NOAA’s New Noise Guidelines for Marine Mammals – What You Need to Know

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In order to make comments on this draft during the next 30 days, you can view the document here (note: there is a list of acronyms on page VII, and a glossary of terms on page 61 – both very helpful!) then place your comment here (which is document  NOAA-NMFS-2013-0177). You have until January 26th, 2013.
Please remember, NOAA will only take seriously comments that address the specific document, which in this case is the science behind the numbers but is also the lack of a broader scope.  NOAA promises to release the peer reviewer reports and NOAA’s response to those reports, but they are not up at the present time.
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By the title “Draft Guidance for Assessing the Effects of Anthropogenic Sound on Marine Mammals“, you might think that NOAA is establishing guidelines for assessing the effects of anthropogenic (manmade) sound on marine mammals.  Guess again.
The promise:

 This guidance is intended to be used by NOAA analysts and managers and other relevant user groups and stakeholders, including other federal agencies, when seeking to determine whether and how  their activities are expected to result in particular types of impacts to marine mammals via  acoustic exposure.

What they deliver:

This document outlines NOAA’s updated acoustic threshold levels and  describes in detail how the thresholds were developed and how they will be revised and updated in the future.

Not included:

NOAA currently is in the process of developing  new thresholds for onset of behavioral effects. When that process is completed, TTS [Temporary Threshold Shift, which are temporary hearing losses] will be  addressed for purposes of take quantification. In the meantime, the TTS thresholds presented represent the best available science and will be used in the comprehensive effects analyses under the MMPA [Marine Mammal Protection Act} and the ESA [Endangered Species Act] and may inform the development of mitigation and monitoring.

In other words,the draft does not cover behavior in any new way, and disregards any science that correlates certain types of sound with strandings and deaths, nor does it address the compounding effect of so many sources of noise invading the marine environment for lengthy time periods.
It is a myopic look through the lens of hard science on how sound effects different species of marine mammals, and although it is based on solid science the data points are few, and NOAA set clear guidelines for updating as new research is published.
Having so little data available, NOAA basically relies heavily on Marine Mammal Noise Exposure Criteria:  Initial Scientific Recommendations in setting the guidelines for PTS (Permanent Threshold Shift, which is permanent hearing loss):

Thus, NOAA accepts the recommendation made by Southall et al. (2007) as guidance for determining PTS onset for impulsive signals for all cetacean [dolphin, porpoise, whale] and underwater pinniped [seals, sea lions, walruses) species, resulting in an approximate 15 dB difference between TTS [temportary] and PTS [permanent] onset.

That study was published in the journal Aquatic Mammals, which is “Supported through Joint Sponsorship by the European Association for Aquatic Mammals, the Alliance of Marine Mammal Parks and Aquariums,
and the International Marine Animal Trainer’s Association.”
From a technical standpoint  NOAA’ draft is a huge step forward in delineating more species-specific guidelines, yet there are no teeth in the document to force compliance with the new standards.

 NOAA recommends that Federal agencies and prospective  applicants evaluating these types of impacts for the purposes of engaging in the aforementioned statutory processes also use these thresholds in the manner described here. However, this guidance does not create or confer any rights for or on any person, or operate to bind the public. An alternative approach may be proposed (by Federal agencies or prospective applicants) and used if case-specific information/data indicate that the alternative approach is likely to produce a more accurate estimate of Level A Harassment, harm, or auditory injury for the project being evaluated and if NOAA determines the approach satisfies the requirements of the applicable statutes and regulations.
The National Research Council (NRC 2004) provided basic guidelines on National Standard  (NS2) under the Magnuson-Stevens Fishery Conservation and Management Act, section 301, which stated “Conservation and management measures shall be based upon the best scientific information available.” They recommended that data underlying the decision-making and/or  policy-setting process be: 1) relevant, 2) inclusive, 3) objective, 4) transparent and open, 5) timely, 6) verified and validated, and 7) peer reviewed.

Of the ten candidates for peer review, NOAA selected four, all specialists in the ability of marine mammals to hear. None of the behavior experts were included, and no one addressed the effect of sound on the animals outside of the hearing structures themselves – so tissue damage resulting directly from noise, or from rapid decompression during escape from sound sources are included.

The following website contains updated information on the peer review process including: the  charge to peer reviewers, peer reviewers’ names, peer reviewers’ individual reports, and NOAA’s response to peer reviewer reports

Below are some samples from the document – which, while long, is logically laid out and easy to navigate (but very science dense).

NOAA has compiled, interpreted and synthesized the best available science to produce new thresholds for the onset of both temporary and permanent hearing threshold shift (“TTS” and  “PTS”, respectively) in marine mammals from underwater sound. In the regulatory context, NOAA uses this information to help quantify “take” and to conduct more comprehensive effects analyses under several statutes.
For applicants/users that have the ability to model moving animals and/or  sources and the accumulating sound at each receiver, NOAA proposes that 24-hours or the length of activity, whichever is less, be used as the accumulation time. 24 hours has been used in other noise assessment planning applications (e.g., community noise planning for aircraft, vehicular traffic, and railway noise) and provides a reasonable outer bound in situations where the model will be able reflect realistic changes in relative distance between the source and likely exposed marine mammals over the course of a day.
However, for models that do not incorporate animal movement, it is not appropriate to make the assumption that animals will remain at a constant distance from the source accumulating acoustic energy for 24 hours. Additionally, if sound accumulation cannot be modeled, an alternative method must be used. For situations where modelling of movement and sound accumulation are not possible, an alternate method that is intended to address the accumulation of sound energy over time, but instead provides a distance from the source (“SEL threshold distance”) that is  simpler to apply in exposure modeling (i.e., would be used in calculations in the same way distance is used to calculate exposures above previous NOAA sound pressure level thresholds) should be used. Based on what we know about typical animal movement and avoidance, we propose a 1-hour accumulation period be used to calculate the “SEL threshold distance”. This “SEL threshold distance” is calculated by determining the distance from the source at which an animal would have to remain for 1 hour in order to accumulate sound to the designated threshold.  While, animals may move closer and farther from the source, this distance is considered a reasonable and conservative approximation.
The 24-hour (for models able to account for movement and sound accumulation) and 1-hour (for models not able to account for movement and sound accumulation) accumulation periods are considered a conservative baseline for accumulation time under most situations. The use ofmodels able to account for movement and sound accumulation may also allow for the inclusion of additional details to provide a more realistic results based on the accumulation of sound (e.g. information on residence time of individuals, swim speeds for transient species, or specific times when activity temporarily ceases). Alternatively, there may be case-specific circumstances where the 1-hour accumulation time should be modified to account for situations where animals are expected to be in closer proximity to the source over a notably longer amount of time, based on activity, site, and species-specific information (e.g., where there is a resident population in a small and/or confined area and a long-duration activity with a large sound source, or a continuous stationery activity nearby a pinniped pupping beach).
NOAA’s previous acoustic threshold levels are expressed as root-mean-square (dBrms), which  uses a different metric from peak sound pressure levels (dBpeak) and SELcum that are being recommended for our TTS and PTS onset acoustic threshold levels. Thus, we recommend caution when comparing past acoustic threshold levels to the acoustic threshold levels presented in this document as because they are based on different metrics, they are not directly comparable. For example, a 180 dBrms level is not equal to a 180 dBpeak level. Furthermore, theSELcum metric incorporates time and is an energy level with a different reference value (re: 1μPa2-13 s), thus it is not directly comparable to other metrics that describe sound pressure levels (re: 1 14 μPa).


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