Towards the definition of Environmental Quality Standards for biota: The influence of food web structure and dynamics on bioaccumulation and biomagnification

With the implementation of the Water Framework Directive and the daughter directive on Environmental Quality Standards (EQS), the development of EQS values for biota has become an important issue. However, for certain hydrophobic compounds, bioaccumulation and biomagnification in the food chain may occur. In this case, it is important to analyze, if depending on the food web and diet preferences, bioaccumulation values could be different for the same species in different ecosystems. To analyze this effect, we have studied four terrestrial and aquatic trophic network models generated previously for three similar lakes and a costal lagoon. In addition a simple ecological plus bioaccumulation model has been developed for analyzing diet preferences which could not be assessed using the developed trophic food webs. The objective was to assess if the similarities and differences between calculated trophic level could have consequences on the bioaccumulation and biomagnification potential of contaminants. The results indicate that differences of around two orders of magnitude can be expected for similar ecosystems. These results are important since they indicate that the ecosystem structure should be first assessed for the development of EQS for biota and that without this information intercomparison exercises between EU ecosystems are not possible.JRC.I.6-Systems toxicolog

Analysis of Toxicity Effects from Molecular to Population Level: Circadian Oscillator Case Study

To analyze how toxic effects propagate from molecular to population level, a simple model of a circadian oscillator has been coupled with a cyanobacteria growth model. It has been assumed that the circadian oscillator synchronizes with light-dark environmental conditions and toxicants affect this synchronization reducing the population growth. Then dose-response curves have been developed. The results evidence that to understand toxic effects we have to focus our study on the interactions that a certain compound may have with proteins, and/or DNA, since the result of these interactions will determine the final mode of action at macroscopic level. Therefore an intermediate step for assessing toxic effects has been proposed.JRC.I.6-Systems toxicolog

A General Bioaccumulation DEB Model for Mussels

A bioaccumulation model to predict, based on the concentration of contaminants in the water column, the concentration in mussels (Mytillus galloprovinciales) has been implemented and calibrated using experimental data from Thau lagoon (France). The model uses input data from a 3D biogeochemical model that provides biomasses in the different compartments, i.e. phytoplankton, zooplankton and bacteria; and from a 3D fate model that provides the concentrations in the water column as well as in the sediments. The bioaccumulation model is based on the Dynamic Energy Budget approach (DEB). The model predicts correctly the concentrations of several POPs families: PCDD/Fs and PCBs. This is the first step for developing a general screening tool able to predict the bioaccumulation of new chemicals in mussels based on its physico-chemical properties that will contribute to the B(bioaccumulative) and vB assessment. In addition, the model could be use by MS to convert measured concentrations in mussels to water concentrations for WFD (Water Framework Directive) compliance checking.JRC.I.3-Consumer products safety and qualit

Analysis and simulation of metabolic networks: Application to HEPG2

Chemical toxicity in most of the cases has a metabolic component and metabolic pathways are the most studied biochemical reactions. For these reasons we have started to analyze modelling approaches for studying toxicity at molecular level using the metabolism and focusing in HepG2 cell lines. Two approaches have been investigated. The first consists on the analysis of metabolic fluxes in HepG2 under different toxicants concentrations by complex network analysis tools. This is important when a correlation between dose-response curves and metabolomic data has to be established. The second approach is based on the development and application of a simplified dynamic model of metabolism. This approach requires the specification of the biochemical reactions as well as their kinetic parameters and, therefore, at the moment, the degree of detail in the description of HepG2 metabolism is reduced. The results suggest that a combined approach starting from metabolic fluxes and then solving the kinetic equations as our experimental data and knowledge of metabolic pathways increases is the most promising avenue to develop a quantitative approach of toxicity at molecular level. In addition, there is the necessity to link the molecular level approach with the cell growth and mortality with an intermediate level that translates metabolism changes into measurable parameters in cell-based assays.JRC.DG.I.6-Systems toxicolog

A biology-based dynamic approach for the reconciliation of acute and chronic toxicity tests: Application to Daphnia magna

There is the need to integrate existing dose-response data in a coherent framework for extending their domain of applicability as well as their extrapolation potential. This integration would also reduce time and cost-consuming aspects of these tests and reduce animal usage. In this work, based on data extracted from literature, we have assessed the advantages that a dynamic biology- toxicant fate coupled model for Daphnia magna could provide when assessing toxicity data, in particular, the possibility to obtain from short-term (acute) toxicity test to long-term (chronic) toxicity values and viceversa; the possibility of toxicity data reconciliation from several sources and the inherent variability of Daphnia magna populations. Implicitly in this approach is the assumption that the mode of action of the toxicant does not change after prolonged exposure.JRC.I.6-Systems toxicolog

An Overview of Chemical Mixtures Assessment and Modelling in the Aquatic Environment

The objective of this review is to assess what is known on the effect of mixtures in order todevelop ecological models that incorporate these effects in a coherent way, allowing for a correct description of the effects of exposure in aquatic ecosystems, and to developthresholds for contaminant concentrations that incorporate the knowledge of the effects of chemical mixtures and are not onlybased on a single compound.JRC.H.5-Rural, water and ecosystem resource

Dynamic Modelling of the Fate of DDT in Lake Maggiore: Preliminary Results

Release of chemical substances significantly impacts European waters. Impacts are both direct and indirect, through degradation products, acute and/or chronic toxicity, and/or long-term effects via bioaccumulation in aquatic food chains. As the number of substances is large and measures to reduce emission are costly and time demanding, there is a necessary prioritisation of the efforts through risk assessment studies requiring exposure data, which are both scarce and difficult to obtain. This is complicated by the fact that contaminants may reach the aquatic environment and hence biota and sediments, through several routes ranging from atmospheric deposition (airshed), diffuse and/or point sources in the watershed. Furthermore, a contaminant may arrive constantly during the year or in a pulse due to an accidental release or periodically driven by environmental fluctuations. For these reasons, as a first step, we have developed a model to simulate the fate of DDT family, i.e. pp’DDT, pp’DDD, pp’DDE, op’DDT, op’DDD, op’DDE, in Lake Maggiore. The model is 0D and consists on a dynamic mass balance that includes a time-variable chemical transport and fate model for calculating DDT concentrations in the water column as well as and in sedimentsJRC.H.5-Rural, water and ecosystem resource

Linking Terrestrial and Aquatic Ecosystems: Complexity, Persistence and Biodiversity in European Food Webs

In this work we have defined and analyzed the network structure, properties and composition of cohesive sub webs in two food web networks at two selected European sites: Ferto lake in Hungary and Ria Formosa lagoon in Portugal, respectively. The main objective of this work was to test and to apply a coherent methodology for the definition and analysis of trophic networks in typical European ecosystems. Persistence and cohesion of the two networks have been determined and studied. Moreover the biodiversity in terms of number of species have been measured. Several preliminary conclusions can be drawn on a basis of results obtained from application of network analysis indices and dynamical simulation. In terms of ecosystem stability the lake Ferto network (persistence 0.42) seems more stable than Ria Formosa (persistence 0.26), but if we consider the stability of the main k-core, we obtain opposite results (0.48 and 0.50 respectively). Taking into account the distribution of species in the k-core partition, the general structure of Ria Formosa network appears more complex than Ferto lake. In both networks a main core containing species taxonomically different is present, but in the Ria Formosa network (37.7%) the proportion of species inside the core is lower than in Ferto lake (60%), this can be an indication that the dimension of the main core is not related to size of the network in real ecosystems. This hypothesis is confirmed by results obtained from k-core partition of simulated networks. In both studied networks the cohesion (measured in terms of mean density and degree) of k-cores is greater than k-cores extracted from simulated networks generated by different models, this may indicate a complex and not arbitrary structure of ecological networks, not easily reproducible by models. In general the approach used appears to be able of defining the main proprieties of the trophic networks examined. The extension to other European ecosystems is needed for having a clearer and complete picture and to use data collected to simulation of different scenarios, afterwards the effects on network structure and ecosystem biodiversity as a function of different European environmental policies could be assessedJRC.H.5-Rural, water and ecosystem resource

The Use of Data and Models for Assessing the Equilibrium Partitioning Approach for Analysising Environmental Quality Standards in the Water Column and in the Sediments

An analysis of experimental and simulated data has been performed to study the relationships between EQS defined for surface waters in the Daughter Directive (COM (2006) 397) and possible EQS defined for sediments. From the above analysis of experimental and simulated data, it is clear that even though there is a coupling between water column and sediments, it is not possible to assess the chemical quality status of sediments based on water column data and viceversa. At the moment EQS have been defined for the water column and therefore these EQS will assess only the compliance with good chemical status of surface waters. If EQS were to be defined for sediments, these EQS will not reflect systematically the surface water quality and therefore they could not be used for this purpose, being the contrary is also true, i.e. compliance with EQS values for water column does not reflect sediment chemical status. However, it is clear that the good chemical quality of a water body will depend on having good chemical quality of surface water and sediments and that to assess both it is necessary to measure in both media. The same EQS developed for water could, in principle, be applied to porewater, hence, there is no need of developing another set of EQS. If porewater could not be measured, then the partitioning approach to pass to sediment concentrations should be applied. However, in this case an additional uncertainty is added to the procedure and therefore it is necessary to develop to develop new techniques and better databases since at the moment the predictions are between several orders of magnitude, which are not adequate for setting EQS. Additionally, the use of this approach would certainly require the characterization of the sediments in terms of its physical (grain size, material, temperature), chemical (organic matter content, black carbon, pH, redox, etc.) and biological (e.g. bioturbation), which at the moment are not obtained from standard environmental monitoring.JRC.H.5-Rural, water and ecosystem resource

Application of multielectrode array (MEA) chips for studying the neurotoxicity of mixtures

In vitro neuronal networks are a simplified and accessible model of the central nervous system. Moreover, they exhibit morphological and physiological properties and activity-dependent path-specific synaptic modification similar to the in vivo tissue. Cortical neurons grown on multi electrode array (MEA) chips have been shown to be a valuable tool to study fundamental properties of neuronal network activity, synaptic plasticity, learning in vitro, and functional pharmacological screening. The variation of spontaneous activity of in vitro neuronal networks coupled to MEAs has been studied using several binary mixtures (inhibitors with different mode of action: Verapamil and Muscimol, Fluoxetine and Muscimol; inhibitors with the same mode of action: Deltamethrin and Permethrin; and an excitatory and an inhibitory compound with different mode of action: Kainic acid and Muscimol) with the aim of characterize and assess their combined effects. Individual dose-response and binary mixtures curves have been generated. Concentration Addition (CA) and Independent Action (IA) frameworks have been used to compare calculated and experimental results. In addition, Nuclear Magnetic Resonance (NMR) spectroscopy has been employed to assess that no chemical reaction or complexation took place between mixtures components, as well as to monitor the presence of potential impurities and, in this case, to evaluate their relative amount in the tested samples. The results suggest that additivity: CA and IA are able to predict in most of the cases the total toxicity of the mixture. The variability of the results makes difficult to assess which of both approaches is the most accurate. The presence of both excitatory and inhibitory effects as in the case of Kainic acid may further complicate the analysis of the experimental datasets and biphasic concentration-dose response curves may be need to analyze the joint effect.JRC.I.6-Systems toxicolog