Role of oceans as biogenic sources of selenium

The pathways leading to the volatilisation and atmospheric transfer of sele nium from oceanic environments are poorly understood. They may however affe ct the global distribution of selenium and its impact on marine and terrest rial ecosystems. In this paper we describe the results of experiments which provide a reasonable estimate of the global selenium budget. Gaseous selen ium compounds were determined in the North Atlantic Ocean during a Spring b loom of phytoplankton species which are known to be a large source of atmos pheric sulphur. The results demonstrate that significant concentrations of gaseous selenium species occur in surface ocean waters, and their productio n is closely linked to the gaseous sulphur species turnover. Selective upta ke and biotransformation of dissolved selenium in seawater by phytoplankton is a major pathway for the production of gaseous selenium compounds in mar ine environments and their emission to the atmosphere. It is therefore sugg ested that such a major selenium source supplies the terrestrial environmen t with selenium that can be used as an essential nutrient for animal and hu man life. (C) 2001 Elsevier Science B.V. All rights reserved.