Coral Propagation – Monthly Progress
At Landaa during May, we transplanted 14 new coral frames using a total of 542 coral fragments. In addition, we have been busy monitoring (cleaning, repairing, photographing) a total of 846 coral frames across all sites around the island. This month, we also relocated the last of our 300 Moon frames to the Elephant site; we arranged them neatly and mapped their QGIS coordinates.
At Kuda Huraa this month, we transplanted 15 new coral frames using a total of 1153 coral fragments. We spent time repairing some Gulhifalhu rescue colonies that were damaged in a storm brought in by the south-west monsoon (some coral colonies detached from frames and sustained damage). Also this month, we removed 100 Drupella snails from several corals colonies at the House reef, and monitored for predation by fish and Crown of Thorns starfish (COTs).
References
• Boström-Einarsson, L. & Rivera-Posada, J. (2016). Controlling COTs using household vinegar. Coral Reefs 35, 223–228
• Dumas, P., Gereva, S., Moutardier, G., Ham, J., Kaku, R. (2015). Lime juice for COTs outbreaks in Vanuatu. SPC Fisheries Newsletter. 146, 47–52.
• Great Barrier Reef Marine Park Authority (2017). COTs control guidelines. GBRMPA, Townsville.
• Moutardier G, Gereva S, Mills SC, Adjeroud M, Beldade R, Ham J. (2015). Lime Juice and Vinegar to Control COTs. PLoS ONE 10(9): e0137605.
• NOAA Satellite and Information Service. Coral Reef Watch, updated 26 May 22.
Pale coral colonies regaining their healthy colour (photosynthetic zooxanthellae) as the ocean cools (April to May 2022) [click]
Drupella snails removed from Acropora digitifera, and predation by COTs (bottom left) [click]
We conducted our coral watch assessment during the first week of May. Mature coral colonies are well settled, exhibit good health, and have survived the seasonal temperature peaks. We will continue to monitor the stressed colonies at shallow sites (Water Villas, Turtle) to assess their health and recovery in the coming weeks.
The stressed corals (in April) are regaining colour (in May) as the warmest season (Feb-April) turns into the SW monsoon
As coral colonies mature, they become more resilient to stress from warmer waters (same colonies, 2021-2022)
Rescue Coral Health Monitoring
We continue to monitor our Gulhifalhu rescue corals:
- 10% Healthy: no dead or decaying areas since introduction.
- 18% Pale: discolouration due to temperature stress (can transition to bleaching).
- 41% Bleached or fluorescing: due to the loss of symbionts; >20% alive.
- 6% Predated: predation caused decay or death (<80%); caused by Drupella, fish, algae or sand smothering.
- 25% Dead: >80% of total surface.
Kuda Huraa Temperature Profiles
The temperature profiles in our coral propagation sites follow similar patterns to the official NOAA bleaching alerts.
- 22 March to 10 May – average temperatures above 31°C were regularly recorded.
- 26 March – highest recorded temperature of 34.7°C.
- 7 April – highest recorded temperature of 35.5°C.
- 26-27 April – peak coral bleaching period (from field observations across all sites).
Sea surface temperatures (2022) recorded by our temperature loggers at Kuda Huraa (‘Channel North’ site)
Spawning Monitoring
Since October 2021 at Kuda Huraa, we have recorded gametes in 11 coral species, and witnessed spawning events in four different species (A. secale, A. plantaginea, A. tenuis, Montipora digitata).
During May, eggs were observed in three species on coral frames at the Water Villas. Interestingly, frames of A. digitifera that were relocated from the Water Villas to the Starfish site in January did not show signs of spawning. We also did not find any eggs in the Gulhifalhu rescue colonies.
Measuring April Spawned Colonies
This month, we measured the 52 colonies that spawned in April. Increasing our knowledge on corals and their reproductive biology is important for assessing connectivity of regional coral populations. We hope to determine when corals mature by measuring the spawning colonies (ecological volume using callipers to measure height-length-width).
Coral Settlement Update
In our lab, the settled coral polyps continue to grow well, especially the Acropora plantaginea fertilised and settled in November 2021.
Coral polyp growth – Acropora plantaginea
Coral polyp growth – Acropora millepora
Coral Plates in Aquarium One (plates KH01, KH02, KH05) and Aquarium Two (plates KH03, KH04, KH06)
- KH01 (Galaxea fascicularis; Acropora species) – removed for cleaning.
- KH02 (Galaxea fascicularis) – good health.
- KH03 (Acropora species) – removed for cleaning.
- KH04 (Acropora species, mushroom coral) – the fragments continue to be healthy.
- KH05 (Galaxea fascicularis) – the fragments continue to be healthy.
- KH06 (Galaxea fascicularis) – the fragments are healthy, fusing and growing.
