OS53G-01
Wind, Rain and Whales Quantified with Ambient Sound
Underwater ambient sound in the ocean contains quantifiable information about the marine environment. In the frequency range from 1 to 50 kHz, persistent sound is generated by breaking wind waves and can be used to quantify wind speed. On a shorter time scale, the sound of raindrops splashing on the ocean surface is loud and distinctive, allowing oceanic rainfall to be detected and quantified acoustically. On an even shorter time scale, vocalizations of marine mammals (especially whales, but also other marine wildlife), and anthropogenic sounds from ships and sonars, are present and can be used to detect and quantify activity. These sounds are generally distinctive and can be sorted to generate quantitative sound budgets. Long-term ambient sound measurements using a low duty cycle recorder (Passive Aquatic Listeners - PALs) have been collected from different oceanic environments, including deep ocean moorings in the Pacific Ocean (tropical, mid and high latitudes), continental shelf moorings (Washington coast and Bering Sea) and inland waterways (Haro Strait and Puget Sound). These data will be contrasted to report the components of the sound budget that dominate in different marine environments. Sound levels, quantitative wind speed and rainfall climatologies, and the temporal patterns of biological and anthropogenic activities will be reported. Passive acoustic measurements are available in many ocean locations where more conventional instrumentation is unavailable or does not survive, including ice-covered and extreme high wind situations. Furthermore, long-time series of ambient sound will provide a baseline for trends and levels that are needed to aid decision makers regarding the impact of sound-producing human activities in the ocean environment. [Work supported by ONR Ocean Acoustics.]
OS53G-02
Marine Animal Acoustic Windows and Human-Generated Noise. What Activities Pose a Risk and Which Organisms are Vulnerable
In the often dark and turbid marine environment many animals rely heavily on acoustic communication and acoustic sensing for their functional behaviour. Sound travels fast and far in water; low-frequency sound also travels well in water-saturated sediments. Acoustic communication can differentiate in function depending on frequency: highly specific as to information content at higher frequencies and capable of travelling far at low frequencies. Different phyla can perceive different frequency ranges; the height of frequencies that can be perceived depends largely on physiology. Most marine mammals have highly sophisticated hearing at frequency ranges far above those perceivable by human; pelagic fish with a swim bladder can hear considerable better than benthic fish, without such organ. Most invertebrates are able to perceive low-frequency vibrations, while cephalopods have a more sophisticated hearing (as are several of their other sensory functions, such as vision, chemoreception, touch and proprioception). Apart from mammals and some pelagic fish, most marine animals only perceive low-frequency sounds, with an optimum sensitivity level. Those species that are known to produce sound, do so at roughly similar frequencies as their window of perception. Most human-made noise in the sea is in the low frequency range as well (shipping, seismic exploration, mineral extraction, propagated sound from airplanes) at sound levels that often exceed the levels of optimum animal acoustic perception. To estimate the potential risk of man-made noise for acoustic perception and functional behaviour, the overlap in frequencies and excess of human-generated sound levels has been mapped for the North Sea with a view to recognise which activities pose a high risk and which are risk zones.
OS53G-03
Acoustic Communication in the North Atlantic Right Whale ({\it Eubalaena glacialis}) and Potential Impacts of Noise
The North Atlantic right whale produces a variety of sounds used for social communication. The functional role of these sound types are beginning to be understood, with specific sounds associated with long-range contact, formation of social groups, and potential reproductive advertisement by males and females. North Atlantic right whales live in a highly urbanized environment, with their known habitat extending along the east coast of the U.S. and Canada. These whales are regularly exposed to noise from vessels, both chronic levels of increased noise from distant shipping and shorter-term, higher intensity, transient exposures when vessels pass close to the whales. It is likely that an increase in the ambient noise in the same frequency range of their vocalizations impacts their ability to communicate by limiting the range over which they can communicate. There appear to be both short- and long-term changes in right whale sound production that are associated with increased noise levels. Over the short-term (minutes), both the fundamental frequency and peak frequency of tonal calls were found to increase. Over the longer term (decades), the minimum and maximum frequency of the most stereotyped right whale call type, the upcall, were found to increase from the late 1950's through 2004, with a gradual increase in frequency documented through the decades. A comparison of the upcalls recorded from the North Atlantic right whale and the Southern right whale ({\it Eubalaena australis}) indicate a significant difference in start and end frequency, which, given the previous findings, may be a result of differing ambient noise conditions in their habitats. These results are significant, as they present evidence for a long-term, chronic behavioral change in the North Atlantic right whale calling behavior that may be a result of increased levels of anthropogenic noise.
OS53G-04
Predicting acoustic impact on marine mammals: use of satellite observations and ocean models in globally deriving sound speed profiles for estimates of transmission loss
Global estimates of sound speed profiles are a necessary component of a global system to predict the impact of noise on marine mammals. Given a known signal level for a sonar system or other sound source, acoustic propagation models can predict received sound level in the surrounding environment. Combined with spatial distributions of marine mammal populations, an acoustic impact tool can identify regions where sound levels exceeding specified thresholds overlap with marine mammal populations. Operational plans can be adjusted to account for these conditions if the data for the acoustic propagation models are sufficiently accurate. What is the influence of accurate real-time prediction of sound speed profiles (SSP) in such a system? For example, surface ducts can form, strengthen and weaken over the course of a day. Using unassimilated observations for validation, we examine the accuracy of ocean sound speed profiles (SSP) estimated by various methods. The baseline approach is a seasonal climatology from the Modular Ocean Data Assimilation System (MODAS). A better representation of daily variability is provided by a MODAS projection of satellite sea surface height and temperature into vertical profiles of temperature and salinity. To represent acoustic changes on shorter time scales we rely on ocean models, using profiles from global and higher-resolution regional implementations of the Navy Coastal Ocean Model (NCOM). Standard values are used for bottom and surface loss to focus on the influence of the water column. The various SSP fields are used in a regional case study to demonstrate the influence of SSP accuracy on predictions of acoustic impact on marine mammals.
http://www7320.nrlssc.navy.mil/global_ncom/ncom.html
OS53G-05
The Effects of Noise Intensity and Exposure Duration and Potential Protective Mechanisms in the Bottlenose Dolphin ({\it Tursiops truncatus})
Anthropogenic sounds in the ocean are increasing from such influences as shipping, drilling, sonars, and scientific exploration. Marine mammals, being adapted to utilizing sound in the ocean, are consequently of particular concern regarding the effects of this noise. Several recent marine mammal strandings have been definitively linked to anthropogenic noise induced events and a few studies exist demonstrating that anthropogenic sound affects marine mammals. However, there is a paucity of information regarding how sound affects marine mammals. Further, there is no published data examining the relationship between sound intensity and exposure duration. Understanding this connection would allow us to predict how sounds would affect marine mammals, predictions that may be useful for ocean policy and legislative decisions. This study explores the effects of octave-band noise, from 4-8 kHz, on the hearing of a bottlenose dolphin (Tursiops truncatus) by inducing temporary hearing threshold shifts (TTS). Sound pressure levels (SPL) were increased from 160 to 172 dB re: 1$\mu$Pa and time of sound exposure was decreased from 30 to 1.8 min to measure the effects of noise duration and intensity. Sound energy was calculated in sound exposure level (dB re: 1$\mu$Pa$^{2}$s$^{-1}$). To rapidly examine the effects of noise on frequency and map recovery, auditory evoked potentials were used to measure hearing thresholds at 5.6, 8, 11.2, 16, and 22.5 kHz at 5, 10, 20, 40, and 80 min post-noise exposure. Shifts were always frequency dependent, with maximum shifts of 7-12 dB at 11.2 and 8 kHz. Recovery time depended on shift and frequency, but full recovery was relatively rapid, usually within 20 and always within 40 minutes. As exposure time was halved, TTS generally occurred with an increase in noise SPL of 3 dB. Thus, to induce TTS in a bottlenose dolphin with octave-band noise, there appears to be an inverse relationship of exposure time and SPL. However in this study, when exposed to shorter, louder noise threshold shifts were not linear but rather shorter sounds required greater sound exposure levels. This is in contrast to an assumed equal energy linear trade-off between sound intensity and time found in the literature. Thus, bottlenose dolphins may have a protective mechanism that reduces harmful physiological noise damage at shorter duration exposures. From the data a novel algorithm was written that predicts the physiological effects of anthropogenic noise if the intensity and duration of exposure are known.
OS53G-06
Dodge-Lummus Island Turning Basin Project: Acoustic Measurements and Quantification to Determine Impacts to Marine Mammals during Construction Blasting Operations at the Port of Miami
In 1990, Congress authorized the deepening and expansion of the Miami Harbor, Port of Miami, Miami-Dade County, Florida. Part of the project included deepening of the Dodge Lummus Island Turning Basin and Fisherman's Channel to -42'. The Port of Miami (Port) previously attempted to complete the project without underwater blasting. The contractor and subsequent surety company were unable to successfully complete the authorized work primarily due to the limestone bedrock that was resistant to dredging. In 2000, the Port approached the Jacksonville District, U.S. Army Corps of Engineers (District) to complete this dredging project. The District determined that blasting would be required as a construction technique and that Miami Harbor is routinely occupied by a number of marine species that are protected under the Endangered Species Act of 1973 including the Florida manatee, Trichechus manatus and marine turtles (Caretta caretta and Chelonia mydas). As a result the Corps initiated consultation with the National Marine Fisheries Service (NOAA Fisheries) and the U.S. Fish and Wildlife Service under Section 7 of the Endangered Species Act was required. The District also determined that a population of bottlenose dolphins, Tursiops truncatus, a species protected under the Marine Mammal Protection Act of 1972 (MMPA), had been documented transiting through the Port and could be affected by the proposed blasting. The District submitted an application for an Incidental Harassment Authorization (IHA) under the MMPA in June 2002, which was issued in 2004 and renewed in April 2005. Construction began in June 2005. A key determination made by NOAA was that marine mammals were unlikely to be seriously harmed by the detonations due to the District's conservative monitoring and mitigation measures aimed to ensure that neither dolphins, nor manatees would be within a pre-determined safety zone when the detonations occurred. Additionally acoustic and pressure monitoring was conducted for a selected group of blasts, with additional acoustic measurements collected for each blast during construction activities. This presentation reviews the preliminary analysis of the results from marine mammal monitoring; an overview of acoustic and pressure measurement data collected during construction; and potential implications for future work using blasting as a construction technique in Florida by the Jacksonville District or elsewhere by others.