Abstract
Light pollution is a rapidly growing threat to biodiversity, with many unknown or poorly understood effects on species and ecosystems spanning terrestrial and aquatic environments. Relative to other taxa, the effects of artificial light at night on aquatic invertebrates are poorly understood, despite the abundance and integral significance of invertebrates to marine and freshwater ecosystems. We affixed heart rate and acceleration biologgers to adult Caribbean spiny lobster (Panulirus argus), an ecologically, culturally and economically significant species in the western Atlantic ocean, to test the effect of artificial light at night on this species' physiology and behaviour relative to appropriate controls. The experiment was conducted in a simulated reef mesocosm in The Bahamas with incandescent lighting used to illuminate it at 1 lux, approximating light levels offshore of urban areas. In the conditions tested here, artificial light at night was found to have no effect on heart rate or locomotor activity in P. argus. We observed a dissociation between activity and heart rate at both short-term and long-term temporal scales. Lobsters were more active at night and nocturnal activity was higher in trials closer to new moon; however, heart rate did not vary with diel or lunar cycle. There was less than 8% difference between daytime and night time average heart rate despite the average percentage of time spent active almost tripling in nights versus days, to 19.5% from 7.2%, respectively. Our findings suggest P. argus may have some resilience to low levels of light pollution, which warrants further research on aspects of this species' life history, performance and fitness in the face of this potential anthropogenic disturbance.