Poster Presentation Society for Freshwater Science 2026 Annual Meeting

A nitrogen river continuum model (135477)

Alicia Dixon 1 , Joanna Blaszczak 2 , Deandre Presswood 2 , Arial Shogren 3 , Shannon Speir 4 , Alex Webster 5 , Adam Wymore 1
  1. University of New Hampshire, NH, United States
  2. Department of Natural Resources and Environmental Science, University of Nevada, Reno, Reno, Nevada
  3. Department of Biological Sciences, University of Alabama, Tuscaloosa, Alabama
  4. Crop, Soil and Environmental Sciences, University of Arkansas, Fayetteville, Arkansas
  5. Department of Biology, University of New Mexico, Albuquerque, New Mexico

 The River Continuum Concept (RCC; Vannote et al., 1980) is a historically and ecologically important framework for predicting community structure, energetic flow, and geomorphic characteristics of lotic ecosystems as they increase in size. While the RCC is helpful in making predictions of stream community ecology, source of energy, and the balance between primary production and respiration, it does not encompass the change in nitrogen (N) balances along the continuum. Here we asked the question: how does the stoichiometry of total dissolved nitrogen (TDN) and dissolved organic matter (DOM) change along Stahler stream orders gradients and across environmental gradients? We used stream chemistry data from five watersheds in different biomes that each included a range of 0 to 4th order streams to assess the elemental composition of TDN and the change in DOM C:N ratios (as DOC: DON ratios) along a river continuum. Preliminary results from the northern temperate ecosystem site indicate that while DON dominated the composition of TDN, relative abundance of NH4+ was greater than that of NO3- in 1st and 2nd order streams, while the opposite was true of 3rd and 4th order streams. These data suggest changes in nitrogen cycle reaction rates with increasing stream order. Additionally, DOC:DON ratios significantly decreased as stream order increased pointing to changes in how the nutrient fraction of DOM is used along the RCC. Understanding how the availability and processing of nitrogen changes along a stream order gradient can better inform energy flow and biogeochemical cycling in the context of the RCC.

  1. Robin L. Vannote, G. Wayne Minshall, Kenneth W. Cummins, James R. Sedell, and Colbert E. Cushing. 1980. The River Continuum Concept. Canadian Journal of Fisheries and Aquatic Sciences. 37(1): 130-137. https://doi.org/10.1139/f80-017