Outcomes - Helmholtz-Centre for Environmental Research

The main advancement in understanding was achieved within the context of the Plan-B framework (Nutrient–People–Loading–Anthropogenic impacts) across these topics:

Nutrient dynamics and attenuation processes in streams and catchments across several spatial and temporal scales (seasonal, annual and multidecadal) (Borriero et al., 2023; Borriero, Musolff, et al., 2024; Borriero, Nguyen, et al., 2024; Chen et al., 2024; Dehaspe et al., 2021; Ebeling, Dupas, et al., 2021, 2021; Ebeling, Kumar, et al., 2021; Ehrhardt et al., 2021; Heinemann et al., 2025; Hubig et al., 2025; Jähkel et al., 2022; Javed, Arnillas, et al., 2025; Javed, Loudoun, et al., 2024a; Javed, Saber, et al., 2025; Li et al., 2025; Liu et al., 2023; Nicholls & Hoffmann, 2025; F. Saavedra et al., 2024, 2024, 2025, 2025; F. A. Saavedra et al., 2022; Schauer et al., 2025; Shin et al., 2025; Teran-Velasquez et al., 2022, 2023; Wachholz et al., 2022, 2023, 2024; Wang et al., 2025; Wang, Merz, Yang, & Basso, 2023; Wang, Merz, Yang, Tarasova, et al., 2023, 2023; Winter et al., 2021, 2021, 2024, 2024; X. Zhang et al., 2020, 2020)
Mechanisms of nutrient uptake by microbial biofilms with a focus on the distinct roles of the benthic and hyporheic biofilms in nutrient processing in streams (Große, Graeber, et al., 2025; Große, Perujo, et al., 2025; Große, Reisinger, et al., 2025; Pasqualini et al., 2024; Sunjidmaa et al., 2022, 2025)
Stoichiometric imbalances from microbial to global scales: experimental work and a global analysis revealed a consistent pattern of unbalanced stoichiometric ratios which impairs ecological processes (Große, Perujo, et al., 2025; Große, Reisinger, et al., 2025; Wachholz et al., 2022, 2023, 2024)
Long-term trends in groundwater: Analysis of extensive datasets has revealed long-term trends in European and North-America groundwater, providing insights into its quality, quantity, and regional variability (Ben-Salem et al., 2023, 2023; Chávez García Silva et al., 2024; Ebeling, 2025; Ebeling et al., 2024; Javed, Neumann, et al., 2024; Rouhani et al., 2025)
Large Rivers and Floodplains: Lagrangian sampling along a large river, combined with systematic floodplain surveys, has advanced understanding of hydrological connectivity and nutrient fluxes between rivers, groundwater, and floodplain ecosystems under both natural flow regimes and extreme events (Coder et al., 2025; Meyer et al., 2024; Zill et al., 2023, 2024, 2025)
Ecosystem Responses to Climate and Land-Use Change: Deforestation and extreme hydrological events can markedly impact water quality in both catchments and reservoirs, driving changes in local reservoir conditions, such as phytoplankton community composition, and affecting nutrient dynamics across the broader catchment (Determann et al., 2023; Fárez‐Román et al., 2025; Javed, Arnillas, et al., 2025; Javed et al., 2019; Javed, Loudoun, et al., 2024b; Kong et al., 2022; Liu et al., 2023; Nakulopa et al., 2024; F. Saavedra et al., 2024; F. A. Saavedra et al., 2022; C. Zhang et al., 2019)
Hydro-ecological trajectories of human impacts on water systems assessment of the effects of water on society—by assessing the effectiveness of management practices and legislative frameworks in reducing nutrient loads in streams (Hildebrandt et al., 2024; Javed, Arnillas, et al., 2025; Javed, Loudoun, et al., 2024a; Javed, Saber, et al., 2025)
Nutrient and pollutant dynamics in urban setting through the application of high-frequency monitoring: Continuous monitoring combined with data-driven models has provided insights into nutrient and pollutant dynamics in urban water systems and the role of waste water treatment plans (Benisch et al., 2024, 2025, 2025; Rojas-Gómez et al., 2023)
Pollutant (Methylmercury and PFAS) production and transport: landscape characteristics, hydrology, and land use collectively regulate methylmercury formation and export from catchments (Cromwell, 2023; Harrow-Lyle et al., 2023; Holden et al., 2024; Lam et al., 2022, 2024a, 2024b; Mangal et al., 2022; L. Peter et al., 2025; L. G. Peter & Lee, 2025).
Land-Use Impacts: Agricultural practices, fine sediment transport, and broader land-use shifts significantly influence nutrient cycling and ecological processes underscoring the importance of integrated ecosystem and catchment management (Abbas et al., 2023, 2024; Jähkel et al., 2022; Javed, Arnillas, et al., 2025; Javed, Saber, et al., 2025; Pasqualini et al., 2024, 2025; Sunjidmaa et al., 2022)

Contact

Coordinators:

Dr. Sandra Hille
Phone: +49 341 6025 4674

sandra.hille@ufz.de

Dr. Julia Pasqualini
Phone: +49 341 6025 4541

julia.pasqualini@ufz.de

Brückstraße 3a | 39114 Magdeburg | Germany

Final General Assembly

Final General Assembly from 9-11 July 2025

We started with Posters and continued with a synthesis of the generated knowledge of the past 6 years of TRACER. Our research has primarily focused on processes related to the natural attenuation of nutrients (especially NO3+), examining this phenomenon across various temporal scales (multidecadal, yearly, seasonal) and spatial scales (from biofilms to reaches and catchment levels). Additionally, some of us have investigated the effectiveness of different management practices and legislative frameworks in reducing nutrient loads in streams.
We made a great progress, but there are still a lot of new challenges coming up, especially considering that the boundary conditions are changing due to climate change. During the last day of the workshop we focused on different career opportunities after the PhD. Thanks to our external guests from UBA, BfG, UFZ and the state agencies. The insights from their jobs were really valuable!