Mechanistic Effect Modelling

Analyze - Understand - Forecast

Development and application of ecological models in environmental risk assessment

Mechanistic effect modelling

Ecological numeric modelling becomes increasingly important for the environmental risk assessment (ERA) of plant protection products. Models can be used, for example, to support the evaluation of experimental studies as well as to extrapolate experimental results to complex field situations.

gaiac has many years of experience in the use of dynamic simulation models, and offers the application, adaptation and development of models for ERA and Risk Management.

Our toolbox

Effect models:

  • Lethal effects: TKTD model framework GUTS
  • Sub-lethal effects: DEB-TKTD approach

Individual-based population models (IBMs):

  • Daphnia magna
  • Chaoborus crystallinus
  • Asellus aquaticus
  • Mayfly population model (Cloeon dipterum)
  • Earthworm-2D-migration model in soil for: Lumbricus terrestris, Aporrectodea caliginosa, Eisenia fetida 

Ecosystem models:

  • StoLaM (Stoichiometric Lake Model): a complex, dynamic water quality model for lakes and shallow waters including modules for zooplankton and phytoplankton
  • Phytoplanktonmodell as a building block in the lake model StoLaM, applicable for the modeling of algae species from bioassays in the laboratory to aquatic ecosystems (according to the pelagic microalgae model, EFSA Scientific Opinion on TKTD models, 2018)
  • DaLaM (coupled hybrid model of GUTS, IDamP, and StoLaM)
  • STREAMcom (DEB-IBM based community model for streams, includes organisms such as mayflies, amphipods, isopods, snails, and others)
  • GraS-Modell (spatially-explicit and process-based succession model for plant communities)
more about landscape modeling
Schematic illustration of the models used at gaiac in effect modelling

Our modelling concept

In the area of modeling, we believe it is important that…

  • data and modelling go hand in hand
  • model development is target oriented
  • models are tested against independent data

Our mechanistic population and ecosystem models…

  • combine difference equation models, TK-TD and individual-based model approaches to extrapolate population responses under field conditions from laboratory toxicity tests
  • link time-variable exposure and effects
  • are tested based on laboratory tests, outdoor mesocosms, or field studies
  • allow for quantitative evaluation of direct and indirect effects as well as delayed effects and ecological recovery
  • enable the simulation of variable species specific ecological scenarios (laboratory to field conditions), including dynamic resources, climate or weather conditions and spatial dimensions
  • allow the combined simulation of natural and anthropogenic stressors

Our tiered modelling approach

Effect models

For modeling lethal effects on individuals, we use toxicokinetic-toxicodynamic (TK-TD) models and, in particular, the GUTS (General Unified Threshold model of Survival) approach, which integrates several TK-TD models into one framework and allows the simulation of survival under predefined assumptions.

In addition, Dynamic Energy Budget (DEB) models offer a coherent way to interpret sublethal effects on life history processes of individuals such as growth and reproduction (DEB-TKTD approach).

Population models

We simulate populations under field and laboratory conditions. For this, we use Individual Based population Models (IBMs) which allow the straight forward propagation of chemical effects observed at the organism level to responses at higher levels of biological complexity, such as populations and communities.

Ecosystem models

We simulate communities, i.e. interacting populations, in standing waters under field and semi-field conditions for phytoplankton, zooplankton, aquatic insects and other invertebrates. Both simple and complex ecosystem and hydrodynamic models can be added to provide an appropriate environment containing the most important biological and physico-chemical drivers (StoLaM model).

We are also developing spatially explicit individual-based population and community models for running waters and streams, whose aquatic assemblages include focal species from various groups such as mayflies, amphipods, isopods, snails and fish (STREAMcom model).

The dynamic and spatially explicit GraS-Model enables analyses and projections of plant communities and thus vegetation dynamics of real landscapes depending on different environmental stressors (e.g. soil properties, temperature, management).

more about landscape modeling

First use of a gaiac model in the risk assessment of pesticides


Number of modeling studies for risk assessment


Contributions to the Add-my-Pet database for species specific DEB parameters


Number of implemented individual-based population models


Number of implemented ecosystem models


Dr. Tido Strauss

Phone: +49 241 – 8027601
E-Mail: strauss@gaiac-

Kim Rakel

Phone: +49 241 – 8027106

Dr. Josef Koch

Phone: +49 241 – 8027106


Mechanistic effect modelling

Good Laboratory Practice


Taxonomic expertise



Preparation and organization of an international workshop in January 2020: FORESEE - (In)Field Organism Risk modelling by coupling Soil Exposure and Effects | ECPA, the European Crop Protection Association
Modelling approaches for a scenario based assessment of chemically induced impacts on aquatic macroinvertebrate communities | CEFIC, The European Chemical Industry Council
SIGN - CLIENT China Verbundprojekt SIGN: Sino-German water supply network - Clean water from the source to the tap, Teilprojekt J | BMBF, FKZ 02WCL1336J
MeTox - Integration and calibration of a biodynamic toxicity module for metals in the ecological modell AQUATOX - Teil Durchführung von Biotests mit aquatischen Nichtstandard-Invertebraten | Öffentliches Forschungszentrum (CRP) Henri Tudor

Publications & Presentations

Gergs, A., Rakel, K., Liesy, D., Zenker, A., Classen, S. (2019): Mechanistic effect modeling approach for the extrapolation of species sensitivity. Environmental science & technology, 53(16), 9818-9825.
Hammers-Wirtz, M., Classen, S., Strauss, T. (2019): Non-standard biotests – Intelligent testing to combine different needs and requirements for experimental and modelling approaches. Poster presentation, 29th SETAC- Europe Annual Meeting, 26.05.-30.05.2019, Helsinki, Finland.
Rakel, K., Strauss, T., Gergs, A. (2019): The STREAMcom model - Linking time variable exposure to effects on individuals, populations and community in realistic landscapes. Poster presentation, 29th SETAC- Europe Annual Meeting, 26.05.-30.05.2019, Helsinki, Finland.
Strauss, T., Klein, J., Rakel, K. (2019): Measure or extrapolate? Extended parameterisation of TKTD models for population modeling under outdoor conditions. Platform presentation, 29th SETAC- Europe Annual Meeting, 26.05.-30.05.2019, Helsinki, Finland.
Ladermann, K., Classen, S., Strauss, T., Hammers-Wirtz, M., Gergs, A . (2018): Impact of temperature on species sensitivity distribution in aquatic invertebrates. Poster presentation, 28th SETAC-Europe Annual Meeting 13-17 May 2018. Rome, Italy.
Rakel, K., Liesy, D., Classen, S., Strauss, T., Zenker, A., Gergs, A. (2018): Bridging the gap across species by the means of TK-TD modelling. Poster presentation at SETAC Europe 13th Special Science Symposium, Brussels, Belgium, October 2018.
Strauss, T. (2018): Integration of temperature-dependent TKTD kinetics in individual-based population modelling – A case study with Chaoborus crystallinus. Platform presentation, 28th SETAC-Europe Annual Meeting 13-17 May 2018. Rome, Italy.
Strauss, T., Gergs, A., Ladermann, K., Hammers-Wirtz, M. (2018): Defining ecological lake scenarios for population modelling as part of the Ecological Risk Assessment of chemicals. Poster presentation, 28th SETAC-Europe Annual Meeting 13-17 May 2018. Rome, Italy.
Gergs, A., Thorbek, P., Finnegan, M., Strauss, T. (2017): Individual-based analysis of mayfly meta-population dynamics. 27th SETAC- Europe Annual Meeting 07-11 May 2017, Brussels, Belgium.
Strauss, T., Gabsi, F., Hammers-Wirtz, M., Thorbek, P., Preuss, T.G. (2017): The power of hybrid modelling: An example from aquatic ecosystems. Ecological Modelling 364:77-88.
Strauss, T., Preuss, T.G. (2017): Modelling laboratory standard biotests with Daphnia magna. Poster presentation, 27th SETAC- Europe Annual Meeting 07-11 May 2017, Brussels, Belgium.
Dohmen, P., Preuss, T.G., Hamer, M., Galic, N., Strauss, T., Van den Brink, P. J., De Laender, F., and Bopp, S. (2016). Population‐level effects and recovery of aquatic invertebrates after multiple applications of an insecticide. Integrated environmental assessment and management 12:67-81.
Strauss, T., Bruns, E., Witt, J., Preuss, T.G. (2016): Modelling the impact of herbicides on phytoplankton for relevant ecological scenarios of varying complexity. Poster presentation, 26th SETAC- Europe Annual Meeting 22-26 May 2016, Nantes, France.
Strauss, T., Kulkarni, D., Preuss, T.G., Hammers-Wirtz, M. (2016): The secret lives of cannibals: Modelling density-dependent processes that regulate population dynamics in Chaoborus crystallinus. Ecological Modelling 321:84-97.
Strauss, T. (2013): Incorporating ecological scenarios into population modelling for use in aquatic risk assessment - A simulation study for the emerging insect Chaoborus. Poster presentation, 23th SETAC- Europe Annual Meeting 12-16 May 2013, Glasgow, Scotland.
Kulkarni, D., Strauss, T., Hommen, U., Ratte, H.T., Preuss, T.G. (2012): Using a modelling approach to compare sensitivities to Triphenyltin at the individual and population levels for three planktonic organisms. Platform presentation, 22th SETAC- Europe Annual Meeting 20-24 May 2012, Berlin, Germany.
Strauss, T., Preuss, T.G. (2012): Aquatic ecosystem model framework for use in refined environmental risk assessment. Poster presentation 6th SETAC World Congress, Berlin, Germany.
Strauss, T., Bruns, E., Goerlitz G, Preuss, T.G. (2011): Modelling toxic effects on Chaoborus populations under field conditions - an individual-based simulation study. Poster presentation, 21th SETAC- Europe Annual Meeting 15-19 May 2011, Milano, Italy.
Preuss, T., Bruns, E., Thorbek, P., Hammers-Wirtz, M., Schäfer, D., Goerlitz, G., Ratte, H.T., Strauss, T. (2010): Can population modelling answer urgent unresolved questions for ecological risk assessment - lessons learnt from Daphnia. Poster presentation, SETAC Europe 20th Annual Meeting, 23-27 May 2010, Seville, Spain.
Strauss, T. (2010): Density-dependent compensation of toxic effects in Chaoborus crystallinus populations - an individual-based simulation study. Poster presentation, SETAC Europe 20th Annual Meeting, 23-27 May 2010, Seville, Spain.
Strauss, T. (2009): Dynamische Simulation der Planktonentwicklung und interner Stoffflüsse in einem eutrophen Flachsee. Shaker, Aachen, ISBN 978-3-8322-8501-2.
Strauss, T., Ratte, H.T., Hammers-Wirtz, M., Thorbek, P., Preuss, T.G. (2009): Modeling toxic effects on Daphnia magna populations under natural field conditions. Poster presentation, 19th SETAC- Europe Annual Meeting 01-04 June 2009, Göteborg, Sweden.
Strauss, T., Sevim, S., Ratte, H.T.: Individual-based modelling of the recovery of Chaoborus crystallinus in aquatic mesocosm pond studies. Poster presentation, SETAC Europe 17th Annual Meeting, 20.-24. Mai 2007, Porto, Portugal.
Strauss, T., Ratte, H.T. (2003): Individuenbasierte Modellierung in der Ökotoxikologie am Beispiel von Chaoborus crystallinus. Vortrag, SETAC GLB-Jahrestagung, 21.-23. September 2003, Universität Heidelberg, Germany.

We look forward to hearing from you!