Organic Nitrogen Compounds in Atmospheric Precipitation: Their Chemistry and Availability to Phytoplankton

Urea accounted for 30, 36, and 56%, respectively, of the water-soluble organic nitrogen (DON) compounds deposited from the atmosphere at two sites in New Zealand and one site in japan. The other DON compounds were not identified but they were all of low molecular size, apparently anionic, and did not include detectable quantities of amino acids or uric acid. In axenic culture, Chlorella spp. grew successfully using DON from New Zealand precipitation as its only source of N; Pediastrum biwae, a phytoplankton endemic to Lake Biwa in Japan, also achieved successful growth using DON separated from Japanese precipitation. Ammonium-N and DON were deposited from the atmosphere in the absence of rain or snow, and we suggest that particulate matter, possibly soil, is a major source of these N compounds in atmospheric precipitation.