北部湾冬季的生物固氮作用

Biological fixed nitrogen of Tokin Gulf in winter

2006年12月至2007年1月(冬季)期间,对北部湾海区的生物固氮作用进行了初步研究,结果表明:当培养时间为2 h时,水体浮游生物固氮速率最高,且固氮速率随着培养时间的延长而逐渐降低。北部湾冬季固氮速率存在周日变化,8∶10～11∶10时段内固氮速率达到最高值。10 m和30 m水深在夜间仍能检测到固氮活性,这可能是浮游生物昼夜垂直移动引起的。北部湾冬季固氮速率的范围为447.5～1447.2 pmol/(L.h),固氮速率呈现出从湾内往湾外不断增加的趋势,湾口海区(B06站)的积分固氮速率为319.5μmol/(m2.d)。B06站Fe加富实验表明,添加100 nmol/L Fe能够明显促进生物固氮作用,北部湾冬季湾口海区生物固氮作用可能受到Fe限制。

The biological nitrogen fixation rates were investigated in Tokin Gulf waters in winter from Dec. 2006 to Jan. 2007. The ni- trogen fixation rates were decreased as extension of culture time, the optimal culture time was 2 h. The nitrogen fixation rates showed diurnal variations, the highest nitrogen fixation rate appeared at 8：10 - 11： 10, the diazotrophs still have the nitrogen fixation activity during the night at the depths of 10 m and 30 m, which may result from the diurnal migration of planktons. The nitrogen fixation rates ranged from 447.5 pmol/（ L· h） to l 447.2 pmol/（ L · h） of Tokin Gulf waters in winter. Which showed a longitudinally increasing trend, the integral nitrogen fixation rate at station B06 was 319.5 μmol/（m2 · d）. The iron enrichment experiment at the mouth of the bay （ B06 ） showed that the biological nitrogen fixation significantly promoted by adding iron concentration of 100 nmol/L. The bi- ological nitrogen fixation rates at the bay mouth might be iron limited.