DISCIPLINE BY DISCIPLINE:
In 2000 and 2001, scientists reported troubling indications that the melting of sea ice in the Arctic Ocean above the North American mainland is disrupting a variety of sea creature populations. Since 1978, 15 percent of the ice that covered the Arctic Ocean has melted, and the remaining ice is now an average of 6 feet thick, compared to 10 feet thick in the 1950s. The melting ice has resulted in a thick layer of fresh water underneath the ice. As a result, scientists reported, tiny diatoms that were commonly found under the ice in the 1970s and served as an important food source have largely disappeared and have been replaced by a few common species of freshwater alga.
The thinness of the ice seems to have affected larger mammals as well. In the 1980s and 1990s, the ice broke up earlier than usual, forcing polar bears to move from food-rich ice packs to land earlier in the year when cubs are young, which is resulting in thinner, less fertile bears. An early breakup of ice in 1998 seriously affected ringed seal pups. Although the ice breakup was beneficial for older seals, giving them a longer feeding period, it was a disaster for young pups, who usually live in dens in the ice until they are weaned. Many young pups found that year were small and underfed, indicating that the loss of their dens had a serious impact on their ability to survive.
The findings have prompted further study of the Arctic. Starting in 2002, the National Science Foundation and the U.S. Office of Naval Research will fund a $17.5 million program to investigate how climate change affects creatures living in the western Arctic.
In the June 28, 2001, issue of Nature, researchers at Southern Illinois University in Carbondale announced that they had isolated two strains of bacteria that can break down benzene even in the absence of air. Benzene, which is used as a solvent and is also found in vehicle exhaust fumes, is a carcinogen and one of the most common organic pollutants in groundwater. Benzene does not break down easily and it can dissolve in water, which makes it especially problematic as a pollutant.
One relatively fast and inexpensive way to clean up hydrocarbons like benzene is to use bacteria that feed on the material. Other bacteria have been found that break down benzene, but they can only do so in the presence of oxygen. Benzene contamination is often found in soil, and many soils have air-free spots, so such bacteria are of little practical use.
In some cases, mixtures of unknown bacteria did break down benzene an air-free environment. Researchers finally isolated two strains of bacteria that work in the absence of oxygen, provided that some nitrate is present. The two benzene eaters are both strains of the bacteria Dechloromonas, which live in a wide variety of natural aquifers, soils, and sediments. The two strains are called RCB and JJ, and they break benzene down into carbon dioxide. Scientists note that Dechloromonas is a very hardy organism and would be easy to use as a tool for cleaning up polluted soil.