On the horizon

Where plankton goes, clouds follow

What do poplar trees and oaks have in common with tiny plantlike plankton? Like these trees, phytoplankton exhale isoprene, a chemical that encourages clouds to form. Now, scientists suggest that these marine organisms may have a profound effect on regional and global climate by stimulating the growth of clouds over the ocean.

A team at Georgia Tech came up with the idea after looking at satellite photos of the southern ocean off the east coast of South America. The scientists noticed that when phytoplankton blooms occurred, cloud cover increased over the area. Scientists had previously noted that phytoplankton give off a type of sulfide that helps water vapor condense into droplets. Isoprene can substantially boost this process. The dense clouds, in turn, reflect sunlight back into space, acting as a brake on warming.

So far, the team has tested their idea with computer models; it says the results will need to be confirmed with field measurements. Assuming those measurements also see the effect, it will show a "very strong influence of marine biology on oceanic clouds," says Athanasios Nenes, a member of the team. The results currently appear on Science Express, the online service of the journal Science.

How to improve the ocean's diversity

Due in large part to overfishing and pollution, the ocean's ecosystems are rapidly losing biodiversity and with it their ability to feed people, cleanse themselves, and survive natural or man-made assaults. But the trend is reversible, and the tools to reverse it are well in hand, say an international team of marine scientists.

The group reviewed data from 32 small-scale biodiversity experiments, examined 1,000 years' worth of information on biological diversity in 12 key coastal areas, then looked at global catch data from 64 large ocean ecosystems. They found that since 1950, 29 percent of fish and seafood species have collapsed; their catch has fallen by 90 percent. If that trend is left unchecked, all fish and seafood species will experience the same collapse by 2048, the team concludes.

The study's conclusions – the first attempt at spotting oceanwide trends – parallel those looking at the effects of biodiversity loss on land-based ecosystems. They also found that fishery closures and marine "wildlife reserves" could be powerful tools for reversing the trend. In 148 areas protected by marine reserves or affected by fishery closures, the team found that species' diversity rebounded, along with the ecosystem's productivity and resilience in the face of stresses. The results appear in the current issue of the journal Science.

What exactly is a 'moon burp'?

Astronomers have long pronounced the moon geologically dead. Except for "moonquakes" triggered by the tug of Earth's gravity and an occasional whack by a meteoroid, it seems to be a pretty quiet place.

Maybe not, caution a team of scientists from Brown University in Providence, R.I., and the Planetary Science Institute in Tucson, Ariz. They claim to have found evidence for structures on the surface that may have formed as recently as 10 million years ago – and may still be forming.

While the last lava appeared to flow across the lunar surface 1 billion years ago, the latest sculpting appears to be driven by moon burps – sudden releases of gases pent up deep beneath the surface. The evidence comes from an analysis of an Apollo-15 photo of the "Ina structure," a heel-shaped dent on the summit of a larger dome. Peter Schultz, a crater expert at Brown and a member of the team, notes that the heel mark and the many dents inside are unlike typical impact craters and appear to be growing over time.

The moon-burp hypothesis could help explain why Apollo missions detected gases that formed in the presence of radioactivity. Assuming those gases are still deep inside the moon and rising to the surface, he says, monitoring them should help uncover a buried library of lunar geochemical history dating back some 4 billion years. The results appear in Thursday's issue of the journal Nature.

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