Artificial Light at Night Disrupts Fish Behavior and Health, Study Finds
New research reveals that even low levels of artificial light along coastlines can harm marine life, disrupting sleep, increasing aggression, and raising markers of cellular stress in a common reef fish.
Key Findings
- Disrupted Sleep & Behavior: Blue-green damselfish (Chromis viridis) exposed to artificial light at night (ALAN) experienced reduced and more fragmented sleep, along with increased aggression and abnormal feeding times.
- Cellular Stress Markers: The study observed elevated levels of markers associated with DNA damage in the brain region responsible for sleep-dependent functions. The research does not prove direct DNA damage, but suggests that sleep disruption may interfere with the body's natural repair processes.
- Rapid, Persistent Effects: Behavioral changes appeared after just a few nights of exposure and continued throughout a five-month field experiment conducted on a coral reef.
"Artificial light at night is expanding across coastal environments, and even low illumination levels can disrupt natural sleep patterns and are associated with changes in markers of neuronal health." — Prof. Oren Levy, Bar-Ilan University
The Scope of the Problem
The study, published in Current Biology by researchers at Bar-Ilan University, highlights a growing environmental threat.
- Widespread Impact: Approximately 22% of coastal regions and 35% of marine protected areas are now affected by artificial light at night.
- Extreme Local Conditions: In the Gulf of Eilat, nighttime light levels near developed areas can reach up to 60 times that of natural starlight.
- Broader Ecosystem Threat: Previous work from the same lab has already shown that ALAN harms coral physiology and disrupts the crucial symbiotic relationship between corals and algae.
"If artificial light affects both corals and fish, consequences could ripple throughout the reef ecosystem." — Prof. Oren Levy
Why Sleep Matters for Marine Life
The research underscores that sleep is not just a luxury, but a critical biological necessity, even for fish.
Prof. Lior Appelbaum emphasized that sleep is essential for biological repair processes. Disrupting sleep with artificial light may have clear, measurable consequences for wild marine animals, potentially compromising their long-term health and survival.
Recommendations for Action
The researchers are calling for immediate improvements in coastal lighting practices to mitigate these impacts. Key recommendations include:
- Reducing unnecessary illumination along shorelines.
- Directing light away from the water and sensitive habitats.
- Adopting smart lighting systems that dim or turn off when not needed.
- Using wavelengths that are less disruptive to wildlife.
Looking Ahead
Future research will aim to determine whether the observed effects are reversible and to assess how widespread these disruptions are across different marine species.