A branching coral (Acropora eurystoma) in the Gulf of Eilat/Aqaba, northern Red Sea, spawns pink egg-sperm bundles. TOM SHLESINGER (2019)

When the water temperature and moon phase are just right, thousands of corals on the same reef release gametes in sync once a year. During this broadcast spawning, millions of eggs and sperm are released into the ocean, where they rise to the water’s surface and undergo fertilization. Most coral species spawn this way. But a study published in Science on September 6 has found that the timing of gamete release in some coral species in the Red Sea has shifted—and changing environmental conditions may be to blame.

The authors, Tom Shlesinger and Yossi Loya of Tel Aviv University, found that some species of corals in the Gulf of Eilat/Aqaba are spawning out of sync. Some species spawned over a period of several days during different months each year, drastically reducing the chances of successful fertilization. The authors suggest that spawning asynchrony could be caused by rising water temperatures and ocean pollution.

T. Shlesinger, Y. Loya, “Breakdown in spawning synchrony: A silent threat to coral persistence,” doi:10.1126/science.aax0110, Science, 2019.

Emily Makowski is an intern at The Scientist. Email her at emakowski@the-scientist.com.