Coral Spawning in the Maldives 2023 Q1-Q2 Updates
Please also see our main Coral Spawning reports page, from 2013 onwards, including our pioneering lab work in Oct-Nov 2021.
January 2023 Observations
Coral spawning at Kuda Huraa (2022-23)
Coral gamete monitoring (Acropora digitifera) [RIGHT]
Tracking Gametogenesis
At Landaa during January, we recorded pale pigmented eggs in Acropora secale, and white immature eggs in five species of Acroporidae (A. gemmifera, A. millepora, A. digitifera, A samoensis, A. nasuta).
At Kuda Huraa this month, we conducted 14 night-snorkels to monitor for the presence of coral gametes, around the periods of the full moon and the new moon. Immature gametes of various species were recorded, which are predicted to mature in time for the next mass coral spawning event in April-May.
To allow for easier gamete collection, we relocated corals with pigmented gametes to the Water Villas – a total of 16 colonies of A. gemmifera and five colonies of A. humilis.
Daily gamete checks were carried out at the Starfish site, and spawning was presumed (due to gamete loss) in both A. humilis and A. tenuis (no evidence of spawning in A. gemmifera).
Mature coral gametes in Acropora tenuis
Coral polyp releasing gamete bundle (close-up)
Coral Settlement Update
Over the past months, our coral biology teams have worked tirelessly on our Coral Reproduction Program, and at Kuda Huraa we have successfully fertilised and settled three coral species (Acropora secale, A. tenuis, A. muricata).
This month, the A. muricata polyps exhibit stable health, and symbiodinium (zooxanthellae) were observed within their tissues for the first time (symbiont uptake occurs one month after settlement for all three species).
Being the oldest, the survival rate for A. secale has decreased over time as expected, mainly down to algal overgrowth (despite regular cleaning of the aquaria and the coral settlement units).
Coral settlement – polyp growth over time
Acropora tenuis polyps, at 2-months post-settlement
Coral polyps – settled, growing, healthy (Acropora secale)
Coral polyps (Acropora muricata) update of symbionts
February Observations
Coral Settlement
Acropora tenuis settlers continue to display growth and steady health, more than three months post-settlement.
Monitoring for Coral Gametes and Spawning
During February, immature gametes of different species were found at Kuda Huraa’s Water Villas and Starfish sites, in preparation for the next mass spawning wave expected in April-May. One specific colony of Acropora retusa (on a frame at the Water Villas site) has presented white gametes since way back in August 2022!
Temperature Loggers
This month, we added two extra temperature loggers at Landaa’s House Reef (at depths of 2m and 5m) and two loggers at the ‘watersports bommie’, where we witnessed wild coral colonies spawning in November 2022. We also transplanted an experimental frame with fragments that spawned in November 2022 (A. humilis, A. secale, A. globiceps). We want to see if these corals will spawn next season, or whether they put all their energy into growth.
