Light pollution a threat to annual coral spawning

December 15, 2015

University of Queensland research has pinpointed artificial light as a threat to coral reproduction, in a discovery that will help guide reef and marine ecosystem protection plans.

UQ Global Change Institute researcher Dr Paulina Kaniewska said work at UQ's Heron Island Research Station revealed that the Great Barrier Reef's annual coral spawning was dependent on an intricate mix of conditions, with moonlight playing a vital role.

"The introduction of artificial light competes with moonlight and can prevent corals from spawning," she said.

Dr Kaniewska said the research provided insight into how corals fine-tuned and coordinated the release of eggs and sperm into the water for fertilisation.

"Even though corals don't have a brain, they have a spread-out nervous system that allows them to transmit signals in response to sensing changes in light conditions on a cellular level," she said.

The study suggests that the release of sex cells in corals is triggered by a protein similar to the photosensitive melanopsin molecule.

"In mammals, melanopsin plays an important role in synchronising circadian rhythms with the daily light-dark cycle."

She said the research resolved long-standing questions about how corals synchronised the mass release of sex cells with the phases of the moon or bio-rhythms.

"Effects of light on the timing of spawning are so important because sexual reproduction is vital to reef survival," she said.

"This research suggests that urban light pollution from excessive artificial light can be a real threat to coral reproduction."

Dr Kaniewska and colleagues exposed the coral Acropora millepora -- one of the dominant coral species that make up the Great Barrier Reef -- to different light treatments and sampled the corals before, during and after spawning.

"The annual coral spawning on the Great Barrier Reef is a spectacular synchronised reproduction event where changes in water temperature, tides, sunrise and sunset and the intensity of the moonlight trigger large-scale mass spawning of hundreds of coral species over several nights" Dr Kaniewska said.

"The egg and sperm cells combine and develop into larvae. These settle back on the reef to form new coral colonies," she said.

"Many different coral species commonly spawn simultaneously to improve their chances of successfully reproducing."

The research is published in eLifeSciences.

Paulina Kaniewska

Rachael Hazell
61-07-3443-3150 or 61-415-814-529

University of Queensland

Related Great Barrier Reef Articles from Brightsurf:

The Great Barrier Reef has lost half its corals
Populations of corals on the Great Barrier Reef have halved in the past three decades - in both shallow and deeper water, and across virtually all species - especially branching and table-shaped corals.

Great Barrier Reef 'glue' at risk from ocean acidification
Scientists have suspected that increasing ocean acidity would weaken and thin the structures underpinning tropical reefs.

How people and ecosystems fit together on the Great Barrier Reef
A world-first study examines the scales of management of the Great Barrier Reef.

Reef sharks in decline
Though many people find them intimidating, menacing or just plain scary, sharks are vital to the health of the world's oceans.

Climate change triggers Great Barrier Reef bleaching
The Great Barrier Reef is suffering through its worst bleaching event.

Yale-NUS research shows airborne microbes link Great Barrier Reef and Australian continent
A team of researchers led by Yale-NUS College Professor of Science (Environmental Studies) Stephen Pointing has discovered a link between two different ecosystems, continental Australia and the Great Barrier Reef, due to airborne microbes that travel from the former to the latter.

Great Barrier Reef study shows how reef copes with rapid sea-level rise
A survey of coral reef cores on the Great Barrier Reef has revealed how it has responded to recent periods of rapid sea-level rise.

Pesticide management is failing Australian and Great Barrier Reef waterways
Scientists say a failure of Australian management means excessive amounts of harmful chemicals -- many now banned in countries such as the EU, USA and Canada -- are damaging the country's waterways and the Great Barrier Reef.

Great Barrier Reef island coral decline
A long-term study of coral cover on island groups of the Great Barrier Reef has found declines of between 40 and 50 percent of live, hard corals at inshore island groups during the past few decades.

Longest coral reef survey to date reveals major changes in Australia's Great Barrier Reef
An in-depth look at Australia's Great Barrier Reef over the past 91 years concludes that since 1928 intertidal communities have experienced major phase-shifts as a result of local and global environmental change, leaving few signs that reefs will return to their initial state in the near future.

Read More: Great Barrier Reef News and Great Barrier Reef Current Events is a participant in the Amazon Services LLC Associates Program, an affiliate advertising program designed to provide a means for sites to earn advertising fees by advertising and linking to