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SFS Annual Meeting

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SOURCE-SPECIFIC DISSOLVED ORGANIC CARBON UPTAKE BY STREAM MICROBES

Streams play a major role in the global carbon cycle, through mineralizing dissolved organic carbon (DOC) and transporting DOC downstream. Yet, DOC is a heterogeneous mixture of compounds and our knowledge of how different carbon sources are cycled within streams is limited. Bioassays were conducted using water collected from two streams and amended with DOC sources: beet sugar, malted barley, and roasted barley. We predicted DOC uptake would differ as a function of DOC source. Ambient DOC uptake rates (kDOC) in each stream were 0.012/day and 0.037/day. In both streams, kDOC for all DOC amendments was significantly greater than ambient kDOC (p<0.001). Roasted barley kDOC was lower than sugar and malted barley (p<0.001) and closest to ambient kDOC. We tested the extent to which other nutrients limited carbon metabolism. Adding PO4 with roasted barley led to higher kDOC than with roasted barley alone (p=0.021). While carbon is most limited, PO4 also limits metabolism in these streams. Ongoing work compares bioassay DOC uptake with rates of carbon metabolism calculated from diel oxygen to better understand the fate of DOC in streams.

Melissa Castillo (Primary Presenter/Author), Virginia Tech Hotchkiss Lab, melissatheclimber@gmail.com;


Erin Hotchkiss (Co-Presenter/Co-Author), Virginia Tech, ehotchkiss@vt.edu;


Stephen Plont (Co-Presenter/Co-Author), Virginia Tech, plontste@vt.edu;