Heron Island, Australia

A cay ( /ˈkiː/ or /ˈkeɪ/), also spelled caye or key, is a small, low-elevation, sandy island formed on the surface of a coral reef. Cays occur in tropical environments throughout the Pacific, Atlantic and Indian Oceans (including in the Caribbean and on the Great Barrier Reef and Belize Barrier Reef), where they provide habitable and agricultural land for hundreds of thousands of people. Their surrounding reef ecosystems also provide food and building materials for island inhabitants.

Formation and composition[link]

Cay sand under a microscope

A cay is formed when ocean currents transport loose sediment across the surface of a reef to a depositional node, where the current slows or converges with another current, releasing its sediment load. Gradually, layers of deposited sediment build up on the reef surface (Hopley 1981, Gorlay 1998). Such nodes occur in windward or leeward areas of reef surfaces and sometimes occur around an emergent outcrop of old reef or beach rock.

The island resulting from sediment accumulation is made up almost entirely of biogenic sediment – the skeletal remains of plants and animals – from the surrounding reef ecosystems (Hopley 1982). If the accumulated sediments are predominantly sand, then the island is called a cay; if they are predominantly gravel, the island is called a motu.

Cay sediments are largely composed of calcium carbonate (CaCO₃), primarily of aragonite, calcite, and high magnesium calcite. They are produced by myriad plants (e.g., coralline algae, species of the green algae Halimeda) and animals (e.g., coral, molluscs, foraminifera). Small amounts of silicate sediment are also contributed by sponges and other creatures (Chave 1964, Folk and Robles 1964, Scoffin 1987, Yamano 2000). Over time, soil and vegetation may develop on a cay surface, assisted by the deposition of sea bird guano.

Development and stability[link]

A range of physical, biological and chemical influences determines the ongoing development or erosion of cay environments. These influences include: the extent of reef surface sand accumulations, changes in ocean waves, currents, tides, sea levels and weather conditions, the shape of the underlying reef, the types and abundance of carbonate producing biota and other organisms such as binders, bioeroders and bioturbators (creatures which bind, erode and mix sediments) living in surrounding reef ecosystems (Harney and Fletcher 2003, Hart and Kench 2007).

Significant changes in cays and their surrounding ecosystems can result from natural phenomena such as severe El Niño Southern Oscillation (ENSO) cycles. Also, tropical cyclones can help build or destroy these islands (Scoffin 1993, Woodroffe 2003).

There is much debate and concern over the future stability of cays in the face of growing human populations and pressures on reef ecosystems, and predicted climate changes and sea level rise (Kench and Cowell 2003, Hart 2003). There is also debate around whether these islands are relict features which effectively stopped expanding two thousand years ago during the late Holocene or, as recent research suggests, they are currently still growing with significant new additions of reef sediments (Woodroffe et al. 2007).

Understanding the potential for change in the sediment sources and supply of cay beaches with environmental change is an important key to predicting their present and future stability. Despite, or perhaps because of all the debate around the future of cays, there is consensus that these island environments are very complex and somewhat fragile.

Examples[link]

Warraber Island, Torres Strait

Examples of cays include:

• Heron Island, a coral cay on the southern Great Barrier Reef
• Warraber Island in central Torres Strait (10°12' S, 142°49' E), Australia, a small ‘vegetated sand cay’ according to the classification schemes of McLean and Stoddart (1978) and Hopley (1982). Approximately 750 by 1500 m wide, this island is situated on the leeward surface of a large 11 km² emergent reef platform. This cay and the surrounding reef flat are Holocene in origin, having formed over an antecedent Pleistocene platform (Woodroffe et al. 2000).
• The Florida Keys are composed primarily of exposed ancient coral reefs and oolite beds formed behind reefs. A few of the Florida Keys, such as Sand Key, are "cays" as defined above.
• Tobacco Caye, Dangriga, Belize
• Prickly Pear Cays

See also[link]

• Quay
• Archipelago

References[link]

v t e Corals and coral reefs Stony corals Scleractinia Blue coral Brain coral Elkhorn coral Hermatypic coral Pillar coral Staghorn coral Table coral Soft corals Alcyonacea Black coral Bamboo coral Organ pipe coral Sea fans Sea pens Coral reefs Atoll reef Cay Fringing reef Microatoll Coral reef fish Census of Coral Reefs The Structure and Distribution of Coral Reefs Coral regions Deep-water coral Andros, Bahamas Belize Barrier Reef Coral Sea Islands Coral Triangle Florida Keys National Marine Sanctuary Great Barrier Reef Maldives Mesoamerican Barrier Reef System New Caledonia Barrier Reef Pulley Ridge Raja Ampat Islands Red Sea Southeast Asian coral reefs Coral diseases Coral bleaching Black band disease Skeletal eroding band White band disease White pox disease Protection Coral reef protection Project AWARE Reef Check Reef Ball Coral Reef Alliance International Society for Reef Studies Other Artificial reef Coral aquaculture Coral dermatitis Coral (precious) Coral rag Coral reef organizations Coral sand Coralline algae Human impact Fire coral Reef resilience Rugosa (extinct) Tabulate (extinct) Zooxanthella

Coordinates: 10°12′S 142°49′E / 10.2°S 142.817°E / -10.2; 142.817

Rum Cay is an island and district of the Bahamas. Lat.: N23 42' 30" - Long.: W 74 50' 00" - Size: 30 Sq. mls

Rum Cay is 20 miles (32 km) southwest of San Salvador Island, has many rolling hills that rises to about 120 feet (37 m). Christopher Columbus called it Santa Maria de la Concepción. The island is believed to have acquired its modern name from a shipwrecked cargo of rum. The main settlement is Port Nelson.

First known as Mamana by the Lucayan Indians, the cay was later renamed Santa María de la Concepción by Columbus. Spanish explorers once found a lone rum keg washed up on a shore and changed the name again to Rum Cay (pop: 53 1990 census). In the north there is a cave containing Lucayan drawings and carvings. Various artifacts from the Arawak period have been found by farmers in the fertile soil, which the Indians enriched with bat guano. In common with other islands, Rum Cay has gone through a series of industry specific economic peaks. Pineapple, salt and sisal have all been important industries, but competition and natural disasters, such as the 1926 hurricane, have all taken their toll and today tourism is the main source of employment. Plantation boundaries known as ‘margins’ can be seen all over the island, which date from the beginning of the 19th century when Loyalists settled here. Nearly everybody lives in Port Nelson where cottages can be rented. Settlements such as Port Boyd, Black Rock and Gin Hill are now deserted and overgrown.

Deep reefs and drop-offs surround this former pirates’ haven. There is staghorn coral at Summer Point Reef and diving at Pinder’s Point. At the Grand Canyon, 60-foot coral walls almost reach the surface. Sumner Point Marina has dockage, fuel, moorings, WiFi, bar and restaurant. There is a small guesthouse available from former Constable Ted Bain. The Last Chance Yacht Supply has groceries. Batelco office for phone calls closes at lunchtime. Yachts wait here before sailing to Mayaguana or the Turks and Caicos Islands, or before returning to Georgetown and points north.

Adventuresome divers can still find the shaft, anchor chains and hawser holes of HMS Conqueror. It sank in 1861 and can still be found in 30 feet of water in a staghorn gully near the breaking reef.

HMS Conqueror[link]

The wreck of the 101-gun man of war HMS Conqueror, built in Devon in 1855 and which served in the Crimean War, lies in 30 feet of water off Rum Cay where it sank in 1861, is preserved as the Underwater Museum of the Bahamas. It is the property of The Bahamas Government and none of the contents of the ship may be removed.

She was lost on Sumner Point Reef, Rum Cay, on December 13, 1861. All 1,400 aboard survived.

"She was 20 nm out in estimating her position and, after making her landfall, cut rounding the southeast point of Rum Cay too fine and went hard on the reef. Her captain, fearing that his crew (most of whom could not swim in those days) would drink themselves insensible when it became obvious the ship was lost, ordered all ale, wine, and spirit casks to be broken and their contents ditched. He then sent the two largest ship’s company unloaded everything they could salvage, and set about making a camp on the island. The captain remained on board with one midshipman and ten seamen until the ship broke up. Then all of them, less the boat parties, were marooned on Rum Cay. They were rescued soon after the news of the disaster was known."

"HMS Conqueror is still there. You can dive her, in some 30 feet of water." (The Bahamas Cruising Guide)

Before 1996 the island was part of a combined district of San Salvador and Rum Cay.

External links[link]

• General information about Rum Cay

Coordinates: 23°41′N 74°52′W / 23.683°N 74.867°W / 23.683; -74.867