Inside Science News Briefs

A collection of brief stories from the world of science

By Jim Dawson
Inside Science News Service
October 13, 2008

Global Warming Brings Louder Oceans

As the world's oceans absorb increasing amounts of human-generated carbon dioxide from the atmosphere, they will become both more acidic and noisier, according to researchers with the Monterey Bay Aquarium Research Institute in Moss Landing, Cal. Their study, published recently in the journal Geophysical Research Letters, says the noise increase will correspond to underwater sound actually travelling up to 70 percent farther in the more acidic seawater by 2050. That could dramatically improve the ability of marine mammals to communicate over long distances, but it could also increase the amount of background noise that the mammals have to live with. Ocean chemists have known for years that the absorption of sound in seawater changes with the water's chemistry, according to a release about the research from the American Geophysical Union (AGU). The absorption of sound involves a variety of chemical interactions, some understood and some not, but the bottom line, according to the researchers, is the more acidic the seawater, the less low-and mid-frequency sound it absorbs. The increasing acidity, caused by a change in seawater pH as it pulls carbon out of the atmosphere, will have the greatest effect on sounds below about 3,000 cycles per second, the range that includes most low-frequency sounds used by marine mammals in finding food and mates. According to the AGU, it also includes underwater sounds generated by industrial and military activity, as well as boats and ships. "The waters in the upper ocean are now undergoing an extraordinary transition in their fundamental chemical state at a rate not seen on Earth for millions of years, and the effects are being felt not only in biological impacts but also on basic geophysical properties including ocean acoustics," the researchers, led by postdoctoral fellow Keith Hester, wrote in their paper.

Warming Pushing Yosemite Animals to Higher Elevations

Scientists updating a 1918 survey of Sierra Nevada birds, mammals, reptiles and amphibians in the Yosemite National Park have discovered that global warming is causing major shifts in the range of small mammals, forcing many of them to seek higher, cooler ground. The study by University of California, Berkeley, biologists found that mammals like shrews, mice and ground squirrels have moved to higher ground, essentially shuffling the species living together in any one spot. "We didn't set out to study the effects of climate change but to see what has changed and why" since the 90-year-old survey was complete, said Craig Moritz, director of UC Berkeley's Museum of Vertebrate Zoology. "But the most dramatic finding . . . was the upward elevational shift of species. When we asked ourselves, 'What changed?' it hit us between the eyes: the climate." Moritz said general warming of Yosemite has occurred in recent years, as evidenced by about a 5.4 degree Fahrenheit increase in nighttime low temperatures and by the receding of glaciers and the increase in precipitation as rain instead of snow. The researchers found that, of the 28 small mammals observed in the area of the study, half had expanded their range upward by more than 1,600 feet. The shifting of the range of various species has been going on forever, UC Berkeley biologist James Patton said, but the speed with which the Yosemite species have shifted their range in response to warming "gives us pause."

Circadian Clock Critical for Remembering

Most people become aware of their internal circadian clock when they cross several time zones and experience jet lag, but scientists have known for decades that the rhythm of the internal human clock regulates almost every biological system, from blood pressure to sex drive. Now researchers at Stanford University have shown that when the circadian system breaks down, so does memory. In a paper published in the Proceedings of the National Academy of Sciences, biologist Norman Ruby found that hamsters with disabled circadian systems were, unlike "normal" hamsters, unable to remember their environment. "They can't remember anything," Ruby said of the hamsters. Scientists have long suspected that learning and memory might be related to different levels of brain function, or alertness, that change over a day due to normal circadian rhythms, but it hadn't been shown that the circadian system is crucial to learning and memory. Ruby found that learning and memory appears to hinge on the amount of the neurochemical GABA, which is found in the brains of all animals. GABA, which inhibits brain activity, is released rhythmically by the body in accordance to the circadian clock controlling sleep and wake cycles. When Ruby disabled the hamsters' clocks by manipulating their exposure to light the hamsters experienced chronically high levels of GABA and essentially lost their ability to remember. The findings have implications for people with Down syndrome, who grow up with what amounts to an over-inhibited brain, according to the research. It also may have implications for the decline in memory that older adults often experience. "In aging humans, one of the big things that happens is the circadian system starts to degrade and break down," Ruby said. "It might be that the degradation of circadian rhythms in elderly people may contribute to their short-term memory problems."

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