Data from: Influence of natural and novel organic carbon sources on denitrification in forest, degraded urban, and restored streams

Organic carbon is important in regulating ecosystem function, and its
source and abundance may be altered by urbanization. We investigated
shifts in organic carbon quantity and quality associated with urbanization
and ecosystem restoration, and its potential effects on denitrification at
the riparian–stream interface. Field measurements of streamwater
chemistry, organic carbon characterization, and laboratory-based
denitrification experiments were completed at two forested, two restored,
and two unrestored urban streams at the Baltimore Long-Term Ecological
Research site, Maryland, USA. Dissolved organic carbon (DOC) and nitrate
loads increased with runoff according to a power-law function that varied
across sites. Stable isotopes and molar C:N ratios suggested that stream
particulate organic matter (POM) was a mixture of periphyton, leaves, and
grass that varied across site types. Stable-isotope signatures and lipid
biomarker analyses of sediments showed that terrestrial organic carbon
sources in streams varied as a result of riparian vegetation. Laboratory
experiments indicated that organic carbon amendments significantly
increased rates of denitrification (35.1 ± 9.4 ng N·[g dry
sediment]−1·h−1; mean ± SE) more than nitrate amendments (10.4 ± 4.0 ng
N·[g dry sediment]−1·h−1) across streamflow conditions and sites.
Denitrification experiments with naturally occurring carbon sources showed
that denitrification was significantly higher with grass clippings from
home lawns (1244 ± 331 ng N·g dry sediment−1·h−1), and overall unrestored
urban sites showed significantly higher denitrification rates than
restored and forest sites. We found that urbanization influences organic
carbon sources and quality in streams, which can have substantial
downstream impacts on ecosystem services such as denitrification.