Institute of Water Research, University of Granada, c/ Ramón y Cajal, 4, 18071, Granada Spain; Department of Ecology, University of Granada, Campus Fuentenueva s/n, 18071, Granada Spain.
Institute of Water Research, University of Granada, c/ Ramón y Cajal, 4, 18071, Granada Spain; Department of Ecology, University of Granada, Campus Fuentenueva s/n, 18071, Granada Spain.
Sci Total Environ. 2024 Nov 15;951:175777. doi: 10.1016/j.scitotenv.2024.175777. Epub 2024 Aug 25.
Mediterranean lakes are facing heightened exposure to multiple stressors, such as intensified Saharan dust deposition, temperature increases and fluctuations linked to heatwaves. However, the combined impact of dust and water temperature on the microbial community in freshwater ecosystems remains underexplored. To assess the interactive effect of dust deposition and temperature on aquatic microbes (heterotrophic bacteria and phytoplankton), a combination of field mesocosm experiments covering a dust gradient (five levels, 0-320 mg L), and paired laboratory microcosms with increased temperature at two levels (constant and fluctuating high temperature) were conducted in a high mountain lake in the Spanish Sierra Nevada, at three points in time throughout the ice-free period. Heterotrophic bacterial production (HBP) increased with dust load regardless of the temperature regime. However, temperature regime affected the magnitude and nature of the interactive Dust×T effect on HBP. Specifically, constant and fluctuating high temperature showed opposing interactive effects in the short term that became additive over time. The relationships between HBP and predictor variables (soluble reactive phosphorus (SRP), excreted organic carbon (EOC), and heterotrophic bacterial abundance (HBA)), coupled with an evaluation of the mechanistic variable photosynthetic carbon use efficiency by bacteria (%CUEb), revealed that bacteria depended on primary production in nearly all treatments when dust was added. The %CUEb increased with dust load in the control temperature treatment, but it was highest at intermediate dust loads under both constant and fluctuating high temperatures. Overall, our results suggest that while dust addition alone strengthens algae-bacteria coupling, high temperatures lead to decoupling in the long term at intermediate dust loads, potentially impacting ecosystem function.
地中海湖泊面临着多种压力源的加剧暴露，例如撒哈拉沙尘沉积的加剧、与热浪有关的温度升高和波动。然而，尘埃和水温度对淡水生态系统中微生物群落的综合影响仍未得到充分探索。为了评估尘埃沉积和温度对水生微生物（异养细菌和浮游植物）的相互作用影响，在西班牙内华达山脉的一个高山湖泊中进行了组合现场中观实验，该实验涵盖了尘埃梯度（五个水平，0-320mg/L），以及在两个温度水平（恒定和波动高温）下进行的配对实验室微宇宙实验，实验时间横跨无冰期的三个时间点。无论温度制度如何，异养细菌生产力（HBP）都随尘埃负荷的增加而增加。然而，温度制度影响了 Dust×T 对 HBP 的相互作用的幅度和性质。具体来说，恒定和波动高温在短期内表现出相反的相互作用效应，随着时间的推移，这些效应变得相加。HBP 与预测变量（可溶解反应磷（SRP）、排泄有机碳（EOC）和异养细菌丰度（HBA））之间的关系，以及对细菌光合作用碳利用效率（%CUEb）的机制变量的评估，表明在添加尘埃的情况下，细菌几乎在所有处理中都依赖于初级生产。在对照温度处理中，%CUEb 随尘埃负荷的增加而增加，但在恒定和波动高温下，尘埃负荷适中时，%CUEb 最高。总的来说，我们的研究结果表明，虽然尘埃的单独添加会增强藻类-细菌的耦合，但在尘埃负荷适中时，高温会导致长期的脱耦，可能会影响生态系统功能。
