Saba - Ladder Labyrinth
Part of the regional summary: Saba
More about this place: Saba on Wikipedia
More info
Leeward Caribbean Islands (NOAA CRW virtual station)A true labyrinth of low volcanic walls separated by winding sand alleys where several nurse sharks rest, with a spiny lobster under a ledge and an old fish trap wedged in the sand. The ridges hold patchy coral of star, brain, and mustard hill corals, though almost all colonies are small.
Een echt labyrint van lage vulkanische wanden, gescheiden door kronkelende zandgangen waar verscheidene verpleegsterhaaien rusten, met een langoest onder een richel en een oude vissersfuik die vastzit in het zand. Op de ruggen groeit verspreid koraal van ster-, hersen- en mosterdkoralen, al zijn bijna alle kolonies klein.
AI translation of this summary; the English is authoritative.
Three other CRD dive sites with their own pages within 5 km shown in orange — click a marker to open its page.
These are unedited originals; edited versions will replace them.
This page shows 50 of the 98 photographs from this site, including every one the text cites.
17 of the 50 photographs on this page are shown beside the text that discusses them under "Site description" below.
Site description
Setting
A maze of boulder-strewn rock ridges separated by narrow sand channels, matching the site's "Labyrinth" name directly: one frame looks straight down a sandy corridor flanked by two rock walls, a nurse shark visible resting on the sand ahead, and a second frame shows the same or a similar nurse shark (Ginglymostoma cirratum, confirmed by its rounded snout and barbels) resting tucked under a rock ledge (e.g., Image 14, Image 20, Image 45).
Visibility is good to excellent throughout, with strong ambient blue light in the open-water frames.
General benthic features
Coral cover on the ridges is real but patchy and small-colony: scattered knobby/lobed star-coral heads (olive-green, several photographed in clusters of three to five small colonies on a single boulder), a scoop-shaped mustard-hill or star coral, and one notably large, evenly ridged colony photographed close-up under blue ambient light, its tissue pale where the light falls and tan in its shaded grooves, a lighting effect rather than paling (e.g., Image 26, Image 27, Image 28, Image 34, Image 43).
Sponges and octocorals recur throughout: mustard-yellow tube sponges, orange encrusting sponges, a purple sea fan, black sea rods, and a delicate pale gorgonian branching from a crevice (e.g., Image 4, Image 44, Image 50).
Boulder and brain corals (some fluorescing bright blue/green under lights) top the boulders alongside barrel sponges and sea fans, with an old fish trap wedged in the sand (e.g., Image 30, Image 41, Image 49).
Coral cover
- Reference: Claude CV point count (this site's photos)
- Coral cover: 8.9% — a blind Claude computer-vision point count of 82 of Anderson's unedited photographs (20 points per photo; water, fish, and obstructions excluded). Other computer-vision methods are listed in the method table.
- Frames were screened before scoring: open sand, mid-water, blown-out, and burst-duplicate frames, dive computers, topside, and diver shots, blue-light fluorescence, and macros were all removed.
Stressors
No disease or physical damage is visible on any of the small star-coral colonies reviewed. No corallivores were evident.
Fish and other fauna
Reef fish include blue and brown chromis and sergeant majors, blue tangs (e.g., Image 9), and two jacks (crevalle or horse-eye) cruising in open blue water off the structure (e.g., Image 19).
Multiple nurse sharks rested in the sandy alleys, plus a spiny lobster under a ledge, schools of blue chromis/creole wrasse, and jacks in the blue (e.g., Image 23).
Comparisons with other data
Klomp & Kooistra (2003) surveyed this site (Ladder Labyrinth). If you have survey data from this site to share, please email us.
CV model comparison
More info
A few colony-focused photos raise the mean; the median is the typical photo. No computer-vision method yet estimates coral cover accurately on new images, so treat this as indicative rather than a measurement; it is revised as the methods improve.More info
DINOv3 and CoralSCOP were run on the same photos and are listed for comparison. No diver transect exists for this trip, so agreement between the rows is not accuracy, and no computer-vision method yet estimates coral cover accurately on new images; treat every row as indicative.| Method | Hard coral cover (%) | Photos (n) ± SE |
|---|---|---|
| In-house DINOv3 | 18.3 | n = 82 · SE 1.0 |
| CoralSCOP unedited | 23.1 | n = 82 · SE 1.6 |
| Claude | 8.9 | n = 82 · SE 1.1 |
The two computer-vision methods agree within 4.8 pp (18.3–23.1%) and read 9.4–14.2 pp above Claude's blind point count (8.9%); the headline is Claude's blind point count because no transect or manual count exists here.
See a more detailed, stand-alone version of this table.
Data & links
All images from Coral Reef Diagnostics. Data are from Coral Reef Diagnostics.
© Coral Reef Diagnostics.
References
- Klomp KD, Kooistra DJ (2003). A post-hurricane, rapid assessment of reefs in the windward Netherlands Antilles (stony corals, algae and fishes). Atoll Research Bulletin 496:404-437. DOI