At Landaa Giraavaru, we transplanted 33 new coral frames around the island during July, and a total of 405 frames were monitored (at the Coral Garden and Water Villa sites). Following the recent seasonal coral bleaching event, we have also been very busy re-transplanting many of the frames from the Water Villas, and taking a double set of monitoring photographs (before and after coral transplantation).
The relatively shallow Coral Garden site is very popular with guests for daily for snorkelling. We have observed some mechanical damage on a few frames (stepping or fin kicking) but many of the mature frames are now completely covered with corals and no significant bleaching has been observed here. Examples of mature frames are LG0023 (2008, mainly E. horrida) and LG0606 (2010, A. muricata and A.intermedia).
34 new frames were transplanted in August, mainly at the Water Villas, Coral Trail and Blu sites, and we now have an impressive total of 2679 coral frames around the island, covering an approximate area of 5,000 square metres.
We monitored 609 coral frames across the Water Villa and Dive Sites, and relocated some older frames using lift bags, to move them further away from the boat channel. We also completed the re-transplantation work following the unusual coral bleaching mortality at the end of the dry monsoon during April/May.
Many of the youngest frames (less than one and a half years old) showed 50% bleached or dead coral fragments, with frames from January to April 2015 the most affected and requiring completely new corals (e.g.: LG2387, 2436, 2551, 2557 at the Water Villas). Older frames transplanted before 2012 were much less affected, and more resistant to the increased ocean temperatures (e.g.: from 2011, LG0825/0921 at the Water Villas).
We transplanted 22 new coral frames at Kuda Huraa during July, and have been completing our frame monitoring of the Spa site. Coral frames in the Channel site have been cleaned of algae (sea pork and cyanobacteria).
16 new frames were transplanted during August, mainly at the Channel, House Reef and Turtle sites due to the depth and presence of currents (for extra resilience against warmer ocean temperatures). We have also completed monitoring at the Water Bungalows site this month, and have progressed through 70% of the coral frames in the Channel area. And we have been busy re-transplanting/relocating to the Turtle site a total of 37 frames that had been bleached by the recent high ocean temperatures.
We have also been seeing predation by several Crown Of Thorns, as well as Drupella snails, which can kill the coral colonies and lead to growth of cyanobacteria and other algae. One coral species (Acropra secale) is susceptible to Black Band Disease, so we have removed all the affected tissue to prevent reinfection.
For the last few months, we have been puzzled by the appearance of gaps of dead and missing corals in large Acropora aspera colonies on some frames. But we now have exciting evidence that our mature coral frames are supporting a thriving marine ecosystem… we photographed a large female hawksbill turtle, feeding and digging into the corals!
Coral Bleaching update
Coral reefs are very susceptible to increases in water temperatures above the normal narrow range of 26°C to 30°C. After several days at elevated temperatures, the symbiotic algae that give the corals their wonderful colours are reduced in quantity or die off completely, giving rise to a ‘bleaching’ effect.
Following the very warm ocean temperatures during April, some of our youngest coral frames suffered from bleaching during May (the time at which the 2015 El Nino alert was declared for the Indian Ocean). Coral frames less than 18 months old showed between 50% to 100% dead fragments, whilst frames from 2012 were much less affected.
We have been very busy, re-transplanting over 2500 coral fragments of various Acropora coral species – A.humilis, A.digitifera, A.gemmifera, A.tenuis, A.latistella, A.secale. Most of the fragments have attached well, although coral species A. tenuis and longer branches of A. humilis have been least successful.
Water temperature logger at Villas site, 2m depth
Coral frames – age specific mortality rate
Bodu Huraa School Visit
We recently welcomed to our Centre over 100 school children from Boda Huraa, during the Marine Education Summer Camp.
Working with the Manta Trust team, we organised games, activities and lectures to generate a fun and stimulating educational 2 days. Topics included manta ray biology and identification, the adverse effects of littering on marine life, the importance of corals, and threats to sea turtle hatchlings after leaving the nest.
The children also helped to make a coral frame, and learnt about the sea turtles in our care. Great fun was had by all and we look forward to future school visits!