John E. Noakes

Radiocarbon dating of Danube Delta deposits

Abstract The Holocene history of the Danube Delta has been studied using 14C analyses of faunal material. The principal phases of development include: (1) initial Letea Caroarman spit, 11,700–9800 yr B.P. in its central part, 8800-5500 yr B.P. in its southern part; (2) Sf. Gheorghe I Delta, 8900-7200 yr B.P.; (3) Sulina Delta, 7200-2000 yr B.P., and (4) Sf. Gheorghe II Delta-Chilia Delta 2000 yr B.P.-present. Other smaller-scale features have also been dated, including secondary deltas (Cosna and Sinoe Deltas) and littoral bars. Age determinations carried out on whole samples were erratic and it was found that individual species had to be separated and dated. In all cases, the older dates were of transported material whereas the younger dates gave the true age of the formation.

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.

Tritium measurements with a new liquid scintillation counter

Abstract A new concept in liquid scintillation counting has been employed in developing an instrument for the purpose of quantitatively measuring low specific activity tritium samples. The instrument design differs from present commercial instrumentation in that it utilizes electronics that measure fast-pulse time intervals rather than performing pulse height analysis. The liquid counter was built to accomodate samples as large as 100 ml of solution. The solutions can be counted as a combination of water and scintillator or as pure benzene synthesized from water. As much as 20 g of water can be counted directly as a solubilized cocktail or an equivalent of 66 g of water converted to benzene. Direct counting of aqueous cocktails can be accomplished to sensitivity levels below 10 T.U. Tritiated benzene samples of 25 ml volume have been counted at 53% counting efficiency with background count rates contributing less than 1.75 c/m. This new instrument utilizes massive graded shielding and an electronic guard to minimize external radiation for low background counting.

Distribution and Diversity of Bacteria and Archaea in Marine Sediments Affected by Gas Hydrates at Mississippi Canyon in the Gulf of Mexico

The microbial community structures of gas hydrate-bearing (Core 9) and non-hydrate-bearing (Core 1) marine sediments were investigated at Mississippi Canyon (MC) 118 in the Gulf of Mexico. Quantification by quantitative competitive (QC)-PCR showed that bacterial abundance was 2–3 orders of magnitude higher than archaeal abundance in these cores. Sulfate-reducing bacteria (SRB) were present at 103–104 dsrAB gene copies/g in both cores; methanogens or anaerobic methanotrophs were only present in Core 9 (102–105 mcrA gene copies/g). Denaturing gradient gel electrophoresis (DGGE) showed distinct patterns of bacterial community structure between Core 9 and Core 1 with ϵ-Proteobacteria predominating in the former and γ-Proteobacteria in the latter. Clone libraries were successfully constructed for both Archaea and Bacteria using functional genes (mcrA and dsrAB, respectively). The mcrA gene was present in Core 9, suggesting enhanced abundance or activity of methanogens or methane-oxidizing archaea in the hydrate-impacted sediment. The mcrA gene sequences were dominated by group c-d and group e. The majority (80%) of the dsrAB gene sequences fell into Syntrophobacteraceae-related group. This study indicates that microbial community structures are considerably different between the hydrate-bearing and non-hydrate-bearing sediment at MC 118. Our study is among the initial steps toward a comprehensive and long-term monitoring of microbial dynamics associated with gas hydrates in the Gulf of Mexico.

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.

Community Structure of Archaea in the Water Column above Gas Hydrates in the Gulf of Mexico

Microorganisms play fundamental roles in the ecosystem of the Gulf of Mexico (GOM), yet their vertical distributions along the depth continuum of water column are not well known. In this study, we presented the 16S rDNA sequences and lipid profiles in the context of water chemistry to characterize the archaeal community structure above a gas hydrate mound (MC 118) in GOM. Our results showed that all archaeal sequences were related to unknown species of Crenarchaeota or Euryarchaeota. Phylogenetically, group II –β Euryarchaeota dominated the surface water and mid-depth (400-m) water (74% and 58% of total archaeal species, respectively) whereas the marine group I-γ Crenarchaeota dominated the bottom (869 m) water (61% of total archaeal species). Estimates of the Shannon index showed the highest diversity of planktonic Archaea at the 400 m depth. Glycerol dialkyl glycerol tetraether (GDGT) lipids were detected from the 400- and 869-m depths only and characterized by relatively high abundances of GDGT-5 (crenarchaeol) and GDGT-0. Our studies suggested a possible zonation of archaeal community in the water column, which did not seem to be affected by the possible venting of hydrocarbons from the hydrate location in GOM.

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.

Geoenvironmental application of statistical techniques used in marine mineral exploration

Recent research efforts have involved the development of computer programs and quantitative techniques designed specifically to facilitate the reduction and interpretation of large geochemical data sets acquired during marine mineral exploration surveys. The purpose of this study is to examine the applicability of these same techniques in developing meaningful interpretations of geoenvironmental data. A suite of sediment samples from the Mobile‐Tombigbee River system in southern Alabama were subjected to bulk geochemical and mineralogical analyses. A Q‐mode factor analysis of the geochemical data suggests reveals that > 98% of the total variance in data is explained by two factors: (1) a relatively labile component of predominantly detrital aluminosilicates and iron and manganese oxyhydroxides, and (2) a mixture of quartz, feldspar, and ilmentite. The geochemical associations in both of these factors primarily reflect differences in sediment grain size. A linear modeling procedure was used to determine sp...

GAMMA SLED FOR SEAFLOOR LITHOLOGY SURVEY

The Gamma Isotope Mapping System (GIMS) has two main components. The first component is a stainless steel sled that is towed on the seafloor by a survey vessel. The second component is the shipboard electronics. The sled houses a gamma radiation detector and battery pack. As the sled is towed along the seafloor at approximately 3 knots, the detector measured the natural gamma radioactivity of the surface sediment. The signal from the detector is sent by armoured cable to the ship. The gamma signal is received and processed by a spectrometer mounted in the electronics package. The gamma radiation data, along with time, latitude, longitude, and water depth is logged automatically at 60 second intervals on a computer diskette. During the survey, two- and three-dimensional maps are created with the collected data. These maps show the differences in the sediment seafloor lithology. This data can be used in the location of surface mineral deposits on the seafloor or to track sediment distribution as a result of disposal activities during dredging operations from near-shore environments. Since the results are obtained during the survey, additional studies can proceed immediately after the GIMS survey allowing for a more economical merging of various studies.