HR: 14:15h
AN: NB13A-04    [Abstracts]
TI: The Utility of Decomposition and Associated Microbial Parameters to Assess Changes in Stream Ecosystems due to Eutrophication
AU: * Gulis, V
EM: v.gulis@ua.edu
AF: Department of Biological Sciences, University of Alabama, Box 870206, Tuscaloosa, AL 35487 United States
AU: Ferreira, V J
EM: veronica@ci.uc.pt
AF: Institute of Marine Research, Department of Zoology, University of Coimbra, Coimbra, 3004-517 Portugal
AU: Graca, M A
EM: mgraca@ci.uc.pt
AF: Institute of Marine Research, Department of Zoology, University of Coimbra, Coimbra, 3004-517 Portugal
AB: Traditional approaches to assess stream ecosystem health rely on structural parameters, e.g. a variety of biotic indices. The goal of the Europe-wide RivFunction project is to develop methodology that uses functional parameters (e.g. plant litter decomposition) to this end. Here we report on decomposition experiments carried out in Portugal in five pairs of streams that differed in dissolved inorganic nutrients. On average, decomposition rates of alder and oak leaves were 2.8 and 1.4 times higher in high nutrient streams in coarse and fine mesh bags, respectively, than in corresponding reference streams. Breakdown rate correlated better with stream water SRP concentration rather than TIN. Fungal biomass and sporulation rates of aquatic hyphomycetes associated with decomposing leaves were stimulated by higher nutrient levels. Both fungal parameters measured at very early stages of decomposition (e.g. days 7-13) correlated well with overall decomposition rates. Eutrophication had no significant effect on shredder abundances in leaf bags but species richness was higher in disturbed streams. Decomposition is a key functional parameter in streams integrating many other variables and can be useful in assessing stream ecosystem health. We also argue that because decomposition is often controlled by fungal activity, microbial parameters can also be useful in bioassessment.
DE: 9810 New fields (not classifiable under other headings)
SC: North American Benthological Society [NB]
MN: 2005 Joint Assembly