Coastal city light pollution impacts coral spawning threatening reef health

Artificial light at night disrupts coral reef reproduction cycles, impeding recovery

  • Coastal city light pollution alters coral reef reproduction cycles, causing spawning events to occur closer to the full moon.
  • Artificial light at night disrupts fertilisation and hinders the recovery of reefs after bleaching events.
  • Coral reefs in the Red Sea and Persian Gulf are particularly affected by light pollution due to heavy coastal development.

Light pollution from coastal cities has been discovered to disrupt the reproduction cycles of coral reefs, according to a recent study. The research, conducted by an international team of scientists, including researchers from the University of Plymouth, UK, reveals that artificial light at night (ALAN) can deceive corals into spawning or laying eggs at inappropriate times, deviating from their natural reproductive patterns.

Coral broadcast spawning events, which occur when lunar cycles prompt the release of eggs on specific nights each year, play a vital role in the survival and recovery of reefs following events such as mass bleaching. However, the study indicates that corals exposed to light pollution spawn one to three days earlier in relation to the full moon compared to those in undisturbed areas.

This alteration in spawning timing could diminish the chances of successful fertilization and subsequent production of new adult corals, crucial for reef regeneration after disturbances like bleaching events. The researchers obtained data on light pollution and observed spawning events, combining them to demonstrate the correlation between ALAN and the advancement of spawning triggers. Artificial light creates a perceived period of minimal brightness between sunset and moonrise following the full moon, potentially influencing coral reproductive behavior.

The study, published in Nature Communications, is part of the Artificial Light Impacts on Coastal Ecosystems (ALICE) project, funded by the UK's Natural Environment Research Council. It builds upon previous research from December 2021, which identified the areas in the ocean most affected by light pollution.

The earlier study unveiled that approximately 1.9 million square kilometers of coastal ocean, equivalent to around 3.1% of the global Exclusive Economic Zones, experience significant artificial light pollution at a depth of one meter. An Exclusive Economic Zone refers to an oceanic region where a coastal nation has jurisdiction over both living and nonliving resources, extending approximately 370 kilometers beyond its territorial sea.

In addition to the global analysis, the researchers specifically highlighted the impact of light pollution on coral reefs in the Red Sea and Persian Gulf. These coastal regions have witnessed extensive development in recent years, posing a particular risk to coral reefs situated close to the shore.

The findings emphasize the urgent need to address light pollution and its consequences for marine ecosystems. Implementing measures to minimize the effects of artificial lighting near coastal areas can help protect the reproductive cycles of coral reefs, supporting their resilience and recovery in the face of various disturbances. Preserving the delicate balance of these ecosystems is crucial for safeguarding their biodiversity and the multitude of benefits they provide to both marine life and human populations.