frequency (<5kHz) acoustic pollution from the above mentioned human marine activities with regard to cetacean disorientation and death remains poorly understood, available evidence is strongly suggestive of some negative direct or indirect effects: There is an increasing mortality rate from shipping collisions, and cetacean mass strandings after military maneuvers have also been recently related with the use of active sonar, both suggesting that some populations may already be suffering from acoustic impact (i.e. TTS, PTS or blast injuries). The control of noise impact on the marine environment constitutes a scientific challenge and requires a dynamic analysis of the situation based on the parallel development of applied solutions to balance human interests and the conservation of marine species. This objective implies the ambitious synthesis of many advanced acoustic technologies that must be designed to monitor the real-time presence of determined cetacean populations in conflictive areas. Many cetacean species can be identified by their specific calls. The recording of these signature acoustic signals can reveal their presence in monitored areas. Since sound propagates efficiently in water, the detection range of these signals can be quite large, exceeding 100 km in favourable conditions for low-frequency calls far above visual detection methods. This acoustic potential to non-intrusively detect and monitor cetacean species in their environment gave rise to Passive Acoustic Monitoring (PAM) techniques, for which research is very active. The localisation of whales from their sounds in their habitats was initiated in the 1970s. This was rapidly applied to tracking whales over large distances.

Real‐time acoustic monitoring of the deep‐ocean environment

ESONET is a European Network of Excellence (NoE) associating 50 partners (research centres, universities, industrials and SMEs) from 14 countries: France, Germany, Italy, UK, Spain, Portugal, Greece, Belgium, Ireland, the Netherlands, Norway, Sweden, Bulgaria, and Turkey. More than 300 scientists and engineers will participate to its activities. The aim of the ESONET NoE is the lasting integration of European research on deep‐sea multidisciplinary observatories. ESONET is particularly sensitive on the effects of noise on marine organisms. Because our knowledge is still quite limited, ESONET is developing a Demonstration Mission, called LIDO, Listening to the Deep‐Ocean Environment, a research program that will help establishing a scientific base to allow (1) the real‐time automatic identification and classification of nonbiological and biological sounds, (2) the monitoring of marine organisms and population dynamics, (3) the assessment and control of the long term effects of anthropogenic sources on marin...

Sperm whale long-range echolocation sounds revealed by ANTARES, a deep-sea neutrino telescope

Despite dedicated research has been carried out to adequately map the distribution of the sperm whale in the Mediterranean Sea, unlike other regions of the world, the species population status is still presently uncertain. The analysis of two years of continuous acoustic data provided by the ANTARES neutrino telescope revealed the year-round presence of sperm whales in the Ligurian Sea, probably associated with the availability of cephalopods in the region. The presence of the Ligurian Sea sperm whales was demonstrated through the real-time analysis of audio data streamed from a cabled-to-shore deep-sea observatory that allowed the hourly tracking of their long-range echolocation behaviour on the Internet. Interestingly, the same acoustic analysis indicated that the occurrence of surface shipping noise would apparently not condition the foraging behaviour of the sperm whale in the area, since shipping noise was almost always present when sperm whales were acoustically detected. The continuous presence of the sperm whale in the region confirms the ecological value of the Ligurian sea and the importance of ANTARES to help monitoring its ecosystems.

The use of deep water berths and the effect of noise on bottlenose dolphins in the Shannon Estuary cSAC

The Shannon Estuary on the west coast of Ireland is one of Europes premier deepwater berths catering for ships up to 200,000 deadweight tonnage. It is also Irelands only designated candidate special area of conservation for bottlenose dolphins under the EU Habitats Directive. Long-term static acoustic monitoring was carried out at a number of intensive shipping sites. In 2012, noise monitoring took place over a 6-month period (at 1 site) as part of Irelands requirements under the Marine Strategy Framework Directive (MSFD). This is the first assessment of the potential effect of vessel traffic on the behavior of this discrete dolphin population.

Extraction of pulse repetition intervals from sperm whale click trains for ocean acoustic data mining

The analysis of acoustic data from the ocean is a valuable tool to study free ranging cetaceans and anthropogenic noise. Due to the typically large volume of acquired data, there is a demand for automated analysis techniques. Many cetaceans produce acoustic pulses (echolocation clicks) with a pulse repetition interval (PRI) remaining nearly constant over several pulses. Analyzing these pulse trains is challenging because they are often interleaved. This article presents an algorithm that estimates a pulses PRI with respect to neighboring pulses. It includes a deinterleaving step that operates via a spectral dissimilarity metric. The sperm whale (SW) produces trains with PRIs between 0.5 and 2 s. As a validation, the algorithm was used for the PRI-based identification of SW click trains with data from the NEMO-ONDE observatory that contained other pulsed sounds, mainly from ship propellers. Separation of files containing SW clicks with a medium and high signal to noise ratio from files containing other pulsed sounds gave an area under the receiver operating characteristic curve value of 0.96. This study demonstrates that PRI can be used for the automated identification of SW clicks and that deinterleaving via spectral dissimilarity contributes to algorithm performance.