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Cold Seep Ecosystems European Margins or collective redistirbution of any portion of this article by photocopy machine, reposting, or other means is permitted only with the approval of The approval portionthe ofwith any articlepermitted only photocopy by is of machine, reposting, this means or collective or other redistirbution This article has This been published in HERMES SPECIAL ISSUE FEATURE Oceanography , Volume 22, Number 1, a quarterly journal of The 22, Number 1, a quarterly , Volume Biodiversity of Cold Seep Ecosystems O Along the Society. ceanography © European Margins The 2009 by O BY Ann Vanreusel, Ann C. ANDersen, AntJE BOetius, reproduction, systemmatic Republication, article for use and research. this copy in teaching to granted rights Society. All reserved. is ceanography Permission DOUGlas COnnellY, Marina R. Cunha, CarOle DecKer, O Ana HilariO, KOnstantinOS A. KOrmas, or Th e [email protected] Send Society. ceanography to: correspondence all LOÏS MaiGnien, Karine Olu, Maria PachiaDAKI, BeneDicte Ritt, Clara RODriGues, JOZÉE SarraZin, Paul TYler, SasKia Van Gaever, anD Heleen Vanneste O ceanography Society, P Society, ceanography O Box 1931, Rockville, M ROV Victor 6000 taking a water sample above a bush of Siboglinidae polychaetes in the central Nile Deep Sea Fan. D Image courtesy of Ifremer/MEDECO Cruise 2007 20849-1931, USA. 110 Oceanography Vol.22, No.1 Abstract. During the European Commission’s Framework Six Programme, HERMES, we investigated three main areas along the European margin, each characterized by the presence of seep-related structures exhibiting different intensity of activity and biological diversity. These areas are: (1) the Nordic margin with the Håkon Mosby mud volcano and many pockmarks, (2) the Gulf of Cádiz, and (3) the eastern Mediterranean with its hundreds of mud volcanoes and brine pool structures. One of the main goals of the HERMES project was to unravel the biodiversity associated with these seep-associated ecosystems, and to understand their driving forces and functions, using an integrated approach. Several multidisciplinary research cruises to these three areas provided evidence of high variability in ecosystem processes and associated biodiversity at different spatial scales, illustrating the “hotspot” nature of these deep water systems. IntrODuctiON observation of the European continental (Sloan, 1990) to transform seawater Soon after the discovery of the spec- margins using in situ video and photog- sulfate, thus producing high fluxes of tacular hydrothermal vent communities raphy with adapted deep submersibles hydrogen sulfide (Jorgensen and Boetius, 30 years ago, other types of chemo- provided evidence for a wide range of 2007). Chemosynthetic microorgan- synthetic assemblages—so-called “cold active cold-seep ecosystems associated isms are the primary producers in seep seeps”—were found along continental with fluid, gas, and mud escape struc- food webs, depending on such reduced margins during submersible dives to tures. These structures include pock- chemicals as methane and sulfide as the deep Gulf of Mexico (Paull et al., marks (seafloor depressions), brine lakes, their energy sources. 1984), subduction zones off Oregon in and elevated or flat mud volcanoes. Similar to their hydrothermal vent the eastern Pacific (Suess et al., 1985), As with hot vents, cold seeps are counterparts, most cold seeps support and trenches off Japan in the western characterized by the flow of reduced highly productive ecosystems (high Pacific (Juniper and Sibuet, 1987). Cold chemical compounds from the sub- biomass) that consist of specialized seeps are now among the most geologi- surface to the seafloor, but they are not metazoan communities dominated by cally diverse and widely distributed of directly associated with high thermal a few adapted taxa that can cope with the deep-sea reducing environments anomalies. Most known cold seeps elevated concentrations of chemical explored to date, and new sites are are associated with reduced environ- compounds and low oxygen levels at still being discovered every year. Since ments that are linked indirectly to gas and below the sediment-water interface. their initial discovery, active seeps hydrates or to hydrocarbon reservoirs. Other harsh conditions, such as high have been reported from shallow to Hence, in contrast to the majority of concentrations of hydrocarbons or hadal (> 6000-m) depths (Sibuet and marine deep-water ecosystems, which high-salinity brines, may locally reduce Olu-Le Roy, 2002; Levin, 2005, and depend on photosynthetically derived faunal diversity (MacDonald et al., 2004; references therein), along other active food (phytoplankton and plant mate- Bergquist et al., 2005). Among the most and passive margins, and from all parts rial), methane and other hydrocarbon remarkable of the fauna exploiting the of the global ocean, even Antarctic seeps are colonized by specific anaerobic abundant chemical energy of seeps are regions (Domack et al., 2005). It is only subsurface microbiota; these organisms the symbiont-bearing invertebrate spe- during the last decade that more intense use hydrocarbons as an energy source cies, often similar or related to the fauna Oceanography March 2009 111 found at hydrothermal vents. These Both symbiont-bearing and associated pockmarks were also visited (Figure 1A). large taxa, such as vesicomyids (clams), nonsymbiotic fauna were investigated, Håkon Mosby mud volcano was first bathymodiolids (mussels), and siboglin- as well as different size classes, from fish observed in 1989 during a side-scan ids (formerly known as Pogonophora or and large invertebrates (megafauna), to sonar survey (Vogt et al., 1997). An tube worms), and some motile species small endofaunal organisms (meio- and expedition in 1995 measured very such as shrimps and gastropods, cluster macrofauna), including the very specific high temperature gradients in the sedi- in areas where fluids rich in reduced seep-related microbial communities. In ments, recovered methane hydrate from chemicals reach the seafloor (Sibuet and addition to biodiversity patterns in rela- 2-m subbottom depth and sampled Olu, 1998; Sibuet and Olu-LeRoy, 2002; tion to the high habitat heterogeneity siboglinid polychaetes, suggesting active Bergquist et al., 2003; Van Dover et al., within a region, similarities in communi- chemosynthesis (Vogt et al., 1997). The 2003; Cordes et al., 2007). ties among regions are currently under concentric structure of the mud volcano During HERMES, three main areas investigation in order to gain better can be divided into several subhabitats harboring prominent seep ecosystems insight into the biology, biodiversity, and characterized by different biogeochemi- were investigated, including the Nordic biogeography of seep-associated biota cal sediment conditions (de Beer et al., margin and its Håkon Mosby mud vol- along Europe’s continental margins. 2006; Niemann et al., 2006b). cano, the Gulf of Cádiz, and the eastern The Storegga area is well known for Mediterranean. After a short introduc- HERMES COLD Seep its giant Holocene slide, one of the larg- tion of the three main study areas, which StuDY Sites est ever mapped on continental margins are more extensively discussed elsewhere Along the Nordic margin, the highly (Paull et al., 2008). On the northeastern (see Foucher et al., this issue), we pro- active Håkon Mosby mud volcano flank of the Storegga slide, complex vide an overview of the main results (72°N) at 1280-m water depth on the pockmarks are located in the so-called from biodiversity studies performed dur- Barents Sea slope south of Svalbard, was Nyegga area at 740-m water depth. These ing HERMES. An integrated approach the target of several multidisciplinary pockmarks are circular in plan view and combined detailed habitat mapping and cruises (Figures 1A, 2). The Storegga feature up to 190-m-long ridges of car- characterization of associated fauna. slide at 64°N and associated Nyegga bonate rock (Hovland et al., 2005). Ann Vanreusel ([email protected]) is Professor, Marine Biology Research Group, Universiteit Gent, Gent, Belgium. Ann C. Andersen is Professor, Université Pierre et Marie Curie (UPMC), and a researcher in Equipe Ecophysiologie: Adaptation et Evolution Moléculaires, UMR 7144 - Centre national de la recherche scientifique (CNRS) - UPMC, Station Biologique, Roscoff, France.Antje Boetius is Head, Microbial Habitat Group, Max Planck Institute for Marine Microbiology, and Professor, Jacobs University Bremen, Germany. Douglas Connelly is a researcher in the Geology and Geophysics Group, National Oceanography Centre, University of Southampton, Southampton, UK. Marina R. Cunha is Professor, Centro de Estudos do Ambiente e do Mar (CESAM), Departemento de Biologia, Universidade de Aveiro, Campus Universitário de Santiago, Aveiro, Portugal. Carole Decker is PhD Candidate, Deep-Sea Ecosystem Department, Institut français de recherche pour l'exploitation de la mer (Ifremer), Centre de Brest, Plouzané, France. Ana Hilario is a postdoctoral researcher at CESAM, Departemento de Biologia, Universidade de Aveiro, Campus Universitário de Santiago, Aveiro, Portugal. Konstantinos Ar. Kormas is Assistant Professor, Department of Ichthyology and Aquatic Environment, University of Thessaly, Nea Ionia, Greece.Loïs Maignien is PhD Candidate, Laboratory of Microbial Ecology and Technology (LabMET) and Renard Center for Marine Geology (RCMG), Universiteit Gent, Gent, Belgium. Karine Olu is a researcher in the Deep-Sea Ecosystem Department, Ifremer, Centre de Brest, Plouzané,
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