Be sure to read our monthly updates from Marine Savers – direct from our teams resident at
the Marine Discovery Centres at Landaa & Kuda Huraa – our long-term partnership with Four Seasons Resorts Maldives.

Landaa Giraavaru

At Landaa this month, we transplanted 41 coral frames, kindly sponsored by guests (29), the Resort (10), and online (2), adding more than 2000 coral fragments to the reef. We monitored (cleaned, repaired, photographed) a total of 855 established coral frames at various sites around Landaa and Voavah.

A total of 20 frames (10 small, 10 medium) were sponsored by a group staying at Landaa, and built in a single day as part of an event held at Voavah. The group engaged enthusiastically with the activity, and we were delighted to see the Voavah reef looking healthy at the time of fragment collection.

To see the progress of your frame, please visit our dedicated Four Seasons monitoring page where we upload new photos every 6 months or so.

Gametogenesis

This month, pigmented eggs were observed in 6 different Acropora species, followed by spawning over the April full moon period.

Coral Spawning

🗓️ New Moon (8 April) – we conducted nightly snorkel monitoring around the period of the April new moon, but no spawning was observed. As always, we recorded a full set of environmental parameters.

🗓️ Full Moon (23 April) – we performed nightly snorkels around the full moon, and observed coral spawning in 84 different colonies representing 9 species of Acropora. The following night, we observed spawning in 24 different colonies of 6 species of Acropora, plus a single colony of Goneastria spp.

Harvesting and Fertilising Coral Gametes

We placed four of our bespoke coral spawning nets over gravid (egg-carrying) colonies and successfully collected coral gametes. The gametes were removed from the collection bottles, and poured into a fat-separating jug filled with saltwater for sperm washing. Saltwater was slowly poured into the jug, allowing spoiled water to be poured away via the bottom spout, with buoyant gametes floating to the surface. Fertilisation occurred, and the ‘bowl stage’ of development was successfully observed the following morning.

Reefscapers coral spawning Maldives (Amelia)

Coral spawning (Acropora aspera)

Reefscapers coral spawning Maldives (Amelia)

Coral spawning (Acropora millepora)
Note the paling branches due to heat stress

Maldives Coral Bleaching Season

Reefscapers coral bleaching E14 April 5-15

Monitoring for coral bleaching: colony #E14 photographed 5 April  – 15 April 2024
From paling to fully bleached within the 10 day period

The ‘summer’ hot season in the Maldives runs from January to May, with March and April being particularly hot and dry. The extra hours of seasonal sunshine, combined with the current elevated global sea surface temperatures (SSTs) cause increased stresses on coral reefs (April-June), which can lead to temporary paling of the coral colonies, or even permanent coral bleaching and death.

Global climatologists are forecasting 2024 to be exceptionally hot, due to a combination of the cyclical El Niño event and the ever-increasing effects of anthropogenic climate change. Over on our Reefscapers Climate Change page, we are following developments very closely by curating the news reports from climate experts and marine scientists worldwide.

Reefscapers coral bleaching - before (March)

A healthy, fluorishing Reefscapers coral frame photographed in March…

Reefscapers coral bleaching - after (April)

… but just a few weeks later in April, the coral colonies had started to pale and fluoresce due to heat stress

Coral Bleaching Watch

We have been tracking NOAA’s Coral Reef Watch bleaching guidelines. Baa Atoll will move into “Alert Level 1” for 5-8 weeks, meaning “severe bleaching and mortality” is expected. It is imperative we track the effects of coral bleaching on our reefs in the coming weeks.

In March, moderate paling was observed in some colonies along Landaa’s House Reef. Towards the end of April, bleaching and fluorescence has been observed at all sites across Landaa, at depths from 1m-15m. Corals of the genus Acropora are bleaching more severely than other genera (as expected), with colonies in shallow water at the Water Villas and Elephant site almost completely bleached. Bleaching has also been noted in some Pocillopora and massive genera such as Porites. Our monitoring work will provide insights into coral resilience across sites and species, useful towards future allocations of frame and species.
From 25 to 27 April, we surveyed coral recruitment at 5 wild reef sites across Baa Atoll. Bleaching of both mature and juvenile colonies was recorded at all sites and both survey depths (5m and 10m).

Reefscapers coral bleaching Maldives HR32 HR90 (March-April)

Coral bleaching in our monitored colonies # HR32 (top) & HR90 (bottom)
📷 2024: March (left) – April (right)

Reefscapers coral bundling when bleached (A.hyacinthus)

Coral bundling of gametes, while bleached (Acropora hyacinthus)

Kuda Huraa

At Kuda Huraa this month, we transplanted 5 new coral frames, and monitored a further 90 mature frames at various sites around the island. As part of our bleaching mitigation work, we relocated a total of 130 frames (see below).

To see the progress of your frame, please visit our dedicated Four Seasons monitoring page where we upload new photos every 6 months or so.

Gamete Development & Coral Spawning

During April, our Kuda Huraa team conducted spawning monitoring of 3 sites over 7 days, totalling 25 hours in the water. Approximately 195 colonies across 8 different Acropora species were observed to spawn in April.

Looking back at our records from previous years, it is noteworthy that coral spawning seems to have occurred earlier (relative to the moon timings) than previous years. This is consistent with research that found earlier spawning times during periods of elevated water temperatures (Lin & Nozawa, 2023).

Although many colonies successfully spawned this month, there were still gravid colonies (corals with pink eggs) found in 2 species of Acropora, that are likely to spawn during the May new moon period.

Reefscapers coral spawning Maldives (April 2024)

CORDAP Maldives Coral Larval Restoration Training Program

The Reefscapers team had been kindly invited to join the CORDAP Maldives Coral Larval Restoration Training Program, led by Distinguished Professor Peter Harrison, and facilitated by The Maldives Coral Institute (MCI) and The Maldives Marine Research Institute (MMRI).

This month, coral restoration practitioners from around the Maldives came together to learn from Professor Harrison. The objective was to cover the biology of coral spawning, and learn how coral larvae collection and distribution can be used to repopulate damaged reef ecosystems. Our coral experts at Kuda Huraa were fortunate to represent Reefscapers throughout the workshop, and our Manager Charlie was also invited to present our spawning work and results of our paper, published last year. We were honoured to host the group on the House Reef for one night of spawning, so that gametes could be collected for fertilisation.
We are very grateful to Peter, his team and all the participants for an invaluable collaboration experience and exchange of marine knowledge. We look forward to more in the future!

BBC TV

We are proud to report that our project caught the attention of BBC TV producers, and a camera team joined us under the waves to film our work. While we are excited by the filming project, the shift we observed from healthy to bleached coral colonies was shocking, and should make for some dramatic documentary footage. This emphasised the importance of our relocation project, and we hope it increases the survival chances of some of our oldest coral colonies.

Reefscapers Maldives BBC coral film
Reefscapers Maldives BBC coral film

Maldives Coral Bleaching Season

April saw the inevitable start of coral bleaching around Kuda Huraa. From our observations, the first corals to start paling were species of Acropora (across our shallow 1-2m sites: Channel, Turtle, Water Villas).

  • On 7 April, we recorded pale colonies of 5 different Acopora species (at the Turtle site) that surprisingly turned fully bleached overnight.
  • Pocillopora colonies also started paling at the Water Villas, but are showing a higher resistance than Acropora at all other sites.
  • Our temperature logger data recorded consistent temperatures of 29-30°C at a depth of ~10m from March into April. Despite these elevated temperatures, we have not yet observed bleaching of colonies below 4m.
Bleached corals Maldives Reefscapers (Acropora muricata)

Bleaching in Acropora muricata 🗓️ 4 March – 29 April 🗓️ 

Bleached corals Maldives Reefscapers

Smaller coral colonies at shallow depth were the first to start bleaching

Bleached Coral Spawning

When corals bleach, they lose the microscopic algae that are the main energy source for coral polyps. If corals are bleached but were able to produce mature gametes, they can either preserve energy and reabsorb the gametes, or use their limited reserves to spawn. Of the 195 colonies that spawned this month, 56% of these (n=110) were either partially or fully bleached. Only three of these bleached colonies spawned alongside healthy colonies, the remainder spawned at the end of the month.

Interestingly, colonies of Acropora muricata were seen to spawn underdeveloped egg bundles (white, and smaller than is typical for the species). We will continue to monitor the health of these bleached colonies to see if spawning hinders the ability to recover.

Reefscapers coral spawning when bleached
Reefscapers coral spawning when bleached

Bleaching Mitigation Efforts

During April, our team continued the ambitious project of moving 260 of our most established frames to deeper, cooler waters. After moving 120 frames in March, the team continued into April. A total of 115 frames were moved with the barge this month, and 15 frames were moved with the pully-system to deeper locations on the House Reef. As bleaching had already started at the beginning of the month, some of our frames had to be moved while paling and fluorescing. Big thanks to Reefscapers founders Thomas & Marie, who joined Aku from Landaa to lend extra experienced hands to our relocation efforts.

Our team continued with the ongoing bleaching monitoring at 5 different sites around Kuda Huraa. It will be particularly interesting to see if the relocated frames will start to recover over the next few months.

Reefscapers relocating vulnerable corals Maldives