Maldives - Big Sand Bank
Part of the regional summaries: Maldives - Central (Male Atolls / Ari / Vaavu) and Maldives
2017-05-18
More info
Maldives (NOAA CRW virtual station)Big Sand Bank hides a canyon maze of sponge- and soft-coral-draped swim-throughs beneath sunlit staghorn and tabletop terraces, photographed in January 2016.
Big Sand Bank ގައި، އިރުގެ އަލި ވައްޓާ ސްޓެގްހޯން އާއި ޓޭބަލް ހިރިގާގެ ފަށަލަތަކުގެ ދަށުގައި، ސްޕޮންޖް އާއި ސޮފްޓް ކޯރަލުން ނިވާވެފައިވާ، ފަތައިގެން ދެވޭ ހިސާބުތައް ހުރި ކަނޑިތަކުގެ ވަޅުވަޅެއް ފޮރުވިފައި ހުރެއެވެ. މި ފޮޓޯތައް ނެގީ 2016 ގެ ޖަނަވަރީގައެވެ.
AI translation of this summary; the English is authoritative. (low confidence)
mean; range 29.1–29.9°C
Five independent survey stations shown with the program’s logo — click one to see how far it is from this site.
Six other CRD dive sites with their own pages within 5 km shown in orange — click a marker to open its page.
8 of the 25 photographs on this page are shown beside the text that discusses them under "Site description" below.
Site description
Setting
Big Sand Bank hides a secret beneath its sunny name: a maze of canyons and swim-throughs where sheer walls squeeze the light into pale blue keyholes overhead (e.g., Image 5).
General benthic features
The passage walls drip with life that loves the shade — blue rope sponges slung like cables, red encrusting sponge, white lacework hydroids, feather stars, and soft corals in lavender and crimson (e.g., Image 2, Image 8, Image 9).
Then the reef climbs into the light and changes character completely: staghorn thickets boiling with blue-green chromis, tabletop corals stacked along the spurs, and pink cauliflower corals crowding the crests (e.g., Image 14).
Coral cover
- Reference: Claude CV point count (this site's photos)
- Coral cover: 10% — a blind Claude computer-vision point count of 21 of Anderson's edited photographs (20 points per photo; water, fish, and obstructions excluded). Other computer-vision methods are listed in the method table.
Stressors
During a crown-of-thorns removal survey in May 2017, divers from Coral Reef CPR and Carpe Diem Maldives removed 60 crown-of-thorns starfish from this reef (Coral Reef CPR 2017). By the May 2017 return visit, photo-derived cover had fallen from 26% in January 2016 to 10%. In January 2016 a few small stark-white colonies among living ones were already recently dead, cause unstated (e.g., Image 12).
Fish and other fauna
A Clark's anemonefish guards its anemone, a moorish idol works the spur tops, electric-blue fusiliers rip past in formation, and anthias spill over every rim like orange confetti (e.g., Image 4, Image 20).
Comparisons with other data
Coral Reef CPR and Carpe Diem Maldives surveyed this site for crown-of-thorns sea stars in May 2017. Within 5 km, five independent stations recorded station-year means of 5.5–60% hard coral cover between 2012 and 2025; the nearest, Montefalcone et al. 2026 at Bajiy Giri, 2.59 km away, read 43–60% between 2024 and 2025.
Dive record
Photographed in January 2016, three months before the El Niño bleaching rewrote these reefs, and again in May 2017, after it.
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. Same site, January 2016 → May 2017: 26% → 10% (Same site and method: Claude computer vision on Anderson's photos, January 2016 → May 2017). January 2016: 26% on 49 photos (before the 2016 bleaching); May 2017: 10% on 21 photos.More info
Other rows are for comparison only and are never averaged. No diver transect exists for these photos, so agreement between rows is not accuracy.| Method | Hard coral cover (%) | Photos (n) ± SE |
|---|---|---|
| In-house DINOv3 | 15.8 | |
| CoralSCOP edited | 19.6 | |
| Claude (edited photos) | 10.3 | n = 21 · SE 1.9 |
| Claude, January 2016 photos (earlier point) | 25.6 |
The two computer-vision methods agree within 3.8 pp (15.8–19.6%) and read 5.5–9.3 pp above Claude's blind point count (10.3%); 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.
Independent surveys nearby
| Agency / program | Year(s) | Stations / distance | Link |
|---|---|---|---|
| Montefalcone et al. 2026 | 2024–2025 | 2 stations, 2.59–3.78 km | Records ↓ |
| Reef Check | 2012 | 1 station, 3.61 km | Records ↓ |
| XL Catlin Seaview Survey | 2015–2017 | 2 stations, 4.33 km | Records ↓ |
Coral Reef DiagnosticsYear-average (illustrative only, programs differ)Within 5 km, 5 independent survey stations recorded hard coral cover in 10 surveys between 2012 and 2025. Of the 3 stations surveyed in more than one year, 2 were scored by divers or by people annotating photographs: 2 declined (by 4.0–17 points) between their first and latest surveys. The other 1 was scored by automated image analysis: changed by 7 points or less, inside the 7-point method-noise floor (inconclusive). The longest record, transect 37035 (XL Catlin Seaview Survey, 4.33 km away), went from 7.1% in 2015 to 5.5% in 2017. Since 2021, station-year means average 46% (range 39–60%; n = 4 station-years from 4 surveys). This site's own estimate (10%) is not compared with these surveys: none lies within 2 km.
Collected by other programs using different methods (Reef Check uses point-intercept transects; the XL Catlin Seaview Survey uses photo-transects with automated image annotation), so these are context for the figures above, not a like-for-like comparison. Where a station was surveyed more than once, the cell shows either the range of its values or, as a single value, the mean of surveys made in one year. Station names are not dive-site names.
| Agency | Site / location | Date | Hard coral cover (%) | Distance | Link |
|---|---|---|---|---|---|
| Reef Check | Biyadhoo House Reef | 2012 | 18%, mean of 3 surveys (4 m, 7 m, and 12 m) | 3.61 km | — |
| XL Catlin Seaview Survey | transect 37035 | 2015–2017 | 5.5–7.1% (2 surveys) | 4.33 km | doi:10.14264/uql.2019.930 |
| XL Catlin Seaview Survey | transect 37036 | 2015 | 38% | 4.33 km | doi:10.14264/uql.2019.930 |
| Montefalcone et al. 2026 | Bajiy Giri | 2024–2025 | 43–60% (2 surveys) | 2.59 km | doi:10.1007/s00338-026-02850-x |
| Montefalcone et al. 2026 | Kuda Giri Wreck | 2024–2025 | 39–43% (2 surveys) | 3.78 km | doi:10.1007/s00338-026-02850-x |
Data & links
All images from Coral Reef Diagnostics. Data are from Coral Reef Diagnostics and the organizations named in the data sources above.
© Coral Reef Diagnostics.
References
- Montefalcone M, Bianchi CN, Morri C, Ahmed H, Pancrazi I (2026). Outcomes of the fourth global coral bleaching (2023–2024) in the Maldives. Coral Reefs. DOI
- Coral Reef CPR & Carpe Diem Maldives Pvt. Ltd. (2017). Crown-of-thorns starfish removal report, North and South Malé Atolls, 13-20 May 2017. PDF
- Gonzalez-Rivero M, et al. (2019). Seaview Survey photo-quadrat and image classification dataset. The University of Queensland (UQ eSpace) data collection. DOI