Proximity is essential for them. A new study reveals that corals must be only a few meters away from each other to reproduce successfully. This leaves them vulnerable in a warming world. Corals must be close to reproduce. The international research is led by Professor Peter Mumby of the University of Queensland. He measured the success of a natural spawning event in March of this year.
«It was a surprise. We saw that the corals needed to be 10 meters from each other. And preferably closer, so that fertilization could occur. That’s what Professor Mumby said in a statement.
Close, or nothing
«We knew that the corals couldn’t be too far apart. But we discovered that they had to be closer than we expected. The impacts of climate change, such as bleaching, are killing and reducing the density of corals. “We are concerned that individuals will end up too far apart to reproduce successfully.”
How to quantify the success of reproduction? They placed containers over 26 coral colonies on a reef in Palau, Micronesia. It was at the time when corals, mostly hermaphrodites, released eggs and sperm. “The containers captured some of the eggs from each coral and went to the surface. They followed the tide,” Professor Mumby said.
«The eggs could not escape. But sperm could enter the container and fertilize the eggs. After one hour of drifting, the proportion of fertilized eggs for each coral type was recorded. “And the distance to similar established corals.”
Fertilization averaged 30% when corals were very close. It decreased to less than 10% at a separation of 10 meters. It was practically nil at 20 meters. The bottom line: Corals must be nearby to reproduce. Coral reproduction is essential for the resilience and evolution of the population.
Identifying neighborhoods
“In the future, we may need to help corals continue this key part of their lives. We must understand the importance of local neighborhoods. It provides us with tangible objectives for interventions such as coral restoration,” he explained.
«The ideal would be to monitor the density of corals in important places. We must do this to return it to the levels required for successful reproduction,” he added. The research is published in PNAS (Proceedings of the National Academy of Sciences).
