[en] The methods of radioactive labelling the sea water and the conditions for reaching the equivalence of physico-chemical states of radiotracers and corresponding stable nuclides in sea water are analyzed. The process of bioassimilation, the uptake and release of radionuclides by plankton organisms, is considered as the way of fast stabilization of physico-chemical forms of radiotracers in sea water. Data are presented on the sorption of iron, cobalt, nickel, and manganese by typical ocean bottom sedimants (deep-water red clay, diatomic coze, carbonate deposit). Investigating the process of sorption capture of microelements by the suspended matter and bottom sediments it was shown, that various data might be obtained: values characterizing extraction of microelement in bottom sediment (as well as to estimate the capture itself), the quantity of element forms dissolved in sea water, the charge and dimension of absorbed ions. All this information is useful for studying the transportation of microelements to the bottom and their behaviour in sea water. (T.G.)