Biogeochemistry

, Volume 121, Issue 1, pp 23–44

Longitudinal patterns in carbon and nitrogen fluxes and stream metabolism along an urban watershed continuum

  • Sujay S. Kaushal
  • Katie Delaney-Newcomb
  • Stuart E. G. Findlay
  • Tamara A. Newcomer
  • Shuiwang Duan
  • Michael J. Pennino
  • Gwendolyn M. Sivirichi
  • Ashley M. Sides-Raley
  • Mark R. Walbridge
  • Kenneth T. Belt
Article

DOI: 10.1007/s10533-014-9979-9

Cite this article as:
Kaushal, S.S., Delaney-Newcomb, K., Findlay, S.E.G. et al. Biogeochemistry (2014) 121: 23. doi:10.1007/s10533-014-9979-9

Abstract

An urban watershed continuum framework hypothesizes that there are coupled changes in (1) carbon and nitrogen cycling, (2) groundwater-surface water interactions, and (3) ecosystem metabolism along broader hydrologic flowpaths. It expands our understanding of urban streams beyond a reach scale. We evaluated this framework by analyzing longitudinal patterns in: C and N concentrations and mass balances, groundwater-surface interactions, and stream metabolism and carbon quality from headwaters to larger order streams. 52 monitoring sites were sampled seasonally and monthly along the Gwynns Falls watershed, which drains 170 km2 of the Baltimore Long-Term Ecological Research site. Regarding our first hypothesis of coupled C and N cycles, there were significant inverse linear relationships between nitrate and dissolved organic carbon (DOC) and nitrogen longitudinally (P < 0.05). Regarding our second hypothesis of coupled groundwater-surface water interactions, groundwater seepage and leaky piped infrastructure contributed significant inputs of water and N to stream reaches based on mass balance and chloride/fluoride tracer data. Regarding our third hypothesis of coupled ecosystem metabolism and carbon quality, stream metabolism increased downstream and showed potential to enhance DOC lability (e.g., ~4 times higher mean monthly primary production in urban streams than forest streams). DOC lability also increased with distance downstream and watershed urbanization based on protein and humic-like fractions, with major implications for ecosystem metabolism, biological oxygen demand, and CO2 production and alkalinity. Overall, our results showed significant in-stream retention and release (0–100 %) of watershed C and N loads over the scale of kilometers, seldom considered when evaluating monitoring, management, and restoration effectiveness. Given dynamic transport and retention across evolving spatial scales, there is a strong need to longitudinally and synoptically expand studies of hydrologic and biogeochemical processes beyond a stream reach scale along the urban watershed continuum.

Keywords

NitrogenCarbonNew Watershed ConceptUrban watershedNutrient retention

Copyright information

© Springer International Publishing Switzerland 2014

Authors and Affiliations

  • Sujay S. Kaushal
    • 1
    • 6
  • Katie Delaney-Newcomb
    • 1
  • Stuart E. G. Findlay
    • 2
  • Tamara A. Newcomer
    • 1
    • 6
  • Shuiwang Duan
    • 1
    • 6
  • Michael J. Pennino
    • 3
    • 6
  • Gwendolyn M. Sivirichi
    • 1
  • Ashley M. Sides-Raley
    • 1
  • Mark R. Walbridge
    • 4
  • Kenneth T. Belt
    • 5
  1. 1.University of Maryland Center for Environmental ScienceSolomonsUSA
  2. 2.Cary Institute of Ecosystem StudiesMillbrookUSA
  3. 3.University of Maryland Baltimore CountyBaltimoreUSA
  4. 4.USDA Agricultural Research ServiceBeltsvilleUSA
  5. 5.USDA Forest Service, Northern Research StationBaltimore Field Station at University of Maryland Baltimore CountyBaltimoreUSA
  6. 6.Department of Geology & Earth System Science Interdisciplinary CenterUniversity of MarylandCollege ParkUSA