1. Modelling the PCB bioaccumulation in the hake (Merluccius merluccius) from the Gulf of Lions (Mediterranean sea)
X. Bodiguel1, V. Loizeau1, C. Mellon2, F. Ferraton2
1IFREMER, BP 70, Plouzané, France ; 2IFREMER, B.P. 171, Av. J. Monnet Sète Cedex France
Objectives
To evaluate the PCB contamination in hakes from the Gulf of Lions.
To establish the bases of a bioaccumulation model of PCBs in a female hake.
Study area
Introduction
Golfe du
Lion
Gulf of Lion
Sector 2 1
Rhône river
Gulf of Lions
Polychlorinated Biphenyls (PCBs), are characterized by a high persistence in the environment, bioaccumulation by the marine organisms and potentially toxic character. Bioaccumulation depends on physical and chemical properties of the compounds and biological factors like feeding, growth and reproduction. At the top of a complex trophic web, the Mediterranean hake (Merluccius merluccius; L, 1758) is potentially exposed to these contaminants and it is significant to evaluate its contamination level and contamination mechanisms.
Evaluate the fate of PCBs in hakes from the gulf of Lions.
44 liver analyses (individuals from 10 to 34 cm)
17 PCBs congeners (CBs) by GC – ECD.
Major occurrence of CB153 and CB138
Important presence of DDE (metabolite of DDT)
CB153 : 230 to 1700 ng.g-1 DW (for a juvenile hake of 11,5 cm and a male adult of 34 cm)
Concentrations 5 to 8 times higher than
in hakes from the Bay of Biscay
No influence of the Rhone river between the two studied areas
High inter-individual variability, probably due to their physiological properties.
Assumptions explaining the variations:
Hake lenght (growth)
Hake sex
Sexual maturation degree
Diet evolution
PCB Analysis
Results
CB 153 concentration in the hake livers
function of their length
PCB chromatogram in a male hake liver of 34 cm.
Modelling the PCB bioaccumulation (Dynamic Energy Budget approach)
Principle
Objective
Quantify the contribution and elimination of CB 153 during all the life of a female hake.
Uptake : food
Losses : excretion, spawning, dilution by growth.
Growth model
Food contained energy is assimilated proportionally to the hake surface area and stocked in the energy storage compartment (constant efficiency).
Stored energy is allocated to the soma and for maturity (for juvenils) or reproduction (for adults).
Maintenance is proportional to the amount of structure
Adults spawn one time each year, at a fixed date.
Starvation during winter
Initial condition: - Egg energy content
Forcing variables: - Water temperature
- No limiting food
Coupled contaminant model
PCB allocation is described likely and proportionally to the fixed energy allocation
PCB food content varying with hake diet
Stored PCB are allocated to somatic and gonadic compartments, proportionally to the energy flow to biovolume and gonads respectively. PCB mobilisation from reserves is function to the PCB storage concentration.
PCBs are expulsed during the annual spawning.
Forcing variable : - PCB prey concentration
- Energy prey value.
Conceptual diagram
Results
The comparison between growth model outputs and hake weight and length measurements validates the growth model during the whole life of a female hake.
The PCB bioaccumulation simulation seems to be acceptable compared to the few analysis results.
Conclusions
Future model development:
Taking into account bio-transformation.
Validation for other PCB congeners and other contaminants (Hg).
Extension to male hakes.
Extension to the hake population and its trophic web.
Contribution of contamination by water during breathing.
Mediterranean hakes are significantly contaminated by PCBs. This contamination seems to be correlated according to growth, probably with the diet evolution and maturation degree.
The bioaccumulation model simulates rather well the growth and contamination of an immature hake female.