Artificial light at night (ALAN) has been recently recognized as a threat for aquatic systems, but a comprehensive knowledge of its effects is still lacking. A fundamental question is whether and how ALAN might affect temporal variability of communities, thus undermining the stability of mature assemblages or influencing the colonization process. Here we investigated the role of ALAN on temporal variability of total biomass and maximum photosynthetic efficiency of marine autotrophic biofilms colonizing Mediterranean high-shore rock surfaces while controlling for density of their main grazers. Results showed stability in total biomass, but an increase in maximum photosynthetic efficiency from unlit to lit conditions, which suggested a temporal change in composition and/or abundance of different taxa within mature assemblages. The effect was weaker during the colonization process; in this case, density of grazers acted in the opposite direction of ALAN. We suggest that the addition of light at times when it would not be naturally present may affect the temporal variability of a variety of functioning in aquatic systems, depending on species-specific sensitivities to ALAN within microbial assemblages and/or indirect effects mediated by their consumers. We highlight to further investigate the role of this emergent topic in aquatic ecology.

中文翻译：

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光污染增强了成熟和发育中生物膜光合活性的时间变异性

夜间人造光 (ALAN) 最近被认为是对水生系统的威胁，但仍缺乏对其影响的全面了解。一个基本问题是 ALAN 是否以及如何影响群落的时间变异性，从而破坏成熟组合的稳定性或影响殖民过程。在这里，我们研究了 ALAN 对殖民地中海高岸岩石表面的海洋自养生物膜的总生物量的时间变异性和最大光合效率的作用，同时控制其主要食草动物的密度。结果显示总生物量稳定，但从无光照到光照条件下最大光合效率增加，这表明成熟组合内不同分类群的组成和/或丰度随时间发生变化。定植过程中效果较弱；在这种情况下，食草动物的密度与 ALAN 的方向相反。我们建议，在不自然存在的情况下添加光可能会影响水生系统中各种功能的时间变异性，这取决于微生物组合内对 ALAN 的物种特异性敏感性和/或由其消费者介导的间接影响. 我们强调进一步研究这个新兴话题在水生生态学中的作用。取决于微生物组合内对 ALAN 的物种特异性敏感性和/或由其消费者介导的间接影响。我们强调进一步研究这个新兴话题在水生生态学中的作用。取决于微生物组合内对 ALAN 的物种特异性敏感性和/或由其消费者介导的间接影响。我们强调进一步研究这个新兴话题在水生生态学中的作用。