New research using innovative underwater infrared cameras reveals how human-generated light is transforming nocturnal coral reef communities, keeping daytime fish awake and creating unexpected hunting opportunities for predators.
Published in Global Change Biology | Estimated reading time: 4 minutes
As the sun sets on coral reefs around the world, a remarkable transformation typically takes place. Daytime fish retreat to their coral sanctuaries while nocturnal creatures emerge from their hiding places to hunt. However, this ancient rhythm is being disrupted by artificial light, with potentially far-reaching consequences for reef ecosystems.
“When the sun sets, coral reefs undergo a dramatic transformation. The vibrant fish we see in the day retreat to sleep among the corals and elusive nocturnal species emerge from caves and cervices in pursuit of prey,” explains Dr. Emma Weschke from the University of Bristol’s School of Biological Sciences, who led the study.
Professor Andy Radford, the study’s senior author, adds that “The night usually brings a veil of darkness that allows marine life to hide from nocturnal predators. But artificial light generated by human activities exposes coral reef inhabitants to unexpected danger.”
Using specially designed underwater infrared night-vision cameras, the research team could observe reef activity without disturbing the fish, as these marine creatures cannot detect infrared light. Their observations revealed significant changes in reef communities exposed to artificial light, with more species present than at unlit control sites. Most notably, these additional species were predominantly predatory fish that feed on zooplankton, smaller fish, and invertebrates.
The study found that these changes emerged after approximately 25 consecutive nights of artificial light exposure. Shorter periods didn’t produce noticeable differences in fish communities compared to control sites. This finding suggests that relatively simple solutions might help protect reef ecosystems.
Dr. Weschke points out a silver lining in these findings: “Unlike greenhouse gasses and plastics, artificial light is a pollutant that doesn’t leave a residue when switched off.” This unique characteristic offers hope for relatively straightforward mitigation strategies, such as limiting artificial light’s intensity and duration, and prioritizing essential lighting needs over aesthetic uses.
Glossary
- Zooplankton: Tiny floating or weakly swimming organisms that serve as food for many marine creatures
- Nocturnal Species: Animals that are primarily active during the night
- Light Pollution: Excessive or inappropriate artificial light that disrupts natural patterns and behaviors in ecosystems
Test Your Knowledge
What type of special cameras did researchers use to observe reef fish at night?
The researchers used underwater infrared night-vision cameras.
How many consecutive nights of artificial light exposure were needed to see changes in fish communities?
Changes were observed after an average of 25 consecutive nights of exposure to artificial light.
What types of fish were found in greater numbers around artificially lit reefs?
Predatory fish that feed on zooplankton, small fish, and invertebrates were found in greater numbers, including species that are usually only active during the day.
How does artificial light pollution differ from other environmental pollutants, and what implications does this have for conservation?
Unlike greenhouse gases and plastics, artificial light pollution leaves no residue when switched off, suggesting that immediate solutions through light reduction could help restore natural nighttime reef conditions.
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