Bonaire

Bonaire is an oceanic island rising from deep water north of Venezuela and ringed by continuous fringing reefs (Wells 1988). Along the sheltered leeward coast a gently inclined submarine terrace, 20–160 m wide, runs out to a drop-off near 10 m, below which the reef slope falls at anything from 30° to vertical down to 50–60 m (Wells 1988; Spalding et al. 2001). Wells (1988) outlines a leeward zonation that grades from encrusting Diploria clivosa at the shoreline, through Acropora palmata with Millepora at 1–4 m and A. cervicornis at 4–7 m, to Montastraea annularis at the drop-off and M. annularis with Agaricia agaricites on the upper slope, and credits the island with about 55 stony coral species. Spalding et al. (2001) add that spur-and-groove structure is prominent on the slope, particularly off the northwest shore, whereas the windward east coast carries little coral above 12 m. White-band disease killed more than 90% of the A. cervicornis standing stock across the Dutch Leeward Islands in 1980–1982 (Wells 1988). At four sites on Curaçao and Bonaire, cover at 10–20 m fell from 50–55% to 25–30% between 1973 and 1992, while cover at 30–40 m changed little (Spalding et al. 2001). The Bonaire Marine Park, set up in 1979, takes in all waters from the high-water mark to 60 m. Spalding et al. (2001) estimate about 420 km² of coral reef for the former Netherlands Antilles, a combined figure for Bonaire, Curaçao, Saba, St. Eustatius, and St. Maarten.

Souter et al. (2021) report recent trends only for the Eastern and Southern Caribbean as a whole, a subregion that groups the Lesser Antilles with Trinidad and Tobago, Aruba, Bonaire, Curaçao, and Venezuela. Across it, mean hard coral cover fell from about 26% in 1999 to 15% in 2019, the largest decline among the five Caribbean subregions, while algal cover nearly tripled between 1987 and 2019 to reach 48.3%. For the Caribbean as a whole, the same report links these losses to the 2005 mass bleaching, hurricanes, nutrient-laden, polluted coastal water, and overfishing of herbivores such as parrotfishes, and it names invasive lionfish, Sargassum influxes since 2011, and stony coral tissue loss disease (SCTLD) as newer threats; SCTLD, first seen in Florida in 2014, had been confirmed in 19 Caribbean countries and territories by October 2021. Earlier, Wilkinson (2006), drawing on the 2004 Caribbean Reefs at Risk assessment, placed the southern Caribbean among the areas where coastal development posed the greatest threat.

The twelve Bonaire sites were dived over 20-24 February 2017 along the island's leeward coast, from Wayaka II and Karpata in the north to Vista Blue, The Chairs, and Chogogo in the south. Maximum depths ran from 31.1 m at the Hilma Hooker and Weber's Joy to 39.9 m at Alice in Wonderland, with average depths of 12.5 to 17.4 m. Most sites are fringing reefs that step from shallow sand, rubble, or algal pavement onto a steep slope or wall. The Cliff, Oil Slick Leap, La Dania's Leap, Wayaka II, and Weber's Joy all carry walls of dense, overlapping plate and lettuce corals above fields of massive boulder and brain corals. Alice in Wonderland is a double reef, with two parallel crests separated by a broad rippled sand channel.

The sites differ in their dominant benthos. At Karpata the slope is an unbroken carpet of boulder star coral heads. Between Pink Beach and White Slave, Chogogo, and Vista Blue are octocoral-dominated, where sea rods, whips, and plumes provide most of the vertical structure over sand aprons with garden eels. Living elkhorn, Acropora palmata, was photographed in the shallows at Karpata, Alice in Wonderland, The Cliff, La Dania's Leap, and The Chairs, which has several large colonies, and Chogogo has an elkhorn colony or remnant. Extensive staghorn thickets, Acropora cervicornis, grow on the reef beside the Hilma Hooker wreck, which lies on its side, its hull crusted with sponges and carrying very few, if any, corals. Context (dive-operator and press sources): the Hilma Hooker is a 236-foot (72 m) freighter that sank at anchor in 1984 while held as evidence.

No broad bleaching was visible at any site, and most colonies retained pigmented tissue. Old partial mortality is common on large brain corals, notably at Karpata, La Dania's Leap, and Weber's Joy. Wayaka II is a reef of two halves: a healthy wall and slope, but a shallow field of old, eroded dead branching framework. Blind Claude computer-vision point counts of Anderson's edited photographs put coral cover from 8.6% at Between Pink Beach and White Slave to 36% at Karpata; the earlier CoralSCOP indices, which read high, are comparisons on each page. For context, Reef Check recorded 28% at Karpata Reserve in 2003 (yearly means 24–34% across eight surveys, 2000–2003) and 43% at Twin Peaks near Wayaka II in 1998 (50% in 1997). Hawksbill turtles, tarpon, stingrays, and spotted eagle rays were among the larger animals seen.