Compound-specific isotope analysis of amino acids (CSIA-AA) from a subset of siphophore samples collected during four research cruises on the R/V Wester Flyer in the California Current Ecosystem between 2019 and 2021

Samples of siphonophores (Cnidaria, Hydrozoa) were collected using blue‑water diving, midwater trawls, and remotely operated vehicles in the California Current Ecosystem, from 0 to 3,000 meters depth. Siphonophore samples were collected on four research cruises on the R/V Wester Flyer between 2019-2021. To remove potential biases associated with tissue‑specific variability in stable isotope values, the gelatinous swimming bells (nectophores) of siphonophores were sampled. This approach was possible for most specimens, except for physonect species that are extremely fragile or have nectosomes that are a small fraction of the colony length and are often not collected. For these species (e.g., Apolemia spp.), the gelatinous bracts and pieces of the siphosome, excluding gastrozooids, were used. For small individuals (Diphyes dispar, Nanomia bijuga, and Sphaeronectes koellikeri), nectophores from several colonies that were captured at the same time and sampling location were pooled to obtain an adequate mass for isotope analyses. A subset of samples was selected for compound-specific isotope analysis of amino acids. These specific taxa were selected as representatives of different depth habitats, suborders, and hypothesized diets. Bulk and compound-specific isotope analyses were performed at the University of Hawaii's Biogeochemistry Stable Isotope Facility. This dataset includes the compound-specific isotope analysis data.