Raja Ampat - Pulau Koon dive 1

Setting

Pulau Koon, the first of the trip's three dives on this island, off the eastern tip of Seram in the Banda Sea, not in Raja Ampat itself. That combination — a mobulid (manta-type) ray in the blue, a wall of planktivores over the reef crest, and a scoured sand-and-rubble bottom — reads as a current-swept site, and Anderson's dive log confirms it: "Strong current pushing us off the reef", which meant running low on air after only 25 minutes. Visibility was moderate: the close-down frames are clear at short range but the mid-water frames go quickly hazy blue, and the ray shots are grainy and low-contrast. Light in the deeper frames is dim and blue-shifted, consistent with a mid-to-deep slope; the logged maximum was 33.8 m.

General benthic features

What the frames from this dive show is a low-relief, sediment-influenced lower slope rather than a coral garden. Open white carbonate sand and coral rubble take up a large share of every benthic frame, with the hard substrate between the sand patches heavily overgrown by crustose coralline algae — pink, mauve, and lilac crusts are the single most conspicuous encrusting cover in the close-down frames — along with dark red encrusting algae or sponge (e.g., Image 1).

1

Hard corals are present as scattered discrete colonies rather than as continuous framework. The most striking are large thin plating and foliose colonies: a tiered, shingled stack of deep maroon-brown plates with pale living margins and a finely pitted surface, most consistent with Montipora; broad, near-horizontal gray-purple plates lying almost flat on the sand-rubble floor with clean white growing rims, consistent with Turbinaria or a plating Montipora; and one very large low-domed to encrusting colony over a meter across on the deeper slope, smooth-surfaced and olive-gray with a whorled skirted margin, which the imagery does not resolve to genus (e.g., Image 2).

2

Small tan encrusting-to-submassive colonies with fine porous surfaces, consistent with Porites, sit low among the coralline crusts. There are no big tabulate Acropora, no staghorn thickets, and no massive brain corals in this sample. Soft corals and other invertebrates carry much of the color. Pale lilac and white arborescent soft corals of the Nephtheidae type grow in small clumps through the coralline pavement, with orange and salmon soft corals on the flanks of rubble mounds. A single very large barrel sponge, deep red-purple with strongly grooved ridged walls and roughly a meter tall, is the set piece of one frame — consistent with Xestospongia testudinaria (e.g., Image 3).

3

Other sponges include orange encrusting crusts, a small purple-brown barrel, and dark ball sponges growing directly on the big dome coral. Black-coral bushes (Antipathes-type) are frequent in the deeper, sandier frames, standing as dark feathery shrubs straight out of the sand-rubble floor, along with a fine gray-white mesh gorgonian sea fan and free-living crinoids. A recurring yellow-ochre colony with a finely anastomosing, net-like or lace-like skeleton appears in two frames pressed against the plating corals; photographs alone cannot separate a lace bryozoan of the Triphyllozoon type from a reticulate hydrocoral (e.g., Image 2). Several frames also carry yellow-brown bushy growths on rubble that read as either macroalgae or dense turf.

Coral cover

• Too few images to estimate coral cover (about ten frames from this dive).

Stressors

Condition looks generally healthy in the frames available, though Anderson's dive log records some pale and bleached Seriatopora caliendrum in the shallows at 10 m. There is no bleaching front, no crown-of-thorns, no obvious disease lesion, and no anchor or blast damage. Two small white patches of bare skeleton show on the upper surface of one maroon plating colony — too small and too few to call anything more than minor partial mortality. The abundance of open rubble, sand, and coralline-crusted pavement is worth noting, but seven benthic frames cannot show whether that reflects long-standing sedimentary habitat, past disturbance, or simply where the photographer chose to point the camera.

Fish and other fauna

The vertebrate highlights are what mark this dive. A green turtle (consistent with Chelonia mydas) was photographed twice, first at rest on a sand patch among black-coral bushes and crinoids and then swimming low over the sand, with two other divers and their strobes in frame both times (e.g., Image 4).

4

Two frames show a mobulid (manta-type) ray in open blue water: one is a distant silhouette above a dark reef top with a dense cloud of small planktivores filling the water column, the other is a clean lone ray against blue with no substrate at all (e.g., Image 5).

5

Reef fish in the frames are modest: a black-and-yellow striped sweetlips, scattered dark damselfishes and chromis over the plate corals, a small yellow-tailed fish over the sand, and a few unidentifiable planktivores in the mid-water.

Comparisons with other data

Ceccarelli et al. (2022) surveyed this site (Koon MPA) in 2016, 2018, and 2020. Within 5 km, eleven independent stations recorded station-year means of 18–47% hard coral cover between 2016 and 2023; the nearest, Institut Pertanian Bogor (IPB) at KOE02, 0.42 km away, read 29% in 2023.

Regional context, not a survey of this site: Razak et al. (2026) found no significant trend in hard coral cover at Koon, the marine protected area off eastern Seram (a rise of 0.2% per year at 17 sites, surveyed by point-intercept transect at about 8–10 m in 2016, 2018, and 2020 by Yayasan WWF Indonesia); this is a trend for that location, not this site’s cover. Koon warmed by 0.25°C per decade over 1985–2023, and the only NOAA bleaching alerts the study lists there ran from December 2022 to February 2023 (73 days at Bleaching Alert Level 1).

Dive record

Anderson's dive log records three separate dives at Pulau Koon on 17 October 2018, and the camera's own file numbering here is consistent with that date; site 1, site 2, and site 3 are three different sites and are described separately.

Other notes

The only man-made objects in frame are the divers themselves, their fins, tanks, and camera-strobe rigs.