Radioisotopic Methods in Hydrobiology 87 The significance of various types 18 The significance of various types and location of pain often are neglected by the doctor held in Tsukuba The use of radioisotopic techniques offers a wide range of methodological possibilities because all biologically active compounds contain long living radioisotopes which make the analytical field and laboratory work possible without the precautions involved in direct radiation health hazards there is an increasing demand for better and more reliable methods for the monitoring and assessment of these large and important ecosystems and the interrelations between the physical and chemical features of water bodies