This work deals with regularities in the transfer and transformation of organic matter in the river-sea system. By investigating different objects (soils, water, suspended matter, bottom sediments), the author reveals the peculiarities of the behaviour and the mechanism of transfer and transformation of organic matter on its way from the river into the sea at various stages of mixing of riverine and sea water, and determines the regularities of organic matter transformation in the line "suspended matter-bottom sediments". Completed explorations may be used for the detection of migration routes and places of anomalous concentrations of organic matter, including pollution, at the bottom of seas and oceans into water areas adjoining estuaries. The book is intended for oceanologists, marine chemists, geochemists, specialists in ecological and environmental problems, postgraduate students, lecturers in universities and staff members of state organizations studying the problems of estuaries.