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doi:10.2204/iodp.proc.327.106.2011

Microbiology

Microbiologists collected whole-round core and sediment pore water samples from sediments and pieces of hard rock basement from five holes at Site U1363. Eleven sediment depths were sampled for microbiology in Hole U1363B. Most samples were taken from clay/mud layers, although some sandy turbidite layers were also sampled. The deepest sediment sample was taken from a carbonate-rich layer near the sediment/basalt interface. Thirteen sediment depths and one basement basalt were sampled from Holes U1363C and U1363D. Again, sediment samples were mostly from clay-rich layers, although some samples contain sand. The basement sample from Core 327-U1363D-6X is relatively unfractured basalt with spots of light green and orange alteration crusts. Nineteen sediment and basement samples were taken from Hole U1363F. Most samples contain either clay or sandy layers, with the exception of samples from Section 327-U1363F-4H-2 and deeper, which also contain manganese crusts, basalt fragments, and lighter tan-colored sediment resembling foraminifer-rich carbonate sediments from Hole U1363B. Sixteen samples were collected from Hole U1363G. All samples are clay rich, and no hard rock samples were recovered in this hole.

At each sampling location, whole-round core samples were collected for shore-based DNA analysis, shore-based characterization of halogenated organic matter, and shore-based incubation experiments to examine dehalogenation reaction activities. Syringe samples also were collected for headspace gas analysis and microsphere contamination checks from the interior and exterior of the cores. Headspace samples were analyzed on board; only a few samples had quantifiable levels of methane or higher hydrocarbon gases, as anticipated for sediments in which there is still considerable sulfate in pore fluids. Microsphere samples were returned to a shore-based laboratory for postcruise analysis because of time limitations at the end of the cruise. These samples will be used for shore-based cell counting analysis and FISH analysis. A subset of samples was collected for analysis of DOC/DN, POC/PN, amino acids, low molecular weight organic acids, and lipid biomarkers.

Microsphere contamination tests

All sediment core sections sampled for microbiological analysis were sampled for microsphere contamination testing. Sterile cut-end 3 mL plastic syringes were inserted into the interior (center) and exterior (next to core liner) portions of freshly cut core sections, and sediment of a known volume was immediately fixed on the catwalk with 10 mL of cold 3.73% paraformaldehyde in 1× phosphate-buffered saline (PBS) buffer. Samples were stored cold until analysis in a shore-based laboratory. Aliquots of the homogenized sample were filtered onto 25 mm diameter, 0.2 µm mesh polycarbonate filters. Filters were examined under 100–400× total magnification with epifluorescence microscopy to quantify the number of fluorescent microspheres per sample.

Samples from Site U1363 had variable amounts of microsphere contamination (Tables T5, T6, T7, T8). None of the samples from Hole U1363B had any microspheres (Table T5). A majority of samples from the deeper sediment in Holes U1363C and U1363D were also microsphere free, with the exception of three samples (two exterior and one interior) from the deepest sediment depths near the sediment/basalt interface (Table T6). Many of the sandy sediment layers from Hole U1363F had microsphere contamination in the exterior samples, whereas the interiors were less contaminated (Table T7). In addition, the deepest sample from this hole, taken near the sediment/basalt interface, and the two shallowest samples also had microsphere contamination. Six of the sediment layers sampled in Hole U1363G, concentrated in Cores 327-U1363G-1H (sandy) and 3H (clay rich), exhibited microsphere contamination (Table T8). Much of Core 327-U1363G-3H shows evidence for flow-in (see “Operations” and “Lithostratigraphy”), which likely contributed to microsphere contamination below ~17 mbsf (depth of basement, as determined by drilling).

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