Comparison of selected biomarkers in flounder (Platichthys flesus L.) from the Douro (Portugal) and Vistula (Poland) River estuaries

- Female flounder were sampled from the mouths of the two rivers and corresponding open sea sites.
- Several differences in biomarkers between the sampling sites were found.
- Salinity and pollution seem to be the main factors that affect the biomarkers.
- Effects of chronic pollution were found in the mouths of both rivers.

Sixty female flounder (Platichthys flesus) were collected in Autumn 2011, 15 from each of the following sampling sites: at the mouths of the Douro and Vistula Rivers, and at nearby open sea locations. The aim of the study was to assess several biomarkers in the two geographically distant regions. Hepatic EROD, GST, SOD, GPx, POx, LP; muscular AChE, BChE, LP; and branchial Na+/K+-ATPase were analysed. Moreover, BTI, PY, and three gross morphometric indices were calculated. The results were analysed with t-test, ANOVA, and PCA. Many differences were found between the open sea sites and the river mouths, mainly in Portugal, and between the two rivers. Salinity and pollution seem to be the main factors that affected the biomarkers. Effects of chronic pollution were observed at the river mouths, and an indication of a possible temporary exposure to pollutants was found at the open ocean site in Portugal.