It has long been known that a diversity of plants and animals can be a good indicator of a healthy ecosystem. But University of Washington research, to be published in the Feb. 17 edition of the journal Nature, suggests the health of the ecosystem is rooted in a complex codependency between plants and animals that produce organic matter and simple organisms that break it down.

Plants and algae - referred to as producers - acquire nutrients from inorganic sources supplied by fungi and bacteria - called decomposers. Decomposers in turn acquire the carbon they need from the producers. The number of species in each group appears to correlate with how well the ecosystem functions, with greater diversity bringing more efficiency, said Shahid Naeem, a UW assistant zoology professor and lead author of the study described in Nature.

"The effects of producer diversity on ecosystem function is only part of the picture," he said. "Decomposer diversity is also important. You can't separate them."

The research, conducted by Naeem and UW graduate students Daniel Hahn and Gregor Schuurman, provides insights into what occurs when a complex ecosystem is turned into a simpler one, clearing rain forest to make way for a banana plantation, for instance, or converting a prairie to a wheat field.

The findings came from the yearlong study of 112 microcosms created in petri dishes, each containing 50 milliliters of a growth medium and kept in the same temperature and light conditions. Each petri dish was loaded with zero, one, two, four, eight or 12 species of bacteria and zero, one, two, four or eight species of algae. (The only combination not used was zero bacteria and zero algae.)

The researchers found that algae production varied greatly, depending on the number of bacteria species introduced, and correlated directly to the diversity of both algae and bacteria species. They also discovered that increasing the number of algal or bacterial species could influence
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Contact: Vince Stricherz
vinces@u.washington.edu
206-543-2580
University of Washington
15-Feb-2000