Seasonal rhythm of physiological indexes, liver protein level, and biotransformation biomarkers in Zosterisessor ophiocephalus and Gobius niger from a low contaminated lagoon (Ghar El Melh lagoon, Tunisia)

This study assessed seasonal variation of total liver proteins level (LPLs) and biotransformation biomarkers in two fish species, G. niger and Z. ophiocephalus, during a one year-survey in the low contaminated Ghar-El-Melh lagoon, Tunisia. Analyzed biomarkers were compared with physiological indexes such as the condition index, hepato-somatic index, and gonado-somatic index and environmental parameters. A significant annual rhythms of glutathione-S-transferase and ethoxyresorufin-O-deethylase activities were validated by cosinor. The highest peak (acrophase) of activities occurred in summer likely related to the elevated seawater temperature. Midline Estimating Statistic of Rhythm and amplitudes were higher in Z. ophiocephalus than in G. niger. The results showed, as well, an acrophase of (LPLs) in spring coinciding with reproductive period in Z. ophiocephalus and beginning of reproductive period in G. niger. This study established a baseline for the selected enzymatic activities in gobies, which required information for a correct interpretation of biomarker responses in environmental monitoring.