Page 42 - Summer 2015

Underwater Noise and Marine Protected Species
ficient modeling capabili- ties. Nevertheless, NOAA must ensure that those with less sophisticated means can use the more complex acoustic thresholds provid- ed in the Guidance. As a re- sult, NOAA is working on a companion "User Guide" to be released with the Final Guidance that will assist applicants to apply updated acoustic threshold levels correctly. Developing sim- ple, alternative approaches that are broad enough to encompass the scope of ac- tivities authorized is chal- lenging but essential for the Guidance implementation.
Figure 2. Unweighted annually averaged ambient sound pressure level for the Atlantic (1/3-octave band centered at 100 Hz at a depth of 5 meters) associated with global shipping created for the CetSound project.
Furthermore, NOAA rec-
ognizes that when the
Guidance becomes final-
ized, applicants will be in varying stages of the application process. NOAA is considering how best to address applica- tions and actions that are “in the pipeline” and will provide a transition plan when the Guidance is finalized (expected in late 2015).
addressing nonmarine mammal species (note: NOAA still is able to evaluate the impacts on these species via numerous means, including qualitative assessments or regional guid- ance). However, there have been numerous recent advances in understanding the impacts of man-made sound on these other important species that should facilitate the develop- ment of national guidance documents (Popper et al., 2014).
Chronic Noise Exposure and NOAA Cetacean and Sound Mapping Project
The acoustic thresholds mentioned above focus on discrete, often loud acute acoustic sources and their impact on ma- rine mammals. However, NOAA recognizes that in addition to understanding acute sound sources, there is a need to bet- ter incorporate and consider chronic sound to comprehend the complete soundscape these protected species inhabit and the potential impacts of increased background noise on their fitness and habitat (Hatch et al., 2008; Slabbekoorn et al., 2010).
In 2011, NOAA convened two working groups, the Under- water Sound Field Mapping Working Group (SoundMap) and the Cetacean Density and Distribution Mapping Work- ing Group (CetMap), with the overarching effort of both groups referred to as CetSound. These groups consisted of
Impacts Beyond Effects on Hearing
Although the physics associated with sound propagation in the ocean environment can be complex, with access to the proper tools and software, received levels can be estimated and predicted. However, understanding what a particular received level means to a marine species in terms of imme- diate behavioral responses and impacts to growth, survival, or reproduction as well as long-term consequences to popu- lations is difficult. Due to the inherent complexity and vari- ability of marine mammal behavioral responses, NOAA is starting the challenging process of developing national guid- ance for better predicting significant behavioral effects.
Although the focus of the draft Guidance is marine mam- mals, NOAA also must assess the potential for acoustic take for other species under its jurisdiction. Thus there is a need to establish national acoustic guidance for ESA-listed ma- rine fishes and sea turtles and National Marine Sanctuary resources. Admittedly, NOAA is farther behind in its work
40 | Acoustics Today | Summer 2015