| 反硝化脱氮对太湖蓝藻水华态势的影响 |
| 摘要点击 1211 全文点击 373 投稿时间：2022-10-04 修订日期：2022-11-18 |
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| 中文关键词 氮 反硝化 蓝藻水华 太湖 气候变暖 |
| 英文关键词 nitrogen denitrification cyanobacterial blooms Lake Taihu climate warming |
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| 中文摘要 |
| 反硝化作用是水生生态系统的主要脱氮过程，与蓝藻生长之间存在对氮素的竞争作用，然而气候变化背景下反硝化脱氮对蓝藻水华发生动态的影响仍不清楚.基于2017~2021年北太湖为期5 a的水质监测历史数据，结合不同温度下蓝藻生长和沉积物泥浆培养实验，探究了湖体反硝化脱氮与蓝藻水华之间的相互影响.监测数据表明，太湖水体藻类生物量（以Chla表示）高值主要出现在夏秋季节，而总氮浓度季节变化规律与藻类生物量完全相反，冬春季较高，夏秋季显著降低，溶解态无机氮主要以硝态氮为主，并且硝态氮浓度在夏秋季节几乎接近于零.总磷浓度与Chla浓度变化一致.蓝藻培养实验结果表明，20℃以下蓝藻不能大量生长繁殖.泥浆培养实验结果发现，太湖反硝化作用的最高温度阈值为25℃，在10~25℃之间反硝化潜力与温度呈现显著的线性关系（R2=0.99）.反硝化作用发生的最高硝态氮浓度阈值为4 mg ·L-1，远高于太湖水体的硝态氮浓度，反硝化潜力最高达到（62.98±21.36）μmol ·（kg ·h）-1.太湖水体反硝化速率受到硝态氮浓度的限制，而气候变暖导致湖泊温度提前升高，会使蓝藻提前生长，蓝藻生长对硝态氮的同化吸收会和反硝化作用产生竞争，使得大量氮还未被反硝化作用脱除就被藻类吸收利用，从而加剧蓝藻水华暴发的态势.研究结果对于解释近年来气候变化背景下太湖蓝藻水华反弹的机制具有重要科学意义. |
| 英文摘要 |
| Denitrification is a major process in aquatic ecosystems, and it competes with cyanobacterial growth for nitrogen. However, the effect of denitrification on cyanobacterial blooms under the background of climate change remains unclear. This study explored the interaction between lake denitrification and formation of cyanobacterial blooms, using the historical water quality monitoring data of North Lake Taihu over five years from 2017 to 2021 and via incubation experiments of cyanobacteria and sediment denitrification. The monitoring data showed that algal biomass (Chla as a proxy) primarily peaked during summer and autumn. The seasonal variations in total N concentration showed a completely opposite trend than that of algal biomass, which peaked in winter and spring. Nitrate was the major component of dissolved inorganic nitrogen, and the nitrate concentration was approximately zero in summer and autumn. The total phosphorus concentration varied in the same way as the Chla concentration. The experimental results showed that Cyanobacteria did not grow when the temperature was below 20℃. In comparison, denitrification showed a significant linear relationship with temperatures between 10-25℃ (R2=0.99) and reached the maximum value of (62.98±21.36) μmol·(kg·h)-1 in Lake Taihu at 25℃. Additionally, the nitrate concentration threshold at the maximum denitrification rate was 4 mg·L-1. Cyanobacteria assimilate nitrate for growth, thereby reducing the concentration of nitrate required for denitrification. This study indicated that the advance in lake temperature warming due to climate change may result in earlier growth of cyanobacteria, thereby leading to large amounts of N being assimilated by algae before denitrification, further affecting the dynamics of cyanobacterial blooms. The present results are scientifically important for explaining the mechanism of cyanobacterial bloom rebound in Lake Taihu under the background of recent climate changes. |
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