Behavioural Responses of the Black Sea Urchin Arbacia lixula to Artificial Light and Underwater Noise

This study investigated behavioural responses of the black sea urchin Arbacia lixula to underwater anthropogenic noise, artificial light at night (ALAN), lunar phase, and seawater temperature under semi-controlled conditions, over eight weeks. The degree of mobility, the rate of dislocation, as well as spatial distribution of the sea urchins within the tank of locomotion after approximately three weeks of exposure, followed by a return towards baseline activity levels by the final week, suggesting a temporary behavioural suppression followed by acclimation. Continuous sound treatments produced greater movement under several tested frequencies, whereas pulse-burst exposure produced fewer apparent effects, with the clearest response occurring at 10,000 Hz after prolonged exposure. Spatial patterns should be interpreted cautiously since the light and sound gradients across the quadrants were not instrumentally measured and the experimental tank restricted the available movement space. Within the observed range, seawater temperature and lunar phase were not clearly associated with movement responses. No spawning was observed during the trials, indicating that short-term exposure to these stimuli did not trigger spawning under the present experimental conditions. Overall, Arbacia lixula showed behavioural plasticity in response to an array of anthropogenic stimuli, but the effects appeared transient and should be interpreted in light of the exploratory statistical design and calibration limitations.