Abstract <p>For the first time, the isotope compositions of total carbon (δ¹³C_tot) and nitrogen (δ¹⁵N_tot) for organogenic deposits and isotope compositions of oxygen (δ¹⁸O_cell) with carbon (δ¹³C_cell) for cellulose from the Holocene organogenic deposits were studied for the southern Far East of Russia. The study focused on the section of lacustrine-boggy deposits of the Shufan Plateau (Southern Primorye), which accumulated during 9720 cal BP. The greatest variability of isotope ratios was determined for the Early Holocene and the last thousand years. The effects on the isotope composition of such factors as hydroclimatic changes, including the dynamics of the hydrological regime of the paleolake around which a peat bog developed, the botanical composition of peat-forming plants, and peat accumulation rates were analyzed. An increase in moisture had different effects on isotope fractionation in peat composed of bryophytes and vascular plants. The age was determined, and positive and negative peaks of stable isotope values were interpreted and compared with the data for the region. One of the leading factors of isotope fractionation was moisture changes associated with monsoon circulation. It is suggested that isotope ratios may be influenced by a decrease in lake depth, evaporation, and snow contribution to groundwater recharge. Comparison of δ¹³C_tot and δ¹⁵N_tot records and C/N ratios downsection revealed periods with different degrees of organic matter degradation. Direct correlations were established for the δ¹³С_cell and δ¹⁸О_cell values and inverse correlations for the δ¹³С_tot and δ¹⁵N_tot values, which change regularly in different peat generations. Changes were identified in the isotope composition of peat and turf formed after the Little Ice Age in warmer conditions and under increasing anthropogenic impact.</p>