Indonesia - Halmahera: Merida Cavern

Setting

Merida Cavern is two dives in one, and Anderson's field note draws the line: “an amazing cavern with beautiful lighting, nice corals outside the cave, less spectacular along drop-off.” The cavern is a limestone chamber and swim-through worked at 15 m: bare eroded rock walls, a rippled white sand floor, divers on torches, and shafts of surface light coming down through the roof openings (eleven frames are the classic light-shaft frames) (e.g., Image 8, Image 18, Image 21, Image 38, Image 41, Image 42).

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Almost no coral grows in there, and these are the dive's lowest readings (e.g., Image 25).

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General benthic features

Outside the cave the reef opens onto a hard pavement and sand slope studded with coral bommies, and this is where the site earns its cover: enormous flat-topped tabulate Acropora, many more than a meter across, sit alone on pale pavement with clear sand around them, alongside massive Porites and Diploastrea domes, branching and corymbose Acropora thickets, green digitate Acropora, foliose and encrusting plates, brown leathers (Lobophytum and Sarcophyton) and, on the drop-off wall, plenty of crustose coralline pavement with comparatively little live coral — matching the “less spectacular along drop-off” half of the note (e.g., Image 1, Image 3, Image 4, Image 5, Image 6, Image 9, Image 10, Image 11, Image 12, Image 13, Image 15, Image 19, Image 20, Image 22, Image 23, Image 24, Image 28, Image 30, Image 31, Image 32, Image 33, Image 35, Image 36, Image 40, Image 43, Image 45, Image 46, Image 47, Image 48, Image 50, Image 51, Image 52, Image 53, Image 54).

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Coral cover

• Reference: Claude CV point count (this site's photos)
• Coral cover: 27% — a blind Claude computer-vision point count of 125 of Anderson's unedited photographs (20 points per photo; water, fish, and obstructions excluded). Other computer-vision methods are listed in the method table.

Stressors

A crown-of-thorns starfish was photographed on this dive (e.g., Image 56), tucked under an overhang, and the lumpy massive coral directly above it is stark white over most of its visible surface, with no algal film and live tan tissue only at its margin.

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The photograph cannot separate freshly killed skeleton from bleached tissue, but a starfish directly beneath it is consistent with feeding. The next frame (Image 57) shows two massive colonies with sharply bounded white patches of the same appearance; no starfish is visible there, so those patches may be feeding scars or partial bleaching.

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Two very large table colonies carry white to gray bare patches at their centers, recent mortality, cause not stated (e.g., Image 6, Image 13). The spread in cover is the cavern-versus-reef split, not measurement scatter.

Comparisons with other data

In 2024, WCS Indonesia surveyed a station named Legoma in the Guraici islands (Guraici MPA 2024; data via MERMAID), recording 19% hard coral cover. This pin's position is approximate (an island-level placement on the Legoma station, not a dive-site fix), so the station is not compared with this site by distance or treated as this site; station names are not dive-site names.