Dataset: Amino acid compound specific isotope analyses of abyssal deposit feeders, gut contents, and surrounding surface sediments collected on R/V Atlantis cruise AT42-10 and R/V Western Flyer Pulse 72 in the eastern North Pacific in 2019

Sediment cores and megafauna were collected in May and October 2019 using the HOV Alvin and the ROV Doc Ricketts, respectively. Upon retrieval to the surface, samples were placed in a cool room (5º C) for further processing. Sediment cores of 7 centimeters diameter were sliced and the surface sediments (0–0.5 cm) were placed in petri dishes and stored frozen at -80º C. Specimens of megafauna were weighed and measured, then dissected using a scalpel. We made a longitudinal cut along the digestive tract and took a sample of the foregut and hindgut contents, avoiding gut tissue. Then we removed the remaining guts and took a sample from cleaned body tissue, or in the case of echinoids, from the test. All samples were placed in cryovials and frozen in liquid nitrogen, and subsequently stored at -80º C. In the laboratory, samples of sediments, gut contents and body tissue were freeze dried and ground to a homogenous powder using mortar and pestle.

For analysis of bulk nitrogen and carbon isotopic composition, samples were placed in silver capsules in the following amounts: ~ 0.7 milligrams of body tissue from holothurians, 3 miligrams of body tissue from echinoids, ~ 5 miligrams of gut content, and ~ 20 miligrams of sediment. Samples were acidified to remove carbonates with 1M HCl, which was added dropwise until bubbling ceased, then dried at 60ºC and packed.

For δ15N and δ13C analysis of individual amino acids, samples were analyzed following the methods of Hannides et al. (2013). For the analysis of carbon isotope composition, we also derivatized and analyzed under the same conditions a sample containing a set of 13 pure amino acids. δ13C values were corrected based on the analysis of that set of pure amino acids (Silfer et al. 1991; Arthur et al. 2014).