Monthly report updates from our Reefscapers coral biologists at Kuda Huraa and Landaa Guraavaru.
You may also be interested in our extensive report on Coral Bleaching (2016), last year’s Reefscapers Diary (2017), and the public gallery Coral Frame Collection to view photographs of your own sponsored coral frame as part of our Reefscapers coral propagation project.
During January, at Landaa Giraavaru we made 33 new coral propagation frames and recycled a further 50 frames, and at Kuda Huraa we made 16 new frames. We continue to line the Water Villa walkways with our small-sized frames, and hope to attract herbivorous grazing fish to the area to control algal growth by extending outwards towards the natural reef. We are siting larger frames along the boat channel at approximately 9m depth, close to large healthy colonies of Acropora species.
A storm at the start of the month displaced and even flipped some of our coral frames, so we righted these frames and verified their GPS mapping coordinates. We also noticed some juvenile Pocillopora coral colonies were showing signs of bleaching (on our frames and the natural reef), although no Drupella snails were seen.
Acropora coral colonies from the reef crest remain our go-to source for new propagation fragments, with new coral growth seen to quickly encrust the frame and cable tie (more successfully than Pocillopora fragments).
Our Junior Marine Savers busy attaching coral fragments to a frame
New Experiment – ‘Multiple Breaks’
In order to test whether or not fragments with multiple breaks can survive, two small coral frames were created. Photos were taken of each side of the frame, so the fragments can be seen clearly; we hope to gain a better understanding of the survival and growth rates of different coral fragments.
We regularly maintain our coral frames – replacing dead or missing coral fragments, removing any algae, and taking reference photos from each of the 4 sides (to study survival rates and growth patterns, and to email to our coral frame sponsors).
During February, we transplanted 17 new coral frames at Kuda Huraa and 35 at Landaa Giraavaru. Many old frames have also been ‘recycled’ (replenished with new coral fragments), and we have been targeting the frames found across our popular snorkelling sites. We have also finished relocating vulnerable frames to a harder rubble substrate to minimise sand accretion and protect the lower bars (with rocks under the feet of some large frames).
During the past 12 months, one of our primary goals has been to diversify the sites where we deploy our coral frames, to increase resilience towards future bleaching events. Some of the variety of locations include:
- “Blue Holes” (5m deep) from sand dredging.
- 25m depths (staff beach).
- Shaded along the Water Villa Pathway, to receive lower levels of direct sunlight.
- “Coral Bommies” (separated from the natural reef by large sand patches), featuring large healthy wild colonies of Acropora and bouldering corals at depths of 9m.
This month at Landaa Giraavaru we also relocated the Blu site frames to form a striking new Turtle shape that can be seen from the air (via aerial drone or arrival by seaplane). We arranged the turtle frames using empty containers and lift bags as flotation devices. The corals in this area are growing very well and there seems to be limited mortality (mainly along the bottom bar, due to sand or predation).
Predation Recovery Experiment
A large colony of Acropora pulchra under attack from Drupella snails was identified and collected from the wild reef. We divided and transplanted the coral fragments onto a single test frame, and plan to take twice-weekly photographs to monitor how individual fragments recover from predation.
All current drone photographs for Kuda Huraa and Landaa Giraavaru have been successfully mapped with consistent and reproducible Ground Control Points (GCPs) for accurate alignment with future photographs. The image maps will enable detailed comparisons of the marine landscape over time (corals, sand movement, seagrass coverage). For example:
– areas of wild coral coverage (Montipora digitata and Porites cylindrica) on the easterly reef flats can be monitored for future growth or recession,
– the natural movement of sand around our Spa Island has already been revealed (which can help in siting future coral frames). The animation below shows 3 images in sequence from May 2017, Nov 2017 and Feb 2018.
As part of a project that started early last year, we have been using our aerial drone to photograph overlapping images of the two Four Seasons resorts and the surrounding lagoons. These photographs were then imported, merged and processed in PIX4D mapper, to generate high resolution geo-referenced graphic images (slideshow, below).
3D generated image
3D generated image
3D generated image
Ground control points (GCPs)
This month at Landaa Giraavaru, we transplanted 25 new coral propagation frames (and recycled 10 old frames), and at Kuda Huraa we deployed a total of 18 new frames. We have been relocating our coral frames around Landaa’s Water Villa site, to create an unbroken chain of frames to encourage the movement of herbivorous fish to graze and remove any algae. The coral frames here are very healthy due to the plentiful shade from the over-water villas (reduced stress from the sun’s heat/UV rays). We have also been seeing more Acropora species recruits around this area.
The jetty pillar frames have been recycled (with mostly Acropora and some Pocillopora coral fragments) and we will closely monitor them for survival and mortality. Some fish predation has recently been observed in the house reef, so we are trialling transplantation of Acropora (and possibly Pocillopora) coral species to monitor potential predation.
Predation Recovery Test Frame
Last month, a large colony of Acropora pulchra that was being eaten by Drupella snails was transplanted onto a single frame. Fragments with scars were monitored for tissue loss or growth along the scar. In most cases, we observed no change or some overgrowth by algae. If the fragments overcome the initial bleaching, they may be able to overcome the algal growth and begin growing tissue over the scarred area.
NOAA Bleaching Outlook
NOAA has placed the Maldives at Alert Level 1 (from 3 April), with a 60% chance of bleaching in the first week of May due to seasonally warm ocean temperatures. If bleaching does occur as predicted, it will hopefully only last three weeks, and corals should be able to recover as the waters start to cool again. We will be closely monitoring our coral frames during this period, particularly at the Water Villas site where vulnerable frames can be moved into the shade under the board walks at the first sign of bleaching.
Gili Lankanfushi Coral-line Workshop
We recently attended a coral-line workshop, organised by Clare Baranowski and Emma Bell, resident marine biologists from Gili Lankanfushi. In attendance were marine biologists from resorts and projects around the Maldives including Bandos, Atoll Volunteers and Manta Trust. The aim of the workshop was to learn about the process and benefits of the coral-line methodology.
The coral line-method uses rope attached to a frame (frames are 2x3x5m, 5m lines) with coral fragments twisted into the rope at 5cm intervals to support 100 fragments per line. Since the programme started, large colonies have grown and the resultant heavy lines were moved to hang on the edge of the frame. As all the lines are in the same area, they are easily monitored and maintained, to provide stock for fragmenting. Predatory crown of thorns starfish are not able access the suspended corals, and a nearby sand patch prevents Drupella snails from reaching the nursery. Algal growth is removed from the lines simply by shaking them.
Out-planting and Resilience to Bleaching
During the 2016 El Nino event, an impressive 68% of the corals on the Gili lines survived, higher than seen for both local reefs and other coral regeneration projects; the specific reasons for this comparative success remains unclear. The lines are located on the western side of the island at 6m depth on a sandy area exposed to minimal predation. Perhaps the exposure to local currents was a factor, or the high position of the ropes in the water column.
However, despite the success of the coral-lines, out-planting the growing coral colonies has been more challenging. Corals are transplanted to the same depth (using epoxy putty on bare reef-rock substrate), but often suffer from heavy fish predation as the surrounding natural reef is otherwise devoid of living coral. This is where the use of Reefscapers coral frames is more successful, being a single step process with no out-planting, the frames quickly establish to become part of the reef. As the primary goal of any coral propagation programme is to repopulate natural reefs, this is probably the largest downfall with the programme. However, the resilience of the coral-lines to bleaching effects cannot be ignored, so maybe a combination of propagation techniques, using both lines and frames, could yield better long-term results. Practically, lines could provide additional coral nurseries for fragment harvesting, to better withstand future bleaching events.
At Landaa Giraavaru, we made a total of 29 new coral frames, monitored 250 frames (repaired, cleaned, photographed) and removed 70 frames from Parrot Reef for recycling (re-transplanting with healthy coral fragments, following bleaching).
Pocillopora coral species has been the primary coral deployed due to its relative abundance. Acropora species are growing well on our frames at the Water Villas site, and colonies have even been observed growing on the jetty columns. We have installed structural bracing to our coral storage tank, allowing larger volumes of corals to be collected and stored for longer periods, aiding our frame recycling efforts.
The seasonally warm ocean temperatures have reached 31°C in the lagoon, increasing the temperatures in our large 3000L aquarium, which cycles fresh water directly from the sea. We have seen increased growth of filamentous algae, mainly at the top of the aquarium where the light is brighter, and we are closely monitoring our corals.
At Kuda Huraa, we transplanted 11 new coral frames and recycled an additional 15 frames. We have also been creating two new frame patterns in the lagoon, to be visible from the air. Our completed Flower site consists of 1 medium and 42 small frames, and our Geometric site is almost finished (to consist of 56 flat and 20 small frames). Once the new frames darken due to coral growth (and algae spreading on the bars), a drone picture will be taken.
This month, we have started to repair and replenish the House Reef site with coral fragments of Acropora, Monitpora digitata and Porites cylindrica, and will be monitoring for predation from corallivores. Whilst diving in pairs, we lifted more than 40 dead frames onto our boat using rope hoists. These frames will be recoated with sand-resin mixture before recycling.
Fish predation continues to be an issue on the house reef. We recently observed a black-spotted pufferfish feeding on the branch tips of multiple Acropora species, although it’s unlikely that this fish species is responsible for the complete consumption of coral fragments we have witnessed on our Christmas tree frame and other parts of the house reef. So far, there are no signs of predation on Montipora and Porites corals, so we will increase their deployment alongside Acropora and Pocillipora species to ensure that some fragments survive predation stress.
This month, we removed over 40 crown of thorns (COT) from the Channel area, mainly from the wild coral colonies. These patches of wild Montipora corals in the lagoon seem to act as a buffer zone for the main channel site in terms of COT and Drupella predation.
Some Acropora coral paling was seen towards the end of April, so we relocated the most affected frames to the shade of the water villa boardwalk. A few fragments are fully bleached, and we will continue to monitor closely during these warmest few weeks of the year.
Black-spotted pufferfish (Arothron nigropunctatus)
Signs of pufferfish predation on Acropora tenuis
Our aquarium coral experiments are continuing, and the Acropora plate fragments continue to grow well. On the mixed coral plate, Psammacora abtusangula (the largest specimen) is spreading further, and fragments that are not close to others are growing freely without competition.
Coral plate (January)
Coral plate (April)
At Landaa Giraavaru, we transplanted 23 new coral frames and monitored 260 frames across our Parrot Reef, Coral Trail and Water Villa sites (this involved cleaning, photographing and updating QGIS satellite data). Our recycling work of old frames is also continuing at both Parrot Reef and Coral Garden. Very large mature frames are too heavy to relocate, but their coral skeletons provide a valuable habitat for marine life, so we are filling any empty bars with new coral fragments.
We have been developing our Marine Biologist Course for the Four Seasons Apprenticeship Programme, and have expanded the coral propagation component this month. We cover coral reef ecosystems and summarise our Reefscapers coral restoration project. We also outline coral structure and identification, and discuss threats to coral reefs. This is followed by ‘Build A Reef’, where the apprentices get hands-on with our coral biologist, transplanting their own coral frame. Field work involves placing and photographing the new frame out in the lagoon, and updating our coral frame database with the QGIS satellite location and new photos. Apprentices Hulaam and Saaniu have both completed our coral training, and are progressing well at our Marine Discovery Centre.
New coral fragments added to old frames
At Kuda Huraa, we transplanted 12 new coral frames in the lagoon, and removed over 50 dead frames from our House Reef and Green Lagoon sites for recycling. We have observed ‘moderate’ levels of bleaching of Acropora fragments in the Channel this year, with corals in shallower (warmer) waters being most affected, particularly species of A.pulchra and A. digitifera.
We were lucky to see one of the mushroom coral specimens in our aquarium in the act of spawning, as it started to excrete a fluorescent orange slime. We collected a sample and examined what we think are eggs under the microscope.
We have taken some time out this month to help staff at fellow resort ‘Club Med’ with their own Reefscapers programme, after being without an onsite marine biologist for some time. Club Med staff came to visit our Centre at Kuda Huraa, and then we went to visit their current setup. Interestingly, they have many healthy Pocillipora colonies growing on frames out in the lagoon, and in a good location (rocky substrate, strong current, close to the jetty). We visited the reef crest with the new onsite marine biologist, to harvest some Acropora coral fragments for propagation and transplanting onto empty frames.
Bleached coral fragments – Acropora puchra & Acropora digitifera