Wednesday, May 28, 2008 - 2:15 PM
430

Modeling sources of seston, particulate organic carbon and particulate nitrogen within a stream ecosystem

David C. Richardson1, Anthony K. Aufdenkampe2, J. Denis Newbold2, and Louis A. Kaplan2. (1) Cary Institute of Ecosystem Studies, Box AB, Millbrook, NY 12545, (2) Stroud Water Research Center, 970 Spencer Road, Avondale, PA 19311

Quantitatively distinguishing allochthonous and autochthonous organic matter sources to stream ecosystems has long been a challenge.  We used a new approach that defines seston end-members by particle type – mineral-dominated, terrestrial plant detritus and algal – with well separated percent organic carbon and nitrogen values.  We then used a mixing model analysis with Monte-Carlo error estimation to quantify fractions of seston, in a 3rd-order southeastern Pennsylvania stream.  We observed that seston mass concentrations were dominated by mineral particles (65% ± 1%: mean ± SE).  However, algal and terrestrial plant particles, because of their high organic content, still represented a large fraction of the particulate organic carbon (89% ± 0.3%: mean ± SE) and nitrogen (87% ± 0.4%: mean ± SE) in transport.  Furthermore, seasonal patterns in seston sources reflected cycles of autumnal leaf litter inputs and vernal algal production.  Our results argue that the biological view of seston (organic matter) in small streams as fragmented and egested leaf-litter is compatible with the biogeochemical perspective that seston (mass) is mineral-derived.  However, the biological view should be expanded to include algal-derived particles.  The source of organic matter can indicate lability for biological use and should ultimately influence rates of heterotrophic respiration in downstream rivers.


Web Page: seston, modeling, carbon

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