An interview with Earthwatch-supported scientist Ken Balcomb reveals the physical damage sustained by whales that died in the Bahamas following Navy sonar tests.
One of the most contentious environmental issues of recent times is the debate over the U.S. Navy's new sonar system that uses extremely loud, low-frequency sounds to locate submarines over wide areas of ocean. That system, many researchers and environmental advocates contend, has the potential to interfere with or even kill sound-sensitive whales and dolphins. The issue came to a head on March 15, 2000, when 17 cetaceans of 4 species stranded themselves in the Bahamas right after the Navy conducted a low-level sonar test anti-submarine warfare Gap Exercise in the area. Although the sonar used was "normal standard" and operating at midrange frequencies, (3.5-7.5 kHz, 235 dB), an ocean duct 125-150 meters deep may have contributed to the sound traveling much farther and at higher intensity than anticipated. The unusually large numbers of whales stranded and the timing of their strandings have been taken by people to be evidence of a correlation between the sonar and whale deaths.
Two of those people are Earthwatch researchers Kenneth Balcomb and Diane Claridge, who have been working on a cetacean census in the Bahamas with Earthwatch teams since 1992 on their project Bahamas Whales and Dolphins. They were the scientists who documented most of the 16 stranded whales and a dolphin, assisted in rescue efforts to return some of the whales to sea, and collected data that may prove vital in the controversy over experimental, low-frequency sonar tests the navy has been conducting. An astonishing 14 of the 17 stranded cetaceans were beaked whales, which are uncommon and rarely strand because they are deep-divers of the open ocean. In the Bahamas study, Blainville's (dense)-beaked whales (Mesoplodon densirostris) are sighted more frequently than Cuvier's beaked whale (Ziphius cavirostris). Moreover, six of the seven stranded animals known to have died were beaked whales, all but one of them Cuvier's beaked whales. All six beaked whales that died showed evidence of pressure trauma, which the National Marine Fisheries Service and the Navy consider is "highly likely" linked to the sonar tests. High-decibel sonar tests in other parts of the world have also coincided with stranded whales, but the Bahamas' whales showed the first clear sign of internal damage that might have been linked to the tests. And the stranded whales may only have been the tip of the iceberg. This year's Earthwatch teams have sighted no Cuvier's beaked whales.
Balcomb, who is the founder of the Center for Whale Research in Washington state, has reported his findings to the Navy and the National Marine Fisheries Service, which is now in the process of deciding whether to grant the Navy permission to conduct intense low-frequency sonar operations on a global basis for five years.
Since Balcomb's report was partly responsible for a series of hearings to be held by the National Marine Fisheries Service on this issue, we thought it would be useful to talk to the man who is at the center of the controversy. The following is an interview Earthwatch conducted with Balcomb on April 12, 2001, about his findings from the stranded whales and their implications for the use of high-decibel sonar.
EWI: The evidence you and your colleagues have found in stranded whales points to something else going on than mere hearing loss. What you're saying is a bit different from other folks who claim that LFAS disrupts cetaceans' sensitive hearing and therefore disorients them. You're claiming there's actual physical damage-hemorrhaging-around ears and brain.
KB: Yes there's actually hemorrhaging going on. It isn't an auditory injury per se. It affects the ears, but this pressure damage is not related to whether or not the whales have temporary threshold shift in their hearing [a hearing loss]. The National Marine Fisheries Service (NMFS) says these injuries are survivable-and they are, but only with hospitalization. And whales don't have that option.
EWI: So what's actually happening?
KB: Think of resonance in an air chamber: A sound vibration produces an acoustic pressure wave that goes through an air chamber, expanding and contracting a millimeter or a micron or so if that vibration is not in resonance. But if the sound wave is in resonance, it will expand and contract many times that. An air chamber, like a whale's lung or a fish's swim bladder, shrinks in volume the deeper the animal goes. It's just like squeezing a balloon; the harder you squeeze, the smaller it gets. At the same time, since the air chamber is getting smaller, its resonance frequency will increase. So will any sound wave's amplitude when it is in resonance. Aside from potential auditory trauma from underwater sound, we have been concerned about the other potentially damaging resonance effects from the resonance of underwater sound, such as had been previously reported in U.S. Navy studies: vertigo in immersed laboratory animals, hemorrhage in lungs, liver. That is exactly what we have seen in the beaked whales that stranded.
EWI: Why are beaked whales apparently hypersensitive to sound waves?
KB: All the dolphins are jaw-hearers-they hear through the lower jaw. The fat of the lower jaw connects directly to the earbone. Now the beaked whales have a lot more of that fat plus they have an acoustic, reflective surface on the inside of the mouth, so that basically they're not losing any of the energy of the incoming sound. They've developed an anatomical gain in their hearing so that, overall, I believe they're twice as sensitive to sound as delphinids and other odontocetes are. Beaked whales are deep-diving squid-eaters. Bottle-nosed beaked whales routinely go 500 to 1,500 meters, and studies of beaked whales in Japan and elsewhere clocked them going deeper than 1.5 kilometers. They may compete with sperm whales for the deep diving record.
EWI: Are sperm whales at risk from LFA sonar?
KB: I think so, but nothing's documented. I've got to learn more about sperm-whale hearing anatomy. They do produce loud, echo-location clicks, while beaked whales do not. Beaked whales are primarily passive: they just listen, whereas sperm whales are active. They 'ping,' kind of like big sonars.
EWI: Are other, deep-diving marine species besides certain cetaceans potentially at risk from LFA sonar?
KB: Anything that has a gas bladder [swim bladder] or an airspace in it, especially swordfish, marlins, etc.). I'd like to talk with a billfish biologist. Of course, if a marlin is affected at depth, it doesn't have to come to the surface to breathe, so if it dies, the carcass is probably going to sink. Injured whales do have to come to the surface to breathe, and that's when we see them, when they flounder into shore. Some of the whales, I'm sure, died and sank, because they couldn't make it to the surface. This year we haven't seen any of the 35 Cuvier's beaked whales we had identified. And, for the first time, we've seen some dense-beaked whales with shark bites. We are seeing more sperm whales, perhaps because the squid-feeding niche has opened up a bit.
EWI: Has the Navy funded any research on the potentially vastly increased impact of its LFAS at depth?
KB: I think that a lot of [cetacean] research the Navy is funding on contract is for a specific answer that they want: It isn't like, 'Let's go out and find out what the problem is.' It's, 'tell us what the hearing threshold of a dolphin is in a captive situation' where you can hook him up. If they hit dolphins with 182 dB, then the dolphins can't hear that noise for a little while, but, two days later, they can hear it again. Obviously they're conducting this research in a shallow-water environment at a high-frequency level in the whale's range of hearing, and those are the figures you see in the LFAS (low-frequency active sonar] statements. It's not equivalent to the LFA sonar or in the environment where the whales that are having problems. It's a nice study, but it's not the answer to the problem. I think those people who have studied whales in other arenas besides Navy contracts need to speak up about [their findings].
EWI: What's your next step?
KB: I think my letter's got the Navy's and NMFS' attention. I have to respond to NMFS's dismissal of this whole thing. Basically they said, 'Well, it's a different sonar.' I'll have to point out that you can't just point to a frequency and say, well that's a problem, but this isn't. If I'm right about resonance effects, the potential to inflict damage occurs over a range of frequencies in airspaces whose resonance varies with a whale's depth. You can't dismiss physics.
I'm just delighted that EW has stood by us here. The participants were wonderful when they were here. That was the first day of a team [when the whales stranded]! We were just briefing them that you can't expect a whale every day-that they might even be here the whole 10 days and not see any whales-you try to play it down. And boom! There's one right on the beach in front of us. That was a big day.
For further details, vist The Center for Whale Research.
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