Synergistic Roles of Microorganisms in Mineral Precipitates Associated with Deep Sea Methane Seeps

Abstract

The discovery of huge deep sea methane reservoirs in the form of ice-like solid crystals of methane clathrate hydrates (methane hydrates or gas hydrate for short) and carbonate deposits at the Hydrate Ridge in the Cascadia subduction zone (Suess et al. 1985) has stimulated global exploration and extensive studies of cold methane seeps and vents associated with the hydrate deposits (Paull and Dillon 2001; Trehu et al. 2004). Many deep sea methane hydrate deposits have been discovered around the world, for instance, in the Gulf of Mexico (Pohlman et al. 2008; Sassen et al. 1998, 2004), Monterey Bay of California (Gieskes et al. 2005; Lorenson et al. 2002; Stakes et al. 1999), Black Sea (Peckmann et al. 2001), Sea of Okhotsk, Eastern Siberia (Greinert and Derkachev 2004), the Gulf of Cadiz (Stadnitskaia et al. 2008), the Kuroshima Knoll of southern part of the Ryukyu Arc (Takeuchi et al. 2007), and South China Sea (Han et al. 2008; Lu 2007). It has been estimated that there are about 1,000 ∼24,000 Gt of carbon in global methane hydrate zones (Dickens et al. 1997; Harvey and Huang 1995; Kvenvolden 1988; MacDonald 1990; Makogon and Makogon 1997). Methane hydrates have the potential to be a future energy source however methane is also a greenhouse gas. The release of methane from the methane hydrate can have a profound effect on the global climate (Kvenvolden 1998). In geological record, the rapid global temperature change at the Paleocene-Eocene boundary at ∼55 millions of years ago, the Paleocene–Eocene Thermal Maximum (PETM), may be related to catastrophic methane release from sea sediments (Dickens et al. 1995; Katz et al. 2001; Zachos et al. 2005). At the interface between uprising methane from dissociation of methane hydrate and sulfate from sea water, a distinct microbial consortium mediates anaerobic oxidation of methane (AOM) through a net reaction of

$$ {\text{CH}}_{4}+{\text{SO}}_{4}{}^{2-}\to {\text{HS}}^{-}+{\text{HCO}}_{3}{}^{-}+{\text{H}}_{2}\text{O}.$$

(15.1)