Reefscapers Diary 2021

Coral Propagation – Monthly Progress

At Landaa during December, we transplanted 75 new coral frames (59 guest-sponsored, 10 resort-sponsored, six online) including one incredibly generous sponsorship (with frames organised into a customised pattern). We used a total of 3454 coral fragments this month, and monitored (cleaned, repaired, photographed) a total of 356 frames at various sites around the island.

Due to the strong wave action that has periodically overturned some of our coral frames at Parrot Reef, we have relocated 100 out of 300 frames to a more sheltered area towards the turtle cage (at 4 to 7m depth). Thanks to our team of five volunteers (three on the boat and two in the water) who mastered the ‘hook’ method to great effect.

Annual Totals: at Landaa Giraavaru during 2021, we created 351 new coral frames, recycled 44 old frames, and monitored 3145 frames, adding an impressive total of 18,949 coral fragments back onto the reef.

At Kuda Huraa during December, we transplanted six recycled coral frames and seven new frames, using a total of 621 fragments (from eight different coral species).

Annual Totals: at Kuda Huraa during 2021, a total of 126 coral frames (new and recycled) were transplanted using 6848 coral fragments (from 21 different coral species), and we monitored a further 1028 frames.

• Water Villas (WV) – we relocated 159 frames this month, due to continued sand movement around the lagoon (a total of 933 frames have now been relocated this year). The dolphin frame shape is now under threat, comprising many healthy, mature coral colonies (important for spawning) and harbouring diverse fish and invertebrate populations.
• Blue Hole (BH) – coral colonies remain healthy.
• Channel (CH) – coral frames have been rearranged into lines, simplifying our mapping and monitoring work, and enhancing the aspect for resort guest snorkelling. Some frames have been removed, washed, recoated, and recycled. Some of our retransplanting efforts have been unsuccessful, despite close monitoring and using the most resilient coral species (Montipora digitifera, M. foliosa, Pocillopora damicornis, P. verrucosa, Porites species). Colonies have been lost to disease and overgrowth by algae.
• Sea Star (SS) – our warmest site, with low species diversity and some fish predation, however, the species transplanted here are consistently healthy and seem well-adapted to the conditions.
• House Reef (HR) – currently, the northern area (cool and deep) is our preferred site for newly transplanted coral frames.
• Spa island – this month, we removed the 14 frames from this site, to be relocated or recycled. They presented very few healthy colonies (of Porites cylindrica, Pocillopora damicornis, P. verrucosa).

Echinopora horrida (EHO)
Montipora digitata (MDI)
Pocillopora Meandrina (PME)
Pocillopora verrucosa (PVE)

Coral Plates in Aquarium One (plates KH01, KH02, KH05) and Aquarium Two (plates KH03, KH04, KH06)

• KH01 (Galaxea fascicularis; Acropora species replenished Sep-Dec 2021) – growing and healthy; added new fragments of A. tenuis.
• KH02 (G. fascicularis) – fragments have recovered. The plate was rotated two times this month.
• KH03 (Acropora species, replenished Oct-Dec 2021) – newest fragments are already well-encrusted to the plate; added new Acropora.
• KH04 (Acropora species, mushroom coral; replenished Oct-Nov 2021) – the small mushroom corals have adapted and started to grow.
• KH05 (G.fascicularis) – steady health; plate needs to be regularly cleaned of cyanobacteria.
• KH06 (G.fascicularis) – healthy fragments, fusing and growing. Fast-growing but delicate, requiring high irradiance and good water circulation to thrive. New polyps have started growing, indicating excellent environmental conditions for growth.

Reef Futures Virtual Event

The Coral Restoration Consortium (CRC) hosted a free two-part virtual gathering to disseminate new and interesting content to the world’s coral reef restoration community. We listened to the group’s presentations on the ‘latest advancements in holistic approaches, monitoring techniques, propagation, global coral restoration initiatives and more’ to identify how Reefscapers’ restoration efforts had evolved in comparison to other organisations around the world. An example of what Reefscapers has already identified and been working on over the years is reducing the genetic bottleneck of breeding F1 and F2 genets, by collecting coral fragments from a diverse reef environment encompassing the whole reef situated around the island (including a large depth range). Moreover, we have out-planted over half a million coral fragments to date, at Four Seasons Resorts Maldives, compared with smaller initiatives in other international regions planning to out-plant 10,000 fragments over 10 years.

Interest in Our Work

As a result of our recent exposure in local news sites, we have been in communication with a variety of Maldivian organisations with regards to our Reefscapers research, with particular interest in our coral spawning and settlement work. This has included:

• Mihaaru and Dhauru news websites,
• presenting to the International Ocean Institute,
• meeting with the Maldives Marine Research Institute (MMRI),
• meeting with Maldives University to increase our involvement in Maldivian Reef Ecosystems.

Using AI Technology to Analyse Coral Photographs

In order to identify coral growth and overall volume (since 2017), we have been using our in-house AI technology to analyse our small-sized coral frames (at Kuda Huraa and Landaa Giraavaru). This has revealed a steady increase in volume of both Acropora and Pocillopora species from 2017 to 2021.

 Acropora species

• Volume of growth = 1000 litres (at the start of 2020), increasing to 4000 litres by the end of 2021.
• Overall average survival rate = 88% of coral colonies (most frames show a 95% survival rate).
• Highest growth rates at sites: Dive Site, Blu Deep and Anchor Point.
• This species thrives along reef slopes (Suzuki et al., 2008).

 Pocillopora species

• Volume of growth = 5000 litres (at the start of 2020), increasing to 15,000 litres by the end of 2021.
• Overall average survival rate = 80% of coral colonies (most frames show a 90-95% survival rate).
• Highest growth rates at sites: Coral Trail, Parrot Reef, Turtle, Water Villas, Blu.
• This species thrives in shallow water reefs exposed to strong wave action.

Coral Propagation – Monthly Progress

At Landaa during November, we transplanted 26 new coral frames, sponsored by guests (16), the Resort (9), and online (1), using a total of 1311 coral fragments. We also monitored (cleaned, repaired, photographed) a further 238 coral frames at various sites around the island.

• Simon (our MDC Manager) and Margaux (our Coral Biologist) were interviewed by local news media – Dhauru and Mihaaru – to highlight the success of Reefscapers coral spawning and settlement research.
• The International Ocean Institute (Maldives Branch) reached out to us, to discuss the Reefscapers coral spawning and settlement work. We participated in an online presentation to inform participants about our work, sharing photos and video along with our results to date.

Coral Spawning

We have continued to monitor for new signs of coral spawning by carrying out night surveys from 20 to 25 November. Since 21 October, coral eggs have been sighted in five different species of Acropora, and we have successfully recorded coral spawning on 27 different frames (mainly at the Water Villas site).

Three spawning events were recorded this year (27 October and 24-25 November), and there may be additional events due to similar tidal patterns in October and November, plus reports of other spawning events in the Maldives. Following the two November spawning events, eggs have been observed in several Acropora species (A. gemmifera, A. tenuis, A. humilis, A. plantaginea). Additionally, we have observed that not all mature coral colonies of the same species have produced eggs (asynchronous spawning – weeks apart and for the same species – is a known phenomenon even within the same site).

Coral Plates in Aquarium One (plates KH01, KH02, KH05) and Aquarium Two (plates KH03, KH04, KH06)

• KH01 (Galaxea fascicularis; Acropora species replenished Sep-Nov 2021) – new fragments are starting to grow; additional fragments of Acropora plantaginea and tenuis were added, as the blue corals (Heliopora coerulea) did not survive.
• KH02 (G. fascicularis) – fragments are stressed and darker brown in colour.
• KH03 (Acropora species, replenished Oct-Nov 2021) – the newest fragments are already well-encrusted to the plate; replenished with additional Acropora fragments this month.
• KH04 (Acropora species, mushroom coral; replenished Oct-Nov 2021) – fragments are healthy. Two mushroom corals have been added (after three days of quarantine) and are adapting well.
• KH05 (G.fascicularis) – fragments are in good health. The plate continues to accumulate cyanobacteria, which is regularly removed.
• KH06 (G.fascicularis) – fragments are healthy and growing well.

Coral Propagation – Monthly Progress

At Landaa during October, we transplanted 1043 coral fragments onto 21 new coral frames (10 guest-sponsored, 10 hotel-sponsored, one online order). We also monitored (photographed, maintained) a total of 410 frames at various sites around Landaa Giraavaru, plus 30 old frames were recycled back onto the reef.

At Kuda Huraa this month, we transplanted 6 new coral frames and recycled a further 12 frames, using a total of 732 coral fragments (from 13 different coral species).

Water Villas (WV) – this site continues to be badly affected by the seasonally shifting sands in the lagoon, with one mid-October storm burying 17 frames overnight. We have been busy dismantling our aerial patterns, relocating 124 frames this month, bringing the yearly relocation total to 710 frames (including 30 recycled old frames).

The Dolphin-shape is at risk of the shifting sands, totalling 183 healthy frames that harbour a good diversity of mature coral colonies, with abundant resident populations of fish and invertebrates.
On 21 October, we spotted coral eggs on many mature colonies of Acropora tenuis. We hastily constructed several spawn-collection devices to harvest the eggs in-situ, but the spawning did not occur when predicted so we continued to monitor the corals closely. Changes in egg pigmentation were observed in Acropora tenuis, but the other Acropora hermaphroditic broadcasters were not yet close to spawning.

Blue Hole (BH) – we continue to remove the accumulated marine debris and drifting sea grass from this site, and the coral colonies remain healthy. On 27 October, mature coral eggs were spotted on colonies of Acropora secale (3m depth) and we observed coral spawning from 20:00 to 20:15 (Maldives time, GMT+5). We were able to harvest some eggs and placed them into our aquarium for observation, along with a dead coral skeleton as a settlement substrate. Some eggs were observed attached by 20:45 (30 mins after spawning) but we did not see coral larvae.
From our notes, we observed this spawning event occurred:
– 1.5 hours before the lowest tide (which was at 21:42);
– Seven days after the full moon (which was on 20 October);
– One day later than in Landaa Giraavaru (Baa Atoll).

Channel (CH) – 14 of the new monthly frames were located here, plus two mini coral frames, each with 19 fragments of Blue Coral (Heliopora coerulea, a reef-building octocoral with high resistance to thermo-stress and bleaching). A total of 54 frames were monitored and retransplanted (using fragments of Montipora digitata, Porites cylindrica and species of Acropora).

Sea Star (SS) – Aerial photographs of this site were taken to correct the QGIS location mapping, and we plan to construct a new aerial crab-shape.

House Reef (HR) – the temperature logger was redeployed on 8 October, and we removed two corallivorous predators (one Cushion starfish, one Crown of Thorns). The two new monthly coral frames at this site were transplanted with species of Acropora and Pocillopora verrucosa.

Coral Plates in Aquarium One (plates KH01, KH02, KH05) and Aquarium Two (plates KH03, KH04, KH06)

• KH01 (Galaxea fascicularis; Acropora species replenished Sep-Oct 2021) – added six new fragments of Heliopora coerulea.
• KH02 (G. fascicularis) – algal overgrowth has caused some coral tissue death.
• KH03 (Acropora species, replenished July 2021) – healthy and encrusting.
• KH04 (A.digitifera, A.millepora) – healthy and growing well.
• KH05 (G.fascicularis) – fragments continue to grow and fuse; cyanobacterial growth regularly removed.
• KH06 (G.fascicularis) – steady health, growing, fusing.

Preparation for Coral Spawning

This month, we took part in the second series of a two-day online coral larvae workshop in partnership with CSIRO, the MMRI and MUI (among others) to further understand and identify coral spawning events across the Maldives. This informative workshop detailed the use of coral larvae in reef restoration, to upscale future efforts. It is evident that sexual propagation will result in higher genetic diversity amongst species in comparison to asexual propagation. Moreover, corals are extremely fecund, meaning a large number of juvenile corals could be produced if mortality at early life stages of fertilisation and settlement are reduced. This technique could enhance coral propagation programs here in the Maldives, if the asexual technique is coupled with sexual broadcast spawning and rearing.

At Marine Savers, we have transplanted and grown many different species of corals over the years which are large enough to produce mature spawning colonies. Our large database allows us to pinpoint transplantation dates, identify age of maturity, track mature colonies, and record coral spawning across multiple years. This data can be used to ensure genetic diversity, as we can confirm gamete collections from different frames based on these dates.

To expand our knowledge of coral spawning around Landaa Giraavaru, we reviewed the data from our previously documented spawning events (2013 – 2020). It is incredibly difficult to predict when coral might spawn, therefore it is important to take note of tidal cycles, lunar cycles, and water temperatures from previous years, to be utilised as indicators for predicting spawning this year.

Coral Propagation – Monthly Progress

At Landaa during September, we used 342 individual coral fragments to transplant nine new coral frames (sponsored by guests and the resort) and a further 250 fragments were used for repairs and recycling.

Temperature Loggers

This month, we analysed the Sea Surface Temperature (SST) data from our temperature logger at Kuda Huraa’s House Reef site, and noted the following:

• The seasonal increase in SST during 2021 lasted from March-June (one month longer than we have recorded for previous years).
• Lowest SST was 27.2°C (28 January, 11:00 pm).
• Highest SST was 30.6°C (10 May, 5:00am).
• Overall, average House Reef SST (January to September 2021) is 29.1°C.
• Of all our sites, the House Reef recorded the lowest average SST during the critical May to June period, making it the preferred refuge.

At Kuda Huraa this month, a total of seven new coral frames were transplanted and deployed around Kuda Huraa. We focused our efforts on improving the frame layout in the Channel area, and relocating Water Villas frames due to seasonally shifting sands.

• Water Villas (WV) – Coral colonies remain healthy, with a little evidence of predation from corallivorous fish species. We relocated a total of 136 frames, as the seasonal water currents continue to shift sand around the island (corals on the lower bars of 10 frames suffered some mortality). This month’s new frames were sited to the North (away from the problem) using a variety of coral species (Pocillopora meandrina, Acropora austera, A. digitifera, A. gemmifera, A. hyacinthus, A. latistella, A. muricata, A. tenuis).
• House Reef (HR) – 59 frames were monitored (photographed, cleaned) and some were unburied from the shifting sands.
• Blue Hole (BH) – most coral colonies remain healthy, although drifting ocean debris tends to accumulate here, causing some mechanical damage.
• Channel (CH) – All the frames were rearranged into lines, enhancing the snorkel experience for guests, and simplifying our monitoring and mapping tasks. A total of 45 old frames were removed and brought ashore for cleaning and recycling.
• Channel – coral species list (18 species of 6 genera):
  • Acropora aspera, A. austera, A. digitifera, A. gemmifera, A. humilis, A. hyacinthus, A. latistella, A. muricata, A. secale;
  • Heliopora coerulea; Isopora palifera; Montipora foliosa, M. digitata;
  • Pocillopora damicornis, P. meandrina, P. verrucosa; Porites cylindrica, Porites rus.
• Sea Star (SS) – coral colonies are in good health; frames were fully remapped, and missing tags were noted (for future tagging and retransplanting).
• Sea Star – coral species list (11 species of two genera):
  • Acropora digitifera, A. hyacinthus, A. gemmifera, A. hemprichii, A. humilis, A. monticulosa,
  • Pocillopora damicornis, P. meandrina, P. verrucosa, P. elegans, P. eydouxi.

Coral Plates in Aquarium One (plates KH01, KH02, KH05) and Aquarium Two (plates KH03, KH04, KH06)

• KH01 (Galaxea fascicularis; Acropora species replenished September 2021) – suffered tissue loss in 90% of fragments (probably due to disease). The plate was removed, disinfected, and completely retransplanted with Galaxea fascicularis and Acropora fragments.
• KH02 (G. fascicularis) – healthy and adapting well to a new location within the aquarium.
• KH03 (Acropora species, replenished July 2021) – continuing to grow; the newest fragments are already well encrusted to the plate.
• KH04 (A.digitifera, A.millepora) – mainly healthy and growing (any dead fragments were removed).
• KH05 (G.fascicularis) – healthily growing and fusing. Cyanobacterial growth is removed regularly from the top of the plate.
• KH06 (G.fascicularis) – healthily growing and fusing.

Coral Experiments

Quiet this month, due to staff leave.

Coral Propagation – Monthly Progress

At Landaa during August, we used 1147 individual coral fragments to transplant 27 new coral frames, sponsored by guests (11) and the Resort (16), and we monitored a total of 132 sponsored frames around the island.
We have continued our frame relocation efforts, to optimise coral growth rates while ongoing work takes place around the island, and have cordoned off several areas for protection (using buoys and rebar). A total of 93 frames were retagged and remapped in QGIS, and 10 old frames were cleaned for recycling.

At Kuda Huraa this month, a total of six new coral frames and one recycled frame were transplanted and deployed around the island, mainly using fragments of Acropora and Pocillopora corals. 

• Water Villas (WV) – a total of 497 frames were monitored, and the photographs uploaded to our website for our kind sponsors to monitor the growth of their personal coral frame. Coral colonies remain healthy, and the site continues to preserve a high diversity of fish species. Loose ‘fragments of opportunity’ of Montipora foliosa were collected for later transplanting (at the Blue Hole).
• Blue Hole (BH) – most coral colonies (eight different species) present good health.
• Channel (CH) – before being photographed, frames were retransplanted with fragments of Pocillopora verrucosa, Montipora digitata and Porites cylindrica. Following extensive retagging and maintenance work, the remapping of the entire site was completed this month (600 frames). Some old frames were removed completely for recoating as recycled frames. Certain coral species are thriving (particularly Montipora digitifera, Pocillopora damicornis, Porites) and seem more resistant to algae, disease, and higher temperatures.

Coral Plates in Aquarium One (plates KH01, KH02, KH05) and Aquarium Two (plates KH03, KH04, KH06)

• KH01 (Galaxea fascicularis; Acropora species replenished July 2021) – fragments continue to grow and fuse. Most of the new fragments have started to encrust (any dead fragments were removed).
• KH02 (Galaxea fascicularis) – healthy and growing, especially the upper fragments closer to the light (so we rotated the plate).
• KH03 (Acropora species, replenished July 2021) – the newly introduced fragments are encrusting (any dead fragments were removed).
• KH04 ( digitifera, A. millepora) – mainly healthy and growing (any dead fragments were removed).
• KH05 (Galaxea fascicularis) – well adapted, continuing to grow and fuse. We cleaned a patch of bryozoans and cyanobacteria.
• KH06 (Galaxea fascicularis) – good health, fusing and growing.

Blue Coral Growth Experiment

Blue Coral (Heliopora coerulea) is a reef-building octocoral with high resistance to thermo-stress and bleaching (Richards et al., 2018) with warmer seawater temperatures promoting substrate colonisation (Guzman et al., 2019). In addition, species of Heliopora were one of two massive corals to affect the reef flat carbonate budget located in Huvhadoo Atoll (South Maldives) during the 2016 bleaching event (Ryan et al., 2019).

Blue coral possesses homologues of biomineralisation genes resembling that of hard corals (as Guzman) so it could be a key reef-building coral against future climatic changes. However, restoration efforts of large densities of H. coerulea should not inhibit the growth and recruitment of other coral species (Courtney et al., 2021, Artigenio et al., 2020; Guzman et al., 2019).

In order to continue expanding our coral restoration techniques, we have out-planted our first frame of Blue Coral.

On 13 August, we moved a small frame to the Al Barakat site (at 3m depth), and attached 14 coral fragments of H. coerulea. We will monitor the frame closely, and record information on health and bleaching. To track growth rates, we will take regular measurements for height, length, and width for each individual fragment.
The ecological volume is calculated using the formula: EVi = 3.14 * POWER (R,2)*H

Microfragmenting Experiment

During August, we started preliminary investigations using microfragments of Brain (honeycomb) coral, transplanted to a newly designed coral frame.

At Landaa’s Dive Site (5m depth), we harvested a healthy coral specimen of Diploastrea heliopora (taking less than 10% of the donor colony). The specimen was kept temporarily in our open-flow seawater tank, before being fragmented and super-glued onto the prototype microfragment frame. The frame consists of a flat panel with legs, for ‘wedging’ into hard substrate to ensure the frame and future coral growth becomes integrated into the reef. Each fragment was labelled (1 – 12), assessed for health and bleaching, and then photographed for surface area analysis, using FIJI by Image-J.

Coral Propagation – Monthly Progress

At Landaa, we transplanted 30 new coral frames, sponsored by guests (15), the Resort (13) and online (2), using a total of 1537 individual coral propagation fragments. We also monitored (cleaned and photographed) a total of 135 frames at various sites around the island, and sent out the regular updates to our kind sponsors.

We also focused on recycling and relocating older coral frames, with the help of a simple ‘raft’ made from three unused paddleboards. Frames were cleaned of dead corals and algae, and replanted with healthy new coral fragments (mainly species of Acropora and Pocillopora). This way, we added a total of 790 new coral fragments to the reefs around Landaa (including Bissie’s Reef, and select frames at the Coral Trail and Dive Site). In addition, we removed and cleaned a further 50 frames and sent them to Voavah for recycling.

A total of 1533 new fragments were transplanted, from a variety of coral species (Pocillopora verrucosa, P. meandrina, Acropora tenuis, A. vermiculata, A. digitifera, A. gemmifera, a. humilis, A. loripes, A. muricata, A. hyacinthus, A. grandis).

• Water Villas – corals remain healthy; any broken colonies from our relocation exercise were quickly retransplanted onto other frames.
• Turtle site – two additional frames were lost due to shifting lagoon sands (bringing the total to six).
• Blue Hole – mostly healthy, with some mortality. We harvested healthy donor fragments for the travel-group frames from here (subsequently deployed at the House Reef site).
• Channel – continued remapping the northern area (230 frames now mapped); cleaned affected frames of algae; repositioned 40 sunken frames.
• Sea Star – corals are very healthy; some Pocillopora colonies were found broken or unattached from their frames (due to unknown reasons) so these were reattached.
• House Reef – one Pillow starfish and two Crown of Thorns starfish (COTs) were removed; 24 frames have been recently deployed in this site; dedication tags were added to 15 frames.
• A heart-shaped frame [KH2833] was transplanted with Pocillopora fragments to commemorate PADI Women’s Dive Day (12 July).

Coral Plates in Aquarium One (plates KH01, KH02, KH05) and Aquarium Two (plates KH03, KH04, KH06)

• KH01 (Galaxea fascicularis; Acropora species replenished July 2021) – original fragments remain healthy and fusing. Twenty new Acropora fragments were attached to the plate (A. tenuis, A. digitifera, A. gemmifera, A. hyacynthus).
• KH02 (G.fascicularis) – overall healthy; upper fragments (closer to the light source) continue to grow faster.
• KH03 (Acropora species, replenished July 2021) – original fragments are in good health; 15 new Acropora fragments were added to the plate (A. tenuis, A. vermiculata, A. digitifera).
• KH04 (A. digitifera, A. millepora) – healthy and growing well.
• KH05 (G.fascicularis) – well-adapted, continuing to grow and fuse.
• HK06 (G.fascicularis, new Feb-21) – healthy, growing, fusing.

Coral Bleaching Experiment

A fragment of Galaxea fascicularis was placed into our aquarium and allowed to acclimatise for 24 hours before starting our coral bleaching observations. Coral bleaching occurs due to elevated temperature (and light intensity), leading to photo-oxidative stress within the coral.
After a few days of increased water temperature, the coral tissue demonstrated a high degree of swelling, likely due to the coral expelling symbionts (no additional nutrients were added to the water, which have been shown to effect polyp extension and coenenchyma swelling).

• Morris et al. (2019) – explained that nutritional mechanisms may be a factor, in which a “coral–Symbiodiniaceae symbiosis shifts from a mutualistic to a parasitic relationship under thermal stress”.
• Landsberg et al. (2020) – identified the disruption of zooxanthellae physiology in ‘Stony Coral Tissue Loss Disease’ and described similar ‘swelling’ (and necrosis).
• Kerswell & Jones (2003) – concluded that low-salinity seawater “involves impairment of the capacity of the algal symbiont for photosynthesis” that could prompt the dissociation of the coral-algal relationship during unfavourable conditions.
• Morabito et al. (2013) – revealed that when jellyfish (Cnidarian family, same as corals) are exposed to hypoosmotic media, the cells ‘swell’ within minutes.

Benthic Survey

On 12 July, we conducted a rapid health assessment of the east side of Landaa by using quadrats along the reef crest (see map ‘Points’). Within a given area, we can estimate percentage cover of specific categories of benthic communities (hard coral, soft coral, sponge, algae, etc).
We used 14 quadrats (2 m x 2 m) along a 1.5 km radius. Unknown species were photographed for later identification as part of our time-effective estimation (a future LIT survey would be more accurate).

Results revealed:

• Most common hard coral species: Porites, Pocillopora, Brain corals, Galaxea fascicularis.
• Locations one to ten showed a higher degree of coral diversity.
• Location 5 revealed the highest degree of benthic diversity (14 species).

Temperature loggers

This month, we retrieved our temperature loggers from the lagoon at Kuda Huraa, and plotted temperature profiles for the recorded sea surface temperatures (SST) from 30 April to 2 July 2021.

• The temperatures decreased significantly after 26 May.
• Highest recorded temperature was at the Sea Star site.
• The SST averages from the three sites are very similar.
• Compared to March-April, SSTs for May-June decreased by 0.4°C (consistent with regional SST values reported by NOAA Coral Reef Watch).

Coral Propagation – Monthly Progress

June was a busy month for us at Landaa, transplanting 56 new coral frames (using 4,000+ individual coral fragments) plus retransplanting 37 existing frames (3,000+ fragments), plus recycling a further 20 frames from the ‘Moon’ site (700+ fragments). A big THANK YOU to our resort colleagues for all their invaluable assistance in our efforts to regenerate the reefs this month. In addition, we also monitored 380 frames at various sites around the island, and updated the QGIS mapping.

At Kuda Hura, we transplanted two new coral frames and retransplanted eight existing frames. We also continued our Coral Watch monitoring, relocated (and cleaned) 310 frames at the Water Villas, and remapped (and cleaned) 89 frames at the Channel site. While monitoring the reefs, we spotted and removed seven crown of thorns starfish (COTs) plus a pillow starfish (Clucita sp.), which can be destructive to living corals.

• Water Villas site – our frames remain healthy, and no additional bleaching has been observed. The site continues to be an important nursery area for a great diversity of reef fish.
• Blue Hole site – most of the coral colonies remain stressed (either bleaching or fluorescing) and a few of the colonies have died.
• Channel site – our frames continue to fight against the smothering cyanobacteria and overgrowth of algae.
• Sea Star site – species of both Pocillopora and Acropora are thriving, and all colonies have regained their colour since the paling observed in March.
• House Reef site – on 14 June, our resort Dive Team colleagues helped with a new coral frame in the shape of a ‘Cinderella Carriage’, transplanted with 200+ fragments of Pocillopora. The growth and encrustation of the fragments will be closely monitored in the upcoming months.

Coral Plates in Aquarium One (plates KH01, KH02, KH05) and Aquarium Two (plates KH03, KH04, KH06)

Overall, the coral plates in both aquaria remain healthy. Plates in Aquarium-Two continue to collect more algae, and weekly cleaning is necessary to prevent coral mortality.

• KH01 (Acropora digitifera, A.millepora, Galaxea fascicularis) – fragments remain very healthy and encrusting.
• KH02 (G.fascicularis) – healthy, with significant growth (especially towards the top of the plate, with more light). Crabs broke one fragment, which we promptly reattached.
• KH03 (A.valida) – overall good health, however, the one bleached fragment is now almost dead.
• KH04 (A. digitifera, A. millepora) – healthy and encrusting correctly, despite continuing to present significantly more algal growth than the other plates.
• KH05 (G.fascicularis) – the fragments continue to adapt to last month’s 90-degree rotation.
• HK06 (G.fascicularis, new Feb-21) – continuing to grow steadily; the six lowest fragments have now fused.

Coral Bleaching Experiment

In order to identify the threshold at which a coral species can recover post-bleaching, we are trialling various parameters to promote recovery. Once the coral fragment has bleached, the heater is turned off and the water flow turned on, to allow the water to return to ambient ocean temperature. After a few days, the coral fragment displayed no signs of recovery, likely because the seawater is filtered (50um), and most zooplankton and rotifers are larger than this (food shortage could have hindered early recovery).

Therefore, after four days, we added 450ml of rotifers into the tank and turned off the flow for 24 hours to allow the coral to feed. Coral polyp movement was not visible after a few days, however, this is likely due to the fact the coral had died before feeding. Next, we hope to trial a variety of post-bleaching ‘feeding’ options in the coming months.

Coral Larval Workshop

This month, our coral biologist took part in a two-day workshop run by CSIRO and the Maldives Marine Research Institute. This was primarily to understand the best coral larvae collection protocols and to gain a more in-depth knowledge of rearing larvae for large scale restoration on Maldivian reefs.
One of the key benefits from this workshop was the collaboration with other scientists within the Maldives, to help identify spawning events (which are dependent on coral species and atoll).

The workshop consisted of:

1. Coral Reproduction
2. Larval Cultivation
3. Technical processes of upscaling in previous countries
4. Ability to conduct larval restoration in Maldives

   
   Coral Cooling Experiment

   The previous analysis from our cooling experiment (at one month) revealed that outside temperature significantly affected the closed-tank system water temperature. Fluctuations in water temperature were more variable in comparison to the open-flow system in which seawater temperature remained fairly constant. In the open-flow system, microfragment fusion of Galaxea was also seen, and fragments have self-attached to the plate, in comparison to the closed flow system in which Galaxea did not display self-attachment or fusion.

   We have now started a new experiment in which both tanks are in closed-flow systems. One tank will be aerated overnight, to determine if this cools the water mass.

Bleaching Monitoring Surveys (Coral Watch)

On 15 May, we started our Coral Watch surveys at the Water Villas site, and will expand to other sites throughout June. At each site, 24 selected healthy coral colonies of four different species (both robust and less resilient species) will be monitored weekly (ideally). We will photograph each colony and assign colour codes.

From our initial results, we can see that colonies of Acropora tenuis and A. humilis remain healthy, with no signs of paling or bleaching (photos, below).

However, aside from our official survey sites, we have observed some coral colonies of various species start to show signs of stress. During the second week of May, colonies of A. valida were observed fluorescing, which increased during the month in other Acropora species, and was seen alongside some paling colonies (severe bleaching has not been yet observed.)

Bleaching Alerts

According to the NOAA Bleaching Alerts, North Malé atoll changed from “Watch” to “Warning” (on 10 May) before returning to “Watch” status (20 May). For the first days of May, NOAA reported sea surface temperature (SST) values above 30°C, with an increase of 0.2 to 0.5°C compared to April. The lower air temperatures and sunlight levels have lowered the bleaching risks, although a few coral colonies have been observed fluorescing and paling.

Coral Plates in Aquarium One (plates KH01, KH02, KH05) and Aquarium Two (plates KH03, KH04, KH06)

Overall, the coral plates in both aquaria remain healthy. Plates in Aquarium-Two continue to collect more algae, and weekly cleaning is necessary to prevent coral mortality.

• KH01 (Acropora digitifera, millepora, Galaxea fascicularis) – healthy, growing steadily and fusing.
• KH02 (Galaxea fascicularis) – healthy and encrusting successfully.
• KH03 (Acropora valida) – 26% of the fragments present old mortality. The other fragments continue to calcify and grow steadily.
• KH04 (replenished December, digitifera, A. millepora) – although this plate is the most overgrown with algae, the fragments are healthy and encrusting.
• KH05 (Galaxea fascicularis) – continues to grow steadily (we rotate regularly for even light distribution).
• HK06 (Galaxea fascicularis, new Feb-21) – remains healthy (we rotate regularly for even light distribution).

Temperature Loggers

We retrieved our temperature loggers from Kuda Huraa’s lagoon (at the Water Villas, Channel, and Sea Star sites) and plotted the data to visualise the seasonal increases in ocean temperatures. The maximum recorded temperatures peaked during the first week of April at the Water Villas site.

Coral Plates in Aquarium One (plates KH01, KH02, KH05) and Aquarium Two (plates KH03, KH04, KH06)

Our coral plates in both aquaria remain healthy, and we continue to perform weekly cleaning (Aquarium Two suffers more from algal growth). Most of the coral fragments in Aquarium One have an obvious growth direction towards the light source, so we are regularly rotating the affected plates.

• KH01 (Acropora digitifera, millepora, Galaxea fascicularis) – continues to grow steadily. The fragments of A. millepora continue to fuse, and the Galaxea (added in November) remain healthy.
• KH02 (Galaxea fascicularis) – healthy and growing.
• KH03 (Acropora valida) – 4 dead fragments overgrown with algae; 2 fragments with partial bleaching.
• KH04 (replenished December, digitifera, A. millepora) – 8 dead fragments overgrown with algae at the bottom of the pate.
• KH05 (Galaxea fascicularis) – growing steadily, especially the upper fragments (more light).
• HK06 (Galaxea fascicularis, new Feb-21) – continuing to grow well, with encrusted teeth.

Gulhi Falhu Coral Rescue

This month, our Kuda Huraa team conducted a mass coral collection at the industrialised zone in Gulhi Falhu, rescuing corals in danger of becoming smothered by the dredging and land reclamation in the area. We collected 250-300 colonies of various species of Acropora & Pocillopora colonies, to be retransplanted at various sites around Kuda Huraa.
Most of the rescued coral colonies survived the harvesting and transportation, and have started to stabilise in their new location at the Blue Hole site, which acts as a natural refuge and coral nursery thanks to the depth and good water flow.

At the House Reef, we retransplanted some of the rescued Gulhi Falhu colonies to our existing frames, and also to solid rock substrate in the area.

Coral Plates in Aquarium One (plates KH01, KH02, KH05) and Aquarium Two (plates KH03, KH04, KH06)

Overall, our experimental coral plates remain healthy. Cleaning is performed every 3 days to prevent the accumulation of algae on the plates and in the aquarium.

• KH01 (Acropora digitifera, A.millepora, Galaxea fascicularis) – growing steadily; the fragments of A. millepora continue to fuse. The Galaxea fragments added in November remain healthy and are continuing to encrust and expand on the plate.
• KH02 (Galaxea fascicularis) – making a steady recovery. Weekly rotation of the plate is performed to ensure all fragments receive enough light, and we continue to take weekly monitoring photos to monitor recovery.
• KH03 (Acropora valida) – 2 of the 8 older fragments lost tissue and died; the 16 newer fragments are healthy, gradually calcifying and encrusting.
• KH04 (replenished December, digitifera, A. millepora) – continuing to grow steadily and encrust on the plate; 2 fragments show tissue loss and algal growth
• KH05 (Galaxea fascicularis) – – healthy and growing steadily; some encrusting and fusing together. We added new fragments to the lower parts of the plate.
• HK06 (Galaxea fascicularis, new Feb-21) – all 14 fragments are encrusting on the plate. We are photographing weekly to closely monitor the encrusting process.

Coral Propagation – Monthly Progress

At Landaa during February, we transplanted 33 new coral frames and sited them in the lagoon around the resort.

At Kuda Huraa this month, we transplanted 3 new sponsored frames and recycled a further 6 frames. We focused our monitoring efforts on the Channel and Water Villas sites, working to reduce the effects of the shifting lagoon sands, which have caused some mortality on the lower coral colonies. We are also on the lookout for any corallivorous COTs (crown-of-thorns starfish).

On Valentine’s Day, we transplanted two special heart-shaped frames with Pocillopora, made by Kuda Huraa’s Dive Team.

At the Channel site, with have started a mass re-transplantation project, replacing any dead coral colonies with new Pocillopora fragments, replacing missing tags and remapping the GPS co-ordinates. Any unmapped frames without tags are being relabelled with ‘RK’ recycle tags.

Artificial Intelligence and Coral Identification

Read the full project history of our autonomous catamaran and AI coral identification project over at Reefscapers AI-4Corals.

We started training a new AI software model to detect the shape of corals on monitoring photographs. The existing model is useful for small colonies, but they start to merge with each other as they grow, making the monitoring of individual colonies impossible. Therefore, we hope that this new model will be able to measure total surface cover.

Bleaching Alerts

As we approach the hottest part of the year, we will be closely monitoring the NOAA’s Bleaching Alerts. Every year, this resource is consulted to allow us to prepare for the annual rise in sea surface temperature.

The latest NOAA model predicts “Watch” status in the Maldives for weeks 5-8 (from the end of February), and “Watch/Warning” during weeks 9-12. This is a marked improvement from the predictions at the same time last year, which predicted “Alert Level 2” for May 2020 (although in reality, the highest rating thankfully only averaged “Warning”).

Coral Plates in Aquarium One (plates KH01, KH02, KH05) and Aquarium Two (plates KH03, KH04)

Overall, the coral plates in both aquaria remain healthy. We perform weekly cleaning of algae to prevent the corals from being smothered.

• KH01 (Acropora digitifera, A.millepora, Galaxea fascicularis) – Growing steadily. The A. millepora fragments continue to fuse; the Galaxea fascicularis (added in November) are healthy and encrusting to the plate.
• KH02 (Galaxea fascicularis) – This plate was transplanted onto a frame in the Water Villa area, as it had been thriving in the aquarium. It did not adjust to the new environment, however, and bleached almost entirely. It was subsequently returned to Aquarium 1, and is making a steady recovery. Weekly photos are being taken to monitor the recovery of the fragments; we are assessing the relocation options.
• KH03 (Acropora valida) – The 8 older coral fragments continue to grow and encrust steadily. One fragment shows partial death with algal growth; the 16 newer fragments are gradually calcifying and encrusting.
• KH04 (replenished December, digitifera, A. millepora) – Continuing to grow steadily and encrust on the plate. Fragments that were planted as both bases and tips are growing equally well.
• KH05 (Galaxea fascicularis) – Healthy overall, with the uppermost fragments growing faster than the lower shaded fragments.
• HK06 (Galaxea fascicularis, new Feb-21) – Encrusting and healthy. Weekly photos are taken to record the encrusting period of 3 particular fragments.

Woodstock Presentation

On 24 February, Simon and Gaetan held a Zoom meeting with students and alumni of Woodstock School (India).

This session was designed to showcase the work conducted at the Marine Discovery Centre and included a tour of our facilities, some short educational videos, and a question-and-answer session.

The recorded Zoom call can be viewed here on YouTube (and embedded below).

… on a mini-frame housed in a marine aquarium (Kuda Huraa).

Coral Propagation – Monthly Progress

At Landaa during January, we transplanted 24 new coral frames and monitored a total of 397 existing frames (mainly at the Dive and Water Villas sites).

At Kuda Huraa, we transplanted 10 new coral frames and recycled 2 of our old frames with fresh coral fragments (mainly using Acropora digitifera and A. tenuis). We continue to mitigate against sand accumulation by relocating any affected frames, although we have suffered some coral mortality. We also removed 3 crown of thorns starfish (COTs) that had made their home at the Water Villas site and were feasting on our coral frames.

At the House Reef site, we have continued monitoring and mapping our frames, and we observed that frames relocated from the Blue Hole are growing very well.

Crown of thorns starfish (COTs) are deadly to corals.
Photographed on our coral frames at Kuda Huraa (January 2021)

Artificial Intelligence and Coral Identification

Read the full project history of our autonomous catamaran and AI coral identification project over at Reefscapers AI-4Corals.

We have developed an inhouse software program to visualise all the information generated by our Artificial Intelligence analysis. It will be used internally by our Coral biologists, but we also hope to expand the data that is presented online to our coral frame sponsors.

Features of our program:

• Run Analysis – updates the database with data from any new coral frame photographs.
• Display Results – shows ‘bounding boxes’ of the coral fragments for a specific frame, and the growth in overall coral volume on the frame.
• Statistics – generates charts on the whole restoration program. Currently we have four options:
  1. Survival rates: Compares data for Pocillopora and Acropora in two different geographical areas (or on custom sets of frames).
  2. Mortality by zone: coral mortality over time, to identify abnormal events (bleaching, or local disturbances).
  3. Growth rates: distribution by geographical area and by genus.
  4. Volume: evolution of live and dead coral volume on the frames.

Coral Plates in Aquarium One (plates KH01, KH02, KH05) and Aquarium Two (plates KH03, KH04)

All 5 coral plates in both aquaria are regularly cleaned to remove algae. There were a few mortalities, and the crabs continue to push the fragments out, but the plates remain healthy overall.

• KH01 – (recently replenished) – fragments of Acropora millepora just beginning to fuse. The fragments of Galaxea fascicularis that were added last month remain healthy and are starting to encrust.
• KH02 – (exclusively Galaxea fascicularis) – showing a little mortality, so we have rotated the plate several times to allow all fragments to receive more light.
• KH03 – thoroughly cleaned of algae. The calcified areas are growing and about to fuse. The fragments of Acropora valida remain healthy and continue to grow, although they haven’t yet calcified onto the plate.
• KH04 (replenished December) – also cleaned of algae. Only two original fragments remain (due to the loss from algal overgrowth) and of the 11 newly transplanted fragments, 4 have started to calcify onto the plate (photos, below).
• KH05 (exclusively Galaxea fascicularis) – 1 fragment died after bleaching, but the others have now regained a healthy colouration and continue to grow (2 fragments are encrusting).

Coral plate (KH01) showing fragments of Acropora millepora, fusing (left) and encrusting (right)