A recent study has revealed that the artificial light pollution generated by coastal cities can disrupt the natural reproductive cycles of coral reefs. Coral broadcast spawning, a crucial event for reef maintenance and recovery, is triggered by lunar cycles and typically occurs on specific nights throughout the year. However, the study found that corals exposed to artificial light at night (ALAN) were spawning one to three days earlier in relation to the full moon compared to corals in unlit areas.
This shift in spawning timing could have detrimental effects on the fertilization and survival of coral eggs, hampering the production of new adult corals necessary for reef recovery after events like mass bleaching. The research, conducted as part of the Artificial Light Impacts on Coastal Ecosystems (ALICE) project, utilized data on light pollution and coral spawning observations to establish a correlation between ALAN and altered spawning patterns.
A previous study published in December 2021 had already identified the areas of the ocean most affected by light pollution. The research revealed that approximately 1.9 million square kilometers of coastal ocean, representing around 3.1% of the global Exclusive Economic Zones, were exposed to biologically significant ALAN at a depth of one meter.
To conduct the recent study, scientists combined this light pollution data with a global dataset of 2,135 coral spawning observations from the 21st century. This analysis allowed them to propose that ALAN may be advancing the triggers for spawning by creating a perceived period of minimum illuminance between sunset and moonrise on nights following the full moon.
Dr. Thomas Davies, the lead author of the study and a marine conservation lecturer at the University of Plymouth, emphasized that corals are vital for the health of the world’s oceans but are increasingly affected by human activities. He suggested that delaying the activation of nighttime lighting in coastal regions could help preserve the natural dark period between sunset and moonrise, which serves as a crucial trigger for spawning. However, he acknowledged that such a measure would raise economic and safety concerns but may be necessary to ensure the survival of coral reefs.
Dr. Tim Smyth, the study’s senior author and head of science for marine biogeochemistry and observations at Plymouth Marine Laboratory, highlighted the significance of artificial light pollution as a stressor for coastal and marine ecosystems. He noted that the study contributes to quantifying the impacts on biodiversity and highlights the importance of recognizing and addressing this issue.
While the study examined coastal regions worldwide, it particularly focused on coral reefs in the Red Sea and Persian Gulf, which are heavily affected by light pollution. These areas have witnessed extensive coastal development in recent years, posing significant risks to coral reefs situated close to the shore. Professor Oren Levy, a co-author of the study and head of the Laboratory for Molecular Marine Ecology at Bar-Ilan University, stressed the urgency of reducing the impact of ALAN on these fragile marine ecosystems. Implementing measures to limit light pollution can protect these vital habitats and ensure the future of the world’s oceans, preserving biodiversity and fostering a sustainable environment for future generations.
Source: University of Plymouth