EGU23-13252, updated on 10 Jan 2024
EGU General Assembly 2023
© Author(s) 2024. This work is distributed under
the Creative Commons Attribution 4.0 License.

Stoichiometry on the edge - Humans induce strong imbalances of reactive C:N:P ratios in streams

Alexander Wachholz1, Joni Dehaspe2,3, Pia Ebeling2, Rohini Kumar4, Andreas Musolff2, Felipe Saavedra5, Carolin Winter2, Soohyun Yang1, and Daniel Graeber1
Alexander Wachholz et al.
  • 1Department of Aquatic Ecosystems Analysis and Management, Helmholtz Center for Environmental Research (UFZ), Magdeburg, Germany
  • 2Department of Hydrogeology, Helmholtz-Centre for Environmental Research (UFZ), Leipzip, Germany
  • 3Unit Environmental Modeling, Flemish Institute for Technological Research NV- VITO, Mol, Belgium
  • 4Department for Computational Hydrosystems, Helmholtz-Centre for Environmental Research (UFZ), Leipzig, Germany
  • 5Department of Catchment Hydrology, Helmholtz-Centre for Environmental Research (UFZ), Halle, Germany

Anthropogenic nutrient inputs lead to severe degradation of surface water resources, affecting aquatic ecosystem health and functioning. Ecosystem functions such as nutrient cycling and ecosystem metabolism are not only affected by the over-abundance of a single macronutrient but also by the stoichiometry of the reactive molecular forms of dissolved organic carbon (rOC), nitrogen (rN), and phosphorus (rP). So far, studies mainly considered only single macronutrients or used stoichiometric ratios such as N:P or C:N independent from each other. We argue that a mutual assessment of reactive nutrient ratios rOC:rN:rP relative to organismic demands enables us to refine the definition of nutrient depletion versus excess and to understand their linkages to catchment-internal biogeochemical and hydrological processes. Here we show that the majority (94%) of the studied 574 German catchments show a depletion or co-depletion in rOC and rP, illustrating the ubiquity of excess N in anthropogenically influenced landscapes. We found an emerging spatial pattern of depletion classes linked to the interplay of agricultural sources and subsurface denitrification for rN and topographic controls of rOC. We classified catchments into stoichio-static and stochio-dynamic catchments based on their degree of intra-annual variability of rOC:rN:rP ratios. Stoichio-static catchments (4036% of all catchments) tend to have higher rN median concentrations, lower temporal rN variability and generally low rOC medians. Our results demonstrate the severe extent of imbalances in rOC:rN:rP ratios in German rivers due to human activities. This likely affects the inland-water nutrient retention efficiency, their level of eutrophication, and their role in the global carbon cycle. Thus, it calls for a more holistic catchment and aquatic ecosystem management integrating rOC:rN:rP stoichiometry as a fundamental principle.

How to cite: Wachholz, A., Dehaspe, J., Ebeling, P., Kumar, R., Musolff, A., Saavedra, F., Winter, C., Yang, S., and Graeber, D.: Stoichiometry on the edge - Humans induce strong imbalances of reactive C:N:P ratios in streams, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-13252,, 2023.

Supplementary materials

Supplementary material file