Geomicrobiology of Cave Ferromanganese Deposits: A Field and Laboratory Investigation

Abstract

Unusual ferromanganese deposits are found in several caves in New Mexico. The deposits are enriched in iron and manganese by as much as three orders of magnitude over the bedrock, differing significantly in mineralogy and chemistry from bedrock-derived insoluble residue. The deposits contain metabolically active microbial communities. Enrichment cultures inoculated from the ferromanganese deposits produced manganese oxides that were initially amorphous but developed into crystalline minerals over an 8-month period and beyond; no such progression occurred in killed at Carlsbad Caverns National Park for their help and support. Larry Mallory contributed greatly to the design and debugging of the AO/INT procedure, and John Craig and John Husler often contributed their efforts to make analytical equipment and procedures work properly. We thank Jim Werker and Val HildrethWerker for help with field logistics in Lechuguilla Cave, Sue Barns and Tina Vesbach for assistance with the phylogenetic tree, and David Estes for sequence editing. Gratitude is expressed to Brad Tebo and three anonymous reviewers for constructive comments and criticism.controls. Phylogenetic analyses of sequences from clone libraries constructed from culture DNA identified two genera known to oxidize manganese, but most clones represent previously unknown manganese oxidizers. We suggest that this community is breaking down the bedrock and accumulating iron and manganese oxides in an oligotrophic environment.

Mn(II)-oxidizing Bacteria are Abundant and Environmentally Relevant Members of Ferromanganese Deposits in Caves of the Upper Tennessee River Basin

“…A Mn:Fe ratio of ca. 1:1 in cave ferromanganese deposits is a common ratio found in deep, oligotrophic systems in the southwest United States such as Lechuguilla and Spider Caves (Northup et al 2003;Spilde et al 2005). Previous research demonstrates the role of microsite geochemistry in establishing environmental niches (Engel et al 2010;Macalady et al 2008;Rossmassler et al 2012), structuring microbial communities Goldscheider et al 2006;Shabarova and Pernthaler 2010), and influencing mineral precipitation (Frierdich et al 2011) and composition (Post 1999;White et al 2009) in subsurface karst systems.…”

“…The predominance of Fe over Mn in a variety of natural systems is well documented in studies of marine (Edwards et al 2004;Nitahara et al 2011) and freshwater systems (Johnson et al 2012;Stein et al 2001). However, in cases where the concentration of Mn is equal to or outweighs the concentration of Fe (Gradziński et al 1995;Krumbein and Jens 1981) or where secondary mineral deposits are enriched in metal concentration relative to substrate geochemistry (Cunningham et al 1995;Northup et al 2003;Spilde et al 2005Spilde et al , 2006, biomineralization processes are invoked as a causal factor in the formation of Mn-enriched geochemical environments.…”

“…However, more recent geomicrobiology research lends support to the hypothesis that microbes play a role in the formation and dissolution of cave mineral deposits via direct and indirect metabolic activities and biomineralization processes (Barton and Luiszer 2005;Cañaveras et al 2006;Jones 2001;Melim et al 2001;Northup et al 1997;de los Ríos et al 2011;Spilde et al 2005;Taboroši 2006). In particular, microbial reactions have been shown to promote the formation of cave manganese oxide and ferromanganese (mixed Fe and Mn oxides) deposits, such as crusts (Northup et al 2000(Northup et al , 2003Spilde et al 2005), manganese flowstones (Gradziński et al 1995), rock coatings (Allouc and Harmelin 2001;Peck 1986), and manganese stromatolites (Rossi et al 2010).…”

“…However, our knowledge of the microbial consortia associated with cave ferromanganese deposits is limited to research conducted in cave systems located in the southwest United States (Cunningham et al 1995;Northup et al 2003;Spilde et al 2005Spilde et al , 2006, which formed via hypogene speleogensis (characteristically deeper cave formation via sulfuric acid in ascending groundwater) rather than epigene speleogensis (typically shallow cave formation via carbonic acid in descending meteoric water). Therefore questions remain unanswered regarding 1) the nature of these shallow, epigenic cave systems in the southern Appalachians, 2) how similar these shallow cave systems are to their deeper, hypogene counterparts and 3) to what extent surface waters and biota influence microbial consortia and biomineralization processes within shallow cave systems.…”

New insight into the origin of manganese oxide ore deposits in the Appalachian Valley and Ridge of northeastern Tennessee and northern Virginia, USA

“…To date, all of the known Mn oxides formed by microorganisms either in the laboratory or via in situ field cultures have been composed of poorly crystalline birnessite-group minerals (layer structure Mn oxides) or poorly crystalline todorokite group minerals (3x3 tunnel structure Mn oxides) (see reviews by Saratovsky et al, 2006;Spiro et al, 2010;Tebo et al, 2004). It is possible that gradual reordering of tiny, poorly crystalline Mn oxide crystals may lead to increased crystallinity over time (described in laboratory experiements by Hinkle et al, 2016;Spilde et al, 2005). This recrystallization process has not been observed in cave systems where microbial Mn deposits have ages of 1 Ma (Rossi et al, 2010), however, and the reason for these discrepancies remains unresolved within the literature at this time.…”