Maldives

The Maldives are a chain of 22 atolls running some 800 km from north to south, the central and largest section of the Chagos-Laccadive Ridge, which traces the path of the Réunion hotspot (Spalding et al. 2001). The atolls rise steeply from the ridge in two parallel rows. The northern end holds the world's biggest surface-level atolls, Thiladhunmathi and Miladhunmadulu, two names for a single structure covering some 3,680 km²; the southern end holds Huvadhoo, over 3,200 km², and lies within what the atlas calls the 'Chagos Stricture', a narrow belt of peak coral diversity that links the reef faunas of the eastern and western Indian Ocean. Atoll rims are broad reef flats cut by deep channels, and the 15-55 m lagoons hold patch reefs, knolls, and faros, ring-shaped reefs like miniature atolls that are rare outside the Maldives. At least 209 scleractinian species are recorded nationally, with diversity highest in the south. Coral cover on atoll edges, faros and lagoon knolls had exceeded 60% to at least 20 m, but in 1998 some areas lost up to 90% of their hermatypic corals. Spalding et al. (2001) estimate about 8,920 km² of reef for the country; Souter et al. (2021) give 6,372 km² for the Maldives ecoregion from a newer map.

This page gathers 44 pins: two units, North and Central, plus Huvadhoo in the far south. North holds six: five photographed pins in Baa Atoll and the Raa Atoll pin, which carries Coral Reef CPR's 2016 bleaching surveys rather than photographs of its own. Central holds 37, five of them atoll-level markers and the rest individual dive sites. Huvadhoo (Gaafu) carries Coral Reef CPR's 2016 transects from the Maamuta house reef, lagoon patch reef and outer reef. The dived sites come from two periods of fieldwork. In January 2016, research dives in Baa and in the Male atolls tagged coral colonies with numbered plates and measured them against rulers along transect lines, at Landaa Giraavaru, Kashidhoo Faru, Gaagandufaruhuraa, the Anantara Kihavah house reef, Small Sand Bank, Raaeundi Reef, Veli, Stage, Maafushi, Big Sand Bank, and the Anantara Dhigu house reef. A later liveaboard covered thilas, channels, walls, and wrecks across North and South Male and Ari, including two night dives dated May 2017.

Cover here is a photo-derived computer-vision index, not a diver transect, and it exists for only 35 of the 44 pins. Across those 35 it averaged 20.8% and ranged from 8.1% at Fish Tank to 44.5% at Gaagandufaruhuraa. The northern pins read higher, at 30.3% over five sites, than the central pins at 19.2% over 30, but the two sets are not comparable: the northern figures come from five monitoring reefs photographed on one January 2016 research trip, while the central figures mix monitoring reefs, thilas, walls, and wrecks from two trips a year apart. The two computer-vision methods disagree by about 15 percentage points at Landaa Giraavaru and by as much as 18.9 at Maafushi, so only ranges are quoted. The reefs themselves vary as much as the numbers. Landaa Giraavaru is an unbroken carpet of staghorn thickets and meter-wide table corals stacked in tiers; Kashidhoo Faru is a rolling slope of whorled plate-coral rosettes; Dhega Thila, Hodeli Bodu Giri and Camel Point carry dense staghorn and table gardens, while Dhigga Thila and Vaadhoo Caves are draped in soft corals and Fish Tank, Fish House, Ghuli Faru, and Moofushi Kandu hold little coral.

What makes this set unusual is that it brackets the 2016 bleaching. The January 2016 frames were made about three months before the El Niño event, and the pins describe them as a portrait of reefs on the verge. Stress was already visible: a crown-of-thorns starfish below table corals bearing fresh white feeding scars on the Kihavah wall, scattered bone-white branch tips among the tagged colonies at the last Baa monitoring site, and a few white branch tips and one ghost-white staghorn at Veli. Then the April 2016 resurvey found every recorded colony at Raaeundi Reef bleached, more than nine in ten at Stage, about 95% at Maafushi, four in five at Small Sand Bank, and nearly half the corals on the neighboring Veli Channel reef, while the sheltered Veli Lagoon reef escaped almost untouched. Tagged colonies at Big Sand Bank were largely dead by the May 2017 revisit. The later frames show what followed: algae-covered table skeletons at Dhigga Thila and Lohosfushi Corner, and Pocillopora recruiting across rubble at Back Faru with small colonies recolonizing Miyaru Bay.

Crown-of-thorns starfish are the second recurring problem, recorded at ten central sites and one northern one. At Ari Atoll's south tip the photographer labeled it an outbreak, with starfish wedged two to a crevice amid fresh white skeletons of eaten staghorn and cauliflower corals; at Hodeli Bodu Giri the crew removed them with a collection stick. Derelict gear is a third: coral-farming tables near the Kuda Giri wreck with most transplanted fragments long dead, toppled nursery transplants at Anantara Dhigu, and a length of PVC pipe on Dhigga Thila. In the south, Coral Reef CPR's 2016 transects at Huvadhoo recorded 69.1% live coral in April and 39.1% in July, during the 2016 mass bleaching; at Raa in the north the same surveys recorded 45.8% and 26.4%.