Bacterial Biomass and Activity in the Deep Sediment Layers of the Japan Sea, Hole 798B

Abstract

Sediment whole-round cores from a dedicated hole (798B) were obtained for detailed microbiological analysis, down to 518 m below the seafloor (mbsf) These sediments have characteristic bacterial profiles in the top 6 mbsf, with high but rapidly decreasing bacterial populations (total and dividing bacteria, and concentrations of different types of viable heterotrophic bacteria) and potential bacterial activities. Rates of thymidine incorporation into bacterial DNA and anaerobic sulfate reduction are high in the surface sediments and decrease rapidly down to 3 mbsf. Methanogenesis from CO 2 /H 2 peaks below the maximum in sulfate reduction and although it decreases markedly down the core, is present at low rates at all but one depth. Consistent with these activities is the removal of pore-water sulfate, methane gas production, and accumulation of reduced sulfide species. Rates of decrease in bacterial populations slow down below 6 mbsf, and there are some distinct increases in bacterial populations and activities that continue over considerable depth intervals. These include a large and significant increase in total heterotrophic bacteria below 375 mbsf, which corresponds to an increase in the total bacterial population, bacterial viability, a small increase in potential rates of sulfate reduction, and the presence of thermogenic methane and other gases. Bacterial distributions seem to be controlled by the availability of terminal electron acceptors (e.g., sulfate), the bioavailability of organic carbon (which may be related to the dark/light bands within the sediment), and biological and geothermal methane production. Significant bacterial populations are present even in the deepest samples (518 mbsf) and hence it seems likely that bacteria may continue to be present and active much deeper than the sediments studied here. These results confirm and extend our previous results of bacterial activity within deep sediments of the Peru Margin from Leg 112, and to our knowledge this is the first comprehensive report of the presence of active bacterial populations from the sediment surface to in excess of 500 mbsf and sediments > 4 m.y. old.

Organic phosphorus in marine sediments : chemical structure, diagenetic alteration, and mechanisms of preservation

“…A similar pattern is observed in the Santa Barbara Basin, where foraminifera are observed only to depths of 3 to 4 centimeters (Bernhard & Reimers, 1991), but bacteria have been observed to depths of 70 meters (Cragg et al, 1995). Based on an increasing number of observations of deep bacterial biomass at depths of hundreds of meters in marine sediments (e.g., Cragg et al, 1990;Cragg et al, 1992;Getliff et al, 1992;Parkes et aI., 1994), it is likely that bacteria exist at depths greater than 70 meters in the Santa Barbara Basin, as well.…”

Bacterial profiles in Amazon Fan sediments, Sites 934 and 940

“…2). This relationship has been commonly observed in Pacific Ocean sites Cragg et al, 1992;1995a, 1995bCragg and Parkes, 1994;Cragg and Kemp, 1995). Between 70 mbsf and the last sample at 108 mbsf, DDC were detected only once at 89 mbsf.…”

“…Recent Ocean Drilling Program (ODP) research on marine sediments (Whelan et al, 1986;Tarafa et al, 1987;Parkes et al, 1990Parkes et al, , 1994Cragg and Parkes, 1994;Cragg and Kemp, 1995;Cragg et al, 1990Cragg et al, , 1992Cragg et al, , 1995aCragg et al, , 1995b has confirmed the presence of a deep bacterial biosphere in marine sediments. Previously, this had only been predicted from the extensive amount of indirect geochemical evidence, that is, chemical changes in pore water, gas production, kerogen modification, concretion formation, and isotopic evidence (Krumbein, 1983;Suess and Whiticar, 1989;Kvenvolden and Kastner, 1990;Kastner et al, 1991).…”

Methane Hydrate Production From Alaskan Permafrost

“…primarily by microscopic counts of cells stained with fluorescent DNA dyes were over 10 6 cells/cm 3 at depths exceeding 500 m below the sediment surface (Cragg, Wimpenny et al 1990;Cragg, Parkes et al 1992;Cragg 1994;Cragg and Parkes 1994;Parkes, Cragg et al 1994;Cragg, Parkes et al 1996;Wellsbury, Goodman et al 1997;Cragg, Law et al 1999;Parkes, Cragg et al 2000). In addition, other evidence exists that a high biomass of microbial life occurs deep within sediments and that these populations are active including 1) the presence of high molecular weight DNA that can be amplified using molecular techniques (Rochelle, Cragg et al 1994;Bidle, Kastner et al 1999;Li, Kato et al 1999;Vetriani, Jannasch et al 1999;Lanoil, Sassen et al 2001;LopezGarcia, LopezLopez et al 2001;Marchesi, Weightman et al 2001); 2) rapid growth of bacteria in mixed cultures (Getliff, Fry et al 1992); 3) isolation of bacteria that are uniquely adapted to the deep-sea environment such as barophiles (Bale, Goodman et al 1997;Barnes, Bradbrook et al 1998), and; 4) rapid activities determined by growth and radiotracer techniques (Cragg, Parkes et al 1992;Parkes, Cragg et al 1994;Patching and Eardly 1997).…”

“…In addition, other evidence exists that a high biomass of microbial life occurs deep within sediments and that these populations are active including 1) the presence of high molecular weight DNA that can be amplified using molecular techniques (Rochelle, Cragg et al 1994;Bidle, Kastner et al 1999;Li, Kato et al 1999;Vetriani, Jannasch et al 1999;Lanoil, Sassen et al 2001;LopezGarcia, LopezLopez et al 2001;Marchesi, Weightman et al 2001); 2) rapid growth of bacteria in mixed cultures (Getliff, Fry et al 1992); 3) isolation of bacteria that are uniquely adapted to the deep-sea environment such as barophiles (Bale, Goodman et al 1997;Barnes, Bradbrook et al 1998), and; 4) rapid activities determined by growth and radiotracer techniques (Cragg, Parkes et al 1992;Parkes, Cragg et al 1994;Patching and Eardly 1997). In addition, rates of bacterial processes within deep sediment samples vary vertically with mineralogical and geochemical changes, suggesting that the measured activities reflect in situ activities (Cragg, Parkes et al 1992;Parkes, Bale et al 1995). Some of these deposits are millions of years old yet still support relatively active bacterial communities (Ingebritsen, Sanford et al 2000).…”