| Abstrak/Abstract |
The aims of this study were to know the nitrification potential of the mud sediment of the Ariake sea
tidal flat, and to investigate the individual influence of environmental parameters such as temperature, pH,
salinity and ammonium concentration on its nitrification rate. The Ariake Sea is a semi-closed shallow sea with
macro-tidal and the largest tidal flat in Japan. Nitrification Potential Rate (NPR) and Nitrification Rate (NR)
of the tidal flat mud sediment were determined by amending sodium chlorate to inhibit the oxidation of NO2-N
to NO3-N. NPRs of the sediment were 91.4, 71.2 and 64.8 nmol N/g Dry Weight Sediment (DWS)/h at the
depth of 0-3, 3-6 and 6-9 cm, respectively. NRs were relatively high in the temperatures range of 20-35oC with
the optimum temperature of 29.3oC. Relatively high NRs were determined in the range of pHs 7.5-8 with the
optimum pH 7.7. The optimum salinity for nitrification was 15 ppt. NRs increased drastically in the range of
salinity 10 to 15 ppt, but it decreased sharply at 15 to 20 ppt. Relationship between ammonium concentration
and NR resulted a hyperbolic Michaëlis-Menten type curve (R2 = 0.98) with the maximum NR rate (Vmax) 32.5
nmol N/g DWS/h at NH4-N concentration 3,000 mM and the half saturation constant (Ks) 700 mM NH4-N. To
our knowledge, this is the first report on nitrification of mud sediment of the Ariake sea tidal flat, and its
optimal temperature, pH, salinity and NH4-N concentration as a single parameter. |
