In their research paper - Signaling cascades and the importance of moonlight in coral broadcast mass spawning- Levy et al. have found that coral exposed to artificial light cannot detect moonlight and therefore fail to spawn.
An association between light pollution and the health of coral reefs has been suspected since the 2007 discovery that moonlight triggers the mass release of eggs and sperm. The current study is the first to confirm the effect with field trials during a spawning event. It is also the first to show all the genes that are switched on and off during mass spawning.
The researchers collected 20 colonies of the stony coral Acropora millepora eight days before they were due to spawn on the Heron Island reef flat in the southern Great Barrier Reef. Four were left in the field and the remaining 16 were transferred to large outdoor aquaria flushed with seawater and exposed to sunlight and moonlight.
Colonies in the open aquaria system were divided into three groups. Six were exposed to natural day and night cycles. Five were exposed to natural light in the day and to artificial light in the evening - from 6.15pm just after sunset, until midnight, from when they were left in the dark. The remaining five were exposed to natural daylight and then left in the dark between 6.15pm and sunrise.
The colonies exposed to normal conditions spawned at around the same time as those on the reef. However, there was no sign of spawning behaviour in either of the corals exposed to artificial light or those left in the dark. The activity of genes was shown to be disrupted and these colonies did not release sperm or eggs.
The results also suggest that the effects of light pollution can occur much more rapidly than previously thought, with disruption occurring within seven days, rather than several months, of coral being exposed to changes in nocturnal light.
Examples of media coverage featuring this study can be found below:
