The GEMCO PROJECT -2- The foodweb model

The GEMCO project (Generic Estuarine Modelling system to evaluate transport, fate and impact of COntaminants) aims to build an user-friendly software application for the evaluation of concentrations of given chemical substances in water, suspended particulate matter (SPM), sediment and biota in any european estuary predefined by its main physical, physico-chemical and biological characteristics.

ABARNOU, A.(1), LOIZEAU, V.(1), ROMAÑA, L.A.(2), BAART, A.(3), van HATTUM, B.(4), THOMAS, P.(5)

(1) IFREMER, Direction de l’Environnement et de l’aménagement Littoral, Ecologie Côtière, B.P. 70, F-29280 PLouzané (2) IFREMER, Direction de l’Environnement et de l’aménagement Littoral, Polluants Chimiques, B.P. 330, F-83507 La Seyne/Mer(3) WL/DELFT Hydraulics, Marine and Coastal Management, P.O.Box 177, 2600 MH Delft, The Netherlands(4) VRIJE UNIVERSITEIT AMSTERDAM, Institute for Environmental Studies, De Boeleaan,1115, 1081 HV Amsterdam, The Netherlands(5) ATOFINA , Direction Sécurité Environnement, Cours Michelet, La Défense10, F- 92091 Paris La Défense

Key-words : virtual estuary, risk assessment, predicted environmental concentrations, modelling, trophic chain

The GEMCO model includes two interacting sub-models 1. An abiotic model which predicts - the substance concentrations in abiotic compartments (water, SPM, sediment) - the SPM distribution and the Primary Production,

2. A foodweb model which calculates concentrations of these substances in species using data generated by the first sub-model.

The FW model relies upon the biological processes .

This generic model will be validated by data from previously studied

estuary (e.g.Scheldt, Seine)

4. Processes.

How the key-processes should be represented by simple and generic equations ? Should metabolization be considered as a function depending on compounds and species ?

Expected results 1. Processes/parameters the foodweb model will highlight the mains processes acting on the distribution of chemicals in organisms and the relative importance of these processes on the fate of contaminants in biota.

2. Concentrations and chemical risk assessment the foodweb will predict concentrations of chemicals in biota and their variations. These PEC in biota (PEC : predicted environmental concentrations) are to be compared with PNEC (predicted non effects concentrations).

The further step : the virtual estuary model. This FW model should be able to predict concentration of chemicals in the species , whether bioaccumulated or not, which live in main european estuaries. Initial research will be directed at answering the following questions.

The GEMCO estuarine modelling project sets out to predict concentrations of contaminants in estuaries and subsequent bioaccumulation with a view to its use in marine risk assessment. The project is in its early stages and no results have been obtained so far. This poster is presented with a particular attention to the foodweb aspects of the model. The project aims to generalize existing bioaccumulation models to other chemical compounds that could reach estuarine organisms.

Data base : measurements, processes

GEMCO

Abiotic model

Delft Hydraulics

Validation Ifremer Toulon

Foodweb modelIfremer Brest

Validation

IVM AmsterdamPrimary ProdSPM

VIRTUAL ESTUARY MODELCharacteristics

estuaryorganismschemicals

PEC in water sediment and biota

Structure of the project and role of partnersGeneral objective

Acknowlegements

1. Estuarine context.

The physical (bathymetry, sediment, ...) and physico-chemical features (salinity, SPM,...) of the estuaries determine the species distribution and the structure of the foodwebs. How many types of foodwebs are to be considered ? which one, benthic and/or pelagic, freshwater, estuarine and/or marine foodweb. ?

2. Species.

Which are the target-species ? Are they selected according to their biomass, their commercial value, their role in the trophic chain or their sensitivity to chemicals ? How many species need to be included ?

3. Contaminants. How the substances will be choosen according to their hydrophobicity (Kow) and their persistence (half-lifes) ? How metabolization will be described, depending on the species and on the chemical compounds ?

Model equation :

For each organism, the concentration of a contaminant results from a mass balanced budget between uptake via respiration and feeding and their decrease by dilution growth, excretion, metabolization. The rates of biological processes depend on the weight of the animal (age dependent) and of environmental conditions (T°C, O2, …). Metabolization of persistent compounds such as PCBs can be considered to be negligible.

..

0

100

200

300

400

CB

28

CB

52

CB

101

CB

118

CB

153

CB

138

CB

180

Calculated concentrationsMeasured concentrations

0

250

500

750

1000

1250

1500

1 y+

Age

4 y+3 y+2 y+

Validation of the PCB bioaccumulation models

PCB distribution in dab Dynamic model of PCB contaminationin seabass

The dab foodweb : a coastal benthic foodweb

The seabass foodweb : an estuarine pelagic foodweb

PCB bioaccumulation model in marine and coastal foodwebs

The starting point : bioaccumulation models

Sediment

Phytoplankton

x5

x2

x4

x1

x3

Limanda limanda

Bathyporeia pelagica

Acrocnida brachiata

Tellina fabula

- concentrations in water (dissolved), SPM and phytoplankton are forced variables- environmental conditions (temperature, dissolved oxygen, chlorophyll,...) vary seasonally- biological functions (reproduction, growth, ...) depend on environmental conditions

Calculated concentrationsMeasured concentrations

ng.g -1 d.w.

dCi/dt = Ri . Aiw . Cw + Fi. Pij .aij . Cj - (Ei + Gi + Repi + Mi) . Ci

CD, CP, CSed

Pectinariakoreni

CBiota

ng.g -1 d.w.