Indonesia - Halmahera: Siko Pinnacle

Setting

Siko Pinnacle (Halmahera dive 25) is a mid-water seamount rising from open blue water, dived to a maximum of 34.3 m in 26-27°C water.

General benthic features

The opening frames confirm the log note directly — small tuna and jacks in silhouette over blue water and a diver signaling with a dive computer against open water — before the pinnacle's flank closes in: a crowded, coralline-pink and maroon encrusting wall dense with sponges, small gorgonians, and scattered coral (e.g., Image 2, Image 6, Image 12, Image 15, Image 17).

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Prominent among the stony corals here are large plate and table corals, gray, tan, and olive-green foliose discs up to a meter or more across, recurrent through the dive and often the main subject in frame; several show visible bite/graze marks or thin margins consistent with normal turnover rather than damage (e.g., Image 1, Image 5, Image 13, Image 20, Image 26, Image 30, Image 40, Image 43, Image 49, Image 52).

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Massive smooth colonies, olive-green to gray-brown domes consistent with Porites/Diploastrea-type, recur through the mid-dive stretch (e.g., Image 3, Image 35, Image 41).

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A pair of white sea whips or wire corals stands up from the substrate in two frames, alongside a banded shrimp with long white antennae, and a chain of pale yellow encrusting ascidians/polyps is shot in close-up against green water (e.g., Image 10, Image 25, Image 32).

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Extensive stretches of the pinnacle's flank carry a dense, fuzzy brown-olive turf that reads as either a soft-coral/zoanthid mat or dense fine-branching coral seen at range — not resolvable to genus at this distance — interspersed with small cream and pink coral colonies and crustose coralline patches (e.g., Image 19, Image 22, Image 34, Image 54).

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Coral cover

• Reference: Claude CV point count (this site's photos)
• Coral cover: 12% — a blind Claude computer-vision point count of 48 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

No bleaching, disease, crown-of-thorns, or predation was seen in any of the 60 frames reviewed; growth forms and pigmentation throughout are normal for the depth and light.

Fish and other fauna

Fauna is the strongest part of this dive, exactly as logged: a striking cream-and-black honeycomb-patterned nudibranch, consistent with a Phyllidia/Jorunna-type species, across four consecutive frames; an emerald-green, black-spotted nudibranch consistent with Nembrotha/Tambja-type across four frames; a small orange dorid shot close against pink substrate; and a pair of slender fish with vertical white-and-orange banding tucked in orange sponge, consistent with juvenile sweetlips or a shrimpfish/pipefish pair, not settled from the frame (e.g., Image 9, Image 11, Image 33).

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Comparisons with other data

In 2024, WCS Indonesia surveyed two stations, Inti Siko and Inti Gafi, for its Guraici MPA project (data via MERMAID), recording 25–50% hard coral cover. This pin's position is approximate (an island-level placement on the Inti Siko station, not a dive-site fix), so no station is compared with this site by distance or treated as this site; station names are not dive-site names.

Dive record

Anderson's field note: “switched to larger tank; small tuna, small jacks, plentiful reef fish, tons of nudibranchs”

Other notes

Divers with bubble trails and gorgonian fans recur on the outer wall in the closing stretch (e.g., Image 4).

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