Few people know more about the sex-life of coral than the Horniman Museum’s Aquarium Curator, Jamie Craggs.
He is the founder of Project Coral, a pioneering multi-year research project which aims to understand the impact of climate change on corals, their resilience and ability to reproduce.
Using the latest microprocessor technologies, Project Coral replicates environmental stimuli to trigger broadcast coral sexual reproduction in the museum’s research facility. In 2013, this resulted in the world’s first predictable coral spawning in a closed system.
Ahead of his presentation at the 19th IAC (International Aquarium Congress) in Vancouver later this month, Jamie Craggs (above) spoke to Blooloop about the implications of his work for the future of the world’s depleted and endangered coral reefs.
On The Brink
Coral reefs are among the world’s most diverse ecosystems, supporting thousands of marine species. Generally associated with shallow, tropical ocean environments, there are also deep-water corals that thrive in cold, dark water habitats such as the North Sea.
Most are very slow-growing. Colonies that have built up over thousands of years are now increasingly at the mercy of climate change, pollution, over-fishing and over-harvesting.
“A significant number – there’s an estimate that says a third – of the world’s reefs have become functionally extinct in the last 20-30 years, and that trend is only increasing, ” says Craggs.
Global Bleaching Events – A Climate Change Catastrophe
Global coral bleaching events, a direct result of climate change, have become an increasing, and devastating, phenomenon. Over the past century, sea temperatures worldwide have risen by one degree closer to the coral’s bleaching threshold.
Bleaching is caused when the water becomes too warm, rising by a couple of degrees above the summer maximum for longer than around two weeks. The coral expells the photosynthetic zooxanthellae (algae) living in their tissues, dying and turning white in the process.
The coral and zooxanthellae have a symbiotic relationship ie. they depend on one another for survival. The coral gives the algae the compounds required for photosynthesis and a protected environment, while the algae provides the coral with both oxygen and the products of photosynthesis (amino acids, glucose and glycerol, with which the coral can make fats, proteins, carbohydrates and produce calcium carbonate).
The first global event occurred in 1998, triggered by an underwater heatwave caused by El Niño that wiped out 16% of the world’s coral reefs.
Within two years, a second global bleaching event was again triggered by El Niño. The third global bleaching event was announced by The US National Oceanic & Atmospheric Administration (NOAA) in October 2015, and it has already become the longest event recorded, predicted to last for an unprecedented third year.
“As we’re increasing CO2, we’re putting more temperature anomalies into the ocean systems, so events like El Niño are becoming increasingly extreme, ” says Craggs.
“In terms of looking at global bleaching events, there have been three in our human recorded history. When you map out the temperature increase over time, it’s constantly rising, reaching a point where these bleaching events become increasingly frequent, and the corals don’t have a chance to recover.
“They can recover from bleaching events; studies have shown a site that has almost 90% mortality can still bounce back. The problem is that if it keeps on getting hit year after year with these bleaching events it just doesn’t recover- corals don’t have the ability to adapt that quickly. There are incredibly worrying signs around the world, and the impacts are increasing.”
Being able to reseed damaged areas with healthy coral is seen as increasingly important for the survival of coral reefs and the complex ecosystems they support.
And, so to the sex-life of the coral.
Corals are divided, broadly, into two sexually reproductive modes. Brooders fertilise internally, and have been reproducing in people’s aquariums for years, while broadcast corals have mass spawning events once a year.
While there have been captive coral spawn events, they have previously always been always accidental. Initially, the aim of Craggs and his team was to establish whether this type of coral could be induced to reproduce in captivity.
“We put together all the parameters, looking at what goes on in the wild, in nature, to try and replicate all those conditions using a computer that ran an aquarium.
“It worked at the first attempt: within eight months we got a coral that I’ve had for fifteen years, and has never reproduced within that fifteen years, to spawn by applying this approach, and we managed to get some great video footage.
“And, that was the foundation of then setting up Project Coral.”
“The idea behind the project is to develop a protocol or an understanding and a husbandry approach, so that these corals can be spawned in a very controlled, planned way which then opens up the whole area of in vitro fertilisation, climate change research, reef restoration and so on.
“The first area we hope we can support is climate change research, the pure research into reproduction: there’s a whole raft of experiments going on round the world looking at impacts of climate change, impacts of pollution on reproduction, and how it detrimentally affects reproduction.
“The second area is restoration. There are a number of organisations that are using sexual reproductive events to get the coral through the bottle-neck of survival. Coral produce hundreds of thousands of eggs, but very few become adult corals.”
“If, for example, we had twelve replica systems, we could have twelve spawnings, one every month of the year, and then provide that platform for researchers to be able to study the impacts of climate change and get answers much quicker.
“That’s the essence behind what we’re trying to do.”
Coral Spawning – A Natural Wonder
“There is quite a lot of scientific literature looking at some of the stimuli that occur in the wild that trigger the annual spawning events: factors like seasonal temperature change in the ocean to photoperiods, and the final trigger is the lunar cycle, which is known to synchronise the coral to the exact day of spawning of a year.
“The thought is that each day you move past a full moon, the period of absolute darkness from the sun setting before the moon rising extends by about fifty minutes, and the corals appear to be sensitive to that period of darkness; it that seems to be the thing that triggers them. On some reefs you can literally almost set your clock by a certain species going at a certain time.
“It’s phenomenal. These are animals that, like trees, can’t move, so they need a mechanism of swapping their eggs and sperm. The corals that we’re studying are hermaphrodites: they produce eggs and sperm within the same individual, but the sperm can’t self-fertilise their own eggs, so the mechanism of that species where all the individuals of that species release all their eggs and sperm at the same time is a mechanism to ensure that there is mixing – good fertilisation, in essence. So, that’s why there is tight synchronisation.”
“Understanding all those factors on the reef, we’ve applied them in captivity using LED lighting to control to a very tight degree not just when the sun rises and sets, but also the intensity of sun, and we’ve used lots of data sets that are online and available from NASA, NOAA, the Australian Institute of Marine Science; we’ve also got loggers on the reef in Singapore.
“All of those data sets are put into our computers to simulate the various environments that we’re replicating, so we’re focusing on two areas of the world: Singapore and the Great Barrier Reef in Australia.
“The idea is that once we’ve developed these techniques, they can be applied anywhere in the world, so any institution that has access to coral and data sets from that location could use the same principles.”
Organisations that are using sexual reproduction are caring for corals in the first couple of months of life, when they would naturally have experienced massive mortality, then transplanting the nursery-grown youngsters back on to a damaged reef to try to help rebuild it.
“Using sexual reproduction as a way of rebuilding reefs is very much in its infancy, but it’s already very well established using asexual reproduction: with coral, particularly branching corals, in exactly the same way that you take a cutting from a rose and create a new plant, you can do the same with coral, taking a branch off, planting it onto a new area of the reef and it continues growing into an adult coral.
“Using asexual fragmentation in this way has been well established for the last fifteen years, and you can get a lot of biomass down by swimming along the reef pruning corals, then taking those fragments and transplanting them onto another area.”
The limitation with asexual fragmentation is that the transplanted fragments are genetic clones, so if the coral from which the cuttings are taken isn’t resistant to the impacts of climate change, all of the offspring, because they’re genetically identical, are similarly vulnerable.
A Limited Time Frame
“The idea behind sexual reproduction is you’re hoping that a percentage of your new, sexually diverse offspring have some sort of genetic resistance built in to them, and there will be those that go on and survive, ” says Craggs.
“The limitation that currently exists is that these corals literally spawn over one or two nights a year and then that’s it, so the research that’s going on focuses on these reproductive events, and has to wait for the following year for it to happen again, ” he explains.
“A lot of things can happen. Either it becomes a very bad year for reproduction, or the corals may skip a year, so the time frame to actually do the study is very limited. What we’re hoping is, if we can predictably spawn corals in captivity, to take it a step further and make them spawn out of their natural cycle, so we can determine when we want a spawning to occur.”
Added to this, Craggs points out, events don’t always run smoothly:
“Things can go wrong: storms can come in, the actual reproductive event can be very minimal, because of climate change and some of these issues. So the idea is to see if we can approach it in an almost agricultural sense of – can we spawn them in a predictable way in captivity; can that increase the amount of material that’s used for restoration purposes.
“This isn’t work that we’re going to be able to do at The Horniman because there isn’t the space, but we’re looking at providing the knowledge about how other institutions could pick up these protocols and run with them.”
Another challenge of sexual reproduction is that scientists are working with incredibly small organisms right at the beginning of their life cycle, so it is impossible to put as much biomass down on the reef as with asexual fragmentation.
However, this is an expanding area which will become increasingly important as time goes on. There has been a lot of work done in the Caribbean with asexual fragmentation, and there is more now happening with sexual reproduction as well in both the Caribbean and in the Philippines.
“I was in Hawaii at a conference about six weeks ago, and the restoration section had really expanded compared to the conference four years before, so there is an acknowledgement that it is really important to develop these tools while we still have the opportunity before, potentially, all the reef are lost, ” says Craggs.
To be meaningful, restoration needs to work in conjunction with a reduction in pollution, overfishing and factors such as the deforestation of vast areas of rainforest, particularly for palm oil plantations. This practice causes run-off, filling rivers and ultimately the ocean with sediment which blocks out the light and smothers the coral.
Hope for the Future
Craggs believes the corals and the oceans themselves will, beyond all doubt, be changed, but that there is hope for the future.
“There will always be some pockets that survive, and scientists are already seeing there is resilience and resistance in certain populations that don’t seem to be getting affected, so there is definitely cause for hope out there. But, the impact that’s going on is very extensive, particularly this latest global bleaching event. The true impact of that won’t be known for a number of years yet.
“The local impacts can be largely mitigated through good management plans and protected areas, whereas the global impacts are a global political issue that needs tackling, but if you deal with the local impacts then it gives the corals a fighting chance to adapt and withstand some of these global impacts. I definitely think there is hope, for sure.”
International Aquarium Congress
Jamie Craggs will be speaking about his work on coral spawning at the International Aquarium Congress at the Vancouver Aquarium Marine Science Centre in Vancouver which runs from 25th-30th September 2016. The IAC is widely recognised as the most important event for the public aquarium and marine science industry, drawing scientists and aquarists from across the global public aquarium community to share developments in the fields of research, technology, education, animal husbandry, sustainability and conservation.
This year, it is following a different format – a group of experts will be delivering a comprehensive overview of the current state of the world’s oceans and freshwater ecosystems.
“I’m going to give a complete overview, rather than focusing on one specific facet of the project, of what the coral is, what we’re aiming to achieve with it, some of the successes so far, and where we’re going in the future with it, ” explains Craggs.
“The presentation is only fifteen minutes, ” he adds. “There’s a lot of information; I could talk for hours.”
All Images kind courtesy The Horniman Museum & Gardens and Jamie Craggs except Bleached Coral kind courtesy J. Roff and coral bleaching poster kind courtesy NOAA.