HR: 11:45h
AN: NB42B-06    [Abstracts]
TI: Rapid Changes In Carbon-13 During Periphyton Biomass Development
AU: * Hill, W R
EM: wrhill@uiuc.edu
AF: Walter Hill, Illinois Natural History Survey, Champaign, IL 61820 United States
AU: Middleton, G
EM: Gerry.Middleton@state.tn.us
AF: Gerry Middleton, T.D.E.C. , Oak Ridge, TN 37931 United States
AU: Adams, M
EM: adamssm@ornl.gov
AF: Marsall Adams, Environmental Sciences Division Oak Ridge National Laboratory, Oak Ridge, TN 37930 United States
AB: Stable isotopes are widely used to infer trophic relationships with little attention paid to temporal variability at the base of the food web. We examined the link between biomass development and temporal changes in the carbon-13 content of periphyton, sampling periphyton that developed on bare ceramic tiles at four sites on a weekly basis for two months. Periphyton became enriched in carbon-13 at all sites as biomass increased on the tiles. Delta values increased from -26 to -19 in two weeks at one site, then declined precipitously after a large spate scoured periphyton biomass to low levels. Delta values increased once again as biomass built up on the tiles. Current velocity, measured on each sampling occasion, was uncorrelated with temporal changes in carbon-13 but was related to site-to-site differences. The effect of developing periphyton biomass on carbon-13 appeared to be nonlinear, with the greatest increase in delta values occurring at low levels of biomass. Depletion of inorganic carbon within the periphyton matrix is the likely cause of increased carbon-13 fixation as periphyton biomass develops. Dynamic isotope composition in algal cells creates problems for the use of stable isotopes in identifying food sources in aquatic food webs.
DE: 9810 New fields (not classifiable under other headings)
SC: North American Benthological Society [NB]
MN: 2005 Joint Assembly