Continental Margin Ecosystems (COMARGE)
An integrated effort that documented and explained biodiversity patterns on gradient-dominated continental margins, including the potential interactions among their variety of habitats and ecosystems.
Myriam Sibuet, Ph.D., Institut Océanographique, Paris, France
Robert Carney, Ph.D., Lousiana State University, Baton Rouge, Louisiana, USA
Lenaick Menot, Ph.D., Institut Océanographique, Paris, France, & Ifremer, Brest, France
The continental margins are the ribbons of seafloor beginning at the edge of the continental slope and extending rapidly to abyssal plain depths. During the past few decades, our understanding of deep continental margin habitats has changed more than for any other large area of Earth. While it has been known for a long time that the ocean margins are a mixture of rugged mountainous scenery and sediment- covered slopes, it is only in recent times, with higher-resolution bathymetry and increased bottom sampling, that areas once envisioned as monotonous landscapes are now acknowledged to have a high degree of complexity and diversity. Continental margins furthermore support some of the ocean's strongest gradients (e.g. depth, pressure, organic matter flux, oxygen). Collectively, these processes create unique ecosystems, some only now being discovered and which we are just beginning to understand. As exploitation of living and mineral resources is advancing faster than ecological knowledge on continental slopes, a comprehensive analysis of species distribution, biodiversity patterns and processes on continental margins was needed.
Structural complexity of continental margins: A 3D bathymetry of the
Equatorial West African margin, cut by the Zaire canyon (© Ifremer - Zaiango project)
COMARGE was a field project of the Census of Marine Life launched in 2005. The project aimed to:
2. Identify the contribution of environmental heterogeneities to these patterns.
Variety of ecosystems on continental margins: Most continental margin fauna is fed by a rain or rather a drizzle of organic matter from the sunlit ocean but locally, the natural seepage of methane provides an alternative energy source for chemosynthetic ecosystems [from Sibuet M and Olu-Le Roy K (2002) in Wefer G, Billet D, Hebbeln D, Jorgensen BB, Schlüter M, van Weering T (eds) Ocean Margin Systems. Springer, Berlin, p 235-251].
Interactions: Organic matter flux, faunal biomass and densities are enhanced at the edge of an Oxygen Minimum Zone (The Oman Margin, 3200 m depth - © National Oceanographic Center, Southampton, UK).
The deep-sea macrobenthos: We currently know about 250,000 marine species;
those small animals living in or near sediments may add up to 10 million species to the list.
Rich and fragile: Either patchily distributed at the meter scale or forming km-wide and
thousand year-old carbonate mounds, deep-sea corals harbor 1300 known species in
the North East Atlantic (© Ifremer - Caracole - 2001).
* For the off shore oil and gas and fishing industries, where scientific expertise is needed to advise on environmental survey protocols, to provide a taxonomic clearing house and to forecast environmental risks.
* For the conservation stakeholders, enabling them to address conservation issues in the deep sea on a sound scientific basis.
* For national interests (governments) that wish to protect the biodiversity and natural resources within their Exclusive Economic Zones (EEZs).