Bivalves have a known ability to accumulate different contaminants from ambient water and can therefore serve as bioindicators. The paper analyses certain biochemical and physiological parameters of blue mussels in response to varying oil product concentrations. The heart rate (HR) of blue mussels from the sublittoral zone exposed to different levels of oil products was investigated in a long-term experiment using non-invasive monitoring. A sharp rise in HR was observed at oil concentrations of 8.0 and 38.0 mg/l. A decreasing in mussel HR under the effect of lower concentrations (0.4 and 1.9 mg/l) was significant on the fourth day. Strong fluctuations of the cardiac activity were noted under all concentrations. After 6 days of oil treatment, tissues of the mussels were sampled to determine the total lipid composition. Low concentrations of oil products produced no reliable changes in the lipid composition whereas high concentrations induced significant changes in the ratio of lipid components (cholesterol and phospholipids).