Split spawning can give coral reefs a second chance

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Split spawning can give coral reefs a second chance

August 08, 2019 - 06:04
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Researchers discover that split spawning, in which coral reefs divide their spawning over two separate occasions, can improve the reefs' resilience and the robustness of coral larval supply.

Coral larvae being released into the water column, off Maui in 2003

When investigating whether corals that split their spawning over multiple months are more successful at spreading their offspring across different reefs, researchers discovered that split spawning can indeed improve the coral reef's resilience.

The findings of the study was published in the Nature Communications journal recently.

According to Dr Karlo Hock, from the School of Biological Sciences at University of Queensland (UQ), the coral colonies at the Great Barrier Reef typically spawn once a year over several nights after the full moon, as the water warms up in late spring.

Sometimes, in a bid to synchronise their reproduction to the best environmental conditions and moon phrases, the corals may split their spawning over two successive months, said coauthor Dr Christopher Doropoulos from the CSIRO Oceans & Atmosphere.

The split spawning process may boost the recovery potential in the region, as it can increase the reliability of larval supply, as the reefs tend to be better connected and have more numerous and more frequent larval exchanges.

The more reliable supply of coral larvae could thus benefit reefs that have experienced disturbances, when coral populations need new coral recruit the most, added UQ’s Professor Peter J Mumby.

"This will become more important as coral reefs face increasingly unpredictable environmental conditions and disturbances,” he added.

Although split spawning can help to alleviate the effects of coral reef degradation, there are limits to what can be achieved if the current environmental threats like river runoff and excessive carbon dioxide emissions are not reduced or eliminated.

"It all ends up being the matter of scale: any potential benefits from split spawning might be irrelevant if we don't have enough coral on these reefs to reproduce successfully,” said Hock.

"While reproductive success during split spawning may be lower than usual because it can lead to reduced fertilisation, we found that the release of eggs in two separate smaller events gives the corals a second and improved chance of finding a new home reef." - Dr Christopher Doropoulos, CSIRO Oceans & Atmosphere

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