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.

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

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

• 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)

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

• 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

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).

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.

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).