SCIENCE NOTEBOOK

Placing Blame for Corals' Demise

Climate change and overfishing, rather than pollution, are primarily responsible for killing off coral reefs in the Caribbean, according to a new study.

The paper, by researchers from the Wildlife Conservation Society, Columbia University and the University of Maryland, examined the effects of two of the most common pollutants: phosphorus and nitrogen. They concluded that nitrogen is the more damaging of the two, but its effects are mostly felt after a reef is dead or dying, because it stimulates the growth of microscopic green algae that break down the calcium carbonate skeleton of the coral.

The team concluded that the massive die-offs of Caribbean corals in recent decades stemmed mostly from warming ocean temperatures and declines in fish and invertebrates that protect reefs by feeding on the algae.

In an e-mail, Wildlife Conservation Society senior conservation zoologist Tim McClanahan said the study helps explain why coral reefs are struggling across the globe.

"Pollution has been seen as one of the major culprits in the loss of coral reefs around the world, but our study indicates that it cannot explain the widespread changes we are seeing, which leave climate change and overfishing as the major culprits," wrote McClanahan, lead author of the paper in the December issue of Marine Pollution Bulletin. "This helps us further pinpoint the causes of coral loss, but neither climate change or fishing are easy problems to solve."

Pollution still matters, he added, because once global warming or overfishing damages corals, "their skeleton will erode away faster in the presence of pollution."

-- Juliet Eilperin

Cellphone Talkers Tie Up Traffic

People who yak on their cellphones while driving are not just prone to accidents; they may also contribute to traffic jams.

University of Utah psychology professor Dave Strayer and doctoral student Joel Cooper studied 36 undergraduates as they drove in a highway simulator through six 9.2-mile-long traffic scenarios.

Each student spoke on a hands-free cellphone during one drive at each of three levels of traffic density and did not use a cellphone during three other drives. They were told to obey the 65-mph speed limit and use turn signals, but they could decide how fast to go and how often to change lanes.