Lipid biomarker data from Escanaba Trough sediments, off the coast of Northern California, USA, from May-June 2022.

SEDIMENT COLLECTION. Samples were collected aboard the R/V Thomas Thompson via push coring using the ROV Jason. Once recovered shipboard, pore waters were extracted via rhizon samplers, cores were subsectioned into one to five cm slices, the exterior sediment which was in contact with the core liner was removed, and remaining sediment was stored frozen in pre-combusted glass jars.

SEDIMENT BIOMARKER CONCENTRATIONS (N-ALKANES, PAHS AND STEROLS): The biomarker composition of sediment samples was determined by gas chromatography-mass spectrometry (GC MS) at the USGS Organic Geochemistry laboratory in Santa Cruz, California. The samples were extracted using a modified version of the method presented in Bligh and Dyer (1959). Two bed volumes of hexanes were added to each sample and samples were mixed, sonicated for 15 minutes (min), then centrifuged for five min at 2000 revolutions per min. The supernatant was piped to a combusted Turbovap flask. This process was repeated two more times with hexanes and three times with 9:1 DCM:MeOH, combining the supernatant from each sample. Prior to extraction, internal standards were added (5-alpha-androstane and 5-alpha-androstan-3-beta-ol). The lipid extracts were passed though glass funnels containing sodium sulfate to remove excess water, followed by separation into compound classes by silica gel column chromatography (silica gel 60) as described in Prouty and others (2020). The following fractions were eluted: F1: alkanes (100 percent hexane eluant); F2: polycyclic aromatic hydrocarbons (PAHs) (50 percent hexane, 50 percent toluene eluant); F3a: alcohols and sterols (20 percent ethyl acetate, 80 percent hexane eluant); F3b: fatty acids and glycosidic polar lipids (40 percent ethyl acetate, 60 percent hexane); F4: phosphatic polar lipids (100 percent methanol eluant). F3a was converted to trimethylsiloxyl derivatives by addition of bis (trimethylsilyl) trifluoroacetamide (BSTFA with 10 percent TMCS) and pyridine, then heated at 70 degrees Celsius for 1 h prior to GC MS analysis. Extracts were analyzed by splitless injection onto an Agilent 8890 gas chromatograph interfaced to an Agilent 7000D triple quad mass spectrometer. To measure n-alkanes, the gas chromatograph oven program began at 90 degrees Celsius for 5 min, increased to 240 degrees Celsius at a rate of 4 degrees Celsius/min, held for 5 min, then increased to a final temperature of 300 degrees Celsius at a rate of 10 degrees Celsius/min and held for 18 min. To measure PAHs, the oven program begam at 90 degrees Celsius, held for 5 min, increased to 240 degrees Celsius at a rate of 8 degrees Celsius/min, held for 5 min, then increased to a final temperature of 300 degrees Celsius at a rate of 8 degrees Celsius/min which was held for 18 min. To measure sterols, the oven program began at 100 degrees Celsius, held for 4 min, and increased to a final temperature of 315 degrees Celsius at 4 degrees Celsius/min, which was held for 5 min. The capillary column (Agilent DB-5MS: 30 m length x 0.25 mm interior diameter with a 0.025 micron phase thickness) was directly interfaced to the ion source of the mass spectrometer. Hexane instrument blanks, extraction blanks, and procedural sample duplicates were run and analyzed every 10 samples. Compound identification was through individual standard spectra, published reference spectra, and by relative retention times/elution order. Concentrations of individual lipids were determined based on peak area in relation to internal and external standards.