|Title||Cross-stream comparition of substrate-specific denitrification potential|
|Publication Type||Journal Article|
|Year of Publication||2010|
|Authors||Findlay, S, Mulholland, JP, Hamilton, LS, Tank, J, Bernot, MJ, Burgin, AJ, Crenshaw, C, Dodds, WK, Grimm, NB, Dowell, WHMc, Potter, JD, Sobota, DJ|
|Keywords||Comparative, Comparison of potential with realized denitrification, DEA, denitrification, stream, Substrate-specific|
Headwater streams have a demonstrated ability to denitrify a portion of their nitrate (NO3-)load but there has not been an extensive consideration of where in a stream this process is occurring and how various habitats contribute to total denitriﬁcation capability. As part of the Lotic Intersite Nitrogen Experiment II (LINX II) we measured denitriﬁcation potential in 65 streams spanning eight regions of the US and draining three land-use types. In each stream, potential denitriﬁcation rates were measured in common substrate types found across many streams as well as locations unique to particular streams. Overall, habitats from streams draining urban and agricultural land-uses showed higher potential rates of denitriﬁcation than reference streams draining native vegetation. This difference among streams was probably driven by higher ambient nitrate concentrations found in urban or agricultural streams. Within streams, sandy habitats and accumulations of ﬁne benthic organic matter contributed more than half of the total denitriﬁcation capacity (mg N removed m-2h-1). A particular rate of potential denitri-ﬁcation per unit area could be achieved either by high activity per unit organic matter or lower activities associated with larger standing stocks of organic matter. We found that both small patches with high rates (hot spots) or more widespread but less active areas (cool matrix) contributed signiﬁcantly to whole stream denitriﬁcation capacity. Denitriﬁcation estimated from scaled-up denitriﬁcation enzyme assay (DEA) potentials were not always dramatically higher than in situ rates of denitriﬁcation measured as 15N gas generation following 24-h 15N–NO3 tracer additions. In general, headwater streams draining varying land-use types have signiﬁcant potential to remove nitrate via denitriﬁcation and some appear to be functioning near their maximal capacity.