Can we use stable isotopes for ecotoxicological studies? Effect of DDT on isotopic fractionation in Perca fluviatilis.

Nitrogen and carbon stable isotope analyses are frequently used to assess contaminant biomagnification in animals in the wild. Previous studies, mainly on plant but also on animal tissues, have shown that chemical stress can lead to shifts in delta(15)N. In order to assess if an exposure to DDT at realistic concentration disrupted stable isotope signature in animals, delta(15)N and delta(13)C were studied in several tissues (liver, muscle, gill) of Perca fluviatilis fed with the same commercial diet uncontaminated or contaminated with DDT. We observed no DDT effect on the delta(15)N and delta(13)C of fish tissues. Our results show that stable isotopes can remain useful for field ecotoxicological studies despite food-chain contamination. However, correlations between the delta(13)C or delta(15)N values measured in the different organs were only found in DDT treated fish, suggesting some disruption of major biochemical compound metabolism in tissues.

Organochlorines in the Vaccarès Lagoon trophic web (Biosphere Reserve of Camargue, France).

During a decade (1996-2006), ecotoxicological studies were carried out in biota of the Vaccarès Lagoon (Biosphere Reserve in Rhone Delta, France). A multicontamination was shown at all levels of the trophic web due to a direct bioconcentration of chemical from the medium combined with a food transfer. Here, the pollutants investigated were organochlorines, among which many compounds banned or in the course of prohibition (or restriction) (PCB, lindane, pp'-DDE, dieldrin, aldrin, heptachlor, endosulfan...) and some substances likely still used in the Rhone River basin (diuron, fipronil). The results confirmed the ubiquity of contamination. It proves to be chronic, variable and tends to regress; however contamination levels depend on the trophic compartment. A biomagnification process was showed. A comparison of investigation methods used in other Mediterranean wetlands provides basis of discussion, and demonstrates the urgent need of modelling to assess the ecotoxicological risk in order to improve the management of such protected areas.

Rice fields regulate organochlorine pesticides and PCBs in lagoons of the Nature Reserve of Camargue.

In order to assess pollutant transfer in Camargue ponds from bordering agrosystems, a biomonitoring assay was conducted in irrigation and drainage channels of rice fields in the Rhone Delta (France). A filter-feeding bivalve, the Asian clam, Corbicula fluminea, was used as bioindicator and caged in upstream and downstream channels of an area of conventional rice fields. After 6 weeks incubation, many lipophilic biocides were identified in Corbicula tissues, including pesticides used in rice plantations (pretilachlor, oxadiazon), pesticides presumed in use in the Rhone basin [diuron and its metabolite 3,4 dichloroaniline (3,4-DCA)] and organochlorine pesticides (OCPs) banned for several decades. In addition, PCBs were highly bioaccumulated in Corbicula. Downstream bivalves had significantly lower concentrations of OCPs, PCB and 3,4-DCA. However, the exposure biomarkers (glutathione S-transferase, catalase and propionylcholinesterase) were not correlated with the decreased concentrations. The results of this experiment raise several questions concerning the potential role of immersed plants in a retention process.

Bioaccumulation of polychlorinated biphenyls in the eel (Anguilla anguilla) at the Camargue Nature Reserve - France.

Fish consumption is a potential source of human exposure to pollutants. Here, we study residue levels of PCBs in the eel, Anguilla anguilla, from the Nature Camargue Reserve in southern France. Chromatographic analysis (GC-ECD) found seventy identifiable congeners, among which, 10 are considered as dioxin-like PCBs, such as the non-ortho PCB 81 and the mono-ortho chlorobiphenyls PCB105, 114, 118, 123, 156, 157, 167, 170, 180. Toxic Equivalents (TEQ, WHO 2005 TEF-Toxic Equivalent Factors) varied among sites with a maximum in eels from Mornès (29.6pgg(-1) dry weight). Indicator PCBs (28, 52, 101, 118, 138, 153 and 180) were 22% and 29% of the total PCBs in livers and muscles respectively. Greater homogeneous bioaccumulation in muscle than that in liver suggests an increase risk for humans due to fish consumption.

Bioaccumulation and the effects of organochlorine pesticides, PAH and heavy metals in the Eel (Anguilla anguilla) at the Camargue Nature Reserve, France.

Pesticides (organochlorines-OC), polycyclic aromatic hydrocarbons (PAH) and heavy metals are toxic to fish and may be taken in through gills, skin and contaminated foods. Here we measure concentrations of OC, PAH and heavy metals, and their effects in the eel Anguilla anguilla from three locations in the Camargue Reserve in southern France. The Camargue Biosphere Reserve is the largest coastal wetland in Western Europe, and A. anguilla is a common predator at the top of the food chain. Livers and spleens were analyzed for histopathological, chemical and organo-somatic (HSI and SSI) effects. Gill, liver and spleen samples were collected for histopathological studies. Livers and muscles were sampled for metabolic parameters and persistent organic pollutant analysis. Total lipids were estimated by spectrophotometry and lipid-free residues were used in protein and glycogen analysis. OC pesticides were extracted from lipids of muscles and livers, analyzed by gas chromatography, and PAH from bile were analyzed by fixed wavelength fluorescence spectrofluorimetry. Heavy metals were measured by inductively coupled plasma with optical or with mass spectrometers. High concentrations of contaminants were found in eel tissues. La Capelière had the greatest OC and PAH concentrations; unexpected lesions in gills, livers and spleens were more common at the other sites. Liver and spleen tumors and lipidosis in livers were associated with chronic, and gill lesions with acute exposure. High pesticide and PAH concentrations and lesions in eels from the Camargue reserve demonstrate the contamination of the area. A more complete study in the Camargue reserve is necessary to better understand the impact on wildlife and humans. Also, this study suggests that eel biology must be better understood before continued use of this species as a biomonitor of polluted areas.