New Delhi: A recent study has revealed that exposure to artificial light at night (ALAN) can cause severe anxiety in fish, altering their behaviour and even passing these stress-related traits to their offspring. The research, published in Science of The Total Environment, highlights how human-induced light pollution affects aquatic ecosystems in ways previously underestimated.
The study focused on zebrafish, a commonly used species in behavioural and genetic research. Scientists exposed female zebrafish to different types of artificial light, including blue light (470 nm), over a period of nine nights. The intensity of light used in the experiment was 20 Lux, comparable to the brightness of distant streetlights that many animals experience in outdoor environments.
The results were alarming fish exposed to artificial light at night showed increased signs of anxiety. They exhibited restricted movement, preferred staying close to the walls of the aquarium, and clustered together more frequently than usual. These are well-documented signs of stress and fear in aquatic animals. Interestingly, blue light had the most significant impact, triggering anxiety-like behaviour within just five days of exposure, whereas other light wavelengths took longer to produce similar effects.
Anxiety Passed on to Offspring, Even Without Direct Exposure
One of the most concerning findings was the discovery that anxiety-related traits were inherited by the next generation. The offspring of zebrafish that had been exposed to artificial light at night for 15 days displayed anxious behaviour—even though they had never been directly exposed to night-time lighting themselves. This suggests that the stress induced by artificial light can have long-lasting genetic or developmental effects, influencing future generations.
Scientists believe that sleep deprivation is the key factor driving these behavioural changes. Like humans, fish rely on regular sleep cycles to maintain their health and cognitive function. Disruptions caused by artificial light can lead to chronic stress, weakening their ability to adapt to their natural environment.
Growing Concern Over Light Pollution’s Impact on Ecosystems
This study adds to a growing body of evidence highlighting the negative effects of artificial light on wildlife. Many species, including birds, insects, and mammals, have been shown to experience behavioural disruptions due to excessive night-time lighting. For fish, whose survival depends on natural light cues for activities such as breeding, foraging, and migration, the consequences could be particularly severe.
Environmentalists and researchers are now calling for stricter regulations on artificial lighting near water bodies. Some proposed solutions include using motion-activated lighting, adjusting light wavelengths to reduce blue light emissions, and implementing “dark sky” policies to minimize unnecessary light pollution.
The Need for Further Research and Conservation Efforts
While this study provides crucial insights, researchers emphasize the need for further investigations to fully understand the long-term impact of artificial light on aquatic life. Future studies may explore whether different species respond differently to light pollution and whether behavioural changes can be reversed over time.
With rapid urbanization and increasing artificial light sources, scientists warn that the effects on ecosystems could be far-reaching. The findings serve as a wake-up call to policymakers and urban planners to consider wildlife-friendly lighting solutions and take action to mitigate the growing problem of light pollution.