Departamento de Microbiología del Suelo y Sistemas Simbióticos, Estación Experimental del Zaidín, Consejo Superior de Investigaciones Científicas, Granada, Spain; Instituto Universitario de Investigación del Agua, Universidad de Granada, Granada, Spain.
Departamento de Microbiología del Suelo y Sistemas Simbióticos, Estación Experimental del Zaidín, Consejo Superior de Investigaciones Científicas, Granada, Spain.
Sci Total Environ. 2023 Feb 1;858(Pt 2):159901. doi: 10.1016/j.scitotenv.2022.159901. Epub 2022 Nov 2.
High-mountain lakes and rivers are usually oligotrophic and strongly influenced by atmospheric transport processes. Thus, wet deposition of reactive N species (Nr), mainly in the form of nitrate (NO), is a major source of N input in these high-mountain ecosystems. Bacterial denitrifiers are thought to be largely responsible for reduction of NO to nitrous oxide (NO) and molecular dinitrogen (N) as main biological pathway of N removal in these ecosystems. Nitrifiers, through the oxidation of ammonium to NO, can also be a source of NO and NO. However, there is uncertainty regarding the abiotic and biotic factors controlling Nr elimination from aquatic ecosystems at different altitudes and seasons. We examined the efficiency of Nr removal as NO and N (total removal) or N only (clean removal) in a model lake and its downwater river ecosystem (Sierra Nevada, Spain) representative of Mediterranean high-mountain freshwater ecosystems along an altitudinal gradient during the warm period of the year. Denitrification activity and the abundance of nitrifiers and denitrifiers in sediments were measured at thaw, mid ice-free and late ice-free periods. We found the efficiency of total and clean removal of Nr increased from the downwater river to the high-mountain lake. Regardless of the location, the efficiency of total removal of Nr decreased over the ice-free period whereas that of clean removal of Nr peaked at mid ice-free period. The efficiency of total removal of Nr was mainly controlled by the abundance of archaeal nitrifiers and bacterial denitrifiers. Abiotic (ammonium and NO concentration) and biotic (mainly nosZI-type denitrifiers) factors drove changes in the efficiency of clean removal of Nr. Our results suggest that abiotic and biotic factors can control the efficiencies of Nr removal in Mediterranean high-mountain lakes and their downwater rivers, and that these efficiencies increase with altitude and vary over the ice-free period.
高山湖泊和河流通常为贫营养型，并且强烈受到大气传输过程的影响。因此，活性氮（Nr）物质（主要以硝酸盐（NO）的形式）的湿沉降是这些高山生态系统中氮输入的主要来源。细菌反硝化菌被认为是这些生态系统中氮去除的主要生物学途径，将 NO 还原为一氧化二氮（NO）和氮气（N）。硝化菌通过将铵氧化为 NO，也可以成为 NO 和 NO 的来源。然而，对于不同海拔和季节的水生生态系统中 Nr 消除的非生物和生物因素控制因素仍存在不确定性。我们在一个模型湖中及其下游河流生态系统（西班牙内华达山脉）中研究了 Nr 去除为 NO 和 N（总去除）或仅 N（清洁去除）的效率，该模型代表了沿海拔梯度的地中海高山淡水生态系统。在一年的温暖时期，在解冻、无冰中期和无冰后期测量了沉积物中的反硝化活性以及硝化菌和反硝化菌的丰度。我们发现，从下游河流到高山湖泊，Nr 的总去除和清洁去除效率增加。无论位置如何，Nr 的总去除效率在无冰期间下降，而 Nr 的清洁去除效率在无冰中期达到峰值。Nr 的总去除效率主要受古菌硝化菌和细菌反硝化菌的丰度控制。非生物（氨和 NO 浓度）和生物（主要是 nosZI 型反硝化菌）因素驱动了 Nr 清洁去除效率的变化。我们的结果表明，非生物和生物因素可以控制地中海高山湖泊及其下游河流中 Nr 去除的效率，并且这些效率随着海拔的升高而增加，并在无冰期间发生变化。
