Key Laboratory of Lake and Watershed Science for Water Security, Nanjing Institute of Geography and Limnology, Chinese Academy of Sciences, Nanjing 210008, China; State Key Laboratory of Lake Science and Environment, Nanjing Institute of Geography and Limnology, Chinese Academy of Sciences, Nanjing 210008, China; University of Chinese Academy of Sciences, Beijing 100039, China.
Key Laboratory of Lake and Watershed Science for Water Security, Nanjing Institute of Geography and Limnology, Chinese Academy of Sciences, Nanjing 210008, China; State Key Laboratory of Lake Science and Environment, Nanjing Institute of Geography and Limnology, Chinese Academy of Sciences, Nanjing 210008, China.
Sci Total Environ. 2024 Dec 1;954:176323. doi: 10.1016/j.scitotenv.2024.176323. Epub 2024 Sep 17.
Cyanobacterial blooms induced by excessive loadings of nitrogen (N) and other nutrients are a severe ecological problem in aquatic ecosystems. Previous studies of N removal have primarily focused on sediment-water interface, yet the role of cyanobacterial colonies has recently been attracting more research attention. In this study, N cycling processes were quantified for cyanobacterial colonies (primarily Microcystis colonies) and their contribution to N removal was estimated for a large, shallow eutrophic lake in China, Lake Taihu. Various N cycling processes were determined via stable N isotope, together with 16S rRNA gene sequencing and quantitative microbial element cycling (QMEC) chip. Denitrification was found to be the most prominent process, estimated to be 36.63, 9.85, 3.35, and 3.15 times higher than dissimilatory nitrate reduction to ammonium (DNRA), nitrification, ammonium (NH) uptake and nitrate (NO) uptake rates, respectively. Denitrifiers accounted for a large part of the bacterial taxa (35.50 ± 24.65%), and the nirS gene was the most abundant among N cycling-related genes, with (2.54 ± 0.51) × 10 copies gMicrocystis colonies. A field investigation revealed a positive correlation between the potential denitrification rate and the Chl-a concentration (mostly derived from Microcystis colonies). Based on a multiple stepwise regression model and historical data from 2007 to 2015 for Lake Taihu, the total amount of N removed via denitrification by Microcystis colonies was estimated at 171.72 ± 49.74 t yr; this suggests that Microcystis colonies have played an important role in N removal in Lake Taihu since the drinking water crisis in 2007. Overall, this study revealed the importance of denitrification within Microcystis colonies for N removal in eutrophic lakes, like Lake Taihu.
富营养化水体中氮（N）和其他营养物质的过量负荷会引发蓝藻水华，这是水生生态系统中的一个严重生态问题。先前的 N 去除研究主要集中在水-沉积物界面，但蓝藻聚集体的作用最近引起了更多的研究关注。在本研究中，对中国太湖这一大而浅的富营养化湖泊中的蓝藻聚集体（主要是微囊藻聚集体）的 N 循环过程进行了量化，并估算了它们对 N 去除的贡献。通过稳定的 N 同位素、16S rRNA 基因测序和定量微生物元素循环（QMEC）芯片确定了各种 N 循环过程。反硝化被认为是最主要的过程，其估计值分别比异化硝酸盐还原为铵（DNRA）、硝化、氨（NH）吸收和硝酸盐（NO）吸收速率高 36.63、9.85、3.35 和 3.15 倍。反硝化菌占细菌分类群的很大一部分（35.50±24.65%），nirS 基因是 N 循环相关基因中最丰富的基因，其拷贝数为（2.54±0.51）×10 个 gMicrocystis colonies。野外调查显示，潜在反硝化速率与 Chl-a 浓度（主要来自微囊藻聚集体）之间存在正相关关系。基于太湖 2007 年至 2015 年的多元逐步回归模型和历史数据，估算出由微囊藻聚集体反硝化去除的 N 总量为 171.72±49.74 t yr；这表明，自 2007 年饮用水危机以来，微囊藻聚集体在太湖的 N 去除中发挥了重要作用。总的来说，本研究揭示了富营养化湖泊中蓝藻聚集体内反硝化作用对 N 去除的重要性，如太湖。
