Organochlorine levels in viperine snake Natrix maura carcasses from the ebro delta (NE Spain): Sexual and size-related differences

• Published in: Chemosphere (Oxford) Vol. 39; no. 15; pp. 2641 - 2650
• Main Authors: Santos, X., Pastor, D., Llorente, G.A., Albaigés, J.
• Format: Journal Article
• Language: English
• Published: Oxford Elsevier Ltd 01-12-1999; Elsevier
• Subjects: age differences; Animal, plant and microbial ecology; Applied ecology; Biological and medical sciences; biomagnification; DDD (pesticide); DDE (pesticide); DDT (pesticide); DDTs; Ecotoxicology, biological effects of pollution; Effects of pollution and side effects of pesticides on vertebrates; Fundamental and applied biological sciences. Psychology; fungicide residues; gender differences; hexachlorobenzene; indicator species; insecticide residues; lindane; natrix; Natrix maura; organochlorine compounds; PCBs; pollutants; pollution; polychlorinated biphenyls; reproductive cycle; Reptilia. Amphibia; seasonal variation; Spain, Ebro Delta; Spain, Ebro R; wetlands; Spain; Europe; DDTs; Natrix maura; PCBs; reproductive cycle; biomagnification; pollutants; Brackish water environment; Ebro River; Insecticide; Pesticides; Sex; Biological indicator; Polychlorobiphenyl; Ophidia; Vertebrata; DDT; Organochlorine compounds; Body size; Interindividual comparison; Reptilia; Water pollution; Biological effect; Biological accumulation; Reproductive cycle; Biomagnification
• ISSN: 0045-6535; 1879-1298
• DOI: 10.1016/S0045-6535(99)00199-X

Organochlorine compounds (PCBs, DDTs and HCB) in carcasses from a population of the Viperine Snake (
Natrix maura) living in the Ebro Delta were analyzed. This is a wetland area on the Mediterranean coast where the natural ecosystem has been partially substituted by rice fields. High levels of pollutants (mainly DDTs and PCBs) have been detected in several species living in this area, due to the production of these compounds by a former industrial activity upstream as well as agricultural activity in the Delta. Organochlorines were analyzed in adult males and females, and in immature snakes. DDTs (mainly p,p′-DDE) were the most abundant pollutant present. The DDT/PCB ratio was higher than expected, which is consistent with the position of the Viperine Snake in the trophic web as well as the type of prey consumed. Immature snakes had more organochlorines than adults. However, the broad range of concentrations shown by immature snakes, suggested that part of the organochlorine load is transferred from gravid females to their eggs. In adults, organochlorine concentrations increased with carcass weight in both males and females. This increase was higher in males since females lost contaminants through fat investment during vitellogenesis. Seasonally, PCBs and DDTs levels increased in spring when snakes showed higher feeding activity, whereas higher levels of HCB were present at the end of summer, when the river input increased. Furthermore, HCB does not seem to biomagnify well across the trophic chain. Organochlorine concentrations in Viperine Snake carcasses were high since: 1) the dry tissue had less than 5% of fat, and 2) snakes were caught many years after the DDT ban, supporting the fact that cleaning of the ecosystem does not occur easily. These results indicate that snakes are adequate as indicators of the contamination in natural ecosystems but sex and body size of the samples should be taken into account for interpretation of results.