Spawning of corals is a natural wonder. In addition, tracking this event is an extraordinarily challenging process for coral research.
Once a year, corals along a reef release floating bundles of eggs and sperm into the ocean at a time determined by a combination of water temperature, length of days, and moon phase. The result is like a snow globe turned on its side with a blizzard of tiny pearls rising to the surface.
This situation also has a mystical aspect. It also drives researchers into a frenzied late-night frenzy as they race against time to collect enough eggs and sperm for a year's worth of research before the next ovulation.
Now Australian scientists have joined a small group of labs around the world exploring how to plan ovulation. Announcing a major development on the Australian National Marine Simulator (SeaSim) on 22 August is an important step in the effort to grow coral on a large scale and save the Great Barrier Reef, which has been destroyed by climate change.
According to ecologist Carly Randall, who participated in the spawning research from the Australian Institute of Marine Sciences, “what is most striking to me in this program is the scale at which we are trying to industrialize and operationalize coral production.”
We are trying to develop a system that will produce coral throughout the year. In other words, they want to grow coral.
The magnitude of the problem is also reflected in the scope of the vision. A quarter of all ocean species are thought to live on coral reefs. But corals face threats from pollution, acidification and rising ocean temperatures. Coral polyps release microscopic algae that settle in their tissues during underwater heat waves. Polyps resembling small sea anemones are heavily dependent on algae for their food source. Corals go through a process known as bleaching, which causes them to turn completely white when living plants are removed. If the problem is not resolved, the corals may starve to death.
As a result, according to scientists, coral reefs around the world could experience up to 20% reduction in the next 90 years.
The solution to the problem is to stop the pollution caused by greenhouse gases. But as greenhouse gas concentrations in the atmosphere continue to rise, coral experts have recently welcomed more direct interventions.
Much of the work focuses on developing corals that can withstand the increased heat. But conducting the research requires mass-producing coral polyps and performing genetic research on them, not to mention the application of any findings on a scale to repair reefs.
In 2018 I was lucky enough to see corals spawn on SeaSim. As night fell, tiny coral DNA packets began to rise to the top of the aquarium tanks.
These were meticulously placed in plastic containers by people. Some hurriedly took the bundles to an area where sperm and eggs from various corals were mixed and screened to produce hybrids. Others rushed upstairs to a room with frozen coral sperm for storage. In another building, a lone researcher was leaning over the microscope, injecting a genetic change into newly unfertilized embryos to discover which genes influence heat tolerance. Many expressed how wonderful it would be if they could plan to spawn instead of traveling far for these annual shows.
Jamie Craggs, a researcher at the Horniman Museum and Gardens in London, published a paper a year ago, in 2017, detailing the initial success of artificially inducing coral spawning in the lab.
Five years later, several labs are now mimicking Craggs' example. According to Phillip Cleves, a coral geneticist at the Carnegie Institute for Science in Baltimore, Maryland, "this kind of technology is transforming our work." He was the one who examined coral embryos under a microscope in 2018. Last time we spoke, a few weeks ago, he predicted that corals would start spawning in his lab in a matter of days. “If we can get corals to breed like we did in Baltimore this week, we can now do a lot more experiments,” he explains.
The most recent success in the lab in Australia involved tricking six coral species into spawning six months earlier from Great Barrier Reef corals during the Australian winter. Corals that spawned in 2014 were born during spawning in 2014 and have spent their entire lives in the laboratory.
“These corals were never presented with natural environmental cues. According to Lonidas Koukoumaftsis, senior aquarist at SeaSim, they have spent their entire lives feeding in artificial environments.
Artificial spawning of four of these six species resulted in larvae that successfully established new coral colonies of their own.
Jonathan Daly, director of a coral cryopreservation program in Australia who also participated in spawning in 2018, said he would be interested in studying the quality of sperm from these new, stimulated ovulation states. “Anything that increases capacity is something that will have a multiplier effect in various other research programs,” Daly said. Scientists are scrambling to figure out how to develop a coral aquaculture system.
Yet the natural cycle is still the main event for now. Spawning, which will begin shortly after sunset on a night in November or December, is something Daly has already been waiting for. “We are starting to accelerate,” he says.