Ouch, blue whale feels the heat (Image: Diane Gendron)

Whales in the Gulf of California are starting to blister in the sun, say researchers who have studied them for three years.

They blame the blisters on exposure to harmful ultraviolet radiation as the Earth’s protective stratospheric ozone layer struggles to repair itself.

The whales get sunburned when they come up for air, rest on the surface and feed their young. “It’s the first evidence that ultraviolet light can damage their skin, but it’s difficult to say what the impact on their health might be,” says Laura Martinez-Levasseur of the Institute of Zoology in London and Queen Mary, University of London, and co-leader with Karina Acevedo-Whitehouse of the team that observed the whales between 2007 and 2009.


Over that period, she and her colleagues studied blue whales, sperm whales and fin whales. They monitored the prevalence of blisters by taking 156 high-resolution photographs of skin on individual whales. They also took skin biopsies from 142 whales so they could analyse them for melanocytes, skin cells that react to sunlight by producing the protective chemical, melanin.

Over the three years the proportion of blue whales with blisters rose from 10 to 60 per cent. As you might expect the melanocyte counts also varied according to lifestyle and natural differences between the species.

Fin whales, which have very dark pigmentation and which are resident year round in the sun-soaked Gulf of California, had counts twice those of blue whales, which only visit in the summer to calve and raise their young.

Martinez-Levasseur and her colleagues found that the blue whales suffered their worst blistering early on in the season. “When they arrive in the gulf from much colder areas, they are suddenly exposed to all this ultraviolet,” she says. But they had fewer blisters by the end of the season, so like humans acquiring tans, they do adapt to the extra radiation.

Sun-worshipping sperm whales

The sperm whales also suffered quite severe blistering compared with the fins, but mainly because they spend much longer than the other two species resting at the surface. “They can spend all day on the surface,” says Martinez-Levasseur, who found that the sperm whales had intermediate melanocyte counts.

Although the researchers conclude that the increased blistering is probably down to increasing UV exposure through depletion of protective ozone, meteorologists contacted by New Scientist were more doubtful. “I’d be cautious with the link to ozone depletion,” says Guus Velders of the Netherlands Environmental Assessment Agency in Bilthoven.

“Since about 2000, the levels of ozone have been about constant,” he says. “So I don’t think the link between UV and sun damage found in whales can be associated, as proposed, with depletion of the ozone layer.”

But John Turner of the British Antarctic Survey says that the ozone layer won’t be fully healed till 2060 at the earliest. “So we’re still bumping along the bottom, and we’re still getting huge increases in UVB, even when there’s cloud cover,” he says.

The researchers found no evidence of worse effects of UV exposure, such as cancers and melanomas. But as a follow-up, Martinez-Levasseur and her colleagues are monitoring the whales for increases in the activity of genes involved in repairing UV damage to DNA.

Journal reference: Proceedings of the Royal Society B, DOI: 10.1098/rspb.2010.1903