Contributions of Atmospheric CO and Hydrogen Uptake to Microbial Dynamics on Recent Hawaiian Volcanic Deposits

Abstract

A series of sites were established on Hawaiian volcanic deposits ranging from about 18 to 300 years old. Three sites occurred in areas that supported tropical rain forests; the remaining sites were in areas that supported little or no plant growth. Sites >26 years old consumed atmospheric CO and hydrogen at rates ranging from about 0.2 to 5 mg of CO m ؊2 day ؊1 and 0.1 to 4 mg of H 2 m ؊2 day ؊1 , respectively. Respiration, measured as CO 2 production, for a subset of the sites ranged from about 40 to >1,400 mg of CO 2 m ؊2 day ؊1 . CO and H 2 accounted for about 13 to 25% of reducing equivalent flow for all but a forested site, where neither substrate appeared significant. Based on responses to chloroform fumigation, hydrogen utilization appeared largely due to microbial uptake. In contrast to results for CO and hydrogen, methane uptake occurred consistently only at the forest site. Increasing deposit age was generally accompanied by increasing concentrations of organic matter and microbial biomass, measured as phospholipid phosphate. Exoenzymatic activities (acid and alkaline phosphatases and ␣-and ␤-glucosidases) were positively correlated with deposit age in spite of considerable variability within sites. The diversity of substrates utilized in Biolog Ecoplate assays also increased with deposit age, possibly reflecting changes in microbial community complexity.Lava, tephra, and volcanic ash contain negligible amounts of organic matter and fixed nitrogen when first deposited (35). The absence or scarcity of vegetation at many active volcanic sites exacerbates the situation by limiting postdepositional inputs. The lack of organic matter substantially constrains the nature and rates of microbial colonization and succession. In such systems, atmospheric inputs or reduced substrates released by weathering (e.g., Mn 2ϩ ) may support metabolism and growth. Nonexclusive carbon and energy sources for microbial community development under these conditions include (i) phototroph colonization, (ii) aeolian or aqueous organic matter inputs, and (iii) dry and wet deposition of NH 4 ϩ and trace gases (e.g., CO, H 2 , and CH 4 ).Relatively few studies have examined the significance of these sources or temporal patterns of microbial succession under extreme conditions (2). Data from cryptoendolithic communities suggest that bacterial colonization and succession depend on autochthonous photosynthesis (27,47). Other studies indicate that desert varnishes form in part from substrates released by weathering (48). Microbiological analyses of recent volcanic materials have led to isolations of thermophiles, psychrotrophs, and other heterotrophs, but the activities and functions of these organisms remain essentially unknown (7, 22-24, 39, 45, 46, 49). In addition, it is unclear if the observed isolates represent dominant populations or fast-growing opportunistic strains.Data from Hawaii and other systems indicate that various bacterial functional groups colonize lava and tephra relatively quickly. Burleigh and Dawson (6) cultured ...

Temperature responses of carbon monoxide and hydrogen uptake by vegetated and unvegetated volcanic cinders

“…We show, for example, that H 2 uptake activation energies for Bare cinders and Canopy material (82.9 kJ mol À1 and 50.8 kJ mol À1 , respectively; Figure 2) fall within ranges reported for bacterial activity (about 50-140 kJ mol À1 ), and markedly exceed values for exoenzymatic activity (10-30 kJ mol À1 ; Schuler and Conrad, 1991). This is consistent with the outcome of a previous inhibitor study (King, 2003a), which demonstrated that H 2 uptake was largely bacterial rather than exoenzymatic (Conrad, 1996). Thus, the relative importance of bacteria versus exoenzymes as a H 2 sink does not appear to be greatly affected by vegetation due to ecosystem succession, at least over the short term (that is, decades).…”

“…Canopy site surface material is characterized by an organic-rich peat-like material, while Bare site material consists of organic-poor cinders approximately 1 cm in diameter. Numerous details of this system have been described previously (King, 2003a;King and Weber, 2008;Weber and King, 2009). Temperature regimes for Bare and Canopy sites differ significantly.…”

“…Although many CO-oxidizers also consume H 2 (Hudson et al, 1988;King, 2003b), and as H 2 uptake by various material on Kilauea volcano has been previously attributed primarily to bacteria (King, 2003a), we also measured responses of H 2 consumption to varied temperature regimes and to an extended incubation at 55 1C.…”

“…Although changes in uptake rates and in the significance of the atmosphere as sources of these gases during ecosystem succession have been addressed previously (King, 2003a;King and Weber, 2008), specific responses of CO and H 2 uptake to environmental variables that change during succession, for example, organic carbon, soil texture, pH, and temperature, have not been documented (Weber and King, 2009). More generally, the responses of CO and H 2 uptake by soils to these and other variables have received limited attention, even though it is clear that soils have significant roles in the global budgets of both atmospheric CO and H 2 (Conrad, 1996;King and Weber, 2007).…”

“…Bacteria actively consume carbon monoxide (CO) and hydrogen (H 2 ) in both young, organic matterpoor volcanic deposits and in older, more mature deposits with well-developed plant communities (King, 2003a;King and Weber, 2008). Although changes in uptake rates and in the significance of the atmosphere as sources of these gases during ecosystem succession have been addressed previously (King, 2003a;King and Weber, 2008), specific responses of CO and H 2 uptake to environmental variables that change during succession, for example, organic carbon, soil texture, pH, and temperature, have not been documented (Weber and King, 2009).…”