Michael Stocker

Fish, Mollusks and other Sea Animals' use of Sound, and the Impact of Anthropogenic Noise in the Marine Acoustic Environment

Many marine animals use sound and acoustic energy sensors to adapt to their environment. Most biological studies closely examine a particular species’ relationship to a specific stimulus. This report examines the fields of research on marine biological adaptations to sound since 1950, assembling an overview of the biological importance of sound in the ocean. It also examines the various sources of anthropogenic noise in the sea with a focus on the potential impacts of that noise on the marine acoustic environment. [Work sponsored by Earth Island Institute.]

Noise sources from the industrialization of the ocean

Increasingly technology is opening up hostile and challenging marine environments for industrial exploitation. This is occurring in the energy sector with fossil fuel exploration and extraction operations and developing wind and hydrodynamic energy projects. It is also occurring with the deep-water expansion of other extraction industries such as minerals mining and fishing. All of these operations and enterprises are introducing loud and complex noise sources into marine bioacoustic habitats. This presentation will be an overview examination of existing and developing noise sources that are a consequence of the industrialization of the outer continental shelf and high seas.

Is the ocean really getting louder

In 1975 Donald Ross indicated a long term trend of low frequency anthropogenic noise increase of 0.55dB/year between 1958 and 1975. This trend in ocean ambient noise levels due to expansion in global shipping has yielded an increase in the ambient noise floor of the ocean that is anywhere from 6dB to 12dB higher than what it was in 1958 (depending on location). What became known as the “Ross Prediction” did not incorporate other anthropogenic sources of noise such as navigation and communication signals, noise from offshore fossil fuel exploration and extraction, and the noises from other marine industrial enterprises. There is a concern that the increase in ambient noise is masking biologically significant sounds, although the evidence for this is still scarce and somewhat speculative. Meanwhile perhaps 90 percent of the biomass of complex vertebrates has been removed from the ocean since 1850 due to industrialized whaling and fishing operations. This paper examines whether the ocean ambient noise floor ...

Some reflections on chorusing.

Sound and song production in many animals is sexually dimorphic inasmuch as the males of most species either exclusively produce sounds, or produce the more complex sounds of the species. As a consequence, chorusing is commonly framed under the rubric of competitive strategies of breeding fitness advertisement for individual animals while ambiguating the individual sources of sound from predators within the sound of the group. Chorusing can be either synchronous (common in many stridulating insects) or asynchronous (common in anurans and fish). Other strategies may also be present in chorusing, including collective annunciation of the group fitness and physical extents, and identification of external threats to the chorusing “acoustic community.” This paper explores some other aspects of “chorusing” that includes other group‐acoustic behaviors such as fish schooling and synchronous bird flocking behaviors.

Deep water fossil fuel extraction and production technologies: A developing source of ocean noise pollution.

The era of easy oil is rapidly closing and more challenging reservoirs are being developed offshore on outer continental shelves using a suite of developing technologies. Deep water (1000–10 000 ft) development occurs under ambient pressures of 30–300 atm (400–4000 psi) and wellhead differential pressures of up to 20 000 psi. Active processing equipment is mounted on the sea floor to diminish the risks and costs of the multiple pipe runs that would be required for above sea‐level processing. The equipment includes separators, multi‐phase and multi‐stage pumps, injectors, and metering equipment. Given the potential for extreme pressure differentials and the multi‐phase nature of the product (liquids, gas, and solids) it is likely that some of these processes generate substantial noise. This paper is a review of the deep water extraction and production technologies and an overview of the physical conditions found in global deep water fossil fuel extraction and production.

New and developing seafloor petroleum extraction technologies: The noise of processing equipment operating in extreme environments.

Fossil fuel demands are driving petroleum extraction operations into deeper marine settings and into oil reservoirs that are also deeper beneath the sea bed. To facilitate this new operating paradigm, operators are commonly placing processing equipment on the sea floor at 5000 feet or deeper where depth pressures can easily be 100–200 atm (1400–2800 psi). In areas such as the Gulf of Mexico, the reservoir pressures alone can reach 20 000 psi at the well head. The extracted product can be a mix of oil, gas, sand, and water, which all route through a chain of processing equipment such as separators, pumps, de‐sanders, and routing manifolds under high pressures and high volumes. This paper will evaluate the new and developing fossil fuel extraction and production equipment to determine the scope and scale of the mechanical noises that these new technologies generate.

The importance of incorporating signal characteristics in the evaluation of noise exposure impacts on marine life

Auditory thresholds are used to establish mitigation guidelines for anthropogenic noise exposure on marine animals. These thresholds are determined using either sinusoidal signals at specific frequencies or band limited, sinusoidal‐derived Gaussian noise. Given that the preponderance of naturally occurring noise in the marine environment is sinusoidal, marine animals may have lower thresholds and, thus, lower tolerance to non‐sinusoidal noise. Fast rise time impulse noise, continuous non‐sinusoidal noise, or a combination of these characteristics may induce biological responses at lower levels than sinusoidal noise with an equivalent power density. The author proposes a metric to evaluate and express signal characteristics as a component of determining noise exposure impacts on marine animals.

A simple acoustical exposure metric based on biological thresholds and integrating a temporal characteristics exposure axis

Anthropogenic noise is compromising habitat for marine mammals, fish and potentially other marine organisms. Determining acceptable exposure thresholds is confounded by the fact that marine animals have adapted to some exceedingly loud naturally occurring sounds, while exposure to certain anthropogenic noises at equivalent or lower amplitudes causes harm. It is clear that mitigation levels can not be established by signal amplitude alone and that other signal characteristics are significant factors in biological responses to noise exposure. This proposed metric continues ongoing work on a simple exposure metric based on broadband frequency and amplitude representation of a subject noise with the time domain represented in the Z axis.

A simple ocean noise exposure metric based on naturally occurring noise levels and biological thresholds

Anthropogenic noise is compromising the habitat for marine mammals, fish, and, potentially, other marine organisms. Determining acceptable thresholds is confounded by the fact that marine animals have adapted to some exceedingly loud naturally occurring sounds, whereas exposure to certain anthropogenic noises at equivalent or lower amplitudes causes harm. It is clear that mitigation levels cannot be established by signal amplitude alone. This proposed metric helps establish exposure levels based on broadband and temporal representation of a subject noise compared to a set of spectral curves based on ambient noise levels and biological thresholds.

Examination and evaluation of the effects of fast rise‐time signals on aquatic animals

Increasingly human enterprise is subjecting the ocean environment to acoustic signals to which marine animals are not biologically adapted. This is evidenced by a marked rise in marine mammal strandings, as well as hearing and other physiological damage to fish and other marine organisms as a result of, or coincident to, human‐generated noise events. Determining phonotoxic thresholds of marine organisms is complicated by the fact that various marine animals are adapted to sense either pressure gradient or particle motion acoustic energy, or some combination or gradient between the two. This has been addressed to some degree by exposure metrics that consider either net or accumulated acoustical flux densities from various noise sources. This paper examines the role and effects of signal rise time both in terms of physiological impulse response of the exposed organisms, as well as broadband saturation flux densities of fast rise‐time signals on animal sense organs. Case studies from the literature will be p...