太湖水体固氮速率时空变化

使用乙炔还原法及原位模拟对太湖水体的固氮作用进行季节性研究.结果表明,太湖水体的平均固氮速率为1.53 ng·L~(-1)·h~(-1),年固氮量为10.73 t.比较不同湖区的固氮速率可发现:梅梁湾、竺山湾等北部湖区是水体固氮作用的热点区域,而其他如湖心区、贡湖湾等水体的固氮作用较微弱.太湖水体固氮作用表现出明显的周期性季节特征,4个季节的固氮速率分别为0.10 ng·L~(-1)·h~(-1)(春季)、5.88 ng·L~(-1)·h~(-1)(夏季)、0.14 ng·L~(-1)·h~(-1)(秋季)和5.62×10-5ng·L~(-1)·h~(-1)(冬季).太湖水体中固氮蓝藻生物量是导致固氮速率空间差异的主要原因(p0.05);同时,固氮速率与水温之间的极显著正相关关系(p0.01)也证明了温度对固氮速率季节差异的影响.

Spatial-seasonal variations of nitrogen fixation of water column in Taihu Lake

The seasonal changes of nitrogen fixation in water column in Taihu Lake were studied in situ simulation with acetylene reduction technique (ART). Results show that the average nitrogen fixation rate was 1.53 ng·L^-1·h^-1,and annual fixed nitrogen was 10.73 t in Taihu Lake. Compared with different areas in Taihu Lake,Meiliang Bay and Zhushan Bay, which locate in the north of Taihu Lake, had higher nitrogen fixation rates,than those in others areas, like the Gonghu Bay located at Centre of the lake. The seasonal variation of the nitrogen fixation was also great with 0.10 ng·L^-1·h^-1 in spring,5.88 ng·L^-1·h^-1 in summer,0.14 ng·L^-1·h^-1 in autumn and 5.62×10^-5 ng·L^-1·h^-1in winter. Through correlation analysis, the biomass of nitrogen-fixing cyanobacteria would be the main rate controlling factor for spatial variations(p<0.05),and the water temperature was the major reason for seasonal changes(p<0.01).