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The presence of persistent organic pollutants in the environment manifests itself most strongly in the marine trophic chain, where the highest link is comprised of seabirds. At the same time, seabirds are excellent indicators of contamination in their habitat. The present study concentrates on toxic substances: polychlorinated dibenzo-p-dioxin (PCDDs), polychlorinated dibenzofurans (PCDFs) and chlorinated organic pesticides (OCPs) accumulated in the livers, pectoral muscles and brains of dead gulls collected along the Polish coast of the Baltic Sea in the years 2010–12. The highest toxic equivalence was determined in the livers of Larus argentatus (TEQ (birds TEF) −28.3 pg g −1 ww) and Larus marinus (TEQ (birds TEF) −29.9 pg g −1 ww.). However, the toxic equivalence of muscles was lower and amounted to 3.9 pg g −1 ww. and 7.8 pg g −1 ww. respectively for the two species. The lowest toxic equivalence was found in the brains of birds, where only one, the most toxic, 2,3,7,8 TCDD congener was found (TEQ (birds TEF) 0.87 pg g −1 ww). The highest concentration of chloroorganic pesticides was determined in the brains of the birds (total OCP 167.8 pg g −1 ww.), lower concentrations were found in the livers (total OCP 92.1 pg g −1 ww.) and muscles (total OCP 43.1 pg g −1 ww.). With regard to pesticides, the highest proportion in the total OCP content was constituted by DDT and its isomers (liver 81%, muscles 77% and brain 55%). High concentrations of the studied pollutants in the livers of gulls found dead on the coast of the Southern Baltic could have been effected by levels of contamination in the birds’ last meals, which resulted in a seven-fold increase of the liver’s toxic equivalence and a two-fold increase in OCP concentration in relation to muscles. [ABSTRACT FROM AUTHOR]

Diet is the major route of exposure to environmental contaminants in biota and, after penetration into an organism, xenobiotics continue to accumulate in the body. In birds the egg-laying process acts as a transfer mechanism for the accumulated pollutants and results in the burdening of the next generation at an early stage of development. This transfer has a strong influence on developmental disorders and even breeding success. With this in mind polybrominated diphenyl ethers (PBDE), polychlorinated dibenzo-p-dioxins and polychlorinated dibenzo furans (PCDD/Fs), as well as polychlorinated biphenyls (PCBs), were analyzed in the eggs of aquatic birds from different habitats and with different diet preferences. The highest concentration of PBDE was noted in gull eggs (198.31 ng g−1 dw.) and the lowest in tern eggs (sandwich tern: 76.96 ng g−1 dw.; common tern: 113.73 ng g−1 dw). Deca-BDE was detected only in herring gull eggs from the Wloclawek reservoir. PCDDF/s were found in the eggs of terns from the southern coast of the Baltic Sea and gulls from an inland reservoir (dam) on the River Vistula close to the town of Wloclawek. The highest toxicity (birds Toxic Equivalent Factor) was found in the eggs of terns (sandwich tern – 93.97 pg g−1 dw., common tern – 68.35 pg g−1 dw.), and this was found to be several times higher than in herring gull eggs (18.80 pg g−1 dw.). Non-dioxin like PCBs were ten times higher than other analyzed PCB congeners, but the congener pattern was similar to other studies. • Deca-BDE was found only in gull eggs from an inland reservoir. • Highly chlorinated furans have the lowest concentration in birds' eggs. • Chlorinated compounds dominated in tern eggs, brominated in gull eggs. [ABSTRACT FROM AUTHOR]