Abstract

13C Tracer Method
In streams and rivers, dissolved organic carbon (DOC) supplies energy and carbon (C) to heterotrophic bacteria. The complexity of the DOC pool combined with simultaneous processes that continually produce, transform and consume DOC molecules in transport, makes in situ measurements of DOC uptake challenging. A tracer approach is a logical solution and we prepared a 13 C tracer of semi-labile DOC from soil-aged 13 C-labeled Liriodendron tulipifera tissues with a chemical composition reflective of the heterogeneity of terrestrially produced C that has been modified by sorptive fractionation onto mineral surfaces and oxidation by soil bacteria.

Results
We used the tracer in a whole-stream injection coupled with bioreactor-based lability profiling to measure an uptake length of 4.5 km for semi-labile DOC constituents in a headwater piedmont stream and estimate support of ~10% of ecosystem metabolism.

Citation

Kaplan, L.A., J. D. Newbold and A. K. Aufdenkampe. (2011): A 13C DOC tracer approach to estimate the contribution of semi- labile dissolved organic carbon to stream ecosystem metabolism. Goldschmidt 2011 conference, Prague, Czech Republic, August 14-19. p. 1147.

This Paper/Book acknowledges NSF CZO grant support.