Randy Culp

Lipid Biomarkers, Carbon Isotopes, and Phylogenetic Characterization of Bacteria in California and Nevada Hot Springs

Microbial mats were collected from hot springs in California (Eagleville) and Nevada (Paradise Valley and Crescent Valley) to determine bacterial community structure and pathways of carbon cycling in different geothermal environments of the western United States. Phospholipid fatty acids (PLFA) at Eagleville contained even-numbered fatty acids, with 16:0 being the most abundant (48.8%), followed by 18:1ω 9c (17.2%), 16:1ω 7c/t (6.3%), and 18:0 (6.2%), which are consistent with lipid profiles of cyanobacteria or other phototrophic bacteria. The PLFA profiles at Paradise Valley and Crescent Valley were dominated by similar even-numbered fatty acids; however, branched fatty acids such as iso- and anteiso- 15:0 and 17:0 were also abundant (up to 7.1% compared to 2.0% at Eagleville), suggesting greater relative abundance of heterotrophic bacteria in these springs. Analysis of neutral lipids was only performed on Eagleville and Paradise Valley springs, which revealed abundant bacterial hopanoids including the 2–methylbacteriohopane-32,33,34,35-tetrol (2-methylBHT) that is specific to cyanobacteria; however, the diversity of hopanoid compounds was significantly lower at Eagleville than at Paradise Valley. The carbon-isotope composition of individual PLFA averaged −30.7 ± 1.3‰ (n = 7) at Eagleville, −28.0 ± 1.8‰ (n = 3) at Crescent Valley, and −29.7 ± 3.1‰ (n = 12) at Paradise Valley. Carbon isotope fractionation between PLFA and CO 2 was only available for Eagleville (−11.7‰) and Paradise Valley (−21.7‰), which indicated the predominance of the Calvin cycle for CO 2 fixation in these hot springs. Bacterial 16S rRNA genes were extracted from environmental samples at Eagleville and Paradise Valley but not Crescent Valley. Clone libraries indicated the predominance of cyanobacteria (50–75%) at these locations, which is consistent with the lipid profiles. Phylogenetic tree of the 16S rRNA genes indicated that most of the cyanobacterial sequences are unknown and may be specific to the Nevada and California hot springs. Phototrophic green non-sulfur bacteria were also present at Eagleville (13%) and Paradise Valley (7%). The remaining sequences were related to α-, β -, and γ -Proteobacteria, Acidobacteria, Deinococcus/Thermus, Bacteroidetes, and Spirochaetes. However, not all of these sequences were present at each of the springs. Results of this study demonstrate the consistency among lipid profiles (phenotypes), carbon isotopes (biogeochemistry), and 16S rRNA genes (genotypes) of the bacterial community in these hot springs, which cumulatively suggest the importance of cyanobacteria in primary production of biomass under the environmental conditions examined.

Rapid coastal survey of anthropogenic radionuclides, metals, and organic compounds in surficial marine sediments.

A towed survey system, the GIMS/CS3, has been developed to enable the rapid measurement and mapping of a variety of physical and geochemical parameters in the surficial sediments of aquatic environments while the survey vessel is underway. With its capability for measuring radiometric, elemental and organic compound constituents of sediments, as well as bathymetry and water quality parameters, the GIMS/CS3 provides a cost-effective means of performing reconnaissance determinations of contaminant distributions and environmental monitoring tasks over broad geographic regions.

Archaeal Lipids and 16S rRNA Genes Characterizing Non-hydrate and Hydrate-Impacted Sediments in the Gulf of Mexico

This study reports the intact lipids and the phylogenetic compositions of archaea from marine sediments adjacent to or within a region of methane seeps and hydrate mounds in the Mississippi Canyon (MC) Block 118 in the Gulf of Mexico. An aliquot of lyophilized sediment (∼5 g) was extracted for total lipids. Fractions of the glycerol dialkyl glycerol tetraethers (GDGTs) were obtained through column fractionation and determined using liquid-chromatography-mass spectrometry. DNA was extracted from a different aliquot of the sample (∼7 g) that was kept at −80°C. GDGTs showed distinct patterns between non-hydrate and hydrate-impacted samples, suggesting dramatically different archaeal communities caused by the presence of gas hydrates or cold seeps. Clone libraries of 16S rRNA genes were constructed to provide a phylogenetic explanation of the archaeal populations possibly causing the variation in lipid profiles. In contrast to the non-thermophilic crenarchaeota-dominant species in the normal marine sediment, the hydrate-impacted samples showed the predominance of ANME-1 subgroups with Thermoplasmatales being secondarily abundant; both of them are known to produce tetraether lipids and may be responsible for the enhanced archaeal lipids in the hydrate samples. MC 118 is designed to be a seafloor observatory in the Gulf of Mexico and our study represents the initial efforts in characterizing archaeal populations and their role in carbon cycle at this location.

Comparison of radiocarbon techniques for the assessment of biobase content in fuels.

A comparison was made between various radiocarbon measurement techniques for the purpose of quantifying each methods capability for the proper apportionment of biobase-derived additives to gasoline. Measurement techniques include (1) direct liquid scintillation counting, (2) carbon dioxide absorption followed by liquid scintillation counting, (3) conversion to benzene followed by liquid scintillation counting and (4) accelerator mass spectrometry. In addition, stable isotope ratios of carbon and hydrogen were determined to assist in the authentication of a fuels source with regard to petrochemical or biobase origin is required for the confirmation of minimum anti-knock components, consumer awareness and proper assessment for regulatory taxation. Accelerator mass spectrometry was found to be the most precise technique followed by conversion of fuel to benzene with liquid scintillation counting and direct counting by liquid scintillation counting. Finally, liquid scintillation counting of absorbed carbon dioxide was found to be the least precise and should not be used for this analysis. The high to low precisions correlate with the high to low cost of equipment and support required by each of these methods except for direct liquid scintillation counting. Therefore, laboratories interested in developing capability to perform such authentication can use this data to consider the economics of the optimum technique to use for radiocarbon measurement.

Comparison of Data Logger Operational Parameters Aboard Ship and Towed on the Seafloor

A number of new, submersible water quality data loggers(probes) have recently been introduced to the market place which have interesting applications to developing Environmental Impact Statements (EIS) and future surveys in the Exclusive Economic Zone (EEZ). The probe chosen for this study is typical of today. This probe has the capability for multi-parameter measurement of temperature (degrees Centigrade), dissolved oxygen (mg/1), conductivity (mmhos/cm), salinity (ppt), pH (units), and depth (meters). It can be preprogrammed for remote data logging, tethered by underwater cable to a surface readout, or operated aboard ship by a flow cell connected to a submersible pump. A new operational parameter was tested using the probe mounted inside a towed seafloor sled. A pump mounted inside the sled allowed a sediment-water slurry from the seafloor to be pumped aboard ship. A second probe was mounted on the survey ship with a flow cell connected to the submersible pump. With one probe on the surface and the other on the seafloor, a simultaneous comparison was made utilising the data collected on the same sediment water sample. Advantages gained from this study can be used to cross-calibrate in situ seafloor analyses with those made aboard ship. It also demonstrates the probes durability for seafloor measurements either in the static or towed mode of operation.