Biogeography of Deep-Water Chemosynthetic Ecosystems

A global study of the biogeography of deep-water chemosynthetic ecosystems and the processes that drive them.

Project Leaders:

Professor Paul Tyler, National Oceanography Centre Southampton, Southampton, UK

Professor Chris German, Woods Hole Oceanographic Institution, Woods Hole, MA, USA

The Biogeography of Deep-Water Chemosynthetic Ecosystems (ChEss) is one of the six initial field projects of the Census of Marine Life (CoML). ChEss is a global study of the biogeography and biodiversity of deep-water chemosynthetic ecosystems and the processes that drive them. Directed from the National Oceanography Centre Southampton (SOC) in the United Kingdom, ChEss aims to improve our knowledge of the diversity, abundance and distribution of species form chemosynthetically-driven ecosystems.


Deep-sea hydrothermal vents and their associated exuberant fauna were first discovered along the Galapagos Rift in the eastern Pacific in 1977. Vents are now known to occur along all active mid ocean ridges and back-arc spreading centres. On these mountain chains, hydrothermal fluid, originating from seawater seeping through the earth's crust, emerges from the seafloor at temperatures of 350°C. The fluid is charged with dissolved metals and sulphur, which precipitate when the fluid mixes with the surrounding cold seawater, appearing as dense black smoke. The deposition of these particles forms the vent chimneys reaching up to 20 m! One of the striking characteristics of the fauna living at vents is that the organisms live independently from the sun and solar-based production. Instead, it is mircoorganisms that are at the base of the food web in the vent habitats, producing organic compounds from CO2 and the energy of reduced chemicals in the hydrothermal fluid. These bacteria are both free living and also in symbiotic relationships with many invertebrate species, and their production supports dense populations of exotic organisms.

The interest in large chemosynthetic environments was strengthened by the discovery of chemosynthetic-based fauna at cold seeps along the base of the Florida Escarpment in 1983. Cold seeps are areas where methane seeps through sediments in the ocean floor. Sulfide is also an important element of some cold seeps, produced by sulphate reduction in the sediments. Both methane and sulfide play a critical role in the maintenance of the highly productive cold seep communities. Cold seeps occur along active and passive continental margins.


Other systems have also been found to support chemosynthetic based fauna, such as the communities developing on carcasses of dead whales, on sunken wood, or in the sediments of minimum oxygen zones intersecting with subduction margins.


Combining research on all the above-mentioned systems is critical to understand the biogeography and biodiversity of deep-water chemosynthetic ecosystems.


Aims of the project
To achieve its objectives, ChEss will follow two approaches:

  • To create a web-based relational database for species from chemosynthetic systems, available through the ChEss web site and integrated in OBIS.
  • To develop a long-term international field programme for the discovery and exploration of new vent and seep sites and the study of their fauna.

Exploring for new sites
The field phase of ChEss aims to develop a long-term, international exploration programme that will target key locations for the understanding the biogeography of chemosynthetic ecosystems at the global scale. The selection of these key locations has been based on a number of specific scientific questions related to the distribution, isolation, evolution and dispersal of deep-water species from chemosynthetically-driven systems.


Two large areas of combined systems have been chosen as endorsed areas for ChEss:

  • The Equatorial Belt spans from the Costa Rica cold seeps to the African continental margin, including the Cayman Trough, the Gulf of Mexico cold seeps, the Barbados Prism, the Mid-Atlantic Ridge north and south of the Romanceh Fracture Zone and the northern Brazilian continental margin.
  • The SE Pacific includes the Chile Rise, the cold seeps and oxygen minimum zone of the southern Chilean continental margin and an important migration area for whales.

ChEss also endorses research on a number of specific locations that already have important national and/or international support. These areas have been grouped under the section Pole-Indian Ocean-Pole (PIP). PIP comprises the Gakkel Ridge in the Arctic, the East Scotia Ridge on the Antarctic, and the central and southwest Indian Ridges in the Indian Ocean.

Into the future
During the field programme, ChEss will promote the development and refinement of deep-towed, remotely operated (ROV) and autonomous underwater (AUV) vehicle technologies to locate, map and sample new chemosynthetic systems. Using optical, chemical and acoustic techniques, ChEss researchers hope to gain a better understanding of not only biogeographical patterns, but also to determine the processes driving these ecosystems.


Since the fist discovery of hydrothermal vents more than 25 years ago, more than 500 species have been described from vents and seeps. This is the equivalent of 1 new description every 2 weeks! As biologists, geochemists, and physics combine research efforts in these systems, new species will certainly be discovered. Moreover, because of the extreme conditions of the vent and seep habitat, certain species may have specific physiological adaptations with interesting results for the biochemical and medical industry.


Also, these globally-distributed, ephemeral and insular habitats that support endemic faunas offer natural laboratories for studies on dispersal, isolation and evolution. Here, hydrographic and topographic controls on biodiversity and biogeography might be much more readily resolved than in systems where climate and human activity obscure their role.


In addition, hydrothermal vents have been suggested to be the habitat of the origin of life. These hypotheses are being used by ChEss researchers in collaboration with NASA to develop programmes for search of life in planets or moons of the outer space.


Visit the ChEss web site.

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