St. Eustatius - STENAPA Reef

Setting

STENAPA Reef, St. Eustatius National Marine Park, dived 24 February 2026 — the first dive of the day. This is a purpose-built artificial reef, not a natural one, and the photographs make that unmistakable: the whole dive works a scatter of engineered objects set down on an open sand plain. Conditions were hazy with visible suspended particulate; several wide frames are blue-cast and low-contrast, which limits color-based condition scoring (e.g., Image 9).

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Visibility was poor to moderate; wide shots go milky within 10-15 m while close work stays sharp.

General benthic features

Frames show large steel hoops and rebar rings lying flat on the sand, cast concrete blocks with arched window-like openings standing in a line, right-angled concrete beam-and-slab frameworks, and flat plates with drilled circular ports (e.g., Image 7, Image 21, Image 36).

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Sponges, not corals, are the dominant cover on the structures (e.g., Image 16).

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Yellow and orange tube sponges (Aplysina-type), branching lime-green rope sponges, maroon and scarlet encrusting sheets, pale green encrusting patches, and a pink-brown vase sponge cover most of the hard surface, with pink crustose coralline algae, filamentous turf, and small purple gorgonian sprigs filling the gaps (e.g., Image 29, Image 30, Image 34).

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Stony coral is present but sparse and small-colonied: a cluster of knobby mustard-brown Porites-type colonies with pale pink margins, a single clean circular meandroid brain coral (Pseudodiploria/Diploria-type) about a hand-span across, a small yellow-green ridged coral resting on open sand beside a rope sponge, scattered mustard Porites astreoides-type domes on the flat plates, and a few small recruits dotting the concrete (e.g., Image 26, Image 40, Image 42, Image 46, Image 47).

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Between the built objects the bottom is fine gray-green volcanic sand, and one stretch of the dive crosses a dense seagrass meadow where dark-bodied fish with trailing dorsal filaments, consistent with French angelfish, drift over the blades — too dim to confirm the identification (e.g., Image 33).

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Stony corals are small, isolated heads rather than builders (e.g., Image 11).

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Four blurred macros show a cream-pale colony with fully extended polyps — too out of focus to call bleaching either way.

Coral cover

• Reference: Claude CV point count (this site's photos)
• Coral cover: 4.6% — a blind Claude computer-vision point count of 103 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

The photo review resolved no clearly bleached coral tissue, and the few colonies present look normally pigmented; a computer-vision point count called 3.4% of coral points bleached (2 of 103 photos), but one of those two frames shows a marginal tissue-loss band (possible disease) rather than bleaching: a cream-white band around the whole margin of one colony, edged by a thin yellow rim (photo not shown). The other is a pale massive colony in blue-cast light that cannot be confirmed as bleaching. Two introduced species are on record here: lionfish and orange cup coral Tubastraea coccinea (e.g., Image 8).

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Fish and other fauna

Fish use the structure heavily (e.g., Image 3).

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One frame holds a dense mixed aggregation of grunts and squirrelfish packed into the concrete framework; another shows yellow-lined goatfish and snapper working the sand alongside the structure line (e.g., Image 18).

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A long-spined sea urchin (Diadema antillarum) is tucked into a crevice, spines intact.

Comparisons with other data

Hoeksema et al. (2022) surveyed this site (STENAPA), 0.02 km from the pin. Within 5 km, eight independent stations (Reef Check and XL Catlin Seaview Survey) recorded station-year means of 0.7–38% hard coral cover between 2005 and 2013; the nearest of these, XL Catlin Seaview Survey at transect 25015, 1.63 km away, read 2.0% in 2013.

Other notes

A historic glass bottle lies on the sand.