At Landaa Giraavaru, a total of 24 new coral frames were transplanted in January 2020 (sponsored equally by guests and Four Seasons) and a total of 191 frames were monitored (cleaned, repaired, photographed) at various sites.
At Kuda Huraa, we transplanted a total of 19 new coral frames around the island. Since September 2019, we have re-transplanted and monitored a total of 810 frames (averaging 5.5 frames per day). We continue to remove any Rhodophyta turf algae from our frames as we encounter it, to prevent the algae from blocking the light and smothering our corals. Frames in the Channel are starting to mature nicely, so we plan to use these as donor colonies, fragmenting and re-transplanting them to our new frames.
With the warmer weather approaching, we will start relocating vulnerable frames under the shade of the boardwalks, so they are partially shaded during the day. We also plan to relocate some frames into a heart shape, sited in deeper cooler waters, again to help mitigate against thermal stress.
Coral Plates in Aquarium One (plates KH01, KH02, KH05) and Aquarium Two (plates KH03, KH04)
Some coral bleaching was observed for a short period earlier this month, despite comfortable water temperatures of 28°C in both of our small aquaria. Acropora cytherea and A. hyacinthus variant 2 were affected the most. There has been a general decrease in competitive growth on all our coral plates, suggesting the adjacent species might not threaten to outcompete each other when transplanted onto our frames.
KH01 – 2 fragments died; 33 out of 40 remaining encrusting fragments. Competitive growth between A. cytherea and A. hyacinthus has continued to slow (neither species has a dominant growth pattern) although A. hyacinthus continues to calcify over A. digitifera (corroborating field observations).
KH02 – the Galaxea fascicularis polyps have recovered; they generally continue to grow well and bud. Some lifting and tissue loss are still visible, and one polyp has died.
KH03 – 35 out of 40 fragments encrusting onto the plate (down from 38/46 fragments last month). Six fragments were lost; A. millepora was badly affected by the water quality problems at the start of the month (A. hyacinthus is recovering; A. valida and A. cytherea seemed unaffected).
KH04 – 24 out of 26 fragments encrusting (2 down from last month); competitive growth between A. hyacinthus variants has also slowed down.
KH05 (new) – transplanted with 28 Galaxea fascicularis fragments, which we hope will grow to be as resilient as those on plate KH02.
Workshop: Global Coral Reef Monitoring Network (GCRMN) [28-29 January 2020]
During January, our coral biologist Sam Burrell attended the GCRMN workshop in Malé. Established in 1995, the main goal of the GCRMN is to gather long-term global reef monitoring data, covering hard corals and fish. The Maldives are part of the South Asia region (with Sri Lanka and India) and the workshop aimed to reinvigorate the regional network, develop inter-country communication and present findings. In brief summary:
- David Souter (GCRMN Coordinator) – outlined goals and report objectives (assess damage to coral reefs).
- Maldives (Minister of Fisheries) – ecological initiatives to meet a 2020 deadline on coral reef protection.
- India – status of coral cover and species diversity; problems of sedimentation and illegal harvesting, invasive soft corals and coral diseases. Urgent need for ecologically sustainable tourism.
- Sri Lanka – reef microbialisation and overall phase shifts from coral to algae; socio-economic and environmental impacts of coral reef loss need to be defined for legitimate policy change.
- Maldives – (Banyan Tree, the Maldives Marine Institute and Small Island Research Group) – following the 2016 bleaching event, southern reefs are thought to have been less badly impacted. Long-term data monitoring in the Maldives is challenging, so it is difficult to assess the impacts of the fishing and tourism industries without long-term data to determine baselines.
- There is urgent need for better-quality data on coral reefs, collected and collated regularly. How can privately employed marine biologists around the Maldives contribute to long term monitoring? Can the GCRMN provide training and sponsorship?
Online Database of Maldivian Corals
A further 4 coral species were added to our Maldivian Corals Database, bringing the total to 26 species; extra photographs and more species will be added over time. Relevant data and photographs were collated and summarised for Acropora gemmifera, Acropora pulchra, Heliopora coerulea and Porites cylindrica.
Started last month, our experimentation with coral cores is progressing well. Most plugs are healthy, with some initial paling likely due to the extraction and transplantation process. There are signs of colonisation of the neighbouring rock, which we initially thought (but no longer think) are ‘Mesenterial filaments’; there is little published research on how massive corals might grow to bridge a small gap.
‘Mesenterial filaments’ are string-like extensions of the internal folds of tissue which create the structure within a coral polyp’s body, typically bright white and full of nematocysts to capture and kill prey.
The parent donor colony now looks less healthy, likely due to an extended period in our storage tanks for (exposing it to sedimentation, fixed water flow and variable light levels). However, the scarring from plug extraction has diminished considerably and tissue recovery on the edges of the holes continues.
We are extending the experiment to an in-situ trial on the reef, with 3 lines of holes/plugs (>5cm apart) made to randomise the positioning (for water flow and light levels). We aim to locate a donor colony and outplant rock within proximity of each other to mimic environmental conditions. We will monitor on a weekly basis, with close attention to predation and to the effect of the epoxy on regrowth.
Reefscapers AI Catamaran
We have installed stronger replacement propellers for the Catamaran, and started to conduct sea trials. The propulsion system works well at slow speeds but shuts down when the propellers try to draw more power, so we have ordered a new battery. We also installed and configured the cameras, which successfully recorded underwater photographs and video.
We are making good progress with our new AI software model, which can accurately detect the position of coral frame subjects in 85% of monitoring pictures. This model is a combination of the frame-shape algorithm with new deep-learning to detect texture.
Coral Spawning Experiment
Unfortunately, none of the Pocillopora damicornis planulae settled on the offered substrate. We observed several bleached polyps and recorded a 0% survival rate from ≈400 larvae (perhaps due to insufficient suitable substrate, or temperature fluctuations). We noticed that none of the planulae settled on the aquarium glass in this experiment (as was previously observed with P. verrucosa). We will be starting further experiments with P. damicornis with extra substrate and more controlled temperatures.
A total of 15 colonies remain from the initial settlement of P. verrucosa, with polyp counts varying from 1 primary polyp to 8 individuals. There was some competition with the faster crowing crustose coralline algae, and this interaction will be closely monitored. There is little published information, although Elmer (2016) reported that Pocilloporid species won 68% of interactions, and Pocillopora/Porites coral recruits won 50%+ of interactions with their benthic neighbours (CCA, cyanobacteria, algae, etc).