Monthly report updates from our Reefscapers coral biologists at Kuda Huraa and Landaa Giraavaru.

You may also be interested in:

  • previous yearbooks from 2016 – 2020 (including our extensive 2016 coral bleaching report);
  • sponsoring your very own coral frame as part of our Reefscapers coral propagation and reef regeneration projects;
  • viewing the latest photographs of your coral frame (uploaded every 6 months) – see our Coral Frame Collection.
Reefscapers coral reef propagation Maldives

Reefscapers Diary August 2021

Reefscapers Acropora coral colonies

Close-up detail of a ‘massive’ coral

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.
Reefscapers Acropora coral species artificial reef propagation Maldives

Various species of Acropora corals, growing on our Reefscapers coral frames

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.

Reefscapers Diary July 2021

Reefscapers Acropora coral colonies

Monitoring for signs of coral bleaching – Acropora colonies on our frames, photographed 1 month apart (May-July 2021) at Kuda Huraa

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.

At Kuda Huraa, we transplanted a total of 19 new coral frames (9 frames on a single day, thanks to the generous support of a travel-group). We also recycled three old coral frames, monitored 16 frames, retagged 38 frames, and completed the relocation and remapping of the frames at the Water Villas site.

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.
Reefscapers coral quadrat survey sites Maldives

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).

Reefscapers Diary June 2021

Reefscapers healthy Acropora

Healthy Acropora growing on our frames, photographed 1 month apart (May-June 2021) Kuda Huraa

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)
Reefscapers coralwatch Acropora Maldives

Coralwatch health chart – colour range of Acropora humilis corals

We started our Coral Watch surveys in May at the Water Villas site, and expanded to other sites around Kuda Huraa this month.

A total of 174 colonies from 68 frames have been monitored and photographed each week since mid-May and the 1200 photos from 11 surveys were individually analysed with Coral Watch methodology (recording the lightest and darkest colour for each coral colony in each survey).

  • 7% coral colonies were identified as bleached/dead, mostly due to disease or overgrowth (cyanobacteria or filamentous algae) and not due to increased ocean temperatures.
  • 59% coral colonies presented paling during one or more of the surveys; 41% were healthy throughout.
  • Coral health by species: Acropora hyacinthus (55% healthy), digitifera (39%), A. humilis (23%) and A. tenuis (21%).
  • Our best site for coral health and species diversity is the Water Villas.
Reefscapers coralwatch Maldives
Reefscapers CoralWatch bleaching evolution of A.digitifera, Maldives

Bleaching evolution of A.digitifera, growing on Reefscapers coral frames [photographed weekly, May-June 2021, Kuda Huraa]

Reefscapers Diary May 2021

Reefscapers Acropora digitifera bleaching Maldives

Acropora digitifera colony – coral bleaching over 10 days (lab conditions)

Coral Propagation – Monthly Progress

At Landaa during May, a total of 18 new coral frames were transplanted, sponsored by guests (6), online (1) and the Resort (11). We also monitored (cleaned, repaired, photographed) a total of 669 coral frames.

At Kuda Huraa, we transplanted 280 coral fragments on five frames, and we maintained the frames around the Water Villas. During the middle of May, we experienced a period of bad weather caused by the unusually powerful Cyclone Tauktae, which increased the movement of sand around the island. We had to relocate 140 Water Villas frames for protection from the shifting sands (four small frames were lost), delaying some of our Reefscapers coral propagation and monitoring work.

At the Blue Hole site, many of the coral colonies were paling and fluorescing, and a few colonies had died. At the Channel site, there was some coral bleaching and mortality; Montipora digitata continues to proliferate, outcompeting the other species. We also observed some areas of poor water circulation, which leads to higher water temperatures and lower oxygen levels, and results in algal overgrowth and the presence of cyanobacteria.

Reefscapers coral frames healthy corals

Healthy corals growing on our reefscapers coral frames (May 2021)

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.)

Reefscapers coral frames Acropora humilis (May 15th & 26th)

Acropora humilis (May 15th & 26th)

Reefscapers coral frames Acropora tenuis (May 15th & 26th)

Acropora tenuis (May 15th & 26th)

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.

Reefscapers coral bleaching Acropora valida

Coral bleaching – Acropora valida

Reefscapers coral frame Acropora digitifera colony

Coral paling – Acropora digitifera

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).

Reefscapers Coral-Cooling Experiment

Due to the increased threat of climate change to coral reefs exacerbated by warming oceans, we are conducting ongoing experiments to study the overnight cooling of a water mass. The key aim was to identify how long it takes a mass of water to then reach ambient seawater temperature again, post-cooling.

Newton’s Law of Cooling’: the temperature of a body changes at a rate proportional to the difference in temperature between the body and its surroundings; i.e., the rate at which a body loses heat is directly proportional to the difference between the temperature of the body and its surroundings. (This is highly dependent on the nature of the material and the surface area of the body).

Method

We used two outdoor water tanks (white in colour), connected to a constant ocean water flow, and fitted with HOBO temperature loggers. A pump was used to continually stir the water, to distribute the heat evenly. We used an additional temperature logger to record the ambient air temperature.

  • Tank 1: ‘Open Flow’ system with constant flow of seawater.
  • Tank 2: ‘Closed Flow’ system, which was open during the day and closed overnight (with a stirring pump).

Five fragments of Acropora tenuis and five fragments of Galaxea fascicularis were placed in each Tank, a total of 10 fragments per species.

  • The surface area (SA) for Galaxea was calculated by analysing photographs using FIJI by Image J.
  • Growth rates for Acropora were monitored every two weeks using a series of Height, Width and Length to determine ecological volume using the equation: 3.14*POWER(R,2)*Height

Week 1 – The Tank 2 ‘Closed Flow’ cooled overnight, and took 2 to 3 hours to warm to ambient ocean temperature once the flow was opened in the morning. As expected, when the air temperature was low, the water temperature remained lower as well. (The temperature spikes are caused by the morning inflow of warmer water, before it became mixed into the water mass.)

Week 2 revised methodology – Tank 2: now completely closed, to identify the warming rate of the water mass. As expected, this time the water remained cool for much longer, so we will study this in upcoming weeks.

Results of Our Growth Rate Analysis

Following a period of rain, we used a refractometer to test the salinity (as expected, salinity was slightly reduced in the closed-system Tank 2).

  • Tank 1: Galaxea +7%; Acropora +1%; salinity 32 PPT.
  • Tank 2: Galaxea +1%; Acropora +8%; salinity 31 PPT.
  • Galaxea – our results correspond to published studies, showing decreased growth rates in the absence of water flow (Schutter et al., 2010), perhaps due to decreased feeding ability (Wijgerde et al., 2012).
  • Acropora – by contrast, our results showed that Acropora preferred the closed flow system. This is contrary to published literature that shows a consistent flow of water does increase growth rates. (However, our experiments ran for a short time period of just 2 weeks, so are likely unrepresentative of long-term growth rates.)
  • See our results (below), plotting the temperatures for week 1 and week 2, and analysing the growth of both coral species in both tank configurations.
Reefscapers Maldives coral cooling expt wk1

Temperature plots, week 1

Reefscapers Maldives coral cooling expt wk2

Temperature plots, week 2

Reefscapers Diary April 2021

Reefscapers coral fragments new (right) and encrusted (left)

Reefscapers coral fragments – encrusted (left); newly transplanted (right).

Coral Propagation – Monthly Progress

At Landaa during April, we monitored a total of 343 coral frames around the island, and transplanted 24 new frames (9 sponsored by guests, 15 by the Resort).

At Kuda Huraa, we transplanted 4 new coral frames, recycled 5 of our older frames, and monitored a total of 185 existing frames (mainly at the Water Villas site). We spotted (and removed) several Crown of Thorns starfish (COTs) eating our corals, and we relocated a total of 102 frames to protect them from shifting sands and increased sedimentation.

Corals at the House Reef site and the deep Blue Hole refuge (rescued Gulhi Falhu corals) are healthy and remain unaffected by  sand sedimentation and the seasonally elevated ocean temperatures.

Microfragmenting Trial – Studying Surface Area Growth Rates

During April, we started a new experiment to build on our micro-fragmenting coral propagation techniques explored in 2019-2020.

Experiments using “massive” coral species are often overlooked due to their slow growth rates, so this is an important area for us to explore, given their apparent resilience to warmer temperatures.

Read more: Micro-fragment Techniques in Coral Propagation.

Coral bleaching Maldives alerts NOAA

Bleaching Alerts – The NOAA coral bleaching alerts system categorises Maldives in “Watch” status for April-May, rising to “Warning” for June. Currently, we have not observed any coral bleaching on the natural reef or our coral frames.

Reefscapers coral fragments recovering from bleaching and starting to encrust

Coral fragments recovering from initial bleaching (due to stress) and starting to encrust

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.

Ocean temperatures at 4 sites April 2021 Maldives

Ocean temperatures for the month of April 2021, at 4 different sites around the lagoon at Kuda Huraa

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.

Reefscapers Diary March 2021

Reefscapers artificial reefs Maldives house reef

Healthy coral frames photographed this month at Kuda Huraa’s House Reef site

Coral Propagation – Monthly Progress

During March at Landaa, we transplanted 14 new coral frames, and at Kuda Huraa a total of 7 new frames were located to the lagoon.
We are closely monitoring the health of our frames and currently, none of our colonies present any bleaching (as has been recorded elsewhere in the Maldives).
The frames at the Water Villas site can become buried by the shifting sands, but the seasonal thunderstorms are now pushing the sand in the opposite direction. We have now been focusing on CoralWatch monitoring, looking out for signs of bleaching (the flat frames here are an important source of coral fragments for our day-to-day reef reclamation work).

Bleaching Alerts – The global NOAA Bleaching Alerts lists the Maldives’ Baa Atoll at “Watch” status, rising to “Warning” in the upcoming weeks as ocean surface temperatures are expected to rise seasonally. Malé atoll remains in “Watch” status, with elevated temperatures expected to peak at levels lower than last year’s peak.

NOAA bleaching alerts Maldives

2021 NOAA coral bleaching alerts for the Maldives

Reefscapers artificial reefs Maldives healthy coral frame Channel

Healthy coral frames at Kuda Huraa’s Channel site

Reefscapers artificial reefs Maldives water villas

Healthy coral frames at Kuda Huraa’s Water Villas site

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.

Reefscapers coral rescue Maldives Gulhi Falhu
Reefscapers coral rescue Maldives Gulhi Falhu

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.

Reefscapers Diary February 2021

Reefscapers coral frames Valentine hearts Maldives

Reefscapers coral frames – Valentine hearts

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.

Reefscapers healthy coral propagation colonies

Healthy coral colonies photographed on our frames this month

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.

Reefscapers AI training data coral cover

AI training data – detecting total coral cover for larger colonies

Reefscapers AI data analysis coral volumes

AI data analysis – total coral volumes

Reefscapers AI species ID

Identifying coral species using AI

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”).

NOAA coral bleaching alerts Maldives (2020)

2020 NOAA coral bleaching alerts Maldives

NOAA coral bleaching alerts Maldives (2021)

2021 NOAA coral bleaching alerts Maldives

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).

Reefscapers Diary January 2021

Reefscapers coral fragments encrusting

Coral fragments, healthily encrusting over their cable ties …

Reefscapers coral fragments encrusting

… 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.

Reefscapers coral frames shifting sands

Shifting sands can be a problem caused by seasonal currents, stormy weather or construction/dredging work.

Reefscapers crown of thorns starfish

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.
AI software data analysis coral propagation reef regeneration

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).
Reefscapers coral plate (KH01) A.milepora fusing (left) and encrusting (right)

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

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