San Diego

The US Congress is considering proposals that will make it easier to get permission to use high-volume sonars in the ocean — just as fresh evidence suggests that their noise can harm marine mammals.

Capitol Hill is looking at two measures to loosen the 1972 Marine Mammal Protection Act (MMPA), which sets guidelines for noisy experiments in the oceans. One would simplify the rules, making it easier to get permission to do the experiments. The second would exempt the US Navy from the regulations on the grounds of national security.

The changes are supported by the navy and by some geophysicists, who want to use noise-generating devices to study geological formations on the ocean floor. But they are strongly opposed by many marine biologists. “There is a huge split over the issue,” says John Hildebrand, who studies marine mammal acoustics at the Scripps Institution of Oceanography in La Jolla, California.

In a Brief Communication in this issue of Nature, a team led by Paul Jepson of the Institute of Zoology in London concludes that 14 whale deaths off the Canary Islands last year may have been caused by decompression sickness after the animals shot to the surface to escape sonars during Spanish-led international naval exercises (page 575). The team says the sonar appears to have caused gas bubbles to form in the blood, damaging the whales' livers and kidneys.

Experts say that the study provides some of the most direct evidence to date that sonars can kill marine mammals. “This report has the potential to be the 'smoking gun' on the cause of sonar-related mammal strandings,” says Hildebrand. “It certainly focuses on the potential dangers of sonar, which need to be thoroughly investigated.”

On 25 September, however, the oceans subcommittee of the House of Representatives Committee on Resources passed a 'reauthorization' of the MMPA that would give government agencies more freedom to permit experiments in the oceans. Agencies could also ask for stronger proof that a study might cause damage. The bill will soon be considered by the full committee, where some Democrats will seek to tighten its provisions.

Meanwhile, a House–Senate conference committee is due to consider a 2004 military spending authorization bill that would exempt the navy from the sonar rules. “We fear something bad” is going to come out of the conference, says Karen Wayland, a geologist with the National Resources Defense Council, an environmental group that took successful court action to block the navy's use of some sonar devices (see Nature 425, 6; 200310.1038/425006a).

John Orcutt, a geophysicist and deputy director of Scripps, says that he favours the proposed modifications to the MMPA, so that researchers can secure permits more easily than at present. “The process is tremendously flawed,” he says. Orcutt is worried, however, that the navy exemption would encourage the military to do all of its own experiments and stop supporting external researchers, who would remain constrained by the law.

But marine biologist Ken Balcomb, director of the Center for Whale Research in Friday Harbor, Washington, says recent deaths and strandings of marine mammals should persuade physical oceanographers — and Congress — to worry more about protecting these animals instead of loosening research regulations.