Endocrine disrupting bisphenol A, 4-tert-octylphenol and 4-nonylphenol in gonads of long-tailed ducks Clangula hyemalis wintering in the southern Baltic

This paper focuses on determining the concentrations of phenol derivatives in the gonads of seabirds and examining the potential factors (age, sex and region) affecting the degree of their bioaccumulation. The study involved assays of bisphenol A (BPA), 4-tert-octylphenol (4-t-OP) and 4-nonylphenol (4-NP) in the gonads of long-tailed ducks taken as bycatch from the Southern Baltic region in 2015-2016. Among phenol derivatives, 4-NP was found to reach the highest concentrations in the gonads of long-tailed ducks, and its concentrations were in the range of <0.1-717.5 ng g(-1) dw. The concentrations of BPA and 4-t-OP were similar and amounted to <0.4-181.6 ng g(-1) dw and <0.1-192.4 ng g(-1) dw respectively. The concentration levels of phenol derivatives in the birds' gonads were similar to the levels which had been observed to have negative endocrine effects in other authors studies. This shows that the studied xenoestrogens can interfere with the reproduction and development of birds. Moreover, adult long-tailed ducks had higher concentrations of phenol derivatives compared to immature ones, possibly resulting from long-term bioaccumulation, as well as from diverse pollution in their respective habitats. Particularly in the case of 4-NP, the median concentrations in gonads of adult birds were 2-fold higher than in immature ones. In turn, among adult long-tailed ducks, phenol derivatives were characterized by higher concentrations in males than in females, with almost 3 times and approx. 3.5 times higher median concentrations of BPA and 4-t-OP, respectively. Lower concentrations of phenol derivatives in female gonads may result from the additional elimination of pollutants from their bodies through the transfer of pollutants from mother to egg. The results show the need for further research on phenol derivatives in the gonads of birds, focusing on their impact on the reproductive system and early development.