The direct, indirect and synergistic effects of nutrients, metals and organic chemical on the aquatic ecosystems are modelled with AQUATOX, an integrative ecological and ecotoxicological model developed by Park and Clough (Park et al., 2008) and released by EPA (United States Environmental Protection Agency). 

AQUATOX combines: (i) an aquatic ecosystem model which simulates in-stream processes, sediment transport and food web processes; (ii) a chemical fate model which calculates partitioning and bioaccumulation of the pollutants; and (ii)  an ecotoxicological model which predicts effects on aquatic biota. In the Figure 1 a scheme of the processes and compartments included in AQUATOX ecological and bioaccumulation models are shown.

AQUATOX has been successfully applied for different purposes, such as the prediction of fate and toxic effect of accidental releases of pollutants (e.g. Bingli et al., 2008), the bioaccumulation of pollutants after long term exposure (e.g.  Rashleigh et al., 2009) or the evaluation of biological impairment due to nutrients enrichment (e.g.: Carleton et al., 2009; Morkoç et al, 2009).

The model furthermore provides multiple analytical tools for evaluating uncertainty analysis, nominal range sensitivity analysis and comparison of perturbed and control simulations (e.g. Sourisseau et al., 2008).

Two applications in two case study catchments in Luxembourg, the Wark and Mamer river basins, subject to strong agricultural and urban pressure, are calibrated and validated. AQUATOX is  fed with data on: (i) agricultural emission of pesticides and urban pressure provided by SWAT simulations (see Action 5); (ii) food webs composition and biomass provided by public authorities (Water administration Luxembourg AGE; Environmental Agency NRW); (iii) oxygen and nutrients dynamics as well as sediment and periphyton budgets provided by a set of experimental campaigns (see Action 3). The parameterization of AQUATOX models is realized based on best available literature data.

In order to make meaningful predictions with AQUATOX, nutrients and pesticides loads are related to specific community structures, reflecting the ecological state. Simplified food webs corresponding to lead species of the saprobic index classification and matching the corresponding water quality classes are built within AQUATOX, calibrating nutrients and contaminant tolerance. Based on the expected macroinvertebrate assemblages, the simulations in AQUATOX estimate the presence of indicator species for the different saprobic classes, under the corresponding pollution level.

This approach allows to predict ecological status in water bodies as it is measured under the WFD and to distinguish between nutrients/organic and toxicants effects as well as between direct and indirect effects.

The models will be hence tested in the implementation of scenario simulations based on the national program of measures.

To top