The effect of different concentrations of heavy metal ions Hg+2, Cd+2, Zn+2, Cu+2 on growth and respiratory activity of neustonic and planktonic bacteria derived from the Deep of Gda?sk was studied. The laboratory experiments demonstrated that all heavy metals examined exhibited toxic effects on the development and oxygen uptake by neustonic and planktonic bacteria. This effect depended on the kind of the metal and its concentration.