增温对南极湖泊沉积物反硝化过程的影响

Effects of warming on the denitrification in Antarctic lake sediments

全球变暖导致的极地地区增温正深刻地改变着极地地区生态系统物质循环过程和速率。目前,增温对南极地区湖泊沉积物氮循环关键过程的影响还鲜有报道。中国第29次南极科学考察期间在南极中山站附近选取了5个湖泊,采集了1处含企鹅粪土的湖泊沉积物(莫愁湖)和4处自然湖泊沉积物(团结湖、大明湖、米尔湖和玉珍湖),利用样品瓶泥浆恒温培养法进行增温模拟,设置低温(1℃)、中温(5℃)、高温(11℃)培养实验。结果表明,低温条件下莫愁湖沉积物反硝化速率和反硝化潜势明显高于自然湖泊沉积物(277.37倍、244.13倍)。一定程度的增温促进了沉积物反硝化速率与反硝化潜势,但过高温度也会抑制部分样点的反硝化速率与反硝化潜势。总体而言,高温条件下自然湖泊沉积物平均反硝化速率分别是中、低温条件下的1.57倍、3.56倍,反硝化潜势为1.91倍、6.31倍;而含企鹅粪土湖泊沉积物反硝化速率为1.17倍、2.08倍,反硝化潜势为0.72倍、1.01倍。增温对自然湖泊沉积物反硝化速率和潜势的影响高于莫愁湖沉积物,但含企鹅粪的莫愁湖沉积物的反硝化速率和潜势具有更高的绝对增量。企鹅粪中较高的硝酸盐、铵盐、磷酸盐以及有机碳含量是莫愁湖具有很高的反硝化速率的主导因素。在全球变暖的背景下,南极地区企鹅外源氮输入将加速湖泊沉积物氮循环。

Global warming in the polar regions strongly influences the processes and rates of material cycling in the polar region ecosystems.In this study,the effects of global warming on the key process of nitrogen cycle processes in Antarctic lake sediments are reported.During the 29th Chinese National Antarctic Research Expedition,five lakes located near the Zhongshan Station were selected,one with sediments containing penguin manure(Mochou Lake)and four with natural lake sediments(Tuanjie Lake,Daming Lake,Mier Lake and Yuzhen Lake).The“sample-bottle mud constant-temperature mud culture method”was used to simulate temperature increases.Culture experiments were set at low temperature(1℃),medium temperature(5℃)and high temperature(11℃).Results showed that the denitrification rate and denitrification potential of Mochou Lake sediments at low temperature were significantly higher(277.37 times and 246.73 times,respectively)than those of natural lake sediments.Limitted warming enhanced the sediment denitrification rate and potential,but excessive temperature increase inhibited the denitrification in some samples.At high temperature,the average denitrification rate of natural lake sediments under high temperature was 1.57 times and 3.56 times higher than at medium and low temperature,respectively,while the denitrification potential represented 1.91 times and 6.31 times the medium and low-temperature rates,respectively.For Mochou Lake sediments at high temperature,the denitrification rate was 1.78 and 2.07 time higher,and the denitrification potential was 0.72 and 1.01 times higher,respectively,than at medium and low temperature.Although the warming-induced relative increase in denitrification rate and denitrification potential was higher for natural lake sediments than for the Mochou Lake sediments,the absolute increase was higher at Mochou Lake.Higher contents of nitrate,ammonium salt,phosphate and organic carbon in penguin manure explain this high denitrification rate.Under global warming conditions,exogenous nitrogen input from penguins accelerates the nitrogen cycle in Antarctic lake sediments.