Assessment of the ecological status of two Black Sea areas using elemental contaminant concentrations and biochemical parameters in tissues of the blunt-snouted mullet Mullus ponticus Essipov, 1927

This study aimed to compare tissue trace-element concentrations and hepatic biochemical biomarkers in blunt-snouted mullet Mullus ponticus from two Black Sea coastal areas, Sevastopol and Adler. Fish were collected in December 2021. Separate trace-element and biochemical datasets together comprised females from Adler (n = 44) and Sevastopol (n = 34). Females from Sevastopol averaged 12.86 ± 0.09 cm in total length and 24.45 ± 0.57 g in body mass, whereas those from Adler averaged 13.14 ± 0.08 cm and 24.56 ± 0.50 g, respectively. Concentrations of Hg, Pb, Cd, As, Fe, Cu, and Zn were measured in muscle and liver. Hepatic biomarkers included lipid peroxidation, oxidized proteins, albumin, urea, and enzyme activities. In muscle, Hg was significantly higher in Sevastopol fish, whereas Pb and Cd were higher in Adler fish; the other elements did not differ. In liver, only Zn was significantly higher in Sevastopol fish. Catalase (CAT), peroxidase (PER), alanine aminotransferase (ALT) activities, and urea content were significantly higher in Adler fish. Superoxide dismutase (SOD), aspartate aminotransferase (AST), and alkaline phosphatase (ALP) showed higher but nonsignificant mean values in Adler, whereas albumin and oxidative-damage markers did not differ. Region-adjusted analyses suggested selective biochemical covariation, but no association remained significant after global false-discovery-rate correction. This pattern indicates a compensated hepatic response. Warmer conditions off Adler may have contributed, although temperature effects could not be separated from other site-specific factors. The findings support further evaluation of M. ponticus as a component of integrated coastal monitoring.