Sayama, M. National Institute for Resources and Environment, sayama@nire.go.jp

 
DON FLUX AND METABOLISM AT SEDIMENT-WATER INTERFACE IN A COASTAL MARINE ENVIRONMENT
 
Sediment DON dynamics is important, since polymer hydrolysis is the rate-limiting step in sediment nitrogen flow, and DON is directly utilizable by phytoplankton. The purpose was to evaluate the significance of sediment-water DON exchange, and to examine DON dynamics in PON mineralization in a highly eutrophied shallow bay area. There was a significant correlation between ammonium flux and soluble ammonium pool of the surficial sediment (0-5 mm). This indicates that molecular diffusion is the most important as a transport mechanism between sediment and water. DON pool of the surficial sediment seemed to be roughly equal to ammonium pool in all seasons, but DON flux was negligibly small, and there was no correlation between DON flux and DON pool. This contradiction between DON flux and DON concentration gradients led to the speculation that DON efflux was reduced to be unmeasurable by active consumption just at the sediment-water interface. DON was, however, always produced when the surficial sediments were incubated to measure potential rates of DON and ammonium metabolism. There was no correlation between potential metabolic rates of DON and ammonia, and it seems reasonable to suppose that DON dissolved in the pore water is not a metabolic intermediate in PON mineralization.
 
Day: Tuesday, Feb. 2
Time: 11:15 - 11:30am
Location: Eldorado Hotel
 
Code: CS56TU1115E