AcousticEcology.org Special Report
International Whaling Commission
June 29-July 10, 2004
From Annex K of the Scientific Committee Report, from the Standing Working Group on Environmental Concerns:
Mini-symposium on Anthropogenic Noise [DOWNLOAD SYMPOSIUM REPORT(doc)]
Appendices: Roger Payne, Synergistic Effects of Multiple Stressors [DOWNLOAD(doc)]
John Hildebrand, Acoustics Basics [DOWNLOAD(doc)]
Darlene Ketten, Marine Mammal Auditory Systems [DOWNLOAD(doc)]
From the full Scientific Committee Report
[DOWNLOAD GRAY WHALE SECTION(doc)]
[DOWNLOAD SUMMARY OF NOISE SYMPOSIUM AND RECOMMENDATIONS(doc)]
The annual International Whaling Commission meeting was held this summer in Italy. There were several actions and reports that were of special interest to those of us working on ocean noise issues.
Most encouragingly, the entire IWC unanimously endorsed the Scientific Committee’s report, which contained some very specific recommendations and concerns regarding the effects of both seismic surveys and naval sonars. Further, the Standing Working Group on Environmental Concerns held a mini-symposium on ocean noise, which attracted several papers that addressed noise concerns in new and important ways.
The Scientific Committee (SC) report addressed noise issues in some detail. The first had to do with the ongoing oil and gas development project in the Western Pacific, off Russia’s Sakhalin Island. While the Russian delegates hold that population monitoring programs already in place are sufficient, the SC noted with concern that this population appears to have biological problems (100 members, only 23 of which are breeding females, and relatively low calf survival rates). There is only one known coastal feeding habitat used by females and calves; it is about 60km by 5 km in size, with development plans proceeding on its edges and across its width. The SC also noted that the breeding ground for this population is currently unknown. Annual review of the status of this stock of whales was named as a top priority for future years’ research.
The SC report noted that seismic surveys have been shown to cause displacement of whales from their feeding grounds both off Sakhalin Island, and off the coast of Brazil. The Committee commended Brazil for its work to protect critical marine habitats from noise exposure, and “views with great concern the impacts. . . from exposures to seismic sound impulses, particularly with respect to threatened populations such as the western gray whale.”
Also noted were records showing that between 1960 and 1995, all ten mass strandings of beaked whales around Japan occurred onshore from where US Navy exercises take place, with the implication that mid-frequency sonars may have been responsible here as in several other mass strandings studied more thoroughly in recent years.
The SC report contained a series of detailed recommendations based on an awareness that some “sound sources radiate low-frequency sound over very large areas thereby exposing populations to low sound levels (< 120 dB re 1 µPa) over relatively long periods of time (chronic exposure). In other cases, sound sources radiate mid- to high-frequency sound over relatively small areas and individual animals are exposed to high levels of sound (> 160 dB re 1 µPa) over relatively short periods of time (acute exposure).”
In conclusion, “the Committee agrees that there is now compelling evidence implicating military sonar as a direct impact on beaked whales in particular. The Committee also agrees that evidence of increased sounds from other sources, including ships and seismic activities, were cause for serious concern. The potential for cumulative or synergistic effects of sounds, as found in other taxa, with non-acoustic anthropogenic stressor was noted. Whilst noting that there is considerably more scientific work needed, the Committee emphasises that measures to protect species and habitats cannot always wait for scientific certainty, as encoded in the precautionary principle. This is especially true for cases involving the exclusion of an endangered population from its habitat. As a result, the Committee agrees that noise should remain a standing priority item on its agenda.”
Among the recommendations endorsed by the SC and the entire IWC were: to do full analysis of stranding data related to military activities, to investigate whether there are similar correlations between mass strandings and extreme natural sounds (earthquakes, typhoons), and standardized post-mortem protocols.
Regarding seismic surveys, the SC and IWC endorsed a set of detailed protocols for mitigation and monitoring near seismic surveys, including access to information regarding timing, distribution, and extent of surveys (both planned and historic patterns) in critical habitats or potentially critical habitats, continuous acoustic monitoring of critical habitats before, during, and after seismic surveys, and independent monitoring of critical habitats to evaluate displacement or disruption of important behaviours (further specified to mean “independent and highly experienced shipboard marine observers and a monitoring system and platform that are independent of the seismic source vessel and seismic support vessels”). These (and several other) recommendations were commended to member countries for adoption, and requested to be passed on to representatives of the oil and gas industry and geophysical academic teams and relevant government committees and agencies.
On the general topic of anthropogenic noise, the Committee made a series of important and wide-ranging recommendations:
(1) the convening of a workshop on the impacts of seismic exploration (including both industrial and academic activities) at its 2006 meeting;
(2) the integration and coordination of international research projects to study and describe acoustic ecologies;
(3) the establishment of a working group to derive a series of hypotheses to test for synergistic impacts on cetaceans;
(4) the inclusion of anthropogenic noise assessments and noise exposure standards within the framework of national and international ocean conservation plans (e.g. consideration during designation of critical habitats, marine protected areas and ocean zoning);
(5) support for multinational programmes to monitor ocean noise (e.g. IOOS) and the development of basin-scale, regional and local-scale underwater noise budgets.
Mini-symposium on anthropogenic noise
The Special Working Group on Environmental Concerns held a mini-symposium on acoustics. At this symposium, a number of papers were presented that introduced important ideas and recent research with far-reaching implications.
Among the most important findings presented:
Ambient Noise Increases
Comparisons of some recent recordings and similar surveys taken in the middle of the 20th century indicate that ambient noise has increased in many of the world’s oceans by 3-5dB per decade. This amounts to an increase over the past sixty years of somewhere between one and two orders of magnitude (that is, a 10-fold to 100-fold increase). Sources for this sound are primarily anthropogenic, especially shipping noise.
A recent study highlighted the dramatic differences between an urbanized and relatively pristine oceanic habitat. Ambient noise levels in the fin whale song frequency band were two to three orders of magnitude (20-30db, that is, 100-1000 times) higher in the Ligurian Sea (part of the Mediterranean) than in the Gulf of California. In the Ligurian Sea, ambient noise levels were so high as to mask all but the closest singers. In Cape Cod Bay, a critical habitat for the endangered northern right whale, average spectrum noise levels in the 50-200Hz frequency band were above 110dB re 1uPa2/Hz, levels that could be considered chronically troublesome; similarly high sound levels of ambient low frequency noise were found at other coastal US ports. 10,000 commercial supertankers operate worldwide, especially concentrated near highly-used shipping lanes.
A survey of general ocean acoustics noted that noise from vessel traffic at high latitudes is particularly efficient at propatating over large distances because in these regions the oceanic sound channel (zone of most efficient sound propagation) reaches the ocean surface.
Sound from seismic survey airguns increased the measured ambient noise levels of a blue and fin whale feeding area in the North Atlantic by two orders of magnitude (again, a 100-fold increase). This increase, observed throughout a nearly hundred thousand square kilometer study area (200x400 nautical miles), was nearly continuous for days at a time; such long-range effects contrast with typical effects modeling, which focus on areas very near the survey vessels and consider the effects of a single seismic shot lasting only a fraction of a second.
Questions were raised about the effects of such chronic elevated noise exposure on searches for prey, and finding suitable mates. Roger Payne presented additional information on the role of infrasound in maintaining whale “heards.” He hypothesised that baleen whale populations might live in acoustic contact throughout an ocean basin where very long-range communication can take place; elevated levels of low frequency noise could very well disrupt such long-range communication, with potentially dramatic effects of reproductive success and thus population vitality. In certain Northern Hemisphere ocean regions the area in which a fin whale can hear a compatriot has decreased by four order of magnitude (ie, calls can be heard in an area one ten-thousandth as large as previously). Payne noted that in spite of great efforts to find them, there are no known breeding grounds for open ocean populations of fin whales, suggesting that there may be no need for fin whales to meet en masse at particular times and places, if they are able to get together, simply by calling and listening for each other over great distancesthey may indeed have no breeding grounds simply because they are not necessary.
Roger Payne presented a paper that introduced an important new idea: that the effects of two or more weak population or individual health stresses can combine synergistically to dramatically increase mortality that may be otherwise expected. Two recent studies have shown that when tadpoles of green frogs were exposed for 16 days to the common pesticide carbaryl at a concentration only 1/3 as great as is commonly found in nature, the tadpoles suffered 10% mortality. But when only the smell of a newt, predatory on these tadpoles was added, tadpole mortality increased to 80%, meaning that the introduction of the predator’s smell somehow increased the lethality of carbaryl eight fold. This synergistic effect was even more pronounced with bullfrog tadpoles. Here, carbaryl alone caused only 2% mortality (indistinguishable from carbaryl-free controls) yet the same low carbaryl concentration when combined with just the smell of predatory newts caused 92% mortality, a 46 times amplification of the effect of the pesticide.
It is especially fascinating that the introduction of simply the smell of the predator, which in itself could not cause any direct health effect (besides perhaps stress), can so dramatically increase the detrimental effects of an otherwise modest pollutant. An obvious analogue in the sea is noise (with shipping being the most prevalent source, though extended exposure to other sources such as airgun noise should also be considered) as a non-lethal stressor, somehow synergistically increasing the detrimental effects of known pathogens (such as infections, pollutants, or parasites).
It is interesting that right whale populations are increasing rapidly in the southern hemisphere where contaminant concentrations and ships traffic noise is lower than both are in the Northern Hemisphere (where right whale populations are currently diminishing rapidly). The assumed differences in concentration of pollutants and shipping noise in the two hemispheres fits well with the theory that the different fates of northern and southern right whales may be due in part, to synergistic impacts of shipping noise and pollutants. In any case it seems to be a subject worthy of closer investigation. The subcommittee recommends to the full committee that the process of assessing the effects on whale populations of the possible synergistic effects of stressors as different as chemical contaminants, whaling, and anthropogenic sounds, be encouraged.
Darlene Ketten presented a paper summarizing current knowledge about marine mammal auditory systems. She stressed that auditory damage will occur only when exposed to high levels of sound in the frequency range of the specific species. In response to a question, she also suggested that hearing loss may not necessarily lead to death; there have been some evidence from stranded individuals showing long-term (on the order of several years) bony degradation in the jaw and infections that spread to the inner ear, suggestive of hearing damage or loss. She also noted that “the ocean is a naturally relatively high noise environment and whales and dolphins in particular evolved ears that function well within this high natural ambient noise. This may mean they developed "tougher" inner ears that are less subject to hearing loss. Recent anatomical and behavioral studies do indeed suggest that whales and dolphins may be more resistant than many land mammals to temporary threshold shifts, but the data show also that they are subject to disease and aging processes. This means they are not immune to hearing loss, and certainly, increasing ambient noise via human activities is a reasonable candidate for exacerbating or accelerating such losses.” At the same time, though, she stressed that “unfortunately, existing data are insufficient to accurately predict any but the grossest acoustic impacts on marine mammals. At present, we have relatively little controlled data on how the noise spectrum is changing in oceanic habitats as a result of human activities. We also have little information on how marine mammals respond physically and behaviorally to intense sounds and to long-term increases in ambient noise levels. The hazards are compounded also by the fact that rising concerns about virtually any sound use may also be hampering the development and deployment of even simple devices such as effective acoustic deterrents that could decrease marine mammal by-catch.”
A literature review paper on whale watching reported a number of 2003 and 2004 studies that point to behavioral disruptions in the presence of small boats. In New Zealand, bottlenose dolphins spent more time underwater, with males showing avoidance earlier than females; in Scotland, bottlenose dolphins significantly increased the synchronicity of their breathing, perhaps related to a familiar anti-predator response; and in Patagonia, dusky dolphins decreased their feeding behavior.
Several papers looked at the seeming sensitivity of beaked whales to high-intensity sound (primarily mid-frequency sonars, but perhaps also airguns). A review of historical mass strandings of beaked whales seems to show a recent increase in such events, with a high correlation to military maneuvers or airgun activity, though models suggest received levels in one case (Bahamas) did not exceed 160-170dB re 1uPa, lower than would be expected to cause even temporary threshold shifts (ie hearing loss). Concern was raised that strandings may not give a complete indication of animals harmed by high-intensity sound, since others may be severely affected an not die, or may die and not strand. One paper looked at 10 mass strandings of beaked whales around Japan between 1960 and 1995, all of which took place in areas where US Naval operations take place offshore. Another paper looked at several unusual cetacean stranding events that occurred in Chinese waters in 2004 during a period when large-scale naval exercises were taking place in nearby waters south of Taiwan; these strandings involved primarily pilot whales, and were unusual in terms of the species involved (based on a ten-year record of previous strandings); Darlene Ketten commented that the observed injuries were consistent with blast trauma, relevant given that live ammunition exercises were being conducted.