Page 32 - April 2008

estimated from numerical models of their middle and inner ears (Ketten, 1997 and 2000). There are no captive mysticetes, but at least one attempt has been made to measure AEP signals in the wild on a minke whale, the smallest species of this group. Other mysticete species may be too large to obtain a reliable AEP signal with commercially available electrodes. Efforts in this area need the same level of attention and plan- ning as the BRS on beaked and pilot whales.
Finally, in order to begin to understand “biologically sig- nificant” effects on behavior as defined within the framework outlined in the latest NRC report (NRC, 2005), multi-discipli- nary basic research is needed to understand the primary and synergistic effects of sound on marine ecosystems, including crustaceans, corals, sponges, sea grasses, and all other living things in the sea. Designing experiments to learn about poten- tial changes in the marine ecosystem, including animal habi- tats, over long periods of time is a very difficult task. But changes in the behavior and habitats of marine animals over the long term could significantly affect their populations as well as the overall health and stability of the marine environ- ment.AT
Looking towards the future
Many scientists and others concerned about global warming were deeply troubled when the HITF and ATOC projects came under such heavy fire by a number of environ- mental groups in the early 1990’s. Here was a solution for one environmental problem—long term monitoring of global cli- mate change—that created another very polarized environ- mental concern because there were little data available to address it. This dilemma is surfacing again with the develop- ment of offshore wind farms in many parts of the world in efforts to meet requirements of the Kyoto agreement to sig- nificantly reduce CO2 emissions by 2030. Wind farms really do produce an underwater hum, albeit at a much lower level than the ATOC source, but it can be detected by many fish and marine mammals and potentially mask interspecies communications necessary for reproduction as well as other sounds important to their well being (Wahlberg and Westerberg, 2005, Henriksen et al., 2007). This time though the world is very much aware of the potentially harmful effects of anthropogenic noise in the ocean and many marine scientists are already on top of the problem.
Endnotes
1 The primary environmental laws are the Marine Mammal Protection Act (MMPA) and Endangered Species Act (ESA). In addition the National Environmental Policy Act (NEPA) requires that federal actions affecting the environment be assessed to inform regulators and other decision-makers about potential consequences and alternatives to minimize impacts.
2 Most military sonar use is passive as vessels prefer to remain silent and undetected. When sonar is active, it transmits a sound pulse or “ping” that travels through the water and reflects off objects in its path. The reflected sounds, or echoes, return to a passive receiver and are electronically transformed into images on a display screen, very similar to use of medical ultrasound to form images of internal organs and monitor fetal development. Passive sonar uses only the receivers to “listen” to sounds emit-
ted by vessels or other objects and marine mammals.
3 ‘Ceteceans’ include whales, dolphins and porpoises, while ‘pin- nipeds’ include seals, sea lions, and walrus. Under the Order Cetecea, there are two suborders: (1) odontocetes or toothed whales that include dolphins, porpoises, white whales, killer whales, pilot whales, beaked whales, bottlenose whales, melon- headed whales and sperm whales; and (2) mysticetes or baleen whales that include bowhead whales, right whales, gray whales, minke whales, sei whales, Bryde’s whale, blue whales, fin whales
and humpbacks.
4 NOAA National Marine Fisheries Service (NOAA Fisheries) is
the responsible regulatory agency for issues concerning marine animals. If justified and properly documented, NOAA Fisheries Office of Protected Resources issues permits authorizing inci- dental takes of marine mammals for sound-producing activities in the ocean.
5 Strandings of marine mammals are normal events that occur all the time around the world. Mass strandings involve more than two animals stranding in the same place and time.
6 At this time the UK and Norway were preparing to deploy low frequency active sonar, but with a frequency bandwidth that extended into the low kHz range.
7 Many people have experienced TTS after attending a loud music concert. Currently TTS/PTS is a major concern for soldiers and marines firing high-power weapons in Iraq and Afghanistan as well as for children and teen-agers at home using ear buds to lis- ten to music on personal music players and movies on DVD players.
References
Anderson, I. (1991). “Global hum threatens to ‘deafen’ whales,” New Scientist, 19 January 1991.
Au, W. W. L., Nachtigall, P. E., and Pawloski, J. L. (1997). “Acoustic effects of the ATOC signal (75 Hz, 195 dB) on dolphins and whales,” J. Acoust. Soc. Am. 101, 2973–2977.
Baggeroer, A., and Munk, W. (1992). “The Heard Island feasibility test, Physics Today 45, 22–30.
Bowles, A. E., Smultea, M., Würsig, B., DeMaster, D. P., and Palka, D. (1994). “Relative abundance and behavior of marine mam- mals exposed to transmissions from the Heard Island feasibility test,” J. Acoust. Soc. Am. 96, 2469–2484.
Burgess, W. C., Tyack, P. L., Le Boeuf, B. J. and Costa, D. P., (1998). “A programmable acoustic recording tag and first results from free-ranging northern elephant seals,” Deep-Sea Research Part II 45, 1327–1351.
Caltrans (2001). “Pile installation demonstration project, fisheries impact assessment,” PIDP EA 012081, Caltrans Contract 04A0148, San Francisco-Oakland Bay Bridge East Span Seismic Safety Project, 59 pp.
Carlson, T., Hastings, M., and Popper, A. (2007). “Update on rec- ommendations for revised interim sound exposure criteria for fish during pile driving activities,” Memo to Suzanne Theiss, California Department of Transportation and Paul Wagner, Washington Department of Transportation Caltrans, dated December 21, 2007.
Casper, B. M., Lobel, P. S., and Yan, H. Y. (2003). “The hearing sen- sitivity of the little skate, Raja erinacea: A comparison of two methods,” Environ. Biol. Fishes 68, 371–379.
Cohen, J. (1991). “Was underwater ‘shot’ harmful to the whales?” Science 252, 912–914.
Cook, M. L. H., Varela, R. A., Goldstein, J. D., McCulloch, S. D., Bossart, G. D., Finneran, J. J., Houser, D., and Mann, D. A. (2006). “Beaked whale auditory evoked potential hearing meas-
30 Acoustics Today, April 2008