Coral danger: breakdown in spawning could mean extinction

Written on |

Synchronized coral spawning has become erratic, endangering the long-term survival of coral species, Tel Aviv University researchers say

Coral reefs are among the most diverse and productive ecosystems on our planet. But due to climate change and other human stressors, reef-building corals that reproduce by means of broadcast-spawning — the simultaneous release of eggs and sperm into open water — may now be under threat of extinction.

A new Tel Aviv University study finds that the highly synchronized, iconic spawning events of certain reef-building corals in the Gulf of Eilat/Aqaba, Red Sea, have completely changed over time and lost their vital synchrony, dramatically reducing chances of successful fertilization.

According to the research, led by Prof. Yossi Loya and PhD candidate Tom Shlesinger of TAU’s School of Zoology and published in Science, the breakdown in coral spawning synchrony has led to a dearth of new recruits and stagnant aging populations, creating circumstances for extinction.

It’s all in the timing

“Coral spawning, often described as ‘the greatest orgy in the world,’ is one of the greatest examples of synchronized phenomena in nature,” explains Prof. Loya. “Once a year, thousands of corals along hundreds of kilometers of a coral reef release their eggs and sperm simultaneously into the open water, where fertilization will later take place. Since both the eggs and the sperm of corals can persist only a few hours in the water, the timing of this event is critical.”

Successful fertilization, which can take place only within this narrow time window, has led to the evolution of a precise spawning synchrony. Such synchronicity relies on environmental cues: sea temperature, solar irradiance, wind, the phase of the moon and the time of sunset.

In 2015, the researchers initiated a long-term monitoring of coral spawning in the Gulf of Eilat/Aqaba. Over four years, they performed 225 night field surveys lasting three to six hours each during the annual coral reproductive season from June to September and recorded the number of spawning individuals of each coral species.

“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,” says Shlesinger.

Extinction through reproductive failure

The researchers then investigated whether this breakdown in spawning synchrony translated into reproductive failure. They mapped thousands of corals within permanent reef plots, then revisited these plots every year to examine and track changes in the coral community — i.e., how many corals of a given species had died compared with new juveniles recruited to the reef.

“Although it appeared that the overall state of the coral reefs at Eilat was quite good and every year we found many new corals recruiting to the reefs, for those species that are suffering from the breakdown in spawning synchrony, there was a clear lack of recruitment of new juvenile generations, meaning that some species that currently appear to be abundant may actually be nearing extinction through reproductive failure,” says Shlesinger.

The future of corals?

“Several possible mechanisms may be driving the breakdown in spawning synchrony that we found,” Prof. Loya concludes. “For example, temperature has a strong influence on coral reproductive cycles. In our study region, temperatures are rising fast, at a rate of 0.31 degrees Celsius per decade, and we suggest that the breakdown in spawning synchrony reported here may reflect a potential sublethal effect of ocean warming. Another plausible mechanism may be related to endocrine (hormonal) disrupting pollutants, which are accumulating in marine environments as a result of ongoing human activities that involve pollution.”

“Regardless of the exact cause leading to these declines in spawning synchrony, our findings serve as a timely wake-up call to start considering these subtler challenges to coral survival, which are very likely also impacting additional species in other regions,” says Shlesinger. “On a positive note, identifying early-warning signs of such reproductive mismatches will contribute to directing our future research and conservation efforts toward the very species that are at potential risk of decline, long before they even display any visible signs of stress or mortality.”

related posts

Where Have All the Birds Gone?

August 11, 2021

Tel Aviv Bats Have More Fun

July 22, 2021

The survivability of animal species depends on the number of offspring rather than body size

June 10, 2021

First-of-its-kind study: Researchers used smart watches to monitor changes in quality of life during lockdowns

June 8, 2021

Bats ‘Social Distance’ Too

June 6, 2021

Time Flies and So Do Bats

May 31, 2021

When One Becomes Three

May 19, 2021

Fireflies’ Protective ‘Musical Armor’ Against Bats

May 12, 2021

An Underwater Salute to Grandma Vera

April 8, 2021

Struggling in a Toxic Workplace?

April 6, 2021

Robot “Hears” through the Ear of a Locust

March 4, 2021

An Underwater Journey Following the Vanishing of Sponge Species from the Shallow Water of the Israeli Coast

December 1, 2020

Why Do Bats Fly Into Walls?

November 10, 2020

Pharmaceutical residuals pose a serious threat to Marine life

August 19, 2020

Bats navigate just like humans – using their excellent eyesight and a cognitive map

July 12, 2020

TAU researchers discover unique, non-oxygen breathing animal

February 26, 2020

Pope welcomes Israeli, Jordanian, Palestinian bird experts

June 11, 2019

Inside a bat’s brain

February 13, 2019
Ontario and Western Canada

3130 Bathurst Street, Suite, 214, Toronto, ON | M6A 2A1 
Phone: 416.787.9930 | Toll Free: 833.32.CFTAU (22328)
Email: toronto@cftau.ca

Ottawa, Quebec and Atlantic Canada

6900 Boulevard Décarie, Suite 3480, Montreal, QC | H3X 2T8
Phone: 514.344.3417
Email: montreal@cftau.ca


© CFTAU  | all rights reserved
Charitable registration: 124035643RR0001

TO TOP