Wang Huan, Li Qi, Xu Jun
State Key Laboratory of Marine Resource Utilization in South China Sea, Hainan University, Haikou 570228, China.
Institute of Hydrobiology, Chinese Academy of Sciences, Wuhan 430072, China.
Microorganisms. 2023 Mar 31;11(4):910. doi: 10.3390/microorganisms11040910.
The climate is changing. The average temperature in Wuhan, China, is forecast to increase by at least 4.5 °C over the next century. Shallow lakes are important components of the biosphere, but they are sensitive to climate change and nutrient pollution. We hypothesized that nutrient concentration is the key determinant of nutrient fluxes at the water-sediment interface, and that increased temperature increases nutrient movement to the water column because warming stimulates shifts in microbial composition and function. Here, twenty-four mesocosms, mimicking shallow lake ecosystems, were used to study the effects of warming by 4.5 °C above ambient temperature at two levels of nutrients relevant to current degrees of lake eutrophication levels. This study lasted for 7 months (April-October) under conditions of near-natural light. Intact sediments from two different trophic lakes (hypertrophic and mesotrophic) were used, separately. Environmental factors and bacterial community compositions of overlying water and sediment were measured at monthly intervals (including nutrient fluxes, chlorophyll [chl ], water conductivity, pH, sediment characteristics, and sediment-water et al.). In low nutrient treatment, warming significantly increased chl in the overlying waters and bottom water conductivity, it also drives a shift in microbial functional composition towards more conducive sediment carbon and nitrogen emissions. In addition, summer warming significantly accelerates the release of inorganic nutrients from the sediment, to which microorganisms make an important contribution. In high nutrient treatment, by contrast, the chl was significantly decreased by warming, and the nutrient fluxes of sediment were significantly enhanced, warming had considerably smaller effects on benthic nutrient fluxes. Our results suggest that the process of eutrophication could be significantly accelerated in current projections of global warming, especially in shallow unstratified clear-water lakes dominated by macrophytes.
气候正在发生变化。预计在未来一个世纪，中国武汉的平均气温将至少升高4.5摄氏度。浅水湖泊是生物圈的重要组成部分，但它们对气候变化和营养物污染很敏感。我们假设营养物浓度是水-沉积物界面营养物流通量的关键决定因素，并且温度升高会增加营养物向水柱的移动，因为变暖会刺激微生物组成和功能的变化。在此，我们使用了24个模拟浅水湖泊生态系统的中型生态箱，来研究在与当前湖泊富营养化程度相关的两个营养水平下，温度比环境温度升高4.5摄氏度所产生的影响。本研究在近自然光照条件下持续了7个月（4月至10月）。分别使用了来自两个不同营养状态湖泊（富营养型和中营养型）的完整沉积物。每月对覆水和沉积物的环境因子及细菌群落组成进行测量（包括营养物流通量、叶绿素 [chl]、水电导率、pH值、沉积物特征以及沉积物-水等）。在低营养处理中，升温显著增加了覆水中的chl以及底层水的电导率，还促使微生物功能组成向更有利于沉积物碳和氮排放的方向转变。此外，夏季升温显著加速了沉积物中无机营养物的释放，微生物对此做出了重要贡献。相比之下，在高营养处理中，升温使chl显著降低，沉积物的营养物流通量显著增强，升温对底栖营养物流通量的影响要小得多。我们的研究结果表明，在当前全球变暖的预测中，富营养化过程可能会显著加速，尤其是在以大型植物为主的浅水无分层清水湖泊中。
