Think twice before catching snowflake in mouth: Bacteria

William Atkins
Saturday, 01 March 2008 19:14

Science - Climate

Scientists have known for about forty years that bacteria cling to ice high in the atmosphere in order to produce rain and snow. However, U.S. scientists only recently found out that biological organisms, such as bacteria and other such microorganisms, play a significant role in the formation and distribution of precipitation.         

American biologist Brent C. Christner, from the Department of Biological Sciences at Louisiana State University (Baton Rouge), and colleagues have recently studied the way that rain and snow is formed.

Scientists already knew that biological ice nucleators (IN) are present in precipitation; however, their sources and distributions were not well studied.

Thus, the Christner team decided to learn more. They studied ice nucleators in snowfall from the mid-latitudes to the high-latitudes of the Earth. They found that ice nucleators are most likely biological in nature.

The researchers also found more of them are found in the mid-latitude regions, such as Montana and France, than the high-latitude areas, such as Canada and Antarctica.

Of the ice nucleators examined, the ones that were larger than 0.2 micrometer (one micrometer is equal to one millionth of a meter) in size were most active at temperatures higher than -12.6 degrees Fahrenheit (-7 degrees Celsius) and 69 to 100 percent of them were biological. Of these, most were bacteria.

Their conclusion was that the Earth’s biosphere is a major source of highly active biological ice nucleators and that they have a major affect on the precipitation cycle.

Their result (“Ubiquity of Biological Ice Nucleators in Snowfall”) was published in the February 29, 2008 issue of Science.

Christner’s team consists of Cindy E. Morris (L'Institut Nationale de la Recherche Agronomique, France), Christine M. Foreman (Montana State University, USA), Rongman Cai (Louisiana State University, USA), and David C. Sands (Montana State University, USA).

The finding of the Christner team is likely to help meteorologists and other scientists improve climate forecasts and better understand the relationship between the biosphere and climate. In fact, Christner theorizes that one day this knowledge could help make dry areas on the Earth wetter.

Christner’s team would like to next measure how much precipitation is formed with biological ice nucleators.