Stable isotope and conservative tracer data used to estimate uptake of stream water dissolved organic carbon (DOC) through a whole-stream addition of a ¹³C-DOC tracer coupled with laboratory measurements of bioavailability of the tracer and stream water DOC using lability profiling with bioreactors

We performed a whole-stream addition of a
¹³C-DOC tracer and made laboratory
measurements of the biological availability of the tracer as well as
stream water DOC. The study was performed in October 2002 in a 1.27 km
stretch of the third-order White Clay Creek in southeastern
Pennsylvania. The tracer was prepared as a cold-water leachate of
¹³C-labeled tulip poplar saplings and it
was added to the stream along with sodium bromide, a conservative
tracer, over a 2-h period. Stream water samples were collected at 8
downstream stations over an 8-h period, filtered, and analyzed for
concentrations of bromide and DOC. DOC was measured by Pt-catalyzed,
persulfate oxidation, Br- was analyzed by ion chromatography, and C
isotope samples were rotary evaporated, acidified, lyophilized,
combusted, and the CO₂ analyzed with an
elemental analyzer interfaced with an isotope ratio mass spectrometer.
Lability profiling of the ¹³C-DOC tracer
and stream water DOC were performed with a series of plug-flow
bioreactors of increasing empty-bed contact times with the
concentration of biodegradable DOC operationally defined as the
difference between the DOC concentrations in the influent and effluent
waters of the bioreactors. The bioreactor measurements were performed
2 days after the whole-stream release. Data were analyzed to estimate
the uptake of stream water DOC associated with labile and semi-labile
fraction of biodegradable DOC. These data have been previously used in a 2008 publication in Freshwater Biology, doi:10.1111/j.1365-2427.2007.01941.x.