Concentrations and isotopic ratios of organic classes and compounds isolated from surface sediments in submarine Baltimore Canyon, USA

Baltimore Canyon is a submarine canyon on the mid-Atlantic margin of the United States. Surface sediments were collected from the seafloor along the canyon axis in August 2012 aboard the NOAA ship Nancy Foster as part of a multi-agency, multi-institution effort. Expedition reports are available from the Bureau of Ocean Energy Management (BOEM 2017-061). At the United States Geological Survey (USGS) Pacific Coastal and Marine Science Center (PCMSC), four samples from contrasting depositional locations in the canyon were selected for a range of organic and isotopic analyses. In combination with bulk geochemical characteristics, surface sediments from water depths of ~200-1200 m underwent a sequential extraction procedure, isolating the following organic matter classes: bulk organic matter; total lipid; nonpolar, neutral, and polar lipid classes; an acid-soluble fraction containing amino acids; and an acid-insoluble fraction. Except for the acid-soluble fraction, each class was analyzed for carbon and nitrogen quantities and stable isotope ratios, and radiocarbon content where possible, along with compound-specific carbon and nitrogen isotope analysis of individual amino acids isolated from the acid-hydrolysed fraction. The weight of sediment extracted and measured was used to convert measured quantities of organic classes and compounds to concentrations per dry weight sediment. Research and analyses were conducted by the authors and/or laboratory staff at the USGS PCMSC, University of California Santa Cruz, and Lawrence Livermore National Laboratory.