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Synchronised mass coral reef spawning has been observed for the first time in Cambodian waters. Conservationists from Fauna & Flora’s marine team in Cambodia witnessed the spectacular show during the first week of March. This momentous event is living proof that the Cambodia’s coral reefs remain healthy despite the severe pressures from climate change, pollution and coastal development.
Rare recording
Fauna & Flora and our in-country partners Song Saa Foundation and Bubbles Up! Dive Centre had long suspected that corals were reproducing successfully in this area of the Gulf of Thailand, but the precise timing of these mass spawning events is notoriously tricky to predict. In this instance, our informal marine partners in Thailand – Dr Rahul Mehrotra and the Aow Thai Marine Ecology Center – were instrumental in our success, advising the team when to look.
Close-up of hard coral releasing eggs during synchronised mass spawning in Cambodia. © Matt Glue / Fauna & Flora
Close-up of hard coral releasing eggs during synchronised mass spawning in Cambodia.
Orchestrated manoeuvres in the dark
Coral spawning usually occurs just once a year, with each species timing the release of its eggs and sperm to a specific time on a particular night. The timing is governed by subtle changes in water temperature and the phases of the moon, which provide the cue for the corals to synchronise their reproductive activity. The length of the release, which occurs under cover of darkness, can vary from a couple of minutes to over an hour.
Synchronised reproduction on this massive scale is a familiar survival strategy among species that have no defences against predatory fish and other hazards. It’s the ultimate example of safety in numbers. The vast majority of the fertilised eggs will end up as fish food, but the sheer volume produced ensures that sufficient numbers avoid this fate and go on to seed other coral reefs.
Rare video footage of mass synchronised coral spawning in Cambodia.
Music to our ears
Significant mass spawning is an important sign of coral reef health, so this event is great news for conservation. It shows that Cambodian coral reefs have not been unduly affected by major stressors – such as climate change – that could prevent reproduction.
Coral reefs near the Cambodian coastline are characterised by high sedimentation and are subject to significant variations in temperature between the wet and dry seasons. It appears that Cambodia’s coral reefs may act as important refugia for thermally tolerant coral genotypes that can seed coral reefs elsewhere in the Gulf of Thailand.
The countless life forms that benefit from coral reef ecosystems in Cambodia include hundreds of fish species that feed directly on the coral or use its structure for refuge and other behavioural traits. Many invertebrate species such as giant clams, sea cucumbers, lobsters and shrimps are also closely connected to coral reef habitat, and all play a role in maintaining a harmonious marine ecosystem.
Moray eel on a coral reef in Koh Rong Protected Area, Cambodia. © Matt Glue / Fauna & Flora
Moray eel on a coral reef in Koh Rong Protected Area, Cambodia.
Eyewitness accounts
Matt Glue, Fauna & Flora’s Marine Technical Specialist in Cambodia, was one of those present at the mass spawning: “What a spectacular event to witness along our coastline. It was like an explosion of life as the reef released thousands of eggs – spreading as far as the eye could see.
“Coral reefs provide a crucial habitat for marine life, as well as vital ecosystem services through tourism and fisheries that coastal communities in Cambodia rely on. It is therefore enormously reassuring to see that the coral here remains healthy, and this sighting will help to improve our knowledge of coral reproduction in the Gulf of Thailand.”
Tharamony Ngoun, Marine Species & Ecosystems Officer at Fauna & Flora, was also lucky enough to witness this first recorded mass spawning in Cambodia: “The first time I saw corals releasing their egg bundles which floated up into the water column I felt like I was in a snowstorm. I expect we will have a lot of baby coral in the future.”
The spectacle made a deep impression on Sorn Srenh, Deputy Chief of Koh Sdach Commune: “Coral spawning is truly captivating, and it has left a lasting impact on my soul. It is also an indispensable indicator of a thriving reef ecosystem. When corals spawn, it is a sign that they are flourishing and that the environmental conditions are conducive to their survival and growth. A thriving coral reef is not only a feast for the eyes, but it also plays a crucial role in supporting a wide range of marine species, including commercially significant fish. This, in turn, sustains the livelihoods of coastal communities through fishing and tourism.”
Working in concert
With funding from Blue Action Fund and Fondation Prince Albert II de Monaco, Fauna & Flora is working closely with the Cambodian Fisheries Administration and Ministry of Environment and local NGOs to protect marine and coastal ecosystems in this region. Activities include biodiversity research, such as the mapping of coral reef, seagrass and mangrove habitats; marine protected area development; and the restoration of mangrove forests along the coastline.
Along with our partners, we are also engaging with local communities and other stakeholders along the Cambodian coastline to raise awareness of the value of marine resources and develop sustainable conservation methods and livelihood activities.
Conducting further research
Understanding when coral reproduction occurs is important for coral reef management as it allows conservationists to deploy restoration techniques effectively and assess the health of hard coral communities. Our observations of the mass spawning event, and the vital data collected, will help to inform wider conservation efforts in the area.
Diver with giant barrel sponge in Koh Sdach, Cambodia. © Paul Colley
Diver with giant barrel sponge in Koh Sdach, Cambodia.
Join our movement
Coral reefs and the species that depend on them are in urgent need of protection.
If this incredible footage has struck a chord with you, please support our vital work.
Donate todayClose-up of hard coral on a reef in Cambodia. © Matt Glue / Fauna & Flora
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