Histopathological, histomorphometrical, and immunohistochemical biomarkers in flounder (Platichthys flesus) from the southern Baltic Sea

Flounder (Platichthys flesus), collected in late fall of 2009 from four coastal sites in the southern Baltic Sea including the Gulf of Gdańsk (GoG), were investigated for a suite of biomarkers of contaminant effects. The biomarkers included liver histopathologies, which were diagnosed and assessed using commonly applied lesion categories, the size and density of melano-macrophage aggregates (MMAs), expression of proliferating cell nuclear antigen (PCNA) and of cytochrome P450 1A (CYP1A) in liver as well as the size and density of MMAs and density of Perls'-positive cells in the spleen. The prevalence of liver lesions differed among the sites. Most frequently occurring were non-specific and early toxicopathic non-neoplastic lesions. Mean MMA size was in the range of 264–519 μm2 and 717–2137 μm2 in liver and spleen, respectively, and density was in the range of 6–13 and 15–26 MMA mm−2, respectively. Mean density of PCNA-positive hepatocytes was in the range of 300–1281 cells mm−2. These histomorphometrical biomarkers correlated positively with the muscle Hg, Σ7PCB, and ΣDDT residues and negatively with the indices of general liver condition. They showed significant differences between the sites, which were in line with the spatial prevalence of liver lesions and CYP1A induction. Overall, the biomarker responses were more pronounced in the GoG sites in comparison to those outside the Gulf, which confirms some earlier results and broadens the knowledge of contaminant effects in the Polish coastal zone of the Baltic Sea.

► Clear gradients in biomarker responses differentiated the study sites.
► MMAs proved the utility as a biomarker of contaminant exposure.
► Histopathology score was fairly associated with the Hg, Σ7PCB, and ΣDDT levels.