The efficiency of utilization of low molecular weight organic molecules by neustonic and planktonic bacteria inhabiting the waters of the Gdańsk Deep region has been determined. The most intensive growth was observed in the presence of amino acids, while carbohydrates and organic acids were utilized less actively. Glutamic acid, asparatic acid, histidine, glycine, cysteine and calcium lactate were the most suitable sources of carbon and energy for the bacteria. Significant differences in the level of intensity of assimilation of low molecular weight organic molecules by bacteria inhabiting various water layers occurred.