PARENT SESSION
Oral Session #11: Biodiversity and Ecosystem Function. Presiding: A. Downing.
Monday, August 6, 2001. 1:00 PM to 4:45 PM. Madison Ballroom C.
The Effect of increasing functional redundancy on cellulose degradation.
Wohl, Debra1, 1
ABSTRACT- Within biologically diverse communities, organisms perform overlapping functions. Understanding such functional redundancy (defined as multiple species carrying out a single function (e.g., cellulose degradation)) is essential to understanding the role of biodiversity. To address functional redundancy and biodiversity, ten bacterial species, each capable of degrading cellulose, were isolated from an aquatic microhabitat. The hypothesis was that as the number of functionally redundant organisms increases (cellulose degraders), the rate of the function (cellulose degradation) increases. Our study design 'constructed' functionally redundant assemblages (1, 2, 4 and 8 microbial strains). Experimental runs were 25 days, sampled at 5 day intervals. Sterile microcosms, consisting of minimal media, Hepes K buffer, and 0.025 g cellulose, were inoculated with a final density of 2.0 x 106 cells per ml regardless of species composition. On each date, measures of biomass, enzyme activity (glucopyranosidase, BETA-cellobiosidase and BETA-cellotriosidase), diversity (in terms of redundancy) and rates of cellulose decomposition were recorded. Constructed communities differed in total biomass, enzyme activity, and cellulose degradation per treatment. In all runs of two or more isolates, the greatest levels of enzyme activity and greatest rates of cellulose degradation occurred between days 5 and 15. These findings on functional redundancy provide a basis for further determinations of how the contribution of cellulose degraders change with changing environmental parameters, and whether or not greater redundancy is present in more stochastic environments.
KEY WORDS: biodiversity, functiona redundancy, ecosystem processes, bacteria