Darwin Mounds
Unique deep-water sand mounds with ancient cold-water coral reefs.
Here is the rewritten encyclopedia entry in a plain, factual voice.
Deep beneath the North Atlantic, about 100 nautical miles northwest of Cape Wrath, lies a vast field of sand mounds known as the Darwin Mounds. Discovered in May 1998, these features sit roughly 1,000 meters below the surface. They were identified using remote sensing during surveys funded by the oil industry and coordinated by the Atlantic Frontier Environment Network, a joint industry and UK government group. The mounds take their name from the research vessel that found them, which itself was named after Charles Darwin.
The field covers about 100 square kilometers and contains hundreds of individual mounds. These are typically circular, reaching up to 5 meters in height and 100 meters across. Most mounds also have a distinctive "tail" feature. These tails are teardrop-shaped, oriented to the southwest, and can merge with others. This mound-tail structure appears to be unique in the world.
The mounds are mostly sand, thought to be "sand volcanoes" formed when fluidized sand de-waters and bubbles up, pushing sediment into a cone. While sand volcanoes are common in the Devonian fossil record and in seismically active regions, tectonic activity is unlikely here. Instead, slumping on the southwest side of the Wyville-Thomson Ridge is a more probable cause. The tops of the mounds host living stands of *Lophelia* coral and blocky rubble interpreted as coral debris. This makes the Darwin Mounds one of the largest known northern cold-water coral habitats. Notably, *Lophelia pertusa* grows on sand here, whereas before research in 2000 it was thought this coral required a hard surface to attach.
These deep-water coral systems are especially fragile, unlike shallow-water reefs that can handle wave action. The mounds also support high densities of the xenophyophore *Syringammina fragilissima*, a giant single-celled protozoan that can grow larger than 20 centimeters. The corals themselves provide habitat for a wide range of marine life, including sponges, worms, crustaceans, molluscs, starfish, sea urchins, crabs, and fish such as blue ling, roundnose grenadier, and orange roughy.
Conservation efforts began after the mounds were discovered.
- Discovery date
- May 1998
- Depth
- approximately 1,000 metres (3,300 ft)
- Location
- approximately 100 nautical miles (190 km) north-west of Cape Wrath, Scotland
- Area covered
- approximately 100 square kilometres (39 mi2)
- Individual mound height
- up to 5 metres (16 ft)
- Individual mound width
- up to 100 metres (330 ft)
- Protection date
- 22 March 2004
Lore & Background
The mounds were first discovered in May 1998 using remote sensing techniques during surveys funded by the oil industry and steered by the joint industry and United Kingdom government group the Atlantic Frontier Environment Network (AFEN). They were named after the research vessel, itself named for Charles Darwin. The mounds are mostly sand, interpreted as 'sand volcanoes' formed when fluidised sand 'de-waters' and pushes sediment up into a cone shape. Tectonic activity is unlikely; some form of slumping on the south-west side of the Wyville-Thomson Ridge is a more likely cause.
The tops of the mounds have living stands of Lophelia and blocky rubble interpreted as coral debris. The mounds are unusual in that Lophelia pertusa appears to be growing on sand rather than a hard substratum, contrary to prior belief. The mounds also support significant populations of the xenophyophore Syringammina fragilissima, a giant single-celled organism that occurs in particularly high densities on the mounds and tails. The corals provide habitat for diverse marine life including sponges, worms, crustaceans, molluscs, starfish, sea urchins, crabs, and fish such as blue ling, roundnose grenadier, and orange roughy.
Reader's Guide
The Darwin Mounds are significant as one of the largest known northerly cold-water habitats for coral species, and their mound-tail feature is apparently unique globally. The deep-water coral systems are especially fragile, not adapted to cope with minor disturbances like wave action. After discovery, three well-documented surveys were undertaken in June 1998, August 1999, and twice during summer 2000, using side-scan sonar, stills and video cameras, and piston corers. Deep water bottom trawling had been occurring, with nets as heavy as one tonne dragged across the sea floor. Researcher Jason Hall-Spencer found pieces of coral at least 4,500 years old in trawler nets, and pieces up to 1 square metre were found in French trawling vessels' nets. Much coral was destroyed and mounds were scraped and flattened; the damage is permanent. On 23 October 2001, UK Minister Margaret Beckett committed at WWF's Oceans Recovery Summit in Edinburgh to protect the mounds. On 22 March 2004, EU Fisheries Ministers agreed to give permanent protection, and deep-water bottom trawling in the area was made illegal.
Did You Know?
- Individual mounds are typically circular, up to 5 metres high and 100 metres wide.
- The mound-tail feature of the Darwin Mounds is apparently unique globally.
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