Abstract. In the oligotrophic waters of the Mediterranean Sea, during the stratification period, the microbial loop relies on pulsed inputs of nutrients through atmospheric deposition of aerosols from both natural (Saharan dust) and anthropogenic origins. While the influence of dust deposition on microbial processes and community composition is still not fully constrained, the extent to which future environmental conditions will affect dust inputs and the microbial response is not known. The impact of atmospheric wet dust deposition was studied both under present and future (warming and acidification) environmental conditions through experiments in 300 L climate reactors. Three dust addition experiments were performed with surface seawater collected from the Tyrrhenian Sea, Ionian Sea and Algerian basin in the Western Mediterranean Sea during the PEACETIME cruise in May–June 2017. Top-down controls on bacteria, viral processes and community, as well as microbial community structure (16S and 18S rDNA amplicon sequencing) were followed over the 3–4 days experiments. Different microbial and viral responses to dust were observed rapidly after addition and were most of the time higher when combined to future environmental conditions. The input of nutrients and trace metals changed the microbial ecosystem from bottom-up limited to a top-down controlled bacterial community, likely from grazing and induced lysogeny. The composition of mixotrophic microeukaryotes and phototrophic prokaryotes was also altered. Overall, these results suggest that the effect of dust deposition on the microbial loop is dependent on the initial microbial assemblage and metabolic state of the tested water, and that predicted warming, and acidification will intensify these responses, affecting food web processes and biogeochemical cycles.

中文翻译：

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在当前和未来 pH 和温度条件下，灰尘添加对微生物食物网的影响

摘要。在地中海的贫营养水域，在分层期间，微生物循环依赖于通过来自自然（撒哈拉尘埃）和人为来源的气溶胶的大气沉积而脉冲式输入营养物质。虽然灰尘沉积对微生物过程和群落组成的影响仍未完全受到限制，但未来环境条件对灰尘输入和微生物反应的影响程度尚不清楚。通过在 300 升气候反应器中进行的实验，研究了在当前和未来（变暖和酸化）环境条件下大气湿尘沉积的影响。用从第勒尼安海收集的表层海水进行了三个加尘实验，2017 年 5 月至 6 月 PEACETIME 巡航期间西地中海的爱奥尼亚海和阿尔及利亚盆地。自上而下控制细菌、病毒过程和群落，以及微生物群落结构（16S 和 18S rDNA 扩增子测序）。 3-4 天的实验。添加后迅速观察到不同的微生物和病毒对灰尘的反应，并且在结合未来环境条件时，大多数情况下会更高。营养物质和微量金属的输入改变了微生物生态系统，从自下而上仅限于自上而下的受控细菌群落，可能来自放牧和诱导溶原。混合营养型微真核生物和光养型原核生物的组成也发生了变化。全面的，