HR: 10:45h
AN: NB42B-02    [Abstracts]
TI: Diel changes in stream periphyton extracellular enzyme activity throughout community development on inert and organic substrates
AU: * Rier, S T
EM: srier@bloomu.edu
AF: Department of Biological and Allied Health Sciences, Bloomsburg University, 400 East Second Steet , Bloomsburg, PA 17815 United States
AU: Francoeur, S N
EM: sfrancoeu@emich.edu
AF: Department of Biology, Eastern Michigan University , 316 Mark Jefferson , Ypsilanti, MI 48197 United States
AU: Kuehn, K A
EM: kkuehn@emich.edu
AF: Department of Biology, Eastern Michigan University , 316 Mark Jefferson , Ypsilanti, MI 48197 United States
AB: We tested the hypothesis that algal photosynthesis in stream periphyton communities would influence the activities of extracellular enzymes produced by associated heterotrophic bacteria and fungi to acquire organic compounds and inorganic nutrients. We approached this question by looking for diurnal variation in activities of four extracellular enzymes in periphyton communities that were grown on either inert (glass fiber filters) or organic (leaves) substrata that there were incubated in stream-side channels that were either open to full sun or shaded. Substrata were subsampled for β-glucosidase, alkaline phosphotase, leucine-aminopeptidase, and phenol oxidase activities at 3-5 hr. intervals over two consecutive diurnal cycles that were repeated at an early and later stage of periphyton community development. Activities of all enzymes displayed diurnal periodicity but the strength of the diurnal effects depended largely on the substrate type and stage of community development. The most consistent diurnal change was observed with phenol oxidase activity with significantly greater (p<0.05) activities being observed in during the day for both stages of community development and for both substrate types. It is likely that oxygen produced by algal photosynthesis is driving the activity of this oxidative enzyme and that algae might indirectly influence the decomposition of phenolic compounds.
DE: 4815 Ecosystems, structure and dynamics
DE: 4840 Microbiology
SC: North American Benthological Society [NB]
MN: 2005 Joint Assembly