Сибирский экологический журнал, 2 (2016) 228236 УДК 577.15: 57.042: 57.017.32 DOI 10.15372/SEJ20160207 Seasonal variability of some biochemical parameters in the whitefish (Coregonus muksun and Coregonus lavaretus) E. V. BORVINSKAYA1, I. V. SUKHOVSKAYA1, A. A. KOSСHNEVA2, O. B. VASILYEVA1, M. A. NAZAROVA3, L. P. SMIRNOV1, N. N. NEMOVA1 1 Institute of Biology of the Karelian Research Centre, RAS 185910, Petrozavodsk, Pushkinskaya str., 11 E-mail: katsu@inbox. ru 2 Petrozavodsk State University 185910, Petrosavodsk, Leninа str., 33 3 Vologda State University 160035, Vologda, Leninа str., 15 Статья поступила 02.06.2015 Принята к печати 23.06.2015 ABSTRACT The base levels and seasonal variability of ethoxyresorufin-O-deethylase (EROD) activity, glutathione-S-transferase (GST) activity, reduced glutathione concentration (GSH) and phospholipids concentration (PhL) of Coregonus lavaretus (Linnаeus, 1758) and C. muksun (Pallas, 1814) were investigated. <...> The relationships between this biochemical markers, hepatosomatic index and seasonal growth were also examined. <...> Biochemical adaptation means modification of the functioning and the content of certain macromolecules to maintain homeostasis of the internal environment under the changing conditions. <...> Molecules involved in biochemical adaptation vary in accordance with current metabolic demands and as biomarkers may indicate the general state of the organism. <...> In this context, a number of biochemical parameters (biomarkers) have been investigated to assess disturbances of biological functions in aquatic organisms during biomonitoring studies [Sheehan, Power, 1999; Adams, 2002; Van der Oost et al., 2003; Martнnez-Бlvarez et al., 2005; Lehtonen et al., 2006]. <...> It was established that most of the biochemical responses are not specific and susceptible to environmental factors fluctuations, such as diet, salinity, dis© Borvinskaya E. V., Sukhovskaya I. V., Kosсhneva A. A., Vasilyeva O. B., Nazarova M. A., Smirnov L. P., Nemova N. N., 2016 228 solved oxygen, etc. <...> The metabolic rate of ectotermic organisms is also directly related to water temperature. <...> These confounding factors may mask the effect of contaminant-induced stress signals and make the interpretation of the results quite challenging [Pavloviж et al <...>