Table of Contents

• Coverage
• Dataset Description
  • Methods & Sampling
  • Data Processing Description
• Data Files
• Related Publications
• Related Datasets
• Parameters
• Instruments
• Deployments
• Project Information
• Funding

Materials and methods for analysis are described in detail in the Ruiz_Cooly et al (2014).  Skin tissue samples with enough material (3.5 mg) were selected for compound specific isotope analysis of amino acids (CSIA-AA). Data from 12 samples were obtained for individual amino acid (AA) d15N values, and 9 samples for d13C values. The Southwest Fisheries Science Center/Pacific Islands Fisheries Science Center Institutional Animal Care and Use Committee (IACUC) approved the original animal work that produced the samples. Sex was determined genetically using qPCR sexing assay by the PRD-Genetic Lab at NOAA. These samples consisted of 5 females, 2 males and 2 unidentified individuals possibly corresponding to females or juvenile males. Large adult males were not included.

The relative pattern of AA d15N and d13C values was highly consistent with past work from other organisms and tissues [1-3]. We grouped data as source- or trophic-AAs for d15N values, and essential- or non-essential-AAs for d13C values to increase power in the analysis and evaluate temporal variation. We calculated average values for each AA group. Regression analyses were conducted to evaluate linear relationship between time and each isotopic tracer for both bulk and individual-AA d15N and d13C values.

We hydrolyzed and prepared approximately 3.5 mg of skin as well as a control (Cyanno; bacteria tissue) [1] to quantify d15N values from source- and trophic-AAs and d13C values from essential- and non-essential-AAs. All derivatives were injected with an AA control, N-leucine, to verify accuracy during each run, and analyzed via gas chromatography-IRMS to obtain d15N and d13C values from individual AAs. Each sample was run 3–4 times to maximize accuracy among chromatograms. The associated analytical error among replicates typically <1.0‰ for AAs used in our analysis. For all samples, d15N values were obtained from a total of four source-AAs (phenylalanine, glycine, lysine, tyrosine), and five trophic-AAs (alanine, glutamate + glutamine, isoleucine, leucine, proline). For d13C values, the essential-AAs that we consistently determined were phenylalanine, valine and leucine, and the non-essential-AA were alanine, proline, aspartate + aspartamine, glutamate + glutamine, and tyrosine. Additional AAs were measured for both nitrogen and carbon, but either had chromatographic issues (lost values among samples, high variability) or are known to have unusual and variable isotopic values relatives to others AAs in their category (e.g., threonine).

Cited References:
1. McCarthy, et al, (2007)
2. Popp, et al. (2007
3. Sherwood, et al (2011)

Regression analyses were conducted to evaluate linear relationship between time and each isotopic tracer.

BCO-DMO Processing:
- added conventional header with dataset name, PI name, version date, reference information
- renamed parameters to BCO-DMO standard
- reformatted columns and rows to a simple flat file
- replaced hyphens and NA with nd (no data)

Description from NSF award abstract:
Anthropogenic and natural climatic perturbations drive changes in population dynamics of species, the structure and function of food webs, and biogeochemical processes. The PIs propose a comparative analysis of three major ecosystems to investigate temporal change in the structure of mesopelagic food webs.

The PIs will investigate temporal changes in the structure of mesopelagic food webs in three major ecosystems: the California Current, Eastern Tropical Pacific, and the Peru-Humboldt Current over the past 50 years using a globally distributed apex predator as an indicator species. The predator is the sperm whale, Physeter macrocephalus, and the PIs will use stable isotope ratios of carbon and nitrogen as indicators of habitat and diet. Isotope values from bulk tissues of teeth and skin (C and N) as well as specific amino acids (N) will be used to address two primary objectives: (a) examine temporal patterns in the trophic position of sperm whales (as an indicator of changes in mesopelagic trophic structure) and baseline isotopic values (as indicators of nutrient cycling); and (b) use isotopic values, which vary among systems, to define the population structure of sperm whales from past and present times, and connectivity among populations.

This project will be conducted by researchers from academia and NOAA/NMFS with expertise in stable isotope analysis, trophic ecology, and ecosystem-based management of protected species. As such, it represents an opportunity for collaboration between scientists with complementary skills and from diverse institutions to compare structure and function of ecosystems across the eastern Pacific. Moreover, it represents a collaboration between academia and a federal agency with research and management responsibilities. The project will support a postdoctoral scholar (Iliana Ruiz-Cooley), a Ph.D. student, and undergraduate students to enhance their career and collaborative opportunities. The PIs anticipate that the results of their study will provide unique data to evaluate the effects of perturbations within and among mesopelagic ecosystems. This information may allow the scientific community to relate trends in climate to changes in trophic position of top predators and nutrient cycling, allowing more robust understanding of possible responses to future warming. Finally, as the first systematic applications of compound-specific stable isotope analysis to marine mammals, the project should be highly instructive for future evaluations of the feeding ecology, population structure and dynamics of endangered marine mammals. As such, this novel approach and unique historic perspective will be directly applicable for stock assessment and management.