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Artificial light at night (ALAN) is a growing global problem altering the behavior of organisms and thereby community composition and ecosystem processes. Research has mostly focused on terrestrial ecosystems, but a growing number of studies show that aquatic ecosystems are increasingly affected. Here, we provide a conceptual framework that describes how ALAN can influence aquatic ecosystems through effects on the behavior of ecologically important invertebrates. These organisms provide a range of critical ecological functions, from serving as food for other organisms to nutrient cycling and the translocation of energy and matter within and between ecosystems. In addition, we systematically searched the literature to assess the current state of the field and identify knowledge gaps. The literature search reveals that an increasing number of studies find light pollution to alter the behavior of aquatic invertebrates, such as their movements, habitat choice, and foraging behavior, but that the fitness consequences of these behavioral changes are largely unknown, as are their impacts on populations, communities, and ecosystems. Yet, assessing the consequences of behavioral changes for higher ecological levels is of vital importance given the central role of these invertebrates in ecosystems. Thus, more research needs to be directed to the ecological consequences of behavioral responses of aquatic invertebrates to light pollution. Overall, more effort should be made to assess the ecological consequences of behavioral responses to ALAN, and, importantly, how negative effects of light pollution could be mitigated. Significance statement: Light pollution is of growing ecological concern and influencing ecosystems through effects on the behavior of organisms. Aquatic ecosystems are increasingly exposed and an ecologically important group of organisms in these systems are invertebrates. Here, we discuss how artificial light at night alters the behavior of aquatic invertebrates and how this in turn influences ecosystem structure and function. Such an understanding of the mechanisms and pathways that underlie the effect of light pollution on aquatic ecosystems is needed if we are to develop efficient strategies to reduce negative effects of human-made lighting systems on ecosystems. [ABSTRACT FROM AUTHOR]

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Background: Artificial light at night is recognized as an increasing threat to biodiversity. However, information on the way highly mobile taxa such as bats spatially respond to light is limited. Following the hypothesis of a behavioural adaptation to the perceived risks of predation, we hypothesised that bats should avoid lit areas by shifting their flight route to less exposed conditions. Methods: Using 3D acoustic localization at four experimentally illuminated sites, we studied how the distance to streetlights emitting white and red light affected the Probability of bats Flying Inside the Forest (PFIF) versus along the forest edge. Results: We show that open-, edge-, and narrow-space foraging bats strongly change flight patterns by increasing PFIF when getting closer to white and red streetlights placed in the forest edge. These behavioural changes occurred mainly on the streetlight side where light was directed. Conclusions: The results show that bats cope with light exposure by actively seeking refuge in cluttered environment, potentially due to involved predation risks. This is a clear indication that bats make use of landscape structures when reacting to light, and shows the potential of vegetation and streetlight orientation in mitigating effects of light. The study nevertheless calls for preserving darkness as the most efficient way. [ABSTRACT FROM AUTHOR]