Climate Crisis Is Causing the Breakdown of Annual Coral Spawning: Study
Sat, April 10, 2021

Climate Crisis Is Causing the Breakdown of Annual Coral Spawning: Study

In 2016, corals in the Great Barrier Reef released little balls that floated to the ocean surface. The scientists who were there documenting the fascinating event described it as one of the planet’s most prolific and mysterious rites of reproduction / Photo by: Luca Mason via 123RF

 

In 2016, corals in the Great Barrier Reef released little balls that floated to the ocean surface. The scientists who were there documenting the fascinating event described it as one of the planet’s most prolific and mysterious rites of reproduction. This iconic celebration of sex on the reef was first described in the central Great Barrier Reef by a group of early-career scientists in 1984, which earned them a prestigious Australian Museum Eureka Award for Environmental Research in 1992.

What’s even more fascinating about this is the fact that coral spawning is extremely vital to the continuing life of our coral reefs, which we know are on the brink of extinction due to the climate crisis. According to the National Oceanic and Atmospheric Administration, coral spawning refers to entire colonies of coral reefs simultaneously releasing their tiny eggs and sperm, called gametes, into the ocean. This phenomenon only happens once a year on cues from the lunar cycle and the water temperature.

During coral spawning, billions of colorful flakes cascading in white, yellow, red, and orange would float to the ocean surface. While researchers still don’t understand why mature corals release their gametes all at the same time, they emphasized that synchrony is crucial for them since the gametes of most coral species are viable for only a few hours. Emma L. Hickerson, a veteran diver and research coordinator at the Flower Banks, described this event “like an underwater snowstorm.”

The New York Times, an American newspaper based in New York City with worldwide influence and readership, reported that these billions of coral embryos ride surface currents for hundreds of miles and descend to found new colonies and reefs. The scientists also noted that the Moon’s phase is extremely important in the ritual because it controlled the tides. The reproduction follows “the optimal temperature window,” which means that the average sea temperature during the phenomenon should be cooler by 1.5 degrees Celsius or 2.7 degrees Fahrenheit.

Coral Spawning Improves the Great Barrier Reef’s Resilience

Since the annual coral spawning was discovered in 1984, many scientists have devoted their time to learn about the phenomenon. A recent study conducted by researchers from the University of Queensland and CSIRO investigated the success of coral spawning at spreading their offspring across different reefs when they occurred over multiple months. They examined more than 3,800 reefs found in the Great Barrier.

One key finding from the study is that there are times that corals split their spawning over two successive months to help them synchronize their reproduction to the best environmental conditions and Moon phases. Dr. Karlo Hock, from UQ's School of Biological Sciences, stated that this gives the corals a second and improved chance of finding a new home reef. This is because corals release eggs in two separate smaller events although they might have a lower count of eggs. 

Science Daily, an American website that aggregates press releases and publishes lightly edited press releases about science, reported that the reproduction of corals in two separate events increases the reliability of larval supply since the reefs tend to be better connected. Additionally, the researchers discovered that this increases the recovery potential for reefs in the region, thus improving the resilience of the Great Barrier Reef. 

“A more reliable supply of coral larvae could particularly benefit reefs that have recently suffered disturbances when coral populations need new coral recruits the most. This will become more important as coral reefs face increasingly unpredictable environmental conditions and disturbances,” co-author professor Peter J. Mumby said. 

Since the annual coral spawning was discovered in 1984, many scientists have devoted their time to learn about the phenomenon / Photo by: Brian Kinney via 123RF

 

Coral Spawning Is in Danger

Studies about coral spawning showed that the phenomenon is significant in saving beleaguered coral reefs around the globe. It’s no secret that coral reefs have suffered repeated bouts of mass bleaching mainly due to declining water quality and rising temperatures caused by the climate crisis. Many scientists are hoping to better understand coral reproduction because they believe that it will strengthen efforts to limit coastal pollutants and sediments. Unfortunately, coral spawning is also in grave danger.

A recent study conducted by researchers from Tel Aviv University, Israel analyzed the impacts of global warming and coral bleaching on coral spawning synchronization. They compared spawning behavior on a reef in the Red Sea over recent years with historical data from the 1980s. Tom Shlesinger and Yossi Loya, the authors of the study, conducted 225 night-time surveys, which lasted between 2.5 and 5.5 hours each, between 2015 and 2018. They discovered several changes in the behavior of the corals.

According to The Guardian, an online British site, the release of eggs and sperm in certain reef-building corals in the Gulf of Eilat in the Red Sea has changed over time. The researchers noticed that there has been no consistent pattern relative to the phase of the Moon, sea temperature, or wind speed in coral spawning in recent years. Aside from that, the coral species would spawn in the ocean for several weeks with different colonies spawning on different nights instead of a synchronized mass spawning event.

Studies about coral spawning showed that the phenomenon is significant in saving beleaguered coral reefs around the globe / Photo by: khunta via 123RF

 

“We found that, in some of the most abundant coral species, the spawning synchrony had become erratic, contrasting both the widely accepted paradigm of highly synchronous coral spawning and studies performed on the exact same reefs decades ago,” Shlesinger said. 

While the coral reefs looked healthy, the researchers observed that they have been suffering a breakdown in spawning synchrony. Unlike before, they are producing fewer baby corals, creating circumstances for extinction. However, the reason why this is happening is not yet known, but the researchers found that temperature had a “strong influence” on coral reproductive cycles. They also suggested that endocrine or hormonal disrupting pollutants could be another plausible cause. 

This study showed that the climate crisis has been causing great damage to our marine life. This is a wake-up call for us to start thinking about not only how to address the challenges in coral survival but also how our planet can surpass this dire predicament.