Geomicrobiology of Fluid Venting Structures at the Salse di Nirano Mud Volcano Area in the Northern Apennines (Italy)
Recent studies suggest that geological sources of methane like onshore and marine seeps, micro-seepage and mud volcanoes are an important source of this greenhouse gas (Etiope 2004). They represent the second most important natural emission after wetlands
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1 Introduction Recent studies suggest that geological sources of methane like onshore and marine seeps, micro-seepage and mud volcanoes are an important source of this greenhouse gas (Etiope 2004). They represent the second most important natural emission after wetlands. New estimations indicate a global emission of methane from mud volcanoes in a range of 6-9 Tg year-1 (Etiope and Ciccioli 2009). Mud volcanoes are present in many terrestrial and marine areas worldwide (Mazurenko et al. 2003; Scholte 2005), but their geographical distribution is strongly controlled by the geological settings. The majority is localized in areas of recent tectonic activity, particularly in zones of compression like accretionary complexes, thrust belts and e.g. in the forelands of Alpine orogenic structures (Dimitrov 2002; Kopf 2002). Furthermore, since the sediments in mud volcanoes are often hydrocarbon-rich, a relation between the formation of hydrocarbons and mud volcanoes was suggested (Dimitrov 2002). The geographical occurrence of mud volcanoes in Italy can be divided into three main groups: (i) northern and (ii) central Italy and (iii) Sicily (Martinelli and Judd
C. Heller, M. Blumenberg, and J. Reitner (*) Geoscience Centre, University of G€ ottingen, Geobiology Division, Goldschmidtstraße 3, 37077, G€ ottingen, Germany e-mail: [email protected] S. Kokoschka, C. Wrede, and M. Hoppert Institute of Microbiology and Genetics, University of G€ ottingen, Grisebachstr. 8, 37077, G€ ottingen, Germany M. Taviani ISMAR-CNR, Via Gobetti 101, 40129, Bologna, Italy
J. Reitner et al., Advances in Stromatolite Geobiology, Lecture Notes in Earth Sciences 131, DOI 10.1007/978-3-642-10415-2_14, # Springer-Verlag Berlin Heidelberg 2011
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2004). The study site is located near Modena in Northern Italy, at a mud volcano area named Salse di Nirano. The Salse di Nirano is situated in the Emilia Romagna, covers a surface of approximately 75.000 m2 and represents one of the biggest mud volcano areas in Italy (Martinelli and Judd 2004). Generally, mud volcanoes are formed by the expulsion of water, mud and gases (in particular methane and higher hydrocarbons), exhibit often anoxic niches and contain various electron acceptors. These preconditions potentially promote the activity of microorganisms performing the anaerobic oxidation of hydrocarbons, in particular methane. The anaerobic oxidation of methane (AOM) is suggested to be usually coupled to sulphate reduction (Reeburgh 1980) and is carried out by a symbiotic association of methanotrophic archaea and sulphate reducing bacteria (SRB), namely members of the Methanosarcinales and the Desulfosarcina/Desulfococcus group (DSS) (e.g., Hinrichs et al. 1999; Thiel et al. 1999; Boetius et al. 2000; Orphan et al. 2001a, 2001b, 2002; Elvert et al. 2003; Reitner et al. 2005a, 2005b; Treude et al. 2005), although many aspects are still insufficiently understood. Recent phylogenetic and biochemical studies have suggested that the anaerobic methanotrophic (ANME) archaea have supposed
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