Alor - The Arch
Part of the regional summary: Indonesia - Alor
More info
East Nusa Tenggara (NOAA CRW virtual station) Alor and the Pantar Strait sit in a zone of exceptionally strong upwelling, which holds these reefs several degrees cooler than NOAA’s satellite-derived figures imply. Read the heat-stress numbers here as a regional-scale indication, not as this reef’s own temperature history.A wall dive off West Ternate Island in Alor with ledges of plating corals, massive coral boulders capped by mushroom-shaped overhangs, and a brain coral more than a meter across. The shallower reef is a near-continuous canopy of staghorn and cauliflower corals lit by sunbeams, with feather stars perched on the coral heads.
Penyelaman dinding di lepas Pulau Ternate Barat di Alor, dengan undakan karang lembaran, bongkahan karang masif yang dimahkotai ceruk berbentuk jamur, dan karang otak berukuran lebih dari satu meter. Terumbu yang lebih dangkal merupakan kanopi hampir menyambung dari karang bercabang dan bertipe kembang kol yang disinari berkas matahari, dengan lili laut bertengger di atas koloni-koloni karang.
Terjemahan ringkasan ini oleh AI; versi bahasa Inggris yang berlaku.
Two independent survey stations shown with the program’s logo — click one to see how far it is from this site.
Two 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 158 photographs from this site, including every one the text cites.
24 of the 50 photographs on this page are shown beside the text that discusses them under "Site description" below.
Site description
Setting
Alor, The Arch (West Ternate Island) — a wall/drop-off dive with structurally varied coral cover throughout the sampled frames (e.g., Image 3, Image 28).
Visibility ranged from a hazy blue mid-water background on the wall to clear, sunlit close-range framing in the shallows; no wreck, mooring, tag, or transect gear appeared in any reviewed frame. A steep wall and open-water drop-off combined with shallower mixed coral habitat (e.g., Image 15, Image 49).
General benthic features
The wall face and ledges carry large massive boulder corals, several capped by mushroom-shaped overhangs that create shaded arch-like recesses even where the site's namesake arch is not itself in frame, and a very large meandroid brain coral more than a meter across (e.g., Image 10, Image 35, Image 36, Image 43).
Foliose/plate corals form shelf-like ledges in several frames, often purple-pink or pale gray in tone — natural pigmentation and coralline-algae staining rather than bleaching (e.g., Image 6, Image 18, Image 42).
Cauliflower coral clumps in gray-purple tones and tabular coral plates recur through the mid-depth sections (e.g., Image 20, Image 22).
The shallower part of the dive is dominated by extensive dense staghorn/cauliflower coral thickets forming a near-continuous low canopy, several frames lit by strong sunbeams filtering down from the surface; one thicket includes a cluster of pale-tipped branches that reads as normal pale growing tips against otherwise healthy brown tissue rather than bleaching (e.g., Image 4, Image 14, Image 24, Image 40, Image 44).
Crinoids (feather stars) perch on several coral heads, and red-orange encrusting sponge crusts and small dark ball sponges occupy shaded crevices between colonies (e.g., Image 48).
Sand and exposed framework interrupted living cover; overhangs and strong light transitions carry the arch-and-wall character even where the arch itself is not in frame (e.g., Image 8, Image 13, Image 52).
Coral cover
- Reference: Claude CV point count (this site's photos)
- Coral cover: 23% — a blind Claude computer-vision point count of 155 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 crown-of-thorns predation, disease, or widespread bleaching was seen in the sample.
Fish and other fauna
Reef fish include schooling fusiliers and small planktivores in blue water off the wall, one school hanging over plating corals in sunbeams (e.g., Image 50), and damselfish and anthias among the branching thickets.
Comparisons with other data
We found no other surveys at this site as of 2026. Within 5 km, two independent stations (WCS Indonesia via MERMAID and WWF-US / WWF-Indonesia) recorded station-year means of 0.0–53% hard coral cover between 2014 and 2025; the nearest, WWF-US / WWF-Indonesia at station 5004, 0.72 km away, read 53% in 2014.
Regional context, not a survey of this site: Razak et al. (2026) found no significant trend in hard coral cover around Alor (a decline of 0.6% per year at 23 sites, surveyed by point-intercept transect at about 8–10 m in 2014, 2017, 2021, and 2023 by Yayasan WWF Indonesia); this is a trend for that location, not this site’s cover. Cover at those sites fell by 3% between the 2014 and 2017 surveys, which bracket 75 days of NOAA Bleaching Alert Level 1 from December 2016 to February 2017.
Other notes
Divers are visible at a distance in one gallery frame but are not the subject (e.g., Image 12).
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 | 23.2 | n = 155 · SE 0.8 |
| CoralSCOP unedited | 18.9 | n = 155 · SE 1.1 |
| Claude | 22.7 | n = 155 · SE 1.3 |
The two computer-vision methods agree within 4.3 pp (18.9–23.2%) and read within 3.8 pp of Claude's blind point count (22.7%).
See a more detailed, stand-alone version of this table.
Independent surveys nearby
| Agency / program | Year(s) | Stations / distance | Link |
|---|---|---|---|
| WCS Indonesia via MERMAID | 2025 | 1 station, 2.21 km | Records ↓ |
| WWF-US / WWF-Indonesia | 2014 | 1 station, 0.72 km | Records ↓ |
Coral Reef DiagnosticsYear-average (illustrative only, programs differ)Within 5 km, 2 independent survey stations recorded hard coral cover in 2 surveys between 2014 and 2025. One survey since 2021 recorded 0.0%. This site's own estimate (23%) sits 30 points below the one survey station up to 2 km away (53%); the methods differ, so the comparison is context, not a like-for-like test.
Collected by other programs using different methods (MERMAID is a data platform: each MERMAID row names the organization that did the survey, and its method is in the row's hover text), 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 |
|---|---|---|---|---|---|
| WWF-US / WWF-Indonesia | 5004 | 2014 | 53% | 0.72 km | Amkieltiela, Abdillah T, Amkieltiela A, Andradi-Brown D, Lazuardi E. 2015. MBD 2014 & 2015. MERMAID |
| WCS Indonesia via MERMAID | 1001 | 2025 | 0.0% | 2.21 km | Nurhayati. 2025. Ikan aya. MERMAID |
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
- Razak TB, Alisa CAG, Abrar M, Ardiwijaya R, Bachtiar I, Budaya RR, et al. (2026). Two decades of coral monitoring reveal thermal stress thresholds on Indonesian reefs. Biological Conservation 318:111781. DOI