石垣島マングローブ域堆積物における窒素化合物の動態

概要

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Nitrogen dynamics within mangrove sediments was investigated in Ishigaki Island in December, 2002. More than 95% of dissolved inorganic nitrogen (DIN)was composed of NH4_4^+,but its contribution to total dissolved nitrogen (TDN) was only 10%, whereas that of dissolved organic nitrogen (DON) was achieved to 90%. We conducted a laboratory experiment to examine decomposition of DON and total organic nitrogen (TON) in the sediments. DON decreased 89 μmol N l^<-1> and NH_4^+ increased 212 μmol N l^<-1> during 14 days, though no significant change was detected as for TON. As a result, contribution of NH_4^+ to TDN was achieved to 90%, whereas that of DON was only 10%. It clearly contradicts to the field observation and suggests the process of NH_4^+ to remove most of NH_4^+ from the sediments. N_20 flux from the sediment to the atmosohere was estimated as 13.2 nmol m^<-2>d^<-1> using the data of the decomposition experiment, which is consistent with the values reported as for other mangrove areas.
静岡大学地球科学教室の論文