A synthesis of the risks of marine light pollution across organismal and ecological scales

Light pollution is a pervasive global stressor to natural systems. However, due to the proximity of human activities along the coasts and open ocean, light is a pervasive yet commonly overlooked pollutant in many marine habitats.There is a well-developed body of literature on the visual physiology, behaviour and ecology of many marine taxa, and a re-evaluation of these data can help inform risks of light pollution to impact marine organisms and ecosystems. This paper identifies key knowledge gaps in the study of marine light pollution ecology and recommends research and management foci for future study.Most work on this pollutant has focused on terrestrial ecosystems and taxa, where experts have learned how anthropogenic light influences behaviour, reproduction cycles and population dynamics. However, light pollution bleeds far beyond the shores, affecting many sensitive ecosystems with light available at unnatural times with varied makeup, such as varying intensities or spectra.This review discusses the current understanding of light dynamics underwater, photoreceptive systems of marine taxa and the documented ecological impacts. This lends a critical basis of understanding for the many gaps in marine light pollution biology. For example, little is known about effects of light on broad groups of marine taxa such as cetaceans, ecosystem-level effects, or interactive impacts of light and other anthropogenic stressors. Light is a key structuring factor of the marine environment and can therefore elicit immense downstream effects on marine organisms individually, at the population- or ecosystem-level.Light pollution is an urgent concern for marine ecosystems because marine organisms have tight relationships with their natural light environment. As the world moves deeper into the Anthropocene, assessing and mitigating the risks of this pollutant to key environmental and economic marine systems is critical to maintaining a healthy ocean.