The expedition by vessel 'Nikolai Kolomeets'included sampling of marine water, bottom sediments, benthos and plankton for studies of accumulation and transformation of OCs and estimation of related toxic effects on aqueous biocenoses. The marine studies took place during the period July-October 2000 in areas of the Pechora, Kara, Laptev, East-Siberian and Chukchi Seas.