We have studied the breeding parameters, organochlorine compounds (OCs) concentrations, and fatty acid (FA) composition of egg yolks (n = 47) and plasma (n = 90) of common terns (Sterna hirundo) from two colonies (Banya and Fangar) in the Ebro delta, NE Spain. Terns from Banya tend to have smaller clutch size and lower hatching success than terns from Fangar. p,p'-DDE and polychlorinated biphenyls (PCBs) concentrations were almost 2-fold higher in yolks from Banya in 1998 than from Fangar in 1999, and the percentage of n-6 PUFA was positively correlated with these contaminants. Differences between samplings in OCs concentrations in plasma were less evident, and were affected by breeding chronology. The highest OCs concentrations in yolks from Banya may be explained by two processes involving the increased deposition of n-6 PUFA: (1) higher mobilization of endogenous fat due to lower food resources, or (2) differences in the diet between colonies. Birds from Banya may have been feeding at a higher degree on discards of trawling fisheries composed of demersal and benthic fish species that are more exposed to contaminants from sediment and have lower n-3/n-6 ratio, whereas birds from Fangar would feed mostly on pelagic species of small clupeiformes that are less polluted and have higher n-3/n-6 ratios.
Commercially available butter from Spain (n = 36) and from other European countries (n = 20) has been analyzed by high resolution gas chromatography with an electron capture detector for organochlorine contaminants. The results showed that both groups of samples have a similar pattern of these pollutants, but in all cases where significant differences in concentrations were found, Spanish samples presented higher values. This was especially notable for lindane (median values 11.6 vs. 3.0 ng/g wet weight), hexachlorobenzene (6.4 vs. 0.5) and beta-hexachlorocyclohexane (3.1 vs. 1.2). Total PCBs showed no differences (5.4 vs. 6.6), but detailed analysis of congener composition indicated a higher presence in Spanish samples of the most persistent chlorinated PCBs. No sample presented levels of concern for any single organochlorine compound. It is interesting to note that consumption of butter in Spain is low so, although levels of organochlorines are higher than those found in other countries, consumers are less exposed through this foodstuff than in other European countries. These results also confirm the fact that environmental pollution by organochlorines is more important in Spain than in the rest of Europe.
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