By Sean Henahan, Access Excellence

KEYSTONE, CO- New techniques for measuring the diversity of bacteria in a specific habitat are helping to assess the ecological integrity of the environment at the most fundamental level, reported researchers at the annual meeting of the North American Benthological Society.

"Most people don't realize it, but bacteria run the world. They control most ecosystem level processes, such as nutrient and mineral cycling -- all the things that are necessary for the growth of other organisms. So if we can determine that a habitat contains a healthy and diverse community of microbes, we can say it is a healthy environment. If there are only a few microbes out there, an ecosystem's functions are limited. Waste products are not broken down; they accumulate in the environment," said Dr. J Vaun McArthur, an associate ecologist at the Savannah River Ecology Laboratory, University of Georgia.

Dr. McArthur and colleagues are using molecular biology techniques such as fatty acid analysis, physiological determinations, reverse genome probing and RNA sequencing, to learn more about the microbial communities that inhabit the streams and swamps of the 310-square-mile Savannah River Site, a lab located on a nuclear weapons materials processing facility near Aiken, S.C.

"Few studies have investigated the structure of microbial communities. For example, what is the distribution and abundance of bacteria along any stream in the world? Few, if any, can answer that question. This lack of understanding has been due, in part, to the difficulty in making observations on individual microbes and species assemblages. But these new techniques have allowed some discrimination and description of these important microbial communities," said McArthur.

Much of Dr. McArthur's work centers on a stream called Upper Three Runs Creek, which he has determined to have the highest diversity of aquatic invertebrates in North America and possibly the world. Upper Three Runs is a relatively uncontaminated backwater stream that runs for about 20 miles through the site and spills into the Savannah River. Upper Three Runs is home to a number of invertebrate species found no where else in the world and many that are rare.

The caddisfly, Cheumatopsyche richardsoni is one such rarity. Three other caddisflies of the same genus also live in the stream. The researchers used C. richardsoni as a basis to study the effect of its unique native status on genetic diversity in the stream. As expected, the researchers found that the genetic diversity of C. richardsoni was low, which limits its ability to disperse to other locations.

Dr. McArthur and colleagues also found that invertebrate species diversity and productivity was significantly higher in the streams in the study area than in the floodplain swamp. Because water flow is less in the swamp, less organic matter and prey material is available for invertebrates. Thus the invertebrate populations are smaller and less diverse, he said.

Researchers have also extended their search for invertebrates to the areas of mud and muck that lie from 2 to 4 feet beneath the floodplain of streams. "Only in the past several years did scientists realize that an entirely different set of organisms live underneath the floodplain, so we are just beginning to investigate species diversity in this area," he noted.

An investigation of the fauna that lie beneath the floodplain of the stream area revealed four new species belonging to the invertebrate class called copepods, including and order called Gelyelloida. This is the first time Gelyelloidas have been collected in the United States.

Science Updates Index

What's News Index

Feedback