Effects of artificial light at night on the early benthic stages of the prominent sea urchin Loxechinus albus

Artificial light at night (ALAN) is a growing anthropogenic stressor, yet its effects on marine invertebrates, particularly during early benthic stages, remain understudied. The edible sea urchin Lox- echinus albus, an important herbivore along the Pacific coast of South America, shows behavioural traits such as covering that suggest sensitivity to environmental factors, including light. Therefore, this study examined the potential influence of ALAN on small juvenile sea urchins, hypothesizing effects on their behaviour and physiology. In the field, an exploratory survey revealed aboral surface covering behaviour that suggest a natural avoidance of light by the sea ur- chins. In the laboratory, covering behaviour was quantified, measuring also their preference for contrasting dark and lit (ALAN) conditions in a Y-maze. Additional trials measured food consump- tion, horizontal speed, self-righting, metabolic and growth rates in ndividual exposed to dark and ALAN. Laboratory observations identified covering behaviours that were heightened under ALAN exposure. These behaviours were consistent with a strong preference for dark areas in Y-maze tests, where food consumption was also consistently higher than under ALAN. Speed and self-righting times were higher under ALAN and dark, respectively. Meanwhile, meta- bolic rates and growth rates were lower under ALAN, indicating possible long-term physiological effects. Altogether, ALAN exposure disrupted key behavioural and physiological traits leading juveniles to prioritize survival behaviours like avoiding light and speeding up locomotion and self-righting over foraging and growth. These find- ings suggest that ALAN could alter interactions and energy allocation in L. albus, with potential implications for kelp forest ecosystems and the fisheries of this species. The corrected version of the article, now including the abstract, is available online. The authors would like to apologise for any inconvenience caused.