Deep water corals and new fish found in pioneering deep-water survey of Ascension Island

August 18, 2017 by Paul Brickle

In October 2015, scientists from six major institutes carried out the first-ever exploration of the deep water around Ascension Island, in a survey made possible by BLUE funding. As one team member described it at the time, this was the ‘frontier of science’, going where no one had been before.

 

The results of that deep-water survey have just been published in a special edition of the Journal of the Marine Biological Association of the United Kingdom1, providing a fascinating level of detail on Ascension’s unique marine environment.

The survey provides the first detailed physical and biological investigation of Ascension’s deep-water environment, from 100 to 1000 metres beneath the surface, giving us new insight into the habitats and communities found at those depths. This is an absolutely pioneering piece of work as previous work has focused mostly on turtles, seabirds and shallow water coastal communities. Previous deep-water work has been severely limited by the technical and logistical challenges involved.

The 2015 survey had three objectives: to map the seabed using sonar, to identify deep-water species using various techniques including underwater photography, and to collect specimens from previously unsampled areas.

As a result of the first objective, near-complete coverage of the waters around Ascension Island from 100 to 1000 metres in depth is now available for the first time, depicting habitats at much greater scale and resolution than previously available. Regarding the other two objectives, it was found that species diversity was perhaps higher than might be expected for an island as small, young and isolated as Ascension (Ascension, produced by volcanic eruption, is thought to be only one million years old). The survey found that particularly plentiful species included the brittle star, tube worms, and squat lobsters.

A particularly interesting finding is that the cold-water coral Lophelia cf.pertusa was recorded as deep as 1020 m. Deep water coral communities are not well-known from the South Atlantic and indeed this study provides the first record of substantial collections of reef-building hard, stony (scleractinian) corals from Ascension’s shelves. This is an exciting finding as cold-water coral reefs support high levels of biodiversity and enhance deep-water carbon accumulation. Another exciting finding is that two species of Grenadier fish found during the specimen collection are likely to be new records for Ascension. Both of these discoveries clearly demonstrate how the survey has expanded and improved our understanding of Ascension’s marine biodiversity.

This survey and its results significantly improve our baseline knowledge of Ascension’s marine environment and its biodiversity and contribute to a better overall understanding of tropical Atlantic biogeography. Not only can this type of data provide a solid foundation for further study, it is also absolutely essential for good management of the marine environment as such detailed data enables identification of important or vulnerable habitats which may require protection. This baseline data is also required as a starting point from which responses to future environmental change can be monitored.

In addition, the deep-water survey formed part of a wider detailed study of Ascension’s marine environment where 20 papers reported on the results of 202 sampling events comprising a mixture of quantitative scuba surveys involving belt transects for fish and mobile fauna and quadrat photography for sessile fauna. Intertidal surveys and collections and subtidal collections were also carried out. Highlights included one new species of alga and 2 new species of Heterobranch sea slugs, many new geographical records for fish and invertebrates therefore providing a much improved baseline knowledge of the coastal marine environment.

Dr Judith Brown, director of conservation & fisheries for the Ascension Island Government, commented: ‘The research which is detailed in this special issue, carried out with such a knowledgeable and enthusiastic group of collaborators, established marine conservation research on Ascension and has provided much needed baseline data. Marine research on Ascension is going from strength to strength, with the partnerships that were made here and continued through further funding from the UK Government, Blue Marine Foundation, the Darwin Initiative, and EU Best. These projects will provide the information needed to allow the informed designation of a large MPA in 2019 based on the scientific evidence collected.’

Dr Paul Brewin, director of the Shallow Marine Surveys Group based in the Falkland Islands added ‘This series of expeditions has fulfilled a long-time ambition of SMSG.  Supported through our local Falkland and overseas volunteer team, we worked along-side our Ascension Island partners for the first time, in helping them address an identified urgent need for baseline, high-quality scientific marine understanding.  Through this work we’ve built both strong collaborations and lasting friendships with all the team.’

By Paul Brickle, director of the South Atlantic Environmental Research Institute

 

1Journal of the Marine Biological Association of the United Kingdom. Ascension Island Special Issue. Volume 97 Issue 4 – June 2017. https://www.cambridge.org/core/journals/journal-of-the-marine-biological-association-of-the-united-kingdom/issue/CBA2C78939DA53DD2C532255B01B01A9