NSW Department of Primary Industries, Lord Howe Island Marine Park News, The Lord Howe Island Signal

Just like on other tropical reefs, corals in the LHIMP undertake synchronised mass spawning each year, releasing millions of tiny egg and sperm bundles into the water. This allows fertilisation to take place, resulting in coral larvae with new genetic combinations which can settle back on to the reef and enhance its diversity and resilience.

The timing of mass spawning is influenced by a range of environmental conditions including water temperature, moon phase and tidal height. Different reefs around the world spawn at different times, and in the LHIMP it usually occurs over multiple nights following the full moon in December, January and/or February.

This year coral spawning occurred in both January and February, known as a ‘split spawning’. While less is known about spawning events in the LHIMP, research from other reefs has found split spawning occurs periodically when moon phases and optimal environmental conditions are out of alignment. Like a ‘leap year’ in coral reproduction, split spawning is believed to realign spawning dates with the best conditions for reproductive success.

The split event was documented by LHIMP staff, and many visitors and residents were lucky enough to see floating slicks of pink coral spawn in the lagoon and offshore in the days following. This included Her Excellency the Honourable Margaret Beazley AC KC, Governor of NSW, who kindly reported spawn slicks at North Bay to LHIMP staff during her recent visit to the Island. 

This article appeared in The Lord Howe Island Signal, 30 April 2023.